Aims: One of the characteristics of acute lung injury (ALI) is severe pulmonary edema, which is closelyrelated to alveolar fluid clearance. Mesenchymal stem cells (MSCs) secrete a wide range of cytokines,growth factors and miRNAs through paracrine action to participate in the mechanism of pulmonaryinflammatory response, which increases the clearance of edema fluid, and promotes the repair process ofALI. However, the mechanism by which bone marrow derived MSCs-conditioned medium

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... s edema clearance is unclear. Epithelial sodium channel (ENaC) is the rate-limiting step in thesodium-water transport and edema clearance in the alveolar cavity, and we aim to explore the role of ENaCin BMSCs-CM invloved edema clearance and whether it can alter the function of ENaC via miRNAs.Methods: CCK-8 cell proliferation assay was used to detect the effect of BMSCs-CM on the survival ofAT2 cells. Real-time PCR (RT-PCR) and Western blot were used to detect the expression of ENaC in AT2cells. The effects of exosomes/miR-34c on the transepithelial short-circuit current in the monolayer of H441cells were examined by the Ussing chamber setup. Dual luciferase reporter gene assay was used to detect thetarget gene of miR-34c.Results: BMSCs-CM can increase the viability of mouse AT2 cells. RT-PCR and Western blotting resultsshowed that BMSCs-CM significantly increased the expression of γ-ENaC subunit in mouse AT2 cells.Ussing chamber assay revealed that BMSCs-CM enhanced the amiloride-sensitive currents associated withENaC activity in intact H441 cell monolayers. In addition, we observed higher expression of miR-34c inmouse AT2 cells administrated with BMSCs-CM, and the overexpression or inhibition of miR-34c canregulate the expression of ENaC protein and alter the function of ENaC. Finally, we detected MARCKS maybe one of the target gene of miR-34c.Conclusions: Our results indicate that BMSCs-CM may improve LPS-induced ALI through miR-34ctargeting MARCKS and regulating ENaC indirectly, which further explores the benefit of paracrine effectsof BMSCs on edematous ALI.