Release of inflammatory cytokines by macrophages and synovial cells challenged with tumor necrosis factor

Late aseptic loosening of total joint implants continues to be a common cause of implant failure. However, the pathophysiology of implant loosening remains controversial as to which factors at the implant tissue interface plays a crucial role in implant failure. The most prominent features of the foreign body membrane obtained from patients undergoing revision hip surgery were the presence of lymphocytes, histiocytes, giant cells, and immature collagen formation. The inflammatory sites are often characterized by the infiltration of activated lymphocytes and macrophages into the synovial membrane followed by proliferation of the synovial cells. The present study was conducted to determine if synovial cells in addition to macrophage cells are activated by tumor necrosis factor (TNF), which ultimately leads to foreign body membrane proliferation and ultimately joint space destruction. Macrophages or synovial cells were seeded at a density of 1 x 10(6) cells/ml and 5 ml were placed onto a 12 mm culture dish. The cells were challenged with either tissue culture media or media containing 2 ng/ml LPS or various doses of TNF (0.5, 5 and 50 ng/ml). The result indicated that both cell types were able to produce the inflammatory cytokines (IL-1 and IL-8 as early as 8 hours after a challenge with peak production occurring between 18-24 hours). The data suggest that both cell types are capable of eliciting inflammatory mediators, which can ultimately lead to joint destruction.