Scientists outraged over fusion of male and female embryos

Chimera experiment is branded trivial science while study finds IVF is not harmful to long-term health of children

An experiment that created human "chimeras" by merging male and female embryos in a test tube was condemned yesterday as scientifically vacuous and ethically questionable by leading proponents of research into IVF.

An experiment that created human "chimeras" by merging male and female embryos in a test tube was condemned yesterday as scientifically vacuous and ethically questionable by leading proponents of research into IVF.

A team of privately funded researchers made the herma-phrodite chimeras - a mix of cells from two separate embryos - as part of a study into ways of treating inherited disorders. But their colleagues have denounced the study.

The chimeric embryos, which contained both male and female cells, were not allowed to live beyond six days after conception when they were still microscopic balls of cells. Many scientists believe that the experiment should never have been run.

"It doesn't make any sense to me," Alan Trounson, a leading authority in IVF research at Monash University in Melbourne, said. He criticised the study at the European Society of Human Reproduction and Embryology meeting in Madrid.

"I think it's a flawed experiment. Unless you can be certain that you're doing good with something, you shouldn't do it at all. It is the Hippocratic principle of doing no harm," Professor Trounson said.

He added: "I think we've got to stand up and say we don't understand the point of this and we don't think it should proceed unless you have a much better reason. It is essentially trivial science that's unlikely to be useful. It's difficult to argue why it should be done to the public."

The study was done at the Centre for Human Reproduction in Chicago by a team led by Norbert Gleicher, its founder, who is also a visiting professor of obstetrics and gynaecology at Yale University.

Professor Gleicher injected embryonic cells from male embryos into "high-quality" female embryos that were about three days old. Some of the chimeric embryos continued to develop normally for three days, when the male cells had divided and spread throughout the female embryo.

He said he chose to insert male cells into a female embryo to make it easier to see whether the injected cells had integrated into the embryo.

He saidhe had approval from an in-house ethical committee and took outside legal advice. He also said it would not be done on an embryo he intended to implant into the womb. It was only conducted as part of an investigation into treating singe-gene disorders, such as muscular dystrophy, by introducing healthy cells at an early stage of development.

"If you had an afflicted embryo and if you are able to introduce just 15 per cent healthy cells, you may be able to treat single-gene disorders," Professor Gleicher said.

"Normally you would do this with embryos of the same sex, but we did it with different ones as a model. Our primary purpose was to see if this was feasible and I think we have convincing evidence the answer to that is yes. Now we need to take further steps and that probably means going back to animal experiments," he added.

In ancient Greek mythology, the Chimera was a creature formed by combining a lion, a goat and a snake.