Hormonal Intervention Protects Axon-myelin to Promote Functional Recovery in SCI

严重脊髓损伤（SCI）是一种复杂的、使人衰弱的疾病，可导致永久性的终身神经系统损伤

Severe spinal cord injury (SCI) is a complex, debilitating condition leading to permanent life-long neurological deficits. In addition to neurological dysfunction, individuals with SCI experience neurogenic muscle loss due to immobility. Amelioration of neurological deficits and prevention of skeletal muscle loss are intricately related to recovery of function following SCI. Molecular mechanisms causing neuronal impairment and skeletal muscle loss resulting from SCI, remain incompletely understood. Our laboratory is among the first to demonstrate steroid hormone estrogen (E2) driven neuroprotection in experimental SCI in rats, suggesting E2 warrants clinical evaluation in individuals with neurotrauma. The beneficial effect in SCI was found at a low dose of 10μg/kg E2, but the dose remains at a non-physiologic for human use, and thereby poses a safety concern for clinical use. The emergence of smart drug delivery techniques, such as nanoparticles, may allow for increased drug safety and improved efficacy. Thus, the goal of this proposal is to examine the effects of novel fast and slow release E2-loaded nanoparticles (NP) on neuronal dysfunction and skeletal muscle loss in a rat contusion model of SCI. Since muscle loss may occur as a result of damage to motoneurons in the spinal cord, focal delivery of E2 may reverse denervation and promote nerve sprouting in partially denervated muscle fibers. Preliminary studies suggest that a single administration of a combined fast-release (FNP-E2) and slow-release (SNP-E2) formulation to the contused spinal cord attenuates inflammatory cytokines/chemokines, gliosis, glial scarring, and neurogenic muscle loss. The focal delivery of E2 promotes microglial and astroglial differentiation to subpopulations of anti- inflammatory microglia/astrocytes which inhibit inflammation, axonal damage, and neuronal loss. Preliminary studies also suggest that NP-mediated delivery of E2 gel patch therapy reduces insult-induced muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx) proteins in vitro in myoblast cells and in vivo following mild to moderate SCI (40g/cm injury) in rats. However, whether NP-E2 gel patch therapy alters neuronal impairment and skeletal muscle loss in severe SCI (60g/cm injury) remains unknown. Thus, using a novel combined FNP- E2 and SNP-E2, may allow for suppression of acute inflammation by FNP-E2 and modulation of the inflammatory response by SNP-E2 thereafter. We hypothesize that focal delivery of combined FNP-E2 and SNP-E2 will minimize plasma E2 levels and increase local spinal cord concentrations - thereby reducing acute and subacute inflammation to promote recovery from neurogenic muscle loss in severe SCI. To test the hypothesis, three specific aims are proposed: (Aim 1) Determine the delivery of a combined FNP-E2 and SNP-E2 gel patch therapy and evaluate its kinetics, bio-distribution, toxicity, and effects in severe SCI model in rats; (Aim 2) Investigate the effects of a combined FNP-E2 and SNP-E2 therapy on neuronal impairment, glial scarring, and bladder/locomotor function in severe SCI; and (Aim 3) Examine the effects of a combined FNP-E2 and SNP- E2 therapy on skeletal muscle loss, neuroinflammation, and functional outcomes in severe SCI. Overall, the proposed combination strategy in a severe SCI model may provide insights into the mechanisms of estrogenic- driven neuroprotection and prevention of neurogenic muscle loss in severe SCI in combat veterans. Completion of this project should provide sufficient evidence to support the translation of E2 into clinical trials, with the ultimate goal of providing a safe and effective therapy to treat both veterans and the general population suffering from SCI.