P-170: Animal Models of Human Artificial Ovary, Valuable Tools for Fertility Preservation in Cancer Patients

Background: With all the recent advances in cancer treatments, many young cancer patients find themselves facing the prospect of losing their fertility after aggressive chemotherapy or radiotherapy. Cryopreservation of ovarian cortical tissue has emerged as a potential option to restore fertility in these young women. Materials and Methods: Because autotransplantation of cryopreserved ovarian cortex carries the risk of reintroducing cancer to the patient in remittance, xenotransplantation of frozen-thawed ovarian cortical tissue to immunodeficient animal hosts has been suggested as an alternative, whereby primordial follicles are activated in an immunocompromised animal model and after initial growth are transferred to an in vitro culture system. This approach eliminates the risk of cancer cell reintroduction, and in addition, the hitherto unaccomplished phase of primordial follicle culture is bypassed. This combination of in vivo transplantation and in vitro culture to trigger maturation of primordial follicles has already been achieved in mouse models. Results: Several grafting techniques, including heterotopic or orthotopic, have been reported basically differing only in the location to which the ovarian grafts have been transplanted, such as the bursal cavity, the kidney capsule, and subcutaneous sites. Furthermore, several types of grafts have been reported, including xenotransplantation of human ovarian cortex or isolated primordial/ preantral follicles combined with extracellular matrix (artificial ovary) or without it, to immunodeficient mice. Conclusion: Xenotransplantation of isolated primordial/ preantral follicles combined with extracellular matrix represents a valuable tool for the study of preantral follicular development and will continue as such as long as routine in vitro development of matured follicles derived from primordial follicles, which is unavailable for other species than the mouse. Given the low availability of human reproductive tissue for research purposes, animal models can offer interesting alternatives.