Sertoli cells inhibited apoptosis of pachytene spermatocytes and round spermatids

Apoptosis in the testis represents an important physiological mechanism tha t regulates the number of germ cells in the seminiferous epithelium. This a poptosis is believed to be regulated by many factors, including growth fact ors and cytokines, which appear to suppress apoptosis of the germ cells. In this study, we examined the roles of Sertoli cells On the regulation of pa chytene spermatocyte (PS) and round spermatid (RSd) apoptosis with either a co-culture trans-well system or a direct contact system. Apoptosis was det ected by low molecular weight DNA fragmentation assay, in situ end labeling , and an LDH assay. in addition, the level of Bcl-2, Bax, and ICE mRNAs in PS and RSd by Northern blot analysis. When PS and RSd were cultured with Se rtoli cells in either a trans-well system or direct contact system, the ext ent of apoptotic DNA fragmentation and LDH level were both significantly lo wer than those control values. TUNEL staining also revealed the inhibition of apoptosis of PS and RSd when they were cultured with Sertoli cells compa red with controls (p < 0.05). Moreover, the extent of apoptotic DNA fragmen tation and LDH level were significantly lower in the direct contact system than in the trans-well system. TUNEL staining also demonstrated a more decr ease in apoptosis of PS and RSd in the direct contact system compared with the trans-well system (p < 0.05). PS and RSd cultured with Sertoli cells ex hibited an increase in Bcl-2 mRNA, whereas those cultured with serum-free m edium did not show any change. The levels of Bax and ICE mRNAs decreased in PS and RSd cultured with Sertoli cells in comparison with control values. These results suggest that Sertoli cells can prevent apoptosis of germ cell s, and that the effect of Sertoli cells on germ cells is mediated by cell t o cell interaction or, remote effects of inhibitory factors on apoptosis.