MicroRNAs sequencing of plasma exosomes derived from patients with atrial fibrillation: miR-124-3p promotes cardiac fibroblast activation and proliferation by regulating AXIN1

MicroRNAs (miRNAs) play an important role in the pathogenesis of atrial fibrillation (AF). Exosomal miRNAs may develop as promising biomarkers for AF. To explore significant exosomal miRNAs in AF, plasma exosomes were extracted from 3 patients with AF and 3 patients with sinus rhythm (SR), respectively. Differential expression of exosomal miRNAs were screened by high-throughput sequencing analysis and verified by qRT-PCR from 40 patients with AF and 40 patients with SR. The target genes prediction, biological function, and signaling pathways analysis were conducted by miRanda software, gene ontology (GO), and KEGG analysis. The results showed that there were 40 differently expressed exosomal miRNAs from AF patients compared with SR patients, of which 13 miRNAs were upregulated and 27 miRNAs were downregulated. qRT-PCR validation demonstrated that miR-124-3p, miR-378d, miR-2110, and miR-3180-3p were remarkably upregulated, while miR-223-5p, miR-574-3p, miR-125a-3p, and miR-1299 were downregulated. To explore the function of miR-124-3p associated with AF, plasma exosomes derived from AF patients were co-incubated with rat myocardial fibroblasts. The expression of miR-124-3p was upregulated in myocardial fibroblasts. The viability and proliferation of myocardial fibroblasts were elevated by transfecting with miR-124-3p overexpression plasmids using CCK8 and immunofluorescence-staining methods. AXIN1 was verified to be the target of miR-124-3p by luciferase assay in vitro. Expression of AXIN1 was reduced, while β-catenin, Collagen 1, and α-SMA were increased in myocardial fibroblasts with miR-124-3p overexpression. In conclusion, these findings suggested that circulating exosomal miRNAs may serve as novel biomarkers for AF, and miR-124-3p promotes fibroblast activation and proliferation through regulating WNT/β-catenin signaling pathway via AXIN1.