Platelet-derived growth factor BB secreted from osteoclasts acts as an osteoblastogenesis inhibitory factor.
Osteoclasts and osteoblasts are responsible for strict bone maintenance with a balance between bone formation and resorption by interacting with each other. Recently, it has been revealed that osteoblasts/stromal cells regulate differentiation of osteoclasts/hematopoietic cells by two factors, the receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL) on the plasma membrane, and secreted osteoprotegerin (OPG). However, no factors have yet been reported by which osteoclasts/hematopoietic cells regulate osteoblasts/stromal cells. To elucidate the possibility of signal transduction from osteoclasts to osteoblasts, we studied the conditioned medium of mouse osteoclast-like myeloma cell line RAW264.7 treated with RANKL. We found that this medium contains a factor that inhibits differentiation of mouse osteoblast precursor-like cell line MC3T3-E1 to osteoblasts induced by bone morphogenetic protein 4 (BMP-4) and named this factor osteoblastogenesis inhibitory factor (OBIF). OBIF was purified by successive three-step chromatography by heparin affinity, anion exchange, and reversed-phase columns. Osteoblastogenesis inhibitory activity made one peak in each chromatography step, showing the factor is a single entity. Active fractions were loaded on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and bands of proteins were excised, digested by trypsin, and analyzed by liquid chromatography equipped with tandem mass spectrometry (LC/MS/MS). Consequently, we have identified this factor to be platelet-derived growth factor BB (PDGF BB) homodimer. Furthermore, this identification of PDGF BB as OBIF was confirmed by neutralization of the inhibitory activity of the medium with anti-PDGF antibody. These results show, for the first time, that osteoclasts regulate osteoblasts directly and suggest that PDGF BB is a key factor in bone remodeling.
Kubota
Kazuishi
K
Biomedical Research Laboratories, Sankyo Co, Ltd, Tokyo, Japan.
Sakikawa
Chisa
C
Katsumata
Mutsumi
M
Nakamura
Takemichi
T
Wakabayashi
Kenji
K
D000818:Animals; D000077214:Becaplermin; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010010:Osteoclasts / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000276:immunology / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D008562:Membrane Glycoproteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D000077214:Becaplermin