title: Strontium promotes osteogenic differentiation of mesenchymal stem cells through the Ras/MAPK signaling pathway.
abstract: Strontium ralenate is a new anti-osteoporosis agent. The cellular and molecular mechanism underlying the anabolic effect of strontium on bone remains to be elucidated. Osteoblasts, the main bone forming cells are known to be derived from bone marrow mesenchymal stem cells (MSCs). The present study therefore aimed to investigate the possible effects of strontium on MSCs and signaling pathways possibly involved. It was firstly demonstrated that strontium treatment significantly increased osteoblast-related gene expression and alkaline phosphatase (ALP) of osteogenic-differentiating MSCs. Accompanying the enhanced osteogenic differentiation, the increased phosphorylation of mitogen-activated protein kinase (MAPK) ERK1/2 and p38 was detected in strontium-treated MSCs. PD98059 and SB203580, selective inhibitors of ERK1/2 kinase and p38, attenuated the effect of strontium on osteogenesis. Furthermore, it was demonstrated that Rat Sarcoma viral oncogene homolog (RAS), an upstream regulator of ERK1/2 and p38, was activated by strontium treatment and siRNA-mediated Ras knockdown inhibited strontium-stimulated expression of osteogenic markers. Finally, the transcriptional activity and phosphorylation level of Runx2 was significantly increased in response to strontium treatment in MSCs. PD98059 and Ras siRNA inhibited the effect of strontium on Runx2 activation. Taken together, these results indicated that strontium can promote osteogenic differentiation of MSCs through activating the Ras/MAPK signaling pathway and the downstream transcription factor Runx2.
authors.affiliation: Department of Orthopaedics and Traumatology, the University of Hong Kong, Hong Kong SAR.
authors.forename: Songlin
authors.initials: S
authors.lastname: Peng
authors.forename: Guangqian
authors.initials: G
authors.lastname: Zhou
authors.forename: Keith D K
authors.initials: KD
authors.lastname: Luk
authors.forename: Kenneth M C
authors.initials: KM
authors.lastname: Cheung
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Li
authors.forename: Wing Moon
authors.initials: WM
authors.lastname: Lam
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Zhou
authors.forename: William W
authors.initials: WW
authors.lastname: Lu
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D015151:Immunoblotting; D047468:Immunoprecipitation; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects*; D013324:Strontium / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000469:Alkaline Phosphatase; D018631:ras Proteins; D013324:Strontium