The development of ovarian tissue cryopreservation in Edinburgh: Translation from a rodent model through validation in a large mammal and then into clinical practice.

Ovarian tissue cryopreservation has developed rapidly from its origins in experiments in sheep in the 1990s, and is now becoming recognized as a standard, rather than experimental, procedure. This review summarizes the origins of the technique, and key milestones in its development since the first reported sheep pregnancy in 1994 to the first successful human pregnancy in 2004, and now to the first baby born following cryopreservation of prepubertal ovarian tissue. Many challenges remain to optimize this technique, to improve the survival of follicles within the reimplanted ovarian tissue, to improve its reproducibility and hence the success rate and the lifespan of the graft. The other key area remains the possibility of the grafted tissue containing malignant cells, most importantly in leukemia.