Gonadal tissue cryopreservation and transplantation

Transplantation of ovarian and testicular tissue has been practised for over a century, mainly for experimental purposes. It is now being considered as a potential strategy for preserving fertility in young patients, including children, undergoing sterilizing treatment for cancer and other diseases. Ovarian tissue biopsies can be stored at liquid nitrogen temperatures indefinitely so that, after thawing, they can be returned as either ortho- or heterotopic grafts to the original patient. A different approach is needed for preserving male germ cells to restore fertile potential. Experimental studies have shown that spermatogonial stem cells injected into the rete testis/seminiferous tubules can re-initiate spermatogenesis after sterilizing treatment with alkylating agents; alternatively, in prepubertal cases, testicular biopsies that have been cryopreserved can be grafted subcutaneously to generate enough spermatozoa for intracytoplasmic sperm injection (ICSI). These strategies have been demonstrated in animal models and are now undergoing clinical testing.