Lab-Grown Human Sperm Successfully Used to Create Embryos: A Fertility Breakthrough?

Utah-based biotech startup Paterna Biosciences has announced it successfully grown functional human sperm in a laboratory setting and used it to create early-stage human embryos, marking a potential breakthrough in treating male infertility.

The company states it isolated spermatogonial stem cells from testicular tissue biopsies and guided them through the full maturation process in vitro, a process known as in vitro spermatogenesis. According to Paterna Biosciences, this involved coaxing the stem cells to develop into fully functional sperm capable of fertilizing eggs and forming embryos.

The findings, while preliminary, represent a significant step toward a long-sought goal in reproductive science. Scientists have previously achieved in vitro spermatogenesis in mice, most notably in a 2011 study from Japan, but translating the process to humans has proven far more complex due to stricter biological controls and longer development timelines.

Paterna Biosciences reported that the lab-grown sperm were used to generate what the company described as “visibly healthy-looking” human embryos. The embryos were created using the sperm in what appears to be an in vitro fertilization context, though specific details about the number of embryos, their developmental stage, or implantation attempts were not disclosed in the available sources.

The company emphasized that its work remains in early stages and has not yet been peer-reviewed, independently replicated, or cleared for clinical use. No scientific paper has been published to date, and outside laboratories have not yet verified the results. Experts in reproductive medicine caution that rigorous genetic, developmental, and safety testing will be required before the technology could be considered for use in fertility clinics.

Alexander Pastuszak, CEO and cofounder of Paterna Biosciences and a board-certified urologist and associate professor at the University of Utah School of Medicine, described the achievement as identifying the necessary molecular signals to drive spermatogenesis outside the body. He characterized the work as the first major innovation in the field since the introduction of intracytoplasmic sperm injection over 30 years ago.

Larry Lipshultz, a urologist and specialist in male reproductive health at Baylor College of Medicine, commented on the research as an outside expert for WIRED, noting that scientists had long struggled to determine the specific growth factors needed to mature sperm-forming stem cells in a lab setting. He stated that Paterna Biosciences appears to have identified these critical substances.

The process of natural sperm development takes just over two months in the body. It begins with stem cells in the testes undergoing meiosis to reduce chromosome count, followed by structural changes that enable sperm to swim, and finally transport through the reproductive tract. Paterna Biosciences says it has replicated this sequence in a dish using specific molecular cues, though the exact timeline for their in vitro process was not specified in the sources.

Other companies have previously claimed similar achievements. Kallistem, a French biotech firm, announced in 2015 that it had produced sperm in vitro, but outside researchers questioned whether the sperm were fully functional and capable of fertilization. Paterna Biosciences says its current work addresses those prior limitations by producing sperm that can form embryos.

The company projects that pregnancy initiation trials could begin as soon as next year, a timeline significantly faster than many experts had anticipated. However, this projection remains contingent on further validation, safety assessments, and regulatory review.

Male infertility affects more than one in eight American men between the ages of 25 and 49, according to data from the U.S. Department of Health and Human Services cited in multiple reports. Globally, infertility impacts millions of couples, driving significant investment in reproductive technologies. Paterna Biosciences says its approach could eventually help men with certain types of infertility—particularly those related to sperm production—have biological children.

While the announcement has generated optimism in the reproductive medicine field, scientists stress that independent verification is essential. As of the date of reporting, no peer-reviewed study has been published, and the claims remain under scrutiny. The company has not disclosed the specific culture conditions, growth factors, or quality control measures used in its process.

Paterna Biosciences has received support from the Mayo Clinic in its research efforts, according to multiple news outlets covering the announcement. The company is based in Utah and was cofounded by Alexander Pastuszak, who holds academic and clinical positions at the University of Utah.