Aging in vitro : Growth of cultured cells from the Galapagos tortoise

Skin biopsies from two growing and two fully-grown Galapagos tortoises, a species that lives twice as long as man, were explanted in vitro. Cellular outgrowth was more vigorous from explants of young tortoises but epithelial cells stopped dividing early in the history of all cultures, even at the optimum temperature of 30 °C. Serially subcultured fibroblasts from young tortoises divided more rapidly and achieved longer lifespans than fibroblasts from old tortoises in terms of mean population doublings and to a lesser extent, calendar time. For all cultures the lifespans exceeded those reported for human diploid fibroblasts. The results indicate that a proportionality exists between the potential (remaining) lifespan in vivo and the mitotic capacity of cultured diploid cells in vitro.