New Role Identified for Scars at Site of Injured Spinal Cord

For decades, it was thought that scar-forming cells called astrocytes were responsible for blocking neuronal regrowth across the level of spinal cord injury, but recent findings challenge this idea. According to a new mouse study, astrocyte scars may actually be required for repair and regrowth following spinal cord injury. The research was funded by NINDS and published in Nature. 

“At first, we were completely surprised when our early studies revealed that blocking scar formation after injury resulted in worse outcomes,” said Dr. Michael Sofroniew, professor of neurobiology at the University of California, Los Angeles, and senior author of the study. “Once we began looking specifically at regrowth, though, we became convinced that scars may actually be beneficial. Our results suggest that scars may be a bridge and not a barrier towards developing better treatments for paralyzing spinal cord injuries.”

Neurons communicate with one another by sending messages down long extensions called axons. When axons in the brain or spinal cord are severed, they do not grow back automatically. For example, damaged axons in the spinal cord can result in paralysis. When an injury occurs, astrocytes become activated and go to the injury site, along with cells from the immune system, and form a scar. 

Scars have immediate benefits by decreasing inflammation at the injury site and preventing spread of tissue damage. However, long-term effects of the scars were thought to interfere with axon regrowth.

“This important research provides further evidence about the complexity of the brain and spinal cord’s injury response,” said NINDS program director Dr. Lyn Jakeman. “It shows that scar-forming astrocytes support axon growth and suggests that therapeutics directed only at blocking these cells may not enhance regeneration of the injured spinal cord.” 

Trauma leads to spinal cord injury in about 12,500 people in the U.S. each year. It is estimated that 276,000 individuals in the country suffer from long-term effects of spinal cord injury. The ultimate goal of spinal cord injury research is to enable connections to develop that cross the level of injury and rewire the normal cord below.