Unprecedented in vitro fertilization test reduces risk of hereditary diseases
Eight healthy babies have been born in the UK thanks to a new in vitro fertilization (IVF) technique that successfully reduced the risk of genetic diseases inherited from their mothers, according to the findings of a groundbreaking study published on Wednesday (16).
The findings were hailed as a major breakthrough that raises hope that women with mitochondrial DNA mutations could one day have children without passing on disabling or fatal diseases.
One in 5,000 people is born with mitochondrial diseases, which have no treatment and whose symptoms can include vision loss, diabetes and muscle atrophy.
In 2015, the UK became the first country to approve an in vitro fertilization (IVF) technique that uses a small amount of healthy mitochondrial DNA from a donated egg (along with the mother's egg and the father's sperm).
Babies born through this procedure are sometimes called “three-parent babies,” although researchers reject this term, since only about 0.1 percent of a newborn's DNA comes from the donor.
The results of the long-awaited UK study were published in several articles in the New England Journal of Medicine.
Of the 22 women undergoing treatment at the Newcastle Fertility Centre in northeast England, eight babies were born. The four boys and four girls are currently between the ages of less than six months and over two years.
The amount of mutated mitochondrial DNA – which causes the disease – was reduced by between 95% and 100% in six of the babies, the study found.
In the other two newborns, the amount was reduced by between 77% and 88%, levels below the threshold that causes the disease. This indicates that the technique was "effective in reducing transmission" of diseases between mother and child, according to one of the studies.
All eight children are currently healthy, although one had a heart rhythm disorder that was successfully treated, researchers said.
Their health will be monitored over the next few years to see if any problems arise.
For Nils-Göran Larsson, a Swedish reproduction specialist who was not involved in the study, the breakthrough represents a “milestone.”
The new technique offers “a very important reproductive option” for families affected by “devastating” mitochondrial diseases, he added.
Mitochondrial donation remains a controversial topic and has not been approved in many countries, such as the United States and France.
Religious leaders have opposed the procedure because it involves the destruction of human embryos. Other critics fear it sets a precedent for the creation of genetically engineered "designer babies."
A review by the UK's independent bioethics body Nuffield Health was "critical" to the conduct of the research, its director, Danielle Hamm, said on Wednesday.
Peter Thompson, director of the Human Fertilisation and Embryology Authority (HFEA), which approved the procedure, said only people at “very high risk” of passing on a mitochondrial disease would be eligible for the treatment.
Ethical objections have also been raised about the use of mitochondrial donation for infertility treatment in Greece and Ukraine.
French mitochondrial disease expert Julie Stefann told AFP: "It's a question of risk-benefit: for a mitochondrial disease, the benefit is clear."
“In the context of infertility, it is not proven,” he added.
For Dagan Wells, an expert in reproductive genetics at the University of Oxford, "some scientists will be disappointed that so much time and effort has so far resulted in only eight children."
Among the closely monitored children, three showed signs of what is known as “reversion,” a phenomenon still poorly understood.
This is “a phenomenon in which the therapy initially manages to produce an embryo with very few defective mitochondria, but, at the time of birth, the proportion of abnormal mitochondria in its cells increases significantly,” he explained.
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