One study suggests that a type of nerve cell derived from stem cells can make the correct connections when implanted in the brain, restoring lost motor function.
Parkinson’s disease is a progressive degenerative disorder that affects muscle control.
Its symptoms include tremor, stiffness, slowness of movement, and impaired balance. Swallowing and speaking difficulties are also common, especially later in the course of the illness.
The National Institutes of Health estimate that about 50,000 people are diagnosed with Parkinson’s each year in the United States, and about half a million people are living with the condition.
In the early stages of the disease, before symptoms appear, certain brain cells called “substantia nigra” begin to die. These cells produce dopamine, a nerve signaling molecule or neurotransmitter, which is essential for smooth movement of muscles.
Cell transplants
There is currently no cure for Parkinson’s, but a promising line of research involves transplantation of nerve cells into the brain to replace lost functions. Experts could use the same approach to repair damage caused by other neurodegenerative disorders and trauma.
However, for these therapies to be successful, the transplanted nerve cells must make the right connections.
Inhibitory inputs
Just as important, the two types of implanted nerve cells began to receive distinctive signals from other nerve cells. Glutamate cells were more likely to receive stimulatory stimuli, while dopamine cells were more likely to receive inhibitory stimuli that prevented them from being overstimulated.
Between 4 and 5 months after transplantation of dopamine cells into their brains, the mice showed improved motor skills. In contrast, mice that received glutamate cells did not show such improvements.
Ultimately, the researchers showed that it was the implanted dopamine-producing cells that restored the mice’s motor skills.
Before implanting them in the brain, they inserted genetic “on-off” switches into dopamine cells. These increase or decrease the activity of cells in response to drugs in the animal’s diet or injections.
When the team shut down the cells, the improvements in the animals’ motor skills disappeared, proving that the new circuits created by them had been responsible.
The researchers speculate that specialists could use the same technique to adjust the activity of implanted dopamine cells in Parkinson’s patients.
