The seminal study, co-lead by Dr. Philip Horner, neuroscientist at the University of Washington, Dr. Tim Kennedy, neuroscientist at the Montreal Neurological Institute of McGill University, might help in providing novel therapies for repairing previously irreversible nerve damage in the injured spinal cord.
In the study, the researchers tested numerous proteins and identified netrin-1 as the key molecule responsible for the migratory pattern of stem cells following injury. "Because of their regenerative role, it is crucial to understand the movements of stem cells following brain or spinal cord injury," Horner said.
"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," he said.
In the developing nervous system, netrin-1 acts as a repulsive or attractive signal, guiding nerve cells to their proper targets. The team found that in the adult spinal cord, netrin-1 specifically repelled stem cells away from the injury site, thereby preventing stem cells from replenishing nerve cells.
Very little knowledge is known as to why a wound to the skin repairs itself but the adult nervous system is unable to repair itself following spinal injury. This is in contrast to the developing brain and non-mammals, which can repair, and regenerate after severe injuries.
The sole clue from these systems has been the role of stem cells and their potential to develop into different cell types. "When we block netrin-1 function, the adult stem cells remain at the injury site," Kennedy said.
"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," he said.
The study is published in the Proceedings of the National Academy of Science.