Quinn T M, Allen R G, Schalet B J, Perumbuli P, Hunziker E B
M.E. Mueller Institute for Biomechanics, University of Bern, Switzerland.
J Orthop Res. 2001 Mar;19(2):242-9. doi: 10.1016/S0736-0266(00)00025-5.
Mechanical overloading of cartilage has been implicated in the initiation and progression of osteoarthrosis. Our objectives were to identify threshold levels of strain rate and peak stress at which sub-impact loads could induce cartilage matrix damage and chondrocyte injury in bovine osteochondral explants and to explore relationships between matrix damage, spatial patterns of cell injury, and applied loads. Single sub-impact loads characterized by a constant strain rate between 3 x 10(-5) and 0.7 s(-1) to a peak stress between 3.5 and 14 MPa were applied, after which explants were maintained in culture for four days. At the higher strain rates, matrix mechanical failure (tissue cracks) and cell deactivation were most severe near the cartilage superficial zone and were associated with sustained increased release of proteoglycan from explants. In contrast, low strain rate loading was associated with cell deactivation in the absence of visible matrix damage. Furthermore, cell activity and proteoglycan synthesis were suppressed throughout the cartilage depth, but in a radially dependent manner with the most severe effects at the center of cylindrical explants. Results highlight spatial patterns of matrix damage and cell injury which depend upon the nature of injurious loading applied. These patterns of injury may also differ in terms of their long-term implications for progression of degradative disease and possibilities for cartilage repair.
软骨的机械性过载与骨关节炎的起始和进展有关。我们的目标是确定应变速率和峰值应力的阈值水平，在该阈值下，亚冲击负荷可诱导牛骨软骨外植体中的软骨基质损伤和软骨细胞损伤，并探索基质损伤、细胞损伤的空间模式与施加负荷之间的关系。施加以3×10⁻⁵至0.7 s⁻¹之间的恒定应变速率至3.5至14 MPa之间的峰值应力为特征的单次亚冲击负荷，之后将外植体在培养中维持四天。在较高的应变速率下，基质机械性破坏（组织裂缝）和细胞失活在软骨表层区域附近最为严重，并且与外植体中蛋白聚糖的持续释放增加有关。相比之下，低应变速率负荷与在无可见基质损伤情况下的细胞失活有关。此外，细胞活性和蛋白聚糖合成在整个软骨深度均受到抑制，但呈径向依赖性，在圆柱形外植体中心的影响最为严重。结果突出了基质损伤和细胞损伤的空间模式，这取决于所施加的损伤性负荷的性质。这些损伤模式在对降解性疾病进展的长期影响以及软骨修复可能性方面也可能有所不同。
