New weapon against Parkinson's
There is still no really good therapy for Parkinson's disease. In experiments on rats, Spanish scientists have discovered that certain glandular cells from the neck can compensate for the lack of dopamine when transplanted into the brain. The cells come from a small organ in the neck called the carotid gland. José López-Barneo and his colleagues from the University of Seville transplanted some of them into the brains of rats, causing the animals' Parkinsonian symptoms to disappear (Neuron February 1998).
The carotid gland is located in the carotid artery. It signals the brain to force breathing when the oxygen concentration in the blood drops too much. López-Barneo was particularly interested in how the cells of the carotid gland know when this is the case. But his colleagues, he recalls, repeatedly pointed out that these cells were excellent candidates for implanting in the brains of Parkinson's patients to compensate for their dopamine deficiency. This is because the movement problems and other symptoms of the disease are based on the death of neurons. These are located in a part of the brain called the substantia nigra, which produces the neurotransmitter dopamine. The cells of the carotid gland, in turn, produce a lot of dopamine and could therefore make up for the loss of normal producers.
To test this therapy option, the team from Seville used a common animal model to investigate potential Parkinson's therapies. To do this, the neurons of the substantia nigra on one side of the rat brain were killed. The animals developed a movement imbalance that caused them to walk in circles and cause other symptoms to appear. The researchers then transplanted portions of the carotid gland into the damaged side of the rats' brains and discovered that the transplants not only survived but actually reversed the animals' symptoms, including the movement imbalance. There was also evidence that the cells might be producing growth factors that cause the remaining substantia nigra to form new connections.
Neuroscientist Arnon Rosenthal, who works on Parkinson's therapies at Genentech Inc. in south San Francisco, says the results are promising. But the cells of the carotid gland have to pass many more tests before researchers can even think about trying them on patients. Still, Rosenthal says, they may have an advantage over another possible therapy, fetal neuron transplantation. Carotid cells produce high levels of dopamine-up to 45 times more than fetal neurons-and thrive in the relatively low levels of oxygen in the brain. Therefore, Rosenthal explains, they may be better at correcting Parkinson's symptoms than fetal cells. Finally, carotid cells raise fewer ethical concerns.
