Figure 1.

Initiation of OA and RA cellular pathways in early-stage disease. Immunological signals propagate as the disease progresses to all components of the joint organ system. The key cytokine pathways targeted in current OA and RA therapies primarily include TNF, IL-1, and IL-6, although other cytokines (e.g., IL-17) are now being targeted as well. Abbreviations: TCR: Toll-like receptor; MHC: Major Histocompatibility Complex; MMP: Matrix metallopeptidase; ADAMTS: A disintegrin and metalloproteinase with a thrombospondin type; TNF: Tumor necrosis factor; CCL2: C-C Motif Chemokine Ligand 2; VEGF: Vascular endothelial growth factor; BMP: Bone morphogenetic proteins; SASP: senescence-associated secretory phenotype; RANKL: Receptor activator of nuclear factor kappa-B ligand