Mouse oocyte vitrification: the effects of two methods on maturing germinal vesicle breakdown oocytes

Purpose Evaluation of viability and subsequent developmental ability of mouse germinal vesicle breakdown oocytes vitrified in conventional straws. Methods Oocytes with compact cumulus cells were cultured for 3 h in TCM199 medium GVBD and vitrified by two methods: the step-wise and single-step. After vitrification, the oocytes were thawed, and subjected to in vitro maturation and in vitro fertilization. Oocyte survival (postthaw) was assessed by morphological appearance and staining, using propidium iodide (PI)/Hoechst 33342. The oocyte maturation and fertilization rates were examined in vitro. Results In the single-step method the rates of post thaw survival, maturation to metaphase II and cleavage (2-cell embryos) were 58.68%, 56.41% and 38.63%, respectively. In the step-wise method, the corresponding rates were 81.75%, 68.59% and 51.80%, respectively. Conclusion Vitrification of mouse germinal vesicle breakdown oocytes by the step-wise method had the advantag