Article title: In Vitro Maturation and Embryo Development to blastocyst Mouse Germinal Vesicle Oocytes after Vitrification

Vitrification is a simple and ultra rapid technique for the conservation of fertility. Improving pregnancy rate associate with the use of cryopreserved oocytes would be an important advanced in human assisted reproductive technology (ART). The purpose of this study was to evaluate viability oocytes, In vitro maturation and embryo development vitrified germinal vesicle oocytes after single and stepwise exposure to cryoprotectants. In this experimental study, germinal vesicle oocytes with or without cumulus cells were transferred to vitrification solution which was composed of 30% (v/v) ethylene glycol, 18% (w/v) Ficoll-70, and 0.3 M sucrose, either by single step or in a step-wise way. After vitrification and storage in liquid nitrogen, the oocytes were thawed and washed two times in medium TCM119 and then subjected to in vitro maturation, fertilization and culture. Data analysis was performed by one-way variance and Tukey tests. The oocytes survival rates after vitrifying-warming, maturation rate, the capacity of fertilization and embryonic development to Blastocyst were examined in vitro. The oocytes surviving, maturition and embryo developmental rate in the step-wise exposure were significantly higher (P<0/05) compared with corresponding rate in the single step procedure. The results of present study indicated that oocytes vitrified with cumulus cells and stepwise procedure had positive effect on survival, maturation and developmental rate to blastocyst than oocytes without cumulus cell and single step procedure.