Professor Katsuhiko Hayashi of Osaka University is a globally respected pioneer in the field of fertility treatment development. And yesterday, during the International Summit on Human Genome Editing held at the Francis Crick Institute in London, he claimed to have created the first mammal born from two biological parents. Specifically, he claimed to have seven rodent pups born to male mouse cell ova. A breakthrough that, in his words, could one day pave the way for male human couples to have children.

Hayashi, who presented his research at the Summit to the astonished gazes of the participants, did not hesitate to be optimistic about the possibility of transferring his experiment from rodents to humans within ten years. He also stated that this will be the next step that his team will now take: reproducing the study with human cells. In that regard, he expressed that he would like his discovery to be available as a fertility treatment for men and same-sex couples in the future, if its use proves to be safe. “If people want it and if society accepts this technology, then yes, I’m for it,” he told the BBC.

However, the professor admitted that it could take years and it will be very difficult to make his technique work in human cells. These, he said, require a longer culture period to produce a mature egg. On the contrary, the eggs in his experiment were “poor quality” (in his words) and his system could not be used safely in humans at this time. Anyway, the results of the study by the Japanese researcher have already been submitted for publication in the prestigious scientific journal Nature.

The research, which is still in its early stages, involved converting XY male sex chromosomes to XX female sex chromosomes. To do so, they transformed the male mouse’s skin cells into stem cells, that is, a cell that can transform into other types of cells. Next, Professor Katsuhiko’s team deleted the Y chromosome, copied the X chromosome, and combined the copies with the original X chromosomes. this configuration allows the stem cell to be programmed to become an egg cell. Hayashi’s team then impregnated him with sperm from another mouse.

The researchers say the technique was used to create seven baby mice, which appeared healthy and had normal lifespans. However, they do not rule out the appearance of complications in its development. They also believe this method could one day be used to allow male human couples to have children together using an egg created from their own cells. Likewise, it can be used to help sterile couples in which women they are not capable of producing their own eggs.

And they add that it could also be used to treat Turner syndrome, a genetic disorder that only affects women and that occurs when one or part of the X chromosome is missing. But they still need time for their discovery to be used as a treatment.

Professor George Daley of Harvard Medical School, who was not involved in the research, called it “fascinating” in remarks to the BBC. However, he said that using the technique in human cells would be “more difficult than in mice”. And he added: “We still don’t understand enough biology of human gametogenesis (the formation of reproductive cells) enough to replicate Hayashi’s provocative work in mice.”

In turn, Professor Amander Clark, from the University of California, told the same vehicle that the LBGTQ+ community must have a voice in the use of technology for reproduction. “The LGBTQ+ community has unique needs when it comes to having a family. It is possible that same-sex reproduction in the future will be based on current research using laboratory models to develop the technology.”