Skeletal Muscle progenitors are sensitive to collagen architectural features of fibril size and crosslinking

2021 ◽  
Author(s):  
Lin-Ya Hu ◽  
Cassidy Jane Mileti ◽  
Taryn Loomis ◽  
Sarah E. Brashear ◽  
Sarah Ahmad ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Second Harmonic ◽  
Collagen Fibrils ◽  
Collagen Concentration ◽  
C2c12 Myoblasts ◽  
Skeletal Muscle Myosin ◽  
Muscle Stem Cells ◽  
Primary Mouse ◽  
Significant Difference ◽  
Second Harmonic Generation Imaging

Muscle stem cells (MuSCs) are essential for the robust regenerative capacity of skeletal muscle. However, in fibrotic environments marked by abundant collagen and altered collagen organization, the regenerative capability of MuSCs is diminished. MuSCs are sensitive to their extracellular matrix environment, but their response to collagen architecture is largely unknown. The present study aimed to systematically test the effect of underlying collagen structures on MuSC functions. Collagen hydrogels were engineered with varied architectures: collagen concentration, crosslinking, fibril size, and fibril alignment, and the changes were validated with second harmonic generation imaging and rheology. Proliferation and differentiation responses of primary mouse MuSCs and immortal myoblasts (C2C12s) were assessed using EdU assays and immunolabeling skeletal muscle myosin expression, respectively. Changing collagen concentration and the corresponding hydrogel stiffness did not have a significant influence on MuSC proliferation or differentiation. However, MuSC differentiation on atelocollagen gels, which do not form mature pyridinoline crosslinks, was increased compared to the crosslinked control. In addition, MuSCs and C2C12 myoblasts showed greater differentiation on gels with smaller collagen fibrils. Proliferation rates of C2C12 myoblasts were also higher on gels with smaller collagen fibrils, while MuSCs did not show a significant difference. Surprisingly, collagen alignment did not have significant effects on muscle progenitor function. This study demonstrates that MuSCs are capable of sensing their underlying ECM structures and enhancing differentiation on substrates with less collagen crosslinking or smaller collagen fibrils. Thus, in fibrotic muscle, targeting crosslinking and fibril size rather than collagen expression may more effectively support MuSC-based regeneration.

Interleukin-6 promotes myogenic differentiation of mouse skeletal muscle cells: role of the STAT3 pathway

2013 ◽  
Vol 304 (2) ◽  
pp. C128-C136 ◽  
Author(s):  
Miriam Hoene ◽  
Heike Runge ◽  
Hans Ulrich Häring ◽  
Erwin D. Schleicher ◽  
Cora Weigert
Keyword(s):  
Skeletal Muscle ◽  
Mrna Expression ◽  
Myogenic Differentiation ◽  
Muscle Cells ◽  
C2c12 Cells ◽  
Skeletal Muscle Cells ◽  
Wild Type ◽  
C2c12 Myoblasts ◽  
Sequence Of Events ◽  
Primary Mouse

Myogenic differentiation of skeletal muscle cells is characterized by a sequence of events that include activation of signal transducer and activator of transcription 3 (STAT3) and enhanced expression of its target gene Socs3. Autocrine effects of IL-6 may contribute to the activation of the STAT3-Socs3 cascade and thus to myogenic differentiation. The importance of IL-6 and STAT3 for the differentiation process was studied in C2C12 cells and in primary mouse wild-type and IL-6−/− skeletal muscle cells. In differentiating C2C12 myoblasts, the upregulation of IL-6 mRNA expression and protein secretion started after increased phosphorylation of STAT3 on tyrosine 705 and increased mRNA expression of Socs3 was observed. Knockdown of STAT3 and IL-6 mRNA in differentiating C2C12 myoblasts impaired the expression of the myogenic markers myogenin and MyHC IIb and subsequently myotube fusion. However, the knockdown of IL-6 did not prevent the induction of STAT3 tyrosine phosphorylation. The IL-6-independent activation of STAT3 was verified in differentiating primary IL-6−/− myoblasts. The phosphorylation of STAT3 and the expression levels of STAT3, Socs3, and myogenin during differentiation were comparable in the primary myoblasts independent of the genotype. However, IL-6−/− cells failed to induce MyHC IIb expression to the same level as in wild-type cells and showed reduced myotube formation. Supplementation of IL-6 could partially restore the fusion of IL-6−/− cells. These data demonstrate that IL-6 depletion during myogenic differentiation does not reduce the activation of the STAT3-Socs3 cascade, while IL-6 and STAT3 are both necessary to promote myotube fusion.

Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells

2014 ◽  
Vol 306 (2) ◽  
pp. E150-E156 ◽  
Author(s):  
Mara Fornaro ◽  
Aaron C. Hinken ◽  
Saul Needle ◽  
Erding Hu ◽  
Anne-Ulrike Trendelenburg ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Stem Cells ◽  
Amino Acid ◽  
Growth Factor ◽  
Muscle Stem Cells ◽  
Mechano Growth Factor ◽  
Primary Mouse ◽  
Proliferation And Differentiation ◽  
Vitro Effect

A splice form of IGF-1, IGF-1Eb, is upregulated after exercise or injury. Physiological responses have been ascribed to the 24-amino acid COOH-terminal peptide that is cleaved from the NH3-terminal 70-amino acid mature IGF-1 protein. This COOH-terminal peptide was termed “mechano-growth factor” (MGF). Activities claimed for the MGF peptide included enhancing muscle satellite cell proliferation and delaying myoblast fusion. As such, MGF could represent a promising strategy to improve muscle regeneration. Thus, at our two pharmaceutical companies, we attempted to reproduce the claimed effect of MGF peptides on human and mouse muscle myoblast proliferation and differentiation in vitro. Concentrations of peptide up to 500 ng/ml failed to increase the proliferation of C2C12 cells or primary human skeletal muscle myoblasts. In contrast, all cell types exhibited a proliferative response to mature IGF-1 or full-length IGF-1Eb. MGF also failed to inhibit the differentiation of myoblasts into myotubes. To address whether the response to MGF was lost in these tissue culture lines, we measured proliferation and differentiation of primary mouse skeletal muscle stem cells exposed to MGF. This, too, failed to demonstrate a significant effect. Finally, we tested whether MGF could alter a separate documented in vitro effect of the peptide, activation of p-ERK, but not p-Akt, in cardiac myocytes. Although a robust response to IGF-1 was observed, there were no demonstrated activating responses from the native or a stabilized MGF peptide. These results call in to question whether there is a physiological role for MGF.

scholarly journals Optical Clearing for Improved Contrast in Second Harmonic Generation Imaging of Skeletal Muscle

2006 ◽  
Vol 90 (1) ◽  
pp. 328-339 ◽  
Author(s):  
Sergey Plotnikov ◽  
Vaibhav Juneja ◽  
Ariel B. Isaacson ◽  
William A. Mohler ◽  
Paul J. Campagnola
Keyword(s):  
Skeletal Muscle ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Optical Clearing ◽  
Second Harmonic Generation Imaging

scholarly journals Activation of Cdc6 by MyoD is associated with the expansion of quiescent myogenic satellite cells

2010 ◽  
Vol 188 (1) ◽  
pp. 39-48 ◽  
Author(s):  
Keman Zhang ◽  
Jingfeng Sha ◽  
Marian L. Harter
Keyword(s):  
Stem Cells ◽  
Satellite Cells ◽  
S Phase ◽  
Transcriptional Factor ◽  
C2c12 Cells ◽  
C2c12 Myoblasts ◽  
Muscle Stem Cells ◽  
Primary Mouse ◽  
E Box ◽  
Myogenic Satellite Cells

MyoD is a transcriptional factor that is required for the differentiation of muscle stem cells (satellite cells). In this study, we describe a previously unknown function for MyoD in regulating a gene (Cdc6) that is vital to endowing chromatin with the capability of replicating DNA. In C2C12 and primary mouse myoblasts, we show that MyoD can occupy an E-box within the promoter of Cdc6 and that this association, along with E2F3a, is required for its activity. MyoD and Cdc6 are both expressed after quiescent C2C12 myoblasts or satellite cells in association with myofibers are stimulated for growth, but MyoD appears at least 2–3 h earlier than Cdc6. Finally, knockdown of MyoD impairs the ability of C2C12 cells to express Cdc6 after leaving quiescence, and as a result, they cannot fully progress into S phase. Our results define a mechanism by which MyoD helps myogenic satellite cells to enter into the first round of DNA replication after transitioning out of quiescence.

scholarly journals A defined N6-methyladenosine (m6A) profile conferred by METTL3 regulates muscle stem cell/myoblast state transitions

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Brandon J. Gheller ◽  
Jamie E. Blum ◽  
Ern Hwei Hannah Fong ◽  
Olga V. Malysheva ◽  
Benjamin D. Cosgrove ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Stem Cell ◽  
Muscle Regeneration ◽  
Transcriptional Profile ◽  
Skeletal Muscle Regeneration ◽  
State Transitions ◽  
C2c12 Myoblasts ◽  
Primary Mouse

Abstract Muscle-specific adult stem cells (MuSCs) are required for skeletal muscle regeneration. To ensure efficient skeletal muscle regeneration after injury, MuSCs must undergo state transitions as they are activated from quiescence, give rise to a population of proliferating myoblasts, and continue either to terminal differentiation, to repair or replace damaged myofibers, or self-renewal to repopulate the quiescent population. Changes in MuSC/myoblast state are accompanied by dramatic shifts in their transcriptional profile. Previous reports in other adult stem cell systems have identified alterations in the most abundant internal mRNA modification, N6-methyladenosine (m6A), conferred by its active writer, METTL3, to regulate cell state transitions through alterations in the transcriptional profile of these cells. Our objective was to determine if m6A-modification deposition via METTL3 is a regulator of MuSC/myoblast state transitions in vitro and in vivo. Using liquid chromatography/mass spectrometry we identified that global m6A levels increase during the early stages of skeletal muscle regeneration, in vivo, and decline when C2C12 myoblasts transition from proliferation to differentiation, in vitro. Using m6A-specific RNA-sequencing (MeRIP-seq), a distinct profile of m6A-modification was identified, distinguishing proliferating from differentiating C2C12 myoblasts. RNAi studies show that reducing levels of METTL3, the active m6A methyltransferase, reduced global m6A levels and forced C2C12 myoblasts to prematurely differentiate. Reducing levels of METTL3 in primary mouse MuSCs prior to transplantation enhanced their engraftment capacity upon primary transplantation, however their capacity for serial transplantation was lost. In conclusion, METTL3 regulates m6A levels in MuSCs/myoblasts and controls the transition of MuSCs/myoblasts to different cell states. Furthermore, the first transcriptome wide map of m6A-modifications in proliferating and differentiating C2C12 myoblasts is provided and reveals a number of genes that may regulate MuSC/myoblast state transitions which had not been previously identified.

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