SUNDAY, April 6 (HealthDay News) -- Current therapies using stem cell transplants in the brains of patients with Parkinson's disease may not work long-term, because the disease is an ongoing process that continually causes damage, new findings suggest.

Dopamine cells are sometimes transplanted into the brain of Parkinson's patients in the hope that they can replace those neurons that have degenerated. In theory, this should improve the disease's symptoms, which include tremors, stiffness of the limbs and trunk, slowed movement and impaired balance and coordination.

Researchers at Mount Sinai School of Medicine in New York City and Rush University Medical Center in Chicago studied brain tissue from a patient who had received a dopamine transplant 14 years earlier and found that the transplanted cells developed changes characteristic of Parkinson's disease (PD) and did not appear to function normally.

The patient had improved initially after the transplant but then deteriorated, noted the study, published in the April issue of Nature Medicine.

"While, on the one hand, these results may sound disappointing, this information is crucially important if we are to develop better therapies for PD. The more knowledge we gain about the nature of the disease, the better our chances to find the cause of why cells degenerate and to develop a treatment that can protect them," Dr. C. Warren Olanow, director of the Robert and John M. Bendheim Parkinson's Disease Center at Mount Sinai School of Medicine, said in a prepared statement. "These findings also do not mean that transplant strategies such as stem cells cannot be made to work -- our findings just represent another obstacle that will have to be overcome."

According to researchers, these new findings counter the theory that a single event, like an infection, causes the initial damage to cells and triggers their gradual degeneration over time. Since the newly implanted cells in the Parkinson's patient also became damaged, they suggest that the disease process is ongoing.

More information

The National Institute of Neurological Disorders and Stroke has more about Parkinson's disease.

-- Kevin McKeever

SOURCE: Mount Sinai Medical Center, news release, April 6, 2008

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