The effect of glycosaminoglycan depletion on the friction and deformation of articular cartilage

Abstract

Glycosaminoglycans (GAGs) have been shown to be responsible for the interstitial fluid pressurization of articular cartilage and hence its compressive stiffness and load-bearing properties. Contradictory evidence has been presented in the literature on the effect of depleting GAGs on the friction properties of articular cartilage. The aim of this study was to investigate the effect of depleting GAGs on the friction and deformation characteristics of articular cartilage under different tribological conditions. A pin-on-plate machine was utilized to measure the coefficient of friction of native and chondroitinase ABC (CaseABC)-treated articular cartilage under two different models: static (4 mm/s start-up velocity) and dynamic (4 mm/s sliding velocity; 4 mm stroke length) under a load of 25 N (0.4 MPa contact stress) and with phosphate-buffered saline as the lubricant. Indentation tests were carried out at 1 N and 2 N loads (0.14 MPa and 0.28 MPa contact stress levels) to study the deformation characteristics of both native and GAG-depleted cartilage samples. CaseABC treatment rendered the cartilage tissue soft owing to the loss of compressive stiffness and a sulphated-sugar assay confirmed the loss of GAGs from the cartilage samples. CaseABC treatment significantly increased (by more than 50 per cent) the friction levels in the dynamic model (p < 0.05) at higher loading times owing to the loss of biphasic lubrication. CaseABC treatment had no effect on friction in the static model in which the cartilage surfaces did not have an opportunity to recover fluid because of static loading unlike the cartilage tissue in the dynamic model, in which translation of the cartilage surfaces was involved, ensuring effective biphasic lubrication. Therefore the depletion of GAGs had a smaller effect on the coefficient of friction for the static model. Indentation tests showed that GAG-depleted cartilage samples had a lower elastic modulus and higher permeability than native tissue. These results corroborate the role of GAGs in the compressive and friction properties of articular cartilage and emphasize the need for developing strategies to control GAG loss from diseased articular cartilage tissue.

Regional Effects of Enzymatic Digestion on Knee Meniscus Cell Yield and Phenotype for Tissue Engineering

“…46 Further, the higher compressive properties of P/C constructs relative to LC constructs maybe related to the increased GAG content of P/C constructs compared with LC constructs as GAGs are known to be important for maintaining compressive properties in tissue such as articular cartilage. 47,48 The P/C cells, therefore, appeared to be more active in the self-assembling process than LC cells. These results indicate that P/C cells are a promising population for tissue engineering purposes, and a more comprehensive investigation of their potential to form engineered cartilaginous tissue is warranted in future work.…”

Directing bone marrow-derived stromal cell function with mechanics

“…Actually, with cast immobilization, muscles are still tonic and maintain the tissue under compression, while passive flexion motion increases shear deformations in the damaged tissue. Thus, at short term, cast immobilization most likely preserved a higher relative amount of hydrostatic pressure, known to favor glycosaminoglycan (GAG) synthesis, largely responsible for the properties of normal articular cartilage (Katta et al, 2008;Wong and Carter, 2003).…”

Articular cartilage friction increases in hip joints after the removal of acetabular labrum

“…Biphasic lubrication (Ateshian, 2009;Caligaris and Ateshian, 2008;Caligaris et al, 2009;Gleghorn and Bonassar, 2008;Katta et al, 2008) and boundary lubrication (Crockett et al, 2007;Hou et al, 1992; both depend on joint fluid. Furthermore, the fluid film layer that develops between cartilage surfaces delivers important lubricant molecules to the cartilage surface Crockett et al, 2007;Forsey et al, 2006;Gleghorn et al, 2009;Kawano et al, 2003;Schaefer et al, 2004;.…”