Could epigenetic reprogramming reverse aging?
A range of strategies are being explored to reprogram the body's cells to an earlier state. Most scientists aren't betting on a new fountain of youth just yet - but, in theory, epigenetic reprogramming is a recipe for self-renewal.
Ten thousand years ago, the average human spent a maximum of 30 years on Earth. Despite the glory of Ancient Greece and the Roman Empire, most of their inhabitants didn’t surpass the age of 35. Between the 1500s and 1800, life expectancy (at least in Europe) fluctuated between 30 and 40 years.
Public health advancements like control of infectious diseases, better diet and clean sanitation, as well as social improvements have made it possible for human lifespans to double since 1800. Although lifespan differs widely today from country to country according to socioeconomic health, the average has soared to 73.2 years.
But this may turn out to be on the low side if epigenetic rejuvenation fulfills its great promise: to reverse aging, perhaps even completely. Epigenetic rejuvenation, or partial reprogramming, is the process by which a set of therapies are trying to manipulate epigenetics – how various changes can affect our genes – and the Yamanaka factors. These Yamanaka factors are a group of proteins that can convert any cell of the body into pluripotent stem cells, a group of cells that can turn into brand new cells, such as those of the brain or skin. At least in theory, it could be a recipe for self-renewal.
“Partial reprogramming tries to knock a few years off of people’s biological age, while preserving their original cell identity and function,” says Yuri Deigin, cofounder and director of YouthBio Therapeutics, a longevity startup utilizing partial reprogramming to develop gene therapies aimed at the renewal of epigenetic profiles. YouthBio plans to experiment with injecting these gene therapies into target organs. Once the cargo is delivered, a specific small molecule will trigger gene expression and rejuvenate those organs.
“Our ultimate mission is to find the minimal number of tissues we would need to target to achieve significant systemic rejuvenation,” Deigin says. Initially, YouthBio will apply these therapies to treat age-related conditions. Down the road, though, their goal is for everyone to get younger. “We want to use them for prophylaxis, which is rejuvenation that would lower disease risk,” Deigin says.
Epigenetics has swept the realm of biology off its feet over the last decade. We now know that we can switch genes on and off by tweaking the chemical status quo of the DNA’s local environment. "Epigenetics is a fascinating and important phenomenon in biology,’’ says Henry Greely, a bioethicist at Stanford Law School. Greely is quick to stress that this kind of modulation (turning genes on and off and not the entire DNA) happens all the time. “When you eat and your blood sugar goes up, the gene in the beta cells of your pancreas that makes insulin is turned on or up. Almost all medications are going to have effects on epigenetics, but so will things like exercise, food, and sunshine.”
Can intentional control over epigenetic mechanisms lead to novel and useful therapies? “It is a very plausible scenario,” Greely says, though a great deal of basic research into epigenetics is required before it becomes a well-trodden way to stay healthy or treat disease. Whether these therapies could cause older cells to become younger in ways that have observable effects is “far from clear,” he says. “Historically, betting on someone’s new ‘fountain of youth’ has been a losing strategy.”
The road to de-differentiation, the process by which cells return to an earlier state, is not paved with roses; de-differentiate too much and you may cause pathology and even death.
In 2003 researchers finished sequencing the roughly 3 billion letters of DNA that make up the human genome. The human genome sequencing was hailed as a vast step ahead in our understanding of how genetics contribute to diseases like cancer or to developmental disorders. But for Josephine Johnston, director of research and research scholar at the Hastings Center, the hype has not lived up to its initial promise. “Other than some quite effective tests to diagnose certain genetic conditions, there isn't a radical intervention that reverses things yet,” Johnston says. For her, this is a testament to the complexity of biology or at least to our tendency to keep underestimating it. And when it comes to epigenetics specifically, Johnston believes there are some hard questions we need to answer before we can safely administer relevant therapies to the population.
“You'd need to do longitudinal studies. You can't do a study and look at someone and say they’re safe only six months later,” Johnston says. You can’t know long-term side effects this way, and how will companies position their therapies on the market? Are we talking about interventions that target health problems, or life enhancements? “If you describe something as a medical intervention, it is more likely to be socially acceptable, to attract funding from governments and ensure medical insurance, and to become a legitimate part of medicine,” she says.
Johnston’s greatest concerns are of the philosophical and ethical nature. If we’re able to use epigenetic reprogramming to double the human lifespan, how much of the planet’s resources will we take up during this long journey? She believes we have a moral obligation to make room for future generations. “We should also be honest about who's actually going to afford such interventions; they would be extraordinarily expensive and only available to certain people, and those are the people who would get to live longer, healthier lives, and the rest of us wouldn't.”
That said, Johnston agrees there is a place for epigenetic reprogramming. It could help people with diseases that are caused by epigenetic problems such as Fragile X syndrome, Prader-Willi syndrome and various cancers.
Zinaida Good, a postdoctoral fellow at Stanford Cancer Institute, says these problems are still far in the future. Any change will be incremental. “Thinking realistically, there’s not going to be a very large increase in lifespan anytime soon,” she says. “I would not expect something completely drastic to be invented in the next 5 to 10 years. ”
Good won’t get any such treatment for herself until it’s shown to be effective and safe. Nature has programmed our bodies to resist hacking, she says, in ways that could undermine any initial benefits to longevity. A preprint that is not yet peer-reviewed reports cellular reprogramming may lead to premature death due to liver and intestinal problems, and using the Yamanaka factors may have the potential to cause cancer, at least in animal studies.
“Side effects are an open research question that all partial reprogramming companies and labs are trying to address,” says Deigin. The road to de-differentiation, the process by which cells return to an earlier state, is not paved with roses; de-differentiate too much and you may cause pathology and even death. Deigin is exploring other, less risky approaches. “One way is to look for novel factors tailored toward rejuvenation rather than de-differentiation.” Unlike Yamanaka factors, such novel factors would never involve taking a given cell to a state in which it could turn cancerous, according to Deigin.
An example of a novel factor that could lower the risk of cancer is artificially introducing mRNA molecules, or molecules carrying the genetic information necessary to make proteins, by using electricity to penetrate the cell instead of a virus. There is also chemical-based reprogramming, in which chemicals are applied to convert regular cells into pluripotent cells. This approach is currently effective only for mice though.
“The search for novel factors tailored toward rejuvenation without de-differentiation is an ongoing research and development effort by several longevity companies, including ours,” says Deigin.
He isn't disclosing the details of his own company’s underlying approach to lowering the risk, but he’s hopeful that something will eventually end up working in humans. Yet another challenge is that, partly because of the uncertainties, the FDA hasn’t seen fit to approve a single longevity therapy. But with the longevity market projected to soar to $600 billion by 2025, Deigin says naysayers are clinging irrationally to the status quo. “Thankfully, scientific progress is moved forward by those who bet for something while disregarding the skeptics - who, in the end, are usually proven wrong.”
Gene Transfer Leads to Longer Life and Healthspan
In August, a study provided the first proof-of-principle that genetic material transferred from one species to another can increase both longevity and healthspan in the recipient animal.
The naked mole rat won’t win any beauty contests, but it could possibly win in the talent category. Its superpower: fighting the aging process to live several times longer than other animals its size, in a state of youthful vigor.
It’s believed that naked mole rats experience all the normal processes of wear and tear over their lifespan, but that they’re exceptionally good at repairing the damage from oxygen free radicals and the DNA errors that accumulate over time. Even though they possess genes that make them vulnerable to cancer, they rarely develop the disease, or any other age-related disease, for that matter. Naked mole rats are known to live for over 40 years without any signs of aging, whereas mice live on average about two years and are highly prone to cancer.
Now, these remarkable animals may be able to share their superpower with other species. In August, a study provided what may be the first proof-of-principle that genetic material transferred from one species can increase both longevity and healthspan in a recipient animal.
There are several theories to explain the naked mole rat’s longevity, but the one explored in the study, published in Nature, is based on the abundance of large-molecule high-molecular mass hyaluronic acid (HMM-HA).
A small molecule version of hyaluronic acid is commonly added to skin moisturizers and cosmetics that are marketed as ways to keep skin youthful, but this version, just applied to the skin, won’t have a dramatic anti-aging effect. The naked mole rat has an abundance of the much-larger molecule, HMM-HA, in the chemical-rich solution between cells throughout its body. But does the HMM-HA actually govern the extraordinary longevity and healthspan of the naked mole rat?
To answer this question, Dr. Vera Gorbunova, a professor of biology and oncology at the University of Rochester, and her team created a mouse model containing the naked mole rat gene hyaluronic acid synthase 2, or nmrHas2. It turned out that the mice receiving this gene during their early developmental stage also expressed HMM-HA.
The researchers found that the effects of the HMM-HA molecule in the mice were marked and diverse, exceeding the expectations of the study’s co-authors. High-molecular mass hyaluronic acid was more abundant in kidneys, muscles and other organs of the Has2 mice compared to control mice.
In addition, the altered mice had a much lower incidence of cancer. Seventy percent of the control mice eventually developed cancer, compared to only 57 percent of the altered mice, even after several techniques were used to induce the disease. The biggest difference occurred in the oldest mice, where the cancer incidence for the Has2 mice and the controls was 47 percent and 83 percent, respectively.
With regard to longevity, Has2 males increased their lifespan by more than 16 percent and the females added 9 percent. “Somehow the effect is much more pronounced in male mice, and we don’t have a perfect answer as to why,” says Dr. Gorbunova. Another improvement was in the healthspan of the altered mice: the number of years they spent in a state of relative youth. There’s a frailty index for mice, which includes body weight, mobility, grip strength, vision and hearing, in addition to overall conditions such as the health of the coat and body temperature. The Has2 mice scored lower in frailty than the controls by all measures. They also performed better in tests of locomotion and coordination, and in bone density.
Gorbunova’s results show that a gene artificially transferred from one species can have a beneficial effect on another species for longevity, something that had never been demonstrated before. This finding is “quite spectacular,” said Steven Austad, a biologist at the University of Alabama at Birmingham, who was not involved in the study.
Just as in lifespan, the effects in various organs and systems varied between the sexes, a common occurrence in longevity research, according to Austad, who authored the book Methuselah’s Zoo and specializes in the biological differences between species. “We have ten drugs that we can give to mice to make them live longer,” he says, “and all of them work better in one sex than in the other.” This suggests that more attention needs to be paid to the different effects of anti-aging strategies between the sexes, as well as gender differences in healthspan.
According to the study authors, the HMM-HA molecule delivered these benefits by reducing inflammation and senescence (cell dysfunction and death). The molecule also caused a variety of other benefits, including an upregulation of genes involved in the function of mitochondria, the powerhouses of the cells. These mechanisms are implicated in the aging process, and in human disease. In humans, virtually all noncommunicable diseases entail an acceleration of the aging process.
So, would the gene that creates HMM-HA have similar benefits for longevity in humans? “We think about these questions a lot,” Gorbunova says. “It’s been done by injections in certain patients, but it has a local effect in the treatment of organs affected by disease,” which could offer some benefits, she added.
“Mice are very short-lived and cancer-prone, and the effects are small,” says Steven Austad, a biologist at the University of Alabama at Birmingham. “But they did live longer and stay healthy longer, which is remarkable.”
As for a gene therapy to introduce the nmrHas2 gene into humans to obtain a global result, she’s skeptical because of the complexity involved. Gorbunova notes that there are potential dangers in introducing an animal gene into humans, such as immune responses or allergic reactions.
Austad is equally cautious about a gene therapy. “What this study says is that you can take something a species does well and transfer at least some of that into a new species. It opens up the way, but you may need to transfer six or eight or ten genes into a human” to get the large effect desired. Humans are much more complex and contain many more genes than mice, and all systems in a biological organism are intricately connected. One naked mole rat gene may not make a big difference when it interacts with human genes, metabolism and physiology.
Still, Austad thinks the possibilities are tantalizing. “Mice are very short-lived and cancer-prone, and the effects are small,” he says. “But they did live longer and stay healthy longer, which is remarkable.”
As for further research, says Austad, “The first place to look is the skin” to see if the nmrHas2 gene and the HMM-HA it produces can reduce the chance of cancer. Austad added that it would be straightforward to use the gene to try to prevent cancer in skin cells in a dish to see if it prevents cancer. It would not be hard to do. “We don’t know of any downsides to hyaluronic acid in skin, because it’s already used in skin products, and you could look at this fairly quickly.”
“Aging mechanisms evolved over a long time,” says Gorbunova, “so in aging there are multiple mechanisms working together that affect each other.” All of these processes could play a part and almost certainly differ from one species to the next.
“HMM-HA molecules are large, but we’re now looking for a small-molecule drug that would slow it’s breakdown,” she says. “And we’re looking for inhibitors, now being tested in mice, that would hinder the breakdown of hyaluronic acid.” Gorbunova has found a natural, plant-based product that acts as an inhibitor and could potentially be taken as a supplement. Ultimately, though, she thinks that drug development will be the safest and most effective approach to delivering HMM-HA for anti-aging.
A new study provides key insights in what causes Alzheimer's: a breakdown in the brain’s system for clearing waste.
In recent years, researchers of Alzheimer’s have made progress in figuring out the complex factors that lead to the disease. Yet, the root cause, or causes, of Alzheimer’s are still pretty much a mystery.
In fact, many people get Alzheimer’s even though they lack the gene variant we know can play a role in the disease. This is a critical knowledge gap for research to address because the vast majority of Alzheimer’s patients don’t have this variant.
A new study provides key insights into what’s causing the disease. The research, published in Nature Communications, points to a breakdown over time in the brain’s system for clearing waste, an issue that seems to happen in some people as they get older.
Michael Glickman, a biologist at Technion – Israel Institute of Technology, helped lead this research. I asked him to tell me about his approach to studying how this breakdown occurs in the brain, and how he tested a treatment that has potential to fix the problem at its earliest stages.
Dr. Michael Glickman is internationally renowned for his research on the ubiquitin-proteasome system (UPS), the brain's system for clearing the waste that is involved in diseases such as Huntington's, Alzheimer's, and Parkinson's. He is the head of the Lab for Protein Characterization in the Faculty of Biology at the Technion – Israel Institute of Technology. In the lab, Michael and his team focus on protein recycling and the ubiquitin-proteasome system, which protects against serious diseases like Alzheimer’s, Parkinson’s, cystic fibrosis, and diabetes. After earning his PhD at the University of California at Berkeley in 1994, Michael joined the Technion as a Senior Lecturer in 1998 and has served as a full professor since 2009.
Dr. Michael Glickman