Authors

Ke Li, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical CollegeFollow
Charles Nicaise, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College; Neurodegeneration and Regeneration Unit, L'Unité de Rechercheen Physiologie Moleculaire-Namur Research Institute for Life Sciences, University of Namur
Daniel Sannie, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College
Tamara J Hala, Department of Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University; Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityFollow
Elham Javed, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College
Jessica L Parker, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College
Rajarshi Putatunda, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College
Kathleen A Regan, Department of Neuroscience, Farber Institute for Neurosciences, Thomas Jefferson University Medical College
Valérie Suain, Laboratory of Histology, Neuroanatomy and Neuropathology, Université Libre de Bruxelles
Jean-Pierre Brion, Laboratory of Histology, Neuroanatomy and Neuropathology, Université Libre de Bruxelles
Fred Rhoderick, Department of Biomedical and Pharmaceutical Sciences, University of Montana
Megan C Wright, Department of Biology, Arcadia University
David J Poulsen, Department of Biomedical and Pharmaceutical Sciences, University of Montana
Angelo C Lepore, Department of Neuroscience, Thomas Jefferson University Medical CollegeFollow

Document Type

Article

Publication Date

5-28-2014

Comments

This article has been peer reviewed. It was published in: Journal of Neuroscience.

Volume 34, Issue 22, 2014, Pages 7622-7638.

The published version is available at DOI: 10.1523/JNEUROSCI.4690-13.2014

Copyright © 2014 the author

Abstract

A major portion of spinal cord injury (SCI) cases affect midcervical levels, the location of the phrenic motor neuron (PhMN) pool that innervates the diaphragm. While initial trauma is uncontrollable, a valuable opportunity exists in the hours to days following SCI for preventing PhMN loss and consequent respiratory dysfunction that occurs during secondary degeneration. One of the primary causes of secondary injury is excitotoxic cell death due to dysregulation of extracellular glutamate homeostasis. GLT1, mainly expressed by astrocytes, is responsible for the vast majority of functional uptake of extracellular glutamate in the CNS, particularly in spinal cord. We found that, in bacterial artificial chromosome-GLT1-enhanced green fluorescent protein reporter mice following unilateral midcervical (C4) contusion SCI, numbers of GLT1-expressing astrocytes in ventral horn and total intraspinal GLT1 protein expression were reduced soon after injury and the decrease persisted for ≥6 weeks. We used intraspinal delivery of adeno-associated virus type 8 (AAV8)-Gfa2 vector to rat cervical spinal cord ventral horn for targeting focal astrocyte GLT1 overexpression in areas of PhMN loss. Intraspinal delivery of AAV8-Gfa2-GLT1 resulted in transduction primarily of GFAP(+) astrocytes that persisted for ≥6 weeks postinjury, as well as increased intraspinal GLT1 protein expression. Surprisingly, we found that astrocyte-targeted GLT1 overexpression increased lesion size, PhMN loss, phrenic nerve axonal degeneration, and diaphragm neuromuscular junction denervation, and resulted in reduced functional diaphragm innervation as assessed by phrenic nerve-diaphragm compound muscle action potential recordings. These results demonstrate that GLT1 overexpression via intraspinal AAV-Gfa2-GLT1 delivery exacerbates neuronal damage and increases respiratory impairment following cervical SCI.

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