In a first, scientists have treated a Parkinson's disease patient with his own skin cells -- repurposing them to become key brain cells that the disease kills off. Two years after receiving the experimental treatment, the patient has had no adverse effects, his doctors report. His symptoms, meanwhile, have either stabilized or gotten somewhat better. For now, this patient represents one demonstration that the approach is feasible. But James Beck, chief scientific officer of the Parkinson's Foundation, sounded some cautionary notes.