SAT0057 INCREASED MICRORNA-155 IS ASSOCIATED WITH A SPECIFIC DEFECT OF ANTI-INFLAMMATORY M2 MACROPHAGES POLARIZATION BOTH IN HUMAN RHEUMATOID ARTHRITIS AND IN COLLAGEN-INDUCED-ARTHRITIS MICE
Authors: Audrey Paoletti, Franceline Reynaud, Julien Rohmer, Juliette Pascaud, Bineta Ly, Elodie Rivière, Nicolas Tsapis, Elias Fattal, Gaetane Nocturne, Xavier Mariette
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Monocytes/macrophages are key players in the pathogenesis of Rheumatoid arthritis (RA). Monocytes can differentiate into pro-inflammatory macrophages (M1-like) or into anti-inflammatory. macrophages (M2-like) We previously found a defect of monocytes polarization into M2-like macrophages, in RA patients and not in healthy donors (HD) or in patients with other inflammatory diseases (such as connective tissue diseases or spondyloarthritis), and a propensity for preferential maturation towards M1-like pro-inflammatory macrophages that could contribute to synovial inflammation. MiR-155 expression has been shown elevated in RA synovial macrophages and in blood monocytes. MiR-155 inhibits mRNA of 2 important proteins involved in programming of M2 macrophages (SOCS-1 and C/EBP-β). <h3>Objectives:</h3> We assessed if miR-155 could play a role in the defect of monocytes polarization into M2-like macrophages both in human RA and in a mouse model of collagen-induced-arthritis (CIA) mice. <h3>Methods:</h3> Monocytes were isolated from PBMCs for HD and RA by negative selection. Purified monocytes were transfected using <b>AMAXA technologies</b> with miR-155 mimic (for HD) or antagomiR155 (for RA) or controls miRs. Then monocytes were incubated in the presence of human serum (SAB) (M2-like) for 6 days. Expressions of total macrophages markers (<b>CD11b</b> and <b>CD71</b>), M2-like macrophage markers (<b>CD163</b>, <b>CD206</b> and <b>Arg-1</b>), M1-like macrophage marker (<b>iNOS</b>) were evaluated by flow cytometry, ELISA or immunofluorescence. DBA/1 mice were immunized by intradermal injection at day-0 and at day-21 with a grade chick type II collagen and complexe Freund's adjuvant. Monitoring of arthritis indices was done from day-25 to day-35. At day-35, monocytes were isolated from bone marrow by negative selection. To generate MDMs, purified monocytes were incubated 6 days in the presence of M-CSF+IL-4 (M2-like). Expressions of total macrophages markers (<b>CD11b</b> and <b>F4/80</b>), M2-like macrophage polarization markers (<b>CD206</b>,<b> IL-10</b> and <b>Arg-1</b>) were evaluated by flow cytometry, ELISA or qPCR. <h3>Results:</h3> Overexpression of miR-155 in HD monocytes significantly decreased the gMFI of the pan-macrophages markers, CD11b and CD71, but also the M2-like markers, CD206 and CD163 after 6 days of culture with human SAB. Likewise, we demonstrated a significant reduction of Arg-1 expression and increase in iNOS expression in M2-like macrophages after miR-155 transfection of HD monocytes <b>(Fig. 1A).</b> Conversely, <i>ex vivo</i> silencing of miR-155 with antagomir in RA monocytes restored the defect of M2-like phenotype macrophages by increasing the percentage of pan-macrophages markers, CD11b and CD71 and M2-like macrophages markers CD206 and CD163 after a 6-day culture in human SAB. Moreover, miR-155 antagomir increased significantly the Arg-1 expression and reduced iNOS expression in M2-like macrophages<b> (Fig. 1B).</b> The defect of monocytes capacity of differentiation into M2-like phenotype was also found in in CIA mice as compared to controls, with a decreased expression of CD206, IL-10 secretion and Arginase-1 expression<b> (Fig. 1C).</b> MiR155 was also involved in this defect in mice: its expression level was the same in M1-like macrophages between controls and CIA mice, whereas it was increased in M2-like CIA macrophages compared to controls mice <b>(Fig. 1C).</b> <h3>Conclusion:</h3> MiR155 plays a key role in the specific defect of anti-inflammatory M2 macrophages polarization found both in human rheumatoid arthritis and in CIA mice. MiR155 could represent a new therapeutic target in RA that can be tested in the mouse model of CIA. <h3>Disclosure of Interests:</h3> Audrey Paoletti: None declared, franceline reynaud: None declared, julien rohmer: None declared, Juliette Pascaud: None declared, Bineta Ly: None declared, Elodie Rivière: None declared, Nicolas Tsapis: None declared, Elias Fattal: None declared, Gaetane Nocturne: None declared, Xavier Mariette Grant/research support from: Servier, Consultant for: AstraZeneca, Bristol-Myers Squibb, GlaxoSmithKline, Janssen, Pfizer, UCB Pharma