Pulmonary arterial hypertension (PAH) is a severe disorder of lung vasculature that causes right heart failure. Homoeostatic effects of flow-activated transcription factor Krüppel-like factor 2 (KLF2) are compromised in PAH. Here, we show that KLF2-induced exosomal microRNAs, miR-181a-5p and miR-324-5p act together to attenuate pulmonary vascular remodelling and that their actions are mediated by Notch4 and ETS1 and other key regulators of vascular homoeostasis. Expressions of KLF2, miR-181a-5p and miR-324-5p are reduced, while levels of their target genes are elevated in pre-clinical PAH, idiopathic PAH and heritable PAH with missense p.H288Y KLF2 mutation. Therapeutic supplementation of miR-181a-5p and miR-324-5p reduces proliferative and angiogenic responses in patient-derived cells and attenuates disease progression in PAH mice. This study shows that reduced KLF2 signalling is a common feature of human PAH and highlights the potential therapeutic role of KLF2-regulated exosomal miRNAs in PAH and other diseases associated with vascular remodelling.

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Flow-activated transcription factor Krüppel-like factor 2 (KLF2) signaling is compromised in pulmonary arterial hypertension (PAH). We aimed to identify KLF2-induced endotheliumprotective exosomal microRNAs of potential therapeutic significance. Eight exosomal microRNAs elevated by KLF2 but reduced in PAH were transfected into human pulmonary artery endothelial cells. Of these, only miR-181a-5p and miR-324-5p had anti-apoptotic, anti-inflammatory and anti-proliferative effect on endothelial cells and reduced proliferation of vascular smooth muscle cells in vitro. RNA sequencing of miRNAtransfected HPAECs revealed reduced expression of multiple genes implicated in vascular remodelling, including ETS-1, NOTCH4, ACTA2, TNF-α, IL-1, MMP10, MAPK and NFATC2. KLF2, miR-181a-5p and miR-324-5p were reduced, while their target genes were elevated in blood-derived endothelial colony forming cells and lung tissues from idiopathic and heritable PAH patients with disabling KLF2 mutation and Sugen/hypoxia mice. Supplementation of miR-181a-5p and miR-324-5p or silencing of their target genes attenuated proliferative and angiogenic responses in endothelial cells from idiopathic PAH and prevented development of pulmonary hypertension in Sugen/hypoxia mice.This study highlights potential therapeutic role of KLF2-induced exosomal microRNAs in PAH.

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