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

Grayson DuRaine, Corey P. Neu, Stephanie M T Chan, Kyriakos Komvopoulos, Ronald K. June, A Hari Reddi

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


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-β1 and IL-1β 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-β1 or IL-1β) 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-β1 and IL-1β 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-β1 treatment corresponded to increased depth of SZP staining within the superficial zone, while friction coefficient changes due to the IL-1β treatment were independent of SZP depth of staining. However, the changes induced by the IL-1β 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-β1 and IL-1β treatment and that the friction coefficient depends on multiple factors, including SZP localization and surface roughness.

Original languageEnglish (US)
Pages (from-to)249-256
Number of pages8
JournalJournal of Orthopaedic Research
Issue number2
StatePublished - Feb 2009


  • Cartilage
  • Cytokine
  • Friction coefficient
  • Growth factors
  • SZP/lubricin/PRG4

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Medicine(all)


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