Team Regrows Neurons Controlling Movement in Rats

April 7 -- MONDAY, April 6 (HealthDay News) -- Using genetically engineered cells and a virus as a delivery method, researchers were able to regenerate a type of nerve fiber in rat brains that controls movement.

This isn't the first time researchers have shown it's possible to re-grow some neurons responsible for movement. But the new research showed regeneration of a particular type of neuron -- corticospinal motor axons -- that had so far proven resistant to regeneration efforts.

Corticospinal motor axons are key to controlling fine and gross motor skills, including walking, in humans, said senior study author Dr. Mark Tuszynski, a professor of neurosciences and director of the Center for Neural Repair at the University of California, San Diego.

"Previous research has succeeded in regenerating nerve connections that arise from some types of cells affected by a spinal cord injury," Tuszynski said. "However, until now, there has not been success in eliciting the regeneration of injured connections from corticospinal motor axons, cells which are essential to restoring voluntary movement in humans."

While the goal is to eventually repair spinal cord injuries in people, researchers say they have much yet to learn, and a therapy is at least several years away.

The findings were published in the April 6 online edition of the Proceedings of the National Academy of Sciences.

The corticospinal tract is a massive collection of nerve fibers called axons, long slender projections of neurons. The neurons, which run between the brain's cerebral cortex and the spinal cord, carry signals for movement from the brain.

Voluntary movement occurs when upper motor neurons in the frontal lobe of the brain send signals to the lower motor neurons, which in turn send the nerve impulses to the muscles.

In spinal cord injuries, the axons of the corticospinal tract are severed so that the lower motor neurons below the site of injury can't receive those signals from the brain.