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