Embryoids, models at the scientific and ethical border with the embryo
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What is an embryo? The answer seems obvious: an organism resulting from the fusion of two gametes, male and female, in its early stages of development. However, this evidence has been challenged by the research work of various teams making it possible to obtain cell cultures capable of developing characteristics of embryos without going through the traditional spermatozoid-egg fusion, from stem cells for example. The description this summer, in Cell then Natureof mouse embryoids cultured in vitro for up to 8.5 days – almost half of natural gestation in rodents – offers a striking illustration of this, and invites us to wonder about the increasingly tenuous boundary between these entities. and “classic” embryos.
In France, where the last revision of the bioethics laws dates from 2021, the legal definition of the human embryo is not expressly laid down. Some countries refer to stages of development, the potential to develop an individual. “It is interesting to note that the Court [de justice de l’Union européenne, dans un jugement de 2011] considers that what constitutes an embryo is either a process (fertilization, parthenogenesis) or a result (a cell possessing a mature human nucleus). This dual approach is found in various legislations.underlines the Inserm ethics committee, in a 2019 note devoted to “research on embryos and embryonic models for scientific use”.
“A code of conduct”
“The Inserm ethics committee is involved in a European project (Hybrida) within which we are responsible for producing a guide to good practice and a code of conduct for research on organoidssays Hervé Chneiweiss, its president. We are also linked to the International Society for Stem Cell Research [ISSCR] to harmonize our proposals on the implementation of the necessary regulations in the face of recent developments. »
“For the past ten years, by cultivating embryonic cells from mice but also from humans, we have realized that their potential for self-organization was probably underestimated”notes Nicolas Rivron, whose team, at the Vienna Academy of Sciences, notably obtained in 2018 in mice, then in 2021 in humans, the first “blastoid”, a model of the blastocyst, a term for the embryo before it is implanted in the uterus. Blastoids, but also organoids, teratoids, gastruloids and embryoids: this field of research has seen the emergence of a whole “zoo” of cell assemblies recapitulating more or less faithfully the first stages of organ development, in 2 then 3 dimensions, or d more integrated organizations.
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