Decreased MicroRNA‐153 Promotes Endothelial‐to‐Mesenchymal Transition in Idiopathic Pulmonary Arterial Hypertension

Abstract

IntroductionIdiopathic pulmonary arterial hypertension (IPAH) is a fatal and progressive disease. Pulmonary vascular remodeling and vasoconstriction are the major factors for the increased pulmonary vascular resistance (PVR) and pulmonary arterial pressure in IPAH patients. Endothelial‐to‐mesenchymal transition (EndMT) has been recently implicated in the development and progression of pulmonary vascular remodeling in IPAH. EndMT is a biological process which converts fully differentiated and slowly growing endothelial cells (EC) into the highly‐proliferative myofibroblasts (myoFB). We previously reported that elevated endothelial hypoxia‐inducible factor‐2α (HIF‐2α or EPAS1) due to decreased prolyl hydroxylase domain protein 2 (PHD2 or EGLN1) contributes to EndMT in pulmonary hypertension (PH). However, the underlying molecular mechanisms of EndMT are still unknown. In this study, we aimed to investigate the role of microRNA (miR) in the regulation of EndMT. MiR is a small non‐coding RNA which is able to regulate gene expression post‐transcriptionally by inhibiting mRNA translation and stability. We hypothesize that decreased miR‐153 resultes in upregulating of SNAI1 and SNAI2 and the enhanced EndMT in lung vascular EC (LVEC) and contributes to pulmonary vascular remodeling in PH.MethodsLVEC from healthy subjects and patients with IPAH were used for this study. In silico analysis was perfomed by using standard online software (Targetscan.org). miR‐153 level was measured by real‐time RT‐PCR. Normal LVEC were transfected with miR‐153 inhibitor while IPAH‐LVEC were overexpressed with miR‐153 mimic. mRNA and protein expression SNAI1/2, PHD2, and HIF‐2α were measured by RT‐PCR, Western blot and ICC.ResultsIn silico analysis revealed that miR‐153 directly targets human SNAI1/2. Downregulated miR‐153 is correlated with increased SNAI1/2 expression and EndMT in LVEC from IPAH patients compared to normal LVEC. Transfroming growth factor‐β1 (TGF‐β1), a well‐known stimulus for EndMT, decreases miR‐153 and induces SNAI1/2 in normal human LVEC. PHD2 was downregulated while HIF‐2α was activated in TGF‐β1‐treated normal LVEC. Inhibition of miR‐153 in normal LVEC significantly upregulates SNAI1/2 expression while overexpression of miR‐153 in IPAH‐LVEC decreases SNAI1/2 level. Moreover, miR‐153 level was lower in lung tissues isolated from mice with endothelial specific deletion of egln1, which spontaneously develop severe PH due to increased HIF‐2α and enhanced EndMT.ConclusionThe decreased miR‐153 promotes phenotypical transition of LVEC to highly proliferative myoFB via enhancing HIF‐2α‐associated EndMT, and contributes to neointimal formation, intimal thickening and distal PA obliteration. The concentric PA wall thickening and intraluminal obliteration in arterioles directly increase PVR and right ventricular afterload in IPAH patients. We conclude that PHD2/HIF‐2α/miR‐153/SNAI axis drives the initiation and development of pulmonary vascular remodeling and obliterative lesions contributing to the development of PH.Support or Funding InformationThis work is supported in part by the grants from the National Heart, Lung and Blood Institute of the National Institutes of Health (HL135807).