Jean R. Wrathall - US grants

Develop, test, and validate a standardized, reproducible spinal cord injury model in animals that is characterized in terms of the evolution of behavioral (functional), electrophysiological, and morphological changes arising as a result of the lesion with the primary intent of testing new therapeutic modalities for the treatment of spinal cord injury. Demonstrate that such a model can be used for testing of new therapeutic approaches by utilizing it for evaluating medical therapies reputed to be useful in the treatment of spinal cord injury. In the first phase of the project, we propose to determine the optimal impact conditions to establish three levels of injury (corresponding to 10%, 50%, and 90% residual functional deficit) using a weight droping device (open impact injury) in the rat.

This two-day symposium will feature l4 lectures focusing on 4 main themes covering basic and clinical science and new technology. In addition, over 120 poster presentations will be available for viewing over the two day period. The specific aims of the 12th Annual Neurotrauma Symposium are to: 1. provide the most current information on neurotrauma research to both basic scientists and clinicians investigating and/or treating traumatic and ischemic injuries of the nervous system; 2. encourage the interest of students, residents, and post-doctoral fellows in neurotrauma research; 3. encourage established neuroscientists from other fields to become involved in neurotrauma research. Thus, through formal lectures, poster sessions, and informal discussions between individuals, the overall objective of this symposium is to promote and support communication among basic and clinical scientists concerned with the study and treatment of injuries to the brain, spinal cord, and peripheral nerves.

DESCRIPTION: This is a request for partial support for a two day symposium to be held in conjunction with the Society for Neuroscience Meeting in San Diego, Ca, in November 1995. The primary objective of the symposium is to provide the most current data on and approaches to neurotrauma research to both basic scientists and clinicians studying and/or treating traumatic and ischemic injuries to the nervous system. The secondary objectives are to encourage the interest of students, residents and post-doctoral fellows in neurotrauma research and to encourage established neuroscientists from other fields to become involved in neurotrauma research. The four main themes to be addressed in 1995 are (1) receptor and gene therapy in CNS injury, (2) methodologic issues in neurotrauma modelling, (3) neuroimmunology and intracellular signaling and (4) chronically injured CNS: pathobiology and therapy.

Loss of white matter at the site of traumatic spinal cord injury (SCI) interrupts critical ascending and descending tracts and thus precludes normal function in the spinal cord distal to the site of injury. In the last project period we identified a previously unrecognized process involved in the loss of functional white matter: the AMPA receptor-mediated loss of oligodendrocytes. Approximately twice as much white matter is spared in a standardized contusion SCI model when glial loss is inhibited with the AMPA receptor antagonist, NBQX. Our data support a new understanding of the critical role oligodendrocytes play in trophic support of axons. We have examined the effect of SCI on endogenous glial precursor cell (GPC) populations in vivo, developed an in vitro model to study these cells and identified glial growth factor 2 (GGF2) as an important mitogen for GPC cells in vitro and in vivo. In the new project period we propose to investigate the hypothesis that the endogenous GPCs can be experimentally manipulated to improve recovery of function after incomplete SCI. We have three specific aims. (I) Test the effect of increasing endogenous GPC proliferation on functional recovery in a clinically relevant in vivo model of SCI in the rat.We will compare functional recovery and chronic histopathology in rats that receive GGF2 beginning at different times after SCI, and with or without FGF2 that may produce increased proliferation, or acute TTX treatment that we have shown preserves axons per se. (II). Evaluate the mechanism(s) through which increasing endogenous GPCs with GGF2 improves functional recovery after SCI in the rat,including effects on cell proliferation, survival and differentiation as well as chronic white matter pathology and preservation of axons. (Ill)Develop and use a model of SCI in mice expressing enhanced green fluorescent protein (EGFP) under the control of the CNP promoter that is expressed in glial progenitors to critically evaluate the temporal-spatial effect of SCI on GPC electrophysiological and immunocytochemical phenotypes in situ in tissue slices and the effect of treatment with GGF2 on these properties. We will gain new information about whether endogenous GPCs can be manipulated after SCI to enhance functional recovery. As SCI and brain injury create devastatingand permanent functional deficits for large numbers of Americans, and such injury is especially prevalent in young people and leads to life-long disabilities, therapies to enhance recovery will benefit public health.

DESCRIPTION: (Verbatim from the Applicant's Abstract) Antagonists to excitatory amino acid (EAA) receptors can reduce the extent of chronic histopathology and functional deficits after experimental contusive spinal cord injury. Thus, EAA receptors affect outcome after spinal cord injury. Preliminary evidence now leads to the hypothesis that contusive injury alters EAA receptors in the spinal cord. Receptor subunit expression levels are affected acutely at 1 day and chronically at 1 month after injury. We propose that alterations in expression of specific subunits: (1) result in an altered composition of EAA receptor complexes in neurons and glia in the injured spinal cord: (2) contribute to cell death that occurs in the first 24 h after injury; (3) are triggered, at least in part, by the injury-induced release of EAA; and (4) that some of the acute alterations persist to produce a chronic plasticity of EAA receptors at one month after SCI. We will use a well- characterized rat model of spinal cord contusion to test these hypotheses. We will focus on injury-induced alterations in the GluR2 subunit which regulates the calcium permeability of alpha- amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors and the NR2 subunits which strongly modulate function of N-methyl-D-aspartate (NMDA) receptors. Immunoprecipitation studies will be used to probe the subunit composition and tyrosine phosphorylation status of assembled receptor complexes at 24 hours and 1 month after injury. In situ hybridization and immuno- histochemistry will be used to characterize the temporal development of a specific subunit alteration in particular populations of neurons and glia to determine is correlation with cell death during the first 24 hours after injury. We will also investigate the extent to which the changes in receptor subunit composition can be pharmacologically mimicked with receptor agonists and/or blocked with antagonists. EAA receptors play a critical role in the function of normal spinal cord and are involved in secondary injury after spinal trauma. Further, NMDA and AMPA antagonists are putative therapeutic agents for individuals with acute SCI. Thus, understanding injury-induced alterations in spinal cord EAA receptors has important pathobiological and clinical implications.

DESCRIPTION: (Verbatim from the Applicant's Abstract) The normal spinal cord is a complex community of interacting and interdependent cells. With traumatic spinal cord injury (SCI) this cellular organization is profoundly disturbed and secondary injury mechanisms are triggered that act to exacerbate the loss of cells and functional capacity. Substantial progress has been made in identifying secondary injury mechanisms that contribute to loss of white matter after SCI. Specifically, data has been generated to suggest that tetrodotoxin (TTX)-sensitive Na+ channels play an important role in secondary injury and acute loss of white matter axons. However, the PI also has data implicating ionotropic AMPA and/or kainate receptors in mediating oligodendrocyte cell death and consequently abnormal myelination of surviving axons after incomplete SCI. In the new project period these hypotheses will be tested using a standardized rat model of clinically-relevant contusive SCI. Using electron microscopy and quantitative morphological analysis, they will determine whether: a) acute treatment with TTX will permanently preserve axons 'at risk' after SCI and b) Na channel blockers other than TTX are effective in reducing axonal loss. With immunocytochemistry and in situ hybridization they will determine how treatment with Na channel blockers affects glial loss, the proliferation of glial precursor cells, and myelin gene expression in the injured spinal cord. They will use selective antagonists of specific glutamate receptors to determine their effect on: a) survival of white matter oligodendrocytes acutely over the first 24 h after injury; and b) the myelination of spared axons chronically after SCI. Based on these results they will investigate a third hypothesis: the combination of an acute Na channel blocker and an acute AMPA and/or kainate receptor antagonist will produce an additive effect in reducing chronic white matter pathology and functional deficits after SCI. It is their goal to provide insights to ways of enhancing tissue sparing and functional recovery after SCI.

DESCRIPTION (Adapted From The Applicant?s Abstract): This is an application for a new Institutional Training Grant in Neural Injury and Plasticity. We request support for 2 advanced pre-doctoral (thesis research) students and two post-doctoral fellows who will be trained in research in neural injury and plasticity by faculty participating in the Center for Neural Injury and Recovery (CNIR) at Georgetown University. The purpose of this training program is to prepare scientists and physicians to investigate fundamental mechanisms of neural injury, and basic mechanisms of plasticity in response to injury that may be functionally beneficial or detrimental. Our goal is to train researchers who will be capable of, and committed to, the development of novel and effective treatment strategies to reduce the functional impairments associated with neural injury. An experienced and wellfunded group of 20 faculty with a wide range of research interests and expertise relevant to neural injury and plasticity will participate in training. A key aspect of the program is that students will have comentors and their research will represent collaboration between the laboratories of the training faculty. Pre-doctoral students will enter the Program in Neural Injury and Plasticity after basic training in neuroscience under the auspices of the Georgetown University Interdisciplinary Program in Neuroscience or appropriate departmental Ph.D. programs. Students will have the opportunity for research rotations in the laboratories of the training faculty in their first two years of training while they are completing required and elective courses. They will develop a thesis research proposal in Neural Injury and Plasticity under the direction of mentors chosen from the training program. Both pre-doctoral and post-doctoral trainees will participate in educational programs of the CNIR including Research Minisymposia and specific Journal Clubs focused on current research in areas relevant to neural injury and plasticity.

[unreadable] DESCRIPTION (provided by applicant): This is a revised application for the competitive renewal of an Institutional Training Grant in Neural Injury and Plasticity. We request support for 2 advanced pre-doctoral (thesis research) students and two postdoctoral students as well as one short-term summer research fellow who will be trained in research in neural injury and plasticity by faculty participating in the Center for Neural Injury and Recovery (CNIR) at Georgetown University. The purpose of this training program is to prepare scientists to investigate fundamental mechanisms of neural injury, and basic mechanisms of plasticity in response to injury that may be functionally beneficial or detrimental. Our goal is to train researchers who will be capable of, and committed to, the basic science component of developing novel and effective treatment strategies to reduce the functional impairments associated with neural injury. An experienced and well-funded group of 28 faculty with a wide range of research interests and expertise relevant to neural injury and plasticity will participate in Training: A key aspect of the program is that students will be encourage to have co-mentors and participate in research representing collaborations among the laboratories of the training faculty. Pre-doctoral students will enter the Program in Neural Injury and Plasticity after basic training in neuroscience under the auspices of the Georgetown University Interdisciplinary Program in Neuroscience (IPN). Students will have the opportunity for research rotations in the laboratories of the training faculty in their first two years as graduate students while they are completing required and elective courses. They will develop a thesis research proposal in Neural Injury and Plasticity under the direction of mentors chosen from the training program. Both pre-doctoral and postdoctoral trainees will participate in educational programs of the CNIR including special Seminars and Research Minisymposia and specific Journal Clubs focused on current research in areas relevant to neural injury and plasticity. With respect to public health, this program will create a cadre of future neuroscience researchers who will contribute to the development of therapies to mitigate some of our most pressing health care problems as we increasingly survive to suffer the chronic effects of neural trauma, neurodegenerative diseases and other neurological disorders. [unreadable]