FIGURE 1.

The secretion of cytokines in OA disease. This joint disorder consist of the secretion of cytokines by the cartilage, bone, and synovial membrane. IL-1β, IL-6, and TNF cytokines are produced by macrophages, T cells, chondrocytes, and osteophytes in response to damaged tissue. The released Pro-MMPs by macrophages and synoviocytes, undergo cleavage and turn into functional MMPs contributing to tissue injury. TNF, IL-6, and IL-1β enter the bloodstream, making OA as a systemic disorder. B and T cells in the synovial fluid are engaged by the cytokine milieu and contribute to local synovitis. Furthermore, some cytokines, primarily RANKL and IL-6, are released by bone cells (Chevalier et al., 2013).