Scientists have shown that they can safely and effectively reverse the epigenetic markers of age in middle-aged and elderly mice by partially resetting their cells to more youthful states – reducing many signs of ageing as they do so.
As organisms age, their cells have different epigenetic markers on their DNA compared to younger ones. It is known that adding a mixture of reprogramming molecules, also known as ‘Yamanaka factors’, to cells can reset these epigenetic marks to their original patterns. This approach enables researchers to turn back the clock for adult cells, developmentally speaking, into stem cells.
“We are elated that we can use this approach across the life span to slow down aging in normal animals. The technique is both safe and effective in mice,” said Juan Carlos Izpisua Belmonte, co-corresponding author, professor at the Salk Institute. “In addition to tackling age-related diseases, this approach may provide the biomedical community with a new tool to restore tissue and organismal health by improving cell function and resilience in different disease situations, such as neurodegenerative diseases.”
The Salk Institute research lab reported in 2016 that, for the first time, they were able use the Yamanaka factors to counter the signs of aging and increase life span in mice with a premature ageing disease. More recently, the lab found that the Yamanaka factors can accelerate muscle regeneration even in younger mice. Building on these studies, other scientists have used the same approach to improve the function of other tissues like the heart, brain and optic nerve.
In the new study, the researchers tested variations of the cellular rejuvenation approach in healthy animals as they aged. One group of mice received regular doses of the Yamanaka factors from the time they were 15 months old until 22 months, approximately equivalent to age 50 through 70 in humans. Another group was treated from 12 through 22 months, approximately age 35 to 70 in humans. And a third group was treated for just one month at age 25 months, similar to age 80 in humans.
“What we really wanted to establish was that using this approach for a longer time span is safe,” said Pradeep Reddy, study co-first author. “Indeed, we did not see any negative effects on the health, behaviour or body weight of these animals.”
No blood cell alterations or neurological changes were seen in the mice treated with the Yamanaka factors compared to control mice. Additionally, no cancers were observed in any of the groups of animals.
In terms of normal signs of ageing, the treated mice resembled younger animals in a number of ways. In both the kidneys and skin, the epigenetics of treated animals more closely resembled epigenetic patterns seen in younger animals. When injured, the skin cells of treated animals had a greater ability to proliferate and were less likely to form permanent scars, unlike normal older animals. Metabolic molecules also did not reflect normal age-related changes.
This youthfulness was observed in the animals treated for seven or 10 months with the Yamanaka factors, but not the animals treated for just one month. What’s more, when the treated animals were analysed midway through their treatment, the effects were not yet as evident. This suggests that the treatment is not simply pausing aging, but actively turning it backwards–- although more research is needed to differentiate between the two.
The team is now planning future research to analyse how specific molecules and genes are changed by long-term treatment with the Yamanaka factors. They are also developing new ways of delivering the factors.
“At the end of the day, we want to bring resilience and function back to older cells so that they are more resistant to stress, injury and disease,” said Reddy. “This study shows that, at least in mice, there’s a path forward to achieving that.”
The study was published in Nature Aging.
Source: Salk Institute
