A growth-promoting substance injected into rats stimulated significant recovery from nerve injuries, a new study has shown.
Victims of spinal injuries often severe long-term disability because, for reasons that are poorly understood, nerves in the spinal cord do not spontaneously regrow when they are damaged.
Now, scientists in the US at Tufts University, Boston, have found that a growth factor called artemin can stimulate sensory nerves to regenerate over substantial distances and re-establish functioning connections within the brain.
The team, led by Eric Frank, injected rats with a daily dose of artemin or a harmless placebo. These animals had sustained injury to nerves carrying sensory information from the skin and muscles into the spinal cord.
Immediately following the injury, no sensory signals could be detected in the brain areas where these sensory nerves would normally make connections. But, six months later, electrical signals corresponding to sensory inputs were again detectable in the correct brain areas.
Injections of a nerve-labelling chemical also confirmed that about 25-30% of the sensory nerves that had been injured had grown back and were again conveying sensory information.
The discovery, published this week in PNAS, is a step forward for the field because, previously, scientists had not thought that sensory nerves of the type they were studying would respond to the artemin growth factor.
The findings also give hope that tiny nerve fibres can find their way back to their intended target and re-connect appropriately. They also show that, sometimes, very signficant recovery times may be required before functional improvements are seen.