In a groundbreaking medical trial, doctors in the United States have performed the first human test of a stem cell transplant aimed at restoring fertility in men. The experimental procedure could offer new hope to those affected by azoospermia—a condition that prevents sperm production and affects about one percent of men worldwide.
The patient, Jaiwen, lost his ability to produce sperm after undergoing chemotherapy as a child to treat bone cancer. Chemotherapy can severely damage the reproductive system, leaving many survivors infertile later in life.
Before his treatment, doctors harvested and froze Jaiwen’s sperm-forming stem cells. These cells, known as spermatogonial stem cells (SSCs), are present in the testicles from birth and are responsible for sperm production during puberty.
Years later, doctors at the University of Pittsburgh Medical Center (UPMC) reintroduced Jaiwen’s own stem cells into his testicles. Using ultrasound guidance, they inserted a small needle through the base of his scrotum and into the rete testis—a network of tiny tubes inside the testicles. The aim is to recreate the natural process that happens during puberty, potentially restarting sperm production.
So far, no sperm have been detected in Jaiwen’s semen. However, doctors confirmed that the transplant did not damage his testicular tissue. They plan to test his semen twice a year to track any changes.
“We’re not expecting a miracle result,” said Dr. Kyle Orwig, a reproductive scientist and professor at UPMC’s Department of Obstetrics, Gynecology and Reproductive Sciences. “What we expect is that the transplant of stem cells will produce a small amount of sperm, and that in order to achieve a pregnancy with his partner, he would need a follow-up assisted reproductive technology, like IVF.”
Experts are cautiously optimistic. Dr. Justin Houman, an assistant professor of urology at Cedars-Sinai Medical Center, called the procedure “potentially revolutionary” for restoring fertility. “If refined and proven safe, SSC transplantation could be a game-changer for men who lost the ability to produce sperm, especially cancer survivors treated before puberty or men with genetic or acquired testicular failure,” he told LiveScience.
Until now, this stem cell technique had only been tested in animals. In those studies, male mice and monkeys treated with SSC transplants were able to father offspring.
The human trial results were published on the preprint server medRxiv. While the research team is hopeful, they admit that full fertility may not be restored. One reason is the limited number of stem cells collected from Jaiwen when he was a child. Additionally, there are risks, especially for cancer survivors. Some of the transplanted cells might carry genetic mutations that could lead to new tumors.
“This is promising science—but it’s still early days,” Dr. Houman cautioned. “We need to proceed cautiously and with rigorous oversight.”
Even minor factors, such as using heated car seats, can affect sperm production. But for many men with azoospermia, treatments like this could one day offer the chance to have biological children—a goal once thought out of reach.
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