Follicular development after transplantation of adult bovine ovarian tissue into male NOD SCID mice

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

Lisbon, Portugal

Congreso; European Society of Human Reproduction and Endocrinology Meeting; 2001

European Society of Human Reproduction and Endocrinology

Aim: 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. However, the time course of follicular development in the xenografted ovarian tissue has not been adequately characterized in any species. Our goal was to determine the appropriate interval for xenotransplanted ovarian tissue to develop gonadtropin-responsive follicles in a bovine model. Methods: A total of 12 male NOD SCID mice (6-8 weeks of age, Jackson Laboratories, Bar Harbor, ME) were anesthetized and 1 piece of ovarian cortical tissue obtained from a 2 year-old cow was transplanted into dorsal subcutaneous space. Just before (day 0), and at increasing intervals after surgery (i.e., on days 20, 55, 84, and 124) 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 magnifications 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 a visible nucleolus or primordial and intermediary follicles containing an oocyte with a distinct nuclear membrane were counted. Percentages of growing follicles (primary and secondary stage) at different intervals were analyzed by ANOVA. Differences among means were determined by protected LSD. Results: For each category of follicles data is presented as a percentage of the total number of follicles counted. Results showed an increase (P<0.05) in the proportion of primary and secondary follicles on day 55 after surgery (52 and 48%, respectively) compared to non-grafted (day 0, 6 and 0%, respectively) accompanied by disappearance of primordial follicles, i.e., decrease from 94% at day 0 to 0% on day 55. These results suggest a sudden increase in the proportion in the primary and secondary follicles due to progressive development of primordial follicles. This increase of the proportion of primary and secondary follicles was maintained on days 84 and 124, with a noticeable increase in the proportion of secondary follicles which by day 124 constituted 65% of all follicles counted compared to only 24% for primary follicles. These results differ from those using a newborn calf model (unpublished data) by apparently more rapid development here. Conclusion: In the adult bovine model a greater proportion of primary and secondary follicles emerge around 55 days after xenotransplantation of ovarian cortical tissue into male NOD SCID mice.