Treating acute lung injury in a juvenile animal model using umbilical cord mesenchymal stromal cell-derived extracellular vesicles

Juvenile acute respiratory distress syndrome (ARDS) remains a high-morbidity condition with no approved pharmacological therapy. Studies have shown that umbilical cord-derived mesenchymal stromal cells​ (UC-MSCs) represent a promising source of MSCs for treating ARDS in adult animals, with UC-MSC derived extracellular vesicles (UC-EVs) also demonstrating therapeutic promise given their immunomodulatory and anti-inflammatory potential. The present study investigates the therapeutic potential of using UC-EVs for treating juvenile ARDS. UC-EVs, isolated by ultracentrifugation, were used to treat lipopolysaccharide (LPS)-induced ARDS in juvenile (3–4 weeks of age) C57BL/6 mice via intravenous (IV) injection at three doses (200, 400, 800 µg/kg) 4 h following LPS administration; animals were sacrificed at 48 h to evaluate total protein in the bronchoalveolar lavage (BAL), innate immune cells in the lung and BAL, pro-inflammatory cytokines, surfactant protein-D (SP-D) and epithelial/endothelial barrier integrity. At an optimal dose of 800 µg/kg, IV administerd UC-EVs significantly improved epithelial-endothelial barrier function, reducing BAL protein and Evans Blue dye extravasation. Inflammation was attenuated with marked reductions in BAL IL-1β, TNF-α, and IL-6. UC-EVs also decreased immune cell infiltration and shifted macrophages toward an M2 phenotype, yielding a lower M1/M2 ratio in both lung tissue and BAL. In vitro analyses showed that UC-EVs diminished NLRP3 expression and IL-1β release in activated macrophages. Neutrophil infiltration and MPO expression in lung tissue were reduced, with Neutrophil extracellular trap (NET) formation also significantly decreased. UC-EVs protect against LPS-induced ARDS in juvenile mice by dampening lung inflammation and preserving epithelial-endothelial barrier function. Mechanistically, UC-EVs shift macrophage polarization, reduce NLRP3/IL-1β expression and decrease percentage of MPO/SYTOX-positive HL-60 cells.