Researchers from the Vrije Universiteit Brussel have reported that cryopreservation of testicular tissue may offer a viable strategy to preserve fertility in patients exposed to genotoxic therapies during childhood. The findings, described in a paper that has not yet been published, were presented by Francesca Tondo, biologist at Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico in Milan, Italy, during the 9th National Congress of the Italian Society of Human Reproduction, entitled “Reproductive Medicine 4.0: New frontiers and Strategies for Integrated Health,” held on April 16-18 at the University of Siena in Siena, Italy.

“Last year, the researchers in Belgium reimplanted fragments of testicular tissue into an adult man that had been collected during his childhood and cryopreserved. After 1 year, in March 2026, the tissue was removed again and examined. Researchers confirmed that sperm production was activated within the fragments,” Tondo said.

“This is a crucial step for reproductive medicine. For the first time worldwide, it has been shown that testicular tissue can be frozen and later reactivated in humans. For prepubertal patients, who cannot preserve semen, this opens up a possibility that until now had only been theoretical.”

Adult women and men undergoing genotoxic treatments, including chemotherapy with alkylating agents, can preserve fertility by freezing oocytes or semen. Prepubertal patients do not receive this option. In girls, ovarian tissue cryopreservation is now well established, with 28% of pregnancies being successful following autologous transplantation of thawed tissue. In contrast, the preservation of testicular tissue in prepubertal boys remains experimental.

“The ovary of a young girl already contains oocytes, although immature. To achieve maturation, the tissue only needs vascularization and appropriate hormonal signaling,” Tondo said. “The testis of a child does not contain spermatozoa but spermatogonia, stem cells that must undergo a long and complex differentiation process to become male gametes.”

“The testes contain microscopic tubules where spermatogenesis occurs. If freezing damages this structure, the process is not activated. Because of this greater complexity, transplantation of cryopreserved testicular tissue has only been tested in animal models. In 2018, the first nonhuman primate was born using this technique, a rhesus macaque.”

In recent years, testicular tissue samples from pediatric patients have been collected and stored in experimental programs worldwide. Researchers initiated this practice in 2002. The patient involved in the study had sickle cell anemia and required genotoxic chemotherapy before hematopoietic stem cell transplantation. In 2008, one testis was surgically removed and sectioned while preserving the tubular structure. Prior to freezing, the presence of spermatogonia within the tissue was confirmed.

In 2024, after reaching adulthood and achieving clinical recovery, the patient was diagnosed with azoospermia. Researchers thawed the previously cryopreserved testicular tissue and implanted selected fragments into the remaining testis. Follow-up assessments confirmed that the grafted tissue regained function and resumed spermatogenesis, with detectable sperm production.

In 2025, the European Society of Human Reproduction and Embryology issued 44 recommendations outlining the resources and expertise required to establish testicular tissue cryopreservation programs, including clinical indications, enrollment criteria for pediatric patients, and procedures for tissue collection, transport, and storage.

“Centers collecting and freezing testicular tissue from prepubertal patients formed the international ORCHID-NET consortium in 2022. At that time, participating centers had collected samples from approximately 3000 patients with various diagnoses associated with the risk for infertility,” Tondo concluded. “The Policlinico of Milan, currently the only center in Italy, began sample collection in 2025.”

This story was translated from Univadis Italy, part of the Medscape Professional Network.