title: Differential gene expression and regulation of the bone morphogenetic protein antagonists follistatin and gremlin in normal and osteoarthritic human chondrocytes and synovial fibroblasts.
abstract: OBJECTIVE
  To compare gene expression in normal and osteoarthritic (OA) human chondrocytes using microarray technology. Of the novel genes identified, we selected follistatin, a bone morphogenetic protein (BMP) antagonist, and investigated its expression/regulation as well as that of 3 other antagonists, gremlin, chordin, and noggin, in normal and OA chondrocytes and synovial fibroblasts.
  
  
  METHODS
  Basal and induced gene expression were determined using real-time polymerase chain reaction. Gene regulation was monitored following treatment with inflammatory, antiinflammatory, growth, and developmental factors. Follistatin protein production was measured using a specific enzyme-linked immunosorbent assay, and localization of follistatin and gremlin in cartilage was determined by immunohistochemical analysis.
  
  
  RESULTS
  All BMP antagonists except noggin were expressed in chondrocytes and synovial fibroblasts. Follistatin and gremlin were significantly up-regulated in OA chondrocytes but not in OA synovial fibroblasts. Chordin was weakly expressed in normal and OA cells. Production of follistatin protein paralleled the gene expression pattern. Follistatin and gremlin were expressed preferentially by the chondrocytes at the superficial layers of cartilage. Tumor necrosis factor alpha and interferon-gamma significantly stimulated follistatin expression but down-regulated expression of gremlin. Interleukin-1beta (IL-1beta) had no effect on follistatin but reduced gremlin expression. Conversely, BMP-2 and BMP-4 significantly stimulated expression of gremlin but down-regulated that of follistatin. IL-13, dexamethasone, transforming growth factor beta1, basic fibroblast growth factor, platelet-derived growth factor type BB, and endothelial cell growth factor down-regulated the expression of both antagonists.
  
  
  CONCLUSIONS
  This study is the first to show the possible involvement of follistatin and gremlin in OA pathophysiology. The increased activin/BMP-binding activities of these antagonists could affect tissue remodeling. The data suggest that follistatin and gremlin might appear at different stages during the OA process, making them interesting targets for the treatment of this disease.
authors.affiliation: Osteoarthritis Research Unit, Hôpital Notre-Dame, Montreal, Quebec, Canada.
authors.forename: Ginette
authors.initials: G
authors.lastname: Tardif
authors.forename: David
authors.initials: D
authors.lastname: Hum
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pelletier
authors.forename: Christelle
authors.initials: C
authors.lastname: Boileau
authors.forename: Pierre
authors.initials: P
authors.lastname: Ranger
authors.forename: Johanne
authors.initials: J
authors.lastname: Martel-Pelletier
mesh_terms: D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D002352:Carrier Proteins; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000378:metabolism*; D038681:Follistatin / Q000032:analysis* / Q000502:physiology; D015870:Gene Expression / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology*; D006023:Glycoproteins / Q000032:analysis / Q000502:physiology; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000032:analysis* / Q000502:physiology; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D010003:Osteoarthritis / Q000378:metabolism / Q000503:physiopathology*; D040081:Protein Array Analysis; D011506:Proteins / Q000032:analysis / Q000502:physiology; D013583:Synovial Membrane / Q000166:cytology*; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation; D000099176:Noggin Protein
chemical_list: D055396:Bone Morphogenetic Protein 2; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D038681:Follistatin; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D007371:Interferon-gamma; D007375:Interleukin-1; D011506:Proteins; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D000099176:Noggin Protein; C525718:BMP2 protein, human; C525809:BMP4 protein, human; C486399:GREM1 protein, human; C054234:chordin