Objective: This paper examines the hypothesis that the dermatan sulfate (DS) chain on decorin is a load carrying element in cartilage and that its damage or removal will alter the material properties. Methods: To test this hypothesis, indentation and tensile testing of cartilage from bovine patella were performed before and after digestion with chondroitinase B (cB). Removal of significant amounts of DS by cB digestion was verified by Western blot analysis of proteoglycans extracted from whole and sectioned specimens. Specimens (control and treated) were subjected to a series of step-hold displacements. Elastic modulus during the step rise (rapid modulus) and at equilibrium (equilibrium modulus), and the relaxation function during each step was measured for test (cB and buffer) and control (buffer alone) conditions. Results: cB had no effect on any of the viscoelastic mechanical properties measured, either in indentation or tension. Conclusion: Removing or damaging approximately 50% of the DS had no effect on the mechanical properties, strongly suggesting that DS either carries very low load or no load.
Bibliographical noteFunding Information:
This work was supported by NIH grants AR050731 and AR049900, and the Catharine Mills Davis Chair in Biomechanical Engineering. We thank Dr Ted Oegema, Jr. for helpful discussions.
- Cartilage mechanics
- Chondroitinase B
- Dermatan sulfate