関節軟骨水和層の構造と潤滑特性

抄録

On the articular cartilage surface, proteoglycan molecules protruding from cartilage surface form hydration layer. The hydration layer contributes to excellent lubrication property of articular cartilage, but its detailed mechanism has not been clarified yet. In this study, to elucidate the lubrication mechanism of the hydration layer, we investigated structural and lubrication properties of the hydration layer. Cartilage specimens were harvested in a cylindrical shape from the load-bearing area of the distal femur of immature porcine knee. In addition to intact cartilage samples, rubbed cartilage samples were prepared in which the hydration layer of the samples was removed by rubbing against a flat glass plate with a friction distance of 16 m or 60 m. Surface morphology of cartilage samples was observed by an amplitude-modulation atomic force microscope, and cross-sectional imaging of hydration layer was conducted using a frequency-modulation atomic force microscope. Friction test was performed for the cartilage samples against an alumina ceramic ball of 3 mm in diameter with a friction speed of 0.5, 1.0 and 5.0 mm/s. Surface morphology revealed that the hydration layer was removed with 60 m rubbed cartilage. Cross-sectional imaging revealed that the hydration layer with a thickness of approximately 6 μm was confirmed on intact cartilage surface. Coefficient of dynamic friction of intact cartilage was lower than that of 60 m rubbed cartilage, and coefficient of dynamic friction of intact cartilage tended to decrease with increasing friction speed. These findings suggested that the hydration layer contributes to improvement of lubrication properties of articular cartilage.