Rescue from dominant follicle atresia by follicle-stimulating hormone in mice

We investigated the effects of follicle-stimulating hormone (FSH) on atresia of the dominant follicle and changes in relevant apoptosis genes in granulosa cells of dominant follicles regulated by FSH in vivo. Four-week-old mice were administered FSH by intraperitoneal injection to induce follicular maturation. Granulosa cells of dominant follicles were collected at 48, 72, and 96 h after the first FSH injection. Phosphate-buffered saline was injected as a control. The mRNA levels of relevant granulosa cell apoptosis genes were examined by real-time quantitative polymerase chain reaction, and apoptosis of granulosa cells in dominant ovarian follicles was determined by the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Apoptosis in granulosa cells of dominant follicles was almost TUNEL-negative at 48, 72-66, 72, and 96-90 h after the first FSH injection, but granulosa cell apoptosis in dominant follicles was clearly detected at 96, 102, and 102-96 h by TUNEL. The BIM, caspase-3, and caspase-9 mRNA expression levels were significantly lower after FSH treatment at 72-66 and 96-90 h, compared with that at 72 and 96 h (P < 0.05). Caspase-8 and FasL mRNA expressions did not respond to FSH. FSH rescued granulosa cells from apoptosis when the relevant apoptosis genes were upregulated in early atretic follicles. FSH did not rescue granulosa cells from apoptosis if the DNA was cut into fragments by endonucleases. Thus, the rescue by FSH of granulosa cells from apoptosis and dominant follicle atresia may be accomplished by inhibition of apoptosis in mitochondria.