ABSTRACT
Vitrification of ovarian tissue is an effective method for preservation of fertility. Many attempts have been made to improve cryopreservation conditions. The aim of this study was to compare the effects of two vitrification methods using two carrier systems; straw and cryolock, on the morphology of neonatal mouse ovarian tissue. In this experimental study we used NMRI 7-day-old mice. Their ovaries were excised and divided into non-vitrified, vitrified with straw, vitrified with cryolock and toxicity test groups. In vitrification group, the ovaries were dehydrated in a mixture of 40% ethylene glycol, 30% ficoll 70 and sucrose [EGFS40] for 5 min.Then they were put in a plastic straw or cryolock and were placed into liquid nitrogen and stored for one week. Whereas in the toxicity test group the ovaries were exposed to the cryoprotectant EGFS40 and warming solution procedure without using liquid nitrogen. Then we studied the morphology of ovarian follicles by means of light and electron microscopes. No significant differences were observed between the groups in regard to the percentages of primordialand primary follicles with normal morphology. But the percentages of normal preantral follicles in the vitrified group using straw were significantly lower than those of other groups. Ultrastructural studies showed signs of degeneration and nuclear shrinkage in follicular cells in some of the preantral follicles in vitrified group using straw. Vitrification of ovarian tissue using cryolock is more effective for preserveration of the normal morphology of ovarian tissue, compared to vitrification by using straw