ABSTRACT
Improving pregnancy rate associated with the use of cryopreserved oocytes would be an important advancement in human Assisted Reproductive Technology [ART]. Vitrification allows glasslike solidification of a solution, a physical process, without ice crystal formation in the living cells. The purpose of this study was to evaluate the viability of the oocytes, in vitro maturation and embryo development vitrified germinal vesicle oocytes after single and stepwise exposure to cryoprotectants. Germinal vesicle oocytes or without cumulus cells were transferred to a verification solution composed of 30% M sucrose [v/v] ethylene glycol, 18% [w/v] Ficoll-70, and 0.3 M sucrose either by single step or in a step-wise fashion. After verification and storage in liquid nitrogen, the oocytes were thawed and washed twice in the medium TCM 119 and then subjected to in vitro maturation, the capacity of fertilization and embryonic development to 2-cell were examined in vitro. The oocytes surviving, maturing to MII, fertilization developmental rate in the step-wise exposure were significantly higher [P<0/05], compared with the corresponding rate in single step procedure. The results of the present study indicated that oocytes vitrified with cumulus cells and stepwise procedure had a positive effect on the maturation and developmental rate than oocytes without cumulus cells and single step procedure