Oncostatin M in the normal human testis and several testicular disorders

The immunohistochemical reaction to oncostatin M (OSM) was studied in norma l human testes at different ages (fetuses, newborns, children, pubertal boy s, adults, and elderly men), as well as in several testicular disorders inc luding carcinoma-in-situ cells (CIS), germ cell tumors, benign functioning Leydig cell tumor, androgen insensitivity syndrome, Klinefelter's syndrome, and cryptorchidism. Positive OSM immunostained Sertoli cells were only obs erved in fetuses. In normal testes, intense OSM immunoreaction was found in the Leydig cells of fetuses, newborns, and adults. Leydig cell immunoreact ion was weak in elderly men and absent in children and pubertal boys. In so me testicular disorders (Leydig cell tumor, cryptorchidism, and CIS), Leydi g cell immunoreaction was as intense as in normal adult testes. This immuno reaction was heterogeneous in androgen insensitivity syndrome and was absen t in Klinefelter's syndrome and intratubular seminoma. No recognizable Leyd ig cells were observed in the other testicular tumors. The findings of our study suggest that, in humans, the down-regulation of OSM immunoexpression in Sertoli cells occurs early, and that OSM immunoreaction in the Leydig ce lls is associated with functionally active and differentiated Leydig cells.