In the mid-1990s, researchers were on the cutting edge of technology when they transplanted brain cells from aborted fetuses into patients with Parkinson’s disease. And although patients saw a significant improvement in their symptoms, they were suffering from serious bouts of sudden uncontrolled movement called dyskinesias. It is a common side effect of treatment for the disease, but it is what ultimately led to ending the transplant studies which were very controversial to begin with.

Now researchers in Britain and Sweden are telling Yahoo! Reuters that they have determined why this occurred. Two patients who received the transplants 13 and 16 years ago had a positron emission tomography (PET) scan to observe their brain function and to determine how the transplanted cells are behaving.

They found that although a lot of the transplanted cells replaced the dopamine-secreting brain cells that die in Parkinson’s which result in the symptoms associated with the disease, a higher than normal level of brain cells was secreting serotonin. While dopamine is the neurotransmitter involved in the control of movement, serotonin secreted from brain cells tells other brain cells to secrete dopamine. Because there was an excess of these serotonin-secreting brain cells from the transplant tissue, dopamine was ultimately secreted in very large amounts.

Marios Politis of the Imperial College London, who led the study explained that “The serotonin cells were very very highly excessive compared to what normal people have. This provoked a false action by taking the dopamine and releasing it in an unregulated manner, and this created these involuntary movements.”

Researchers believe that this study will allow them to modify cells, whether from fetuses or other sources, before they are transplanted into the brains of Parkinson’s patients. Researchers plan to begin new trials in 2012. It is also possible that drugs that inhibit the secretion of serotonin-known as serotonin receptor antagonists-could be developed and used in patients who receive these transplants.

This study was published in the journal Science Translational Medicine.

[img credit: NASA]

Tags:

Dopamine, fetal brain cell transplants for Parkinson’s, Parkinson’s disease, serotonin