PRG4 exchange between the articular cartilage surface and synovial fluid

The boundary lubrication function of articular cartilage is mediated in part by proteoglycan 4 (PRG4) molecules, found both in synovial fluid (SF) and bound to the articular cartilage surface. Currently the mechanism by which PRG4 binds to the articular surface is not well understood. The objectives...

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Published in:Journal of orthopaedic research 2007-10, Vol.25 (10), p.1269-1276
Main Authors: Nugent-Derfus, G.E., Chan, A.H., Schumacher, B.L., Sah, R.L.
Format: Article
Language:English
Subjects:
Alkylation
Animals
binding
cartilage
Cartilage, Articular - drug effects
Cartilage, Articular - metabolism
Cattle
Growth Substances - metabolism
Growth Substances - pharmacology
Hyaluronoglucosaminidase - pharmacology
In Vitro Techniques
Oxidation-Reduction
PRG4
Protein Binding
Proteoglycans - metabolism
Proteoglycans - pharmacology
Sodium Dodecyl Sulfate - pharmacology
Stifle
synovial fluid
Synovial Fluid - metabolism
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Summary:The boundary lubrication function of articular cartilage is mediated in part by proteoglycan 4 (PRG4) molecules, found both in synovial fluid (SF) and bound to the articular cartilage surface. Currently the mechanism by which PRG4 binds to the articular surface is not well understood. The objectives of this study were to determine (1) the effect of bathing fluid contents on PRG4 concentration at the articular surface ([PRG4]cart), and (2) whether native PRG4 can be removed from the surface and subsequently repleted with PRG4 from synovial fluid. In one experiment, cylindrical cartilage disks were stored in solutions of various PRG4 concentrations, either in phosphate‐buffered saline (PBS) or SF as the carrier fluid. In a separate experiment, cartilage disks were stored in solutions expected to remove native PRG4 from the articular surface and allow subsequent repletion with PRG4 from SF. [PRG4]cart was independent of PRG4 concentration of the bathing fluid, and was similar for both carrier fluids. PRG4 was removed from cartilage by treatment with hyaluronidase, reduction/alkylation, and sodium dodecyl sulphate, and was repleted fully by subsequent bathing in SF. These results suggest that the articular surface is normally saturated with tightly bound PRG4, but this PRG4 can exchange with the PRG4 in SF under certain conditions. This finding suggests that all tissues surrounding the joint cavity that secrete PRG4 into the SF may help to maintain lubrication function at the articular surface. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1269–1276, 2007
ISSN:0736-0266
1554-527X
DOI:10.1002/jor.20431