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Rescarchers in the US treated healthy mice with a form of gene 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 straightforward, but the findings will fuel interest in new therapiesthat aim to slow or reverse theageing process as a means of tackling age-related diseases such as cancers and Alzheimer’s.

The scientists drew on previous work by the Japanese Nobel winner Prof Shinya Yamanaka, who showed that a mixture of four molecules(原子)—known as Yamanaka factors—can turn adult cells into youthful stem cells that are capable of forming almost any tissue (组织) 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 were similar to younger animals in many ways, with their skin in particular showing signs of rejuvenation(恢复青春).

The experiments showed that rejuvenation was more effective when the therapy was given for a long time—7 to 10 months—starting when the animals were 12 to 15 months old, equal to age 35 to 50 in humans. Whén older animals, equal to 80 years old in human terms, were treated for one month, the scientists saw little impact.

Rather than using Yamanaka factors to rejuvenate aged humans, many scientists suspect that new drugs will be needed to partially 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.