Inflammatory microenvironment in both healthy controls and ARDS patients polarize clinically utilized MSCs towards a pro-inflammatory MSC phenotype

Abstract

Background: Despite increased interest in MSC-based cell therapy to treat acute respiratory distress syndrome (ARDS), our understanding of the in vivo mechanisms of action of MSC are limited. ARDS is driven by an acute severe inflammatory response, but how this inflammatory microenvironment influences MSC therapeutic actions is at present unknown. Aim: To determine how the inflammatory environment present in ARDS lungs alters MSC behaviors, with comparison to healthy controls. Methods: Clinically utilized bone marrow-derived MSCs were exposed to bronchoalveolar lavage fluid (BALF) samples obtained from ARDS patients without sepsis or healthy control subjects (HC). Following exposure, conditioned media were assessed for pro- and anti-inflammatory cytokines and gene expression profiles were analyzed using an RNA seq approach. Results: Following 24 hours of exposure, RNA seq analyses demonstrated that MSCs exposed to BALF samples, both ARDS and HC, induced a pro-inflammatory phenotype compared to saline-exposed control cells. Similar results were observed in conditioned media, with a significant increase production of IL-6, IL-8, and IL-18 in BALF exposed MSCs compared to saline control. Remarkably, the RNA seq data indicated that MSCs exposed to HC BALF were more potent in inducing a pro-inflammatory phenotype compared to ARDS BALF samples. Conclusion: Our data suggest that lung airspace environment in both healthy controls and ARDS patients may polarize MSCs towards a pro-inflammatory phenotype. These results highlight the need to understand how the alveolar environment of both normal and ARDS subjects can influence the phenotype of MSCs.