[Difference of silicon dioxide-stimulated macrophage-derived exosomal miRNA expression profile]

To analyze the differential expression of RAW264.7 macrophage-derived exosomes miRNA stimulated by free silicon dioxide (SiO2).
 Methods: RAW264.7 was stimulated with SiO2 (200 mg/L) for 48 h (exo_48 h group), and the supernatant was collected. The exosomes in the supernatant were extracted by ultracentrifugation. Transmission microscopy, nanoparticle tracking analysis (NTA) and Western blotting were used to identify exosomes. High-throughput sequencing was performed to compare the differential expression of exosome miRNAs between the exo_control group (RAW264.7 cultured for 48 h without SiO2) and the exo_48 h group; miRanda, TargetScan and starBase were used to predict target genes of differential miRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed on target genes to further analyze the biological functions of genes.
 Results: The transmission microscopy showed that the exosomes were lipid membrane coated vesicles, which were heterogeneously distributed, with a diameter ranging from 30 to 100 nm, and the shape was round or elliptical. The volume kurtosis was concentrated between 40 and 100 nm and the exosome marker protein TSG101 was positive. High-throughput sequencing screened 148 differentially expressed exosomal miRNAs. MiR-219c-3p, let-7d-3p, let-7a-1-3p, miR-328-3p, miR-365-3p, and miR-7219-3p were significantly up-regulated, and miR-378d and miR-5106 were significantly down-regulated compared with the control group. Target genes were mainly enriched in mTOR signaling pathway, Wnt signaling pathway, TGF-β signaling pathway, and so on.
 Conclusion: The exosomes secreted by SiO2-induced macrophages contain abundant miRNAs, and their expressions are significantly different. These differential miRNAs may be involved in the activation of lung fibroblasts and epithelial-mesenchymal transition.