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We were the first to examine the mechanical responses of skeletally mature bovine femoral cartilage under large-strain simple shear (up to ±20%) using a multiaxial shear testing device. Since shear loading is critical in both tissue failure and chondrocyte responses, we aimed to probe (1) anisotropy with respect to the split-line direction (principal alignment of the collagen fibers near the articulating surface), (2) heterogeneity between femoral condyles, and (3) the influence of local cartilage thickness. We harvested a total of 48 cuboid cartilage specimens from four bovine knee joints. With each specimen we applied shear strains both parallel and perpendicular to the local split-line direction at a rate of 75 μm/min and calculated the peak-to-peak shear stresses, shear strain–energy dissipation densities, and peak effective shear moduli. The Wilcoxon signed rank test revealed that the medial condyle was anisotropic in some mechanical measures at applied shear strains above 5%, while the lateral condyle was mechanically isotropic at all applied shear strains. The Kruskal–Wallis test revealed no significant differences in the median mechanical behavior of the lateral and medial condyles. Spearman׳s rank correlations revealed statistically significant negative monotonic correlations among thickness and most of our mechanical measures for both lateral and medial condyles at most applied strains and directions of applied shear. These results suggest that large-strain analyses account for nonlinear, anisotropic and location-dependent effects not fully realized at small strains. Our findings may inspire new experiments and models that consider anisotropy and heterogeneity of cartilage in ways previously ignored. [ABSTRACT FROM AUTHOR]

Summary: Objective: By means of scanning white light interferometry, develop a noncontact, nondestructive technique capable of measuring surface topography of viable cartilage. Methods: Using full thickness cylindrical cartilage explants obtained from bovine calf knees, experiments were performed to produce a surface preparation protocol that yields highly repeatable topographical measurements while maintaining cartilage viability. To further validate the technique, a series of human talar cartilage samples, displaying varying degrees of cartilage degeneration, was then subjected to interferometric measurements and compared to their histology. Results: A key aspect of the technique of surface topographic measurement by interferometry was the development of an optimal surface preparation process. The technique was successfully validated against standard 2-D profilometry. The intrinsic variability of the technique is less than 2%, which is much less than the average point-to-point variability of 17% observed across a cartilage specimen. The technique was hence sufficiently sensitive to readily detect differences in roughness between surfaces of healthy cartilage in different locations on the bovine knee. Thus, the average roughness of the medial explants exceeded that of the lateral explants by 0.35μmRa (P =0.003) and the roughness of the trochlear explants exceeded that of the condylar explants by 0.55μmRa (P <0.0001). Also, applying this technique to diseased human talar cartilage samples, a statistically significant increase in the average surface roughness value per unit increase in histological degeneration score was observed (≥0.2μmRa, P ≤0.041), making surface roughness obtained via interferometry a useful parameter for evaluating cartilage health nondestructively. Conclusions: The aim of developing a protocol based on white light interferometry to measure the surface topography of viable articular cartilage was achieved. This interferometric technique opens the door to monitoring the surface topography of live cartilage, as is desirable for ex vivo tests on cartilage explants. [Copyright &y& Elsevier]

Background: This work aimed to show and compare the degradation time of some of cartilage extracellular matrix components using an in vitro model for cartilage degradation induced by interleukin-1α. It is known that elucidation of molecular events under Interleukin-1α induction of bovine nasal cartilage could obtain useful data to understand more about involving mechanisms for tissue breakdown in joint disease., Methods: The cartilage was taken from an adult bovine in a local slaughterhouse. After removing the whole perichondrium, the equal 2 mm diameter pieces of bovine nasal cartilage were punched out and cultured in Dulbecco's modified Eagle's medium DMEM with or without 10 ng/ml Interleukin-1α for 24 days. Each 3 days, the media were removed and exchanged by fresh media, and the removed media were stored in -20 degrees C. Sodium dodecyl sulphate/polyacrylamid-gel electrophoresis SDS-PAGE and Western-blot methods were used for analyzing the samples., Results: The first fragment of fibromodulin (FM) was seen at day 6 and further fragments were appeared at day 18. Cartilage oligomeric matrix protein (COMP) releasing was as a successive pattern during culture period and the first fragment was found at day 6. Collagen IX fragments were seen at day 9 and in a progressive pattern until the end of the study., Conclusion: This study shows that FM and COMP could be considered as the suitable candidates for studying the mechanisms that participate in the cartilage degradations.