MMP9 and rheumatoid arthritis: The peripheral blood mononuclear cells (PBMCs) were isolated from blood samples of patients with rheumatoid arthritis, and various factors levels, including nitric oxide, tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-10, total antioxidative capacity (TAC), superoxide dismutase (SOD), glutathione peroxidase (GPx), as well as the expression levels of TIMP1, MMP9, and RANKL genes were evaluated.