[Capability of oocyte maturation in human cryopreserved ovarian tissue following xenografting].

Objective: To investigate the development and maturation competence of oocytes retrieved from cryopreserved and transplanted human fetal ovarian tissue by techniques of tissue culture, inducing ovary, oocyte retrieval, and in vitro maturation (IVM).

Methods: Fetal ovaries of 20 weeks were frozen-thawed and cultured for 6 days in vitro, then xenografted into kidney capsules of immunodeficient mice. All mice were stimulated with follicle stimulating hormone every second day for 23 weeks, starting 1 week after grafting. Then oocytes were retrieved from antral follicles 13 hours after human chorionic gonadotrophin injection. IVM was performed to evaluate the maturation competence of the oocytes from ovarian grafts. Human fetal ovarian tissues were examined with histological and proliferating cell nuclear antigen (PCNA) evaluation.

Results: There was no difference between fresh ovarian tissues and frozen-thawed ovarian tissues in the percentage of follicles at different growth stages (P > 0.05). The proportion of the primary follicles and preantral follicles in the cultured ovarian tissues was significantly larger than that of fresh ovarian tissues and frozen-thawed ovarian tissues (P < 0.05). The proportion of the primary follicles, preantral follicles, and antral follicles in the transplanted ovarian tissues was significantly higher than that of cultured ovarian tissues, fresh ovarian tissues, and frozen-thawed ovarian tissues (P < 0.05). No significant signals of PCNA in the primordial follicles in all ovarian tissues were observed. PCNA immunoreactivity first appeared in primary follicles. However, the obviously positive signals of PCNA were seen in the oocytes and/or the granular cells of cultured ovarian tissues and transplanted ovarian tissues. Oocytes from antral follicles were collected and matured in vitro, and 21.43% of the oocytes reached to MII within 48 hours IVM.

Conclusions: Human ovarian follicles can survive and develop well after cryopreservation, tissue culture, and xenotransplantation. Furthermore, oocytes recovered from grafts have normal maturation competence.