Concept of fibroblast aging in vitro: implications for cell biology.

Aging in vitro is defined as the progressive growth decline of mass populations of fibroblastlike cells leading to their eventual loss after serial subcultivations. Different species are compared in terms of the doubling potential of their fibroblasts in culture. A gradient like behavior is found with at one end species whose fibroblasts invariably die after a certain number of doublings and at the other end species yielding fibroblasts with infinite growth potential. The relationship of this phenomenon with cancer and aging is reviewed and discussed. The response of chicken, mouse and human fibroblasts to slow dose rate ionizing radiation fits with the relative positions of these species on the scale relating the probability of yielding fibroblastic populations with infinite life spans. This difference between fibroblastlike cultures is interpreted in terms of the presence or absence of repair mechanisms or of a repairable substrate. The growth potential of fibroblasts in vitro seems to be related to their susceptibility to viral, chemical and physical oncogenes, and could have important implications for the study of evolution.