Chick embryo fibroblasts senscence in vitro: pattern of cell division and life span as a function of cell density.

The pattern of cell division, ageing and death of cultured chick embryo fibroblasts inoculated at a wide range of cell densities is described. Cell populations seeded at densities of 2.1 x 10-3 to 3.1 x 10-4 cells per cm-2 double between 39 and 17 times respectively while their life span at all densities remains 57 puls or minus 3 days. Thus, under the experimental conditions employed, the life span of cultured embryonic chick cells is a function of calendar rather than mitotic time. We also find that the duration of phase III and the generation time of the cells during this period are proportional to the density of the culture. Moreover, the division rate of cells inoculated at low densities (4.2-31.0 x 10-2 cells per cm-2) remains constant throughout their entire lifetime. It is suggested that the decline in the proliferative capacity of chick cells ageing in vitro is a function of both their density and their age.