TNF and osteoarthritis: The secreted IL-6 and TNF-α increase the expression of MMPs and theamounts of NO, which in turn induce the loss of extracellular matrix andchondrocyte.21,22 LPS, also known as endotoxin, contributes to low-gradeinflammation including the pathogenesis of osteoarthritis.23 LPS has been considered as a major hidden risk of osteoarthritis.24 In this study, LPS was used to mimic an in vitro model of osteoarthritis inATDC5 cells.