REGENERATION AND FUNCTION OF AXONS IN SCHWANN CELL GRAFTS
Mary B. Bunge, PhD • Blair Calancie, PhD • Brian R. Noga, PhD
Martin Oudega, PhD

It is well established that nerve fiber regeneration in the spinal cord does occur in the presence of Schwann cells inside a “guidance channel.” Questions as to whether these regenerating fibers can exit the other side of the guidance channel and form functional connections are issues addressed in these two studies.

Drs. Noga, Calancie, and Oudega designed a study to test whether regenerated spinal cord axons are capable of carrying electrical messages. Their results demonstrate that some axons within “bridges” implanted in a completely transected cord are capable of being electrically stimulated and can produce measurable evoked responses. Studies such as these help to confirm the potential for the regenerating axon, should it reach another neuron, to communicate or “connect.”

While researchers have been encouraged that regeneration via Schwann cell bridges is achievable, they remain puzzled as to why axons entering the bridges do not continue to grow out the other side. They suspect that the fibers may not exit the bridges because inhibitory molecules form a barrier at the end of the bridge. One group of inhibitory proteins, proteoglycans, are known to inhibit axon growth. In their study, Dr. Bunge and her colleagues set out to document the presence of proteoglycans within the Schwann cell bridges. The concentration of proteoglycans in the end of the bridge where the fibers enter (rostral interface) was lower than the end where the axons need to exit (caudal interface). More proteoglycans present in the caudal interface may help explain why the axons enter the bridge but do not exit.