A cutting-edge operation has restored a man’s ability to produce sperm by transplanting tissue samples that were removed from one of his testicles and frozen 16 years earlier, when he was still a child. Scientists say this remarkable achievement could usher in a new wave of fertility treatments.

The samples were taken shortly before the child received chemotherapy treatments that put his fertility at risk. “This is an important advance,” says Rod Mitchell, a pediatric endocrinologist at the University of Edinburgh, UK, who was not involved in the work. “This offers hope to prepubescent children facing treatments, such as chemotherapy and radiotherapy, that may affect their future fertility.”

The work was presented at the annual meeting of the European Society of Human Reproduction and Embryology in London last week and was published as an unreviewed preprint.¹ on medRxiv earlier this year.

Looking to the future

The growing number of children surviving childhood cancer has focused attention on the long-term consequences (including loss of fertility) of the aggressive therapies they receive. From 2002 to 2022, more than 3,000 boys at 16 sites in Europe, Australia and the United States opted to freeze samples of their testicles in the hope that, if they became infertile, the tissue could be used to restore their ability to have children.². But doctors couldn’t assure their young patients and their families that such a procedure would work, Mitchell says.

Laboratory-grown sperm: Scientists get closer to advancing fertility

In 2008, doctors at Brussels University Hospital removed a ten-year-old boy’s testicle and frozen tissue samples they had taken. The boy then received chemotherapy in preparation for a blood stem cell transplant to treat sickle cell anemia.

More than a decade later, he returned to the hospital as an adult with dreams of having children. Doctors monitored him for two years and confirmed that he could not produce normal sperm on his own. They then grafted 11 of the tissue fragments, which by then had been frozen for 16 years, either into the remaining testicle or under the skin of the scrotum.

The grafts were incubated there for a year, bathed in hormones and other environmental cues found in an adult man. After that, the tissue fragments were removed and examined.

The team found sperm-producing stem cells and signs of active sperm production in several of the transplants. In a sample of a graft, they found a single mature sperm.

At that point, the researchers stopped their analysis and saved the rest of the graft in hopes that they could collect more sperm later and use it to in vitro fertilization, says Ellen Goossens, a reproductive biologist at Vrije Universiteit Brussel and co-author of the preprint.

Future father?