Murine Model of Pulmonary Artery Overflow Vasculopathy Revealed Macrophage Accumulation in the Lung

Chronic thromboembolic pulmonary hypertension (CTEPH) develops as a consequence of unresolved pulmonary embolism or clots in the pulmonary arteries. The obstruction not only reduces the area of the pulmonary vascular bed, but also elicits high pressure and high shear stress in the spared unobstructed arteries. Subsequent overflow of the small pulmonary arteries induces vascular remodeling, termed as overflow vasculopathy (OV). While the development of OV significantly contributes to the occurrence of pulmonary hypertension, its precise molecular mechanisms are yet to be determined.We established a novel murine pulmonary artery OV (PAOV) model, in which we resected left lung and induced redistribution of the cardiac output to the remaining pulmonary artery of the right lung. At 21 days after operation, mice showed an increase in the vascular media area, indicating the development of pulmonary arterial remodeling. In addition, right ventricular hypertrophy was detected in the PAOV model. Intriguingly, marked accumulation of F4/80-positive monocytes/macrophages was visualized in high-flow arteries, implying the role of an inflammatory process in the pathogenesis of overflow-induced vascular remodeling.