FRIDAY, Dec. 12, 2003 (HealthDayNews) -- Scientists have discovered a signaling pathway that helps control the growth of nerve cells up and down the spinal cord.
"We've discovered a signaling pathway to tell the spinal neurons [nerve cells] to project to the brain," says study co-author Yimin Zou, an assistant professor of neurobiology, pharmacology and physiology at the University of Chicago. The research appears in the Dec. 12 issue of Science.
This process is crucial for the proper formation of the central nervous system.
While the Chicago research was done in rodents, "we logically assume that a similar mechanism is present in humans as well," Zou says. "That has not yet been tested, of course."
Eventually, the discovery may play a role in helping to restore function in people who have suffered paralyzing spinal cord injuries, the team hopes.
Neurons are the information messengers of the nervous system. The neurons studied by Zou's team are part of the sensory system, which transmit such messages as pain and temperature from the spinal cord (and other body parts) all the way up to the brain.
The University of Chicago study focused on a kind of neuron in the sensory system called commissural, found in the spinal cord.
Zou and his colleagues found substances called chemoattractants that they think exist in a gradient fashion (a slope-like environment where concentrations are higher in some areas than others). These chemoattractants can entice the neuron's extensions, called axons, to grow toward the higher concentration areas, thus ensuring proper growth toward the brain, Zou believes.
And the chemoattractants are probably formed by a family of proteins called the Wnt family, Zou says.
The gradient itself is detected by a receptor known as Frizzled3, found at the tips of the neurons. When Zou's team looked at mice that did not have the Frizzled3 receptors, they found the neuron's axons (extensions of the neurons) lost the proper direction of growth along the spinal cord.
Zou says if the Wnt proteins could be used to coax damaged commissural neurons to regenerate and re-establish connections between nerve cells of the spinal cord and the brain, the treatment of paralysis from spinal cord injuries could be revolutionized.
The discovery is just part of the puzzle, however, Zou acknowledges. For instance, a patient paralyzed by a spinal cord injury would have to have rebuilt other nerves that carry messages from the brain down to the spinal cord. And the cues that direct these nerves have not been discovered yet, Zou says.
Another expert in the field, Alex Kolodkin, a neuroscientist at Johns Hopkins School of Medicine, calls the University of Chicago study "excellent" and "groundbreaking."
While he sees no shortcomings in the study, he says it does raise some questions: "Will the same cues function in adult neurons?"
That's yet to be determined, Zou says.
The research does lead the way for the eventual possibility of treating those who have been paralyzed, Kolodkin agrees.
More information
For more information on neurons, try the University of Texas or the National Institute of Neurological Disorders and Stroke.
