Figure 2

Increased number of lymphatic vessels in the alveolar compartment in patients with advanced COPD. (A-D) Immunohistochemical staining for podoplanin (brown, arrowheads) and α-smooth muscle actin (α-SMA, red) in sections of a patient with GOLD stage IV COPD. Lymphatic vessels are present in (A) bronchiolar (Br) subepithelial tissue, (B) adventitia of bronchiole-associated arteries (Ar), (C) alveolar parenchyma and (D) patchy fibrotic lesions. Cell nuclei were counterstained with Mayer’s haematoxylin (blue stain). (E-G) Accumulated lymphatic vessel endothelial length (i.e. the total sum of all lymphatic perimeters) in (E) bronchiolar subepithelial tissue, (F) adventitia of bronchiole-associated arteries and (G) non-fibrotic alveolar parenchyma in never smokers, smokers without COPD and patients with COPD. (H-J) Number of lymphatic vessels in (H) bronchiolar subepithelial tissue, (I) adventitia of bronchiole-associated arteries and (J) non-fibrotic alveolar parenchyma in never smokers, smokers without COPD and patients with COPD. Statistical analysis was performed using Kruskal-Wallis nonparametric test and Dunn’s multiple comparison post-test. Horizontal lines indicate median value. * p < 0.05; ** p < 0.01. Scale bars: (A) 200 μm; (B) 100 μm; (C) 50 μm; (D) 150 μm.