title: Wnt5a signaling is a substantial constituent in bone morphogenetic protein-2-mediated osteoblastogenesis.
abstract: Wnts are secreted glycoproteins that mediate developmental and post-developmental physiology by regulating cellular processes including proliferation, differentiation, and apoptosis through β-catenin-dependent canonical and β-catenin-independent noncanonical pathway. It has been reported that Wnt5a activates noncanonical Wnt signaling through receptor tyrosine kinase-like orphan receptor 2 (Ror2). Although it appears that Wnt5a/Ror2 signaling supports normal bone physiology, the biological significance of noncanonical Wnts in osteogenesis is essentially unknown. In this study, we identified expression of Wnt5a in osteoblasts in the ossification zone of the tibial growth plate as well as bone marrow of the rat tibia as assessed by immunohistochemistry. In addition, we show that osteoblastic differentiation mediated by BMP-2 is associated with increased expression of Wnt5a and Ror2 using cultured pre-osteoblasts, MC3T3-E1 cells. Silencing gene expression of Wnt5a and Ror2 in MC3T3-E1 cells results in suppression of BMP-2-mediated osteoblastic differentiation, suggesting that Wnt5a and Ror2 signaling are of substantial importance for BMP-2-mediated osteoblastic differentiation. BMP-2 stimulation induced phosphorylation of Smad1/5/8 in a similar fashion in both siWnt5a-treated cells and control cells, suggesting that Wnt5a was dispensable for the phosphorylation of Smads by BMP-2. Taken together, our results suggest that Wnt5a/Ror2 signaling appears to be involved in BMP-2-mediated osteoblast differentiation in a Smad independent pathway.
authors.affiliation: Department of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai 980-8575, Japan. e-nemoto@dent.tohoku.ac.jp
authors.forename: Eiji
authors.initials: E
authors.lastname: Nemoto
authors.forename: Yukari
authors.initials: Y
authors.lastname: Ebe
authors.forename: Sousuke
authors.initials: S
authors.lastname: Kanaya
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tsuchiya
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Masato
authors.initials: M
authors.lastname: Tamura
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Shimauchi
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D008297:Male; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D000071818:Wnt-5a Protein
chemical_list: D055396:Bone Morphogenetic Protein 2; D034741:RNA, Small Interfering; D051785:Smad Proteins; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; C491837:Wnt5a protein, rat