Scientists Made Functional Human Eggs With Skin Cells in ‘Proof of Concept’ for Advancing Fertility

The research could open up avenues for fertility treatments after additional refinement and trials, but it also raises ethical concerns

Sara Hashemi | Daily Correspondent

October 9, 2025

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Scientists have successfully used human skin cells to create fertilizable eggs, a breakthrough that could revolutionize fertility treatment.

The research, published in the journal Nature Communications on September 30, is still just a proof of concept. But if additional research can refine the procedure and demonstrate its safety, it could one day be clinically available to those who need assistance with fertility.

“The largest group of patients who might benefit would be women of advanced maternal age,” says Shoukhrat Mitalipov, a biologist at Oregon Health and Science University who led the research, to Ian Sample at the Guardian. Advanced maternal age—defined as pregnancy after turning 35—is associated with declining fertility and pregnancy complications.

“Another group are those who have been through chemotherapy, because that can affect their ability to have viable eggs,” Mitalipov tells the Guardian. The procedure could also allow same-sex couples to have children that are biologically related to both parents.

The researchers employed a technique like the one used in 1996 to clone Dolly the sheep, the first mammal cloned from an adult cell. To create the eggs, they transferred a human skin cell nucleus—the part of the cell with the most genetic information—into a human egg stripped of its own nucleus.

Skin cells have 46 chromosomes, while an egg cell has 23, so the researchers had to remove the excess chromosomes. They devised a method to coax the egg to discard half its chromosomes in a process that mirrors natural cell division. Because their method uses elements of both natural cell division processes—named mitosis and meiosis—the team termed their new technique “mitomeiosis.”

With that process, they produced 82 eggs. Then, researchers fertilized them with sperm via in vitro fertilization, or IVF.

Only 9 percent of the embryos that resulted developed for a full six days after fertilization, reaching what’s known as the blastocyst stage—the point at which an embryo would usually be transferred into the uterus during IVF. The researchers note that in natural reproduction, about a third of embryos become blastocysts.

All the embryos resulting from the procedure were chromosomally abnormal, the team says in a statement, and would not have resulted in healthy development.

Perfecting the technique and ensuring its safety for patients could take another decade of work, Mitalipov tells the Guardian. “I think it’s going to be harder than what we’ve done over the years thus far, but it’s not impossible,” he says.

Even though the research is still in its early stages, scientists not involved in the work have praised the study. “While this is still very early laboratory work, in the future it could transform how we understand infertility and miscarriage, and perhaps one day open the door to creating egg- or sperm-like cells for those who have no other options,” says Ying Cheong, a researcher of reproductive medicine at the University of Southampton in England, in a statement.

Others, however, are skeptical that the technique could ever work. “It is unclear whether [the process] is compatible with human development,” Amander Clark, an expert in molecular and developmental biology at the University of California, Los Angeles, tells NPR’s Rob Stein. “Time and more fundamental research will tell.”

In an interview with CNN’s Katie Hunt, Clark says the research is an “important beginning,” but adds that “this approach will not, and should not, be offered in the IVF lab until technical improvements are made.”

Creating human eggs, sperm or embryos in a lab also carries ethical concerns. Some say they worry parents will use the process to create designer babies with specific traits. Another concern is that people might one day steal other people’s skin cells—and the genetic information they contain—to create babies with stolen genetic material.

“We could have Taylor Swift babies all over the world. It’s a theoretical possibility, but not crazy,” Ronald Green, a bioethicist at Dartmouth College, tells NPR.

For now, the team will have to continue their research while also considering the ethical questions it raises—and the people who might benefit from a new way to treat infertility.

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.