Synthetic embryos? A distant but evolving perspective – News

“Synthetic embryos were formed from stem cells placed outside the uterus”, summarizes this work published this week in Cell, one of the largest scientific journals in biology.

The experiment was conducted on mice in an Israeli laboratory, under the direction of Palestinian Jacob Hanna, and achieved unprecedented success in a field of research that emerged a few years ago.

It involves developing structures close to the embryo in the laboratory, extracting individual cells from an animal and acting on them without any fertilization procedure.

The last major advance in this area dates back to 2018. At the time, researchers – led by Frenchman Nicolas Rivron – managed to develop stem cells into a whole similar to a very early embryo, a “blastocyst”. But at this stage, the cells of the embryo are no different from those that will form a future placenta.

– “Organ sketches” –

Jacob Hanna’s team went further. It developed structures similar to an eight-day-old mouse embryo, a third of gestation, and at a time when organs are beginning to differentiate.

To do this, the researchers extracted cells from the skin of mice then artificially brought them back to the state of stem cells, capable of differentiating into different organs. They were placed in a nutrient bath, constantly shaken and supplied with oxygen to closely mimic the conditions of the mother’s womb.

As a result, a small part of the cells organized itself, based on its own information, to form organs. It’s a breakthrough never seen before, but it’s not about the discovery of artificial life.

In most cases the experiment failed, and even when it did succeed the result was an assembly too malformed to be mistaken for a real embryo.

Some scientists don’t even approve of the term “synthetic embryo”. “These are not embryos,” says French researcher Laurent David, a specialist in stem cell development. “Until proven otherwise, they do not produce a viable individual capable of reproduction,” he says.

The researcher, who prefers the term ’embrioids’, specifies that they only present “sketches” of organs. However, he praises the “new and very attractive” work, with the potential to conduct experiments to better understand how organs develop.

– Hope for the transplant? –

These experiments are crucial so that stem cells can one day grow and form transplanted limbs without having to take them from a donor. This is no longer just a theoretical possibility.

Several years ago, researchers succeeded in developing an artificial intestine in the laboratory that worked once implanted in a mouse. In humans, this prospect remains science fiction, although Jacob Hanna believes his research directly paves the way for this advancement. And for that, he founded a startup, Renewal.

Other researchers consider that it is still too early to think of therapeutic advances, even if they admit that this research constitutes an important brick in this construction. But they warn that the next logical step will be to obtain similar results from human cells, paving the way for ethical questions about the status that should be accorded to these “embryoids”.

“Although we are still far from the prospect of synthetic human embryos, it will be essential to have broad debates on the legal and ethical implications of this research”, summarizes the British researcher James Briscoe, expert in embryonic development at Science Media Center. .

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