Nathan Crawford from the UK was just 9-years-old when his testicular tissue was frozen, before undergoing chemotherapy for his brain tumor.
About 16 years later, the cryopreserved immature testicular tissue was reintroduced into his body, which triggered sperm cell production and restored his fertility, according to researchers from the Vrije Universiteit Brussel.
"This is an important step in further scientific research to preserve the fertility of children with cancer or other blood diseases for the future. While the procedure is specifically designed to restore fertility, we cannot at this time guarantee that it will be successful or that patients can go on to have children. This treatment offers lots of perspectives for these young adults. They now have options that they did not have until recently," said Dr Veerle Vloeberghs, part of the novel trial and staff member at Brussels IVF.
What Had Happened To Nathan
Nathan, now 27-years-old, had a type of tumor called a glioma, which develops from the glial cells that support the nerve cells of the brain, The Guardian reported. The tumor was so close to vital brain tissue that surgeons were unable to remove it without causing serious damage to important brain functions.
He underwent radiotherapy and chemotherapy to shrink his tumor, before which surgeons at the John Radcliffe hospital in Oxford in a keyhole surgery removed and froze a wedge of testicular tissue, with the aim that it is one day re-implanted into Nathan.
How Is The Testicular Tissue Preserved?
While Chemotherapy and radiation therapy are lifesaving they can destroy testicular stem cells, the precursors of sperm cells in boys who undergo radical treatments before starting puberty. As it can affect their fertility, preventively removing and freezing testicular tissue is an option pioneered by UZ Brussel.
In 2002, UZ Brussel became the first hospital worldwide to initiate a clinical fertility preservation program for young boys suffering from cancer or diseases of the blood, bone marrow or lymph nodes.
Since then, the hospital has frozen testicular tissue fragments of 141 boys.
The tissue is preserved in liquid nitrogen at -196°C.
Prepubescent boys do not yet produce sperm cells. The removed tissue contains stem cells that would normally produce sperm after starting puberty.
"While the procedure is specifically designed to restore fertility, we cannot at this time guarantee that it will be successful or that patients can go on to have children," Dr Vloeberghs said.
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How Was The Testicular tissue Implanted
The Guardian reported that in 2025, four tissue fragments were grafted back into the remaining testicle and four under the skin of the scrotum.
After a year inside the body, the grafts were removed and analysed in the laboratory. The results are published in a preprint paper, which is yet to be peer reviewed.
Two of the grafts from inside the testicle had produced mature sperm, which was collected and frozen.
Because the tissue fragments are not directly connected to the sperm duct, the researchers do not expect sperm cells to naturally find their way into the semen.
"This is a huge finding," Prof Ellen Goossens, of the Vrije Universiteit Brussel, who led the trial was quoted as saying. "Many more people will have hope that they can have biological children. It's great to see for the patients for whom we already have tissue banked."
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