Doctor of Philosophy in Neuroscience (PhD)
MicroRNA Biomarkers for Acute Traumatic Spinal Cord Injury
Spinal cord injuries (SCI) are one of the most physically and psychologically devastating injuries one can survive. Despite decades of intense research effort, robust therapeutic treatment for this catastrophic condition remains elusive. The nature of the sequelae of SCI is characterized by progressive cell death in the injury penumbra, resulting in further neurological impairments. The intricate relationship between the vascular and nervous systems has become increasingly evident in many aspects of both normal physiology, and various pathological conditions, including SCI. Vascular abnormalities play a central role in the propagation of secondary damage after SCI. The aim of this thesis is to further the understanding of the vascular changes that occur after acute SCI. The endogenous expression of three angiogenic proteins: Angiopoietin-1 (Ang1), Angiopoietin-2 (Ang2) and Angiogenin will be examined after acute traumatic SCI. In the first study, the concentration of these proteins will be measured in a temporal series of cerebrospinal fluid (CSF) samples after human SCI. In the second study, the relative protein expression of Ang1 and Ang2 will be characterized in rat spinal cord after SCI. In human, Ang1 in CSF is not significantly different from non-SCI values after the initial spike at 24 hours post-SCI. Ang2 in CSF shows a delayed but persistent increase through the first 5 days post-SCI. In contrast, Ang1 in rat spinal cord decreases as early as 2 hours post-SCI, while low molecular weight Ang2 increases dramatically after SCI, from 2 hours to 3 days post-injury, peaking with a 13-fold elevation at 24 hours post-injury. These findings represent the first description of these proteins in the acute SCI setting in human CSF and rat spinal cord. The sustained elevation of Ang2 illustrates a possible mechanism by which reported vascular dysfunction and increases in blood-spinal cord-barrier (BSCB) permeability occurs after SCI. The patterns of change reported between the two studies may allude to the feasibility of using CSF as a biological proxy to future investigations into the biochemical events which occur in the spinal cord after SCI, and guide the development of pharmacologic treatments for this devastating condition.
Spinal cord injury (SCI) is a devastating condition that causes paralysis below the level of the injury. To date, there is no convincingly effective treatment. An enormous preclinical and clinical effort is underway to find a treatment, and one approach is to search for pharmacological agents that are already in clinical use (albeit for different indications), but that may also have neuroprotective properties. Examples of such drugs are magnesium, Riluzole (sodium channel blocker), minocycline and statins. While the majority of human SCI occur in the cervical spinal cord, the vast majority of laboratory SCI research employs animal models of thoracic SCI. An important step, therefore, in the preclinical evaluation of novel treatments is to assess their efficacy in a model of cervical SCI. First, I describe the development of a novel unilateral contusive model of cervical SCI with refined biomechanical, functional, and histological parameters using the Infinite Horizon spinal cord injury device. I conducted a series of experiments in which the spinal cord was injured using various impact forces, impact trajectories, and impact locations off the midline. Behavioral deficits were assessed using a variety of forelimb function tests, after which the cords were evaluated histologically. From these series of experiments, I established a new cervical unilateral spinal cord injury contusion model. Next, I evaluated the neuroprotective effects of minocycline and simvastatin in the clinically relevant unilateral cervical contusion model. Minocycline is a commonly prescribed tetracycline antibiotic that is prescribed for acne. Simvastatin is one of many hydroxymethylglutaryl-coenzyme-A reductase inhibitors that lower cholesterol. As both drugs have translational potential and have been reported to have neuroprotective properties in various neurological diseases, I assessed the neuroprotective effects of these drugs using a host of functional and histological assessments. In the end, there were no neurological improvements with minocycline or simvastatin treatment after a cervical contusion injury.