A Startup Says It Grew Human Sperm in a Lab—and Used It to Make Embryos

A startup out of Utah, Paterna Biosciences, says it has successfully grown functional human sperm in a lab and used the sperm to make visibly healthy-looking embryos. The technique could eventually help men with certain types of infertility have biological children.

The findings have not yet been published in a peer-reviewed journal or independently verified. WIRED is the first to report the advance.

The process involves isolating sperm-making stem cells from testicular tissue and coaxing the cells into becoming fully-fledged sperm in a dish. Scientists have been attempting to produce sperm outside the body, known as in vitro spermatogenesis, for almost a century. A Japanese team was the first to produce viable mouse sperm in the lab in 2011, but making human sperm has turned out to be a more difficult task.

Another biotech company, Kallistem in France, claimed it achieved in vitro spermatogenesis in 2015, but some outside researchers questioned whether the sperm were fully developed, and the company did not prove that the sperm were able to fertilize eggs.

It takes a little over two months and several steps for sperm-forming stem cells to become mature sperm in the body. After stem cells are produced in the tightly coiled tubules of the testicles, they undergo meiosis, dividing to create cells with 23 chromosomes. This is when sperm also develop the tail and head structure needed for swimming. From there, sperm move to another part of the testicles, where they gain the ability to swim. A tube called the vas deferens then transports the sperm and releases them into the ejaculate.

“There are very strict control mechanisms at every single one of those steps,” says Alexander Pastuszak, CEO and cofounder of Paterna, who is also a board-certified urologist and an associate professor of surgery at the University of Utah School of Medicine. “We’ve figured out the instructions that are needed to teach these stem cells to become mature, normal sperm.”

Paterna initially tested whether the testicular tubules in which sperm mature could be cultured in the lab and used to derive sperm but found that wasn’t the best approach. Ultimately, the company found a way to nurture just the sperm-forming stem cells in a dish and coax them into becoming sperm. The team used computational biology to predict the molecular signals that are important at every step of the sperm-making process. They then tested various combinations of molecules to induce each of those stages until settling on the right cocktail.