Scientists are planning to create human-rabbit hybrid embryos to speed up research into the causes of inherited conditions such as motor neurone disease and Parkinson’s.
The controversial work, which involves placing the nucleus of a human cell inside a rabbit egg, is rejected as immoral by churches and anti-cloning campaigners. One of the key ethical problems is whether the hybrid embryo should be treated legally as a human or an animal.
Edinburgh University’s Professor Ian Wilmut – who created Dolly the Sheep – and colleagues in London believe the hybrids will help them circumvent a shortage of human eggs which is hampering research.
The procedure has already been carried out with some success by two groups of scientists in China and Mr Wilmut is preparing to write to the Human Fertilisation and Embryology Authority (HFEA) for permission to test it here.
Professor Wilmut told The Scotsman the results of Chinese research appeared to show that the hybrid embryos could be used to study human diseases.
"What we would be doing is using an unusual method to produce a human embryo which could be used to study very unpleasant diseases for which there isn’t a treatment," he said yesterday.
"In effect what we’d do is mimic the disease in the young person who, some unknown number of years in the future, would develop the disease. It gives a way to study the development of the disease which you could not do in any other way."
The embryos would only be about 200 cells and would not be allowed to develop for longer than 14 days or be implanted into a woman’s womb.
However, the Church of Scotland said the proposal violated the distinction between humans, who were "created in God’s image", and animals, who were not.
The HFEA, which governs this field of research, said yesterday any such work would have to be licensed, but did not rule it out.
Although made of rabbit-cell material, the embryos would be controlled by human DNA.
Prof Wilmut said he believed a hybrid embryo should be treated as human by the HFEA. Asked about the moral objections of church groups and others, the scientist said: "A critical element in this is to recognise we would only be working at a very early stage with a maximum of 200 cells.
"I wouldn’t think of a human embryo at that stage as being a person."
His colleague, Professor Chris Shaw, from King’s College London, said the lack of human eggs meant they had to consider an alternative source.
"The fertility of rabbits is legendary. There may be opportunities to use human cells for nuclear transfer to rabbit oocytes [eggs]. Legally, the position is not clear, but that’s something we’d like to discuss with the HFEA," he said.
Experiments using human DNA and rabbit eggs have already been conducted in China.
Dr Huizhen Sheng, of Shanghai Second Medical University, said in a paper two years ago that she had created more than 100 embryos by fusing human skin cells with rabbit eggs whose nuclei had been removed.
The embryos are said to have survived to the blastocyst stage – a ball of no more than about 60 cells the size of a pinhead.
The disgraced South Korean scientist, Professor Woo-Suk Hwang, had about 2,000 human eggs to work with and obtained fresh eggs from women who were willing, or persuaded, to donate them, including female members of his staff, in breach of guidelines.
To collect that many eggs in the UK might take ten years, said Prof Shaw, and despite his huge supply of eggs, Prof Hwang failed to derive any stem-cell lines from them.
"Faced with that challenge, we have to think of alternatives," Prof Shaw said.
Professor Alison Murdoch, from Newcastle University, whose team produced Britain’s first cloned human embryos, said the proposal exposed a "grey area" of the law.
She said: "You have to ask the question, ‘If you take a human nucleus and put it in a rabbit egg, is it a human embryo?’"
But she added: "Is there any harm in a human embryonic stem-cell line made from a rabbit egg?"
The Human Fertilisation and Embryology Act, which sets out the rules for conducting research on human eggs, sperm and embryos, is being reviewed by the government. Dr Chris O’Toole, head of research regulation at the HFEA, said: "The issue of mixing human and animal material is complex.
"The HFEA looked at this issue last September and concluded that any research that involves putting a human cell’s nucleus into an animal egg would require a licence from the HFEA."
Dr Donald Bruce, of the Church of Scotland’s Society, Religion and Technology project, said the Kirk’s General Assembly had taken a position on the creation of hybrid embryos and he had thought it was illegal.
"In historic Christian tradition, humans are made uniquely in God’s image. The mixture of human and animal tissue would breach the distinction which Christian tradition holds between humans and animals," he said, quoting from a document on the church’s position.
Patrick Cusworth, director of the Movement Against The Cloning of Humans, said: "I don’t think there’s any scientific validity in embryonic stem-cell research these days and research upon embryo ‘chimeras’ would not only jeopardise the humanity and dignity of the tiny human being, but also hold out a false mirage of hope to some very vulnerable patients."
But Dr Ainsley Newson, a medical ethicist, said that the public’s reaction to the proposal would largely be framed by their views on early-stage embryos.
"Obviously we need to be careful about species boundaries, but we are not talking about creating a hybrid animal," she said.
"To me, it seems a very sensible solution to the problem of the shortage of embryos for research on diseases."