Elucidation of Adaptive Multimode Lubrication Mechanism, Self-Organization and Restoration Mechanism in Natural Synovial Joints

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The object of this research is to elucidate the adaptive multimode lubrication mechanism in natural synovial joints in relation to the self-organization and restoration from the hierarchic and microscopic viewpoints, to prevent the progress of osteoarthritis and to improve the function in regenerated cartilage.The atomic force microscopy (AFM) was applied to observe the morphological changes in articular cartilage surfaces removed from knee joints with osteoarthritis and porcine cartilage at different friction levels during rubbing experiments. The corresponding force-distance curves were examined to estimate the mechanical properties. The confocal laser scanning microscopy (CLSM) was used to estimate the local strain of articular cartilage under compression by observing the fluorescent images of stained chondrocytes. The morphology and distribution of chondrocytes in articular cartilage were investigated by CLSM. Three-dimensional numerical analysis based on biphasic finite element me … More thod was conducted to examine the influence of compressive stimulation on chondrocyte in articular cartilage. Lubricating gel film composed of proteoglycan appears to protect the bulk cartilage and maintain low friction even under severe rubbing. The proteoglycan in gel film is supplied through production by chondrocyte. The changes in stress-strain around chondrocyte was examined, because appropriate stimulation to chondrocyte can give an influence on the production of proteoglycan. Another protective mechanism with low friction is given by adsorbed film formation on the rubbing surface. The tribological property of polyvinyl-alcohol (PVA) hydrogel specimen as artificial cartilage or a model of cartilage was examined in hyaluronate solution containing globular serum proteins. The appropriate constituents composed of albumin and γ-globulin resulted in lower wear and lower friction. The difference in adsorptional behavior was clearly confirmed with in situ observation of fluorescent images of proteins. The total internal reflection fluorescence microscopy (TIRFM) was successfully applied to observe adsorptional behavior of proteins. Less