Debate over embryo stem cell testing

A panel of American and Canadian experts is debating how best to assess different human embryo stem cell lines for their quality and potential usefulness in treating human disease. One proposed method would involve injecting human embryo stem cells into an early mouse embryo, a test that is thought to be premature or unethical by at least two members of the group, according to a report published in the New York Times last week.

Stem cells are the body's 'master cells', and those obtained from early embryos may be able to develop into any of the different cells that make up an adult body, of which there are around 200. The test, which will be included in a forthcoming paper proposing standards to test human embryo cell lines, could potentially determine the extent to which the human cells were able to contribute to the developing mouse embryo tissues. But it is not yet known if the human cells would survive in an early mouse embryo, or for how long. One scientist at the meeting, Dr Janet Rossant of Mount Sinai Hospital in Toronto, said she did not consider the test necessary, and if the human cells made major contributions to the mouse, she added, 'I think that is something most people would find unacceptable'.

Stem cell expert Dr Irving L Weissman, of Stanford University, said that such an experiment could help scientists follow the behaviour of human cells with genetic diseases, and that studying how they developed in a mouse embryo could offer treatment insights. But he added: 'You must assure yourself and the public that it's ethical. It's not for scientists alone to decide'. Dr Anne McLaren, of the Wellcome/Cancer Research Institute at the University of Cambridge, told BBC News Online that she would have few objections to the technique, as the human stem cells would be unlikely to persist long in any 'chimera' embryo. She also pointed out that human stem cells have already been put into adult mice, and human genes are routinely added to mouse embryos.