Scientists were able to develop “synthetic embryos” without the need for sperm, eggs or a uterus.
Studying these structures in mice can teach us how to grow organs for transplantation.
Making human babies this way remains a distant prospect, fraught with ethical problems.
Scientists created “synthetic embryos” from mouse cells without using sperm, eggs or uterus.
The process, a world first, was described in an August 1 issue of Cell magazine.
The technology could be a starting point for growing organs from scratch, said Jacob Hanna of Weizmann’s Department of Molecular Genetics, who led the research team, in a statement.
Independent experts said much more research would be needed before even considering growing a human embryo in this way.
Still, this research makes that possibility a little more viable, adding urgency to the ethical question, they said.
Breaking the Synthetic Embryo Code
“The embryo is the best organ-making machine and the best 3D bioprinter – we try to mimic what it does,” Hanna said.
Hanna and her group had already managed to grow mouse embryos outside the uterus, in glass containers.
But these embryos were taken directly from real mice and were fertilized. In the latest study, embryos were grown from stem cells.
Cells learn what they are supposed to do by reading chemical signals sent to them by the body.
Scientists can mimic these signals to turn stem cells into fake organs in a dish for research, like mini-brains used to test drugs, for example.
Most of Hanna’s synthetic embryos died early in the process. But some managed to grow for 8.5 days, about half the gestational time of a mouse.
At that point, they were 95% similar to normal mouse embryos and had grown a placenta and the beginnings of a spinal column and brain, a digestive tract, a beating heart, according to the study.
However, these are not “real” embryos, Hanna told The Guardian. For one, they weren’t able to grow when they were placed in a mouse uterus, he said.
Organs growing from synthetic embryos
Because these synthetic embryos are made from stem cells rather than fertilization, it’s easier to scale the process and produce many at once.
This could be invaluable to science, because it could make huge amounts of synthetic embryos available for research without relying on laboratory animals.
If these cells can be induced to make the beginnings of organs, studying them could reveal the building blocks for making organs from scratch to transplant them into humans without the need for donors, Hanna said.
“Our next challenge is to understand how stem cells know what to do — how they self-assemble into organs and find their way to their assigned spots within an embryo,” Hanna said.
Still far from synthetic human embryos
James Briscoe, a group leader at the Francis Crick Institute in London, not involved in the research, told The Guardian that the research raises ethical questions.
“Now is a good time to consider the best legal and ethical framework to regulate research and use of synthetic human embryos and update current regulations,” he said.
We won’t see human embryos grown from stem cells anytime soon, Briscoe said. These synthetic mouse embryos were not able to develop into live mice. We also know much less about human embryos, which take much longer to be born and are much larger.
Still, this innovation could set this field of research in motion, Paul Tesar, a developmental biologist at Case Western Reserve University School of Medicine who was not involved in the study, told STAT News.
“This is just a step, but a very important step for us to study the early development,” said Tesar.
“We’re entering the realm of being able to generate an embryo from scratch and potentially a living organism. It’s been a really remarkable change for the field.”
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