Peripheral nerves extend from the spinal cord to targets in the periphery such as muscle and skin. Individual peripheral nerves contain thousands of individual fibers, called axons, which project to specific targets. When a peripheral nerve is damaged, axons between the injury site and muscle or skin degenerate and function is lost. Although peripheral nerve axons are capable of regenerating after such injuries, in humans this regeneration is modest at best and there currently is no effective clinical treatment.
One reason peripheral nerves do not regenerate well is the presence of growth inhibitory substances, called proteoglycans, within the environment of the damaged nerve. In an effort to improve the ability of axons to regenerate, the Emory scientists attempted to modify this inhibitory environment following peripheral nerve injury in mice. They treated the peripheral portion of severed nerves with each of three enzymes that degrade specific types of proteoglycans.
During the first two weeks after the injury, axons regenerated through enzyme-treated tissues much more effectively than through untreated tissues. Not only did the axons regenerate, those that did extended more than twice as far.
"This study shows that treatment with enzymes that degrade proteoglycans offers the potential to enhance regeneration, and may lead to improved recovery of function after peripheral nerve injuries," says Dr. English.