But this time, according to a report published last week in Science, it worked. Not only did the severed nerve fibers grow across the bridge, but the rats also began to regain function in their lifeless limbs. Although doctors quickly pointed out that it may be years before last week's findings could be turned into an effective therapy, they too were clearly buoyed. The Karolinska team members, led by Henrich Cheng, took special pains to avoid the pitfalls that had tripped up investigators in the past. White matter contains the parts of nerves that are surrounded by a substance called myelin, which acts like insulation around an electric wire.
Gray matter contains the parts that have no insulating myelin.
It's almost impossible to get regeneration in white matter. Growth in gray matter, on the other hand, is relatively easy to stimulate. Using nerves from the rat's chest muscles for the bridge, Cheng carefully connected the insulated white matter on one side of the spinal cord to uninsulated gray matter on the other. That way, the nerves in the gray matter would grow toward the white and, he hoped, re-establish contact. The investigators used a natural adhesive called fibrin to anchor the bridge in place.