Structure-Function Relationships in Enzymatically Modified Articular Cartilage

Abstract

The present study is aimed at revealing structure-function relationships of bovine patellar articular cartilage. Collagenase, chondroitinase ABC and elastase were used for controlled and selective enzymatic modifications of cartilage structure, composition and functional properties. The effects of the enzymatic degradations were quantitatively evaluated using quantitative polarized light microscopy, digital densitometry of safranin O-stained sections as well as with biochemical and biomechanical techniques. The parameters related to tissue composition and structure were correlated with the indentation stiffness of cartilage. In general, tissue alterations after enzymatic digestions were restricted to the superficial cartilage. All enzymatic degradations induced superficial proteoglycan (PG) depletion. Collagenase also induced detectable superficial collagen damage, though without causing cartilage fibrillation or tissue swelling. Quantitative microscopic techniques were more sensitive than biochemical methods in detecting these changes. The Young’s modulus of cartilage decreased after enzymatic treatments indicating significant softening of the tissue. The PG concentration of the superficial zone proved to be the major determinant of the Young’s modulus (r² = 0.767, n = 72, p < 0.001). Results of the present study indicate that specific enzymatic degradations of the tissue PGs and collagen can provide reproducible experimental models to clarify the structure-function relationships of cartilage. Effects of these models mimic the changes observed in early osteoarthrosis. Biomechanical testing and quantitative microscopic techniques proved to be powerful tools for detecting the superficial structural and compositional changes while the biochemical measurements on the whole uncalcified cartilage were less sensitive.

Quantitative analysis of spatial proteoglycan content in articular cartilage with Fourier transform infrared imaging spectroscopy: Critical evaluation of analysis methods and specificity of the parameters

“…With this protocol, Chondroitinase ABC enzyme degrades the PGs only from the superficial cartilage. Samples were fixed with 10% formalin, decalcified, dehydrated, and embedded in paraffin as described earlier (Rieppo et al, 2003).…”

Quantitative Analysis of Collagen Network Structure and Fibril Dimensions in Cartilage Repair with Autologous Chondrocyte Transplantation

“…The degree of collagen fibril parallelism, i.e. anisotropy, was measured with quantitative polarizedlight microscopy [Rieppo et al, 2003[Rieppo et al, , 2008. Measurements were carried out using unstained vertical whole-depth cartilage sections from the surface to the cartilage-bone interface.…”

Physical mechanisms underlying the strain-rate-dependent mechanical behavior of kangaroo shoulder cartilage

“…The protocols used for the constituent degradation is in accordance with the previous studies. 27,28,36 The 4 h Trypsin-PBS treatment and 44 h collagenase treatments are known to remove all the proteoglycans and significantly disrupt superficial collagen, respectively. The alcian-blue test (see Sec.…”

“…5 of the supplementary material 32 ) indicated that collagenase treatment removed only a small amount of proteoglycans from the tissue matrix, similar to the previously reported findings. 28,37 After each enzymatic treatment, samples were subjected to indentation testing at the above mentioned four strain-rates.…”

“…8,27 The main advantage of the artificial degradation is that the level of damage to the tissue can be controlled through enzyme concentration, the type of enzyme used and duration of the exposure. 27,28 Hence, artificial degradation can also be used to understand the role of individual constituents on mechanical behavior of the tissue.…”