title: FHL2 mediates dexamethasone-induced mesenchymal cell differentiation into osteoblasts by activating Wnt/beta-catenin signaling-dependent Runx2 expression.
abstract: The differentiation of bone marrow mesenchymal stem cells (MSCs) into osteoblasts is a crucial step in bone formation. However, the mechanisms involved in the early stages of osteogenic differentiation are not well understood. In this study, we identified FHL2, a member of the LIM-only subclass of the LIM protein superfamily, that is up-regulated during early osteoblast differentiation induced by dexamethasone in murine and human MSCs. Gain-of-function studies showed that FHL2 promotes the expression of the osteoblast transcription factor Runx2, alkaline phosphatase, type I collagen, as well as in vitro extracellular matrix mineralization in murine and human mesenchymal cells. Knocking down FHL2 using sh-RNA reduces basal and dexamethasone-induced osteoblast marker gene expression in MSCs. We demonstrate that FHL2 interacts with beta-catenin, a key player involved in bone formation induced by Wnt signaling. FHL2-beta-catenin interaction potentiates beta-catenin nuclear translocation and TCF/LEF transcription, resulting in increased Runx2 and alkaline phosphatase expression, which was inhibited by the Wnt inhibitor DKK1. Reduction of Runx2 transcriptional activity using a mutant Runx2 results in inhibition of FHL2-induced alkaline phosphatase expression in MSCs. These findings reveal that FHL2 acts as an endogenous activator of mesenchymal cell differentiation into osteoblasts and mediates osteogenic differentiation induced by dexamethasone in MSCs through activation of Wnt/beta-catenin signaling- dependent Runx2 expression.
authors.affiliation: INSERM U606, Hopital Lariboisiere, 2 rue Ambroise Pare, 75475 Paris cedex 10, France.
authors.forename: Zahia
authors.initials: Z
authors.lastname: Hamidouche
authors.forename: Eric
authors.initials: E
authors.lastname: Haÿ
authors.forename: Pascal
authors.initials: P
authors.lastname: Vaudin
authors.forename: Pierre
authors.initials: P
authors.lastname: Charbord
authors.forename: Roland
authors.initials: R
authors.lastname: Schüle
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Marie
authors.forename: Olivia
authors.initials: O
authors.lastname: Fromigué
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000502:physiology; D000469:Alkaline Phosphatase; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002113:Calcification, Physiologic / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis* / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology*; D020536:Enzyme Activators / Q000378:metabolism; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D060850:LIM-Homeodomain Proteins; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; C495270:CTNNB1 protein, human; C495267:CTNNB1 protein, mouse; D024042:Collagen Type I; D050659:Core Binding Factor Alpha 1 Subunit; C501126:DKK1 protein, human; C501127:Dkk1 protein, mouse; D020536:Enzyme Activators; C105987:FHL2 protein, human; C491382:Fhl2 protein, mouse; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D060850:LIM-Homeodomain Proteins; D009124:Muscle Proteins; C493709:RUNX2 protein, human; C493716:Runx2 protein, mouse; D051820:TCF Transcription Factors; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D003907:Dexamethasone; D000469:Alkaline Phosphatase