Researchers at the Oregon Health and Science University have successfully used primates to test a new technique that could be used in the future to prevent mitochondrial diseases being passed from mother to child.

Scientists have developed a method which is aimed at preventing the transmission of mutated mitochondria from mother to child. In the research published in Nature they evaluated the safety and suitability of this new technology by testing it in primates.

The technique involves taking the chromosomes out of the egg from one monkey and transferring it to a donor egg from another monkey. The donor egg has had its own chromosomes previously removed. The donor egg can be fertilised by injecting sperm directly into it. The fertilised egg is then transplanted into the womb of a monkey.

To demonstrate that this technique can potentially be used in humans the scientists had to establish the most efficient way of fertilising the donor eggs in the laboratory following the transfer of the chromosomes. They also had to show that the amount of mitochondria that was transferred along with the chromosomes was very small and that the chromosomes remained undamaged during the transfer.

After successfully creating embryos and analysing them, the scientists continued with their experiments by transferring the embryos into the womb of surrogate monkeys. Three female monkeys have had successful pregnancies with two giving birth to twins and one to a single infant. The researchers looked at the mitochondria in the offspring to determine which egg they came from. They found only the mitochondria that originated from the donor egg demonstrating that no mitochondria were transferred at the same time as the DNA. These results and the fact that all offspring seem to be healthy suggest that the technology has successfully been used in these primates.

The result of this research is very encouraging and scientists express cautious optimism that it might become available for families with mitochondrial myopathy in the years to come. If this technology reaches the clinic it will not only be used for this form of muscle disease, but for all inherited conditions that are caused by a mutation in the mitochondrial DNA.  It will give families affected by mitochondrial diseases the choice of having healthy children.

Under the current UK law - as defined in the Human Fertilisation and Embryology Act - altered human embryos are not allowed to be implanted into the womb.  The use of this technology in humans - even to test it in a clinical trial - would require this to change.

Mitochondrial myopathies are a group of muscle conditions that are characterised by a variety of symptoms including muscle weakness and fatigue. They are caused by a genetic defect in the mitochondria, the powerhouses of the cells that generate energy from the fat and carbohydrates in our food. They are the only structures in the cell that contain their own piece of DNA, and this carries the information for 13 genes - in comparison the DNA in the nucleus carries information for about 25,000 genes.

Every cell has thousands of mitochondria that children inherit only from their mother. Patients with mitochondrial myopathies generally have a mixture of faulty and healthy mitochondria and the ratio contributes to the severity of the condition. This mixture is also the reason why it is very difficult for clinicians to give parents accurate advice of how severely their children will be affected.