The regulatory effect of microRNA-21a-3p on the promotion of telocyte angiogenesis mediated by PI3K (p110α)/AKT/mTOR in LPS induced mice ARDS

Background Telocytes (TCs) are newly identified interstitial cells that participate in tissue protection and repair. The present study investigated the mechanisms underlying the protective effect of TCs in a mouse model of respiratory distress. Methods The mouse model of acute respiratory distress syndrome (ARDS) was established by intratracheal instillation of lipopolysaccharide (LPS). After instillation of TCs culture medium, lung injury was assessed, and angiogenesis markers, including CD31 and endothelial nitric oxide synthase (eNOS), were detected by immunofluorescence. Bioinformatics analysis was used to screen significantly differentially expressed microRNAs (miRNAs) in cultured TCs stimulated with LPS, and the regulation of downstream angiogenesis genes by these miRNAs was analysed and verified. PI3K subunits and pathways were evaluated by using a PI3K p110 alpha inhibitor to study the involved mechanisms. Results In ARDS mice, instillation of TCs culture medium ameliorated LPS-induced inflammation and lung injury and increased the protein levels of CD31 and eNOS in the injured lungs. A total of 7 miRNAs and 1899 mRNAs were differentially regulated in TCs stimulated with LPS. Functional prediction analysis showed that the differentially expressed mRNAs were enriched in angiogenesis-related processes, which were highly correlated with miR-21a-3p. Culture medium from TCs with miR-21a-3p inhibition failed to promote angiogenesis in mouse models of LPS-induced ARDS. In cultured TCs, LPS stimulation upregulated the expression of miR-21a-3p, which further targeted the transcription factor E2F8 and decreased Notch2 protein expression. TCs culture medium enhanced hemangioendothelioma endothelial cells (EOMA cells) proliferation, which was blocked by the miR-21a-3p inhibitor. The PI3K p110 alpha inhibitor decreased vascular endothelial growth factor levels in LPS-stimulated TCs and reversed the enhancing effect of TCs culture medium on EOMA cells proliferation. Conclusions TCs exerted protective effects under inflammatory conditions by promoting angiogenesis via miR-21a-3p. The PI3K p110 alpha subunit and transcriptional factor E2F8 could be involved in this process.