title: Low Oxygen Modulates Multiple Signaling Pathways, Increasing Self-Renewal, While Decreasing Differentiation, Senescence, and Apoptosis in Stromal MIAMI Cells.
abstract: Human bone marrow multipotent mesenchymal stromal cell (hMSC) number decreases with aging. Subpopulations of hMSCs can differentiate into cells found in bone, vasculature, cartilage, gut, and other tissues and participate in their repair. Maintaining throughout adult life such cell subpopulations should help prevent or delay the onset of age-related degenerative conditions. Low oxygen tension, the physiological environment in progenitor cell-rich regions of the bone marrow microarchitecture, stimulates the self-renewal of marrow-isolated adult multilineage inducible (MIAMI) cells and expression of Sox2, Nanog, Oct4a nuclear accumulation, Notch intracellular domain, notch target genes, neuronal transcriptional repressor element 1 (RE1)-silencing transcription factor (REST), and hypoxia-inducible factor-1 alpha (HIF-1α), and additionally, by decreasing the expression of (i) the proapoptotic proteins, apoptosis-inducing factor (AIF) and Bak, and (ii) senescence-associated p53 expression and β-galactosidase activity. Furthermore, low oxygen increases canonical Wnt pathway signaling coreceptor Lrp5 expression, and PI3K/Akt pathway activation. Lrp5 inhibition decreases self-renewal marker Sox2 mRNA, Oct4a nuclear accumulation, and cell numbers. Wortmannin-mediated PI3K/Akt pathway inhibition leads to increased osteoblastic differentiation at both low and high oxygen tension. We demonstrate that low oxygen stimulates a complex signaling network involving PI3K/Akt, Notch, and canonical Wnt pathways, which mediate the observed increase in nuclear Oct4a and REST, with simultaneous decrease in p53, AIF, and Bak. Collectively, these pathway activations contribute to increased self-renewal with concomitant decreased differentiation, cell cycle arrest, apoptosis, and/or senescence in MIAMI cells. Importantly, the PI3K/Akt pathway plays a central mechanistic role in the oxygen tension-regulated self-renewal versus osteoblastic differentiation of progenitor cells.
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.|2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.
authors.forename: Carmen
authors.initials: C
authors.lastname: Rios
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.|3 Department of Orthopaedics, University of Miami Miller School of Medicine , Miami, Florida.|4 Geriatrics Institute, University of Miami Miller School of Medicine , Miami, Florida.|5 Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine , Miami, Florida.|6 Department of Biomedical Engineering, University of Miami , Coral Gables, Florida.
authors.forename: Gianluca
authors.initials: G
authors.lastname: D'Ippolito
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.|2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Curtis
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.|3 Department of Orthopaedics, University of Miami Miller School of Medicine , Miami, Florida.|5 Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Gaëtan J-R
authors.initials: GJ
authors.lastname: Delcroix
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.
authors.forename: Lourdes A
authors.initials: LA
authors.lastname: Gomez
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Jimmy
authors.initials: J
authors.lastname: El Hokayem
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Megan
authors.initials: M
authors.lastname: Rieger
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Parrondo
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.
authors.forename: Alicia
authors.initials: A
authors.lastname: de Las Pozas
authors.affiliation: 2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.|7 Department of Medicine, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Carlos
authors.initials: C
authors.lastname: Perez-Stable
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.|2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.|7 Department of Medicine, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Guy A
authors.initials: GA
authors.lastname: Howard
authors.affiliation: 1 Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine , Miami, Florida.|2 GRECC and Research Service, Veterans Affairs Medical Center , Miami, Florida.|3 Department of Orthopaedics, University of Miami Miller School of Medicine , Miami, Florida.|4 Geriatrics Institute, University of Miami Miller School of Medicine , Miami, Florida.|5 Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine , Miami, Florida.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Schiller
mesh_terms: D000328:Adult; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001854:Bone Marrow Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D019070:Cell Lineage / Q000187:drug effects*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D000066673:Cell Self Renewal / Q000187:drug effects* / Q000235:genetics; D002469:Cell Separation; D016922:Cellular Senescence / Q000187:drug effects* / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D060492:Low Density Lipoprotein Receptor-Related Protein-5 / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D010100:Oxygen / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051880:Receptors, Notch; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D010100:Oxygen