Spinal Cord Regeneration Studies Hinge on Animal Models

The development of promising new treatments for spinal cord injuries in humans depends on animal models--various ways of creating experimental injuries in animals and assessing their response to treatments. An article in the July 15 issue of the journal Spine provides an update on various types of animals models and their essential role in developing techniques of spinal cord regeneration.

Dr. Brian K. Kwon and colleagues of University of British Columbia, Vancouver, outline the different techniques for studying healing of spinal cord injuries in animals, usually mice or rats. The three basic approaches are

* Anatomical--antibodies or other "tracer" substances are placed on one side of the cut spinal cord. If the tracer spreads from one side to the other, that tells researchers that new spinal nerve cells (axons) have regrown across the gap.

* Neurophysiological--similarly, electrical signals can be shown to travel across the cut area.

* Functional--behavioral tests can show how well the injured spinal cord is functioning. Most such studies have used tests of walking ability, although there is an increasing emphasis on tests of sensation and other spinal cord functions.

Another critical question is, what type of injury will be tested? Many studies have used "complete transection" models, in which the cord is cut clean through. This ensures that any sign of recovery--especially on anatomical tests--truly reflects regeneration of spinal cord cells across the gap.

Other studies have used "contusion and compression" models. Compared to a sharp injury, these blunt-injury models more accurately reflect the situation in human spinal cord injuries--not only the initial damage, but also the delayed effects of bleeding, swelling, and scarring.

The drawback of blunt-injury models is that the injury is incomplete, possibly sparing some portions of the spinal cord. This makes it difficult to be sure that communication from one side of the injury to the other truly results from new axon growth. Also, relatively simple injuries produced in mice and rats don't truly reflect the complex bending, twisting, and other forces produced by trauma severe enough to damage the human spinal cord.

In recent years, many experimental approaches have been developed to regenerate spinal tissue and improve neurological function after spinal cord injuries. Animal studies--using both "sharp" models useful in studying the anatomical regeneration of axons and "blunt" models that more closely resemble the complex effects of human spinal cord injuries--will play a critical role in refining these techniques to the point where they can be evaluated in humans.

Recognized internationally as the leading journal in its field, Spine reports on today's most important diagnostic and therapeutic advances regarding spinal pain, deformity, and disability. Distinguished by its broad scope of coverage and emphasis on patient care, this popular biweekly has earned must-read status in the orthopaedic community. For more information, call 1-800-638-3030 or visit http://www.spinejournal.com.

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