Background Pulmonary endothelial cells’ (ECs) injury and apoptotic death are necessary and sufficient for the pathogenesis of the acute respiratory distress syndrome (ARDS), regardless of epithelial damage. Interaction of dysfunctional ECs with circulatory extracellular vesicles (EVs) holds therapeutic promise in ARDS. However, the presence in the blood of long-term ARDS survivors of EVs with a distinct phenotype compared to the EVs of non-surviving patients is not reported. With a multidisciplinary translational approach, we studied EVs from the blood of 33 patients with moderate-to-severe ARDS. Results The EVs were isolated from the blood of ARDS and control subjects. Immunoblotting and magnetic beads immunoisolation complemented by standardized flow cytometry and nanoparticles tracking analyses identified in the ARDS patients a subset of EVs with mesenchymal stem cell (MSC) origin (CD73 + CD105 + Cd34 − CD45 − ). These EVs have 4.7-fold greater counts compared to controls and comprise the transforming growth factor-beta receptor I (TβRI)/Alk5 and the Runx1 transcription factor. Time course analyses showed that the expression pattern of two Runx1 isoforms is critical for ARDS outcome: the p52 isoform shows a continuous expression, while the p66 is short-lived. A high ratio Runx1p66 / p52 provided a survival advantage, regardless of age, sex, disease severity or length of stay in the intensive care unit. Moreover, the Runx1p66 isoform is transiently expressed by cultured human bone marrow-derived MSCs, it is released in the EVs recoverable from the conditioned media and stimulates the proliferation of lipopolysaccharide (LPS)-treated ECs. The findings are consistent with a causal effect of Runx1p66 expression on EC proliferation. Furthermore, morphological and functional assays showed that the EVs bearing the Runx1p66 enhanced junctional integrity of LPS-injured ECs and decreased lung histological severity in the LPS-treated mice. Conclusions The expression pattern of Runx1 isoforms might be a reliable circulatory biomarker of ARDS activity and a novel determinant of the molecular mechanism for lung vascular/tissue repair and recovery after severe injury. Electronic supplementary material The online version of this article (10.1186/s40169-018-0197-2) contains supplementary material, which is available to authorized users.

There is a need for treatments to reduce coronavirus disease 2019 (COVID-19) mortality. Alpha-2 adrenergic receptor (α2 AR) agonists can dampen immune cell and inflammatory responses as well as improve oxygenation through physiologic respiratory parameters. Therefore, α2 AR agonists may be effective in reducing mortality related to hyperinflammation and acute respiratory failure in COVID-19. Dexmedetomidine (DEX) is an α2 AR agonist used for sedation. We performed a retrospective analysis of adults at Rush University System for Health hospitals between March 1, 2020 and July 30, 2020 with COVID-19 requiring invasive mechanical ventilation and sedation (n = 214). We evaluated the association of DEX use and 28-day mortality from time of intubation. Overall, 28-day mortality in the cohort receiving DEX was 27.0% as compared to 64.5% in the cohort that did not receive DEX (relative risk reduction 58.2%; 95% CI 42.4–69.6). Use of DEX was associated with reduced 28-day mortality on multivariable Cox regression analysis (aHR 0.19; 95% CI 0.10–0.33; p < 0.001). Adjusting for time-varying exposure to DEX also demonstrated that DEX was associated with reduced 28-day mortality (aHR 0.51; 95% CI 0.28–0.95; p = 0.03). Earlier DEX use, initiated <3.4 days from intubation, was associated with reduced 28-day mortality (aHR 0.25; 95% CI 0.13–0.50; p < 0.001) while later DEX use was not (aHR 0.64; 95% CI 0.27–1.50; p = 0.30). These results suggest an α2 AR agonist might reduce mortality in patients with COVID-19. Randomized controlled trials are needed to confirm this observation.

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