Vitrification and Subsequent In Vitro Maturation of Mouse Preantral Follicles in Presence of Growth Factors

OBJECTIVE Cryopreservation of ovarian tissue or follicles has been proposed as an alternative method for fertility preservation. Although successful vitrification of follicles has been reported in several mammalian species, the survival rate is generally low. The aim of this study was to investigate the effects of fibroblast growth factor (FGF) and epidermal growth factor (EGF) on in vitro preantral follicle development after vitrification. MATERIALS AND METHODS In this experimental study, preantral follicles with diameter of 150-180 µm were mechanically isolated from ovaries of 18-21 days old NMRI mice. Follicles were vitrified and warmed, then cultured in a-minimal essential medium (α-MEM) without growth factor supplementation as control group (group I), while supplemented with 20 ng/ml FGF (group II), 20 ng/ml EGF (group III), and 20 ng/ml FGF +20 ng/ml EGF (group IV). After 12 days, human chorionic gonadotrophin (hCG)/EGF was added to culture medium, and after 18-20 hours, the presence of cumulus oocyte complexes (COCs) and oocyte maturation were assessed. The chi-square (Χ(2)) test was used to analyze survival and ovulation rates of the follicles. RESULTS Our results showed that the rate of metaphase II (MII) oocytes in FGF group increased in comparison with control and other treatment groups (p<0.027), but there was no difference between control with EGF and EGF+FGF groups in oocyte maturation rate (p>0.05). There was a significant decrease in survival rate of follicles in EGF+FGE group in comparison with other groups (p<0.008). After in vitro ovulation induction, the follicles in EGF group showed a higher ovulation rate (p<0.008) than those cultured in other groups. CONCLUSION FGF has beneficial effect on oocyte maturation, and EGF increases COCs number in vitro. Combination of EGF and FGE decreases the number of survived follicles.