Researchers in the US treated healthy mice with a form of gene1 therapy that refreshed older cells, making the animals more youthful according to biological markers that are used to measure the effects of ageing.
Repeating the trick in humans is far from straightforward2, but the findings will fuel interest in radical3 new therapies that aim to slow or reverse the ageing process as a means of tackling age-related diseases such as cancer, brittle4 bones and Alzheimer's.
"A host of age-related diseases might benefit from this approach," said Heinrich Jasper, a principal fellow and director at the US biotech firm Genentech.
The scientists drew on previous work by the Japanese Nobel laureate Prof Shinya Yamanaka, who showed that a mixture of four molecules5 – known as Yamanaka factors – can rewind adult cells into youthful stem cells that are capable of forming almost any tissue in the body.
Writing in the journal Nature Aging, the US team led by Jasper and Prof Juan Carlos Izpisua Belmonte at the Salk Institute in California and the San Diego Altos Institute, found that mice who received Yamanaka factors for several months resembled younger animals in many ways, with their skin and kidneys in particular showing signs of rejuvenation6.
The experiments showed that rejuvenation was more effective when the therapy was given for a long time – seven to 10 months – starting when the animals were 12 to 15 months old, equivalent to age 35 to 50 in humans. When older animals, equivalent to 80 years old in human terms, were treated for one month, the scientists saw little impact.
Researchers are cautious about using Yamanaka factors in humans because previous work has shown that fully7 reprogrammed cells can turn into clumps8 of cancerous tissue called teratomas.
The latest study shows that partial reprogramming may be able to rejuvenate9 tissues without such risks, but further hurdles10 remain. Rather than using Yamanaka factors to rejuvenate aged11 humans, many scientists suspect that new drugs will be needed to partially12 reprogram cells safely and effectively.
"In theory, biological age reversal or reduction could be possible. However, we are at very early stages where we need to understand the basic science behind it much better," said Dr Tamir Chandra, an expert in the biology of ageing at the University of Edinburgh, who was not involved in the study.