Synovial angiostatic non-ELR CXC chemokines in inflammatory arthritides: does CXCL4 designate chronicity of synovitis?

In our previous studies, we found higher synovial fluid (SF) levels of angiogenic ELR(+) CXC chemokines such as CXCL1, CXCL5, CXCL6 and CXCL8, which play an important role in neutrophil migration and angiogenesis, and more abundant synovial CXCR2 chemokine receptor expression in patients with rheumatoid arthritis (RA) than those with Behçet’s disease (BD), familial Mediterranean fever and osteoarthritis (OA). As a continuation of our previous studies, we investigated synovial levels of angiostatic non-ELR CXC chemokines (CXCL4, CXCL9 and CXCL10) in patients with RA, BD, spondyloarthritis (SpA), and OA. Seventy (17 RA, 15 BD, 19 SpA, and 19 OA) patients were enrolled in the study. The levels of CXCL4, CXCL9, and CXCL10 were measured by ELISA. The SF levels of CXCL4 in patients with RA were higher than those of the patients with BD, SpA, and OA (P = 0.007, P = 0.022, and P = 0.017, respectively). No difference was found with respect to CXCL4 levels among the BD, SpA, and OA patients. The synovial CXCL9 levels of patients with RA and SpA were found to be higher than those of the patients with OA (P = 0.002 and P = 0.005, respectively), while no statistically significant difference was detected among the other groups. With regard to SF CXCL10 levels, patients with RA had higher levels as compared to patients with OA (P = 0.002), but no significant difference was found among the other groups. CXCL9 correlated with CXCL4 and CXCL10 (P < 0.05 for both) in patients with RA. No correlation was found in other parameters. The angiostatic non-ELR CXC chemokines were expressed in synovial inflammation. We proposed that angiostatic non-ELR CXC chemokines may increase to balance angiogenic ELR (+) CXC chemokines in which increased levels were shown in patients with inflammatory arthritides and CXCL4 may contribute to designate the chronicity of synovitis in patients with RA. In addition, as CXCL-9 and CXCL-10 play crucial role in inflammation characterized by Th1 polarization, we suggested that they may contribute to the commencement and the perpetuation of synovitis seen in these groups of arthritides.