New evidence that adult stem cells are critical to human aging has recently been published on a study done on a super-centenarian woman that lived to be 115 years. At death, her circulating stem cell pool had declined to just two active stem cells from stem cell counts that are typically more than a thousand in younger adults. Super-centenarians have survived all the normal diseases that kill 99.9% of us before 100 years of age, so it has been a mystery as to what actually kills these hardy individuals. This recent data suggest that stem cell decline may be the main contributor to aging. If so, stabilizing stem cells may be the best thing one can do to slow your rate of aging.
There are many theories of aging that have been proposed. For example, damage to cells and tissues from oxidative stress has been one of the most popular fundamental theories of aging for more than half a century. Yet antioxidant substances or genes that code antioxidant enzymes have proven largely ineffective in slowing aging when tested in model animals. Thus, interest by scientists has shifted to other hypotheses that might provide a better explanation for the slow declines in function with age.
Stem cells provide one such promising mechanism of aging. Of course, we all know that babies are young and vigorous, independent of the age of their parents. This is because adults have embryonic stem cells that can generate young new cells needed to form a complete young baby. Indeed, these embryonic stem cells are the product of continuously evolving stem cell populations that go back to the beginning of life on earth over 3.5 billion years ago!
In adults, the mostly immortal embryonic stem cells give rise to mortal adult stem cells in all the tissues of the body. These adult stem cells can regenerate your cells and tissues as they wear out and need replacement. Unfortunate, adult stem cells also age, which leads to fewer cells and/or loss of function in cell replacement. As functional stem cells decline, skin and organs decline with age.
The somatic mutation burden in healthy white blood cells (WBCs) is not well known. Based on deep whole-genome sequencing, we estimate that approximately 450 somatic mutations accumulated in the nonrepetitive genome within the healthy blood compartment of a 115-yr-old woman. The detected mutations appear to have been harmless passenger mutations: They were enriched in noncoding, AT-rich regions that are not evolutionarily conserved, and they were depleted for genomic elements where mutations might have favorable or adverse effects on cellular fitness, such as regions with actively transcribed genes. The distribution of variant allele frequencies of these mutations suggests that the majority of the peripheral white blood cells were offspring of two related hematopoietic stem cell (HSC) clones. Moreover, telomere lengths of the WBCs were significantly shorter than telomere lengths from other tissues. Together, this suggests that the finite lifespan of HSCs, rather than somatic mutation effects, may lead to hematopoietic clonal evolution at extreme ages.
Dr Bryant Villeponteau the formulator of Stem Cell 100 and other Life Code nutraceuticals was recently interviewed by Dr Mercola who owns the largest health web site on the internet. Dr. Villeponteau is also the author of Decoding Longevity an new book which will be released during December. He is a leading researcher in novel anti-aging therapies involving stem cells an area in which he has been a pioneer for over three decades.
Stem cell technology could have a dramatic influence on our ability to live longer and replace some of our failing parts, which is the inevitable result of the aging process. With an interest in aging and longevity, Dr. Villeponteau started out by studying developmental biology. “If we could understand development, we could understand aging,” he says. Later, his interest turned more toward the gene regulation aspects. While working as a professor at the University of Michigan at the Institute of Gerontology, he received, and accepted, a job offer from Geron Corporation—a Bay Area startup, in the early ‘90s.
“They were working on telomerase, which I was pretty excited about at the time. I joined them when they first started,” he says. “We had an all-out engagement there to clone human telomerase. It had been cloned in other animals but not in humans or mammals.”
If you were to unravel the tip of the chromosome, a telomere is about 15,000 bases long at the moment of conception in the womb. Immediately after conception, your cells begin to divide, and your telomeres begin to shorten each time the cell divides. Once your telomeres have been reduced to about 5,000 bases, you essentially die of old age.
“What you have to know about telomerase is that it’s only on in embryonic cells. In adult cells, it’s totally, for the most part, turned off, with the exception of adult stem cells,” Dr. Villeponteau explains. “Adult stem cells have some telomerase – not full and not like the embryonic stem cells, but they do have some telomerase activity.”
Most of the research currently being done, both in academia and industrial labs, revolves around either embryonic stem cells, or a second type called induced pluripotent stem cells (iPS). Dr. Villeponteau, on the other hand, believes adult stem cells are the easiest and most efficient way to achieve results.
That said, adult stem cells do have their drawbacks. While they’re your own cells, which eliminates the problem of immune-related issues, there’s just not enough of them. Especially as you get older, there are fewer and fewer adult stem cells, and they tend to become increasingly dysfunctional too. Yet another hurdle is that they don’t form the tissues that they need to form…
To solve such issues, Dr. Villeponteau has created a company with the technology and expertise to amplify your adult stem cells a million-fold or more, while still maintaining their ability to differentiate all the different cell types, and without causing the cells to age. Again, it is the adult stem cell’s ability to potentially cure, or at least ameliorate, many of our age-related diseases by regenerating tissue that makes this field so exciting.
Dr Villeponteau believes you can add many years, likely decades, to your life simply by eating right, exercising (which promotes the production of muscle stem cells, by the way) and living an otherwise clean and healthy lifestyle. Extreme life extension, on the other hand, is a different matter.
His book, Decoding Longevity, covers preventive strategies to prolong your life, mainly diet, exercise, and supplements. A portion of the book also covers future developments in the area of more radical life extension, such as stem cell technology.
Now researchers have found a way not just to stop, but, reverse the aging process. The key is something called a telomere. We all have them. They are the tips or caps of your chromosomes. They are long and stable in young adults, but, as we age they become shorter, damaged and frayed. When they stop working we start aging and experience things like hearing and memory loss.
In a recent study published in the peer reviewed journal Nature scientists took mice that were prematurely aged to the equivalent of 80-year-old humans, added an enzyme and essentially turned their telomeres back on. After the treatment they were the physiological equivalent of young adults. You can see the before and after pictures in the videos above. Brain function improved, their fertility was restored it was a remarkable reversal of the aging process. In the top video the untreated mouse shows bad skin, gray hair and it is balding. The mouse with it’s telomeres switched back on has a dark coat color, the hair is restored and the coat has a nice healthy sheen to it. Even more dramatic is the change in brain size. Before treatment the aged mice had 75% of a normal size brain like a patient with severe Alzheimers. After the telomeres were reactivated the brain returned to normal size. As for humans while it is just one factor scientists say the longer the telomeres the better the chances for a more graceful aging.
The formal study Telomere dysfunction induces metabolic and mitochondrial compromise was published in Nature.
Additional information published by Harvard can be found in the following articles.
While scientists are not yet able to accomplish the same results in humans we believe we have developed a nutraceutical to help prolong youth and possibly extend life until age reversal therapy for humans becomes available.
We do not have to lose our independence and ability to live life in our 70′s or 80′s. Even at the age of 100 years old Fauja Singh completed a marathon.
The race ended just after Fauja Singh crossed the line in 3,851st place. By finishing then he would do what no man before him had ever done. Amid the bundled and cheering crowd in Toronto, underneath a distended but gracious sky, he would complete a marathon. And he would do so at 100 years old.
Was it pain he felt as he approached the end, just footsteps away from redefining the limits of human endurance? No, this wasn’t pain. Fauja knew pain. This wasn’t pain but exhaustion. And Fauja could handle exhaustion, because exhaustion foreshadowed euphoria. When Fauja got tired, it often meant a record would soon fall.
He’d already broken a few. Fastest to run a marathon (male, over age 90), fastest to run 5,000 meters (male, over age 100), fastest to run 3,000 meters (male, over age 100), and on and on they went. But those records didn’t roll off the tongue the way this one would. Oldest person to complete a marathon (male): Fauja Singh.
So Fauja ran in Toronto, arms swinging, yellow turban bobbing, chest-length Zeusian beard swaying in the wind. He was joined by other runners with roots in the Indian region of Punjab, their appearance in keeping with the traditions of their Sikh faith. Fauja trotted for the first three miles, until his coach encouraged him to slow to a jog. Speed was fleeting, the enemy of endurance. By mile 6, he’d downshifted to a toddle. After a break for a rubdown and some tea at mile 18, he settled into a walk.
The exhaustion took hold sometime around mile 20, but Fauja stayed upbeat about the remaining distance. Finally Fauja saw the only mile-marker that mattered: the finish line. What had been silence between footsteps was now music and cheers. The slog to the finish reminded Fauja of his wedding day, of the joy that awaited at the end of the long aisle. He waved to the crowd as he walked across the line, then lifted his arms and accepted a medal. He’d finished in 8 hours, 25 minutes. There were smiles and handshakes and photos with friends and strangers, then a rambling news conference for Fauja to reflect on his record.
Researchers at the University of California, Berkeley, have discovered that the hormone oxytocin plays a critical role in healthy muscle maintenance and repair. After a nine-day treatment of old mice, scientists found that the muscles of the group that had received oxytocin injections healed far better than those of a control group without oxytocin.
“The action of oxytocin was fast,” said Elabd a University of California Researcher. “The repair of muscle in the old mice was at about 80 percent of what we saw in the young mice.”
A few other biochemical factors in blood have been connected to aging and disease in recent years, but oxytocin is the first anti-aging molecule identified that is approved by the Food and Drug Administration for clinical use in humans.
Oxytocin is a hormone associated with maternal nurturing, social attachments, childbirth and sex and is indispensable for healthy muscle maintenance and repair, and that in mice, it declines with age.
The new study published in the journal Nature Communications, presents oxytocin as the latest treatment target for age-related muscle wasting, or sarcopenia.
A few other biochemical factors in blood have been connected to aging and disease in recent years, but oxytocin is the first anti-aging molecule identified that is approved by the Food and Drug Administration for clinical use in humans, the researchers said. Pitocin, a synthetic form of oxytocin, is already used to help with labor and to control bleeding after childbirth. Clinical trials of an oxytocin nasal spray are also underway to alleviate symptoms associated with mental disorders such as autism, schizophrenia and dementia.
Oxytocin is sometimes referred to as the “trust hormone” because of its association with romance and friendship. It is released with a warm hug, a grasped hand or a loving gaze, and it increases libido. The hormone kicks into high gear during and after childbirth, helping new mothers bond with and breastfeed their new babies.
“This is the hormone that makes your heart melt when you see kittens, puppies and human babies,” said Conboy, who is also a member of the Berkeley Stem Cell Center and of the California Institute for Quantitative Biosciences (QB3). “There is an ongoing joke among my research team that we’re all happy, friendly and trusting because oxytocin permeates the lab.”
The researchers pointed out that while oxytocin is found in both young boys and girls, it is not yet known when levels of the hormone start to decline in humans, and what levels are necessary for maintaining healthy tissues.
Christian Elabd and Wendy Cousin, both senior scientists in Conboy’s lab, were co-lead authors on this study.
Previous research by Elabd found that administering oxytocin helped prevent the development of osteoporosis in mice that had their ovaries removed to mimic menopause.
The new study determined that in mice, blood levels of oxytocin declined with age. They also showed that there are fewer receptors for oxytocin in muscle stem cells in old versus young mice.
To tease out oxytocin’s role in muscle repair, the researchers injected the hormone under the skin of old mice for four days, and then for five days more after the muscles were injured. After the nine-day treatment, they found that the muscles of the mice that had received oxytocin injections healed far better than those of a control group of mice without oxytocin.
“The action of oxytocin was fast,” said Elabd. “The repair of muscle in the old mice was at about 80 percent of what we saw in the young mice.”
Interestingly, giving young mice an extra boost of oxytocin did not seem to cause a significant change in muscle regeneration.
“This is good because it demonstrates that extra oxytocin boosts aged tissue stem cells without making muscle stem cells divide uncontrollably,” Cousin added.
The researchers also found that blocking the effects of oxytocin in young mice rapidly compromised their ability to repair muscle, which resembled old tissue after an injury.
The researchers also studied mice whose gene for oxytocin was disabled, and compared them with a group of control mice. At a young age, there was no significant difference between the two groups in muscle mass or repair efficiency after an injury. It wasn’t until the mice with the disabled oxytocin gene reached adulthood that signs of premature aging began to appear.
“When disabling other types of genes associated with tissue repair, defects appear right away either during embryonic development, or early in life,” said Conboy. “To our knowledge, the oxytocin gene is the only one whose impact is seen later in life, suggesting that its role is closely linked to the aging process.”
Cousin noted that oxytocin could become a viable alternative to hormone replacement therapy as a way to combat the symptoms of both female and male aging, and for long-term health. Hormone therapy did not show improvements in agility or muscle regeneration ability, and it is no longer recommended for disease prevention because research has found that the therapy’s benefits did not outweigh its health risks.
In addition to healthy muscle, oxytocin is predicted to improve bone health, and it might be important in combating obesity.
Conboy said her lab plans to examine oxytocin’s role in extending a healthy life in animals, and in conserving its beneficial anti-aging effects in humans.
She noted that there is a growing circle of scientists who believe that aging is the underlying cause of a number of chronic diseases.
“If you target processes associated with aging, you may be tackling those diseases at the same time,” said Conboy. “Aging is a natural process, but I believe that we can meaningfully intervene with age-imposed organ degeneration, thereby slowing down the rate at which we become progressively unhealthy.”
The reduced ability to respond to stress is a major characteristic of aging. Indeed, aging itself is a stressful condition. Therefore, reducing chronic causes of stress can promote longevity. Some of the best protein protectors against stress and aging are the Heat Shock Proteins (HSPs). The protective HSPs are induced whenever your body is exposed to stressing agents such as:
1. Alcohol, which is one of the likely reasons that one drink per day helps prolong life
2. Elevated body temperature
3. Environmental toxins such as heavy metals or toxic chemicals
4. Oxidative stress, which may explain part of the reason that limited exercise is beneficial
Besides their effects on stress response, HSPs also have a protective role in disease and aging. For example, much research has shown that HSPs help with cardiovascular, metabolic, and neurological disorders.
At the recent AGE research conference (May 31 to June 2, 2014), new data on HSPs was presented by Kalie Kavanagh at Wake Forest University in North Carolina. Long lived Centenarians have better heat shock response and some may have gene variants of HSPs that are protective. HSP levels typically decline with age. Experiments in monkeys to raise their HSPs preserved insulin sensitivity, lowered blood pressure, and increased endurance.
The most interesting information to come out of the HSP talk was the potential to increase your own HSP levels. The HSPs can be stimulated by raising your body temperature slightly for 10 to 30 minutes using available methods: soaking in a hot tub at 104 degrees or sitting in a steam sauna bath, or participating in any exercise in which you build up a sweat for 5 minutes or more. These activities all lead to higher HSP levels, which can remain elevated and protective for 24 hours or more.
Have you ever wondered why aging occurs and how one might slow its progression? Aging expert Dr. Villeponteau describes dietary, exercise, and supplement routines that can add decades to your healthspan. Decoding Longevity condenses a wealth of practical information for those interesting in extending their health and longevity. Decoding Longevity also discusses the exponential increases in technology that will likely lead to greatly expanded longevity while maintaining health and indpendence in the next 20 to 40 years.
Decoding Longevity offers a full spectrum biological and genetic analysis of the aging process in layman’s language. Starting with an analysis of why life expectancy increased 57% in the 20th Century, it then focuses on recommended lifestyle choices that can significantly extend your healthspan and youthful fitness. The third part looks in some detail at the last 20 years of aging research, while the final section explores future developments that will provide powerful tools for extending healthspan and longevity in the next 20 to 40 years.
The Author: Dr. Bryant Villeponteau has 25 years of scientific leadership in aging research and some 60 scientific journal and patent publications. He has a Ph.D. in Biology from UCLA and was Assistant Professor of Biological Chemistry at the University of Michigan Medical School in the Institute of Gerontology. Dr. Villeponteau later led the research group at Geron Corporation, where he was the lead inventor in cloning human telomerase, thereby winning the Distinguished Inventor Award for the 2nd best US patent of 1997. Since 2008, Dr. Villeponteau has used genetics and machine learning technologies to develop antiaging supplements and drugs. He also cofounded Centagen, a Colorado stem cell company.
That chicken wing you’re eating could be as deadly as a cigarette. In a new study that tracked a large sample of adults for nearly two decades, researchers have found that eating a diet rich in animal proteins during middle age makes you four times more likely to die of cancer than someone with a low-protein diet — a mortality risk factor comparable to smoking.
“There’s a misconception that because we all eat, understanding nutrition is simple. But the question is not whether a certain diet allows you to do well for three days, but can it help you survive to be 100?” said corresponding author Valter Longo, the Edna M. Jones Professor of Biogerontology at the USC Davis School of Gerontology and director of the USC Longevity Institute.
Not only is excessive protein consumption linked to a dramatic rise in cancer mortality, but middle-aged people who eat lots of proteins from animal sources — including meat, milk and cheese — are also more susceptible to early death in general, reveals the study to be published March 4 in Cell Metabolism. Protein-lovers were 74 percent more likely to die of any cause within the study period than their more low-protein counterparts. They were also several times more likely to die of diabetes.
But how much protein we should eat has long been a controversial topic — muddled by the popularity of protein-heavy diets such as Paleo and Atkins. Before this study, researchers had never shown a definitive correlation between high protein consumption and mortality risk.
Rather than look at adulthood as one monolithic phase of life, as other researchers have done, the latest study considers how biology changes as we age, and how decisions in middle life may play out across the human lifespan.
In other words, what’s good for you at one age may be damaging at another. Protein controls the growth hormone IGF-I, which helps our bodies grow but has been linked to cancer susceptibility. Levels of IGF-I drop off dramatically after age 65, leading to potential frailty and muscle loss. The study shows that while high protein intake during middle age is very harmful, it is protective for older adults: those over 65 who ate a moderate- or high-protein diet were less susceptible to disease.
• High protein intake especially if from animal sources is linked to increased cancer, diabetes, and overall mortality
• Higher protein consumption may be protective for older adults
• Plant-derived proteins are associated with lower mortality than animal-derived proteins
• High IGF-1 levels increased the relationship between mortality and high protein
The latest paper draws from Longo’s past research on IGF-I, including on an Ecuadorian cohort that seemed to have little cancer or diabetes susceptibility because of a genetic mutation that lowered levels of IGF-I; the members of the cohort were all less than five-feet tall.
“The research shows that a low-protein diet in middle age is useful for preventing cancer and overall mortality, through a process that involves regulating IGF-I and possibly insulin levels,” said co-author Eileen Crimmins, the AARP Chair in Gerontology at USC. “However, we also propose that at older ages, it may be important to avoid a low-protein diet to allow the maintenance of healthy weight and protection from frailty.”
Crucially, the researchers found that plant-based proteins, such as those from beans, did not seem to have the same mortality effects as animal proteins. Rates of cancer and death also did not seem to be affected by controlling for carbohydrate or fat consumption, suggesting that animal protein is the main culprit.
“The majority of Americans are eating about twice as much proteins as they should, and it seems that the best change would be to lower the daily intake of all proteins but especially animal-derived proteins,” Longo said. “But don’t get extreme in cutting out protein; you can go from protected to malnourished very quickly.”
Longo’s findings support recommendations from several leading health agencies to consume about 0.8 grams of protein per kilogram of body weight every day in middle age. For example, a 130-pound person should eat about 45-50 grams of protein a day, with preference for those derived from plants such as legumes, Longo explains.
The researchers define a “high-protein” diet as deriving at least 20 percent of calories from protein, including both plant-based and animal-based protein. A “moderate” protein diet includes 10-19 percent of calories from protein, and a “low-protein” diet includes less than 10 percent protein.
Even moderate amounts of protein had detrimental effects during middle age, the researchers found. Across all 6,318 adults over the age of 50 in the study, average protein intake was about 16 percent of total daily calories with about two-thirds from animal protein — corresponding to data about national protein consumption. The study sample was representative across ethnicity, education and health background.
People who ate a moderate amount of protein were still three times more likely to die of cancer than those who ate a low-protein diet in middle age, the study shows. Overall, even the small change of decreasing protein intake from moderate levels to low levels reduced likelihood of early death by 21 percent.
For a randomly selected smaller portion of the sample – 2,253 people – levels of the growth hormone IGF-I were recorded directly. The results show that for every 10 ng/ml increase in IGF-I, those on a high-protein diet were 9 percent more likely to die from cancer than those on a low-protein diet, in line with past research associating IGF-I levels to cancer risk.
The researchers also extended their findings about high-protein diets and mortality risk, looking at causality in mice and cellular models. In a study of tumor rates and progression among mice, the researchers show lower cancer incidence and 45 percent smaller average tumor size among mice on a low-protein diet than those on a high-protein diet by the end of the two-month experiment.
“Almost everyone is going to have a cancer cell or pre-cancer cell in them at some point. The question is: Does it progress?” Longo said. “Turns out one of the major factors in determining if it does is is protein intake.” The study suggests that low protein intake during middle age followed by moderate to high protein consumption in old adults may optimize healthspan and longevity.
The power of regenerative medicine appears to have turned science fiction into scientific reality — by allowing scientists to transform skin cells into cells that closely resemble beating heart cells. However, the methods required are complex, and the transformation is often incomplete. But now, scientists at the Gladstone Institutes have devised a new method that allows for the more efficient — and, importantly, more complete — reprogramming of skin cells into cells that are virtually indistinguishable from heart muscle cells. These findings, based on animal models and described in the latest issue of Cell Reports, offer new-found optimism in the hunt for a way to regenerate muscle lost in a heart attack.
Heart disease is the world’s leading cause of death, but recent advances in science and medicine have improved the chances of surviving a heart attack. In the United States alone, nearly 1 million people have survived an attack, but are living with heart failure — a chronic condition in which the heart, having lost muscle during the attack, does not beat at full capacity. So, scientists have begun to look toward cellular reprogramming as a way to regenerate this damaged heart muscle.
The reprogramming of skin cells into heart cells, an approach pioneered by Gladstone Investigator, Deepak Srivastava, MD, has required the insertion of several genetic factors to spur the reprogramming process. However, scientists have recognized potential problems with scaling this gene-based method into successful therapies. So some experts, including Gladstone Senior Investigator Sheng Ding, PhD, have taken a somewhat different approach.
“Scientists have previously shown that the insertion of between four and seven genetic factors can result in a skin cell being directly reprogrammed into a beating heart cell,” explained Dr. Ding, the paper’s senior author and a professor of pharmaceutical chemistry at UCSF, with which Gladstone is affiliated. “But in my lab, we set out to see if we could perform a similar transformation by eliminating — or at least reducing — the reliance on this type of genetic manipulation.”
To that effect, the research team used skin cells extracted from adult mice to screen for chemical compounds, so-called ‘small molecules,’ that could replace the genetic factors. Dr. Ding and his research team have previously harnessed the power of small molecules to reprogram skin cells into neurons and, more recently, insulin-producing pancreas cells. They reasoned that a similar technique could be used to do the same with heart cells.
“After testing various combinations of small molecules, we narrowed down the list to a four-molecule ‘cocktail,’ which we called SPCF, that could guide the skin cells into becoming more like heart cells,” said Gladstone Postdoctoral Scholar Haixia Wang, PhD, the paper’s lead author. “These newly reprogramed cells exhibited some of the twitching and contracting normally seen in mature heart cells, but the transformation wasn’t entirely complete.”
So, Drs. Ding and Wang decided to add one genetic factor, called Oct4, to the small molecule cocktail. And by doing so, the research team was able to generate a completely reprogrammed beating heart cell.
“Once we added Oct4 to the mix, we observed clusters of contracting cells after a period of just 20 days,” explained Dr. Ding. “Remarkably, additional analysis revealed that these cells showed the same patterns of gene activation and electric signaling patterns normally seen in the ventricles of the heart.”
Dr. Ding and his team believe that these results may point to a more desirable method for reprogramming, as ventricular heart cells are the type of cells typically lost during a heart attack. These findings give the team newfound optimism that the research is well on its way towards an entirely pharmaceutical-based method to regrow heart muscle.
“The fact that the combination of Oct4 and small molecules appears to generate beating heart cells in an accelerated fashion is encouraging,” said Joseph Wu, MD, PhD, Director of the Stanford Cardiovascular Institute, who was not involved in this study. “Future advances by Dr. Ding and others will likely focus on improving the efficiency of conversion as well as duplicating the data in adult human cells.”
Haixia Wang, Nan Cao, C. Ian Spencer, Baoming Nie, Tianhua Ma, Tao Xu, Yu Zhang, Xiaojing Wang, Deepak Srivastava, Sheng Ding. Small Molecules Enable Cardiac Reprogramming of Mouse Fibroblasts with a Single Factor, Oct4. Cell Reports, February 2014 DOI: 10.1016/j.celrep.2014.01.038
One of the major causes of hearing loss is damage to the sound-sensing hair cells in the inner ear. For years, scientists have thought that these cells are not replaced once they’re lost, but new research appearing online February 20 in the journal Stem Cell Reports reveals that supporting cells in the ear can turn into hair cells in newborn mice. If the findings can be applied to older animals, they may lead to ways to help stimulate cell replacement in adults and to the design of new treatment strategies for people suffering from deafness due to hair cell loss.
Whereas previous research indicated that hair cells are not replaced, this latest study found that replacement does indeed occur, but at very low levels. “The finding that newborn hair cells regenerate spontaneously is novel,” says senior author Dr. Albert Edge of Harvard Medical School and Massachusetts Eye and Ear Infirmary.
The team’s previous research revealed that inhibition of the Notch signaling pathway increases hair cell differentiation and can help restore hearing to mice with noise-induced deafness. In their latest work, the investigators found that blocking the Notch pathway increases the formation of new hair cells not from remaining hair cells but from certain nearby supporting cells that express a protein called Lgr5.
“By using an inhibitor of Notch signaling, we could push even more cells to differentiate into hair cells,” says Dr. Edge. “It was surprising that the Lgr5-expressing cells were the only supporting cells that differentiated under these conditions.”
Combining this new knowledge about Lgr5-expressing cells with the previous finding that Notch inhibition can regenerate hair cells will allow the scientists to design new hair cell regeneration strategies to treat hearing loss and deafness.
Naomi F. Bramhall, Fuxin Shi, Katrin Arnold, Konrad Hochedlinger, Albert S.B. Edge. Lgr5-Positive Supporting Cells Generate New Hair Cells in the Postnatal Cochlea. Stem Cell Reports, February 2014 DOI: 10.1016/j.stemcr.2014.01.008