A man who had testicular tissue removed and frozen at age 10, before chemotherapy for sickle-cell disease, has had his ability to produce sperm restored after the tissue was transplanted back into his body 16 years later. The procedure, presented at the European Society of Human Reproduction and Embryology annual meeting in London and published as a preprint on medRxiv, is the first demonstration in humans that prepubertal testicular tissue can be cryopreserved for long periods and later used to restore fertility.
The Case
In 2008, surgeons at University Hospital in Brussels removed one testicle from a 10-year-old boy and froze its tissue in multiple fragments. The boy was about to undergo chemotherapy and a blood-stem-cell transplant to treat sickle-cell disease, treatments that typically destroy the germ cells responsible for sperm production.
More than a decade later, the now-adult patient was found to be incapable of producing normal sperm after a two-year monitoring period. In the transplant procedure, 11 tissue fragments, frozen for 16 years, were grafted either into the remaining testicle or under the skin of the scrotum. After one year in the adult hormonal environment, the grafts were examined.
The researchers, led by Ellen Goossens of the Vrije Universiteit Brussel, found sperm-producing stem cells and signs of active sperm production in several of the grafts. In one sample, they found a single mature sperm. The remaining tissue was preserved in the hope that more sperm could be collected later for use in in vitro fertilization.
What It Means
More than 3,000 boys across 16 sites in Europe, Australia, and the United States had testicular tissue banked between 2002 and 2022 in the hope that future technology would allow them to use it, according to a 2024 survey published in Human Reproduction Open. This case provides the first proof that the approach can work in humans.
“This is an important breakthrough,” said Rod Mitchell, a pediatric endocrinologist at the University of Edinburgh who was not involved in the work. “This offers hope for prepubertal boys who are facing treatments, such as chemotherapy and radiotherapy, that can affect their future fertility.”
The success is particularly significant because the tissue had been frozen for 16 years, demonstrating that long-term cryopreservation does not necessarily compromise viability. For young boys who cannot provide a sperm sample before treatment, tissue banking has been the only option, and it has been offered without any guarantee that it would ever work.
Caveats and Next Steps
The procedure produced a single mature sperm, not a functional pregnancy. Whether that sperm can fertilize an egg and lead to a healthy pregnancy remains to be demonstrated. The finding that the grafts could produce sperm-producing stem cells at all, however, suggests that with further refinement, a reliable supply could be generated.
The work has been presented at a conference and posted as a preprint on medRxiv but has not yet undergone peer-reviewed publication. The authors note that they stopped the analysis after finding the single sperm, saving the remaining graft tissue to attempt collection of more sperm for future IVF use.
Sources
1. H. Ledford, “Man’s ability to make sperm restored after testicular tissue transplant: what scientists think,” Nature News, July 17, 2026. https://www.nature.com/articles/d41586-026-02191-3
2. E. Goossens et al., medRxiv preprint (2026). DOI: 10.64898/2026.03.04.26347483
3. K. Duffin et al., “Fertility preservation for prepubertal boys: lessons from a cross-sectional survey of global experience,” Human Reproduction Open (2024). DOI: 10.1093/hropen/hoae010