p21 is essential for normal myogenic progenitor cell function in regenerating skeletal muscle

2003 ◽  
Vol 285 (5) ◽  
pp. C1019-C1027 ◽  
Author(s):  
T. J. Hawke ◽  
A. P. Meeson ◽  
N. Jiang ◽  
S. Graham ◽  
K. Hutcheson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Skeletal Muscle ◽  
Muscle Regeneration ◽  
Cell Function ◽  
Kinase Inhibitor ◽  
Cell Number ◽  
Skeletal Muscle Regeneration ◽  
Wild Type ◽  
Compensatory Mechanisms ◽  
Myogenic Progenitor

Despite the ability of myogenic progenitor cells (MPCs) to completely regenerate skeletal muscle following injury, little is known regarding the molecular program that regulates their proliferation and differentiation. Although mice lacking the cyclin-dependent kinase inhibitor p21 (p21-/-), develop normally, we report here that p21-/- MPCs display increased cell number and enhanced cell cycle progression compared with wild-type MPCs. Therefore, we hypothesized that p21-/- mice would demonstrate temporally enhanced regeneration following myotrauma. In response to cardiotoxin-induced injury, p21-/- skeletal muscle regeneration was significantly attenuated vs. regenerating wild-type muscle, contrary to the hypothesis. Regenerating p21-/- skeletal muscle displayed increased proliferative (PCNA positive) nuclei coincident with increased apoptotic nuclei (TUNEL positive) compared with wild-type muscle up to 3 wk after injury. Differentiation of p21-/- MPCs was markedly impaired and associated with increased apoptosis compared with wild-type MPCs, confirming that the impaired differentiation of the p21-/- MPCs was a cell autonomous event. No dysregulation of p27, p53, or p57 protein expression in differentiating p21-/- MPCs compared with wild-type MPCs was observed, suggesting that other compensatory mechanisms are responsible for the regeneration that ultimately occurs. On the basis of these findings, we propose that p21 is essential for the coordination of cell cycle exit and differentiation in the adult MPC population and that in the absence of p21, skeletal muscle regeneration is markedly impaired.

Urokinase-dependent plasminogen activation is required for efficient skeletal muscle regeneration in vivo

Blood ◽  
2001 ◽  
Vol 97 (6) ◽  
pp. 1703-1711 ◽  
Author(s):  
Frederic Lluı́s ◽  
Josep Roma ◽  
Mònica Suelves ◽  
Maribel Parra ◽  
Gloria Aniorte ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasminogen Activator ◽  
Muscle Regeneration ◽  
Plasminogen Activators ◽  
Skeletal Muscle Regeneration ◽  
Plasminogen Activation ◽  
Wild Type ◽  
Type Plasminogen Activator ◽  
Deficient Mice

Plasminogen activators urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) are extracellular proteases involved in various tissue remodeling processes. A requirement for uPA activity in skeletal myogenesis was recently demonstrated in vitro. The role of plasminogen activators in skeletal muscle regeneration in vivo in wild-type, uPA-deficient, and tPA-deficient mice is investigated here. Wild-type and tPA−/− mice completely repaired experimentally damaged skeletal muscle. In contrast, uPA−/− mice had a severe regeneration defect, with decreased recruitment of blood-derived monocytes to the site of injury and with persistent myotube degeneration. In addition, uPA-deficient mice accumulated fibrin in the degenerating muscle fibers; however, the defibrinogenation of uPA-deficient mice resulted in a correction of the muscle regeneration defect. A similar severe regeneration deficit with persistent fibrin deposition was also reproducible in plasminogen-deficient mice after injury, suggesting that fibrinolysis by uPA-mediated plasminogen activation plays a fundamental role in skeletal muscle regeneration. In conclusion, the uPA-plasmin system is identified as a critical component of the mammalian skeletal muscle regeneration process, possibly because it prevents intramuscular fibrin accumulation and contributes to the adequate inflammatory response after injury. These studies demonstrate the requirement of an extracellular proteolytic cascade during muscle regeneration in vivo.

scholarly journals Tumor Necrosis Factor Alpha Regulates Skeletal Myogenesis by Inhibiting SP1 Interaction with cis-Acting Regulatory Elements within the Fbxl2 Gene Promoter

2020 ◽  
Vol 40 (12) ◽  
Author(s):  
Michael E. O’Brien ◽  
James Londino ◽  
Marcus McGinnis ◽  
Nathaniel Weathington ◽  
Jessica Adair ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Skeletal Muscle ◽  
Muscle Regeneration ◽  
Cell Cycle Progression ◽  
Myogenic Differentiation ◽  
Core Promoter ◽  
Skeletal Muscle Regeneration ◽  
Skeletal Myogenesis ◽  
Necrosis Factor Alpha ◽  
Tnf Α

ABSTRACT FBXL2 is an important ubiquitin E3 ligase component that modulates inflammatory signaling and cell cycle progression, but its molecular regulation is largely unknown. Here, we show that tumor necrosis factor alpha (TNF-α), a critical cytokine linked to the inflammatory response during skeletal muscle regeneration, suppressed Fbxl2 mRNA expression in C2C12 myoblasts and triggered significant alterations in cell cycle, metabolic, and protein translation processes. Gene silencing of Fbxl2 in skeletal myoblasts resulted in increased proliferative responses characterized by activation of mitogen-activated protein (MAP) kinases and nuclear factor kappa B and decreased myogenic differentiation, as reflected by reduced expression of myogenin and impaired myotube formation. TNF-α did not destabilize the Fbxl2 transcript (half-life [t1/2], ∼10 h) but inhibited SP1 transactivation of its core promoter, localized to bp −160 to +42 within the proximal 5′ flanking region of the Fbxl2 gene. Chromatin immunoprecipitation and gel shift studies indicated that SP1 interacted with the Fbxl2 promoter during cellular differentiation, an effect that was less pronounced during proliferation or after TNF-α exposure. TNF-α, via activation of JNK, mediated phosphorylation of SP1 that impaired its binding to the Fbxl2 promoter, resulting in reduced transcriptional activity. The results suggest that SP1 transcriptional activation of Fbxl2 is required for skeletal muscle differentiation, a process that is interrupted by a key proinflammatory myopathic cytokine. IMPORTANCE Skeletal muscle regeneration and repair involve the recruitment and proliferation of resident satellite cells that exit the cell cycle during the process of myogenic differentiation to form myofibers. We demonstrate that the ubiquitin E3 ligase subunit FBXL2 is essential for skeletal myogenesis through its important effects on cell cycle progression and cell proliferative signaling. Further, we characterize a new mechanism whereby sustained stimulation by a major proinflammatory cytokine, TNF-α, regulates skeletal myogenesis by inhibiting the interaction of SP1 with the Fbxl2 core promoter in proliferating myoblasts. Our findings contribute to the understanding of skeletal muscle regeneration through the identification of Fbxl2 as both a critical regulator of myogenic proliferative processes and a susceptible gene target during inflammatory stimulation by TNF-α in skeletal muscle. Modulation of Fbxl2 activity may have relevance to disorders of muscle wasting associated with sustained proinflammatory signaling.

Plasmin activity is required for myogenesis in vitro and skeletal muscle regeneration in vivo

Blood ◽  
2002 ◽  
Vol 99 (8) ◽  
pp. 2835-2844 ◽  
Author(s):  
Mònica Suelves ◽  
Roser López-Alemany ◽  
Frederic Lluı́s ◽  
Gloria Aniorte ◽  
Erika Serrano ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Regeneration ◽  
Myoblast Fusion ◽  
Skeletal Muscle Regeneration ◽  
Wild Type ◽  
Plasmin Activity ◽  
Type Plasminogen Activator ◽  
Deficient Mice

Abstract Plasmin, the primary fibrinolytic enzyme, has a broad substrate spectrum and is implicated in biologic processes dependent upon proteolytic activity, such as tissue remodeling and cell migration. Active plasmin is generated from proteolytic cleavage of the zymogen plasminogen (Plg) by urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). Here, we have investigated the role of plasmin in C2C12 myoblast fusion and differentiation in vitro, as well as in skeletal muscle regeneration in vivo, in wild-type and Plg-deficient mice. Wild-type mice completely repaired experimentally damaged skeletal muscle. In contrast, Plg−/− mice presented a severe regeneration defect with decreased recruitment of blood-derived monocytes and lymphocytes to the site of injury and persistent myotube degeneration. In addition, Plg-deficient mice accumulated fibrin in the degenerating muscle fibers; however, fibrinogen depletion of Plg-deficient mice resulted in a correction of the muscular regeneration defect. Because we found that uPA, but not tPA, was induced in skeletal muscle regeneration, and persistent fibrin deposition was also reproducible in uPA-deficient mice following injury, we propose that fibrinolysis by uPA-dependent plasmin activity plays a fundamental role in skeletal muscle regeneration. In summary, we identify plasmin as a critical component of the mammalian skeletal muscle regeneration process, possibly by preventing intramuscular fibrin accumulation and by contributing to the adequate inflammatory response after injury. Finally, we found that inhibition of plasmin activity with α2-antiplasmin resulted in decreased myoblast fusion and differentiation in vitro. Altogether, these studies demonstrate the requirement of plasmin during myogenesis in vitro and muscle regeneration in vivo.

scholarly journals Foxk1 recruits the Sds3 complex and represses gene expression in myogenic progenitors

2012 ◽  
Vol 446 (3) ◽  
pp. 349-357 ◽  
Author(s):  
Xiaozhong Shi ◽  
David C. Seldin ◽  
Daniel J. Garry
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Skeletal Muscle ◽  
Protein Kinase ◽  
Muscle Regeneration ◽  
Cell Cycle Progression ◽  
Adaptor Protein ◽  
Skeletal Muscle Regeneration ◽  
Cycle Progression ◽  
Repression Complex

Previous studies have established that Foxk1 (forkhead box k1) plays an important role in skeletal muscle regeneration. Foxk1 regulates the cell-cycle progression of myogenic progenitors by repressing the cell-cycle inhibitor gene p21. However, the underlying mechanism is not well understood. In the present study, we report the identification of Sds3 (suppressor of defective silencing 3) as an adaptor protein that recruits the Sin3 [SWI (switch)-independent 3]–HDAC (histone deacetylase) repression complex and binds Foxk1. Using GST (glutathione transferase) pull-down assays, we defined the interaction between the Foxk1 FHA (forkhead-associated domain) domain and phospho-Thr49 in Sds3. We demonstrated that the transcriptional repression of Foxk1 is dependent on the Sin3–Sds3 repression complex, and knockdown of Sds3 results in cell-cycle arrest. We further identified the protein kinase CK2 as the protein kinase for Sds3 Thr49 and demonstrated that the protein kinase activity of CK2 is required for proper cell-cycle progression. Analysis of CK2 mutant mice reveals perturbation of skeletal muscle regeneration due to the dysregulation of cell-cycle kinetics. Overall, these studies define a CK2–Sds3–Foxk1 cascade that modulates gene expression and regulates skeletal muscle regeneration.

scholarly journals Necdin mediates skeletal muscle regeneration by promoting myoblast survival and differentiation

2007 ◽  
Vol 179 (2) ◽  
pp. 305-319 ◽  
Author(s):  
Daniela Deponti ◽  
Stéphanie François ◽  
Silvia Baesso ◽  
Clara Sciorati ◽  
Anna Innocenzi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transgenic Mice ◽  
Satellite Cell ◽  
Muscle Regeneration ◽  
Muscle Injury ◽  
Muscle Fibers ◽  
Skeletal Muscle Regeneration ◽  
Muscle Degeneration ◽  
Wild Type ◽  
Cell Type

Regeneration of muscle fibers that are lost during pathological muscle degeneration or after injuries is sustained by the production of new myofibers. An important cell type involved in muscle regeneration is the satellite cell. Necdin is a protein expressed in satellite cell–derived myogenic precursors during perinatal growth. However, its function in myogenesis is not known. We compare transgenic mice that overexpress necdin in skeletal muscle with both wild-type and necdin null mice. After muscle injury the necdin null mice show a considerable defect in muscle healing, whereas mice that overexpress necdin show a substantial increase in myofiber regeneration. We also find that in muscle, necdin increases myogenin expression, accelerates differentiation, and counteracts myoblast apoptosis. Collectively, these data clarify the function and mechanism of necdin in skeletal muscle and show the importance of necdin in muscle regeneration.

Delayed angiogenesis and VEGF production in CCR2−/− mice during impaired skeletal muscle regeneration

2007 ◽  
Vol 293 (2) ◽  
pp. R651-R661 ◽  
Author(s):  
Oscar Ochoa ◽  
Dongxu Sun ◽  
Sara M. Reyes-Reyna ◽  
Lindsay L. Waite ◽  
Joel E. Michalek ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Regeneration ◽  
Capillary Density ◽  
Skeletal Muscle Regeneration ◽  
Mouse Strains ◽  
Vascular Endothelial ◽  
Wild Type ◽  
Fiber Size ◽  
Cc Chemokine Receptor 2 ◽  
Endothelial Growth Factor

The regulation of vascular endothelial growth factor (VEGF) levels and angiogenic events during skeletal muscle regeneration remains largely unknown. This study examined angiogenesis, VEGF levels, and muscle regeneration after cardiotoxin (CT)-induced injury in mice lacking the CC chemokine receptor 2 (CCR2). Muscle regeneration was significantly decreased in CCR2−/− mice as was the early accumulation of macrophages after injury. In both mouse strains, tissue VEGF was similar at baseline (no injections) and significantly decreased at day 3 post-CT. Tissue VEGF in wild-type (WT) mice was restored within 7 days postinjury but remained significantly reduced in CCR2−/− mice until day 21. Capillary density (capillaries/mm2) within regenerating muscle was maximal in WT mice at day 7 and double that of baseline muscle. In comparison, maximal capillary density in CCR2−/− mice occurred at 21 days postinjury. Maximal capillary density developed concurrent with the restoration of tissue VEGF in both strains. A highly significant, inverse relationship existed between the size of regenerated muscle fibers and capillaries per square millimeter. Although this relationship was comparable in WT and CCR2−/− animals, there was a significant decrease in the magnitude of this response in the absence of CCR2, reflecting the observation that regenerated muscle fiber size in CCR2−/− mice was only 50% of baseline at 42 days postinjury, whereas WT mice had attained baseline fiber size by day 21. Thus CCR2-dependent events in injured skeletal muscle, including impaired macrophage recruitment, contribute to restoration of tissue VEGF levels and the dynamic processes of capillary formation and muscle regeneration.

Rad is temporally regulated within myogenic progenitor cells during skeletal muscle regeneration

2006 ◽  
Vol 290 (2) ◽  
pp. C379-C387 ◽  
Author(s):  
Thomas J. Hawke ◽  
Shane B. Kanatous ◽  
Cindy M. Martin ◽  
Sean C. Goetsch ◽  
Daniel J. Garry
Keyword(s):  
Skeletal Muscle ◽  
Progenitor Cells ◽  
Cell Population ◽  
Muscle Regeneration ◽  
Progenitor Cell ◽  
Transcriptional Activity ◽  
Skeletal Muscle Regeneration ◽  
Progenitor Cell Population ◽  
Myogenic Progenitor Cells ◽  
Myogenic Progenitor

The successful use of myogenic progenitor cells for therapeutic applications requires an understanding of the intrinsic and extrinsic cues involved in their regulation. Herein we demonstrate the expression pattern and transcriptional regulation of Rad, a prototypical member of a family of novel Ras-related GTPases, during mammalian development and skeletal muscle regeneration. Rad was identified using microarray analysis, which revealed robust upregulation of its expression during skeletal muscle regeneration. Our current findings demonstrate negligible Rad expression with resting adult skeletal muscle; however, after muscle injury, Rad is expressed within the myogenic progenitor cell population. Rad expression is significantly increased and localized to the myogenic progenitor cell population during the early phases of regeneration and within the newly regenerated myofibers during the later phases of regeneration. Immunohistochemical analysis demonstrated that Rad and MyoD are coexpressed within the myogenic progenitor cell population of regenerating skeletal muscle. This expression profile of Rad during skeletal muscle regeneration is consistent with the proposed roles for Rad in the inhibition of L-type Ca2+channel activity and the inhibition of Rho/RhoA kinase activity. We also have demonstrated that known myogenic transcription factors (MEF2, MyoD, and Myf-5) can increase the transcriptional activity of the Rad promoter and that this ability is significantly enhanced by the presence of the Ca2+-dependent phosphatase calcineurin. Furthermore, this enhanced transcriptional activity appears to be dependent on the presence of a conserved NFAT binding motif within the Rad promoter. Taken together, these data define Rad as a novel factor within the myogenic progenitor cells of skeletal muscle and identify key regulators of its transcriptional activity.

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