Optimizing the Outcome of Grafted Ovarian Tissue: Exogenous Gonadotropins to Increase Microvessel Density and Follicular Survival

Background: Fertility preservation by ovarian cryopreservation and heterotopic ovarian transplant is hampered by ischemic damage of the transplanted graft and poor oocyte viability. Design: Two longitudinal experiments were done - phase A: to evaluate if the administration of gonadotrophins (hMG) or vascular endothelial growth factor (VEGF) increases follicular survival after heterotopic autologous ovarian transplantation, and phase B: to determine if the administration of hMG enhanced neovascularization by increase in microvessel density in the heterotopic xenologous ovarian transplant. Methods: A: In three sheep, ovaries were removed and immediately transplanted into the abdominal wall. In one sheep, VEGF was administered at the transplantation site during surgery, the second was treated with hMG after transplantation for 2 weeks, and the third sheep served as control. B: The ovaries from two other sheep were removed, prepared in tissue pieces, and immediately grafted into the subcutaneous space of several combined immunodeficient (SCID-)mice (n=20). Following the transplantation, 10 of these mice (group 1) were treated with hMG until they were sacrificed, the other 10 untreated mice (group 2) served as controls. In each group, two mice were sacrificed at intervals of 2,4,6,10, and 14 days after grafting to permit histologic examination of the grafted tissue. Results: A: Whereas VEGF had no effect on follicular survival after transplantation (12.0% vs. 7.4%.),the administration of hMG increased follicular survival (12.0% vs. 29.0%). B: The use of hMG resulted in significantly higher numbers of microvessels per mm 2 (mean) at all of the time points studied - at 2 days 22 vs. 13 (p < 0.001), 4 days 22 vs. 13 (p < 0.001), 6 days 17 vs. 13 (p = 0.006), 10 days 28 vs. 12 (p < 0.001), and 14 days 35 vs. 16 (p