title: Senescent growth arrest in mesenchymal stem cells is bypassed by Wip1-mediated downregulation of intrinsic stress signaling pathways.
abstract: Human mesenchymal stem cells (hMSCs) have been widely studied as a source of primary adult stem cells for cell therapy because of their multidifferentiation potential; however, the growth arrest (also known as "premature senescence") often found in hMSCs cultured in vitro has been a major obstacle to the in-depth characterization of these cells. In addition, the inability to maintain constant cell growth hampers the development of additional genetic modifications aimed at achieving desired levels of differentiation to specific tissues; however, the molecular mechanisms that govern this phenomenon remain unclear, with the exception of a few studies demonstrating that induction of p16INK4a is responsible for this senescence-like event. Here, we observed that the premature growth arrest in hMSCs occurs in parallel with the induction of p16INK4a, following abrogation of inhibitory phosphorylation of retinoblastoma protein. These stress responses were concurrent with increased formation of reactive oxygen species (ROSs) from mitochondria and increased p38 mitogen-activated protein kinase (MAPK) activity. The introduction of Wip1 (wild-type p53 inducible phosphatase-1), a well-studied stress modulator, significantly lowered p16INK4a expression and led to p38 MAPK inactivation, although it failed to affect the levels of ROSs. Moreover, the suppression of stress responses by Wip1 apparently extended the life span of hMSCs, compared with control conditions, while maintaining their multilineage differentiation potential. Based on these results, we suggest that senescent growth arrest in hMSCs may result from activation of stress signaling pathways and consequent onset of stress responses, due in part to ROS production during prolonged in vitro culture.
authors: Stem Cell Research Laboratory, CHA Stem Cell Institute, Seoul, Korea.
authors: Ji-Seon
authors: JS
authors: Lee
authors: Mi-Ok
authors: MO
authors: Lee
authors: Bo-Hyun
authors: BH
authors: Moon
authors: Sung Han
authors: SH
authors: Shim
authors: Albert J
authors: AJ
authors: Fornace
authors: Hyuk-Jin
authors: HJ
authors: Cha
mesh_terms: D000273:Adipose Tissue / Q000502:physiology; D017209:Apoptosis / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D048708:Cell Growth Processes / Q000502:physiology; D016922:Cellular Senescence / Q000502:physiology; D015536:Down-Regulation; D019942:Genes, p16 / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D010012:Osteogenesis / Q000502:physiology; D010749:Phosphoprotein Phosphatases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D017382:Reactive Oxygen Species / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology
chemical_list: D017382:Reactive Oxygen Species; D016160:Retinoblastoma Protein; D048051:p38 Mitogen-Activated Protein Kinases; C000607458:PPM1D protein, human; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C