Paterna Biosciences, a startup based in Utah, says it has developed functional human sperm in a laboratory and used it to create healthy-looking embryos. The company believes the method could one day allow some infertile men to have biological children.
The research has not yet been peer-reviewed or independently confirmed, though WIRED was the first outlet to report on the breakthrough.
The technique extracts sperm stem cells from testicular tissue and matures them into sperm in a lab dish. Scientists have pursued lab-grown sperm, known as in vitro spermatogenesis, for decades. In 2011, researchers in Japan produced viable mouse sperm in the lab, but human sperm has been much harder to create.
Earlier Lab-Grown Sperm Claims Questioned
In 2015, Kallistem, a biotech firm in France, also claimed progress in lab-grown sperm production. However, outside experts questioned whether the sperm were fully mature, and the company did not demonstrate successful fertilization of eggs.
Normally, sperm stem cells take more than two months to mature inside the body through a tightly controlled process. During development, cells undergo meiosis to form 23-chromosome cells and develop head and tail structures for movement. The sperm later gain swimming ability before traveling through the vas deferens into semen.
Alexander Pastuszak, CEO of Paterna Biosciences and a urologist at the University of Utah School of Medicine, says the company has identified signals that guide stem cells into mature sperm.
Paterna Shifted Focus to Stem Cells and Molecular Signals
Paterna Biosciences first explored growing sperm by culturing the tiny testicular tubules where sperm naturally mature, but the approach proved ineffective. Instead, the company focused on isolating sperm-producing stem cells and guiding them to develop into sperm in a laboratory dish. Using computational biology, researchers identified key molecular signals and tested chemical combinations to find an effective formula.
Larry Lipshultz, a urology professor at Baylor College of Medicine, called the achievement significant, saying scientists have long struggled to identify the growth factors needed to mature sperm cells.
Making sperm in the lab has long been a goal in fertility medicine, as male factors account for about half of infertility cases. Problems can include low sperm count, abnormal sperm structure, or impaired movement. About 10–15% of infertile men have no sperm in their semen and few options for biological children. Paterna Biosciences aims to help them by using stem cells that may still be present to generate sperm.
Recreating a Healthy Environment to Grow Sperm
Research from Paterna Biosciences and others suggests the problem may be the surrounding cellular environment, not the stem cells themselves. By recreating a healthier environment in the lab, the company believes it can generate normal sperm.
The company’s objective is to produce thousands of sperm cells from a routine tissue biopsy, and it reports strong success rates using dozens of samples so far.
Alexander Pastuszak says preliminary studies indicate the lab-grown sperm are virtually indistinguishable from naturally produced sperm. However, the technique is still not ready for use in human pregnancies. The embryos created so far were intended only to confirm that the sperm were functional. Next, Paterna Biosciences plans a larger study in infertile men comparing natural sperm with lab-grown sperm. Researchers will evaluate fertilization success and examine the resulting embryos for physical and genetic abnormalities.
Alexander Pastuszak says the next phase will test the method’s safety and effectiveness, including whether it causes genetic mutations. If results are positive, clinical trials using lab-grown sperm to achieve pregnancies could begin as early as next year.
Men With No Sperm Have Limited Fertility Options
Existing fertility treatments—such as medications, intrauterine insemination, and standard IVF—can help men with low sperm count or poor sperm quality. However, men who produce no sperm face far fewer options.
According to Ryan Flannigan of the Vancouver Prostate Centre in Canada, cases where men have no sperm are among the most difficult situations fertility specialists encounter, both medically and emotionally for patients and couples.
Currently, one possible treatment involves surgery to search for sperm directly within testicular tissue. The procedure requires general anesthesia, may last several hours, and still often fails to locate viable sperm.
Paterna Biosciences hopes to replace that invasive process with a simpler office-based biopsy. The collected tissue would then be sent to the company, where sperm would be generated through in vitro spermatogenesis. Paterna expects the procedure to cost between $5,000 and $12,000.
Potential Future Use for Childhood Cancer Patients
Flannigan also noted that the method could benefit boys who undergo chemotherapy before puberty. Because sperm stem cells exist from birth, clinicians can preserve testicular tissue from young cancer patients for future sperm production. However, although tissue freezing is established, reimplanting it remains experimental and has not yet resulted in any births.
Other researchers are using induced pluripotent stem cells, reprogrammed from skin or blood cells into an embryonic-like state. This process, known as in vitro gametogenesis, has already produced functional sperm and eggs in mice, leading to healthy offspring. Scientists think the approach could one day let same-sex couples have biological children by making eggs or sperm from skin cells.
Justin Dubin of the Baptist Health Miami Cancer Institute says Paterna Biosciences’s work is promising but may be out of reach for many due to high costs and limited insurance coverage, especially in the United States.
Read the original on: wired
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