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標題: | TGFβ1 誘導之骨骼肌胞外體在肌肉分化中的角色 The Roles of TGFβ1-conditioned C2C12 Extracellular Vesicles in Myogenesis |
作者: | Yung-Han Cheng 鄭詠翰 |
指導教授: | 姜至剛(Chih-Kang Chiang) |
關鍵字: | 肌少症,TGFβ1,肌肉生成,萎縮,胞外體, sarcopenia,TGFβ1,myogenesis,atrophy,extracellular vesicle, |
出版年 : | 2019 |
學位: | 碩士 |
摘要: | 人口老化是現今社會一個重要的課題。臨床上甚至有一個領域專門針對老人常見的症狀。「跌倒」是老人常見的症狀之一,而容易跌倒的老人通常也患有「肌少症」。肌少症是指因為年齡或慢性病等因素導致的肌肉質量和力量降低。先前的研究已經提出dexamethasone(DEX)和indoxyl sulfate(IS)皆會導致肌少症。另外,肌少症患者常有肌肉修復能力低下以及肌肉纖維化的現象,而TGFβ1既是調控組織纖維化最常見的因子,也曾經被發現可以抑制肌肉的生長。另外,已知肌肉細胞分泌的胞外體會調控肌肉的生長,但尚未有研究提出胞外體在DEX, IS,和TGFβ1導致的肌肉分化抑制中是否皆扮演重要的角色。因此,本篇研究想要探討在DEX, IS,和TGFβ1的刺激下,肌肉細胞是否皆會透過胞外體調控肌肉的分化。從MHC的蛋白質表現,我們確認DEX, IS,和TGFβ1確實會導致C2C12細胞的肌肉分化受到抑制,但只有在整個分化過程中暴露TGFβ1所產生的胞外體(分化胞外體)會抑制C2C12肌肉分化 (MHC蛋白質表現減少1/3)。接著,我們也收取TGFβ1刺激的C2C12肌束分泌的胞外體(肌束胞外體),並分別加入分化中以及肌束時期的C2C12細胞,藉以深入探討胞外體在TGFβ1刺激的C2C12細胞中扮演的角色。結果顯示在C2C12分化中加入分化胞外體可以減少分化marker MyoG以及磷酸化FOXO1a的蛋白質表現達40~50%,但對C2C12肌束並沒有太大的影響。進一步分析分化胞外體的miRNA表現,發現TGFβ1分化胞外體中有15種miRNA下降,其中包含在肌肉中專一性表現的myomiR—miR1a, miR133, miR206等等。TGFβ1對C2C12肌束並沒有顯著的影響,但肌束胞外體加入分化中的C2C12細胞可增加其MHC的蛋白質表現;而加入C2C12肌束則可使其atrogin1表現下降40%。動物實驗方面,小鼠肌肉注射甘油可使肌肉受傷,並誘導受傷肌肉局部TGFβ1上升。綜合上述,胞外體可能是調控TGFβ1刺激下C2C12細胞分化的因子之一,而肌肉注射了甘油的小鼠可作為觀察TGFβ1導致之受傷後肌肉生成抑制的動物模式。 Nowadays, aging is one of the most serious problem around the world. Clinically, there is an area called “geriatrics” that focus on the specific syndromes of old people. Fall is one of the “geriatric syndromes” due to “sarcopenia”, the age-related loss of skeletal muscle. Our previous studies have indicated that both uremic toxin, indoxyl sulfate (IS), and glucocorticoid, dexamethasone (DEX), induce sarcopenia. In addition, impaired regeneration and excessive extracellular matrix (ECM) deposition in muscle are also observed in sarcopenic patients. It is previously stated that TGFβ1 is the master regulator of ECM production and TGFβ1 is also reported to impair myogenesis of skeletal muscle. Previous studies have indicated that extracellular vesicle (EV) secreted by myoblasts or myotubes can affect the myogenesis. However, whether or not the impact of EV is universal in myogenesis impairment induced by IS, DEX, TGFβ1 was still unclear. Therefore, in the present study, we aimed to investigate the roles of EV released from IS/DEX/TGFβ1-treated C2C12 myoblasts and myotubes. First, we confirmed that IS, DEX, TGFβ1 impaired myogenesis in C2C12, as the protein expression of myosin heavy chain (MHC) decreased by 2/3 to 4/5 compared to control. However, when treated C2C12 cells with conditioned myogenic EV throughout myogenesis only TGFβ1-conditioned myogenic EV had negative impact on C2C12 myogenesis, as the protein expression of MHC decreased by 1/3 compared to control. We focused on the effects of TGFβ1-conditioned EV by collecting myogenic EV and myotubular EV and treating them with C2C12 cells throughout myogenesis or at myotube stage. When C2C12 cells were incubated with TGFβ1-conditioned myogenic EV, the protein expression of myogenin (MyoG) and phosphorylated FOXO1a was 40%~50% less than control EV group. However, TGFβ1-conditioned myogenic EV had little effects on C2C12 myotube. EV miRNA analysis showed that 15 miRNAs reduced in TGFβ1-conditioned myogenic EV, among which contained muscle specific miRNA (myomiR), including miR1a, miR133, miR206, etc. TGFβ1 had little effects on C2C12 myotube. Nevertheless, when it comes to myotubular EV, it could increase MHC protein expression when incubated with C2C12 cells during myogenesis, and decrease protein expression atrogin1 when treated at C2C12 myotube stage. In addition, glycerol injection in soleus could injure skeletal muscle and induce TGFβ1 mRNA expression. In conclusion, EV might be a regulator of C2C12 myogenesis when treated with TGFβ1 and a mouse model with intramuscular injection of glycerol might be suitable to investigate TGFβ1-induced myogenesis impairment in vivo. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/73597 |
DOI: | 10.6342/NTU201903150 |
全文授權: | 有償授權 |
顯示於系所單位: | 毒理學研究所 |
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