Effects of bone morphogenetic protein 4 (BMP4) supplementation during culture of the sheep ovarian cortex

The aim of the present study was to establish the presence of BMP type I and II receptor presence in preantral follicles and to investigate the effect of BMP4 supplementation on preantral follicle activation and development during organotypic culture of prepubertal ovine ovarian cortex pieces. Ovine ovarian fragments were cultured with varying concentrations (0, 25, 50 or 100 ng/ml) of BMP4 in the presence or absence of FSH in the culture media to determine the optimal minimum dose for preantral follicle activation and development. Follicular morphometry, immunohistochemistry for BMPR-IA, BMPR-IB, BMPR-II, proliferating cell nuclear antigen and TUNEL progesterone and 17β-oestradiol production were assessed. Follicle and oocyte diameter were positively influenced by the addition of BMP4 to culture. However, there was no effect of BMP4 on primordial follicle activation. Treatment with BMP4 reduced progesterone synthesis but had no effect on oestradiol. The percentage of primordial follicles stained with TUNEL was significantly greater in the culture without BMP4 compared to other culture systems after 9 days of culture. There was an increase in PCNA immunoreactivity in all follicles regardless of treatment. Treatment with BMP4 increases the size of oocytes and follicles but has minimal effects on follicular dynamics during in vitro culture of ovarian cortical tissue of sheep.