Identification of miR ‐150‐5p in Human Amniotic Membrane Mesenchymal Cell‐Derived Extracellular Vesicles as a Novel Mechanism Driving Cardioprotection

Background Human amniotic membrane mesenchymal stem cells (hAMSCs) hold strong cardioprotective potential, yet their mechanisms of action remain largely elusive. Methods and Results C57BL/6 mice were subjected to cardiac ischemia/reperfusion (I/R) and received intravenous (IV) 2 × 10 5 hAMSCs at 2, 7 or 14 days post‐reperfusion. Cardiac function and MIAT/miR‐150/HOXA4 signalling were assessed. Mice treated 2 days post‐I/R markedly improved LVEF and reduced myocardial necrosis and fibrosis by Day 21. Minimal hAMSC engraftment, evidenced by SSEA‐4 immunostaining, suggests paracrine rather than direct cellular effects. Guided by GWAS implicating miRNAs in myocardial infarction, we identified miR‐150 as a key effector, finding that hAMSC upregulated cardiac miR‐150 and suppressed HOXA4, a profibrotic target in ischemic myocardium. In parallel, hAMSC treatment reduced cardiac MIAT, a lncRNA that sequesters miR‐150, uncovering a mechanism of cardioprotection via MIAT downregulation post‐reperfusion. Notably, CRISPR‐Cas9 miR‐150‐silenced hAMSC exhibited severely impaired cardioprotective effects compared to wild‐type cells, confirming the functional role of miR‐150. miR‐150 was identified as a key extracellular vesicle (EV) cargo released by hAMSC under hypoxic conditions, both in vitro and in hAMSC‐injected I/R mice. Strickingly, administration of miR‐150‐enriched EVs to mice recapitulated the therapeutic benefits of hAMSC, underscoring miR‐150‐5p as central mediator of hAMSC‐iduced cardioprotection. Conclusions hAMSCs promote cardioprotection following I/R via the MIAT/miR‐150‐5p/HOXA4 axis, in which miR‐150‐5p plays a central role. These findings provide loss‐of‐function evidence about the therapeutic potential of hAMSC‐derived EVs as a novel cell‐free exosome‐based strategy for the treatment of acute myocardial infarction.