Colony size distributions as a measure of in vivo and in vitro aging

Individual human diploid cells plated at low cell density and incubated for 2 weeks develop into colonies ranging in size from one cell to several thousand cells. The resultant colony size distribution is an accurate indicator of the number of subsequent in vitro population doublings that can be attained by the parent culture. This relationship holds for both human fetal lung and adult skin fibroblast cultures. In addition, the colony size distributions obtained from fetal, young adult, and old adult human cell cultures at the same low level of in vitro passage are indicative of the in vivo age of the level of in vitro passage are indicative of the in vivo age of the cell culture donor. Cell cultures of fetal origin give rise to the highest percentage of colonies with significant proliferative abilities, whereas cultures from old adults give rise to the lowest percentage of large colonies. Therefore, colony size distributions appear to be good indicators of both in vitro and in vivo human cellular aging.