By PAUL
RECER
AP Science Writer
SAN
FRANCISCO (AP)--Scientists may be on the brink of curing Parkinson's disease using
transplanted embryonic stem cells, but where and when that new treatment is tested
in humans depends on unresolved political decisions, researchers suggested Friday.
Dr. Ole Isacson of Harvard Medical School and Dr. Ronald McKay of the
National Institutes of Health said Friday they have both ``cured'' Parkinson's
in mice and rats, using stem cells removed from embryos of laboratory animals.
In a report at the national meeting of the American Association for the
Advancement of Science, Isacson said mouse and rat embryonic cells, after careful
processing, can be grafted into the animal brains where they transform into replacements
for cells killed by Parkinson's.
``In mouse models (laboratory tests)
these cells have restored function,'' said Isacson.
Using a slightly different
technique, McKay said his NIH lab has also prompted mouse embryonic stem cells
to convert into cells that are lacking in Parkinson's.
McKay and Isacson
said researchers are almost ready to test the technique in humans, but social
and political issues must be resolved in the United States before that step can
be taken in this country.
At the same time, McKay said it may happen soon
in Britain, France or the Netherlands, as those countries are adopting policies
to advance embryonic stem cell research.
``It's going to happen, but just
where may depend on social and political issues,'' McKay said. ``There is a great
sense of optimism shared by many people in the field right now.''
In the
United States, some groups, including some members of Congress, oppose the use
of embryonic stem cells in research because gathering the cells requires the death
of a human embryo.
New NIH guidelines permit federal funding of such stem
cell research, but only if the cells are extracted from embryos in labs not receiving
federal funding.
Tommy Thompson, the new secretary of Health and Human
Services that oversees NIH, said he is reviewing the policy on embryonic stem
cells research.
Some researchers have sought NIH funds to conduct embryonic
stem cell studies, but no grants have been issued, said McKay.
More than
1 million Americans have been diagnosed with Parkinson's, a disease caused by
the death of brain cells that produce dopamine, a key nerve chemical. When patients
lose about 80 percent of these cells, they develop the classic Parkinson's symptoms:
tremors and rigidity.
Parkinson's can be treated with L-dopa, a drug that
makes dopamine in the brain. But L-dopa is effective for only a short time and
after that the disease progresses.
Limited experiments using brain cells
from aborted fetuses have stabilized patients for up to 12 years, Isacson said.
The transplanted cells convert to dopamine-producing cells, replacing those lacking
in patients with Parkinson's.
But using tissue from aborted fetuses in
research also is opposed by many groups. And because of limited availability and
for technical reasons, fetal tissue is not considered ideal for treating Parkinson's.
The best hope, said the researchers, are the embryonic stem cells. These
are master cells that can be coaxed to transform into virtually any type of tissue
in the body.
Embryonic stem cells can be grown in great numbers, making
them readily available for treating thousands of patients, the researchers said.
``You can generate embryonic stem cells with huge efficiencies,'' said
McKay.
McKay said his lab has found ways to cause mouse embryonic stem
cells to change into the dopamine-producing cells lacking in Parkinson's.
``We
can take the embryonic stem cells through a series of transitions until they become
the dopamine cells,'' said McKay.
Isacson said his lab injects into the
brain specific cells extracted from the embryo and that a natural process in the
brain then transforms them into dopamine producers.
``The cells organize
themselves to become very functional,'' he said. ``We see the cells behaving in
a way to reverse the symptoms (of Parkinson's) in the mouse and rat.'' |
