Fibronectin fragments cause release and degradation of collagen-binding molecules from equine explant cultures.
OBJECTIVE
Previous experiments have shown that addition of fragmented fibronectin can induce cartilage chondrolysis. In this study we investigated the fate of the collagen- and cell-binding molecules Cartilage oligomeric matrix protein (COMP) and chondroadherin.


METHODS
Equine articular cartilage explants were stimulated with the C-terminal and the N-terminal heparin-binding fragments of fibronectin respectively, and the conditioned media were analysed by both quantitative (ELISA) and qualitative (mass spectrometry, Western blots) methods.


RESULTS
Both COMP and chondroadherin were released in a dose-dependent manner upon stimulation with the Hep II (C-terminal heparin-binding) fragment of fibronectin. The kinetics of release for the two components differed. Moreover, COMP was degraded while no fragments of chondroadherin could be detected. Stimulation with Hep II also induced production of nitric oxide in a dose-dependent manner. We compared effects of the Hep II fragment with that of Hep I (the N-terminal heparin-binding fragment of fibronectin) and found that while Hep I did indeed elicit release of COMP and chondroadherin, the response was less potent, and production of nitric oxide was negligible. The responses to both fragments were elicited within 24h.


CONCLUSIONS
We suggest that the events described here may be early, critical stages in cartilage destruction preceding collagen destruction.
Johnson
Anna
A
Department of Cell and Molecular Biology, Section for Connective Tissue Biology, Lund University, Lund, Sweden.
Smith
Roger
R
Saxne
Tore
T
Hickery
Mark
M
Heinegård
Dick
D
D000818:Animals; D001386:Azides / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology*; D019902:Chondrocytes / Q000502:physiology; D003094:Collagen / Q000378:metabolism; D003470:Culture Media; D046508:Culture Techniques; D003517:Cyclopentanes / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D016326:Extracellular Matrix Proteins / Q000032:analysis / Q000502:physiology*; D005353:Fibronectins / Q000502:physiology*; D005552:Forelimb; D006023:Glycoproteins / Q000032:analysis / Q000502:physiology; D006736:Horses; D013058:Mass Spectrometry / Q000379:methods; D064235:Matrilin Proteins; D011489:Protein Denaturation
D001386:Azides; D003470:Culture Media; D003517:Cyclopentanes; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D006023:Glycoproteins; D064235:Matrilin Proteins; C088980:chondroadherin; C058189:1,7-dioxa-2,6-diaza-4,7a-dithia-3H,5H-benzo(cd)pentalene; D003094:Collagen