Title: Impact of gonadotropins on oocyte fertilization and early embryo development competence in vitro: an animal model
Abstract: OBJECTIVE: To determine the impact of gonadotropins, either singly or in combination in a dose-response manner on the rates of oocyte fertilization and early embryo development in vitro. DESIGN: Prospective experimental study. MATERIALS AND METHODS: A total of 1500 bovine cumulus-oocytes complexes (COC) were matured in TCM-199 supplemented with 10% FBS in either experimental groups (EGs) (40IU/mL, respectively) or control group (CG) (No hormones). EG1: Repronex+Follistim (R+F); EG2: Menopur+Follistim(M+F); EG3: Repronex +Bravelle(R+B); EG4: Menopur+Bravelle(M+B); EG5: Repronex+Gonal F (R+G); EG6: Menopur+Gonal F(M+G). Following 24 hours of maturation, in vitro fertilization was performed. At 18 to 20 h post-insemination, presumptive zygotes were transferred to SOF supplemented with 10% FBS at 39oC in 5% CO2. The cleavage rates of zygotes and early embryo developments were determined. RESULTS: Fertilization rates were 67.8% (R+F), 68.2% (M+F), 71.5% (R+B), 68.7% (M+B), 72.1% (R+G), 63.1% (M+G) and 33.9% (CG) (P<0.01, EG vs. CG). The rates of 8-16 cells and morula-blastocyst stages in EGs and CG, were 33.3% and 21.2% (R+F); 34.1% and 20.5% (M+F); 40.0% and 26.0% (R+B); 50% and 31.6% (M+B); 50.0% and 30.0% (R+G); 41.5% and 26.8% (M+G); 31.3% and 25.0% (CG); respectively. CONCLUSIONS: Specific combinations of gonadotrophins may change the rate of early embryos development (8-16 cells), morula-blastocyst formation is similar. These data provide support for the responsiveness of bovine oocytes to gonadotrophins in vitro and the need to consider the ratio of combination (FSH/LH or hCG) for optimization of oocytes maturation competence. The results of this study could be applied to clinical therapeutically stimulation protocols and help improve IVF success rates.