Four genes that reprogram adult cells into embryonic-like stem cells can also reverse some signs of ageing.
The four genes encode Yamanaka factors, which are essential for embryonic development, but usually cause tumours when expressed long-term in animals. Juan Carlos Izpisua Belmonte at the Salk Institute in La Jolla, California, and his colleagues switched the genes on for two days per week over several weeks in mice that had an ageing disorder called progeria. The animals lived about 30% longer, and showed improvements in tissue healing and other signs of ageing, such as organ failure. In normal aged mice, switching on the genes led to improved recovery from muscle injury and to other signs of youthfulness. The mice did not develop cancer.
The authors link the rejuvenation to epigenetic remodelling — changes in the chemical marks on DNA that do not alter its sequence but influence gene expression.