title: Differential effects of IGF-binding proteins, IGFBP-3 and IGFBP-5, on IGF-I action and binding to cell membranes of immortalized human chondrocytes.
abstract: Insulin-like growth factor-I (IGF-I) is an important anabolic factor for cartilage tissue and its action is, in part, regulated by IGF-binding proteins (IGFBPs). The object of this study was to investigate the effects of IGFBPs on IGF-I action and on binding of IGF-I to cells using a reproducible immortalized human chondrocyte culture model. Treatment of the C-28/I2 cells with IGF-I or des(1-3)IGF-I in serum-free medium stimulated cell proliferation in a dose-dependent manner. However, the effect of des(1-3)IGF-I was more potent, thereby suggesting that endogenously produced IGFBPs inhibited IGF action. The stimulatory effect of IGF-I was inhibited significantly by addition of IGFBP-3 but enhanced slightly by IGFBP-5. However, neither IGFBP-3 nor IGFBP-5 had an effect on basal cell growth. Binding of (125)I-labeled IGF-I to the cells was displaced by both IGFBP-3 and IGFBP-5, although higher concentrations of unlabeled IGFBP-5 were required to displace IGF-I to the same extent as IGFBP-3. Treatment of the cells with IGF-I increased the levels of IGFBP-5 protein measured by Western ligand blotting, and stimulated a corresponding increase in IGFBP-5 mRNA while increasing type II collagen mRNA. Our findings indicate that the balance between IGFBP-3 and IGFBP-5 influences IGF receptor binding and its action on chondrocyte proliferation, and may thereby modulate cartilage metabolism.
authors.affiliation: Department of Orthopedic Surgery, School of Medicine, Nagasaki University, Nagasaki 852-8501, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Matsumoto
authors.forename: T
authors.initials: T
authors.lastname: Tsurumoto
authors.forename: M B
authors.initials: MB
authors.lastname: Goldring
authors.forename: H
authors.initials: H
authors.lastname: Shindo
mesh_terms: D001667:Binding, Competitive; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000378:metabolism; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism*; D003094:Collagen / Q000235:genetics; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000494:pharmacology; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D013268:Stimulation, Chemical
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D018969:Insulin-Like Growth Factor Binding Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; C058957:insulin-like growth factor 1, des-(1-3)-; D007334:Insulin-Like Growth Factor I; D003094:Collagen