The impact of myelination on axon sparing and locomotor function recovery in spinal cord injury assessed using diffusion tensor imaging

Authors

  • Tsang-Wei Tu,

    1. Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, MO, USA
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    • Present address: Radiology and Imaging Sciences, Clinical Center, National Institute of Health, Bethesda, MD, USA
  • Joong H. Kim,

    1. Department of Radiology, Washington University in St. Louis, MO, USA
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  • Feng Qin Yin,

    1. Department of Physiology & Cell Biology and Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, OH, USA
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  • Lyn B. Jakeman,

    1. Department of Physiology & Cell Biology and Center for Brain and Spinal Cord Repair, Ohio State University, Columbus, OH, USA
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  • Sheng-Kwei Song

    Corresponding author
    1. Department of Radiology, Washington University in St. Louis, MO, USA
    • Correspondence to: S.-K. Song, Department of Radiology, Washington University School of Medicine, 4525 Scott Avenue, St. Louis, MO 63110, USA.

      E-mail: ssong@wustl.edu

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Abstract

The dysmyelinated axons of shiverer mice exhibit impaired conduction characteristics, similar to early postnatal axons before myelination, whereas the patterns of neuronal activity and connectivity are relatively comparable with those of wild-type myelinated axons. This unique dysmyelination pattern is exploited in the present study to determine the role of compact myelin in the loss and recovery of function following traumatic spinal cord injury (SCI). We applied in vivo diffusion tensor imaging (DTI) and post-mortem immunohistochemistry analysis to examine changes in myelin and axonal integrity, and evaluated these changes in concert with the analysis of locomotor function from 1 to 4 weeks following a mid-thoracic contusion injury in homozygous shiverer and heterozygous littermate mice. The DTI biomarkers, axial and radial diffusivities, are noninvasive indicators of axon and myelin integrity in response to SCI of both myelinated and dysmyelinated spinal cord. We show that myelin is critical for normal hind limb function in open field locomotion. However, when the functional outcome is limited during chronic SCI, the extent of recovery is associated with residual axonal integrity and independent of the extent of intact myelin at the lesion epicenter. Copyright © 2013 John Wiley & Sons, Ltd.

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