Infliximab prevents systemic bone loss and suppresses tendon inflammation in a collagen-induced arthritis rat model

Reduced Bone Mineral Density (BMD) and tendon abnormalities, such as tenosynovitis and enthesitis, are prevalent comorbidities in patients with rheumatoid arthritis (RA). The aim of the present study was to investigate the effect of chronic treatment with infliximab on BMD and tendon inflammation in an animal model of inflammatory arthritis. Collagen-Induced Arthritis (CIA) was induced in rats, followed by long-term intraperitoneal administration of infliximab. Two additional groups of animals received methotrexate either as a monotherapy or as a co-treatment to infliximab. BMD was evaluated by Micro-Computed Tomography (Micro-CT) and bone histological examination. Tendon inflammation was assessed histologically and by quantitative ELISA analysis of pro-inflammatory cytokines in tendon tissues. Both methotrexate and infliximab treatment alleviated joint inflammation and reduced paw edema. Infliximab-treated animals exhibited an improved trabecular microarchitecture on micro-CT and histological analysis compared to both non-treated and methotrexate-treated animals. Infliximab almost reversed the pathological changes in tendons induced by CIA. Finally, we observed statistically significant declines in tendon TNF-a and IL-23 levels after infliximab treatment. Our study provides evidence that infliximab prevents arthritis-related osteoporosis and suppresses tendon inflammation in an animal model of inflammatory arthritis, in addition to controlling disease activity. These findings offer perspectives for the management of osteoporosis and enthesitis in RA.