Eight babies in the United Kingdom have been born using DNA from a third person to eliminate the risk of them developing an often fatal genetic disease.
The method, referred to by the BBC as the three-person technique, was pioneered by a group of Newcastle-based British scientists and combines the egg and sperm of a mother and father with the healthy DNA of a second egg, donated by a woman to eliminate the risk of a baby developing mitochondrial disorders.
The technique has been legal in the U.K. for 10 years, but proof that it is effective and leading to children being born without the disease is just beginning to emerge.
Mitochondrial disorders are only passed down from the mother to the baby, and deplete the body of the energy it needs to sustain life. It can also cause severe disabilities, with some babies dying within days of birth.
The National Institute of Neurological Disorders and Stroke says that such disorders can affect one or many parts of the body, including the brain, muscles, kidneys, heart, eyes and ears.
While children born through the three-person technique inherit the majority of their DNA from their parents, about 0.1 per cent is passed on through the donor egg, and then through future generations.
About one in 5,000 babies are born with mitochondrial disease, but this new technique means couples who may have lost one or multiple children to the fatal disorder before can try again while eliminating the risk of passing on the disease.
Embryo selection for IVF, light micrograph.
While the eight couples who used the method to have children have chosen to remain anonymous, they have shared statements detailing their experiences through the Newcastle Fertility Centre, where the procedures took place.
“After years of uncertainty this treatment gave us hope — and then it gave us our baby,” the mother of a baby girl said, as reported by the BBC.
“We look at them now, full of life and possibility, and we’re overwhelmed with gratitude,” she continued.
Another mother of a baby boy said, “Thanks to this incredible advancement and the support we received, our little family is complete.”
“The emotional burden of mitochondrial disease has been lifted, and in its place is hope, joy and deep gratitude,” she added.
How the procedure works
The science was created over a decade ago at Newcastle University and the Newcastle upon Tyne Hospitals NHS Foundation Trust, in northern England, with a specialist NHS service opening in 2017.
The eggs from the mother and the donor woman are fertilized in a lab using the dad’s sperm.
Two embryos develop until the DNA from the sperm and egg can be extracted from a structure known as the pronuclei, which determines features such as hair colour and height.
The pronuclei are then removed from both embryos, and the parents’ DNA is put inside the donor embryo with healthy mitochondria.
Two reports in the New England Journal of Medicine recorded 22 families who have undergone the process at Newcastle Fertility Centre, leading to the birth of four boys, four girls, a set of twins and an existing pregnancy.
“To see the relief and joy in the faces of the parents of these babies after such a long wait and fear of consequences, it’s brilliant to be able to see these babies alive, thriving and developing normally,” Prof. Bobby McFarland, the director of the NHS Highly Specialised Service for Rare Mitochondrial Disorders, told the BBC.
All the babies born so far were born without mitochondrial disease and have met their developmental milestones.
One child was born with epilepsy, which reportedly went away on its own, and another had an abnormal heart rhythm, which is being effectively treated. Neither is thought to be connected to defective mitochondria, though it is not known if they are related to the risks of IVF, the three-person method, or something that has been detected due to intense medical observation.
There is also still doubt over whether defective mitochondria could be transferred to the healthy embryo and the potential consequences.
In five cases, the diseased mitochondria were undetectable. In the other three, between 5 per cent and 20 per cent of mitochondria were defective in blood and urine samples.
Nonetheless, the rate of detection is below the 80 per cent level thought to cause the disease. Still, further research is needed to understand why the defective transfer occurred and if it can be prevented.
Prof. Mary Herbert, from Newcastle University and Monash University, told the BBC: “The findings give grounds for optimism. However, research to better understand the limitations of mitochondrial donation technologies will be essential to further improve treatment outcomes.”
The U.K., as well as developing the science, was the first country in the world the legalize the procedure, which happened in 2015.
The procedure is illegal in Canada and most other countries, but is also available in Australia and Ukraine. Global News reached out to Health Canada for comment but did not hear back by publication time.