Scientists have reversed the aging process for human adult stem cells. Researchers at the Buck Institute for Research on Aging and the Georgia Institute of Technology have shown in laboratory studies that they can turn back the clock on the aging of adult stem cells, which are responsible for maintenance and repair of old and damaged tissues in the body. Adult stem cells are also the gold standard for patient treatments, now being used for dozens of diseases in thousands of patients around the globe.

The modern "stem cell hypothesis of aging" suggests that living organisms are as old as their adult stem cells, which explains the decline in regenerative power of our tissues as we age. Most cells show aging by the shortening of DNA sequences called telomeres, on the ends of chromosomes. As a cell ages, the telomeres get shorter, similar to a fuse burning down. But adult stem cells tend to maintain these fuses, so the researchers hypothesized that these repair stem cells must age by a different mechanism. They found that as we and our adult stem cells age, 65% of the DNA damage in self-renewing adult stem cells occurred within small sections of DNA called "transposable elements" or "retrotransposons". Co-author King Jordan said:

"Retrotransposons were previously thought to be non-functional and were even labeled as 'junk DNA', but accumulating evidence indicates these elements play an important role in genome regulation."

Young adult stem cells were able to suppress the activity of these genetic elements and deal with DNA damage, but older adult stem cells were less able to suppress them. Senior author Victoria Lunyak said:

"By suppressing the accumulation of toxic transcripts from retrotransposons, we were able to reverse the process of human adult stem cell aging in culture."

Next steps will include validating the rejuvenation of adult stem cells in lab animals. The study is published in the journal Cell Cycle.