Mice with a spinal cord injury are walking again after a treatment that allowed their damaged spinal nerves to grow back, Australian researchers say.
The University of Melbourne and University of Queensland team says the treatment allowed the injured mice to walk within weeks of their injury.
The scientists say the research, which is to be published this week in the Journal of Neuroscience, is a major step towards mending spinal cord injuries in humans.
University of Melbourne’s Professor Mary Galea and team found that removing the molecule known as EphA4 resulted in significant regrowth of the spinal nerves.
Mice without EphA4 regained their full stride length within three weeks of injury and within a month had regained ankle and toe movement.
Their ability to bear weight on the affected limbs and to walk and climb also improved for at least three months after the injury.
Galea said it would be some time before human tests could be conducted, but she described the research as the most promising in the area of spinal cord injury for years.
The team believes there is now scope for developing a drug that could block EphA4 in humans and stop a scar from forming on the spinal cord in the first place.
“In the first instance, I think we’ll probably only be able to use this sort of drug in the very acute stages of spinal cord injury because the EphA4 is upregulated soon after injury so that’s the critical point,” she said.
“The emergency treatment would have to be done in the first few days after injury because we’d need to stop the EphA4 being released in significant quantities.
“Down the track it might be possible to look at people with older injuries.”
She said it was likely new drugs would be tested on primates before humans and she expected it would be between five and 10 years before human trials were launched.
Another of the researchers Dr Ann Turnley said most people with spinal cord damage often suffered devastating effects and there was usually little chance they would ever regain much movement.
“In the past it was believed that adult nerves lacked the ability to regrow,” she said.
“But work over the last few years has shown that not to be true and we are now beginning to understand the mechanisms behind regrowth and how to enhance it.
“Our recent findings are a major step forward in this regard.”
How does the critical molecule work?
Scientists have known for some years that the EphA4 molecule was involved in guiding nerves while they developed. But scientists didn’t know what the molecule did in adults.
Turnley said the team was surprised to find it was involved in activating cells called astrocytes.
These star-shaped cells are in turn responsible for scarring in the damaged spinal cord, which prevents the damaged nerves from growing back.
Mice without EphA4 have little scarring in their spinal cord, allowing the nerves to grow once more, the researchers said.