LONDON--The U.K. government today endorsed the cloning of human embryos to harvest stem cells, unspecialized cells that might serve as seed material for growing fresh tissue for treating diseases. The proposal was contained in a report submitted in May by a panel asked to review government policies on the use of embryos in research.
U.K. regulations now allow limited research on human embryos, including studies of infertility treatments and contraceptives. Nearly all embryos used in such projects come from in vitro fertilization clinics, and research is restricted to embryos up to 2 weeks old. But recent advances in stem cell research and other areas prompted the U.K. government last fall to form an expert panel, led by Liam Donaldson, chief medical officer of the U.K. Department of Health.
The panel recommended expanding the use of embryos for research. At the top of its list is permission for researchers to extract stem cells from leftover embryos. Stem cells, which can be coaxed to form various cell types, could help replace many kinds of diseased tissues (see table). Stem cells would be culled from embryos 5 to 6 days old. The report also advocates the limited use of cloning--the creation of new embryos--as a source of stem cells.
Another line of research backed by the report would investigate diseases caused by faulty mitochondria, cellular powerhouses with their own set of DNA. When sperm and egg unite, the resulting embryo keeps mitochondria from only the egg, meaning that mitochondrial DNA is handed down only by the mother. Some 50 rare diseases have been linked to damaged or faulty mitochondrial DNA. One proposed prevention method is to transplant the nucleus from an egg of a mother at risk into a donor egg with its nucleus removed and fertilize the hybrid egg in vitro.
(In the United States, privately funded research on embryonic stem cells is unregulated, but federally funded work is on hold until the National Institutes of Health releases its final guidelines, expected by mid-September. According to the draft version of the guidelines, work with stem cells derived from newly created embryos would be ineligible for NIH funding. Some legislators and members of the public have argued that embryonic stem cell research is unnecessary because stem cells derived from adult tissue might be equally useful.)
Parliament is expected to take up the issue this fall. But wholesale approval is uncertain. "I would not take Parliament's acceptance of these recommendations for granted," says Harry Griffin, assistant director for science at the Roslin Institute in Edinburgh. "There will be vociferous opposition from pro-life groups, and much of the public will see a moral dilemma."
With reporting by Michael Balter.
Chief Medical Officer's Expert Advisory Group on Therapeutic Cloning 
|POSSIBLE USES OF TISSUE DERIVED FROM STEM CELLS TO TREAT DISEASE|
|Cell Type||Target Disease|
|Neural (nerve) cells||Stroke, Parkinson's disease, Alzheimer's disease, spinal cord injury, multiple sclerosis|
|Heart muscle cells||Heart attacks, congestive heart failure|
|Blood cells||Cancer, Immunodeficiencies, Inherited blood diseases, Leukemia|
|Liver cells||Hepatitis, Cirrhosis|
|Skin cells||Burns, wound healing|
|Retinal (eye) cells||Macular degeneration|
|Skeletal muscle cells||Muscular dystrophy|