Progressive Muscle Dysfunction resulting from chronic Remodeling of Cellular Architecture in inherited Muscle Diseases- Advanced Second Harmonic Generation Microcopy and quantitative Morphometry in skeletal Muscles from Animal Models of Duchenne Muscular

骨骼肌是人体最具可塑性的器官之一，既能适应运动，也能适应慢性疾病。慢性退行性/炎症性肌肉疾病与进行性虚弱和静止有关。虽然特定的信号通路可能会识别每种疾病的机制，但组织和细胞结构的慢性重塑是主要的共同原则。组织纤维化已被很好地理解，然而，骨骼肌纤维细胞结构的细胞细节变化还没有被详细讨论。我们认为，慢性肌肉疾病的无力至少有一半是由细胞重构引起的，例如纤维分支或错乱的肌原纤维晶格几何结构。在这个项目中，我们的目标是将最先进的多光子二次谐波(SHG)显微镜应用于两种遗传性退行性疾病的动物模型：缺乏dystrophin的MDX小鼠(Duchenne肌营养不良症模型)和desmin缺失和突变的desmin基因敲入小鼠(Duchenne肌营养不良症模型)。尤其是后一种模型，以前从未使用定量亚细胞形态计量学进行研究，它能够揭示人类退行性蛋白聚集性肌原纤维肌病的结构变化。为此，我们将使用从小鼠到老年鼠的单一纤维进行详细的年龄相关研究，并对它们进行我们先进的成像技术和结构分析。作为一个特别的目标，我们还将结合光学形态测量和同一细胞中等长力产生的记录，为我们的目标提供校准，即使用肌肉纤维和组织中的倍频成像作为一种手段，通过光学手段预测力量损失和虚弱。该项目不仅将有助于我们理解进行性肌肉无力的分子和生物物理起源，而且还将为肌肉研究界提供一种新的强大的成像工具。

Skeletal muscle is one of the most plastic human organs adapting to exercise but also to chronic disease. Chronic degenerative/inflammatory muscle diseases are associated with progressive weakness and immobility. Although specific signaling pathways may fingerprint each individual disease mechanism, chronic remodeling of tissue and cell architecture is the main common principle. Tissue fibrosis is well understood, however, cellular detailed changes in skeletal muscle fibre cytoarchitecture have not been addressed in detail. We believe that at least half of the weakness in chronic muscle disorders is accounted for by cellular remodeling, e.g. fibre branching or deranged myofibrillar lattice geometry. In this project, we aim to apply state-of-the art multiphoton Second Harmonic Generation (SHG) microscopy in two animal models of inherited degenerative disease: mdx mice lacking dystrophin (model for Duchenne muscular dystrophy, DMD) and desmin-null and mutated desmin-knock-in mice (model for desminopathy). Especially the latter model has never been studied before using quantitative subcellular morphometry that is capable of revealing insights into structural alterations in degenerative protein aggregation myofibrillar myopathies in humans. For this, we will perform a detailed age-related study using single fibres from young to old mice and subject them to our advanced imaging technology and structure analysis. As a special goal, we will also combine optical morphometry with recordings of isometric force production in the same cells to provide a calibration for our goal to use SHG imaging in muscle fibres and tissue as a means to predict force loss and weakness by optical means. The project will not only contribute to our understanding of molecular and biophysical origins of progressive muscle weakness but also provide a novel powerful imaging tool to the muscle research community.