title: Superficial Zone Extracellular Matrix Extracts Enhance Boundary Lubrication of Self-Assembled Articular Cartilage.
abstract: OBJECTIVE
  Previous work has shown that increasing the production of boundary lubricant, superficial zone protein (SZP), did not reduce the friction coefficient of self-assembled articular cartilage constructs and was possibly due to poor retention of the lubricant. The aim of this investigation was to reduce the friction coefficient of self-assembled articular cartilage constructs through enhancing SZP retention by the exogenous addition of extracellular matrix (ECM) extracted from the superficial zone of native articular cartilage.
  
  
  METHODS
  Superficial zone cartilage was shaved from juvenile bovine femoral condyles using a dermatome, minced finely with razor blades, extracted with 4 M guanidine-hydrochloride, buffer exchanged with culture medium, and added directly to the culture medium of self-assembled articular cartilage constructs at low (10 µg/mL) and high (100 µg/mL) concentrations for 4 weeks. Biochemical and biomechanical properties were determined at the conclusion of 4 weeks culture.
  
  
  RESULTS
  ECM treatment increased compressive and tensile stiffness of self-assembled articular cartilage constructs and decreased the friction coefficient. Glycosaminoglycan content decreased and collagen content increased significantly in self-assembled constructs by the ECM treatment.
  
  
  CONCLUSIONS
  Friction coefficients of self-assembled articular cartilage constructs were reduced by adding extracted superficial zone ECM into the culture medium of self-assembled articular cartilage constructs.
authors.affiliation: Lawrence Ellison Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California, Davis, Sacramento, CA, USA.
authors.forename: Gordon
authors.initials: G
authors.lastname: Peng
authors.affiliation: Lawrence Ellison Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California, Davis, Sacramento, CA, USA.
authors.forename: Sean M
authors.initials: SM
authors.lastname: McNary
authors.affiliation: Lawrence Ellison Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California, Davis, Sacramento, CA, USA; Department of Biomedical Engineering, University of California, Davis, CA, USA.
authors.forename: Kyriacos A
authors.initials: KA
authors.lastname: Athanasiou
authors.affiliation: Lawrence Ellison Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California, Davis, Sacramento, CA, USA.
authors.forename: A Hari
authors.initials: AH
authors.lastname: Reddi
keywords: SZP; articular cartilage; cartilage lubrication; chondrocytes; extracellular matrix