President George Bush took the unusual move of using a nationally televised address last week to announce that he would allow government supported research on existing embryonic cell lines only, not on any new lines that may be developed.
At the same time he announced that he would create a presidential advisory body to oversee the medical and ethical ramifications. It would not review research proposals.
His decision came two days after the US National Academy of Sciences meeting in Washington, where infertility specialists Panayiotis Zavos and Severino Antinori put their case for reproductive cloning to help childless couples to conceive.
The president's statement, however, was specifically about therapeutic cloning, which is for research and possible treatment of disease, not reproductive cloning—a step that scientists in this field say is premature.
At the academy's meeting Dr Alan Colman, research director of PPL Therapeutics, Edinburgh, said that until the problems with cloning animals had been resolved, cloning humans would be unethical. “There's more chance of a deformed baby by this technique than by any other assisted reproduction procedure,” he said.
The president's decision acknowledged the growing support in the United States for funding stem cell research because of its potential therapeutic benefits. At the same time it attempts to avoid offending an important segment of his political supporters who regard it as unethical.
The stem cells are harvested from 5 day old fertilised human ovum. In the process the embryo is killed. Critics say that this is the destruction of human life, whereas others call it abortion. But by limiting research to cell lines that have already been developed, the president has sidestepped these critics, as the embryos have already been destroyed.
Mr Bush said that there were 60 different cell lines that could be used, a figure provided by the National Institutes of Health. But questions immediately arose over this number and whether the lines were of sufficient quality to be useful.
Moreover, embryonic stem cell research in the United States has been funded by private sources, and some lines are patented. This does not necessarily mean they would be unavailable. Licensing agreements can be worked out that would allow the research to go ahead, said Tommy Thompson, secretary of health and human services.
The National Institutes of Health is setting up a registry of the available cells for the use of investigators. Meanwhile, the UK's Medical Research Council is looking into the feasibility of setting up a bank of several hundred different cell lines. .
Stem cells at a glance
Stem cells are non-specialised cells that have the capacity to renew themselves and differentiate into more mature cells. They can develop into most of the cells and tissues of the body.
In theory these cells could be developed to replace diseased or damaged organs. They are derived from embryos that are 4-5 days old, after in vitro fertilisation for reproductive use or by transferring an adult nucleus to an enucleated egg—a procedure known as somatic cell nuclear transfer.
Stem cells are also present in some mature tissues, but they do not have the same developmental potential.
Stem cell lines are the result of the cultivation of cells through any number of divisions
Figure.
AP PHOTO/JOE MARQUETTE
Dr Severino Antinori (left) and Dr Panayiotis Zavos at the National Academy of Sciences” debate on cloning in Washington