Scientists create artificial mouse embryos, a potential key to human recovery


Stem cell researchers in Israel have created artificial mouse embryos without using sperm or an egg, then grown them in an artificial womb for eight days, a development that opens a window into a fascinating and risky scientific world that could one day be used to create replacement organs for humans.

The scientists involved in the research said the goal is not to create mice or babies outside the womb, but to unlock an understanding of how organs develop in fetuses and use this knowledge to develop new ways to heal people.

From a pool of embryonic stem cells, scientists at the Weizmann Institute of Science have created artificial embryos that closely resemble those of real mice, with primitive beating hearts, blood circulation, folded brain tissue and intestinal tracts. Mice embryos grew in an artificial uterus and stopped growing after eight days, about a third of a mouse’s pregnancy.

This progress, which lasted a decade, arrived in a field crowded with efforts to develop embryo models from human and mouse cells. Scientists can use such models to look at the early stages of embryonic development and study how organs form.

But as models become more and more similar to the real thing, they also open up a morally ambiguous area. At what point do artificial embryos become so similar to the real thing that they are subject to protection similar to that applied to real embryos?

“This is a milestone in our understanding of how embryos build themselves,” said Alfonso Martínez Arias, an evolutionary biologist at Pompeu Fabra University in Barcelona, ​​who was not involved in the research, in an email. He described the experience as a “game changer”.

The research, published Monday in the journal Cell, is far from growing a mouse, let alone a human, outside the womb. It was a proof of concept that an entire artificial embryo could be synthesized from embryonic stem cells, and while the researchers succeeded, it was a highly error-prone process, with only a small portion of the embryos developing the beginnings of the heartbeat and other organs.

Although the artificial mouse embryos bore a close resemblance to normal mouse embryos, they were not exactly the same and were not implanted or conceived in real mice, according to Jacob Hanna, a stem cell scientist at the Weizmann Institute of Science who led the research team. work.

Greeley, a bioethicist at Stanford Law School.

Several researchers said that the research, like other recent studies, puts the possibility of a full-fledged human artificial embryo on the horizon, making it necessary to continue the societal debate about how to deal with these entities. Last year, the International Society for Stem Cell Research relaxed the historic “14-day rule” that says researchers can only grow normal embryos for 14 days in a lab, allowing researchers to gain approval for longer studies. Implantation of human embryo models in the uterus is prohibited.

“The mouse is a starting point for thinking about how one would like to approach this in humans,” said stem cell biologist Alex Messner at the Max Planck Institute for Molecular Genetics. “You don’t have to get upset or panic, but…as we’ve learned, it’s important to have a parallel discussion: How far do we want to take it?”

Hanna said his hope is that the technology can be used not as a substitute for reproduction but as a way to create models of artificial human embryos that could lead to precursors to organs that can be studied and possibly used therapeutically.

For decades, the main hope of stem cell therapy has been to repair the body’s tissues. Stem cells can develop into any tissue or organ, so the possibility of using these cells to repair spinal cord injuries, graft damaged hearts or treat diabetes was enticing. But turning these cells into complex, functional tissues has been a challenge. Hanna hopes that watching this process during early development will provide important clues.

“Our goal is not to make the pregnancy ectopic, whether it’s mice or any other species,” Hanna said. “We are really having difficulties making organs – and in order to get stem cells to become organs we need to know how the fetus does it. We started with this because the uterus is a black box – not transparent.”

Hanna is the founder of Renewal Bio, which plans to use the technology as a treatment. One possible use would be to take skin cells from a woman with fertility problems, reprogram those cells to make stem cells, and then grow artificial embryo models that can be used to produce eggs.

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