title: MicroRNA-34a inhibits osteoblast differentiation and in vivo bone formation of human stromal stem cells.
abstract: Osteoblast differentiation and bone formation (osteogenesis) are regulated by transcriptional and post-transcriptional mechanisms. Recently, microRNAs (miRNAs) were identified as novel key regulators of human stromal (skeletal, mesenchymal) stem cells (hMSC) differentiation. Here, we identified miRNA-34a (miR-34a) and its target protein networks as modulator of osteoblastic (OB) differentiation of hMSC. miRNA array profiling and further validation by quantitative RT-PCR revealed that miR-34a was upregulated during OB differentiation of hMSC, and in situ hybridization confirmed its OB expression in vivo. Overexpression of miR-34a inhibited early commitment and late OB differentiation of hMSC in vitro, whereas inhibition of miR-34a by anti-miR-34a enhanced these processes. Target prediction analysis and experimental validation confirmed Jagged1 (JAG1), a ligand for Notch 1, as a bona fide target of miR-34a. siRNA-mediated reduction of JAG1 expression inhibited OB differentiation. Moreover, a number of known cell cycle regulator and cell proliferation proteins, such as cyclin D1, cyclin-dependent kinase 4 and 6 (CDK4 and CDK6), E2F transcription factor three, and cell division cycle 25 homolog A were among miR-34a targets. Furthermore, in a preclinical model of in vivo bone formation, overexpression of miR-34a in hMSC reduced heterotopic bone formation by 60%, and conversely, in vivo bone formation was increased by 200% in miR-34a-deficient hMSC. miRNA-34a exhibited unique dual regulatory effects controlling both hMSC proliferation and OB differentiation. Tissue-specific inhibition of miR-34a might be a potential novel therapeutic strategy for enhancing in vivo bone formation.
authors.affiliation: Molecular Endocrinology Laboratory (KMEB), Odense University Hospital, University of South Denmark, Odense C, Denmark.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Kim
authors.initials: K
authors.lastname: Holmstrøm
authors.forename: Weimin
authors.initials: W
authors.lastname: Qiu
authors.forename: Nicholas
authors.initials: N
authors.lastname: Ditzel
authors.forename: Kaikai
authors.initials: K
authors.lastname: Shi
authors.forename: Lea
authors.initials: L
authors.lastname: Hokland
authors.forename: Moustapha
authors.initials: M
authors.lastname: Kassem
mesh_terms: D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation / Q000502:physiology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D000072100:Jagged-1 Protein; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010012:Osteogenesis / Q000502:physiology*; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism; D000072099:Serrate-Jagged Proteins
chemical_list: D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D036341:Intercellular Signaling Peptides and Proteins; C000606273:JAG1 protein, human; D000072100:Jagged-1 Protein; C522425:MIRN34 microRNA, human; D008565:Membrane Proteins; D035683:MicroRNAs; C497761:NOTCH1 protein, human; D051881:Receptor, Notch1; D000072099:Serrate-Jagged Proteins
keywords: DifferentiationBone formation; Human stromal stem cells; MicroRNA 34a; Osteoblast