‘Exciting, provocative’: Japanese scientists created eggs from male cells

Research by Japanese scientists raises the hypothesis that same-sex couples can have biological children

Scientists at Osaka University in Japan have succeeded in creating mice using only male cells. This is a new discovery that could open up new possibilities in how humans reproduce, whether you’re female or male.

“This is the first case of producing mammalian oocytes from male cells,” said lead researcher Katsuhiko Hayashi of Osaka University in his presentation at the Human Gene-editing Summit this Wednesday.

To get here, the research followed several steps. The system had the ambition of duplicating the female chromosome, XX, i.e. converting male chromosomes into female ones. To do this, the researchers needed to transform skin cells. As? The male cells changed to the state of stem cells, which are undifferentiated cells that have the potential to turn into one of the 200 existing cell types – and, in doing so, in the male Y chromosome, from the XY crossover, was replaced by the female X, thus producing the pluripotent stem cell with two identical chromosomes.

What followed was incubating the cells in a system that mimics the conditions inside a mouse ovary. When the eggs were fertilized with ordinary sperm, the scientists obtained 600 embryos, which were implanted into the animals – resulting in the birth of seven offspring. Ultimately, the effectiveness of this experiment was 1%, a lower result compared to the 5% achieved by normal female eggs.

According to Hayashi, the mice “look fine, are growing normally” and “have become parents.”

Now, the idea is to achieve the same with human cells and, in the researcher’s plans, it may be possible to create an egg cell using male skin cells. The technique can be used in various forms of infertility, such as in cases of women suffering from Turner syndrome, a rare disease that causes abnormalities in female chromosomes, or in cases of same-sex couples.

However, some believe that this is an optimistic view, as there are still scientists trying to create human eggs from female cells without success.

George Daly, dean of Harvard Medical School, describes the work carried out as “exciting”, but adds that other research shows that creating gametes in laboratories using human cells is more complicated than using mouse cells.

“We don’t yet know enough about the complex biology of human gametogenesis to replicate the very challenging work that Hayashi accomplished in mice,” he says.

Until now, scientists have created precursors for human eggs, but the cells always stop growing at the meiosis stage, which is necessary for the development of mature sperm and eggs.

For now, “we’re stuck,” says Amander Clark, who researches gametes growing in a lab at the University of California. “The next step challenges engineering. But that could take 10 to 20 years.”

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