title: Microarray analysis reveals expression regulation of Wnt antagonists in differentiating osteoblasts.
abstract: Wnt signaling has been implicated in regulating bone formation by controlling osteoblast proliferation and function. Although stabilization of beta-catenin by Wnt has been shown to increase alkaline phosphatase expression and osteoblast differentiation, the precise role of Wnt signaling during the process of osteoblast differentiation is largely unknown. In this study, we used microarray technology to investigate expression regulation of Wnt signaling components during in vitro osteoblast differentiation. Expression was analyzed during bone morphogenetic protein 2 (BMP2)-induced osteoblast differentiation of murine C2C12 and MC3T3 cells and data were compared with expression in BMP2-treated NIH3T3 fibroblasts. During osteoblast differentiation, particularly strong expression regulation of the Wnt antagonists Sfrp2 (secreted frizzled related protein 2) and Wif1 (Wnt inhibitory factor 1) was observed in the late phase of differentiation. In situ expression analysis in murine tail vertebrae supported Wif1 expression during late phase bone cell differentiation, since Wif1 was found to be expressed in vivo in trabecular, but not in cortical bone. We further analyzed the effects of continuous activation of Wnt signaling by lithium chloride and observed that osteoblast differentiation was reduced, as measured by expression of osteoblast marker genes encoding alkaline phosphatase, osteocalcin, and osterix, as well as by the amount of calcium release. Taken together, our data indicate that endogenous expression of Wnt antagonists by osteoblasts provides a negative Wnt feedback loop which is essential in controlling osteoblast maturation.
authors.affiliation: Department of Applied Biology, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Bart L T
authors.initials: BL
authors.lastname: Vaes
authors.forename: Koen J
authors.initials: KJ
authors.lastname: Dechering
authors.forename: Eugene P
authors.initials: EP
authors.lastname: van Someren
authors.forename: José M A
authors.initials: JM
authors.lastname: Hendriks
authors.forename: Cindy J J M
authors.initials: CJ
authors.lastname: van de Ven
authors.forename: Alie
authors.initials: A
authors.lastname: Feijen
authors.forename: Christine L
authors.initials: CL
authors.lastname: Mummery
authors.forename: Marcel J T
authors.initials: MJ
authors.lastname: Reinders
authors.forename: Wiebe
authors.initials: W
authors.lastname: Olijve
authors.forename: Everardus J J
authors.initials: EJ
authors.lastname: van Zoelen
authors.forename: Wilma T
authors.initials: WT
authors.lastname: Steegenga
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002454:Cell Differentiation; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology*; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology*; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051153:Wnt Proteins
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D051153:Wnt Proteins