On the refrigerator, at the entrance to the laboratory, someone taped a small poster: “Embryos. Open slowly! » Inside, in tubes sealed with paraffin, thawed embryos are kept cool. Until a few days ago they were stored in nitrogen tanks. But here, at the Institute for Health Research, placed under the aegis of the National Institute for Health and Medical Research (Inserm) and the University Hospital of Nantes, the study of human embryonic cells is a specialty.
“To study the embryo is to try to understand what happens in the first hours, the first days of development», explains Professor Thomas Fréour, head of the reproductive medicine department at Nantes University Hospital, to his office. On his computer screen, a video shows, in accelerated, how an embryo “differentiate” as the days go by. One cell, then two, then ten… “You see, the structure is getting more complex. » By better understanding what is happening, it is “to improve the chances of success of medically assisted procreation; to consider new avenues of contraception and to understand the pathologies that occur during fetal development, sometimes very early »such as cleft lip and palate (cleft lip) for example.
A special status
So there are the embryos. But in Nantes, the teams are also working on embryonic stem cells. Taken from embryos at the very beginning of development, these can reproduce ad infinitum, or even, when they are pluripotent, transform into any type of cell (cardiac, renal, etc.). «prospects for regenerative medicine », explains Laurent David, head of the stem cell platform. With the hope of being able to repair organs by integrating new cells, healthy this time because they come from famous stem cells.
Frozen, examined, manipulated, is the embryo a biological material like any other? To listen to the researchers, not completely. “We are aware of the preciousness of this resource, we know where it comes from”, specifies Thomas Fréour, who recalls that the embryos used are supernumerary embryos donated by couples who have had recourse to assisted reproduction; but no longer having a parental project.
A material like no other… For more than twenty years now, research on the embryo has been the subject of debate and remains subject to a specific framework. First totally prohibited in 1994 during the first laws relating to bioethics, it was the subject of derogations under conditions in 2004, then in 2011, before being subjected, in 2013, to a regime of supervised authorizations. Faced with the law, the human embryo in fact retains “a special status, says Bernard Baertschi, member of the Inserm Ethics Committee. The law does not consider him as a full person – the legal personality of an individual beginning at birth – but as a potential person. It is in this capacity that the law protects him. In Germany or Italy, this research is outright prohibited. »
Does the end justify the means?
“We can see that the French legislator is uncomfortable on this issue”, commented Blanche Streb, head of training for the Alliance Vita movement, opposed to research on the embryo. On the one hand, “Article 16 of the Civil Code lays down the principle of respect for human beings from the beginning of their lives; the law considers that the embryo is not just a cluster of cells. And at the same time, the safeguards are gradually falling. » Latest development: the law of August 2, 2021 now authorizes researchers to cultivate embryos until August 14e development day, whereas until now it was allowed until the 7e day. They are then destroyed. “However, scientifically, the embryo is a human being from its conception, protested Blanche Streb. Does research on the embryo have an interest? Scientific honesty obliges to say yes. Can an ethic be based on utility alone? No. »
But are there alternatives? « Oui.Research could be carried out on certain primates,” assures Alain Privat, neurobiologist and member of the Academy of Medicine.« Non, contests Laurent David, in Nantes. Researchers are working on models of pigs, mice, but there is necessarily a time when you have to work on the human. »
Could adult pluripotent stem cells be used? Taken from a patient and not from an embryo, unlike their cousins the embryonic stem cells, these can however be brought back to this same embryonic stage, without requiring fertilization. “These are complementary tools, but not totally substitutable, because of possible mutations”, comments Bernard Baertschi. That is. The blastoids, then, these real fake embryos recreated in laboratories? They too are not the result of the encounter between gametes and therefore pose fewer ethical questions. “They have a very similar structure to real embryos. But to what extent having an equivalent structure confers absolute homology, I am unable to tell you at the moment, the discovery is too recent. », nuance Thomas Fréour, co-author of a study on the subject, published in March 2021.
A benefit/risk balance
«A techno-scientific vision leads us still further away, worries Blanche Streb. New dikes are in danger of giving way. » Among the fears: could the researchers ask to cultivate the embryos for up to 21 days? To manufacture for the sole purpose of research, which is, for the moment, prohibited in France? “It is impossible to reassure the opponents”, believes Laurent David, who finds the current law “balanced”. ” What to say ? That I don’t get up in the morning rejoicing to destroy an embryo. That for the moment, there is no alternative, but that if we find a better model, we will stop. »
A confidence in science that does not prevent questions. “I can sometimes wonder if the information obtained justifies my research. Perhaps, one day, I will consider the potential of an embryo too large for my manipulations. For the moment, this is not the case. »
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A hundred protocols in twenty years
Since 2004, in France, 101 protocols have been launched (27 of which concern the human embryo itself).
32 are still active today, led by 26 teams.
Among the advances:
– a protocol carried out on the embryo has enabled the identification of embryonic quality markers, which guarantees better implantation, and therefore a better success rate of in vitro fertilization.
– a protocol conducted using stem cells, now in clinical trials, has enabled patients with retinitis pigmentosa to recover part of their vision. Another is conducted on patients with heart problems.
– Since 2005, approximately 4,000 embryos were included in research protocols.