Anna Asanbaeva

ARTICULAR CARTILAGE TENSILE INTEGRITY: MODULATION BY MATRIX DEPLETION IS MATURATION-DEPENDENT

Articular cartilage function depends on the molecular composition and structure of its extracellular matrix (ECM). The collagen network (CN) provides cartilage with tensile integrity, but must also remodel during growth. Such remodeling may depend on matrix molecules interacting with the CN to modulate the tensile behavior of cartilage. The objective of this study was to determine the effects of increasingly selective matrix depletion on tensile properties of immature and mature articular cartilage, and thereby establish a framework for identifying molecules involved in CN remodeling. Depletion of immature cartilage with guanidine, chondroitinase ABC, chondroitinase AC, and Streptomyces hyaluronidase markedly increased tensile integrity, while the integrity of mature cartilage remained unaltered after depletion with guanidine. The enhanced tensile integrity after matrix depletion suggests that certain ECM components of immature matrix serve to inhibit CN interactions and may act as modulators of physiological alterations of cartilage geometry and tensile properties during growth/maturation.

A Cartilage Growth Mixture Model With Collagen Remodeling: Validation Protocols

A cartilage growth mixture (CGM) model is proposed to address limitations of a model used in a previous study. New stress constitutive equations for the solid matrix are derived and collagen (COL) remodeling is incorporated into the CGM model by allowing the intrinsic COL material constants to evolve during growth. An analytical validation protocol based on experimental data from a recent in vitro growth study is developed. Available data included measurements of tissue volume, biochemical composition, and tensile modulus for bovine calf articular cartilage (AC) explants harvested at three depths and incubated for 13 days in 20% fetal borine serum (FBS) and 20% FBS+beta-aminopropionitrile. The proposed CGM model can match tissue biochemical content and volume exactly while predicting theoretical values of tensile moduli that do not significantly differ from experimental values. Also, theoretical values of a scalar COL remodeling factor are positively correlated with COL cross-link content, and mass growth functions are positively correlated with cell density. The results suggest that the CGM model may help us to guide in vitro growth protocols for AC tissue via the a priori prediction of geometric and biomechanical properties.

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).Copyright

Investigation of Cartilage Biomechanical Properties: Dependence on Strain, Direction, and Biochemical Composition

Articular cartilage (AC) serves as the major load bearing material within synovial joints and provides a low friction and wear resistant interface. As an avascular tissue, AC lacks the ability to repair structural damage or degeneration. Thus, the need for replacement tissue was a motivating factor in the development of cartilage tissue engineering. Recently, a finite element model (FEM) of cartilage growth [1] has been developed to simulate various growth conditions such as in vitro (outside the body) tissue growth experiments. In order to validate growth laws used in the FEM, empirical measurements of AC properties (mechanical and biochemical) before and after in vitro growth are needed. The goal of this study is to design protocols to comprehensively quantify the biomechanical structure-function relations of AC.© 2007 ASME