Paving the way for spinal cord repair.

By laying down bridges of Schwann cells -- cells that normally coat nerves -- researchers have coaxed severed nerve fibers in the spinal cords of adult rats to heal and grow toward each other. Although the researchers cannot determine yet whether the therapy alleviates the rats' partial paralysis, they hope the finding will lead to new ways of treating spinal cord injuries.

Developmental neurobiologist Mary Bartlett Bunge of The Miami (Fla.) Project to Cure Paralysis and Carlos L. Paino of the Hospital Ramon y Cajal in Madrid grew thin layers of Schwann cells in culture dishes coated with collagen, a connective tissue. When they rolled the Schwann cell-collagen sheets up like carpets and transplanted them into the spinal cords of 20 injured rats, they found that the rolls bridged the ends of the severed nerve fibers of all 20 rats.

The new cord tissue contained 20,000 regenerating nerve fibers, Bunge and Paino found. Moreover, the new tissue developed its own blood supply, and some of the budding nerves acquired coatings of myelin, the insulating substance secreted by Schwann cells.

Preliminary results of the experiment appeared in the November 1991 EXPERIMENTAL NEUROLOGY.

Next, Bunge plans to test whether the Schwann-cell transplants can improve the ability of injured rats to move their hind legs. She hopes that such transplants may one day restore at least some motor function to humans with damaged, but not completely severed, spinal cords.