Mesenchymal Stem Cell–Derived Extracellular Vesicles Alleviate Acute Lung Injury Via Transfer of miR-27a-3p*

Objectives: The goal of this study was to determine the role of microRNA transfer in mediating the effects of mesenchymal stem cell–derived extracellular vesicles in acute lung injury. Design: Experimental cell and animal studies. Setting: University-based research laboratory. Subjects: THP-1 monocytes, bone marrow–derived macrophages, and C57BL/6 mice. Interventions: To determine the microRNA transfer in vitro, mesenchymal stem cells and mesenchymal stem cell–derived extracellular vesicles were cultured with THP-1 cells and bone marrow–derived macrophages and then assayed for microRNA expression in the target cells. To examine the role of microRNA transfer in vivo, mesenchymal stem cell–derived extracellular vesicles were administered to mice with lipopolysaccharide-induced lung injury. Measurements and Main Results: Mesenchymal stem cell–derived extracellular vesicles were efficiently taken up by macrophages in vitro and in vivo. miR-27a-3p was one of the most highly expressed microRNAs in THP-1 cells in microarray analysis and was transferred from mesenchymal stem cells and mesenchymal stem cell–derived extracellular vesicles to THP-1/bone marrow–derived macrophages. Mesenchymal stem cell–derived extracellular vesicles promoted M2 polarization in bone marrow–derived macrophages, which was inhibited by lentiviral anti-miR-27a-3p transduction. Mesenchymal stem cell–derived extracellular vesicles administered systemically and intratracheally were as effective as mesenchymal stem cells in alleviating acute lung injury, elevating miR-27a-3p levels in alveolar macrophages, and promoting M2 macrophage polarization. Treatment of mesenchymal stem cell–derived extracellular vesicles concurrently decreased alveolar macrophage expression of nuclear factor kappa B subunit 1, a target of miR-27a-3p. Lentiviral transduction of mesenchymal stem cells with anti-miR-27a-3p or knockdown of miR-27a-3p in vivo abolished the effects of mesenchymal stem cell–derived extracellular vesicles on acute lung injury and M2 macrophage polarization. Conclusions: Mesenchymal stem cell–derived extracellular vesicles mitigate acute lung injury at least partially via transferring miR-27a-3p to alveolar macrophages. miR-27a-3p acts to target NFKB1 and is a crucial regulator of M2 macrophage polarization.