Thompson, M.

Abstract RATIONALE: Endothelial-to-mesenchymal transition (EndMT) is a cellular process in which endothelial cells (ECs) transition into mesenchymal cells, a mechanism recently linked to pulmonary vascular remodeling in pulmonary hypertension (PH). However, the regulatory mechanisms driving EndMT in PH remain largely undefined. MicroRNA-153 (miR-153), a small non-coding RNA, regulates gene expression by targeting the 3'-untranslated region (3'-UTR) of mRNA, affecting mRNA translation and stability. This study investigates miR-153's role in modulating EndMT in PH. METHODS: Human lung vascular endothelial cells (LVECs) were isolated from healthy individuals and patients with idiopathic pulmonary arterial hypertension (IPAH). In vitro, normal LVECs were exposed to hypoxia (3% O₂) for 72 hours or treated with TGF-β1 (10 ng/mL) for 7 days to induce EndMT. Levels of miR-153 and EndMT markers were quantified by qPCR, Western blotting, or immunostaining. Proliferation and apoptosis of ECs were assessed using EdU and TUNEL assays, respectively. LVECs were transfected with miR-153 inhibitor or mimic, then exposed to normoxic or hypoxic conditions, respectively for 72 hours. In vivo, mice were subjected to either hypoxia (10% O₂ for 6 weeks, Hx-PH) or Sugen5416/hypoxia (20 mg/kg i.p. plus 10% O₂ for 6 weeks, SuHx-PH) to induce PH. The PH phenotype in mice was evaluated by hemodynamic measurements and histological analysis of H&E-stained lung tissues. RESULTS:In silico analysis identified miR-153 as a direct regulator of human SNAI1 and SNAI2 genes via binding to their 3'-UTR. Downregulation of miR-153 in IPAH LVECs was correlated with elevated SNAI1/2 expression, increased EndMT, and higher proliferation compared to normal LVECs. Hypoxia or TGF-β1 treatment reduced miR-153 expression, increased EndMT transcription factors (SNAI1/2), mesenchymal markers (SM-22, vimentin), and reduced EC markers (CD31, VE-cadherin). In normoxic LVECs, miR-153 inhibition significantly upregulated SNAI1/2, increased EndMT and EC proliferation, and reduced apoptosis. Conversely, miR-153 mimic abolished hypoxia- and TGF-β1-induced EndMT. Overexpression of miR-153 attenuated hypoxia-induced EC survival. In PH mouse models, reduced miR-153 levels were associated with activated SNAI1/2, EndMT, and pulmonary vascular remodeling. CONCLUSIONS: Downregulation of miR-153 drives phenotypic transition of LVECs to proliferative mesenchymal cells via SNAI-mediated EndMT, contributing to pulmonary vascular remodeling and PH. Therefore, miR-153 could be a potential therapeutic target for PH treatment.