Conception's website says its technology would"potentially allow male-male couples to have biological children," but that kind of procedure is even less certain. Hayashi?s team in Japan reported making eggs from male mouse cells--but it?s a very inefficient process. Their development is "severely disturbed" by genes present on the male Y chromosome that inhibit egg formation, although researchers may eventually be able to correct such imbalances with genetic engineering.
For female-female reproduction, it's the opposite problem. Female cells have two X chromosomes but no copy of the Y chromosome. "If you don't have a Y chromosome you can?t make sperm, because there are genes on the Y chromosome essential for that," says Kyle Orwig, a researcher and sperm biology specialist at the University of Pittsburgh. There do seem to be ways around that barrier; in 2018, Chinese scientists reported constructing mice with two mothers.
But that process involved a head-spinning series of laboratory manipulations that were far from natural. "There are extraordinarily complex ways in which you could achieve this in either direction," says Orwig. "I wouldn't discount the possibility in the long term, as there are a lot of smart people out there."
Fertility doctors are already paying attention to what's coming. Last week at the annual meeting of the American Society for Reproductive Medicine, in Baltimore, presentations on artificial gametogenesis and genetic editing dominated the plenary sessions. "It's remarkably explicit," says Ben Hurlbut, a sociologist of science at Arizona State University, who was at the gathering. "They're talking about how in the future we will move reproduction entirely outside the human body."
Proving it's possible to make eggs in the lab, however, is just a first step--and maybe the easiest one. Even if researchers could generate eggs, they'd then have to prove they were safe to use. "The first thing you would do is science the hell out of that egg," says Henry Greely, a bioethicist and law professor at Stanford University. The next step would be to fertilize manufactured eggs and see if the human embryos that result develop normally in a lab dish.