CXCL10 and its receptor CXCR3 regulate synovial fibroblast invasion in rheumatoid arthritis

Objective: CXCL10 is expressed in increased levels in highly invasive fibroblast-like synoviocytes (FLS) from arthritic DA rats and from patients with rheumatoid arthritis (RA). This study was undertaken to analyze the role of CXCL10 and its receptor CXCR3 in regulation of the invasive properties of FLS.

Methods: FLS were isolated from synovial tissue of RA patients and from DA rats and arthritis-resistant DA.F344(Cia5d) rats with pristane-induced arthritis. We used an in vitro model of invasion through Matrigel, which has been shown to correlate with articular damage in RA and in rat arthritis. FLS were cultured in the presence or absence of CXCL10, anti-CXCR3 antibody, or the CXCR3 Inhibitor AMG487 and then studied for invasion, matrix metalloproteinase (MMP) production (MMPs 1-3), intracellular calcium influx, and cell morphology.

Results: DA rat FLS produced higher levels of CXCL10 compared with minimally invasive FLS from DA.F344(Cia5d) rats. CXCL10 treatment increased the invasiveness of FLS from DA.F344(Cia5d) rats by 2-fold, and this increase was blocked by anti-CXCR3. Both anti-CXCR3 and AMG487 reduced invasiveness of FLS from DA rats, by as much as 77%. AMG487 significantly reduced invasiveness of RA FLS (by 58%). CXCR3 blockade reduced levels of MMP-1 by 65%, inhibited receptor signaling (64-100% reduction in intracellular calcium influx), and interfered with actin Cytoskeleton reorganization and lamellipodia formation in FLS from rats and RA patients.

Conclusion: We describe and characterize a new autocrine/paracrine role of CXCL10/CXCR3 in the regulation of FLS invasion in rats with arthritis and in RA patients. These observations suggest that the CXCL10/CXCR3 axis is a potential new target for therapies aimed at reducing FLS invasion and its associated joint damage and pannus invasion and destruction in RA.