Peripheral nerve injuries can result from tumor resection, reconstructive surgery or trauma and cause life-long disabilities in most affected patients. The current clinical approach is to use scarce nerve autografts, and when available, their performance is unsatisfactory with less than a 50% rate of full functional recovery. The use of bioengineering three-dimensional scaffolds to obviate the need for autografts is a promising approach. However, the current generation of scaffolds is not effective in matching the performance of autografts even when tested in short nerve gaps (<5-7mm) in rodents. We propose to design fabricate and evaluate the next generation of three-dimensional (3D) bioengineered scaffolds that will significantly enhance peripheral nerve regeneration. An understanding of the relevant molecular architecture of nerve autografts inspires the design criterion for these scaffolds. We propose an innovative anisotropic scaffold design to evoke directional stimulation of nerve regeneration. Our scaffolds are engineered to present an increasing concentration gradient of bound laminin-1 and diffusible nerve growth factor (NGF) in nerve growth permissive 3D scaffolds to present an anisotropic biochemical environment to the regeneration nerve stump. Novel methods for spatially controlled 3D presentation of laminin-l, and for the sustained, local delivery of NGF are proposed. Laminin-1 and NGF are the two most critical proteins responsible for nerve autografts' limited success. Our central hypothesis that biomimetic, amsotropic three-dimensional scaffolds that contain an increasing gradient of growth promoting proteins along the axis of the nerve gap will match or exceed the performance of nerve autografts. Specifically, our scaffolds are designed to a) perform better than nerve autografts in the 10 mm gap model in rodents; and b) at least match the performance of autografts in a larger, clinically relevant, 25 mm nerve gap in cats. Importantly, we propose a quantitative evaluation of functional recovery due to regeneration across our scaffolds (to complement standard histological analysis) in both of our animal models as the critical outcome measure of success. When successful, the proposed research will represent a significant advance in the state-of-the-art in 3D biomaterials scaffold design, and has the potential to significantly impact the clinical repertoire available for treating peripheral nerve defects.
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