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Figure 2. Biodistribution of UCMSC-NVs. (A) Fluorescence imaging of healthy and ALI mice at various time points following intravenous injection of DIR-UCMSC-NVs; (B) Ex vivo imaging of major organs from control mice; (C) In vitro visualization of key organs in ALI mice; (D) Uptake of PKH26-labeled UCMSC-NVs by pulmonary macrophages. Scale bar = 50 μm; (E) Confocal laser scanning microscopy showing intracellular localization of UCMSC-NVs following uptake. Scale bar = 20 μm. DIO-UCMSC-NVs: green, DAPI: blue. UCMSC-NVs: Nanovesicles originating from human umbilical cord mesenchymal stem cells; ALI: acute lung injury; DIR: 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindotricarbocyanine iodide; PKH26: a red fluorescent membrane dye used for exosome labeling; DIO: 3,3′-dioctadecyloxacarbocyanine perchlorate; DAPI: 4′,6-diamidino-2′-phenylindole; LPS: lipopolysaccharide.