Association between friction and wear in diarthrodial joints lacking lubricin
نویسندگان
چکیده
OBJECTIVE The glycoprotein lubricin (encoded by the gene Prg4) is secreted by surface chondrocytes and synovial cells, and has been shown to reduce friction in vitro. In contrast to man-made bearings, mammalian diarthrodial joints must endogenously produce friction-reducing agents. This study was undertaken to investigate whether friction is associated with wear. METHODS The lubricating ability of synovial fluid (SF) samples from humans with genetic lubricin deficiency was tested in vitro. The coefficient of friction in the knee joints of normal and lubricin-null mice was measured ex vivo; these joints were also studied by light and electron microscopy. Atomic force microscopy was used to image and measure how lubricin reduces friction in vitro. RESULTS SF lacking lubricin failed to reduce friction in the boundary mode. Joints of lubricin-null mice showed early wear and higher friction than joints from their wild-type counterparts. Lubricin self-organized and reduced the work of adhesion between apposing asperities. CONCLUSION These data show that friction is coupled with wear at the cartilage surface in vivo. They imply that acquired lubricin degradation occurring in inflammatory joint diseases predisposes the cartilage to damage. Lastly, they suggest that lubricin, or similar biomolecules, will have applications in man-made devices in which reducing friction is essential.
منابع مشابه
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INTRODUCTION: Lubricin, also called superficial zone protein (SZP) or Proteoglycan 4 (PRG4), was first identified as the boundary lubricant in synovial fluid. In diarthrodial joints, lubricin is produced by superficial zone chondrocytes and synovial lining cells. It is present in the superficial layer of articular cartilage and coats the articular surface, decreasing surface friction. Lubricin ...
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The diarthrodial, knee joint is a remarkably efficient bearing system; articulating cartilage surfaces provide nearly frictionless performance with minimal wear. The low friction properties of the cartilage surfaces are due in part to the boundary lubricant, superficial zone protein (SZP); also known as lubricin or proteoglycan 4 (PRG4). In previous work, SZP localization and cartilage friction...
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ورودعنوان ژورنال:
- Arthritis and Rheumatism
دوره 56 شماره
صفحات -
تاریخ انتشار 2007