Background/Purpose: Neutrophils are the most abundant cells in synovial fluid, having all the features of activated cells in rheumatoid arthritis (RA), including prolonged cell survival, increased migratory capacity and the ability to produce high levels of inflammatory mediators. MicroRNAs (miRNA) have recently emerged as a new class of modulators of gene expression, regulating inflammation, degradation of extracellular matrix and invasive behavior of the resident cells in RA. Purpose: 1) to investigate the miRNA expression pattern in rheumatoid arthritis (RA) neutrophils and its contribution to their pathogenic profile and 2) to analyze the effect of specific autoantibodies or inflammatory components and its modulation by biological therapies.

Methods: Neutrophils were isolated from peripheral blood and paired synovial fluid samples of 40 RA-patients and 40 healthy donors. A microRNA array was performed using nCounter technology. Healthy-neutrophils were treated in vitro with antibodies to citrullinated protein antigens (ACPAs) isolated from RA patients and TNF-a or IL-6. In vitro treatments of RA-neutrophils with tocilizumab(TCZ) or infliximab(IFX) was carried out. Transfections with the pre-miRNAs miR-223, miR-126 and miR-148 were performed in RA neutrophils. DICER silencing using lentiviral transfection in neutrophils was further carried out.

Results: RA-neutrophils showed a global downregulation of miRNAs and genes involved in miRNA biogenesis, alongside with an upregulation of mRNA targets related to survival, migration and inflammation. Decreased levels of miRNAs and DICER correlated with autoimmunity, inflammation and disease activity. ACPAs and TNF-a decreased the expression of numerous miRNAs and their biogenesis-related genes, and increased their mRNA targets. IFX reversed those effects. Transfections with pre-miRNAs-223, -126 and -148a specifically modulated genes regulating inflammation, survival and migration. DICER depletion influenced the neutrophils’ inflammatory profile.

Conclusion: 1) RA-neutrophils exhibit a global low abundance of miRNAs induced by autoantibodies and inflammatory markers, and responsible for their pathogenic activation. 2)miRNA biogenesis is significantly impaired in RA-neutrophils and further associated with a deeper downregulation of miRNAs related to inflammation, migration and survival of synovial neutrophils. 3) Biological therapies such as anti-TNF-a restore miRNA levels, minimizing the inflammatory profile of neutrophils. Supported by the Minister of Health (ISCIII, CP15/0158, PI17/01316, PI15/01333, RIER RD16/0012/0015) cofinanced with FEDER funds.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/impaired-microrna-processing-in-neutrophils-from-rheumatoid-arthritis-patients-confers-their-pathogenic-profile-modulation-by-biological-therapies/