Retinoic acid is a potent growth activator of mouse primordial germ cells in vitro

Effects of retinoic acid (RA) on the growth of mouse primordial germ cells (PGC) were studied using an in vitro coculture system. Addition of RA to the culture medium markedly increased the number of PGC of the migratory phase and also significantly retarded the depletion of gonadal PGC. We observed stimulation of mitotic activity by RA treatment at all stages of PGC examined (8.5, 11.5, and 13.5 days postcoitum), even in the absence of feeder cells. From these results, we conclude that RA affects PGC directly to promote their survival and proliferation and that the RA-induced intracellular signal may have a crucial role in the development of PGC.