A lack of correlation between decline in growth capacity and nuclear RNA synthesising activity in ageing human embryo cells in culture.

A reduced proliferative capacity has been demonstrated between young (passage 5/24) and middle (passage 17/24) aged human embryo diploid fibroblast cultures. This difference was noted in both logarithmically growing and plateau-phase cultures in terms of growth curves, DNA content per dish and ability to incorporate 3H-thymidine. This reduction in growth potential is not accompanied by any reduction in chromatin template activity, determined in nuclear "ghost" monolayer, using either the endogenous polymerase or an exogenous bacterial enzyme. Therefore the declining division potential as these cells pass from young to middle passage is unlikely to occur as an expression of alterations in nuclear RNA synthesis. It is, however, possible that the apparently continuous decline in growth potential with age might be caused by different events at various stages of the cells's lifespan.