Osteoarthritis of the TMJ and Mechanical Stress

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Excessive mechanical stress has been proposed as a cause breakdown of the articular cartilage. To investigate the effect of mechanical stress on chondrocyte metabolism, we examined the extracellular matrix synthesis and the gene expression of cartilage degradation factors and growth factors.1.15 kPa cyclic mechanical stress (CTF) caused less increase in proteoglycan (PG) synthesis than 5 kPa (230.3 and 179.1% increase at 5 and 15 kPa)2.5 kPa of CTF caused more decrease in DNA synthesis (50.0 and 30.1% decrease, at 5 and 15 kPa).3.The mean normalized IL-1beta mRNA level against the corresponding control transiently increased during both level of CTF.4.The mean normalized bFGF mRNA level against the corresponding control transiently increased during 15 kPa of CTF,while remarkable change was not observed at 5 kPa of CTF.5.The mean normalized MMP-9 mRNA level against the corresponding control progressively increased during 15 kPa of CTF,while the transient increase was observed during 5 kPa of CTF.6.Mean normalized MMP-2, TIMP-1, agrecan, collagen type II and type X mRNA level against the control did not show remarkable change at the both level of CTF.7.When 15 kPa of CTF was applied, the production level of pro-MMP-9 did not change, but the level of active form MMP-9 was slightly increased, while 5 kPa of CTF was applied, the production level of pro-MMP-9 did not show remarkable change and it was not activated to active form MMP-9. Both level of CTF did not change the production of MMP-2.