Stem cell researchers say they have created “synthetic embryos” without using sperm, eggs or fertilization for the first time, but the prospect of using this technique in developing human organs for transplantation remains distant and controversial.
“Synthetic embryos formed themselves, 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 carried out on mice in an Israeli laboratory, under the direction of the Palestinian Jacob Hanna, and was unprecedentedly successful in a field of research that emerged a few years ago.
It is about developing structures close to the embryo in the laboratory, extracting single cells from an animal and acting on them without any fertilization procedure.
The last major breakthrough in this matter dates back to 2018. At the time, the researchers – led by Frenchman Nicolas Rivron – managed to get stem cells to develop into a set similar to a very early embryo, a “blastocyst”. But at this point, the cells of the embryo are no different from those that would form a future placenta.
Jacob Hanna’s team went further. He developed structures similar to an eight-day mouse embryo, that is, a third of the gestation, and at a time when the organs begin to differentiate.
To do this, the researchers extracted skin cells from the mice and then artificially reverted them to the state of stem cells, capable of differentiating into different organs. They were placed in a nutrient bath, constantly shaken and fed with oxygen to reproduce as closely as possible the conditions of a mother’s womb.
As a result, a small part of the cells organized themselves, based on their 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 was successful, the result was a set too malformed to be mistaken for a real embryo.
Some scientists don’t even approve of the term “synthetic embryo”. “They are not embryos,” declares French researcher Laurent David, an expert in stem cell development. “Until proven otherwise, they don’t produce a viable individual capable of reproducing,” he says.
The researcher, who prefers the term ’embryoids’, points out that they only present “sketches” of organs. However, he praises the “new and very attractive” work, with the potential to carry out experiments to better understand how organs develop.
Any hope for the transplant?
These experiments are crucial so that stem cells can one day develop and form limbs that can be transplanted without having to take them from a donor. It is no longer just a theoretical possibility.
Several years ago, researchers managed to develop an artificial intestine in the laboratory that worked once implanted in a mouse. In humans, this perspective 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 about therapeutic advances, although they admit that this research constitutes an important building block 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 given to these “embryoids”.
“Although we are still far from the perspective 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, an expert in embryonic development at the Science Media Center.