Nano-textured self-assembled aligned collagen hydrogels promote directional neurite guidance and overcome inhibition by myelin associated glycoprotein

Abstract

The development of nerve guidance conduits is constantly evolving as the need arises for therapies for spinal cord injury. In addition to providing a path for regrowing axons to reconnect with their appropriate targets, the structural and biochemical cues provided by these conduits should be permissive for directional neurite outgrowth and be protective against inhibition in the vicinity of the injury site. Here, we adapted the use of iso-electric focusing to drive the alignment of supramolecular fibrils into self-assembled collagen hydrogels (similar to 300 mu m diameter), and tested those hydrogels for the ability to direct and enhance the migration of neurites. Structural characterization revealed anisotropic alignment of nanofibrillar aggregates (similar to 20 nm diameter), arranged in micron-scale bundles (similar to 1 to 2 mu m diameter) similar to the hierarchical size scales observed in native tissues. Neurite outgrowth extended bidirectionally along the axes of aligned hydrogels. Furthermore, it was shown that, as opposed to poly-D-lysine, neurite outgrowth on aligned hydrogels is not inhibited in the presence of myelin-associated glycoprotein (p > 0.05). These results highlight for the first time a structural and biochemical role for iso-electrically aligned collagen hydrogels in controlling neuronal growth, and indicate that the short-term signaling associated with these hydrogels can be used in adjunct therapy following injury to the spinal cord.