Runx-2 is not essential for the vitamin D-regulated expression of RANKL and osteoprotegerin in osteoblastic cells.
The differentiation and activity of osteoclasts are positively and negatively controlled by receptor activator of nuclear factor-kappaB ligand (RANKL), which is expressed on the surface of osteoblasts and stromal cells, and its decoy receptor osteoprotegerin (OPG), which is secreted by osteoblasts and stromal cells, respectively. The expression of the genes for RANKL and OPG is regulated by 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)]. Runt-related gene-2 (Runx-2) is essential for osteoblast differentiation and there are several reports that Runx-2 is involved in osteoclast formation. Therefore, to clarify the role of Runx-2 in osteoclastogenesis, we designed a series of experiments using C2 cells and C6 cells, which are derived from calvariae of runx2-deficient mice. Treatment of C2 cells and C6 cells with 1alpha,25(OH)(2)D(3) for 2-4 days increased and decreased the levels of expression of the mRNAs for RANKL and OPG, respectively, and the effects were dose-dependent. However, by day 8, the level of RANKL mRNA had fallen and that of OPG mRNA had risen. Furthermore, C6 cells induced the differentiation of mouse spleen cells into tartrate-resistant acid phosphatase-positive (TRAP-positive) multinucleated cells (osteoclast-like cells) in the presence of 10(-7)M 1alpha,25(OH)(2)D(3). Such formation of osteoclast-like cells was inhibited by exogenous OPG in a dose-dependent manner. Thus, our findings indicate that Runx-2 is not essential for the expression of RANKL and OPG, and the formation of osteoclast-like cells.
Department of Biological Sciences, Tokyo Institute of Technology, 4259-Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Michitaka
M
Notoya
Eri
E
Otsuka
Akira
A
Yamaguchi
Hiromi
H
Hagiwara
D016475:3T3 Cells; D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D002762:Cholecalciferol / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit; D050657:Core Binding Factor alpha Subunits; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism / Q000502:physiology*; D010006:Osteoblasts / Q000378:metabolism*; D010010:Osteoclasts / Q000378:metabolism; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D018124:Receptors, Tumor Necrosis Factor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology; D017154:Stromal Cells / Q000378:metabolism; D000071681:Tartrate-Resistant Acid Phosphatase; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014807:Vitamin D / Q000378:metabolism*
D002352:Carrier Proteins; D050659:Core Binding Factor Alpha 1 Subunit; D050657:Core Binding Factor alpha Subunits; D006023:Glycoproteins; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D014157:Transcription Factors; D014807:Vitamin D; D002762:Cholecalciferol; D000135:Acid Phosphatase; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase