The Blog

Building a Future Free of Age-Related Disease

Crowd Funded Cures

Discussing Crowd Funded Cures with Savva Kerdemelidis

We have written extensively about VitaDAO, a collective dedicated to community-governed, decentralized drug development. Probably the fastest and cheapest way to get geroprotective drugs to the market is by repurposing existing drugs, such as rapamycin, metformin, and acarbose. These drugs cost next to nothing, have a known safety record, and have shown a lot of promise in animal models and/or in human population studies. Unfortunately, pharma companies are not interested in this avenue since those old drugs cannot be patented and sold at a high price. This is why VitaDAO has partnered with LEAF to support Dr. Brad Stanfield’s rapamycin + exercise trial.

While communities like VitaDAO can be effective in crowdfunding and facilitating research, money from big players might still be essential to launch even a repurposed drug. To solve this problem, VitaDAO joined forces with Crowd Funded Cures, an initiative of the Medical Prize Charitable Trust, a non-profit founded by Savva Kerdemelidis.

The idea is to use a flexible prize fund, a type of “pay for success” (PFS) contract, to finance large clinical trials. Simply speaking, an organization, such as a big insurance company or a government agency, promises to pay a sum of money in the event of the success of the clinical trial. This lowers the risk enough to make it palatable for potential investors.

We asked Savva Kerdemelidis a few questions for a deeper dive into the world of DAOs, PFS contracts, and intellectual property on the blockchain.

Tell us briefly about your project Crowd Funded Cures and its partnership with VitaDAO, the rationale, goals, and structure of both organizations, and what has been achieved since their inception.

Crowd Funded Cures is the initiative of the Medical Prize Charitable Trust, the NZ-registered non-profit that I established in 2013 to execute the idea set out in my Masters of Law thesis to use flexible prizes to incentivize the development of unmonopolizable therapies. The impetus for doing the Masters and setting up the charity was that I had noticed that many otherwise viable medical treatments lack a business model under the patent system. These “financial orphans” could be cures for many diseases and save millions of lives and trillions of dollars in healthcare costs.

However, they suffer from a market failure or “tragedy of the commons” because patents cannot be leveraged to enforce a monopoly price, which is necessary to recover the cost of R&D, i.e., of the expensive clinical trials needed for regulatory approval. The main categories of such unmonopolizable therapies include finding new uses for off-patent or generic drugs, dietary supplements, diets, and lifestyle interventions.

The goal of Crowd Funded Cures was to help fix this market failure by raising a pilot flexible prize fund to incentivise an unmonopolizable therapy to treat Crohn’s disease (e.g. low-dose naltrexone or semi-vegetarian diet), which my fiancée at the time was diagnosed with. However, my life and career as a legal consultant and patent attorney intervened, and the project lost steam.

More recently, there has been a perfect storm, with COVID highlighting the opportunity for generic drug repurposing and the public harm due to lack of private incentives to conduct clinical trials (as an example, using low-cost off-patent fluvoxamine to treat COVID-19 vs expensive patented molnupiravir). Web3 and blockchain have also shown how certain projects can raise hundreds of millions of dollars in seconds.

There has been renewed interest in how Web3 and DAOs can help solve global coordination problems and the use of financial innovation to align private incentives with funding public goods. Also, an aging baby boomer population, Eroom’s law, escalating healthcare costs, big data, and cheap DNA testing, wearables, and diagnostics all show that new incentive models must be leveraged if medical innovation is to reach its full potential in this century.

In early 2020 after COVID hit, I was motivated to put more energy into Crowd Funded Cures. Our partnerships advisor Spiro reached out to the leading Web3 DeSci project, VitaDAO, in mid-2021, and we found a lot of synergies with their community – mostly scientists who were also frustrated at the financial bottlenecks for science funding in the “valley of death” for early-stage biopharma research.

As a solution, they proposed the use of IP-NFTs [intellectual property non-fungible tokens], using Molecule.to’s platform, established by Paul Kohlhaas and Tyler Golato. VitaDAO had just raised over $5 million in a token sale to fund longevity research. In less than one year, the 5000-plus-member VitaDAO community has evaluated over 60 research proposals and deployed approximately $2 million dollars in funding – a monumental achievement.

This includes $40 thousand for Crowd Funded Cures to conduct a Generic Drug Repurposing PFS Feasibility Study and $50 thousand to support a pilot IP-NFT x Pay-for-Success contract to fund a Phase 2a rapamycin + exercise study by Dr. Brad Stanfield, a New Zealand doctor and longevity researcher. Crowd Funded Cures has also grown over the past few months to over 100+ members in its Discord, and 10 volunteers. We also plan to conduct a token sale to launch a DAO this year.

PFS (Pay-for-Success) seems like a great idea. Could you please explain how the PFS/IP-NFT framework works?

A Pay-for-Success (PFS) contract is essentially a kind of conditional grant or prize, whereby a payment is made upon fulfilment of certain criteria. Other names used by think tanks such as the Oxford Government Outcomes Lab are outcomes-based financing or Social Impact Bonds (SIBs). The idea is that if the government wishes to incentivize private industry to deliver public goods or services (such as reducing prisoner recidivism or homelessness), they can back a PFS contract and reward certain outcomes (e.g. $10 thousand for keeping a prisoner out of jail for one year after release or putting a homeless person into a home and employment within one year).

SIBs are a relatively new phenomenon, with the first established in 2012 in the UK to reduce prisoner recidivism, but now with over $700m raised globally. Dr. Bruce Bloom of the generic drug repurposing charity Cures Within Reach had the idea to use SIBs to repurpose generic drugs in 2015 [Dr. Bloom left Cures Within Reach in 2019], and helped bring the idea to the NHS with a UK rare disease charity (Findacure UK, renamed as Beacon). Unfortunately, this did not obtain backing from the UK government. Crowd Funded Cures’ mission is to continue this important work and obtain private and public backing for generic drug repurposing PFS contracts.

So, IP-NFTs are a framework established by Molecule.to. It allows fractionalized ownership of IP which can be traded on the crypto markets and benefit from the increased liquidity provided. The other advantage of allowing fractionalization and distributed ownership is greater consistency with open source and consumer co-op business models (e.g., if a drug is owned by patients, then they are less likely to be subject to exploitative pricing).

A PFS contract can be combined with the IP-NFT framework to allow investors to fund unmonopolizable therapies such as repurposing generic drugs. This would otherwise be a non-viable investment for VCs because it would not be possible to enforce a monopoly price (unless the generic drug can be patented as a reformulation, which is not always possible). For example, instead of earning ROI via patent royalties and monopoly pricing, the rewards for the IP-NFT investors are provided by payers backing the PFS contract, upon publication of clinical trial data encrypted in the IP-NFT showing the repurposing of a generic drug to successfully achieve a clinical outcome.

The payers will benefit from the development of a new treatment protocol that can improve patient health and reduce healthcare costs. In essence, a PFS contract allows the payers (which could be a syndicate of public and private health insurers) to put a price on an off-patent treatment protocol in advance. This creates a business model for funding open-source medicines, which would outcompete new patented medicines.

Why would any specific insurance company choose to be the one to shell out the money, if all the insurers would equally benefit from the success?

There is indeed a free-rider problem to the extent that other payers, such as private health insurers, can benefit from the knowledge of new successful treatment protocols without having paid for them. However, there are some first-mover advantages. For example, under a PFS contract, a payer may get exclusive access to the “branded” repurposed generic that has obtained regulatory approval. Other payers would be forced to use the drug off-label, which doctors may be reluctant to prescribe due to increased risk of liability and/or lack of insurance coverage.

There will also be the PR value of helping develop a low-cost open-source medicine, which would have a massive positive impact on public health globally. Payers can have access to the raw clinical trial data encrypted in an IP-NFT, which may be useful to help develop new medicines and/or contain other commercially valuable information. Let’s not forget that large government single-payers such as the NHS and philanthropies that directly fund clinical trials should not have this concern.

What is the relationship between VitaDAO, the Longevity Prize, Crowd Funded Cures and Dr. Stanfield’s rapamycin study? How will you raise funds for the prize, and have you had contacts with insurers?

VitaDAO submitted an application for funding on Gitcoin for a Longevity Prize, which was one of the highest-funded projects, with over $190 thousand raised to date. The goal of the Longevity Prize is to issue smaller prizes to incentivize longevity research. They also intend to set aside $100 thousand for a generic drug repurposing Longevity Prize to support an IP-NFT x PFS pilot with Crowd Funded Cures. We have identified Dr Brad Stanfield’s $400 thousand Phase 2a RCT (randomized controlled trial) for rapamycin + exercise as a case study to apply the PFS model. In essence, having a generic drug repurposing Longevity Prize in place will create a commercial business case for VitaDAO to invest in an RCT for an off-patent therapy via an IP-NFT.

Dr. Stanfield is highly supportive of the PFS model because it has been extremely difficult for him to raise the funds via philanthropic means (despite having 100k subscribers on his YouTube channel and support of lifespan.io). This is a common theme for many charities trying to raise money for clinical trials – finding philanthropic donors is hard. However, with a PFS contract, the “donors” are actually pre-purchasing successful clinical trial data. This is similar to crowdfunding platforms such as Kickstarter, which is effectively a pre-sale.

For Dr. Stanfield’s RCT, the purchased data would be a novel and successful treatment protocol combining exercise three times a week (with a standardized exercise bike) with an intermittent weekly dose of rapamycin when not exercising, that results in a successful primary clinical outcome, i.e. trend towards improvement in the 30-second chair stand test, which is a standard test for strength in the elderly and is strongly correlated with healthy longevity.

We are hoping that with a PFS model and by engaging with the longevity and crypto community, it will be possible to raise a $1 million payer fund. This will allow VitaDAO to fund the entire Phase 2a via an IP-NFT that will be eligible to receive an outcome payment from the payer fund if the primary clinical outcome is met.

In the event that the RCT is not successful, the payer fund can be used to incentivise other generic drug repurposing research (perhaps a different treatment protocol/dosing regimen for rapamycin or another generic drug like metformin, resveratrol, NMN, or NR). This would be a world first and help validate the business model for a PFS contract to incentivize the development of off-patent/open-source medicines, which also transfers risk from payers/donors to investors.

Crowd Funded Cures has had contacts with various payers over the last couple of years, including PHARMAC (NZ government single payer), BARDA (US government agency), NCATS (NIH generic drug repurposing institute), and various philanthropies, including LifeArc (large UK charity), Wellcome Trust, Chan Zuckerberg Initiative, and others. However, these bureaucratic organizations will likely be slow to back a PFS contract.

It is hoped that with our feasibility study, we can show the financial and business case to do so on the basis of overall cost savings/health impact exceeding the costs of outcome payments/payer fund. It is noted that even if the payer fund/prize is too small to incentivize investors to front the money for the clinical trials, it will be possible to create a hybrid PFS model with part of the money funded by investors and the rest funded by philanthropy to increase investor ROI.

What is the importance of this particular study?

Rapamycin is the only drug that have been shown to reproducibly extend lifespan both in male and female mice, according to the Interventions Testing Program. Exercise has also been shown to reduce the age-associated decline in strength. However, the muscle-building enzyme mTOR, target of rapamycin, is also overexpressed in the elderly, but paradoxically, does not lead to improved strength.

Rapamycin downregulates mTOR, and for this reason, Dr. Stanfield had proposed combining exercise during the week with a single intermittent dose on the weekend when the patient is not exercising, with the hypothesis that it could restore mTOR balance and improve muscle performance. The RCT is also small to test whether this approach is safe and won’t cause any adverse effects before scaling to a larger RCT.

This kind of experimentation to “de-risk” optimal dosing regimens is perfectly suited for a PFS or prize-like incentive which does not rely on selling as many drugs as possible to maximize profits, as with the current patent-centric incentive model relied on by the biotech industry. For that reason, we are excited about the opportunity for the PFS model to help researchers to get private funding for their new and innovative ideas even with a weak patent position, which could have a massive impact on longevity and global health generally.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.
Mouse feeding

Caloric Restriction, Feeding Times Lengthen Mouse Lifespan

In a new study published in Science, researchers show that caloric restriction and time-restricted feeding have an additive effect on lifespan in mice [1].

A well-known intervention

Caloric restriction is considered the first intervention to reliably show that aging is a malleable phenomenon. The first trials were conducted on rats back in the 1930s and showed that drastic caloric restriction of 20% to 30% significantly increased lifespan compared to a freely fed (ad libitum) control group [2].

As promising as these early results were, the reality is more complicated. First, lab animals tend to overeat when food is abundant, so caloric restriction could just bring the number of calories to normal levels, hence it might not work as well in people who already count their calories; there have been virtually no human trials of drastic caloric restrictiom, because it’s hard to maintain.

Second, in most experiments with rodents, the animals were fed once a day. They frantically consumed their limited amount of food in roughly two hours and then went on to involuntarily fast for 22 hours straight. Today, this would be called intermittent fasting, another intervention that is gaining popularity for its supposed health-promoting qualities [3]. There are several intermittent fasting regimens, including “day in – day out”, but some of the most popular involve only eating during a 2–12-hour window.

Therefore, it is hard to determine whether it’s fewer calories or fewer feeding hours that cause caloric restriction to work so well in mice and rats. This new study attempts to provide an answer, using something the scientists of the 1930s didn’t have: automatic feeders.

If you’re a mouse, eat at night

The researchers divided male mice into six groups. The control group was fed ad libitum, with food readily available during night and day. All the other groups were calorically restricted – they received 30% less calories than mice in the AL group were consuming. The first calorically restricted group received food throughout the day, with one food pellet being dispensed by an automatic feeder every 160 minutes, which took away the influence of intermittent fasting. The second calorically restricted group was fed only for 2 hours during the day, the third for 12 hours during the day, the fourth for 2 hours during the night, and the fifth for 12 hours during the night.

In the freely fed group, the median lifespan was 792 days, which is quite normal for this particular highly popular strain (Black 6). This is important, because in some studies, controls are short-lived, which can cast doubt on the results.

All the caloric restriction groups demonstrated considerable gains in lifespan compared to controls, but there were major differences. The first group, mice who were being fed throughout the day, lived for only about 10% longer than controls. The two groups that were fed during the day came close to each other: the second group lived 21% longer, and the third group lived 19% longer on average than the controls. The two final groups were clear winners, with a 35% increase in median lifespan for the fourth group and 33.4% for the fifth group.

Caloric Restriction Results

Obviously, mice that were fed at timed intervals throughout the day had their sleep disrupted, which might have diminished the gains in lifespan. The researchers admit that this demands further investigation. Mice are nocturnal animals, so if they are forced to eat during the day, this is unnatural for them and might explain the difference between the night and day groups.

There are two important takeaways from the data: caloric restriction and intermittent fasting have an additive effect, and reducing the feeding window to 2 hours seems to add little value compared to a 12-hour window.

Additional benefits

The researchers confirmed that caloric restriction confers clear metabolic benefits. While insulin levels increased with age in the control group, this increase was attenuated in all of the restricted groups. Even though the insulin levels of young calorically restricted mice were comparable to those of young mice in the control group, the former had lower blood glucose levels, indicating improved insulin sensitivity.

The researchers also analyzed gene expression in the liver. Transcriptomes of young and old mice in the control group clustered separately due to obvious age-related changes. The transcriptomes of young mice in the caloric restriction group clustered separately, meaning that caloric restriction affects gene expression in young mice.

Finally, all old calorically restricted mice also clustered together in their transcriptomes, between old mice in the control group and young calorically restricted mice, showing that the intervention attenuates age-related transcriptomic changes. About 50% of age-related changes in gene expression were reversed by all caloric restriction regimens.

The researchers found 159 genes that responded specifically to intermittent fasting rather than caloric restriction, confirming that their effects are at least somewhat additive. 69 genes were specifically protected against age-related expression changes in groups that were restricted to low-calorie nightly feedings.

Conclusion

This study attempts to disentangle the effects of caloric restriction and intermittent fasting and to give us an improved understanding of how those two interventions work. Since drastic reduction of calories is hardly achievable by humans in real life, the indication that time-based feeding might be partly responsible for the life-prolonging effect of caloric restriction is encouraging. The lack of sex diversity is a serious limitation since many life-prolonging interventions seem to work differently in males and females. Hopefully, this will be addressed in further research.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Acosta-Rodríguez, V., Rijo-Ferreira, F., Izumo, M., Xu, P., Wight-Carter, M., Green, C. B., & Takahashi, J. S. (2022). Circadian alignment of early onset caloric restriction promotes longevity in male C57BL/6J mice. Science, e.

[2] McCay, C. M., Crowell, M. F., & Maynard, L. A. (1935). The effect of retarded growth upon the length of life span and upon the ultimate body size: one figure. The journal of Nutrition10(1), 63-79.

[3] de Cabo, R., & Mattson, M. P. (2019). Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine381(26), 2541-2551.

Fluorescent cells

The Development of Glowing Pluripotent Cells

A team of Chinese researchers has described a novel method of illuminating pluripotent stem cells in a paper published in Aging.

How and why

Using a lentivirus, the researchers genetically engineered mouse embryos to express green fluorescent protein (GFP) when it expresses the Yamanaka factor Oct4. GFP, a harmless protein that glows bright green under ultraviolet light, has been used for decades in the bioengineering field as a visual indicator of various processes [1]. Therefore, the researchers reasoned, it could also be used as a visual indicator for pluripotency: the ability of cells to transform into many other types of cells.

Existing methods for analyzing cells, such as fluorescence-assisted cell sorting (FCAS) and reverse transcriptase polymerase chain reaction (RT-PCR), already use fluorescent tagging to detect what proteins are being expressed. By integrating pluripotency-activated fluorescence right into the cells themselves, this process would logically become much cheaper and easier.

In this paper, the researchers offer several related use cases for this technology, most of which involve reprogramming cancer cells into induced pluripotent stem cells (iPSCs).

Determining if it works

Using the Yamanaka factors, the researchers reprogrammed mouse embryonic fibroblasts (MEFs) into iPSCs and observed the results. 9 days after the introduction of these factors, the fluorescence became slightly apparent, at day 14, it was much more visible, and by day 24, it was strongly visible.

The researchers analyzed these cells with a conventional assay of Oct4 along with other factors known to be linked to pluripotency, such as Nanog, SSEA1, and the Yamanaka factor Sox2, and they found that the expression of GFP was colocalized with these compounds.

Further testing found that these genetically engineered cells induced to pluripotency behaved like normal embryonic stem cells, including in their cellular division cycles. Placing them into embryoid bodies caused these cells to differentiate into functional cells; in this experiment, they differentiated into cardiomyocytes (heart muscle cells). Injecting these iPSCs into mouse blastocysts let them grow into living chimeric mice, and injecting them into older animals generated teratomas, as expected.

Most importantly, Oct4 and GFP, alongside Sox2, decreased smoothly with differentiation, proving the usefulness of GFP as a marker for pluripotency: when the pluripotent state went away, so did the fluorescence.

Conclusion

Despite all the technological advancements made in this regard, biological experiments are neither easy nor cheap. A built-in visual indicator and fluorescence assay helper will surely aid the work of researchers attempting to create therapies that rely on pluripotent iPSCs – or, perhaps, therapies in which pluripotency is something to avoid.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Kain, S. R., Adams, M., Kondepudi, A., Yang, T. T., Ward, W. W., & Kitts, P. (1995). Green fluorescent protein as a reporter of gene expression and protein localization. Biotechniques, 19(4), 650-655.

Joao Pedro de Magalhaes

João Pedro de Magalhães on Reprogramming and Aging Theories

Professor João Pedro de Magalhães leads the Genomics of Ageing and Rejuvenation Lab at the Institute of Inflammation and Ageing in the University of Birmingham. He is also CSO of YouthBio Therapeutics, a US-based biotech company that develops rejuvenation gene therapies based on partial reprogramming by Yamanaka factors. Last year, he co-authored The hoverfly and the wasp: A critique of the hallmarks of aging as a paradigm. Here, we discuss this critique and other fascinating geroscience-related topics.

Most mature scientific fields have a unified theory, but geroscience doesn’t. Why is it important for our field to have such as theory? 

We don’t have a good understanding of a lot of complex diseases, particularly quite a few age-related diseases. For instance, we don’t know what causes Alzheimer’s. Of course, once you understand what causes a certain pathology or a biological process, that makes it a lot easier to intervene in it.

Infectious diseases are probably the best example. If you understand that AIDS is caused by HIV, then you can try targeting HIV to prevent AIDS. Having a pathophysiological, mechanistic understanding of the causes of a given disease allows you to better develop therapies.

That’s why it’s important to have a biological understanding of aging – so we can better intervene in it. One of the biggest questions in the field of aging is still “Why do we age?” There are several theories, or hypotheses, but none of them have been proven yet.

In your recent paper, you offer an interesting, and I think pretty convincing, critique of the hallmarks of aging paradigm, or a false paradigm, as you call it.

The hallmarks paper was a great summary of the field, and if you read it, the authors are fairly cautious about it. It’s a set of hypotheses, but people might have taken the hallmarks of aging a bit too seriously – as the dogma, the Bible of the field, and that’s not what it is.

It’s a great review. But it’s not a paradigm, it does not explain aging. In fact, for decades, we’ve been in a situation where we don’t have a good mechanistic explanation of aging. Again, there’s a lot of hypotheses, and some may turn out to be right, but they may all turn out to be wrong as well, that’s a possibility.

We should focus on really understanding aging, but I feel we’ve shifted focus a bit in that regard. There’s a lot of focus on longevity interventions (and that’s exciting as well), but not so much on understanding why we age, on discovering the underlying mechanisms of aging.

Some scientists hold the opposite view – that we should focus on finding anti-aging interventions, and that might give us clues about why we age.

I would disagree with that. You can have interventions that you don’t understand how they work. We know that aspirin works – it reduces pain, inflammation – but we don’t really understand how it works. So, even if you have an intervention that extends longevity, figuring out how it works is not trivial.

I would agree that interventions, i.e., ways of changing the aging phenotype, are important for us if we want to study the mechanisms of aging. For example, caloric restriction is important because in most model systems, it extends lifespan and retards aging, which gives us a model for studying the mechanisms of aging: you’re going to have experimental groups of animals that live longer than others, and you can then ask questions like: why do these animals age at different paces?

In that regard, I do think that interventions and longevity manipulations can provide insights, because they provide this diversity in the rate of aging that can help us understand its mechanisms. But, given that we know of lots of interventions already, I don’t think you necessarily need more interventions. You can try to figure out why certain interventions work but not necessarily try to come up with more interventions. In model systems, we have already discovered different longevity manipulations.

If I go to our DrugAge database, it has over 3000 entries, over a thousand drugs. So, we already know over a thousand drugs that work (admittedly, a lot of this will be for invertebrate, not mammalian, models). So, we know quite a lot already in terms of interventions, but in the vast majority of cases, we actually don’t know how they work.

Could you elaborate on what you call in your paper the false distinction between aging and the diseases of aging?

The relationship between aging and age-related diseases has been debated for decades. I think it’s more semantics than actual biology. It depends on how you define aging. I would say that aging is a process that predisposes us to a variety of diseases. There are overlapping mechanisms between age-related diseases. For instance, cancer and neurodegenerative diseases have this overlap, although there are also mechanisms that are specific to cancer and neurodegenerative diseases that don’t relate to other age-related pathologies. The overlap is partial. I would say that if we can understand the underlying aging process that predisposes us to various diseases, that would allow us to better understand how to intervene in aging and hence in age-related diseases.

We have drugs like rapamycin that seem to alleviate many age-related pathologies. How do such drugs fit into this picture? 

On one hand, longevity drugs are a fascinating and important topic. Whether a drug can slow down human aging is another big question. As I mentioned, we know over a thousand drugs that can extend longevity (not necessarily slow aging) in model systems. So, there’s a big space in terms of longevity pharmacology that potentially can lead to clinical applications in humans, which would be fantastic.

Rapamycin fits very well into that. It’s quite well-studied. It extends lifespan in mice quite robustly. It is one of the most promising longevity drugs. We have some mechanistic understanding of rapamycin, because, well, TOR, which is “target of rapamycin”, but TOR does quite a lot of things.

I don’t think we fully understand at the mechanistic level how we go from rapamycin inhibiting TOR to retarding aging. From a clinical applications perspective, the development of TOR inhibitors and rapalogs with fewer side effects is a very exciting area of study.

Another interesting distinction I heard in one of your talks is between slowing and reversing aging. Do we have any proven interventions that actually reverse aging in complex models?

You could argue that there are some really simple model systems where we can reverse aging. You could also argue that we can reverse aging in human cells with telomerase and cellular reprogramming with Yamanaka factors, but whether that applies to whole organs is a completely different question. The jury is still out on whether we can actually reverse aging in mammals.

I think this might be a terminology issue. If you take an obese individual, and this individual goes on a diet, they will be healthier. Their risks from various age-related diseases are going to decrease because of the diet, but that doesn’t mean that this person has been rejuvenated, it just means that a lifestyle intervention improved their health.

A lot of times, you can have interventions that improve health and maybe ameliorate elements of epigenetic clocks without necessarily doing anything about the process of aging. I think we’ve had this problem in the field for quite a long time – that you can have interventions that increase longevity without necessarily retarding aging, just because they’re healthy. Do obese individuals age faster? I wouldn’t readily assume so, although some of my colleagues may disagree with me.

You can have interventions, pharmacological interventions, for instance, that extend lifespan, but don’t slow down aging in humans and even in model systems. Mice mostly die of cancer, and if you have a drug that prevents cancer, the mice are going to live longer. It doesn’t mean aging has been retarded, even though longevity has increased.

The problem we have in the field is what do those various interventions mean? Do they really slow aging, do they reverse aging, or are they just healthy? That’s why we sometimes need to be more careful about what we are claiming to have achieved.

How would you show something like aging reversal? To me, there’s still a question mark on it. I think you must have some pretty strong evidence for it – functional evidence, molecular evidence. It has to be something quite substantial to prove that you’ve reversed aging in a mammalian organism, that you’ve rejuvenated a tissue. I think that would require some pretty substantial evidence which I haven’t seen yet. Going back to your question, in complex models, such as mammals – no, I don’t think we have really reversed aging.

You probably don’t think that biomarkers of aging, such as epigenetic clocks, can give us the definitive answer, right? For instance, the thymus rejuvenation study – was there rejuvenation or not? 

In the thymus rejuvenation paper, my recollection is that they didn’t have controls, a placebo group. That’s a big problem. If you don’t have controls, who knows what else those individuals are doing? I believe they’re trying to do a bigger study. Hopefully they will do a follow-up that will validate that, but going back to epigenetic clocks, I think there’s still a lot of question marks about what they are actually measuring. We don’t understand their mechanistic or biological basis.

Just recently, there was this paper showing that patients with COVID-19 show accelerated aging if you use epigenetic clocks. That’s interesting, but maybe that means that the clocks are just looking at inflammation? That’s a possibility. If you get an infection, of course you’re sick, and your clock would go up because of the inflammation, of the immune response.

This doesn’t mean you’re aging faster or that your biological age has increased. It just means you’re sick. When you recover, you’re not infected anymore, your clock goes down, but that doesn’t show rejuvenation, it just means you don’t have an infection anymore.

I think this shows one of the problems with epigenetic clocks in that we don’t really understand what they’re measuring. If they’re measuring health, that’s interesting as well, and of course, that would inversely correlate with aging, but it’s not the same as measuring biological age, it’s measuring how healthy an individual is, which, again, can be influenced by things like infections, or being obese and then going on a diet.

We still don’t know that. I think epigenetic clocks are fascinating, and their accuracy is very impressive. I did not expect clocks to become so accurate, I have to say, I was very impressed and surprised with that, but we still don’t understand what’s the biological and molecular basis behind them.

From the bioinformatics point of view, that’s not necessarily a question we must ask ourselves. If we see a strong correlation, we can just keep using this as a tool.

We can, but I would push back here as a bioinformatician: particularly if we are using human data, we have to be very careful about the correlations we find, because with humans, you can’t really control. If you’re experimenting on animals, you can keep them in a cage, they all have similar genetics, they eat the same food.

People, on the other hand, vary a lot. You can find all kinds of correlations, like wealth correlates with longevity, and rich people tend to live longer. Does that mean that money slows down your aging process? No, it just means wealthier people tend to live healthier lives.

People from the bioinformatics field, in my experience, are mostly okay with this black box approach. It’s like, we have our big data, we see correlations, that’s all we need. 

I think that depends on the application. Epigenetic clocks are fantastic for some things. I know people use them to test interventions, to do studies in different species, studies in wild populations of animals, when they don’t know the age and they use epigenetic clocks to determine that.

In that regard, it’s a fantastic tool, and you don’t need to understand how it works, but if you are asking whether you’re rejuvenating an individual, and you’re using an epigenetic clock to answer that question, then you need to understand a bit more about this clock, about the markers and the readouts you’re using. That’s when it becomes more important.

As a scientist, I’m always curious, how does this work? What cell types are contributing to the clock? What genes, molecules, enzymes, mechanisms? If you can figure out how the clocks work, you may be more able to devise ways of affecting them. You can develop interventions. So, for certain applications, you don’t need to know how it works, but for others, biological understanding becomes important.

Let’s take genetic associations. You can find very statistically significant genetic associations, and that’s interesting, but you also want to know the molecular mechanisms behind it. Having a statistical significance association doesn’t tell you the whole story. Particularly if you want to take the next step, which is to reverse-engineer a process in order to tweak it, you must have a mechanistic understanding of that process.

That brings me to a question about your work. You have studied long-lived mammals, analyzing their genomes – animals like the bowhead whale and the naked mole rat. What have you learned from studying them? 

I see studying long-lived species and the differences between species in terms of lifespan and disease resistance as a complimentary approach. Going back to what I said at the beginning, you need variation in order to study a particular biological process. So, we have variation within species – we have caloric restriction, pharmacological interventions, different types of manipulations of aging.

That’s important: if you want to study mechanisms, if you want to try to understand a process, you want to see how we change it. If you’re studying a disease, generally you study individuals with the disease, individuals without the disease, individuals with different severity of the disease.

If you’re studying a biological process, you want to study different paces of that process. You can do it within species, which we do already, and then a complementary approach is cross-species, because mice age 20-30 times faster than human beings, while some species of turtles and fishes don’t appear to age at all. So, you have a very big spectrum of paces of aging. That gives you diversity in the process of aging that allows you to gather insights.

Of course, if you’re looking across species, the problem is that there’s a lot of other differences. If you’re studying caloric restriction in mice, there’s not that many differences between them, apart from that intervention that you’re studying. On the other hand, if you’re comparing a naked mole rat to a mouse – yes, there’s a difference in lifespan, but there’s also a lot of other differences between them. That’s the difficulty.

We and others have looked at animals like the naked mole rat, the bowhead whale, there were some great recent papers on rockfishes. We published a study last year on the Capuchin monkey, which is a small, long-lived primate. I guess the main message is that you see different genes in these species, but they tend to fall into similar categories, similar pathways.

My overall impression is that when a species evolves longevity, when it is selected for longer lifespan, species tend to use different tricks to achieve that, but these tricks tend to fall into some common themes like tumor suppressors, DNA damage responses, protein homeostasis. There are common themes for how species optimize pathways and processes to extend lifespan.

It is known that if we theoretically could eradicate cancer in humans, that would only extend lifespan by about three years. I guess that’s also true about other species. So, long-lived species must have developed several mechanisms at once, right? There are several tricks up their sleeves?

That’s right. It’s not just one trick. We’ve only really scratched the surface as far as these tricks are concerned, because there’s a lot of differences between species at the genetic level. When you do a comparison between genomes of different species, you’re going to find a lot of differences, and then you can use statistical methods to try to prioritize them.

Through different bioinformatics methods you can try to infer which genes are more important for longevity. You’ll find some clues, but really that’s just the tip of the iceberg. There’s probably a lot we don’t really know in terms of mechanisms that relate to species’ differences in aging, in lifespan. As you say, it’s not just one thing, there are going to be different types of adaptations for life extension in different species.

It’s quite remarkable. If you think about humans and chimpanzees, we are not very different on the genetic level, yet we live considerably longer than chimpanzees, we appear to age slower than them. Which genes are responsible for these differences in lifespan between humans and chimpanzees? It’s not just one thing, but it’s also not an infinite number of things. It’s a finite number, and this number cannot be too big, because there’s not that many differences between humans and chimpanzees. This is an interesting way to look at things.

I think differences in aging between species remains one of the big open questions in the field. Trying to figure it out can also help address the question why we age. We’ve really only scratched the surface as to what is the genetic basis of interspecies differences in age.

It is important to continue in that direction, right?

Absolutely. It’s an important complementary approach. In our lab, we’ve done work on different traditional model systems such as worms, we’ve done some work (mostly with collaborators) on rodents, including with the ITP of the NIA. That’s all interesting, it gives you one line of evidence, because it’s very difficult to study aging in humans.

We’re reliant on short-lived model systems, but they have their own limitations in what they may be teaching us about aging. I would say only a part of it will be relevant to humans, and we’re not sure what part.

On the other hand, we have these long-lived, disease-resistant animals like naked mole rats, whales, Capuchin monkeys, and they can provide a complimentary set of insights and information. That’s why this is important.

Have you seen this new paper that generated quite a lot of buzz, about the rate of somatic mutations and its correlation with lifespan in various species?

I think it’s a fantastic study. It really shows what has been theoretically expected but not really demonstrated in practice, which is that long-lived species accumulate somatic mutations slower than short-lived species. I think, this is primarily due to tumor suppression mechanisms. The question of how relevant this is to other aging pathologies, or aging-related physiological changes, remains to be determined. But it showcases how, if you are evolving long lifespan, one of the things you need to curb is the number of mutations. The data we’ve had so far is mostly from mice and humans, so this is quite an interesting expansion in the repertoire of species.

Another part of your work has to deal with cellular reprogramming, right?

Yes, I’m working with the company called YouthBio, which focuses on cellular reprogramming. I guess we’re not the only company focusing on cellular reprogramming nowadays. We actually were in stealth mode until recently.

Our goal is to develop gene therapies based on cellular rejuvenation and partial reprogramming with Yamanaka factors. It’s a quite interesting topic in itself. As we touched upon already, it does work on cellular models, but there’s still a lot of questions of whether it could work on whole organisms, or how we can make it safe because, of course, reprograming can induce cancer.

As to having bigger, better-funded competitors, I actually don’t see that as a problem. You don’t want to be the only company in a particular field. That’s usually a bad sign. You want to have other companies working in the same space. It shows that this is a dynamic field, a dynamic approach.

Personally, I’m used to always being the underdog. Our lab is not the best funded in the world. There are many bigger, better-funded labs than ours. I’ve always liked that role of being the dark horse and having to compete with bigger labs. I think that helps in a lot of circumstances.

So, the fact that there are much bigger companies working in the same space is not necessarily a problem. It shows the enthusiasm about this particular approach. It also means that if we can make it work, it will have a lot of value, and a big company might buy our technology and knowhow.

Calico is one particularly big and well-funded company that has been around for a long time. Do you know if they have had any breakthroughs in reprogramming?

Not really. They’ve published some nice papers, but certainly, for the amount of funding they have, although you never know what they can come up with, I would say, so far, they’ve been fairly disappointing. When there’s a company with billions of dollars, you expect it to be a leader in the field, to deliver breakthrough after breakthrough.

That’s not happened; they’re not leaders in the field. Yes, they do some nice work, but so far, they haven’t really delivered what nearly everyone expected when they started, and it’s been nearly 10 years. I think it’s fair to say that they’ve been disappointing, unless they come up with something amazing. You never know.

The question is do you maybe see their lack of progress as a sign that cellular reprogramming might be a dead end?

In terms of Altos, NewLife, and Retro, all those big companies working on cellular reprogramming – yes, it could blow up in their faces. I think the best analogy is telomerase. I remember when telomerase came out and it could prevent cellular senescence and rejuvenate cells.

In vitro, telomerase was fantastic. And people were talking about telomerase therapies, curing age-related diseases, reversing aging. It hasn’t really happened, and there are reasons for that. One, because telomerase by itself doesn’t really slow down aging. It prevents aging at the cellular senescence level, but it doesn’t prevent other aspects of aging in vivo. It also has certain risks in terms of cancer, et cetera. The point is that something that worked very well in vitro in terms of preventing aging, in this case telomerase, hasn’t so far worked in organisms, much less in the clinic.

The same could happen with cellular reprogramming. This is a possibility we have to be prepared for. On the other hand, we don’t know yet, and reprogramming has a bigger impact on cells than telomerase. I would be surprised if Yamanaka factors by themselves worked without side effects, but there may be ways of tweaking reprogramming, and that’s some of the work we’re trying to do – to make it more efficient and safer.

Now, maybe it does work, not necessarily at the level of rejuvenating human beings, but maybe it has applications in certain conditions. As I’m sure you’re aware, there’s a lot of interest in reprogramming for regenerative medicine – not rejuvenation, but just regenerative medicine in patients with spinal cord injuries or other conditions that may benefit from reprogramming.

Maybe in ovarian aging.

Exactly. So, there may be specific applications. Even if it doesn’t pan out, if we cannot reverse aging in human beings with programming, maybe it will still have some clinical applications, as a lot of companies even outside of the field of aging are already exploring.

The fact that not just Altos, but several big companies are investing in the space means we’re probably going to have an answer to it – whether it works or not. This would be very beneficial because even if it doesn’t work, if reprogramming is a dead end and we’re just wasting our time, we want to know about it sooner than later, because we want to move on to other things.

We’d also want to have at least one single breakthrough rather sooner than later, so to not scare off the investors.

Yes, absolutely. We need a success story in the field of aging. We still don’t have one. We don’t have a therapy that actually works in human beings. I’m somewhat skeptical that reprogramming is going to be that first success story, because I think the pharmacological approach has better chances as folks have been doing drug development for a long time.

There’s a bunch of companies working on pharmacological approaches to aging, doing clinical trials for senolytics, for caloric restriction mimetics, and some of those approaches might work. Most of them will fail, but hopefully at least one will work. If we can have a success from a pharmacological approach, that would be fantastic.

I would disagree however with your assumption that without a success story, the investors are going to be disappointed. Why? Because people are not getting younger, that’s the bottom line. The incidence of age-related diseases is going to increase. The graying of the population worldwide is going to continue. That’s why we’re going to have more and more motivation to intervene.

We had, I would say, quite a disappointment some years back with resveratrol. You might remember the resveratrol debacle. There was a lot of interest, they were purchased for a huge sum, a lot of excitement, but then it didn’t work out.

You might have expected a big disappointment to hurt the field, but that’s not what happened at all, quite the opposite. The field has flourished. So, we can have some flops. However, if we have a lot of them, that might be an issue, because there are different types of investors. There are investors that believe in the philosophy of life extension, of reversing or at least retarding aging. Such investors are going to stay, no matter the difficulties.

You have a different class of investors that appeared more recently, and they see aging and the longevity industry as a way to make money. If there’s a lot of flops in the field, if many companies fail in a short period of time, I can see those investors going elsewhere.

I agree about the “gray tsunami”. Maybe in this case, governments should step in much more massively, increasing the amount of spending dramatically, because it’s still laughingly small?

Absolutely, but you’re preaching to the converted. We need more government funding for aging. In a way, government funding is the main funding we need because that’s the big money. I think the NIA (National Institute of Aging) budget is around $4 billion a year. It’s like an Altos Labs every year. Most of it goes to Alzheimer’s disease, not to the biology of aging. The biology of aging gets a tiny fraction of that. That’s what we need, we need billions of dollars every year from the government.

Having steady government funding allows you to do blue skies research, to address the basic questions we were talking about, like why we age? No company is going to say: Pedro, here’s a lot of money for you to tell us why we age! That’s not going to happen.

For those kinds of basic biology projects, we’re still relying on government funding and charities. The major driver of science discovery is funding fundamental science, which leads to a lot to startups and ultimately clinical applications. But we need that fundamental science to begin with, and it has to be funded by the government and charities.

I really liked your Twitter description that describes you as a “scientist planning to live forever”. I don’t know how serious you are about that, but I really like how unapologetic you are. However, that’s not a popular position today. How would you defend it?

That’s a good question. Interestingly, there’s been a couple of people in recent times telling me that they like my Twitter description. It also means that there are some people who don’t like it, they just don’t mention it to me.

So, first of all, I think sometimes you have to compromise on tactical decisions – on a grant application, in a talk. But don’t compromise on strategy. If your goal is to cure aging, then say it, don’t compromise on it.

When I started in the field, my PhD supervisor Olivier Toussaint, who sadly passed away a few years ago, asked me: do you really want to be going around telling everybody your goal is to cure aging? I said, yes, because that’s the goal. I could pretend not to, like some people do.

I know scientists in the field whose goal is to cure aging who don’t talk about it because they’re afraid they’re going to miss opportunities, and maybe I’ve missed opportunities because of that, I don’t know. But in the end, that’s the goal and there’s no point in faking it.

That doesn’t mean that everyone is going to agree with me or that this is the best way of selling the field. And we’ve had some discussions about it. I think we need to sell the field in different ways to different people. And there are other ways – to call it geroscience, to focus on healthspan. For certain audiences, that’s going to work better than saying we’re going to try to cure aging.

As I said, sometimes you’ll have to compromise on tactical decisions. Ultimately, what I want to do is to cure aging. And, if people don’t like it, then I’m happy to discuss it.

It’s not like we’re making biological weapons. We’re not doing anything wrong. We’re just trying to eliminate age-related diseases – to prevent people from having Alzheimer’s, cancer, cardiovascular diseases. There’s nothing wrong with that.

Having said that, I don’t think we’re going to cure aging in my lifetime. After all, we don’t have anything that works yet. As you may know, I’ve done some work in cryopreservation as well. Here too, I’ve been open about it. I think human cryopreservation is achievable. And it’s important to keep your long-term goals in mind.

It’s about what you want to achieve in your life. Most of my friends at school wanted to be football players. I was never good enough to be a football player, otherwise I would have wanted to be one.

From a very early age, I wanted to cure aging. I thought that the main thing in life is being healthy, and no matter how much money you have, you’re not going to stay healthy if you’re aging. So, I dreamed about working on this topic and that’s what I’m doing now. Even if we’re not going to cure aging in my life, at least we’ll give it our best shot.

Gene pill

Using an Endemic Virus as a Gene Therapy for Life Extension

In a study printed in PNAS, researchers have shown that telomerase reverse transcriptase (TERT) can be given to cells in living mice through a viral vector, taking the idea of life-extending gene therapies from science fiction to reality.

Why a cytomegalovirus?

The human cytomegalovirus (CMV) is widely known as an endemic virus that, while usually asymptomatic, is known to cause with harmful effects in babies and older adults. However, some of its properties make this virus suitable for delivering gene therapies. As cytomegaloviruses can carry large genetic payloads and don’t overwrite the DNA of their host cells [1], replacing the genes of these viruses with beneficial DNA may be safer than approaches with more potential off-target effects; development in this area is ongoing, and a phase 1 human clinical trial has already been conducted [2].

The role of TERT

Gradually shrinking telomeres lead cells to lose their ability to divide. In ordinary cells, this is known as the Hayflick limit. Stem cells, whose purpose is to grow organisms and replace lost bodily cells, naturally produce TERT in order to restore these telomeres. Aging organisms gradually lose this ability, and previous research has shown that gene therapies that restore TERT can extend lifespan in mice [3].

Combining CMV gene therapies with TERT expression, the researchers hypothesized, might be a way to safely conduct such a gene therapy in human beings. The researchers also chose to try this approach with follistatin (FST), a compound that promotes muscle growth.

An easy-to-administer therapy with substantial effects

The researchers developed two forms of administration of their mouse cytomegalovirus (MCMV): through an injection and through the nose. Both of these forms were almost exactly identical in effectiveness throughout this study.

The TERT-receiving groups had their TERT production doubled by the end of the first week after injection, after which it tapered back to baseline by day 25. This shows that, while effective, CMV gene therapy does not have a permanent effect.

The lifespan portion of this experiment was conducted on standard female Black 6 mice beginning at 18 months of age, which is approximately equivalent to 56 years old for a human. Each group contained nine mice, one of which was sacrificed early for tissue analysis, and the mice were given the treatment steadily except for an interval between 29 and 32 months of age.

The lifespan effects were clear: mice given FST through MCMV lived for nearly three years, nine months longer than the control groups, while mice that received TERT lived for about two months longer than the FST group. One mouse lived for a full 41.2 months, which is approximately equivalent to a human supercentenarian. All of the control groups’ mice had died of age-related causes before a single FST or TERT mouse did.

Telomeres are effectively extended

While not all tissues were affected equally, owing to the differences in the genes and the peculiarities with the CMV vector, both FST and TERT effectively promoted their respective genes within tissue according to an mRNA analysis. Staining and then examining telomeres directly showed that the average telomere length in the TERT group was tripled from baseline, reaching nearly to the level of younger animals in all of the organs studied, including the brain, heart, muscle, kidney, lung, and liver.

Physical effects

The researchers also examined the mice physically, seeing what the biochemical changes did to their morphology. The FST and TERT groups were better able to handle glucose than the control groups. Body weights were fairly similar at 18 months, but the FST groups grew much larger than the others. The control groups’ body weights decreased as they died of age-related diseases, which occurred more slowly in the FST and TERT groups.

At 24 months of age, the FST and TERT mice were many times more efficient in crossing a beam than the control groups. Interestingly, their muscle mitochondria were also much better preserved, suggesting a relationship between telomere attrition and another hallmark of aging, mitochondrial dysfunction.

Conclusion

The researchers did not combine FST and TERT into a single gene therapy, leaving it an open question as to whether such a combination would be more effective in lifespan extension than either one individually.

While this is not a human trial, the stark results shown in this lifespan trial seem to make it a prime candidate. However, aging is not a measurable endpoint in human trials; rather, there must be some measurable physical effect that can be monitored and judged, to a level of statistical significance, over the length of the trial. Biomarkers, such as for frailty and mitochondrial function, may be of help in this respect. If the results in mice can be recapitulated in people, this approach may, in fact, be a safe and effective gene therapy for life extension.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Borst, E. M., & Messerle, M. (2003). Construction of a cytomegalovirus-based amplicon: a vector with a unique transfer capacity. Human gene therapy, 14(10), 959-970.

[2] Adler, S. P., Lewis, N., Conlon, A., Christiansen, M. P., Al-Ibrahim, M., Rupp, R., … & V160-001 Study Group. (2019). Phase 1 clinical trial of a conditionally replication-defective human cytomegalovirus (CMV) vaccine in CMV-seronegative subjects. The Journal of infectious diseases, 220(3), 411-419.

[3] de Jesus, B. B., Vera, E., Schneeberger, K., Tejera, A. M., Ayuso, E., Bosch, F., & Blasco, M. A. (2012). Telomerase gene therapy in adult and old mice delays aging and increases longevity without increasing cancer. EMBO Mol Med 4: 691–704.

Senior man walking

Walking Pace Correlated with Increased Telomere Length

Publishing in Nature Communications, Dr. Tom Yate, Dr. Neliesh J. Samani, and colleagues used data from approximately 400,000 people in the UK Biobank in order to examine the relationship between walking pace and telomere length.

Previous evidence suggests that increased physical activity and cardiorespiratory fitness is associated with longer telomere length [1,2]. However, previous research linking lifestyle factors and telomere length are small and observational. The authors of this study sought to determine the association between self-reported walking pace and the telomere length of specific white blood cells known as leukocytes.

Study participants

The participants were an average of 56.5 years old, with a mean BMI of 27.2. 54% of the participants were female, and 95% of the participants were white. Descriptive statistical differences were seen between the slow, average, and brisk walkers. When compared to the slow walkers, the brisk walkers were slightly younger, more likely to have never smoked, were less likely to have mobility limitations and were less likely to be on cholesterol and/or blood pressure medication.

Slow walkers also reported engaging in less physical activity, had higher rates of obesity, and were more likely to live in a deprived living situation as measured by a multiple deprivation index when compared to the average and brisk walking groups. Accelerometer data was mostly comparable between the walking pace groups.

Walking pace was associated with telomere length 

Compared to the slow walkers, the average and brisk walkers had significantly longer telomere length. After adjusting for potential confounding factors, the associations for average and brisk walkers were decreased. Factoring in self-reported total physical activity and BMI did not alter these results.

More steps were associated with telomere length 

A secondary analysis performed on a subset of 86,002 participants utilized accelerometer data. Results showed that daily physical activity at a higher intensity was associated with longer telomere length. These associations remained even after adjusting for covariates. However, this association was not seen when examining total physical activity. The authors note how self-reported data for physical activity can have limitations, but nonetheless, the accelerometer subset data helped support the findings for walking pace.

Genomic analysis showed walking pace causally associated with telomere length

Using bi-directional Mendelian randomization analysis, no statistical association was shown between telomere length and walking pace genome-wide association (GWAS), regardless of BMI. However, when examined in the other direction, evidence suggested that walking pace is causally associated with telomere length. The authors mention that though Mendelian randomization can help determine causality, such results should be interpreted with caution.

Conclusion

This study implies that movement such as fast walking is associated with longer telomeres. For people without leg mobility issues, this could potentially be a promising intervention to improve healthspan and lifespan. The participants in this study were predominately white and healthy, so its results may not be applicable to all demographic groups.

While it does not conclusively prove causation, this study adds to a growing body of evidence that lifestyle factors affect telomere length. It will be exciting to see future research in this area.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Mundstock, E., Zatti, H., Louzada, F. M., Oliveira, S. G., Guma, F. T., Paris, M. M., Rueda, A. B., Machado, D. G., Stein, R. T., Jones, M. H., Sarria, E. E., Barbé-Tuana, F. M., & Mattiello, R. (2015). Effects of physical activity in telomere length: Systematic review and meta-analysis. Ageing research reviews, 22, 72–80. https://doi.org/10.1016/j.arr.2015.02.004

[2] Marques, A., Gouveira, É. R., Peralta, M., Martins, J., Venturini, J., Henriques-Neto, D., & Sarmento, H. (2020). Cardiorespiratory fitness and telomere length: a systematic review. Journal of sports sciences, 38(14), 1690–1697. https://doi.org/10.1080/02640414.2020.1754739

Drug combination

Drug Cocktail Delays Aging in Mice

Scientists have shown that a combination of rapamycin, acarbose, and phenylbutyrate has a synergetic rejuvenation effect when administered to 20-month-old mice for three months [1].

Fighting on multiple fronts

In this paper, the authors argue that to tackle such a multifaced process as aging, it might be beneficial to target different molecular pathways using several compounds. Therefore, they selected three drugs that had previously demonstrated anti-aging effects on their own: rapamycin, an antibiotic that inhibits mTOR signaling; acarbose, an anti-diabetic medication; and phenylbutyrate, a naturally occurring metabolite and a popular treatment for urea cycle disorders.

The researchers expected these compounds to have a synergistic effect that is greater than simply adding up their individual effects, and impressively, that’s exactly what this study has revealed.

In order to make the study results more translatable to humans, instead of treating young mice through their lifespans, the researchers applied the treatment to 20-month-old mice and limited the treatment to three months. First, the researchers compared the effect of a full-dose cocktail, containing each drug at a dose used in previous studies, and a half-dose cocktail.

Mice in both groups demonstrated decreased cognitive impairment compared to controls. However, the full-dose cocktail was more effective at improving other physical functions and organ rejuvenation, so it was used for further analysis. Along with a control group, the researchers included groups of mice treated with individual drugs.

Physiological improvements

The first major change the researchers in the full-dose cocktail group was weight loss along with decreased body fat mass. This effect seems to be due to acarbose mimicking caloric restriction.

Next, the researchers performed a series of behavioral tests regarding the physiological performance of old mice. Cocktail-treated mice outperformed control mice in all three tests: walking ability, hand grip, and cognitive function. Interestingly, mice in the rapamycin-only group also demonstrated improved cognition compared to controls, suggesting a neuroprotective effect of the drug.

Organ rejuvenation

To determine the organ-specific effects of the treatments, the researchers used a geropathology system that involved organ dissection, staining, and pathology-based grading. They calculated the lesion scores of the heart, lungs, liver and kidneys. The drug cocktail was effective at decreasing lesions in all of the organs and, in general, more so than any individual drug.

However, rapamycin also effectively decreased lesions in the kidney. This organ was shown to have extensive inflammation in the old control group’s tissue samples, prompting further investigation. The researchers then measured the expression of inflammatory cytokines in the kidney and showed that the drug cocktail decreased their expression in old mice, bringing them down to the level of young animals and demonstrating the anti-inflammatory nature of the drug combination.

Sex- and strain-specific differences

This study design included separate analyses of male and female mice, and some differences were observed. Drug cocktail-induced weight loss was not seen in females after three months of treatment, and female mice in the rapamycin-only and acarbose-only groups gained weight, unlike males.

Female mice showed improved grip strength when treated with only acarbose, which was not the case for males. Rapamycin was as effective as the drug combination at decreasing age-associated lesions in the hearts and livers of females but not males. However, acarbose and phenylbutyrate were effective in the kidneys of males but not females.

To test strain-specific drug responses, the researchers validated their results on a second strain of mice used exclusively in lifespan studies. In this part of the research, only the drug cocktail and the control groups were included. In this strain, both female and male mice treated with the drug cocktail lost a significant amount of weight over the three-month period.

Surprisingly, the drug combination did not combat cognitive impairment in these old mice, while the walking speed improved only in males. The drug cocktail was also ineffective in reducing liver and lung lesions in female and male mice, respectively.

Abstract

Pharmaceutical intervention of aging requires targeting multiple pathways, thus there is rationale to test combinations of drugs targeting different but overlapping processes. In order to determine if combining drugs shown to extend lifespan and healthy aging in mice would have greater impact than any individual drug, a cocktail diet containing 14 ppm rapamycin, 1000 ppm acarbose, and 1000 ppm phenylbutyrate was fed to 20-month-old C57BL/6 and HET3 4-way cross mice of both sexes for three months. Mice treated with the cocktail showed a sex and strain-dependent phenotype consistent with healthy aging including decreased body fat, improved cognition, increased strength and endurance, and decreased age-related pathology compared to mice treated with individual drugs or control. The severity of age-related lesions in heart, lungs, liver, and kidney was consistently decreased in mice treated with the cocktail compared to mice treated with individual drugs or control, suggesting an interactive advantage of the three drugs. This study shows that a combination of three drugs, each previously shown to enhance lifespan and health span in mice, is able to delay aging phenotypes in middle-aged mice more effectively than any individual drug in the cocktail over a 3-month treatment period.

Conclusion

This promising study is yet another demonstration of an effective approach that targets multiple pathways. Drug synergy has previously been shown to extend healthy lifespan in C. elegans [2]. Although this study did not study lifespan extension, it clearly showed that this cocktail reverses several aspects of age-related pathologies in mice.

In addition to demonstrating that the drug cocktail is more beneficial than each of its individual components, the study highlights its different effects between mice of different sexes and strains. Therefore, metabolic responses that are dependent on sex and genetic background will have to be taken into account when determining if such a cocktail is effective in people.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Jiang, Z. et al. Short term treatment with a cocktail of rapamycin, acarbose and phenylbutyrate delays aging phenotypes in mice. Sci. Rep. 12, 7300 (2022).

[2] Admasu, T. D. et al. Drug Synergy Slows Aging and Improves Healthspan through IGF and SREBP Lipid Signaling. Dev. Cell 47, 67–79.e5 (2018).

Immunotherapy

NMN Boosts Effectiveness of Immunotherapy in Mice

In a pre-print paper, scientists have shown that treatment with NMN increases the survival and anti-cancer efficacy of CAR-T cells [1].

The problem with immunotherapy

T cells are a central element of the adaptive immune system, and some of them can be cytotoxic: they have the ability to kill other cells. This lets us get rid of cells that are infected with pathogens, such as viruses and bacteria, along with cells that have become cancerous. However, some cancer cells have ways to greatly reduce the effectiveness of cytotoxic T-cells by causing their dysfunction and exhaustion [2].

Scientists have been trying to overcome this problem by genetically modifying T cells to express receptors specifically tuned to recognize various cancers. These are chimeric antigen receptors (CARs), and CAR-T cell therapies are already being used against some types of cancer.

In CAR-T cell-based immunotherapy, a bunch of T cells are procured from the patient’s blood, genetically engineered to express the relevant CAR, and injected back into the patient’s body. Unfortunately, CAR-T therapy is still mostly limited to blood cancers, where it can work marvelously, though not in all patients (CAR-T therapy with no additional treatment has a success rate of 30-40% for lasting remissions). Solid tumors have been much harder to crack because their microenvironment still quickly renders most CAR-T cells dysfunctional.

NMN keeps CAR-Ts healthy and angry

Therefore, it is extremely important to increase the resilience of CAR-T cells, and a group of scientists might have found a way to do so via a molecule that is popular in the longevity field: nicotinamide mononucleotide (NMN).

NMN is a precursor to NAD+, a co-enzyme that carries electrons for redox (reduction/oxidation) reactions. It plays an important role in mitochondrial energy production and other biological processes. The age-related decline of NAD+ levels has been linked to various diseases of aging, including cancer [3], while boosting NAD+ levels through NMN supplementation is known to produce multiple health benefits in mice and humans [4]. Simply speaking, an increase in NAD+ invigorates cells, which is exactly what the authors of this new study had been looking for.

The researchers experimented on the most popular CAR-T cells that express the receptor CD19 and are used against several types of blood cancer, such as B-cell acute lymphoblastic leukemia. After being treated with a dose of NMN, the cells were co-cultured with NALM6 cells, a model of leukemia. NMN-treated T cells showed a superior rate of proliferation and remained active and cytotoxic long after the controls died.

The exhaustion of T cells that prevents them from attacking cancer cells manifests itself, in large part, in cellular senescence and increased apoptosis. In NMN-treated cells, the levels of the most popular senescence marker, ß-galactosidase, were greatly reduced compared to controls. The treated cells also showed greater telomerase activity, which is associated with reduced senescence. Apoptosis markers demonstrated a remarkable decline as well.

The treatment also changed the gene expression profile of the cells. Transcriptomic analysis showed an increased activity of proliferation-related genes and a decreased activity of senescence-inducing genes. Genes responsible for immune response got a boost as well.

NAD+ mediates the activity of sirtuins – an evolutionarily conserved family of proteins that play several important roles related to stress response and longevity. The protein Sirt1, a well-known anti-senescence and proliferation-promoting factor, was particularly upregulated by NMN. The researchers suggest that NMN benefits T cells mostly via the Sirt1 pathway.

The treatment increased the levels of pro-cytotoxic factors, including interferon-gamma (IFN-γ) and downregulated some pro-inflammatory factors such as IL-6, suggesting that NMN treatment can reduce the inflammatory response commonly triggered by CAR-T therapy.

NMN promotes survival in mice

Finally, the scientists tested NMN-CAR-T cells in a mouse model of B-cell lymphoid leukemia. While treatment with regular CAR-T cells also showed some effect, NMN-CAR-T cells caused a statistically significant additional improvement in cancer burden and median survival time.

Since NAD+ mediates many biological processes, NAD+ therapies are being actively explored for various conditions. However, scientists have encountered some delivery problems in vivo. For instance, another NAD+ precursor, nicotinamide riboside (NR), did not extend lifespan in mice in the Intervention Testing Program (ITP) trials because it failed to raise NAD+ levels. Since CAR-T therapy is based on altering and culturing cells in vitro, no such delivery issues are expected in this case; cells can be just directly treated with NMN. This also means that the experiment might be easily translatable to humans, as its design might be close to the actual therapy, and NMN is known to be very safe.

Conclusion

Since low fitness and survivability of T cells seem to be a major hurdle for CAR-T cell immunotherapies, especially for treating solid tumors, the results of this study, if it stands the test of a peer review, might be very influential. It also highlights, yet again, the importance of NAD+ for longevity.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Yu, Z., Tong, S., Zhang, C., Bai, Y., An, Z., Xu, C., … & Zhong, X. (2022). Nicotinamide mononucleotide enhances the efficacy and persistence of CD19 CAR-T cells via NAD+–Sirt1 axis.

[2] Zhang, Z., Liu, S., Zhang, B., Qiao, L., Zhang, Y., & Zhang, Y. (2020). T cell dysfunction and exhaustion in cancer. Frontiers in cell and developmental biology8, 17.

[3] Garrido, Amanda, and Nabil Djouder. “NAD+ deficits in age-related diseases and cancer.” Trends in cancer 3, no. 8 (2017): 593-610.

[4] Shade, C. (2020). The Science Behind NMN–A Stable, Reliable NAD+ Activator and Anti-Aging Molecule. Integrative Medicine: A Clinician’s Journal19(1), 12.

Mouse eating

The Gut Microbiome Affects the Brain, Eyes, and Gut in Mice

Publishing in Microbiome, a team of researchers has ascertained multiple physical effects of aging gut flora in mice.

Antibiotics and fecal transfers

The researchers used three groups of mice: young (3 months), old (18 months), and aged (24 months). Young and old groups were divided into a control group, an antibiotics group, and three recipient groups of gut flora from each of the different ages of mice. Aged mice, due to their limited availability, only had a control group and a recipient group of young gut flora.

The species of bacteria were analyzed, and the researchers found that young gut flora in mice is abundant in bifidiobacteria, while older mice have more prevotella species. However, the antibiotics that were used to allow for this fecal replacement also had strong influences on the bacterial composition of these animals.

Effects on the brain, eyes, and gut

Microglia that expressed Iba-1, a biomarker of inflammation and macrophage activity, were measured in the cortex and corpus callosum. Young mice that received old gut flora had increased levels of this marker, but not to statistical significance; young mice that received aged gut flora had their levels increased well beyond this threshold.

Old mice seemed to have their brain inflammation reduced by a simple treatment of antibiotics, as both the antibiotics group and the old mice receiving old gut flora had Iba-1 levels below baseline; however, young gut flora decreased Iba-1 significantly below baseline, and aged gut flora increased it.

The data in aged mice, although limited in scope, were very clear: aged mice receiving young bacteria had much less Iba-1 brain inflammation than the control group.

Retinal data were also promising. Previous research has shown that gut bacteria have something to do with the development of age-related macular degeneration (AMD) [1]. The researchers show, for the first time, that the gut microbiome significantly affects the functional visual protein RPE65, flaws in which have been implicated in the development of AMD [2]. Young mice given old or aged microbiota had their levels of this protein significantly decreased, while aged mice given young microbiota had the reverse occur.

Gut markers were also promising. The epithelial barrier protecting the intestines from their contents can be eroded, and this phenomenon is known as leaky gut. A critical marker of this damage, I-FABP, was increased in mice receiving aged gut flora and similarly decreased in aged mice receiving young gut flora; the two groups had nearly completely switched places on the chart, suggesting that gut flora are almost entirely responsible for gut health, at least in mice. LPS-binding protein, another indicator of bacterial leaks into the gut, had very similar results.

A lack of behavioral effects

Unfortunately, while the brain biomarkers were significant, the behavioral study did not yield any significant results. The object recognition test that the researchers chose showed basically no differences whatsoever between aged mice at baseline and aged mice receiving youthful gut flora. The researchers mentioned two previous studies on this subject. One of them showed that young mice receiving aged gut flora had significant impairments [3], and the other suggested that behavioral changes only become visible over the longer term [4].

Conclusion

While altering the gut microbiome is by no means a panacea, it is one aspect of aging that is relatively easy to influence without gene therapies or even surgery. This paper adds to a broad body of research showing the relationship between gut bacteria and inflammation in other organs. Its potential influence on the development of eye diseases bears further investigation, and the effects on leaky gut were extremely promising. However, it is clearly not a quick fix for long-term issues, even in mice.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Zinkernagel, M. S., Zysset-Burri, D. C., Keller, I., Berger, L. E., Leichtle, A. B., Largiadèr, C. R., … & Wolf, S. (2017). Association of the intestinal microbiome with the development of neovascular age-related macular degeneration. Scientific reports, 7(1), 1-9.

[2] Cai, X., Conley, S. M., & Naash, M. I. (2009). RPE65: role in the visual cycle, human retinal disease, and gene therapy. Ophthalmic genetics, 30(2), 57-62.

[3] D’Amato, A., Di Cesare Mannelli, L., Lucarini, E., Man, A. L., Le Gall, G., Branca, J. J., … & Nicoletti, C. (2020). Faecal microbiota transplant from aged donor mice affects spatial learning and memory via modulating hippocampal synaptic plasticity-and neurotransmission-related proteins in young recipients. Microbiome, 8(1), 1-19.

[4] Boehme, M., Guzzetta, K. E., Bastiaanssen, T. F., Van De Wouw, M., Moloney, G. M., Gual-Grau, A., … & Cryan, J. F. (2021). Microbiota from young mice counteracts selective age-associated behavioral deficits. Nature Aging, 1(8), 666-676.

CBD oil

Cannabidiol Increases Lifespan and Healthspan in Worms

Scientists have shown that an active ingredient of cannabis significantly upregulates autophagy, extending both lifespan and healthspan in C. elegans nematode worms.

Two of the most well-known components of marijuana are tetrahydrocannabinol (THC) and cannabidiol (CBD). They have the same atomic composition, but differ in structure and in some of their qualities. THC is what makes you high, while CBD can even dampen THC’s effect. Though both THC and CBD seem to have some beneficial qualities, THC is also responsible for the deleterious effects that heavy users might experience, such as mood swings, cognitive decline, and even changes in brain composition [2].

CBD, on the other hand, is considered benign and possesses antipsychotic, pro-cognitive, anti-inflammatory, anti-seizure, and antioxidant properties. In June 2018, the FDA approved Epidolex, the first CBD-based prescription medication, for rare forms of epilepsy, and later for the treatment of seizures associated with tuberous sclerosis complex (TSC). However, the research into both compounds is still in its infancy.

In this new study, scientists dived deeper into the workings of CBD using the nematode worm Caenorhabditis elegans (C. elegans), which is considered a good model for initial studies, including in geroscience. C. elegans was the first multi-cellular organism to have its lifespan extended by gene editing.

Increase in autophagy

Previous research has shown that CBD can increase lifespan in C. elegans and zebrafish [3], but the mechanism had remained unknown. Another study found that CBD induces autophagy in cultured neuronal cells [4]. In this new study, the researchers attempted to investigate the relationship between these two effects.

Autophagy is the process of clearing away various cellular debris, such as misfolded proteins and dysfunctional organelles. Unsurprisingly, this maintenance system appears to be very important for health and longevity in numerous model organisms and in humans.

The CBD treatment greatly increased autophagic activity in several tissues and cell types, most drastically in neurons (by 78%). The researchers then validated those findings in vitro on several types of cells, including mouse primary hippocampal neurons. Importantly, impaired autophagy in the brain is considered a major cause of Alzheimer’s disease [5].

Autophagy is a complex process that can be crippled at several stages. Autophagic flux is a specific measure of how fast the unwanted molecular stuff is being degraded, and it quantifies overall “autophagic health”. In the experiments, CBD drastically increased autophagic flux both in vivo and in vitro.

Long live the worm

Worms on CBD also lived significantly longer than controls. However, numerous compounds and interventions have been shown to increase the short lifespan of C. elegans by much larger margins. Still, a significant lifespan increase is a good indication that the treatment made the worms healthier.

The researchers also measured the worms’ healthspan. Many interventions that prolong lifespan in C. elegans often lead to functional impairment, such as decreased motility. Three popular health metrics in C. elegans that decline with age are pharyngeal pumping rate, reproductive capacity, and locomotion, and all three were significantly restored, rather than impaired, by CBD treatment.

With age, neurons in C. elegans undergo morphological changes, acquiring irregular shape. The CBD treatment was able to mitigate the number of irregularly shaped neurons, though not to youthful levels. CBD also led to an increase in neurite length and spine density, two metrics of neuronal health, in mouse neurons.

To determine whether the increase in lifespan was due to more autophagic activity, the researchers knocked out three different autophagy-related genes, sqst-1, vps-34, and bec-1, using RNA interference. In two of the cases, the knockout shortened the worms’ lifespan, and in all three cases, subsequent CBD treatment failed to extend it, confirming that autophagy is essential for CBD-mediated increase in lifespan.

SIRT1’s ortholog mediates the effect

The gene SIRT1 has been a popular object of study in geroscience. One of its roles is a mediator of autophagy [6]. In C. elegans, there is no gene homologous (identical) to SIRT1, but there is an ortholog – a gene with a different sequence but a similar function – called sir-2.1. The knockout of sir-2.1 mostly blocked the beneficial effects of CBD on autophagy and on neuronal morphology. Mice, on the other hand, do have their own SIRT1 gene, and its knockout in mouse neurons also obliterated many benefits of CBD, pointing at a crucial role of SIRT1 in mediating CBD-induced effects.

Conclusion

Its origin aside, CBD is an intriguing compound that might have numerous beneficial qualities. This study expands our understanding of CBD’s effects, linking them to autophagy, an important process that keeps popping up on geroscientists’ radars. It is encouraging that CBD demonstrates the strongest pro-autophagy effect in neurons, making it a potential anti-Alzheimer’s drug. Obviously, the fact that CBD increases autophagy in worms does not mean that smoking weed makes humans healthier. Our advice would be to wait for human trials before attempting to receive related effects from CBD products.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Wang, Z., Zheng, P., Chen, X., Xie, Y., Weston-Green, K., Solowij, N., … & Huang, X. F. (2022). Cannabidiol induces autophagy and improves neuronal health associated with SIRT1 mediated longevity. GeroScience, 1-20.

[2] Sohn, E. (2019). Weighing the dangers of cannabis. Nature572(7771), S16-S16.

[3] Pandelides, Z., Thornton, C., Faruque, A. S., Whitehead, A. P., Willett, K. L., & Ashpole, N. M. (2020). Developmental exposure to cannabidiol (CBD) alters longevity and health span of zebrafish (Danio rerio). Geroscience42(2), 785-800.

[4] Vrechi, T. A., Leão, A. H., Morais, I., Abílio, V. C., Zuardi, A. W., Hallak, J. E. C., … & Pereira, G. J. (2021). Cannabidiol induces autophagy via ERK1/2 activation in neural cells. Scientific reports11(1), 1-13.

[5] Liu, J., & Li, L. (2019). Targeting autophagy for the treatment of Alzheimer’s disease: challenges and opportunities. Frontiers in molecular neuroscience, 203.

[6] Xu, C., Wang, L., Fozouni, P., Evjen, G., Chandra, V., Jiang, J., … & Berger, S. L. (2020). SIRT1 is downregulated by autophagy in senescence and ageing. Nature cell biology22(10), 1170-1179.

Naked Mole Rat Side

Why The Skin of Naked Mole Rats Ages Slowly

A study published in Aging has shown that the skin of the naked mole rat retains nearly all of its physical and biochemical properties as these animals chronologically age, providing new insight into how and why these animals live so long.

Wrinkly, but not like humans wrinkle

With a wrinkly, largely hairless body, the naked mole rat is well-known for having an “old man” appearance, but this is pure anthropomorphism; even young naked mole rats look like this. Naked mole rats do not live as long as people; they have been reported to live 37 years in captivity and roughly half that long in the wild. However, this mouse-sized animal has also not been reported to increase in mortality with aging, which sets them apart from nearly all other animals and makes them a gerontological curiosity [1].

This lack of conventional aging has been shown in the skin. In this study, the researchers show that standard biological changes of the skin do not occur with aging. Staining for multiple compounds that normally change with age in mammalian skin, including the senescence marker p16, revealed no differences between young and old animals.

The only significant difference was the increased thickness of the epidermis, the outer layer of the skin, with age; the inner layer, the dermis, was not significantly affected. However, this layer stops thickening after middle age, and the researchers have noted the existence of a sixth sub-layer that appears in middle age and does not exist in youth.

Wound healing, which is normally slower in aged animals, was not slower in naked mole rats. In fact, wounds to the skin of middle-aged naked mole rats seemed to disappear slightly, but not significantly, more quickly than their youthful counterparts.

Examining individual cell sub-populations

The researchers looked at specific cell types, examining 10,232 individual cells of the epidermis. 11 different gene clusters that determine cellular identity were identified in total. Three skin layers were determined, and each layer was found to be identifiable by specific genes; the inner (basal) layer expresses Krt14, the middle (suprabasal) layer expresses Krt10, and the outer (corneal) layer expresses Lor.

The researchers then examined cells from middle-aged and young animals to determine the differences between their cells. Aggregate differences in gene expression between young and old animals were statistically insignificant. Cell types were almost completely identical, and cell layer markers were barely distinguishable.

Youthful animals seemed to be more biased towards the corneal layers, while older animals had more basal expression, which matches the results found in the physical examination. Going through cellular progression over time, the researchers found no fundamental differences between young and middle-aged animals. Genes related to reactive oxygen species, which normally increase with age in other species, were not found to increase in naked mole rats.

One of the few notable differences the researchers found was a four-fold increase in lgfbp3 expression in one specific gene cluster of basal cells. This gene modulates the homeostasis of epidermal tissue and is predominantly expressed by stem cells. Five genes related to immune expression were also found to be significantly upregulated.

Conclusion

With its focus on cellular gene expression, this study provides novel and potentially useful insights into how these animals do and do not age. The extra sub-layer of skin may reflect a programmed process rather than damage over time.

One potential flaw of this study is that neither cross-linked collagen nor advanced glycation end-products were mentioned; further investigation may reveal that these compounds contribute to the increased thickness in epidermis, but this might not be the case.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Ruby, J. G., Smith, M., & Buffenstein, R. (2018). Naked mole-rat mortality rates defy Gompertzian laws by not increasing with age. elife, 7, e31157.

Richard Miller

Prof. Richard Miller on the Interventions Testing Program

Richard A. Miller is a Professor of Pathology at the University of Michigan and the Director of Michigan’s Paul F. Glenn Center for Biology of Aging Research. He is also a driving force behind the ITP, the Interventions Testing Program, created in the early 2000s to study the effect of various drugs on lifespan in mice. The ITP is a unique undertaking, with drugs being tested simultaneously in three research facilities to achieve “instant reproducibility” and increased statistical power. The ITP has produced evidence for anti-aging drugs, such as rapamycin, and, in contrast, has shown a lack of effectiveness for several agents, such as metformin. We discuss the ITP findings, including some that have not been published yet, and other geroscience-related topics.

You once said about your early interest in aging: “I decided early on that aging was bad for you. It made people sick and then die”. This sounds so simple and true. Why do you think many people still don’t take seriously the idea that aging can and should be tackled? 

People are easily cowed by scientific information. They get a lot of it, and much of the information comes from people who think about aging in ways that appeal to fantasy and to wish fulfillment. Public personae who talk about aging usually are making things up and hyping it without a lot of detailed evidence behind what they’re saying.

It makes smart people skeptical, and it’s harder for people who actually have some information to rise above that in terms of clarity. If you do a Google search for anti-aging medicines, most of what you get is stuff that somebody wants to sell you and make a profit on but which doesn’t actually work. There’s just no evidence that it can work in people or even in mice. With that kind of a noisy environment, it’s hard for the more accurate information to come to public attention.

So, it’s long been a sort of a truism (not true in this case), that nothing can be done about aging. Once you assume that all is lost, everyone’s going to get old, et cetera, then counterclaims become less credible. No one, of course, is claiming that aging can be prevented completely. That would be fantasy. But there’s now very strong evidence, for mice at least, that it can be delayed in very significant ways, that we can keep animals alive and healthy, cognitively active, and physically active for quite a long time.

The longevity field still has to fight a lot of myths, like the idea that extending lifespan is bad for the economy or even for civilization as a whole. You started a career in geroscience back in the 1970s. How have people’s attitudes changed over that period?

There’s a lot less progress than you might think. When I give a talk in front of many audiences, but particularly in front of audiences of non-scientists, the first or second or third question is, “Wait, what if everybody lived a long time, the economy would collapse, et cetera.” My response to that is, “If people stay healthy and productive longer, that, in general, is a good thing.”

If you think it’s a bad thing, then you might want to stop cancer research, to hand out cigarettes to children, to take insulin out of the pharmacies and seatbelts out of the car, because all of those are designed to keep people active and healthy and not dead for as long as possible.

It’s just as moral to try to develop pills that slow aging as it is to try to develop treatments for strokes, heart attacks, cancer, and diabetes. Both of those are a good thing to do. If we had been having this conversation in the 1800s, someone might have said, wait, you must stop! Because of all the science you’re about to do where you discover anesthesia for surgery, insulin for diabetes, penicillin to treat infections, the world is going to fill up with 50-year-olds, maybe even 60-year-olds!

What about the scientific progress? From many scientists I talk to, I get this mixture of optimism and pessimism: yes, we’ve learned so much, but we still know so little. What would you say?

As recently as the early 1990s, you could publish an article, there were actually several articles published in Nature proving that aging was so complicated that you could never slow it down by a single gene or a single drug or a single manipulation.

That was the prevailing scientific opinion among people who really thought about it and who were very smart. It’s now clear they were wrong. There’s now solid evidence in multiple species, most importantly mice, that some drugs, some diets, and some single-gene mutations can slow aging.

Once those discoveries are made, in addition to the famous work on calorie restriction, this attracts more people into the field because now that it’s clear something can be done to slow all of the aging process, that’s a reason to want to study it. The other thing that made a big difference is that many of these discoveries were made in animals that age very quickly, like the worm C. elegans and the fruit fly Drosophila melanogaster.

That makes it possible for graduate students, post-docs, and junior faculty members to get data in a year, rather than having to wait three or four years. That’s very attractive and it brings a lot of people into the field. It has led to many important discoveries in invertebrate aging of which a small, but not zero proportion also apply to mammals.

So, it’s nice to have an increasingly respected and productive field, where people are getting published in top-notch journals, famous journals. We now need to move further towards the point where research in mammalian and particularly mouse aging has a similar degree of attractiveness to the smartest people and the best money.

We’re not there yet. We’re a step or two closer to that, but it’s still an area where both the number of smart people working in it and the amount of money to support it are too small.

Yes, we’ve had a lot of success in mice, but many drugs that work in mice do not work in humans.

And many drugs that work in mice do work in humans. It would be silly to maintain that the percentage that work is zero, and it would be equally silly to maintain the percentage that fail is zero.

Most of the drugs that were developed for therapeutic effect in people were initially discovered by working on mice and rats. It would be nuts to say that every drug that extends lifespan in mice will do the same thing in humans, but the work in mice is a very important foundation.

Many of the pathways that are discovered, and maybe even some of the druggable targets that are first discovered, in the mice will serve in humans – maybe the same drug, maybe drugs of the same family, maybe drugs that target the same molecule, but through a different chemical grouping. It’s necessary to be neither insanely optimistic nor insanely pessimistic.

We do have a history of failures though, such as with Alzheimer’s, maybe because mice don’t really develop Alzheimer’s.

Yes, that’s true, but it’s important to recognize the brains of people and the brains of mice have a lot of things that are not in common. In terms of aging, if I tell you that I have an individual right here in front of me, in my office, that has cataracts, bad hearing, weakened bones, a poor immune system, and a relatively low cardiovascular system, you would immediately recognize that individual as old, be it a mouse, a dog, a horse, or a person. But you wouldn’t know if that’s a seventy-year-old human, or a 25-year-old horse, or a three-year-old mouse.

So, the effects that aging has on mice and on humans are – not in every case, of course, but in most cases – recognizably quite similar. And that’s true for cells that divide, for cells that don’t divide, for structures like the bones and the tendons that are mostly extracellular material. It’s true for complicated circuits, like neuroendocrine feedback circuits, it’s true for cognition.

There are just so many aspects – not all, but so many aspects of aging in humans, mice, dogs, chimps, et cetera that are the same. So, it’s very reasonable to expect that the drug that could block aging effects in all of those tissues in mice might also do very similar things in people.

But different species die in old age for different reasons. For instance, around 80% of lab mice die of cancer, I think.

The specific thing that kills the animal is of secondary importance when you’re studying the biology of aging. For instance, elephants die because their teeth wear down and they can no longer eat. When they’re 60 or 70, they have lost their last set of molars and they can’t chew food anymore. Mice, at least those that are used in aging research, indeed die mostly of tumors. People that eat a lot of fatty foods and watch TV, die mostly of atherosclerosis. In people that were alive a hundred thousand years ago, the most prevalent cause of death was probably breaking a bone and not being able to keep up with the group.

The point is not what is the specific cause of death in a specific environmental setting and in a specific species. The real question is what is it that postpones age-associated decline in bones, brains, the immune system, the sensory systems, the gut, and everything else for many decades in people, for a few years in mice, and for 20 years in horses. The factors that regulate the timing of the aging process, I would guess, is very similar in nearly all kinds of mammals.

Let’s talk about the ITP. Recently, there have been some very exciting results. Could you give us an update?

Of the two most recent interesting papers, one has to do with a drug called canagliflozin. This was published a couple of years ago. Canagliflozin is very frequently given to people because it’s good for diabetics. It doesn’t prevent glucose absorption, but it prevents very rapid increases in blood glucose levels, so you can see why it would be good for a diabetic.

It turns out that if you give it to mice, in male mice, it leads to about a 15% increase in lifespan and puts off at least five different kinds of non-cancer, non-lethal, non-neoplastic diseases in mice as well. So, it’s authentically an anti-aging drug.

It’s the second of the anti-aging drugs in mice that work apparently by blocking the highest glucose levels during the day. So, for cancer biologists, this ought to be very interesting. You’d really like to know how it is that you can postpone cancer by moderating the highest daily spike in glucose. In terms of humans, it would be really interesting to know whether canagliflozin and other fairly safe drugs that prevent extreme spikes in glucose might also block other kinds of age-associated lesions, independent of the benefits for diabetes.

The other paper, which I think was just submitted this week is one in which we tried a combination of rapamycin plus acarbose. Rapamycin works very well in male and female mice, while acarbose works significantly in both sexes but has a much stronger effect in males.

What we found is that when you give rapamycin and acarbose together, in the males, you do better than either rapamycin by itself or acarbose by itself. And that combination of drugs together gives male survival a 29% boost. That’s the largest percentage increase we’ve seen in males or females.

When you give acarbose and rapamycin together to females, they don’t do any better or any worse than on rapamycin alone. This is not too surprising because acarbose gives only a small effect in females. We expected it wouldn’t have a big boost over rapamycin alone in the female animals, and that’s what we found. So, the combination is the best thing we’ve ever had for any sex, although it is male specific.

Do we have any idea why most geroprotective drugs seem to work better in one sex than in the other?

While we don’t know why several of these drugs either work only in males or work better in males, there are several clues. Let me tell you about three of them.

One has to do with improvements in function like balance and grip, strength, and endurance on a rotating rod. Michael Garrett has studied several of these in mice treated with either 17α-estradiol, which is male-specific for lifespan, or acarbose, which males respond to better.

He finds that most of the performance measures are improved by acarbose and 17α-estradiol only in male mice.  But there are a few that are improved even in female mice. In this way, you can begin to sort out what aspects of improved health are seen in both sexes and what aspects are seen only in males and presumably contribute to their lifespan benefit.

Similarly, people in my lab like Gonzalo Garcia have evaluated biochemical indices. Gonzalo has looked at enzymatic cascades in particular. He’s looked at two sets of kinases, one of which is really important in inflammation and the other in terms of protein translation.

When you look at the cascade that is important in inflammation, all the drugs, rapamycin, acarbose, or 17α-estradiol, cause benefits in that particular set of cascades in both males and females. So that’s not likely to be a key element of the lifespan control pathway because 17α-estradiol does not improve lifespan in females, it’s males only, and yet it does improve this kinase cascade.

The other kinase cascade, the one that focuses on protein translation, does show sexual specificity for 17α-estradiol in Gonzalo’s assays. Only the males benefit from 17α-estradiol. So, this is a hint that of the many cellular changes that these drugs produced, some, like the ones that lead to protein translation, at least show the same pattern of behavior as lifespan and may be important to lifespan. Others, like the inflammatory kinase cascade, respond to all the drugs, and that means that they’re probably not involved in the lifespan effect, which is male-specific for this. The more drugs we have that can be thrown into this analysis, the more likely it is that we’ll zero in on the specific pathways by which these drugs produce health benefits and lifespan improvements.

Our current search is to look for biochemical and physiological changes that are produced by all those drugs, as well as by four single-gene mutations that extend lifespan, and by caloric restriction. So, we have eight such changes so far – things that you can measure in young adult mice after drug treatment, or in the four mutants, or after calorie restriction. And they all change in the same way.

Most, though not quite all of them, are sex-specific for the 17α-estradiol treatment. We think that these physiological changes are our best glimpse as to what aspects of biology have to be changed, at least in mice, to get a lifespan increment.

This is also a link to human biology because you can ask, okay, I’m giving this drug to humans. Do any of these changes happen? If the answer is yes, that’s a sign that the drug may be very important in terms of controlling the human aging processes or at least links to the human biology and human diseases.

I think the ITP is a fantastic initiative. Why hasn’t it been massively expanded? Wouldn’t you want more money, more resources so that you can test more compounds, do more follow-ups? How would you improve the ITP if money wasn’t a problem?

Certainly, I agree with the idea that it deserves a lot more money. The Aging Institute has been pretty generous to us actually. For the first five years, each of the laboratories got half a million dollars a year plus indirect costs, and that was enough to allow us to do about five drugs a year.

They were impressed by the work that we accomplished, and then after I think the 10th year, they doubled our budget. This allows us to do seven drugs a year and to do pathology on any drug that is a winner. It allows us to test in middle age some of the health outcomes that I mentioned to you like grip strength and balance on the rotarod. It also allows us to have freezers full of tissues from these mice so that if any lab in the world wants to know what that drug does to the liver or to the heart or to the kidney, we can say, sure. Here’s some tissues, see what you can find and let us know.

So, the program is well-funded. On the other hand, it’s easy to imagine things that could be done to accelerate discoveries, if more money were available. Some of the obvious things are, for instance, that we would like to know, if a drug starts in young adult mice and has a good effect, what would happen if you started it in middle-aged mice, would you get the same effect? We can do that now, but we have to wait five years before we get the first set of data, and that tells us whether we want to repeat it.

We also want to do dose-response curves. Each time we’d try a drug, we have to pick one dose and try it out. We hope we guessed, and sometimes we did guess, but it’s possible that the best dose of some drug might be three times higher or three times lower than the one we used. Having additional funds would allow us to do dose-response curves. The other thing that would be a lot of fun to do would be to evaluate mice that are known to be prone to specific kinds of diseases.

There are mice that get pathological changes in old age that mimic Huntington’s disease or Parkinson’s disease. There are some kinds of mice that in old age have cardiac problems, for instance, or specific problems in hearing. It would be lovely to know whether these drugs that extend lifespan in our heterogeneous mice would also slow down this or that disease. Those are obviously critical steps towards making this important translational jump to human diseases.

That’s already being done. My lab with Roger Albin looked at a Huntington’s disease model, and several labs in Texas have looked at Alzheimer’s disease models, et cetera, but the money that comes to the ITP labs mostly has to go towards screening new drugs, which is our specialty. So, we don’t have tons of money left over to apply the same kind of analysis to mice prone to individual diseases of importance.

Do you think the ITP with its “instant reproducibility” should become a blueprint for other studies, maybe outside the context of aging? 

I’m sympathetic to that idea, but of course you understand there’s a balance between costs and outcomes. Many experiments are done in a single laboratory, and if they’re published, and people find them exciting, then other labs often do try to replicate them. One of the reasons that with the ITP, we thought it would be better to do the replications from the start, is that these are aging studies, and from the time that mice are born to the time the last one dies, it takes three to four years. If you waited four years to get your result and only then began your replication, you wouldn’t have a solid confidence for eight years. So having replication built in from the start speeds the process up quite dramatically.

The other reason is that each of the three sites had some uncontrolled variables that make it different from the other sites. We do our best to control things – we buy the food from the same kitchen, bedding from the same place, we use the same kind of mice bred in the same month of the year. And despite all the precautions there are site-to-site differences.

The mice at Michigan are always lighter for both sexes than the mice at the Jackson Labs or Texas. The females from all three sites always live the same period of time, but the males from Michigan almost always live longer than the males from the other two sites. The reasons for this are unknown. They may have to do with the temperature in the room or things in the water that we can’t smell or taste, but the mice can.

But if all three sites produce a good, strong effect, we can be fairly confident that the result is reliable and would be seen at any well-managed animal colony using the same drug and the same kind of mice. Often though, we’ll find a drug that works at two sites, but not at the third site. And then we would publish that, and we think it’s important and interesting, but we don’t have the same degree of confidence that we can always replicate it. Those are the advantages of replication.

Human lifespan makes studying anti-aging interventions in humans even harder. How can we even measure aging in humans? What are your thoughts on the design of human trials like TAME? 

That’s an interesting set of conundrums, and it’s partly scientific, partly financial, and partly legal. The smart way, if you are in charge of the universe of designing an aging trial, is taking an awful lot of people when they’re 30 or 40, have them take the drug you are interested in,  and then come back in 60 years.

No one’s going to do that, it’s very expensive. And drug companies really don’t want anti-aging drugs, because they don’t want to invest hundreds of millions of dollars and not get an answer for 20 or 30 years. Also, the FDA explicitly forbids aging as an endpoint for any of their drug trials.

A group of 11 research universities put together a study that attempted to meet some of those obstacles. For instance, they defined an endpoint that is not getting diabetes, not getting Alzheimer’s, not getting cancer, not having a heart attack, not having a stroke – I don’t know the details of it.

And the FDA will take that. As long as you don’t call it aging, but prevention of many diseases, the FDA will say, sure, go ahead. But it’s still a 50-million-dollar trial that will take a minimum of five and more likely eight to ten years.

And even then, you have to start with people who are old, in their sixties, so that the number of people who reached the defined endpoint within a five-to-ten-year period will be high enough to give you statistical power. You are hoping that the drug you’re testing, which is in this case, metformin, will work really fast, even on people who are already pretty old and maybe sick.

That could be the case. But it need not be, it could be that some drugs will work in people, but only if you start giving them to people when they are 40 or 20 years old. The people who put the TAME trial together are hoping that’s not true, at least for metformin.

But if this is true, and we need much more time, they might reach a conclusion that metformin doesn’t work when, in fact, it does.

Yes, if metformin works at all, it may be that it would work only if you start in 30 and 40-year-old people. We now have data on four drugs that gives us a clue of the possible scope of answers to this kind of question. Astonishingly, rapamycin works just as well in terms of increases in median lifespan, whether you started at 9 months or at 20 months of age [in mice]. I thought that was very unlikely to be the case, but I was wrong. It is fully active, even if you start as late as 20 months of age.

For acarbose, the answer is if you started in midlife, you get half the effect. For 17α-estradiol, if you started at 16 months of age, which is early middle age for mice, it works just as well as if you started it at 9 months of age. For canagliflozin, we don’t know yet. We started the study, but we don’t have enough deaths to say for sure. These mouse studies, of course, don’t perfectly predict what you would see in people, but they give you an indication of the range of possible answers. So, of the three drugs we have so far, two work quite well if started in middle age.

They’re hoping metformin too works just great, regardless of how late you start. Metformin does not extend lifespan in mice, but nonetheless it may do so in humans.

That was one of the most high-profile failures in the ITP history, I think. Do you have any guesses about why that happened? Would you like to go back to metformin and maybe test it differently?

Each year, we get 10 or 15 good ideas to test. And if someone said, hey, would you mind going back and testing metformin again, they’d have to make a pretty strong case that it might work the next time. Maybe they have a different dose or a different formulation, or maybe they want us to give it three days out of every seven or something.

They could make a case that retesting metformin is a good idea. My hunch is that it’s not worth retesting. The reason is that it was actually tested twice – once by the ITP, and then once before us by Rafael de Cabo. He found that it did not have any effect in female mice. In male mice, he said it had a small but significant 5% effect, but I don’t put much faith in this conclusion, because he did not use the standard statistical test.

On the other hand, we do have some robust data that metformin benefits humans.

The epidemiological data are quite provocative, I agree. It’s very encouraging. On the other hand, it’s an observational study, and it’s a post-hoc analysis, and those are known to be misleading sometimes. The epidemiological data in humans is pretty strong and make a reasonably good case that you should pay more attention to metformin in humans.

Some of the drugs that the ITP is testing, and I’m thinking in particular canagliflozin, are already being used by tens or hundreds of thousands of people. They are now a mainstay of diabetes therapy. Probably the quickest thing you could do is come back to people who have diabetes and who’ve been on these drugs for a decade and ask, “How about cataracts? How about hearing? How about bone breaking? How about a lot of stuff that’s not clearly related to diabetes, but is clearly related to aging?” If canagliflozin and other SGLT-2 inhibitors are slowing the aging process in humans, then you would predict that the drug not only protects you from diabetes but could protect you from a lot of other problems that occur in old age.

If this is the case, we have a real anti-aging drug. I think that would be at least as informative as the TAME trial. Similarly, acarbose is a mainstay of anti-diabetes therapy – not in America, but in many Asian countries. And one could ask the same kinds of questions in Asian countries for people who have been on acarbose for a good part of their adult life.

That would still be a population study.

I agree. I like controlled trials. But if you’re asking for a 30-year controlled trial, you’re going to get some pushback.

What are the major takeaways from the ITP as of now?

We’ve already talked about some of it today. One major point is establishing definitively that you can slow the aging process down by putting something in the diet. It refutes the commonly held notion that you cannot change the aging process.

The data is now overwhelming that aging can be slowed ad you do that by extending healthy lifespan. The evidence does not support the nightmare scenario where you get people or mice that just won’t die – they’re demented, they’re in pain, they’re in terrible shape, but they just won’t die. The drugs the ITP has tested do not do that at all. Instead, it’s keeping them healthy longer, and that’s why they stay alive longer.

The second point is that it gives you tools for working out the mechanisms by which aging can be slowed. We now have at least four genes, four drugs, and two diets that consistently, reproducibly increase mean and maximum lifespan in mice. So now, you can, for the first time, begin to ask questions through an entirely new paradigm of how to learn about aging. Up until maybe the 1970s, 80s, or 90s, the way you did aging research was that you made a list of things that differentiated old from young mice, rats, or people, and then you fantasize that, oh, this one looks really important, maybe that’s the cause of aging. The new approach is much smarter: you compare young animals that are either normal or that have been treated in a way that makes aging go more slowly.

If you want to know what the cause of slower aging is, you don’t have to wait for aging to take place. You can figure out what is going on at the very earliest parts of the lifespan that slows the aging process down. That’s a whole new paradigm and a very powerful research design.

The third point that’s probably worth mentioning: each of these drugs has a target. Sometimes, we don’t know what the target is. For rapamycin, the target famously is an enzyme called TOR, the target of rapamycin, but we don’t know yet whether the anti-aging effects of rapamycin are accomplished by a change in the brain, in the pineal, in the brown fat, in the white fat, in the liver, or in the arteries.

We have to define the specific cell types that rapamycin influences in ways that create broad healthspan and lifespan benefit. That’s a critically important next step that we can’t take without the drugs. The same is true for acarbose and canagliflozin. They strongly indicate that at least in males, you can slow many aspects of aging, including death by preventing daily surges in glucose. That’s an opening. Why is that? Why is it that the daily surges and glucose are a key element in males for timing the aging process?

You can also begin to ask similar questions about sexual specificity. We have several drugs that seem to work better in males, and we’d like to know what it about the physiology and pathobiology in male animals that makes them susceptible to something that these drugs address.

The last point is that the ITP serves as a foundation for studying possible preventive medicines that might work outside the laboratory environment in people.

The critical next step probably is dog research. Matt Kaeberlein, Dan Promislow and their colleagues are treating dogs with rapamycin, and they’re starting with middle-aged dogs. It won’t take very long – probably five to seven years to get some lifespan data. If they prove that rapamycin at the dose they’ve chosen extends healthy lifespan of dogs, that will be a major breakthrough, because if it works in mice and in dogs, you better think it’s going to work in people too.

If I were in charge and had lots of grant money to give out, I’d want to be sure that there were more dog studies that evaluated other anti-aging drugs that the ITP had developed, to see whether they also had a beneficial effects in a species that’s much larger than mice and has the same kind of genetic heterogeneity that humans have.

By the way, why dogs and not, let’s say, small monkeys?

Oh, that’s easy. Dogs live with people and there are millions of them. So, you don’t have to build a whole building and fill it with experimental dogs. What you do is you tell people, would you like your dog to have a 50/50 shot at getting a medicine that might extend its lifespan? The dog stays with you, lives with you, eats dog food, except we’ll put our drug into it. And you your dog also gets a free checkup once a year. So, it’s really easy to sign up volunteers for the study.

What do you think about other types of anti-aging interventions, such as gene editing and cellular reprogramming?

For gene editing, you’d have to ask a couple of questions. What genes are you going to edit, what cells are you going to edit your genes in, and what makes you think it would do any good? Currently, we don’t know of any genetic change you can do in a specific cell type that slows aging in any mammal. There are lots of exciting, hot, new techniques that in principle could do cool stuff. The notion that they are the secret to slow aging is, as of now, a good point for science fiction. I’m eager to hear from someone who claims they know what cell type they need to edit and what gene they need to edit in that cell type.

Same for cellular reprogramming: why do you think this is going to be good for you? Are you planning to reprogram the cells in my brain, or in testes, or my bone marrow cells? And what are you going to reprogram them to do? Are you pretty darn sure they’re not going to get cancerous?

It’s a valid point, of course, but theoretically, how far could these techniques get us?

These are broadly hyped and potentially very powerful techniques. What is needed is a clear idea about how you can apply these dynamite techniques to ask and answer a well-defined hypothesis about aging. One can imagine such a hypothesis – for instance, that reprogramming a specific cell type in the hypothalamus so that it doesn’t show inflammatory change would slow the aging process down.

Then, one could, in principle, define a viral vector that specifically infects that kind of hypothalamic cell and modifies NF-κB-dependent processes to block inflammation in the hypothalamus. If that’s technically feasible, it could well be very informative.

Plans of that sort, where you have a specific target, a specific genetic manipulation, and at least a plausible model for why that leads to a health benefit, would be thrilling. But simply waving your hands and saying, oh, I’m going to do gene editing, doesn’t substitute for a good plan to test a hypothesis.

So, maybe the ITP could provide the insights that those areas need?

Yes, information about what genetic targets in what cell types need to be manipulated to slow aging. That would be really nice to know, and sometimes, the work in the ITP and other labs that are stimulated by ITP results can move us several steps in that direction.

To give just one example, Gonzalo Garcia has come up with a really nice observation that both in drug-treated slow-aging mice and genetically modified slow-aging mice, a lot of messenger RNA is translated by a special process: – cap-independent translation. That suggests a hypothesis: if you have a drug that can turn on cap-independent translation, that drug might be really good for you. Or if you’re into gene editing and you know what gene controls cap-independent translation, you can imagine a way of modifying cells to promote cap-independent translation.

The ITP could lead us to a greater understanding of the aging process: what controls its rate, what cellular and genetic targets are plausible for genetic engineering and cell therapy? That’s one way in which the work we’re doing could contribute to the overall endeavor.

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Yuri Deigin Interview

Yuri Deigin on Cellular Reprogramming in Humans

In a recent press release, YouthBio Therapeutics announced that it has left stealth mode. YouthBio is a self-proclaimed longevity biotech company with a focus on developing gene therapies that reverse the epigenetic alterations that cause us to age.

The company is hoping to reverse cellular aging in people through partial cellular reprogramming. This approach reverses the changes in gene expression that accumulate over time and cause our cells to become increasingly inefficient and behave in harmful ways.

Studies have shown that when gene expression in cells is reprogrammed from an older to a younger profile, the aged cells behave like young cells again. The race is now on to translate this approach to people in a way that is safe enough to be used. Check out our article on Yamanaka factors and partial cellular reprogramming to learn more about it.

The company is led by CEO Yuri Deigin, a biotech entrepreneur who focuses on translational research. Yuri has led a number of early-stage pharmaceutical companies and has been an active proponent of partial cellular reprogramming since 2017.

The team includes researcher Dr. João Pedro de Magalhães, who has been based at the University of Liverpool for many years where he leads the Integrative Genomics of Aging Group. His lab has been studying aging with a particular focus on its genetic and epigenetic elements. He is the Chief Science Officer at YouthBio.

Dr. Alejandro Ocampo, Lead Research Collaborator of YouthBio, is a pioneer of cellular reprogramming and was the first author of the 2016 paper out of the Salk Institute which first demonstrated that the technique could be successfully used in mice, not just in cells in a dish.

We had the opportunity to speak with Yuri about the company and his thoughts on aging research and why we age.

First off, can you tell us a little bit about yourself and how you got interested in aging research and attempting to slow down or even reverse human aging? 

First of all, I worked in drug development before I got interested in aging, and I just didn’t realize, as many people don’t, that aging is the driver of pretty much all non-infectious diseases, with the exception of inherited ones, of course. You could even say that many infectious diseases have an age-related component too.

Basically, I didn’t realize that aging was a problem, because even drug developers and medical professionals think that aging is the norm. They think that because everybody ages, it’s not a disease, so it’s normal. They just say “We’re here to cure cancer” or “We’re here to cure Alzheimer’s.”

But then someone comes to you and shows you that all of those diseases are driven by aging. Then they suggest you should try to cure aging to stop all these diseases at the root cause. That is the moment your eyes are opened and you realize, “Wow, that makes so much sense, aging is this process that drives all those pathologies.”

I got introduced to this concept – that aging is a thing we should go after – around 2012. This was when the seeds were planted in my head, and by then, there were already a lot of animal studies that showed that aging is malleable. We already can extend lifespan in animal species like rats, mice, and much simpler ones like worms and yeast.

That was the foundation that made me realize that aging was not an immutable process, that aging is something changeable, and that it makes all the sense in the world to try to change it. After all, the goal of medicine is to prevent disease and to keep you healthy for as long as possible. What our field – longevity – is doing is absolutely the same thing.

The elephant in the room is aging. That elephant is preventing all of us from being as healthy as possible for as long as possible – that’s the aging process. If you are interested in saving lives, if you are interested in developing cures for diseases, you should be trying to intervene in the aging processes.

Once you realized that aging was something that was not a one-way street, what did you do?

Once that kind of realization came to me, I got very interested in accelerating this understanding among the general public. Just as I was, first of all, unaware of aging being a problem, and second of all, it being a potentially fixable problem, most of the general public also does not know this.

I thought the best thing to do was to try to spread the word. Initially, I was much more involved as an activist in the longevity movement while still doing drug development that wasn’t related to longevity but was related to age-related diseases. Some time later, I learned about a new approach to intervene in aging, this being partial reprogramming.

This was when the Ocampo paper came out in late 2016, where researchers showed that Yamanka factors could make cells younger in mice by partially reprogramming their epigenetic state, and could then make those mice live longer. Once I learned about this paper in early 2017, that was the point where my two paths crossed. At the time, I was writing a lot about the epigenetic nature of aging and how it would be great if there was a way to rewind our biological clock and epigenetically modulate aging.

For me this was a Eureka moment. I was like, “Wow, this is one way to do it.” Yamanaka factors epigenetically rewind everything back to an essentially embryonic state, and in the process, this also rejuvenates cells. This was when things kind of fell into place and I thought this approach had the most potential to intervene in aging systemically.

Once I had learned about partial reprogramming, I thought there would be people immediately trying to translate it and pushing to create therapies using the approach, and yet I didn’t really see that happening. I thought, “Well, if nobody else is doing it and I believe in it, then I will do it.”

It was also a good time for me because I was transitioning from my previous drug development project, and this was the perfect opportunity. If I wanted to do this, then the time was now. I just did it and started a company to translate and try it.

In 2020, I met Viet Ly, my partner and co-founder, of YouthBio. He suggested we focus on translating partial cellular reprogramming to humans, and by January 2021 we got the company registered in Washington State. This was essentially when the company was born. Since then, I have been working with him, João Pedro de Magalhães, and Alejandro Ocampo on putting together the things we need to do in terms of experiments that would answer some of our hypotheses on the translational pathway.

To set the scene, what do you think aging is? Is it programmed, is it random stochastic damage, or is it both? 

To me, the beauty of partial cellular reprogramming is actually that it doesn’t really matter what aging is. We’re taking a very pragmatic approach. We absolutely know that a lot of epigenetic changes are driving aging. Do those changes happen in response to stochastic damage? Or because of a program? For practical purposes it doesn’t really matter. We have observations that show that partial cellular reprogramming can delay aging and can reverse some hallmarks of aging on the cellular level.

We also see some reversal of those hallmarks on an organ level and potentially on a systemic level. There is definitely a delay of aging in the progeric mouse model (mice designed to age rapidly) where they lived up to 50% longer and exhibited better histology of various tissues.

We are taking a pragmatic approach to translating this research to people. We’re actually trying to make something useful rather than just taking a dive deep into the fundamental science, which of course is also important and interesting, but we ultimately want to create a therapy for people as quickly as possible.

To answer the initial question, I do think aging is programmed, and at some level, damage accumulation absolutely is responsible for aging too. The real question is, does that damage accumulate randomly? Why does it not accumulate for very long periods in a human when we’re young versus a mouse, where it accumulates 20-40 times quicker. To me, the answer to that is that there is a programmed component, which dials down the genes that deal with the damage as we age.

It’s these mechanisms that are responsible for fixing the damage that get dialed down as we age. I think we have an excess capacity for fixing the damage when we’re young. The incoming damage arrival rate is pretty stable and level. It’s always at that baseline level of incoming damage. It doesn’t matter whether you’re 20 or 100 years old, whatever occurs externally or randomly, it’s occurring at about the same rates.

But the accumulation of all of it is different. Obviously, when you’re 20, you can say there’s almost no accumulation of it because we have excess capacity for fixing any incoming damage. As we get older, that ability to prevent damage accumulation and to fix any kind of damage on the fly starts going down.

Also, there’s an interesting process that’s happening where some of the bad stuff in our genome, like retrotransposons and retro-elements, for some reason, also become more active. It’s as if something goes wrong, and for some reason, whatever is epigenetically silenced during youth starts to be released from that epigenetic jail. It starts wreaking havoc on the genome. Retro-elements start inserting themselves into various points in the DNA that could cause mutations and all sorts of bad things.

We see two epigenetic processes occurring, where the levels of good gene expression are gradually decreased, as if the volume is turned down, whereas bad stuff like harmful gene expression is getting activated with age. To me, that’s a big indication that there is a programmed or non-random component.

Taking it to the next level then, is it a program that was designed this way, or is it a program that just kind of goes haywire but wasn’t designed by evolution? Perhaps, evolution beyond some point does not care about or cannot do anything about this program.

This is kind of the merging of antagonistic pleiotropy and the developmental program aging theories. Some researchers, such as Mikhail Blagosklonny, think that aging is a developmental hyperfunction or a shadow of the developmental program, the program that helps us mature. After a certain point, the developmental program enters a mode that evolution doesn’t care about, and it is this programmed element that could be driving aging.

I mean, nobody would argue that there is a developmental program where everything is very tightly regulated in an organism between embryogenesis, sexual maturity, and other stages. These are controlled, coordinated, and have specific time points when things happen.

There is the period of childhood, adolescence, and the journey towards sexual maturity, which are tightly controlled and happen in stages. These are programs, and aging also looks very similar because it happens like these stages that occur in earlier life. There is a similar time schedule for different individuals of the same age. To me, it seems like there’s a large non-random component to aging.

Let’s talk about YouthBio Therapeutics. You’ve just come out of stealth mode; what can you tell us about the company and what is it you are doing?

Basically, we are trying to translate partial cellular programming, but we have a tight focus right now on humans. Our approach is to use gene therapy to deliver reprogramming genes once into tissues of interest and then activate them with a small molecule in a similar manner to Ocampo in 2016, where they used a doxycycline inductor to activate the reprogramming genes.

Ultimately, we feel that partial cellular reprogramming will need a tissue-specific approach. Different organs will probably need different reprogramming factors and definitely different dosing regimens.

Our goal is to move away from doxycycline and create tissue-specific gene induction systems that, for a given tissue, can activate a specific set of genes. That platform doesn’t even have to be used for partial cellular programming. It could potentially be used for any other gene therapy that needs several different gene cargoes that need to be activated in a different manner.

Eventually, we also want to move away from Yamanaka factors, because they weren’t designed for partial programming. They were designed for full reprogramming, and for our purposes are too dangerous, because full reprogramming causes cells to lose their identity.

This is something we obviously do not want, so we’re looking for other factors that are better suited to partial reprogramming. Basically, the holy grail for us is to split the rejuvenation from the dedifferentiation. We want to just rejuvenate cells if it’s possible.

We’re obviously betting that it is possible, or at least we can shift these two states farther apart than we can with Yamanaka factors, so there is a greater margin of error, making it easier to just activate the rejuvenation process.

Thankfully, what we observe from full reprogramming is that rejuvenation happens at the very beginning of the process and dedifferentiation happens later. There’s a point of no return, so this gives us this kind of Goldilocks zone where we can partially reprogram cells without fully resetting their identity. The cell can still remain whatever it is, such as a skin cell, but it’s rejuvenated by the burst of reprogramming that happens in the very beginning.

We’re looking for factors that can maybe delay the point of no return phase but give us a wider therapeutic window where we can hopefully extract more rejuvenation and allow us to push the important genes that are more responsible for the rejuvenating effect of partial reprogramming rather than those involved in dedifferentiation.

There does appear to be a therapeutic window, and research does suggest that different cell types require different levels of exposure to Yamanaka factors to rejuvenate them. Given this and the balance between rejuvenation and the point of no return, how can we get around this without it becoming an exercise in massive complexity?

This goes back to what I said, that we think partial reprogramming will need tissue specificity. You’re saying exactly the same thing as we are, that different cell types might need different approaches. With the Yamanaka factors, this manifests itself in different durations of exposure, but the next stop is to try to find tailored factors for a given tissue. 

For example, the brain might not need the Yamanka factor Sox2, which is already expressed in a lot of brain cell types. That’s why we’re developing a tissue-specific induction platform where you can have, for example, to activate rejuvenation factors in the brain, you would take molecule one, and no other tissues would be activated by it. 

This would mean you could do bouts of brain-specific partial reprogramming. Then, you switch to the next tissue, the next tissue, the next tissue, and each would have specific activation molecules.

You could probably do it in parallel, using the specific molecules to rejuvenate each target tissue without affecting others, or you may want to separate them out. That’s definitely a question to be answered much later on when we’re developing an actual combination therapy, but initially we’re trying to study which organs need which regimens or which cell types will respond better to which factors and which durations of treatments.

The short answer is that to provide that differential treatment for different organs, you need different gene induction mechanisms that won’t overlap. This is a platform that we’re developing.

Can you speak to the shortfalls of gene therapy in the context of delivery? Specifically, it is known that delivering the payload to target cells is not perhaps as effective as we would like. How can we solve this?

Well, the delivery problem is a whole kind of different level and essentially a research project in itself. As we are tissue specific, we can piggyback on best practices in transducing a given tissue. There are many hundreds of gene therapies that are targeting various tissues that we can just pick up and use as the best delivery vehicle for the tissue we want to target.

We’re not tied to any delivery mechanisms, and we will just use whatever the best system is at that time. Hopefully, in the next two years, while we’re working on our partial reprogramming and our research, the delivery area will benefit from the advances made by other companies and research labs. 

There’s also other novel delivery approaches that are being developed, and we are keeping a close eye on that.

Given how things work at the FDA, NIH, and other regulatory agencies, what do you think is a realistic timeframe for partial cellular reprogramming to reach humans?

Well, there are certain disease areas where you can see clinical trials happen much sooner than others. This kind of goes back to our initial strategy of focusing on two therapeutic areas, where there’s a huge unmet clinical need. Potentially, as soon as researchers can demonstrate in animals that partial reprogramming can produce a meaningful therapeutic effect and if we come to the FDA with those data, they’ll be happy to let us conduct a clinical trial.

I think it will not happen in a month or two, but it definitely could within the next few years that clinical trials can happen. Obviously, that depends greatly on the animal data.

If we see in animal models of a particular age-related disease that partial reprogramming produces a clinical effect, we can then take that therapy and try to apply it in humans. This is why we’re going after gene therapy. We think it’s a very effective modality for both partial programing and the disease areas that we’re targeting.

There’s no one timeline for all diseases, and the FDA is not saying “Thou shalt not try clinical translation or clinical testing of partial reprogramming until year X”. As soon as you have compelling data and if you know that a disease area doesn’t really have any treatment options, the FDA will, I’m sure, be more than happy to let you try it for those patients, because those patients don’t have anything else.

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Centenarian

Longevity in Centenarians Linked to Lower Ribosomal Activity

Scientists have discovered a possible mechanism that protects extremely long-lived people from aging [1].

Protected persons

A few days ago, news came of the death of the oldest person in the world (and the oldest ever to have her age indisputably confirmed), 119-year-old Kane Tanaka from Japan. People who live past 100 or 110 years old do not achieve this by making extremely healthy lifestyle choices. Instead, they just seem to age more slowly, being protected from the diseases of aging by currently unknown natural mechanisms. Geroscientists, of course, are eager to study extremely long-lived individuals, hoping to uncover those mechanisms for the benefit of the rest of humanity (read our interview with Nir Barzilai, who has been studying supercentenarians for years).

In this new study, Chinese researchers obtained and analyzed the transcriptomes of white blood cells taken from 193 long-lived Chinese women (around 100 years old, active and living independently, which, according to the authors, indicates good chances of living past 110). As controls, the researchers used 86 other women with an average age of 57. Of course, there cannot be age-matched controls when studying centenarians: age itself is what determines a person’s place in either the study group or the control group.

Ribosomes and proteins

Transcriptomic analysis revealed that the genes related to lysosomal activity were significantly upregulated in the study group compared to the control group. This was hardly surprising, since lysosomes are organelles involved in autophagy – the process of breaking up and clearing intracellular waste. Increased autophagy has been linked to longevity in various model organisms [2].

The main and more surprising finding of the study was the extremely significant downregulation of ribosome-related genes, especially ribosome protein genes (RPGs). Ribosomes are the organelles that produce proteins from amino acids according to the “blueprints” provided by messenger RNAs. If RPGs are downregulated in the cell, it produces fewer building blocks for ribosomes, hence fewer proteins.

The authors interpret this finding in the context of the hyperfunction theory of aging, which has been gaining popularity recently. This theory postulates that some bodily processes are optimized for growth and reproduction, which is all nature cares about. Protein production is one such process: it is indispensable for growth and development, but it also accelerates aging. Protein restriction effectively slows aging in model organisms and provides multiple health benefits in humans [3]. Importantly, protein restriction works at least in part by modulating the mTOR pathway [4], which is also what the well-studied geroprotective molecule rapamycin does.

As the controls were not age-matched, there is a possibility that this and other differences in gene expression can be attributed to natural aging rather than to centenarian-specific anti-aging mechanisms. To minimize this possibility, the researchers confirmed that in the control group, which was relatively heterogeneous in age, the levels of expression of both lysosome-related and ribosome-related genes were age-independent.

One factor to rule them all

Since ribosome-related genes are always co-expressed (their expression levels change simultaneously), the researchers looked for a transcription factor that might bind to the promoters of most of those genes, regulating their expression. The gene ETS1 fitted the profile, showing strong correlation with the ribosome-related genes.

To confirm ETS1’s role, the researchers created human embryonic kidney cells with the ETS1 gene knocked out. Transcriptomic analysis showed that the ribosome-related genes in these cells were significantly downregulated. This result was then reproduced in human dermal fibroblasts. Downregulation of ETS1 resulted in significantly less cellular senescence, as measured by the senescence markers ß-galactosidase, p-16, and p-21 and in increased cell proliferation. Interestingly, a recent study showed that knocking out drosophila’s homolog, ETS1, significantly increases lifespan in those animals. Taken together, these findings point to ETS1 as a potential therapeutic target.

Women only?

The researchers do not report why the study was female-only, but that might be a limitation of the particular dataset (large centenarian transcriptome datasets are hard to come by). However, this issue can be very consequential, since there is a growing understanding that some aging mechanisms are sex-specific, as evidenced by the fact that most compounds found by the ITP (Intervention Testing Program) to prolong lifespan in mice disproportionately benefit one sex.

Conclusion

Studying extremely long-lived humans can provide valuable insights into the very nature of aging. According to this new study, centenarians (at least women) might possess a mechanism that dampens protein production by reducing the activity of ribosome-related genes. This is mostly in line with previous research in model animals and humans. It remains to be seen whether this mechanism is sex-specific and to what extent.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Xiao, F. H., Yu, Q., Deng, Z. L., Yang, K., Ye, Y., Ge, M. X., … & Kong, Q. P. (2022). ETS1 acts as a regulator of human healthy aging via decreasing ribosomal activity. Science Advances8(17), eabf2017.

[2] Hansen, M., Rubinsztein, D. C., & Walker, D. W. (2018). Autophagy as a promoter of longevity: insights from model organisms. Nature reviews Molecular cell biology19(9), 579-593.

[3] Mirzaei, H., Raynes, R., & Longo, V. D. (2016). The Conserved Role for Protein Restriction During Aging and Disease. Current opinion in clinical nutrition and metabolic care19(1), 74.

[4] Hill, C. M., & Kaeberlein, M. (2021). Anti-ageing effects of protein restriction unpacked.

Broken bone

Senescent Cells Slow Bone Healing

A study published in the Journal of Clinical Investigation has reported that senescent cells are largely responsible for slow bone healing in aged animals and that senolytics, which remove these harmful cells, can speed bone regeneration.

A brief outline of bone healing

The researchers begin their study by explaining how bone normally heals, gradually progressing from blood, soft tissue, hard tissue, and ultimately new bone. During this process, cells from internal and external sources provide different types of cartilage [1], and mesenchymal progenitor cells (MPCs), which give rise to bone cells, are recruited to the site. Previous research has found that age-related inflammation (inflammaging) is harmful to the recruitment of these cells in older organisms and that anti-inflammatory drugs are beneficial [2].

However, that research did not focus on one of the major sources of inflammaging: cellular senescence. This study aimed to fill this gap and determine the extent to which senescent cells impede bone healing; as it turned out, the effect was large.

A focus on TGF-ß1

The researchers note that transforming growth factor beta 1 (TGF-ß1) is a signaling component in bone, playing multiple, situationally dependent roles in its maintenance and regeneration [3]. In certain circumstances, TGF-ß1 can be beneficial; combined with IGF1, it has been shown to alleviate bone defects in old rats [4].

However, as part of the senescence-associated secretory phenotype (SASP), senescent cells constantly excrete TGF-ß1. This, the researchers hypothesized, interferes with the signaling process and discourages MPCs from proliferating, thus delaying the healing of bone fractures.

To test their hypothesis, the researchers first examined bone fractures in young (4 months) and old (20 months) mice and measured the levels of senescent cells. The results were striking; while aged animals, as expected, had more senescent cells than their youthful counterparts, the number of senescent cells increased far more a week after fracture in aged mice than young mice, as measured by the well-known senescence biomarkers p16 and p21. Senescent cells that expressed γ-H2AX, a marker of DNA damage, were also significantly overrepresented in the aged mice.

Senolytics significantly increased bone healing

As part of this experiment, the researchers gave young and old mice the well-known senolytic combination of dasatinib and quercetin, examining their senescence biomarkers 10 days after fracture and their bone structure 28 days after fracture.

As it has in previous experiments, the dasatinib and quercetin combination dramatically decreased the number of senescent cells, as measured by p16 and p21 biomarkers, in the aged animals, and it even significantly decreased them in the young animals as well.

Administration of this senolytic combination significantly improved the bone structure of aged animals in every single metric studied. Bone area, cartilage area, and the stiffness, toughness, and strength of bone were all significantly improved in older animals. The bones of younger animals appeared to be improved as well, but not to the level of statistical significance.

The researchers conducted further tests to make sure that it was the senescent cells that were causing the problems with bone healing. Driving cells to senescence through hydrogen peroxide harmed MPCs in cell culture, which was alleviated by the senolytic combination. Taking senescent cells from aged mice also harmed MPCs, which was similarly alleviated by senolytics.

Interestingly, directly affecting TGF-ß1 was found to be beneficial in both cell culture and in aged animals, although the effects of this approach, while significant, were not as stark as the effects of senolytics.

Conclusion

This research is extremely promising, but it should be noted that senolytic interventions that work in mice are not guaranteed to work in people. However, if this technique can be shown to work in human clinical trials, then senescent cell removal might become part of the standard of care when older people suffer from accidents that result in broken bones.

We would like to ask you a small favor. We are a non-profit foundation, and unlike some other organizations, we have no shareholders and no products to sell you. All our news and educational content is free for everyone to read, but it does mean that we rely on the help of people like you. Every contribution, no matter if it’s big or small, supports independent journalism and sustains our future.

Literature

[1] Einhorn, T. A., & Gerstenfeld, L. C. (2015). Fracture healing: mechanisms and interventions. Nature Reviews Rheumatology, 11(1), 45-54.

[2] Josephson, A. M., Bradaschia-Correa, V., Lee, S., Leclerc, K., Patel, K. S., Lopez, E. M., … & Leucht, P. (2019). Age-related inflammation triggers skeletal stem/progenitor cell dysfunction. Proceedings of the National Academy of Sciences, 116(14), 6995-7004.

[3] Janssens, K., Ten Dijke, P., Janssens, S., & Van Hul, W. (2005). Transforming growth factor-ß1 to the bone. Endocrine reviews, 26(6), 743-774.

[4] Blumenfeld, I., Srouji, S., Lanir, Y., Laufer, D., & Livne, E. (2002). Enhancement of bone defect healing in old rats by TGF-ß and IGF-1. Experimental gerontology, 37(4), 553-565.