Nonlinear Constituent Based Viscoelastic Modeling of GAG Depletion Experiments Suggests Strong GAG-Collagen Interactions in Immature Articular Cartilage Tissue

The porous solid matrix (SM) of articular cartilage (AC) contains glycosaminoglycans (GAGs) and collagens (COLs). GAGs provide a fixed negative charge that produces swelling and compressive resistance and the COL network produces tensile and shear resistance. The long-term goal of this study is to improve structure-function relations for characterizing AC growth and remodeling. A recent study using GAG depletion experiments suggested that GAG-COL interactions regulate tissue mechanical properties in a manner dependent on maturational stage [1]. The objective of this study was to characterize GAG-COL interactions on viscoelastic (VE) properties for immature AC tissue. The first aim was to modify a constituent based nonlinear VE model [2] to study AC tissue biomechanics. The second aim was to quantify the VE response for control and GAG depleted immature AC tested in uniaxial tension (UT).