title: Crosstalks between integrin alpha 5 and IGF2/IGFBP2 signalling trigger human bone marrow-derived mesenchymal stromal osteogenic differentiation.
abstract: BACKGROUND
  The potential of mesenchymal stromal cells (MSCs) to differentiate into functional bone forming cells provides an important tool for bone regeneration. The identification of factors that trigger osteoblast differentiation in MSCs is therefore critical to promote the osteogenic potential of human MSCs. In this study, we used microarray analysis to identify signalling molecules that promote osteogenic differentiation in human bone marrow stroma derived MSCs.
  
  
  RESULTS
  Microarray analysis and validation experiments showed that the expression of IGF2 and IGFBP2 was increased together with integrin alpha5 (ITGA5) during dexamethasone-induced osteoblast differentiation in human MSCs. This effect was functional since we found that IGF2 and IGFBP2 enhanced the expression of osteoblast phenotypic markers and in vitro osteogenic capacity of hMSCs. Interestingly, we showed that downregulation of endogenous ITGA5 using specific shRNA decreased IGF2 and IGFBP2 expression in hMSCs. Conversely, ITGA5 overexpression upregulated IGF2 and IGFBP2 expression in hMSCs, which indicates tight crosstalks between these molecules. Consistent with this concept, activation of endogenous ITGA5 using a specific antibody that primes the integrin, or a peptide that specifically activates ITGA5 increased IGF2 and IGFBP2 expression in hMSCs. Finally, we showed that pharmacological inhibition of FAK/ERK1/2-MAPKs or PI3K signalling pathways that are enhanced by ITGA5 activation, blunted IGF2 and IGFBP2 expression in hMSCs.
  
  
  CONCLUSIONS
  The results show that ITGA5 is a key mediator of IGF2 and IGFBP2 expression that promotes osteoblast differentiation in human MSCs, and reveal that crosstalks between ITGA5 and IGF2/IGFBP2 signalling are important mechanisms that trigger osteogenic differentiation in human bone marrow derived mesenchymal stromal cells.
authors.affiliation: Laboratory of Osteoblast Biology and Pathology, INSERM U606, Paris F-75475, France.
authors.forename: Zahia
authors.initials: Z
authors.lastname: Hamidouche
authors.forename: Olivia
authors.initials: O
authors.lastname: Fromigué
authors.forename: Jochen
authors.initials: J
authors.lastname: Ringe
authors.forename: Thomas
authors.initials: T
authors.lastname: Häupl
authors.forename: Pierre J
authors.initials: PJ
authors.lastname: Marie
mesh_terms: D001854:Bone Marrow Cells / Q000166:cytology; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004627:Embryonic Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D039482:Integrin alpha5 / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D046228:Microarray Analysis; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology; D019076:Transgenes / Q000235:genetics
chemical_list: D004791:Enzyme Inhibitors; C035170:IGF2 protein, human; D018971:Insulin-Like Growth Factor Binding Protein 2; D039482:Integrin alpha5; D034741:RNA, Small Interfering; D007335:Insulin-Like Growth Factor II