Oestradiol‐17β is a local factor inducing the early stage of spermatogenesis in mouse testes

Summary This study was undertaken to elucidate the effect of testicular oestradiol‐17β (E 2 ) on spermatogenesis. Spermatogonial development and spermatogenic gene expression in testicular germ cells were investigated using an in vitro culture system supplemented with E 2 . E 2 stimulated spermatocytogenic development of cultured testicular germ cells regardless of the addition of follicle‐stimulating hormone and testosterone to the culture medium. E 2 also induced the expression of genes encoding synaptonemal complex protein 1 and protamine 1, proteins required for spermatogenesis. In conclusion, the results of this study suggest that E 2 is a spermatocytogenic factor that acts via the stimulation of spermatogenic gene expression.