Researchers at University of California, Berkeley have manipulated stem cells in older muscle tissue to produce new muscle fibers at levels comparable to young stem cells.

Old muscle tissue produces elevated levels of the molecule TGF-beta, which is known to inhibit muscle growth. The researchers used RNA interference, which can silence specific genes, to inhibit the TGF-beta pathway in old mice.

Muscle wasting–loss of muscle mass–occurs both during aging and in a number of diseases, such as cancer and muscular dystrophy.