Ever since the 1940s, when researchers discovered that nerves of the spinal column can grow, scientists have tried to devise ways to coax the cells to overcome damaged areas and thereby defeat paralysis, organ degeneration and other problems associated with injury to the central nervous system. Removing scar tissue with drugs, laying down scaffolds and inserting cells have all been tried with varying degrees of success. Recent achievements, such as the restoration of some ability to walk in rodents, and other findings indicate that rather than a single approach, all may be the key. “A combination of drugs and cells gives better results than just any one of the components on their own,” says Naomi Kleitman, a program director at the National Institutes of Health’s National Institute of Neurological Disorders and Stroke.

Injury to nerves produces inflammation, ion imbalance, scar tissue and cysts filled with cerebrospinal fluid, which damage additional neurons and create a barrier against neuron growth. A lesion just one millimeter wide can increase to five to 10 millimeters, too large a gap for neurons to bridge. Surviving neurons often lose myelin, the insulation needed for reliable and quick signal transmission. About 200,000 people in the U.S. live with spinal cord injury.