This essay was written by Metacelsus for Asimov Press.

In March 2023, a research team at Osaka University announced an extraordinary achievement: the production of viable eggs using cells taken from male mice.

Building on years of research into stem cells and reproductive development,¹ the researchers, led by Professor Katsuhiko Hayashi, developed a method to induce male stem cells to lose their Y chromosome and duplicate the X chromosome, thus becoming female. From there, researchers took the female cells and grew eggs from them using an elaborate protocol they had initially published in 2016.

From the paper and ensuing media fanfare, a question emerged: When will this technology become available for people?

For nearly all of human history, there was only one way to make a baby. When a man and a woman love each other very much . . . well, you know the rest. But for many people, the usual method of baby-making doesn’t work. This is especially problematic for biological women, whose ovaries lose the ability over time to release healthy eggs. By age 40, most biological women are no longer able to reproduce.² And in recent years, rates of infertility have increased along with the average age of childbearing.

The first method to circumvent some of the difficulties of conceiving a child, in vitro fertilization (IVF), came in 1978. During IVF, eggs are collected from the ovaries and mixed with sperm. As the fertilized eggs become embryos, they are transferred into the uterus. These basic methods have greatly improved in the last four decades, and more than 10 million people have been conceived using IVF. About 800,000 children are born from IVF every year. However, this technology still relies upon eggs that are formed naturally, which for many couples is simply not an option.³

But what if, as the Osaka team’s breakthrough in mice suggests, there was another way to get eggs? In the last decade, several researchers — myself included — have been exploring the tantalizing prospect of growing eggs in cell culture.

Such an approach would take cells from an adult⁴ — such as skin or blood — and reprogram them into induced pluripotent stem cells, or iPSCs. Much like embryonic stem cells, iPSCs have the ability to form any cell in the adult body; eggs included. Although generating human iPSCs is now routine, coaxing iPSCs to form eggs in a process known as in vitro oogenesi...

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