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Comparison between conventional and "clinical" assessment of experimental lung fibrosis.

Ask K, Labiris R, Farkas L, Moeller A, Froese A, Farncombe T, McClelland GB, Inman M, Gauldie J, Kolb MR - J Transl Med (2008)

Bottom Line: Standard histological and collagen assessment confirmed the persistent fibrotic phenotype as described before.The histomorphological scores correlated both to radiological (r2 = 0.29, p < 0.01) and functional changes (r2 = 0.51, p < 0.0001).This approach directly translates to the management of patients with IPF and allows to monitor therapeutic effects in drug intervention studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Molecular Medicine, Center for Gene Therapeutics, McMaster University, Hamilton, Ontario, Canada. askkj@mcmaster.ca

ABSTRACT

Background: Idiopathic pulmonary fibrosis (IPF) is a treatment resistant disease with poor prognosis. Numerous compounds have been demonstrated to efficiently prevent pulmonary fibrosis (PF) in animal models but only a few were successful when given to animals with established fibrosis. Major concerns of current PF models are spontaneous resolution and high variability of fibrosis, and the lack of assessment methods that can allow to monitor the effect of drugs in individual animals over time. We used a model of experimental PF in rats and compare parameters obtained in living animals with conventional assessment tools that require removal of the lungs.

Methods: PF was induced in rats by adenoviral gene transfer of transforming growth factor-beta. Morphological and functional changes were assessed for up to 56 days by micro-CT, lung compliance (measured via a mechanical ventilator) and VO2max and compared to histomorphometry and hydroxyproline content.

Results: Standard histological and collagen assessment confirmed the persistent fibrotic phenotype as described before. The histomorphological scores correlated both to radiological (r2 = 0.29, p < 0.01) and functional changes (r2 = 0.51, p < 0.0001). VO2max did not correlate with fibrosis.

Conclusion: The progression of pulmonary fibrosis can be reliably assessed and followed in living animals over time using invasive, non-terminal compliance measurements and micro-CT. This approach directly translates to the management of patients with IPF and allows to monitor therapeutic effects in drug intervention studies.

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Correlation Histology – Computed tomography. (A). Low magnification histology 225 days after intratracheal AdTGF-β1 administration (10×) corresponding to CT image of axial slice (B) and to area indicated with red arrow in 3D reconstructed lungs from same animal (C). See insert in Fig 1F for higher magnification of same lung.
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Figure 3: Correlation Histology – Computed tomography. (A). Low magnification histology 225 days after intratracheal AdTGF-β1 administration (10×) corresponding to CT image of axial slice (B) and to area indicated with red arrow in 3D reconstructed lungs from same animal (C). See insert in Fig 1F for higher magnification of same lung.

Mentions: Micro-CT images were acquired over 512 angles, reconstructed at 155 μm3 voxel (volume-pixel) size and converted to Hounsfield Units (HU) using a Matlab program where -1000 is defined as the density of air and 0 the density of water. Axial slices of micro-CT scans of fibrotic lungs at day 21, 35 and 56 showed areas of denser tissues compared to naïve lungs (Figure 2A, upper panel), correlating to fibrotic areas in histology slides. Three-dimensional regions were selected and color-coded as follows: trachea (yellow), normal lung density (blue, -600 to -100 HU), and high lung density (green, -100 to 200 HU). This allowed visualization of lung areas with different densities (Figure 2A, medium panel) and quantification after generating corresponding histograms (Figure 2A, lower panel). A shift to the right (= denser tissue) was observed from (see insert) day 21 to 56. Histograms of fibrotic rats (n = 6) at each time point were selected as described above and the number of voxels in each bin was subtracted from a group of unexposed animals. Figure 2B shows the differential increase and/or decrease of specific voxel ranges compared to naïve lungs: increase of high dense voxels corresponding to fibrotic regions (ranging from-100 to 250 HU), and increase of lower density voxels (ranging from-600 to -400 HU), possibly reflecting airspace enlargement (e.g. compensatory mechanism or traction effect) This increase is accompanied by a decrease of normal density voxels (-200 to -400 HU). A lower magnification histology and CT image is provided in Figure 3 which indicates that this model is persisting up to 225 days after intratracheal AdTGF-β1 (see Fig 1F for higher magnification)


Comparison between conventional and "clinical" assessment of experimental lung fibrosis.

Ask K, Labiris R, Farkas L, Moeller A, Froese A, Farncombe T, McClelland GB, Inman M, Gauldie J, Kolb MR - J Transl Med (2008)

Correlation Histology – Computed tomography. (A). Low magnification histology 225 days after intratracheal AdTGF-β1 administration (10×) corresponding to CT image of axial slice (B) and to area indicated with red arrow in 3D reconstructed lungs from same animal (C). See insert in Fig 1F for higher magnification of same lung.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2365932&req=5

Figure 3: Correlation Histology – Computed tomography. (A). Low magnification histology 225 days after intratracheal AdTGF-β1 administration (10×) corresponding to CT image of axial slice (B) and to area indicated with red arrow in 3D reconstructed lungs from same animal (C). See insert in Fig 1F for higher magnification of same lung.
Mentions: Micro-CT images were acquired over 512 angles, reconstructed at 155 μm3 voxel (volume-pixel) size and converted to Hounsfield Units (HU) using a Matlab program where -1000 is defined as the density of air and 0 the density of water. Axial slices of micro-CT scans of fibrotic lungs at day 21, 35 and 56 showed areas of denser tissues compared to naïve lungs (Figure 2A, upper panel), correlating to fibrotic areas in histology slides. Three-dimensional regions were selected and color-coded as follows: trachea (yellow), normal lung density (blue, -600 to -100 HU), and high lung density (green, -100 to 200 HU). This allowed visualization of lung areas with different densities (Figure 2A, medium panel) and quantification after generating corresponding histograms (Figure 2A, lower panel). A shift to the right (= denser tissue) was observed from (see insert) day 21 to 56. Histograms of fibrotic rats (n = 6) at each time point were selected as described above and the number of voxels in each bin was subtracted from a group of unexposed animals. Figure 2B shows the differential increase and/or decrease of specific voxel ranges compared to naïve lungs: increase of high dense voxels corresponding to fibrotic regions (ranging from-100 to 250 HU), and increase of lower density voxels (ranging from-600 to -400 HU), possibly reflecting airspace enlargement (e.g. compensatory mechanism or traction effect) This increase is accompanied by a decrease of normal density voxels (-200 to -400 HU). A lower magnification histology and CT image is provided in Figure 3 which indicates that this model is persisting up to 225 days after intratracheal AdTGF-β1 (see Fig 1F for higher magnification)

Bottom Line: Standard histological and collagen assessment confirmed the persistent fibrotic phenotype as described before.The histomorphological scores correlated both to radiological (r2 = 0.29, p < 0.01) and functional changes (r2 = 0.51, p < 0.0001).This approach directly translates to the management of patients with IPF and allows to monitor therapeutic effects in drug intervention studies.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Pathology and Molecular Medicine, Center for Gene Therapeutics, McMaster University, Hamilton, Ontario, Canada. askkj@mcmaster.ca

ABSTRACT

Background: Idiopathic pulmonary fibrosis (IPF) is a treatment resistant disease with poor prognosis. Numerous compounds have been demonstrated to efficiently prevent pulmonary fibrosis (PF) in animal models but only a few were successful when given to animals with established fibrosis. Major concerns of current PF models are spontaneous resolution and high variability of fibrosis, and the lack of assessment methods that can allow to monitor the effect of drugs in individual animals over time. We used a model of experimental PF in rats and compare parameters obtained in living animals with conventional assessment tools that require removal of the lungs.

Methods: PF was induced in rats by adenoviral gene transfer of transforming growth factor-beta. Morphological and functional changes were assessed for up to 56 days by micro-CT, lung compliance (measured via a mechanical ventilator) and VO2max and compared to histomorphometry and hydroxyproline content.

Results: Standard histological and collagen assessment confirmed the persistent fibrotic phenotype as described before. The histomorphological scores correlated both to radiological (r2 = 0.29, p < 0.01) and functional changes (r2 = 0.51, p < 0.0001). VO2max did not correlate with fibrosis.

Conclusion: The progression of pulmonary fibrosis can be reliably assessed and followed in living animals over time using invasive, non-terminal compliance measurements and micro-CT. This approach directly translates to the management of patients with IPF and allows to monitor therapeutic effects in drug intervention studies.

Show MeSH
Related in: MedlinePlus