[Freezing effects on the in vitro development of mice preantral follicles]

Comparison of in vitro development, survival and oocyte maturation rates of mice preantral follicles frozen by various methods.Cryopreservation of the germinal cells using the slow freezing method for entire ovary (Ova Cong) or isolated preantral follicles (Iso Cong) and vitrification in a closed system of isolated preantral follicles (Iso Vitr). Non-freezing follicles were considered as the control group. The four groups were simultaneous cultured for 12 days in a microdrop system. At each day of the culture, mean diameter was measured and at the end of the culture, follicular survival and mature oocyte rates were compared.Iso Cong and Ova Cong follicles achieved a smaller diameter (423.0 ± 47.1 μm et 450.3 ± 15.7 μm, respectively) than control group (680.7 ± 12.3 μm) at the 12th day of culture. At the end of the culture 6.21 % of Iso Cong follicles, 53.41 % of Ova Cong follicles and 83,77 % of Control follicles were alive. Mature oocyte rates were similar for the cryopreserved groups, 44.4 % for Iso Cong group and 44.7 % for Ova Cong group, but smaller than the Control group with 90 % of mature oocytes. Only 1/171 of the Iso Vitr follicles survived to the culture.This study shows that mice's ovarian follicles can grow in vitro after cryopreservation but their diameter, survival and oocytes maturation rates are smaller than in the control group.