P-80: Histological Assessment and Oestrous Cycle Restoration after Vit-rified-Warmed Rat Ovarian Tissue Autotransplantation, Using Hyaluronic AcidHydrogel Scaffold

Background: Follicular pool is reduced after transplantation of vitrified ovary. Therefore, methods should be improved to accelerate ovarian function revival and maintain follicular reserve. In this study hyaluronic acid hydrogel as a scaffold was used to improve restoration of ovarian oestrous cycle. Materials and Methods: 79 mature (~8 weeks) rats having normal estrous cycles were divided into two groups: control group (vitrified-warmed ovarian transplant n=39) and the experimental group (vitrified-warmed ovarian transplant that encapsulated with HA n=40). Each group was divided into three subgroups (a: three days after transplantation, b: one full estrous cycle after transplantation and c: five estrous cycles after transplantation). In all groups, ovaries were vitrified and warmed before intramuscular autotransplantation. Histological and oestrous cycle activity of autotransplanted animals were then assessed. Results: Our results showed that in the control group, 37 (94/87%) and in experimental group 36 (90%) of surgeries were successfully transplanted. The first full cycle and 5th full cycle were seen respectively 12-23 and 28-43 days after transplantation in experimental group. 36 (33/33%) rats had irregular cycles in this group. In the control group, these cycles completed 11-20 and 28-35 days after transplantation and 5 (26/31%) rats also showed irregular cycles. 3 days after transplantation in each group, all follicles except primordial and some primary follicles were atretic. Histological assessment of the ovarian graft with regular cycle showed that the average number of primary follicles per section increased in b subgroup of experimental group. There were no significant differences in number of other follicles between the groups. Conclusion: Oestrous cycle restoration and ovarian follicular reserve was similar between the two groups. It seems that hyaluronic acid hydrogel is not sufficient alone to accelerate return.