When a ten-year-old boy faced chemotherapy for sickle cell disease in 2008, doctors removed and froze a sample of his immature testicular tissue. Sixteen years later the man, now an adult, received grafts of that same thawed tissue. One year on, analysis revealed surviving cells, new blood vessels, sperm-producing stem cells and clear signs of active sperm production.
The procedure took place at Vrije Universiteit Brussel and Brussels IVF at University Hospital Brussels. Researchers transplanted 11 fragments either into the man's remaining testicle or beneath the skin of his scrotum. Subsequent examination of the grafts confirmed not only survival and vascularisation but the presence of spermatogonial stem cells and, crucially, mature sperm cells within those placed inside the testicle itself.
This marks the first reported demonstration in a human that prepubertal testicular tissue, cryopreserved before puberty, can generate sperm after autologous transplantation in adulthood. Treatments such as chemotherapy can destroy the cells responsible for sperm production. For boys who have not yet reached puberty and cannot bank mature sperm, freezing immature tissue containing those stem cells has long been an experimental option. Until now, evidence that it would work in people had been absent.
Proof of concept, not immediate solution
The findings appeared in a preprint posted on medRxiv on 12 March 2026. A summary of the case was published by Nature on 17 July 2026. The sperm produced were not connected to the sperm ducts, so natural ejaculation is not possible. Any future use for conception would require assisted reproduction such as IVF with sperm extracted from the grafts.
Researchers stress that success is not guaranteed for every patient. Quantities may remain low, and larger studies are needed before the approach can be considered a standard fertility option. The case nevertheless provides measured hope for preserving the possibility of biological parenthood for boys facing gonadotoxic therapies.
By safeguarding this tissue, clinicians protected a fundamental avenue for family formation that might otherwise have been lost. In doing so they upheld the principle that medical progress should serve the long-term integrity of the person and the family unit, rather than treating fertility as an afterthought. The work, led by Professor Ellen Goossens of Vrije Universiteit Brussel with input from Professor Rod Mitchell of the University of Edinburgh, builds on years of animal and laboratory data that had hinted at this potential.
