Scientists Made Human Eggs from Skin Cells and Used Them to Form Embryos

""The biggest challenge is how to make this egg extrude half of its chromosomes-and the correct half," Amato says. "We're not quite there yet." The team dubbed their technique "mitomeiosis" and is trying to better understand how chromosomes like to pair and how they segregate in order to find a way to experimentally induce those conditions. The ability to make eggs and sperm in the lab-called in vitro gametogenesis, or IVG -has been a growing area of research in recent years."

"In 2016, a group of Japanese researchers led by stem cell researcher Katsuhiko Hayashi reported that they produced healthy mouse pups after making mouse eggs entirely in a lab dish. Later, they generated mouse eggs using cells from males and as a result, created pups with two dads. Those advancements were achieved by reprogramming skin cells from adult mice into stem cells, then further coaxing them to develop into eggs and sperm."

"Mitinori Saitou at Kyoto University first documented in 2018 how his team turned human blood cells into stem cells, which they then transformed into human eggs, but they were too immature to be fertilized to make embryos. US startups Conception Biosciences, Ivy Natal, Gameto, and Ovelle Bio are all working on making eggs or sperm in a lab. But the prospect raises significant ethical questions about how the technology should be used."

The technique dubbed mitomeiosis aims to induce eggs to extrude half their chromosomes and the correct half, with researchers still working to reproduce the required chromosome pairing and segregation conditions. In vitro gametogenesis (IVG) seeks to create eggs and sperm in the lab and has advanced in mice, producing healthy pups and even offspring from two fathers after reprogramming adult cells into gametes. Human work transformed blood cells into immature eggs that remain unsuitable for fertilization. Several US startups pursue lab-made gametes. Ethical concerns include potential embryo farming, broad access to parenthood at any age, mass embryo selection, and gene-editing applications. Clinical testing in humans may require another decade of research.

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