BMP system expression in GCs from polycystic ovary syndrome women and the in vitro effects of BMP4, BMP6, and BMP7 on GC steroidogenesis

Background: The bone morphogenetic proteins (BMPs) are growth factors involved in the folliculogenesis. Alteration in their expression may compromise the reproductive process in disease such as the polycystic ovary syndrome (PCOS). This study investigated the expression and role of granulosa cell (GC) BMP from normal cycling and PCOS women. Methods and results: This prospective study was performed in GCs obtained from 14 patients undergoing IVF: i) six women with normal ovulatory cycles and tubal or male infertility and ii) eight women with PCOS. BMP2, BMP4, BMP5, BMP6, BMP7, and BMP8A and their receptors BMPR1A, BMPR1B, and BMPR2 were identified by RT-PCR in GCs from normally cycling and PCOS women. BMP4, BMP6, and BMP7 expressions were confirmed by immunohistochemistry. Quantitative transcript analysis showed the predominant expression of BMP6. In GCs from PCOS women, an overexpression of BMP6 (P<0.01) and BMPR1A mRNA (P<0.05) was observed. GC culture experiments demonstrated that basal estradiol (E-2) production was threefold higher but FSH-induced E2 increment was twofold lower in PCOS compared with controls. In PCOS, BMP6 and BMP7 exerted a stimulatory effect on basal E-2 production while BMP4 and BMP6 inhibited FSH-induced E2 production. FSH receptor and aromatase expression were not different between both groups. Conclusion: The BMP system is expressed in human GCs from normal cycling and PCOS women. The BMP may be involved in reproductive abnormalities found in PCOS. European Journal of Endocrinology 168 437-444