title: Hypoxia inhibition of adipocytogenesis in human bone marrow stromal cells requires transforming growth factor-beta/Smad3 signaling.
abstract: Although hypoxia and transforming growth factor-beta (TGF-beta) inhibit differentiation of adipocytes from preadipocytes and bone marrow-derived cells in several species, the relationship between hypoxia and TGF-beta signaling in adipocytogenesis is unknown. In this study, we evaluated the mechanisms of inhibition of adipocyte differentiation by hypoxia and TGF-beta in human and murine marrow stromal cells (MSCs) and the role of TGF-beta/Smad signaling in the inhibition of adipocytogenesis by hypoxia. Both hypoxia-mimetic deferoxamine mesylate (DFO) and TGF-beta1 inhibited adipocyte differentiation (1.0% versus the control at 15 microm DFO and 1.4% versus the control at 1 ng/ml TGF-beta1) and adipocyte gene expression (peroxisome proliferator-activated receptor-gamma2 and lipoprotein lipase) in human MSCs after 21 days of treatment. Hypoxia (2% O(2)) and DFO (but not TGF-beta1) increased hypoxia-inducible factor-1alpha as shown by Western blotting. Macroarrays and Western and Northern blot analyses showed that hypoxia activated the TGF-beta/Smad signaling pathway and that both hypoxia and TGF-beta1 modulated adipocyte differentiation pathways such as the insulin-, peroxisome proliferator-activated receptor-gamma-, phosphatidylinositol 3-kinase-, and MAPK-associated signaling pathways. Studies with mouse marrow stromal cell lines derived from Smad3(+/+) or Smad3(-/-) mice revealed that the TGF-beta type I receptor (ALK-5) and its intracellular signaling molecule Smad3 were necessary for the inhibition of adipocyte differentiation by both TGF-beta and hypoxia-mimetic DFO. Thus, the TGF-beta/Smad signaling pathway is required for hypoxia-mediated inhibition of adipocyte differentiation in MSCs.
authors.affiliation: Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Shuanhu
authors.initials: S
authors.lastname: Zhou
authors.forename: Stanislav
authors.initials: S
authors.lastname: Lechpammer
authors.forename: Joel S
authors.initials: JS
authors.lastname: Greenberger
authors.forename: Julie
authors.initials: J
authors.lastname: Glowacki
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000328:Adult; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology*; D002454:Cell Differentiation; D002470:Cell Survival; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D000860:Hypoxia; D008071:Lipoprotein Lipase / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D047495:PPAR gamma / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051899:Smad2 Protein; D051900:Smad3 Protein; D017154:Stromal Cells / Q000166:cytology*; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D047495:PPAR gamma; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D012313:RNA; D008071:Lipoprotein Lipase