Oocyte recovery, embryo development and ovarian function after cryopreservation and transplantation of whole sheep ovary

BACKGROUND: Successful cryopreservation of a whole ovary may provide a solution for women with premature ovarian failure. The aim of this study was to evaluate the function of cryopreserved whole sheep ovaries both in vitro and in vivo. METHODS: Transplantation of frozen-thawed intact ovaries was performed on eight sheep by artery and vein anastomosis to the contralateral ovarian artery and vein. The remaining ovary was removed. Oocyte aspiration was performed 1 and 4 months post-transplantation. Serum progesterone levels were measured after 24 and 36 months. Magnetic resonance imaging (MRI) was carried out 12 months after transplantation. RESULTS: Progesterone activity was detected in three sheep from 24 to 36 months post-transplantation. Oocyte retrieval was successful in two sheep and parthenogenic activation has resulted in embryonic development up to the 8-cell stage. MRI revealed an intact ovary with small follicles and intact blood vessels. CONCLUSIONS: Whole ovaries, and the follicles and blood vessels they contain, are able to survive cryopreservation. In addition, MRI has shown that blood vessels were intact and that normal blood flow had resumed to the transplant. We conclude that immediate and long-term hormonal restoration and normal ovulation is possible after cryopreservation and transplantation of whole ovaries in sheep.