Vitamin A and follicle-stimulating hormone synergistically induce differentiation of type A spermatogonia in adult mouse cryptorchid testes in vitro.

To study the mechanism of vitamin A and FSH action on testicular germ cell differentiation, artificially induced cryptorchid testes of adult mice were cultured in vitro, because such testes contain only type A spermatogonia and Sertoli cells in their seminiferous tubules. A synergistic effect of vitamin A compounds with FSH, but not with LH, on testicular germ cell differentiation was observed. Our data suggested that FSH stimulated the proliferation of type A spermatogonia, whereas retinoids induce spermatogenesis from type A spermatogonia into intermediate or type B spermatogonia. Possible mechanisms of action of retinoids and FSH on testicular germ cell differentiation are discussed.