Proinflammatory cytokines and chemokine production and expression by human osteoblasts isolated from patients with rheumatoid arthritis and osteoarthritis

Objective. To evaluate whether subchondral osteoblasts (OB) are involved in the production of cytokines and chemokines in rheumatic diseases. Methods. OB were isolated from subchondral bone of rheumatoid arthritis (RA), osteoarthritis (OA) and post-traumatic (PT) patients, cultured in vitro in the presence or absence of interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α), and assessed for the production, immunolocalization, and mRNA expression of proinflammatory cytokines (IL-1α, IL-1β, TNF-α) and α and β chemokines [IL-8, growth related gene product (GRO-α), monocyte chemoattractant protein 1 (MCP-1), RANTES, and macrophage inflammatory proteins MIP-1α, MIP-1B]. Results. Cultured OB from different patients did not release IL-1α, IL-1β, or TNF-α, and constitutively secreted IL-8, GRO- α, and MCP-1, while RANTES, MIP-1α, MIP-1β were undetectable or near the lower level of sensitivity of the immunoenzymatic assay. GRO-α was significantly higher in RA than in OA and PT patients. IL-1β and TNF-α alone or in combination strongly stimulated chemokine release by OB. Only RANTES production was not increased by the combination of the 2 cytokines. IL-1α, IL-1β, and TNF-α were expressed as cytoplasmic proteins and were not secreted by OB even after stimulation. Conclusion. OB from subchondral bone release chemokines that could be involved in the mechanisms that directly or indirectly cause bone remodelling and cartilage destruction.