title: The 45 kDa collagen-binding fragment of fibronectin induces matrix metalloproteinase-13 synthesis by chondrocytes and aggrecan degradation by aggrecanases.
abstract: Fragments of fibronectin occur naturally in vivo and are increased in the synovial fluid of arthritis patients. We have studied the 45 kDa fragment (Fn-f 45), representing the N-terminal collagen-binding domain of fibronectin, for its ability to modulate the expression of metalloproteinases by porcine articular chondrocytes in vitro. We report that stimulation of cultured chondrocytes, or cartilage explants, with Fn-f 45 increased the levels of matrix metalloproteinase-13 (MMP-13; collagenase-3) released into the conditioned medium in a dose-dependent manner. Increased levels of MMP-13 were due to stimulation of MMP-13 synthesis, rather than release of MMP-13 from accumulated matrix stores. Fn-f 45 also stimulated the synthesis of MMP-3 (stromelysin-1) from cultured chondrocytes and cartilage cultures. The Fn-f 45-induced increase in MMP-3 and MMP-13 synthesis occurred via an interleukin 1-independent mechanism, since the receptor antagonist of interleukin-1 was unable to block the increased synthesis. The gelatinases, MMP-2 and MMP-9, were not modulated by Fn-f 45 in these culture systems. Fn-f 45 also stimulated the release of aggrecan from cartilage explants into conditioned medium. Neoepitope antibodies specific for aggrecan fragments generated by MMPs or aggrecanases showed that the Fn-f 45-induced aggrecan loss was mediated by aggrecanases, and not by MMPs. Extracts of cultured cartilage contained elevated levels of the aggrecanase-derived ITEGE(373)-G1 domain, whereas levels of the matrix metalloproteinase-derived DIPEN(341)-G1 domain were unchanged. These studies show that Fn-f 45 can induce a catabolic phenotype in articular chondrocytes by up-regulating the expression of metalloproteinases specific for the degradation of collagen and aggrecan.
authors: University of Melbourne, Department of Paediatrics, Cell & Matrix Biology Research Unit and Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville-3052, Australia.
authors: Heather
authors: H
authors: Stanton
authors: Linh
authors: L
authors: Ung
authors: Amanda J
authors: AJ
authors: Fosang
mesh_terms: D053674:Aggrecans; D000818:Animals; D015153:Blotting, Western; D002356:Cartilage / Q000201:enzymology / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism; D003094:Collagen / Q000737:chemistry* / Q000378:metabolism; D017364:Collagenases / Q000096:biosynthesis* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation; D000939:Epitopes; D016326:Extracellular Matrix Proteins; D005353:Fibronectins / Q000737:chemistry*; D019791:Guanidine / Q000494:pharmacology; D007375:Interleukin-1 / Q000378:metabolism; D037181:Lectins, C-Type; D053509:Matrix Metalloproteinase 13; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008856:Microscopy, Fluorescence; D010206:Papain / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000378:metabolism*; D013552:Swine; D013997:Time Factors
chemical_list: D053674:Aggrecans; D000939:Epitopes; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D007375:Interleukin-1; D037181:Lectins, C-Type; D011509:Proteoglycans; D003094:Collagen; D010450:Endopeptidases; D010206:Papain; D017364:Collagenases; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C083641:aggrecanase; D019791:Guanidine