Determination of effective dosage of FSH and hCG in the maturation of preantral follicles and enclosed oocytes in mice

Background: In vitro maturation (IVM) of oocytes reduces the costs and averts the side-effects of gonadotropin stimulation for in vitro fertilization (IVF). Reliable IVM is an intellectual, scientific and clinical challenge with a number of potential applications. Objective: The effect of hCG was evaluated on the timing and regulation of in vitro ovulation for the Syrian mice oocytes in the presence and absence of FSH. Materials and Methods: Preantral follicles, isolated from the ovaries of 6 weeks-old mice, were cultured in TCM-199 medium. The effect of 10-200 mIU/ml FSH and 1.5 IU/ml hCG was seen on the follicle maturation, as well as the changes in ovulation capacity of enclosed oocytes, after the incubation period of 6 days at 37 °C, 92% humidity and 5% CO2 in air. Results: 100 mIU/ml FSH showed increased follicle diameter, survival, germinal vesicle breakdown (GVBD) and oocyte maturation rates (p<0.0001). Significantly higher number of follicles showed cumulus attachment when ovulation started within 16-24 hours post hCG (97% and 80% respectively; p<0.0001) as compared to the cultures without hCG or when the ovulation time increased from 24 hours post hCG. Combination of FSH and hCG showed 97% (p<0.0001) ovulation as compared to that seen for FSH-containing medium only (81%) or control (10%). Conclusion: The combined administration of 1.5 IU/ml hCG and 100 mIU/ml FSH induces the in vitro follicle maturation, ovulation capacity and proper timing of mice oocytes.