Abstract

The structural integrity and mechanical environment of the articular cartilage matrix directly affect chondrocytedeformations. Rabbit models of early osteoarthritis at 9 weeks following anterior cruciate ligament transection (ACLT) have beenshown to alter the deformation behavior of superficial zone chondrocytes in mechanically loaded articular cartilage. However, it is notfully understood whether these changes in cell mechanics are caused by changes in structural macromolecules in the extracellularmatrix. Therefore, the purpose of this study was to characterize the proteoglycan content, collagen content, and collagen orientation at9 weeks post ACLT using microscopic techniques, and relate these changes to the altered cell mechanics observed upon mechanicalloading of cartilage. At 9 weeks following ACLT, collagen orientation was significantly (p<0.05) altered and proteoglycan content wassignificantly (p<0.05) reduced in the superficial zone cartilage matrix. These structural changes either in the extracellular orpericellular matrix (ECM and PCM) were also correlated significantly (p<0.05) with chondrocyte width and height changes, therebysuggesting that chondrocyte deformation response to mechanical compression in early OA changes primarily because of alterations inmatrix structure. However, compared to the normal group, proteoglycan content in the PCM from the ACLT group decreased less thanthat in the surrounding ECM. Therefore, PCM could play a key role to protect excessive chondrocyte deformations in the ACLT group.