There is no Obesity Paradox: Excess Weight is Harmful to Long Term Health

The research results here are from the latest in a line of epidemiological studies to firmly refute the obesity paradox, burying it with more data and better study design, to show that excess weight is very definitely harmful to health and longevity. The obesity paradox was the idea that excess weight - meaning excess fat tissue - could be protective in some circumstances in older individuals, such as in the case of cardiovascular disease. It arose from the combination of (a) flawed study design and (b) human nature. There are a lot of overweight and obese individuals in the world today because technological progress has greatly reduced the cost of calories. As a result more people consume significantly more calories than was the case in even comparatively recent history, and that has the natural consequence of excess fat tissue. People who are overweight, just like all other individuals, tend to want to hear comforting things about their present state. Hard truths are called hard truths for a reason. Thus the incorrect research results, while being widely attacked and then debunked within the scientific community, nonetheless received a great deal of attention from the public at large simply because they said what people wanted to hear.

Unfortunately, excess visceral fat tissue is harmful. The more of that fat tissue carried and the longer it is carried, the greater the negative impact on risk of age-related disease, quality of life, and life span. The more fat tissue, the greater the lifetime medical expense, even as the expected length of life is shorter. Stepping away from epidemiology, the recording of outcomes, to look at the biochemistry of fat tissue, it becomes ever more clear that it would be highly counterintuitive for any overall health benefit to derive from a large amount of visceral fat. Fat tissue generates chronic inflammation through a variety of mechanisms, including generation of senescent cells, and in this way directly accelerates many of the aspects of aging.

How did the original studies - those finding excess weight to be protective - arrive at the incorrect conclusion? Primarily, the researchers failed to account for the weight loss that tends to occur in the more severe stages of age-related disease. Older people who are thin fall into two camps. The first camp have been thin their whole lives, and are comparatively healthy. The second camp have been overweight for much of their lives, and have only recently lost that weight due to the progression of illness. They are comparatively unhealthy and experience higher mortality rates. Without separating out these groups, the ill, thin people greatly distort the overall picture of weight in later life. The open access paper here adds another mechanism that can help to explain the issue, in that obese and overweight individuals appear to be diagnosed with heart disease at earlier stages than is the case for thin people. This breaks some of the assumptions baked into earlier studies regarding duration of illness and time to mortality.

'Obesity paradox' debunked

Obese people live shorter lives and have a greater proportion of life with cardiovascular disease, reports a new study. The study examined individual level data from 190,672 in-person examinations across 10 large prospective cohorts with an aggregate of 3.2 million years of follow-up. The study shows similar longevity between normal weight and overweight (but not obese) people, but a higher risk for those who are overweight of developing cardiovascular disease during their lifespan and more years spent with cardiovascular disease. This is the first study to provide a lifespan perspective on the risks of developing cardiovascular disease and dying after a diagnosis of cardiovascular disease for normal weight, overweight and obese individuals.

"The obesity paradox caused a lot of confusion and potential damage because we know there are cardiovascular and non-cardiovascular risks associated with obesity, I get a lot of patients who ask, 'Why do I need to lose weight, if research says I'm going to live longer?' I tell them losing weight doesn't just reduce the risk of developing heart disease, but other diseases like cancer. Our data show you will live longer and healthier at a normal weight."

The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in overweight middle-aged men 40 to 59 years old was 21 percent higher than in normal weight men. The odds were 32 percent higher in overweight women than normal weight women. The likelihood of having a stroke, heart attack, heart failure or cardiovascular death in obese middle-aged men 40 to 59 years old was 67 percent higher than in normal weight men. The odds were 85 percent higher in obese women than normal weight women. Normal weight middle-aged men also lived 1.9 years longer than obese men and six years longer than morbidly obese. Normal weight men had similar longevity to overweight men. Normal weight middle-aged women lived 1.4 years longer than overweight women, 3.4 years longer than obese women and six years longer than morbidly obese women.

Association of Body Mass Index With Lifetime Risk of Cardiovascular Disease and Compression of Morbidity

Overweight and obesity are highly prevalent in the United States, have increased dramatically over the past 3 decades, and affect approximately 2.1 billion adults worldwide. In recent years, controversy about the health implications of overweight status has grown, given findings of similar or lower all-cause mortality rates in overweight compared with normal-weight groups. However, current studies have not taken into account the age at onset and duration of cardiovascular disease (CVD), limiting the ability to account for proportion of life lived with CVD morbidity in individuals who are overweight and obese compared with normal weight. This is especially important because disease burden associated with development of CVD results in less healthful years of life, poorer quality of life, and increased health care expenditures.

In this large study of US adults free of clinical CVD at baseline, lifetime risk for incident CVD was high for all adults and was greater in adults who were overweight and obese. Adults who were obese had an earlier onset of incident CVD, a greater proportion of life lived with CVD morbidity (unhealthy life years), and shorter overall survival compared with adults with normal body mass index (BMI). In addition, the proportion of adults with incident CVD events (compared with non-CVD death) was significantly higher in adults who were overweight or obese compared with adults in the normal BMI group. Overweight and obesity were associated with increased hazards of incident CVD event after adjustment for competing risks of non-CVD death across all index age ranges.

While health hazards of obesity have long been recognized, recent studies have spurred controversy about the specific relationship between overweight status and mortality. Among these prior analyses, measurement bias may be present owing to inclusion of self-reported height and weight data. Further, inclusion of participants with comorbidities at baseline, specifically prevalent CVD, may contribute to selection and survival bias because of protopathic bias (reverse causation) related to unintentional weight loss. In our study, we were able to leverage long-term follow-up in a large group of adults free of CVD at baseline to estimate risk of incident CVD and associated CVD morbidity (unhealthy years lived with CVD). While we do observe evidence of the well-described overweight and obesity paradox, in which heavier individuals appear to live longer on average after diagnosis of CVD compared with individuals with normal BMI, our data when following up individuals prior to the onset of CVD indicate that this occurs because of a trend toward earlier onset of disease in individuals who are overweight and obese. This false reassurance is akin to the phenomenon of lead-time bias observed in other situations, such as with cancer screening.

Genetic Editing of ANGPTL3 to Greatly Reduce Blood Cholesterol in Mice

There are a few genes in which rare variants have been noted to dramatically lower blood cholesterol and other lipids, thus significantly reducing the progression of atherosclerosis with age. ANGPTL4 is one of them, and based on the work here, so is ANGPTL3. Atherosclerosis is caused by inappropriate reactions to forms of damaged lipids, leading to the formation of plaques that weaken and narrow blood vessels. Lowering overall lipid levels doesn't address these consequences, but it does reduce the input of damaged lipids to the disease process, hence the major industry associated with statin drugs and other methods of reducing lipids in the bloodstream.

In the near future, it seems likely that statins will be replaced by more effective and narrowly targeted genetic means of reducing cholesterol. This has started with therapies in development based on manipulation of PCSK9, producing larger effects than statins. Of interest, studies in recent years have suggested that blood lipids can be reduced to an extremely low level, a tenth of normal amounts or less, with no harm resulting to patients. This may well be a useful general enhancement that everyone undergoes once permanent genetic alteration of adults is a going concern.

People with naturally occurring mutations that cause a loss of function in the gene for ANGPTL3 have reduced blood triglycerides, LDL cholesterol, and risk of coronary heart disease, with no apparent detrimental consequences to their health. This makes the ANGPTL3 protein an attractive target for new heart disease drugs. Earlier studies found that single copies of inactivating mutations in ANGPTL3 are found in about one in every 250 people of European heritage; however, people with mutations in both copies of the gene are more rare.

Researchers assessed in a mouse model whether base editing - a variation of CRISPR genome editing that does not require breaks in the double-strand of DNA - might be used in humans one day to introduce mutations into ANGPTL3 to reduce blood lipid levels. The study took a three-part approach. First, the team injected normal mice with the base-editing treatment for the ANGPTL3 gene. After a week, sequencing of the ANGPTL3 target site in liver samples from the mice revealed a median 35 percent editing rate in the target gene and no off-target mutations. In addition, the mean levels of blood lipids were significantly lower in the treated mice by up to 30 percent compared to untreated mice.

Second, the researchers compared mice with the modified ANGPTL3 gene to those injected with a base-editing treatment for another liver gene, PCSK9, for plasma cholesterol and triglycerides. After a week, ANGPTL3 targeting caused a similar reduction in cholesterol but a much greater decline in triglycerides compared to targeting PCSK9. The PCSK9 protein is the target of currently available medications, including evinacumab, which has been shown to reduce cholesterol (but not triglycerides) as well as the risk of heart attack and stroke.

Third, they looked at how base editing of the ANGPTL3 gene performed in a mouse model of homozygous familial hypercholesterolemia (in which knocking out PCSK9 had little effect). After two weeks, the treated mice showed substantially reduced triglycerides (56 percent) and cholesterol (51 percent) compared to untreated mice. The researchers are now preparing to test CRISPR-based treatments against the human ANGPTL3 gene in human liver cells transplanted into mice. This will provide important information on efficacy and safety that will be needed before human trials can move forward.


A Potential Oxidative Biomarker of Aging in Urine

Since aging is caused by a collection of distinct, interacting processes of damage accumulation and reactions to that damage, it is unlikely that there will ever exist one, unified, undisputed measure of biological age. All present candidate measures of aging are composites of many individual metrics, even the epigenetic clock, which is a specific pattern of many different DNA methylation locations in the genome. New, simple biomarkers of aging that reflect one process or aspect of age-related degeneration are still of interest, however, as they might turn out to improve existing combined measures of aging if added into the mix. So researchers continue to work in this area of development, turning out results such as the data presented in this open access paper.

The rate of aging differs among individuals due to variations in the genetic and environment background. Chronological age, which is simply calculated according to birth date, is an imprecise measure of biological aging. The disconnection between chronological age and lifespan has led to a search for effective and validated biomarkers of aging. A good aging biomarker should be based on mechanisms described by major theories of aging, which mainly include oxidative stress, protein glycation, DNA methylation, inflammation, cellular senescence and hormonal deregulation. The current consensus is that aging is driven by the lifelong gradual accumulation of a broad variety of molecular faults in the cells and tissues.

Any error occurring on a DNA template or in messenger RNA will eventually lead to the production of abnormal proteins. However, the exposure of a double-stranded DNA chain or single-stranded RNA chain to free radicals, which are by-products of normal metabolism, can cause oxidative damage to biomolecules. 8-Oxo-7,8-dihydro-2′-deoxyguanine (8-oxodGsn) is by far the most studied DNA oxidative product. Similarly, mismatch of 8-oxo-7,8-dihydroguanine (8-oxoGsn) in RNA leads to transcriptional errors and produces abnormal protein. These excision products can be transported across the cell membranes and excreted into cerebrospinal fluid, plasma, and urine without any further metabolism.

Under the free radical theory of aging, urinary 8-oxodGsn and 8-oxoGsn are molecules that may reflect the oxidative state of the whole body rather than a specific organ, and these are promising biomarkers of aging. We previously established a liquid chromatography-mass spectrometry system and determined the oxidized nucleosides in senescence-acceleration-resistant mouse 1 (SAMR1), demonstrating that the measurement of 8-oxoGsn in urine had potential as a novel means of evaluating the aging process. In the present study, we applied this procedure to human urine samples to see if such samples can be used to estimate the physiologic age.

We have taken a keen interest in the relationship between oxidation markers and age. Most previous studies have reported a rise in the urinary 8-oxodGsn level with age. Our previous study showed an age-dependent increase in the two biomarkers in mice, rats and monkeys. In the present study, the same trend was noted in humans. Compared with other studies, the current studies covered larger range of ages, from neonates to 90-year-olds. The lowest 8-oxodGsn and 8-oxoGsn levels appeared in the young adults (11-30 years of age). As people age, the antioxidant defense systems degenerate, and the levels of 8-oxodGsn and 8-oxoGsn increase gradually until the end of life.

To date, most studies have dealt with urinary 8-oxodGsn, and a very limited number of studies have focused on 8-oxoGsn. Our study demonstrated that 8-oxoGsn is a better aging marker than 8-oxodGsn in two respects. First, the level of 8-oxoGsn was higher (approximately 2-fold) than 8-oxodGsn in age-matched counterparts. Second and more importantly, the levels of 8-oxoGsn correlated better with the rate of aging. The 8-oxoGsn content does not always correlate with chronological aging but instead reflects the actual physiological stage of aging.


Reporting on an Attempted Study of One with Candidate Senolytic Pharmaceuticals

This post describes the results of an attempt to run a self-experiment using senolytic drug candidates derived from chemotherapeutics. Based on animal study data, these pharmaceuticals are potential means to selectively destroy some fraction of senescent cells in some tissues. This is of interest because the accumulation of senescent cells is one of the root causes of aging. The pharmaceuticals have been tested for the ability to kill senescent cells in mice, and tested in humans for other uses, but as of yet are only just now entering initial human trials to test their ability to replicate the destruction of senescent cells observed in mice. This particular effort at self-experimentation involved a combination of dasatinib, quercetin, and venetoclax, with an outline somewhat close to the suggested approach to self-experimentation that I published not so very long ago.

Setting Expectations

This is a description of a learning experience, rather than of any compelling or interesting data on the efficacy of presently available senolytics in humans. The points to take away are near entirely related to the utility (or lack thereof) of various approaches to gathering data, and our expectations regarding the size of effects in different age groups.

The only changes observed in the recorded data were temporary and related to the side-effects of the senolytics. The only relevant outcome of the test that might be related to removal of senescent cells should be treated as an anecdote, as it was neither anticipated nor recorded in any way. Read through the details, learn from this, and do better if considering an attempt.

In hindsight, the chief challenges were that (a) the subject wasn't old enough to reasonably expect sizable effects to emerge in cardiovascular measures, (b) the commercially available methods of obtaining cardiovascular data, popularized by the quantified self movement, are too unsteady to detect anything other than sizable effects, and (c) user error sabotaged the most potentially interesting of the tests. Even simple things are hard, it seems.

Test Schedule and Dosing

The test schedule and oral dosing of senolytics is described below. The amounts below are scaled to a 60kg human for convenience. You might look over the past outline on self-experimentation for a lengthy dose scaling discussion. Note the use of an initial low test dose - the idea being that if this produces a reaction, the self-experiment is aborted. Caution is the watchword.

  • Day 1: Bloodwork and an epigenetic clock test.
  • Day 1-14: Take baseline cardiovascular metrics, daily.
  • Day 15: Test dose of 80mg venetoclax, 20mg dasatinib, 250mg quercetin.
  • Day 16-22: 400mg venetoclax.
  • Day 16: 100mg dastanib, 1200mg quercetin.
  • Day 20: 100mg dastanib, 1200mg quercetin.
  • Day 23: Bloodwork.
  • Day 23-36: Repeat cardiovascular metrics, daily.
  • Day 36: Bloodwork and an epigenetic clock test.
  • Day 36-49: Repeat cardiovascular metrics, daily.

Subject Details

The subject for the self-experiment is in the 45-50 age range, BMI 21.4 at the outset, and BMI of 21.0 following the experiment. See the anecdotal notes for an explanation of that change.

Measurement Details

The bloodwork was the standard baseline test from WellnessFx. The epigenetic clock test was DNAge developed by Zymo Research. The cardiovascular measures attempted on a daily basis were:

Measurements were taken at a consistent time of day, using left and right arm for the Omron 10 and iHeart, and twice in succession for the Polar H10.

These tests were picked on the basis of (a) being easy to run, and (b) matching up with physiological changes in aging that have been tied to the growing presence of senescent cells, such as stiffening of blood vessels and consequent effects on the cardiovascular system. There are other possible tests that could be attempted, but most are expensive, require a physician, or both. See the past outline on self-experimentation or an earlier discussion of testing for more details on this front.

Measurement Results

Heart Rate Variability

The Polar H10 system is well spoken of, but here the output was garbage: non-physical values, varying constantly. Thus heart rate variability was abandoned as an option fairly quickly.

Pulse Wave Velocity

Pulse wave velocity from a fingertip device is roughly consistent between two measures on left and right fingers taken at the same time, but jumps around over a large range from day to day. Reading the research literature on this class of metric and the devices used, it is expected that peripheral measurements will be less reliable and subject to more influences than core measurements, taken closer to the heart. Unfortunately, without access to specialized medical equipment and a second pair of hands, peripheral devices are all that is available.

For a 45-50 year old, the reference range for pulse wave velocity - measured centrally rather than peripherally - is 6.0-8.5 m/s or so. In that context, the following is an example set of data for left fingertip / right fingertip taken over consecutive days prior to the test, while attempting to keep lifestyle, position, and other factors consistent. As one can see, it is quite varied from day to day:

  • Day 1: 8.08 / 8.39
  • Day 2: 8.01 / 7.52
  • Day 3: 7.95 / 7.7
  • Day 4: 6.76 / 6.89
  • Day 5: 8.29 / 8.42
  • Day 6: 7.17 / 7.34
  • Day 7: 8.15 / 7.99
  • Day 8: 7.13 / 6.75
  • Day 9: 8.47 / 8.14
  • Day 10: 7.7 / 7.24
  • Day 11: 7.35 / 6.84
  • Day 12: 7.27 / 7.07
  • Day 13: 7.19 / 7.87
  • Day 14: 7.98 / 7.85

The data following the test is more of the same, with little difference. It would require a fairly sizable change, say much larger than the standard deviation of ~0.5 m/s, to be visible, and more than two weeks of measurements to have confidence in that result. No change of that size, or any size that could be more than just chance, was apparent.

Heart Rate and Blood Pressure

The Omron 10 is a solid device. Heart rate and blood pressure came out as follows, showing no meaningful change.

  • Baseline: systolic BP 113 ± 6.0, diastolic BP 69 ± 4, heart rate 58 ± 3
  • First repeat: systolic BP 109 ± 4.0, diastolic BP 66 ± 3, heart rate 60 ± 4
  • Second repeat: systolic BP 111 ± 5.0, diastolic BP 67 ± 4, heart rate 60 ± 3


The interesting changes in bloodwork are noted below, which all take the form of an alteration following the dosage that is mostly recovered a month later. Other values remained more or less consistent - any change of less than 15% was ignored for the purposes of this list.

  • Baseline: Apo B 66 mg/dL, Eosinophil Count (absolute) 0.072 x 10^3/μL, LDL cholesterol 83 mg/dL, Lp(a) 14 nmol/L, Lymphocyte Count (absolute) 1.576 x 10^3/μL, TSH 1.67 mIU/L, Total Cholesterol 159 mg/dL, White Blood Cell Count 4 x 10^3/μL
  • First repeat: Apo B 53 mg/dL, Eosinophil Count (absolute) 0.03 x 10^3/μL, LDL cholesterol 56 mg/dL, Lp(a) 10 nmol/L, Lymphocyte Count (absolute) 1.086 x 10^3/μL, TSH 1.24 mIU/L, Total Cholesterol 136 mg/dL, White Blood Cell Count 3.3 x 10^3/μL
  • Second repeat: Apo B 57 mg/dL, Eosinophil Count (absolute) 0.049 x 10^3/μL, LDL cholesterol 70 mg/dL, Lp(a) 14 nmol/L, Lymphocyte Count (absolute) 1.391 x 10^3/μL, TSH 1.45 mIU/L, Total Cholesterol 144 mg/dL, White Blood Cell Count 3.8 x 10^3/μL

The temporary cull of immune cells is entirely expected from the action of these chemotherapeutics. The drop in LDL cholesterol is not expected. The mechanisms by which LDL cholesterol is maintained at a given level and how that changes in response to circumstances and aging are in fact not well understood in detail. There is an interesting open access paper that covers the present state of knowledge. A possible hypothesis is that the change is the result of dramatic temporary alteration in gut microbiota due to the impact of dastinib and loss of immune cells. A more honest hypothesis for this particular case is a shrug; it is simply impossible to know. Nonetheless, it is interesting, albeit not relevant to the point of the exercise, to see a temporary effect on the same scale as that produced by some lesser statins.

Epigenetic Clock

The epigenetic clock test failed. A few weeks after sending off the blood sample, the company responded to say there wasn't enough blood in the sample to run the tests. They were kind enough to supply a new kit with updated instructions - which are the same as the old instructions, except that the part discussing blood now heavily emphasizes that more is better than less. Unfortunately, by that point it was too late. This is very aggravating, as with the benefit of hindsight, the epigenetic clock was probably the most useful item in the lineup of tests.

Anecdotal Experiences with the Chemotherapeutics

Quercetin is innocuous. The low test doses of venetoclax and dasatinib produced no evident effects at all. At the higher dose, venetoclax results in a subtle running down of energy and wellbeing; at the end of a week, one feels worn. At the higher dose, dasatinib has the sort of immediate outcomes one might expect from an assault on the microbial population of the gut, such as due to stomach flu or a heavy dose of indiscriminate antibiotics. That lasts half a day to a day. Anti-nausea medication is recommended. The effects of dastinib mean that weight will likely be lost between the start and end of the dosage schedule.

Anecdotal Results

One of the items that has been reported, anecdotally, by a couple of the self-experimenters using dasatinib is the improvement of skin lesions, troublesome scars, and the like. This happened here, for an patch of skin that failed to heal correctly after an injury years ago, and that as a result has been persistently annoying and painful since then. It improved notably within a week following the end of the dosage; not completely, but more than enough to feel that something useful was achieved at the end of the day. It has remained thus improved in the time since.

While we can speculate as to mechanisms involving senescent cells in troublesome lesions, one should of course assign this report exactly the same weight as the others, which is to say zero. It wasn't the aim of the experiment to look at results there, nothing was measured or recorded, and you have only the assertion in this post to go by. Nonetheless, I think that someone should consider running a formal study on the varieties of non-healing wounds in older individuals with the presently available senolytics; even absent anecdotal reports, there is a decent theoretical foundation for thinking that it might be beneficial.


The primary conclusion is that the measurement devices available to consumers for cardiovascular metrics are not as useful as hoped. Greater and longer experimentation with measurement techniques prior to running a self-experiment would have been most helpful in this case. Realizations on the usefulness of various measurement techniques could have been reached beforehand, and the strategy adapted in response. My current thinking on cardiovascular measures is that they might be useful for older individuals, where we could expect to observe larger changes, but they are not useful in the 45-50 age range, and the commercial tools are largely not up to the task at this time.

Secondly, the effects of current senolytic pharmaceuticals for people in the younger age range, just starting to show visible signs of aging, at doses equivalent to the mouse studies in which 25-50% of senescent cells were removed in multiple tissues, are modest in size. They are not large enough to be detected using standard approaches to measurement of cardiovascular and blood chemistry. If using better and more reliable medical devices, the story might be different, but even there I think, based on the results here, that the odds of observing changes would only be significant in people considerably older than 50, and much more impacted by cellular senescence. We shall see how the current trial of dasatinib at Betterhumans pans out, where the participants are in the 65+ age range.

If it were possible to start over, the approach would be adjusted to focus primarily on epigenetic age measures, or other protein expression tests such as that offered by AgeCurve, or some form of assay that actually measures counts of senescent cells. (Though the latter would be hard to obtain at this point, given that there is only the one useful test so far as I know, and it isn't yet commercially available to consumers). There are considerable advantages to tests in which you take a sample and send it off - assuming that one is actually competent to accomplish that simple task, which seems in doubt at this end of the world. All of the complexity and sophistication of the test is baked in, and requires little to no effort on the part of the self-experimenter.

Companion Dogs as a Model for the Details of Human Aging

For research purposes, dogs are argued to be a good compromise between the very long life span of humans, meaning costly and lengthy studies that result in high quality data, and the very short lives of mice, meaning less expensive, shorter studies, but questions regarding the relevance of the data to human medicine. Mice are not humans, and any number of efforts to produce new medical technologies have been shipwrecked on that rock. Dogs, of course, are also not humans, but they are much closer than mice in terms of aging and its relationship with cellular biochemistry and metabolism. To pick one example from the scientific community, the recently established Dog Aging Project is an ongoing effort to produce useful data on methods of modestly slowing aging, run by one of a number of research groups who think along these lines.

Age is the greatest risk factor not only for the probability of death, but also for the majority of morbidities associated with mortality. However, studies to identify factors that alter patterns of aging using animal models have focused on lifespan and age-specific mortality, rather than the underlying patterns of morbidity that lead to death. This gap is due in part to the difficulty of measuring causes of mortality in the standard animal models in aging studies. For example, age-related morbidity and causes of mortality in the commonly studied models of aging range from the not well understood (and often not studied) in mice, to the poorly understood in flies and worms, to nonexistent in yeast.

In addition, many diseases important to human aging (e.g., cardiovascular disease and dementia) do not develop spontaneously in our commonly studied model organisms. To this end, we need a model organism that allows us to understand not only age-related mortality, but also age-related morbidity and causes of death. The companion dog (i.e., dogs that reside under their owner's care) has the potential to fill this gap and to enable us to better understand the genetic and environmental factors that affect lifespan, and the underlying forces that shape age-specific morbidity and mortality.

Over the last 200 years, individual dog breeds have been highly inbred, with the result that genetic variation is relatively limited within breeds, but considerable among breeds. Thanks in large part to this history of intense breeding for specific morphological and behavioral traits, dogs are the most phenotypically diverse mammalian species on the planet. This diversity is found not only in morphology and behavior, but also in life-history traits, where across breeds, dogs exhibit an almost twofold difference in average longevity and enormous variation in risk of specific diseases.

Dogs also have a sophisticated veterinary healthcare system, second only to that of humans, allowing clinicians to diagnose and treat specific diseases, and to identify exact causes of death. For example, unlike mice, companion dogs experience a diversity of spontaneously occurring diseases similar to those of humans, such as age-related neurologic disease, renal disease, endocrine disease, and also experience obesity and its attendant risks. These phenomena allow researchers not only to study the pathologies that influence mortality, but also to understand different comorbidities and multiple chronic conditions that canines exhibit.

Surprisingly, while we know a great deal about the age-specificity of human morbidity, substantially less is known about the degree to which other species, including dogs, show similar disease-specific patterns of aging. Such comparisons are critical in our efforts to develop powerful models to identify the genetic and environmental determinants of morbidity and mortality. Here, we present a comparative analysis of causes of mortality in both humans and companion dogs. We determine the extent to which the companion dog may provide an excellent model of human aging and the degree to which causes of mortality correlate between the two species. Our results lay the groundwork for future use of the domestic dog as a model of human aging and longevity.


LyGenesis Aims to Transplant Liver Tissue into Lymph Nodes

For many organs, useful function is not all that dependent on shape and location in the body. In the case of filtration or chemical factory organs, such as the kidney and liver, many of the necessary tasks can be carried out in varied locations, not just the one that evolution resulted in, and can be carried out piecemeal by small sections of tissue. For example, some years ago researchers demonstrated that it is possible to place functional liver, kidney, and thymus tissue into lymph nodes and have that tissue function correctly. The tissue engineering community is now well into the decellularization and organoid phase of development, in which small sections of complex functional tissue can be grown from a cell sample, and donor tissues repopulated with a patient's own cells. Why not grow organoids in lymph nodes, or place transplanted tissue into a patient's lymph nodes, where they can do some good? This line of work is now being carried forward to the clinic by the staff at LyGenesis.

LyGenesis, Inc. is an organ regeneration company enabling a patient's own lymph nodes to be used as bioreactors to regrow functioning ectopic organs. Our initial target organ for clinical development is liver regeneration, with a focus on helping patients with end stage liver disease (ESLD). Instead of one donor organ treating one patient, LyGenesis enables one donor organ to treat dozens of patients. Instead of major surgery, LyGenesis uses outpatient endoscopy for transplantation of donor cells, which grow and become a functioning ectopic organ.

A decade age, scientists in the field of ectopic transplantation research began a series of experiments that would form the foundation for LyGenesis. They discovered that hepatocytes (liver cells) transplanted into lymph nodes would not just survive, but thrive, organize and begin to function as miniature ectopic livers. The research confirms that it is possible to harness the body's lymph nodes as bioreactors for organ regeneration.

Strange as it might sound, it appears to work in mice, where the surrogate mini-livers made up for the missing function of a diseased liver. Tests in pigs have been encouraging, too, and now trials in humans could begin late in 2018 if the founders can raise about $10 million for their startup, LyGenesis.


Paligenosis as a Potential Source of Methods to Target Many Types of Cancer with One Type of Therapy

The future of the treatment of cancer will be, must be, dominated by classes of therapy that can be easily and cost-effective applied to many different types of cancer. Such therapies can only exist as a result of targeting mechanisms that are shared by many or all types of cancer. It must also be challenging or impossible for cancerous cells to do without these mechanisms. The biggest issue in cancer research over the past few decades, in my opinion, is the specificity of therapies, the amount of time and resources poured into efforts to produce treatments that can only work on one type or a few types of cancer, and that often target mechanisms that cancerous cells in any given tumor can lose or replace. Cancers evolve rapidly, frantic growth coupled with a high rate of mutation. Cancer therapies that operate on replaceable mechanisms may just pressure the cancer to evolve in a new direction. There is only so much funding, only so many researchers, and only so much time. The work must be efficient if cancer is to be controlled within our lifetimes.

When it comes to our own personal future engagements with cancer - it will happen, just live long enough - it is reassuring to see the signs of more research programs that are focused on universal or widely applicable approaches to cancer. These are cost-effective ways forward for the research community, and are the only way to gain the necessary efficiency for significant progress in the near future, the next twenty years. Among these technologies, approaches, and promising early stage research: targeted blockade of telomere lengthening, by sabotaging telomerase, and interfering in alternative lengthening of telomeres (ALT); the chimeric antigen receptor immunotherapies that have a comparatively low cost of adaptation to different cancers; restoring circadian mechanisms broken in cancerous cells; using a kill switch in cells that is targeted by huntingtin, explaining why Huntington's disease patients experience very low cancer risk.

The work here is a new addition to this list. This line of research is early stage, but it outlines an area of cellular behavior that appears to be common to many different tissues and thus types of cancer. With further investigation, scientists may find targets that could shut down cancerous tissue if developed into treatments. It is far too early to say how useful this will turn out to be in the fullness of time, when compared with the other options on the table, most of which are still yet to reach the clinic, but it is exactly the sort of fundamental work that we'd all like to see more of from the cancer research community.

Similarities found in cancer initiation in kidney, liver, stomach, pancreas

Mature cells in the stomach sometimes revert back to behaving like rapidly dividing stem cells. Now, researchers have found that this process may be universal; no matter the organ, when tissue responds to certain types of injury, mature cells seem to get younger and begin dividing rapidly, creating scenarios that can lead to cancer. Older cells may be dangerous because when they revert to stem cell-like behavior, they carry with them all of the potential cancer-causing mutations that have accumulated during their lifespans. However, because mature cells in the stomach, pancreas, liver and kidney all activate the same genes and go through the same process when they begin to divide again, the findings could mean that cancer initiation is much more similar across organs than scientists have thought. That could support using the same strategies to treat or prevent cancer in a variety of different organs.

The process by which mature cells begin dividing again has been named paligenosis. "When we began the war on cancer in the 1970s, scientists thought all cancers were similar. It turned out cancers are very different from one organ to another and from person to person. But if, as this study suggests, the way that cells become proliferative again is similar across many different organs, we can imagine therapies that interfere with cancer initiation in a more global way, regardless of where that cancer may appear in the body."

Studying cells from the stomach and pancreas in humans and mice, as well as mouse kidney and liver cells, and cells from more than 800 tumor and precancerous lesions in people, the researchers found when tissue is injured by infections or trauma, mature cells can revert back to a stem-cell state in which they divide repeatedly. Paligenosis appears similar to apoptosis - the programmed death of cells as a normal part of an organism's growth and development - in that it seems to happen the same way in every cell, regardless of its location in the body. "Nature has provided a way for mature cells to begin dividing again, and that process is the same in every tissue we've studied."

Regenerative proliferation of differentiated cells by mTORC1-dependent paligenosis

In 1900, it was speculated that a sequence of context-independent energetic and structural changes governed the reversion of differentiated cells to a proliferative, regenerative state. Accordingly, we show here that differentiated cells in diverse organs become proliferative via a shared program. Metaplasia-inducing injury caused both gastric chief and pancreatic acinar cells to decrease mTORC1 activity and massively upregulate lysosomes/autophagosomes; then increase damage associated metaplastic genes such as Sox9; and finally reactivate mTORC1 and re-enter the cell cycle.

Blocking mTORC1 permitted autophagy and metaplastic gene induction but blocked cell cycle re-entry at S-phase. In kidney and liver regeneration and in human gastric metaplasia, mTORC1 also correlated with proliferation. In lysosome-defective Gnptab-/- mice, both metaplasia-associated gene expression changes and mTORC1-mediated proliferation were deficient in pancreas and stomach.

Our findings indicate differentiated cells become proliferative using a sequential program with intervening checkpoints: (i) differentiated cell structure degradation; (ii) metaplasia- or progenitor-associated gene induction; (iii) cell cycle re-entry. We propose this program, which we term "paligenosis", is a fundamental process, like apoptosis, available to differentiated cells to fuel regeneration following injury.

A Few of the Important Differences in Regeneration Between Young and Old Hearts

Young enough hearts, soon after birth, are much more regenerative than adult hearts. Some species, such as zebrafish, never lose the youthful ability to regenerate damaged or lost sections of heart tissue. Mammals, however, all too quickly grow into an inferior regenerative capacity, most evident after injury to the nervous system or the heart. Is it possible to find the systems of molecular regulation that shut down very early in life, and at least temporarily and partially restore the ability to regenerate the heart without scarring, or to turn back heart failure? Finding the important parts of the complex network of genes and proteins that controls regeneration is a work in progress, and this open access paper covers some of what has been discovered to date. Answering the question of whether or not these discoveries can be used to safely enable regeneration, without risk of cancer or other issues, is similarly in progress. There have been interesting demonstrations in mice in the past few years, for example.

While a regenerative response is limited in the mammalian adult heart, it has been recently shown that the neonatal mammalian heart possesses a marked but transient capacity for regeneration after cardiac injury, including myocardial infarction. These findings evidence that the mammalian heart still retains a regenerative capacity and highlights the concept that the expression of distinct molecular switches (that activate or inhibit cellular mechanisms regulating tissue development and regeneration) vary during different stages of life, indicating that cardiac regeneration is an age-dependent process. Thus, understanding the mechanisms underpinning regeneration in the neonatal-infarcted heart is crucial to develop new treatments aimed at improving cardiovascular regeneration in the adult.

The present review summarizes the current knowledge on the pathways and factors that are known to determine cardiac regeneration in the neonatal-infarcted heart. In particular, we will focus on the effects of microRNA manipulation in regulating cardiomyocyte proliferation and regeneration, as well as on the role of the Hippo signaling pathway and Meis1 in the regenerative response of the neonatal-infarcted heart. We will also briefly comment on the role of macrophages in scar formation of the adult-infarcted heart or their contribution for scar-free regeneration of the neonatal mouse heart after myocardial infarction. Although additional research is needed in order to identify other factors that regulate cardiovascular regeneration, these pathways represent potential therapeutic targets for rejuvenation of aging hearts and for improving regeneration of the adult-infarcted heart.


Evidence for Senescent T-Cells to Promote Bone Loss, a Phenomenon Accelerated in Rheumatoid Arthritis Patients

Senescent cells cause harm throughout the body, accumulating in number with advancing age. They are found in all tissues, and this includes the cells of the immune system. The growing presence of senescent cells, and the harmful signals they generate, is one of the root causes of degenerative aging. There is a good amount of evidence for senescent cells to contribute to osteoporosis, of which the most compelling is that osteoporosis can be partially reversed in mice through targeted clearance of these unwanted cells. The study here is a different view into the link between cellular senescence and bone loss, with a focus on the autoimmune condition rheumatoid arthritis. While not an age-related disease, rheumatoid arthritis is associated with a greater risk of osteoporosis and greater number of senescent T cells. As such it is a useful point of comparison with normal aging.

Bone loss is one of the most common comorbidities of patients with rheumatoid arthritis (RA). Depending on the population studied, 10-56% of RA patients suffer from osteoporosis. In healthy individuals, bone homeostasis is maintained by a balance between bone formation and bone resorption. A link between inflammation and bone loss has been suggested for decades, and it was supported by in vitro observations and animal models showing enhanced bone resorption under the influence of pro-inflammatory cytokines. T-cells are one of the most important promoters of osteoclastogenesis, and the first evidence for the capacity of T-cells to cause bone loss was provided in 1999 by illustrating that T-cell-produced RANKL triggered osteoclastogenesis directly in a mouse model of arthritis. More recently, another study showed that T-cell-deficient mice were resistant to bone loss.

Premature immunosenescence including the accumulation of senescent CD4+ T-cells seems to be a hallmark feature of RA. Senescent T-cells are characterized by the loss of CD28, eroded telomeres, the lower content of T-cell receptor excision circles, the expression of pro-inflammatory molecules, and the gain of effector functions. Notably, senescent CD28- T-cell prevalence correlated with disease severity in RA. The role of immunosenescence in the context of osteoporosis, however, is elusive so far. The aim of this study was to investigate whether senescent CD4+28- T-cells are associated with early bone loss in RA patients.

We show that patients with systemic bone loss have a higher prevalence of circulating senescent CD4+CD28- T-cells than individuals with normal bone mineral density (BMD). RANKL is expressed at higher levels on senescent CD4+ T-cells compared to that on CD28+ T-cells, and its production can be stimulated with IL-15, a key cytokine in the pathogenesis of RA. Senescent CD4+ T-cells induce osteoclastogenesis more efficiently than CD28+ T-cells. Several studies demonstrated that T-cells are involved in the bone-remodeling system and that RANKL-expressing T-cells promote local and systemic osteoporosis. Besides, it has been demonstrated that senescent CD4+ T-cells were increased in patients with severe disease manifestations, and at the same time, these patients were at an increased risk of osteoporosis. These findings support our conclusion that senescent CD4+CD28- T-cells play an important role in the promotion of osteoporosis in RA as well as in non-RA individuals. Interestingly, we observed similar frequencies of CD4+CD28- T-cells in our RA and non-RA cohorts.


Quantifying Nuclear DNA Mutation Rates in Stem Cells Doesn't Tell Us the Degree to which those Mutations Contribute to Aging

The study noted here provides numbers for the mutation rates in muscle stem cells, the stochastic damage that occurs over time as small numbers of errors slip past the highly efficient molecular machinery of cellular replication and DNA repair. The researchers used single cell genomic sequencing, a very useful and still comparatively new capability. It produces a much more detailed view of the state of nuclear DNA inside a cell population, showing the enormous variations in stochastic mutational damage that takes place over the years. Every cell has thousands of different areas of damage in their DNA, and it is becoming apparent that the damage in stem cell populations is cloned out into tissues. Stem cells maintain tissues by providing a supply of somatic cells, and those somatic cells divide many times before they reach the Hayflick limit. So the mutations present in a stem cell will over time propagate into a fraction of the supported tissue.

Is this important? Mutation in nuclear DNA is certainly a contributing cause of cancer, though it can be argued that the decline of the immune system - responsible for killing cancers before it gets underway - is actually more significant than mutations when it comes to the age-related nature of cancer risk. One can look at the numbers for mutational damage in old cells and it sounds fairly horrific out of context, but everything irelated cells and cellular biochemistry involves huge numbers. We know that nuclear DNA becomes more mutated over time, and we know that many of the methods of slowing aging, such as calorie restriction, produce reduced levels of mutation at a given age in comparison to normally aging individuals. However: at present there is no compelling causal evidence to show that nuclear DNA damage alone has a significant effect over the present human life span in comparison to other contributions to degenerative aging. If anything, the slight tilt in the present indirect evidence is in the opposite direction, towards skepticism for a significant role over the present human life span.

Nonetheless, it is the present consensus that nuclear DNA damage does cause meaningful metabolic dysfunction; a lot of research proceeds upon this assumption. The authors of the open access paper here are quite ready to theorize a connection between stem cell mutation level and age-related declines in muscle mass and strength, but their data only shows a correlation. A great many things happen over the course of aging, and not all are directly connected to one another: aging is a tree, a spreading set of damage and issues stemming from a few root causes. The far branches will appear correlated even if they have little to do with one another.

I'm in the camp of those who would like to see more work directed towards the production of a compelling demonstration to show that nuclear DNA damage either is or is not a major factor in aging beyond cancer risk. The best way to do that is to repair a significant amount of the damaged DNA, but that is exceptionally challenging, beyond present capabilities. It might be possible in the near future to use one of the new forms of genetic technology to tackle the clonal expansions of specific mutations, provided there are only a few of them and they are present in large numbers of cells. Once we start talking about scores or hundreds of mutations, however, then that is just not a near term prospect. So a less direct approach is called for, something clever yet to be assembled, that will be obvious in hindsight to the rest of us.

Stem cell study may result in stronger muscles in old age

It has already been established that natural ageing impairs the function of our skeletal muscles. We also know that the number and the activity of the muscles' stem cells decline with age. However, the reasons for this has not been fully understood. In a new study, researchers have investigated the number of mutations that accumulate in the muscle's stem cells (satellite cells). "What is most surprising is the high number of mutations. We have seen how a healthy 70-year-old has accumulated more than 1,000 mutations in each stem cell in the muscle, and that these mutations are not random but there are certain regions that are better protected."

The researchers have benefited from new methods to complete the study. The study was performed using single stem cells cultivated to provide sufficient DNA for whole genome sequencing. The mutations occur during natural cell division, and the regions that are protected are those that are important for the function or survival of the cells. Nonetheless, the researchers were able to identify that this protection declines with age. "We can demonstrate that this protection diminishes the older you become, indicating an impairment in the cell's capacity to repair their DNA. And this is something we should be able to influence with new drugs."

"We achieved this in the skeletal muscle tissue, which is absolutely unique. We have also found that there is very little overlap of mutations, despite the cells being located close to each other, representing an extremely complex mutational burden." The researchers will now continue their work to investigate whether physical exercise can affect the number of accumulated mutations. Is it true that physical exercise from a young age clears out cells with many mutations, or does it result in the generation of a higher number of such cells?

Somatic mutagenesis in satellite cells associates with human skeletal muscle aging

Satellite cells (SCs) are a heterogeneous population of stem and progenitor cells that have been demonstrated to play a pivotal role in skeletal muscle (SkM) regeneration. The SCs are normally kept in a quiescent state and activated upon exposure to stimuli, such as exercise or SkM injury. When committed to myogenic differentiation, SCs proliferate further, fuse to existing SkM fibers, and contribute new nuclei to the growing and regenerating fibers. Aged human SkMs show a decline in the number and proliferative potential of the SCs. As a consequence, a dysfunctional SC compartment is envisaged as a major contributor to age-related defects, including reduced capacity to respond to hypertrophic stimuli such as exercise and impaired recovery from muscle disuse and injury.

A well-known factor in the decline of stem cell function is the loss of genome integrity, for example, caused by the appearance of somatic mutations. These modifications of the genome range from single-base changes (single-nucleotide variants) to insertions or deletions of a few bases (indels) to chromosomal rearrangements and occur during the whole life, starting from the first division of the embryo. In contrast to germline variants, somatic variants are not propagated to the whole individual but to a subpopulation of cells in the body, with the final consequence that adult human tissues are a mosaic of genetically different cells. Moreover, somatic mutation burden increases during a lifetime as a result of accumulating errors occurring either during cell division or because of environment-induced DNA damage. At present, nothing is known about somatic mutation burden in human SCs or SkM.

Here, we investigate the genetic changes that occur with aging in the genome of human adult SCs and use the results to elucidate mutational processes and SC replication rate occurring in vivo in adult human muscles. We assess the functional effects of somatic mutations on SC proliferation and differentiation and predict the global consequence on muscle aging and sarcopenia. Our analyses reveal an accumulation of 13 mutations per genome per year that results in a 2-3-fold higher mutation load in active genes and promoters in aged SCs. High mutation burden correlates with defective SC function. Overall, our work points to the accumulation of somatic mutations as an intrinsic factor contributing to impaired muscle function with aging.

The Latest Rejuvenation Research Commentary on Relevant Papers

The "commentary on some recent theses" section is a regular feature of the Rejuvenation Research journal, penned by Aubrey de Grey and collaborators. Historically it has been behind a journal paywall, but it is presently open access - and in this day and age of organized copyright heretics who assemble online databases of papers normally locked away, it is ceasing to much matter whether or not journals maintain a paywall when it comes to access. The most recent commentary touches on a range of different topics; reading it all is recommended. The quoted material here relates to an interesting discovery regarding the senescence of astrocytes in the aging brain, which, as noted, offers the promise of effective near future treatments for a range of neurodegenerative conditions.

Of the seven strands of the SENS platform, the ablation of senescent cells (ApoptoSENS) has thus far made the most progress towards the clinic; drugs that selectively eliminate these toxic and superfluous cells are referred to as senolytics, and several are now undergoing or are soon to enter clinical trials. Recent evidence from preclinical work has indicated that the role of senescent cells in the aging process is remarkably significant, such that resolving this single form of damage yields dramatic benefits across the spectrum of age-related decline - simultaneously extending both lifespan and healthspan in mouse models.

Although the existence of a true senescent phenotype in postmitotic cells such as neurons is still unproven, its existence in their crucial support cells, the astrocytes, has been recognized since the beginning of this decade. A recent dissertation makes vital progress towards proving the clinical relevance of the phenomenon - laying the groundwork for the translational application of senolytics to major neurodegenerative diseases. Glutamate (together with aspartate) is the major excitatory neurotransmitter in the human brain, and dysfunctions of its handling are clearly associated with both acute and chronic neurological conditions. That such dysfunction is here shown to be an intrinsic consequence of physiologically realistic levels of astrocyte senescence leaves little doubt that a mechanistic connection must exist. In Alzheimer's disease specifically, it is notable that the loss of glutamate receptors in postmortem samples tracks both the brain's major excitatory pathways and also the very well-established progressive staging of the disease. These results are good news indeed!

Replacing intrinsically aged neurons without disrupting synaptic connectivity has always been accepted to be a daunting task, but astrocyte turnover - while low in healthy tissue - is a routine process following injury (albeit one that has side effects of its own when driven to excess in the context of chronic inflammation, although these appear somewhat treatable). Thus, depleting senescent astrocytes and so neutralizing their inflammatory effects may well automatically induce their replacement by healthy new cells; and even if not, stimulating that process is not an insurmountable challenge. At the very least, such a therapy should prevent further degeneration - and perhaps even create the conditions for the repair of pre-existing neuronal decline as well, especially since a subset of those astrocytes may be able to function as neural stem cells.


Calorie Restriction Boosts Intestinal Stem Cell Numbers and Improves Regeneration

Researchers here look at the effects of calorie restriction on the stem cell populations that support intestinal tissue. There is plenty of evidence for calorie restriction to improve stem cell activity in other tissues, not to mention aiding many other mechanisms relevant to health. The practice of calorie restriction is very broadly beneficial. It slows aging over the long term, and in the short term improves near all measures of health. Despite the similarities in short term effects between mice and humans, however, it is the case that human life spans are not extended by anywhere near as much as those of mice. The evolutionary argument for this outcome involves the length of seasonal famine in comparison to length of life: the degree to which life spans are plastic in response to circumstances depends on the usual length of adverse circumstances. A mouse requires a much greater proportional extension of life to pass through a seasonal famine into a time of plenty again, and so that greater extension is selected for.

Years of research have demonstrated that existing on a calorie restricted diet can boost healthy lifespan, reducing the risk of heart attack, diabetes, and other age-related conditions. Other, more recent work has shown that calorie-restricted animals regenerate tissue more effectively following injury. "The beneficial effects of calorie restriction are at this point not really up for debate; it's quite clear. But there are all sorts of questions about the cellular and molecular basis to these benefits."

One theory has been that calorie restriction slows age-related degeneration and enables more efficient tissue function by influencing the integrity and activity of adult stem cells, the precursor cells that dwell within specific tissues and give rise to the diversity of cell types that compose that tissue. Recent studies focused on the effects of calorie restriction on the active intestinal stem cells. While these active stem cells bear the burden of daily tissue turnover and act as the workhorses of intestinal function, they are also known to be highly susceptible to DNA damage, such as that induced by radiation exposure, and thus are unlikely to be the cells mediating the enhanced regeneration seen under calorie restriction. Instead of looking at these active stem cells, researchers examined a second population of intestinal stem cells known as reserve stem cells. The team had previously shown that these reserve stem cells normally reside in a dormant state and are protected from chemotherapy and radiation. Upon a strong injury that kills the active cells, these reserve stem cells "wake up" to regenerate the tissue.

To investigate this hypothesis, the scientists focused on how a subpopulation of mouse intestinal stem cells responded under calorie restriction and then when the animals were exposed to radiation. When mice were fed a diet reduced in calories by 40 percent from normal, the researchers observed that reserve intestinal stem cells expanded five-fold. Paradoxically, these cells also seemed to divide less frequently, a mystery the researchers hope to follow up on in later work. When the research team selectively deleted the reserve stem cells in calorie-restricted mice, their intestinal tissue's regeneration capabilities were cut in half, implicating these cells as having an important role in carrying out the benefits of calorie restriction.

"These reserve stem cells are rare cells. In a normal animal they may make up less than half a percentage of the intestinal epithelium and in calorie restricted animals maybe slightly more. Normally, in the absence of injury, the tissue can tolerate the loss, due to the presence of the active stem cells, but, when you injure the animal, the regeneration is compromised and the enhanced regeneration after calorie restriction was compromised in the absence of the reserve stem cell pool. These reserve stem cells that we had shown were important for the beneficial effects of calorie restriction, were repressing many pathways that are all known to be regulated by the protein complex mTOR, which is most well known as being a nutrient-sensing complex. Curiously, we see that, when they're injured, the calorie-restricted mice were actually better able to activate mTOR than their counterparts. So somehow, even though mTOR is being suppressed initially, it's also better poised to become activated after injury. That's something we don't fully understand.

The researchers conducted experiments using leucine, an amino acid that activates mTOR, and rapamycin, a drug which inhibits mTOR, to confirm that mTOR acted within these reserve stem cells to regulate their activity. Reserve stem cells exposed to leucine proliferated, while those exposed to rapamycin were blocked. Pretreating the animals with leucine make the reserve stem cells more sensitive to radiation and less able to regenerate tissue following radiation injury, while rapamycin protected the reserve stem cells as they were more likely to remain dormant. The researchers caution, however, that rapamycin cannot be used as a stand-in for calorie restriction, as it would linger and continue to block mTOR activation even following injury, hindering the ability of the reserve stem cells to spring into action and regenerate intestinal tissue.


TET2 Overexpression Enhances Neurogenesis and Cognitive Function in Old Mice

Heterochronic parabiosis is the process of linking the circulatory systems of an old and young animal. It improves measures of aging in the older individual, and worsens measures of aging in the younger individual. Researchers use this technique to try to pinpoint the important signaling and other cell behavior changes that take place with advancing age. This isn't just a matter of looking at signals in the bloodstream, however. Researchers can analyze any of the changing gene expression patterns and biochemical relationships inside cells, as they respond to the altered environment. That is the case in the open access paper I'll point out here; a research team experimenting with heterochronic parabiosis found that it increased expression of TET2 in old mice, and they present evidence to implicate reduced levels of TET2 in age-related cognitive decline.

Tet2 Rescues Age-Related Regenerative Decline and Enhances Cognitive Function in the Adult Mouse Brain

During aging, the number of neural stem/progenitor cells (NPCs), and subsequently neurogenesis, precipitously declines in the subgranular zone of the dentate gyrus (DG) in the hippocampus. Mounting evidence in animal models indicates the potential for rejuvenation of regenerative and cognitive functions in the aging brain through interventions, such as heterochronic parabiosis (which exposes aged animals to young blood). However, the ability to utilize this neurogenic potential is predicated on identifying molecular targets that reverse the effects of aging in the brain.

Recent studies have begun to link changes in the functions of epigenetic mediators to age-related regenerative decline. Interestingly ten eleven translocation methylcytosine dioxygenase 2 (Tet2) is emerging as a potential epigenetic regulator of aging. Human genetic studies identified an increased frequency of somatic TET2 mutations with age that are associated with elevated risk for aging-associated disorders, such as cancer, cardiovascular disease, and stroke. Notwithstanding, the involvement of Tet2 in mediating the aging process in the adult brain has yet to be investigated.

Here we demonstrate that Tet2 offsets age-related neurogenic decline and enhances cognition in the hippocampus of adult mice. We detect an age-dependent decrease in the levels of Tet2 in the aging hippocampus coincident with decreased adult neurogenesis. Mimicking an age-related loss of Tet2 in the adult neurogenic niche of the hippocampus, or adult NPCs, impairs regenerative capacity and associated hippocampal-dependent learning and memory processes. Conversely, increasing Tet2 in the hippocampus of mature animals increases restores adult neurogenesis to youthful levels and enhances cognitive function.

Recently, it has been demonstrated that constitutive whole-body loss of Tet2 yields opposing effects on neurogenic processes, resulting in increased adult NPC proliferation but decreased neuronal differentiation. In contrast, our data indicate that decreasing Tet2 expression acutely in the adult neurogenic niche impairs all stages of hippocampal neurogenesis, while loss of Tet2 in adult NPCs impairs neuronal differentiation processes. These data point to differential regulation of distinct stages of neurogenesis by Tet2 that arise from the loss of Tet2 at the level of the whole organism, neurogenic niche, and adult NSC during development versus adult ages. In the context of aging, our data implicate decreased Tet2 in the aging hippocampus with age-related regenerative decline.

Aging is a process of layers. At the bottom of it, the root causes are forms of molecular damage: an accumulation of broken, misbehaving cells; growing deposits of metabolic waste; mutated mitochondrial DNA; and so on. Above this is a very complicated and poorly mapped middle layer in which cells react to damage, changing countless signals and behaviors in response. Some of this is compensation, with varying degrees of success, and some of it wild flailing that makes everything worse. Then at the upper layer we find the familiar age-related diseases and classes of organ dysfunction, the sort of thing that is described in terms of the capacity that is failing or lost rather than how that failure or loss happened: kidney failure; dementia; heart disease; and so on.

Most research into aging starts at the top layer, with the evident symptoms of age-related disease, and then works just a little way back down into the upper part of the middle layer, trying to make sense of the final part of the chain of cause and effect. Then the researchers usually try to build therapies rather than carry on deeper. The work here is an excellent example of the way in which this proceeds. Having identified reduced levels of TET2 as a proximate cause of loss of neurogenesis and cognitive function, the next step is not to ask why levels of TET2 are lower, but to try to override that change. When this strategy is repeated over and again across the research community, is it any wonder that we have very little detailed knowledge of how the known root causes of aging - those summarized in the SENS rejuvenation research portfolio - interact and progress to give rise to all the various measures of aging.

Not that I think it is necessarily the right thing to do to work further downwards through the middle layer to the bottom. Quite the opposite, in fact. I think the most economical way forward is to build repair therapies capable of addressing the damage that causes aging, changing the bottom layer, and then see what happens next as those repairs propagate their effects. In the case of senescent cells and aging, this approach is ongoing, and generating new knowledge at a much, much faster pace than was the case in the years prior to the emergence of the first senolytic therapies capable of selectively destroying these cells. In a better world, the research community would have enough funding to energetically pursue all options: compensatory treatments as well as those that address root causes. As it is, it is largely the former that take place, while the latter remain neglected. Given that repairing the root causes should be far more effective than compensating for a small slice of their downstream effects, this is a real problem.

DAMPs May Link Age-Related Mitochondrial Dysfunction and Chronic Inflammation

Mitochondria-derived damage-associated molecular patterns (DAMPs) are a range of DNA and protein fragments that are thought to be generated as a result of mitochondrial damage, insufficient mitochondrial quality control, or some combination of the two. Mitochondria are the power plants of the cell, each cell having its own small herd of these descendants of ancient symbiotic bacteria. They have long since evolved into integrated cellular components, but retain a little of their original DNA. There is copious evidence to point to a sizable role for mitochondria in the harms caused by aging. In the SENS view, the most important problem is that mitochondrial DNA (mtDNA), less protected than the DNA in the cell nucleus, becomes damaged in ways that both cause dysfunction and make the broken mitochondria more resistant to removal by the machinery responsible for quality control.

The focus of this open access paper is on understanding how mitochondrial dysfunction can be linked to the characteristic chronic inflammation that occurs with age. There are many contributions to inflammation among the processes of aging. Obviously, issues internal to the immune system account for much of the problem, but any cell is, in principle, given the right circumstances, capable of generating signals that will induce local immune cells to adopt an inflammatory state. This is one of the ways in which senescent cells cause significant harm, for example, forcing the immune system into consistent overactivation, a state that disrupts the usual beneficial activities of immune cells. Do cells that are not senescent, but are suffering significant mitochondrial damage produce similar outcomes? Do they also rouse the immune system into constant activation, via different mechanisms? Possible so.

Due to the relevance of mitochondria to cell physiology and whole-body metabolism, a comprehensive set of adaptive quality control mechanisms is in place to ensure the preservation of mitochondrial structural and functional integrity. Mitochondrial quality control (MQC) mechanisms also allow for the dynamic modulation of organelle function and number to meet the heterogeneous energy demands of the various tissues. MQC is accomplished through a set of interrelated processes (i.e., protein folding and degradation, mitochondrial autophagy, mitochondrial fission and fusion, and mitochondrial biogenesis).

The regulation of mitochondrial content is achieved through the dynamic balance between mitochondrial biogenesis and degradation. Mitochondrial biogenesis is a multistage process finalized to producing new mitochondria upon the coordinated expression of nuclear and mtDNA-encoded genes. Mitochondrial fusion allows for mtDNA mixing within the network, thereby preventing focal accumulation of mutant mtDNA and preserving mtDNA integrity. Mitochondrial fission, instead, segregates defective or unnecessary organelles for their subsequent removal through mitophagy. The integration of mitochondrial dynamics with the selective removal of dysfunctional mitochondria, referred to as mitophagy, ensures an efficient MQC process and preserves metabolic cellular "fitness."

Derangements of the MQC axis have been described during aging and in the context of a number of disease conditions, including cancer, cardiovascular disease, diabetes, and neurodegenerative disorders. Along with mitochondrial dysfunction, chronic inflammation is a hallmark of both aging and degenerative diseases. The two phenomena may be linked to one another. Indeed, emerging evidence indicates that circulating cell-free mtDNA, one of the damage-associated molecular patterns (DAMPs), may establish a functional relationship between mitochondrial damage and systemic inflammation. mtDNA can be released into the circulation in response to cell insults. Here, it is able to induce an inflammatory response through hypomethylated CpG motifs resembling those of bacterial DNA. These regions, indeed, bind and activate membrane or cytoplasmic pattern recognition receptors (PRRs), such as the Toll-like receptor (TLR), the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR), and cytosolic cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) DNA sensing system-mediated pathways.

The possible contribution of mitochondrial DAMPs to the inflammatory milieu that characterizes muscle wasting disorders has not yet been explored. However, this hypothesis is worth being pursued as it could help identify novel biological targets for the management of muscle loss. Here, we summarize the current evidence on circulating mtDNA as a trigger for age-related systemic inflammation. We first describe two candidate mechanisms generating and releasing cell-free mtDNA: (1) dysregulation of TFAM binding to mtDNA, and (2) impairment of mitophagy. Subsequently, we illustrate the pathways linking mitochondrial dysfunction with systemic inflammation during aging. Finally, we propose a role for the triad "MQC failure/cell-free mtDNA/inflammation" in two major muscle wasting disorders, sarcopenia and cachexia.


Present Medical Practice is Not Configured to Manage a Future of Ever-Improving Rejuvenation Therapies

The present day organization of medical practice and its regulation is built atop the infectious disease model, even where it engages with age-related diseases. Prevention is a comparatively thin thread in an industry largely focused on the strategy of waiting until there is a problem, then attacking the symptoms of that problem with every available tool, as aggressively as possible. This isn't all that useful for age-related disease to start with, but it simply doesn't work for a world in which rejuvenation therapies that can repair the damage that causes aging initially arrive in a prototype form and then grow more capable over time. In that world - our world! - prevention quickly becomes enormously important and effective, and should be prioritized accordingly. This will require major change in a large number of conservative, hidebound organizations and communities, and will no doubt proceed only slowly and reluctantly.

A mainstay of preventive medicine innovators and medical futurists has been the concept of longevity escape velocity (LEV). LEV represents the time at which someone is gaining greater than 1 year of predicted healthy life expectancy per year, essentially making his or her healthy life expectancy unlimited. But practically, what are the likely requirements to reach such a "longevity escape velocity"? Around 95% of medical service budgets today are spent on acute medicine, with only around 5% on preventive care. How can today's medicine adapt to bring around a care system that provides LEV on a population scale?

To help patients achieve and maintain LEV, medical knowledge is required from diverse medical specialties and from outside specialties typically practiced by doctors. General practice (also known as primary care or family medicine) is the current specialty with the most similarity to LEV medicine; however it lacks in knowledge in many key areas, as well as in availability of time. An LEV medical specialty could be a subspecialty training of general practice, internal medicine, geriatrics, or clinical research. Core elements of an LEV medical specialty training would include education in prioritization of clinical problems according to magnitude and probability of clinical outcome or surrogate marker impact to a specific person's budget; understanding clinical biogerontology frameworks, including pathology based frameworks (such as the Strategies for Engineered Negligible Senescence [SENS] framework) and process based frameworks (such as the Hallmarks of Aging framework) and the associated markers and current state of therapies and clinical or research access to these.

How can LEV be measured accurately? Initial models are needed that take into account a minimum number of quality measurements across broad clinical outcomes and frameworks of aging (such as SENS and Hallmarks of Aging). Optimal ranges for clinical outcomes can be established for diverse markers and used to create an effective "biological age" for individual organs or systemic aging pathologies. Combined with current best risk prediction calculators for broad sets of diseases as well as a current annual "coefficient of baseline gain in life expectancy" due to current innovation rates, and taking into account a qualitative measure of a person's financial budget, motivation, and "LEV-related education," a client's LEV might be be determined to fall within a certain range.

Research is paramount to accelerate the generation of evidence of efficacy and safety of new measurements, therapies, and clinical pathways that are relevant to LEV. A core element of LEV medicine should be that any novel practice across any aspect of LEV medicine, be it a new annual screening panel, an off label pharmaceutical, an experimental stem cell or gene therapy, should be part of a formal registry, with all data captured and published open access, and ideally collated to a central LEV society or organization for analysis, methodological and ethical critique, and distribution to parties that may benefit. For example, what proportion of potentially useful surrogate marker or clinical outcomes data is captured, collated, and distributed from the proportion of people globally experimenting with novel therapies? It is likely under 0.01%; global standards to capture such data usefully - such as via guidelines for basic experimental protocol that doctors and patients may follow for each novel intervention, as well as systems to capture, collate, analyze, and disseminate such data - could have ensured perhaps 1000 or 10,000 times more data on all novel practices to date, providing benefits for everyone.


How Would One Go About Building a Company to Bring Cheap Senolytics to the World?

Let us for a moment choose to believe that the dasatinib and quercetin combination is a senolytic treatment that does as well in humans as it does in mice. This is to say it kills about 25-50% of senescent cells in the tissues usually most affected by oral medications, meaning the kidney, liver, and cardiovascular system, and some unknown but lower fraction elsewhere. Whether or not this is the case has yet to be determined; the first pilot studies are still running at Betterhumans, and they likely won't tell us the size of the effect in terms of fraction of cells removed. Viable assays for cellular senescence that can be used in human medicine are in short supply - there is only the one that I know of that is ready to go, and even that has just reached the final stage of laboratory proof of concept. If it is the case, however, that treatment with dasatinib and quercetin works in much the same way in humans, then it should have a notably positive effect on the state of health for older individuals, given that the accumulation of senescent cells is one of the causes of aging.

The distinguishing feature of dasatinib and quercetin are that they are cheap. A senolytic therapy would be undergone perhaps once every few years at most; it kills the unwanted cells it can kill, and it is pointless to do it again before there has been enough time for new senescent cells to emerge at their slow pace. Quercetin is a widely used supplement, and enough of it for a single treatment costs less than a dollar. Dasatinib can be purchased from manufacturers for between $20 and $150 for a single dose suitable for senolytic therapy, depending on where the manufacturer is based. The FDA approved packaging of dasatinib, called Sprycel, costs $300-600 for the same amount, assuming you can find someone willing to break down a bottle of tablets to sell you the small amount needed. It is certainly possible to purchase Sprycel for less than this by ordering from outside the US.

If this pharmaceutical does work in humans as imagined above, then at these prices it is a therapy that would be affordable for a sizable portion of the world's population. It isn't the only candidate senolytic drug that is cheap enough to consider in this way. Once the first of these treatments are proven to be at least passably useful in human patients, what is the path to putting these low-cost rejuvenation therapies into the hands of hundreds of millions of people, the majority of which are not wealthy, as soon as possible? We should give this some thought, as it is a opportunity that will likely arrive much sooner than most of us expected it to. This is a big deal: early senolytics could provide a gain in health for much of humanity if the opportunity is managed correctly. That makes it worth consideration even prior to proof arriving in human studies.

There are always roadblocks. Like all such matters, the use of dasatinib is tied up by patents and regulation. No-one can build a large-scale business selling a pharmaceutical where the intellectual property and regulatory approval are owned by a large and influential concern - in this case Bristol-Myers Squibb (BMS). It is certainly the case that there is a healthy marketplace of scofflaws outside the US who sell directly from manufacturers, but they are not a single target, and it is hardly worth BMS's time to try to squash them while dasatinib is generating only the level of revenue possible for a cancer drug. That economic calculus may well change if it suddenly becomes a viable treatment for every older individual, and physicians show interest in off-label use - that is a vastly larger potential market. Certainly, BMS exerted their influence to block attempts to produce a cheaper generic version in India. That was associated with the Indian government and thus had a convenient single point of attack, unlike the manufacturer marketplace.

Dasatinib is still patent protected, at least until 2020, which means that any earnest effort to make dasatinib a household term in the near future would have to engage with BMS and gain at last tacit approval in order to grow. After 2020, no permission is needed. BMS will continue to tinker with their formula to extend patent protection on the versions of Sprycel that they sell, but they will no longer be able to directly make life difficult for those who wish to manufacture and sell dasatinib per the original formulation. The price will likely drop considerably at that point. So how could a group proceed if willing to found a company to work on distribution of low-cost senolytics?

The Non-Profit Approach

The most obvious option is to build a non-profit that focuses on education and partnership. The goal would be to deliver low-cost dasatinib and the understanding needed for widespread use to less wealthy regions of the world. The non-profit would focus on building relationships with physicians, medical organizations, manufacturers, and the product owner, BMS. There is considerable precedent for this sort of endeavor, and many larger pharmaceutical companies carry out in-house programs of this nature. It can benefit the pharmaceutical company considerably even if they make little to no revenue from the use of their product in those markets. It is usually the case that they wouldn't have been able to sell at profitable prices there anyway, and the program can be very good for their public image - something that Big Pharma entities are always in need of, for some strange reason.

The For-Profit Scofflaw Approach

Prior to 2020, one would require deep pockets and to be based outside the US, preferably in a country that doesn't regard the US with any great favor, in order to build something large that undercuts BMS, or even simply to sell into markets that BMS chooses not to serve. Being a small company that ships dasatinib at low cost from China to other parts of the world is probably viable, but growth to any significant size would bring a quick end to the endeavor. As mentioned, an attempt was made in India, where there is a history of threatening to break international intellectual property agreements in order to bring low-cost medications to that part of the world. That failed, and I'd say that India is probably the most likely region to successfully host a defensible patent breaking exercise.

The For-Profit BMS Enabler Approach

The enabler approach runs something like this: establish a path to obtain Sprycel in bulk at a workably low cost, and in an approved manner for the regulatory framework, and then build a revenue stream based on selling wrapped packages of services and Sprycel to physicians, nursing home operators, and other interested groups. Businesses and other organizations are better customers to start with in less wealthy regions, as there is a greater chance of being able to gain sufficient revenue to expand. Optionally, partner with BMS, though this is typically hard to do without connections.

The packages sold might include: educational materials and classes; professional services to assist with insurance and other regulatory concerns for prescribing off-label usage; membership of a network that helps bring in patients interested in the treatment and thus contributes to a physician's bottom line; tests and organization of testing services to evaluation results; and so forth. Everything is carried out in a such a way that it benefits BMS, such that the company has incentives to allow the business to grow. There are many possible variations on this theme, some of which are similar to the promotional activities carried out by the pharmaceutical companies themselves, while others look more like patient or physician associations or service organizations.

The Wait Until 2020 Approach

In either non-profit or for-profit models by which dasatinib might be distributed to the less wealthy regions of the world in volume, the prospects look a lot better once BMS is no longer the gatekeeper. The price of manufacture will fall precipitously, and an enterprising group with a good approach and competent execution might be able to do quite well in markets traditionally neglected by large pharmaceutical concerns. "Quite well" in this case would mean - under the assumptions at the top of this post - a significant number of people living incrementally longer in better health at a cost that is reasonable for them, considering the benefits achieved. That seems a worthwhile goal to aim for.

A Measure of Cerebrospinal Fluid Flow Suggests that Brain Aging Commences Early

There is a growing faction in the neurodegenerative research community whose members think it likely that rising levels of metabolic waste in brain, such as tau and amyloid aggregates, are due to failing drainage of cerebrospinal fluid. That drainage is a primary method of removal, and as it declines the wastes build up. The Methuselah Foundation is somewhat ahead of the game here, having incubated Leucadia Therapeutics to develop a possible solution. A number of other groups have turned their attention to this topic, and it has been interesting to see a flurry of papers in the last year or so. The work noted here is related, though the researchers are looking at circulation of cerebrospinal fluid within the brain, driven by cardiovascular activity, rather than drainage. The open access paper - worth looking at, but very dry - describes a low-cost way of assessing this flow and some exploration of the findings. Their measurements start to show changes at a comparatively early age, much earlier than one would expect for a process linked to cardiovascular function. This is quite interesting, though it is far too early to do more than speculate on why this might be the case.

Physicists have devised a new method of investigating brain function. This new non-invasive technique could potentially be used for any diagnosis based on cardiovascular and metabolic-related diseases of the brain. The researchers deciphered oscillations in the cerebrospinal fluid which lies between the scalp and skull; a device for non-invasive recordings of this translucent fluid was developed and recordings on healthy subjects were made.

It has been shown that the circulation throughout the brain of this fluid is highly fluctuating, and that these fluctuations are slow but interconnected by the rhythms of breathing and the heart rate. Researchers found that some of these oscillations are linked with blood pressure, but are generally slower, occurring at lower frequencies, which have been shown in previous studies to be related to oscillations in vascular motion and blood oxygenation.

Preliminary results showed evidence of a decline in the coherence between these oscillations in participants over the age of 25, indicating that brain ageing may begin earlier than expected. "Combining the technique to noninvasively record the fluctuation corresponding to cerebrospinal fluid and our sophisticated methods to analyse oscillations which are not clock-like but rather vary in time around their natural values, we have come to an interesting and non-invasive method that can be used to study ageing."


Arguing for Tau to be More Important than Amyloid-β in Alzheimer's Disease

This isn't the first paper I've seen to argue the point that there should be a greater focus on tau aggregation in Alzheimer's disease, and that tau may be more important to the progression of the condition. As I'm sure the readers here are aware, Alzheimer's is characterized by the buildup of both amyloid-β and tau in the brain. Forms of these normally soluble proteins precipitate into solid deposits that are accompanied by a complex halo of biochemistry that degrades the function of neurons and ultimately kills these cells. The primary focus for development of therapies has long been the removal of amyloid-β, but despite enormous effort there is no light at the end of the tunnel yet. The history of clinical trials for amyloid-β clearance is one of unremitting failure, even recently in trials that produced evidence for amyloid-β to be removed to some degree in patients.

It is much debated as to whether trials are failing because amyloid-β is the wrong target, despite being harmful in and of itself, or because Alzheimer's is a hard problem. Alzheimer's research has proceeded in parallel with mapping the brain at the necessary level to talk about how exactly it is damaged by protein aggregates, and also in parallel with the development of immunotherapy technologies, both of which are challenging areas of research and development. The biochemistry of the brain, its operation, and its failure modes are all enormously complex. We seem to be reaching a tipping point, however, in which discontent with the focus on amyloid-β is spilling over into greater emphasis and funding for alternatives. Rightly or wrongly in this specific case, I think that diversity in approaches is almost always better in the long term.

The hallmarks of Alzheimer's disease (AD) pathology are marked by accumulation of extracellular amyloid-β (Aβ) plaques in the brain followed by intracellular neurofibrillary tangle (NFT) growth. Aβ upregulates the generation of NFTs by increasing glycogen synthase kinase-3 (GSK-3) activity, leading to the phosphorylation of tau. Phosphorylated tau (pTau) begins to self-assemble to form NFTs. Aβ plaques, soluble Aβ oligomers, and NFTs interfere with normal neuronal cell function by disrupting synaptic signaling. Each protein's accumulation leads to neuron damage, eliciting diminished brain mass and cognitive function.

The removal of Aβ plaques does not influence elimination of NFTs after NFTs have been established in the brain, but early intervention can prevent pTau development. Therefore, targeted late stage treatments may specifically eliminate Aβ without impacting pTau levels that have already accumulated, which enables NFTs to continue amplifying cognitive deficits. Comparison of differences in pTau and Aβ levels in treated mice illuminate differences between the proteins' impact on cognitive function. For example, pTau levels were reduced by chemical treatment as Aβ levels continued to increase, yet cognitive function improved. This result implies that there is a quantitative difference between how the two proteins effect cognitive deterioration, and moreover, that decreasing pTau may ultimately be more important than reducing Aβ in the quest to successfully treat AD.

The Amyloid Cascade Hypothesis states that Aβ is the center piece in AD pathology leading to hyperphosphorylation of tau and numerous neurotoxic pathways causing cell death. Treatments targeting Aβ and Aβ precursors have failed to pass clinical trials to improve patient outcomes. The presence of Aβ is associated with a decrease in cognitive performance; however, the quantitative level of Aβ inconsistently predicts the amount of cognitive decline. Instead, it is suggested that other contributors, such as the hyperphosphorylation of tau, are the functional cause of degeneration after the initial onset of AD.

The present study compares the effects of Aβ and pTau levels on cognitive performance in the Morris water maze (MWM) and Novel Object Recognition (NOR) through a large-scale meta-analysis of 3xTg-AD mouse model experiments. The triple-transgenic mouse model (3xTg-AD) of AD expresses tangle and plaque pathology as well as synaptic dysfunction. Multiple linear regression confirmed pTau is a stronger predictor of MWM performance than Aβ. Despite pTau's lower physical concentration than Aβ, pTau levels more directly and quantitatively correlate with 3xTg-AD cognitive decline.


An Energetic Exploration of the Biochemistry of Cellular Senescence is Underway

In 2011 a research group published the results from an animal study that demonstrated, in a way that couldn't be ignored, that the accumulation of senescent cells is a significant cause of aging and age-related disease. In fact, the evidence for this to be the case had been compelling for a very long time - this demonstration came nearly a decade after Aubrey de Grey, on the basis of the existing evidence at the time, included cellular senescence as one of the causes of aging in the first published version of his SENS research proposals. Yet nothing had been done to move ahead and achieve something with this knowledge. That did not change until researchers obtained sufficient philanthropic funding to run the 2011 animal study, using a sophisticated genetic mechanism that eliminated senescent cells as they formed.

From that point on, a slow-moving avalanche of interest and funding fell into this part of the field of aging research. All of the groups with an existing interest in cellular senescence, and that had previously struggled to raise sufficient resources to make progress, could now move rapidly. With the aim of selectively destroying senescent cells to reverse aspects of aging, small molecule senolytic pharmaceuticals and then other methods such as gene therapies and immunotherapies were discovered or constructed. Today there are at least a dozen such small molecule drugs, published and in the works, and a handful of increasingly well-funded startup biotech companies bringing these therapies to human trials and the clinic.

That is the practical side that will lead to rejuvenation treatments in the near future. But the pure scientific impulse isn't to build new technology, it is to learn how our biochemistry works. Much of the funding for further work on cellular senescence goes towards mapping and understanding its details. Now that it is inarguable that this phenomenon is important in the progression of degenerative aging, scores of research groups are picking apart the biochemistry of senescent cells. They are categorizing, trying to understand whether all senescence is essentially the same, or whether there are significant differences in different cell types. They are attempting to better grasp all of the relevant mechanisms that operate inside cells as senescence occurs, and how the triggering change works - or, indeed, whether or not it is a single trigger. They are exploring the details of the senescence-associated secretory phenotype (SASP), the means by which these cells cause harm to tissues.

The four open access papers noted here are recent examples of this sort of thing. There is a great deal to learn, and while the work is largely irrelevant to the senolytic therapies currently in development, there will no doubt be discoveries that steer and inform development of the second generation of more subtle and sophisticated therapies. Those will likely commence development five to ten years from now, and be mature and in widespread use by the early 2030s.

TNFα-senescence initiates a STAT-dependent positive feedback loop, leading to a sustained interferon signature, DNA damage, and cytokine secretion

Cellular senescence is a cell fate program that entails essentially irreversible proliferative arrest in response to damage signals. Tumor necrosis factor-alpha (TNFα), an important pro-inflammatory cytokine secreted by some types of senescent cells, can induce senescence in mouse and human cells. However, downstream signaling pathways linking TNFα-related inflammation to senescence are not fully characterized. Using human umbilical vein endothelial cells (HUVECs) as a model, we show that TNFα induces permanent growth arrest and increases p21CIP1, p16INK4A, and SA-β-gal, accompanied by persistent DNA damage and ROS production. By gene expression profiling, we identified the crucial involvement of inflammatory and JAK/STAT pathways in TNFα-mediated senescence. We found that TNFα activates a STAT-dependent autocrine loop that sustains cytokine secretion and an interferon signature to lock cells into senescence.

3′ UTR lengthening as a novel mechanism in regulating cellular senescence

Cellular senescence has been viewed as a tumor suppression mechanism and also as a contributor to individual aging. Widespread shortening of 3′ untranslated regions (3′ UTRs) in messenger RNAs (mRNAs) by alternative polyadenylation (APA) has recently been discovered in cancer cells. However, the role of APA in the process of cellular senescence remains elusive. Here, we found that hundreds of genes in senescent cells tended to use distal poly(A) (pA) sites, leading to a global lengthening of 3′ UTRs and reduced gene expression. Genes that harbor longer 3′ UTRs in senescent cells were enriched in senescence-related pathways. Rras2, a member of the Ras superfamily that participates in multiple signal transduction pathways, preferred longer 3′ UTR usage and exhibited decreased expression in senescent cells. Depletion of Rras2 promoted senescence, while rescue of Rras2 reversed senescence-associated phenotypes.

The SCN9A channel and plasma membrane depolarization promote cellular senescence through Rb pathway

Oncogenic signals lead to premature senescence in normal human cells causing a proliferation arrest and the elimination of these defective cells by immune cells. Oncogene-induced senescence (OIS) prevents aberrant cell division and tumor initiation. In order to identify new regulators of OIS, we performed a loss-of-function genetic screen and identified that the loss of SCN9A allowed cells to escape from OIS. The expression of this sodium channel increased in senescent cells during OIS. This upregulation was mediated by NF-κB transcription factors, which are well-known regulators of senescence. Importantly, the induction of SCN9A by an oncogenic signal or by p53 activation led to plasma membrane depolarization, which in turn, was able to induce premature senescence. Computational and experimental analyses revealed that SCN9A and plasma membrane depolarization mediated the repression of mitotic genes through a calcium/Rb/E2F pathway to promote senescence.

Mitochondrial (Dys) Function in Inflammaging: Do MitomiRs Influence the Energetic, Oxidative, and Inflammatory Status of Senescent Cells?

A relevant feature of aging is chronic low-grade inflammation, termed inflammaging, a key process promoting the development of all major age-related diseases. Senescent cells can acquire the senescence-associated (SA) secretory phenotype (SASP), characterized by the secretion of proinflammatory factors fuelling inflammaging. Cellular senescence is also accompanied by a deep reshaping of microRNA expression and by the modulation of mitochondrial activity, both master regulators of the SASP. Here, we synthesize novel findings regarding the role of mitochondria in the SASP and in the inflammaging process and propose a network linking nuclear-encoded SA-miRNAs to mitochondrial gene regulation and function in aging cells. In this conceptual structure, SA-miRNAs can translocate to mitochondria (SA-mitomiRs) and may affect the energetic, oxidative, and inflammatory status of senescent cells.

Assembling Cells and Scaffolds into a Suitable Trachea Replacement

Researchers here report on their efforts to build a suitable structure to replace a trachea, starting with patient cells and artificial scaffolds. Since the trachea is a thin-walled pipe, engineered tissue can be constructed in this way without the need for complex blood vessel networks, as at no point is the tissue so thick as to prevent direct perfusion of nutrients and oxygen to the inner cells. Unfortunately, it remains the case that decellularized donor tissue is the only reliable solution for the production of capillaries to support thicker tissues, scores of such vessels passing through every square millimeter. This is why most of the more ambitious work, closer to clinical application, involves thin tissues and tubular structures - larger blood vessels, skin, and so forth - while everyone else is working with the tiny sections of engineered tissue known as organoids.

Biomedical engineers are growing tracheas by coaxing cells to form three distinct tissue types after assembling them into a tube structure - without relying on scaffolding strategies currently being investigated by other groups. "The unique approach we are taking to this problem of trachea damage or loss is forming tissue modules using a patient's cells and assembling them into a more complex tissue." Recent tissue engineering approaches using synthetic or natural materials as scaffolding for cells have met with challenges. Difficulties have included uniformly seeding cells on the scaffolding, recreating the multiple different tissue types found in the native trachea, tailoring the scaffolding degradation rate to equal the rate of new tissue formation, and recreating important contacts between cells because of the intervening scaffold.

The trachea engineering strategy now being pursued, however, wouldn't have those problems because it doesn't rely on a separate scaffold structure. A new trachea replacement must do three critical things to function properly: (1) maintain rigidity to prevent airway collapse when the patient breathes; (2) contain immunoprotective respiratory epithelium, the tissue lining the respiratory tract, which moistens and protects the airway and functions as a barrier to potential pathogens and foreign particles; and (3) integrate with the host vasculature, or system of blood vessels, to support epithelium viability.

The self-assembling rings developed by researchers meet all three of those requirements because they can fuse together to form tubes of both cartilage and "prevascular" tissue types. Prevascular refers to tissues potentially ready to participate in the formation of blood vessels, though not yet functional in that way. The cartilage rings are formed by aggregating marrow-derived-stem cells in ring-shaped wells. Polymer microspheres containing a protein that induces the stem cells to become "chondrocytes," or cells that form cartilage, are also incorporated into the cell aggregates. These prevascular rings are comprised of both these marrow-derived stem cells and endothelial cells, the thin layer of cells that line the interior of blood vessels.

The researchers then coat the tubes with epithelial cells to form multi-tissue constructs that satisfy all of those requirements: cartilage provides rigidity, epithelium serves the role of immunoprotection and the vascular network would ultimately permit blood flow to feed and integrate the new trachea tissue. Using this method, the team has been able to engineer highly elastic "neo-tracheas" of various sizes, including tissues similar to human trachea. When these tracheas were implanted under the skin in mice, there was evidence the prevascular structures could join up with the host vascular supply.


Astrocytes Become Inflammatory in the Aging Brain

Astrocytes are one of the common types of support cell in the brain, performing a wide variety of tasks that range from repair to maintaining the balance of various signal and electrolyte molecules. Researchers find evidence to suggest that astrocytes shift into an inflammatory mode in large numbers with advancing age. Chronic inflammation is a feature of most neurodegenerative conditions, and of aging in the broader sense. It disrupts the complex relationships between cell types that are needed for most sophisticated behavior in tissues, such as regeneration, or any number of cell communication processes required for correct function of the brain.

This is particularly interesting in the context of recent findings regarding cellular senescence in astrocytes. A large fraction of these cells show some signs of senescence in older individuals, and one of the characteristic bad behaviors of senescent cells is the generation of chronic inflammation through the senescence-associated secretory phenotype. Researchers have pinned down astrocyte senescence as a contributing factor in Parkinson's disease, for example. It is also worth noting that this business of cells shifting into an inflammatory mode in greater numbers with advancing age is also observed in macrophages, where it disrupts regenerative processes, and in microglia, another of the support cells of the brain. They also generate chronic inflammation in brain tissue, which contributes to the complicated breakdown of the normal operation of the brain.

The decline of cognitive function occurs with aging, but the mechanisms responsible are unknown. Astrocytes instruct the formation, maturation, and elimination of synapses, and impairment of these functions has been implicated in many diseases. These findings raise the question of whether astrocyte dysfunction could contribute to cognitive decline in aging. We performed RNA sequencing of astrocytes from different brain regions across the lifespan of the mouse. We found that astrocytes have region-specific transcriptional identities that change with age in a region-dependent manner.

Detailed analysis of the differentially expressed genes in aging revealed that aged astrocytes take on a reactive phenotype of neuroinflammatory A1-like reactive astrocytes. Hippocampal and striatal astrocytes up-regulated a greater number of reactive astrocyte genes compared with cortical astrocytes. Moreover, aged brains formed many more A1 reactive astrocytes in response to the neuroinflammation inducer lipopolysaccharide.

We found that the aging-induced up-regulation of reactive astrocyte genes was significantly reduced in mice lacking the microglial-secreted cytokines (IL-1α, TNF, and C1q) known to induce A1 reactive astrocyte formation, indicating that microglia promote astrocyte activation in aging. Since A1 reactive astrocytes lose the ability to carry out their normal functions, produce complement components, and release a toxic factor which kills neurons and oligodendrocytes, the aging-induced up-regulation of reactive genes by astrocytes could contribute to the cognitive decline in vulnerable brain regions in normal aging and contribute to the greater vulnerability of the aged brain to injury.


Recent Genetic Studies Claiming a Slowing of Aging may be Largely Incorrect

It is fair to ignore most studies showing extension of life span in laboratory species conducted much prior to the turn of the century. A majority failed to control for calorie restriction, and thus the (usually small) effects evaporate when more rigorously tested. The way this works is that an intervention makes mice nauseous or otherwise uncomfortable, they eat less as a consequence, and thus live longer solely due to lowered calorie intake. This is on top of the usual estimate that most of all published research results are flawed in some way. That includes animal studies that use too few animals, and thus tend to be prone to statistical happenstance, for example. Small studies with few animals are distressingly common in the study of aging, where funding is typically very restricted. Matters did improve once it was no longer possible to be ignorant of the size of the calorie restriction effect on longevity in short-lived species, as that research gained increasing popularity and interest after the 1990s. But as the open access paper I'll point out here suggests, not improved enough.

I think that part of the problem is that too many people were - and still are - trying to evaluate marginal effects on aging. It is hard to accurately detect and quantify small effects in animal studies. A 10% life span extension observed in a group of twenty mice, as compared to a control group of twenty mice, tells us just about nothing other than perhaps it would be good to seek corroboration in a group five times that size - and this example is around the size of effect for most reported interventions based on adjusting the operation of metabolism to slow aging.

One thing I wish was better understood and discussed in our community of advocates, supporters, and researchers is that size of effect and reliability of effect matter enormously. They are the point of the exercise, and the future of our health depends upon them. Everything shown to result in either small or only intermittently apparent outcomes should be rapidly dropped in favor of the continuing search for truly useful approaches to aging. Senescent cell clearance is a shining example of reliability: it always works; it works on many different aspects of aging; it works to treat many different age-related diseases; in fact it puts just about everything else tried to date to shame. The only item from the camp of metabolic manipulation that is as reliable in animal studies is the use of mTOR inhibitors such as rapamycin - and they are notably less effective when it comes to impact on specific age-related diseases. All in all, far too much time and effort is wasted on hoping that unreliable approaches with small effects are magically hiding something useful.

A Reassessment of Genes Modulating Aging in Mice Using Demographic Measurements of the Rate of Aging

The discovery that single gene manipulations can significantly modulate longevity is arguably the major breakthrough in biogerontology thus far. Genetic manipulations of aging in mice are crucial to gather insights into the underlying mechanisms of aging, to discover pathways modulating longevity and to identify candidate genes for drug discovery. Moreover, the manipulation of the aging process in mammalian models (particularly mice) via genetic manipulation (gene knockouts, overexpression, etc.) is crucial to test mechanistic hypotheses of aging. However, determining if such genetic interventions actually affect the aging process and not some others factor of health is not always straightforward.

For example, should a genetic intervention reduce an organism's resistance to disease, this could conceivably reduce the lifespan of the organism, although the rate of aging would not have been affected. Differentiating between genetic interventions that affect the lifespan of an organism through altered health as opposed to changes in the rate of aging is therefore essential to gain insights on aging, and determine interventions with wide ranging effects.

There are two fundamental methods to determine if a life-extending genetic intervention has altered the rate of aging rather than general health. One can track the onset and progression of age-related ailments and physiological degeneration to determine if there is a shift in the onset and on progression of the ailment. In addition, efforts have been made to quantify aging rates with mathematical models such as the Gompertz law of mortality. From the Gompertz parameters, the mortality rate doubling time (MRDT) can be calculated. The MRDT is the amount of time it takes for the mortality rate to double for a given cohort.

A change in MRDT indicates a change in the demographic rate of aging, which is not a perfect reflection of biological aging but a metric that correlates with physiological deterioration and health. Although some studies have investigated MRDT, many authors still often assume that changes in the lifespan of mice following a genetic intervention directly equates to changes in the rate of aging, leading to the misrepresentation of certain genes as having a causal role in aging, when in reality they do not.

Many studies have reported altered median and/or maximum lifespan as a result of an intervention but lifespan alterations may have a number of causes, including altered age at onset of senescence and age-independent mortality. To address this lack of distinction, we previously used linear regression to fit the Gompertz model to longevity data from published mouse studies, and statistically compared the rates of aging in these cohorts. For example, we showed that caloric restriction increases the MRDT and thus retards the demographic rate of aging. Here, the same methodology was employed to reassess mouse longevity data published since 2005 and to identify which genes are more important in determining the demographic rate of aging.

Overall, only 7 of 54 genes were found to have a statistically significant effect on the demographic rate of aging as expected from longevity manipulations. These results suggest that only a relatively small proportion of interventions reported to affect longevity in mice do so through directly influencing the demographic rate of aging. Surprisingly, 20 of 54 genes had a statistically significant impact on the demographic rate of aging in the opposite direction than would be expected for the published longevity effects. One possible explanation is that many mutations impacted on various parameters affecting longevity in non-linear ways, and indeed we observed that increases in aging independent mortality correlated with a slower demographic aging rate. For instance, Sirt1 deficiency extended lifespan but increased the demographic rate of aging; its effect appeared to be exerted instead by delaying the age of onset of mortality rate escalation. This highlights the complex relationship between lifespan and the demographic rate of aging.

Another caveat of our approach concerns the number of mice used in some of the original studies, which ranged from 10 to 146 animals per cohort. Whilst research reported here has attempted to compensate for this by using the Gompertz equation which allows for small sample sizes, one cannot escape the low statistical power that accompanies such small sample sizes. Interestingly, caloric restriction has been shown to significantly retard the demographic rate of aging, but this was a large study with over 200 animals in total. Therefore, caution must be taken when interpreting some of the results detailed here from studies with small sample sizes. Indeed, we observed that in smaller experimental cohorts subjective decisions in estimating Gompertz parameters can significantly affect the results.

Our main conclusions are: 1) most genetic manipulations of longevity in mice do so by modulating aging-independent mortality; 2) there is substantial variation in the lifespan of controls of the same strain across experiments; 3) studies in which the lifespan of the controls is short have a greater lifespan increase, emphasizing the importance of having adequate control groups; 4) mouse lifespan studies employing small cohorts can yield unreliable results; 5) lifespan-reducing experiments tend to be noisier and more difficult to analyze for demographic parameters than life-extending experiments; 6) a greater aging-independent mortality is usually accompanied by a slower demographic aging rate.

How Does Age Affect Induced Pluripotency for Regenerative Medicine?

One of the more intriguing discoveries relating to the cell reprogramming used to produce induced pluripotent stem cells is that this process appears to reverse some aspects of cell aging. It perhaps triggers some fraction of the mechanisms at work in early embryonic development, those that ensure that children are born young, with nowhere near the load of persistent damage present in the adult parents. This is not a well-explored topic, unfortunately - it is still too recent for much to be said in certainty, and a sizable fraction of the evidence is conflicting. Related to all of this is the question of how exactly the age of the donor affects the reprogramming of donated cells. Near all potential uses of regenerative medicine based on reprogrammed cells involve age-related disease and older individuals. It is important to understand whether it is safe to proceed, how effective approaches might be in practice, and where the problems lie, so that they can be addressed.

Induced pluripotent stem cells (iPSCs) avoid many of the restrictions that hamper the application of human embryonic stem cells, and the donor's clinical phenotype is often known when working with iPSCs. Therefore, iPSCs seem ideal to tackle the two biggest tasks of regenerative medicine: degenerative diseases with genetic cause (e.g., Duchenne's muscular dystrophy) and organ replacement in age-related diseases (e.g., end-stage heart or renal failure), especially in combination with recently developed gene-editing tools.

In the setting of autologous transplantation in elderly patients, donor age becomes a potentially relevant factor that needs to be assessed. Here, we review and critically discuss available data pertinent to the questions: How does donor age influence the reprogramming process and iPSC functionality? Would it even be possible to reprogram senescent somatic cells? How does donor age affect iPSC differentiation into specialised cells and their functionality? We also identify research needs, which might help resolve current unknowns.

Until recently, most hallmarks of ageing were attributed to an accumulation of DNA damage over time, and it was thus expected that DNA damage from a somatic cell would accumulate in iPSCs and the cells derived from them. In line with this, a decreased lifespan of cloned organisms compared with the donor was also observed in early cloning experiments. Therefore, it was questioned for a time whether iPSC derived from an old individual's somatic cells would suffer from early senescence and, thus, may not be a viable option either for disease modelling nor future clinical applications. Instead, typical signs of cellular ageing are reverted in the process of iPSC reprogramming, and iPSCs from older donors do not show diminished differentiation potential nor do iPSC-derived cells from older donors suffer early senescence or show functional impairments when compared with those from younger donors.

Thus, the data would suggest that donor age does not limit iPSC application for modelling genetic diseases nor regenerative therapies. However, open questions remain, e.g., regarding the potential tumourigenicity of iPSC-derived cells and the impact of epigenetic pattern retention.


Towards Lasting Therapeutic Manufactories that Operate Inside the Body

Gene therapies involve delivering instructions into cells to ensure that specific proteins are manufactured, either temporarily or permanently. This is effectively a hijacking or programming of cellular mechanisms. There is another approach, which is to deliver suitable DNA machinery into the body, capable of manufacturing the desired proteins outside cells. This isn't helpful for all types of protein, but in many cases it is. That machinery needs protection, however: naked, it would be quickly removed by the immune system or otherwise broken down. One possibility is to employ engineered bacteria, which removes the need to introduce changes into a patient's cells, but adds a sizable set of other complications. Another approach is to build a suitable structure from scratch, such as a membrane that will not alert the immune system, containing a carefully limited set of DNA machinery that will turn out the desired proteins for a lengthy period of time, but is incapable of any other activity. These constructs would in many ways resemble extracellular vesicles more than cells, and the research community has been capable of building such things for a few years now.

Researchers have successfully treated a cancerous tumor using a "nanofactory" - a synthetic cell that produces anti-cancer proteins within the tumor tissue. The research combines synthetic biology, to artificially produce proteins, and targeted drug delivery, to direct the synthetic cell to abnormal tissues. The synthetic cells are artificial systems with capacities similar to, and, at times, superior to those of natural cells. Just as human cells can generate a variety of biological molecules, the synthetic cell can produce a wide range of proteins. Such systems bear vast potential in the tissue engineering discipline, in production of artificial organs and in studying the origins of life. Design of artificial cells is a considerably complex engineering challenge being pursued by many research groups across the globe.

The researchers integrated molecular machines within lipid-based particles resembling the natural membrane of biological cells. They engineered the particles such that when they "sense" the biological tissue, they are activated and produce therapeutic proteins, dictated by an integrated synthetic DNA template. The particles recruit the energy sources and building blocks necessary for their continued activity, from the external microenvironment (e.g., the tumor tissue).

After experiments in cell cultures in the lab, the novel technology was also tested in mice. When the engineered particles reached the tumor, they produced a protein that eradicated the cancer cells. The particles and their activity were monitored using a green fluorescent protein (GFP), generated by the particles. This protein can be viewed in real-time, using a fluorescence microscope. "By coding the integrated DNA template, the particles we developed can produce a variety of protein medicines. They are modular, meaning they allow for activation of protein production in accordance with the environmental conditions. Therefore, the artificial cells we've developed may take an important part in the personalized medicine trend - adjustment of treatment to the genetic and medical profile of a specific patient."


HDAC3 Knockout Mice Exhibit Greatly Reduced Loss of Memory Function with Age

Work on the decline of memory formation with aging was presented at a recent conference and is doing the rounds in the press. The core of it was published and presented last year, so the overall topic isn't particularly new, but I didn't notice it at the time. The scientific group in question is interested in the role of histone deacetylases (HDACs) in memory. This is a long-running thread of research. Looking back in the Fight Aging! archives, inhibition of HDACs in the context of improved neural function was mentioned in 2012, and a trail of publications exists prior and since.

The processes of acetylation and deacetylation of histones are important to gene regulation, a core part of the machinery that controls the packaged state of nuclear DNA in the cell nucleus. Genes must be accessible to the machinery of the cell in order to begin transcription, the first step in the complex operations involved in constructing proteins from their genetic blueprints. Whether a specific gene is accessible or inaccessible is determined by the state of various different histones, among other mechanisms. What does this have to do with memory? The formation of memory requires reliable access to certain genes, and the production of their proteins, but it is apparently the case that access becomes less available with age. One of the histones, HDAC3, becomes overactive, keeping DNA more tightly packaged than was the case in younger individuals.

Researchers have now demonstrated that mice lacking HDAC3 do not seem to suffer much in the way of side-effects, and also do not suffer age-related loss of memory - though this effect differs in detail for the various types of memory tested to date. It is worth considering that these mechanisms are a snapshot of some middle layer of the long chain of cause and effect that stretches between the root causes of aging and the ultimate consequences of age-related disease and organ failure. Why does HDAC3 become more active in older individuals? What underlying process is taking place, and what other harms is that process causing? Leaping to interventions has a way of short-cutting the conversation about deeper causes that should be taking place, especially when the interventions are comparatively easy to implement - there are plenty of approaches to HDAC3 inhibition that might be taken at low cost and in the near future, even given the need to bypass the blood-brain barrier. But what is shut out by taking that path as the primary focus?

Research cracks code to restoring memory creation in older or damaged brains

Aging or impaired brains can once again form lasting memories if an enzyme that applies the brakes too hard on a key gene is lifted. "What we've discovered is that if we free up that DNA again, now the aging brain can form long-term memories normally. In order to form a long-term memory, you have to turn specific genes on. In most young brains, that happens easily, but as we get older and our brain gets older, we have trouble with that." That's because the 6 feet of DNA spooled tightly into every cell in our bodies has a harder time releasing itself as needed. Like many body parts, "it's no longer as flexible as it used to be." The stiffness in this case is due to a molecular brake pad called histone deacetylase 3, or HDAC3, that has become "overeager" in the aged brain and is compacting the material too hard, blocking the release of a gene called Period1. Removing HDAC3 restores flexibility and allows internal cell machinery to access Period1 to begin forming new memories.

Researchers had previously theorized that the loss of transcription and encoding functions in older brains was due to deteriorating core circadian clocks. But it was found that the ability to create lasting memories was linked to a different process - the overly aggressive enzyme blocking the release of Period1 - in the same hippocampus region of the brain. That's potentially good news for developing treatments. "New drugs targeting HDAC3 could provide an exciting avenue to allow older people to improve memory formation."

NIH Summit Examines What Makes a Healthy Aging Brain

Histone deacetylase HDAC3 is expressed predominantly in the brain and represses gene expression. Researchers knocked out the HDAC3 gene in the dorsal hippocampi of mice, then trained them at young or old ages on a novel object-location task. Young mice performed equally well, regardless of whether they expressed HDAC3. In older animals the story was different. Wild-type animals became forgetful, whereas HDAC3-deficient mice remembered just as well as did young mice. This suggests HDAC3 hampers memory as mice age. In keeping with this, long-term potentiation weakened with age in wild-type but not HDAC3 knockout mice. Since knocking out HDAC3 restored hippocampal expression of Period1 (Per1), a master regulator of the cellular circadian clock, HDAC3 might function to help regulate circadian genes in the hippocampus.

Distinct roles for the deacetylase domain of HDAC3 in the hippocampus and medial prefrontal cortex in the formation and extinction of memory

Histone deacetylases (HDACs) are chromatin modifying enzymes that have been implicated as powerful negative regulators of memory processes. HDAC3 has been shown to play a pivotal role in long-term memory for object location as well as the extinction of cocaine-associated memory, but it is unclear whether this function depends on the deacetylase domain of HDAC3. Here, we tested whether the deacetylase domain of HDAC3 has a role in object location memory formation as well as the formation and extinction of cocaine-associated memories. Using a deacetylase-dead point mutant of HDAC3, we found that selectively blocking HDAC3 deacetylase activity in the dorsal hippocampus enhanced long-term memory for object location, but had no effect on the formation of cocaine-associated memory.

When this same point mutant virus of HDAC3 was infused into the prelimbic cortex, it failed to affect cocaine-associated memory formation. With regards to extinction, impairing the HDAC3 deacetylase domain in the infralimbic cortex had no effect on extinction, but a facilitated extinction effect was observed when the point mutant virus was delivered to the dorsal hippocampus. These results suggest that the deacetylase domain of HDAC3 plays a selective role in specific brain regions underlying long-term memory formation of object location as well as cocaine-associated memory formation and extinction.

Further Investigation of the Role of Osteopontin in Hematopoietic Stem Cell Aging

The Hematopoietic stem cell population resident in bone marrow is responsible for generating blood cells and immune cells. Like all stem cell populations, their activity alters and declines with aging. This is one of the causes of the progressive disarray of the immune system in older individuals. If we want to rejuvenate the immune system, then restoring the youthful activity of hematopoietic stem cells is one of the items on the to-do list, alongside regrowth of the thymus, and clearing out the accumulation of exhausted, senescent, and misconfigured immune cells.

The protein osteopontin appears to have a sizable role in maintaining the hematopoietic stem cell population, but levels fall in older individuals. Researchers have demonstrated, in mice, that restoring high levels osteopontin can also restore a significant degree of hematopoietic stem cell activity. This is promising because it is comparatively simple to achieve and package as a therapy, but equally it isn't addressing whatever root causes underlie this narrow view of the picture. The open access paper here continues the investigation of osteopontin in the context of hematopoietic aging in mice, adding further evidence for its relevance.

In mammalian tissues that undergo high cell turnover, such as the hematopoietic system, a small population of stem cells maintains organ regeneration throughout the animal's life span. However, the functionality of stem cells declines during aging and can contribute to aging-associated impairments in tissue regeneration. Accumulating evidence indicates that aged hematopoietic stem cells (HSCs) increase in number due to a higher rate of self-renewal cell divisions while displaying reduced ability to reconstitute the immune system.

The phosphorylated glycoprotein osteopontin (OPN) is an extracellular matrix component of the bone marrow with important roles in tissue homeostasis, inflammatory responses, and tumor metastasis. The expression of OPN within the bone marrow is highly restricted to the endosteal surface, a location where HSCs have been found to reside preferentially. OPN binds to cells through integrins or the CD44 receptor, subsequently activating multiple signaling pathways. When HSCs are transplanted into wild-type (WT) or OPN knockout mice, they exhibit aberrant attachment and engraftment, suggesting the dependence of HSCs on OPN in these processes. Moreover, OPN deficiency within the bone marrow microenvironment results in an increase in primitive HSC numbers. More recently it has been reported that osteopontin exposure to aged HSC can attenuate their aging-associated phenotype.

Here, we study the impact of OPN on HSC function during aging using an OPN-knockout mouse model. We show that during aging OPN deficiency is associated with an increase in lymphocytes and a decline in erythrocytes in peripheral blood. In a bone marrow transplantation setting, aged OPN-deficient stem cells show reduced ability to reconstitute the immune system likely due to insufficient differentiation of HSCs into more mature cells. In serial bone marrow transplantation, aged OPN knockout bone marrow cells fail to adequately reconstitute red blood cells and platelets, resulting in severe anemia and thrombocytopenia as well as premature deaths of recipient mice. Thus, OPN has different effects on HSCs in aged and young animals and is particularly important to maintain stem cell function in aging mice.


Bacteria Engineered to Deliver CXCL12 Accelerate Wound Healing in Mice

Researchers here report on an interesting approach used to deliver a therapeutic molecule into wounds, and thereby accelerate regeneration. They engineered a common bacterial species to produce the molecule of interest, CXCL12, which is implicated in the processes of wound healing. Those processes are an intricate dance between various types of immune cell, stem cell, senescent cell and somatic cells in the injured tissue. In recent years researchers have gained an increased understanding of the scope of involvement of immune cells known as macrophages; the participation of the immune system has turned out to be much more important to the quality and pace of regeneration than was thought a few decades ago. Macrophages can adopt different states, or polarizations. Of the two commonly observed polarizations, one is inflammatory and harmful to regeneration, while the other assists regeneration. There appears to be some potential in therapies that adjust the proportions of a macrophage population in injured tissue to favor the second type - and this is one of the goals that the researchers here aimed to achieve in their study.

During the inflammation phase of wound healing, immune cells accumulate in response to alarm signals, cytokines, and chemokines released by injured or activated cells. The chemokine CXCL12 (Stromal cell-Derived Factor 1α) is associated with beneficial effects in models of cutaneous wounds and binds CXCR4 expressed by immune cells and keratinocytes. Macrophages and neutrophils represent the major immune cell populations at the wound site, where they are essential for keeping invading microorganisms at bay and also for fueling the healing process by secreting additional chemokines, growth factors, and matrix digesting enzymes. During the course of healing, macrophages shift phenotype toward an anti-inflammatory one and subsequently promote tissue restitution. This shift is induced by macrophage phagocytosis of cell debris and by microenvironmental signals such as CXCL12.

Chronic wounds are often associated with underlying pathologic processes that increase susceptibility for acquiring wounds (e.g., peripheral neuropathies) and/or reduced healing abilities as seen in persons with arterial or venous insufficiencies. Several experimental and clinical trials have investigated the effects of local application of growth factors alone or coupled to different biomaterials on different types of chronic wounds, but with modest results so far.

This study aimed to accelerate wound healing by targeting the function of immune cells through local bioengineering of the wound microenvironment. To achieve this, a technology optimized to deliver chemokines directly to wounded skin was developed, whereby lactic acid bacteria were used as vectors. Lactobacillus reuteri bacteria were transformed with a plasmid encoding the chemokine CXCL12 previously associated with beneficial effects in models of healing and blood-flow restoration. Bacteria-produced lactic acid reduced the pH in the wound and thereby potentiated the effects of the produced CXCL12 by prolonging its bioavailability. The overall result of topical wound treatment with this on-site chemokine delivery system was strongly accelerated wound closure to an extent not reported before.

Importantly, treatment with CXCL12-delivering Lactobacilli also improved wound closure in mice with hyperglycemia or peripheral ischemia, conditions associated with chronic wounds, and in a human skin wound model. Further, initial safety studies demonstrated that the topically applied transformed bacteria exerted effects restricted to the wound, as neither bacteria nor the chemokine produced could be detected in systemic circulation.


Development of Exosome Delivery as a Regenerative Therapy Continues Apace

If many stem cell therapies produce their benefits largely through the signaling generated by the transplanted cells, in a brief window of time before these cells die, unable to integrate into the local tissue, then why not skip the cells entirely and just deliver the signals? This is made an easier prospect by the fact that a great deal of cell to cell signaling takes the form of extracellular vesicles such as exosomes, tiny membrane-bound packages of various molecules. Thus researchers don't need to completely map and understand the entire set of signals used in order to recreate most of the signaling effects of stem cells. Given a cultured stem cell population, the exosomes that the cells produce can be harvested and then employed as a therapy. Further down the line, after the mapping and the understanding is complete, then manufacture of exosomes from scratch will probably become the standard approach. For now, cells are required for that much, at least.

The research noted here is an illustrative example of present work on exosome-based regenerative therapies; a fair number of research groups are working towards treatments for various tissue types and age-related conditions. As a class, exosome therapies seem about as promising as early stem cell therapies, based on the results to date in animal models, and are arguably more easily controlled and managed than cells. Just considering the logistics of manufacture and storage, the costs should be significantly lower. Scientists are working their way up from mice to larger animal models, and the first human clinical trials for various conditions are on the near horizon. It is a significant shift in focus for the stem cell research community, and it will be interesting to see where this leads in the next few years.

Stem-cell based stroke treatment repairs brain tissue

A team of researchers and ArunA Biomedical, a startup company, have developed a new treatment for stroke that reduces brain damage and accelerates the brain's natural healing tendencies in animal models. The research team created a treatment called AB126 using extracellular vesicles (EV), fluid-filled structures known as exosomes, which are generated from human neural stem cells. Fully able to cloak itself within the bloodstream, this type of regenerative EV therapy appears to be the most promising in overcoming the limitations of many cell therapies ­- with the ability for exosomes to carry and deliver multiple doses - as well as the ability to store and administer treatment. Small in size, the tiny tubular shape of an exosome allows EV therapy to cross barriers that cells cannot.

Following the administration of AB126, the researchers used MRI scans to measure brain atrophy rates in preclinical, age-matched stroke models, which showed an approximately 35 percent decrease in the size of injury and 50 percent reduction in brain tissue loss - something not observed acutely in previous studies of exosome treatment for stroke. Outside of rodents, the results were replicated using a porcine model of stroke. Based on these pre-clinical results, ArunA Biomedical plans to begin human studies in 2019. The company has plans to expand this initiative beyond stroke for preclinical studies in epilepsy, traumatic brain and spinal cord injuries later this year.

Human Neural Stem Cell Extracellular Vesicles Improve Tissue and Functional Recovery in the Murine Thromboembolic Stroke Model

Over 700 drugs have failed in stroke clinical trials, an unprecedented rate thought to be attributed in part to limited and isolated testing often solely in "young" rodent models and focusing on a single secondary injury mechanism. Here, extracellular vesicles (EVs), nanometer-sized cell signaling particles, were tested in a mouse thromboembolic (TE) stroke model. Neural stem cell (NSC) and mesenchymal stem cell (MSC) EVs derived from the same pluripotent stem cell (PSC) line were evaluated for changes in infarct volume as well as sensorimotor function.

NSC EVs improved cellular, tissue, and functional outcomes in middle-aged rodents, whereas MSC EVs were less effective. Acute differences in lesion volume following NSC EV treatment were corroborated by MRI in 18-month-old aged rodents. NSC EV treatment has a positive effect on motor function in the aged rodent as indicated by beam walk, instances of foot faults, and strength evaluated by hanging wire test. Increased time with a novel object also indicated that NSC EVs improved episodic memory formation in the rodent. The therapeutic effect of NSC EVs appears to be mediated by altering the systemic immune response. These data strongly support further preclinical development of a NSC EV-based stroke therapy and warrant their testing in combination with FDA-approved stroke therapies.

Macrophages Make a Significant Contribution to Heart Failure

Researchers here implicate the immune cells known as macrophages in the progression of a particularly problematic form of heart failure. Macrophages are very important to the processes of tissue maintenance and regeneration, but they have several different characteristic states, or polarizations: one is inflammatory and aggressive, hindering regeneration, while the other is actively beneficial for regeneration. Researchers are finding that adjusting the proportion of these two states can be beneficial. The situation in heart failure - and a number of other age-related conditions - may well be made worse due to the balance in macrophage populations tipping away from assisting regeneration and towards chronic inflammation. In support of that view, stem cell therapies that have the primary outcome of reducing inflammation have been shown to be helpful in treating the form of heart failure examined here.

Researchers have discovered that the immune cells called macrophages contribute to a type of heart failure for which there currently is no effective treatment, heart failure with preserved ejection fraction (HFpEF). The concept of heart failure traditionally referred to a loss of the organ's pumping capacity, which is called systolic heart failure. But in HFpEF the heart retains the ability to pump or eject blood into the circulation. What is compromised is the ability of the heart muscle to relax and allow blood to flow into the left ventricle, reducing the amount of blood available to pump into the aorta. Symptoms of HFpEF are similar to those of heart failure in general, but since factors contributing to the condition are not well understood, it has been difficult to find promising therapies.

Interactions among cells within the heart - including macrophages - are essential to normal cardiac function but can also contribute to problems. For example, after the heart muscle is damaged by a heart attack, macrophages induce the cells called fibroblasts to generate the connective tissues that help reinforce damaged tissue. But excessive fibroblast activation can lead to the distortion and stiffening of tissues, further reducing cardiac function.

To explore a potential role for macrophages in HFpEF, the team examined cardiac macrophages in two mouse models that develop the sort of diastolic dysfunction - impaired relaxation of the heart muscle - that characterizes HFpEF. Those animals were found to have increased macrophage density in the left ventricle and exhibited elevated levels of a factor called IL-10, which is known to contribute to fibroblast activation. Deletion of IL-10 from cardiac macrophages in one model, in which the development of hypertension is induced, prevented the upregulation of macrophages and reduced the numbers and activation of cardiac fibroblasts. Levels of cardiac macrophages were also elevated in tissue biopsies from human patients with HFpEF, as were levels of circulating monocytes, which are precursors of macrophages.

"Not only were numbers of inflammatory cardiac macrophages increased in both the mice and in humans with HFpEF, but their characteristics and functions were also different from those in a healthy heart. Through their participation in the remodeling of heart tissue, these macrophages increase the production of extracellular matrix, which reduces diastolic relaxation. Our findings regarding the cell-specific knockout of IL-10 are the first to support the contribution of macrophages to HFpEF. Heart muscle cells and fibroblasts have been considered the major contributors to HFpEF. Our identification of the central involvement of macrophages should give us a new focus for drug development."


BACE1 Deletion Eliminates Amyloid Deposits in a Mouse Model of Alzheimer's Disease

BACE1 is one of the proteins involved in early stages of the production of amyloid-β, a form of metabolic waste that aggregates into solid deposits in the aging brain, and is characteristic of Alzheimer's disease. Inhibition of BACE1 so as to reduce levels of amyloid-β is a strategy pursued by a number of research groups, though it has to be said that disenchantment with the years of failure in the dominant strategy of clearing amyloid-β appears to be reaching a tipping point these days. While it is clear that amyloid-β is harmful, it may not be the most effective point of intervention. Or perhaps earlier efforts to remove amyloid-β were not going about it in the right way, and different approaches would work. It is very hard to say, as the aging brain is a complex mix of many different, interacting forms of damage and dysfunction.

The research here can be read as strong support for the BACE1 inhibition approach to Alzheimer's disease, given the size of the effect, though the same questions remain as in any other success in reducing amyloid from the mouse models of Alzheimer's disease. If none of the others successfully translated to human therapies, and failed in trials, how confident or hopeful should we be here? A great many people are asking themselves exactly that these days, which is why we can observe the growth of support for the impaired cerebrospinal fluid drainage model of Alzheimer's disease, or the microbial model of the condition, and a range of further theorizing on different causes and different priorities in research and development.

With a large swath of the population entering its senior years, the number of Alzheimer's disease (AD) cases are expected to skyrocket, placing a tremendous burden on the healthcare system. Yet, a glimmer of hope may have just emerged as investigators report that gradually depleting an enzyme called BACE1 completely reverses the formation of amyloid plaques in the brains of mice with AD, subsequently improving the animals' cognitive function. "To our knowledge, this is the first observation of such a dramatic reversal of amyloid deposition in any study of AD mouse models."

One of the earliest events in AD is an abnormal buildup of the beta-amyloid (Aß) peptide, which can form large, amyloid plaques in the brain and disrupt the function of neuronal synapses. Also known as beta-secretase, BACE1 helps produce the Aß peptide by cleaving the amyloid precursor protein (APP). Drugs that inhibit BACE1 are therefore being developed as potential AD treatments but, because BACE1 controls many important processes by cleaving proteins other than APP, these drugs could have serious side effects.

Mice completely lacking BACE1 suffer severe neurodevelopmental defects. To investigate whether inhibiting BACE1 in adults might be less harmful, the research team generated mice that gradually lose this enzyme as they grow older. These mice developed normally and appeared to remain perfectly healthy over time. "To mimic BACE1 inhibition in adults, we generated BACE1 conditional knockout (BACE1fl/fl) mice to induce deletion of BACE1 after passing early developmental stages. Strikingly, sequential and increased deletion of BACE1 in an adult AD mouse model was capable of completely reversing amyloid deposition. This reversal in amyloid deposition also resulted in significant improvement in gliosis and neuritic dystrophy. Moreover, synaptic functions, as determined by long-term potentiation and contextual fear conditioning experiments, were significantly improved, correlating with the reversal of amyloid plaques."

Remarkably, the loss of BACE1 also improved the learning and memory of mice with AD. However, when the researchers made electrophysiological recordings of neurons from these animals, they found that depletion of BACE1 only partially restored synaptic function, suggesting that BACE1 may be required for optimal synaptic activity and cognition.


Greater Activity Slows the Progression of Age-Related Neurodegeneration

Here I'll point out two papers, one looking at exercise and the aging of grey matter in the brain, the other looking at exercise and the aging of white matter in the brain. It is well known that cardiovascular health is linked to cognitive health. An entire category of neurodegenerative disease is related to the age-related failure of the cardiovascular system to remain intact and supply adequate nutrients to the brain. A sizable portion of cognitive decline is linked to incidences of rupture of tiny blood vessels in the brain, each killing a comparatively small number of cells, but over the years that damage adds up. Further, the cellular biochemistry of the brain is kept separate from the body by the blood brain barrier, a layer of cells that lines the blood vessels of the brain. As blood vessels age, that barrier breaks down, allowing molecules present in the rest of the body to leak into the brain, producing disruption and damage. All in all, the quality of blood vessels matters greatly, just as much as the ability of the heart to pump enough blood to the energy-hungry brain. Scores of studies provide evidence to support a strong link between the cardiovascular system and the brain, with data at every layer of scientific investigation, from epidemiology to physiology to cellular biochemistry.

Since true, actual, working rejuvenation therapies are still very new and limited in scope, the way in which researchers presently observe the effects of cardiovascular health on the aging of the brain is by comparing people with different levels of fitness. Exercise modestly slows the pace at which the corrosive damage of aging harms the function and integrity of the vascular system and the heart, though animal studies suggest that exercise, while beneficial for long-term health, doesn't greatly extend life span. A sizable fraction of declines in measures of cardiovascular function across the middle of life results from a reduction in exercise rather than the intrinsic processes of damage that come to dominate the progression of aging in late life. Yet even in late life, undertaking physical exercise is beneficial - the cell and tissue damage of aging may be the dominant factor in reduced health and increased dysfunction, but exercise still helps to a degree that makes it worth the effort.

Ultimately, we should look at the data from the two studies noted here, and from the many other similar studies carried out over the years, and think: "if a modest positive impact on the biochemistry of the vascular system has this effect, how much better would it be to repair the underlying damage that causes aging?" The decline of the physical structure of the brain - and the mind it supports - will one day be prevented through the advent of rejuvenation therapies after the SENS model: repairing the root causes of aging, the cell and tissue damage that results in loss of function and catastrophic failure of organs and other systems in the body. A world absent aging is something to strive for, and the differences in aging of individuals that we observe today are just a tiny fraction of what will become possible through new medical science in the years ahead.

Poor fitness linked to weaker brain fiber, higher dementia risk

A new study from suggests that the lower the fitness level, the faster the deterioration of vital nerve fibers in the brain. This deterioration results in cognitive decline, including memory issues characteristic of dementia patients. The study published focused on a type of brain tissue called white matter, which is comprised of millions of bundles of nerve fibers used by neurons to communicate across the brain. Researchers enrolled older patients at high risk to develop Alzheimer's disease who have early signs of memory loss, or mild cognitive impairment (MCI). The researchers determined that lower fitness levels were associated with weaker white matter, which in turn correlated with lower brain function.

Unlike previous studies that relied on study participants to assess their own fitness, the new research objectively measured cardiorespiratory fitness with a scientific formula called maximal oxygen uptake. Scientists also used brain imaging to measure the functionality of each patient's white matter. Patients were then given memory and other cognitive tests to measure brain function, allowing scientists to establish strong correlations between exercise, brain health, and cognition.

The study leaves plenty of unanswered questions about how fitness and Alzheimer's disease are intertwined. For instance, what fitness level is needed to notably reduce the risk of dementia? Is it too late to intervene when patients begin showing symptoms? Some of these topics are already being researched through a five-year national clinical trial. The trial, which includes six medical centers across the country, aims to determine whether regular aerobic exercise and taking specific medications to reduce high blood pressure and cholesterol levels can help preserve brain function. It involves more than 600 older adults at high risk to develop Alzheimer's disease.

Everyday Activities Associated with More Gray Matter in Brains of Older Adults

The gray matter in the brain includes regions responsible for controlling muscle movement, experiencing the senses, thinking and feeling, memory and speech and more. The volume of gray matter is a measure of brain health, but the amount of gray matter in the brain often begins to decrease in late adulthood, even before symptoms of cognitive dysfunction appear. "More gray matter is associated with better cognitive function, while decreases in gray matter are associated with Alzheimer's disease and other related dementias."

The study measured the levels of physical activity by 262 older adults in the Memory and Aging Project, an ongoing epidemiological cohort study. Participants in the lifestyle study wore a noninvasive device called an accelerometer continuously for seven to 10 days. The goal was to accurately measure the frequency, duration, and intensity of a participant's activities over that time. The use of accelerometers was only one of the ways in which this analysis differed from some other investigations of the health of older people. Most research that explores the effects of exercise relies on questionnaires. The real problem with questionnaires, though, is that "sometimes, we get really inaccurate reports of activity."

Another departure from some other investigations was the opportunity to assess the effects of exercise on individuals older than 80. In fact, the mean age in this study was 81 years, compared with 70 for other studies used as a reference. The study compared gray matter volumes as seen in participants' MRIs with readings from the accelerometers and other data, which all were obtained during the same year. Analysis found the association between participants' actual physical activity and gray matter volumes remained after further controlling for age, gender, education levels, body mass index and symptoms of depression, all of which are associated with lower levels of gray matter in the brain.

Liver Organoids Come Ever Closer to Natural Liver Tissue

Tissue engineers continue to improve the quality of their creations. The liver is one of the easier organs to work with, given the much greater regenerative capacity of liver cells. It is, nonetheless, an organ with a complex small-scale internal structure, and getting that right is a process of incremental advances. The tissues created via present state of the art approaches are usually still small, lacking the capillary networks needed to support tissue larger than a few millimeters in depth. The only way to provide those networks is to use decellularized donor organs, the cells destroyed, and the organ thus reduced to the scaffold of the extracellular matrix, complete with blood vessels and chemical cues. If the starting point is a cell sample without such a scaffold, blood vessels remain a challenge. By the time that challenge is reliably solved, however, it seems likely that the research community will be ready to build fairly accurate replicas of at least a couple of different real organs, even without donor tissue to provide a scaffold.

The creation of living mini-organs is a relatively new area of science with the potential to replace animal models that are not always accurate. The liver organoids, made with human cells, are less than one-third inch in diameter. While scientists have already created liver organoids to screen new drugs for liver toxicity, the livers developed in this research represent several "firsts" in the quest to build a functional model of human liver development. To make the organoids, scientists allow fetal liver progenitor cells, an immature cell that is destined to become a specialized liver cell, to self-assemble on a small disc. The discs are made of ferret liver that has been processed to remove all of the animal's cells. The resulting organoids, which assemble within two to three weeks, are the first to model actual human liver development.

The research is significant in two ways. First, the scientists showed that these organoids generated hepatocytes, the main functional cells of the liver. This achievement represents a milestone in work to create truly functional bioengineered liver tissue for transplantation into patients. Second, while other scientists have shown that lab-grown livers can generate bile ducts, this is the first study to show the stepwise maturation of bile ducts exactly as can be observed in the human fetal liver. Bile ducts carry bile, a fluid that is secreted by the liver and collected in the gall bladder to digest fats.


DNA Machinery that can Sabotage the Blood Supply of Tumors

Researchers have been building simple molecular machines out of DNA for some years now. This approach to molecular machinery is well suited to applications that involve conditional activation based on the proteins present in the surrounding environment; a lot of the necessary functional parts already exist in DNA and just have to be assembled in the right way. The Oisin Biotechnologies cell-killing technology is a smaller example of the type than the approach here, in which sizable DNA containers are constructed. They carry a cargo that will disrupt local blood flow, and are triggered into opening by cancerous cell surface proteins, thereby sabotaging the nutrient supply to tumors without harming other tissues. It is all quite clever and quite mechanical.

DNA nanorobots that travel the bloodstream, find tumors, and dispense a protein that causes blood clotting can trigger the death of cancer cells in mice. The researchers started with the goal of finding a path to design nanorobots that can be applied to treatment of cancer in humans. They first generated a self-assembling, rectangular, DNA-origami sheet to which they linked thrombin, an enzyme responsible for blood clotting. Then, they used DNA fasteners to join the long edges of the rectangle, resulting in a tubular nanorobot with thrombin on the inside. The authors designed the fasteners to dissociate when they bind nucleolin - a protein specific to the surface of tumor blood-vessel cells - at which point, the tube opens and exposes its cargo.

The scientists next injected the nanorobots intravenously into nude mice with human breast cancer tumors. The robots grabbed onto vascular cells at tumor sites and caused extensive blood clots in the tumors' vessels within 48 hours, but did not cause clotting elsewhere in the animals' bodies. These blood clots led to tumor-cell necrosis, resulting in smaller tumors and a better chance for survival compared to control mice. The team also found that nanorobot treatment increased survival and led to smaller tumors in a mouse model of melanoma, and in mice with xenografts of human ovarian cancer cells. The next step is to investigate any damage - such as undetected clots or immune-system responses - in the host organism, as well as to determine how much thrombin is actually delivered at the tumor sites. The authors showed in the study that the nanorobots didn't cause clotting in major tissues in miniature pigs, which satisfies some safety concerns, but more work is needed.


Weaponizing the Biochemistry of Huntington's Disease as a General Cancer Therapy

An interesting observation that has arisen over the years of epidemiological study of human age-related disease is that there are a number of distinct inverse relationships between incidence of cancer and incidence of some forms of neurodegeneration. This was in the news a few years ago in the case of Alzheimer's disease for example. Why would people with a higher risk of cancer suffer lower rates of Alzheimer's disease, however? We can only speculate at this point, but the more recent discovery I'll point out here adds fuel for that speculation. The Alzheimer's-cancer relationship is modest in size and somewhat complex in detail in comparison to the quite dramatic and straightforward Huntington's-cancer relationship. People with the dysfunctional forms of the huntingtin gene that cause this neurodegenerative condition have a greatly reduced cancer risk.

Why is this the case? Researchers have now discovered that the aberrant huntingtin proteins implicated in Huntington's disease are actually a lot more damaging to cancerous cells than to neurons in the brain. While that is no great comfort to those who suffer the slow deterioration of Huntington's disease, the prospect of turning this discovery into a general cancer therapy is quite real. Something that reliably and rapidly kills all of the cancers it is tested against, while harming neurons only very slowly, is a much better class of candidate treatment than most chemotherapeutics. (And meanwhile, a number of groups are working on gene therapies to address harmful huntingtin gene variants; Huntington's disease - and most other inherited diseases - will vanish from the wealthier parts of the world over the next few decades).

This approach to killing cancerous cells is noteworthy because it appears to be non-specific, reliably attacking many different types of cancer. The only way to make earnest progress in bringing cancer under control is for the research community to focus on treatments that can be applied to many different cancers - or, for preference, to all cancers - with minimal cost of adjustment by cancer type. There are hundreds of types of cancer, and attempting to produce therapies specialized to the molecular peculiarities of a specific type is too inefficient. Too much time and funding has been poured into such approaches, and both of those resources are limited. That is not the way forward. The future of the field of cancer therapeutics lies in treatments that can be applied as-is to defeat near any type of cancer. So we should watch for promising examples such as the research here.

Huntington's disease provides new cancer weapon

Patients with Huntington's disease, a fatal genetic illness that causes the breakdown of nerve cells in the brain, have up to 80 percent less cancer than the general population. Huntington's is caused by an over abundance of a certain type of repeating RNA sequences in one gene, huntingtin, present in every cell. The defect that causes the disease also is highly toxic to tumor cells. These repeating sequences - in the form of so-called small interfering RNAs (siRNA) - attack genes in the cell that are critical for survival. Nerve cells in the brain are vulnerable to this form of cell death, however, cancer cells appear to be much more susceptible.

"This molecule is a super assassin against all tumor cells. We've never seen anything this powerful." To test the super assassin molecule in a treatment situation, researchers delivered the molecule in nanoparticles to mice with human ovarian cancer. The treatment significantly reduced the tumor growth with no toxicity to the mice. Importantly, the tumors did not develop resistance to this form of cancer treatment. The molecule was also used to treat human and mouse ovarian, breast, prostate, liver, brain, lung, skin, and colon cancer cell lines. The molecule killed all cancer cells in both species.

Earlier research had identified an ancient kill-switch present in all cells that destroys cancer. "I thought maybe there is a situation where this kill switch is overactive in certain people, and where it could cause loss of tissues. These patients would not only have a disease with an RNA component, but they also had to have less cancer." The researchers started searching for diseases that have a lower rate of cancer and had a suspected contribution of RNA to disease pathology. Huntington's was the most prominent. When they looked at the repeating sequences in huntingtin, the gene that causes the disease, she saw a similar composition to the earlier kill switch. Both were rich in the C and G nucleotides (molecules that form the building blocks of DNA and RNA). "Toxicity goes together with C and G richness. Those similarities triggered our curiosity. We believe a short-term treatment cancer therapy for a few weeks might be possible, where we could treat a patient to kill the cancer cells without causing the neurological issues that Huntington's patients suffer from."

Small interfering RNAs based on huntingtin trinucleotide repeats are highly toxic to cancer cells

Trinucleotide repeat (TNR) expansions in the genome cause a number of degenerative diseases. A prominent TNR expansion involves the triplet CAG in the huntingtin (HTT) gene responsible for Huntington's disease (HD). Pathology is caused by protein and RNA generated from the TNR regions including small siRNA-sized repeat fragments. An inverse correlation between the length of the repeats in HTT and cancer incidence has been reported for HD patients.

We now show that siRNAs based on the CAG TNR are toxic to cancer cells by targeting genes that contain long reverse complementary TNRs in their open reading frames. Of the 60 siRNAs based on the different TNRs, the six members in the CAG/CUG family of related TNRs are the most toxic to both human and mouse cancer cells. siCAG/CUG TNR-based siRNAs induce cell death in vitro in all tested cancer cell lines and slow down tumor growth in a preclinical mouse model of ovarian cancer with no signs of toxicity to the mice. We propose to explore TNR-based siRNAs as a novel form of anticancer reagents.

Evidence for Tau Accumulation and Failing Cerebrospinal Fluid Clearance to be the Starting Point for Alzheimer's Disease

Alzheimer's disease might be considered as the consequence of the related, interacting buildup of two primary forms of metabolic waste in the brain, tau and amyloid-β. Either, independently, can cause neurodegeneration, but they have a complicated relationship with one another in which the presence of both makes the pathology worse. Which comes first? There is evidence to suggest that amyloid aggregation leads to tau aggregation, and there is also evidence for things to be the other way around, such as that presented in the research materials here.

Both of these options could be the case, in that either tau or amyloid-β produces disruption that can accelerate aggregation of the other. Or it may be that a third mechanism, such as loss of effective drainage of cerebrospinal fluid, causes aggregation of both, and interactions between the two are less important to the amount present and more important to the damage done. Alzheimer's is a very complex area of study. Until therapies start to make some inroads into improving the condition, thereby quantifying some of the mechanisms and their effects, it is likely that greater understanding of the details of the progression of the condition, and the degree to which different aspects contribute to cognitive decline, will be slow to arrive.

In the commonly held definition of Alzheimer's disease, one type of amyloid-beta (Aβ42) starts to form clumps between nerve cells, injuring them. Worsening injury is then marked by the release and toxic buildup of a second protein called tau. Together, changes in Aβ42 and tau levels represent the standard international measure of a patient's risk for future cognitive decline. A new study found that the build-up in the brain of amyloid beta cannot be the sole trigger of subsequent nerve damage because many relatively younger people who develop disease later do not show signs of the buildup. "Once you stop assuming that the starting point of Alzheimer disease is marked by the buildup of Aβ42 in brain cells, a different picture emerges. By recognizing an earlier disease phase, we may be able to start treating earlier and in tailored ways based on a better understanding of disease biology."

For many years, neuroscientists have sought to predict AD risk by tracking protein levels in the cerebrospinal fluid (CSF) that fills the spaces around brain tissue, and which can be sampled by lumbar puncture as part of a spinal tap. In 1999, researchers started collecting clinical and CSF protein level data from healthy normal subjects every two years. Combining this database with two others, the current study is the largest of its kind to date, including roughly 700 patients. The study found that the best predictor of future AD risk was not, as currently thought, decreased CSF Aβ42 levels with elevated tau. Elevated CSF Aβ42 levels were also found to confer future AD risk.

The results add to the evidence that an increase in CSF tau over a lifetime may be the more relevant, early feature of AD than a drop in CSF Aβ42 (taken as evidence of a buildup in brain cells). While the actual mechanism behind Alzheimer's disease and the trajectory of Aβ42 and tau levels remains obscure, the results provide evidence in support of the "clearance theory." It holds that the pumping of the heart, along with constriction of blood vessels, pushes cerebrospinal fluid through the spaces between brain cells, clearing potentially toxic proteins into the bloodstream. Mid-life cardiovascular changes that bring on heart failure and hypertension may lessen the CSF flow needed to clear tau, and perhaps disease-causing proteins yet to be identified.

Aside from Aβ42 which is readily deposited into the brain, the team found that CSF levels of two other common forms of amyloid beta that are less able to build up, Aβ38 and Aβ40, increase in proportion to rising tau throughout the normal older adult lifespan, even after CSF Aβ42 starts to decrease. This is further evidence of a decline in clearance with age. "Future CSF studies need to follow normal subjects, starting at age 40, for decades to get an unbiased look at the trajectory of CSF proteins and the likelihood of developing cognitive impairment decades later."


Inhibition of Wnt Signaling as a Treatment for Osteoarthritis

Researchers here find that inhibition of Wnt signaling can improve the state of cartilage and joint function in a mouse model of osteoathritis. Wnt and its closely related proteins are a complex topic, but the short version is that they are involved in the regulation of growth, regeneration, and embryonic development. They are also significant in cancer, as well as in other, less dramatic ways in which regeneration can run wild or fail, producing fibrosis and functional problems rather than a useful restoration of tissue. Numerous research groups are investigating ways in which Wnt signaling can be adjusted to produce beneficial effects such as enhanced healing, or a reduction in function damage to tissues following injury. This is a representative example.

Wnt family proteins are a class of morphogens associated with embryonic skeletal formation, tissue repair, fibrosis, and joint homeostasis. Wnts regulate multiple signaling cascades, including the β-catenin-dependent (canonical) pathway. The Wnt/β-catenin pathway, which is typically quiescent in many adult organs, is activated in response to injury. Its role in tissue repair and regeneration is complex and incompletely understood, although an increasing body of data suggests that its activation augments fibrotic repair. Our group recently published studies demonstrating that brief therapeutic Wnt inhibition following both full thickness cutaneous or ischemic cardiac injury resulted in improved regenerative repair with less fibrosis.

Osteoarthritis (OA) is a degenerative joint disease typically characterized by articular cartilage degeneration, bone remodeling, and osteophytosis as well as fibrosis and hyperplasia of the synovial membrane. In OA pathogenesis, activation of canonical Wnt signaling is observed in both articular cartilage and synovium following injury, with increased expression of both Wnt ligands and target genes. Induced overexpression of β-catenin within mature chondrocytes has been shown to exacerbate cartilage degeneration, chondrocyte hypertrophy, and expression of matrix proteases. However, significant or complete ablation of β-catenin in chondrocytes also results in the deleterious effect of chondrocyte apoptosis. Moreover, increased canonical Wnt expression in the synovium resulted in strong induction of cartilage pathology. Although the sum of the published data using genetic modulation of Wnt suggests deleterious effects of Wnt on OA pathogenesis, there is little known about the therapeutic effect of inhibiting the Wnt pathway within the context of disease.

Multiple Wnt inhibitory therapeutics are being investigated at various stages of clinical development due to Wnt pathway activation, not only in fibrotic diseases, but also cancers. We sought to study Wnt signaling and the effect of local therapeutic Wnt inhibition in a murine model of traumatic OA caused by destabilization of the medial meniscus (DMM). To assess the effect of Wnt inhibition on OA progression, we injected the small-molecule Wnt inhibitor, XAV-939, in the intra-articular space. We further studied the cell-specific effects of Wnt modulation in vitro using primary human synovial fibroblasts and chondrocytes in order to understand the cellular basis for the disease-modifying effects.

Our study demonstrated that traumatic joint injury through DMM surgery induced robust activation of canonical Wnt signaling, most striking in the synovium, and this upregulation was downregulated with intermittent (every 10 days), local (intra-articular) treatment using a small-molecule Wnt inhibitor, resulting in amelioration of both synovitis and cartilage loss. An important advantage of identifying therapeutic benefits with local administration is avoiding systemic effects of Wnt inhibition on Wnt-dependent tissues, such as intestinal stem cell/intestinal turnover, hematopoiesis, and bone density. The use of small-molecule Wnt inhibitors bypasses the restrictions of genetic approaches by targeting the entire injury milieu, rather than a particular cell type, as is the case in genetic models. Additionally, since different cell types exhibit different levels of Wnt activation and sensitivity to Wnt inhibition, one can also fine-tune the degree and timing of Wnt inhibition using dosing strategies that are calibrated.


Can Two Dozen Marginal Ways to Treat Aging be Combined into One Useful Therapy?

Comparatively little work on combinations of therapies takes place in the research community. I suspect this to be a matter of regulatory incentives. For example there is little room for commercial entities to be able to make money by combining established treatments owned by other entities. Similarly for researchers, the world of possible approaches is balkanized by intellectual property, while the disposition of the majority of research funding is ultimately guided by the promise of a pot of gold at the end of the road. That pot of gold is much harder to obtain when someone else owns the therapies involved, and all that is being done is to apply them together. The edifice of intellectual property is a great evil, and this is one of many reasons why that is the case.

Given this long-standing state of affairs, there is at present little data to guide our expectations on the bounds of the possible when it comes to combining large numbers of therapies in search of additive and synergistic effects. Some people think that we should forge ahead in the matter of slowing aging: take every intervention with good evidence to date, and run large numbers of them in the same mice to see what happens. Should we believe that various ways of manipulating the operation of cellular metabolism demonstrated to achieve 5-10% life extension in mice can combine to double life span in that species? Intuition suggests not, but I don't think it to be completely out the question. Nor is it unreasonable to try it and see, given a rigorous approach to experimental design. Sadly, no established funding institution would go for this; it would have to be funded through philanthropy.

Why do I think that this is unlikely to produce large enough results to make it worthwhile? Because the evidence to date strongly suggests that the scores of methods of manipulating metabolism to modestly slow aging are operating on just a few core processes, such as autophagy. These are the stress responses that produce the lengthening of life observed in calorie restriction, and we know that these mechanisms don't produce anywhere near the same degree of life extension in humans as they do in short-lived species. Everything is connected to everything else in cellular biochemistry. A given interaction between two proteins can be influenced by adjusting levels of any number of other proteins, with widely varying degrees of effectiveness and side-effects. So most methods of slowing aging are different views into the same mechanism of action. The few combinations of approaches tried to date, involving only two methods, have resulted in mixed outcomes. Calorie restriction and mTOR inhibition may be additive, while growth hormone receptor knockout and mTOR inhibition interfere with one another, for example. That gives little insight as to the rest. It is hard to predict other results, beyond noting that a majority of interventions do appear to function through enhanced autophagy, and thus we might expect them not to combine in an additive way to any great degree.

What of the SENS rejuvenation biotechnology approach to aging, in which independent fundamental forms of cell and tissue damage are repaired? How will repair therapies combine? In this case we should expect additive effects: removing damage should be beneficial in proportion to the amount removed, at least when considered from a fundamental, reliability theory perspective. The mortality risk and longevity of a complex system of many redundant parts is dependent on its current load of damage. At this point we have no idea as to how that will turn out in practice, however. The contributions of different forms of damage may be significantly larger or smaller than one another. The results of two independent root cause forms of damage are not themselves independent: they interact, and probably significantly. Functional decline in one system spurs greater damage and functional decline in others, which is why age-related degeneration accelerates greatly in later life. It is a complex business. It isn't unreasonable to think that in some circumstances the results of rejuvenation therapies A and B will be indistinguishable from A alone, or that B will never achieve a great deal without being combined with C.

Can we envisage a world in which repairing cellular senescence alone produces no extension to life span because other, largely independent chains of damage and consequence are still life-limiting for old humans? That is becoming increasingly hard given the evidence to date for reversal of numerous age-related diseases to result from removal of senescent cells, not to mention the PAI-1 mutants who exhibit increased life span - but we know far more about senescent cell clearance than we do about any of the other SENS strategies. No-one is in a position to do more than make educated guesses about the results of combining senescent cell destruction with removal of mitochondrial DNA damage, or with clearance of specific lysosomal aggregates. Beyond "two should be better than one, but perhaps not in some specific cases" everything else will remain a mystery until the biotechnology is ready and the work is carried out. Making predictions seems a fool's game, given the degree to which the people closest to senescent cell research have been surprised by the scope and size of benefits observed in mice over the past few years.

Jagged-1 as a More Selective Signal to Spur Bone Regrowth

Researchers here report on a more selective way to trigger the accelerated or enhanced regeneration of bone tissue, delivering jagged-1 to injuries rather than the bone morphogenetic proteins (BMPs) that have been used in the past. It appears to cause fewer issues related to inappropriate excess bone growth, as it influences mechanisms that are more closely associated with the process of regeneration in response to damage. The delivery of signals rather than cells or pharmaceuticals to produce regeneration will be a growing theme in the years ahead, and the approaches will only grow in sophistication and degree of control. The advance here is a small step in the grand scheme of the possible and the plausible; it will be interesting to see how this part of the industry evolves over the next few decades.

When a patient breaks a bone, there's a possibility the fracture won't heal properly or quickly, and use of a restorative tactic known as bone morphogenetic proteins, or BMPs, is increasingly less likely. Designed to promote spinal fusion and bone repair more than a decade ago, these molecules can overperform, causing excessive or misdirected bone growth, studies have shown. But because bone-healing biological research has often been limited, few other options exist. "Novel therapies have gone underdeveloped because of this assumption that bones heal without problem. The reality is there's a huge number of fractures that occur each year that don't heal very well."

The divide recently inspired scientists to examine a new therapeutic approach. Their method: deliver additional Jagged-1 - a potent osteoinductive protein known to activate the Notch signaling pathway that regulates bone healing - at the spot of a bone injury. "We've hypothesized for many years that by binding the Jagged-1 to a biomaterial and delivering it to a bone injury site, we could enhance healing." The results affirm that hunch: Rodents that received Jagged-1, applied via wet collagen sponge, saw improvements to skull and femoral bone injuries. Rodents treated with BMPs, by contrast, also benefited but developed the same problematic bone hypertrophy associated with human use of those proteins. Those findings suggest that the former therapy could one day benefit people.

It's not fully known why some bones don't heal the way they should - nor do scientists know whether a genetic component plays a role. What researchers have studied for years, meanwhile, is the capacity of the Jagged-1 ligand to promote bone-forming cells. The signaling is unique because this particular ligand typically binds to a delivery cell to activate bone healing in an adjacent cell - a vital trait to help ensure that a supplemental Jagged-1 dose, administered at the spot of injury, stays in place (and on task) to carry out its intended function. As a result, bone will only form where bone is supposed to form. BMPs, by comparison, are soluble, so they can migrate from the site of delivery and settle elsewhere in the body, triggering other cells that aren't supposed to form bone.


There are Many Possible Paths to Immunotherapy for Senescent Cell Destruction

Rising numbers of senescent cells are one of the root causes of aging, a process that arises from the normal operation of youthful metabolism, yet results in accumulated damage and failure over time. Senescent cells generate signaling that degrades tissue function, breaks down and remodels tissue structure, spurs chronic inflammation, and alters the behavior of surrounding cells for the worse. Evidence shows their presence to be a contributing cause of a range of common fatal age-related conditions. In a youthful body, near all cells that become senescent and fail to self-destruct as a result are promptly eliminated by the immune system. In an aged body, the immune system is worn and degraded; as a consequence many more senescent cells survive to linger. We are machines of interacting, dependent parts. Damage and failure in one component speeds the onset of damage and decline in others. The age-related failure of the immune system is an important part of the acceleration of functional decline in later life.

Much of the current work on methods to selectively destroy senescent cells, and thus produce a narrow form of rejuvenation, is focused on pharmaceuticals. Given that the immune system is already capable of destroying senescent cells in the normal course of events, why not immunotherapies, however? I'm only aware of the one company working along those lines, SIWA Therapeutics, and I believe that their immunotherapy approach doesn't interact at all with the natural immunosurveillance of senescent cells. Is it possible to do better than this, to build on the existing evolved mechanisms to induce high levels of clearance even in old and damaged immune systems? Alternatively, could the general methods of immune rejuvenation currently under consideration (such as restoring the thymus, destroying malfunctioning or overspecialized immune cells, or inducing greater stem cell production of immune cells) result in youthful levels of senescent cell destruction?

Whilst there is currently little understanding concerning the mechanisms governing macrophage mediated recognition of senescent cells, the processes are probably not specific to senescent cells. Rather, the more characterised molecular mechanisms associated with macrophage recognition during cancer immunosurveillance and apoptotic cell clearance may also be pertinent for senescence surveillance. Apoptotic cells have been shown to preferentially express specific cell surface antigens which can be recognised by naturally occurring antibodies (IgMs) that enable phagocytosis by macrophages. As such, it can be speculated that senescent cells may also express specific cell surface antigens which would not only provide insights into the mechanisms mediating immune clearance, but would also provide a means to specifically identify senescent cells in tissues.

Surface expression of CD47 acts as a "don't eat me" signal, sending inhibitory signals through SIRPα, a receptor expressed on the surface of macrophage, ensuring that healthy cells are not inappropriately phagocytosed. Therefore, the downregulation of CD47 would be required for macrophages to target damaged "self" cells. One study has demonstrated that induction of tumour cell senescence via c-Myc inactivation leads to the downregulation of CD47 which consequently promoted tumour regression. Whether CD47 downregulation in this instance is a specific response to c-Myc inactivation or activation of the senescence program is unclear. It would make biological sense to downregulate CD47 during cell senescence to enable removal of damaged "self" cells, but further research is required.

Immunotherapeutic strategies already in development for combating cancer may one day be repurposed for targeting senescent cells for the alleviation of age-related diseases. In addition, identifying further molecular changes associated with senescent cells, especially cell-type specific alterations, would be advantageous for developing therapeutic approaches for targeting senescent cells. Since senescent cells can also be beneficial in the short term, the elimination of acute senescent cells could be problematic. Therefore, the identification of therapeutic targets specific to chronic senescence which are absent in acute senescent cells would be highly desirable.

One of the mechanisms by which natural killer (NK) cells specifically recognise and kill senescent cells is via the surface expression of NKG2D ligands. Since many tumour cells also express NKG2D ligands, such ligands have been suggested to be a useful target for immunotherapeutic approaches in cancer, and so could be adapted for senescent cell clearance. For example, the use of engineered immune cells such as chimeric antigen receptor (CAR) T cells to target specific molecules on cancer cells has great potential as an anti-cancer therapy. As such, it may be possible to target senescent cells by engineering T cells to express a NKG2D CAR which recognise NKG2D ligands on the surface of senescent cells.

An adaption of cancer vaccines could also be considered for boosting immune clearance of senescent cells. Although a universal biomarker of cell senescence has not been identified, the exposure of senescent cell membranes to immune cells may evoke an immune response to antigens not yet identified. In one approach, senescence vaccines would involve the isolation of senescence specific antigens (SSAs) which are then exposed to dendritic cells, professional antigen presenting cells. In response to SSA uptake, dendritic cells process and express these antigens on their cell surface which can then be recognised by T cells. T cell interaction with these antigens promotes T cell activation, differentiation, and ultimately killing of target cells.


A Few Recent Advances in Tissue Engineering and Regenerative Medicine

The tissue engineering and regenerative medicine communities are too large and energetic to do more than sample their output, or note the most interesting advances that stand out from the pack. The publicity materials I'll point out here are a recent selection of items that caught my eye as they went past. Dozens more, each of which would have merited worldwide attention ten or fifteen years ago, drift by with little comment every year. The state of the art is progressing rapidly towards both the ability to build complex tissues from a cell sample, such as patient-matched organs for transplantation, and the ability to control regeneration and growth inside the body. Ultimately we may not need transplantation if native organs can be persuaded to repair themselves ... but this will likely also require significant progress towards repairing the cell and tissue damage of aging, the forms of molecular breakage that degrade regenerative capacity.

Even though the research community has progressed a long way past the capabilities of even a decade ago, there remains a longer road ahead. Transplants of cell populations are still very challenging; only a small fraction of those cells survive to take up residence and contribute over the long term. The best technology demonstrations manage 10% survival or thereabouts. Standard approaches to finding the best methodology for each cell type and situation have yet to arise. There is a lot of trial and error. Yet replacement of cell populations, reliably, and with high quality, youthful, undamaged cells, is needed to treat many of the consequences of aging. Consider the loss of dopamine-generating neurons in Parkinson's disease, for example, or the wearing down of the stem cell population responsible for generating the immune system, or the structural remodeling and weakening of the heart in response to hypertension. Removing the damage that caused those issues will not automatically restore all of the losses.

Researchers report first lung stem cell transplantation clinical trial

For the first time, researchers have regenerated patients' damaged lungs using autologous lung stem cell transplantation in a pilot clinical trial. In 2015, the researchers identified p63+/Krt5+ adult stem cells in a mouse lung, which had potential to regenerate pulmonary structures including bronchioles and alveoli. Now they are focusing on lung stem cells in humans rather than mice. The researchers found that a population of basal cells labeled with an SOX9+ marker had the potential to serve as lung stem cells in humans. They used lung bronchoscopy to brush off and amplify these lung stem cells from tiny samples.

In order to test the capacity of lung stem cells to regenerate lung tissue in vivo, the team transplanted the human lung stem cells into damaged lungs of immunodeficient mice. Histological analysis showed that stem cell transplantation successfully regenerated human bronchial and alveolar structures in the lungs of mice. Also, the fibrotic area in the injured lungs of the mice was replaced by new human alveoli after receiving stem cell transplantation. Arterial blood gas analysis showed that the lung function of the mice was significantly recovered.

The team launched the first clinical trial based on autologous lung stem cell transplantation for the treatment of bronchiectasis. The first two patients were recruited in March 2016. Their own lung stem cells were delivered into the patients' lung through bronchoscopy. One year after transplantation, two patients described relief of multiple respiratory symptoms such as coughing and dyspnea. CT imaging showed regional recovery of the dilated structure. Patient lung function began to recover three months after transplantation, which maintained for one year.

Scientists create functioning kidney tissue

Kidney glomeruli - constituent microscopic parts of the organ - were generated from human embryonic stem cells grown in plastic laboratory culture dishes containing a nutrient broth known as culture medium, containing molecules to promote kidney development. They were combined with a gel like substance, which acted as natural connective tissue - and then injected as a tiny clump under the skin of mice. After three months, an examination of the tissue revealed that nephrons: the microscopic structural and functional units of the kidney - had formed.

Tiny human blood vessels - known as capillaries - had developed inside the mice which nourished the new kidney structures. However, the mini-kidneys lack a large artery, and without that the organ's function will only be a fraction of normal. So, the researchers are working with surgeons to put in an artery that will bring more blood the new kidney. "We have proved beyond any doubt these structures function as kidney cells by filtering blood and producing urine - though we can't yet say what percentage of function exists. What is particularly exciting is that the structures are made of human cells which developed an excellent capillary blood supply, becoming linked to the vasculature of the mouse. Though this structure was formed from several hundred glomeruli, and humans have about a million in their kidneys - this is clearly a major advance. It constitutes a proof of principle - but much work is yet to be done."

New tissue-engineered blood vessel replacements closer to human trials

Researchers have created a new lab-grown blood vessel replacement that is composed completely of biological materials, but surprisingly doesn't contain any living cells at implantation. The vessel, that could be used as an "off the shelf" graft for kidney dialysis patients, performed well in a recent study with nonhuman primates. It is the first-of-its-kind nonsynthetic, decellularized graft that becomes repopulated with cells by the recipient's own cells when implanted.

The researchers generated vessel-like tubes in the lab from post-natal human skin cells that were embedded in a gel-like material made of cow fibrin, a protein involved in blood clotting. Researchers put the cell-populated gel in a bioreactor and grew the tube for seven weeks and then washed away the cells over the final week. What remained was the collagen and other proteins secreted by the cells, making an all-natural, but non-living tube for implantation.

To test the vessels, the researchers implanted the 15-centimeter-long (about 5 inches) lab-grown grafts into adult baboons. Six months after implantation, the grafts grossly appeared like a blood vessel and the researchers observed healthy cells from the recipients taking up residence within the walls of the tubes. None of the grafts calcified and only one ruptured, which was attributed to inadvertent mechanical damage with handling. The grafts after six months were shown to withstand almost 30 times the average human blood pressure without bursting. The implants showed no immune response and resisted infection.

Mitochondrially Targeted Antioxidant SS-31 Improves Cognitive Function in Old Mice

Oxidative damage has long been linked to aging, but the general use of antioxidants does nothing for life span. In fact, the evidence suggests this approach is modestly harmful, possibly due to blocking the oxidative signaling needed for exercise and other, similar mild stresses to produce benefits via hormesis. Antioxidant compounds targeted to the mitochondria are a different story, however, and have been shown to slow aging or partially reverse some aspects of aging in mice and lower animals - as is the case in this open access paper.

Mitochondria are the power plants of the cell, and generate reactive molecules that raise oxidative stress as a side-effect of the processes that produce chemical energy stores. This flow of reactive molecules influences the behavior of the cell in numerous ways; methods of slightly slowing aging have been demonstrated that either lower production, leading to less oxidative damage, or raise it, spurring increased maintenance activities in the cell. In the research here, benefits are derived indirectly: damping down oxidative damage improves the function of blood vessels in the aged brain, which helps to restore some degree of lost cognitive function in old mice. The brain is an energy-hungry organ, and age-related neurodegenerative conditions are characterized by a general decline in the capacity of of the blood supply and mitochondria in cells to supply as much energy as is needed.

Normal functioning of the central nervous system (CNS) requires a continuous, tightly controlled supply of oxygen and nutrients as well as washout of harmful metabolites through uninterrupted cerebral blood flow (CBF). The energetic demands of neurons are very high, yet the brain has very little energetic reserves. During periods of intense neuronal activity, there is a requirement for adjusting oxygen and glucose delivery to local neuronal activity through rapid adaptive increases in CBF. This is ensured by a mechanism known as neurovascular coupling (NVC). The resultant functional hyperemia is a vital mechanism to maintain optimal microenvironment of cerebral tissue and thereby ensuring normal neuronal function.

There is an increasing appreciation that (micro)vascular contributions to cognitive impairment and dementia in elderly patients are critical. Importantly, neurovascular coupling responses are impaired both in elderly patients and aged laboratory animals. Experimental studies support this concept, showing that pharmacologically induced neurovascular uncoupling in mice mimics important aspects of age-related cognitive impairment. On the basis of these findings, we proposed that novel therapeutic interventions should be developed to rescue functional hyperemia in elderly patients to prevent/delay cognitive impairment. Previous studies demonstrate that aging exacerbates generation of reactive oxygen species (ROS) in the cerebromicrovascular endothelial cells, which contribute to age-related neurovascular uncoupling in aged mice by promoting endothelial dysfunction. We hypothesize that pharmacological treatments, which attenuate endothelial oxidative stress, will have the capacity to improve neurovascular coupling in aged individuals.

The mitochondrial free radical theory of aging posits that mitochondria-derived ROS (mtROS) production and related mitochondrial dysfunction are a critical driving force in the aging process. In support of this theory, it was demonstrated that attenuation of mitochondrial oxidative stress (by mitochondria-targeted overexpression of catalase) increases mouse lifespan. There is particularly strong evidence that mitochondrial oxidative stress is implicated in cardiovascular aging processes. Yet, although drugs that improve mitochondrial function have been shown to exert beneficial effects both on the vasomotor function of peripheral arteries, their potential protective effects on the aged cerebral microvasculature has not been investigated.

This study was designed to test the hypothesis that pharmacological attenuation of mtROS can restore cerebromicrovascular endothelial function and thus improve neurovascular coupling in aged mice. To achieve this goal, in aged mice mitochondrial oxidative stress was manipulated by treatment with the mitochondrial-targeted peptide SS-31. We found that neurovascular coupling responses were significantly impaired in aged mice. Treatment with SS-31 significantly improved neurovascular coupling responses by increasing cerebromicrovascular dilation, which was associated with significantly improved spatial working memory, motor skill learning, and gait coordination. These findings are paralleled by the protective effects of SS-31 on mitochondrial production of reactive oxygen species and mitochondrial respiration in cultured cerebromicrovascular endothelial cells derived from aged animals.


MDM2 Antagonists Attenuate Harmful Signaling from Senescent Cells

A fair number of the scientists working towards therapies to address cellular senescence, one of the causes of aging, are more interested in suppressing signaling from these cells than in destroying them. Cynically, a treatment one has to keep using consistently is much more interesting to pharmaceutical companies than a treatment that only has to be applied once every few years at most. Until researchers encounter a population of senescent cells that cannot be safely removed, destruction continues to look like the far better option. Senescent cells are harmful because of the mix of signals they generate, a mix that is still comparatively poorly mapped and understood. Suppressing it may well prove to be a lengthy and difficult process of progress by small degrees, while destruction can be achieved in the near future and removes all of the harmful signaling whether or not it is understood.

Astrocytes are one potential candidate for a population of senescent cells that might be challenging to remove. It isn't completely clear that all of the astrocytes showing markers of senescence are actually senescent, but if so it represents a large portion of all astrocytes in the aging brain. Abrupt clearance of these cells would probably not be healthy, regardless of the incremental harms they are causing. With this sort of thing in mind, it is prudent to have a backup strategy under development, whether that is some form of careful incremental winnowing and replacement of these cells over time, or a form of suppression of their bad behavior while allowing them to live.

One of the common features of aging is low-level chronic inflammation, termed sterile inflammation or inflammaging. Even though all the sources of inflammaging are unclear, it likely derives at least partly from senescent cells. Mammalian cells undergo senescence in response to stressful stimuli. An important feature of senescent cells is the secretion of a myriad of biologically active factors, termed the senescence-associated secretory phenotype (SASP).

The SASP is similar between mice and humans, and comprises inflammatory cytokines such as IL-6 and IL-8. The SASP can disrupt the surrounding microenvironment and normal cell functions, and stimulate malignant phenotypes in nearby cells. Senescent cells can also promote tumor growth in mice. Because senescent cells increase with age and are frequently found within hyperplastic and degenerative tissues, the SASP may be a major cause of inflammaging. Compounds that modulate the SASP hold promise for ameliorating a number of diseases of aging, including cancer.

Nutlins were originally identified as potent small molecules that inhibit the interaction between p53 and MDM2, which promote p53 degradation. Nutlin therefore stabilizes p53, thereby promoting the apoptotic death of cancer cells. Importantly, in cancer cells, nutlin-3a inhibits the activity of NF-κB, a potent transcriptional stimulator of genes encoding inflammatory cytokines, in a p53-dependent manner. The clinical importance of small-molecule MDM2 inhibitors like nutlin-3a spurred the discovery of similar compounds, such as MI-63, which are more efficient inhibitors of the MDM2-p53 interaction.

We investigated the effects of small-molecule MDM2-p53 interaction antagonists on senescent phenotypes, including the SASP, of primary human fibroblasts and epithelial cells. We used nutlin-3a, as well as the non-peptide small molecule inhibitor of MDM2, MI-63. We compared these compounds for their ability to induce a growth-arrested state, whether quiescence or senescence, in human cells, and evaluated their ability to modulate the SASP. We found that both compounds trigger selected markers of a senescent-like state, but the growth arrest was reversible, and both significantly suppressed the SASP, suggesting potential utility as therapeutic agents.


How Old is a Transplanted Organ?

Heterochronic parabiosis involves joining the circulatory system of two animals, one old, one young, in order to observe the results. At a high level, the older individual exhibits reversal of some aspects of aging, and the young individual exhibits acceleration of some aspects of aging. The details are complex, and still debated in many cases, however. Researchers see this phenomenon as one of the more effective paths forward to identifying the important age-related changes in the environment of signals generated by cells that find their way into the bloodstream. A more effective approach would be to repair the underlying damage that causes aging - and thus also causes signaling changes - but the technologies to achieve that goal barely exist yet. Of the needed approaches, only clearance of senescent cells via senolytic pharmaceuticals is both easily studied in the laboratory and producing a great deal of useful data.

Branching out from the initial focus on joined circulatory systems, there are numerous other possible approaches to mixing young and old signals and tissues. Groups are assessing the results of transfusions of blood or plasma from young to old, for example, with Alkahest and Ambrosia as two of the more public examples. There is mixed data for the effectiveness of this strategy in comparison to parabiosis, however. The nature of the interactions when blood is circulating through two bodies is significantly different from that of even regular transfusions, and that may be important. For example, what if outcomes depend upon young tissues reacting to signals present in old blood and stepping up beneficial activities in response?

Looking further afield, we might consider investigating the transplantation of organs and other large tissue sections. The organ donation and transplant industry is, in effect, an enormous natural experiment in what happens when tissues are placed into an older or younger environment. It further has the advantage of providing human data rather than animal data. What would we expect to happen when an old organ is placed into a younger body? We might expect a degree of functional rejuvenation, and that can be measured, and the details of the biochemistry assessed. Equally, we may expect that some of the damage of aging and consequent impairment of organ function will not be reverted. Human biochemistry doesn't appear to be capable of effectively clearing persistent cross-links that stiffen tissues, for example.

The logistics of obtaining data from this experiment are not quite straightforward, however. While tens of thousands of organ transplants take place every year, and there are at least hundreds of thousands of recipients still alive, tracking down past patients and connecting them reliably with medical records is an expensive proposition. Also, the more recent data is the more interesting data. The viable approach is thus to work with medical establishments for ongoing transplant procedures and the necessary followups. In this way a fair-sized study set and database could be accumulated in a year or two. The authors of this paper have made a start on such an effort, and it is interesting to see that the narrow slice of data they elected to survey shows little rejuvenating effect when old livers are transplanted into young recipients. There is, however, a negative impact when young livers are transplanted into old recipients.

Biological age of transplanted livers

The scarcity of human donor organs in terms of availability for transplants is a renowned problem. The high request of organs moves toward an increased use of marginal donors, including organs from old or very old donors usually transplanted into younger recipients. Within the context of orthotopic liver transplants, clinical evidence suggests that livers from aged donors (≥ 70 years) do have function and duration comparable to those achievable with livers from younger donors. Paradigmatic are the cases of 26 octogenarians livers being transplanted between 1998 and 2006, 15 patients out of 26 are currently alive and 2 of those organs being centenarians.

Our team was deeply involved in an Italian national project to collect biological data to answer the question - why livers from old donors may be successfully used for transplants. The first evidence was a relative low grade of aging signs of liver donors at histological and cytological level, also including the three major proteolytic activities of proteasome, comparing young and old livers. Further, we tried to investigate the epigenetic age-related modifications in terms of liver microRNAs (miRs). We discovered that at 60-70 years of chronological age, three miRs start to increase their expression level, i.e. miR-31-5p; miR-141-3p; miR-200c-3p, and we assumed such an increase as markers of aging in human liver. When a relatively young liver was transplanted into a relatively older recipient (Δ age-mismatch average: +27 years) the expression of these miRs significantly increased in the organ (follow up after graft at 15 ± 7 months). It is interesting that we were not able to document the reverse. Indeed, when a relatively old liver was transplanted into a relatively young recipient (Δ age-mismatch average: -17 years), the expression of the three above-mentioned miRs did not change (follow up after graft at 10 ± 2 months).

On the whole, these observations suggest that in the setting of liver transplantation the aging phenotype can be "transmitted/propagated" more easily than the young phenotype via the body microenvironment. Recently, we studied the above mentioned miRs using single-miR real time-RT qPCR on blood serum samples from 34 recipients stratified on the basis of donor liver chronological age. No difference was observed, thus suggesting that the phenomenon previously found was tightly related to the organ itself without miR-specific exocytosis and changes at circulating level, at least for the identified miRs.

The biological effect of donor and recipient age-mismatch is a topic rather neglected despite its great potential, biological and clinical interest. The possibility that a centenarian liver can still function properly may suggest not only the intrinsic peculiarity of this organ (slowed down ageing; regeneration phenomena), but also the interaction with the younger recipients. This interaction was previously demonstrated in heterochronic parabiosis experiments in mice models, but deep analyses need specifically in humans, aiming at explain the reason of the variability associated with the duration of transplant.

The Longest-Lived Bats Have Unusual Telomere Biology

Researchers here find that the longest lived bats have unusual telomere biochemistry, and in fact unusual enough that the new knowledge may turn out to be of little relevance to the understanding of telomeres, telomerase, and aging in other mammals. It appears that they rely upon alternative lengthening of telomeres (ALT) to maintain telomere length, a process that doesn't operate in any normal adult human cell. Given that loss of telomere length appears to be a marker of aging rather than a cause, and a fairly loosely coupled marker at that, the real relevance of this area of biochemistry probably lies in the relationship between telomerase and important cellular activities, such as ability and willingness of somatic cells to replicate, or stem cells to support tissue function.

Bats exhibit cellular biochemistry that is somewhat different from that of ground-based species in a number of other ways. The metabolic demands of flight have led to, for example, greater resilience to stress and damage arising from the normal operation of cellular metabolism. When charting life span against metabolic rate, where high metabolic rates usually imply short life spans, some small bat species are noteworthy outliers. Brandt's bat, for example, has a life span of four decades despite being the same size as ground-dwelling mammals that live for only a couple of years.

One of the principal caveats at the present stage of research into telomeres and the use of telomerase gene therapies - or other means of enhancing telomerase activity - as a treatment for aspects of aging is that mice and humans have quite different telomere dynamics and patterns of natural telomerase activity. The balance between cancer risk and beneficially increased stem cell activity resulting from telomerase therapies may turn out to be significantly different in different species. That these bats have their own unique evolved dynamics, ones that are much further removed, suggests that this portion of the comparative biology might not be as useful to the practical science of aging as hoped. The fastest path to understanding is probably to extend present work on telomerase therapies to species more like humans in their telomere biology, such as dogs and pigs perhaps. Or, as some advocate, running human trials immediately.

We urgently need to better understand the mechanisms of the aging process, with a view to improving the future quality of life of our aging populations. Most aging studies have been carried out in shorter-lived laboratory model species, given the ease of manipulation, housing, and length of life span. Although they are excellent study species, it is difficult to extrapolate experimental findings in these short-lived laboratory species to long-lived, outbred species such as humans. Therefore, it has been argued that long-lived, outbred species such as bats may be better models to investigate the aging processes of relevance to people.

Only 19 species of mammal are longer-lived than humans in proportion to their body size, and 18 of these species are bats. Bats are the longest-lived mammals relative to their body size, with the oldest bat recaptured (Myotis brandtii) being more than 41 years old, weighing ~7 g, and living ~9.8 times longer than predicted for its size. Although an excellent model species to study extended healthspan, logistically, it is difficult to study aging in bats because they are not easily maintained in captivity. Here, uniquely drawing on more than 60 years of cumulative long-term, mark-recapture studies from four wild populations of long-lived bats, we determine whether telomeres, a driving factor of the aging process, shorten with age in Myotis myotis (n = 239; age, 0 to 6+ years), Rhinolophus ferrumequinum (n = 160; age, 0 to 24 years), Myotis bechsteinii (n = 49; age, 1 to 16 years), and Miniopterus schreibersii (n = 45; age, 0 to 17 years).

We show that telomeres shorten with age in Rhinolophus ferrumequinum and Miniopterus schreibersii, but not in the bat genus with greatest longevity, Myotis. As in humans, telomerase is not expressed in Myotis myotis blood or fibroblasts. Selection tests on telomere maintenance genes show that ATM and SETX, which repair and prevent DNA damage, potentially mediate telomere dynamics in Myotis bats. Twenty-one telomere maintenance genes are differentially expressed in Myotis, of which 14 are enriched for DNA repair, and 5 for alternative telomere-lengthening mechanisms. These results, coupled with differential expression of ATM, SETX, MRE11a, RAD50, and WRN across all tissues in the genus Myotis compared to other mammals, suggest a potential role for alternative lengthening of telomeres (ALT) mechanisms in the maintenance of telomeres in these species. If telomeres are maintained by ALT mechanisms in Myotis species, then these genes may represent excellent therapeutic targets given that cancer incidence in bats is rare.


Naked Mole-Rats Experience Cellular Senescence, but Seem Largely Unaffected by It

Naked mole-rats are distinguished by an exceptionally long life span in comparison to similarly sized rodents, and a near immunity to cancer. Unlike other mammals, their mortality rates stay fairly constant until very late life. They accumulate all the signs of significant oxidative damage in cells and tissues, but seem resilient to it. Similarly, researchers here note that naked mole-rats do in fact accumulate senescent cells, one of the root causes of aging, but appear resilient to the harmful presence and activities of these cells. Exactly why this is the case has yet to be determined.

Cells become senescent in response to potentially cancerous damage or reaching the Hayflick limit on replication. The vast majority destroy themselves or are destroyed by the immune system, but a tiny fraction linger. They generate signals that spur chronic inflammation, change surrounding cell behavior for the worse, and destructively remodel nearby tissue structures. This results in functional decline in organs and other important tissues and systems. It is interesting to see that while there are differences in the detailed behavior of senescent cells between naked mole-rats and other mammals, they nonetheless still generate the same damaging signals, and yet the naked mole-rats appear to shrug it off.

With their large buck teeth and wrinkled, hairless bodies, naked mole rats won't be winning any awards for cutest rodent. But their long life span - they can live up to 30 years, the longest of any rodent - and remarkable resistance to age-related diseases, offer scientists key clues to the mysteries of aging and cancer. That's why researchers studied naked mole rats to see if the rodents exhibit an anticancer mechanism called cellular senescence.

Previous studies indicated that when cells that had undergone senescence were removed from mice, the mice were less frail in advanced age as compared to mice that aged naturally with senescent cells intact. Researchers therefore believed senescence held the key to the proverbial fountain of youth; removing senescent cells rejuvenated mice, so perhaps it could work with human beings. But is eliminating senescence actually the key to preventing or reversing age-related diseases, namely cancer?

Researchers compared the senescence response of naked mole rats to that of mice, which live a tenth as long - only about two to three years. Their unexpected discovery? Naked mole rats do experience cellular senescence, yet they continue to live long, healthy lives; eliminating the senescence mechanism is not the key to their long life span. The researchers found that although naked mole rats exhibited cellular senescence similar to mice, their senescent cells also displayed unique features that may contribute to their cancer resistance and longevity.

The cellular senescence mechanism permanently arrests a cell to prevent it from dividing, but the cell still continues to metabolize. The researchers found that naked mole rats are able to more strongly inhibit the metabolic process of the senescent cells, resulting in higher resistance to the damaging effects of senescence. "In naked mole rats, senescent cells are better behaved. When you compare the signals from the mouse versus from the naked mole rat, all the genes in the mouse are a mess. In the naked mole rat, everything is more organized. The naked mole rat didn't get rid of the senescence, but maybe it made it a bit more structured."


Models Suggest that Declining T Cell Production is the Primary Reason for Age-Related Increases in Cancer Risk

In the open access paper noted here, researchers use modeling to suggest that age-related decline of the thymus, and thus of the immune system, is more important than mutation as a determinant of cancer risk. Cancer is at root caused by mutational damage to DNA. While DNA repair and replication mechanisms are highly efficient, mutations nonetheless occur - and must occur at some rate in order for evolution to take place. It is a numbers game, in that the more time, the more cells, and the more cell activity, the greater the odds that a cancerous mutation will occur. Mutation rates are also affected by external factors such as radiation, toxic molecules in the cellular environment, and other forms of stress put upon cells. But this is just the primary cause, the trigger enables a cell to replicate without restraint.

After a mutation occurs, there are several classes of process that work to shut down or destroy potentially cancerous cells. We suffer countless potential cancers in our lives, but near all are suppressed before they start. The first line of defense is internal to cells: mechanisms such as those related to p53 that can respond to cancerous mutations and aberrant behavior by inducing immediate programmed cell death or inducing the state of cellular senescence. The latter shuts down replication, sets the cell on the path to self-destruction via apoptosis, and further issues signaling that calls in the immune system to destroy the errant cell. The immune system is the second, and perhaps more important line of defense. Immune cells of various types aggressively seek out and destroy cells that show signs of cancer or other undesirable behavior.

Unfortunately, the immune system declines in effectiveness with age. One of the reasons for this decline is a slowing of the rate at which new T cells are created. This is in part a question of the loss of stem cell activity that occurs throughout the body, reducing the generation of new cells of all sorts. Perhaps more important in the case of T cells is the age-related atrophy of the thymus, however. This organ is where T cells mature before taking up their assigned roles in the body. It is highly active in childhood, but the active tissue begins to be replaced by fat at the onset of maturity, a process called involution. This continues over a life span and into old age, and the pace at which new T cells mature falls along with it.

A slow rate of T cell replacement causes the existing specialized and active T cell populations to become ever more worn and ragged, lacking reinforcements that can respond effectively to new challenges. This affects most of the aspects of immune function, from the response to invading pathogens to the ability to catch and destroy cancerous cells before they start in earnest the process of generating a tumor. For this reason there is considerable interest in the research community in finding ways to rejuvenate the thymus, to restore the active tissue that acts as a nursery for T cell maturation. If successful, this should go some way towards regaining the lost capacity of the immune system.

Thymic involution and rising disease incidence with age

T cells develop from hematopoietic stem cells as part of the lymphoid lineage and have the ability to detect foreign antigens and neoantigens arising from cancer cells. In the thymus, lymphoid progenitors commit to a specific T cell receptor and undergo selection events that screen against self-reactivity. Cells that pass these selection gates then leave the thymus, clonally expanding to form the patrolling naive T cell pool.

The vast majority of vertebrates experience thymic involution (or atrophy) in which thymic epithelial tissue is replaced with adipose tissue, resulting in decreasing T cell export from the thymus. In humans, this is thought to begin as early as 1 year of age. The rate of thymic T cell production is estimated to decline exponentially over time with a half-life of ∼15.7 years. Declining production of new naive T cells is thought to be a significant component of immunosenescence, the age-related decline in immune system function. With the recent successes of T cell-based immunotherapies, it is timely to assess how thymic involution may affect cancer and infectious disease incidence.

It is clear from epidemiological data that incidence of infectious disease and cancer increases dramatically with age, and, specifically, that many cancer incidence curves follow an apparent power law. The simplest model to account for this assumes that cancer initiation is the result of a gradual accumulation of rare "driver" mutations in one single cell. Furthermore, the fitting of this power law model (PLM) can be used to estimate the number of such mutations. Exponential curves have also been used to fit cancer incidence data, resulting in worse fits than the PLM overall. Nevertheless, it is worth noting that exponential rates close to the declining curve for thymic T cell production can be seen to emerge from the incidence data, indicating the relevance of the thymic involution timescale. While the PLM fits well, it does not account for changes in the immune system with age. To better determine the processes underlying carcinogenesis, we asked whether an alternative model, based only on age-related changes in immune system function, might partly or entirely explain cancer incidence.

Our model outperforms the power law model with the same number of fitting parameters in describing cancer incidence data across a wide spectrum of different cancers, and provides excellent fits to infectious disease data. Our hypothesis and results add to the understanding of infectious disease and cancer incidence, suggesting in the latter case that immunosenescence, rather than gradual accumulation of mutations, serves as the predominant reason for an increase in cancer incidence with age for many cancers. For future therapies, including preventative therapies, strengthening the functionality of the aging immune system appears to be more feasible than limiting genetic mutations, which raises hope for effective new treatments.

Ventricular Decline Correlates Well with Other Forms of Damage in the Aging Brain

Here, researchers examine the correlation between ventricular dsyfunction, other noted forms of damage observed in brain aging, and the onset of cognitive decline. The ventricular system is where cerebrospinal fluid is created and circulates throughout the brain. Many things go wrong in the aging brain, all stemming from the same few root cause processes of damage accumulation in and around cells. Thus correlations between specific observed changes and the progression of dementia should be expected, but don't necessarily imply direct causation - though a particularly good correlation always indicates that further investigation is probably merited.

This line of investigation ties in to a growing area of research regarding the impairment of drainage of cerebrospinal fluid in aging. This impairment may explain the slowly rising levels of protein aggregates and other molecular waste in the brains of older individuals, a state of affairs known to contribute to the development of neurodegenerative conditions. Normally these wastes are removed at some pace through various filtration and drainage channels for cerebrospinal fluid, but the channels become dysfunctional, just like all other biological systems in older individuals. Leucadia Therapeutics is an example of a company working to intervene and restore youthful levels of drainage to what they consider the more important path. Other groups are looking into different areas of impaired fluid flow in the brain. All in all it is a most interesting and promising area of development.

The human brain's ventricular system is essential for the movement of nutrient-rich cerebrospinal fluid (CSF) throughout the central nervous system. A special epithelial lining along the ventricle walls composed of ependymal cells allows for the movement of CSF nutrients into the brain parenchyma as well as clearance of proteins and metabolites from the interstitial fluid (ISF). This ependyma-mediated bidirectional CSF-ISF exchange, as well as the formation of a cell barrier to prevent movement of proteins and metabolites from the CSF back into the ISF, relies on the presence of an intact ependymal cell monolayer. Pathological conditions in humans that are characterized by ependymal cell stretching and/or loss, including hydrocephalus, typically result in decreased CSF turnover rates and impaired clearance of proteins and metabolites resulting in a harmful buildup of these substances in brain parenchymal tissue.

Longitudinal magnetic resonance imaging (MRI)-based studies have established that expansion of the brain's fluid-filled lateral ventricles (LVs), or ventriculomegaly, is a defining feature of the aging brain. Ventricle expansion rates correlate strongly with declining cognitive performance and the rate of ventricle volume increase has been linked to an increase in Alzheimer's disease (AD)-related amyloid-beta (Aβ) plaques and tau neurofibrillary tangles, as well as alterations in CSF biomarker composition. Together, these point towards defective CSF-ISF exchange and impaired clearance mechanisms that are characteristic of AD.

Degeneration of periventricular brain tissue and declines in associated white matter tract integrity are common with normal aging and the extent of periventricular tissue abnormalities has been linked to dementia and AD. Periventricular hyperintensities (PVH), as measured using MRI, are indicative of fluid accumulation, or edema, often located in the parenchymal tissue directly adjacent to the frontal and occipital horns of the LV. The precise etiology of PVH is not clear; however, studies have implicated impaired drainage of ISF from the periventricular white matter resulting in aberrant fluid accumulation.

In previous studies, we found that enlarged ventricles from aging humans exhibited regional gliosis in the place of functional ependymal cell coverage. We predict that replacement of the ependymal lining with stratified layers of astrocytes at the ventricle surface adversely affects CSF/ISF bulk flow mechanisms, leading to fluid accumulation or edema and harmful buildup of proteins and metabolites in the periventricular space. Due to the rarity of longitudinal MRI data sets and associated subject-matched periventricular tissue biospecimens, this has never been directly demonstrated.

Using data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) and the Baltimore Longitudinal Study of Aging (BLSA), we investigated the relationships among the following variables: ventricle expansion, PVH, periventricular white matter tract integrity, and degree of cognitive impairment. We also investigated the histopathological correlates of these measures, including LV wall gliosis and periventricular protein accumulation. We found that both LV and PVH volumes increase with age, and this expansion is more rapid and dramatic in cognitively impaired (CI) subjects. We also found a direct relationship between LV volume and PVH volume increase. Case studies from the BLSA allowed us to link ventricle expansion with regional gliosis, where an intact ependymal cell monolayer was replaced with stratified layers of astrocytes in regions of LV expansion. Additionally, adjacent parenchymal regions exhibited edema (as indicated by PVH), white matter deterioration, decreased vascular integrity, and harmful buildup of proteins including Aβ and tau.


Reviewing What is Known of Extracellular Vesicles and Cellular Senescence

The research community has been devoting more time and energy to the investigation of extracellular vesicles of late. These membrane-bound packages of proteins and other molecules are an important facet of the way in which cells communicate with one another. Signaling between cells is itself very significant, a potential point of intervention for many classes of therapy. For example, most current stem cell therapies appear to work largely due to the signaling provided by transplanted cells - given sufficient understanding of the signaling, the cells could be dispensed with and the signals applied directly.

As another example, the growing presence of cellular senescence with age has a large detrimental impact on tissue function, despite the comparatively small numbers of senescent cells present even in older individuals, because these negative effects are mediated by signaling. In this way, a handful of errant cells can put the entire local environment into disarray. On that topic, the open access paper here takes a short tour of what is known about extracellular vesicles in the context of cellular senescence.

Cellular senescence prevents the proliferation of cells exposed to potentially oncogenic stresses, such as DNA-damaging reagents, irradiation, telomere shortening, and oncogene activation. Mutations in genes essential for the senescence-induced cell cycle arrest predispose cells to immortalization and shorten lifespan by increasing cancer incidence. However, cellular senescence not only arrests the cell cycle but also changes how the cell impacts its microenvironment. The way in which senescent cells influence their microenvironment is highly context dependent. It promotes tumor development in many cases, but can also be tumor suppressive in certain circumstances. Removal of senescent cells that accumulated in the body during aging alleviates atherosclerosis, hepatic steatosis, tumor development, and functional declines of heart, kidney, and fat tissues, resulting in prolonged healthspan and lifespan. These effects may be attributable to so-called , whereby cells secrete high levels of inflammatory cytokines, chemokines, growth factors, and metalloproteinases.

Although the involvement of typical secretory proteins in the non-cell-autonomous effects of senescent cells has been well studied, the functions of membrane-enclosed vesicles secreted by senescent cells have not been studied until recently. These extracellular vesicles (EVs) were once thought to be cellular trash, but now it is clear that they are critical mediators in intercellular communication. Emerging evidence indicates that EVs also play important roles in cellular senescence and aging. This field is rapidly advancing especially since it was reported that EVs deliver functional RNA to the recipient cells. Extracellular vesicles contain a huge variety of proteins and nucleic acids in a cell type-dependent manner.

Senescence-associated increase in EV secretion seems to be a general feature of cellular senescence and has been observed in fibroblasts, epithelial cells, and cancer cells. This increase is at least partially mediated by p53 and one of its targets, TSAP6, although the mechanism whereby TSAP6 regulates EV secretion is not well understood. It is known that EV secretion contributes to the clearance of harmful molecules in cells, such as cytoplasmic DNA. It has been shown that EV-mediated removal of cytoplasmic DNA is essential for the survival of senescent cells, which may explain why EV secretion is increased in senescent cells.

Recent findings implicate senescent cell EVs in cancer development, vascular calcification, and age-related decline in bone formation. Increased secretion of EV-associated DNA from senescent cells is likely to be pro-inflammatory and may contribute to age-related chronic inflammation. Whether senescent cell EVs promote or suppress cancer development may be context dependent. Despite this progress, it should be noted that the functions of senescent cell EVs are still understudied, at least partially due to inadequate understanding of EVs themselves. This research field is immature and the methods used are not sufficiently standardized yet. Nevertheless, EVs are now shown to be critical players in cellular senescence and aging, and more functions will be revealed in the future as the EV research field matures.


Decline in the Supporting Cells of the Blood-Brain Barrier Precedes Dementia

The brain is locked away from the biochemistry of the rest of the body behind the blood-brain barrier, the sheath of specialized cells surrounding blood vessels in the brain that prevents most unwanted molecular traffic to and from neural tissues. The brain is biochemically quite different from the rest of the body, and many of the commonplace molecules found elsewhere can be harmful to brain tissue or degrade neural function. Pericytes are one of the supporting cell types involved in the structure of the blood-brain barrier, and in the research noted here, pericyte dysfunction is linked to other known aspects of biochemical disarray in the vascular system that take place with aging. These include: the leakage of fibrinogen into the brain and its damaging effects on nerves; the progressive failure of blood-brain barrier integrity, allowing other forms of leakage; the buildup of protein aggregates that harm neurons; and the general vascular dysfunction that impacts the delivery of nutrients to the energy-hungry brain.

What can be done about this? The research here identifies the functional failure of pericytes as the earliest cause in the stack of consequences that the authors examined, but they look at managing fibrinogen as the first option for therapies. This is a sadly common sort of approach, meaning to work on the manipulation of consequences rather than addressing lower causes. To my eyes, the better way forward would be to dig deeper into the dysfunction of the cells of the blood-brain barrier, to ask why they are declining. There is a rich literature of investigation regarding blood vessel dysfunction, one that is starting to touch on the contributions of the root causes of aging, such as cellular senescence. More could certainly be done in that direction, rather than immediately preparing the ground for attempts at clinical translation of what has been learned so far.

Half of all dementias, including Alzheimer's, start with damaged 'gatekeeper cells'

Nearly 50 percent of all dementias, including Alzheimer's, begins with the breakdown of the smallest blood vessels in the brain and their protective "gatekeeper cells," according to a new study. That catastrophe causes a communications failure called small vessel disease. Many people with that disease also have white matter disease, the wearing away of fatty myelin that allows neurons to transfer messages within the brain network. In an animal model, researchers found that brain deterioration associated with dementia may start as early 40 in humans.

For more than 25 years, scientists have known that white matter disease impedes a person's ability to learn or remember new things, slows thinking and causes people to fall more often due to balance issues. They identified a link between crippled small blood vessels in the brain and white matter disease but didn't know what started that process until now. "Many scientists have focused their Alzheimer's disease research on the buildup of toxic amyloid and tau proteins in the brain, but this study and others from my lab show that the problem starts earlier - with leaky blood vessels in the brain. The collapse of pericytes - gatekeeper cells that surround the brain's smallest blood vessels - reduces myelin and white matter structure in the brain. Vascular dysfunctions, including blood flow reduction and blood-brain barrier breakdown, kick off white matter disease."

The study explains that pericytes play a critical role in white matter health and disease via fibrinogen, a protein that circulates in blood. Fibrinogen develops blood clots so wounds can heal. When gatekeeper cells are compromised, an unhealthy amount of fibrinogen slinks into the brain and causes white matter and brain structures, including axons (nerve fibers) and oligodendrocytes (cells that produce myelin), to die. The researchers are the first to show that fibrinogen is a key player in non-immune white matter degeneration. The protein enters the brain through a leaky blood-brain barrier. The study found about 50 percent fewer gatekeeper cells and three times more fibrinogen proteins in watershed white matter areas in postmortem Alzheimer's brains of humans compared to healthy brains.

To confirm that fibrinogen proteins are toxic to the brain, researchers used an enzyme known to reduce fibrinogen in the blood and brain of mice. White matter volume in mice returned to 90 percent of their normal state, and white matter connections were back to 80 percent productivity. "Our study provides proof that targeting fibrinogen and limiting these protein deposits in the brain can reverse or slow white matter disease. It provides a target for treatment, but more research is needed. We must figure out the right approach. Perhaps focusing on strengthening the blood-brain barrier integrity may be an answer because you can't eliminate fibrinogen from blood in humans. This protein is necessary in the blood. It just happens to be toxic to the brain."

Pericyte degeneration causes white matter dysfunction in the mouse central nervous system

Diffuse white-matter disease associated with small-vessel disease and dementia is prevalent in the elderly. The biological mechanisms, however, remain elusive. Using pericyte-deficient mice, magnetic resonance imaging, viral-based tract-tracing, and behavior and tissue analysis, we found that pericyte degeneration disrupted white-matter microcirculation, resulting in an accumulation of toxic blood-derived fibrin(ogen) deposits and blood-flow reductions, which triggered a loss of myelin, axons, and oligodendrocytes. This disrupted brain circuits, leading to white-matter functional deficits before neuronal loss occurs.

Fibrinogen and fibrin fibrils initiated autophagy-dependent cell death in oligodendrocyte and pericyte cultures, whereas pharmacological and genetic manipulations of systemic fibrinogen levels in pericyte-deficient, but not control mice, influenced the degree of white-matter fibrin(ogen) deposition, pericyte degeneration, vascular pathology and white-matter changes. Thus, our data indicate that pericytes control white-matter structure and function, which has implications for the pathogenesis and treatment of human white-matter disease associated with small-vessel disease.

A More Subtle Demonstration that Telomere Length is Not a Good Measure of Aging

Researchers here find a disconnect between DNA methylation patterns shown to correlate well with age and processes associated with longer telomere length. Telomeres are caps of repeated DNA at the ends of chromosomes that shorten with each cell division, a part of the mechanism limiting the life span of somatic cells. Their average length tends to shorten with age when considered across large populations in a statistical analysis, but this is a tenuous relationship that has also failed to appear in some smaller studies. Here, it seems that older ages as assessed by DNA methylation can correlate with differences in telomerase, the enzyme responsible for lengthening telomeres, that are associated with longer telomeres.

In any given individual, average telomere length as currently measured in leukocytes from a blood sample is dynamic in response to circumstances; it reflects pace of cell division and the rate at which new cells with long telomeres are generated by stem cells. Unfortunately the large degree of individual and circumstantial variation means that there is little to be meaningfully said about the present value - the information is not actionable in all but rare cases of exceptionally short average length due to disease. The epigenetic clocks derived from DNA methylation measurements are much more solid, repeatable, useful metrics, judging from the evidence to date.

In that broader context, it is interesting to find signs that these two approaches to measuring an aspect of aging are not on the same page, though I think the researchers here overstate the significance of their work and/or engage with a strawman to some degree in their comments. What they have found does fit in with the evidence to date supporting the idea that telomere length is only very loosely associated with aging, with considerable variation between individuals. That is somewhat distinct from the question of whether or not telomerase gene therapies are a useful approach to the treatment of aging or other conditions.

Researchers analyzed blood samples from nearly 10,000 people to find that genetic markers in the gene responsible for keeping telomeres (tips of chromosomes) youthfully longer, did not translate into a younger biologic age as measured by changes in proteins coating the DNA. DNA methylation age is a biomarker of chronological age and predicts lifespan, but its underlying molecular mechanisms are unknown.

In this genome-wide association study, researchers found gene variants mapping to five loci associated with intrinsic epigenetic age acceleration (IEAA) and gene variants in three loci associated with extrinsic epigenetic age acceleration. Variants in the gene called Telomerase Reverse Transcriptase (TERT) on chromosome 5 that were associated with older IEAA were also associated with longer telomeres indicating a critical role for TERT in regulating the epigenetic clock, in addition to its established role of compensating for cell replication-dependent telomere shortening.

"We calculated the epigenetic aging rate for each person using a previously described epigenetic clock method. Next, we related the epigenetic aging rate to millions of genetic locations (SNPs) across all of the chromosomes. Then we studied the SNPs that had very significant associations with epigenetic aging rates. To our surprise, one of these locations was the TERT locus. The finding is surprising because this was not a study of telomere length. TERT is a subunit of the enzyme telomerase, which is widely known because it has been touted as an anti-aging enzyme. Our study highlights the error in the notion that activation of telomerase (as advocated by some) will cure aging. Instead, our study shows that an anti-aging therapy based on telomerase expression would be accompanied by continued aging."


Immunosenescence and Inflammaging, Two Sides of the Same Coin

The aging immune system falls apart in a number of different ways, and as the researchers here note, the process probably isn't just one of decline, but of a continual adaptation to that decline. Present nomenclature tends to categorize aspects of immune system aging into broad categories by the type of outcome produced. These are (a) immunosenescence, the weakening of the immune response to pathogens and failure of immune surveillance of potentially dangerous cells, (b) inflammaging, progressively raised levels of chronic inflammation, and (c) autoimmunity, in which the immune system begins to attack tissues. In reality, everything in biochemistry is connected to everything else, and these outcomes are the consequences of interacting, shared processes of decline and damage.

Any successful effort to turn back immune system aging, such as by selectively destroying malfunctioning or unhelpfully configured immune cells, and restoring the generation of new immune cells to youthful levels, should go some way to addressing all of these issues. The researchers here suggest caution on selective reversal of symptoms of immune aging, as some are beneficial adaptations, but in my opinion this shouldn't apply to efforts to address the lower level causes of immune aging. Where adaptations occur, they are adaptations to those causes, an attempt to claw back some functionality in the face of decline. That becomes moot, and the adaptation should cease, if its trigger is removed.

Aging is one of the most intricate and complex biological phenomenon. One physiological system that shows marked changes during aging is the immune system. The interest of the immune system in aging is related to the fact that this is an interacting master regulatory system that keeps the organism free of invaders, either internal or external. Since the introduction of the notion of immunosenescence, many scientists have questioned the justification for unidirectional implication of the immune system and its decreased efficiency associated with aging. Whereas some functions are indeed decreased, others are increased. Therefore; changes are not as uniform as the designation would suggest.

Accordingly, we can propose a new paradigm for dynamic immune changes with aging. We suggest that aging leads to modified/modulated responses of the immune system, making it more adapted to cope with challenges (pathogens) in a given (local) environment, and not just to an eventually terminal deterioration of the immune system. From an evolutionary perspective, this is a simple optimization of the resources of the aging body, even if it ultimately leads to pathologies and death. Immunosenescence may be necessary for an adequate response to known antigens, but detrimental for responses to new antigens in most circumstances. From this perspective, many or most age-related changes in the immune system may be desirable adaptations to the aging process, and thus no need for rejuvenation seems to be necessary.

In conclusion, most experimental data on immune changes with aging show a decline in many immune parameters when compared to young healthy subjects. The bulk of these changes is termed immunosenescence. Immunosenescence has been considered for some time as detrimental because it often leads to subclinical accumulation of pro-inflammatory factors and inflammaging. Together, immunosenescence and inflammaging are suggested to stand at the origin of most of the diseases of the elderly, such as infections, cancer, autoimmune disorders, and chronic inflammatory diseases. However, an increasing number of gerontologists have challenged this negative interpretation of immunosenescence with respect to its significance in aging-related alterations of the immune system.

If one considers these changes from an evolutionary perspective, they can be viewed preferably as adaptive or remodeling rather than solely detrimental. Whereas it is conceivable that global immune changes may lead to various diseases, it is also obvious that these changes may be needed for extended survival/longevity. Recent cumulative data suggest that, without the existence of the immunosenescence/inflammaging duo (representing two sides of the same phenomenon), human longevity would be greatly shortened.


To Cure Aging as Though it Were a Disease

Aging and cancer are conceptually similar in many ways, and by this I mean that they are both collections of processes that are fundamental to the way in which the biology of complex organisms works. They are not states that can be cured or eliminated through medicine as we presently understand it, but the aspiration is instead to bring these undesirable outcomes under control - to continually cut back the offshoots, to suppress the causes, and nip in the bud the results of those causes in their earliest stages. To actually cure either aging or cancer, to remove it from the human condition, would require a radical reworking of our cellular biochemistry, to the point at which it would cease to be biology in any meaningful sense and become a hybrid form of molecular nanotechnology. That sort of project lies far distant in the future. Today's concerns are entirely directed towards the control of aging and cancer, something that can be achieved through forms of medicine we can recognize and understand.

Regardless, we all use words carelessly. We search for cures for cancer. We call cancer a disease, though in reality this probably stretches that term as well. We choose not to call aging a disease, though not for any particularly rational reason. Having watched the progression of rejuvenation research since just after the turn of the century, it is both gratifying and interesting to see the changing tone in media coverage of the science, the message of the patient advocates, and the aspirations of those involved. Ten years ago, mockery was commonplace. Now journalists are taking it a lot more seriously; it is hard to do otherwise, given the earnest levels of funding and many scientific papers devoted to - to pick one example - the clearance of senescent cells, an actual, honest-to-goodness rejuvenation therapy now under development in various startup companies.

Nonetheless, journalistic habits of balance remain. Faced with a movement whose members want to prevent the majority of all death and suffering in the world by bringing an end to aging, and are mustering increasingly credible science to that cause, the authors of the old media still feel obliged to put in a word for the other side. After all, what about the view that everyone should just suffer and die? Why shouldn't that be presented with equal weight? After a certain point, balance becomes a caricature of itself - isn't this the sort of thing that would be put forth as satire in an earlier era? And yet here we are, death for everyone as the balance viewpoint in articles on the future rejuvenation biotechnology.

The Ambitious Quest to Cure Aging Like a Disease

The list of diseases humankind has managed to defeat is impressive. But throughout history, humans have suffered from a condition that they have never been able to escape - ageing. As we get older, our cells stop working as well and can break down, leading to conditions like cancer, heart disease, arthritis and Alzheimer's disease. Together, ageing-related diseases are responsible for 100,000 deaths per day and billions are spent around the world trying to slow their steady march on our bodies.

Some researchers, however, believe we may be thinking about these conditions in the wrong way. They say we should start treating ageing itself as a disease - one that can be prevented and treated. Their hopes are founded on recent discoveries that suggest biological ageing may be entirely preventable and treatable. From a biological perspective, the body ages at different rates according to genetic and environmental factors. Tiny errors build up in our DNA and our cells begin developing faults that can accumulate into tissue damage. The extent of these changes over time can mean the difference between a healthy old age or one spent housebound and afflicted by chronic diseases.

The scientists who hope to do this sit on the fringes of the mainstream medical landscape. But there are now a number of research centres around the world that have made identifying ways of preventing biological ageing a priority. Studies in animals have shown that it is indeed possible to dramatically extend the lifespan of certain species, giving hope that it could also be possible in humans. One of the leading figures in human longevity research, Aubrey de Grey, is the chief science officer at the Strategies for Engineered Negligible Senescence (SENS) Research Foundation, a California-based regenerative medicine research foundation focused on extending the healthy human lifespan. Their goal is to develop a suite of therapies for middle-aged and older people that will leave them physically and mentally equivalent to someone under the age of 30. They want "to fix the things we don't like about the changes that happen between the age of 30 and the age of 70". There are seven biological factors de Grey argues are predominantly responsible for cellular damage that accompanies ageing and underlies ageing-related diseases.

De Grey doesn't think that it will be possible stop ageing altogether with these types of approaches, but they may give patients an extra 30 years or so of life. He envisages a future where "rejuvenation technologies" can be administered to old people in order to revert their cells to what they were like when they were in their youth, buying them extra time. The idea is that someone who is treated at the age of 60 will be biologically reverted to 30. But because the therapies are not permanent fixes, their cells will end up becoming 60 years old again in another 30 years time. By then de Grey hopes the therapies could be reapplied as "version 2.0" to revert the same individuals once again to become younger in their cells. As a result, that person's cells wouldn't become 60 again until they're about 150 years old.

And he is not alone in believing ageing-related diseases can be solved. George Church, a geneticist at Harvard Medical School, told us that while some of his colleagues argue many age-related diseases are so complex that they simply can't be treated, he finds such thinking to be incorrect. "If you can control both the environment and the genetics, you can get people that live youthful healthy lives for exceptionally much longer than others. In industrialised nations, most of the diseases are due to age-related diseases and I think those too can be handled."

But regardless of how it is achieved, extending human lifespans by decades or even hundreds of years will present us with some difficult social realities. There could be major societal impacts if we all start living longer. There are some that fear greater longevity could lead to swelling populations and raise doubts that our planet could support such numbers. Aubrey de Grey has little time for such questions and believes that other technologies - such as artificial meat, desalination, solar energy and other renewables - will increase the carrying capacity of the planet, allowing more people to live longer lives. But this rationale suffers from a dependence on uncertain techno-fixes that may not alleviate suffering in an equally distributed manner. Yet, if concerns like these had paralysed the early pioneers of vaccination and antibiotics, it is unlikely many of us today could expect to live much beyond the age of 40-years-old. Advances in medicine over the last two centuries have taught us that we have the power to defeat the diseases that afflict us. Perhaps if we apply ourselves, then we can beat ageing too.

Why is Life Span Inherited to any Significant Degree?

Why do the life spans of parents exhibit some degree of correlation with the life spans of their children? "Genetics" is probably not an acceptable answer, given present evidence for natural genetic variation to contribute comparatively little to human life expectancy in all but a few rare cases. So is it cultural, where culture influences lifestyle choices closely correlated with health, such as weight gain or smoking? Or is it due to wealth effects, for much the same reasons? If so, then why is there such variation in life expectancy within specific social groups and wealth strata? These are tough questions to answer with any reliability given snapshot data from groups within human populations. Any given large study is just a single data point in the ongoing process of analysis and debate that spans decades and the entire scientific community.

In the long run, I have my doubts that good answers will be established for this and many other questions regarding the details of natural aging today. We may never know. The urge to investigate the demographics of aging will be swept away by the advent of rejuvenation therapies such as the senolytics presently under development. All natural variations in pace of aging and life expectancy will be buried beneath the size of the gains made possible through periodic repair of the cell and tissue damage that causes aging. The data will evaporate, and different concerns will occupy the scientific community of tomorrow. After all, how many members of today's scientific community spend any time on the demographics of smallpox in populations lacking treatment options? Few indeed. It will be the same for natural aging.

Mortality, life expectancy, and age-at-death are all strongly socially structured. Despite economic growth, welfare state provisions, modern medicine and a fundamental change in disease panorama, we find a negative social gradient in mortality generation after generation. Because education, occupation, and income all predict health and survival we should also expect such characteristics in the parental generation to predict the next generation's health prospects, resulting in "inheritance of longevity". It is possible, however, that this influence from previous generations is considerably broader than that working through the children's own education, occupation, and income. Variation in mortality risk within social groups is great. To understand "inheritance of longevity" we need a conceptual framework that also identifies those within-class influences.

Already in 1934 it was suggested that the first 15 years of life could determine your mortality risk during the entire lifecourse. Similarly, the so-called DOHaD (Developmental Origins of Health and Disease) theory suggests that early life experiences is an important determinant of adult health and disease. DOHaD theory has focused on specific aetiologies and influences, such as that of foetal growth restriction on blood pressure and circulatory disease. Another, earlier school of thinking argued for more general disease-causing mechanisms. Concepts like frailty, general susceptibility, or differential vulnerability refer to individual differences in the ability to survive hardship.

Demographic concepts like frailty, epidemiological ones like general susceptibility, and psychological ones like resilience all refer to the same real-life-phenomenon: a general rather than specific vulnerability to disease. Some have stressed its social roots, while others perhaps assumed it to have a more genetic basis. Resilience, in turn, may be related to both views. It could be thought of as the opposite extreme to susceptibility/frailty on the same underlying dimension. In this study, we argue that resilience is acquired early and maintained throughout life. Resilience should therefore influence the ability to survive up to a high age and be linked to longevity, as a number of studies indeed suggest.

"Inheritance of longevity" has been discussed at length in the literature. Its precise nature is somewhat elusive. Studying the entire Icelandic population, researchers concluded that longevity was inherited within families, probably because of shared genes. Other groups, looking at twin data, concluded that genetic influences on the lifespan were minimal before age 60 and only increase after that age. On the other hand, other work has rejected any idea that mortality in old age is genetically programmed. Consistent with that view, a Swedish study of men born in 1913, found that a number of social and behavioural factors measured at age 50, but not their parents' survival, predicted longevity.

Evolutionary theorists have debated whether there is any evolutionary pressure to promote survival into old age. Nevertheless, we observe a steady lifespan extension in modern societies, especially among women, partly based on falling mortality rates across their long post-reproductive period. That children tend to live longer than their parents is likely to be determined both by what experience parents brings to the next generation, and by the improved life circumstances of the children themselves in their childhood and adult life. The importance of genetic factors for longevity, we suggest, may lie in their interaction with other factors, perhaps especially if this interaction takes place at an early age.


A New Blood Test Approach can Assess Levels of Amyloid-β in the Brain

Researchers have developed a blood test that correlates well with levels of amyloid-β in the brain, offering an opportunity to reduce the cost of assessing potential therapies to treat Alzheimer's disease. Currently the only reliable methods are invasive or expensive, requiring access to cerebrospinal fluid or the use of scanning technologies. This work might be considered in the broader context of a range of studies linking amyloid-β in blood vessels and bloodstream with amyloid-β in the brain; it is thought that the relationship between amyloid-β inside and outside the brain may be a two-way street, a form of equilibrium. On the one hand that means that it might be possible to leach amyloid-β from the brain by clearing it from the cardiovascular system. On the other hand, it may be the case that increased amyloid-β in the cardiovascular system due to aging is an early source of the amyloid protein aggregates that emerge in the brain.

Researchers have developed the first blood test to detect amyloid-β protein buildup in the brain, one of the earliest hallmarks of Alzheimer's disease. The findings show that measurements of the protein and its precursors in the blood can predict neural amyloid-β deposition and could pave the way for a cheap and minimally invasive screening tool for the disease. "This study has major implications. It is the first time a group has shown a strong association of blood plasma amyloid with brain and cerebrospinal fluid."

Current methods to identify amyloid-β buildup in living people are limited to costly and sometimes highly invasive procedures, such as brain imaging with a PET scanner and spinal cord fluid extraction. So researchers set out to test whether the same information could be obtained from a blood sample. Using immunoprecipitation and mass spectrometry, the team isolated and characterized amyloid proteins in the blood from a cohort of 121 people in Japan spanning a range of cognitive function, from normal to developed Alzheimer's. They showed that blood test results could predict amyloid-β levels in the brain with about 90 percent of the accuracy achieved using PET scanning. A repeat of the approach with a validation cohort of 252 people in Australia confirmed the blood test's performance.

Such a test could one day be used to detect early signs of Alzheimer's in people with no obvious symptoms. "I can see in the future, five years from now, where people have a regular checkup every five years after age 55 or 60 to determine whether they are on the Alzheimer's pathway or not. If a person knows they are on this pathway well before the onset of any cognitive impairment some would want to alter their lifestyles. It's good to see this type of study advance, as we desperately need noninvasive and low-cost markers for Alzheimer's disease. But still, at this point it is not ready for prime time."


The Sizable First Volume of the 2017 Longevity Industry Landscape Overview

Over on the other side of our still quite modestly sized longevity science community you will find the network that includes Deep Knowledge Ventures, the Biogerontology Research Foundation, and the Aging Analytics Agency, source of the report I'll point out today. "Other side" is a relative term; it isn't far, and you'll recognize many of the names as also being involved in the US research and advocacy ventures more often mentioned here. Portions of our community have long pursued an interest in mapping the initiatives, people, and funding involved in aging research; see the International Aging Research Portfolio, for example. As the fields of geroscience and rejuvenation research have solidified and gathered increasing support, producing an overview of research aimed at the treatment of aging has become a sizable task. That point is well illustrated by the large first volume of the Longevity Industry Landscape Overview series, to be followed up by another four volumes in 2018, and then, if I understand the intent correctly, to be updated yearly going forward. It represents an imposing amount of work, and those involved are to be thanked for their dedication.

This sort of undertaking might be viewed as the building of a foundation, laying a part of the groundwork needed for large-scale investment in the future, particularly from governments and other entities capable of devoting enormous resources to a task (albeit usually clumsily, wastefully, and late). Organizations of that nature tend not to move at all until the topic at hand is buried beneath paper, committees, and years of consideration. All that the relevant functionaries know comes from digests and reports such as the Longevity Industry Landscape Overview, not first-hand understanding. At present the industry of treating aging is just moving out of the laboratory and into the stage of startup companies and handshake deals on investment, of funds whose principals can educate themselves on the science, and of people willing to make leaps of faith and risk. Somewhere in the future, that will slow down and become far more conservative; far greater sums will be moved around as treatments to modestly slow aging and treatments to repair the damage of aging move into the mainstream medical system.

Regarding the science, the first volume quoted here is a set of disparate views on how to proceed, from the pharmaceutical metabolic manipulation to slow aging that characterizes the geroscience community to the SENS vision of regenerative medicine applied to aging, the periodic repair of the cell and tissue damage that causes aging. There is no integration between these different paths ahead, because there really can't be; the purpose is to show the diversity of opinions in the context of a young and rapidly growing industry, not smooth over the sizable differences and many disagreements on the best approach to take. In the years ahead, the evidence from studies in mice and humans will guide the way. The best approaches will stand out and be taken forward to the clinic - just so long as we, the advocates, manage to argue well and raise sufficient philanthropic funding to allow the most promising studies to be carried out in the first place. Standing aside and letting matters progress without that intervention isn't an option, as it only leads to years of unnecessary delay.

Longevity industry systematized for first time

For scientists, policy makers, regulators, government officials, investors and other stakeholders, a consensus understanding of the field of human longevity remains fragmented, and has yet to be systematized by any coherent framework, and has not yet been the subject of a comprehensive report profiling the field and industry as a whole by any analytical agency to date. Experts on the subject of human longevity, who tend arrive at the subject from disparate fields, have failed even to agree on a likely order of magnitude for future human lifespan. Those who foresee a 100-year average in the near future are considered extreme optimists by some, while others have even mooted the possibility of indefinite life extension through comprehensive repair and maintenance. As such the longevity industry has often defied real understanding and has proved a complex and abstract topic in the minds of many, investors and governments in particular.

A report entitled 'The Science of Longevity', standing at almost 800 pages in length, seeks to rectify this. Part 1 of the report ties together the progress threads of the constituent industries into a coherent narrative, mapping the intersection of biomedical gerontology, regenerative medicine, precision medicine, and artificial intelligence, offering a brief history and snapshot of each. Part 2 lists and individually profiles 650 longevity-focused entities, including research hubs, non-profit organizations, leading scientists, conferences, databases, books and journals. Infographics are used to illustrate where research institutions stand in relation to each other with regard to their disruptive potential: companies and institutions specialising in palliative technologies are placed at the periphery of circular diagrams, whereas those involved with more comprehensive, preventative interventions, such as rejuvenation biotechnologies and gene therapies, are depicted as central.

Since these reports are being spearheaded by the UK's oldest biomedical charity focused on healthspan extension, the Biogerontology Research Foundation is publishing them online, freely available to the public. While the main focus of this series of reports is an analytical report on the emerging longevity industry, the reports still delve deeply into the science of longevity, and Volume I is dedicated exclusively to an overview of the history, present and future state of ageing research from a scientific perspective. Volume 2, is set to be published shortly thereafter, and will focus on the companies and investors working in the field of precision preventive medicine with a focus on healthy longevity, which will be necessary in growing the industry fast enough to avert the impending crisis of global aging demographics.

These reports will be followed up throughout the coming year with Volume 3 ("Special Case Studies"), featuring 10 special case studies on specific longevity industry sectors, such as cell therapies, gene therapies, AI for biomarkers of aging, and more, Volume 4 ("Novel Longevity Financial System"), profiling how various corporations, pension funds, investment funds and governments will cooperate within the next decade to avoid the crisis of demographic aging, and Volume 5 ("Region Case Studies"), profiling the longevity industry in specific geographic regions.

Longevity Industry Landscape Overview 2017, Volume 1: the Science of Longevity (PDF)

The greatest problem threatening global economic prosperity and social stability is demographic aging. The only sustainable solution is to extend healthy lifespan (healthspan). Clearly it would be desirable to add life to our years rather than merely years to our lives. But few are aware that health span extension is becoming routine in the laboratory. Scientific breakthroughs have demonstrated up to 30% increased healthspan extension in mice, and much more in non-mammalian model organisms by various pharmacological, environmental, and genetic interventions. In recent years, scientists have elucidated the fundamental mechanisms or hallmarks of aging, opening the field of geroscience - the understanding and manipulation of the fundamental biological processes in age-related disease.

The widest ceiling over the aspirations of geroscience has always been the inextricability of disease from aging and the inextricability of aging from human metabolism, which, being so complex and integral to our day-to-day functioning, can only be amended rather than reconstructed. This limits us because it robs us of the most obvious approach to radical life extension: radical interference in human metabolism. For just as we might like to be able to alter a car's inner workings so that they inflict less wear and tear, so too might we like to be able to somehow rearrange metabolism so that it inflicts less wear and tear on body tissues.

Sadly this is not an option. While subtle interventions in areas such as calorie restriction mimetics hold some promise to appreciably increase life expectancy, anything amounting to a successful radical intervention in metabolism which radically extends life span is inconceivable for the foreseeable future for the above reasons. This brings us to the alternative approach to vehicle longevity: repair and maintenance. Which in human terms means the continuous restoration of human tissues, irrespective of the various processes that age them.

These two approaches differ starkly. The former could be thought of as like meddling with the inner mechanisms of a clock, cogs and all, in order to slow it down. The latter could be imagined as forcing back the hands of a clock, setting back the progress, while inner clockwork, the process, remains unaffected. In human terms 'setting back the hands' means taking knowledge obtained by geroscience, fashioning it into a damage report and devising a repair strategy. And just as setting back a clock does not require the same extensive knowledge of horology as would be involved with meddling with the clockwork, nor does the restoration of aging tissue require an unfeasibly extensive knowledge of geroscience, only enough to enumerate the manifest differences between old and young tissue. So could we then aspire to repair these enumerated damages comprehensively enough and rapidly enough to appreciably postpone disease? In other words might there be an extent to which we can afford to allow aging to proceed as it normally does while simultaneously clearing up the damage it leaves behind, kicking the can disease down the road?

We are in effect describing the application of regenerative medicine to aging. Regenerative medicine is an area of biotechnology which aims to restore damaged tissues and organs. So why not tissues and organs damaged by the miscellaneous ravages of age?

An Impressive Performance in Clearing Cancer from Mice via Immunotherapy

Immunotherapy is a cut above chemotherapy and radiotherapy: at its best, it is significantly more effective and significantly less harmful to the patient. It has still required years, a great deal of funding, and many failures for those best approaches to arise. Nonetheless, the report here is a cheering example for the sizable fraction of us expected to suffer cancer at some point in the years ahead if the condition is not soon brought under medical control. This immunotherapy appears highly effective, and just importantly, adaptable to many types of cancer. This potential for broad application is the most important aspect of any potential new cancer therapy. There are hundreds of subtypes of cancer, and the research community cannot make acceptably rapid progress by dealing with them one at a time - too many years and too much funding has gone to that type of strategy in the past. The only viable way forward towards the control of cancer in our lifetime is the production of very general anti-cancer technologies, those that are effective and easily, quickly, and cheaply adapted to each type of cancer.

Injecting minute amounts of two immune-stimulating agents directly into solid tumors in mice can eliminate all traces of cancer in the animals, including distant, untreated metastases. The approach works for many different types of cancers, including those that arise spontaneously. The researchers believe the local application of very small amounts of the agents could serve as a rapid and relatively inexpensive cancer therapy that is unlikely to cause the adverse side effects often seen with bodywide immune stimulation.

Some immunotherapy approaches rely on stimulating the immune system throughout the body. Others target naturally occurring checkpoints that limit the anti-cancer activity of immune cells. Still others, like the CAR T-cell therapy recently approved to treat some types of leukemia and lymphomas, require a patient's immune cells to be removed from the body and genetically engineered to attack the tumor cells. Many of these approaches have been successful, but they each have downsides - from difficult-to-handle side effects to high-cost and lengthy preparation or treatment times. Cancers often exist in a strange kind of limbo with regard to the immune system. Immune cells like T cells recognize the abnormal proteins often present on cancer cells and infiltrate to attack the tumor. However, as the tumor grows, it often devises ways to suppress the activity of the T cells.

The new method works to reactivate the cancer-specific T cells by injecting microgram amounts of two agents directly into the tumor site. One, a short stretch of DNA called a CpG oligonucleotide, works with other nearby immune cells to amplify the expression of an activating receptor called OX40 on the surface of the T cells. The other, an antibody that binds to OX40, activates the T cells to lead the charge against the cancer cells. Because the two agents are injected directly into the tumor, only T cells that have infiltrated it are activated. In effect, these T cells are "prescreened" by the body to recognize only cancer-specific proteins. Some of these tumor-specific, activated T cells then leave the original tumor to find and destroy other identical tumors throughout the body.

The approach worked startlingly well in laboratory mice with transplanted mouse lymphoma tumors in two sites on their bodies. Injecting one tumor site with the two agents caused the regression not just of the treated tumor, but also of the second, untreated tumor. In this way, 87 of 90 mice were cured of the cancer. Although the cancer recurred in three of the mice, the tumors again regressed after a second treatment. The researchers saw similar results in mice bearing breast, colon and melanoma tumors. "This is a very targeted approach. Only the tumor that shares the protein targets displayed by the treated site is affected. We're attacking specific targets without having to identify exactly what proteins the T cells are recognizing."


Where Next for Cellular Reprogramming and Regenerative Medicine?

Over the past decade researchers have gained ever more expertise in reprogramming cells from one type to another. The most useful form of reprogramming devised so far is the change from normal differentiated somatic cell, fixed in its role, to pluripotent stem cell, capable of generating any type of cell given the right instructions. Surprising recent developments in this line of research include (a) evidence that performing this transformation in a living animal is beneficial rather than cancerous, producing effects similar to those resulting from a stem cell transplant, and (b) that reprogramming cells to pluripotency erases some of the markers of age in cells from old tissues.

This repair is thought to be much the same process as takes place in early embryonic development: the mechanism by which old parents can produce young children, or perhaps conceptually similar to the constant, aggressive repair and regeneration that takes place in the immortal hydra. What can be done with this knowledge? Can portions of these mechanisms be split off from the whole, understood, tamed, and selectively applied? Will that replace the current paradigm for regenerative medicine in the near future? Some people are thinking along these lines, as illustrated by this interview with a researcher in the field.

What impact will your work have on aging research?

I'm studying whether we can separate the process of functional reprogramming of cells from the process of aging reprogramming of cells. Typically these two processes happen at the same time. My hypothesis is that we can induce cellular rejuvenation without changing the function of the cells. If we can manage to do this, we could start thinking about a way to stall aging.

What is the difference between functional and aging reprogramming?

The function of a skin cell is to express certain proteins, keratins for example that protect the skin. The function of a liver cell is to metabolize. Those are cell-specific functions. Reprogramming that function means that you no longer have a liver cell. You now have another cell, which has a totally different function. Age, on the other hand, is just the degree of usefulness of that cell, and it's mostly an epigenetic process. A young keratinocyte cell is younger than an older keratinocyte but it is still a keratinocyte. The amazing thing is that if you take an aged cell that is fully committed to a certain function, and you transplant its nucleus into an immature egg cell called an oocyte, then you revert its function to a pluripotent, embryonic one, which means it can become any other cell of the body-and you also revert the age of that cell to the youngest age possible. It's mind-blowing to me.

How close are we to using pluripotency induction in therapies?

The production of induced pluripotent stem (iPS) cells in mice was described in 2006, and in humans in 2007, so it's been already 10 or 11 years. The first clinical trials using iPS cells are just about to get to early phase I and phase II. There has been a lot of hope and promise but it's been a little slow. The reason being that when it comes to clinical applications, you have to consider a number of complications. You need to know how to make the cells very efficiently, and then they need to be safe. There will be more clinical trials coming up based off iPSs. For example, I am collaborating with an iPS-based platform for the cure of a skin disease called epidermolysis bullosa. We're trying to move this to the pre-clinical stage over the next few years, and then if we pass that, we will potentially start moving into a phase I clinical trial. Things are moving forward pretty fast now.

Are germ cells immune to aging?

Yes and no. They definitely do age, but not to the same extent as other cell types. In males, spermatogenesis continues all the way from puberty to old life. If you take a 90-year-old man, there are still germ cells and spermatogonial stem cells. They do age, because it's clear that the sperm of an older man is different from the sperm of a younger man, but they do not age as heavily as other cells. This is fascinating because we do not understand the process. Female cells do age, and the consensus is that there are no germ stem cells in the ovary so these cells lack a molecular program to stay young. But once you put together an egg and a sperm, then there is an aging erasure mechanism, which is embryonic-specific, that we also do not understand.

Why are you interested in separating aging reprogramming from functional reprogramming?

The experiments of somatic cell nuclear transfer and iPS cell derivation clearly indicate that both functional and aging reprogramming can be achieved. However, these technologies are very inefficient and cannot be used as whole-body anti-aging measures because the process of reprogramming to an embryonic stage can lead to tumorigenic cells. Instead, if we could separate the two types of reprogramming and achieve only reprogramming of age without touching the function of a cell, then in principle we could apply reprogramming in vivo to every single cell in the body and rejuvenate them. This could be a paradigm shift in the way we approach aging.


Aubrey de Grey on Progress and Timescales in Rejuvenation Research

Aubrey de Grey of the SENS Research Foundation maintains an active schedule of presentations, and the interview here is one of a series of recent discussions in which he talks about timelines, funding, and progress in recent years. We're in the midst of a tipping point of sorts, as the SENS view of rejuvenation research gathers more attention and legitimacy in the eyes of the public and various sources of funding. Senolytic therapies to clear senescent cells are well into the first stages of clinical development, with new compelling data for cellular senescence to contribute to specific age-related diseases arriving every month now. Targeting senescent cells for destruction was one of the strategies that de Grey started to advocate all the way back in 2002, when the research community was much less welcoming of any discussion of the treatment of aging as a medical condition, and there was little to no funding for such approaches despite the extensive supporting evidence. It doesn't hurt to be proven right when it comes to reinforcing an agenda.

What is the future timeline for the advent of rejuvenation therapies sufficiently effective to grant a few decades of additional healthy life, and substantially rescue aged people from the immediate consequences of high levels of cell and tissue damage? In one sense we can put together a decently robust timeline for SENS research and development and estimate ten years to get to robust mouse rejuvenation in the laboratory, followed by a further ten years to push the first implementations into the clinic. We can feel fairly good about that, and indeed that planning has been carried out at the Methuselah Foundation and later the SENS Research Foundation several times over the past fifteen years. But that best possible pace of progress is entirely dependent on sufficient funding, $100 million or more each year, as well as the rapid cooperation of regulatory bodies. Both of these are sticky, complicated persuasion and human interaction problems. Thus no-one can predict how long it will take to (a) bootstrap SENS rejuvenation research to the necessary funding levels and (b) solve or work around the roadblock to the treatment of aging set up by the FDA and other regulatory bodies sufficiently well to allow rapid clinical implementation of therapies.

We should be optimistic, however, given that this does boil down to persuasion and funding as the limiting factors. That the science is a relatively clear road, and that the delay is all a matter of gathering sufficient support, means that everyone and anyone can help to accelerate progress towards the medical control of aging, and an end to age-related disease. It doesn't require years of schooling to support a field of medical research as a patient advocate or a fundraiser or an entrepreneur. When interested scientists with promising plans are limited entirely by a lack of funding, we can all step up to make a difference. That has happened already: it is possible to look back at the fifteen year history of SENS advocacy and research, and track its progress from an idea with zero funding to the existence of several non-profit foundations devoting millions of dollars in philathropic funding every year to the challenge. Our community achieved a great deal over the course of the early, challenging years, and that success can and will continue, with it becoming ever easier to raise ever more funding for research and development.

Anti-Aging Pioneer Aubrey de Grey: "People in Middle Age Now Have a Fair Chance"

Your foundation is working on an initiative requiring $50 million in funding-

Well, if we had $50 million per year in funding, we could go about three times faster than we are on $5 million per year.

And you're looking at a 2021 timeframe to start human trials?

That's approximate. Remember, because we accumulate in the body so many different types of damage, that means we have many different types of therapy to repair that damage. And of course, each of those types has to be developed independently. It's very much a divide and conquer therapy. The therapies interact with each other to some extent; the repair of one type of damage may slow down the creation of another type of damage, but still that's how it's going to be. And some of these therapies are much easier to implement than others. The easier components of what we need to do are already in clinical trials - stem cell therapies especially, and immunotherapy against amyloid in the brain, for example. Even in phase III clinical trials in some cases. So when I talk about a timeframe like 2021, or early 20s shall we say, I'm really talking about the most difficult components.

What recent strides are you most excited about?

Looking back over the past couple of years, I'm particularly proud of the successes we've had in the very most difficult areas. If you go through the seven components of SENS, there are two that have absolutely been stuck in a rut and have gotten nowhere for 15 to 20 years, and we basically fixed that in both cases. We published two years ago in Science magazine that essentially showed a way forward against the stiffening of the extracellular matrix, which is responsible for things like wrinkles and hypertension. And then a year ago, we published a real breakthrough paper with regard to placing copies of the mitochondria DNA in the nuclear DNA modified in such a way that they still work, which is an idea that had been around for 30 years; everyone had given up on it, some a long time ago, and we basically revived it.

What do you think are the biggest barriers to defeating aging today: the technological challenges, the regulatory framework, the cost, or the cultural attitude of the "pro-aging" trance?

One can't really address those independently of each other. The technological side is one thing; it's hard, but we know where we're going, we've got a plan. The other ones are very intertwined with each other. A lot of people are inclined to say, the regulatory hurdle will be completely insurmountable, plus people don't recognize aging as a disease, so it's going to be a complete nonstarter. I think that's nonsense. And the reason is because the cultural attitudes toward all of this are going to be completely turned upside down before we have to worry about the regulatory hurdles. In other words, they're going to be turned upside down by sufficiently promising results in the lab, in mice. Once we get to be able to rejuvenate actually old mice really well so they live substantially longer than they otherwise would have done, in a healthy state, everyone's going to know about it and everyone's going to demand - it's not going to be possible to get re-elected unless you have a manifesto commitment to turn the FDA completely upside down and make sure this happens without any kind of regulatory obstacle.

I've been struggling away all these years trying to bring little bits of money in the door, and the reason I have is because of the skepticism as to regards whether this could actually work, combined with the pro-aging trance, which is a product of the skepticism - people not wanting to get their hopes up, so finding excuses about aging being a blessing in disguise, so they don't have to think about it. All of that will literally disintegrate pretty much overnight when we have the right kind of sufficiently impressive progress in the lab. Therefore, the availability of money will also open up. It's already cracking: we're already seeing the beginnings of the actual rejuvenation biotechnology industry that I've been talking about with a twinkle in my eye for some years.

I'm sure you hate getting the timeline question, but if we're five years away from this breakthrough in mice, it's hard to resist asking - how far is that in terms of a human cure?

When I give any kind of timeframes, the only real care I have to take is to emphasize the variance. In this case I think we have got a 50-50 chance of getting to that tipping point in mice within five years from now, certainly it could be 10 or 15 years if we get unlucky. Similarly, for humans, a 50-50 chance would be twenty years at this point, and there's a 10 percent chance that we won't get there for a hundred years.

You famously said ten years ago that you think the first person to live to 1000 is already alive. Do you think that's still the case?

Definitely, yeah. I can't see how it could not be. Again, it's a probabilistic thing. I said there's at least a 10 percent chance that we won't get to what I call Longevity Escape Velocity for 100 years and if that's true, then the statement about 1000 years being alive already is not going to be the case. But for sure, I believe that the beneficiaries of what we may as well call SENS 1.0, the point where we get to Longevity Escape Velocity, those people are exceptionally unlikely ever to suffer from any kind of ill health correlated with their age. Because we will never fall below Longevity Escape Velocity once we attain it.

Could someone who was just born today expect-

I would say people in middle age now have a fair chance. Remember - a 50/50 chance of getting to Longevity Escape Velocity within 20 years, and when you get there, you don't just stay at biologically 70 or 80, you are rejuvenated back to biologically 30 or 40 and you stay there, so your risk of death each year is not related to how long ago you were born, it's the same as a young adult. Today, that's less than 1 in 1000 per year, and that number is going to go down as we get self-driving cars and all that, so actually 1000 is a very conservative number.

Towards Therapies Based on Klotho

Klotho is one of the few definitively longevity-associated genes. The protein it produces is associated with a range of important processes, though its roles are far from fully understood. Evidence exists for increased klotho to improve stem cell function, enhance cognitive function and increase synaptic plasticity in older animals, though whether or not this extends to humans is a question yet to be resolved. We might take the studies showing correlations between klotho and cognition in aged human patients as a positive sign, however. As this article notes, research groups are presently working on therapies based on delivery or otherwise enhanced levels of klotho. Given the usual relationship between degree of life extension observed in mice (large) versus humans (small) for therapies of this nature, this is probably better thought of as a potential treatment for age-related neurodegeneration, or a modest enhancement for brain function at all ages, rather than a way to extend life significantly.

Neuroscientists are taking an innovative approach to battling neurodegenerative diseases like Alzheimer's disease and dementia. Rather than trying to understand the specific mechanisms that cause each disease, they took a step back and asked, "What do all these conditions have in common?" The answer: old age. Over time, something happens to our cells and organs, and in the past three decades scientists have begun to unravel exactly what that something is - and the cellular mechanisms our bodies use to fight it.

"Aging is the biggest risk factor for cognitive problems, and cognitive problems are one of the biggest biomedical challenges that we face. Why don't we just block aging?" Blocking aging is easier said than done, but researchers jumped head first into the problem by studying a protein called klotho. The researchers who named the protein found that the amount of klotho produced by mice could affect how long the rodents lived. Other researchers later discovered that humans who naturally have more klotho tend to live longer. Living longer is one thing, but the researchers wanted to know if klotho could help our brains stay healthier and more resilient to cognitive problems. Could klotho levels predict how quickly subjects solved a variety of puzzles that test cognition? In both humans and mice, they found the same result: more klotho meant better cognitive function. To bring this boost in brain health to everyone, and not just the 20 percent of people who happen to have naturally high klotho, researchers are testing the protein's potential as a therapeutic.

The protein can exist in two forms: the first is anchored to the cell membranes of your organs, mostly your brain and kidneys; and the second occurs when the protein is cut loose from its anchor and freed to float around the bloodstream. Researchers found that by simply injecting this floating form into mice, they could re-create the cognitive boost found by genetically increasing klotho. "We found that those mice that had been treated, within four hours had better brain function. This worked in young mice, old mice, and mice that had a condition similar to Alzheimer's. Next, researchers will try to understand how klotho acts on the brain without crossing the blood-brain barrier. And ultimately, could klotho become a therapy for humans to improve brain health and protect against aging and disease? "For humans, the end game really is: how can we increase our healthspan? And that may go hand in hand with an increase in life span, because the things that help us to live longer are also the things that help us to live better."


Rapamycin Does Not Interact Favorably with Growth Hormone Receptor Knockout

The scientific community is, on the whole, very focused on exploring the effects and understanding the mechanisms of single interventions. Studies that investigate potential synergies between two or more interventions are comparatively rare. This need not be the case; it seems to be a cultural thing, a product of many various influences on funding, planning, and development. There are numerous well-established methods of slowing aging in mice, and it would be interesting to learn how they interact, whether they stack or not, even though these are largely not useful roads to greatly enhanced human longevity. Accordingly, here is one of the rare studies to examine the combined effect on life span of two interventions at once. In this case it is found that they work against one another, which at least has the potential to extend our understanding of the biochemistry of both.

Mechanistic target of rapamycin (mTOR) plays central roles in growth, metabolism, and aging. It acts via two distinct complexes: mTORC1 and mTORC2, defined by Raptor and Rictor, respectively. Rapamycin, an inhibitor of mTOR, inhibits mTORC1, and longer rapamycin treatment also inhibits mTORC2. Rapamycin was the first drug shown to extend longevity in a mammal. The effects of rapamycin on longevity were accounted for by mTORC1 inhibition, whereas information on mTORC2 is generally lacking. However, it seems that many of the negative adverse effects of rapamycin treatment are mediated by inhibition of mTORC2.

Rictor has positive effects on a variety of functions involved in whole-body homeostasis. Although at this time, the role of mTORC2 in the regulation of longevity is uncertain, several lines of evidence imply that mTORC2 may have opposite effects on aging compared with mTORC1. For instance, Rictor loss-of-function mutants in Caenorhabditis elegans had decreased life spans by 24-43% on a standard diet. Interestingly, transcriptional down-regulation of mTORC1 and transcriptional up-regulation of mTORC2 was reported to be associated with human longevity. It is vital to understand how mTORC2 regulates aging in a mammal.

mTORC2 is regulated by growth hormone (GH)-dependent growth factors. GH is essential for growth and metabolism and is involved in the control of aging. It binds and signals through GH receptor (GHR). Therefore, deletion of GHR eliminates GH signaling and its biological functions. GHR-KO (GHR knockout) mice have been a valuable tool to study GH functions, including its relationship to longevity. GHR-KO mice are dwarf, extremely insulin sensitive, and have their life span extended up to 40%. Importantly, compared with their normal littermates, GHR-KO and several other long-lived mice have decreased mTORC1 and increased mTORC2 signaling, which may play a role in their extended longevity. Therefore, we decided to examine how prolonged rapamycin treatment alters mTORC1 and mTORC2 signaling in GHR-KO mice.

In long-lived GHR-KO mice, prolonged rapamycin treatment did not further extend, but unexpectedly shortened, life span. One possible reason could be that prolonged rapamycin treatment further decreases the already low levels of mTORC1 signaling in these animals, which could adversely affect the benefits of mTORC1 inhibition. However, mTORC1 signaling was not further reduced in three key metabolic tissues of GHR-KO mice with prolonged rapamycin treatment compared with control GHR-KO mice. We cannot explain why prolonged rapamycin treatment did not further decrease mTORC1 signaling in these animals, and also cannot rule out the possibility that mTORC1 signaling may have been further reduced in other tissues.

In contrast, a significant reduction of mTORC2 signaling was evident in each of the examined tissues of GHR-KO mice treated with rapamycin. Decreased mTORC2 signaling and impaired whole-body homeostasis (which could result from reduced mTORC2 signaling) in rapamycin-treated GHR-KO mice might have contributed to the effect of prolonged rapamycin treatment on the life span of GHR-KO mice. Thus, our data indicated that mTORC2 may play a beneficial role in longevity via improving or maintaining whole-body homeostasis. Based on our data and data from previous studies, we propose the following concept: if whole-body homeostasis is impaired (which was associated with the significant reduction of mTORC2 in our study), life span could be shortened, and if mTORC2 signaling is unaltered or enhanced, inhibition of mTORC1 will lead to extension of life span. The effects of altered mTOR signaling on longevity would thus reflect a balance between inhibition of mTORC1 and enhancement, or maintenance, of mTORC2.