Ploidy of human embryonic fibroblasts during in vitro aging.

The DNA content of single nuclei in confluent cultures of aging human embryonic fibroblasts, TIG-3, was measured by means of flow cytofluorometry. In the early and late stages of their in vitro lifespan, they had considerable numbers of 4C, 8C and 16C nuclei. In the other period more than 95% of their nuclei were 2C nuclei. These results were confirmed by karyotype analysis. Presumably, the polyploid cells in young cell populations are removed due to their low growth potential and those in old cell populations are accumulated as a result of cellular aging. The saturation density of TIG-3 cells increased at the beginning of their lifespan and thereafter decreased. The rise in their saturation density seems to reflect cell selection advantageous for young diploid cells.