WEDNESDAY, June 30 -- Researchers believe they know why Parkinson's disease patients who received fetal cell transplants in the 1990s developed uncontrolled, involuntary movements, and they think they can prevent the troublesome side effect.
The findings could potentially make the transplant trials viable again, they said.
"These findings lend much optimism to new human trials testing the safety and efficiency of fetal or stem cell transplantation in Parkinson's patients," said study author Dr. Marios Politis, a clinical scientist at Imperial College London, whose report is published in the June 30 issue of Science Translational Medicine.
In the early 1990s, scientists were excited about promising results of clinical trials using fetal cell transplants to treat Parkinson's disease.
But the excitement was short-lived. A few years later, trials were halted after patients who received the transplants began to experience dyskinesias, or uncontrolled movements.
The new research attributes the involuntary movements in two patients who received transplants in Britain in 1993 and 1996 to an excess of serotonin cells in the transplanted tissue.
Parkinson's disease is a degenerative disorder in which the brain has a shortage of the neurotransmitter dopamine, leading to muscle rigidity, tremors and gait difficulties, and eventually cognitive trouble.
The hope for fetal cell transplants was that the tissue from midbrains of aborted fetuses could be put into Parkinson's patients' brains, replacing the dopamine-producing cells destroyed by the disease.
But results in human studies were unpredictable and controversial, Politis said. In the 1980s, the U.S. government banned fetal cell research, but lifted the ban in the early 1990s.
While some patients who had the transplants showed remarkable improvement -- the two in the study, for example, nee
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