Challenge to Bush in New Stem Cell Breakthrough

Scientists have perfected a way of making embryonic stem cells without destroying the embryos from which they derive, a breakthrough that will challenge George Bush's opposition to the research.

The discovery of a technique to extract stem cells without impairing the embryos could remove a major hurdle facing scientists who are trying to develop treatments for diseases such as diabetes and motor neurone disease. Religious and rightwing groups claim embryonic stem cell research is unethical because the cells are produced by creating embryos which are later destroyed.

The Bush administration has banned scientists from using federal funds to create new embryonic stem cells, a policy many believe has stifled progress and discouraged investment in research.

Last year, the US threw its weight behind an alliance of several countries to call on the UN to draw up a treaty banning all cloning, including therapeutic cloning, the technique used to create embryonic stem cells.

The new research, carried out by Robert Lanza at the Massachusetts-based stem cell company Advanced Cell Technology, shows embryonic stem (ES) cells can be created without resorting to the creation of embryos themselves - a process known as therapeutic cloning, which was legalised in Britain in 2001.

In work carried out in mice, the researchers let fertilised eggs divide for two to three days until they formed a ball of eight cells. They then removed one of the cells and cultured it in a dish. They found it grew into a mass of cells, some of which turned into ES cells. The remainder of the cells were reimplanted into surrogate mothers and allowed to develop normally. In 48 attempts, foetuses developed in 29 mothers, a success rate comparable to that seen in surrogate fertility clinics, the researchers claim.

Embryonic stem cells are thought to be unique in their ability to grow into any of the tissues in the body and scientists believe they will lead to powerful therapies for diseased and damaged body parts.