Micro- and Nano-Scopic Biomechanics of Articular Cartilage Focusing Chondrocytes and Surrounding Tissue

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The increase of elder persons disabled with walking ability due to osteoarthritis, rheumatoid arthritis or damages of natural synovial joints is anticipated with progress of population of aged people particularly in Japan. In natural synovial joint, the articular cartilage plays important roles in load-carrying mechanism and lubrication mechanism. The initiation of osteoarthritis is considered to be brought about by the deficiency of lubricating ability in synovial joints and loss of load-carrying capacity of articular cartilage. The articular cartilage is composed of extracellular matrix (ECM) and chondrocyte. The object of this research is to elucidate the stress-strain behaviors of articular cartilage including chondrocytes and the adaptive multimode lubrication mechanism in natural synovial joints from the macro-, micro- and nanoscopic viewpoints, to prevent the progress of osteoarthritis and to improve the function in regenerated cartilage.The confocal laser scanning microscopy (C … More LSM) was used to estimate the local strain of articular cartilage under compression by observing the fluorescent images of stained chondrocytes. The time-dependent and depth-dependent strain behaviors of articular cartilage were investigated by CLSM. These mechanical behaviors were evaluated by the biphasic finite element method (FEM). These stress-strain behaviors have an influence on metabolism controlled by chondrocytes which is expected to produce surrounding ECM including proteoglycan and collagen. The depth-dependent profile deformation and time-dependent strain behavior of semi-cylindrical cartilage specimen was simulated by biphasic finite element analyses considering depth-depending elastic modulus. The correspondence to the peak compressive stress and following stress relaxation immediately after compression at high strain rate was attained by consideration of one order raising of elastic modulus or by introducing of spring element like collagen fiber to biphasic model. Furthermore, the effect of cyclic compressive stimulation on cultured chondrocytes was indicated by an increase in elastic modulus of chondrocyte-agarose construct. Less