Objective      To determine the effect of titanium (Ti) particles

and cytokines TNF-α and IL-1β on the expression and activity of MMP-2 in human synovial cells so as to explore the probable mechanism of post-operative osteolysis of metal-on-metal total joint arthroplasty in human synovial cells induced by Ti particles.       Methods      Human synovial cells were freshly isolated and cultured from normal knee joint synovium

and then those at passage 4 were treated with Ti particles in size of ≥10

5-10

and ≤5 μm respectively for 12

24

48 or 72 h. TNF-α

and IL-1β at different doses were used to treat the cells in presence

or absence of Ti particles for above time periods. Gelatin zymography was performed to detect the activity of MMP-2 in the cell supernatant.       Results      Compared with the cells without any treatment

the expression level of MMP-2 treated by Ti particles in size of ≤5 μm was significantly increased by 4 times

that treated by Ti particles

TNF-α

and IL-1β respectively or combined of any 2 agents were also increased significantly (

P

0.01)

and that treated by the combination of the 3 agents were most significantly higher (P0.01). Ti particles

TNF-α

and IL-1β induced the stimulation of MMP-2 activities in human knee joint synovial cells

and exerted synergetic effect.       Conclusion      Synovial cells may be involved in aseptic loosening after metal-on-metal arthroplasty through increasing the degradation of bone matrix and declining of osseous support structure mechanics.