November 10, 2005
Source: University of Toronto:
Nerve guidance channel research will aid nerve repair damage
Different combinations of materials will impact different brain neurons to regenerate
by Elizabeth Raymer
Two innovative new studies in nerve guidance channels have significant implications for peripheral nerve repair and spinal cord injury repair strategies.
In a paper to be published in the January issue of Biomaterials and now available online, researchers describe the development of a new nerve guidance channel design that has shown equivalence to the "gold" standard for peripheral nerve repair. A second paper in the same journal describes how material and growth factor combinations within a nerve guidance channel influence the type of regeneration achieved, which has potential for spinal cord injury repair strategies.
The first study shows that "the innovation is in the design of the nerve guidance channel," says Professor Molly S. Shoichet of the Departments of Chemistry, Chemical Engineering and Applied Chemistry, the Institute of Biomaterials and Biomedical Engineering, and the Canada Research Chair in Tissue Engineering.
The design used coil-reinforced hydrogel tubes that promoted nerve regeneration equivalent to that of nerve autografts; a polymeric coil embedded within the wall structure of the nerve guidance channel created a reinforced polymeric channel that significantly enhances regeneration by ensuring that the tube stays open, allowing severed peripheral nerve ends to regenerate both inside and beyond the tube.
"What was innovative about this design was that it used a coil-reinforced hydrogel," a soft material, says Shoichet. "Nerve is a very soft tissue, and we wanted to match the mechanical properties of soft tissue to the channel we’re implanting." A mismatch can cause cell death. At the same time, "the problem with soft material is that over time it can collapse; that’s what we saw with an earlier study. So we reinforced these tubes with a coil imbedded into the tube wall. We’re still matching the properties of soft tissue, but it won’t collapse because of the coil."
The second study employed similar strategies, says Shoichet, using nerve guidance channels designed for implantation into soft tissue to repair spinal cord transection, which can be caused by gunshot or stabbing. "Here, the innovation is in what we are filling the tubes with."
The researchers found that depending on the materials placed in the nerve guidance channel, "we stimulated different parts of the brain to regrow," thus helping the repair of the spinal cord. The materials experimented with included collagen, fibrin, Matrigel and methylcellulose. The use of fibrin, and smaller "tubes within channels," both showed a consistent improvement in locomotor function at seven and eight weeks.
"In no way did we overcome spinal cord injury, but we did demonstrate that different combinations of materials placed in the nerve guidance channels will impact different brain neurons to regenerate."
Research for the first paper was a collaborative effort between the laboratories of Shoichet, Rajiv Midha of Sunnybrook and Women’s College Health Sciences Centre (now at the University of Calgary), and Matregen Corp., and was funded by the Ontario Research and Development Challenge Fund’s Advanced Regenerative Tissue Engineering Centre. Research for the second paper was conducted in the laboratories of Shoichet and Charles Tator of the Toronto Western Hospital Research Institute, and was funded by the Natural Sciences and Engineering Research Council.
Elizabeth Raymer, U of T Public Affairs, 416-946-3048; e-mail: email@example.com