In vitro differentiation of Type A spermatogonia from mouse cryptorchid testes in serum-free media

Artificially induced cryptorchid testes of adult mice were cultured in serum-free media. Pedersen Type III fetuin activated cell division in Type A spermatogonia and stimulated them to differentiate; it also had a synergistic effect with follicle-stimulating hormone (FSH) on testicular germ cell differentiation. However, Pedersen Type IV, Deutsch, and Spiro fetuin did not show any stimulatory effect on the differentiation of germ cells. It was suggested that some serum factor(s) which copurifies with Pedersen Type III fetuin may be the active principle rather than fetuin itself in the differentiation of testicular germ cells in vitro.