WASHINGTON Transplants of brain cells given to Parkinson's disease patients survive for 10 years or more, three teams of researchers reported on Sunday, but at least some of the transplants were damaged.
The researchers disagree about whether this damage shows that Parkinson's disease is a long-term, ongoing process that continues to attack the brain into old age, or the result of the transplants themselves.
But they agree that their studies, published in the journal Nature Medicine, demonstrate the benefits of the sometimes controversial brain cell transplants.
"I think these findings lend much optimism to future work," said Dr. Ole Isacson of McLean Hospital and Harvard Medical School in Massachusetts, who worked on one of the studies.
Parkinson's disease, which affects more than a million patients in the United States alone, is marked by the death of brain cells that produce dopamine, a message-carrying chemical associated with movement. Drugs can delay symptoms for a while but there is no good treatment and no cure.
Patients report shakiness, which progresses to paralysis and sometimes dementia and death.
A few teams tried transplanting brain cells, some from aborted fetuses, to replace cells destroyed by the disease.
Jeffrey Kordower of Rush University Medical Center in Chicago and colleagues described the case of a 61-year-old woman who died 14 years after she got a transplant.
She initially got better but then deteriorated until she died. Her brain showed signs of damage similar to that caused by Parkinson's, Kordower's team reported.
"This case reveals that pathological changes typical of Parkinson's disease can develop in human fetal neurons grafted into a host with Parkinson's disease," they wrote.
Patrik Brundin of Wallenberg Neuroscience Center in Lund, Sweden, and colleagues found some damage to cells transplanted into the brains of patients. But they said the transplants had survived for as long as 16 years and the patients had reported relief from their symptoms.
Kordower believes the findings suggest that Parkinson's is caused by an ongoing process that lasts for years. "Whatever the offending agent is, it is still present in the Parkinson's brain," he said in a telephone interview.
He said only about 5 percent of the cells were damaged.
"If you ask me whether this spells doom and gloom for cell replacement, the answer is absolutely not," said Kordower, who is pursuing another treatment for Parkinson's by using gene therapy to repair the damaged cells.
Isacson found no such damage in the brains of five patients who died nine to 14 years after getting transplants.
He said transplanting purified brain cells may provide better results. Isacson, who examined brain tissue from the patient studied by Kordower's team, said whole chunks of brain tissue had been transplanted into her -- including cells that could have provoked damaging inflammation.
"I think that the transplant is basically triggering an immune reaction," Isacson said in a telephone interview.
Isacson wants to continue to try to treat Parkinson's patients with brain cell transplants, perhaps using stem cells that have been trained to grow into the specific brain cells affected in Parkinson's.
(Editing by Will Dunham and Philip Barbara)