INDUCED-DIFFERENTIATION OF OVINE FETAL GONOCYTES AFTER GRAFTING IN THE SCROTUM OF NUDE-MICE

This work was designed to elucidate, in foetal ovine testis, whether t he reason why gonocytes do not differentiate into spermatogonia and do not initiate spermatogenesis is due to inadequate foetal environment (temperature and/or hormonal balance) or if somatic testicular cell pr oliferation is a prerequisite for initiation of male meiosis. The deve lopment and differentiation of gonocytes were analysed by grafting 60- day-old foetal ovine testes into the scrotum of immunotolerant adult N ude mice. Forty days after grafting, nine of the ten grafted testes ha d survived but had not increased in weight as compared to 60-day-old t estes. Moreover, only one third of the graft was occupied by testicula r tissue, in which the relative proportions of intertubular tissue and sex cords were not altered when compared with those of normal foetal testes. The remainer of the graft was occupied by teratoma. The total number of Leydig (-80%) cells, Sertoli (-66%) cells, gonocytes (-90%) and the total length of sex cords (-63%) per grafted testis were alway s significantly reduced (P < 0.02), whereas the sex cords were signifi cantly increased in diameter (+36%; P = 0.02) as compared to those of non-grafted 60-day-old foetuses. However, in seven out of the nine tes tes, type A spermatogonia were obtained and in two of the seven a few type B or leptotene primary spermatocytes could be observed. The graft ing of foetal testis in an adult scrotum induces differentiation of go nocytes into spermatogonia, independently of proliferation of Sertoli and Leydig cells.