Cryopreservation of ovarian tissue: state of the art in 2007

The endeavor to cryopreserve gonadal tissues and gametes in young patients who must undergo severe systemic anti-cancer treatment is entirely focused on the possibility of preserving their fertility potential. In this Review we deal with the development of ovarian tissue cryopreservation and the efforts to optimise the number of variables that appeared to affect frozen tissue survival, particularly the type and the concentration of the cryoprotectants that can best preserve the tissue integrity. We will discuss firstly the need to avoid both freezing and osmotic injury in cryopreserved tissues, secondly the question as to whether it is more useful to preserve follicles or whole ovarian tissue, and finally experiences in the animal model and in human tissues. The clinical application of these procedures are the ultimate focus of the whole discussion: what to do once a patient’s disease is cured and a patient considers reproduction? The clinicians considerations as to whether an auto-graft to the patient or engraft to immunologically nude animals, or indeed an attempt to develop an oocyte to maturity in vitro? Currently, only autografting techniques are able to lead to the resumption of both follicular growth and endogenous hormone production and even to a small number of pregnancies, either spontaneous or IVF-induced. Finally, we review our past experiences of ovarian tissue cryopreservation, from the choice of propanediol as the best cryoprotectant to the choice of the protein support which best assists tissue cryopreservation, and the recent experiences on long-term cultures of follicles from primordial to antral stage.