Restoring Mobility to Injured Spinal Cord

The spinal cord is like a super highway of nerves. When an injury occurs, the body's policing defenses put up a roadblock in the form of a scar to prevent further injury, but this roadblock stops all neural traffic from moving forward.

The researchers, from Case Western Reserve University (Cleveland, OH, USA), bypassed this roadblock in the spinal cord. They first regenerated the severed nerve fibers, or axons, around the initial large lesion with a segment of peripheral nerve taken from the leg of the same animal that suffered the injury. Next, they jump-started neural traffic by allowing many nerve fibers to exit from the end of the bridge. This was done by using an enzyme that stopped growth inhibitory molecules from forming in the small scar that forms at the exit ramp of the bridge. This allowed the growing axons to reconnect with the spinal cord.

For more than 100 years, researchers have used grafts of peripheral nerves from the rib area or parts of the leg. Although peripheral nerves can be used successfully as grafts in the limbs, spinal cord injuries put up defenses called inhibitory chondroitin sulfate proteoglycans that create molecular guardrails within scars at the lesion site. These scars act as a barrier to regenerating axons and result in loss of the ability to breathe or move arms or legs, depending upon the injury site.

In the current study, about 20% of the nerve fibers left the bridge and reconnected with the spinal cord, which brought about a markedly improved mobility for the seven rats given the chondroitinase treatment, noted Jerry Silver, a professor of neurosciences at the Case School of Medicine and senior author of the study. In a control group of five rats that underwent the same procedure but were given a saline solution instead of chrondroitinase, none showed any nerve growth out of the bridge or improvement in their limbs.



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