Reconstructing the Spinal Cord with Stem Cells

Montreal Neurological Institute and Hospital, November 13, 2007

Critical information has been unveiled that could lead to novel therapies for repairing previously irreversible nerve damage in the injured spinal cord. Key elements in the in the body's reaction to spinal cord injury have been discovered in this seminal study which has been published in this week's Proceedings of the National Academy of Science.

Why the adult nervous system is unable to repair itself following spinal injury is still unknown. This is unlike a skin wound for example, where the repair process is well documented.

Even following severe injuries, repair and regeneration is common place in non-mammals and the developing brain. The role of stem cells and their potential to develop into different cell types has been suspected to play a major role in the rejuvenation of these cases.

"Because of their regenerative role, it is crucial to understand the movements of stem cells following brain or spinal cord injury," says Dr. Philip Horner, co-lead investigator and neuroscientist at the University of Washington. "We know that stem cells are present within the spinal cord, but it was not known why they could not function to repair the damage. Surprisingly, we discovered that they actually migrate away from the lesion and the question became why - what signal is telling the stem cells to move."

The migratory pattern of stem cells following injury is controlled by a key molecule called netrin-1. This was discovered after scientists tested numerous proteins. Guiding nerve cells to their proper targets, netrin-1 acts as a repulsive or attractive signal in the developing nervous system. Preventing stem cells from replenishing nerve cells, scientists found that netrin-1 specifically repels stem cells away from the injury site in the adult spinal cord.

"When we block netrin-1 function, the adult stem cells remain at the injury site," says Dr. Tim Kennedy, co-lead investigator and neuroscientist at the Montreal Neurological Institute of McGill University. "This is a critical first step towards understanding the molecular events needed to repair the injured spinal cord and provides us with new targets for potential therapies."

The National Institutes of Health and the Craig H. Nielsen Foundation funded the study.