title: Cell adhesion signaling regulates RANK expression in osteoclast precursors.
abstract: Cells with monocyte/macrophage lineage expressing receptor activator of NF-κB (RANK) differentiate into osteoclasts following stimulation with the RANK ligand (RANKL). Cell adhesion signaling is also required for osteoclast differentiation from precursors. However, details of the mechanism by which cell adhesion signals induce osteoclast differentiation have not been fully elucidated. To investigate the participation of cell adhesion signaling in osteoclast differentiation, mouse bone marrow-derived macrophages (BMMs) were used as osteoclast precursors, and cultured on either plastic cell culture dishes (adherent condition) or the top surface of semisolid methylcellulose gel loaded in culture tubes (non-adherent condition). BMMs cultured under the adherent condition differentiated into osteoclasts in response to RANKL stimulation. However, under the non-adherent condition, the efficiency of osteoclast differentiation was markedly reduced even in the presence of RANKL. These BMMs retained macrophage characteristics including phagocytic function and gene expression profile. Lipopolysaccharide (LPS) and tumor necrosis factor -αTNF-α activated the NF-κB-mediated signaling pathways under both the adherent and non-adherent conditions, while RANKL activated the pathways only under the adherent condition. BMMs highly expressed RANK mRNA and protein under the adherent condition as compared to the non-adherent condition. Also, BMMs transferred from the adherent to non-adherent condition showed downregulated RANK expression within 24 hours. In contrast, transferring those from the non-adherent to adherent condition significantly increased the level of RANK expression. Moreover, interruption of cell adhesion signaling by echistatin, an RGD-containing disintegrin, decreased RANK expression in BMMs, while forced expression of either RANK or TNFR-associated factor 6 (TRAF6) in BMMs induced their differentiation into osteoclasts even under the non-adherent condition. These results suggest that cell adhesion signaling regulates RANK expression in osteoclast precursors.
authors.affiliation: Department of Biochemistry, School of Dentistry, Showa University, Shinagawa, Tokyo, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Mochizuki
authors.forename: Masamichi
authors.initials: M
authors.lastname: Takami
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakamaki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Tomoyasu
authors.forename: Yuho
authors.initials: Y
authors.lastname: Kadono
authors.forename: Sakae
authors.initials: S
authors.lastname: Tanaka
authors.forename: Tomio
authors.initials: T
authors.lastname: Inoue
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Kamijo
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D005822:Genetic Vectors; D006801:Humans; D016023:Integrins / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D053245:RANK Ligand / Q000494:pharmacology; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D000071681:Tartrate-Resistant Acid Phosphatase; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010455:Peptides; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D048029:TNF Receptor-Associated Factor 6; D014409:Tumor Necrosis Factor-alpha; C057986:echistatin; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase