The broad, long-term objective of this research is to develop an implantable construct for peripheral nerve regeneration following nerve trauma. Peripheral neurons can regenerate their axons after nerve injury and reinnervate peripheral targets. Despite the robust regenerative potential, the clinical outcome of nerve repair is often disappointing, and regrowth of severed peripheral motor axons to improper targets is considered a major reason for poor functional recovery. We have developed peptide mimics of two carbohydrates carried by neural cell adhesion molecules that are important in targeted innervation during development and that promote neuron survival and neurite growth in vitro and in vivo: the human natural killer cell epitope HNK-1, and 2,8 Polysialic acid (PSA). These carbohydrates and peptide mimics appear to induce preferential motor reinnervation in regenerating motor axons, thereby making them receptive to distal cues that sort the axons into their function-appropriate tracts. We have demonstrated that a soluble mimic of HNK-1 increases the accuracy of regenerating motor neurites into the muscle branch of the femoral nerve and enhances recovery of motor function following peripheral nerve injury, and that soluble mimics of HNK-1 and PSA together improve motor function recovery follow spinal cord injury. The goal of this proposal is to enhance the clinical potential of these peptides by incorporating them on to a biomaterial scaffold for peripheral nerve regeneration, rather than have them introduced in a soluble form, which limits their resident time within the graft. We will graft the peptide mimics on to a three-dimensional fibrillar collagen scaffold, which is ideal as a supporting scaffold for a bioartificial entubulation graft. We will evaluate neurite growth from isolated mouse spinal cord neurons through gels grafted with either HNK-1 or PSA mimics, and then optimize the dual presentation of the mimics in vitro. We will then test the performance of the optimum biomaterial in vivo in a mouse peripheral nerve injury model.
In Specific Aim 1, we evaluate the ability of individual HNK-1 or PSA grafted peptide mimics to accelerate axon regeneration and improve the accuracy of regeneration in vitro in 3D collagen gels.
In Specific Aim 2, we optimize combinations of grafted HNK-1 and PSA mimics for accurate and accelerated regeneration in vitro.
In Specific Aim 3, we test the promising combinations in vivo in a mouse model of peripheral nerve injury. Following completion of these aims we will have identified promising combinations of immobilized peptide mimics of growth-promoting carbohydrates in an implantable collagen matrix. We will have tested the collagen matrix in vitro and in vivo in a mouse model of femoral nerve injury. The collagen matrix is essentially identical to FDA approved substrates for bioartificial skin and peripheral nerve grafts, and could therefore fast-track the translation of the results to clinical practice.
Despite the robust regenerative potential of peripheral nerves, the clinical outcome of nerve repair is often disappointing. Regrowth of severed peripheral motor axons to improper targets is considered a major reason for poor functional recovery. We have developed peptide mimics of two carbohydrates carried by neural cell adhesion molecules that are improve the accuracy of regenerating motor axons at the decision point between entry into the muscle branch vs. cutaneous branch of a peripheral nerve: HNK-1, and 2,8 polysialic acid (PSA). We propose to incorporate these peptide mimics into a biomaterial therapy for peripheral nerve regeneration by covalently grafting the peptides on to collagen to improve the bioactivity of the scaffold. The peptide mimic- grafted collagen biomaterial would be the first engineered grafting therapy to specifically induce preferential motor reinnervation, and would provide a major step forward towards the successful clinical translation of these guidance molecules.
|Masand, Shirley N; Perron, Isaac J; Schachner, Melitta et al. (2012) Neural cell type-specific responses to glycomimetic functionalized collagen. Biomaterials 33:790-7|
|Masand, Shirley N; Chen, Jian; Perron, Isaac J et al. (2012) The effect of glycomimetic functionalized collagen on peripheral nerve repair. Biomaterials 33:8353-62|
|Monteiro, Gary A; Fernandes, Anthony V; Sundararaghavan, Harini G et al. (2011) Positively and negatively modulating cell adhesion to type I collagen via peptide grafting. Tissue Eng Part A 17:1663-73|
|Masand, Shirley N; Mignone, Lindsay; Zahn, Jeffrey D et al. (2011) Nanoporous membrane-sealed microfluidic devices for improved cell viability. Biomed Microdevices 13:955-61|
|Sundararaghavan, Harini G; Masand, Shirley N; Shreiber, David I (2011) Microfluidic generation of haptotactic gradients through 3D collagen gels for enhanced neurite growth. J Neurotrauma 28:2377-87|