Scientists were able to grow “synthetic embryos” without the need for sperm, eggs or wombs.
Studying these structures in mice can teach us how to grow organs for transplantation.
Making human babies that way remains a distant prospect, fraught with ethical problems.
Scientists grew “synthetic embryos” from mouse cells without using sperm, eggs or wombs.
The process, a world first, was described in an issue of the peer-reviewed journal Cell on 1 August.
The technology could be a starting point for growing organs from scratch, Jacob Hanna of the Weizmann Department of Molecular Genetics, who led the research team, said 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 feasible, and gives the ethical question a more pressing one, they said.
Cracking the Synthetic Embryo Code
“The embryo is the best organ-making machine and the best 3D bioprinter — we tried to mimic what it does,” Hanna said.
Hanna and his group had previously managed to grow mouse embryos outside the womb, in glass containers.
But these embryos were taken directly from real mice, and were fertilized. In the latest study, the embryos were grown from stem cells.
Cells learn what to do by reading chemical signals that the body sends to them.
Scientists can mimic these signals to turn stem cells into fake organs in a dish for research, such as mini-brains used to test drugs.
Most of Hanna’s synthetic embryos died early in the process. But a few managed to grow for 8.5 days, about half the gestation of a mouse.
At that point, they looked 95% like normal mouse embryos and had grown into a placenta and the beginnings of a spine and brain, a digestive tract, a beating heart, according to the study.
However, these are not “real” embryos, Hanna told The Guardian. First, they were unable to grow to term when placed in a mouse womb, he said.
Growing organs from synthetic embryos
Because these synthetic embryos are made from stem cells, rather than via fertilization, it is easier to scale the process and create mass at once.
It could be invaluable to science, because it could make vast quantities of synthetic embryos available for research without relying on laboratory animals.
If these cells can be coaxed into making the beginnings of organs, studying them could reveal the building blocks for making organs from scratch to transplant 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 locations inside an embryo,” Hanna said.
Still a long way from synthetic human embryos
James Briscoe, a group leader at the Francis Crick Institute in London who is 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 human synthetic embryos and to update current regulations,” he said.
“We’re not going to see human embryos grown from stem cells anytime soon,” Briscoe said. These synthetic mouse embryos were unable to develop into a living mouse. We also know much less about human embryos, which take much longer to arrive and are much larger.
Still, this innovation could jump-start this field of research, 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 one step, but a very important step for us to be able to study early development,” Tesar said.
“We’re crossing into 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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