Fight Aging! Newsletter, July 25th 2016

July 25th 2016

Fight Aging! provides a weekly digest of news and commentary for thousands of subscribers interested in the latest longevity science: progress towards the medical control of aging in order to prevent age-related frailty, suffering, and disease, as well as improvements in the present understanding of what works and what doesn't work when it comes to extending healthy life. Expect to see summaries of recent advances in medical research, news from the scientific community, advocacy and fundraising initiatives to help speed work on the repair and reversal of aging, links to online resources, and much more.

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  • Matching Fund Donors Sought for SENS Universal Cancer Therapy Crowdfunding
  • Aubrey de Grey AMA at /r/Futurology: the SENS Approach to Cancer and More
  • Targeting CD47 to Reduce Atherosclerotic Plaques in Blood Vessels
  • Effective Therapies to Extend Healthy Life May Well be Widely Available for a Decade or More in Advance of Definitive Proof
  • Another Set of Popular Science Articles on the Prospects for Aging Research
  • Latest Headlines from Fight Aging!
    • More on Gadd45a and Muscle Atrophy
    • Claiming Stroke Incidence to be Largely Preventable
    • A Novel Role for the Lysosome in Macular Degeneration
    • Introducing Viral Cancer Therapies into the Spleen Greatly Improves Outcomes
    • A Popular Science Article on Slowing Aging, Parabiosis, and Other Topics
    • Cytomegalovirus Infection Accelerates Age-Related Epigenetic Changes
    • Most People will be Surprised by Dramatic Increases in Human Longevity Due to the Introduction of Rejuvenation Therapies Over the Next Forty Years
    • Tissue Engineering of Liver Organoids
    • AUF1 Linked to Stem Cell Function and Muscle Regeneration
    • Killifish in Aging Research


There is a month left to go in the SENS crowdfunding campaign that aims to accelerate development of an important component of a universal cancer therapy, a way to block the mechanisms of telomere lengthening that every type of cancer depends upon. The SENS Research Foundation and volunteers are looking for donors to put up matching funds of a few thousand or more, in order to take that news and that inducement to a number of conferences and other events over the next few weeks. More than 150 people have donated to the campaign to date, and we'd like to triple that number in the next 30 days.

To start things off, I'll offer up 2,000 of my own funds: the next 2,000 in donations to this SENS cancer research initiative will be matched. That is a start, and if you can join in to help out, please contact me to let me know. Can you help to make a difference here?

With last week's 10 million pledge in support of other portions of the SENS rejuvenation research portfolio, we can clearly see that grassroots fundraising works. It lights the way, and as we grow the community and show our determination, that success draws in larger donors. When this is amply demonstrated by the arrival of large amounts of new funding ... well, that is precisely the time to pile on and keep up the good work. All major medical research non-profits have several tiers of fundraising, from grassroots to high net work philanthropy, and all of these tiers are essential: they can't exist without one another. The SENS Research Foundation is transitioning to become a solid organization with a high end tier of fundraising to complement our efforts, and that couldn't exist without the support of the grassroots. It is a sign that we are winning.

We have been very focused on senescent cells, mitochondrial DNA damage, and glucosepane clearance these past few years, but don't forget that there are other parts of the SENS program that are just as important in the bigger picture of human rejuvenation. Building a universal, cost-effective therapy that works for all forms of cancer is one of those parts. The random mutations to nuclear DNA, different in every cell, that accumulate with age will be one of the hardest types of damage to fix, and mutation is the root cause of cancer. There will be a transitional era ahead in which people will live for decades longer in far better health than do today's elderly, thanks to first generation rejuvenation therapies, but they will still have high levels of nuclear DNA damage and thus high cancer risk. The rejuvenation toolkit needs to include a far better approach to cancer. You can see the SENS approach to speeding progress towards this goal in the recent interviews linked below, and at the /r/futurology AMA with Aubrey de Grey and Haroldo Silva that will be held tomorrow:

Siebel Scholar Haroldo Silva is Working Toward a Universal Cancer Therapy

Haroldo Silva is a research scientist at the SENS Research Foundation (SRF), a non-profit organization focused on transforming the way the world researches and treats age-related disease. Since 2013, Haroldo has led a project at SRF that aims to treat and prevent cancers that rely on a process known as Alternative Lengthening of Telomeres (ALT). The ALT mechanism is present in 10-15% of all cancers, including some of the most clinically challenging cancers to treat, such as pediatric and adult brain cancers, soft tissue sarcoma, osteosarcoma, and lung cancers.

Every time a healthy cell divides, the DNA at the ends of its chromosomes, called telomeres, gets shorter. When the telomeres shorten too much, the cell permanently stops dividing and either remains dormant or dies. Telomere shortening acts as a natural biological mechanism for limiting cellular life span, but virtually all types of cancer cells bypass this process, allowing them to replicate indefinitely until they impair healthy tissue and organ function. A "universal" cancer treatment absolutely needs to address the two ways by which cancer cells lengthen and maintain their telomeres: i.e., they either express an enzyme called telomerase or they switch on ALT. The ALT process enables cancer cells to continue to elongate their telomeres, but without telomerase. The exact mechanism by which this occurs is not well understood by scientists, but a reliable biomarker that clearly indicates when ALT is happening was discovered by Silva's collaborator, Dr. Jeremy Henson, back in 2009.

In the war against cancer, there are several anti-telomerase therapies in advanced stages of clinical development, but nothing currently exists that is capable of specifically targeting ALT. Silva's current research project "Control ALT Delete Cancer" aims to find drugs that specifically shut down the ALT pathway, therefore preventing cancer growth and paving the way toward the first ever ALT-specific anticancer therapeutics.

Methuselah Foundation Podcasts: Episode 007 - Control Alt Delete Cancer

Hello and welcome to Episode 7! On this episode, we'll talk with Dr. Haroldo Silva and David Halvorsen of the SENS Research Foundation. They've launched a new crowdfunding campaign designed to attack and stop cancer using a new approach. You'll hear what that approach is, why they think it has a good chance of success, and you can help in the fight.


Today, July 19th, Aubrey de Grey of the SENS Research Foundation and Haroldo Silva, lead SENS cancer researcher, are hosting an AMA - Ask Me Anything - event at /r/futurology. They will be there for a few hours to answer questions on rejuvenation research, fundraising for work on aging and cancer, and other aspects of the work of the SENS Research Foundation. This is a chance to ask about the SENS approach to a universal cancer therapy, one that targets the common mechanism of telomere lengthening that all cancers must employ to grow. The SENS researchers are focused on alternative lengthening of telomeres, ALT, a collection of processes that are still comparatively unexplored, yet essential to this approach to cancer therapies. The AMA started at 1PM EST and is ongoing at the time of posting, so if you jump in there is still the chance to have questions answered.

Below, I've digested a number of the questions and responses, with some light editing for clarity where necessary. As you can see, quite the range of topics are covered, from the cancer research that is the subject of the present SENS crowdfunding initiative at to the newly announced large-scale funding initiative Project|21, from present day politics and economics relevant to research to the personal organization of future longevity assurance therapies, and more besides.

Aubrey de Grey AMA! Ask about the quest to cure cancer's root causes, increasing healthy human longevity, or anything else!

Would the anti-ALT small molecules just prevent the cancer cells from dividing eventually, or would they actually kill the cancer cells?

It really depends on how exactly the small molecules we find inhibit the ALT pathway. They could just prevent telomere elongation which will eventually result in complete cessation of tumor growth as you pointed out. On the other hand, these molecules can interfere in the process in such a way as to cause abnormal chromosome fusions which will actually kill cancer cells.

How can you be certain that telomeric C-circles are the only method for cancer cells to achieve ALT? Or that there are a finite number of ways for cells to achieve ALT?

C-circles are currently the best biomarker identified to date that is most closely associated with ALT activity. It represents our best chance to help us develop ALT-specific cancer therapies as well as demystify how this mechanism of telomere maintenance works. However, we do not know which specific role(s) C-circles are playing in the ALT pathway. We also do not know how cancer cells initiate ALT activity.

Given small molecules often have side effects, why not use an intra-cellular method such as DRACO to target telomeric C-circles and induce apotosis? Or alternatively, do telomeric C-circles present material on major histocompatibility complexes (MHCs) that could be targeted with genetically engineered T cells?

C-circles are composed of DNA with the repetitive sequences found at telomeres. Targeting C-circles directly and specifically is not feasible since there is no way to differentiate between C-circles and regular telomeres. Additionally, there is no evidence at present that targeting C-circles would actually inhibit ALT activity. Since C-circles are just DNA strands, they cannot be presented on MHCs for T cell signaling or other stimulation of the immune system.

Given that an anti ALT therapy will probably be given along with an anti-telomerase therapy, won't this affect cell replacement by regular stem cells that can no longer replace tissues for the duration of the treatment? We produce a million new T cells per second, how long can a dual therapy be endured before damaging the subject?

We envision that the side-effects associated with telomerase inhibition will be worked out in the current clinical trials by the time that ALT-specific experimental treatments reach such advanced stages in development. The ALT-specific therapy will of course have no effect on stem cells.

Will the human clinical trials resulting from Project|21 address all 7 categories of aging damage? If not, what is their goal?

No. The goal of Project|21 is to clear the path to the first genuine clinical trials in rejuvenation biotechnology. This will involve building better collaborations, better regulatory frameworks for rejuvenation clinical work, and pushing the first technologies specific to rejuvenation that are available and at a stage where early clinical work is truly feasible. We think this will involve technologies in intracellular damage repair, and technologies in senescent cell work, and other likely candidates for the first clinical work. The comprehensive solution, however, will require a larger selection of technologies and the investment and development power of more industrial partners (and the early successes of Project|21 will be used to precipitate that).

Robust mouse rejuvenation (RMR) will probably require simultaneous, high-quality implementation of all the SENS strands in mice, because the omission of any one strand will probably cause the mice to die on schedule. Project|21, on the other hand, is only about getting part-way to the equivalent stage in humans: first of all we would only be implementing a subset of the SENS therapies, and secondly we'd only be beginning the experiment (the clinical trial), whereas RMR is defined in terms of the outcome.

How satisfied are you with the progression of science in regards to human longevity?

We're about where I thought we'd be in the context of the funding that has been available, but that's only about 1/3 as far forward from 2005 as I'd have expected to be with even 10x more funding, i.e. with on the order of 30 to 100 million per year. We really need to ramp up that funding!

An important question would be what we can actively do to convince our leaders to give the billions from our national budget not to neverending wars and killing people, but instead to curing aging medical and scientific research?

Political leaders don't lead, they follow, in order to get re-elected. So, the sequence is painfully clear: first convince the mainstream biogerontologists. Once they are on board it's easy: they convince the likes of Oprah, they convince the public, and they in turn convince the politicians. Or we could just convince one billionaire...

How does Liz Parrish's work at BioViva impact what you are accomplishing at SENS?

There are a lot of strong feelings about BioViva swirling around the net at the moment, but it's really not as alarming as is being suggested. To address the various aspects of this issue: Stimulating expression of telomerase and follistatin are plausible ways to derive some aspects of rejuvenation; if I were to choose two genes with which to do what Liz has done, those would be quite high on my list. Yes, the SENS strategy for addressing cancer is the opposite of stimulating telomerase, but that doesn't take away from the fact that such stimulation can have beneficial effects. Gene therapy is certainly highly experimental still, so there is a definite risk to doing what Liz did. However, we must also remember that the public's attitude to medical risk is way over-conservative; for illustration, Mary Ruwart calculated that at least 50x more people die from slow approval of good drugs than from approval of bad drugs. Self-administration has a long and distinguished history in biology research. Even such luminaries as Haldane used to do it. The tests that have been done thus far to determine the effect of the therapy are certainly very inadequate, but I'm guessing that that is mainly because of budget limitations. As far as I know, BioViva has not thus far offered this therapy (or any other) to the public for money.

What you do guys think about all this Nicotinamide Riboside business? Will this have an impact on longevity in humans?

I'm generally pessimistic about the human longevity potential for any intervention that seeks to mimic calorie restriction, i.e. to induce the same changes of gene expression that CR induces, because the best that can be expected from such an approach is what CR itself gives, and that seems to be much less in long-lived species than in short-lived ones. But there may nonetheless be good health benefits, so I'm all for this research.

Are there any well-known people who support human longevity? Couldn't the support of people like Bill Gates or Elon Musk considerably boost funding of any projects?

We have support from a few celebrities, such as Steve Aoki and Edward James Olmos, but we definitely need more. Yes, any billionaire would do!

I'm concerned that there will be a mad rush for volunteers or a price gauge for treatments. How can I become a volunteer? How may the average human being access early treatments?

I'm quite sure that the arrival of these therapies will be preceded by at least a decade by the widespread realisation that they are coming. During that decade, society will do whatever is necessary to ensure universal access.

I am among the minority of people who have said at a every young age that I want to live a very long time, 150+, but all my friends and family all say they would never want to live that long. How do we change people's perception of growing old and make them think long term?

That's the wrong thing to try to convince people of. Instead, convince them that the diseases of old age are inseparable from the aspects of age-related ill-health that we don't label as diseases, so that the only way we'll ever "cure" Alzheimer's, etc, is by defeating the whole lot together. Then they won't be distracted by the unnerving side-effect that they might end up living a long time.

What's your take on why parabiosis seems to rejuvenate mice? Is damage cleared or what's going on? If not, why do the aged mice seem to perform better?

It presumably works by a combination of restoring good things that are less abundant in old blood and removing bad things that are more abundant in old blood. What those things are is still a huge research area. Damage in the SENS sense is probably not cleared except that there may be some stimulation of stem cell division and thus restoration of cell number, though "pre-damage" may well be cleared somewhat via shifts in the kinetics of its creation and repair. There are bound to be epigenetic mediators of the effect.

Recently, there seems to be an uptick in startups focused on reversing aging. Does that seem to be the case to you?

Yes, there certainly are more such startups around, including ones spun out of our own work such as Ichor Therapeutics. It's happening simply because more and more rejuvenation research is getting to a stage of sufficient proof of concept that the more visionary investors are seeing the light at the end of the commercial tunnel.


In recent news, researchers have identified CD47, mainly of interest in cancer therapies up until this point, as a potential therapeutic target to diminish the vicious circle of mechanisms that causes fatty plaques to grow in blood vessel walls. Everyone suffers from this problem as they age, and it leads to the condition known as atherosclerosis. The plaques start as tiny areas of inflammation, spawned by an overreaction to damaged lipid molecules, but this can spawn a cycle of ever greater inflammation, futile immune system intervention, and cell death that produces a growing graveyard of cell debris and fats. The resulting plaque narrows and remodels its blood vessel, contributing to vascular stiffening and consequent hypertension that in turn results in other forms of cardiovascular disease. Ultimately, one or more plaques grow fragile and fragment, rupturing or blocking blood vessels to cause a stroke, heart attack, or similar likely fatal event.

The SENS rejuvenation research point of view here, as for all age-related disease, is to focus on root causes or other important differences between young and old tissues, and consider how to revert or block these changes in a narrow, targeted manner. For example, the damaged lipids that seed lesions in blood vessel walls arise in part as the end result of a lengthy Rube Goldberg chain of events that starts with forms of mitochondrial DNA damage. Therefore allotopic expression gene therapy to duplicate mitochondrial genes in the cell nucleus, and thus ensure that they can continue to supply necessary proteins even if damaged in the mitochondria, should reduce incidence of atherosclerosis. That experiment lies perhaps five to ten years in the future at the present time, depending on funding. Another SENS approach is to clear out the worst of the waste compounds in plaques that can overwhelm and kill the macrophage immune cells that are drawn in to clean up the mess. Macrophage death is an important component of the vicious cycle that causes plaques to grow once established, making it a beacon of inflammation that draws in immune cells to their death. If the cell death could be cut down, then the immune system could successfully clean up atherosclerotic plaques. Similarly, making macrophages much more resilient would also be helpful, and for exactly the same reasons.

At a high level the progression of atherosclerosis is fairly well understood, with the vicious cycle of inflammation and immune cell death sitting at the heart of it. At the detailed level of cellular mechanisms, however, there is a steady process of new discoveries as researchers find and map the blind spots. For example, the smooth muscle cells in blood vessel walls are now known to play a more active role than was once thought, and, considered overall, the various types and states of cells involved are not at all as clearly demarcated as was the case a decade ago. It is a complex process. That complexity is a good reason to focus in on specific mechanisms likely to disrupt the cycle - that cells arrive to clean up the mess, become overwhelmed, die, and add to the debris. Anything that keeps macrophages alive and working efficiently to remove the compounds making up the plaque should be beneficial.

Anti-tumor antibodies could counter atherosclerosis

Normally, as a cell approaches death, its CD47 surface proteins start disappearing, exposing the cell to macrophages' garbage-disposal service. But atherosclerotic plaques are filled with dead and dying cells that should have been cleared by macrophages, yet weren't. In fact, many of the cells piling up in these lesions are dead macrophages and other vascular cells that should have been cleared long ago. Researchers performed genetic analyses of hundreds of human coronary and carotid artery tissue samples. They found that CD47 is extremely abundant in atherosclerotic tissue compared with normal vascular tissue, and correlated with risk for adverse clinical outcomes such as stroke.

Much of what's now known about CD47's function stems from pioneering work in cancer research. In the late 1990s and early 2000s, researchers first identified CD47 as being overexpressed on tumor cells, which helps them evade destruction by macrophages. They went on to show that blocking CD47 with monoclonal antibodies that bind to and obstruct the protein on tumor cells restores macrophages' ability to devour those cells. Phase-1 clinical safety trials of CD47-blocking antibodies in patients with solid tumors and blood cancers are now underway.

In a laboratory dish, anti-CD47 antibodies induced the clearance of diseased, dying and dead smooth muscle cells and macrophages incubated in conditions designed to simulate the atherosclerotic environment. And in several different mouse models of atherosclerosis, blocking CD47 with anti-CD47 antibodies dramatically countered the buildup of arterial plaque and made it less vulnerable to rupture. Many mice even experienced regression of their plaques - a phenomenon rarely observed in mouse models of cardiovascular disease. Looking at data from other genetic research, the scientists learned that surplus CD47 in atherosclerotic plaques strongly correlates with elevated levels, in these plaques, of a well-known inflammation-promoting substance called TNF-alpha. Further experiments showed that TNF-alpha activity prevents what would otherwise be a progressive decrease of CD47 on dying cells. Hence, those cells are less susceptible to being eaten by macrophages, especially in an atherosclerosis-promoting environment. "The problem could be an endless loop in which TNF-alpha-driven CD47 overexpression prevents macrophages from clearing dying cells in the lesion. Those cells release substances that promote the production of even more TNF-alpha in nearby cells."


Five years from now, it will be possible to take a trip overseas to have most of the senescent cells that have built up in your tissues cleared away via some form of drug or gene therapy treatment. That will reduce your risk of suffering most age-related diseases, and in fact make you measurably younger - it is a narrow form of rejuvenation, targeting just one of the various forms of cell and tissue damage that cause aging, age-related disease, and ultimately death. I say five years and mean it. If both of the present senescent cell clearance startup companies Oisin Biotechnologies and UNITY Biotechnology fail rather than succeed, and it is worth noting that the Oisin founders have a therapy that actually works in animal studies, while drugs and other approaches have also been shown to both clear senescent cells and extend life in mice, then there will be other attempts soon thereafter. The basic science of senescent cell clearance is completely open, and anyone can join in - in fact the successful crowdfunding of the first Major Mouse Testing Program study earlier this year was exactly that, citizen scientists joining in to advance the state of the art in this field.

Five years from now, however, there will be no definitive proof that senescent cell clearance extends life in humans, nor that it reduces risk of age-related disease in our species over the longer term. There will no doubt be a few more studies in mice showing life extension. There will be initial human evidence that clearance of senescent cells causes short-term improvements in technical biomarkers of aging such as DNA methylation patterns, or more easily assessed items such as skin condition - given how much of the skin in old people is made up of senescent cells - or markers of chronic inflammation. These are all compelling reasons to undertake the treatment, but if you want definite proof of life extension you'll have to wait a decade or more beyond the point of first availability, as that is about as long as it takes to put together and run academic studies that make a decent stab at quantifying effects on mortality in old people.

Uncertainty is the state of affairs when considering the effects of potentially life-extending therapies on human life span. Consider the practice of calorie restriction, for example, where theory suggests the likely outcome is a few extra years, but certainly not a large number of extra years or else it would be very apparent in epidemiological data. I think that an enterprising individual could, given a good relationship with the Calorie Restriction Society, put together a 20-year or 40-year study to that would - in theory - produce a decent set of data on practitioners and outcomes in the wild. It won't happen, most likely, because for one the funding isn't there for such a study, and secondly we'll be well into the era of widely available rejuvenation therapies along the way. Those calorie restriction practitioners will be taking advantage of treatments to repair the causes of aging just like everyone else.

Further, consider the possible effects of bisphosphonate treatment. There is some suggestion that this could add five years to life expectancy, a huge effect to go otherwise unnoticed for a treatment that quite a lot of people undergo in old age - but that may be exactly what has happened, for all we know. There is little work on replication or investigation, sadly. I point this out as an example of the degree to which uncertainty can and does exist for human data, as well as just how hard and expensive it is to dispel. It would take a large study, a lot of work, and waiting for a decade or so to figure out whether this bisphosphonate effect is real.

Now, consider that five years of additional life is not so far off a realistic expectation for the first prototype of any SENS-style rejuvenation therapy, such as senescent cell clearance, that repairs just one of the forms of damage that cause aging. Fixing one thing only gets you so far, as all the other forms of damage will still, on their own, kill you. Aubrey de Grey of the SENS Research Foundation believes that only small gains in overall life span are possible without addressing all of the causes of aging. This is a position well supported by statistical evidence for what would happen if, say, all cardiovascular disease or all cancer was eliminated without affecting other age-related disease. Only a few years of life expectancy would be gained in either of those cases. Arguments against that position run along the lines of suggesting that any repair of damage should produce incremental increases in life span, with reference to reliability theory, or that since all forms of damage and disease interact with one another, removing one will tend to slow the others. But we really won't know for sure until these therapies are out there in use and data is being gathered. You can only go so far in mice, especially given that their life spans are very much more plastic in response to circumstances than ours.

The reason I point out all of this is to note that the next couple of decades are going to be an increasingly confusing time for people who want to purchase elective therapies to extend healthy life. Things that actually work to a significant degree are going to be available alongside increasingly effective stem cell therapies and the same old garbage from the "anti-aging" marketplace that does absolutely nothing but part fools from their money. There will be infinite shades of grey between all of those things. You only have to look at the opportunists selling supposed longevity-enhancing supplements today based on calorie restriction mimetic research, and the articles in which that research is presented as equivalent and equal to SENS rejuvenation research approaches such as clearing senescent cells, to see how this is going to go. To navigate this near future market, for the decade or two it will take for the approaches that actually work to definitively prove their worth in human studies, you must understand more of the underlying science. You must be able to explain to yourself why damage repair approaches like those of the SENS portfolio are more likely to be effective than calorie restriction mimetic supplements - in short, your participation in the market will be guided by your take on the science. This is far from an academic exercise; time matters greatly.


Science News recently lumped together a few popular science articles on aging research into a special issue on the subject. As the blurb notes, aging is very much neglected in comparison to its importance, and accepted despite the damage it does. Defeating aging should be the primary focus of medical research, given that it kills about twice as many people as all of the other causes of death put together, and is the root cause of an even larger proportion of disability, pain, suffering, and medical expense. That it isn't is just another sign that we humans are not good at priorities and common sense.

Everyone ages. Growing old is a fundamental feature of human existence. But, our scientific understanding of aging pales in comparison to its significance in our lives. While new studies reveal exciting prospects for slowing the effects of aging, its causes and extensive effects remain enigmatic. Scientists are still divided on some fundamentals of aging, and that's why aging research raises some interesting questions. For example, how does it change the brain? How did different life histories evolve? How old is the oldest blue whale? This special report addresses those questions and more.

I'll link to the first of the articles below, and leave an exploration of the others as an exercise for the reader. That first article is a fairly standard example of this sort of thing, covering a few recent and more publicly discussed research initiatives in the field. As is usually the case, it largely focuses on ways to modestly slow aging, such as calorie restriction mimetic research, or to spur greater stem cell activity in old individuals, such as some of the leads resulting from parabiosis research. It omits any explicit mention of the SENS approach to rejuvenation research, which is, sadly, still par for the course, even as it examines some of the current progress in senescent cell clearance, a topic that has been on the SENS list for fifteen years at this point. That was a decade in advance of any meaningful attempts to remove senescent cells in the laboratory, and it is worth recalling that, as for other aspects of SENS, this was mocked within the scientific community at the time. Those who said as much back then now largely pretend that they agreed this was a viable approach all along; such is human nature. The SENS vision for medical control of aging hasn't changed, and is well known in the field now, but still working its way to greater material support. So when a journalist calls up half a dozen researchers to chat about their research the odds are still pretty good that none of those worthies will have any aspect of the presently active SENS programs in his or her list of pet topics.

This is unfortunate, as it means that most popular science journalism continues to propagate an unrealistic view of the near future of aging research, especially when it comes to expectations for the odds of greatly extending the healthy human life span. There is an opportunity to be seized here, a way to build rejuvenation therapies that can extend life to a far greater extent than is possible via approaches such as calorie restriction mimetics, trials of drugs like metformin, or other marginal strategies that aim to alter the operation of metabolism so as to slightly slow aging. Putting SENS repair strategies like senescent cell clearance side by side with calorie restriction mimetics is to create a false equivalence - these things are not the same at all. Repair can in principle create rejuvenation and indefinite healthy life spans, only limited by the quality of the repair implementation. All of these other technologies to slightly slow aging can do no such thing: they are very limited in comparison, and even if perfected can at most add a few years to human life spans. There is a huge difference between repairing the damage that causes aging and merely slowing down the accumulation of that damage, and that difference is being ignored by people who should know better. Why does this matter? Because building the rejuvenation therapies envisaged in great detail in the SENS proposals, some of which are coming into being in a few startup companies at the present time, requires large-scale support: money, advocacy, discussion, and most importantly widespread understanding.

A healthy old age may trump immortality

On the inevitability scale, death and taxes are at the top. Aging is close behind. It's unlikely that scientists will ever find a way to avoid death. And taxes are completely out of their hands. But aging, recent research suggests, is a problem that science just might be able to fix. As biological scientists see it, aging isn't just accumulating more candles on your birthday cake. It's the gradual deterioration of proteins and cells over time until they no longer function and can't replenish themselves. In humans, aging manifests itself outwardly as gray hair, wrinkles and frail, stooped bodies. Inside, the breakdown can lead to diabetes, heart disease, cancer, Alzheimer's disease and a host of other problems.

Scientists have long passionately debated why cells don't stay vigorous forever. Research in mice, fruit flies, worms and other lab organisms has turned up many potential causes of aging. Some experts blame aging on the corrosive capability of chemically reactive oxygen molecules or "oxidants" churned out by mitochondria inside cells. DNA damage, including the shortening of chromosome endcaps (called telomeres) is also a prime suspect. Chronic, low-grade inflammation, which tends to get worse the older people get, wreaks so much havoc on tissues that some researchers believe it is aging's prime cause, referring to aging as "inflammaging." All these things and more have been proposed to be at the root of aging.

Some researchers, like UCLA's Steve Horvath, view aging as a biological program written on our DNA. He has seen evidence of a biological clock that marks milestones along life's path. Some people reach those milestones more quickly than others, making them older biologically than the calendar suggests. Others take a more leisurely stroll, becoming biological youngsters compared with their chronological ages. Many others, including Richard Miller, a geroscientist at the University of Michigan, deny that aging is programmed. Granted, a biological clock may measure the days of our lives, but it's not a ticking time bomb set to go off on a particular date. After all, humans aren't like salmon, which spawn, age and die on a schedule. Instead, aging is a "by-product of running the engine of life," says biodemographer Jay Olshansky of the University of Illinois at Chicago. Eventually bodies just wear out. That breakdown may be predictable, but it's not premeditated.

Despite all the disputes about what aging is or isn't, scientists have reached one radical consensus: You can do something about it. Aging can be slowed (maybe even stopped or reversed). But exactly how to accomplish such a counterattack is itself hotly debated. Biotechnology and drug companies are developing several different potential remedies. Academic scientists are investigating many antiaging strategies in animal experiments. (Most of the research is still being done on mice and other organisms because human tests will take decades to complete). Even researchers who think they have finally come up with real antiaging elixirs say they don't have the recipe for immortality, though. Life span and health span, new research suggests, are two entirely separate things. Most researchers who work on aging aren't bothered by that revelation. Their goal is not necessarily extending life span, but prolonging health span - the length of time people live without frailty and major diseases.

The glass half full view, to counter my glass half empty points above, is that one of the SENS approaches to treating the causes of aging has finally taken wing and left the nest in these past few years. Senescent cell clearance now appears in popular science articles, is worked on by a number of unaffiliated research groups, has demonstrated life extension in mice, and is under clinical development in multiple companies. As removal of senescent cells proves its worth, other lines of SENS research, other forms of damage to be repaired to create rejuvenation, and the overall strategic approach of focusing on damage and its repair, will gain greater support.



The protein gadd45a and its relatives in the same group are involved in many processes relevant to aging, and can be adjusted to modestly extend life in flies. Gadd45a is in particular implicated in muscle atrophy, a process that significantly contributes to frailty in aging, and here researchers continue to dig into the biochemistry of this relationship:

Skeletal muscle atrophy is a serious and highly prevalent condition that remains poorly understood at the molecular level. Previous work found that skeletal muscle atrophy involves an increase in skeletal muscle Gadd45a expression, which is necessary and sufficient for skeletal muscle fiber atrophy. However, the direct mechanism by which Gadd45a promotes skeletal muscle atrophy was unknown. To address this question, we biochemically isolated skeletal muscle proteins that associate with Gadd45a as it induces atrophy in mouse skeletal muscle fibers in vivo.

We found that Gadd45a interacts with multiple proteins in skeletal muscle fibers, including, most prominently, MEKK4, a MAP kinase kinase kinase that was not previously known to play a role in skeletal muscle atrophy. Furthermore, we found that, by forming a complex with MEKK4 in skeletal muscle fibers, Gadd45a increases MEKK4 protein kinase activity, which is both sufficient to induce skeletal muscle fiber atrophy and required for Gadd45a-mediated skeletal muscle fiber atrophy. Together, these results identify a direct biochemical mechanism by which Gadd45a induces skeletal muscle atrophy and provide new insight into the way that skeletal muscle atrophy occurs at the molecular level.


Researchers suggest, from an examination of epidemiological data, that stroke is for most patients a preventable occurrence largely driven by hypertension, inactivity, and obesity. In this the implication is that better life choices in the environment of present day medical technologies could push stroke to occur at greater ages, such that most older people would die from other consequences of aging first - more a matter of postponement than prevention per se. Lowering age-related increases in blood pressure is known to lower the risk of all cardiovascular issues, and the effects of inactivity and obesity on life expectancy and risk of age-related disease are well proven. Hypertension is driven by stiffening of blood vessels, which is caused at root by fundamental damage processes such as cross-linking in blood vessel walls, inflammation due to the presence of senescent cells, and so forth. The bad life choices mentioned above will speed up stiffening in blood vessels and consequent hypertension, but this end state will still exist, further down the line, even for those people who live the healthiest lives. This will continue to be the case until new therapies are built to repair the root causes - which should in my opinion be the highest priority, over and above campaigns aimed at adjusting behavior.

Hypertension (high blood pressure) remains the single most important modifiable risk factor for stroke, and the impact of hypertension and nine other risk factors together account for 90% of all strokes, according to an analysis of nearly 27,000 people from every continent in the world. Stroke is a leading cause of death and disability, particularly in low-income and middle-income countries. The two major types of stroke include ischaemic stroke (caused by blood clots), which accounts for 85% of strokes, and haemorrhagic stroke (bleeding in the brain), which accounts for 15% of strokes. Prevention of stroke is a major public health priority, but needs to be based on a clear understanding of the key preventable causes of stroke. This study builds on preliminary findings from the first phase of the INTERSTROKE study, which identified ten modifiable risk factors for stroke in 6,000 participants from 22 countries. The full-scale INTERSTROKE study included an additional 20,000 individuals from 32 countries in Europe, Asia, America, Africa and Australia, and sought to identify the main causes of stroke in diverse populations, young and old, men and women, and within subtypes of stroke.

To estimate the proportion of strokes caused by specific risk factors, the investigators calculated the population attributable risk for each factor (PAR; an estimate of the overall disease burden that could be reduced if an individual risk factor were eliminated). The PAR was 47.9% for hypertension, 35.8% for physical inactivity, 23.2% for poor diet, 18.6% for obesity, 12.4% for smoking, 9.1% for cardiac (heart) causes, 3.9% for diabetes, 5.8% for alcohol intake, 5.8% for stress, and 26.8% for lipids (the study used apolipoproteins, which was found to be a better predictor of stroke than total cholesterol). Many of these risk factors are known to also be associated with each other (e.g. obesity and diabetes), and when combined together, the total PAR for all ten risk factors was 90.7%, which was similar in all regions, age groups and in men and women.


With age, harmful waste products accumulate in cells as a normal side-effect of cellular processes. Some of these cannot be easily degraded and build up inside the recycling units called lysosomes, especially in the long-lived cells of the nervous system. This includes retinal cells, and there this process contributes to conditions such as macular degeneration. Lysosomes become bloated and dsyfunctional, unable to perform their normal tasks of braking down waste and damaged cellular structures. Here, researchers identify another essential role for lysosomes in retinal cells, and it is not unreasonable to propose that this, too, suffers because of the build up of waste materials. The SENS approach to this problem is to create new drugs, usually based on mining the bacterial world for suitable enzymes, that can break down some of the worst of the problem waste compounds. This is presently under active development at Ichor Therapeutics.

A research team has pinpointed how immune abnormalities beneath the retina result in macular degeneration, a common condition that often causes blindness. Although macular degeneration eventually damages or kills the light-sensitive rods and cones, it starts with injury to the retinal pigment epithelium (RPE). The RPE, a single layer of cells beneath the rods and cones at the back of the eye, performs many functions essential for healthy vision. The damage starts with a disturbance of immune proteins called complement, which normally kill disease-causing organisms by boring holes in their cell membranes.

"The light-detecting cells in the retina are totally dependent on the RPE for survival. but the RPE cells are not replaced through the lifespan. So we asked, 'What are the innate protective mechanisms that keep the RPE healthy, and how do they go awry in macular degeneration?'" Researchers focused on two protective mechanisms: the protein CD59, which regulates complement activity when attached to the outside of RPE cells; and lysosomes, spherical structures that plug pores created by the complement attack. Together, they offer an in-depth defense. "CD59 prevents the final step of attack that forms the pore. Once a pore forms, the cell can move a lysosome to close it."

If the complement attack is not defeated, the opening in the RPE cell membrane allows the entry of calcium ions, which spark a long-term, low-grade inflammation that inhibits both protective mechanisms, creating a vicious cycle of destruction. The inflammation in the RPE damages mitochondria, structures that process energy inside all cells. This could eventually lead to a decline or death of the photoreceptor cells, once they are deprived of their essential housekeepers. The result is the loss of central, high-resolution vision. Crucially, the study identified the enzyme aSMase that is activated by excess cholesterol in the RPE, which neutralizes both protective mechanisms, and found that drugs such as desipramine used to treat depression neutralized that enzyme and restored the protection - and the health of RPE cells - in a mouse model.


There are plenty of results from the past decade to illustrate that the methodology by which a therapy is delivered makes a great deal of difference to the outcome in patients. Here, for example, researchers have found a way to improve the performance of viruses engineered to preferentially target cancer cells. We've been hearing less of this approach to cancer in the past few years, given the progress and more widespread support for cancer immunotherapy as a technology platform, but there are still many researchers working on the use of viruses in targeted cancer therapy, and a number of promising studies have resulted.

The researchers found that injecting oncolytic viruses (viruses that target cancer cells) intravenously into the spleen boosts immune response faster and higher than traditional vaccine methods. Typically, physicians need to wait weeks or months to administer a booster vaccine, with the down time potentially deadly. "Normally, you have to wait until the immune response is down to administer the booster vaccine, but this means that, with severe and dangerous diseases, the response would wane. You don't want to give cancer any time to spread. What injecting the viruses into the spleen does is it allows us to bypass the regulatory mechanism that would limit its effectiveness. When we conducted these tests in animals, we saw high success rates in treatment of cancer."

The findings apply to many types of cancer, including breast cancer, leukemia, prostate cancer and osteosarcoma (bone cancer), and tumours in the brain, liver and skin. The researchers conducted the tests in mice, and in cats brought to their veterinary center. Trials on dogs should begin within the next year. Under traditional treatment options, the tumours grew and mice died. When the researchers started injecting the viruses into the spleen, the tumours disappeared. "By getting the vaccine to this unique location in the body, we were able to get an unprecedented immune response in minimal time. This is a fundamentally new way to treat cancer that bypasses many common side effects. These therapies are safer and more targeted." The findings are already leading to clinical trials for people, and the study could help researchers in other fields, including those looking to treat virulent diseases. "This research focuses on cancer, but certainly these findings would be applicable to other diseases. We just need to connect with people in those fields."


This popular science article examines a few of the current efforts to build the foundation for therapies to treat aging and its consequences, with a particular focus on parabiosis research in which the circulatory systems of old and young individuals are linked. This approach is being used to investigate differences in levels of gene expression that occur with age, most likely in reaction to rising levels of cell and tissue damage, and especially those changes connected to decline in stem cell function. A promising sign for the near future of advocacy for longevity science is that journalists, such as the author of this piece, are starting to understand the importance of treating the root causes of aging and age-related disease, rather than focusing on each disease of aging in its late stages and trying to patch over the consequences.

First, let's go over what will happen to us as we grow old. Sometime after age 50, depending on personal genetics and life history, our gums withdraw, we lose our hair, our saliva glands falter, and our teeth grow brittle and break off or fall out. Our skin gets thinner, less flexible; it sags, wrinkles, and is discolored by "liver spots." Our bones lose density and strength and shrink in size as our joints swell. Our shoulders slump, our spines buckle and hump. Our muscles atrophy and waste away so we lose mobility as we grow progressively weaker. Our balance and hearing deteriorate. Our eyes dry and lose their ability to focus, so we're more likely to fall, and our bones break more easily. We're slower to heal and more vulnerable to infection as we do, if we do. Hormone levels change. Our memory fails, and most of us, almost all of us, will develop dementia if we live long enough.

Living until 120, the life-span traditionally attributed to Moses, seems more like a curse than a blessing. But it doesn't have to be that way. I've spent the last year talking with scientists around the world about why we've been so successful treating the diseases of youth and middle age and yet haven't made similar progress against end-of-life afflictions. What I found is that scientists at Stanford, Harvard, USC, Wake Forest, UC Berkeley, San Francisco, USC, and Cambridge University, at Scripps Institute, the SENS Research Foundation, and Buck Institute for Research on Aging are unanimous in agreement: Science has gained the ability to intervene successfully in the aging process and to delay and to selectively reverse its effects. The speed at which these new technologies and techniques - which now exist - move from the lab to the clinic is directly dependent on public awareness and support.

Scientists have traditionally studied diseases separately because they have separate pathologies. Heart disease mostly comes from accumulated fat deposits clogging arteries, cancers from DNA damage, Alzheimer's and other dementias from damaged brain cells, etc. - and each disease has multiple contributing factors. But they share a common feature: Aging drives them all. If we delay aging and rejuvenate organs, tissues, and cells, we can prevent or remediate them all. Although aging is the major risk factor for developing most adult-onset diseases, systematic investigations into the fundamental physiology, biology, and genetics of aging are only just beginning. Yet there's good reason to be confident that moving away from the "infectious disease" model and shifting research funding from individual diseases of aging to the basic biology of aging will be productive.


Cytomegalovirus (CMV) is one of the most prevalent of the many forms of persistent herpesvirus that our immune system cannot effectively clear from the body. It has few obvious immediate effects in most people, and you probably never noticed when you were first infected. The overwhelming majority of people test positive for infection by the time old age rolls around. There exists a range of fairly compelling evidence to suggest that long-term CMV infection is a primary cause of immune system dysfunction in aging, and the paper linked here adds to that collection. There are only so many immune cells that can be supported at once by our adult biology, and an ever larger fraction of this capacity becomes uselessly specialized to CMV, unable to respond to new threats. The best treatment for this problem isn't to get rid of CMV, as that probably won't greatly help people with very damaged immune systems, but to remove the unwanted immune cells and replace them with fresh new cells that can do their jobs.

Epigenetic mechanisms such as DNA methylation (DNAm) have a central role in the regulation of gene expression and thereby in cellular differentiation and tissue homeostasis. It has recently been shown that aging is associated with profound changes in DNAm. Several of these methylation changes take place in a clock-like fashion, i.e. correlating with the calendar age of an individual. Thus, the epigenetic clock based on these kind of DNAm changes could provide a new biomarker for human aging process, i.e. being able to separate the calendar and biological age.

Information about the correlation of the time indicated by this clock to the various aspects of immunosenescence is still missing, however. As chronic cytomegalovirus (CMV) infection is probably one of the major driving forces of immunosenescence, we now have analyzed the correlation of CMV seropositivity with the epigenetic age in the Vitality 90+ cohort of birth year 1920 (122 nonagenarians and 21 young controls, CMV seropositivity rates 95% and 57%, respectively). The data showed that CMV seropositivity was associated with a higher epigenetic age in both of these age groups (median 26.5 vs. 24.0 in the young controls and 76.0 vs. 70.0 in the nonagenarians). Thus, these data provide a new aspect to the CMV associated pathological processes.


Most people and most organizations consider the present to be a good model for the future, and base long-term plans on present trends. They are always surprised by change, despite living in an era characterized by rapid change driven by technological progress. The present slow upward trend in remaining human life expectancy at age 65 - perhaps a year every decade - is not the result of any deliberate effort to intervene in the aging process. It is a byproduct of general improvements in the medical technology that is used to attempt to patch over the consequences of aging at the late stage: efforts to keep a damaged machine running without fixing the damage, in other words. This is challenging and expensive, but nonetheless as biotechnology advances small gains are achieved. How very much faster and more effective will this be when the research community redirects its attention to the causes of aging? That is the question, and it isn't hard to see that there is a world of difference between repairing the damage that causes dysfunction and ignoring that damage.

Yet most people don't pay attention to what is going on in the lab, to what is under development in startups, or to what the scientific community is saying, but rather only to existing products that are widely available and well advertised. As a consequence they will be surprised, and potentially unprepared to take advantage of new options that can actually achieve rejuvenation to some degree. Retirement will be transformed radically by rejuvenation biotechnology within our lifetimes. New therapies that collectively add decades to life by repairing the damage that causes aging - an option unavailable today - will certainly be a reality in the 2030s, since the first are in clinical development today. You won't hear any of this from the mainstream of financial planning, as illustrated in this article, but as it is reasonably priced rejuvenation therapies and continued participation in the workforce may be the only good option for many people given the absence of savings in most societies today:

First, you were supposed to die at 85. Then 90. Now 95 and even 100 are common defaults when financial planners tell people how much to save for retirement. Except that's nuts. In the U.S., the typical man at age 65 is expected to live another 18 years. The typical woman, about 20. Yet many financial planners contend we should save as if we're all going to be centenarians. That notion so offends adviser Carolyn McClanahan that she confronted a speaker at a financial planning conference who contended that death at 100 should be the default assumption. "Even when you have a 350-pound guy who smokes?" says McClanahan. Advances in medical science "aren't happening that fast."

Some saving is essential. Obviously. But saving for a retirement that ends at age 100 means you'll need a nest egg that's about 40 percent larger than what you'd need for a normal life expectancy. While there's a 70 percent chance that at least one member of a married couple will make it to 85, the odds are only 20 percent either partner will make it to 95, and even lower that anyone will see 100. "Most of our improvements in life expectancy are coming from the decline in child mortality. The actual survival rate of people in their 80s and 90s is not increasing very fast."

If a 35-year-old wanted to replace 60 percent of her current 60,000 salary at age 65, she would need about 1.2 million at retirement age if she expects to live to 85. Stretch that to 100, and she'll need about 1.7 million. (These figures assume 3 percent average annual inflation and a 7 percent return on investments. Your mileage may vary.) Currently most workers (54 percent) have less than 25,000 saved for retirement. Uncertainty about longevity is just one of many unknowns in financial planning, says Bob Veres, a financial planning industry consultant. So-called "safe" withdrawal rates of 4 percent annually may actually be too conservative in most markets. Also, people often spend less as they age, which makes planners' typical assumptions that spending will increase with inflation each year too conservative. Cautious assumptions may stave off lawsuits, Veres says, but they "diminish the spending capacity of people who retire today."


Researchers have demonstrated the ability to build organoids of many different tissue types, starting with just a cell sample. The open access paper linked here is one example of many at the present time. These organoids are tiny sections of functional or partially functional organ tissue, limited in size because the research community has yet to develop a reliable means of incorporating the intricate branching vasculature needed to support thicker and larger masses. Still, this is enough to build useful products, either for research such as drug development or even for transplantation in some cases. For organs that are essentially chemical factories, that function doesn't require the original organ to be exactly replicated in shape and size - transplanting a few dozen organoids grown from the patient's own cells might be good enough to form the basis for a viable therapy.

The idea to construct in vitro 3D tissue-like structures to be used as model system for the respective organ is an appealing experimental approach. The main focus hereby is to exploit the in vivo physiological mechanism that occurs during organ development or healing (regeneration) and to implement similar mechanisms to develop a functional tissue in vitro. Such 3D liver-like structures would for example meet the needs of the pharmacological and toxicological industry for drug screening. The main techniques to generate 3D cellular constructs are either the formation of spheroids or building of tissue-like structures by placing sheets of cells and extracellular matrix components on top of each other. The disadvantage of spheroids is that the cells are distributed randomly without formation of spatial organization i.e., liver spheroids neither possess typical hepatic cord-like alignment of polarized hepatocytes nor sinusoids lined with endothelial cells reflecting the in vivo situation. Similarly, 3D liver models generated using sandwich cultures can never fully recapitulate the true in vivo architecture of the organ. Such ex vivo formation of tissue for most complex organs such as heart, kidney or brain would be very challenging.

However, the liver is exceptional in its ability to regenerate. It is well established that fully differentiated adult liver is capable of regeneration as long as a sufficient amount of intact liver remains after damage. Therefore, in principle any differentiated adult liver cell should harbor the potential to proliferate and regenerate to a complex and functional organ under suitable conditions. Indeed, induced-pluripotent stem cells (iPSC) stimulated to become hepatic endoderm-like cells (iPSC-HE) together with mesenchymal stem cells (MSC) and human umbilical vein endothelial cells (HUVEC), self-organize in vitro into macroscopically visible 3D cell clusters by an intrinsic organizing capacity. When these structures were transplanted into mice, they became vascularized, engrafted into the recipient's tissue and produced hepatic factors like albumin. Possible applications of such an organoid structure include replacement therapy but also the possibility to study hepatotoxic effects of new compounds. They could as well be used as simplified model system to investigate processes like liver regeneration, fibrogenesis or malignant transformation. Due to the fact that these organoids are formed out of different cell types, which are in 3D contact to each other, they can be expected to represent a system which is much closer to the depicted in vivo situation than conventional approaches.

In the present work we analyzed if liver organoids could also be generated from adult, differentiated cells and if these organoids can be cultured for long-term to study liver functions. Instead of stem cells, hepatocytes were used to reflect the parenchymal cells of the liver. In order to depict the native physiological condition of liver, we further used liver sinusoidal endothelial cells (LSECs) instead of conventional endothelial cells like HUVECs. LSECs are a specialized type of scavenger endothelial cells that are able to endocytose an array of physiological and foreign macromolecules and colloids from the blood. The generation of these cells involves stable transduction of primary cells with lentiviral constructs carrying sequences which code for certain proliferation-inducing factors. These cells are cultured in medium containing a defined mixture of growth factors, allowing tighter control over proliferation (up to 40 population doublings). Employing this process, almost unlimited numbers of cells from one donor can be obtained. Our results show that liver organoids can be generated and these organoids after culturing them for a period of 10 days, express several marker proteins, genes and enzymes to a degree that is comparable to adult human liver. Furthermore, the architecture of these liver organoids to some degree resembles typical hepatic structures.


The stem cells responsible for muscle growth and regeneration are perhaps the best studied of such populations. It seems that most of the new and interesting insights into the nuts and bolts of stem cell biology are coming from this part of the field, in any case. The therapies emerging from research along these lines should include ways to restore the diminished activity of stem cells in older people, with effects most likely similar to present stem cell therapies, but with greater control and selectivity in outcomes. In particular, researchers are very interesting in finding ways to boost muscle growth in older people in order to compensate for the characteristic loss of muscle mass and strength that occurs with aging.

Researchers found that levels of a single protein known as AUF1 determine whether pools of stem cells retain the ability to regenerate muscle after injury and as mice age. Changes in the action of AUF1 have also been linked by past studies to human muscle diseases. More than 30 genetic diseases, collectively known as myopathies, feature defects in this regeneration process and cause muscles to weaken or waste away. Clinical presentation and age of diagnosis vary, but "this work places the origin of certain muscle diseases squarely within muscle stem cells, and shows that AUF1 is a vital controller of adult muscle stem cell fate."

The study results revolve around one part of gene expression, in which the instructions encoded in DNA chains for the building of proteins are carried by intermediates known as messenger RNAs (mRNAs). Proteins comprise the body's structures, enzymes and signals. The expression of certain genes that need to be turned on and off quickly is controlled in part by the targeted destruction of their mRNA intermediates, a job assigned to proteins like AUF1. The investigators found that among the functions controlled by mRNA stability is the fate of stem cells. Following skeletal muscle injury, muscle stem cells receive a signal to multiply and repair damaged tissue, a process that the researchers found is controlled by AUF1. Among the mRNA targets of AUF1 in muscle stem cells, they discovered one that encodes a "master regulator" of adult muscle regeneration, a protein known as MMP9. This enzyme breaks down other proteins, ultimately controlling their expression levels.

The investigators showed that they could restore normal muscle stem cell function and related muscle regeneration in mice lacking AUF1 by repurposing a drug developed for cancer treatment that blocks MMP9 activity. "This provides a potential path to clinical treatments that accelerate muscle regeneration following traumatic injury, or in patients with certain types of adult onset muscular dystrophy. We may be able to treat a variety of degenerative diseases by enhancing resident tissue stem cells through targeting MMP9 and its pathways, even those with normal AUF1."


Most aging research starts in short-lived species far removed from our own in the tree of life. There is a trade-off involved: it is much cheaper to explore and experiment with interventions in aging in a short-lived species, but the more distant the species the less likely that the results will be useful for longer-lived mammals. Fortunately many of the fundamental mechanisms relevant to aging are very similar across most of the animal kingdom, and even between yeast and humans. Low-cost exploration is very necessary in a field with little funding and an enormous, complex problem space. Without the use of flies, worms, and other short-lived species, most aging research would simply never happen. In recent years killifish have been inducted into the list of species used for aging research, which is an involved process in and of itself. This article looks at some of the high points:

Of the many varieties of killifish, the turquoise killifish (Nothobranchius furzeri) has the shortest lifespan - the briefest of any vertebrate bred in captivity, ranging from 3 to 12 months depending on strain and living conditions. Using killifish to study ageing is not a new idea. In the late twentieth century, scientists studied ageing in one species, Nothobranchius guentheri, that lives for about 14 months. But given techniques available at the time, they could come up with only basic descriptions of ageing features. Now, however, advances in molecular analysis have set up excellent conditions in which to develop the model and investigate mechanisms behind its dotage. The killifish's brief lifespan, relative to those of longer-lived models such as mice and zebrafish, enables ageing research to progress apace. And because the fish is a vertebrate, the research is more directly relevant to people than are studies of short-lived organisms such as fruit flies or nematodes.

The ephemeral existence that so appeals to scientists is an evolutionary adaptation to the fish's natural environment: their accelerated development enables them to live and reproduce in transient mud pools during the wet season in equatorial Africa. But that begged another question: would killifish age in a way that parallels the human process? The answer is yes: the fish do get 'old' before they die. Having shown that killifish decline with age, scientists now want to understand how the process occurs. One key resource is the collection of several strains from Africa whose genomes are not identical. By cross-breeding two strains, researchers created fish with a range of lifespans. They then compared the genomes and longevities of parent and second-generation progeny, and identified a few chromosomal regions, each with hundreds of genes that might influence ageing. Although these did not directly reveal genes involved in longevity, they suggested possible candidates. From this study, the scientists estimated that about 32% of variation in lifespan among turquoise killifish results from genetics, a figure comparable to the 20-35% estimated genetic contribution in mice.


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