Rodent of the Week: Reconnecting axons in spinal cord injuries

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For many years, researchers have toiled to find ways to heal the kinds of spinal cord injuries that lead to paralysis. In another step toward that goal, scientists at UC San Diego have demonstrated that regenerated axons -- the part of nerves needed to transmit signals -- can be guided to their correct targets to re-form neural connections.

Previous research has led to the ability to regenerate axons but researchers did not know how to coax the axons to grow into the correct target cells that would restore sensory functions.

‘The ability to guide regenerating axons to a correct target after spinal cord injury has always been a point of crucial importance in contemplating translation of regeneration therapies to humans,’ the senior author of the report, Dr. Mark Tuszynski, said in a news release. ‘While our findings are very encouraging in this respect, they also highlight the complexity of restoring function in the injured spinal cord.’

The researchers showed that regenerating axons can be guided to the correct targets using a type of chemical hormone called a growth factor. In the experiment, performed on rats, when the growth factor was placed in the correct target as a guidance cue, axons regenerated into it and formed synapses, the electrical connections that allow signals to travel. When the growth factor was placed in the wrong target, the axons grew in the wrong direction.

The synapses, however, were not electrically active, probably because the regenerating axons were not covered in myelin, the insulating material that protects nerves. ‘It appears that these regenerating axons require restoration of the myelin sheath to ultimately restore function,’ Tuszynski said.

That will be the next step in the team’s research, he said. The paper is published online in Nature Neuroscience.

-- Shari Roan