Satellite cell depletion does not inhibit adult skeletal muscle regrowth following unloading-induced atrophy

Resident muscle stem cells, known as satellite cells, are thought to be the main mediators of skeletal muscle plasticity. Satellite cells are activated, replicate, and fuse into existing muscle fibers in response to both muscle injury and mechanical load. It is generally well-accepted that satellite cells participate in postnatal growth, hypertrophy, and muscle regeneration following injury; however, their role in muscle regrowth following an atrophic stimulus remains equivocal. The current study employed a genetic mouse model (Pax7-DTA) that allowed for the effective depletion of >90% of satellite cells in adult muscle upon the administration of tamoxifen. Vehicle and tamoxifen-treated young adult female mice were either hindlimb suspended for 14 days to induce muscle atrophy or hindlimb suspended for 14 days followed by 14 days of reloading to allow regrowth, or they remained ambulatory for the duration of the experimental protocol. Additionally, 5-bromo-2′-deoxyuridine (BrdU) was added to the drinking water to track cell proliferation. Soleus muscle atrophy, as measured by whole muscle wet weight, fiber cross-sectional area, and single-fiber width, occurred in response to suspension and did not differ between satellite cell-depleted and control muscles. Furthermore, the depletion of satellite cells did not attenuate muscle mass or force recovery during the 14-day reloading period, suggesting that satellite cells are not required for muscle regrowth. Myonuclear number was not altered during either the suspension or the reloading period in soleus muscle fibers from vehicle-treated or satellite cell-depleted animals. Thus, myonuclear domain size was reduced following suspension due to decreased cytoplasmic volume and was completely restored following reloading, independent of the presence of satellite cells. These results provide convincing evidence that satellite cells are not required for muscle regrowth following atrophy and that, instead, the myonuclear domain size changes as myofibers adapt.

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Skeletal muscle regeneration is altered in the R6/2 mouse model of Huntington's disease

10.1101/2022.01.11.475914 ◽

2022 ◽

Author(s):

Sanzana Hoque ◽

Marie Sjogren ◽

Valerie Allamand ◽

Kinga Gawlik ◽

Naomi Franke ◽

...

Keyword(s):

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Muscle Damage ◽

Satellite Cell ◽

Mouse Models ◽

Satellite Cells ◽

Muscle Fibers ◽

Cag Repeat ◽

Skeletal Muscle Regeneration

Huntington's disease (HD) is caused by CAG repeat expansion in the huntingtin (HTT) gene. Skeletal muscle wasting alongside central pathology is a well-recognized phenomenon seen in patients with HD and HD mouse models. HD muscle atrophy progresses with disease and affects prognosis and quality of life. Satellite cells, progenitors of mature skeletal muscle fibers, are essential for proliferation, differentiation, and repair of muscle tissue in response to muscle injury or exercise. In this study, we aim to investigate the effect of mutant HTT on the differentiation and regeneration capacity of HD muscle by employing in vitro mononuclear skeletal muscle cell isolation and in vivo acute muscle damage model in R6/2 mice. We found that, similar to R6/2 adult mice, neonatal R6/2 mice also exhibit a significant reduction in myofiber width and morphological changes in gastrocnemius and soleus muscles compared to WT mice. Cardiotoxin (CTX)-induced acute muscle damage in R6/2 and WT mice showed that the Pax7+ satellite cell pool was dampened in R6/2 mice at 4 weeks post-injection, and R6/2 mice exhibited an altered inflammatory profile in response to acute damage. Our results suggest that, in addition to the mutant HTT degenerative effects in mature muscle fibers, expression of mutant HTT in satellite cells might alter developmental and regenerative processes to contribute to the progressive muscle mass loss in HD. Taken together, the results presented here encourage further studies evaluating the underlying mechanisms of satellite cell dysfunction in HD mouse models.

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Changes in Gene Expression of the MCU Complex Are Induced by Electrical Stimulation in Adult Skeletal Muscle

Frontiers in Physiology ◽

10.3389/fphys.2020.601313 ◽

2021 ◽

Vol 11 ◽

Author(s):

Esteban R. Quezada ◽

Alexis Díaz-Vegas ◽

Enrique Jaimovich ◽

Mariana Casas

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Electrical Stimulation ◽

Muscle Fibers ◽

Low Frequency ◽

Extracellular Atp ◽

Mrna Levels ◽

Dependent Manner ◽

Adult Skeletal Muscle ◽

Muscle Plasticity

The slow calcium transient triggered by low-frequency electrical stimulation (ES) in adult muscle fibers and regulated by the extracellular ATP/IP3/IP3R pathway has been related to muscle plasticity. A regulation of muscular tropism associated with the MCU has also been described. However, the role of transient cytosolic calcium signals and signaling pathways related to muscle plasticity over the regulation of gene expression of the MCU complex (MCU, MICU1, MICU2, and EMRE) in adult skeletal muscle is completely unknown. In the present work, we show that 270 0.3-ms-long pulses at 20-Hz ES (and not at 90 Hz) transiently decreased the mRNA levels of the MCU complex in mice flexor digitorum brevis isolated muscle fibers. Importantly, when ATP released after 20-Hz ES is hydrolyzed by the enzyme apyrase, the repressor effect of 20 Hz on mRNA levels of the MCU complex is lost. Accordingly, the exposure of muscle fibers to 30 μM exogenous ATP produces the same effect as 20-Hz ES. Moreover, the use of apyrase in resting conditions (without ES) increased mRNA levels of MCU, pointing out the importance of extracellular ATP concentration over MCU mRNA levels. The use of xestospongin B (inhibitor of IP3 receptors) also prevented the decrease of mRNA levels of MCU, MICU1, MICU2, and EMRE mediated by a low-frequency ES. Our results show that the MCU complex can be regulated by electrical stimuli in a frequency-dependent manner. The changes observed in mRNA levels may be related to changes in the mitochondria, associated with the phenotypic transition from a fast- to a slow-type muscle, according to the described effect of this stimulation frequency on muscle phenotype. The decrease in mRNA levels of the MCU complex by exogenous ATP and the increase in MCU levels when basal ATP is reduced with the enzyme apyrase indicate that extracellular ATP may be a regulator of the MCU complex. Moreover, our results suggest that this regulation is part of the axes linking low-frequency stimulation with ATP/IP3/IP3R.

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β-Cryptoxanthin Improves p62 Accumulation and Muscle Atrophy in the Soleus Muscle of Senescence-Accelerated Mouse-Prone 1 Mice

Nutrients ◽

10.3390/nu12082180 ◽

2020 ◽

Vol 12 (8) ◽

pp. 2180

Author(s):

Mari Noguchi ◽

Tomoya Kitakaze ◽

Yasuyuki Kobayashi ◽

Katsuyuki Mukai ◽

Naoki Harada ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Mass ◽

Muscle Atrophy ◽

Soleus Muscle ◽

Muscle Fibers ◽

Skeletal Muscle Atrophy ◽

Related Factor ◽

Related Factors ◽

Cross Sectional ◽

Senescence Accelerated Mouse

We investigated the effects of β-cryptoxanthin on skeletal muscle atrophy in senescence-accelerated mouse-prone 1 (SAMP1) mice. For 15 weeks, SAMP1 mice were intragastrically administered vehicle or β-cryptoxanthin. At 35 weeks of age, the skeletal muscle mass in SAMP1 mice was reduced compared with that in control senescence-accelerated mouse-resistant 1 (SAMR1) mice. β-cryptoxanthin increased muscle mass with an increase in the size of muscle fibers in the soleus muscle of SAMP1 mice. The expressions of autophagy-related factors such as beclin-1, p62, LC3-I, and LC3-II were increased in the soleus muscle of SAMP1 mice; however, β-cryptoxanthin administration inhibited this increase. Unlike in SAMR1 mice, p62 was punctately distributed throughout the cytosol in the soleus muscle fibers of SAMP1 mice; however, β-cryptoxanthin inhibited this punctate distribution. The cross-sectional area of p62-positive fiber was smaller than that of p62-negative fiber, and the ratio of p62-positive fibers to p62-negative fibers was increased in SAMP1 mice. β-cryptoxanthin decreased this ratio in SAMP1 mice. Furthermore, β-cryptoxanthin decreased the autophagy-related factor expression in murine C2C12 myotube. The autophagy inhibitor bafilomycin A1, but not the proteasome inhibitor MG132, inhibited the β-cryptoxanthin-induced decrease in p62 and LC3-II expressions. These results indicate that β-cryptoxanthin inhibits the p62 accumulation in fibers and improves muscle atrophy in the soleus muscle of SAMP1 mice.

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Depletion of resident muscle stem cells negatively impacts running volume, physical function, and muscle fiber hypertrophy in response to lifelong physical activity

AJP Cell Physiology ◽

10.1152/ajpcell.00090.2020 ◽

2020 ◽

Vol 318 (6) ◽

pp. C1178-C1188 ◽

Cited By ~ 8

Author(s):

Davis A. Englund ◽

Kevin A. Murach ◽

Cory M. Dungan ◽

Vandré C. Figueiredo ◽

Ivan J. Vechetti ◽

...

Keyword(s):

Physical Activity ◽

Skeletal Muscle ◽

Physical Function ◽

Satellite Cell ◽

Muscle Fiber ◽

Satellite Cells ◽

Cell Depletion ◽

Muscle Adaptation ◽

Adult Skeletal Muscle

To date, studies that have aimed to investigate the role of satellite cells during adult skeletal muscle adaptation and hypertrophy have utilized a nontranslational stimulus and/or have been performed over a relatively short time frame. Although it has been shown that satellite cell depletion throughout adulthood does not drive skeletal muscle loss in sedentary mice, it remains unknown how satellite cells participate in skeletal muscle adaptation to long-term physical activity. The current study was designed to determine whether reduced satellite cell content throughout adulthood would influence the transcriptome-wide response to physical activity and diminish the adaptive response of skeletal muscle. We administered vehicle or tamoxifen to adult Pax7-diphtheria toxin A (DTA) mice to deplete satellite cells and assigned them to sedentary or wheel-running conditions for 13 mo. Satellite cell depletion throughout adulthood reduced balance and coordination, overall running volume, and the size of muscle proprioceptors (spindle fibers). Furthermore, satellite cell participation was necessary for optimal muscle fiber hypertrophy but not adaptations in fiber type distribution in response to lifelong physical activity. Transcriptome-wide analysis of the plantaris and soleus revealed that satellite cell function is muscle type specific; satellite cell-dependent myonuclear accretion was apparent in oxidative muscles, whereas initiation of G protein-coupled receptor (GPCR) signaling in the glycolytic plantaris may require satellite cells to induce optimal adaptations to long-term physical activity. These findings suggest that satellite cells play a role in preserving physical function during aging and influence muscle adaptation during sustained periods of physical activity.

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Single-fiber isolation and maintenance of satellite cell quiescence

Biochemistry and Cell Biology ◽

10.1139/o05-046 ◽

2005 ◽

Vol 83 (5) ◽

pp. 674-676 ◽

Cited By ~ 24

Author(s):

Ashley C Wozniak ◽

Judy E Anderson

Keyword(s):

Skeletal Muscle ◽

Satellite Cell ◽

Satellite Cells ◽

Muscle Fibers ◽

Single Fiber ◽

Skeletal Muscle Regeneration ◽

Mouse Muscle ◽

Collagenase Digestion ◽

Cell Quiescence ◽

Gentle Agitation

The activity of satellite cells during myogenesis, development, or skeletal muscle regeneration is strongly modelled using cultures of single muscle fibers. However, there are variations in reported features of gene or protein expression as examined with single-fiber cultures. Here, we examined the potential differences in activation of satellite cells on normal mouse muscle fibers produced during a standard isolation protocol, with or without agitation during collagenase digestion. Activation was detected in satellite cells on fibers after 24 and 48 h of culture in basal growth medium using immunodetection of the incorporation of bromodeoxyuridine (BrdU) into DNA and quantification of the number of BrdU-positive cells per fiber. After 24 and 48 h in culture under nonactivating conditions, the number of activated (BrdU+) satellite cells was greater on fibers that had received gentle agitation during collagenase digestion than on those that were subject to digestion without agitation during isolation. The findings are interpreted to mean that at least some of the variation among published reports may derive from the application of various methods of fiber isolation. The information should be useful for maintaining satellite cell quiescence during studies of the regulatory steps that lead to satellite cell activation.Key words: activation, skeletal muscle, proliferation, single-fiber culture, myogenesis.

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Muscle satellite cells adopt divergent fates

The Journal of Cell Biology ◽

10.1083/jcb.200312007 ◽

2004 ◽

Vol 166 (3) ◽

pp. 347-357 ◽

Cited By ~ 552

Author(s):

Peter S. Zammit ◽

Jon P. Golding ◽

Yosuke Nagata ◽

Valérie Hudon ◽

Terence A. Partridge ◽

...

Keyword(s):

Skeletal Muscle ◽

Satellite Cell ◽

Satellite Cells ◽

Muscle Regeneration ◽

Cell Phenotype ◽

Proliferating Cells ◽

Cell Compartment ◽

Adult Skeletal Muscle ◽

Muscle Stem Cells ◽

Cell Pool

Growth, repair, and regeneration of adult skeletal muscle depends on the persistence of satellite cells: muscle stem cells resident beneath the basal lamina that surrounds each myofiber. However, how the satellite cell compartment is maintained is unclear. Here, we use cultured myofibers to model muscle regeneration and show that satellite cells adopt divergent fates. Quiescent satellite cells are synchronously activated to coexpress the transcription factors Pax7 and MyoD. Most then proliferate, down-regulate Pax7, and differentiate. In contrast, other proliferating cells maintain Pax7 but lose MyoD and withdraw from immediate differentiation. These cells are typically located in clusters, together with Pax7−ve progeny destined for differentiation. Some of the Pax7+ve/MyoD−ve cells then leave the cell cycle, thus regaining the quiescent satellite cell phenotype. Significantly, noncycling cells contained within a cluster can be stimulated to proliferate again. These observations suggest that satellite cells either differentiate or switch from terminal myogenesis to maintain the satellite cell pool.

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Brain-derived Neurotrophic Factor Regulates Satellite Cell Differentiation and Skeltal Muscle Regeneration

Molecular Biology of the Cell ◽

10.1091/mbc.e10-02-0154 ◽

2010 ◽

Vol 21 (13) ◽

pp. 2182-2190 ◽

Cited By ~ 73

Author(s):

Charlene Clow ◽

Bernard J. Jasmin

Keyword(s):

Skeletal Muscle ◽

Satellite Cell ◽

Satellite Cells ◽

Neurotrophic Factor ◽

Cell Function ◽

Brain Derived Neurotrophic Factor ◽

Postnatal Growth ◽

Adult Skeletal Muscle

In adult skeletal muscle, brain-derived neurotrophic factor (BDNF) is expressed in myogenic progenitors known as satellite cells. To functionally address the role of BDNF in muscle satellite cells and regeneration in vivo, we generated a mouse in which BDNF is specifically depleted from skeletal muscle cells. For comparative purposes, and to determine the specific role of muscle-derived BDNF, we also examined muscles of the complete BDNF−/− mouse. In both models, expression of the satellite cell marker Pax7 was significantly decreased. Furthermore, proliferation and differentiation of primary myoblasts was abnormal, exhibiting delayed induction of several markers of differentiation as well as decreased myotube size. Treatment with exogenous BDNF protein was sufficient to rescue normal gene expression and myotube size. Because satellite cells are responsible for postnatal growth and repair of skeletal muscle, we next examined whether regenerative capacity was compromised. After injury, BDNF-depleted muscle showed delayed expression of several molecular markers of regeneration, as well as delayed appearance of newly regenerated fibers. Recovery of wild-type BDNF levels was sufficient to restore normal regeneration. Together, these findings suggest that BDNF plays an important role in regulating satellite cell function and regeneration in vivo, particularly during early stages.

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Nuclear factor E2-related factor 2 (NRF2) deficiency accelerates fast fibre type transition in soleus muscle during space flight

Communications Biology ◽

10.1038/s42003-021-02334-4 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Takuto Hayashi ◽

Takashi Kudo ◽

Ryo Fujita ◽

Shin-ichiro Fujita ◽

Hirona Tsubouchi ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Atrophy ◽

Soleus Muscle ◽

Space Flight ◽

Skeletal Muscle Atrophy ◽

Muscle Fibres ◽

Type I ◽

Muscle Plasticity ◽

Type Transition

AbstractMicrogravity induces skeletal muscle atrophy, particularly in the soleus muscle, which is predominantly composed of slow-twitch myofibre (type I) and is sensitive to disuse. Muscle atrophy is commonly known to be associated with increased production of reactive oxygen species. However, the role of NRF2, a master regulator of antioxidative response, in skeletal muscle plasticity during microgravity-induced atrophy, is not known. To investigate the role of NRF2 in skeletal muscle within a microgravity environment, wild-type and Nrf2-knockout (KO) mice were housed in the International Space Station for 31 days. Gene expression and histological analyses demonstrated that, under microgravity conditions, the transition of type I (oxidative) muscle fibres to type IIa (glycolytic) was accelerated in Nrf2-KO mice without affecting skeletal muscle mass. Therefore, our results suggest that NRF2 affects myofibre type transition during space flight.

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Canonical NF-κB signaling regulates satellite stem cell homeostasis and function during regenerative myogenesis

Journal of Molecular Cell Biology ◽

10.1093/jmcb/mjy053 ◽

2018 ◽

Vol 11 (1) ◽

pp. 53-66 ◽

Cited By ~ 3

Author(s):

Alex R Straughn ◽

Sajedah M Hindi ◽

Guangyan Xiong ◽

Ashok Kumar

Keyword(s):

Skeletal Muscle ◽

Satellite Cell ◽

Satellite Cells ◽

Muscle Regeneration ◽

Cell Function ◽

Skeletal Muscle Regeneration ◽

Cell Homeostasis ◽

Adult Skeletal Muscle ◽

Adult Mice ◽

And Function

Abstract Skeletal muscle regeneration in adults is attributed to the presence of satellite stem cells that proliferate, differentiate, and eventually fuse with injured myofibers. However, the signaling mechanisms that regulate satellite cell homeostasis and function remain less understood. While IKKβ-mediated canonical NF-κB signaling has been implicated in the regulation of myogenesis and skeletal muscle mass, its role in the regulation of satellite cell function during muscle regeneration has not been fully elucidated. Here, we report that canonical NF-κB signaling is induced in skeletal muscle upon injury. Satellite cell-specific inducible ablation of IKKβ attenuates skeletal muscle regeneration in adult mice. Targeted ablation of IKKβ also reduces the number of satellite cells in injured skeletal muscle of adult mice, potentially through inhibiting their proliferation and survival. We also demonstrate that the inhibition of specific components of the canonical NF-κB pathway causes precocious differentiation of cultured satellite cells both ex vivo and in vitro. Finally, our results highlight that the constitutive activation of canonical NF-κB signaling in satellite cells also attenuates skeletal muscle regeneration following injury in adult mice. Collectively, our study demonstrates that the proper regulation of canonical NF-κB signaling is important for the regeneration of adult skeletal muscle.

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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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