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Still
Hope for Stem Cells in Parkinson's Disease By Karla Gale, Reuters Health August
22, 2003 NEW
YORK - Even though stem cell
transplants have yet to clearly benefit Parkinson's disease (news
- web
sites) patients, there is promise that further refinement of the
technique could lead to long-term relief of symptoms. Parkinson's
disease occurs when specific kinds of brain cells die. Patients with the
disorder develop involuntary movements and tremor that progress over time
because the brain cells no longer produce a chemical called dopamine.
Drugs used to treat the disease work by replacing dopamine, but the drugs
are less effective over time, so the disease usually worsens despite
treatment. It
was hoped that replacing the cells that produce dopamine would reverse the
disease. Initial experiments where stem cells from fetuses were surgically
implanted into the brains of laboratory animals were
"spectacular," Dr. C. Warren Olanow, from Mount Sinai School of
Medicine in New York, told Reuters Health. And
when the same technique was first performed in patients with Parkinson's
disease, their symptoms improved. However,
Olanow and other neurosurgeons then conducted a trial in which 22 patients
underwent surgery and 11 patients underwent a fake, or "sham,"
procedure. Two years after the surgery, the patients treated with stem
cells were no better off than the ones who had the sham treatment. This
was puzzling to the research team, because when the patients' brains were
scanned, their cells looked almost normal, according to the report in the
Annals of Neurology. In
addition, autopsy results in five of the patients who died from unrelated
causes showed healthy-appearing nerve cells in the region of the
transplants and evidence that the stem cells had properly grown into the
brain. So
the doctors decided to reexamine their data based on different subgroups
of patients. And in fact, in those who underwent the real procedures,
there was a significant improvement for the first 9 months after surgery. This
time frame coincided with the time in which patients were taking a drug
called cyclosporine to prevent graft rejection. It appears that when this
drug was discontinued, their bodies rejected the grafts and impaired the
new cells' ability to produce dopamine. The
researchers also observed that patients without advanced disease
experienced more lasting benefits from the stem cells and that patients
who had been treated with more cells were better off. More
than half of the transplanted patients developed abnormal, disabling
involuntary movements. Even though this is a serious symptom, Olanow told
Reuters Health, he believes that it is not a sign of damage from the stem
cells. Instead, he and his colleagues attribute it to poor graft survival
that could not produce enough dopamine in the brain. "There
has been a lot of hype about stem cell transplants and optimism that it
could be a revolutionary new treatment," Olanow commented. While some
may see his group's results as discouraging, he wants them to recognize
that new techniques are rarely 100 percent perfect when they are first
tried. Now
he will perform more experiments in the laboratory to see if they could
overcome the side effects by continuing immunosuppressive drugs long-term,
treating the disease earlier, and transplanting more cells. SOURCE:
Annals of Neurology, September 2003.
Copyright
© 2002 Global Action on Aging
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