ICAM1 and pulmonary arterial hypertension: The authors investigated whether circulating EVs from a rat model of severe PAH stimulate localized ICAM-1 on pulmonary endothelium, demonstrating that circulating EVs from late-stage, but not early-stage PAH rats did upregulate ICAM-1 expression on the endothelium and also that ICAM-1 expression was localized to the pulmonary arterial but not to the microvascular endothelium.