The birth of baby mice made from eggs grown in a lab has sparked an ethical debate over whether the technique should ever be offered for humans by fertility clinics.
The experiment is a step up (or down, depending on how you look at it) from creating human organs from stem cells, which scientists at the University of Edinburgh successfully did for the first time in 2014.
Scientists created early-stage mouse eggs via 2 different experiments, 1 using stem cells, and 1 using skin cells from a mouse’s tail. These eggs were nurtured in the lab until they matured to the point that they could be fertilized by mouse sperm. 
Hundreds of embryos were made and implanted in female mice, leading to the birth of nearly a dozen healthy mouse pups. 
It will be many years before the procedure can be used in humans, but already researchers are looking to improve the process and make it safe enough to treat infertility, a problem affecting 1 in 6 couples.
Technologically speaking, it may someday be possible for fertility clinics to make viable eggs from the skin cells of an infertile woman.
According to Katsuhiko Hayashi at Japan’s Kyushu University, he and his colleagues first created some of the eggs from embryonic stem cells, and later from the skin tissue.
Out of 300 eggs, only 11 pregnancies ended in normal births. That’s just 3% of the embryos. 
Before the same process can be used to create human eggs and, later, human babies, scientists will have to overcome 2 major hurdles: the high failure rate, and potential risks to the young. 
When the team tested the artificial eggs made from stem cells, they found unusual patterns of gene expression in many of them, which suggests they did not develop the same way as normal eggs. Yet, more than 75% of the eggs made in the lab had the correct number of chromosomes. 
Creating mouse eggs in a petri dish is complicated work, and the team had to use ovary cells that support egg growth, Hayashi said. Originally, the scientists had reprogrammed stem cells to produce primordial germ cells, which give rise to eggs. However, they had to implant those cells into mice to finish developing into eggs in the ovary.
It’s not known how support cells in ovaries stimulate egg development. It may require something made by support cells or physical contact with them in order to fully mature.
Since scientists are not yet able to reproduce the supporting cells in a lab, so they need to get them from embryos. That could be another hurdle when trying to replicate the experiment in humans.
The (Far Off) Future
Azim Surani, a stem cell scientist at the Gurdon Institute at Cambridge University, who was not involved in the latest work, explained that it’s never too early to consider how this might be used to impregnate human females. 
“Ethically, this issue has yet to be discussed fully by scientists and society. This indeed is the right time to start a debate and involve the wider public in these discussions, long before, and in case, the procedure becomes feasible in humans.”
Some researchers warn that taking a crack at recreating a human embryo in the lab is a sure-fire way to omit important factors that have yet to be understood. Each lab-based manipulation introduces possible abnormalities, which make it a challenge to determine what factors are playing a crucial role. 
The report appears online in the October 17 edition of the journal Nature.
Yes, it will be years before lab-made eggs can be implanted in humans, but this takes humanity another step closer to creating “designer babies,” and the science behind this frightening prospect is developing rapidly.
In early 2016, scientists in Britain were cleared to start editing the genes of human embryos. Right now, the experiment is for the purpose of research. In the future, however, it could be used to create humans with certain genetic advantages over people born into the world with the help of nothing but nature.
And, just last month, scientists announced that the world’s first 3-parent baby was born in April.
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Julie Fidler is a freelance writer, legal blogger, and the author of Adventures in Holy Matrimony: For Better or the Absolute Worst. She lives in Pennsylvania with her husband and two ridiculously spoiled cats. She occasionally pontificates on her blog.