• Journal of the Korean Society of Physical Medicine
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• v.14 no.2
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• pp.63-70
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• 2019

PURPOSE: While electrical stimulation (ES) is known to be a safe and flexible tool in rehabilitation therapy, it has had limited adoption in muscle regeneration. This study was performed to investigate whether ES can induce myogenic differentiation and to clarify the mechanism underlying the effects of ES on myogenic differentiation. METHODS: This study used rat L6 cell lines as myoblasts for myogenic differentiation. Electric stimulation was applied to the cells using a C-Pace EP culture pacer (IonOptix, Westwood, Ma, USA). The gene expressions of myogenic markers were examined using qPCR and immunochemistry. RESULTS: Our study showed that ES increased the thickness and length of myotubes during myogenic differentiation. It was found that ES increased the expression of myogenic markers, such as MyoD and Myogenin, and also activated the fusion of the myoblast cells. In addition, ES suppressed the expression of small GTPases, which can explain why ES promotes myogenic differentiation. CONCLUSION: We found that ES induced myogenic differentiation by suppressing small GTPases, inhibiting cell division. We suggest that ES-based therapies can contribute to the development of safe and efficient muscle regeneration.

• The Korean Journal of Physiology
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• v.23 no.2
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• pp.225-236
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• 1989

1) At the isolated perfused guinea-pig and rat heart heterometric autoregulation of the myocardium and myogenic autoregulation of the coronary vessels were induced by means of stepwise increases of perfusion pressure. 2) According to this loading test Frank-Starling function curves of the left ventricle and pressure-flow curves of the coronary vessels can be drawn. This graphic evaluation gives more information about the condition of the heart and the coronary vessels than simple evaluation under hemodynamic equilibrium. 3) There are significant differences in both curves between animal species and between different perfusate Mg concentration. 4) Myogenic autoregulation is not affected by the cyclooxygenase inhibitors indometacin and me- clofenamate. Thus it appears unlikely that prostanoides are involved in myogenic autoregulation. 5) Ca antagonists (Gallopamil, prenylamine) depress myogenic autoregulation dose-dependently. Enhanced myogenic autoregulation, induced by low extracellular magnesium, can be reduced effectively by Gallopamil. 6) Ginsenosides from Panax ginseng as well as the ginsenoside 'Rg' are effective inhibitors of myogenic autoregulation without major negative inotropic effects.

• BMB Reports
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• v.53 no.11
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• pp.605-610
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• 2020

Skeletal myogenesis is a complex process that is finely regulated by myogenic transcription factors. Recent studies have shown that saturated fatty acids (SFA) can suppress the activation of myogenic transcription factors and impair the myogenic differentiation of progenitor cells. Despite the increasing evidence of the roles of miRNAs in myogenesis, the targets and myogenic regulatory mechanisms of miRNAs are largely unknown, particularly when myogenesis is dysregulated by SFA deposition. This study examined the implications of SFA-induced miR-183-5p on the myogenic differentiation in C2C12 myoblasts. Long-chain SFA palmitic acid (PA) drastically reduced myogenic transcription factors, such as myoblast determination protein (MyoD), myogenin (MyoG), and myocyte enhancer factor 2C (MEF2C), and inhibited FHL1 expression and myogenic differentiation of C2C12 myoblasts, accompanied by the induction of miR-183-5p. The knockdown of FHL1 by siRNA inhibited myogenic differentiation of myoblasts. Interestingly, miR-183-5p inversely regulated the expression of FHL1, a crucial regulator of skeletal myogenesis, by targeting the 3'UTR of FHL1 mRNA. Furthermore, the transfection of miR-183-5p mimic suppressed the expression of MyoD, MyoG, MEF2C, and MyHC, and impaired the differentiation and myotube formation of myoblasts. Overall, this study highlights the role of miR-183-5p in myogenic differentiation through FHL1 repression and suggests a novel miRNA-mediated mechanism for myogenesis in a background of obesity.

• BMB Reports
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• v.55 no.2
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• pp.104-109
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• 2022

Skeletal myogenesis is essential to keep muscle mass and integrity, and impaired myogenesis is closely related to the etiology of muscle wasting. Recently, miR-141-3p has been shown to be induced under various conditions associated with muscle wasting, such as aging, oxidative stress, and mitochondrial dysfunction. However, the functional significance and mechanism of miR-141-3p in myogenic differentiation have not been explored to date. In this study, we investigated the roles of miR-141-3p on CFL2 expression, proliferation, and myogenic differentiation in C2C12 myoblasts. MiR-141-3p appeared to target the 3'UTR of CFL2 directly and suppressed the expression of CFL2, an essential factor for actin filament (F-actin) dynamics. Transfection of miR-141-3p mimic in myoblasts increased F-actin formation and augmented nuclear Yes-associated protein (YAP), a key component of mechanotransduction. Furthermore, miR-141-3p mimic increased myoblast proliferation and promoted cell cycle progression throughout the S and G2/M phases. Consequently, miR-141-3p mimic led to significant suppressions of myogenic factors expression, such as MyoD, MyoG, and MyHC, and hindered the myogenic differentiation of myoblasts. Thus, this study reveals the crucial role of miR-141-3p in myogenic differentiation via CFL2-YAP-mediated mechanotransduction and provides implications of miRNA-mediated myogenic regulation in skeletal muscle homeostasis.

• Molecules and Cells
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• v.38 no.4
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• pp.362-372
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• 2015

Setdb1, an H3-K9 specific histone methyltransferase, is associated with transcriptional silencing of euchromatic genes through chromatin modification. Functions of Setdb1 during development have been extensively studied in embryonic and mesenchymal stem cells as well as neurogenic progenitor cells. But the role of Sedtdb1 in myogenic differentiation remains unknown. In this study, we report that Setdb1 is required for myogenic potential of C2C12 myoblast cells through maintaining the expressions of MyoD and muscle-specific genes. We find that reduced Setdb1 expression in C2C12 myoblast cells severely delayed differentiation of C2C12 myoblast cells, whereas exogenous Setdb1 expression had little effect on. Gene expression profiling analysis using oligonucleotide microarray and RNA-Seq technologies demonstrated that depletion of Setdb1 results in downregulation of MyoD as well as the components of muscle fiber in proliferating C2C12 cells. In addition, exogenous expression of MyoD reversed transcriptional repression of MyoD promoter-driven luciferase reporter by Setdb1 shRNA and rescued myogenic differentiation of C2C12 myoblast cells depleted of endogenous Setdb1. Taken together, these results provide new insights into how levels of key myogenic regulators are maintained prior to induction of differentiation.

• The Korean Journal of Physiology and Pharmacology
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• v.27 no.3
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• pp.277-287
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• 2023

Actin dynamics play an essential role in myogenesis through multiple mechanisms, such as mechanotransduction, cell proliferation, and myogenic differentiation. Twinfilin-1 (TWF1), an actin-depolymerizing protein, is known to be required for the myogenic differentiation of progenitor cells. However, the mechanisms by which they epigenetically regulate TWF1 by microRNAs under muscle wasting conditions related to obesity are almost unknown. Here, we investigated the role of miR-103-3p in TWF1 expression, actin filament modulation, proliferation, and myogenic differentiation of progenitor cells. Palmitic acid, the most abundant saturated fatty acid (SFA) in the diet, reduced TWF1 expression and impeded myogenic differentiation of C2C12 myoblasts, while elevating miR-103-3p levels in myoblasts. Interestingly, miR-103-3p inhibited TWF1 expression by directly targeting its 3'UTR. Furthermore, ectopic expression of miR-103-3p reduced the expression of myogenic factors, i.e., MyoD and MyoG, and subsequently impaired myoblast differentiation. We demonstrated that miR-103-3p induction increased filamentous actin (F-actin) and facilitated the nuclear translocation of Yes-associated protein 1 (YAP1), thereby stimulating cell cycle progression and cell proliferation. Hence, this study suggests that epigenetic suppression of TWF1 by SFA-inducible miR-103-3p impairs myogenesis by enhancing the cell proliferation triggered by F-actin/YAP1.

• Journal of Animal Science and Technology
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• v.49 no.1
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• pp.25-32
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• 2007

The current study was undertaken to determine the effect of conjugated linoleic acid(CLA) isomers, cis-9, cis-11(c9c11), cis-9, trans-11(c9t11), trans-9, trans-11(t9t11), trans-10, cis-12(t10c12) on differentiation of pig preadipocytes and myogenic satellite cells during culture. Cells were isolated from new born pigs. The t10c12 isomer decreased differentiation of pig preadipocytes(92%), but not that of myogenic cells. The t9t11 isomer decreased differentiation of preadipocytes(14%) and increased that of myogenic cells (26%). No other CLA isomers affected differentiation of preadipocytes or myogenic cells. The effects of CLA on proliferation of preadipocytes and myogenic cells were small, compared to the effects on differentiation. These results suggest that CLA isomers have different effects on differentiaton of pig preadipocytes and myogenic cells.

• Animal Bioscience
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• v.35 no.4
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• pp.614-623
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• 2022

Objective: The objective of this study was to investigate the effects of sheep slaughter age on myogenic characteristics in skeletal muscle satellite cells (SMSCs). Methods: Primary SMSCs were isolated from hind leg biceps femoris muscles of Wurank lambs (slaughtered at three months, Mth-3) and adults (slaughtered at fifteen months, Mth-15). SMSCs were selected by morphological observation and fluorescence staining. Myogenic regulatory factors (MRF) and myosin heavy chain (MyHC) expressions of SMSCs were analyzed on days 1, 3, 4, and 5. Results: The expressions of myogenic factor 5 (Myf5), myogenic differentiation (MyoD), Myf6, and myogenin (MyoG) in Mth-15 were significantly higher in Mth-15 than in Mth-3 on days 1, 3, and 4 (p<0.05). However, MyoG expression in Mth-15 was significantly lower than in Mth-3 on day 5 (p<0.05). The expressions of MyHC I, MyHC IIa, and MyHC IIx in Mth-15 were significantly higher than in Mth-3 on days 1 and 3 (p<0.05), and MyHC IIb were significantly lower than in Mth-3 on days 3 and 4 (p<0.05). In contrast, the expression of MyHC IIx in Mth-15 was significantly lower and MyHC IIb was significantly higher than in Mth-3 on days 5 (p<0.05). Conclusion: The slaughter age altered the expression of MRFs and MyHCs in SMSCs while differentiation, which caused the variation of myogenic characteristics, and thus may affect the meat quality of Wurank sheep.

• The Korean Journal of Physiology and Pharmacology
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• v.6 no.1
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• pp.33-39
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• 2002

It has been suggested that $Ca^{2+}$ sensitization mechanisms might contribute to myogenic tone, however, specific mechanisms have not yet been fully identified. Therefore, we investigated the role of protein kinase C (PKC)- or RhoA-induced $Ca^{2+}$ sensitization in myogenic tone of the rabbit basilar vessel. Myogenic tone was developed by stretch of rabbit basilar artery. Fura-2 $Ca^{2+}$ signals, contractile responses, PKC immunoblots, translocation of PKC and RhoA, and phosphorylation of myosin light chains were measured. Stretch of the resting vessel evoked a myogenic contraction and an increase in the intracellular $Ca^{2+}$ concentration $([Ca^{2+}]_i)$ only in the presence of extracellular $Ca^{2+}$. Stretch evoked greater contraction than high $K^+$ at a given $[Ca^{2+}]_i.$ The stretch-induced increase in $[Ca^{2+}]_i$ and contractile force were inhibited by treatment of the tissue with nifedipine, a blocker of voltage-dependent $Ca^{2+}$ channel, but not with gadolinium, a blocker of stretch-activated cation channels. The PKC inhibitors, H-7 and calphostin C, and a RhoA-activated protein kinase (ROK) inhibitor, Y-27632, inhibited the stretch-induced myogenic tone without changing $[Ca^{2+}]_i.$ Immunoblotting using isoform-specific antibodies showed the presence of $PKC_{\alpha}$ and $PKC_{\varepsilon}$ in the rabbit basilar artery. $PKC_{\alpha},$ but not $PKC_{\varepsilon},$ and RhoA were translocated from the cytosol to the cell membrane by stretch. Phosphorylation of the myosin light chains was increased by stretch and the increased phosphorylation was blocked by treatment of the tissue with H-7 and Y-27632, respectively. Our results are consistent with important roles for PKC and RhoA in the generation of myogenic tone. Furthermore, enhanced phosphorylation of the myosin light chains by activation of $PKC_{\alpha}$ and/or RhoA may be key mechanisms for the $Ca^{2+}$ sensitization associated with myogenic tone in basilar vessels.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.10
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• pp.1447-1460
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• 2009

Myogenic satellite cells have been isolated and identified by several recently elucidated molecular markers. Furthermore, knowledge about the precise function of these markers has provided insight into the early and terminal events of satellite cells during proliferation, differentiation, transdifferentiation, specification and activation. Recently, quiescent myogenic satellite cells have been associated with possession of Pax 3 and 7 that represent pluripotent stem cells capable of differentiating into other lineages. However, the mechanism by which myogenic satellite cells attain pluripotent potential remain elusive. Later, transdifferentiating ability of these cells to another lineage in the absence or presence of certain growth factor/ or agents has revolutionized the scope of these pluripotent myogenic satellite cells for manipulation of animal production (in terms of quality and quantity of muscle protein) and health (in terms of repair of skeletal muscle, cartilage or bone).