In an approach that might someday be used to treat traumatic nerve damage, researchers have used neurotrophic factors to regenerate sensory axons into the spinal cords of adult rats (Nature 403, 312–316, 2000). “These experiments relate to a specific type of spinal cord injury where the nerve roots of the brachial plexus are damaged or torn away from the spinal cord,” says first author Matt Ramer, a researcher at Guy's, King's, and St. Thomas' School of Biomedical Sciences (London, UK). Such injuries, which cause incurable paralysis, are seen in motorcycle crash victims and can occur in infants as a result of complications during childbirth. In rats given a similar injury, the scientists found that injection of the neurotrophic factors nerve growth factor, neurotrophin-3, or glial-derived neutrotrophic factor into the cerebrospinal fluid caused sensory neurons to regenerate into the spinal cord. Behavioral and electrophysiological analysis showed that the regenerated axons are apparently functional. Though the initial results are promising and some neurotrophic factors have already been approved for use in humans, Ramer concedes that the few clinical trials to test these factors for other indications have all failed: “Whether this is due to delivery problems associated with these proteins, the doses employed or other factors is not yet known.”