The oocyte actively participates in the regulatory mechanisms associated with cumulus oocyte complex (COC) maturation via secretion of paracrine factors, which include fibroblast growth factors (FGF). In cattle, FGF10 is expressed in the oocyte and its receptors in cumulus cells, which suggests its involvement in the regulation of differentiation of cumulus cells. The pre-ovulatory LH surge stimulates the expression of FGF2 in bovine cumulus cells, whose receptors are expressed in mural granulosa , theca and cumulus cells, which suggests paracrine and autocrine actions on antral follicles and associated COC. Among oocyte-secreted factors (OSFs), recombinant bone morphogenetic protein 15 (BMP15) has received special attention because it is exclusively expressed in oocytes. Apparently, BMP15 participates in the paracrine regulation of oocyte maturation and differentiation of cumulus cells and is essential for the normal development of preantral and antral follicles. In mice, BMP15 and FGF interact in controlling the metabolism of nuclear maturation and cumulus cell expansion. This project proposes to investigate the involvement of FGFs and BMP15 in controlling the differentiation of bovine cumulus cells. The objectives are to test the effects of FGF2 and 10, interaction of BMP15 and FGFs with BMP15 on cumulus expansion, apoptosis, production of steroids (estradiol and progesterone) and gene expression markers of developmental competence of bovine COC during in vitro maturation.
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