Endothelial progenitor cell-derived exosomal miRNA-31 alleviates septic peritonitis by inhibiting E-selectin expression: an investigation on the mechanism of action

Purpose: The critical role played by miRNAs in sepsis-induced acute peritonitis has been repeatedly validated. This research focuses on elucidating the influence of endothelial progenitor cells (EPC)-derived exosomal miRNA-31 (exo-miR-31) on septic peritonitis (SP) and the role of E-selectin (SELE) in this process. Methods: : Differences in serum miRNA-31 and soluble SELE (sSELE) expression between SP cases and healthy controls (HCs) were identified. Additionally, we built a mouse colon ascendens stent peritonitis (CASP) model and an in vitro sepsis model via lipopolysaccharide (LPS) stimulation of mouse venous endothelial cells to verify the specific mechanism of EPC-derived exo-miR-31 on SP in vitro and in vivo . Results: : As indicated by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR) results, SP cases showed markedly reduced serum miR-31 levels and evidently elevated sSELE expression than HCs, with the expression of both genes altered more significantly as the condition worsened. Correlation analysis suggested a strong association between serum miRNA-31 and sSELE levels and sepsis severity. miR-31 in the peritoneal lavage fluid (PLF) of CASP model mice was down-regulated, while sSELE and inflammatory factors (IFs) TNF-α, IL-6 and IL-10 were notably increased. Gimsa staining revealed the massive recruitment and aggregation of nucleated cells in the abdominal cavity of CASP mice, and HE staining showed extensive neutrophilic infiltration in lung, liver and colon tissues, with obvious inflammatory tissue destruction. Besides, large numbers of bacteria were detected in the peripheral blood and PLF of CASP mice, with many CASP mice dying within 48 hours, as indicated by the bacterial smears and culture tests. EPC-derived exo-miR-31 was effective in elevating PLF miR-31 expression in CASP mice while suppressing sSELE, TNF-α, IL-6 and IL-10 levels. In EPCs-Exos miR-31 group, significant reductions in nucleated cell counts in the mouse PLF, neutrophil infiltration in lung, liver and colon tissues, and peripheral blood and PLF bacterial loads were observed, as well as an obvious extension in survival. In addition, in vitro experimental results of cell sepsis showed that miR-31 could obviously block the inhibitory effect of LPS stimulation on the proliferation level of mouse venous endothelial cells and inhibit the level of apoptosis. SELE, Caspase-3 and Bax protein levels were markedly lower in LPS+miR-31 group as compared to LPS and LPS-miR-NC groups, while Bcl-2 was increased ( P <0.05). Dual luciferase reporter gene assay identified the role of miR-31 as the direct target of SELE. Conclusions: : EPC-derived exo-miR-31 can effectively alleviate SP, possibly through targeted inhibition of SELE, providing a potential new direction for future prevention and treatment of SP.