Parkinson's disease is a neurodegenerative disorder characterized by tremor, rigidity, postural instability and slowed ability to start and continue movements. Most patients with PD require therapy with the medication levodopa to control symptoms three to five years after a diagnosis of PD.

Motor Fluctuations

However, disease progression and long-term oral treatment with levodopa may lead to the development of motor fluctuations and difficulty in performing voluntary movements (dyskinesias).

Human retinal pigment epithelial (RPE) cells produce levodopa and can be isolated from post-mortem human eye tissue, grown in culture, and implanted into the brain attached to microcarriers. (The retinal pigment epithelium is the pigment cell layer found in the inner layer of the retina of the eye.)

These implants have been shown to ease motor problems in animal models of Parkinson's disease in earlier research, according to the article.

48 Percent Improvement

Natividad P. Stover, MD, of the University of Alabama at Birmingham and colleagues conducted an open-label pilot study to evaluate the effect of unilateral implantation of human RPE cells attached to gelatin microcarriers.

Six patients with advanced Parkinson's disease received cell implants, which were inserted into the brain tissue. The researchers performed efficacy evaluations at one and three months after surgery, and then at six, nine, 12, 15, 18 and 24 months. Yearly follow-up visits are ongoing and will continue.

"The implants were well tolerated," the authors report. "We observed an average improvement of 48 percent at 12 months after implantation in the Unified Parkinson's Disease Rating Scale motor subscore with the patient in the off state, which was sustained through 24 months."

Quality of Life

"Improvement was also observed in activities of daily living, quality of life and motor fluctuations. No off-state dyskinesias were observed," they add.

"On the basis of the motor improvement and tolerability observed in this open-label study, a randomized, double-blind, placebo-controlled study has been initiated to more objectively test efficacy and continue to assess safety," the authors conclude.