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Relating Histopathology and Mechanical Strain in Experimental Contusion Spinal Cord Injury in a Rat Model

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ABSTRACT

During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n = 12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R2 = 0.19), but varied in strength between individual animals (R2 = 0.06–0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.

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Related in: MedlinePlus

Linear regression of NeuN-positive density against transverse-plane strain types for pooled data. Scatter plots with trendlines and calculated R2 values are shown for each transverse-plane strain: lateral normal strain (eXX-blue); transverse-plane shear strain (eXY-green); dorsoventral normal strain (eYY-red); minimum principal strain (emin-black); and maximum principal strain (emax-purple). Asterisk (*) indicates a significant relationship at α = 0.05. NeuN, neuronal nuclei.
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f5: Linear regression of NeuN-positive density against transverse-plane strain types for pooled data. Scatter plots with trendlines and calculated R2 values are shown for each transverse-plane strain: lateral normal strain (eXX-blue); transverse-plane shear strain (eXY-green); dorsoventral normal strain (eYY-red); minimum principal strain (emin-black); and maximum principal strain (emax-purple). Asterisk (*) indicates a significant relationship at α = 0.05. NeuN, neuronal nuclei.

Mentions: Linear regression analysis of the pooled data indicated dependence of the NeuN-positive density values in the ventral horns on each of the transverse-plane strain types (Fig. 5) at a 95% confidence level. The transverse-plane shear strain (absolute value) exhibited a data range of 0–20%, whereas all other transverse-plane strain types exhibited a range of 0–50% strain (tension in lateral normal strain and compression in dorsoventral normal strain). Analyses of the lateral normal strain (eXX), transverse-plane shear strain (eXY), dorsoventral normal strain (eYY), minimum principal strain (emin), and maximum principal strain (emax) showed R2 values of 0.15, 0.12, 0.16, 0.19, and 0.11 (all p < 0.001), respectively. Thus, of the strains analyzed, the greatest amount of variation of the NeuN-positive density was explained by the minimal principal strain.


Relating Histopathology and Mechanical Strain in Experimental Contusion Spinal Cord Injury in a Rat Model
Linear regression of NeuN-positive density against transverse-plane strain types for pooled data. Scatter plots with trendlines and calculated R2 values are shown for each transverse-plane strain: lateral normal strain (eXX-blue); transverse-plane shear strain (eXY-green); dorsoventral normal strain (eYY-red); minimum principal strain (emin-black); and maximum principal strain (emax-purple). Asterisk (*) indicates a significant relationship at α = 0.05. NeuN, neuronal nuclei.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5035832&req=5

f5: Linear regression of NeuN-positive density against transverse-plane strain types for pooled data. Scatter plots with trendlines and calculated R2 values are shown for each transverse-plane strain: lateral normal strain (eXX-blue); transverse-plane shear strain (eXY-green); dorsoventral normal strain (eYY-red); minimum principal strain (emin-black); and maximum principal strain (emax-purple). Asterisk (*) indicates a significant relationship at α = 0.05. NeuN, neuronal nuclei.
Mentions: Linear regression analysis of the pooled data indicated dependence of the NeuN-positive density values in the ventral horns on each of the transverse-plane strain types (Fig. 5) at a 95% confidence level. The transverse-plane shear strain (absolute value) exhibited a data range of 0–20%, whereas all other transverse-plane strain types exhibited a range of 0–50% strain (tension in lateral normal strain and compression in dorsoventral normal strain). Analyses of the lateral normal strain (eXX), transverse-plane shear strain (eXY), dorsoventral normal strain (eYY), minimum principal strain (emin), and maximum principal strain (emax) showed R2 values of 0.15, 0.12, 0.16, 0.19, and 0.11 (all p < 0.001), respectively. Thus, of the strains analyzed, the greatest amount of variation of the NeuN-positive density was explained by the minimal principal strain.

View Article: PubMed Central - PubMed

ABSTRACT

During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n&thinsp;=&thinsp;12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R2&thinsp;=&thinsp;0.19), but varied in strength between individual animals (R2&thinsp;=&thinsp;0.06&ndash;0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.

No MeSH data available.


Related in: MedlinePlus