In an experimental procedure, stem cells responsible for sperm production were injected into the male reproductive system to treat infertility. (Image credit: LYagovy/Getty Images)
In the United States, an estimated 645,000 men between the ages of 20 and 50 suffer from azoospermia, a condition in which their ejaculate contains no sperm. Researchers are currently testing a potential treatment: transplanting sperm-producing stem cells into the reproductive system.
“If spermatogonial stem cell (SSC) transplantation is improved and proven safe, it could be a breakthrough technology for restoring fertility in men who have lost the ability to produce sperm,” Dr. Justin Howman, an assistant professor of urology at Cedars-Sinai Medical Center who was not involved in the study, told Live Science in an email.
He added that it could be particularly useful for “cancer survivors who were treated before puberty, or men with genetic or acquired testicular defects.”
What is this experimental treatment?
The basis of the therapy is sperm-generating stem cells. These cells, which are present in the testicles before puberty, usually turn into sperm when testosterone levels rise in adolescence.
However, medical conditions such as blockages in the reproductive tract, certain genetic mutations or hormonal disorders, and treatments such as chemotherapy can damage these stem cells or prevent them from turning into sperm, leading to infertility.
If a young patient wishes to preserve his sperm-forming stem cells for future use, doctors can use a needle, guided by ultrasound, to remove stem cells from the rete testis, a network of small tubes that connect to the seminiferous tubules where sperm are normally made. The needle is carefully inserted through the base of the scrotum into these tubes, and the stem cells are frozen after removal.
Doctors can later reintroduce the stored stem cells into the rete testes using a similar ultrasound-guided technique. The goal is to implant the cells into the seminiferous tubules, where they can mature and begin to generate sperm, mimicking the natural process that occurs during puberty.
The procedure has previously been tested on animals and has successfully allowed male mice and monkeys to produce sperm and become fathers.
Now, researchers have documented the first use of the technique in humans. According to a paper published March 26 on the preprint server medRxiv, a man in his early 20s received a transplant of his own previously frozen stem cells. His sperm-forming stem cells were stored as a child, before he underwent chemotherapy for bone cancer.
If the stem cell transplant is successful, the man's body should begin producing sperm, which was impossible before the procedure due to azoospermia. So far, ultrasound has confirmed that the transplant procedure did not harm the patient's testicular tissue and his hormone levels remain normal.
No sperm have yet been found in his semen, but researchers continue to test him twice a year to check for reproductive cells.
One possible reason for the lack of detectable sperm, the researchers say, is that only a small number of stem cells were collected from the patient as a child to minimize damage to his tissue. This means that the number of cells that can develop into sperm that are stored and transplanted remains low. As a result, sperm production may be limited.
If sperm do not appear in a patient's ejaculate but he or she wishes to have children, doctors may attempt to surgically restore a small amount of sperm produced by stem cells.
Dr. Laura Gemmell, a research fellow in reproductive and endocrinology at Columbia University, has suggested another alternative: a method called the Sperm Tracking and Recovery (STAR) System. This device, developed at the Fert
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