Post-transcriptional regulation of satellite cell quiescence by TTP-mediated mRNA decay

Skeletal muscle satellite cells in their niche are quiescent and upon muscle injury, exit quiescence, proliferate to repair muscle tissue, and self-renew to replenish the satellite cell population. To understand the mechanisms involved in maintaining satellite cell quiescence, we identified gene transcripts that were differentially expressed during satellite cell activation following muscle injury. Transcripts encoding RNA binding proteins were among the most significantly changed and included the mRNA decay factor Tristetraprolin. Tristetraprolin promotes the decay of MyoD mRNA, which encodes a transcriptional regulator of myogenic commitment, via binding to the MyoD mRNA 3′ untranslated region. Upon satellite cell activation, p38α/β MAPK phosphorylates MAPKAP2 and inactivates Tristetraprolin, stabilizing MyoD mRNA. Satellite cell specific knockdown of Tristetraprolin precociously activates satellite cells in vivo, enabling MyoD accumulation, differentiation and cell fusion into myofibers. Regulation of mRNAs by Tristetraprolin appears to function as one of several critical post-transcriptional regulatory mechanisms controlling satellite cell homeostasis.

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Metformin Delays Satellite Cell Activation and Maintains Quiescence

Stem Cells International ◽

10.1155/2019/5980465 ◽

2019 ◽

Vol 2019 ◽

pp. 1-19 ◽

Cited By ~ 11

Author(s):

Theodora Pavlidou ◽

Milica Marinkovic ◽

Marco Rosina ◽

Claudia Fuoco ◽

Simone Vumbaca ◽

...

Keyword(s):

Satellite Cell ◽

Muscle Tissue ◽

Satellite Cells ◽

Cell Activation ◽

Myogenic Differentiation ◽

Metabolic State ◽

Cell Pool ◽

Age Related ◽

Satellite Cell Activation

The regeneration of the muscle tissue relies on the capacity of the satellite stem cell (SC) population to exit quiescence, divide asymmetrically, proliferate, and differentiate. In age-related muscle atrophy (sarcopenia) and several dystrophies, regeneration cannot compensate for the loss of muscle tissue. These disorders are associated with the depletion of the satellite cell pool or with the loss of satellite cell functionality. Recently, the establishment and maintenance of quiescence in satellite cells have been linked to their metabolic state. In this work, we aimed to modulate metabolism in order to preserve the satellite cell pool. We made use of metformin, a calorie restriction mimicking drug, to ask whether metformin has an effect on quiescence, proliferation, and differentiation of satellite cells. We report that satellite cells, when treated with metformin in vitro, ex vivo, or in vivo, delay activation, Pax7 downregulation, and terminal myogenic differentiation. We correlate the metformin-induced delay in satellite cell activation with the inhibition of the ribosome protein RPS6, one of the downstream effectors of the mTOR pathway. Moreover, in vivo administration of metformin induces a belated regeneration of cardiotoxin- (CTX-) damaged skeletal muscle. Interestingly, satellite cells treated with metformin immediately after isolation are smaller in size and exhibit reduced pyronin Y levels, which suggests that metformin-treated satellite cells are transcriptionally less active. Thus, our study suggests that metformin delays satellite cell activation and differentiation by favoring a quiescent, low metabolic state.

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A Role for Nitric Oxide in Muscle Repair: Nitric Oxide–mediated Activation of Muscle Satellite Cells

Molecular Biology of the Cell ◽

10.1091/mbc.11.5.1859 ◽

2000 ◽

Vol 11 (5) ◽

pp. 1859-1874 ◽

Cited By ~ 275

Author(s):

Judy E. Anderson

Keyword(s):

Nitric Oxide ◽

Satellite Cell ◽

Satellite Cells ◽

Knockout Mice ◽

Cell Activation ◽

Mdx Mice ◽

Muscle Repair ◽

Muscle Satellite Cells ◽

Satellite Cell Activation

Muscle satellite cells are quiescent precursors interposed between myofibers and a sheath of external lamina. Although their activation and recruitment to cycle enable muscle repair and adaptation, the activation signal is not known. Evidence is presented that nitric oxide (NO) mediates satellite cell activation, including morphological hypertrophy and decreased adhesion in the fiber-lamina complex. Activation in vivo occurred within 1 min after injury. Cell isolation and histology showed that pharmacological inhibition of nitric oxide synthase (NOS) activity prevented the immediate injury-induced myogenic cell release and delayed the hypertrophy of satellite cells in that muscle. Transient activation of satellite cells in contralateral muscles 10 min later suggested that a circulating factor may interact with NO-mediated signaling. Interestingly, satellite cell activation in muscles of mdx dystrophic mice and NOS-I knockout mice quantitatively resembled NOS-inhibited release of normal cells, in agreement with reports of displaced and reduced NOS expression in dystrophin-deficient mdx muscle and the complete loss of NOS-I expression in knockout mice. Brief NOS inhibition in normal and mdx mice during injury produced subtle alterations in subsequent repair, including apoptosis in myotube nuclei and myotube formation inside laminar sheaths. Longer NOS inhibition delayed and restricted the extent of repair and resulted in fiber branching. A model proposes the hypothesis that NO release mediates satellite cell activation, possibly via shear-induced rapid increases in NOS activity that produce “NO transients.”

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Myostatin negatively regulates satellite cell activation and self-renewal

The Journal of Cell Biology ◽

10.1083/jcb.200207056 ◽

2003 ◽

Vol 162 (6) ◽

pp. 1135-1147 ◽

Cited By ~ 483

Author(s):

Seumas McCroskery ◽

Mark Thomas ◽

Linda Maxwell ◽

Mridula Sharma ◽

Ravi Kambadur

Keyword(s):

Satellite Cell ◽

Satellite Cells ◽

Cell Activation ◽

Unit Length ◽

Immunohistochemical Analysis ◽

Cell Number ◽

Negative Regulator ◽

Self Renewal ◽

Satellite Cell Activation

Satellite cells are quiescent muscle stem cells that promote postnatal muscle growth and repair. Here we show that myostatin, a TGF-β member, signals satellite cell quiescence and also negatively regulates satellite cell self-renewal. BrdU labeling in vivo revealed that, among the Myostatin-deficient satellite cells, higher numbers of satellite cells are activated as compared with wild type. In contrast, addition of Myostatin to myofiber explant cultures inhibits satellite cell activation. Cell cycle analysis confirms that Myostatin up-regulated p21, a Cdk inhibitor, and decreased the levels and activity of Cdk2 protein in satellite cells. Hence, Myostatin negatively regulates the G1 to S progression and thus maintains the quiescent status of satellite cells. Immunohistochemical analysis with CD34 antibodies indicates that there is an increased number of satellite cells per unit length of freshly isolated Mstn−/− muscle fibers. Determination of proliferation rate suggests that this elevation in satellite cell number could be due to increased self-renewal and delayed expression of the differentiation gene (myogenin) in Mstn−/− adult myoblasts. Taken together, these results suggest that Myostatin is a potent negative regulator of satellite cell activation and thus signals the quiescence of satellite cells.

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Culture conditions influence satellite cell activation and survival of single myofibers

European Journal of Translational Myology ◽

10.4081/ejtm.2018.7567 ◽

2018 ◽

Vol 28 (2) ◽

Cited By ~ 2

Author(s):

Alessandra Renzini ◽

Anna Benedetti ◽

Marina Bouché ◽

Leopoldo Silvestroni ◽

Sergio Adamo ◽

...

Keyword(s):

Satellite Cell ◽

Satellite Cells ◽

Cell Activation ◽

Culture Conditions ◽

Experimental Conditions ◽

Direct Observations ◽

Satellite Cell Activation ◽

Indispensable Tool

Single myofiber isolation protocols allow to obtain an in vitro system in which the physical association between the myofiber and its stem cells, the satellite cells, is adequately preserved. This technique is an indispensable tool by which the muscle regeneration process can be recapitulated and studied in each specific phase, from satellite cell activation to proliferation, from differentiation to fusion. This study aims to clarify the effect of different culture conditions on single myofibers, their associated satellite cells, and the physiological behavior of the satellite cells upon long term culture. By direct observations of the cultures, we compared different experimental conditions and their effect on both satellite cell behavior and myofiber viability.

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A role for calcium-calmodulin in regulating nitric oxide production during skeletal muscle satellite cell activation

AJP Cell Physiology ◽

10.1152/ajpcell.00471.2008 ◽

2009 ◽

Vol 296 (4) ◽

pp. C922-C929 ◽

Cited By ~ 30

Author(s):

Ryuichi Tatsumi ◽

Adam L. Wuollet ◽

Kuniko Tabata ◽

Shotaro Nishimura ◽

Shoji Tabata ◽

...

Keyword(s):

Nitric Oxide ◽

Skeletal Muscle ◽

Methyl Ester ◽

Satellite Cell ◽

Satellite Cells ◽

Cell Activation ◽

Calcium Ionophore ◽

Ester Hydrochloride ◽

Methyl Ester Hydrochloride ◽

Satellite Cell Activation

When skeletal muscle is stretched or injured, myogenic satellite cells are activated to enter the cell cycle. This process depends on nitric oxide (NO) production by NO synthase (NOS), matrix metalloproteinase activation, release of hepatocyte growth factor (HGF) from the extracellular matrix, and presentation of HGF to the c-met receptor as demonstrated by a primary culture and in vivo assays. We now add evidence that calcium-calmodulin is involved in the satellite cell activation cascade in vitro. Conditioned medium from cultures that were treated with a calcium ionophore (A23187, ionomycin) for 2 h activated cultured satellite cells and contained active HGF, similar to the effect of mechanical stretch or NO donor treatments. The response was abolished by addition of calmodulin inhibitors (calmidazolium, W-13, W-12) or a NOS inhibitor NG-nitro-l-arginine methyl ester hydrochloride but not by its less inactive enantiomer NG-nitro-d-arginine methyl ester hydrochloride. Satellite cells were also shown to express functional calmodulin protein having a calcium-binding activity at 12 h postplating, which is the time at which the calcium ionophore was added in this study and the stretch treatment was applied in our previous experiments. Therefore, results from these experiments provide an additional insight that calcium-calmodulin mediates HGF release from the matrix and that this step in the activation pathway is upstream from NO synthesis.

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Expression of Cd34 and Myf5 Defines the Majority of Quiescent Adult Skeletal Muscle Satellite Cells

The Journal of Cell Biology ◽

10.1083/jcb.151.6.1221 ◽

2000 ◽

Vol 151 (6) ◽

pp. 1221-1234 ◽

Cited By ~ 572

Author(s):

Jonathan R. Beauchamp ◽

Louise Heslop ◽

David S.W. Yu ◽

Shahragim Tajbakhsh ◽

Robert G. Kelly ◽

...

Keyword(s):

Skeletal Muscle ◽

Satellite Cell ◽

Satellite Cells ◽

Myosin Light Chain ◽

Cell Activation ◽

Cell Marker ◽

Alternate Splicing ◽

Adult Skeletal Muscle ◽

Hematopoietic Stem ◽

Cell Quiescence

Skeletal muscle is one of a several adult post-mitotic tissues that retain the capacity to regenerate. This relies on a population of quiescent precursors, termed satellite cells. Here we describe two novel markers of quiescent satellite cells: CD34, an established marker of hematopoietic stem cells, and Myf5, the earliest marker of myogenic commitment. CD34+ve myoblasts can be detected in proliferating C2C12 cultures. In differentiating cultures, CD34+ve cells do not fuse into myotubes, nor express MyoD. Using isolated myofibers as a model of synchronous precursor cell activation, we show that quiescent satellite cells express CD34. An early feature of their activation is alternate splicing followed by complete transcriptional shutdown of CD34. This data implicates CD34 in the maintenance of satellite cell quiescence. In heterozygous Myf5nlacZ/+ mice, all CD34+ve satellite cells also express β-galactosidase, a marker of activation of Myf5, showing that quiescent satellite cells are committed to myogenesis. All such cells are positive for the accepted satellite cell marker, M-cadherin. We also show that satellite cells can be identified on isolated myofibers of the myosin light chain 3F-nlacZ-2E mouse as those that do not express the transgene. The numbers of satellite cells detected in this way are significantly greater than those identified by the other three markers. We conclude that the expression of CD34, Myf5, and M-cadherin defines quiescent, committed precursors and speculate that the CD34−ve, Myf5−ve minority may be involved in maintaining the lineage-committed majority.

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