Adaptive mechanically controlled lubrication mechanism found in articular joints
Adaptive mechanically controlled lubrication mechanism found in articular joints
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DOI：
10.1073/pnas.1101002108
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发表时间：
2011-03-29
影响因子：
11.1
通讯作者：
Israelachvili, Jacob N.
中科院分区：
文献类型：
--
作者：
Greene, George W.;Banquy, Xavier;Israelachvili, Jacob N.
关节软骨是一种高效的水基摩擦学系统，经过优化，可在低负载和高负载（压力）以及滑动速度下提供低摩擦和磨损保护，且必须持续终生。尽管已经提出了许多不同的润滑机制，但越来越明显的是，软骨的摩擦学性能不能归因于单独作用的单一机制，而是归因于多种润滑“模式”的协同作用，这些“模式”适合在法向载荷、剪切应力和速率变化时提供最佳润滑。透明质酸（HA）在软骨和滑液中含量丰富，被广泛认为在关节润滑中发挥着主要作用，尽管这一作用仍不清楚。众所周知，HA 很容易与糖蛋白润滑素 (LUB) 复合，形成交联网络，这也被证明对关节的磨损预防机制至关重要。使用表面力装置和酶消化对猪软骨进行的摩擦实验揭示了 HA-LUB 复合物的“适应性”作用，其中在压缩下，名义上游离的 HA 扩散出软骨，变得机械地（即物理地）被日益收缩的胶原蛋白孔网络捕获在界面处。机械捕获的 HA-LUB 复合物现在充当有效的（化学结合的）“边界润滑剂”，略微降低摩擦力，但更重要的是消除摩擦/剪切表面的磨损损坏。本文重点讨论HA在软骨润滑方面的贡献；然而，系统作为一个整体需要 HA 和 LUB 在所有条件下都能以最佳状态运行。
Articular cartilage is a highly efficacious water-based tribological system that is optimized to provide low friction and wear protection at both low and high loads (pressures) and sliding velocities that must last over a lifetime. Although many different lubrication mechanisms have been proposed, it is becoming increasingly apparent that the tribological performance of cartilage cannot be attributed to a single mechanism acting alone but on the synergistic action of multiple "modes" of lubrication that are adapted to provide optimum lubrication as the normal loads, shear stresses, and rates change. Hyaluronic acid (HA) is abundant in cartilage and synovial fluid and widely thought to play a principal role in joint lubrication although this role remains unclear. HA is also known to complex readily with the glycoprotein lubricin (LUB) to form a cross-linked network that has also been shown to be critical to the wear prevention mechanism of joints. Friction experiments on porcine cartilage using the surface forces apparatus, and enzymatic digestion, reveal an "adaptive" role for an HA-LUB complex whereby, under compression, nominally free HA diffusing out of the cartilage becomes mechanically, i.e., physically, trapped at the interface by the increasingly constricted collagen pore network. The mechanically trapped HA-LUB complex now acts as an effective (chemically bound) "boundary lubricant"-reducing the friction force slightly but, more importantly, eliminating wear damage to the rubbing/shearing surfaces. This paper focuses on the contribution of HA in cartilage lubrication; however, the system as a whole requires both HA and LUB to function optimally under all conditions.