Inflammatory cytokine-primed MSC-derived extracellular vesicles ameliorate acute lung injury via enhanced immunomodulation and alveolar repair

Background: Acute lung injury (ALI) is characterized by excessive inflammation and alveolar damage, arising from pathogens or systemic insults such as sepsis, and can progress to severe acute respiratory distress syndrome (ARDS). Despite its severity, effective pharmacological treatments remain unavailable, and current clinical interventions are limited to supportive care such as mechanical ventilation. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have emerged as promising candidates for lung repair, but insufficient immunosuppressive capacity often limits their efficacy. Methods: Human adipose-derived mesenchymal stem cells (hADMSCs) were primed with IFN-γ and TNF-α to enhance the immunomodulatory properties of their secreted EVs. We characterized unprimed control MSC-EVs (C-MEVs) and primed MSC-EVs (P-MEVs) by transmission electron microscopy, nanoparticle tracking analysis, and western blotting for EV markers. Functional assays in THP-1 and A549 cells examined anti-inflammatory potency and barrier regeneration against lipopolysaccharide (LPS)-induced damage. A preclinical mouse model of LPS-induced ALI was used to evaluate inflammatory cytokine expression, immune cell infiltration, pulmonary edema, and vascular leakage. Finally, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected Vero E6 cells were tested whether P-MEVs could mitigate the inflammatory damage characteristic of virus-triggered acute lung injury. Results: Primed hADMSCs exhibited elevated expression of immunosuppressive molecules (e.g., COX-2, IDO, TSG-6), without changing EV morphology or yield. P-MEVs mitigated LPS-induced inflammation more effectively than C-MEVs in THP-1 and A549 cells. In vivo, P-MEVs more robustly attenuated inflammatory cytokines, immune cell recruitment, and lung injury markers in mice challenged with LPS. In SARS-CoV-2-infected Vero E6 cells, P-MEVs suppressed cytopathic effects and inflammatory responses more potently than C-MEVs. Mechanistic analyses revealed that these enhancements were associated with elevated miRNA levels, including miR-221-3p, involved in inhibiting inflammatory pathways. Conclusion: Inflammatory cytokine priming substantially augments the immunomodulatory and tissue-regenerative efficacy of hADMSC-derived EVs, offering superior therapeutic effects in ALI models and promising activity against SARS-CoV-2-induced lung damage. These findings underscore the therapeutic potential of P-MEVs as an innovative, cell-free platform for treating severe pulmonary disorders, including ARDS.