An experimental drug may one day help paralyzed individuals walk again. The key lies with a bacterial enzyme, or protein, which has helped rats with spinal cord injuries walk, almost as if they had never been hurt. However, researchers caution the treatment is not a magic bullet.
Once a person suffers a spinal cord injury, paralysis is almost certain due to molecular and physiological changes that begin to take place almost immediately after the injury, which is why experts say the development reported in the current issue of Nature is not a panacea.
One of those adverse events, according to study-lead author Elizabeth Bradbury, is the development of scar tissue around the spinal injury, which forms a barrier to nerve regeneration. "So this is why you get permanent paralysis and loss of sensation," she said.
Professor Bradbury led a team of researchers at King's College London that sought to eliminate scar tissue in spine-injured rats. "If we can try to get nerve cells to grow through this barrier, we might be able to then get some recovery of function in these animals," she explained.
The rats, while not completely paralyzed, had a great deal of difficulty walking.
The scientists gave the paralyzed animals an enzyme called chondroitinase ABC for ten days. The bacterial enzyme acted like scissors, chopping up the scar tissue so damaged nerve cells could reconnect.
Using electrical stimulation tests, researcher Elizabeth Bradbury was able to see results six weeks later. "We could record activity below the spinal cord injury," she said. "So, this was good evidence that these nerve fibers have actually regenerated through this scar tissue and formed connections with new cells. So they could talk to new cells."
But the actual proof of how well the rats had fared came a short time later. "The spinal cord-injured animals that were treated with our enzymes recovered really well over time," said Elizabeth Bradbury. "They recovered six weeks after the lesion. They were walking almost as normally as control animals, so they would cross this beam without making any such slips."
"This enzyme could be used in people," points out Jerry Silver is a researcher at Case Western Reserve University in Cleveland, Ohio who pioneered work with chondroitinaise ABC.
"How beneficial this would be in humans is unknown," he said. "This was a very acute treatment, so the animals were injured, and then the enzyme is delivered."
The paper's authors say they next want to see if the bacterial enzyme works in chronically paralyzed animals. Human trials could come in two to five years.