Elucidation of condylar cartilage resorption mechanism in TMJ-osteoarthritis and search of a new regulatory factor

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The TMJ- osteoarthritis (OA) of the condylar cartilage absorption with movement disorder and dysfunction is one of the disease that are difficult for treatment in dental field Excessive mechanical loading to be added to the condyle as the muse is thought about with key factor of onset of OA On the other hand, it is speculated that the cartilage destruction is induced by an unknown new factor in synergy with a mechanical loading, bemuse there is the case that OA progress in a normal physiological condition. Mandibular condyle is composed of several different zone, as superficial zone from surface, cartilaginous layer, subchondral bone and bone, each layer has a different function and respond to various mechanical irritation by jaw movement Superfical zone has a lubrication function to decrease the friction, and a bone underlying in the cartilaginous layer supports the above tissues rigidly. In order to elucidate an inducing mechanism of metabolic abnormality in each layer it is importan … More t for clarifying the mechanisms of condylar cartilage destruction. We confirmed the expression of superficial zone protein which had boundary lubrication function in superficial zone of condylar cartilage in 1118 year and clarified the expression level was regulated selectively by cytokine and the magnitude of mechanical loading. In this study, we particularly focused on the downward layer (subchondral bone), and investigated the influences of subchondral bone damaged with excessive mechanical loading on the metabolisim of condylar cartilage. As a result of a 200 grams metal object was dropped to the mandibular condyle as a high magnitude impact loading, in particular, the expression of IL -1β was found in subchondral bone immunohistologically. Next, to investigate interactions between osteoblasts and chondrocytes, we used a co-culture system to culture osteoblasts monolayer together with chondrocytes in alginate beads. The mRNA expression of MMP-1, 3 and 13 in the chondrocytes by co-culture with mechanical stress-loaded osteoblasts showed increased, and the mRNA expression type II, X collagen and DNA, proteoglycan syntheses were decreased- From these results, the aggression to mandibular condyle head from the outside induce IL -1 β from subchondral bone. The results from the present study suggest that physical interactions between subchondral osteoblasts and articular chondrocytes could be responsible for the cartilage degradation in pathological changes of proceeding OA. Less