Basser P J, Schneiderman R, Bank R A, Wachtel E, Maroudas A
Julius Silver Institute of Biomedical Sciences, Department of Biomedical Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel.
Arch Biochem Biophys. 1998 Mar 15;351(2):207-19. doi: 10.1006/abbi.1997.0507.
We have used an isotropic osmotic stress technique to assess the swelling pressures of human articular cartilage over a wide range of hydrations in order to determine from these measurements, for the first time, the tensile stress in the collagen network, Pc, as a function of hydration. Osmotic stress was applied by means of calibrated solutions of polyethylene glycol. Calculations of osmotic stress were based on the balance, at equilibrium, between the applied stress, the collagen stress, and the proteoglycan osmotic pressure, piPG, acting within the extrafibrillar matrix compartment. Pc vs hydration was determined for several normal human samples, both native and trypsin-treated, and for cartilage from one osteoarthritic (OA) joint. We found that for normal cartilage the collagen network does not become "limp" until the volume of cartilage has decreased by 20-25% of its initial value and that its contribution to the balance of forces in cartilage therefore must be taken into account over a much wider range of hydrations than was previously thought. For normal cartilage, the Pc vs hydration curves exhibit a steep increase with increasing hydration; trypsin treatment does not change their slope, showing that PG concentration does not influence the inherent stiffness of the collagen network. By contrast, the curves for OA specimens are considerably shallower and displaced to higher hydrations. Our findings thus highlight the role of the stiffness of the collagen network in limiting hydration in normal cartilage and ensuring a high PG concentration in the matrix, which is essential for effective load-bearing and is lost in OA.
我们采用了各向同性渗透应激技术，在广泛的水合范围内评估人体关节软骨的肿胀压力，以便首次从这些测量中确定胶原网络中的拉伸应力Pc与水合作用的关系。通过聚乙二醇校准溶液施加渗透应激。渗透应激的计算基于在平衡状态下，施加的应力、胶原应力和在纤维外基质隔室中起作用的蛋白聚糖渗透压πPG之间的平衡。测定了几个正常人体样本（包括天然样本和胰蛋白酶处理样本）以及一个骨关节炎（OA）关节软骨的Pc与水合作用关系。我们发现，对于正常软骨，直到软骨体积减少其初始值的20 - 25%，胶原网络才会变得“松弛”，因此在比以前认为的更广泛的水合范围内，必须考虑其对软骨中力平衡的贡献。对于正常软骨，Pc与水合作用曲线随水合作用增加呈现陡峭上升；胰蛋白酶处理不会改变其斜率，表明蛋白聚糖浓度不会影响胶原网络的固有刚度。相比之下，OA样本的曲线要平缓得多，且向更高水合方向偏移。因此，我们的研究结果突出了胶原网络刚度在限制正常软骨水合以及确保基质中高浓度蛋白聚糖方面的作用，这对于有效承载负荷至关重要，而在OA中则会丧失这种作用。
