Regulation of the friction coefficient of articular cartilage by TGF-β1 and IL-1β

Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, University of California, Davis, Medical Center, Sacramento, CA 95817, USA.
Journal of Orthopaedic Research (Impact Factor: 2.97). 02/2009; 27(2):249-56. DOI: 10.1002/jor.20713
Source: PubMed

ABSTRACT Articular cartilage functions to provide a low-friction surface for joint movement for many decades of life. Superficial zone protein (SZP) is a glycoprotein secreted by chondrocytes in the superficial layer of articular cartilage that contributes to effective boundary lubrication. In both cell and explant cultures, TGF-beta1 and IL-1beta have been demonstrated to, respectively, upregulate and downregulate SZP protein levels. It was hypothesized that the friction coefficient of articular cartilage could also be modulated by these cytokines through SZP regulation. The friction coefficient between cartilage explants (both untreated and treated with TGF-beta1 or IL-1beta) and a smooth glass surface due to sliding in the boundary lubrication regime was measured with a pin-on-disk tribometer. SZP was quantified using an enzyme-linked immunosorbant assay and localized by immunohistochemistry. Both TGF-beta1 and IL-1beta treatments resulted in the decrease of the friction coefficient of articular cartilage in a location- and time-dependent manner. Changes in the friction coefficient due to the TGF-beta1 treatment corresponded to increased depth of SZP staining within the superficial zone, while friction coefficient changes due to the IL-1beta treatment were independent of SZP depth of staining. However, the changes induced by the IL-1beta treatment corresponded to changes in surface roughness, determined from the analysis of surface images obtained with an atomic force microscope. These findings demonstrate that the low friction of articular cartilage can be modified by TGF-beta1 and IL-1beta treatment and that the friction coefficient depends on multiple factors, including SZP localization and surface roughness.

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    • "Cartilage explants were completely immersed in 10 mL of PBS throughout the duration of testing to maintain tissue hydration. Prior to the initiation of testing, each explant was allowed to equilibrate [23] for 2 min under the applied normal load [19] [24]. Data were acquired in 0.1 s intervals for 60 min using Labview (National Instruments, Austin, TX). "
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    ABSTRACT: Friction and wear of four common orthopaedic biomaterials, alumina (Al2O3), cobalt-chromium (CoCr), stainless steel (SS), and crosslinked ultra-high-molecular-weight polyethylene (UHMWPE), sliding against bovine articular cartilage explants were investigated by reciprocating sliding, nanoscale friction and roughness measurements, protein wear assays, and histology. Under the experimental conditions of the present study, CoCr yielded the largest increase in cartilage friction coefficient, largest amount of protein loss, and greatest change in nanoscale friction after sliding against cartilage. UHMWPE showed the lowest cartilage friction coefficient, least amount of protein loss, and insignificant changes in nanoscale friction after sliding. Although the results are specific to the testing protocol and surface roughness of the examined biomaterials, they indicate that CoCr tends to accelerate wear of cartilage, whereas the UHMWPE shows the best performance against cartilage. This study also shows that the surface characteristics of all biomaterials must be further improved to achieve the low friction coefficient of the cartilage/cartilage interface. [DOI: 10.1115/1.4004760]
    Journal of Tribology 10/2011; 133(4):041201. DOI:10.1115/1.4004760 · 0.90 Impact Factor
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    • "This was observed under almost all combinations of contact pressure and equilibration time. The authors have previously demonstrated the location dependence of cartilage friction (Neu et al., 2007; DuRaine et al., 2009) for contact pressures in the lower end of the physiological range (Brown and Shaw, 1984; Lee et al., 2006). "
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    ABSTRACT: Friction and adhesion of articular cartilage from high- and low-load-bearing regions of bovine knee joints were examined with a tribometer under various loads and equilibration times. The effect of trapped lubricants was investigated by briefly unloading the cartilage sample before friction testing, to allow fluid to reflow into the contact interface and boundary lubricants to rearrange. Friction and adhesion of high-load-bearing joint regions were consistently lower than those of low-load-bearing regions. This investigation is the first to demonstrate the regional variation in the friction and adhesion properties of articular cartilage. Friction coefficient decreased with increasing contact pressure and decreasing equilibration time. Briefly unloading cartilage before the onset of sliding resulted in significantly lower friction and adhesion and a loss of the friction dependence on contact pressure, suggesting an enhancement of the cartilage tribological properties by trapped lubricants. The results of this study reveal significant differences in the friction and adhesion properties between high- and low-load-bearing joint regions and elucidate the role of trapped lubricants in cartilage tribology.
    Journal of Biomechanics 06/2011; 44(11):2015-20. DOI:10.1016/j.jbiomech.2011.04.015 · 2.50 Impact Factor
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    • "Osteochondral explants from 1–3 week old bovine femoral condyles were harvested aseptically as previously described (DuRaine et al., 2009; Chan et al., 2010). For each condyle, one explant was obtained from a medial anterior location and one from a medial posterior location. "
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    ABSTRACT: Boundary lubrication of articular cartilage by conformal, molecularly thin films reduces friction and adhesion between asperities at the cartilage-cartilage contact interface when the contact conditions are not conducive to fluid film lubrication. In this study, the nanoscale friction and adhesion properties of articular cartilage from typical load-bearing and non-load-bearing joint regions were studied in the boundary lubrication regime under a range of physiological contact pressures using an atomic force microscope (AFM). Adhesion of load-bearing cartilage was found to be much lower than that of non-load-bearing cartilage. In addition, load-bearing cartilage demonstrated steady and low friction coefficient through the entire load range examined, whereas non-load-bearing cartilage showed higher friction coefficient that decreased nonlinearly with increasing normal load. AFM imaging and roughness calculations indicated that the above trends in the nanotribological properties of cartilage are not due to topographical (roughness) differences. However, immunohistochemistry revealed consistently higher surface concentration of boundary lubricant at load-bearing joint regions. The results of this study suggest that under contact conditions leading to joint starvation from fluid lubrication, the higher content of boundary lubricant at load-bearing cartilage sites preserves synovial joint function by minimizing adhesion and wear at asperity microcontacts, which are precursors for tissue degeneration.
    Journal of Biomechanics 02/2011; 44(7):1340-5. DOI:10.1016/j.jbiomech.2011.01.003 · 2.50 Impact Factor
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