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Stem Cells Normalize Behavior in Monkeys with Parkinson's

Parkinson's disease is a neurological disorder affecting millions of people worldwide. The disease is marked by a decrease in the brain's ability to make dopamine, an important neuro-chemical messenger. Without enough dopamine, a patient's ability to move voluntarily steadily deteriorates. Eventually, complications from Parkinson's disease lead to death.

Dr. Eugene Redmond, a professor of psychiatry and neurosurgery at Yale University in Connecticut, has been exploring the use of human stem cells in the brains of people and animals with Parkinson's disease. "First we treated the monkeys with a chemical that induces Parkinson's disease by destroying dopamine cells," he explains. "And then after they were Parkinsonian, we implanted their brains with stem cells that we then observed to see what kinds of effects they would have on behavior and what types of changes they produced in the brain."

Stem cells are derived from human fetal tissue. Scientists believe these cells retain the ability to differentiate themselves into a variety of types of adult cells. They're looking at ways stem cells could be used for treating many diseases marked by cell deterioration, including Parkinson's.

Redmond says the approach seemed to benefit the monkeys in his experiment. "Before we put the stem cells in, the monkeys were extremely Parkinsonian, practically unable to move and they needed a lot of assisted care," he says. "And after the cells started working, they got significantly better and were able to move around and feed themselves and move more normally. So, it was a dramatic normalizing effect on their behavior."

Redmond says these findings indicate that there are still chemical signals in adult brains that direct the stem cells to do certain things, such as to turn into new dopamine cells. "We did demonstrate that some new dopamine neurons seemed to come from the stem cells. So that cell replacement idea was confirmed in this study, although it was a very, very small number of cells." However, he adds, the researchers also noticed the normalization and augmentation of the existing dopamine cells that were still in the brain.

The monkeys in this experiment were monitored for several months. Redmond says he'd like his next study to run for a longer period of time. Eventually, he hopes stem cell therapy could be used in humans. Redmond's results are published in the Proceedings of the National Academy of Sciences.