Cryopreservation of ovarian tissue for a decade in Denmark: a view of the technique

This paper presents the Danish 10-year experience (1999–2009) with cryopreservation (n = 386) and autotransplantation of ovarian tissue (n = 18). Before applying the technique to humans, the method was thoroughly tested and validated. The cryoprotectant solution was chosen after histological evaluation of mouse and human ovarian tissue after freezing with four different combinations of cryoprotectants. Viability was confirmed by transplantation of frozen–thawed human ovarian tissue (n = 49) to oophorectomized Nude mice. Viability after transport of fresh tissue 4–5 h prior to freezing had previously been validated. Overnight transport of fresh ovarian tissue prior to cryopreservation was evaluated when human ovarian tissue was kept on ice for 20 h and then cryopreserved. The thawed ovarian tissue was transplanted to an oophorectomized Nude mouse and histology confirmed viability. In Denmark 12 women have received a total of 18 autotransplantations of ovarian tissue. All women resumed ovarian function and three healthy babies were born to two women. In both women, the tissue was transported on ice for 4–5 h prior to cryopreservation. Ovarian tissue cryopreservation is an important method for fertility preservation; however, before applying the method clinically, each laboratory should perform thorough validation of their technique.Young female patients with cancer may be deprived of future fertility due to the side-effects of cancer treatment. This paper presents the Danish 10-year experience with development and validation of techniques to preserve female fertility. One method, which has been an area of interest in Denmark, is freezing of ovarian tissue. The tissue is taken out surgically before the toxic chemotherapy is initiated and can be transplanted back to the patient if she is cured and has become infertile because of the treatment. However, before the method was used on humans, we performed a series of laboratory and animal experiments to ensure the survival of the tissue and the safety of the technique. Once the protocol had been validated, the clinical use of the technique was implemented. To date, we have frozen the ovarian tissue of almost 400 patients and 12 patients have received transplantation with their own frozen–thawed tissue. So far, three healthy children have been born in Denmark as a result of the procedure. We conclude that freezing of ovarian tissue is an important part of preservation of fertility in young patients with cancer but each centre should validate their protocols prior to applying the technique to humans.