Follicle Development of Xenotransplanted Sheep Ovarian Tissue into Male and Female Immunodeficient Rats

Background: This study aimed to assess follicle survival after xenotransplantation of sheep ovarian tissue into male and female immunodeficient rats. We evaluated the effects of gonadotropin treatment on follicular development in the transplanted tissue. Materials and Methods: In this experimental study, sheep ovarian cortical strips were transplanted into the neck back muscles of 8 male and 8 female immunodeficient, castrated rats. Fourteen days after surgery, each rat was treated with human menopausal gonadotropin (hMG) for 9 weeks. One day after the last injection, ovarian tissues were removed and fixed for histology assessment. Histology analyses were performed before and after grafting. Estradiol (E2) levels were measured before and after gonadectomy, and at the end of the experiment. The control group consisted of 7 male and 7 female noncastrated/ non-grafted rats and the sham group comprised 7 male and 7 female castrated/ non-grafted rats for comparison of serum E2 concentrations. Results: The percentage of primordial follicles decreased after transplantation in male (25.97%) and female (24.14%) rats compared to the control group (ovarian tissue nongrafted; 37.51%). Preantral follicles increased in the male (19.5%) and female (19.49%) transplanted rats compared to the control group (11.4%). Differences in antral follicles between male (0.06 ± 0.0%) and female (0.06 ± 0.0%) rats were not noticeable compared to control (1.25 ± 0.0%) rats. We observed a significantly higher percent of mean E2 secretion in grafted males compared to grafted females (P?0.05). Conclusion: Despite significant differences in E2 secretion between xenografted male and female rats, we observed no statistical differences in terms of follicular development.