Time Course of Follicular Development after Bovine Ovarian Tissue Transplantation in NOD SCID Mice

HERNANDEZ-FONSECA, H. J.; BOSCH, P.; SIRISATHIEN, S; WININGER, J. D.; MASSEY, J. B.; BRACKETT, B. G.

USA

Congreso; 57 Annual Meeting of the American Society for Reproductive Medicine; 2001

American Society for Reproductive Medicine

Objective: To preserve potential fertility many young female cancer patients are electing to have ovarian tissue cryopreserved before being exposed to chemotherapy. Xenotransplantation of this tissue into immunodeficient mice has resulted in the development of antral follicles. Antral development is dependent on gonadotropins and the presence of gonadotropin-dependent secondary follicles. However, the time course of follicular development in xenografted ovarian tissue has not been characterized in any species. The aim of this study, using a bovine model, was to determine the appropriate interval for xenotransplanted ovarian tissue to develop gonadotropin-responsive follicles. Design: Prospective randomized study. Materials/Methods: A total of 12 male NOD SCID mice (6-8 weeks of age, Jackson Laboratories, Bar Harbor, ME) were anesthetized and 3-4 pieces of newborn calf ovarian cortico-medullary tissue were transplanted in dorsal subcutaneous spaces. Just before (day 0), and at increasing intervals after surgery (i.e. on days 20, 55, 84, 124 and 160) 2-3 mice were euthanized and grafts were recovered, fixed in Bouins and embedded in paraffin. Six-micron sections (40 sections/ graft) were stained with hematoxylin and eosin. Five high magnification fields (HMF, 400 X) were examined per section. In each HMF follicles were counted and classified as primordial, primary, secondary or antral. Only follicles containing an oocyte with visible nucleolus or primordial follicles containing an oocyte with distinct nuclear membrane were counted. Percentage of growing follicles (primary and secondary stage) at different intervals was analyzed by ANOVA. Differences among means were determined by protected LSD. Results: For each category of follicles data is presented as percentage of the total number of follicles counted. Results showed an increase (p<0.05) in the proportion of the primary and secondary follicles on day 124 after surgery (59%) compared to non-grafted (day 0, 17%) and previous intervals (day 20, 21%; day 55, 10% and day 84, 15%) accompanied by a decrease in proportions of primordial follicles. These results suggest increase in the proportion of primary and secondary follicles due to progressive development of primordial follicles. Preliminary results on day 160, show even greater increase especially in the relative proportion of primary and secondary follicles (86%).