O-11: Embryo development from oocytes retrieved from cryopreserved human ovarian tissue after heterotopic autotransplantation

Abstract

Ovarian cryopreservation and transplantation has been recognized as a valuable strategy for fertility preservation in cancer patients. Several cases of successful ovarian transplantation, either orthotopic or heterotopic, have been reported. Nevertheless, it is still experimental. To date, only two babies were born after orthotopic transplantation of ovarian tissue, but none with heterotopic transplantation. The purpose of this study was to demonstrate the feasibility of obtaining viable embryos necessary to establish a pregnancy after heterotopic transplantation of cryopreserved human ovarian tissue. Clinical prospective study The study was approved by the institutional review board. A 28-year-old woman with cervical cancer consented for ovarian tissue cryopreservation in 2002 before chemotherapy and radiotherapy. Two years later, the patient requested ovarian tissue transplantation to restore her fertility. Eighteen sections of stored ovarian tissue (5x5x1 mm) were thawed rapidly in a warm water bath (30°C), rehydrated in a stepwise manner, and transplanted into the space between the rectus sheath and the rectus muscle. After transplantation, ovarian function was monitored with serial blood tests (FSH, LH, E2, P4) and ultrasound. Once restoration of the normal ovarian function was established, hormone profiles were obtained weekly, and the ovarian grafts were stimulated with rFSH. When a dominant follicle size reached at 14mm in diameter, 250μg of rhGC was administered, and 36 hours later oocytes were retrieved under ultrasound-guidance. Retrieved oocytes were matured in vitro for 24 hours before fertilization by intracytoplasmic sperm injection (ICSI) technique. Embryos were cultured for 3 days and cryopreserved while waiting for a surrogacy. Restored ovarian function was evidenced by hormonal profiles (FSH 13.5, E2 227.6) about 4 months after transplantation and has remained for more than 2 years. At the same time, a sonogram revealed growing follicles in the graft. The first oocyte retrieval was performed 9 months after transplantation, and the second retrieval was done 5 months after the first one. Total of five oocytes were collected (four MI oocytes and one MII oocyte). Three out of four MI oocytes were developed to full maturity in vitro. All four MII oocytes (1+3) were successfully fertilized by ICSI. Two embryos were cultured in vitro for 3 days before cryopreservation (one 6-cell embryo, one 3-cell embryo). Other two were cryopreserved on day 2, as the embryo quality appeared to be somewhat poor. This study demonstrated that long term ovarian function can be restored by heterotopic ovarian transplantation, and that oocytes retrieved from the ovarian graft can be successfully fertilized. Furthermore, the normal developmental potential of the fertilized oocytes originated from frozen-thawed ovarian grafts was confirmed by 3-day in vitro culture for the first time. Although heterotopic autotransplantation of cryopreserved ovarian tissue can be a viable strategy to restore fertility in cancer patients, the efficacy and safety of this technique should be further investigated before full clinical applications.