Article

Activation of hypoxia-inducible factor 1 in skeletal muscle cells after exposure to damaged muscle cell debris

Institute of Biochemistry I, Goethe-University Frankfurt, Frankfurt, Germany.
Shock (Augusta, Ga.) (Impact Factor: 2.73). 06/2011; 35(6):632-8. DOI: 10.1097/SHK.0b013e3182111f3d
Source: PubMed

ABSTRACT Skeletal muscle damage provokes complex repair mechanisms including recruitment of leukocytes as well as activation of myogenic precursor cells such as satellite cells. To study muscle cell repair mechanisms after muscle fiber damage, we used an in vitro model of scrape-injured myotubes. Exposing vital C2C12 myoblasts and myotubes to cell debris of damaged myotubes revealed mRNA upregulation of adrenomedullin (ADM), insulin-like growth factors 1 and 2, metallopeptidase 9, and monocyte chemoattractant protein11. When cell debris was treated with ultrasound, frozen in liquid nitrogen, or heat inactivated before addition to C2C12 cells, gene expression was drastically reduced or completely absent. Moreover, incubations of myoblasts with debris separated by transwell inserts indicated that direct cell contact is required for gene induction. Incubation with albumin and PolyIC ruled out that ADM induction by cell debris simply results from increased protein or nucleic acid concentrations in the supernatant. Because the genes, which were upregulated by cell debris, are potential target genes of hypoxia-inducible factor (HIF), cells were analyzed for HIF-1α expression. Western blot analysis showed accumulation of the α-subunit upon contact to cell debris. Knockdown of HIF-1α in C2C12 cells proved that activation of HIF-1 in response to cell debris was responsible for upregulating ADM and monocyte chemoattractant protein 1. Furthermore, by incubating cells on gas-permeable culture dishes, we excluded a reduced pericellular pO2 induced by cell debris as the cause for ADM upregulation. Our data suggest that damaged myofibers activate HIF-1 in neighboring myotubes and precursor myoblasts by direct contact, concomitantly upregulating factors necessary for angiogenesis, tissue regeneration, and phagocyte recruitment.

Download full-text

Full-text

Available from: Nathalie Dehne, Sep 05, 2015
0 Followers
 · 
142 Views
 · 
83 Downloads
  • Shock (Augusta, Ga.) 06/2011; 35(6):539-41. DOI:10.1097/SHK.0b013e31821a7408 · 2.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Matrix metalloproteinases (MMPs) are members of an enzyme family that require a zinc ion at their active site. Active at neutral pH, they catalyze normal turnover of extracellular matrix (ECM) and are critical for maintaining tissue allostasis. Subtle coordination between MMP activity and its inhibition by tissue inhibitors of metalloproteinases (TIMPs) insures ECM homeostasis. Loss of control of MMPs expression/activity in numerous pathologies usually associates with host response to injuries, facilitation of disease progression and significant tissue damage. In skeletal muscles, fragmentary knowledge of MMPs/TIMPs regulation and function underscores the need for a better understanding of their role which may lead to therapeutic alternatives. This review presents the current knowledge of MMPs in the biology and pathology of skeletal muscles and puts into perspective therapeutic alternatives that could be challenged in experimental models or that might emerge from in depth investigation of MMPs/TIMPs status in neuromuscular diseases.
    Neurobiology of Disease 08/2012; 48(3):508-18. DOI:10.1016/j.nbd.2012.07.023 · 5.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Biomaterials that are similar to skeletal muscle extracellular matrix have been shown to augment regeneration in ischemic muscle. In this study, treatment with a collagen-based matrix stimulated molecular myogenesis in an mdx murine model of necrosis. Matrix-treated animals ran ≥40% further, demonstrating functional regeneration, and expressed increased levels of myogenic transcripts. In contrast, matrix treatment was unable to induce transcriptional or functional changes in an MLC/SOD1G93A atrophic mouse model. In vitro, satellite cells were cultured: 1) under standard conditions, 2) on matrix, 3) in the presence of myocyte debris (to simulate a necrotic-like environment), or 4) with both matrix and necrotic stimuli. Exposure to both stimuli induced the greatest increases in mef2c, myf5, myoD and myogenin transcripts. Furthermore, conditioned medium collected from satellite cells cultured with both stimuli contained elevated levels of factors that modulate satellite cell activation and proliferation, such as FGF-2, HGF and SDF-1. Application of the conditioned medium to C2C12 myoblasts accelerated maturation, demonstrated by increased mef2c, myf5 and myogenin transcripts and fusion indexes. In summary, the collagen matrix required a necrotic stimulus to enhance the maturation of satellite cell and their secretion of a myogenic cocktail. Considering that matrix treatment supports myogenesis only in in vivo models that exhibit necrosis, this study demonstrates that a necrotic environment is required to maximize matrix-mediated myogenesis.
    Disease Models and Mechanisms 02/2013; 6(3). DOI:10.1242/dmm.011072 · 5.54 Impact Factor
Show more