Regulation of osteoclast differentiation and function by receptor activator of NFkB ligand and osteoprotegerin.
The differentiation and functions of osteoclasts (OCs) are regulated by osteoblast-derived factors. Receptor activator of NFkB ligand (RANKL) is one of the key regulatory molecules in OC formation. Osteoprotegerin (OPG) is a novel secreted member of the TNF receptor superfamily that negatively regulates osteoclastogenesis and binds to RANKL. We examined the biological actions of macrophage-colony-stimulating factor (M-CSF), RANKL, and OPG on the differentiation of OCs isolated from cocultures of mouse osteoblastic cells and bone marrow cells. Preosteoclasts (pOCs) and OCs were characterized by their ultrastructure and the expression of OC markers such as tartrate-resistant acid phosphatase (TRAP) and vacuolar-type H(+)-ATPase. pOCs formed without any additives expressed TRAP, but showed little resorptive activity on cocultured dentine slices. TRAP-positive pOCs treated with M-CSF began to fuse with each other, but lacked a ruffled border (RB) and showed almost no resorptive activity. pOCs treated with RANKL became TRAP-positive multinucleated cells, which expressed intense vacuolar-type H(+)-ATPase along the RB membranes and exhibited prominent resorptive activity. Such effects of RANKL on pOCs were completely inhibited by the addition of OPG. OPG inhibited RB formation in mature OCs and reduced their resorptive activity, and also induced apoptosis of some OCs. These results suggest that 1) RANKL induces differentiation of functional OCs from pOCs, 2) M-CSF induces macrophage-like multinucleated cells, but not OCs, 3) OPG inhibits RB formation and resorptive activity in mature OCs, 4) OPG also induces apoptosis of OCs, and 5) RANKL and OPG are, therefore, important regulators of not only the terminal differentiation of OCs but also their resorptive function.
Shiotani
Aya
A
Department of Orthodontics, School of Dentistry, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Takami
Masamichi
M
Itoh
Kanami
K
Shibasaki
Yoshinobu
Y
Sasaki
Takahisa
T
D000818:Animals; D015415:Biomarkers; D001854:Bone Marrow Cells / Q000166:cytology; D002352:Carrier Proteins / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D006023:Glycoproteins / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000648:ultrastructure; D007150:Immunohistochemistry; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D051379:Mice; D008854:Microscopy, Electron; D010006:Osteoblasts / Q000166:cytology*; D053244:Osteoprotegerin; D006180:Proton-Translocating ATPases / Q000032:analysis; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; D014617:Vacuoles / Q000201:enzymology / Q000648:ultrastructure
D015415:Biomarkers; D002352:Carrier Proteins; D006023:Glycoproteins; 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; C505687:Tnfrsf11a protein, mouse; C506031:Tnfrsf11b protein, mouse; C505689:Tnfsf11 protein, mouse; D016173:Macrophage Colony-Stimulating Factor; D006180:Proton-Translocating ATPases