Evidence to date suggests that we retain diverse populations of stem cells - and the resulting processes by which new cells and tissue are generated - throughout our lives. Stem cells don't go away as we age, but rather age-related changes in our biochemistry act to suppress the action of those cells. When we better understand these biochemical changes, it may be possible to restore the regenerative capacities of the aged through comparatively simple manipulation of signaling processes in the body. Here are a couple more papers to add to the weight of science behind this supposition:

Neurogenesis in the aging brain:

Neurogenesis, or the birth of new neural cells, was thought to occur only in the developing nervous system and a fixed neuronal population in the adult brain was believed to be necessary to maintain the functional stability of adult brain circuitry. However, recent studies have demonstrated that neurogenesis does indeed continue into and throughout adult life in discrete regions of the central nervous systems (CNS) of all mammals, including humans. Although neurogenesis may contribute to the ability of the adult brain to function normally and be induced in response to cerebral diseases for self-repair, this nevertheless declines with advancing age. Understanding the basic biology of neural stem cells and the molecular and cellular regulation mechanisms of neurogenesis in young and aged brain will allow us to modulate cell replacement processes in the adult brain for the maintenance of healthy brain tissues and for repair of disease states in the elderly.

Epidermal stem cells are retained in vivo throughout skin aging:

In healthy individuals, skin integrity is maintained by epidermal stem cells which self renew and generate daughter cells that undergo terminal differentiation. It is currently unknown whether epidermal stem cells influence or are affected by skin aging. We therefore compared young and aged skin stem cell abundance, organisation, and proliferation. We discovered that despite age associated differences in epidermal proliferation, dermal thickness, follicle patterning, and immune cell abundance epidermal stem cells were maintained at normal levels throughout life. These findings, coupled with observed dermal gene expression changes, suggest that epidermal stem cells themselves are intrinsically aging resistant and that local environmental or systemic factors modulate skin aging.

Cancer is the big potential problem associated with any "put the stem cells back to work" strategy. It is probable that evolutionary pressures have led to biochemistries in which generative processes diminish with age, thereby reducing the risk of cancer due to damaged stem cells. It's a balanced trade-off between losing capacity and the harm caused by runaway, damaged cells. But we have to fix cancer anyway, if we'd like to live much longer, healthier lives - and the near-term for cancer medicine is very rosy, even if complete prevention and absolute cures are still decades in the future.

I pointed out a paper in passing a few weeks back, in which researchers put forward a model to explain how some species can evolve extreme longevity, or even agelessless (or negligible senescence).

How can evolution, biased to early reproductive success at all reasonable cost, produce such a species?

As it turns out, there may be some plausible scenarios - which is a good thing, given the fact that many extremely long-lived animal species exist, and that some might indeed be ageless. Problems arise for any theory that cannot explain the outliers. Chris Patil has given this work a great deal more attention over at Ouroboros, and you should take look.

The evolution of negligible senescence:

The authors describe in detail two organisms - the Bristlecone pine and Arctic quahog - that exhibit density-dependent recruitment. In both species, sessile adults live in crowded but stable conditions in which new opportunities for maturation arise rarely. In such situations, it behooves an individual organism to outlive its neighbors, so that when they die its seedlings or larvae have a place to dig in and grow up. In such contexts, the authors argue, natural selection can trigger an anti-aging arms race that results in negligible senescence as a consequence of runaway selection.

The evolution of negligible senescence, part II: Organisms that are remotely like us:

But does the evolutionary theory that explains the emergence of negligible senescence in trees and clams have anything to teach us about how long-lived species arise from short-lived stock? If so, are those lessons in any way portable to mammals? Possibly.

...

One famous example of a species with far greater longevity than similarly sized species of comparable body plan, the naked mole rat, is also territorial and eusocial. It is tempting to speculate that mole rat queens, like their peers among the harvester ants, have evolved long lifespans in order to wait out their competitors in other burrows.

...

Mole rats are no less similar to humans than lab mice are. Therefore, biogerontologists are very interested in learning the detailed mechanisms by which mole rats have delayed senescence, since it’s likely (more likely than for clams and trees, anyway) that these details might be of some practical use to us.

The most important lesson to learn from an examination of the huge range in animal - even mammal - longevity is that it is possible to design better humans with the biotechnology of tomorrow. Longer lived, less diseased, less prone to aging. That is the driving goal behind much of the mainstream work in metabolism, genetics and aging these days. It'll be a long time in the making, however - a truly massive undertaking of great scope and complexity.

While that great work is underway, we should devote more resources to the easier path to longevity: learning how to repair the humans we have now.

My attention was drawn to a Spanish article on one of the many research groups investigating the role of p53 in aging and cancer. There has been a great deal of interest in finding ways around the "cancer or aging, choose one" limitation to this set of biochemical mechanisms, thought to apply until recently. This Spanish article is somewhat in advance of the scientific publication; I'm not sure why that is the case.

The translation via Google is fair (suggestions taken on a better translation automaton):

In this line, Serrano said that the genomes of a chimpanzee and humans are virtually identical at 99.8%. However, the maximum life of a chimpanzee is 60 years and the human rarely exceeds 110. The average of a chimpanzee is 40 years and that of a human, 80. There must be something in our genes very subtle changes made to live 50 years to live 100. Then, along with the team of Mary Blasco, we are going to make some genetic manipulation to see if we can increase longevity in mice much more. That is our challenge If we get a mouse in the privileged environment of a laboratory comes to live three years to live six passes, it would be proof that longevity is flexible and would know how to enlarge it.

So it seems compelled to ask the molecular biologist in this battle if they have undertaken together against cancer and aging, it is just a matter of putting telomerase a mouse to make it immortal. The answer is no, because telomerase makes more cancer. To ensure a tumor, which has activated telomerase, and if a mouse has more telomerase than normal, for example, on transgenic mice, we know that you have more tumors. What we have done is to use the superratones Manuel, because p53 protects cancer and a 18% lengthens the life of mice, and if we add to this the gene of immortality, telomerase, which got these mice [to] live an average of 50% more, without cancer, which are words older. That is what we have discovered now.

Because this extension of life, 50% in superratones is the longest that has been described in mammals.

You get the gist, despite the breakdown of translation in the last few sentences: there are combinations of metabolic and genetic states in mammals not selected for by evolution that nonetheless lead to a clearly superior beast, from our perspective at least. Well, more or less. If you head over to the Methuselah Foundation forums, you'll find that Michael Rae wrote a long piece on this research back in mid-2007, before the life span studies were complete:

The standard reading is that the "Super p53" mice are getting less cancer, but are having their [life spans] restrained by lack of tissue replenishment due to stem cell loss, while the telomerase transgenics are on the opposite horn of the same dilemma. It seems at least possible that if one overlaid the strong cancer resistance conferred by the former, with the increase in stem cell mobilization and proliferative capacity of the latter, you'd wind up with a long-lived, slow-aging mouse.

There are a lot of caveats and details both prior and after that statement, many of which still apply even with these final life span study results. It's not all completely clear-cut, as is often the case, but I can see this impressive work garnering a great deal of attention in the popular press once it jumps the language gap for the English-speaking world.

The full content of the December 2007 issue of Rejuvenation Research is presently freely available. These promotions don't last too long, so take a look while it's available - there's a lot of good reading in there. For example, Aubrey de Grey's piece on the balkanization of gerontology (PDF):

In my view, the divide between biogerontologists and other gerontologists concerning the desirability of combating aging is a symptom of the pitifully limited amount of communication between these subfields. Though they study facets of the same phenomenon, these researchers' actual contact is very nearly nil. It is thus no surprise that such fundamental differences of opinion persist. Whether anyone is really to blame for this "balkanization" of the field is debatable: it exists in a more limited way even within biogerontology, and the reasons are probably the same, revolving around the much higher priority (in career terms) of maintaining prestige among those who know and understand one’s work best than of disseminating it to others.

There has long been a recognition that this balkanization is regrettable, and token measures have been taken to diminish it: for example, the Gerontological Society of America (GSA) brings together all the gerontological specialties under one roof every November. But token is all these measures are: as anyone who has attended the GSA’s annual meeting will tell you, the event is indistinguishable from a coincidence of three or four conferences going on in the same building at the same time.

Alternately, William Bains' pointed commentary on views of death and aging (PDF):

no one will ever be in a position to ask, "Should I live forever?" We will be asked another, harder question. It is my contention that we should debate that question, and yes debate it in terms of its possible, long-term, science fictional implications if you like, but do not pretend the debate is ‘about’ whether people should seek physical immortality. It is about something more complicated, less black-andwhite, and much more immediate.

...

The question is not, "Do you want to live forever?" The question is, "Do you want to die tomorrow?" Replacing "should we live forever" with "do you want to die tomorrow?" strips away the sheer nonsense that is spouted about what 'might be,' and brings us back to specifics. Many people state firmly that they do not want to live forever. Many say they would not want to live beyond 100. Usually they are less than 60 years old when they say it (few 95-year-olds hold this view; very few 99-year-olds). But these people appear genuinely to feel that they do not want to live to be 100. So they do not want to live another 50 years. Do they want to die tomorrow? No. If I ask again tomorrow, will they want to die the day after? No.

Also an interview with Paul F. Glenn of the Glenn Foundation for Medical Research (PDF):

In our view, aging research is drastically underfunded. Promising opportunities must be pursued, such as the emergence of stem cell research, which offers the possibility of new therapies for treating or renewing diseased tissues or organs.

The growth of an aging population will bring treasury-breaking healthcare costs unless health can be maintained and age-related diseases delayed or cured. Human suffering that accompanies age-related disease is not just a financial burden.

It's a pity that all this more broadly interesting content ends up behind the paid firewall. I can imagine that all parties involved in publishing Rejuvenation Research would be better served by a journal in which the content above - very interesting and accessible to the layperson - is open while the research publications remain as paid access only. If you want more people to see what you have to say, open access is the way to go, and those in the research community who pay for the journal will pay for it regardless of the non-research content.

Far too much is going on in the field of stem cell research to give more than a flavor of progress in any document of a reasonable length, but here are a few interesting items that caught my eye today.

Elusive pancreatic stem cells found in adult mice:

Just as many scientists had given up the search, researchers have discovered that the pancreas does indeed harbor stem cells with the capacity to generate new insulin-producing beta cells. If the finding made in adult mice holds for humans, the newfound progenitor cells will represent "an obvious target for therapeutic regeneration of beta cells in diabetes"

If the past couple of years have made anything clear, it's that an absence of stem cells in a particular organ or tissue means that researchers aren't looking hard enough. A steady stream of newly identified stem cell populations flows through the popular science press, sometimes one a month. An identified population is raw material for first generation stem cell therapies, often based on autologous transplantation, that aim to kick-start existing regenerative and growth processes to heal what the body will not heal on its own.

Meanwhile, the existing drug research and development community is giving rise to a hybrid school aiming to produce (or repurpose) drugs that can manipulate stem cell behavior in desired ways, controlling growth or regrowth in damaged or wasted tissue:

Building stronger bones, 1 stem cell at a time:

These studies raise the possibility that drug-induced progenitor/stem cell differentiation could be used in vivo to therapeutically modulate bone formation from a primitive reservoir of cells and that an existing clinical-grade drug can be "repurposed" to modulate stem biology. This strategy may be applicable to increase bone volume in the osteolytic disease of malignancy or in osteoporosis, where the function of more mature populations of cells has been compromised.

Aiding the variety of paths presently followed to manipulate stem cell behavior are those researchers who untangle stem cell biochemistry. You can get a machine to do the job if you only have half the instructions, but it's a lot easier with the full set.

Protein that controls hair growth also keeps stem cells slumbering:

Like fine china and crystal, which tend to be used sparingly, stem cells divide infrequently. It was thought they did so to protect themselves from unnecessary wear and tear. But now new research from Rockefeller University has unveiled the protein that puts the brakes on stem cell division and shows that stem cells may not need such guarded protection to maintain their potency.

...

"It seems like the resting phase isn't as necessary as was once thought," says Horsley. "Even though these stem cells are highly proliferative, they still maintain their stem cell character."

This particular immediate application - restoration of hair growth - isn't all that interesting for someone who cares about whether their organs are aging them to death. It will no doubt garner intense interest and investment from the hair restoration industry (which is larger and more involved in fundamental research than you might imagine) and people whose priorities are not quite so in line with healthy longevity. You can live without hair - it's harder to do so with the other degenerations of age, and repairing those other degenerations should be higher on everyone's priority list.

You might recall I posted on the work of Skulachev back in 2006, lamenting the language barrier that causes interesting Russian research to fail to appear in the popular science press. A high level view of the research in question:

The life time of such mice increased by one third on average as compared to that of the reference group mice. Even more demonstrative are experiments with mutant rats, where accelerated ageing - progeria - was observed. SkQ prolonged their life span by three times, besides, it cured them from a large number of senile diseases. They include infarctions, strokes, osteoporosis, hemogram abnomality, reproductive system disorders, behavior change, visual impairment.

...

Instead of gene therapy, Skulachev's group has found a viable biochemical strategy for effectively localizing ingested antioxidants in the mitochondria; clever.

Skulachev's past results appear to lead to similar life span extension in mice to the work of Rabinovitch in gene engineering antioxidant catalase into mitochondria. All this adds to the general weight of evidence suggesting that antioxidants are spectacularly useless unless carefully directed in our biochemistry. Of all the places you can target antioxidants, it seems that the mitochondria is the most effective discovered to date: not too surprising considering the role of mitochondria in oxidative damage related to aging.

Your mitochondria are a source of a whole lot of biochemical trouble as the years go by. Damaged mitochondria proliferate in some cells and, like damaged factories, pollute those cell with excess reactive oxygen species and free radicals produced as metabolic byproducts. Each damaged cell then tries to maintain itself by exporting more reactive oxygen species and free radicals from its cell membrane structures, spreading the damaging pollution far and wide in the body.

I noticed a more recent paper from Skulachev while meandering through PubMed today:

A biochemical approach to the problem of aging: "megaproject" on membrane-penetrating ions. The first results and prospects.

Antioxidants specifically addressed to mitochondria have been studied for their ability to decelerate aging of organisms. For this purpose, a project has been established with participation of several research groups from Belozersky Institute of Physico-Chemical Biology and some other Russian research institutes as well as two groups from the USA and Sweden, with support by the "Mitotechnology" company founded by "RAInKo" company (O. V. Deripaska and Moscow State University). This paper summarizes the first results of the project and estimates its prospects.

...

In mammals, the effect of SkQs on aging is accompanied by inhibition of development of such age-related diseases as osteoporosis, involution of thymus, cataract, retinopathy, etc. ... Thus, it seems reasonable to perform clinical testing of SkQ preparations as promising drugs for treatment of age-related and some other severe diseases of human and animals.

Investment and further outside scientific collaboration are afoot: it looks like we'll be hearing more of this approach in the years to come.

The weight of research into the biomechanisms of fat tissue continues to grow. It just isn't sensible to be overweight - at least if long-term health and longevity happen to be on your list of goals. Here's the latest update on one of the ways in which excess fat tissue slowly destroys you from the inside:

a team of University of Michigan Cardiovascular Center scientists reports direct evidence of a link between inflammation around the cells of visceral fat deposits, and the artery-hardening process of atherosclerosis.

...

The discovery came partly by chance. He and his colleagues had been studying mice that lack the gene for leptin, a hormone generated by fat cells that plays a role in appetite and metabolism as well as reproduction. In an effort to get these obese mice to produce some leptin, the team developed a technique to transplant clusters of fat cells from normal mice of the same strain, into the leptin-deficient mice.

The result surprised them. “In addition to producing leptin and preventing obesity, the fat transplants became inflamed, attracting immune cells called macrophages” Eitzman explains. “Since the mice were genetically identical except for leptin, this shouldn’t have happened. But the inflammation was there, and it was chronic.”

The inflammation occurred around individual fat cells, or adipocytes. Further tests showed it was regulated by the same factors that regulate the inflammation that other researchers have seen in the naturally occurring fat deposits of obese mice - specifically a chemokine called MCP-1.

But because the fat was transplanted, the inflammation could be attributed directly to the fat, and not to overfeeding of the mice, or the metabolic problems that overfeeding and obesity bring, such as diabetes. Armed with this discovery, the researchers set out to see what was causing inflammation to occur, and what implications it had.

...

“There appeared to be an interaction between the macrophages causing the inflammation in the visceral fat, and the process of atherosclerosis,” says Eitzman, who notes that blood vessels far from the site of the fat transplant developed increased atherosclerosis.

All that excess fat hanging around over the years generates atherosclerosis, which then kills you:

Most commonly, soft plaque suddenly ruptures, [causing] the formation of a thrombus that will rapidly slow or stop blood flow, that is, within 5 minutes, leading to death of the tissues fed by the artery. This catastrophic event is called an infarction. One of the most common recognized scenarios is called coronary thrombosis of a coronary artery, causing myocardial infarction (a heart attack). Another common scenario in very advanced disease is claudication from insufficient blood supply to the legs, typically due to a combination of both stenosis and aneurysmal segments narrowed with clots. Since atherosclerosis is a body-wide process, similar events occur also in the arteries to the brain, intestines, kidneys, legs, etc.

...

According to United States data for the year 2004, for about 65% of men and 47% of women, the first symptom of atherosclerotic cardiovascular disease is heart attack or sudden cardiac death (death within one hour of onset of the symptom).

This is one of the many reasons why people who keep in shape and stick to the health basics tend to live longer, healthier lives.

Change is the one constant you can count on; radical, ongoing change driving and in turn being driven by the relentless advancement of technology. So if you're planning on placing yourself into cryonic suspension on death, how best to ensure that the provision of that storage will continue for the unknown length of time it will take for revival technologies to be developed?

Cryonics, for those new to the party, is a form of low temperature storage of the body, vitrified rather than frozen to preserve the fine structure of your brain and all the information it contains - preserve your self, in other words, waiting for the likely technology of the 2040s or later that can repair and revive a cryopreserved individual. It is very plausible, very sensible and less supported than it should be. Just like serious research into rejuvenation technology, cryonics suffers from the mass acceptance of - and even empassioned advocacy for - aging and death we see in the world today.

But back to the question: how to best ensure the contination of an organization and its resources such that cryopreservation of vitrified customers continues solidly for half a century or longer? For added value, you'd want an organization that contributes to and helps to build the research communities developing revival technologies. You can be sure that a lot of thought has gone into this matter over the decades that cryonics providers have already existed:

For persons entering cryonic suspension in the twentieth century, and for some decades beyond, the success of their venture will be determined primarily by two contingent future circumstances: the development of repair technologies; and the survival of the organizational vehicle which they selected to transport them into the future when those technologies will exist.

...

A fundamental rationale for selecting the self perpetuating Board structure was its ability to provide continuity of purpose over a long period of time. Existing Board members select those new Board members who they believe are best able to preserve Alcor's core values and carry out its mission.

...

Board members have a strong incentive to choose carefully because the success of Alcor and the survival of our members - including our Board members - is heavily dependent on the abilities and character of future Boards of Directors.

...

One of the original rationales for Alcor's self perpetuating Board was to prevent a takeover of Alcor. Because the Patient Care Trust Fund has significant assets, and is growing, the incentive for such a takeover continues to be present today. This argument seems most effective against a member elected Board if all members - even recent members or members whose motives might be viewed as suspect by the majority of established cryonicists - are allowed to vote. Various limitations might be imposed which would significantly reduce this risk. It is clear, though, that this issue would need to be thoroughly explored before making any significant change in Alcor's structure. It is essential that the risk of a takeover - a catastrophic failure mode - be held to a minimum.

Change is like water; it tends to flow along the paths of incentive. Humans are incented by the prospect of obtaining resources, and looting is as much a part of modern society as it ever was in ancient times. The forms are more baroque these days, but the thievery as just as real. You have to do your best to ensure the continuation of resources - and the intent to protect those resources - while you are not going to be there to help out. That has always been a challenge:

Putting your body and brain into cryonic suspension is an educated gamble, we must recognize that much. I think it's a good gamble, since technology is advancing rapidly and comparatively few interests are aligned against you in the matter of revival and returning to a place in society. Trying to put your resources, your wealth, on ice strikes me as a much more risky endeavor - the long history of human attempts to take action or enforce a decision after death should amply demonstrate the futility of attempting to preserve post-mortem vision and wealth from the predations and honest choices of your fellow human beings.

The present Alcor managers recently posted an update that reflects some of their philosophy and intent in these matters. It's well worth reading:

When the Alcor management changed in September 2005 to the current team, we developed a new policy of not talking about what grand plans we have for the organization, instead choosing to talk about things that we have completed. We implemented this policy change because the management team (consisting of Steve Van Sickle, Jennifer Chapman, and myself) were disappointed members. We were all weary of the empty promises, the distinct lack of improvement in technical capability and the lack of responsible fiscal oversight. We very deliberately set out to rebuild Alcor into an organization of which we could be proud, and we were enthusiastic about bringing positive change. Though it is a lengthy process, in my opinion we are succeeding, and we’d like to present a little perspective on the changes of late and on the challenges yet ahead.

Our staff is highly motivated and productive. We have an internal plan of action that the staff has been implementing for the last eighteen months. This plan relates directly to the two things Alcor needs most in order to transition beyond the tiny startup company it has been for the past 35 years: better evidence and professionalism. It presents a plan for developing an infrastructure to meet both technical and administrative requirements that are necessary to a growing membership.

It is good to see management at Alcor, as the leading light of the cryonics industry, saying the right things. Transition from volunteerism to professionalism is vital - it is the good form of change for an organization set on growth. Equally important is the continual critique and improvement of core assumptions, marketing, technology and business models. Alcor has suffered in the past for its failure to generate growth as an organization, but it is encouraging to see the potential for the industry - in terms of investment for research and spin-off technologies, public acceptance, and growth into professional status - to be far greater now than in past years.

For all to many of us, cryonics providers will be the only shot at a much longer, healthier life in the future. It's an ugly reality that we have to face up to and do our best to overcome through work, resources and research.

There have been repeated rumblings on the topic of longevity insurance in the past few years:

Here is a knee-jerk response: unless these products are stunningly bad value for money under very conservative estimates for growth in life expectancy in the old, those companies to offer longevity insurance packages will be taking a bath twenty to thirty years from now. You might recall that the actuaries are wavering on their estimates for life expectancy, and a healthy debate is taking place in the actuarial community as to just how to account for the ongoing revolution in biotechnology and medicine. An insurer that offers fair valued, competitive products today based on the actuarial trends of the past few years will find themselves in trouble down the line if the efforts of groups like the Methuselah Foundation succeed, or even if the systems biologists have their more modest way.

In general, betting against increasing longevity seems to be a fool's game. But even the venerable tontine is making a comeback as the vast - and consequently archly conservative - insurance industry grapples in slow motion with uncertainty brought on by radical change and progress in biotechnology and aging science:

If you die earlier than your scheme's age range, your family receives your original lump sum without any investment gains. But if you live, you will be paid an income which goes up every year depending initially on your investment growth - this is offshore in Ireland so tax is minimised - but also on how many others in the plan die.

The clever part, according to the company, is the so-called "birthday units" - although "deathday units" would be more accurate, as survivors get a regular investment boost from the funds of plan holders who die. Helped by the death of others, a man on an 80 to 100 plan with £50,000 originally invested would get £19,600 a year at 80, rising to £30,600 at 90 and increasing to £257,000 a year 10 years later when he reaches 100. But do its figures stack up? And is it the only solution? "It sounds like a tontine to me," says retirement income expert Nigel Callaghan at Hargreaves Lansdown. A tontine is an old-fashioned form of life insurance where everyone pays in but the last one living scoops the pool.

Looking at the Wikipedia entry for "tontine", I note:

Tontines were the first government bonds issued anywhere in the world, and the British government first issued tontines in 1693 to fund a war against France. However, tontines soon caused problems for their issuing governments, as they would increasingly underestimate the longevity of the population.

Sound familiar? The monolithic, regulated insurance industry of today, faced with the potential of true rejuvenation medicine in the next few decades, isn't looking much better than 17th century governments. It just isn't smart to bet against healthy longevity in the midst of revolution in biotechnology. A great many people will wind up losing their shirts - just make sure you aren't one of them.

Does the accumulation of DNA damage in the cellular nucleus contribute to significantly to aging? How, if so? It is a topic for debate, with a weight of papers behind many of the consensus interpretations, but most of the community would answer "yes" with some variety of qualifications. On the other side, biomedical gerontologist Aubrey de Grey argues that DNA damage - mutations to the DNA contained in the chromosomes - is not important over a normal human life span, except where it causes cancer:

we don't actually need to fix chromosomal mutations at all in order to stop them from killing us: all we need to do is develop a really really good cure for cancer.

Looking back in the Fight Aging! archives, you'll find plenty of theories on how DNA damage might contribute to degenerative aging. A short selection:

• Double strand breaks are the real problem
• Cancer stem cells arise from DNA damage
• DNA damage causes disarray in gene expression, which contibutes to aging
• DNA damage causes age-related reduction in stem cell capacity

And so forth - it isn't hard to find academic arguments for the role of DNA damage in most of the better known age-related degenerations. It's a matter of time, resources for research and scientific debate as to which pan out. Here's another different point of view from a recent paper, focusing on longevity genes and metabolic changes - such as those brought on by calorie restriction - that lead to greater longevity:

Age to survive: DNA damage and aging

Aging represents the progressive functional decline and increased mortality risk common to nearly all metazoans. Recent findings experimentally link DNA damage and organismal aging: longevity-regulating genetic pathways respond to the accumulation of DNA damage and other stress conditions and conversely influence the rate of damage accumulation and its impact for cancer and aging. This novel insight has emerged from studies on human progeroid diseases and mouse models that have deficient DNA repair pathways. Here we discuss a unified concept of an evolutionarily conserved 'survival' response that shifts the organism's resources from growth to maintenance as an adaptation to stresses, such as starvation and DNA damage. This shift protects the organism from cancer and promotes healthy aging.

It's a broad, interesting topic for study, I think you'll agree that much.