Stem cell experts seek rabbit-human embryo
· Hybrid will hasten research, say scientists
· Grey area exposed in regulation procedures
Ian Sample, science correspondent
Friday January 13, 2006
British scientists are seeking permission to create hybrid embryos in the lab by fusing human cells with rabbit eggs. If granted consent, the team will use the embryos to produce stem cells that carry genetic defects, in the hope that studying them will help understand the complex mechanisms behind incurable human diseases.
The proposal drew strong criticism from opponents to embryo research who yesterday challenged the ethics of the research and branded the work repugnant.
Plans for the experiments have been put forward by Professor Chris Shaw, a neurologist and expert in motor neurone disease at King's College London, and Professor Ian Wilmut, the Edinburgh University-based creator of Dolly the sheep, as a way of overcoming the shortage of fresh human eggs available for research.
"The fertility of rabbits is legendary," said Prof Shaw. "The most important thing is that with animal eggs, we have a much better chance of generating stem cells and if we wait for human eggs, it's going to be maybe a decade before we can do this. If we can use animal eggs, we could maybe have stem cells within one or two years," he added.
Scientists use eggs in research to create cloned embryos, from which they harvest stem cells. By producing stem cells that carry the genetic defects of diseases, researchers believe they will be able to unravel how a cell's molecular machinery goes wrong, potentially leading to new cures for disease. But the research is progressing slowly, hampered by a severe shortage of "spare" eggs donated by couples undergoing fertility treatment.
Prof Shaw's team will need a licence from the Human Fertilisation and Embryology Authority before they are allowed to pursue the research. "As with all research involving human embryos, the research team would have to show that the research is both necessary and desirable, and that any embryo created could not be allowed to develop for longer than 14 days or be implanted in a woman," said Dr Chris O'Toole, head of research regulation at the HFEA.
If the researchers are granted consent, they will not be the first to fuse human cells with rabbit eggs. In 2003, Huizhen Sheng at Shanghai Second Medical University published work in which she claimed to have extracted stem cells from hybrid embryos made from rabbit eggs.
To make a hybrid embryo, a human skin cell would be taken from a person with motor neurone disease and injected into a hollowed-out rabbit egg. The resulting embryo would contain only a tiny amount of rabbit DNA in a microscopic structure that generates energy in the cell. The rest of the DNA would be human. If the experiment is successful, within a week, the egg will have divided to form a tiny ball of a 200 or so cells, from which stem cells could be extracted.
The embryos could not legally be implanted into a woman's womb and the stem cells would not be safe to implant because they would be rejected by the immune system. "They will never grow beyond the 200 cell stage and they will have no human features," said Prof Shaw.
The proposal exposes a grey area in British regulation, however, as officials at the HFEA admitted it was questionable whether the resulting embryo was human. "That's the question and it's for the government, the HFEA and lawyers to work out," said Prof Shaw.
Josephine Quintavalle of the lobby group Comment on Reproductive Ethics said: "There is a lot of innate wisdom in the yuk factor, or repugnance as it is also known. My question is: what will they actually create? It is simplistic or deliberately deceptive to say they are simply making stem cells. In order to obtain stem cells they surely have to go through the blastocyst stage; they have to create a 'something' from which to derive the new cells. What is this something? It must be human to be of any use to researchers."
Professor Sir John Gurdon, a Cambridge University researcher, already uses similar technology to investigate how eggs appear to be capable of converting adult cells into stem cells that can potentially grow into any tissue in the body. His experiments have so far focused on injecting DNA from human cells into frog eggs.
He said: "I don't see there's any ethical problem with what they are proposing. I don't see it as a human embryo, but it all comes back to the question of when you think life begins. Scientifically, though, I'm not persuaded it will work. If you put cells from one species into the egg of another, the egg may divide, but you could get a lot of genetic abnormality that won't lead to good quality stem cells."