Stem cell scientists say they have created “synthetic embryos” for the first time without using sperm, eggs or fertilization, but the prospect of using such a technique to grow human organs for transplantation remains remote.
The breakthrough was hailed as a major advance, although some experts said the result could not be considered fully embryonic and warned of future ethical considerations.
In research published this week in the journal Cell, scientists at the Weizmann Institute of Science in Israel described mouse stem cells that self-assemble into embryo-like structures in the laboratory.
The research built on research from 2018 in which a bunch of mouse stem cells had self-assembled to create something resembling the beginnings of an embryo – but with far fewer cells.
The Weizmann team around the Palestinian stem cell researcher Jacob Hanna went much further.
They first collected cells from the skin of mice and then artificially restored them to the state of stem cells.
The stem cells were then placed in a special incubator that moved continuously to mimic the womb.
The vast majority of cells formed nothing.
But 50 — 0.5 percent of the 10,000 total — clustered into spheres, then embryo-like structures, the researchers said.
After eight days — about a third of the mouse’s 20-day gestation period — there were early signs of a brain and a beating heart, they added.
They have been described as being 95 percent similar to normal mouse embryos.
“The embryo is the best organ-making machine and the best 3D bioprinter — we tried to mimic what it does,” Hanna said in a statement from Weizmann.
– ‘No embryos’ –
Despite being the most advanced synthetic embryo-like structures ever created, some scientists not involved in the research cautioned against calling them “embryos”.
“These are not embryos,” French stem cell researcher Laurent David told AFP.
“Until proven otherwise, they do not result in a viable individual capable of reproduction,” he added.
He preferred to call them embryoids, the term for a group of cells resembling an embryo, emphasizing that they only showed the beginnings of organs.
However, David welcomed the “very convincing” research, which he says could allow for further experiments to understand exactly how organs form.
Hanna said the team’s “next challenge is to understand how stem cells know what to do – how to self-assemble into organs and find their way to their assigned sites in an embryo.”
– Ethical implications –
If human organs could one day be grown in a laboratory, thousands of people could receive life-saving transplants every year without the need for donors.
There have been advances in this new field – a few years ago, researchers succeeded in developing an artificial intestine in the laboratory that could be implanted in a mouse.
For humans, however, such organ implants remain science fiction.
Still, Hanna has started a company, Renewal Bio, with the goal of finding a way to use the technology for therapeutic purposes.
Researchers not involved in the study said it’s still very early days to use such a technique in humans.
Alfonso Martinez Arias of Spain’s Pompeu Fabra University said the breakthrough “opens the door to similar studies using human cells, although there are still many regulatory hurdles to overcome and human systems lag behind mouse systems from an experimental point of view.” .
And the goal of achieving similar results with human cells will likely open an ethical can of worms.
“Although the prospect of synthetic human embryos is still a long way off, it will be crucial to engage in broader discussions about the legal and ethical implications of such research,” said James Briscoe of the UK’s Francis Crick Institute.
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