Release of membrane vesicles, a process conserved in both prokaryotes and eukaryotes, represents an evolutionary link, and suggests essential functions of a dynamic extracellular vesicular compartment (including exosomes, microparticles or microvesicles and apoptotic bodies). Compelling evidence supports the significance of this compartment in a broad range of physiological and pathological processes. However, classification of membrane vesicles, protocols of their isolation and detection, molecular details of vesicular release, clearance and biological functions are still under intense investigation. Here, we give a comprehensive overview of extracellular vesicles. After discussing the technical pitfalls and potential artifacts of the rapidly emerging field, we compare results from meta-analyses of published proteomic studies on membrane vesicles. We also summarize clinical implications of membrane vesicles. Lessons from this compartment challenge current paradigms concerning the mechanisms of intercellular communication and immune regulation. Furthermore, its clinical implementation may open new perspectives in translational medicine both in diagnostics and therapy.

BackgroundIdentification of parameters for early diagnosis and treatment response would be beneficial for patients with early rheumatoid arthritis (ERA) to prevent ongoing joint damage. miRNAs have features of potential biomarkers, and an altered expression of miRNAs was shown in established rheumatoid arthritis (RA).ObjectiveTo analyse RA associated miRNAs in the sera of patients with ERA to find markers of early disease, clinical activity or predictors of disease outcome.MethodsTotal RNA was isolated from whole sera in ERA patients (prior to and after 3 and 12 months of therapy with disease modifying antirheumatic drugs), in patients with established RA and in healthy controls (HC) using phenol–chloroform extraction. Expression of miR-146a, miR-155, miR-223, miR-16, miR-203, miR-132 and miR-124a was analysed by TaqMan Real Time PCR.ResultsFrom all analysed miRNAs, levels of miR-146a, miR-155 and miR-16 were decreased in the sera of ERA patients in comparison with established RA. A change in circulating miR-16 in the first 3 months of therapy was associated with a decrease in DAS28 in long term follow-up in ERA (p=0.002). Levels of circulating miR-223 in treatment naïve ERA correlated with C reactive protein (p=0.008), DAS28 (p=0.031) and change in DAS28 after 3 months (p=0.003) and 12 months (p=0.011) of follow-up. However, neither miR-16 nor miR-223 could distinguish ERA from HC.ConclusionsDifferential expression of circulating miR-146a, miR-155 and miR-16 in the sera of ERA patients may characterise an early stage of the disease. We suggest miR-223 as a marker of disease activity and miR-16 and miR-223 as possible predictors for disease outcome in ERA.

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Objective To investigate the role of protein tyrosine phosphatase nonreceptor type 2 (PTPN2) in the pathogenesis of rheumatoid arthritis (RA). Methods Synovial tissue samples from patients with RA and patients with osteoarthritis (OA) were stained for PTPN2. Synovial fibroblasts were stimulated with tumor necrosis factor (TNF) and interleukin‐1β (IL‐1β), lipopolysaccharide (LPS), TRAIL, or thapsigargin. The expression of PTPN2 in synovial fibroblasts and peripheral blood mononuclear cells (PBMCs) was analyzed by real‐time polymerase chain reaction and Western blotting. Cell death, the release of IL‐6 and IL‐8, and the induction of autophagy were analyzed after PTPN2 silencing. Methylated DNA immunoprecipitation analysis was used to evaluate DNA methylation–regulated gene expression of PTPN2. Results PTPN2 was significantly overexpressed in synovial tissue samples from RA patients compared to OA patients. Patients receiving anti‐TNF therapy showed significantly reduced staining for PTPN2 compared with patients treated with nonbiologic agents. PTPN2 expression was higher in RA synovial fibroblasts (RASFs) than in OASFs. This differential expression was not regulated by DNA methylation. PTPN2 was further up‐regulated after stimulation with TNF, TNF combined with IL‐1β, or LPS. There was no significant difference in basal PTPN2 expression in PBMCs from patients with RA, ankylosing spondylitis, or systemic lupus erythematosus or healthy controls. Most interestingly, PTPN2 silencing in RASFs significantly increased the production of the inflammatory cytokine IL‐6 but did not affect levels of IL‐8. Moreover, functional analysis showed that high PTPN2 levels contributed to the increased apoptosis resistance of RASFs and increased autophagy. Conclusion This is the first study of PTPN2 in RASFs showing that PTPN2 regulates IL‐6 production, cell death, and autophagy. Our findings indicate that PTPN2 is linked to the pathogenesis of RA via synovial fibroblasts.

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