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Jury Still Out on Cell Transplants for Parkinson's

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WebMD Health News

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 dopamine.

 

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 transplants.

 

"[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 problems."

 

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 WebMD.

 

"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.

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