If proven, the feat could revolutionize medicine and resolve many cases of sterility. Paterna Biosciences, a start-up from Utah, USA, claims to manufacture functional human sperm in the laboratory. Embryos generated from these would also be viable. Their technique? Take the stem cells responsible for sperm production from testicular tissue, then cause them to develop fully in the laboratory. The process, revealed by the media WIRED, has not yet been verified by peers.
“The goal is to create thousands of sperm from a simple sample of tissue”exclaims Alexander Pastuszak, co-founder and boss of Paterna, also a urologist and professor of surgery at the University of Utah. The company touts its high success rate in manufacturing sperm from dozens of tissue samples. “The first tests show that these spermatozoa in vitro appear identical to the natural version”says Alexander Pastuszak. The fact remains that the technique is not yet ready to launch real pregnancies, and tests in this direction could begin as early as 2027.
In nature, the stem cells in question take more than two months to become mature sperm, and several steps complicate any laboratory copy. They are first produced in the tubules of the testes, then comes meiosis, that is to say their double division to form cells with 23 chromosomes. This is when the sperm acquires a head and a tail to move around. He learns to swim, as it were, in another part of the testicles. It is finally ready to join the ejaculate released by the vas deferens.
This hectic life constitutes so many “very strict control mechanismssays Alexandre Pastuszak. But we managed to understand all the instructions needed to raise the stem cells into normal, mature sperm.” Paterna initially tried to grow the testicular tubules in the laboratory, without success. Ultimately, it was the cultivation of stem cells in test tubes that worked. Scientists relied on computational biology to predict the crucial molecular signals in sperm formation. We then had to test lots of combinations of molecules until we found the right formula.
Between 5,000 and 12,000 dollars per procedure
If spermatogenesis in the laboratory has been stirring research for almost a century, successes have accelerated over the last fifteen years. Japanese researchers were the first to produce viable mouse sperm in 2011. But for humans, it is more complicated: a French company, Kallistem, claimed to have succeeded in human spermatogenesis in vitro in 2015. Except that other scientists have questioned the viability of these artificial sperm… And Kallistem has never proven their ability to fertilize an egg.
The subject is fascinating because in half of the cases of infertility, the problem comes from the men: their spermatozoa may be too few in number, have an abnormal shape, not swim vigorously enough… Between 10% and 15% of infertile men simply do not produce any. It is this group of people that Paterna targets.
These men may not have sperm, but they still have the stem cells necessary to produce them. However, Paterna’s results confirm what other studies have already indicated: the stem cells are not at fault; it is the microenvironment around them that creates sterility. By reproducing the healthy version of this environment in the laboratory, we could therefore produce fertile sperm.
“When it comes to male infertility, the most difficult cases are indeed men who do not produce sperm.confirms to WIRED Ryan Flannigan, a surgeon specializing in sperm collection in Vancouver (Canada), unrelated to Paterna. We can bear witness to the emotional burden suffered by these individuals and their couples.”
For these men, surgery is indeed one of the few options. It aims to collect sperm from the testicular tissue. The maneuver can last up to four hours, under general anesthesia, with no certainty of success. If Paterna succeeds in manufacturing the sperm in vitro, the surgery step will be replaced by a small biopsy in the doctor’s office. The company will then begin in vitro spermatogenesis after receiving the sample. On the other hand, count on between 5,000 and 12,000 dollars (between approximately 4,200 and 10,000 euros) until possible reimbursement, in France, by social security.
