Today's Editorial

Today's Editorial - 16 April 2023

Mice with two biological fathers

Source: By Alind Chauhan: The Indian Express

Japanese scientists have created mice with two biological fathers after they generated eggs from male cells for the first time — an advancement which has the potential to radically alter the course of reproductive biology.

The details of the study, ‘Generation of functional oocytes from male mice in vitro’, were published in april 2023 in the journal Nature. The research was led by Katsuhiko Hayashi of Kyushu University (Japan) and his team of 15 other scientists.

Notably, the breakthrough has opened new possibilities for gay-male couples — or even single men — to have their biological child without needing a female egg. However, scientists involved in the study pointed out that the research is in a very early stage.

Speaking to CNN, Hayashi said, “It is expected that application into humans takes a long time, maybe 10 years or more. Even if it is applied, we never know whether the eggs are safe enough to produce (a) baby”.

What are the details of the study?

For the experiment, the scientists first took skin cells from the tail of a male mouse, which, just like male humans, contained both an X and Y chromosome, and then converted them into induced pluripotent stem cells or iPSCs — they can be transformed into any kind of cell.

During this process, a slight percentage of the cells lost their Y chromosome, generating “XO” cells. The scientists then cultured the XO cells in the lab and treated them with a drug called reversine. This helped them duplicate the existing X chromosome in these cells, creating an XX set.

While presenting the details of the research at the Third International Summit on Human Genome Editing at the Francis Crick Institute in London earlier in March, Hayashi said, “The trick of this, the biggest trick, is the duplication of the X chromosome”. He added, “We really tried to establish a system to duplicate the X chromosome.”

Hayashi and his team then embedded the XX cells in an artificial ovary — also created by the use of stem cells — to generate eggs, which were fertilised with the sperm of another male mouse to obtain hundreds of embryos that were implanted into the uterus of surrogate female mice.

Only seven out of 630 implanted embryos produced living pups. According to the scientists, the baby mice had a normal lifespan and they went on to have their own babies as adults.

Raising concern regarding how only a tiny fraction of the embryos placed into surrogate mice grew into living mice, Evelyn Telfer, a reproductive biologist at the University of Edinburgh in Scotland, who was not involved in the new research, told Scientific American magazine, “Although they get quite a lot of eggs, these eggs are clearly not fully competent because they really get a very, very small proportion of them that are capable of being fertilised and forming embryos”.

“It’s a huge achievement, but it’s still an indication that there are problems with these in vitro–derived oocytes (eggs) from the stem cells, so there’s a lot of work that has to be done,” she added.

Can the technique be used in humans?

Given the one per cent success rate of the method used by the scientists to create mice with two biological fathers, Hayashi said although it is theoretically possible to produce babies from male human couples, it would take around a decade to do so.

Besides the technical aspect, the technique being used in the case of humans also poses a wide range of ethical questions.

Talking to CNN, Glenn Cohen, the faculty director of Harvard Law’s Petrie-Flom Center for Health Law Policy, Biotechnology & Bioethics, said, “What happens to all the embryos created but not used? Does it violate ethical norms of respect to create so many potential human lives knowing that the vast majority will be destroyed or indefinitely stored?”

“In the most extreme case, imagine an individual using sloughed skin cells left on a bathtub by Brad Pitt, for example, to derive sperm or egg in order to reproduce,” he added.