Influence Of Growth Hormone And Insulin-like Growth Factor-I On The In Vitro Maturation Of Mouse Oocytes

Objective: To determine the effect of growth hormone (GH) and insulin-like growth factor-I (IGF-1) on the in vitro maturation of mouse oocytes.Methods: Mouse were executed by cervical vertebra luxation. Premature oocytes were extracted and divided randomly to four groups at the density of 15~20/well, then cultivated in four 96-well plates containing different drugs respectively. Each well was added with 90μlα-MEM. The other additions to group 1 were 10% FCS, 0.075 U/ml FSH and 0.05 U/ml hCG; group 2 were 50 ng/ml IGF-1 and others same as that of group 1; group 3 were 100 ng/ml GH and others same as that of group 1; group 4 were 50 ng/ml IGF-1, 00 ng/ml GH and others same as that of group 1. All were cultured at 37°C in a 5%CO2 incubator for 24 hours. After incubation oocyte maturation was identified by phase contrast microscope. According to the observation index as germinal vesicle rupture (GVBD) and first polarbody discharge (MII), the results were classified into two groups as GVBD and MII. We only analyzed the adosculation and the result of embryonic development of MII. The significance test of rates was performed using the chi-square test including oocyte maturing rate, fertility rate and blastulation rate.Result:A total of 625 ova were investigated, after IVM 459 matured, 276 fertilized and 101 blastulation. Cultured with IGF-1, the ovum maturation and fertilization of group 2 were not different, only the two-cell rate was obviously increased, compared to that of group 1 (75.93% vs 57.14%,P<0.05). The ovum maturation rates of group 3 and 4 incubated with GH were remarkably increased with 84.11% and 78.46%, respectively (P<0.01 and P<0.05, respectively); and the blastulation rates were also notably elevated with 40.70% and 42.42%, respectively (P<0.05, both).Conclusion:Addition with GH can significantly elevate the maturation rate, fertility rate and blastulation rate of IVM. Addition with IGF-1 can only increase the postfertilization two-cell rate and have no effect on ovum maturation rate. There are no significantly differences between ovum maturation rate, fertility rate and blastulation rate of the group treated with the combination of GH and IGF-1 and that of the group treated with GH alone (P>0.05). Compared to the GH alone group, the two-cell rate and blastulation rate of the combination group have increased tendencies which are of no statistical significance. Therefore, under this culture condition, GH could promote the maturation and embryonic development of oocyte in vitro; IGF-1 could improve embryonic development, but could not improve the GH promotion further.