Han, Sang KuyRonkainen, Ari P.Saarakkala, Simo J.Rieppo, LassiHerzog, WalterKorhonen, Rami K.2018-10-092018-10-092018-01Han, S. - K., Ronkainen, A. P., Saarakkala, S., Rieppo, L., Herzog, W., & Korhonen, R. K. (2018). Alterations in structural macromolecules and chondrocyte deformations in lapine retropatellar cartilage 9 weeks after anterior cruciate ligament transection. Journal of Orthopaedic Research, 36(1), 342-350. doi:10.1002/jor.236501554-527Xhttp://hdl.handle.net/1880/108797The structural integrity and mechanical environment of the articular cartilage matrix directly affect chondrocyte deformations. Rabbit models of early osteoarthritis at 9 weeks following anterior cruciate ligament transection (ACLT) have been shown to alter the deformation behavior of superficial zone chondrocytes in mechanically loaded articular cartilage. However, it is not fully understood whether these changes in cell mechanics are caused by changes in structural macromolecules in the extracellular matrix. Therefore, the purpose of this study was to characterize the proteoglycan content, collagen content, and collagen orientation at 9 weeks post ACLT using microscopic techniques, and relate these changes to the altered cell mechanics observed upon mechanical loading of cartilage. At 9 weeks following ACLT, collagen orientation was significantly (p < 0.05) altered and proteoglycan content was significantly (p < 0.05) reduced in the superficial zone cartilage matrix. These structural changes either in the extracellular or pericellular matrix (ECM and PCM) were also correlated significantly (p < 0.05) with chondrocyte width and height changes, thereby suggesting that chondrocyte deformation response to mechanical compression in early OA changes primarily because of alterations in matrix structure. However, compared to the normal group, proteoglycan content in the PCM from the ACLT group decreased less than that in the surrounding ECM. Therefore, PCM could play a key role to protect excessive chondrocyte deformations in the ACLT group. 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:342350, 2018.enUnless otherwise indicated, this material is protected by copyright and has been made available with authorization from the copyright owner. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.articular cartilagechondrocytecollagen fibreosteoarthritisproteoglycansunknowndoi:10.1002/jor.2365010.11575/PRISM/342622017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.