In young rats, researchers find a reaction to spinal cord injury that speeds recovery

November 08, 2006

WASHINGTON, D.C.− Neuroscientists have long believed that the only way to repair a spinal cord injury was to grow new neural connections, but researchers at Georgetown University Medical Center recently found that, especially in young rats, powerful cells near the injury site also work overtime to restrict nerve damage and restore movement and sensation.

The same process does not work as efficiently in adult rats and thus recovery time is much longer, the researchers also discovered. But they say that now that they know such a mechanism exists, it may be possible one day to "switch" these cells on therapeutically − and possibly help humans function better following serious spinal cord injuries.

"No one knew cells in the spinal cord acted to protect nerves in this way, so it gives us some hope that in the future we could stimulate this process in the clinic to enhance recovery and ensure the best outcome possible for patients," said the senior author, Jean R. Wrathall, Ph.D., professor in the Department of Neuroscience.

"This is an animal study, however, and there is much work to do to understand more about this process and how it might be altered," Wrathall said. The study, whose first author is graduate student Philberta Y. Leung, is published in the November 2006 issue of the journal Experimental Neurology.

At the least, Wrathall said, the study reveals surprising new information about nerve cell recovery that neuroscientists can now explore.

In vertebrates, the nervous system uses a two-way transmission system to communicate the electrical impulses that lead to muscle movement and the perception of sensation. In humans, hundreds of thousands of nerve fibers (axons), which can be several feet in length, run through the spinal cord like a two-lane road. Half of these axons connect the brain to distant muscles, and the other half links the body to the brain.

Axons cannot regenerate when they are completely severed, but researchers believe that in a partial injury, surviving nearby axons that serve the same general body area and function can "sprout" new connections to those injured nerve cells that have lost some of their axons. In studying spinal cord injury in rats − the usual model for this kind of investigation − researchers had thought that younger rats ("pups") regain function faster because this sprouting occurs more quickly and proficiently than in older rats. "Just as young trees grow more quickly if you prune them than do older trees, we thought than in young animals, surviving axons would sprout new, and longer, axonal connections more readily," Wrathall said.

But their findings surprised them. "We didn't see that sprouting was faster or better in younger than in adult rats after a partial spinal cord injury," she said. Instead, they saw distinctions in what occurred in cells within the spinal cord at the site of injury. Leung and Wrathall specifically discovered that in the pups, specialized neural stem cells grew vigorously after injury and within one week, many oligodendrocytes, cells whose function is to provide a protective myelin sheath to axons, were produced..

The researchers believe that these activated cells wrap nearby surviving axons with extra myelin sheathing in order to protect them and support their function after injury.

"The ability of axons to transmit their signals is greatly dependent on the insulation provided by their myelin sheaths, and we know that axons near the site of injury eventually can die due to loss of this myelin," Wrathall said. "So we believe these stem cells work to protect healthy axons against toxic factors in the microevironment."

Adult rats do not activate these specialized cells to the same extent as the pups do after injury, for reasons that are not understood, she added.

"We hadn't expected these results, but they are exciting for the field of spinal cord injury and recovery," Wrathall said. "Now that we know that the difference in the local cell response to injury means a quicker recovery, we might be able to eventually exploit that innate healing ability in humans."

She added that these new findings might also be relevant to multiple sclerosis, a disease caused by loss of an axon's protective myelin sheath.
-end-
The study was funded by grants from the National Institutes of Health.

About Georgetown University Medical Center

Georgetown University Medical Center is an internationally recognized academic medical center with a three-part mission of research, teaching and patient care (through our partnership with MedStar Health). Our mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis--or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing and Health Studies, both nationally ranked, and the world renowned Lombardi Comprehensive Cancer Center.

Georgetown University Medical Center

Related Spinal Cord Injury Articles from Brightsurf:

Stem cells can help repair spinal cord after injury
Spinal cord injury often leads to permanent functional impairment. In a new study published in the journal Science researchers at Karolinska Institutet in Sweden show that it is possible to stimulate stem cells in the mouse spinal cord to form large amounts of new oligodendrocytes, cells that are essential to the ability of neurons to transmit signals, and thus to help repair the spinal cord after injury.

Spinal cord injury increases risk for mental health disorders
A new study finds adults with traumatic spinal cord injury are at an increased risk of developing mental health disorders and secondary chronic diseases compared to adults without the condition.

Co-delivery of IL-10 and NT-3 to enhance spinal cord injury repair
Spinal cord injury (SCI) creates a complex microenvironment that is not conducive to repair; growth factors are in short supply, whereas factors that inhibit regeneration are plentiful.

IU scientists study link between energy levels, spinal cord injury
A team of researchers from Indiana University School of Medicine, in collaboration with the National Institute of Neurological Disorders and Stroke, have investigated how boosting energy levels within damaged nerve fibers or axons may represent a novel therapeutic direction for axonal regeneration and functional recovery.

UBCO professor simplifies exercise advice for spinal cord injury
Professor Kathleen Martin Ginis says a major barrier to physical activity for people with a spinal cord injury is a lack of knowledge or resources about the amount and type of activity needed to achieve health and fitness benefits.

Robotic trunk support assists those with spinal cord injury
A Columbia Engineering team has invented a robotic device -- the Trunk-Support Trainer (TruST) -- that can be used to assist and train people with spinal cord injuries (SCIs) to sit more stably by improving their trunk control, and thus gain an expanded active sitting workspace without falling over or using their hands to balance.

Does frailty affect outcomes after traumatic spinal cord injury?
A new study has shown that frailty is an important predictor of worse outcome after traumatic spinal cord injury in patients less than 75 years of age.

Sleep and sleepiness 'a huge problem' for people with spinal cord injury
A new study led by a University of Calgary researcher at the Cumming School of Medicine (CSM) finds that fatigue and sleep may need more attention in order to prevent issues like stroke after spinal cord injury.

From spinal cord injury to recovery
Spinal cord injury disconnects communication between the brain and the spinal cord, disrupting control over part of the body.

Transplanting adult spinal cord tissues: A new strategy of repair spinal cord injury
Spinal cord injury repair is one of the most challenging medical problems, and no effective therapeutic methods has been developed.

Read More: Spinal Cord Injury News and Spinal Cord Injury Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.