Some 50,000 Americans each year are diagnosed with the neurodegenerative disease known as Parkinsons,in which progressive destruction of so-called dopamine neurons eventually leads to loss of muscle control and function. Recent studies have sought out ways to replace the dopamine neurons or interrupt faulty neural circuitry, but these approaches have been tested only on patients in advanced stages of the disease. Halting disease progression has not yet been achieved. The results of a report published today in the journal Science, however, may offer hope. According to the new findings, gene therapy with a neural growth and repair protein known as GDNF may provide a treatment option.

Earlier research had indicated that GDNF might protect against a loss of dopamine neurons if only it could be delivered to the right neural targets. To that end, Jeffrey H. Kordower of Rush-Presbyterian-St. Lukes Medical Center and his colleagues created what is known as a lentiviral vector to carry the GDNF. The investigators then injected the vector into the brains of monkeys that were aging and into monkeys in which they had induced neural damage. The treatment salvaged dopamine neuron function in both monkey groups and fought motor degeneration in the neurally damaged monkeys. Moreover, the gene therapy even prompted neural regeneration.

"The Kordower study provides an optimistic outlook for treating not only PD but also other fatal neurodegenerative diseases, such as amyotrophic lateral sclerosis," Lars Olson of the Karolinska Institute wrote in a commentary that accompanied the report. "Before GDNF gene therapy can enter the clinical arena, however, there are a number of hurdles that must be overcome," he cautions. "These include controlling the dose of the GDNF gene and protein, and circumventing the inherent risks associated with gene delivery by viruses."