The effect of anti-IL-6 receptor antibody for the treatment of McH-lpr/lpr-RA1 mice that spontaneously developed ankylosing arthritis

Abstract[Background]McH-lpr/lpr-RA1 mice are a new strain of mice which spontaneously develop arthritis in the ankle, leading finally to ankylosis. There is no published data that drug treatment has been trialed on these mice.[Objectives]This study examined the effect of the mouse anti-IL-6 receptor antibody, MR16-1, for the treatment of ankylosis in McH-lpr/lpr-RA1 mice.[Methods]Male McH-lpr/lpr-RA1 mice were randomly divided into control and treatment groups. MR16-1 was administered from 10 weeks of age for the treatment group. Saline was applied for the control group. The drug was administered once a week, at an initial dose of 2 mg, then maintained at 0.5 mg once per week thereafter. The effects were evaluated by the histopathological synovitis score, in vivo imaging using indocyanine green liposomes, and analysis of the gene expression of inflammatory cytokines.[Results]Tissue analyses were carried out at 14, 17 and 20 weeks of age. The synovitis scores of treated groups were significantly lower compared with those of the control group at every age. The kappa coefficient was 0.77. However, progression of ankylosis persisted in the MR16-1 treated group. In vivo imaging using indocyanine green liposomes showed significant decreases in signal intensities of treated groups at week 14, but no significant differences were observed at week 18. Blood serum amyloid A levels in treated groups were significantly lower at 17 weeks of age. The gene expression levels of Tnf and Il17 were also significantly lower in MR16-1 treated groups.[Conclusions]Administration of the anti-IL-6 receptor antibody is effective for the treatment of synovitis and bone destruction of McH-lpr/lpr-RA1 mice. McH-lpr/lpr-RA1 mice may be a suitable experimental model for the development of new treatments for spondyloarthritis. IL6 signal blockade could contribute to the treatment of spondyloarthritis, and further studies should be carried out to confirm its potential in the prevention of deformity associated with ankylosis.