Typical microscopic views of pulmonary hypertension (PH) in a 14-week-old pig at 6 weeks after injection of monocrotaline; Panel A, control group; Panels B-F, MCT group.

<p>Panel A: Typical microscopic view of a small muscular pulmonary artery (arrows) in a 14-week-old minipig from the control group. The lumen of normal pulmonary artery is surrounded by a uniform thin wall with no fibrosis or inflammatory cell infiltration (Hematoxylin and Eosin staining; original magnification:×200; scale bar = 100 µm); Panel B: The vessel lumen is narrowed, occluded, twisted or deformed with formation of plexiform lesions (arrows) as a result of proliferating and hypertropic endothelial and smooth muscle cells, intimal fibrosis and accompanying hyalinization (Hematoxylin and Eosin staining; original magnification:×400; scale bar = 50 µm). Panel C: Pulmonary vascular remodeling in the lung tissue. There was intimal thickening accompanied with plexiform lesions (arrows) (Hematoxylin and Eosin staining; original magnification:×100; scale bar = 200 µm). Panel D: Uneven thickening of the pulmonary arterial wall (arrows). (Hematoxylin and Eosin staining; original magnification:×100; scale bar = 200 µm); Panel E: The presence of large amount of mucus (arrows) in bronchioles led to luminal obstruction and lymphocyte infiltration. In the periphery of lungs, congestion of capillaries, thickening of interstitium and focal lymphocyte infiltration were observed (Hematoxylin and Eosin staining; original magnification:×100; scale bar = 200 µm). Panel F: Parabronchus arteries (arrows) were largely occluded owing to extensive neointimal proliferation and medial hypertrophy accompanied with hyalinization (Hematoxylin and Eosin staining; original magnification:×100; scale bar = 200 µm).