Changes in the messenger RNA expression levels of Bcl-2 family members and caspase-8 and -3 in porcine ovarian follicles during follicular atresia.

Follicular atresia is mainly modulated by the mitochondrial apoptotic pathway, which is regulated primarily by interactions between pro- and anti-apoptotic genes at the mitochondrial level. The Bcl-2 family members (e.g. Bak, Bax, Bid, Bim, Bcl-xL, Bcl-2 and Mcl-1), caspase-8 and -3 play a crucial role in the mitochondrial apoptotic pathway. In this study, we used single follicles to measure the messenger RNA (mRNA) expression levels of Bak, Bax, Bid, Bim, Bcl-xL, Bcl-2, Mcl-1, caspase-8 and caspase-3 in healthy (H), early atretic (EA), and progressed atretic (PA) porcine follicles by quantitative real-time RT-PCR. Follicular atresia was assessed based on morphology and the ratio of progesterone to 17β-estradiol. Our results indicate weak mRNA expression of Bim, Bid, Mcl-1 and Bcl-2 in the H group and significantly increased expression in the EA and PA groups (P < 0.01). The expression levels of Bak, caspase-3 and Bcl-xL were low in the H and EA groups and increased in the PA group (P < 0.01). Finally, the expression of Bax and caspase-8 rose gradually with the progression of follicular atresia. Our findings indicate the mRNA expression levels of both pro-apoptotic genes (Bak, Bax, Bid, Bim, caspase-8 and caspase-3) and anti-apoptotic genes (Bcl-xL, Bcl-2 and Mcl-1) were increased in the follicles during atresia in porcine ovaries. We propose that the increase in anti-apoptotic gene transcription may prevent apoptosis by protecting against the effects of pro-apoptotic gene expression. However, alterations in the balance of pro- and anti-apoptotic gene expression may lead to follicular atresia.