It is a discovery that sheds new light on the early days of human life. Researchers have just highlighted the mechanisms by which our first cells combine to form a whole: the embryo.
This is “the first study on the mechanics of morphogenesis of the human embryo,” summarizes this work published this Wednesday, April 1, in the journal Nature.
“Compaction” stage
We are located a few days after fertilization. From the meeting between the sperm and the egg, a stem cell has already emerged, which has divided into a dozen more cells.
Then comes the time when these cells come together and group together, forming a single whole. The embryo, in its earliest stage, is there. Only then will the cells differentiate to gradually reveal organs and then, little by little, a human form.
Therefore, this first step, called “compaction,” is crucial. It is the subject of this study, carried out mainly by the researcher Julie Firmin and in which the CNRS, Inserm and the Curie Institute participate.
cell contract
Their conclusions call into question the way in which we have been viewing the formation of an embryo for several decades. The main mechanism was considered to be that by which cells stuck to each other, through the adhesion of their walls.
However, according to this study, this factor only plays a secondary role. Most crucial is each cell’s ability to contract, a mechanism by which they attract each other.
“You have to imagine a circle of people holding hands” that progressively closes, explains researcher Jean-Léon Maître, who led the study.
To reach this conclusion, the researchers examined cells from several embryos not used during in vitro fertilization, and frozen at different stages between three and five days.
The more advanced your stage, the stronger your cells will be to contract. However, there were no changes in the degree of adhesion of the walls, which remained stable. The researchers conclude that it is the first mechanism, and not the second, that plays a central role in the approach of the cells and the formation of the embryo.
A role for in vitro fertilization
“What makes the cells adhere to each other is not the amount of glue, but these contraction efforts,” insists Jean-Léon Maître.
“It’s no surprise,” he says.
Over the past twenty years, studies have successively demonstrated similar mechanisms in flies and then in mammals such as mice. However, if all these animals and humans have in common the predominance of the contraction mechanism, the details vary: it is not distributed, for example, in the same way within the cell.
Therefore, it is the human embryo that the study published this Wednesday allows us to better understand, without having to immediately wait for very specific consequences.
Of course, we can imagine that one day, thanks to this knowledge, the formation of embryos intended for in vitro fertilization will be facilitated. But currently, we still choose to implant embryos that have successfully passed this stage of formation.
A breakthrough
If this study represents an important advance, it is above all in the knowledge of the very origin of human life, a field of research that has been gaining momentum in recent years.
We can also include the recent laboratory manufacturing, by several research teams, of structures close to the embryo. Sometimes called “synthetic embryos,” although the term is controversial, these structures should make it possible to study how cells and then organs differentiate during the first weeks of gestation.
Like this work, this new study first aims to better understand how a human organism is built, what brings it closer to other animals and what differentiates it.
With the promise of “discovering how nature uses the laws of physics to produce so many forms of life, with their impressive diversity,” this work concludes.
Source: BFM TV
