B66-05 Mirna-29b Mediates Ca2+ Signaling in Pulmonary Arterial Smooth Muscle Cells Under Hypoxic Conditions

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.