Fig. 3

Collagen deposition in small airways from non-smokers, smokers without COPD and smokers with COPD. Photomicrographs of blue staining showing collagen expression around the small airway walls from non-smokers (a), smokers without COPD (b), and smokers with COPD (c) (all images are × 400 magnification); Measurement of collagen deposition in small airways. Smokers with COPD showed increased collagen deposition compared to both the non-smokers, smokers without COPD (d); Collagen deposition was positively correlated with serum YKL-40 levels (r = 0.57; p < 0.001) (e). Horizontal bars represent median values