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Differential Histopathological and Behavioral Outcomes Eight Weeks after Rat Spinal Cord Injury by Contusion, Dislocation, and Distraction Mechanisms

View Article: PubMed Central - PubMed

ABSTRACT

The objective of this study was to compare the long-term histological and behavioral outcomes after spinal cord injury (SCI) induced by one of three distinct biomechanical mechanisms: dislocation, contusion, and distraction. Thirty male Sprague-Dawley rats were randomized to incur a traumatic cervical SCI by one of these three clinically relevant mechanisms. The injured cervical spines were surgically stabilized, and motor function was assessed for the following 8 weeks. The spinal cords were then harvested for histologic analysis. Quantification of white matter sparing using Luxol fast blue staining revealed that dislocation injury caused the greatest overall loss of white matter, both laterally and along the rostrocaudal axis of the injured cord. Distraction caused enlarged extracellular spaces and structural alteration in the white matter but spared the most myelinated axons overall. Contusion caused the most severe loss of myelinated axons in the dorsal white matter. Immunohistochemistry for the neuronal marker NeuN combined with Fluoro Nissl revealed that the dislocation mechanism resulted in the greatest neuronal cell losses in both the ventral and dorsal horns. After the distraction injury mechanism, animals displayed no recovery of grip strength over time, in contrast to the animals subjected to contusion or dislocation injuries. After the dislocation injury mechanism, animals displayed no improvement in the grooming test, in contrast to the animals subjected to contusion or distraction injuries. These data indicate that different SCI mechanisms result in distinct patterns of histopathology and behavioral recovery. Understanding this heterogeneity may be important for the future development of therapeutic interventions that target specific neuropathology after SCI.

No MeSH data available.


Related in: MedlinePlus

Micrographs of myelinated axons in the (a) gracile fasciculus and (b) dorsal corticospinal tract (CST). Representative confocal micrographs of the regions of interest used in the quantitative analysis of white matter damage immunostained for neurofilament H/β-tubulin for axons (in red) and myelin basic protein for myelin/myelin debris in green. The normal control tracts show a dense packing of small myelinated axons in the gracile fasciculus (GF) and even smaller ones in the dorsal CST. These intact fibers display the typical green myelin rings surrounding a red axon in the middle. Contusion and (somewhat less so) dislocation injuries destroy both tracts from the epicenter distally, leaving in the wake of Wallerian degeneration myelin debris (green dots) and a few large axons (displaced or sprouted). Distal is rostral in the ascending GF and caudal in the descending CST. The damage proximal to the epicenter is indicative of some dieback in both tracts. The damage after distraction is less focal in the GF showing a gradual thinning of this ascending tract from caudal to rostral and appearance of a few larger profiles in the rostral segments that are likely displaced axons from the cuneate fascile (entering the spinal cord rostral to injury). The CST shows a loss of the typical small myelinated axons at all levels with some partial preservation rostrally. The apparent preservation of the CST in the caudal segments is from displaced/sprouted larger sensory axons. Scale bar 20 μm. MBP, myelin basic protein.
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f6: Micrographs of myelinated axons in the (a) gracile fasciculus and (b) dorsal corticospinal tract (CST). Representative confocal micrographs of the regions of interest used in the quantitative analysis of white matter damage immunostained for neurofilament H/β-tubulin for axons (in red) and myelin basic protein for myelin/myelin debris in green. The normal control tracts show a dense packing of small myelinated axons in the gracile fasciculus (GF) and even smaller ones in the dorsal CST. These intact fibers display the typical green myelin rings surrounding a red axon in the middle. Contusion and (somewhat less so) dislocation injuries destroy both tracts from the epicenter distally, leaving in the wake of Wallerian degeneration myelin debris (green dots) and a few large axons (displaced or sprouted). Distal is rostral in the ascending GF and caudal in the descending CST. The damage proximal to the epicenter is indicative of some dieback in both tracts. The damage after distraction is less focal in the GF showing a gradual thinning of this ascending tract from caudal to rostral and appearance of a few larger profiles in the rostral segments that are likely displaced axons from the cuneate fascile (entering the spinal cord rostral to injury). The CST shows a loss of the typical small myelinated axons at all levels with some partial preservation rostrally. The apparent preservation of the CST in the caudal segments is from displaced/sprouted larger sensory axons. Scale bar 20 μm. MBP, myelin basic protein.

Mentions: The cross-sectional area of spared tissue (blue-labeled pixels that were darker than the background, representing myelin), the density of myelinated axons (NF/Tub/MBP staining), and the number of surviving cells (NeuN/Fluoro Nissl staining) were measured in the regions of interest (ROIs) in these sections (Fig. 2). In addition, the cross-sectional area of spinal cords, including the anterior median fissure and central canal, was outlined and measured from the LFB-stained sections. The central lesion cavity in the LFB-stained sections was also outlined to calculate the volume and rostrocaudal extent of the lesion. Sections at certain distances from the epicenter were selected from each set of spinal cords for analysis (see Fig. 5, 6, 9 for the specific locations).


Differential Histopathological and Behavioral Outcomes Eight Weeks after Rat Spinal Cord Injury by Contusion, Dislocation, and Distraction Mechanisms
Micrographs of myelinated axons in the (a) gracile fasciculus and (b) dorsal corticospinal tract (CST). Representative confocal micrographs of the regions of interest used in the quantitative analysis of white matter damage immunostained for neurofilament H/β-tubulin for axons (in red) and myelin basic protein for myelin/myelin debris in green. The normal control tracts show a dense packing of small myelinated axons in the gracile fasciculus (GF) and even smaller ones in the dorsal CST. These intact fibers display the typical green myelin rings surrounding a red axon in the middle. Contusion and (somewhat less so) dislocation injuries destroy both tracts from the epicenter distally, leaving in the wake of Wallerian degeneration myelin debris (green dots) and a few large axons (displaced or sprouted). Distal is rostral in the ascending GF and caudal in the descending CST. The damage proximal to the epicenter is indicative of some dieback in both tracts. The damage after distraction is less focal in the GF showing a gradual thinning of this ascending tract from caudal to rostral and appearance of a few larger profiles in the rostral segments that are likely displaced axons from the cuneate fascile (entering the spinal cord rostral to injury). The CST shows a loss of the typical small myelinated axons at all levels with some partial preservation rostrally. The apparent preservation of the CST in the caudal segments is from displaced/sprouted larger sensory axons. Scale bar 20 μm. MBP, myelin basic protein.
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Related In: Results  -  Collection

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f6: Micrographs of myelinated axons in the (a) gracile fasciculus and (b) dorsal corticospinal tract (CST). Representative confocal micrographs of the regions of interest used in the quantitative analysis of white matter damage immunostained for neurofilament H/β-tubulin for axons (in red) and myelin basic protein for myelin/myelin debris in green. The normal control tracts show a dense packing of small myelinated axons in the gracile fasciculus (GF) and even smaller ones in the dorsal CST. These intact fibers display the typical green myelin rings surrounding a red axon in the middle. Contusion and (somewhat less so) dislocation injuries destroy both tracts from the epicenter distally, leaving in the wake of Wallerian degeneration myelin debris (green dots) and a few large axons (displaced or sprouted). Distal is rostral in the ascending GF and caudal in the descending CST. The damage proximal to the epicenter is indicative of some dieback in both tracts. The damage after distraction is less focal in the GF showing a gradual thinning of this ascending tract from caudal to rostral and appearance of a few larger profiles in the rostral segments that are likely displaced axons from the cuneate fascile (entering the spinal cord rostral to injury). The CST shows a loss of the typical small myelinated axons at all levels with some partial preservation rostrally. The apparent preservation of the CST in the caudal segments is from displaced/sprouted larger sensory axons. Scale bar 20 μm. MBP, myelin basic protein.
Mentions: The cross-sectional area of spared tissue (blue-labeled pixels that were darker than the background, representing myelin), the density of myelinated axons (NF/Tub/MBP staining), and the number of surviving cells (NeuN/Fluoro Nissl staining) were measured in the regions of interest (ROIs) in these sections (Fig. 2). In addition, the cross-sectional area of spinal cords, including the anterior median fissure and central canal, was outlined and measured from the LFB-stained sections. The central lesion cavity in the LFB-stained sections was also outlined to calculate the volume and rostrocaudal extent of the lesion. Sections at certain distances from the epicenter were selected from each set of spinal cords for analysis (see Fig. 5, 6, 9 for the specific locations).

View Article: PubMed Central - PubMed

ABSTRACT

The objective of this study was to compare the long-term histological and behavioral outcomes after spinal cord injury (SCI) induced by one of three distinct biomechanical mechanisms: dislocation, contusion, and distraction. Thirty male Sprague-Dawley rats were randomized to incur a traumatic cervical SCI by one of these three clinically relevant mechanisms. The injured cervical spines were surgically stabilized, and motor function was assessed for the following 8 weeks. The spinal cords were then harvested for histologic analysis. Quantification of white matter sparing using Luxol fast blue staining revealed that dislocation injury caused the greatest overall loss of white matter, both laterally and along the rostrocaudal axis of the injured cord. Distraction caused enlarged extracellular spaces and structural alteration in the white matter but spared the most myelinated axons overall. Contusion caused the most severe loss of myelinated axons in the dorsal white matter. Immunohistochemistry for the neuronal marker NeuN combined with Fluoro Nissl revealed that the dislocation mechanism resulted in the greatest neuronal cell losses in both the ventral and dorsal horns. After the distraction injury mechanism, animals displayed no recovery of grip strength over time, in contrast to the animals subjected to contusion or dislocation injuries. After the dislocation injury mechanism, animals displayed no improvement in the grooming test, in contrast to the animals subjected to contusion or distraction injuries. These data indicate that different SCI mechanisms result in distinct patterns of histopathology and behavioral recovery. Understanding this heterogeneity may be important for the future development of therapeutic interventions that target specific neuropathology after SCI.

No MeSH data available.


Related in: MedlinePlus