Viscoelastic shear properties of articular cartilage and the effects of glycosidase treatments

Abstract

The objectives of this study were to determine the viscoelastic shear properties of articular cartilage and to investigate the effects of the alteration of proteoglycan structure on these shear properties. Glycosidase treatments (chondroitinase ABC and Streptomyces hyaluronidase) were used to alter the proteoglycan structure and content of the tissue. The dynamic viscoelastic shear properties of control and treated tissues were measured and statistically compared. Specifically, cylindrical bovine cartilage specimens were subjected to oscillatory shear deformation of small amplitude (gamma degrees = 0.001 radian) over a physiological range of frequencies (0.01-20 Hz) and at various compressive strains (5, 9, 12, and 16%). The dynamic complex shear modulus was calculated from the measurements. The experimental results show that the solid matrix of normal articular cartilage exhibits intrinsic viscoelastic properties in shear over the range of frequencies tested. These viscoelastic shear properties were found to be dependent on compressive strains. Our data also provide significant insights into the structure-function relationships for articular cartilage. Significant correlations were found between the material properties (the magnitude of dynamic shear modulus, the phase shift angle, and the equilibrium compressive modulus), and the biochemical compositions of the cartilage (collagen, proteoglycan, and water contents). The shear modulus was greatly reduced when the proteoglycans were degraded by either chondroitinase ABC or Streptomyces hyaluronidase. The results suggest that the ability of collagen to resist tension elastically provides the stiffness of the cartilage matrix in shear and its elastic energy storage capability. Proteoglycans enmeshed in the collagen matrix inflate the collagen network and induce a tensile prestress in the collagen fibrils. This interaction of the collagen and proteoglycan within the cartilage matrix provides the complex mechanism that allows the tissue to resist shear deformation.

Biosynthetic response and mechanical properties of articular cartilage after injurious compression

“…In this study, we also characterize the effect of injury on the shear stiffness of the cartilage, since the shear stiffness of the tissue is known to be very sensitive to the strength and integrity of the collagen network [3 11. Although the proteoglycan content also contributes to shear strength [11,31], changes in proteoglycan content were relatively small among treatment groups in this experiment. Our results, demonstrating a decrease in mechanical properties before gross fissuring was visible (at a strain rate of 0.1 s-I), suggests damage to the collagen network by injury at the higher strain rates used in this study.…”

Selective and non-selective metalloproteinase inhibitors reduce IL-1-induced cartilage degradation and loss of mechanical properties

“…Compression and shear moduli are indicators of tissue mechanical function and depend on the abundance and integrity of ECM constituents Setton, et al, 1999;Zhu, et al, 1993). Whereas IL-1-stimulated tissue retains compression properties approximately 0-4% of the initial (t = 0) values by day 24, treatment with the non-selective metalloproteinase inhibitor was effective at preserving 15% and 42% of the initial equilibrium and dynamic compression moduli, respectively.…”

Hyaluronan-dependent pericellular matrix☆

“…At the tissue level, the swelling pressure provided by proteoglycan-hyaluronan aggregates has been shown to contribute directly to the compressive stiffness, as well as the shear modulus, of cartilage and fibrocartilage [23][24][25]. Proteoglycans enmeshed in the collagen matrix inflate the collagen network and induce a tensile pre-stress in the collagen fibrils [25].…”

“…Proteoglycans enmeshed in the collagen matrix inflate the collagen network and induce a tensile pre-stress in the collagen fibrils [25]. This interaction of collagen and proteoglycan aggregates within cartilage matrix provides the complex mechanism that allows the tissue to resist shear deformation.…”