Three parent babies' take a step closer to reality
Scientists are a step closer to producing a controversial "three parent baby" after they successfully fertilised an egg with two biological mothers.
Researchers used eggs from young donors to repair damaged eggs of older women in order to increase their chances of fertilisation.
They have not yet used the eggs to produce babies, but they have injected them with sperm to produce an early stage embryo in the laboratory.
While the move breathes new life into "old eggs" and could also remove genetic illnesses, it is likely to provoke an ethical storm as critics believe it could lead to hybrid or genetically modified children.
"If we could transfer these constructed new embryos, I believe the success rate would be high," Atsushi Tanaka, the lead author told the New Scientist.
IVF often fails in older women because there are abnormalities in the outside of their eggs, known as cytoplasm, which surrounds the nucleus.
The team at St Mother Hospital in Kitakyushu, Japan, believe one way around the problem would be too implant the healthy nucleus - which contains most of the information to produce a baby - into the cytoplasm of a donor, usually a younger mother.
The team successfully did this in 31 eggs and of these seven formed "early stage embryos" when injected with sperm in a test tube.
Under the Human Fertilisation and Embryology Act, this kind of treatment – or any that involves genetically modifying an egg – remains illegal in Britain but the government has put in place a framework to relax the rules if and when science shows it can have positive impact on health.
In August, a team at Oregon National Primate Research Center and Oregon Health & Science University successfully bred monkeys from "fixed" eggs.
They replaced damaged Mitochondria - the power pack of cells - from an egg with those of a donor to produce the healthy offspring.
They believe it is so successful that they could begin human trials if the law allowed it.
In 2001, a furore erupted in the US when mitochondria from young eggs was injected into older women's eggs to improve their quality. Fifteen babies were born at the time using the technique, it was claimed.
A number of universities including a collaboration from Newcastle and Durham Universities claim to have created sperm in the laboratory from human stem cells.