Significance Of Epidermal Growth Factor (EGF) In The In-Vitro Maturation Of Immature Oocytes And The Correlation Analysis

Objective: To investigate the significance of EGF in the in-vitro maturation, fertilization, and pre-implantation development of the immature oocytes. Methods: The immature oocytes were acquired from the ovaries of the hCG-stimulated and non-hCG-stimulated rats. The germinal vesicle (GV) oocytes were cultured in the different EGF solutions with concentration of 0(control), 0.5, 1, 2.5, 5 and 10ng/ml Ham's F10 culture media. Observations were made for the status of germinal vesicle break-down(GVBD) and the extrusion of the first polar body(PB1). The achieved Mâ…¡oocytes were then inseminated in-vitro; and the pronuclei(PN) and the pre-implantaon development were observed. The gradeâ… ~â…¡4-cell embryos were selected and implanted into the fallopian tube of the rats with the 1 day pseudogestation. Follow-up observations were made till the delivery. Results: Observations showed that after being cultured via in-vitro maturation in the EGF solutions with concentration of 1, 2.5, 5 and 10ng/ml Ham's F10 for the period of 12, 16, 20, and 24 hours, the GVBD in the GV cumulus-oocyte complexs(COC) occurring in both the hCG-stimulated and non-hCG-stimulated groups have better outcomes than that of the control group(P<0.05,P<0.01). After being cultured for 20, 24, and 36 hours in the 2.5, 5 and 10ng/ml EGF cases, the elimination ratio of PB1 was higher than that of the control group(P<0.05,P<0.01) , particularly the 5ng/ml EGF(P<0.01). The peak times of the GVBD and PB1's occurrence for the G-UPR group were in 20~24 hours and 24-36 hours; while the peak times were in 12-16 and 20~24 hours for the G-PR group. The degenerating rates of the two COC groups cultured in the 1, 2.5, 5 and 10ng/ml EGF were lower than that of the control group(P<0.05,P<0.01). The fertilization rate of the oocytes in the G-UPR and G-PR groups, and the incidence rate of 2-cells and 4-cells in the 5ng/ml EGF were higher than that of the control group; and the difference was significant(P<0.01). After implanting the embryos into the female rat's uterine, we obtained the normal live offspring. Conclusion(s): The study indicated that EGF not only promoted the maturation of COC in the GV phase, but also promoted the fertilization and pre-implantation development. It inhibited the apoptosis of the oocytes during the maturation; and promoted the cumulus spreading. The enhancing effect of EGF was closely related to the dosage of EGF. Stimulation with gonadotrophin can speed up the maturation of the oocytes, and enhance the fertilization rate.