Abstract Rationale Pulmonary hypertension (PH) is a progressive cardiopulmonary disorder characterized by sustained pulmonary vasoconstriction and dysregulated intracellular calcium (Ca2+) signaling, contributing to pathological remodeling of pulmonary arterial smooth muscle cells (PASMCs). Store-operated Ca2+ entry (SOCE) plays a key role in Ca2+ homeostasis in PASMCs, yet its regulation in PH remains incompletely defined. We previously demonstrated that miR-29b directly targets Kv1.5 in PASMCs isolated from PH patients. Here, we hypothesized that miR-29b regulates the STIM1/Orai1 axis in PASMCs under chronic hypoxia, thereby promoting PASMC proliferation and contributing to PH pathogenesis. Methods Primary human PASMCs were exposed to normoxia (21% O2) or hypoxia (3% O2) for 72 hours. Expression of miR-29b, Orai1, STIM1/2, and Kv1.5 were quantified by qPCR, Western blotting, and immunostaining. PASMC proliferation and apoptosis were assessed using EdU incorporation and TUNEL assays, respectively. Cells were transfected with a miR-29b mimic or inhibitor and exposed to normoxia or hypoxia for 72 hours. Results Hypoxia induced robust upregulation of miR-29b, STIM1/2, Orai1, p-AKT, and HIF-1α, concurrent with downregulation of Kv1.5 in PASMCs compared with normoxic controls. Hypoxic exposure enhanced PASMC survival by increasing proliferation and reducing apoptosis. miR-29b overexpression elevated STIM1/2 and Orai1 levels, whereas miR-29b inhibition markedly suppressed their expression. Under normoxia, miR-29b overexpression diminished Kv1.5 expression and promoted PASMC proliferation. Conversely, miR-29b inhibition prevented hypoxia-induced Kv1.5 downregulation. Conclusions miR-29b promotes hypoxia-induced PASMC proliferation by activating STIM1/Orai1-dependent Ca2+ signaling and suppressing Kv1.5 expression. Targeting miR-29b may represent a promising therapeutic strategy for hypoxia-induced PH and potentially other PH subtypes characterized by aberrant Ca2+ handling. This abstract is funded by: grants from the University of Minnesota Hormel Institute Eagles Telethon Postdoctoral Fellowship (I.E.), University of Minnesota Hormel Institute Transformative Ideas Program (A.B.), American Heart Association Undergraduate Student Training Award 25IAUST1363304 (A.B.), Minnesota Partnership for Biotechnology and Medical Genomics program MNP#24.04 (A.B.).
Elmadbouh et al. (Fri,) studied this question.