LAUSR

Background & Aim: One of the most severe complications of the current COVID-19 pandemic is acute respiratory distress syndrome (ARDS). ARDS is mediated by increased amounts of pro-inflammatory cytokines, leading to lung damage. ARDS remains an important unmet medical need. Mesenchymal stem cells (MSCs) and MSC-derived small extracellular vesicles (sEVs) have been suggested as a potential treatment for ARDS due to their significant immunomodulatory properties. While MSCs and their sEVs share immunomodulatory properties, sEVs have the added advantages of increased safety and improved tissue penetration. Methods, Results & Conclusion: In this study we compared the effect of two types of sEVs: sEVs isolated from naïve MSC (Exo MSC) or sEVs isolated from MSCs which were induced to secrete increased levels of neurotrophic and immunomodulatory factors (Exo MSC-NTF). Exo MSC or Exo MSC-NTF were administered intratracheally to mice following induction of ARDS using lipopolysaccharide. We found that the beneficial effect of Exo MSC-NTF was superior to Exo MSC in multiple parameters, including increase in blood oxygen saturation and reduction in lung pathology, neutrophil infiltration and bronchoalveolar lavage fluid (BALF) levels of proinflammatory cytokines. Specifically, Exo MSC-NTF significantly decreased interferon gamma (IFN-γ), interleukin 6 (IL-6), and regulated upon activation, normal T cell expressed and presumably secreted (RANTES) levels, while Exo MSC were not able to do so. To explore the differences between Exo MSC and Exo MSC-NTF we evaluated modifications in protein cargo. ELISA measurements revealed that amphiregulin (AREG) was 16-fold higher and leukemia inhibitory factor (LIF) was greater than 3-fold higher in Exo MSC-NTF than in Exo MSC. Both AREG and LIF are reported to have beneficial effects in ARDS models, either through immunomodulation or cellular repair. The observed positive preclinical results suggest that intratracheal administration of Exo MSC-NTF may be suitable as a therapy for ARDS due to COVID-19 or other causes, and may be more effective at modifying ARDS physiological, pathological, and biochemical outcomes than sEVs isolated from naïve MSCs. Increased expression of LIF and AREG in Exo MSC-NTF may contribute to the effectiveness of this innovative treatment modality.