Objective We undertook this study to examine microRNA (miRNA) expression across rheumatoid arthritis (RA) phenotypes, along with the effects and mechanisms of action of miRNA‐17‐5p (miR‐17). Methods A miRNA array was performed in synovial tissue biopsied from patients with naive erosive RA (n = 3) and patients with nonerosive RA (n = 3). MicroRNA‐17 lipoplex was delivered intraarticularly in the murine collagen‐induced arthritis model. Clinical, histologic, and structural effects were studied over the course of arthritis. In‐depth studies of the mechanisms of action of miR‐17 were performed in primary RA fibroblast‐like synoviocytes (FLS) isolated from synovial tissue. Results Fifty‐five miRNAs including miR‐17 were reduced in erosive RA. The miR‐17 transfection into arthritic paws reduced the clinical inflammation score between day 2 and day 7 (2.8 versus 1.9; P = 0.03). Synovial B cell, T cell, macrophage, and polynuclear neutrophil infiltration was significantly reduced. Structural damage was also decreased, as shown by a reduction in the number of osteoclasts detected using tartrate‐resistant acid phosphatase staining (osteoclast surface/bone surface 32% versus 18%; P = 0.005) and erosion score by computed tomography analysis (2.9 versus 1.7; P = 0.023). Proinflammatory cytokines from the interleukin‐6 (IL‐6) family and IL‐1β expression were also significantly reduced, but tumor necrosis factor was not. MicroRNA‐17 directly targeted the 3′‐untranslated regions of STAT3 and JAK1. STAT3 and JAK1 messenger RNA (mRNA) and protein expression were reduced in RA FLS following miR‐17 transfection. STAT3 and JAK1 mRNA and activation of STAT3, as assessed by immunohistochemistry, were also reduced in injected paws (% stained area 93% versus 62%; P = 0.035). Conclusion We demonstrate an antiinflammatory and antierosive role of miR‐17 in vivo. This effect involves the suppression of the IL‐6 family autocrine‐amplifying loop through the direct targeting of JAK1 and STAT3.

Background:micro-RNAs (miR) are strong regulators of gene expression. Their involvement in RA key cytokines pathway regulation entitles them as important players in RA pathophysiology. The miR 17-92 cluster has been widely studied in cancer as they regulate cell apoptosis.Objectives:The aims of this study were to screen miR 17-92 cluster’s expression in different RA phenotypes (erosive and non erosive), further elucidate the mechanisms and direct targets involved in miR-17-5p anti-inflammatory role and to investigate miR-17-5p therapeutic effect in arthritis.Methods:A miR array was performed in synovial tissue from naïve erosive and non-erosive RA patients. Intra-articular delivery of miR-17 lipoplex was performed in collagen induced arthritis model in mice. Clinical, histological and structural effects were studied over the course of arthritis. In depth studies of miR-17 mechanisms of action were performed in primary RA-FLS isolated from RA synovial tissue.Results:Among others, miR-17-5p expression was reduced in erosive RA. miR-17 transfection in arthritic paws significantly reduced clinical inflammation. Moreover, synovial B cells, T cells, macrophages and polynuclear neutrophils infiltrates were significantly reduced. Structural damage was also decreased as shown by a reduction in the number of osteoclasts and erosion score by CT analysis. Pro-inflammatory cytokines of the IL-6 family, STAT3 target genes and IL-1β expression were also significantly reduced, but not TNF-alpha. miR17 directly targeted the 3’-untranslated region of STAT3 and JAK1. STAT3 and JAK1 mRNA and protein expression were reduced in RA-FLS following miR-17 transfection. STAT3 and JAK1 mRNA and activation of STAT3 as assessed by immunohistochemistry were also reduced in injected paws.Conclusion:We demonstrate an anti-inflammatory and anti-erosive role of miR-17 in vivo. This effect involves the suppression of the IL-6 family autocrine amplifying loop through the direct targeting of JAK1 and STAT3 as shown in RA-FLS.FigureEffect of miR-17 lipoplex injection in Collagen induced arthritis (CIA) mice’s ankles.Disclosure of Interests:None declared