Mechanisms of MSC regulation of macrophage intracellular signalling in the pre-clinical models of ARDS

Methods

Human monocyte derived macrophages (MDMs) were stimulated with LPS or plasma samples from ARDS patients (these samples were previously classified into hypo- and hyper-inflammatory phenotype) and treated with MSC conditioned medium (CM) or EVs. Protein expression was measured by Western blot. EV miRNA content was determined by miRNA seq.

In vivo: LPS-injured C57BL/6 mice were given EVs isolated from MSCs in which miR-181a had been silenced by miRNA inhibitor or overexpressed using miRNA mimic. <br><br>Results: EVs were the key component of MSC CM responsible for anti-inflammatory modulation of human macrophages. EVs significantly reduced secretion of TNF-a and IL-8 by LPS- or ARDS plasma-stimulated MDMs and this was dependent on SOCS1. Transfer of miR-181a in EVs downregulated PTEN and subsequently activated pSTAT5 leading to upregulation of SOCS1 in macrophages.

In vivo, EVs alleviated lung injury and upregulated pSTAT5 and SOCS1 expression in alveolar macrophages in a miR181-dependent manner. Overexpression of miR-181a in MSCs significantly enhanced therapeutic efficacy of EVs in this model. <br><br>Conclusion: miR-181a-PTEN-pSTAT5-SOCS1 axis is a novel pathway responsible for immunomodulatory effect of MSC EVs in ARDS.<br>