As your body develops, neural stem cells transform into the specialized neurons, glia and other cells that make up your brain. Researchers have long hoped to harness these stem cells to grow replacements for neurons damaged in degenerative disorders such as Parkinson's disease. But there is also some risk that neural stem cells will form tumors when implanted in a patient's brain. Now there may be an alternative.

Dennis Steindler of the McKnight Brain Institute at the University of Florida and other scientists were able to extract a population of neural progenitor cells from glia of adult human brains. Proteins in the progenitor cell membranes clearly distinguished them from stem cells. Nevertheless, the progenitors possessed stem cell–like abilities, although—unlike stem cells—they exhibited no tendency to form tumors.

“Glial cells have been viewed as the support cells of the brain,” Steindler says, in contrast to neurons, the message-sending cells. For example, one type of glial cell provides the myelin sheath that wraps around neurons and insulates them. But when Steindler's group implanted the extracted human glial cells into the brains of mice, the cells grew into a wide variety of neurons.

The progenitors also have tremendous potential for growth. Normally glia can divide only 20 times in the test tube before the cells shut down. In this study, the scientists immersed the cells in a special broth known to sustain stem cells. The progenitors survived more than 60 divisions. The authors believe hormones in the broth triggered a mechanism to protect the cells' DNA, which accumulates damage as cells age.

“Of course, we're not jumping into clinical trials,” Steindler says. But in the future, glia cultured on the lab bench may produce biological factors that can protect neurons at risk in patients with Parkinson's or Alzheimer's disease. And should you need to repair damage in your brain, you may be able to generate your own replacement cells.