Create an embryo without resorting to an egg or sperm, or any fertilization process. This is what a team of Israeli researchers did, according to a study published in the journal Cell August 1st.
These scientists have designed mouse embryos from stem cells, which have the particularity of being able to be reprogrammed into any other cell or any organ. The stem cells then grew in an incubator, acting as an artificial uterus, until they resembled an eight-day-old mouse embryo.
A scientific first
This is not the first time that such an experiment to create “synthetic” embryos has been carried out – in December 2021, the same process had been used for human embryos. But never before have researchers managed to preserve them for such a long time. “Eight days, for a murine embryothis corresponds to a third of its development (gestation in mice lasts an average of twenty days, Editor’s note)», explains Laurent David, professor of cell biology at the University Hospital of Nantes. At this stage, the organs begin to differentiate: the embryos designed by the Israeli team showed the first folds of the brain and the outline of a heart, specifies the study of Cell.
The interest of such an experience? « This shows that the understanding of embryonic development is progressing and could complement our knowledge of organ formation, for example,” says Laurent David. For the scientific community, the research published in Cell are above all only a first step, opening the way to a possible transposition from animals to humans.
For that, it would be necessary to obtain the same results (the creation of synthetic embryos therefore) from human stem cells, this time. Such embryos would be useful in research for, among other things, “Understand the early disturbances during pregnancy (infertility, miscarriage, endometriosis)…”, pleads Jacob Hanna, the Palestinian researcher who oversaw the study, joined by email.
Alternatives to real embryos that raise questions
In France, the law prohibits the conception of real embryos only for research: the embryos used are supernumerary embryos given by couples in the process of ART and who no longer have a parental project, and they must be destroyed after fourteen days. In this context, synthetic embryos could represent alternatives “technical and ethical”continue Jacob Hanna.
However, wouldn’t they also be “a step towards the creation of artificial living beings? »asks Vincent Grégoire-Delory, lecturer in science ethics at the Catholic Institute of Toulouse, echoing the questions that have been agitating the scientific world for a few days. “These synthetic embryos are not real embryos, but embryoids, in the sense that they only have the shape, answers Jacob Hanna. They can’t even implant themselves in a mouse’s uterus. » In Nantes, Laurent David confirms. Because they are not derived from gametes, “they do not have the potential to grow and become viable”.
Extending the deadlines for research on the embryo: a step forward or a danger?
It prevents, “we are here faced with a medicine that is no longer restorative but demiurgic, which models and manufactures living things, even if it is with an objective that may seem completely legitimate, asks Vincent Grégoire-Delory. Not really embryos, but still conceived from human cells, what would be the status of these structures? “. And, because of this special status, “until what time limit could we study these entities?, adds Laurent David. When would this become problematic? We will have to weigh the risks and the benefits. » Reflections, assures the researcher, who “never leave us”.