TL;DR: a "partial reboot" is possible to "rewind" cells back to when the epigenome gives correct instructions. cells "age" due not to mutations but incorrect instructions. scientists have currently restored bad vision in mice. could possibly apply to various types of cells to "reboot" them or to "entire animal".
excerpt:
That reversibility makes a strong case for the fact that the main drivers of aging aren’t mutations to the DNA, but miscues in the epigenetic instructions that somehow go awry. Sinclair has long proposed that aging is the result of losing critical instructions that cells need to continue functioning, in what he calls the Information Theory of Aging. “Underlying aging is information that is lost in cells, not just the accumulation of damage,” he says. “That’s a paradigm shift in how to think about aging. “
His latest results seem to support that theory. It’s similar to the way software programs operate off hardware, but sometimes become corrupt and need a reboot, says Sinclair. “If the cause of aging was because a cell became full of mutations, then age reversal would not be possible,” he says. “But by showing that we can reverse the aging process, that shows that the system is intact, that there is a backup copy and the software needs to be rebooted.”
In the mice, he and his team developed a way to reboot cells to restart the backup copy of epigenetic instructions, essentially erasing the corrupted signals that put the cells on the path toward aging. They mimicked the effects of aging on the epigenome by introducing breaks in the DNA of young mice. (Outside of the lab, epigenetic changes can be driven by a number of things, including smoking, exposure to pollution and chemicals.) Once “aged” in this way, within a matter of weeks Sinclair saw that the mice began to show signs of older age—including grey fur, lower body weight despite unaltered diet, reduced activity, and increased frailty.
The rebooting came in the form of a gene therapy involving three genes that instruct cells to reprogram themselves—in the case of the mice, the instructions guided the cells to restart the epigenetic changes that defined their identity as, for example, kidney and skin cells, two cell types that are prone to the effects of aging. These genes came from the suite of so-called Yamanaka stem cells factors—a set of four genes that Nobel scientist Shinya Yamanaka in 2006 discovered can turn back the clock on adult cells to their embryonic, stem cell state so they can start their development, or differentiation process, all over again. Sinclair didn’t want to completely erase the cells’ epigenetic history, just reboot it enough to reset the epigenetic instructions. Using three of the four factors turned back the clock about 57%, enough to make the mice youthful again.
Beyond that, the implications of being able to age and rejuvenate tissues, organs, or even entire animals or people are mind-bending. Sinclair has rejuvenated the eye nerves multiple times, which raises the more existential question for bioethicists and society of considering what it would mean to continually rewind the clock on aging.
This study is just the first step in redefining what it means to age, and Sinclair is the first to acknowledge that it raises more questions than answers. “We don’t understand how rejuvenation really works, but we know it works,” he says. “We can use it to rejuvenate parts of the body and hopefully make medicines that will be revolutionary. Now, when I see an older person, I don’t look at them as old, I just look at them as someone whose system needs to be rebooted. It’s no longer a question of if rejuvenation is possible, but a question of when.”
https://pubmed.ncbi.nlm.nih.gov/2271979 ... onclusions.
In the tai chi cohort all six marks demonstrate significant slowing (by 5-70%) of the age-related methylation losses or gains observed in the controls, suggesting that tai chi practice may be associated with measurable beneficial epigenetic changes.