Surgical repair of peripheral nerve transection is dependent on nerve autografts that produce morbidity and are often insufficient in number or size. A substitute for grafting is the nerve guide, developed to direct regenerating axons and support cells from proximal to distal ends of a transected nerve. Most nerve guides produce inferior results, even when filled or coated with extracellular matrix proteins (ECM) or growth factors that promote neurite outgrowth. The best of these have approached the success of autografts by slowly releasing growth factors and ECM from a resorbable polymer. Although topographical features play a large role in guiding neurites, only a handful of investigators have used polymer fibers to direct regenerating axons. Methods for producing aligned fibers with nano- and micro-scale diameters in which growth factors and ECM can be incorporated, have been developed for the purpose of neural regeneration. A proposal to fabricate and test these fibers is presented.
Specific aim 1 begins with production and characterization of aligned fibers from degradable polymers. Fibers will be fabricated with varying alignments, diameters and inter-fiber spacing. Growth factors and ECM binding domains will be immobilized in the fibers. Mechanical strength, crystalline structure, spacing, alignment, and size of fibers will be characterized. A method to place fibers into a nerve guide will be developed.
In specific aim 2, these fibers will be tested for their ability to promote adhesion of and neurite outgrowth from dissociated motor neurons and dorsal root ganglia (DRG) neurons in primary culture. Neuron cell body attachment, and neurite length and alignment will be quantified as functions of fiber material, alignment, diameter, spacing, and incorporated growth factor and ECM. The effect of Schwann cells on neurite outgrowth will be examined in co-culture experiments.
Specific aim 3 continues this testing using explant models. Both sensory neurons from DRG explants and motor neurons from spinal cord explants will be used. Effects of Schwann cells on neurite outgrowth will be examined in this aim, also. It is hoped that this project will further knowledge of both the production of advanced fibrous scaffoldings and their potential to be harnessed as a tool for nerve regeneration.
