Transpulmonary Expression of Exosomal microRNAs in Idiopathic and Congenital Heart Disease–Related Pulmonary Arterial Hypertension

BACKGROUND: Pulmonary artery hypertension (PAH) is a fatal disease characterized by a complex pathogenesis. Exosomes containing microRNAs (miRs) have emerged as a novel biomarker. Transpulmonary exosomal miRs offer valuable insights into pulmonary circulation microenvironments. Hereby, we aimed to explore the potentials of transpulmonary exosomal miRs as differentiating factors between idiopathic PAH and congenital heart disease (CHD)–related PAH. METHODS AND RESULTS: During right heart catheterization, we collected exosomes at pulmonary arteries in 25 patients diagnosed with idiopathic PAH and 20 patients with CHD-related PAH. Next-generation sequencing identified several candidate exosomal miRs. Using quantitative polymerase chain reaction, we validated the expressions of these miRs and revealed significantly elevated expressions of miR-21, miR-139-5p, miR-155-5p, let-7f-5p, miR-328-3p, miR-330-3p, and miR-103a-3p in patients with CHD-related PAH, in contrast to patients with idiopathic PAH. Among these miRs, miR-21 exhibited the highest expression in patients with CHD-related PAH. These findings were further corroborated in an external cohort comprising 10 patients with idiopathic PAH and 8 patients with CHD-related PAH. Using an in vitro flow model simulating the shear stress experienced by pulmonary endothelial cells, we observed a significant upregulation of miR-21. Suppressing miR-21 rescued the shear stress– induced downregulation of the RAS/phosphatidylinositol 3-kinase/protein kinase B pathway, leading to a mitigation of apoptosis. CONCLUSIONS: Our study identified a pronounced expression of transpulmonary exosomal miR-21, particularly in patients with CHD-related PAH, through next-generation sequencing analysis. Further investigation is warranted to elucidate the regulatory mechanisms involving miR-21 in the pathophysiology of PAH.