University of Pittsburgh (Pennsylvania, USA) scientists improved the lifespan of mice with an aging disease (progeria) by injecting them with normal stem cells, prolonging their lifespan by two to three times.  Importantly, the stem cells, which were derived from the muscle of young, healthy rodents, did not migrate to other tissue in the body and appear to have secreted a growth factor, or protein, that delayed the aging process. Instead of losing muscle mass and moving slowly, the animals grew as large as normal ones.  Writing that: “These results establish that adult stem/progenitor cell dysfunction contributes to ageing-related degeneration and suggests a therapeutic potential of post-natal stem cells to extend health,” the study authors are hopeful the animal research can be translated to human application.