Groundbreaking new evidence demonstrates that the clock of aging may be reversible, based on recent studies conducted at the Salk Institute in La Jolla, California, and published in the Thursday issue of the journal Cell.

The first attempt to reverse aging has been discovered by reprogramming the genome of mice: lengthening the animals’ life spans by 30%, and rejuvenating their organs. While the technique requires genetic engineering and cannot currently be applied to people, the discovery reveals an enhanced understanding of the human aging process—and the possibility of revitalizing human tissues through other practices and protocols.

Experts who study the aging process and its biology at MIT and the Albert Einstein College of Medicine in New York call the results “exciting” and “novel,” with the potential to slow down, if not reverse, aging. These findings are based upon the idea that the aging process is clocklike, and can—at least in principle—be ‘wound back’ to a more youthful, earlier state.

A decade ago, a Japanese biologist named Shinya Yamanaka identified the four necessary genes in order to reset the clock of the fertilized egg. The power of the four genes indicated that they could reprogram and reset the genomes of intestinal cells and skin back to the embryonic state, and Yamanaka’s method is now regularly used to alter adult tissue cells into cells similar to the embryonic stem cells generated during the first divisions of a fertilized egg.

At the Salk Institute, doctors and researchers considered a slightly different approach, initially conceived in the idea of regenerating lost tails and limbs. When animals lose certain apendages, the cells near the lost body part revert to a stage halfway in between an embryonic cell and an adult cell—before rebuilding. Because of this, scientists thought it possible that reprogramming with a small dose of Yamanaka factors might rejuvenate cells without the complete reprogramming that ultimately converts cells to their embryonic states.

Delivering a nonlethal dose of Yamanaka factors to mice by genetically engineering the animals with extra copies of the four genes, in addition to activating the genes when the mice received a certain drug in their water, resulted in improved organ health and overall beneficial effects.

These results were conclusively obtained by resetting the clock of the aging process, which is created by the epigenome: the system of proteins that covers cell’s DNA, and controls which genes are active. As eggs develop into entire animals, the epigenome allows cells to activate genes inherent and specific to respective roles—like the heart—but suppresses all genes used by other cell types. Through this process, an embryo’s cell is able to differentiate into the multiple cell types required by the body. Throughout life, the epigenome is additionally responsible for cell maintenance, ‘switching them on and off’ as required.

It is only recently that biologists have understood the critical importance of the epigenome in causing aging: if it is damaged, the cell’s efficiency is subsequently degraded. The Yamanaka genes in mice are eradicating these negative alternations, and thus reverting cells to more youthful states.

Because of the Yamanak genes’ ability to reactivate genes responsible for health and vitality of embryonic cells, they rejuvenate tissues and cause changes in the epigenome. Lead scientists are currently testing various drugs and pharmaceuticals to see if they can achieve the same transformation as with the Yamanaka factors, stating that the use of chemicals “will be more translatable to human therapies and clinical applications.”