Frictional Response of Bovine Articular Cartilage Under Creep Loading Following Proteoglycan Digestion With Chondroitinase ABC

Abstract

SummaryThe specific aim of this study was to investigate the effect of chondroitinase ABC treatment on the frictional response of bovine articular cartilage against glass, under creep loading. The hypothesis is that chondroitinase ABC treatment increases the friction coefficient of bovine articular cartilage under creep. Articular cartilage samples (n=12) harvested from two bovine knee joints (1-3 monthsold) were divided into a control group (intact specimens) and a treated group (chondroitinase ABC digestion), and tested in unconfined compression with simultaneous continuous sliding (±4 mm at 1 mm/s) under a constant applied stress of 0.5 MPa, for 2,500 s. The time-dependent response of the friction coefficient was measured. With increasing duration of loading, treated samples exhibited a significantly higher friction coefficient than control samples as assessed by the equilibrium value (treated: μ eq = 0.19 ± 0.02; control: μ eq = 0.12 ± 0.03; p=0.002), though the coefficient achieved immediately upon loading did not increase significantly (treated: μ min = 0.0053 ± 0.0025; control: μ min = 0.037 ± 0.0013; p=0.19). Our results demonstrate that removal of the cartilage glycosaminoglycans using chondroitinase ABC significantly increases the overall time-dependent friction coefficient of articular cartilage. These findings strengthen the motivation for developing chondroprotective strategies by increasing cartilage chondroitin sulfate content in osteoarthritic joints.

Influence of chondroitin sulfate on the biochemical, mechanical and frictional properties of cartilage explants in long-term culture

“…The friction measurements (cartilage-on-glass) were performed in unconfined compression creep, under reciprocal sliding motion consisting of 100 cycles over a range of ±4.5mm, at 1 mm/s. Under this testing configuration, the friction coefficient rises monotonically over time, from a minimum value denoted by μ min to a steady-state equilibrium value denoted by μ eq , as shown in previous studies (Krishnan et al 2004; Basalo et al 2006). The pausing interval between two consecutive sliding cycles was gradually increased as the friction coefficient increased.…”

“…First, it was shown that cartilage that was enzymatically degraded with chondroitinase ABC exhibits a significantly higher friction coefficient than normal tissue (Basalo et al 2005; Basalo et al 2006), complementing the findings of an earlier study(Kumar et al 2001); then it was shown that normal cartilage that had been incubated or tested in a saline bath with 100 mg/ml CS, exhibited much lower friction than tissue tested in saline with 10 mg/ml CS, or saline alone(Basalo et al 2007). …”

“…Furthermore, when endogenous GAG was significantly lowered by enzymatic digestion, the friction coefficient of cartilage explants increased in the absence of exogenous CS (Scenario 2)(Basalo et al 2006). In this study, as shown in Figure 1 C-D, the endogenous GAG content of the CS100 group only became significantly lower than the control on Day 28.…”

Reinforcement of articular cartilage with a tissue-interpenetrating polymer network reduces friction and modulates interstitial fluid load support

“…A creep stress of 0.78 MPa was selected to mimic the contact stresses experienced in the knee during jogging, 42 and effective perimeter velocity of 22 mm s −1 was selected to mimic the upper physiologic range of daily femoral-tibial sliding velocities. 43 This procedure yields COFs that increase as a function of time 44 as shown in Figure 2, with COFs equilibrating concurrent with creep deformation equilibrium. The differences in COF became statistically significant between 60 w/v% treated and non-treated tissue approximately half-way into the three-hour test (24% reduction in COF compared to non-treated tissue at the test’s completion), whereas the difference in COF between 20 w/v% and non-treated tissue demonstrated a non-statistically significant (p = 0.48) 5% reduction in COF compared to non-treated tissue.…”

Investigation of the frictional response of osteoarthritic human tibiofemoral joints and the potential beneficial tribological effect of healthy synovial fluid

“…Prior in vitro and in vivo friction studies have induced degradation of bovine articular cartilage by enzymatic action [1, 2, 3, 4, 5] or by mechanical abrasion [6, 7] as a means to simulate osteoarthritis (OA), generally reporting that the friction coefficient increases with degradation. Gene knockout studies have examined the frictional response of animal joints lacking expression of lubricin/superficial zone protein by PRG4 [8, 9], also showing an increase in friction and wear.…”