Exosomes derived from TGF-β1-modified mesenchymal stem cells protect septic mice by inducing macrophage M2 polarization.

Abstract

BACKGROUND: Exosomes derived from mesenchymal stem cells (MSCs) have been reported to improve the prognosis in septic mice. Additionally, we have confirmed that TGF-β1 plays a critical role in MSC-mediated protection against sepsis. In this study, we aimed to investigate whether exosomes derived from TGF-β1-overexpressing MSCs (TGF-β1-Exo) offer protective effects in sepsis. METHODS: MSCs were collected from mouse MSCs stably transfected with TGF-β1 using a lentiviral vector. Exosomes were isolated and purified from MSCs (Exo), GFP-MSCs (GFP-Exo), and TGF-β1-MSCs (TGF-β1-Exo). A sepsis model was induced in mice via cecal ligation and perforation (CLP). After 6 h, exosomes from different sources were intravenously administered into septic mice. Mice were euthanised 24 h later, and histopathological changes were assessed using hematoxylin and eosin (H&E) staining. Inflammatory cytokine levels were measured using ELISA and RT-PCR. Flow cytometry was employed to evaluate macrophage phenotypes in lung tissues and in vitro macrophages. Additionally, we co-cultured fluorescently labeled exosomes with macrophages in vitro. RESULTS: TGF-β1-Exo significantly ameliorated histopathological damage and improved survival rates in septic mice. ELISA and RT-PCR analyses revealed that several pro-inflammatory cytokines were notably suppressed in the TGF-β1-Exo group. Furthermore, TGF-β1-Exo promoted the polarization of M1 macrophages to M2 macrophages both in vivo. In vitro, TGF-β1-Exo were internalized by LPS-pretreated macrophages, promoting the shift from the M1 to M2 phenotype, reducing the expression of pro-inflammatory cytokines, and enhancing the production of anti-inflammatory factors. CONCLUSIONS: Our findings suggest that TGF-β1-Exo exert therapeutic effects in septic mice by modulating macrophage polarization and inhibiting macrophage-mediated inflammation.