Orthotopic grafting of cryopreserved prepubertal testicular tissue: in search of a simple yet effective cryopreservation protocol

Male infertility, due to depletion of spermatogonial stem cells, is a common side effect of gonadotoxic treatments or can be a symptom of a genetic disorder. As prepubertal patients cannot benefit from sperm banking because of the lack of complete spermatogenesis, they will be at risk of life-long sterility. The banking of testicular tissue before spermatogonial stem cell loss followed by auto-transplantation at adult age might be an option. A good cryopreservation protocol is therefore inevitable. Nowadays, most of the centers offering testicular tissue banking use a controlled freezing protocol (CSF). However, this method is expensive and time-consuming.
We evaluated the outcome of two inexpensive and simple freezing methods: uncontrolled slow freezing (USF) and solid surface vitrification on mouse and human testicular tissue. In mice, allografting tissue after both USF and vitrification resulted in a recovery of spermatogenesis similar to fresh samples. In human, USF preserved the seminiferous epithelial, the interstitial compartment and the spermatogonial potential to divide. More cryodamage was observed using CSF or vitrification.
These data provide evidence that USF can be considered as an inexpensive, simple, but efficient alternative for cryopreservation of prepubertal testicular tissue.