title: Biomechanical regulation of matrix metalloproteinase-9 in cultured chondrocytes.
abstract: Abnormal mechanical loading of joints may induce degeneration of articular cartilage. Shear stress is one mode of mechanical loading that may regulate chondrocyte metabolism. We investigated the mechanism by which shear stress induces the gene encoding matrix metalloproteinase-9, a mediator of the progressive degradation of articular cartilage in osteoarthritis. In vitro experiments using passaged rabbit chondrocytes in monolayer culture subjected to a shear stress of 16 dyn/cm2 (1.6 Pa) in a flow channel showed increased expression of the matrix metalloproteinase-9 gene. The induction of matrix metalloproteinase-9 appeared to depend on a region in the 5' promoter of the gene that contains a 12-0-tetradecanoylphorbol 13-acetate-responsive element. Transfection experiments using a construct containing a luciferase reporter driven by a 12-0-tetradecanoylphorbol 13-acetate-responsive element indicated that shear stress activated a 12-0-tetradecanoylphorbol 13-acetate-responsive element-mediated transcription in chondrocytes. Similar experiments showed that shear stress induced a matrix metalloproteinase-9 promoter construct (matrix metalloproteinase-9-luciferase). Shear stress activated c-Jun NH2-terminal kinase, extracellular signal-regulated kinase, and p38. Transfection of matrix metalloproteinase-9-luciferase together with the dominant negative mutant of c-Jun NH2-terminal kinase, but not with that of extracellular signal-regulated kinase or p38, attenuated the shear-induced matrix metalloproteinase-9 promoter activity. In addition, transfection of constructs encoding dominant negative mutants of Ras, Rac, and Cdc42 attenuated the induction of c-Jun transcriptional activity by shear stress. Thus. shear stimulation of chondrocytes stimulates Ras, Rac, and Cdc42, which subsequently activate c-Jun NH2-terminal kinase to induce a 12-0-tetradecanoylphorbol 13-acetate-responsive element-mediated expression of matrix metalloproteinase-9.
authors.affiliation: Department of Bioengineering and Institute for Biomedical Engineering, University of California-San Diego, 92093-0412, USA.
authors.forename: G
authors.initials: G
authors.lastname: Jin
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
authors.forename: Y S
authors.initials: YS
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Lotz
authors.forename: J Y
authors.initials: JY
authors.lastname: Shyy
authors.forename: S
authors.initials: S
authors.lastname: Chien
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002478:Cells, Cultured / Q000378:metabolism* / Q000473:pathology; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D010812:Physical Stimulation / Q000009:adverse effects*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011817:Rabbits; D020218:Response Elements / Q000502:physiology; D013314:Stress, Mechanical; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D016474:Weight-Bearing / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020780:Matrix Metalloproteinase 9; D020559:Monomeric GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate