Science: Clone first, discuss ethics afterwards: American scientists' success in splitting human embryos may at last result in a debate about the morality of the issue, says Liz Hunt

Last week a group of American scientists announced that it had cloned human embryos for implanting in the womb to help infertile women have babies. Pleased as they were at their scientific success, the researchers were delighted at the impact of the announcement itself. Some of the headlines may not have been to their liking, with predictable references to Jurassic Park, The Boys from Brazil and Brave New World, but the news has at long last triggered national debate about embryo research in the United States.

That was exactly what Dr Jerry Hall and colleagues at George Washington University School of Medicine in Washington DC intended. 'It was clear that it was just a matter of time until someone was going to do it, and we decided that it would be better for us to do it in an open manner and get the ethical discussion moving,' said Dr Hall.

Research into reproductive technologies such as in vitro fertilisation (IVF) has been described as a 'nether world' of American science, largely ignored by the Government. It has been starved of federal funding because techniques that permit childless couples to have children became tied up with the abortion issue, and attracted the wrath of the moral majority.

Many scientists who wanted to pursue research - particularly those who recognised its financial potential - therefore left government laboratories to set up or work in private companies. No national board has ever debated the ethical issues surrounding embryo research, nor have the private clinics been subjected to scrutiny by a national body. The US Congress appointed a Biomedical Ethics Advisory Committee in the Eighties, but it was wound up in 1989 without issuing a report. Dr John Fletcher, an ethicist at the University of Virginia in Charlottesville, admitted last week: 'Our policy on embryo research is in total disarray.'

Although anti-abortionists want to protect human embryos, the effect of their campaigns has been to block attempts at regulating IVF treatment and research. The lack of regulation has had the effect of permitting US researchers to interfere with human embryos in a way that would be illegal in Britain. The cloning of human embryos for the purpose of implantation in the womb is illegal in Britain.

In the UK the issues surrounding embryo research were well aired throughout the Eighties and in 1991 the Human Fertilisation and Embryology Authority was established in response to 'deep public concern about the implications which the new techniques might have for the perception and valuing of human life . . .' The authority licenses and oversees the work of clinics and laboratories where embryo research is carried out.

Cloning of embryos is allowed in British laboratories for the purposes of pre-implantation diagnosis for couples who carry a genetic defect such as cystic fibrosis. Following in vitro fertilisation, the embryo is allowed to develop to the four- or eight-cell stage. A single embryonic cell or blastomere is then removed. This single cell is screened for genetic abnormalities, and if found to be normal, the three- or seven-cell embryo from which the single cell was removed can then be implanted, and will develop as normal in the womb. In some instances, the single cell will have been cultured overnight to increase the number of cells available for analysis, but this is not always successful, according to Karin Dawson, head of the IVF Laboratories at the Hammersmith Hospital, London.

The American scientists had a quite different aim. Dr Hall wanted to increase the number of embryos available to an infertile couple and saw cloning as a way of achieving this.

The team used techniques that are common in livestock breeding programmes. Animal embryos are cloned by fusing individual embryonic cells with unfertilised eggs from which the nuclei have been removed. The embryo then has an intact jelly-like coat, known as the zona pellucida, which provides nutrients for the developing cells and aids implantation in the womb. Until two years ago this technique could not be applied to human cloning, because eggs were in short supply. But in 1991, Dr Hall and a co-worker, Sandra Yee, showed that human embryonic cells could be coated with a synthetic form of zona pellucida and the chances of cloning human embryos took a leap forward.

The team took 17 embryos of between two and eight cells in size that had been fertilised in the IVF Clinic at the George Washington Medical School. They were unsuitable for implantation because they were genetically abnormal; the eggs had been penetrated by more than one sperm in vitro. The individual cells of the embryos were then separated, coated in the artificial jelly- layer and cultured in nutrient solutions to see if they would begin dividing again. Forty-eight embryos were obtained, an average of almost three per original embryo.

Cloning was most successful in cells disaggregated from the smallest embryos; blastomeres from the two-cell embryo developed into 32 cells - the stage at which they would implant in the uterus. Those from the eight-cell embryo developed to the eight-cell stage, while blastomeres from the four-cell embryos divided to the 16-cell stage. Dr Hall said none of these embryos were suitable for implantation and all were later discarded. He said the cloned embryos appeared similar to non-cloned embryos.

The work has no clinical application - as yet. Dr Hall told Science magazine that he would not attempt to implant the cloned embryos until the American Fertility Society had established some guidelines.

British scientists are sceptical that the work has any clinical potential. Dr Marilyn Monk, a molecular embryologist at the Institute of Child Health in London, said that 'growing on' a few cloned embryos was far removed from producing a healthy foetus. 'Trying to justify it on the grounds that it would produce more embryos for IVF treatments is very poor.'