Self cells ease Parkinson's in monkeys.

When a portion of the brain fails to produce its normal yield of the message transmitter dopamine, Parkinson's disease can result. A shortage of dopamine keeps brain cells from consistently firing messages to nerves that reach the muscles, resulting in the tremors and rigidity that characterize this condition.

Scientists report in the April NEURON that monkeys with Parkinson's disease regained partial control of their movements and recouped fine motor skills after surgery that transplanted cells from another part of their body into their brain.

The cells came from the carotid bodies, two tiny glands in the neck that sense when oxygen in the blood is running low. They respond by releasing dopamine and other substances that signal the brain to boost blood pressure, heart rate, and breathing. Because the glands produce dopamine prodigiously, they make good candidates for Parkinson's disease repair, says coauthor Jose Lopez-Barneo, a physiologist at the University of Seville in Spain.

To test this novel source of cells, he and his colleagues gave two cynomolgus macaques a drug known to induce Parkinson's disease. After 3 to 5 months, the researchers transferred cells from the monkeys' carotid bodies to the putamen, an area of the brain damaged in Parkinson's. Although they didn't multiply, many of the carotid cells survived and produced dopamine. They also appeared to make growth-inducing chemicals that stirred brain cells into resuming dopamine production.

Within a few weeks, the animals showed striking gains in their ability to do tasks, the scientists report. Postmortem examination of the monkeys' brains, 3 or 5 months after the transplant, revealed that many brain cells had functioned throughout the experiment.

Research has shown that transplantation of human fetal brain cells or pig cells into Parkinson's patients can produce some improvement. However, the recipient's immune system often must be suppressed in these operations, and even so the grafted cells are sometimes rejected. Moreover, use of fetal tissue raises difficult ethical questions. Transplanting tissue from animals carries risks of cross-species viral infection.

These difficulties make self-transplants appealing. However, experiments that moved dopamine-making cells in patients from the adrenal glands to the brain have shown poor results because most of the cells died, says Paul R. Sanberg, a neuroscientist at the University of South Florida in Tampa.

More carotid body cells survived in the recent experiment on monkeys, Lopez-Barneo says. The cells spring into action when oxygen is low, a trait that may make them better able to withstand the rigors of transplantation, he suggests.

The monkeys' brains eventually harbored more cells producing dopamine than the researchers had put there, notes Greg A. Gerhardt, a neuroscientist at the University of Colorado Health Sciences Center in Denver. Thus, the apparent manufacture of growth factors by carotid body cells is "the diamond in the rough in this study," he says.