Male infertility is a sensitive subject, yet it’s a prevalent issue affecting about 1 in 10 couples trying to conceive. Notably, half of infertility cases are linked to sperm quality. Traditional fertility solutions often fall short, but a pioneering U.S. startup, Paterna Biosciences, aims to revolutionize the field.

Paterna proposes that stem cells can be extracted from the testicles and transformed into viable sperm cells in a laboratory setting. This breakthrough could potentially enable almost all men who face infertility challenges to achieve fatherhood.

However, some experts express skepticism, suggesting that the method’s viability may hinge on the integration of CRISPR gene editing—essentially enabling the creation of gene-edited offspring.

Let’s delve deeper. Male infertility can stem from various issues, including low sperm count, poor sperm motility, or sperm failing to penetrate the egg. In such cases, direct injection of sperm into the egg, known as intracytoplasmic sperm injection (ICSI), can often yield successful results.

Approximately 1 in 100 men may face a complete absence of sperm in their semen. This might be due to blockages preventing sperm from reaching the prostate, which can often be corrected through medical procedures to retrieve sperm directly from the testicles.

In instances where no sperm is found, it’s frequently due to the testicles producing little or none. According to Alex Pastuzak, Co-founder and President of Paterna, the process begins with a small testicular tissue sample, which can yield anywhere from a few to tens of thousands of sperm cells.

Pastuzak claims they identified signals that stimulate sperm stem cells to differentiate into sperm within about a month in the lab.

The question of validity arises. Paterna has yet to release conclusive evidence to back their claims, citing the need to protect their intellectual property. Pastuzak states, “I won’t disclose anything to the public until our protections are established.”

Previous efforts, such as those by French biotech firm Callistem, made similar announcements but did not deliver substantial outcomes.

Paterna asserts that the sperm produced successfully fertilized human eggs, leading to early embryonic development.

While acknowledging Paterna’s scientific team’s qualifications, independent researchers await more evidence before drawing conclusions. “If they can achieve this, it represents a significant advancement,” remarks Helt Hammer from the Amsterdam Institute of Reproductive Development.

Potential Genetic Risks

If Paterna’s claims hold true, the next critical inquiry is their safety. Sperm originate from stem cells in the testes, which undergo a complex meiotic process to develop into spermatozoa. Any disruption during meiosis may lead to genetic abnormalities—a potential risk heightened in laboratory environments.

Moreover, imprinting errors during sperm development can lead to serious developmental issues. Although Paterna believes its approach minimizes these risks, past research indicates common errors in mouse sperm derived from stem cells.

Pastuzak asserts, “Molecular studies show our in-vitro sperm is identical to natural sperm produced in the testes. In some cases, it even surpasses natural quality.”

Paterna envisions implanting embryos fertilized with laboratory-grown sperm into women as early as next year. “Our inaugural clinical trial will likely occur outside the U.S., still awaiting regulatory approvals,” Pastuzak adds.

However, it’s unclear what evidence regulators require before sanctioning the use of lab-grown sperm in fertility treatments. Historically, fertility specialists have employed techniques like IVF and micromanipulation without comprehensive safety validations.

If deemed safe, it remains to be seen how many men can benefit from this technique. A small segment may not possess functional sperm stem cells, confining this approach’s applicability.

For others, infertility could stem from genetic mutations, complicating treatment efficacy. Professor Hammer suggests that if a mutation hampers spermatogenesis, lab methods are likely to replicate the same issues. The most likely beneficiaries may be men who became infertile due to childhood cancer treatments and had testicular tissue preserved prior to that.

“We could provide hope for young boys rendered infertile by chemotherapy,” he asserts, though this demographic is limited.

Wilkinson notes that another potential group could be men with restricted spermatogenesis, who currently undergo invasive procedures like microdissecting testicular sperm extraction (mTESE). “Avoiding such invasive techniques would be a significant improvement,” he claims.

Lab-Grown Sperm and Future Generations

Pastuzak claims that their lab successfully harvested sperm from men whose testicles do not naturally produce it. “Most of these germ cells exhibit maturation potential. The defect seems linked to the signaling from supportive cells,” he states.

Despite skepticism, the possibility that lab-grown sperm could offer solutions to infertility is encouraging. However, it raises the concern that boys born from such sperm may inherit genetic mutations associated with fertility issues—paralleling concerns raised with ICSI techniques.

“I do ponder this,” Pastuzak admits, noting that there are various stages in the process where harmful mutations can be screened out during testing.

If lab-grown sperm extraction fails for most men with infertility-causing mutations, an alternative solution may arise through CRISPR gene editing to rectify such mutations, potentially resulting in gene-edited children.

This approach, while promising, comes with challenges, mainly due to limited knowledge about potential infertility mutations and their complexities. “Evidence remains scarce,” Wilkinson warns.

Nonetheless, if precise mutations are identified, utilizing gene editing might be justified. Pre-implantation genetic screening could also mitigate unintended modifications during the process.

Paterna is open to exploring these avenues, with Pastuzak stating, “I’m not ruling anything out. Advancements in science should benefit as many people as possible.”