Assessment of long-term function of heterotopic transplants of vitrified ovarian tissue in cynomolgus monkeys.

BACKGROUND: Ovarian tissue cryopreservation by rapid cooling (vitrification) is a convenient fertility preservation option. However, the progress of vitrified ovarian tissue after transplantation is not well understood in primates.

METHODS: For tissues from cynomolgus monkeys, we used closed straw vitrification and open cryosupport vitrification in which tissues are immersed directly into liquid nitrogen. Following warming, ovarian cortical pieces were autotransplanted and their function was monitored by computed tomography (CT), hormone assays and oocyte recovery, ICSI and embryo transfers (ETs).

RESULTS: Hormone cycles were restored in 6 of 7 animals in a mean of 126 days with no significant difference between the two vitrification regimens. The presence of new blood vessels supplying the grafted ovarian tissue was confirmed by contrast-enhanced CT. Oocyte retrieval from two monkeys after transplantation of the ovarian cortex vitrified by cryosupport vitrification yielded a total of nine oocytes of which six fertilized after ICSI, but ETs did not lead to any pregnancies.

CONCLUSIONS: This work shows that CT can give insight into ovarian function after heterotopic transplantation, and that heterotopic autografts of vitrified ovarian cortex can give rise to long-term ovarian function and embryos in a primate model. It remains to be established how outcomes following rapid vitrification compared with outcomes following conventional slow cooling procedures.