Decellularized lung extracellular matrix-assisted delivery of mesenchymal stem cell-derived extracellular vesicles in acute lung injury.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as promising cell-free therapeutics for inflammatory and tissue injury. However, their pulmonary application may be limited by rapid redistribution and the lack of a tissue-specific microenvironment. In this study, lung-derived decellularized extracellular matrix (dECM) was investigated as a biologically relevant matrix for pulmonary delivery of MSC-derived extracellular vesicles. The physicochemical characteristics of the extracellular vesicles were evaluated using nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), scanning electron microscopy (SEM), and cryogenic electron microscopy (Cryo-EM). To examine early pulmonary localization, Coumarin-6-labeled extracellular vesicles were administered intratracheally, and frozen lung sections were examined 2 h after administration. Free Coumarin-6 produced a diffuse fluorescence pattern, whereas labeled extracellular vesicles exhibited discrete punctate fluorescence. The dECM-containing formulation showed a more clustered fluorescence pattern, suggesting altered local distribution of extracellular vesicle-associated material within the lung. In vitro, MSC-EVs reduced TNF-α production by activated THP-1-derived macrophages without detectable cytotoxicity in L929 cells. In a lipopolysaccharide (LPS)-induced rat model of acute lung injury, extracellular vesicle treatment reduced TNF-α and increased IL-10 in bronchoalveolar lavage fluid, accompanied by partial preservation of lung architecture. Notably, ECM-assisted extracellular vesicle treatment produced a greater reduction in MMP-9 and a more favorable MMP-9/TIMP-1 ratio than extracellular vesicles alone. These findings suggest that lung-derived dECM can provide a biologically relevant matrix environment for pulmonary extracellular vesicle delivery and may contribute to modulation of extracellular matrix remodeling during early acute lung injury. Further studies using quantitative biodistribution, longitudinal retention, release kinetics, and cellular uptake analyses are warranted to establish the mechanisms underlying dECM-assisted extracellular vesicle delivery.