Characterization of Chronic Contusive Spinal Cord Injury and Promotion of Corticospinal Tract Regeneration

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Characterization of Chronic Contusive Spinal Cord Injury and Promotion of Corticospinal Tract Regeneration Summary Chronic spinal cord injury (SCI) is a post-injury stage when the injury is stable with little additional change. Although the vast majority of SCI are chronic, there are few studies to characterize the chronic injury at histological, cellular, and molecular level in clinical relevant animal models. There are even fewer studies for development of therapeutic treatment of chronic SCI, especially for promotion of supraspinal motor axonal regeneration, including the corticospinal tract (CST) system that is the most important voluntary motor control system in humans. Therefore, we propose to use a chronic clinical relevant moderate bilateral lower cervical contusion model for characterization it at cellular and molecular levels and development of new therapies for improvement of skilled hand function. There are three Specific Aims in this proposal. Aim 1 is to identify cellular mechanisms associated with chronic contusive SCI, to guide discovery of new molecular mechanisms to promote regeneration. We will develop a moderate chronic bilateral lower (C6) cervical contusion model since the majority of SCI patients (65%) are quadriplegic, with loss of hand function that is critical for independence and quality of life. The injured rats survive for up to 12 months to a chronic stage of SCI for characterization of glial scar, extra cellular molecules (ECM) and axonal state. Aim 2 is to identify transcriptional mechanisms associated with chronic contusive SCI, to guide discovery of new molecular mechanisms to promote regeneration. We will use a newly developed technique developed in our lab, Cre-dependent Ribotag vectors, to isolate mRNA specific from chronically injured CST neurons for characterization of their transcriptome using RNAseq. We then compare this transcriptome to intact and sub-acutely injured CST neurons (we already have these datasets) and chronically injured CST neurons that regenerate into neural progenitor cell (NPC) graft to identify key molecular pathways related to cellular/axonal growth that are disrupted, We can therapeutically target these molecular pathways in Aim 3 and future studies. Aim 3 is to test candidate mechanisms to promote recovery of chronically injured CST neurons and promote axonal regeneration after chronic SCI. We will first perform in vitro screen for the potential candidate targets identified in Aim2 to promote neurite growth of postnatal cortical neurons and adult dorsal root ganglion (DRG) neurons. We then test these candidate genes to promote regeneration of chronically injured CST in combination with NPC transplants that serve as a permissive cellular substrate. Findings of this work will substantially extend our knowledge of chronic SCI and develop potential treatment for chronic SCI.