Approximately 1 million Americans have Parkinson’s, with 50,000 new cases diagnosed every year, of which about 4% are diagnosed in patients under age 50. Parkinson’s disease is a neurodegenerative disorder in which the body's immune system attacks neurons (brain cells) causing loss of high motor functions as the release of a neurotransmitter called dopamine decreases. This loss affects fine motor movements and memory; symptoms generally include difficulty walking, tremors, loss of balance, and changes in speech. The exact cause is unknown, though it is increasingly thought that Parkinson’s may have a hereditary (inherited) component.
Currently there is no cure. Symptoms are treated with medications that replace lost dopamine or prevent the breakdown of dopamine in order to prolong its effects. In some cases, electrodes are surgically implanted in the brain to facilitate deep brain stimulation, which can reduce symptoms. These different approaches to treatment can all improve functioning to some degree, but involve many adverse side effects.
For patients with Parkinson's disease, induced pluripotent stem cells can be used in two ways to improve treatment outcomes. Because induced pluripotent stem cells can be generated from adult blood cells and then reprogrammed in vitro to transform into patient-specific neurons and other brain cells, these cells can then be used for disease modeling outside the body to test drug effectiveness before using those drugs in the patient so that the ideal drug or combination of drugs and dosage can be selected for a patient's unique physiology. Eventually, it is possible that induced pluripotent stem cell-generated functional neurons will be reintroduced into patients' brains in order to stabilize dopamine production and promote substantial recovery in patients suffering from Parkinson's.