Cell Senescence and Aging

Abstract

Most higher eukaryotic cells that can divide in vivo cannot do so indefinitely. Thus, normal cells are said to have a finite division potential or replicative life span. The process that limits the division potential of cells has been termed cellular or replicative senescence. Replicative senescence was first observed when it became possible to culture cells outside the organism. Nearly a century ago, Carrel reported that cell proliferation was unlimited once cells were removed from the organism and cultured ex vivo. This result was sporadically challenged over the ensuing decades. However, it was not until about three decades ago that the finite replicative life span of cells was first formally described. Since then, many cell types from a variety of animal species have been shown to have a finite replicative life span. Most studies of replicative senescence have used cells grown in culture. However, a limited number of studies using cells passaged in intact animals, or cells identified in intact tissues, strongly suggest that cells undergo replicative senescence in vivo (reviewed in 1–3).