BACKGROUND Cartilage surface contact geometry influences the deformational behavior and stress distribution throughout the extracellular matrix (ECM) under load. OBJECTIVE To test the correlation between the mechanical and cellular response of articular cartilage when loaded with two different-sized spherical indenters under dynamic reciprocating sliding motion. METHODS Articular cartilage explants were subjected to a reciprocating sliding load using a 17.6 mm or 30.2 mm spherical ball for 2000 cycles at 10 mm/s and 4 kg axial load. Deformation of the cartilage was recorded and contact parameters were calculated according to Hertzian theory. After mechanical loading cartilage samples were collected and analyzed for ECM collagen damage, gene regulation and proteoglycan (PG) loss. RESULTS Significantly higher ECM deformation and strain and lower dynamic effective modulus were found for explants loaded with the smaller diameter indenter whereas contact radius and stress remained unaffected. Also, the 17.6 mm indenter increased PG loss and significantly upregulated genes for ECM proteins and enzymes as compared to the 30.2 mm indenter. CONCLUSION Sliding loads that increase ECM deformation/strain were found to induce enzyme-mediated catabolic processes in articular cartilage explants. These observations provide further understanding of how changes in cartilage contact mechanics under dynamic conditions can affect the cellular response.

中文翻译：

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使用两个不同尺寸的球形压头对滑动载荷的关节软骨反应1。

背景技术软骨表面接触几何形状在载荷下影响整个细胞外基质（ECM）的变形行为和应力分布。目的研究在动态往复滑动运动下加载两个不同尺寸的球形压头时关节软骨的力学反应与细胞反应之间的相关性。方法使用17.6 mm或30.2 mm球形球以10 mm / s和4 kg轴向载荷对关节软骨外植体施加往复滑动载荷2000次。记录软骨的变形并根据赫兹理论（Hertzian theory）计算接触参数。机械加载软骨样品后，收集并分析ECM胶原蛋白损伤，基因调控和蛋白聚糖（PG）丢失。结果发现，带有较小直径压头的外植体的ECM变形和应变显着较高，而动态有效模量较低，而接触半径和应力却不受影响。此外，与30.2毫米压头相比，17.6毫米压头增加了PG损失，并显着上调了ECM蛋白和酶的基因。结论发现增加ECM变形/应变的滑动载荷可诱导关节软骨外植体中酶介导的分解代谢过程。这些观察结果进一步了解了在动态条件下软骨接触力学的变化如何影响细胞反应。与30.2毫米压头相比，6毫米压头增加了PG损失，并显着上调了ECM蛋白和酶的基因。结论发现增加ECM变形/应变的滑动载荷可诱导关节软骨外植体中酶介导的分解代谢过程。这些观察结果进一步了解了在动态条件下软骨接触力学的变化如何影响细胞反应。与30.2毫米压头相比，6毫米压头增加了PG的损失，并显着上调了ECM蛋白和酶的基因。结论发现增加ECM变形/应变的滑动载荷可诱导关节软骨外植体中酶介导的分解代谢过程。这些观察结果进一步了解了在动态条件下软骨接触力学的变化如何影响细胞反应。