SPP1 and Arthritis: Furthermore, in the conventional dendritic cells of an arthritis rodent model, integrin-α9β1 collaborates with TNC and OPN to induce secretion of IL-6 and IL-23 through both the NF-κB and MEK/ERK signalling pathways (Figure 2), which promotes the generation of pathogenic Th17 cells involved in osteoclast differentiation and bone destruction (119).