People with Parkinson’s disease showed marked improvement after surgeons implanted in their brains chemical-producing cells taken from the eye of a dead donor, researchers said Monday.
Cells from the inner, or pigment, layer of the eye’s retina make levodopa, which Parkinson’s patients commonly take in pill form to replace lost production of the neurotransmitter dopamine.
Dopamine allows the brain to control and smooth the body’s movements.
For most patients, the levodopa pills lose their effectiveness over five years or less, and larger and larger doses are needed to keep at bay the involuntary movements and shaking symptomatic of the disease.
Many people on the drug develop involuntary writhing or dance-like movements.
The retina cells were cultivated and implanted in the brains of six patients with advanced Parkinson’s, researcher Natividad Stover of the University of Alabama said.
One year later, the patients scored 48 percent higher on tests of movement and coordination, and the improvement was sustained after two years, Stover wrote in the journal Archives of Neurology.
“The implants were well tolerated,” the report said. ”Improvement was also observed in activities of daily living (and) quality of life.”
Parkinson’s is a degenerative disease in which key brain cells that produce dopamine die off. Symptoms start with tremors and rigidity and patients can end up paralyzed. The cause of the disease that attacks 2 percent of men and 1.3 percent of women is unknown, and there is no cure.
Some scientists have viewed implanting fetal stem cells into the brains of Parkinson’s patients as a promising avenue to restoring dopamine production. But preliminary human trials were disappointing, and animal experiments have yielded mixed results.
Other treatments showing promise include deep brain stimulation with implanted electrodes, drugs that promote brain cell growth, and gene therapy.
The researchers said a larger study has been started to test the efficacy and safety of retina cell implants.
