Shunt-type plexiform lesions identified in the Sugen5416/hypoxia rat model of pulmonary arterial hypertension using synchrotron-based phase-contrast micro-CT

We recently described four distinct types of plexiform lesions in human idiopathic and familial pulmonary arterial hypertension (PAH) [1], visualising the three-dimensional lesion structure using synchrotron-based phase-contrast micro-computed tomography (SPµCT). Two types, 1 and 2, are shunt-type lesions that connect pulmonary arteries to the bronchial circulation: type 1 to the vasa vasorum, and type 2 to peribronchial vessels. Type 3 lesions are found peripherally in the lung as spherical structures abruptly terminating the distal pulmonary artery/arteriole, and type 4 lesions are characterised by recanalisation of an occluded artery/arteriole. Our observation of type 1 and type 2 lesions in PAH supports previous work that demonstrated intrapulmonary bronchopulmonary anastomoses (IBAs) connected to plexiform lesions in human PAH, suggesting that shunting of blood can occur within lesions in the setting of supra-systemic pulmonary arterial pressure [2]. Further haemodynamic studies of distinct subtypes of plexiform lesions have been hampered by the lack of available animal models with plexiform lesions representative of the full range of lesion types found in human disease. Plexiform lesions have previously been described in the Sugen5416/hypoxia rat model of pulmonary hypertension when time until sacrifice following hypoxia is extended to 13–14 weeks. Initially plexiform lesions were identified within the pulmonary artery, as well as in the form of aneurysm-like lesions projecting outside the vessel lumen [3], and recently the latter type was shown to form in supernumerary arteries [4]. However, neither study observed plexiform lesions communicating with the bronchial circulation, possibly because of methodological limitations of the histological analysis. Human like plexiform lesions identified in the prolonged Sugen5416/hypoxia rat model, visualised by synchrotron tomography imaging https://bit.ly/3KQvDHg