EXTRACELLULAR VESCICLES CHARACTERIZATION, miRNA PROFILING AND GENE TARGET NETWORK ANALYSIS IN PATIENTS WITH IDIOPATHIC INFLAMMATORY MYOPATHIES AND DISEASE SUBSETS. A CROSS-SECTIONAL COMPARATIVE ANALYSIS FROM A MONOCENTRIC COHORT

ABSTRACT Introduction: Idiopathic inflammatory myopathies (IIM) are a heterogenous group of immune-mediated disorders with different clinical phenotypes, pathogenesis, and autoantibody signatures. Extracellular vesicles (EVs) are small particles released by any cell type and mediating intercellular communication through the transport of small non-coding RNAs able to modify the gene expression of the target cell. Aims of the study: To investigate, with a cross-sectional study, the epigenetic footprint of IIM through characterization of EVs and the expression of EVs-derived microRNAs (miRNAs). Patients and methods: a size-exclusion chromatography-based protocol was used for EVs isolation from plasma of patients affected with IIM and matched healthy donors (HD). EVs-derived miRNAs were sequenced and quantified using Next-Generation Sequencing (NGS). Filtered count reads were used for miRNAs differential expression analyses after quality control and normalization. Putative gene targets enriched for pathways implicated in IIM were then analysed. Patients’ clinical and laboratory characteristics at the time of sampling were recorded. Results: Forty-seven IIM patients and 45 HD were enrolled in the study. Plasma EVs levels were significantly increased in cancer-associated myositis (CAM, n=12) versus non-CAM IIM (n=35, p=0.02) and HD (p<0.01). MiR-486-5p (p<0.01), miR-122-5p, miR-192-5p, and miR-32-5p were significantly upregulated (p<0.05 for all), while miR-142-3p (p<0.001), miR-141-3p (p<0.01), let-7a-5p (p<0.05) and miR-3613-5p (p<0.05) downregulated in EVs from IIM patients versus HD. MiR-486-5p was associated with raised muscle enzymes. The gene target network analysis highlighted that several target genes of up/downregulated miRNAs in IIM participate in inflammation, necroptosis, interferon, and immune signalling. Within IIM subgroups, miR-335-5p was selectively upregulated and miR-27a-5p downregulated in dermatomyositis (n=21, p<0.01), while let-7f-5p resulted significantly hyper-expressed and miR-143-3p hypo-expressed in CMA patients. Conclusions: Through an unbiased screening of EVs-derived miRNAs, we characterized miRNAs expression profile in IIM patients compared to HD and across diverse IIM subsets. Our results attest different epigenetic footprints among disease subtypes contributing to their peculiar pathogenesis and helping in the comprehension of the disease development.