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Fig. 1 | Arthritis Research & Therapy

Fig. 1

From: S100A8/A9 increases the mobilization of pro-inflammatory Ly6Chigh monocytes to the synovium during experimental osteoarthritis

Fig. 1

S100A8/A9 mRNA and protein expression is strongly increased in the synovium at day 7 of collagenase-induced osteoarthritis (CiOA), leading to elevated Ly6Chigh monocytes locally into the joint. a Monocytes are strongly infiltrated during early CiOA as shown by highly expressed Ly6C protein staining and based on cell morphology in the synovial lining layer of the knee joints at CiOA day 7. b IgG control staining for the Ly6C antibody of the same joint shows no aspecific staining. c S100A9 protein is expressed in synovial monocytes at CiOA day 7 as shown by immuno-localization. d IgG control staining for the S100A9 antibody of the same joint shows no aspecific staining. e S100A8 and S100A9 mRNA expression is strongly induced in the synovium at CiOA day 7 when compared to saline-injected controls. f, g Monocyte marker Ly6C, and the more monocyte-subset-specific markers, CCR2 (Ly6Chigh) and CX3CR1 (Ly6Clow) are strongly induced (f), together with the monocyte attracting chemokines CCL2 (Ly6Chigh) and CX3CL1 (Ly6Clow) (g) in synovium at CiOA day 7, when compared to saline-injected controls. h Monocyte gating strategy for flow cytometric analysis: single viable cells were plotted for B220/CD90/CD49b/NK1.1/Ly6G and CD11b, in which myeloid cells were selected, and next the monocyte subsets could be identified based on their F4/80/MHCII/CD11c and Ly6C expression. i The relative number of Ly6Chigh monocytes were increased, whereas Ly6Clow monocyte subpopulations remained unaffected locally in the joint at CiOA day 7 compared to saline-injected controls, as observed using flow cytometry. Data represent mean ± SD of five individual mice. *Significantly different from saline-injected control (**p < 0.01, ***p < 0.001). Ct cycle threshold

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