Human and animal trial of a controversial new IVF treatment has yielded promising results, say US scientists.
The findings in Nature magazine show healthy-looking embryos can be created from a mix of three adult donors.
Human embryos were grown in the lab and some appeared normal, while monkeys born using the same technique remained fit and well, now aged three.
Its findings will be reported to the health secretary in spring 2013.
The technique is designed to prevent debilitating and fatal “mitochondrial” diseases, which are passed down only from mother to child and which cause muscle weakness, blindness and heart failure.
By using two female egg donors, these DNA errors could be cancelled out, scientists believe.
Three-person IVF uses the core genetic information from mother and father as usual, but puts it into a donor egg which contains healthy mitochondria.
Mitochondria sit in the cytoplasm of the egg – akin to the white of a hen’s egg. They contain only a tiny fraction of our genetic material, with the bulk that determines things like our hair and eye color housed in the nucleus – a speck in the yolk if you use the hen’s egg analogy.
Scientists have been studying two ways of creating three person embryos.
One way is to take the nucleus from the mother’s egg and put it into a donor egg that has healthy mitochondria and has had its own nucleus removed. This new egg can then be fertilized with the father’s sperm.
Another way is to fertilize the mother’s egg first before removing the nucleus and putting it into the donor egg.
The latest study looked at the first method.
The Oregon Health team took eggs from seven women who had volunteered to take part in the research.
The scientists were able to replace the mitochondrial DNA in 65 of the eggs and then looked to see how well these fared over the next week or so.
The fertilization rate afterwards was similar to the 33 control eggs that had not been manipulated, although over half had abnormal qualities.
Those that did fertilize normally developed to blastocyst stage – five or six days later, the point at which IVF embryos are normally transferred into the mother’s womb – at a similar rate to the controls.
Dr. Masahito Tachibana and colleagues say their research shows that the technique can work, at least in the lab. It is still not clear if it could lead to a healthy baby.
The scientists now want to be able to do more studies to ensure the treatment is also safe.