RhoA within myofibers controls satellite cell microenvironment to allow hypertrophic growth

Abstract Satellite cells are required for postnatal development, skeletal muscle regeneration across the lifespan, and skeletal muscle hypertrophy prior to maturity. Our group has aimed to address whether satellite cells are required for hypertrophic growth in mature skeletal muscle. Here, we generated a comprehensive characterization and transcriptome-wide profiling of skeletal muscle during adaptation to exercise in the presence or absence of satellite cells in order to identify distinct phenotypes and gene networks influenced by satellite cell content. We administered vehicle or tamoxifen to adult Pax7-DTA mice and subjected them to progressive weighted wheel running (PoWeR). We then performed immunohistochemical analysis and whole-muscle RNA-seq of vehicle (SC+) and tamoxifen-treated (SC−) mice. Further, we performed single myonuclear RNA-seq to provide detailed information on how satellite cell fusion affects myonuclear transcription. We show that while skeletal muscle can mount a robust hypertrophic response to PoWeR in the absence of satellite cells, growth, and adaptation are ultimately blunted. Transcriptional profiling reveals several gene networks key to muscle adaptation are altered in the absence of satellite cells.

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RhoA within myofibers controls satellite cell microenvironment to allow hypertrophic growth

10.1101/2021.01.18.426685 ◽

2021 ◽

Author(s):

Chiara Noviello ◽

Kassandra Kobon ◽

Léa Delivry ◽

Thomas Guilbert ◽

Francis Julienne ◽

...

Keyword(s):

Satellite Cell ◽

Inflammatory Cell ◽

Muscle Growth ◽

Adult Skeletal Muscle ◽

Ecm Remodeling ◽

Cell Recruitment ◽

Hypertrophic Growth ◽

A Cell ◽

Inflammatory Cell Recruitment ◽

Collagen Disorganization

SummaryAdult skeletal muscle is a plastic tissue that can adapt its size to workload. Here, we show that RhoA within myofibers is needed for overload-induced hypertrophy by controlling satellite cell fusion to the growing myofibers without affecting protein synthesis. At the molecular level, we demonstrate that, in response to increased workload, RhoA controls in a cell autonomous manner Erk1/2 activation and the expressions of extracellular matrix (ECM) regulators such as Mmp9/Mmp13/Adam8 and of macrophage chemo-attractants such as Ccl3/Cx3cl1. Their decreased expression in RhoA mutant is associated with ECM and fibrillar collagen disorganization and lower macrophage infiltration. Moreover, Mmps inhibition and macrophage depletion in controls phenocopied the lack of growth of RhoA mutants. These findings unravel the implication of RhoA within myofibers, in response to increase load, in the building of a permissive microenvironment for muscle growth and for satellite cell accretion through ECM remodeling and inflammatory cell recruitment.

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Fusion-Independent Satellite Cell Communication to Muscle Fibers During Load-Induced Hypertrophy

Function ◽

10.1093/function/zqaa009 ◽

2020 ◽

Vol 1 (1) ◽

Cited By ~ 5

Author(s):

Kevin A Murach ◽

Ivan J Vechetti ◽

Douglas W Van Pelt ◽

Samuel E Crow ◽

Cory M Dungan ◽

...

Keyword(s):

Satellite Cell ◽

Cell Fusion ◽

Satellite Cells ◽

Cell Biology ◽

Mechanical Load ◽

Muscle Fibers ◽

Cell Communication ◽

Hypertrophic Growth

Abstract The “canonical” function of Pax7+ muscle stem cells (satellite cells) during hypertrophic growth of adult muscle fibers is myonuclear donation via fusion to support increased transcriptional output. In recent years, however, emerging evidence suggests that satellite cells play an important secretory role in promoting load-mediated growth. Utilizing genetically modified mouse models of delayed satellite cell fusion and in vivo extracellular vesicle (EV) tracking, we provide evidence for satellite cell communication to muscle fibers during hypertrophy. Myogenic progenitor cell-EV-mediated communication to myotubes in vitro influences extracellular matrix (ECM)-related gene expression, which is congruent with in vivo overload experiments involving satellite cell depletion, as well as in silico analyses. Satellite cell-derived EVs can transfer a Cre-induced, cytoplasmic-localized fluorescent reporter to muscle cells as well as microRNAs that regulate ECM genes such as matrix metalloproteinase 9 (Mmp9), which may facilitate growth. Delayed satellite cell fusion did not limit long-term load-induced muscle hypertrophy indicating that early fusion-independent communication from satellite cells to muscle fibers is an underappreciated aspect of satellite cell biology. We cannot exclude the possibility that satellite cell-mediated myonuclear accretion is necessary to maintain prolonged growth, specifically in the later phases of adaptation, but these data collectively highlight how EV delivery from satellite cells can directly contribute to mechanical load-induced muscle fiber hypertrophy, independent of cell fusion to the fiber.

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Histological Analysis and Gene Expression of Satellite Cell Markers in the Pectoralis Major Muscle in Broiler Lines Divergently Selected for Percent 4-Day Breast Yield

Frontiers in Physiology ◽

10.3389/fphys.2021.712095 ◽

2021 ◽

Vol 12 ◽

Author(s):

Sara K. Orlowski ◽

Sami Dridi ◽

Elizabeth S. Greene ◽

Cynthia S. Coy ◽

Sandra G. Velleman ◽

...

Keyword(s):

Satellite Cell ◽

Muscle Fiber ◽

Muscle Development ◽

Fiber Diameter ◽

Negative Impact ◽

Pectoralis Major ◽

Fiber Formation ◽

Hypertrophic Growth ◽

Selection For ◽

The Impact

Muscle development during embryonic and early post-hatch growth is primarily through hyperplastic growth and accumulation of nuclei through satellite cell contribution. Post-hatch, muscle development transitions from hyperplasia to hypertrophic growth of muscle fibers. Commercial selection for breast yield traditionally occurs at ages targeting hypertrophic rather than hyperplastic growth. This has resulted in the production of giant fibers and concomitant challenges with regard to muscle myopathies. The current study investigates the impact of selection during the period of hyperplastic growth. It is hypothesized that selection for percentage breast yield during hyperplasia will result in an increased number of muscle cells at hatch and potentially impact muscle fiber characteristics at processing. This study characterizes the breast muscle histology of three broiler lines at various ages in the growth period. The lines include a random bred control (RAN) as well as lines which have been selected from RAN for high (HBY4) and low (LBY4) percentage 4-day breast yield. Post-rigor pectoralis major samples from six males of each line and age were collected and stored in formalin. The sample ages included embryonic day 18 (E18), post-hatch day 4 (d4), and day 56 (d56). The samples were processed using a Leica tissue processor, embedded in paraffin wax, sectioned, and placed on slides. Slides were stained using hematoxylin and eosin. E18 and d4 post-hatch analysis showed advanced muscle fiber formation for HBY4 and immature muscle development for LBY4 as compared to RAN. Post-hatch d56 samples were analyzed for fiber number, fiber diameter, endomysium, and perimysium spacing. Line HBY4 had the largest muscle fiber diameter (54.2 ± 0.96 μm) when compared to LBY4 (45.4 ± 0.96 μm). There was no line difference in endomysium spacing while perimysium spacing was higher for HBY4 males. Selection for percentage 4-day breast yield has impacted the rate and extent of muscle fiber formation in both the LBY4 and HBY4 lines with no negative impact on fiber spacing. The shift in processing age to later ages has exposed issues associated with muscle fiber viability. Selection during the period of muscle hyperplasia may impact growth rate; however, the potential benefits of additional satellite cells are still unclear.

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Depletion of resident muscle stem cells inhibits muscle fiber hypertrophy induced by lifelong physical activity

10.1101/588731 ◽

2019 ◽

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 ◽

Muscle Growth ◽

Free Access ◽

Running Wheel ◽

Hypertrophic Growth

AbstractBackgroundA reduction in skeletal muscle stem cell (satellite cell) content with advancing age is thought to directly contribute to the progressive loss of skeletal muscle mass and function with aging (sarcopenia). However, we reported that the depletion of satellite cells throughout adulthood did not affect the onset or degree of sarcopenia observed in sedentary old mice. The current study was designed to determine if lifelong physical activity would alter the requirements for satellite cells during aging.MethodsWe administered vehicle or tamoxifen to adult (5 months old) female Pax7-DTA mice for 5 consecutive days to effectively deplete satellite cells. Following a 2-month washout period, mice were assigned to physically active (free access to a running wheel) or sedentary (locked running wheel) conditions. Thirteen months later, at a mean age of 20 months, mice were sacrificed for subsequent analysis.ResultsSatellite cell depletion throughout adulthood negatively impacted physical function and limited muscle fiber hypertrophy in response to lifelong physical activity. To further interrogate these findings, we performed transcriptome-wide analyses on the hind limb muscles that experienced hypertrophic growth (plantaris and soleus) in response to lifelong physical activity. Our findings demonstrate that satellite cell function is muscle type-specific; fusion with fibers is apparent in oxidative muscles, while initiation of Gαi2 signaling appears to require satellite cells in glycolytic muscles to induce muscle growth..ConclusionsThese findings suggest that satellite cells, or their secretory products, are viable therapeutic targets to preserve physical function with aging and promote muscle growth in older adults who regularly engage in physical activity.

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Hypertrophic growth

Journal of Applied Chemistry and Biotechnology ◽

10.1002/jctb.5020220111 ◽

1972 ◽

Vol 22 (1) ◽

pp. 71-78 ◽

Cited By ~ 15

Author(s):

E. O. Powell

Keyword(s):

Hypertrophic Growth

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CARP Plays a Key Role in Cellular Growth Under Hypertrophic Stimuli in Neonatal Rat Ventricular Myocytes

Vanderbilt Undergraduate Research Journal ◽

10.15695/vurj.v9i0.3790 ◽

2013 ◽

Vol 9 ◽

Author(s):

Tara A Shrout

Keyword(s):

Gene Expression ◽

Ventricular Myocytes ◽

Cellular Growth ◽

Neonatal Rat ◽

Transcriptional Level ◽

Dual Nature ◽

Hypertrophic Growth ◽

Rat Ventricular Myocytes ◽

Neonatal Rat Ventricular Myocytes ◽

Over Time

Cardiac hypertrophy is a growth process that occurs in response to stress stimuli or injury, and leads to the induction of several pathways to alter gene expression. Under hypertrophic stimuli, sarcomeric structure is disrupted, both as a consequence of gene expression and local changes in sarcomeric proteins. Cardiac-restricted ankyrin repeat protein (CARP) is one such protein that function both in cardiac sarcomeres and at the transcriptional level. We postulate that due to this dual nature, CARP plays a key role in maintaining the cardiac sarcomere. GATA4 is another protein detected in cardiomyocytes as important in hypertrophy, as it is activated by hypertrophic stimuli, and directly binds to DNA to alter gene expression. Results of GATA4 activation over time were inconclusive; however, the role of CARP in mediating hypertrophic growth in cardiomyocytes was clearly demonstrated. In this study, Neonatal Rat Ventricular Myocytes were used as a model to detect changes over time in CARP and GATA4 under hypertrophic stimulation by phenylephrine and high serum media. Results were detected by analysis of immunoblotting. The specific role that CARP plays in mediating cellular growth under hypertrophic stimuli was studied through immunofluorescence, which demonstrated that cardiomyocyte growth with hypertrophic stimulation was significantly blunted when NRVMs were co-treated with CARP siRNA. These data suggest that CARP plays an important role in the hypertrophic response in cardiomyocytes.

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