Stem Cell Snag: Implanted cells may show signs of Parkinson’s

For the first time, researchers have found evidence that Parkinson’s disease might spread to healthy nerve cells implanted into a patient’s brain.

In postmortem studies, researchers found that a small minority of implanted cells in three patients had acquired traits associated with the disease. But for five other transplant recipients, the implanted neurons appeared healthy and functioning at the time of death, up to 16 years after surgery.