Human and rodent fibroblasts - model systems for studying senescence and immortalization (review).

Normal mammalian fibroblasts cultured in vitro will not divide indefinitely but undergo senescence and give rise to cells that can no longer be induced to divide. It is possible to overcome this finite life span by either cellular mutation or by the exogenous introduction of some viral or cellular oncogenes. This review describes the characteristics of senescence and the different ways in which it can be overcome.