Fig. 1

An increased volume of distal pulmonary arteries in COPD patients. a The image illustrates the method for measurement of muscular area of pulmonary arteries in this study (× 400). The total area of artery (TA, area inside the red line), luminal area of artery (LA, area inside the blue line), the vascular wall area (WA, the area between red line and blue line) were measured by Image-Pro Plus software 6.0. b Weigert-van Gieson staining showed more abundant collagen and connective tissues in arteries of COPD lung relative to controls; (c) comparison of external diameter (ED) and vascular diameter (WT) determined by IHC staining of α-SMA between normal and COPD lungs; (d) comparison of the pulmonary artery smooth muscle area accounted for the percentage of total vascular area (WA%) and the pulmonary artery smooth muscle thickness accounted for the percentage of vascular diameter (WT%) determined by IHC staining of α-SMA between non-COPD and COPD lungs. Compared to non-COPD lung, *: p < 0.05 01 (N = 19 for non-COPD; N = 15 for COPD)