I-12: Optimal Strategy toward Fertility Preservation: In Vivo and In Vitro Post-Thaw Options in Gamete, Embryo and Ovarian Tissue Cryostorage

Background: Oocyte, embryo and ovarian tissue cryopreservation are proposed for fertility preservation to cancer patients who hope to be mothers after getting rid of the disease. Materials and Methods: Embryo cryopreservation is not possible for unmarried single girls without sperm partner and oocyte retrieval is a long time procedure. Thus ovarian tissue cryopreservation is suggested for fertility preservation. The main goal of ovarian cryopreservation is getting back of tissue in to the body in order to fertility and hormonal cycle restoration. Different cryopreservation methods have been performed including vitrification of biological samples. In the recent years, whereas many studies have focused on using of different carriers, we used Cryopin, as a novel tool, so as to plunge the ovarian tissue into the nitrogen. Although successful ovarian tissue re-implantation could help the patients who want to be a mother, the malignancy returning to the original place is still remained a concerned issue. To find a solution, ovarian tissue (organ) or isolated follicle culture and xeno-grafting are safer and possible methods to obtain a mature oocyte ready for fertilization. Results: In seven years experience, vitrification mostly could help us to reach to our scientific aims in fertility preservation. To obtain enough healthy vitrified-warmed embryos, 93.89% were considered as surviving embryos. Re-vitrifying 4-cell mouse embryos using closed pulled straw (CPS) was not discernibly detrimental to embryos. In the case of blastomere damage after vitrification, both laser assisted hatching (LAH) and necrotic blastomere removal (NBR) techniques could reduce the incidence of embryo cell death, but have no significant effect on development and cell number. In comparison of different ovarian vitrification methods, because of the better primordial follicular preservation and more survivability, it appears that the combination of EG + DMSO with sucrose is better suited for vitrification of human, sheep, monkey and rat ovarian tissues, particularly at the initial stage could relatively restore ovarian function after vitrification and autotransplantation. Additionally, fewer cell death incidences occurred after 2-step dehydration procedure as compared to the 4-step vitrification method and using of therapeutic ultrasound may accelerate and increase re-angiogenesis and can help to promote ovarian follicular growth. Ultrastructural changes of the vitrified ovaries using EG + DMSO with sucrose, were considerably compared to the control but this result did not differ in comparison to the sucrose-free group. Both of the vitrified and nonvitrified ovarian autotransplantation caused restoration of the hormone cycle and ovarian function; these results approximated the controls after gonadectomy. In the last groups the percentage of follicular maturation and ultrastructure of transplanted ovaries were in better condition. Also the rate of expression of angiogenic factors in all of the transplanted ovaries, were comparable with the control ones (non-published data). Conclusion: Although vitrification is a reliable method for cryostorage of gamete, embryo and ovarian tissue, now it is a challenge that: can vitrified oocyte, embryo or ovarian tissue lead to a completely healthy delivery? And this is the main future vision in the field of fertility preservation.