A groundbreaking fertility treatment could one day restore the ability to produce sperm in men affected by cancer, genetic disorders, or other conditions that leave them infertile. For the first time, scientists have conducted a clinical trial involving spermatogonial stem cell (SSC) transplantation, a technique that implants sperm-forming stem cells back into the testes in hopes of jumpstarting sperm production.
“If refined and proven safe, SSC transplantation could be a revolutionary fertility-restoring technique for men who’ve lost the ability to produce sperm,” said Dr. Justin Houman, assistant professor of urology at Cedars-Sinai Medical Center, in a statement to Live Science. Dr. Houman was not involved in the study.
Roughly 645,000 men between the ages of 20 and 50 in the U.S. suffer from azoospermia, the complete absence of sperm in their semen. Sperm are produced from spermatogonial stem cells, which exist in the testicles even before puberty and become active when testosterone levels increase. However, certain medical treatments—like chemotherapy—and some genetic conditions can destroy these crucial cells, resulting in permanent infertility.
The SSC transplantation process involves harvesting stem cells from a patient’s testes using a fine needle inserted into the rete testis, a small network of tubes inside the testicle. These cells are then frozen for preservation and later reintroduced into the testis using a similar method.
Once implanted, the hope is that the stem cells will migrate into the seminiferous tubules—the sperm-producing structures in the testes—and restart spermatogenesis, or the process of sperm production.
This method has already shown promising results in animal studies, with mice and monkeys regaining fertility and even fathering offspring following the procedure. Now, early evidence suggests humans might one day see similar success.
A recent medRxiv preprint detailed the first known human trial of this therapy. The subject, a man in his early 20s, had his own SSCs preserved during childhood before undergoing chemotherapy for bone cancer. Years later, the cells were transplanted back into his testes.
Early signs are encouraging: the procedure did not damage the surrounding testicular tissue, and his hormone levels have remained stable. However, sperm has yet to be detected in his semen. One possible reason is that only a small quantity of stem cells was harvested during childhood to reduce the risk of complications, potentially limiting the number of mature sperm that can now be produced.
Despite the promise, the procedure is not without risks. For cancer survivors, particularly those with leukemia, there’s a chance that the transplanted cells could carry genetic mutations, which might increase the risk of tumor formation.
Even though patients receive their own cells, there’s also a slight chance of triggering an immune response. Beyond the medical risks, ethical concerns arise as well—especially regarding the long-term storage of cells harvested from young children. Can minors truly provide informed consent for a decision that may affect them decades later?
While it’s still early days for SSC transplantation, the science is progressing rapidly. If future trials confirm the treatment’s safety and effectiveness, this could become a lifesaving fertility option for boys undergoing cancer treatment or men with untreatable infertility. For now, researchers remain cautiously optimistic.
“There’s still a long road ahead,” said Dr. Houman, “but this is a critical first step toward turning what was once a dream into a viable path to parenthood.”
By Impact Lab
