A UK experiment has shown that a group of children can avoid serious diseases thanks to genetic modification during their development. However, this study cannot be conducted in France or the United States due to strict regulations.
The study, published Wednesday in the New England Journal of Medicine and eagerly awaited by the scientific community, presents the results of an unprecedented experiment: About 20 women received "mitochondrial donation" to avoid passing on a rare genetic disease to their children.
Mitochondria are tiny structures found in our cells that play a key role in converting nutrients into energy.
In some cases—one in every 5,000 people—mitochondrial dysfunction occurs. This causes a mitochondrial disease that can manifest in various, often serious and disabling forms, including vision problems, diabetes, and muscle degeneration.
However, these mitochondria operate on their own DNA, separate from the rest of the cell. The concept of mitochondrial donation involves replacing the mother's mitochondrial DNA with that of another woman immediately after embryo formation. All other genetic material remains the property of both parents.
Some commentators consider these embryos "three-parent babies," although this term, often used by opponents of the procedure, is not widely accepted among specialists in the field, who consider it an oversimplification.
The United Kingdom is a pioneer in this field: mitochondrial donation has been permitted there since 2015, enabling the trial whose results were recently published.
Many scientists consider these results very encouraging. Of the approximately 20 patients, eight have given birth to children, currently aged between six months and three years.
This demonstrates that mitochondrial donation allows for healthy pregnancies. But more importantly, it turns out that these children were born with very low levels of damaged mitochondrial DNA. This demonstrates that the treatment "reduces the transmission" of mitochondrial diseases, the study concluded.
There are several caveats to this approach. First, two children experienced medical complications. The study authors believe this was unrelated to the procedure, but some commentators believe this may be a hasty ruling.
More importantly, three of the children had increased levels of defective mitochondria from birth, raising questions about the sustainability of these effects.
Nevertheless, these results are "very significant and represent a paradigm shift in mitochondrial medicine," according to Swedish Professor Nils-Göran Larsson, one of the world's leading experts in the field, in a comment to the UK Science Media Centre.
Not only is the scientific progress receiving positive reviews, but so are the regulations chosen by the UK, which many researchers have praised for allowing this research to proceed with close ethical oversight.
This choice contrasts with many other countries. In the United States, health authorities have regularly expressed opposition in recent years. In France, the Agence Public de Médecine Biologique (APMB) has sought to launch research but has repeatedly faced legal challenges, even though bioethics laws only permit experiments on embryos less than two weeks old, derived from assisted reproduction and destined for destruction.
Mitochondrial donation primarily raises ethical questions. Some observers fear that this procedure, which involves the introduction of a small dose of DNA from a third party, could disrupt the child's personal development.
Above all, critics of this procedure point to it as a form of genetic manipulation of the embryo, which is strictly prohibited under some international agreements.
Moreover, children have been born in recent years, outside the British experiment, from mitochondrial donations under less restrictive regulatory frameworks, in Greece or Ukraine, sometimes for less clear justifications, such as infertility treatment.
French researcher Julie Stephan, a specialist in mitochondrial diseases, told AFP, "The problem is the benefit-to-risk ratio: for mitochondrial diseases, the benefit is clear. In the context of infertility, this has not been proven."
However, the ban on research in France is "unfortunate for patients," according to Stephan, who believes it is inappropriate to equate mitochondrial donation with the creation of a "genetically modified" embryo.
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