Objectives: To study the molecular mechanism of human follicular atresia by exploring the effects of estrogen, androgen on human granulosa cell (GC) apoptosis.
Methods: Ovarian GC DNA fragments of both atretic and developing follicles before and after estrogen (1 microgram/ml), androgen (1 microgram/ml) treatments were analysed by agarose gel electrophoresis. The expression of bcl-2 mRNA was also determined by northern blotting in GC of developing follicle after sex steroids addition.
Results: Internucleosomal DNA cleavage occurred in granulosa cells in atretic follicles and after androgen treatment. In granulosa cells of developing follicles, estrogen treatment increased the expression of bcl-2 mRNA by 45%, while androgen treatment downregulated the expression of bcl-2 mRNA by 35%.
Conclusion: Androgens increase apoptotic DNA fragmentation, and decrease the expression of bcl-2 mRNA in GC of developing follicles, while estrogens produce the opposite effect. Therefore, expression of bcl-2 may be involved in the mechanism of follicular development and atresia.