In vivo role of the fibroblast in muscular dystrophy

摘要 肌营养不良症是遗传性疾病，其在很大程度上影响横纹肌组织， 进行性肌肉无力、消瘦，在许多情况下，过早死亡。许多特征 导致肌营养不良症（MD）的人类突变是由结构附着的改变引起的， 将潜在的收缩蛋白质固定在基底膜上的蛋白质，为骨骼提供刚性 肌细胞膜（sarcolemma）。肌营养不良蛋白-糖蛋白中选择性附着蛋白的缺失 复合物（DGC）允许收缩诱导的膜撕裂和钙离子内流，导致细胞内钙离子的释放。 肌纤维变性和坏死。在此坏死过程中，细胞因子，趋化因子和生长 因子作为炎症和修复过程的一部分被释放，尽管诱导纤维化和瘢痕形成， 是一种有害的副作用，会导致疾病。转化生长因子-β是一种重要的细胞因子 (TGFβ），其是MD中纤维化反应和肌肉病理恶化的主要调节剂。 虽然成纤维细胞直接受TGF β调节，但还没有人研究成纤维细胞在肿瘤中的功能。 骨骼肌直接在体内，作为介质或纤维化和肌营养不良症。在这里，我们生成了一个独特的 小鼠遗传模型，将选择性地调节心脏和骨骼肌的活动 成纤维细胞在体内和在营养不良的小鼠疾病模型中。因此，在这里，我们将测试新的假设 肌成纤维细胞在介导心脏和骨骼肌纤维化和组织重塑中起选择性作用， 肌肉对MD细胞脱落的反应，而在其 相应的组织是生理ECM/胶原蛋白产生和基底层产生的基础， 发展和持续的体内平衡的一部分。该应用程序有2个全面的具体目标：1） 从遗传学上解析小鼠MD期间骨骼肌和心脏中肌成纤维细胞的作用，2） 研究TGF β、SMAD2/3和p38 α信号通路如何通过体内肌成纤维细胞介导MD疾病。 本申请将试图明确说明活化的成纤维细胞（肌成纤维细胞）在 肌肉在MD疾病发作和进展期间。它还将试图阐明TGF β的重要性， 在体内介导肌成纤维细胞形成和疾病活动的信号传导，作为典型的和非典型的 将从遗传学角度剖析经典途径。

Abstract The muscular dystrophies are inherited disorders that largely affect striated muscle tissue resulting in progressive muscle weakness, wasting, and in many instances, premature death. Many characterized mutations in humans that cause muscular dystrophy (MD) result from alterations in structural attachment proteins that affix the underlying contractile proteins to the basal lamina, providing rigidity to the skeletal muscle cell membrane (sarcolemma). Loss of select attachment proteins in the dystrophin-glycoprotein complex (DGC) permits contraction-induced membrane tears and influx of calcium that causes cellular degeneration and necrosis of muscle fibers. During this necrotic process cytokines, chemokines and growth factors are released as part of the inflammatory and repair process, although induction of fibrosis and scarring are an unwanted side effect that worsens disease. One prominent cytokine is transforming growth factor-β (TGFβ) that serves a master regulator of the fibrotic response and worsening of muscle pathology in MD. While fibroblasts are directly regulated by TGFβ, no one has yet to examine the function of the fibroblast in skeletal muscle directly in vivo, as a mediator or fibrosis and muscular dystrophy. Here we generated a unique genetic model in the mouse that will selectively modulate the activity of the cardiac and skeletal muscle fibroblast in vivo and in dystrophic mouse models of disease. Thus, here we will test the novel hypothesis that myofibroblasts play a selective role in mediating fibrosis and tissue remodeling in heart and skeletal muscle in response to cellular dropout from MD, while resident myofibers and cardiomyocytes in their respective tissues underlie physiologic ECM / collagen production and basal lamina production during development and as part of ongoing homeostasis. The application has 2 comprehensive specific aims: 1) To genetically parse the role of myofibroblasts in skeletal muscle and heart during MD in the mouse, 2) To examine how TGFβ, SMAD2/3 and p38α signaling mediate disease in MD through the myofibroblast in vivo. The application will attempt to definitively address the function of the activated fibroblast (myofibroblast) in muscle during MD disease onset and progression. It will also attempt to elucidate the importance of TGFβ signaling in mediating myofibroblast formation and disease activity in vivo, as both canonical and non- canonical pathways will be genetically dissected.