Synovial fibroblasts spread rheumatoid arthritis to unaffected joints

Abstract

Rheumatoid arthritis usually begins in one joint but spreads to other joints as the disease progresses. Elena Neumann and her colleagues show that rheumatoid arthritis synovial fibroblasts (RASFs) may be key mediators of this process. They show, using a SCID mouse model, that human RASFs can migrate long distances through the bloodstream from diseased cartilage to unaffected cartilage, where they can mount a new attack. Active rheumatoid arthritis originates from few joints but subsequently affects the majority of joints. Thus far, the pathways of the progression of the disease are largely unknown. As rheumatoid arthritis synovial fibroblasts (RASFs) which can be found in RA synovium are key players in joint destruction and are able to migrate in vitro, we evaluated the potential of RASFs to spread the disease in vivo. To simulate the primary joint of origin, we implanted healthy human cartilage together with RASFs subcutaneously into severe combined immunodeficient (SCID) mice. At the contralateral flank, we implanted healthy cartilage without cells. RASFs showed an active movement to the naive cartilage via the vasculature independent of the site of application of RASFs into the SCID mouse, leading to a marked destruction of the target cartilage. These findings support the hypothesis that the characteristic clinical phenomenon of destructive arthritis spreading between joints is mediated, at least in part, by the transmigration of activated RASFs.