UCLA scientists restore walking after spinal cord injury

[Guest guest]

UCLA scientists restore walking after spinal cord injury

Study shows nervous system can reorganize itself, use new pathways

to issue commands to move

http://www.eurekalert.org/pub_releases/2008-01/uoc--usr010308.php

Spinal cord damage blocks the routes that the brain uses to send

messages to the nerve cells that control walking. Until now, doctors

believed that the only way for injured patients to walk again was to

re-grow the long nerve highways that link the brain and base of the

spinal cord. For the first time, a UCLA study shows that the central

nervous system can reorganize itself and follow new pathways to

restore the cellular communication required for movement.

Published in the January edition of Nature Medicine, the discovery

could lead to new therapies for the estimated 250,000 Americans who

suffer from traumatic spinal cord injuries. An additional 10,000

cases occur each year, according to the and Dana Reeve

Foundation, which helped fund the UCLA study.

" Imagine the long nerve fibers that run between the cells in the

brain and lower spinal cord as major freeways, " explained Dr.

Sofroniew, lead author and professor of neurobiology at the

Geffen School of Medicine at UCLA. " When there's a traffic

accident on the freeway, what do drivers do? They take shorter

surface streets. These detours aren't as fast or direct, but still

allow drivers to reach their destination.

" We saw something similar in our research, " he added. " When spinal

cord damage blocked direct signals from the brain, under certain

conditions the messages were able to make detours around the injury.

The message would follow a series of shorter connections to deliver

the brain's command to move the legs. "

Using a mouse model, Sofroniew and his colleagues blocked half of

the long nerve fibers in different places and at different times on

each side of the spinal cord. They left untouched the spinal cord's

center, which contains a connected series of shorter nerve pathways.

The latter convey information over short distances up and down the

spinal cord.

What they discovered surprised them.

" We were excited to see that most of the mice regained the ability

to control their legs within eight weeks, " said Sofroniew. " They

walked more slowly and less confidently than before their injury,

but still recovered mobility. "

When the researchers blocked the short nerve pathways in the center

of the spinal cord, the regained function disappeared, returning the

animals' paralysis. This step confirmed that the nervous system had

rerouted messages from the brain to the spinal cord via the shorter

pathways, and that these nerve cells were critical to the animal's

recovery.

" When I was a medical student, my professors taught that the brain

and spinal cord were hard-wired at birth and could not adapt to

damage. Severe injury to the spinal cord meant permanent paralysis, "

said Sofroniew.

" This pessimistic view has changed over my lifetime, and our

findings add to a growing body of research showing that the nervous

system can reorganize after injury, " he added. " What we demonstrate

here is that the body can use alternate nerve pathways to deliver

instructions that control walking. "

The UCLA team's next step will be to learn how to entice nerve cells

in the spinal cord to grow and form new pathways that connect across

or around the injury site, enabling the brain to direct these cells.

If the researchers succeed, the findings could lead to the

development of new strategies for restoring mobility following

spinal cord injury.

" Our study has identified cells that we can target to try to restore

communication between the brain and spinal cord, " explained

Sofroniew. " If we can use existing nerve connections instead of

attempting to rebuild the nervous system the way it existed before

injury, our job of repairing spinal cord damage will become much

easier. "

Spinal cord injury involves damage to the nerves enclosed within the

spinal canal; most injuries result from trauma to the vertebral

column. This affects the brain's ability to send and receive

messages below the injury site to the systems that control

breathing, movement and digestion. Patients generally experience

greater paralysis when injury strikes higher in the spinal column.

The UCLA study was supported by grants from the National Institute

of Neurological Disease and Stroke, the Adelson Medical Foundation,

the Roman Spinal Cord Injury Research Fund of California and

the and Dana Reeve Foundation.

Sofroniew's coauthors included Gregoire Courtine, Dr. Bingbing Song,

Roland Roy, Hui Zhong, Herrmann, Dr. Yan Ao, Jingwei Qi and

Reggie Edgerton, all of UCLA