• BMB Reports
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• 제52권1호
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• pp.64-69
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• 2019

The loss of skeletal muscle, called sarcopenia, is an inevitable event during the aging process, and significantly impacts quality of life. Autophagy is known to reduce muscle atrophy caused by dysfunctional organelles, even though the molecular mechanism remains unclear. Here, we have discuss the current understanding of exercise-induced autophagy activation in skeletal muscle regeneration and remodeling, leading to sarcopenia intervention. With aging, dysregulation of autophagy flux inhibits lysosomal storage processes involved in muscle biogenesis. AMPK-ULK1 and the $FoxO/PGC-1{\alpha}$ signaling pathways play a critical role in the induction of autophagy machinery in skeletal muscle, thus these pathways could be targets for therapeutics development. Autophagy has been also shown to be a critical regulator of stem cell fate, which determines satellite cell differentiation into muscle fiber, thereby increasing muscle mass. This review aims to provide a comprehensive understanding of the physiological role of autophagy in skeletal muscle aging and sarcopenia.

• 한국발생생물학회:학술대회논문집
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• 한국발생생물학회 2003년도 제3회 국제심포지움 및 학술대회
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• pp.100-100
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• 2003

Pluripotent embryonic stem (ES) cells differentiate spontaneously into beating cardiomyocytes via embryo-like aggregates. We describe the use of mouse embryonic stem (mES03) cells as a reproducible differentiation system for cardiomyocyte. To induce cardiomyocytic differentiation, mES03 cells were dissociated and allowed to aggregate (EB formation) at the presence of 0 75% dimethyl sulfoxide (DMSO) for 4 days and then another 4 days without DMSO (4+/4-). Thus treated EBs were plated onto gelatin-coated dish for differentiation. Spontaneously contracting colonies which appeared in approximately 4-5 days upon differentiation. Expression of cardiac-specific genes were determined by RT-PCR. Rebust expression of myosin light chain (MLC-2V), cardiac myosin heavy chain $\alpha$, cardiac muscle heavy polypeptide 7 $\beta(\beta$-MHC), cardiac transcription factor GATA4 and skeletal muscle-specific ${\alpha}_1$-subunit of the L-type calcium channel (${\alpha}_1 CaCh_{sm}$) were detected as early as 8 days after EB formation, but message of cardiac muscle-specific $\alpha$$_1$-subunit of the L-type calcium channel (${\alpha}_1$CaCh) were revealed at a low level. Strikingly, the expression of atrial natriuretic factor (ANF) was not detected. When spontaneous contracting cell masses were examined their electrophysiological features by patch-clamp technique, it showed ventricle-like action potential 17 days after the EB formation. This study indicates that mES03 cell-derived cardiomyocytes displayed biochemical and electrophysiological properties of cardiomyocytes and DMSO enhanced development of cardiomyocytes in 4+/4- method.

• 약학회지
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• 제40권6호
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• pp.734-738
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• 1996

The development of the alpha2 isoform of (Na,K)ATPase which is high affinity ouabain receptors was studied in the differentiating nonfusing muscle cell line BC3H-1. T he differentiation process of BC3H-1 cell line was confirmed by 2-dexy-D-[$^3$H] glucose uptake experiment and the quantity of the expression of ${\alpha}_2$ isoform was measured using a whole cell [$^3$H] ouabain-binding assay. Undifferentiated growing BC3H-1 cells, myoblasts, exhibited low levels of insulin-stimulated glucose uptake and [$^3$H] ouabain-binding sites. In contrast, differentiated BC3H-1 cells, myocytes, had a 5.6-fold increase in insulin-stimulated glucose uptake and 5-fold increase in [$^3$H] ouabain-binding sites. Scatchard analysis showed that myocytes developed more [$^3$H] ouabain-binding sites than myoblasts vath a dissociation constant (kd) of 6${\times}10^{-8}$M and capacity of 6.l${\times}10^{-5}$ sites/cell. Therefore. it seems that myoblasts express low levels of ${\alpha}_2$ subunit and probably the majority of ${\alpha}_1$ subunit, whereas myocytes express high levels of ${\alpha}_2$ isoform. The results indicate that the expression of ${\alpha}_2$ isoform is developmentally regulated during differentiation and that BC3H-1 culture system provides an excellent model for the study of differentiation and mechanism of (Na,K)ATPase action in muscle which requires electrical excitability.

• Journal of Nutrition and Health
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• 제56권6호
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• pp.602-614
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• 2023

본 연구는 근생성 및 근위축 완화효능을 가진 유효소재 발굴의 필요성에 의해 polygalacin D가 근원세포 분화 및 미토콘드리아에 미치는 영향과 항암제 유도 근위축에 대한 완화효과를 각각 세포 및 동물실험을 통해 확인하고자 하였다. 그 결과, polygalacin D는 다핵을 지닌 근관세포의 수와 분화 종결인자인 MHC isoforms의 발현량을 증가시켰고 근육 내 단백질 분해 인자인 MuRF1, Smad2/3의 발현량은 유의적으로 감소시켰다. 또한 미토콘드리아 생합성 조절인자인 Pgc1α의 발현은 증가시키고 미토콘드리아 분열인자인 Drp1과 Fis1의 발현은 감소시켰다. 한편 zebrafish 동물모델을 통해 항암제 유도 근위축에 대한 개선효과를 확인한 결과, polygalacin D는 항암제에 의해 유도된 근위축과 미토콘드리아 손상을 완화시켰다. 이상의 결과들은 polygalacin D가 미토콘드리아 기능 증진을 매개로 근원세포 분화 촉진 및 근육 단백질 분해 저하 효과를 지닐 뿐만 아니라, 미토콘드리아 손상을 개선하여 항암제로 유도된 근위축에 대한 완화 효과를 나타냄을 시사한다. 따라서 본 연구를 통해 polygalacin D가 근생성 및 근위축 예방과 치료를 위한 잠재적인 유효소재로서의 가능성을 제시하였다.

• Molecules and Cells
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• 제21권2호
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• pp.294-301
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• 2006

We have previously reported that phosphorylation of eukaryotic elongation factor 2 (eEF2) is related to the differentiation of chick embryonic muscle cells in culture. In the present study, we found that eEF2 phosphorylation declined shortly after induction of differentiation of L6 myoblasts, when the cells prepare for terminal differentiation by withdrawing from the cell cycle. This decrease in phosphorylation was prevented by inhibitors of phosphoinositide 3-kinase (PI3-kinase) that strongly inhibit myoblast differentiation. We hypothesized that PI3-kinase plays an important role in myoblast differentiation by regulating eEF2 phosphorylation in the early stages of differentiation. To test this hypothesis, myoblasts were synchronized at in $G_2/M$ and cultured in fresh differentiation medium (DM) or growth medium (GM). In DM the released cells accumulated in $G_0$/$G_1$ while in GM they progressed to S phase. In addition, cyclin D1 was more rapidly degraded in DM than in GM, and eEF2 phosphorylation decreased more. Inhibitors of PI3-kinase increased eEF2 phosphorylation, but PI3-kinase became more activated when eEF2 phosphorylation declined. These results suggest that the regulation of L6 myoblast differentiation by PI3-kinase is related to eEF2 phosphorylation.

• 대한약리학회:학술대회논문집
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• 대한약리학회 2006년도 The 6th Congress of the Federation of Asian and Oceanian Physiological Societies
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• pp.103.2-103.2
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• 2006

• BMB Reports
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• 제43권2호
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• pp.140-145
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• 2010

The present study investigated whether the mammalian target of rapamycin (mTOR) signal pathway is involved in the regulation of high glucose-induced intramuscular adipogenesis in porcine muscle satellite cells. High glucose (25 mM) dramatically increased intracellular lipid accumulation in cells during the 10-day adipogenic differentiation period. The expressions of CCAAT/enhancer binding protein-$\alpha$ (C/EBP-$\alpha$) and fatty acid synthase (FAS) protein were gradually enhanced during the 10-day duration while mTOR phosphorylation and sterol-regulatory- element-binding protein (SREBP)-1c protein were induced on day 4. Moreover, inhibition of mTOR activity by rapamycin resulted in a reduction of SREBP-1c protein expression and adipogenesis in cells. Collectively, our findings suggest that the adipogenic differentiation of porcine muscle satellite cells and a succeeding extensive adipogenesis, which is triggered by high glucose, is initiated by the mTOR signal pathway through the activation of SREBP-1c protein. This process is previously uncharacterized and suggests a cellular mechanism may be involved in ectopic lipid deposition in skeletal muscle during type 2 diabetes.

• 생명과학회지
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• 제17권7호통권87호
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• pp.976-982
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• 2007

본 연구는 분화 전단계인 C2C12 myoblast세포에 중요한 후천적 기작의 하나인 DNA 히스톤 단백질의 아세틸화를 조절하였을 때 일어나는 변화를 살펴본 결과, 히스톤 탈아세틸화 효소를 trichostatin A로서 억제시키자 C2C12 myoblast 세포가 smooth muscle로 분화하였다. 이는 immunofluorescentstaining을 통해 smooth muscle ${\alpha}-actin$의 발현 증가를 trishostatin A로 처리한 세포에서 관찰하였으며, DAPI 염색을 통해 대조군 세포와 비교하여 세포의 증식이 많이 억제됨을 관찰하였다. 또한 real-time PCR 결과는 smooth muscle ${\alpha}$-actin과 transgelin mRNA의 발현이 trichostatin A 처리군 세포에서 현저히 증가함을 보여주었다. 이러한 결과를 바탕으로 히스톤 단백질의 탈아세틸화 억제는 C2C12 myoblast 세포의 분화에 매우 중요한 역할을 하며, 또한 C2C12 myoblast 세포를 골격근인 다핵의 myotube로 분화시키지 않고, smooth muscle로 분화시킴을 알 수 있었다. 이것은 분명히 HDAC억제제 인 trichostatin A가 DNA 히스톤 단백질의 HDAC 효소에 의한 탈아세틸화를 강력히 억제하고, 이러한 HDAC효소의 억제는 세포주기에 있어서 증식과 분화를 조절하는 유전자들의 발현을 조절하였음을 시사한다. 이를 검증하기 위해 세포주기 조절인자인 p21과 cyclin Dl mRNA의 발현을 조사한 결과 세포를 증식단계로 진행하는데 있어서 필수적인 cdk 억제제인 p21 mRNA의 발현이 trichostatin A로 처리한 세포에서 현저히 증가함을 보였으며, 세포 증식을 유도하는 cyclin Dl mRNA의 발현은 trichostatin A를 처 리 한 후 24시간 후 유의하게 감소함을 보였는데 이는 trichostatin A가 세포증식을 억제하는 초기단계에서 cyclin Dl 유전자의 발현을 조절함을 보여준다. 향후 연구에서는 또 하나의 중요한 후천적 기작인 DNA 메틸화와 히스톤 아세틸화가 유전자 발현을 조절하는데 있어서 상호작용에 대한 연구가 필요할 것으로 생각된다.

• IMMUNE NETWORK
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• 제1권3호
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• pp.179-186
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• 2001

Bone marrow stroma is a complex tissue encompassing a number of cell types and supports hematopiesis, differentiation of erythreid, nyel and lymphoid lineages, and also maintains undifferentiated hematopoietic stem cells. Marrow-derived stem cells were composed of two populations, namely, hematopoietic stem cells that can differentiate into blood elements and mesenchymal stem cells that can give rise to connective tissues such as bone, cartilage, muscle, tendon, adipose and stroma. Differentiation requires environmental factors and unique intracellular signaling. For example, $TGF-{\beta}$ or BMP2 induces osteoblastic differentiation of mesenchymal stem are very exciting. However, the intrinsic controls involved in differentiation of stem cells are yet to be understood properly in order to exploit the same. This review presents an overview of the recent developments made in mesenchymal stem cell research with respect to osteogenesis.

• Molecules and Cells
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• 제21권2호
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• pp.206-212
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• 2006

We have established in culture a spontaneously immortalized bovine embryonic fibroblast (BEF) cell line that has lost p53 and $p16^{INK4a}$ functions. MyoD is a muscle-specific regulator capable of inducing myogenesis in a number of cell types. When the BEF cells were transduced with MyoD they differentiated efficiently to desmin-positive myofibers in the presence of 2% horse serum and 1.7 nM insulin. The myogenic differentiation of this cell line was more rapid and obvious than that of C2C12 cells, as judged by morphological changes and expression of various muscle regulatory factors. To confirm that lack of the p53 and $p16^{INK4a}$ pathway does not prevent MyoD-mediated myogenesis, we established a cell line transformed with SV40LT (BEFV) and introduced MyoD into it. In the presence of 2% horse serum and 1.7 nM insulin, the MyoD-transduced BEFV cells differentiated like the MyoD-transduced BEFS cells, and displayed a similar pattern of expression of muscle regulatory proteins. Taken together, our results indicate that MyoD overexpression overcomes the defect in muscle differentiation associated with immortalization and cell transformation caused by the loss of p53 and Rb functions.