Breathing Easier after Spinal Cord Injury

Researchers at Case Western Reserve University School of Medicine have regrown lost nerve connections, restoring breathing in rodent models of upper spinal cord injuries. The new nerves essentially bridged the gap between the models' spinal cords and their semi-paralyzed diaphragms

In research published in the July 14 issue of Nature, the scientists restored 80 to 100 percent of breathing ability—"a remarkable return of function," in the words of neuroscientist Jerry Silver, PhD, who for 30 years has worked to bring back function to the nearly 1.2 million people with spinal cord injury.

The researchers used a combination "bridge-enzyme" approach. They bridged the spinal cord using a peripheral nerve autograft— an approach used routinely to restore function to damaged nerves in the arms and legs, but which has previously shown little or no success in the spinal cord. And to quell scarring that has forever stymied scientists by blocking nerve cells from regenerating and reconnecting, Silver's team injected the enzyme chondroitinase ABC, which opened passageways for nerves to grow through. "The enzyme chews up all the bad-guy proteoglycans involved in scarring to allow fibers freer entrance and freer exit from the graft," explains Silver, senior author on the Nature article.

Hundreds of nerves not only entered the scientist-built bridge, but grew out the other side, allowing breathing signals—but not unrelated messages—to come through the regenerated spinal cord. "The spinal cord is smart," Silver says of this discernment. "People feared that such rewiring could cause catastrophic misfiring of muscles, but there was actually no physiological chaos when function returned."

While more testing is needed, Silver is optimistic that trials to restore breathing will be conducted in people in the near future. Meanwhile, his lab has begun preliminary work using similar techniques to restore bladder function. He is uncertain whether the technique will be able to revive elaborate functions such as walking. But, he notes, "While those with paralysis would love to be able to walk, they rank quality-of-life issues like bladderand bowel function as much higher among their priorities."