Humans and monkeys exhibit greater motor recovery than rats after similar spinal cord injury, new research shows.
Spontaneous improvement occurs during the first six months after a spinal cord injury, allowing a hemiplegic patient to recover partial motor control.
The neuronal mechanisms underlying this extensive recovery in primates are nearly absent in laboratory rats, researchers said.
"Research on rats is essential for developing regenerative therapies, but rodents show fundamental differences from primates in terms of neuronal reorganisation and functional recovery," said research leader Gregoire Courtine from Ecole Polytechnique Federale De Lausanne (EPFL), Switzerland.
The reason for this lies in differences in anatomy and function of the corticospinal tract, which are the fibres through which the cortex communicates with the spinal cord.
In rats, the corticospinal tract is mainly located in the dorsal column and is restricted to one side of the spinal cord, whereas in monkeys and humans this pathway migrated to the lateral column, expand in size, and became bilateral.
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"Because of these anatomical specificities, many fibres are spared after an injury," said Courtine.
"The corticospinal tract forms detour circuits around the lesion, restoring communication between the brain and the neuronal circuits that control the movement of the arms and legs," Courtine explained.
The identification of this primate-specific mechanism of recovery has major implications for future research to design therapies to repair the human spinal cord, scientists said.
The study was published in Science Translational Medicine.