A Window On the Mind

Unlike most other kinds of cells, the neurons that make up the adult central nervous system do not divide and multiply. Once they die, they cannot be replaced -- a fact that makes brain and spinal damage so devastating. But, in an unprecedented experiment, scientists at the Johns Hopkins School of Medicine chanced upon a kind of human brain cell that could be nourished and cultivated. The researchers have kept a laboratory culture of the neurons alive -- and multiplying -- for nearly two years. The new technique, reported last week in Science, should make it easier for scientists to study how the cells function and could someday lead to better treatments for nervous-system injuries and disorders.

The Johns Hopkins cells originally came from the brain of an 18-month-old girl. In 1988 the child, who suffered uncontrollable seizures, had nearly one- third of her right cortex removed. Within minutes of the surgery, Solomon Snyder, director of the Johns Hopkins department of neuroscience, and his colleagues had the tissue in the lab. There the team used a blender to separate the gray matter into individual cells and soaked them in a combination of growth hormones and nutrients. Although most of the cells died within three weeks, two clusters survived and have since flourished.

Cells from the lab-grown culture, which can be shared with other research centers, may help scientists explore the causes of such debilitating diseases as Alzheimer's, Huntington's and multiple sclerosis. And testing the effects of various chemicals on neurons could speed the development of drug therapies. One of the most exciting prospects: the possibility of learning how to introduce new genes into the cultured cells and then use those cells as a replacement for brain tissue lost because of illness or injury. Already researchers are exploring the idea of inserting a gene to stimulate the production of dopamine, a chemical that is in short supply in the brains of patients with Parkinson's disease.

As a first step in this line of research, Snyder is considering injecting altered cells into the brains of rats. It will be years before similar experiments can be done in humans. But in the meantime, the new technique promises great advances in knowledge of how the human mind works.