Cryobiology of ovarian and testicular tissue.

Cryopreservation of ovarian and testicular tissue can be used in young individuals who are likely to lose their gonadal function prematurely because of chemotherapy, radiotherapy or a known genetic condition causing gonadal failure. Tissue cryopreservation is relatively well established, but freezing techniques have still to be optimized. Slow programmed freezing using propanediol or dimethylsulphoxide as a cryoprotectant is the most established method. Tissue cryopreservation is highly experimental. No human pregnancies have been achieved as yet, although re-implantation experiments have been started. Maturation of gametes in vitro from cryopreserved tissue is far from being clinically applicable. Cryopreservation of spermatozoa and embryos is an established method, whenever applicable. Cryopreservation of oocytes is still experimental, but successful pregnancies have been achieved by several clinics. Cryopreservation of testicular spermatozoa for intracytoplasmic sperm injection (ICSI) is an established method and should be performed whenever a testicular biopsy is being carried out.