US considers future of embryo research

Human embryos are one source of stem cells

The new US administration says it will decide by the middle of the year whether state-funded research can continue on human stem cells taken from embryos.

US health and human services secretary Tommy Thompson said on Tuesday that an independent review of the issue was under way.

The new US government is putting policy under the microscope

"I will be making a decision based on those reviews," he told a hearing in the Senate, adding that a decision should come in "spring or early summer".

Government-funded scientists in the US are banned from creating or destroying a human embryo to gain access to stem cells.

These "master cells" form the basis of experimental treatments for degenerative diseases like Parkinson's and Alzheimer's.

But in 1999, under the Clinton administration, the US National Institutes of Health issued guidelines saying that the scientists could work with such cells provided that they did not create or destroy an embryo themselves.

President George Bush is opposed to abortion, and said in January that he would also oppose research using stem cells from foetuses. Mr Thompson is former governor of Wisconsin, and in that office supported the research.

Scientific potential

Human stem cells are interesting for researchers because they are undifferentiated.

This means that they have the potential to become virtually any kind of cell in the body. Experiments on rats have shown that stem cells can grow into brain cells, potentially replacing cells killed by a stroke.

Blood from umbilical cords yields stem cells

But there may be other means of obtaining the valuable cells.

Less flexible stem cells can be obtained from adult bone marrow, and research is going on to try to find a way of "reprogramming" adult cells to behave like embryonic stem cells.

Other research on rats in the US suggests that blood from umbilical cords could also yield stem cells. It could lead eventually to the routine storage of the umbilical cords from newborn babies.

In Britain, Parliament gave its backing in January to a plan to legalise the use of embryos to harvest stem cells. The regulatory changes will also permit a limited form of human cloning.

The research is strongly opposed by religious leaders who say they fear it will open the door to full-scale reproductive human cloning.