Originally Published MDDI February 2004

R&D DIGEST

Erin Bradford

If axons could be directed, axon growth could be promoted in adults with spinal cord injuries.

A research team at the University of Chicago has discovered a signaling pathway that controls the growth of nascent nerves within the spinal cord. This guidance pathway steers the nerve cells toward the brain during development.

The team cautions that this is only the first step in understanding how the brain and spinal cord are connected during embryonic development. However, the implications of the discovery are numerous. 

This research “could be used to devise ways to regenerate axons in adults or to promote or guide axon growth in adults after a paralyzing spinal cord injury,” says Yimin Zou, PhD, assistant professor of neurobiology, pharmacology, and physiology at the University of Chicago.

Zou hopes the signal-carrying proteins will be able to be used in a way similar to current treatments of spinal cord injuries. “People use pumps to introduce molecules into the body,” explains Zou. “So we might be able to include these molecular reagents in the pump, and then pump them into the injured area to stimulate growth.” While this form of treatment is still only imagined, the study provides a step in that direction.

The study shows that a gradient of chemoattractants along the spinal cord, formed by Wnt proteins, lures growing commissural neurons toward the brain. “This is a discovery about how spinal cord axons are guided to grow toward the brain during embryo genesis,” says Zou. “We found that Wnt proteins are involved in guiding these axons to grow anterior, toward the brain.”

Neurons are the primary model system that scientists use to understand the assembly of the nervous system. The study focused on commissural neurons, which are found in the spinal cord. These neurons receive sensory signals and relay them up the spinal cord to the nerve cells that process the information in the brain.

The mechanism that Zou's team discovered is an attractant; the molecules can attract the axons and guide them toward a certain area of the brain or spinal cord. However, the environment of the central nervous system in an adult with a spinal cord injury inhibits the axons from growing. If scientists could use these molecules, they could potentially promote growth as well as overcome the inhibition. 

“Together with other kinds of molecular and therapeutic approaches that we have, our study may provide tools for a more well-rounded approach to regenerating axons and controlling the regeneration of axons,” says Zou. “It will at least be an additional mechanism for doing that kind of repair work.”

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