Stem-Cell Advances Stoke Debate on Cloning ; Breakthrough with Adult Cells Comes as Senate Mulls a Ban on Cloned Embryos

Article excerpt

For months, congressional efforts to ban the cloning of humans have been smoldering in the Senate.

Now, research results from two teams of scientists may inflame the debate over whether to ban all forms of human cloning or allow cloning human embryos for stem-cell research.

Embryonic stem cells form within the first few days of an embryo's development. Many researchers say they hold great potential for treating a range of degenerative diseases, because with the right cues, stem cells give rise to the full range of major cell types found in the human body.

That trait, however, no longer appears to be confined to embryonic stem cells. A team led by Catherine Verfaillie, who heads the University of Minnesota's Stem Cell Institute in Minneapolis, says it has demonstrated that adult "progenitor" cells act like their youthful counterparts in several critical aspects once thought unique to embryonic stem cells, including differentiation into the body's three broad cell lines.

Proponents of a ban on all forms of cloning say such advances in research in adult stem cells bolster their case. They argue that cloning, then destroying, embryos for science not only is morally repugnant, it is increasingly unnecessary. They say scientists could be tempted to allow a cloned embryo to come to term.

The second team, led by Ron McKay of the National Institute of Neurological Disorders and Stroke in Bethesda, Md., says it has used embryonic stems cells from mice to generate properly functioning new nerve cells in the brains of rats bred to model Parkinson's disease. The team says the treated rats showed promising signs of recovery during behavioral tests.

Dr. McKay's results dovetail with the hope of those who believe that Congress should ban any cloning that would result in a fully- grown person, but not the cloning of embryos for research and therapeutic, purposes.

Both sets of results were released online today by the journal Nature.

"While the two papers will no doubt rekindle the debate on the relative merits of embryonic versus adult stem cells, together they emphasize the outstanding potential of stem cells, and the need for continued research in all areas of stem-cell biology," says Natalie DeWitt, a senior biological-sciences editor at Nature.

Unresolved ethical questions

Verfaillie agrees. She acknowledges that the use of embryonic stem cells is ethically contentious. But "it is far too early to say which cells, embryo or adult, will provide the best benefit to a particular patient or for a particular disease."

Indeed, her research center recently hired a specialist in embryonic stem cells in preparation for those types of experiments.

In their research, Verfaillie and her colleagues essentially found that adult stem cells can yield a wide variety of cell types. The team took their cue from a rare cell type they isolated from human bone marrow. …