Fertility preservation for prepubertal boys: are we ready for autologous grafting of cryopreserved immature testicular tissue?

Fertility preservation in prepubertal boys is a matter that has been gaining ground fast during the past 20 years. As the life expectancy for childhood cancer survivors continues to increase (5-year survival rate>80%), and as the risk of permanent infertility in adulthood is still high with current treatment options, offering a testicular biopsy to cryopreserve immature testicular tissue (ITT) containing spermatogonial stem cells is now recommended as an experimental option for fertility preservation. Transplantation of cryopreserved testicular prepubertal tissue fragments back to the cured patient appears to be one of the most feasible and promising techniques for fertility restoration. In 2019, the birth of a healthy female baby rhesus monkey after intracytoplasmic sperm injection using spermatozoa recovered from frozen-thawed ITT autografts fueled the hopes of translating the technique to humans. While gonadal tissue autotransplantation has already been successfully achieved in clinical practice for females, it has never been attempted in males to date. In this work, we review acquired knowledge on ITT transplantation in animal models and share our vision on the remaining challenges to autograft currently banked human ITT within pilot clinical trials in the near future.