216 SPERMATOGONIAL STEM CELL ACTIVITY IN CRYPTORCHID TESTES

Abstract

INTRODUCTION AND OBJECTIVES: Male infertility is a serious complication of cryptorchidism. In this study, we focused on early stage spermatogenesis and spermatogonial stem cell (SSC) activity in undifferentiated spermatogonia in cryptorchid testes to elucidate the mechanism of infertility caused by cryptorchidism. METHODS: Histological findings and expression patterns of the stem cell marker, undifferentiated embryonic cell transcription factor 1 (UTF1), were examined in a unilateral cryptorchid rat model induced by flutamide and in cryptorchid patinents. We removed both unilateral descended testis (UDT) and contralateral descended testis (DT), respectively, from cryptorchid and normal rats (control) 18 days postcoitum (dpc) to 144 days postpartum (dpp). Human testicular tissues were also excised from 5 boys (8–20 months old) during orchiopexy between January 2003 and December 2008. Hematoxylin and eosin staining, real-time RT-PCR, western blot analysis, and immunohistochemical analysis with UTF1 were performed to assess early stage spermatogenesis and SSC activity. RESULTS: Histopathological analysis showed that gonocyte differentiation into early A spermatogonia occurred at 9 dpp; however, this transformation was disturbed in UDT. Quantitative study revealed that UTF1 expression decreased with testicular development, but did not disappear in adulthood. Immunohistochemical analysis showed that all gonocytes and some early type A spermatogonia expressed UTF1 in rat DT. Furthermore, the UTF1-negative early A spermatogonia/positive early A spermatogonia ratio was significantly higher in the UDT group (0.69 0.04) than in the control (0.46 0.10; p 0.037) and DT (0.44 0.05; p 0.022) groups, indicating decreased early A spermatogonia with SSC activity in cryptorchid testes. In humans, UTF1-negative Ad spermatogonia/positive Ad spermatogonia ratios in UDT were also significantly higher than in the DT (0.55 0.36, 0.16 0.07, respectively; p 0.006). CONCLUSIONS: In cryptorchid testes, the differentiation from gonocytes into early A spermatogonia, as well as the stem cell activity of early A spermatogonia, were altered during the early stage of spermatogenesis, suggesting that the loss of SSC activity in cryptorchid rats resulted in altered spermatogenesis, thus interfering with fertility.