Many academic researchers still believe making eggs is a subtle, complex undertaking that should not be rushed. That includes the biologists in Japan who first turned cells from a mouse’s tail into eggs and then into mice. Last year, Hayashi fretted to me that commercial ventures trying to copy the technique in humans may be “premature.”
Hayashi said he worries about the medical consequences if someone makes a human this way. He has warned that while mice from artificial eggs appear healthy, and even have their own mouse babies, they could have “cryptic anomalies” or hidden defects. Before anyone risks making a human being from an artificial egg, there needs to be wide societal debate, much more research, and extensive safety tests, he and Saitou wrote in the journal Science
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.
If IVF embryos made from artificial eggs do appear normal, fertility doctors might conclude it’s safe to proceed. That’s what Varsavsky thinks. “The path is to make embryos, genetically test them, and see if you can detect any difference between an embryo made this way and the usual way. And if you can’t, I think this should be approved by the FDA,” he says.
Greely says he’s concerned that ambitious doctors will rush to test the technology too soon, like what happened when researchers created the first gene-edited babies
in China in 2018. In his own speech to the convention of fertility doctors last week, Greely said he believed it will take 15 years before the technology can be used widely. He urged them to go slow and first use try out artificial eggs to make monkeys, maybe even chimpanzees.
Anyone who moves too fast and makes “disabled or dead babies,” he warned, deserves a special “circle of hell.”