Endocrine Abstracts

Ovarian aging is a naturally occurring physiological process, marked by dynamic changes in ovarian function and hormone secretion. Ovarian ageing is associated with several co-morbidities, including; osteoporosis, diabetes, cardiovascular disease and impaired cognitive function, therefore, understanding the physiological processes regulating this is imperative for identifying novel treatment modalities. A key endocrine regulatory of ovarian function is the heterodimer glycoprotein hormone, follicle stimulating hormone (FSH). FSH is secreted as two glycosylation variants; partially glycosylated FSH (FSH21) and fully glycosylated FSH (FSH24). These variants have different bioactivities, FSH21 is more biologically active than FSH24. Interestingly, the ratio of FSH21:FSH24 changes with age, with FSH21 predominant in women of reproductive prime, and FSH24 predominant in menopausal women. Yet, if these FSH glycosylation variants differentially modulate follicle growth and survival remains unknown. This study aimed to determine the effects of FSH21 and FSH24 on follicle growth and survival. To do this, mouse ovarian follicles were isolated from 3-4wk-old-C57/BL6 mice and treated +/− 10 ng/ml, FSH21(n=31), FSH24(n=30), a ratio of 80:20 FSH21:FSH24 (to mimic reproductive prime; n=32) or 20:80 FSH21:FSH24 (to mimic late peri-menopause; n=22). Follicles were cultured for up to 96hrs and imaged daily to evaluate follicle morphology. Follicle growth was markedly increased at 48, 72, and 96 h time points, when cultured in the presence of FSH21 or 80:20 FSH21:FSH24, in comparison to control, FSH24 alone and 20:80 FSH21:FSH24 conditions. Follicles treated with FSH24 or 20:80 FSH21:FSH24 tended to undergo basement membrane rupture and oocyte extrusion. Moreover, survival rates were significantly increased in follicles treated with FSH21 or 80:20 FSH21:FSH24. These data suggest that the nature of FSH glycosylation modulates the follicular cellular environment to regulate follicle growth and survival. These findings have important implications for IVF ovarian hyperstimulation treatment regimens. Moreover, the ratio of FSH21:FSH24 may be an important novel biomarker of ovarian ageing.