title: Insulin-like growth factor-I extends in vitro replicative life span of skeletal muscle satellite cells by enhancing G1/S cell cycle progression via the activation of phosphatidylinositol 3'-kinase/Akt signaling pathway.
abstract: Interest is growing in methods to extend replicative life span of non-immortalized stem cells. Using the insulin-like growth factor I (IGF-I) transgenic mouse in which the IGF-I transgene is expressed during skeletal muscle development and maturation prior to isolation and during culture of satellite cells (the myogenic stem cells of mature skeletal muscle fibers) as a model system, we elucidated the underlying molecular mechanisms of IGF-I-mediated enhancement of proliferative potential of these cells. Satellite cells from IGF-I transgenic muscles achieved at least five additional population doublings above the maximum that was attained by wild type satellite cells. This IGF-I-induced increase in proliferative potential was mediated via activation of the phosphatidylinositol 3'-kinase/Akt pathway, independent of mitogen-activated protein kinase activity, facilitating G(1)/S cell cycle progression via a down-regulation of p27(Kip1). Adenovirally mediated ectopic overexpression of p27(Kip1) in exponentially growing IGF-I transgenic satellite cells reversed the increase in cyclin E-cdk2 kinase activity, pRb phosphorylation, and cyclin A protein abundance, thereby implicating an important role for p27(Kip1) in promoting satellite cell senescence. These observations provide a more complete dissection of molecular events by which increased local expression of a growth factor in mature skeletal muscle fibers extends replicative life span of primary stem cells than previously known.
authors.affiliation: Department of Integrative Biology, University of Texas Medical School, Houston, Texas 77030, USA.
authors.forename: M V
authors.initials: MV
authors.lastname: Chakravarthy
authors.forename: T W
authors.initials: TW
authors.lastname: Abraha
authors.forename: R J
authors.initials: RJ
authors.lastname: Schwartz
authors.forename: M L
authors.initials: ML
authors.lastname: Fiorotto
authors.forename: F W
authors.initials: FW
authors.lastname: Booth
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002455:Cell Division; D002478:Cells, Cultured; D016922:Cellular Senescence; D056746:Cyclin G; D056766:Cyclin G1; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004789:Enzyme Activation; D016193:G1 Phase; D006984:Hypertrophy / Q000473:pathology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D006656:Protamine Kinase / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016196:S Phase; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D025521:Tumor Suppressor Proteins; D015854:Up-Regulation
chemical_list: D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D056746:Cyclin G; D056766:Cyclin G1; D051357:Cyclin-Dependent Kinase 2; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D016213:Cyclins; D007334:Insulin-Like Growth Factor I; D008869:Microtubule-Associated Proteins; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D006656:Protamine Kinase; D017346:Protein Serine-Threonine Kinases; D025521:Tumor Suppressor Proteins; C534703:Ccng1 protein, mouse; C493961:Cdkn1b protein, mouse; C495893:Cdk2 protein, mouse