Scientists have created human eggs containing genes from adult skin cells, a step that someday could help women who are infertile or gay couples have babies with their own genes but would also raise difficult ethical, social and legal issues.
"It's a significant step forward," says Shoukhrat Mitalipov of the Oregon Health & Science University in Portland, who led the research published in the journal Nature Communications.
Millions of women can't have children using their own eggs because of their age or other reasons. So scientists have been trying to create human eggs in the lab that carry the genes of people struggling to have children. The field is known as in vitro gametogenesis, and involves researchers around the world, including in Japan, as well as at U.S. biotech companies.
"This technology would allow many of these women to have genetically their own eggs and to have a genetically related child," says Mitalipov.
Mitalipov and his colleagues used a different technique than most researchers pursuing this goal.
The most common approach involves converting adult cells, such as skin or blood, into cells known as induced pluripotent stem, or iPS, cells. Scientists then have tried to coax those iPS cells into becoming eggs or sperm. The closest anyone has come to success for eggs has been very primitive human egg cells that are too immature to be fertilized.
Mitalipov's team instead used the technique that was used to clone Dolly the sheep: The scientists removed most of the DNA from a healthy donor egg and replaced it with most of the DNA from another woman's skin cell.
Next, the researchers essentially tricked the reconstituted egg to skip normal forms of cell division known as mitosis and meiosis. Instead, they coaxed the eggs to go through a different process they dubbed "mitomeiosis." That produced 82 functional eggs, the researchers reported.
The scientists then fertilized the eggs with sperm to see if they could develop into embryos. And it appears to have worked, at least in a small number of tries, the researchers report. Nine percent of the resulting embryos developed to the blastocyst stage, which is when embryos would be transferred into a woman's womb, the researchers reported.
Tricky issues with a promising technology
However, none of the embryos would have been suitable to actually implant into a womb to develop further. That's because all the embryos still had genetic abnormalities that would prevent healthy development.
Mitalipov, however, is hopeful he'll eventually solve that problem. And other scientists are aggressively pursuing other approaches to accomplish the same goal.
Some other scientists praised the new research.
"I think it's a very significant step in terms of moving forward to the ability to use skin cells to make egg cells for human reproduction at some point in the future, once we can prove this is safe and effective," says Dr. Sigal Klipstein, a reproductive endocrinologist with the American Society of Reproductive Medicine. "The proof of concept is fascinating."
If IVG is ever perfected, the technology could have applications beyond helping infertile women. IVG could, for example, also allow gay couples to have babies genetically related to both partners. Scientists could create eggs from a skin cell of one male partner and fertilize it with sperm from the other male partner.
"The implications are huge," Mitalipov says.
But some scientists warn that the genetic abnormalities in Mitalipov's embryos raise questions of whether this approach could ever work.
"It is unclear whether skipping meiosis in half the genome is compatible with human development," says Amander Clark, a professor of molecular and developmental biology at the University of California, Los Angeles. "Time and more fundamental research will tell."
Ethical concerns abound
And even if it did work, the technology would create lots of tricky issues. Some worry this could help create "designer babies," where parents can pick and choose the traits of their children.
"We could see more efforts to try to use it for so-called enhancement purposes — to try to get embryos that would be stronger or more athletic or more musical or better at math or more intelligent," says Hank Greely, a Stanford University bioethicist who wrote The End of Sex and the Future of Human Reproduction. "Some people view that as a terrible prospect. Some people view that as a wonderful prospect."
Another concern is that this could enable people to steal a skin cell from another person, such as a celebrity, and make a baby with their DNA without their knowledge or permission.
"We could have Taylor Swift babies all over the world. It's a theoretical possibility, but not crazy," says Ronald Green, a Dartmouth College bioethicist. "It's a technology that's very promising. But it raises a number of daunting ethical questions."
Another possibility is using this technology to create a "uni-baby," a child containing only one person's genetic material.
"That's a very weird possibility," Greely says. "Would anyone want to do that? Well, there are 8 billion people in the world and some of them have very strong egos and some are very rich. So I wouldn't guarantee that no one would want to do that."
While all those possibilities need to be debated, Greely and others argue that the technology is worth pursuing with proper oversight.
"If it was safe, it would offer relief to literally millions of people around the world who desperately want to have kids who are genetically theirs," says Greely.
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