Bank R A, Soudry M, Maroudas A, Mizrahi J, TeKoppele J M
Gaubius Laboratory, Netherlands Organization for Applied Scientific Research Prevention and Health, Leiden.
Arthritis Rheum. 2000 Oct;43(10):2202-10. doi: 10.1002/1529-0131(200010)43:10<2202::AID-ANR7>3.0.CO;2-E.
To provide evidence for the hypothesis that the loss of tensile strength of osteoarthritic (OA) cartilage (resulting in swelling-the hallmark of OA) is due to an impaired collagen network and not to loss or degradation of proteoglycans.
The amount of degraded collagen molecules, the fixed charge density (FCD) on a dry-weight basis, the degree of swelling in saline, and the instantaneous deformation (ID; a test reflecting the tensile stiffness of the collagen network) were measured in full-depth OA femoral condyle samples. In addition, levels of the crosslink hydroxylysylpyridinoline (HP), the amount of degraded collagen molecules, and the degree of swelling were determined in the 3 zones (surface, middle, and deep) of OA cartilage. We also compared the ID of normal and OA cartilage.
In full-depth OA cartilage, a close relationship was found between swelling and ID. Swelling and ID correlated strongly with the amount of degraded collagen molecules, and were not related to FCD. OA cartilage showed the same zonal pattern in HP levels as normal cartilage (i.e., an increase with depth). No relationship was found between collagen crosslinking and swelling of the surface, middle, and deep zones. In all 3 zones, swelling was proportional to the amount of degraded collagen molecules. Compared with that of normal cartilage, the change in ID of OA cartilage was most pronounced at the surface in a direction parallel to the direction of the collagen fibrils.
The decreased stiffness of the OA collagen network (as measured by swelling and ID) is strongly related to the amount of degraded collagen molecules. The anisotropy in ID parallel and perpendicular to the direction of the fibrils revealed that the impairment of strength resides mainly in, and not between, the fibrils. Proteoglycans play only a minor role in the degeneration of the tensile stiffness of OA cartilage.
为以下假说提供证据，即骨关节炎（OA）软骨拉伸强度的丧失（导致肿胀——OA的标志）是由于胶原网络受损，而非蛋白聚糖的丢失或降解。
对全层OA股骨髁样本测量降解胶原分子的量、基于干重的固定电荷密度（FCD）、在盐水中的肿胀程度以及瞬时变形（ID；一种反映胶原网络拉伸刚度的测试）。此外，还测定了OA软骨3个区域（表层、中层和深层）的交联羟赖氨酸吡啶啉（HP）水平、降解胶原分子的量以及肿胀程度。我们还比较了正常软骨和OA软骨的ID。
在全层OA软骨中，发现肿胀与ID之间存在密切关系。肿胀和ID与降解胶原分子的量密切相关，与FCD无关。OA软骨的HP水平呈现出与正常软骨相同的区域模式（即随深度增加）。在表层、中层和深层区域，未发现胶原交联与肿胀之间存在关系。在所有3个区域中，肿胀与降解胶原分子的量成正比。与正常软骨相比，OA软骨ID的变化在表层沿与胶原纤维方向平行的方向最为明显。
OA胶原网络刚度的降低（通过肿胀和ID测量）与降解胶原分子的量密切相关。ID在平行和垂直于纤维方向上的各向异性表明，强度损伤主要存在于纤维内部，而非纤维之间。蛋白聚糖在OA软骨拉伸刚度退变中仅起次要作用。
