Fibroblast growth factor signal requirement for bovine oocyte maturation and developmental competence

Poor reproductive efficiency in cows impacts profitability in the dairy industry. Inferior oocyte quality is one major contributor to reproductive failure in cows. Superior oocyte quality relies on an optimal ovarian follicle environment, which is regulated by various endocrine, paracrine, and autocrine factors. Accordingly, a series of studies have been conducted to evaluate the fibroblast growth factor (FGF) signal requirement for bovine oocyte maturation and developmental competence.;The first study was to determine if FGF10 is an oocyte competence factor. FGF receptor 1 (FGFR1) transcripts predominated in cumulus cells whereas FGFR2 was most abundant in oocytes. FGF10 addition during in vitro maturation improved the nuclear maturation rate, promoted cumulus expansion, and increased developmental potential. These characteristics were compromised by addition of FGF10 antibody. In addition, FGF10 influenced the expression of CTSB, SPRY2 in cumulus cells and BMP15 in the oocyte.;The second study was to describe how FGF2 may facilitate oocyte maturation and improve subsequent embryo development. FGF2 (≥0.5 ng/ml) increased the percentage of blastocysts at day 7 post-IVF. FGF2 increased cumulus expansion index scores and nuclear maturation rate after 21 h. Also, 0.5 and 5 ng/ml FGF2 reduced the proportion of apoptotic cumulus cells after 21 h culture.;The third study evaluated the role of comprehensive FGFR signal in oocyte maturation and developmental potential. FGFR1 and R2 were dynamically expressed throughout in vitro maturation process and responsive to FSH. Meiotic maturation and cumulus expansion was inhibited by the addition of a FGFR inhibitor, SU5402. This effect was associated with reduced MAPK activity in oocytes. SU5402 and another FGFR inhibitor, PD173074, both inhibited the developmental potential of oocytes.;The last study was completed to determine if FGF2 and FGF10 were still able to increase embryo development when using serum-containing maturation medium. The percentage of embryos with ≥8-cells was improved by FGF10 but not by FGF2. At day 7 and 8 post-IVF, the blastocyst rate and the advanced blastocyst (expanded and hatched) rate were increased by FGF10. The percentage of blastocysts at day 7 was increased by oocyte supplementation with FGF2.;Overall, results indicate that FGFR signaling is involved in regulating oocyte maturation, cumulus expansion and subsequent embryonic development. The characterization of this signaling could lead to the identification of potential markers of oocyte quality and the development of strategies to control female fertility in mammals.