Fibroblast growth factor 2 inhibits induction of aggrecanase activity in human articular cartilage.
OBJECTIVE
Articular chondrocytes are surrounded by an extracellular pool of fibroblast growth factor 2 (FGF-2). We undertook this study to investigate the possible role of FGF-2 in aggrecan catabolism by aggrecanase in human articular cartilage.


METHODS
Aggrecan catabolism was induced by interleukin-1alpha (IL-1alpha) in normal human articular cartilage and assessed by measuring the release of glycosaminoglycan (GAG) and aggrecanase-dependent fragments by Western blotting with antibodies against neoepitopes. ADAMTS-4 and ADAMTS-5 messenger RNA (mRNA) expression was measured by quantitative real-time reverse transcriptase-polymerase chain reaction. Production of matrix metalloproteinases (MMPs) 1, 3, and 13 and tissue inhibitors of metalloproteinases (TIMPs) 1 and 3 was measured by Western blotting. IL-6 and IL-8 were measured by enzyme-linked immunosorbent assay. Proteoglycan synthesis was monitored by 35S-sulfate incorporation.


RESULTS
IL-1alpha caused cleavage of aggrecan in cultured human articular cartilage explants, with release of GAG and aggrecan fragments containing ARGS and AGEG neoepitopes. This was inhibited by FGF-2 (1-100 ng/ml). Tumor necrosis factor alpha and retinoic acid also stimulated release of neoepitope, and this was also suppressed by FGF-2. IL-1alpha induced ADAMTS-4 and ADAMTS-5 mRNA in primary human chondrocytes, and this was inhibited by FGF-2. IL-1alpha-induced aggrecan breakdown was inhibited by TIMP-1 or by the N-terminal portion of TIMP-3, although FGF-2 did not affect production of the inhibitors TIMP-1 and TIMP-3 when IL-1alpha was present. FGF-2 did not prevent IL-1alpha suppression of proteoglycan synthesis and did not negate its ability to stimulate the production of IL-6, IL-8, and MMPs 1, 3, and 13.


CONCLUSIONS
Our findings suggest that FGF-2 may play a chondroprotective role in human articular cartilage by controlling the expression and activity of the aggrecanases ADAMTS-4 and ADAMTS-5.
Sawaji
Yasunobu
Y
Imperial College London, London, UK. y.sawaji@imperial.ac.uk
Hynes
Judith
J
Vincent
Tonia
T
Saklatvala
Jeremy
J
D051722:ADAM Proteins / Q000032:analysis; D000071121:ADAMTS4 Protein; D000071116:ADAMTS5 Protein; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000201:enzymology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000201:enzymology; D010450:Endopeptidases / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D016222:Fibroblast Growth Factor 2 / Q000502:physiology*; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D053582:Interleukin-1alpha / Q000494:pharmacology; D015850:Interleukin-6 / Q000032:analysis; D016209:Interleukin-8 / Q000032:analysis; D020781:Matrix Metalloproteinase 1 / Q000032:analysis; D053509:Matrix Metalloproteinase 13 / Q000032:analysis; D019278:Matrix Metalloproteinase 3 / Q000032:analysis; D011348:Procollagen N-Endopeptidase / Q000032:analysis; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013431:Sulfates; D013462:Sulfur Radioisotopes; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000032:analysis; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000032:analysis
D006025:Glycosaminoglycans; C508584:IL1A protein, human; D053582:Interleukin-1alpha; D015850:Interleukin-6; D016209:Interleukin-8; D011509:Proteoglycans; D012333:RNA, Messenger; D013431:Sulfates; D013462:Sulfur Radioisotopes; C088390:TIMP3 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; D019717:Tissue Inhibitor of Metalloproteinase-3; D016222:Fibroblast Growth Factor 2; D010450:Endopeptidases; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C121532:ADAMTS5 protein, human; D053509:Matrix Metalloproteinase 13; D011348:Procollagen N-Endopeptidase; D019278:Matrix Metalloproteinase 3; D020781:Matrix Metalloproteinase 1; D000071121:ADAMTS4 Protein; C000603918:ADAMTS4 protein, human; C083641:aggrecanase