Inhbition of DNA synthesis in young cycling human diploid fibroblast-like cells upon fusion to enucleate cytoplasts from senescent cells

Abstract

Previous studies have demonstrated that upon fusion with actively cycling human diploid fibroblast-like (HDFL) cells, senescent HDFL are capable of inhibiting the young nucleus from entry into DNA synthesis (Norwood et al. (1974) [10]; Rabinovitch et al. (1980) [1]). These studies have been interpreted as evidence in favor of the existence of cell cycle inhibitors in senescent cells. Enucleate cytoplasts derived from senescent HDFL cells are also capable of inhibiting the young nucleus from entry into DNA synthesis upon fusion with whole cycling HDFL cells. In contrast, no inhibition was observed in fusions between enucleate young cells and whole cycling cells. These results provide evidence for transmissible cell cycle-inhibitory factors in the cytoplasm of senescent cells.