In-vitro immunomodulatory efficacy of extracellular vesicles derived from TGF-β1/IFN-γ dual licensed human bone marrow mesenchymal stromal cells.

Background: Mesenchymal stromal cells (MSCs) possess strong immunomodulatory properties, making them attractive candidates for regenerative medicine and immune-related therapies. Pre-activation, or licensing, of MSCs with cytokines such as interferon-gamma (IFN-γ) and transforming growth factor-beta 1 (TGF-β1) has been shown to enhance their immunosuppressive efficacy. Recent attention has turned to extracellular vesicles (EVs) released by licensed MSCs as a cell-free therapeutic alternative.

Methods: Small EVs were isolated from MSCs licensed with a combination of IFN-γ and TGF-β1. These EVs were characterized according to standardized criteria. Their immunomodulatory effects were assessed in vitro using two human immune models: a THP-1-derived macrophage polarization system and a peripheral blood mononuclear cell (PBMC) co-culture assay. Pro/anti-inflammatory molecules secretion, T cell proliferation, and regulatory T cell induction were quantified. Dimensionality reduction using t-distributed stochastic neighbor embedding (t-SNE) was applied to multiparametric flow cytometry data for immune profiling. In addition, publicly available transcriptomic datasets (GSE122091 and GSE46019) were analyzed to identify differentially expressed genes (DEGs) in IFN-γ- and TGF-β1-licensed MSCs, providing insight into potential molecular drivers of EV-mediated immunoregulation.

Results: Licensed EVs significantly inhibited pro-inflammatory THP-1 macrophage activation and promoted an anti-inflammatory phenotype, with reduced secretion of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), increased IL-10 production, and decreased nitric oxide (NO) levels.. Compared to EVs from non-licensed MSCs, licensed EVs induced a greater proportion of regulatory T cells and exhibited enhanced suppression of allogeneic T cell proliferation. t-SNE analysis revealed a distinct immunoregulatory signature induced by licensed EVs, characterized by the emergence of a non-proliferative lymphocyte subset with elevated co-expression of CD4, CD25, and FOXP3. Transcriptomic analysis further revealed seven overlapping DEGs between IFN-γ- and TGF-β1-licensed MSCs, including both upregulated (GPR68, LIMK2, LIPG) and downregulated (EFNA5, PRKG1, DCLK1, TRIM2) genes, several of which are functionally implicated in EV-mediated immune regulation.

Conclusions: Small EVs derived from IFN-γ and TGF-β1-licensed MSCs exhibit demonstrate dose-dependent immunomodulatory trends in vitro, with enhanced effects observed at higher concentrations.. These findings suggest their potential utility in modulating both innate and adaptive immune responses, warranting further investigation for their application as a cell-free therapeutic strategy in immune-mediated conditions.