Jury Still Out on Cell Transplants for Parkinson's
March 7, 2001 -- In Parkinson's disease, brain cells stop
making a crucial chemical called dopamine. Without it, muscle movement is
poorly controlled, making it increasingly difficult to write, walk, or even
speak. Drugs that replenish dopamine do provide some relief, but there is no
cure, and the search for a better solution continues.
Now researchers have found that transplanting
dopamine-producing fetal cells into the brains of Parkinson's patients may be a
viable option. But results haven't been quite as good as hoped for.
The researchers randomly assigned 40 patients with severe
Parkinson's disease to receive either the fetal cell transplant or a "sham
surgery," where they did not receive the cells.
"We demonstrated without question that transplanted fetal
tissue survives in patients with Parkinson's -- and at least in younger
patients, it produces enough dopamine to [improve symptoms]," says
researcher Paul E. Greene, MD, associate professor of clinical neurology at
Columbia University College of Physicians and Surgeons in New York City.
The researchers, using a special imaging technique, were able
to prove that the tissue was alive and functioning within the patients who had
received the transplants, and that they were producing increased levels of
Tests that measured the severity of various Parkinson's
symptoms revealed improvements in the younger transplant patients, but not in
the older transplant patients or in the patients who had not received the
"[However,] some of the patients who had improved
[symptoms] did not really have improved functioning," Greene tells WebMD.
"They still had ups and downs; they still had significant
And older patients did not even show those modest improvements,
"although [imaging] scans showed that the grafts survived and were
producing dopamine," he says. "You can't ignore that, because the vast
majority of Parkinson's patients are over 50."
And the problems did not stop there. Five of the patients who
initially did quite well went on to develop dyskinesias -- those involuntary,
"twisty turny" movements that are normally a side effect of Parkinson's
drugs, Greene says. A few switched to weaker drugs to control the dyskinesia,
but "some had unbearable dyskinesias even when they stopped all
medication," he says.
For now, it is impossible to know why these particular patients
reacted this way, Greene says. One possibility is that the transplanted cells
are putting out too much dopamine in especially sensitive areas of the brain.
But that question will remain unanswered until scanning technology is improved
that can look more closely at very small brain regions.
In the meantime, says J. William Langston, MD, "there
should be real concern about these dyskinesias. We have to ... deal with this
issue before we continue working in this area with humans. We need to go back
to animals to sort this out." Langston, who is scientific director and CEO
of the Parkinson's Institute in Sunnyvale, Calif., reviewed the paper for
"I'd call the results modestly encouraging," Langston
says. "We had great hopes for this being a cure, but to go through this
kind of surgery for only a modest benefit is probably not going to be a
long-term solution for Parkinson's."
The findings are published in the March 8 issue of The New
England Journal of Medicine.