Oocyte maturation, follicle rupture and luteinization in human cryopreserved ovarian tissue following xenografting

BACKGROUND: Previous studies have demonstrated development of antral follicles in cryopreserved human ovarian tissue after autografting and xenografting, thus indicating successful preservation of follicular function. The study aim was to assess whether these follicles could also undergo periovulatory changes in response to hCG. METHODS: Ovarian tissue from three patients were dehydrated in propanediol (PROH)/sucrose and cryopreserved using the slow cooling/rapid thaw procedure. Thawed tissue was placed under the kidney capsule in immunodeficient mice. Following growth (>20 weeks) in the presence of gonadotrophin, hCG was administered and ovarian tissue examined histologically. RESULTS: Thirty-two antral follicles (diameter range 0.6 to 5 mm) were examined. Histological evidence of a response to hCG was evident in all follicles. Disruption of the concentric layers of mural granulosa and theca cells was apparent in all antral cavities. In 17 (53%) follicles the exterior follicular wall had reduced to a few cells thick, and in eight (25%) the wall had ruptured. Mucified oocyte-cumulus cell complexes were present in 32 follicles, 17 of which had begun to detach from the pedicle. Resumption of meiosis had occurred in over half the oocytes (five metaphase II and seven metaphase I oocytes, eight germinal vesicle breakdown). Two corpora lutea were also detected. CONCLUSIONS: Follicles cryopreserved within human ovarian tissue using the PROH procedure, can develop to the antral stage and undergo periovulatory changes following xenografting and exposure to a luteinizing stimulus.