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

Abstract

Rationale: A better understanding of the mechanism of action of mesenchymal stromal cells (MSCs) and their extracellular vesicles (EVs) is needed to support their use as novel therapies for ARDS. Macrophages are important mediators of ARDS inflammatory response. Suppressor of Cytokine Signalling (SOCS) proteins are key regulators of the macrophage phenotype switch. We therefore investigated whether SOCS proteins are involved in mediation of the MSC effect on human macrophage reprogramming.

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.

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.

Conclusion: miR-181a-PTEN-pSTAT5-SOCS1 axis is a novel pathway responsible for immunomodulatory effect of MSC EVs in ARDS.

Thesis embargoed until 31 July 2024.

Date of Award	Jul 2022
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	China Scholarship Council
Supervisor	Anna Krasnodembskaya (Supervisor) & Derek Brazil (Supervisor)