title: Transforming growth factor-beta controls human osteoclastogenesis through the p38 MAPK and regulation of RANK expression.
abstract: Although RANK-L is essential for osteoclast formation, factors such as transforming growth factor-beta (TGF-beta) are potent modulators of osteoclastogenic stimuli. To systematically investigate the role of TGF-beta in human osteoclastogenesis, monocytes were isolated from peripheral blood by three distinct approaches, resulting in either a lymphocyte-rich, a lymphocyte-poor, or a pure osteoclast precursor (CD14-positive) cell population. In each of these osteoclast precursor populations, the effect of TGF-beta on proliferation, TRAP activity, and bone resorption was investigated with respect to time and length of exposure. When using the highly pure CD14 osteoclast precursor cell population, the effect of TGF-beta was strongly dependent on the stage of osteoclast maturation. When monocytes were exposed to TGF-beta during the initial culture period (days 1-7), TRAP activity and bone resorption were increased by 40%, whereas the cell number was reduced by 25%. A similar decrease in cell number was observed when TGF-beta was present during the entire culture period (days 1-21), but in direct contrast, TRAP activity, cell fusion, cathepsin K, and matrix metalloproteinase (MMP)-9 expression as well as bone resorption were almost completely abrogated. Moreover, we found that latent TGF-beta was strongly activated by incubation with MMP-9 and suggest this to be a highly relevant mechanism for regulating osteoclast activity. To further investigate the molecular mechanism responsible for the divergent effects of continuous versus discontinuous exposure to TGF-beta, we examined RANK expression and p38 MAPK activation. We found the TGF-beta strongly induced p38 MAPK in monocytes, but not in mature osteoclasts, and that continuous exposure of TGF-beta to monocytes down-regulated RANK expression. The current results suggest that TGF-beta promotes human osteoclastogenesis in monocytes through stimulation of the p38 MAPK, whereas continuous exposure to TGF-beta abrogates osteoclastogenesis through down-regulation of RANK expression and therefore attenuation of RANK-RANK-L signaling.
authors.affiliation: Nordic Bioscience A/S, CCBR, Herlev/Ballerup, Herlev DK-2730, Denmark. mk@nordicbioscience.com
authors.forename: Morten A
authors.initials: MA
authors.lastname: Karsdal
authors.forename: Pernille
authors.initials: P
authors.lastname: Hjorth
authors.forename: Kim
authors.initials: K
authors.lastname: Henriksen
authors.forename: Tove
authors.initials: T
authors.lastname: Kirkegaard
authors.forename: Karina L
authors.initials: KL
authors.lastname: Nielsen
authors.forename: Henriette
authors.initials: H
authors.lastname: Lou
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Delaissé
authors.forename: Niels T
authors.initials: NT
authors.lastname: Foged
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000368:Aged; D001862:Bone Resorption; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D002459:Cell Fusion; D002469:Cell Separation; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008214:Lymphocytes / Q000502:physiology; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000187:drug effects; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D018124:Receptors, Tumor Necrosis Factor; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D016212:Transforming Growth Factor beta; D016173:Macrophage Colony-Stimulating Factor; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000135:Acid Phosphatase; D020780:Matrix Metalloproteinase 9