Washington: Scientists have found an unexpected natural recovery of spinal cord injury in primates, a discovery which they say could lead to the development of new treatments for patients with such injuries.
A team of researchers from the University of California in San Diego(UCSD) and the University of Zurich in Switzerland found that primates recover almost by 60 per cent within 24 weeks after mild spinal cord injury.
Although regeneration after severe brain and spinal cord injury is limited, good functional recovery following milder injuries are also very surprising, according to the team.
The scientists, who reported their study in the journal Nature Neuroscience, also said that the findings may one day lead to the development of new treatments for patients with
spinal cord injuries.
The researchers, who looked at adult rhesus monkeys for their study, were surprised to see that connections between circuits in the spinal cord in the animals re-grew
spontaneously and extensively, restoring fully 60 per cent of the connections 24 weeks after a mild spinal cord injury.
"The number of connections in spinal cord circuits drops by 80 per cent immediately after the injury," said Ephron Rosenzweig, assistant project scientist in UCSD Department of Neurosciences.
"But new growth sprouting from spared axons -- the long fibbers extending from the brain cells, or neurons, which carry signals to other neurons in the central nervous system
-- restored more than half of the original number of connections."
He added that this was particularly surprising since the phenomenon does not appear in rodents -- the traditional study model.
It was not previously known that an injured spinal cord could naturally restore such a high proportion of connections. More profoundly, the spontaneous recovery was accompanied by extensive recovery of movement on the affected side of the body.
Mark H Tuszynski, senior author of the study, said the team is now investigating how the nervous system is able to generate so much natural growth after injury.
This knowledge could lead to development of drugs or genes that could transmit high-growth signals to spinal cord damage sites after more severe spinal cord injury, he said.
The work highlights an important role for primate models in translating basic scientific research into practical, therapeutic treatments for people.
According to scientists, the spinal cords of humans and other primates are different from rodents, both in overall anatomy and in specific functions.
For example, the corticospinal tract -- a collection of nerve cell fibbers linking the cerebral cortex of the brain and the spinal cord -- is much more important for muscle
movement in primates than in rats.
"With similar injuries, rodents show much less regrowth and recovery of limb function," said Rosenzweig. The challenge now is to determine what exactly is prompting neuronal axons to sprout new connections, leading to recovered movement.
That has exciting clinical relevance because discoveries resulting from further research could be applied to patients with severe injury to their central nervous system, Rosenzweig added.