Human chorionic gonadotropin induces all stages of spermatogenesis in vitro in the male Japanese eel ( Anguilla japonica)

In the cultivated male Japanese eel, spermatogonia are the only germ cells present in the testis. Using a newly developed organ culture system, we obtained evidence that human chorionic gonadotropin (HCG) can induce the entire process of spermatogenesis, in vitro, from spermatogonia to spermatozoa within 24 days. The HCG-induced spermatogenesis in vitro was accompanied by a marked activation of Sertoli cells and Leydig cells, occurring prior to the beginning of spermatogonial proliferation. These results indicate that gonadotropin triggers spermatogenesis in the Japanese eel and further suggest that this effect of gonadotropin is mediated through the actions of testicular somatic cells.