Allergy Asthma Immunol Res.  2014 Jan;6(1):75-82. 10.4168/aair.2014.6.1.75.

A Quantitative Study of Airway Changes on Micro-CT in a Mouse Asthma Model: Comparison With Histopathological Findings

• Paik SH
• Kim WK
• Park JS
• Park CS
• Jin GY

• KMID: 2166943
• DOI: http://doi.org/10.4168/aair.2014.6.1.75

Abstract

PURPOSE
To evaluate airway changes in ovalbumin-induced asthmatic mice in terms of postmortem micro-CT images and pathological findings.
METHODS
Asthma was induced in mice by intraperitoneal injection and nasal instillation of ovalbumin aluminium hydroxide into mice (experimental group, n=6), and another group of mice received intraperitoneal injection and nasal instillation of distilled phosphate-buffered saline (control group, n=6). Bronchial lumen area was measured in the main bronchial lumen of the distal third bronchial branch level (6 parts per each mouse) on axial scans of Micro-CT, using a Lucion's smart pen (semi-automated) and a curve pen (manual). Bronchial wall thickness was obtained in 4 sections (2 levels on either side) after the third bronchial branch by measuring the diameter which was perpendicular to the longitudinal axis of the main bronchus on curved Multi-planar reconstruction (MPR) images. Histologic slides were obtained from the lesion that was matched with its CT images, and bronchial wall thicknesses were determined.
RESULTS
The mean bronchial lumen area was 0.196+/-0.072 mm2 in the experimental group and 0.243+/-0.116 mm2 in the control group; the difference was significant. Bronchial wall thickness on micro-CT images (mean, 0.119+/-0.01 vs. 0.108+/-0.013 mm) and in pathological specimens (mean, 0.066+/-0.011 vs. 0.041+/-0.009 mm) were thicker in the experimental group than in the control group; bronchial wall thickness on micro-CT images correlated well with pathological thickness (for the experimental group, r=0.712; for the control group, r=0.46). The thick bronchial wall in the experimental group demonstrated submucosal hypertrophy along with goblet cell hyperplasia and smooth muscle hyperplasia.
CONCLUSIONS
The results of this study suggest that asthma may induce thickening of bronchial wall and narrowing of the lumen area on micro-CT images and that these results may significantly correlate with pathological findings.

Keyword

Bronchial asthma; mice Laboratory; x-ray Micro-CT scans; airway remodeling; quantitative evaluation; histopathology; case comparison studies

MeSH Terms

Airway Remodeling
Animals
Asthma*
Axis, Cervical Vertebra
Bronchi
Case-Control Studies
Evaluation Studies as Topic
Goblet Cells
Hyperplasia
Hypertrophy
Injections, Intraperitoneal
Mice*
Muscle, Smooth
Ovalbumin
X-Ray Microtomography
Ovalbumin

Figure

• 

  Fig. 1 Time table of this study. Day 0 and 14: intraperitoneal injection of ovalbumin-aluminium hydroxide into BALB/c mice and distilled phosphate-buffered saline injection into controls. Day 21, 22, and 23: airway stimulation by intranasally instilled OVA. Day 24: measuring bronchial wall thickness after methacholine-challenged bronchial irritation. Day 25: performed micro-CT and tissue extraction.

• 

  Fig. 2 Bronchial lumen area as measured on micro-computed tomography images in the experimental and control groups. Vertical axis scale: mm2. P<0.01.

• 

  Fig. 3 Axial micro-CT images reveal normal airway wall thickness and lumen area in the control group (A, arrow) and diffuse bronchial wall thickening and narrow lumen area in the experimental group (B, arrow head).

• 

  Fig. 4 Bronchial wall thickness as measured on micro-computed tomography images in the experimental and control groups. Vertical axis scale: mm. var 1: murine asthma models; var 2: controls. P<0.01.

• 

  Fig. 5 Curved multiplanar reformation images show normal main bronchus wall thickness on the right side in the control group (A, arrow) and diffuse bronchial wall thickness in the experimental group (B, arrow head). A magnified picture shows measurement of the diameter perpendicular to the bronchial wall (A-1, small arrows).

• 

  Fig. 6 Bronchial wall thickness as measured by pathological findings in the experimental and control groups. Vertical axis scale: mm. P<0.01.

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  Fig. 7 Normal bronchus in the control group (A) (hematoxylin and eosin [H&E], ×200). Mucosal epithelium proliferation and submucosal smooth muscle hypertrophy in the experimental group (B) (H&E, ×200).

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  Fig. 8 Airway changes in the experimental group. Goblet cell hyperplasia of the bronchial epithelium (A) (periodic acid-Schiff stain, ×200). Immunohistochemical staining for smooth muscle actin shows characteristic submucosal smooth muscle hypertrophy (B) (×200).

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  Fig. 9 Correlation of micro-CT and pathologic findings in terms of bronchial wall thickness in the experimental groups (Pearson correlation; r=0.7119, P=0.0001).

• 

  Fig. 10 Correlation of micro-CT and pathologic findings in terms of bronchial wall thickness in the control groups (Pearson correlation; r=0.4640, P=0.0224).

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