Fig. 2

Dispersion of the inhaled coal dust into murine lungs and induction of lung fibrosis progression. The coal dust suspension was instilled via the nose, b.i.w., to accumulate 20 mg coal dust weight. Mice were examined at 3th, 6th and 9th months post-exposure. A Representative histological images (H&E) show the progress of pneumoconiosis tissue injury at 3, 6, and 9 months post-exposure. Green arrowheads pointed to the AT2. B Schematic diagram depicting lung injury and repair during coal pneumoconiosis at 9 months post-exposure (AT1: alveolar epithelial cell type 1, AT2: alveolar epithelial cell type 2, AAT2: Activated alveolar epithelial cell type 2, CDPs: coal dust particles, FN: fibronectin, RFs: repair related factor, BEC: blood endothelial cells, ExCM: extracellular matrix). C1–C4 A representative sample of lung tissue showing a central-to-peripheral decline of lung interstitial cell density at 6 months, graded as severe (S), moderate (M), or light (L). D The lung section is divided into three regions, based on the density gradient of interstitial cells, representing severe, moderate, and mild damage. The proportion of the area of different lung interstitial cell density grades at the 6th month. E Representative histological images (Masson trichrome) showing pulmonary fibrosis progression in mice lungs at 3, 6, and 9 months after coal dust exposure (black arrows pointed to peripheral fibroblasts), 40× and 100× magnifications. F Collagenous volume fraction (CVF) at 3, 6, and 9 months, the area of collagen staining in lung tissue. G Alveolar volume fraction (AVF) at 3, 6, and 9 months, the area of the alveolar air cavity gradually shrinks. Both AVF and CVF were measured by free software Image J (NIH, http://rsbweb.nih.gov/ij/). The 40×, 200×, 400 × visual field were used and Semi-quantification under 200x (*p < 0.05, **p < 0.01, ***p < 0.001)