title: Role of insulin-like growth factor binding protein-3 (IGFBP-3) in the differentiation of primary human adult skeletal myoblasts.
abstract: Although muscle satellite cells were identified almost 40 years ago, little is known about the induction of their proliferation and differentiation in response to physiological/pathological stimuli or to growth factors/cytokines. In order to investigate the role of the insulin-like growth factor (IGF)/IGF binding protein (IGFBP) system in adult human myoblast differentiation we have developed a primary human skeletal muscle cell model. We show that under low serum media (LSM) differentiating conditions, the cells secrete IGF binding proteins-2, -3, -4 and -5. Intact IGFBP-5 was detected at days 1 and 2 but by day 7 in LSM it was removed by proteolysis. IGFBP-4 levels were also decreased at day 7 in the presence of IGF-I, potentially by proteolysis. In contrast, we observed that IGFBP-3 initially decreased on transfer of cells into LSM but then increased with myotube formation. Treatment with 20 ng/ml tumour necrosis factor-alpha (TNFalpha), which inhibits myoblast differentiation, blocked IGFBP-3 production and secretion whereas 30 ng/ml IGF-I, which stimulates myoblast differentiation, increased IGFBP-3 secretion. The TNFalpha-induced decrease in IGFBP-3 production and inhibition of differentiation could not be rescued by addition of IGF-I. LongR(3)IGF-I, which does not bind to the IGFBPs, had a similar effect on differentiation and IGFBP-3 secretion as IGF-I, both with and without TNFalpha, confirming that increased IGFBP-3 is not purely due to increased stability conferred by binding to IGF-I. Furthermore reduction of IGFBP-3 secretion using antisense oligonucleotides led to an inhibition of differentiation. Taken together these data indicate that IGFBP-3 supports myoblast differentiation.
authors.affiliation: Division of Surgery, University of Bristol, Bristol Royal Infirmary, Bristol, England. foulstone@bristol.ac.uk
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Foulstone
authors.forename: Paul B
authors.initials: PB
authors.lastname: Savage
authors.forename: Anna L
authors.initials: AL
authors.lastname: Crown
authors.forename: Jeff M P
authors.initials: JM
authors.lastname: Holly
authors.forename: Claire E H
authors.initials: CE
authors.lastname: Stewart
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000378:metabolism; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D017077:Culture Media, Conditioned; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D016376:Oligonucleotides, Antisense; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I