Targeting fibrocytes in Duchenne muscular dystrophy

描述(由申请人提供)： 摘要：肌肉纤维化是包括肌营养不良在内的慢性肌肉疾病的显著病理特征。它直接导致肌肉功能障碍和临床肌肉无力。Duchenne肌营养不良症(DMD)是最常见的遗传性肌肉疾病，目前尚无治愈方法。我们实验室和其他人之前的研究已经证明，改善肌肉纤维化是改善DMD小鼠模型MDX小鼠肌肉营养不良表型的一种可行的治疗方法。纤维化是由细胞外基质(ECM)蛋白过度沉积引起的，ECM主要由组织效应成纤维细胞产生。对非肌肉组织纤维化疾病模型的广泛研究表明，循环来源的成纤维细胞是组织纤维化形成的重要细胞介质，可以产生ECM蛋白和促纤维化细胞因子，并分化为组织效应性成纤维细胞。趋化因子系统对纤维细胞的募集和纤维化功能是必不可少的。我们的初步研究表明，纤维细胞也存在于DMD患者的肌肉活检和MDX横隔肌中，MDX横隔肌是MDX小鼠中唯一经历进行性纤维化的骨骼肌。我们进一步发现MDX横隔膜纤维细胞表达趋化因子受体CCR1、CCR2、CCR5和CXCR4。本研究旨在解决我们的中心假设，即纤维细胞在DMD相关的骨骼肌纤维化形成中起致病作用，趋化因子和趋化因子受体参与骨骼肌的募集和纤维细胞的纤维化功能，阻断相关的趋化因子受体及其配体可以抑制纤维细胞募集和纤维形成功能，改善营养不良肌肉的纤维化。我们将通过三个具体目标来阐述我们的假设。具体目标1将描述MDX横隔膜纤维细胞的肌肉募集和效应器特性。具体目标2将描述参与MDX横隔膜纤维细胞募集和纤维化功能的趋化因子受体和配体。特定目标3将测试抑制目标2中确定的趋化因子受体和配体的治疗干预措施，以建立DMD的新治疗靶点。我们的长期目标是利用从这些研究中获得的知识来开发治疗DMD的新型抗纤维化疗法。 公共卫生相关性： 项目简介：杜氏肌营养不良症(DMD)是最常见和致命的肌肉疾病，目前还没有治愈的方法。DMD患者的肌肉中有明显的进行性瘢痕形成。它会导致肌肉功能障碍和虚弱。纤维细胞是已经被证明在肺、肾和肝脏的疾病小鼠模型中促进瘢痕形成的细胞。我们发现，在DMD患者的肌肉活检组织中以及在DMD的小鼠模型MDX小鼠中经历进行性瘢痕形成的肌肉中存在纤维细胞。因此，我们建议进行这项研究，以确定肌肉纤维细胞的功能及其在mdx小鼠肌肉瘢痕形成中的作用。我们还将确定哪些趋化因子和趋化因子受体调节肌肉纤维细胞的功能，并测试抑制这些调节蛋白是否可以抑制纤维细胞的功能和减少肌肉瘢痕的形成。我们的长期目标是利用从这些研究中获得的知识来开发新的治疗方法，以减少瘢痕形成并改善DMD患者的肌肉功能。

DESCRIPTION (provided by applicant): Abstract: Muscle fibrosis is a prominent pathological feature of chronic muscle diseases, including muscular dystrophies. It directly leads to muscle dysfunction and clinical muscle weakness. Duchenne muscular dystrophy (DMD) is the most common genetic muscle disease with no cure at this point. Previous studies by our lab and others have demonstrated that ameliorating muscle fibrosis represents a viable therapeutic approach to improve muscular dystrophy phenotype in mdx mice, a mouse model for DMD. Fibrosis is caused by excessive deposition of extracellular matrix (ECM) proteins, which are primarily produced by tissue effector fibroblasts. Extensive research in fibrotic disease models of non-muscle tissues has shown that the circulation-derived fibrocyte is an important cellular mediator of tissue fibrogenesis by producing ECM proteins and profibrotic cytokines as well as differentiating into tissue effector fibroblasts. The chemokine system is essential to the recruitment and fibrogenic functions of fibrocytes. Our preliminary study showed that fibrocytes were also present in a DMD patient muscle biopsy and in mdx diaphragm, the only skeletal muscle in mdx mice that undergoes progressive fibrosis. We further showed that mdx diaphragm fibrocytes expressed chemokine receptors CCR1, CCR2, CCR5, and CXCR4. This study is to address our central hypothesis that fibrocytes play a pathogenic role in skeletal muscle fibrogenesis associated with DMD, the chemokines and chemokine receptors are involved in skeletal muscle recruitment and fibrogenic functions of fibrocytes, and blocking relevant chemokine receptors and their ligands can inhibit fibrocyte recruitment and fibrogenic functions and ameliorate fibrosis in dystrophic muscles. We will address our hypothesis through three Specific Aims. Specific Aim 1 will characterize muscle recruitment and effector properties of mdx diaphragm fibrocytes. Specific Aim 2 will characterize the chemokine receptors and ligands involved in mdx diaphragm fibrocyte recruitment and fibrogenic functions. Specific Aim 3 will test therapeutic interventions to inhibit chemokine receptors and ligands identified in Aim 2 to establish novel therapeutic targets for DMD. Our long-term goal is to utilize the knowledge gained from these studies to develop novel antifibrotic therapies for DMD. PUBLIC HEALTH RELEVANCE: Project Narrative: Duchenne muscular dystrophy (DMD) is the most common and lethal muscle disease with no cure at this point. Scar formation is evident and progressive in muscles of DMD patients. It causes muscle dysfunction and weakness. Fibrocytes are cells that have been shown to contribute to scar formation in the disease mouse models of lung, kidney, and liver. We have found that fibrocytes were present in muscle biopsy tissue of a DMD patient and in the muscle which undergoes progressive scar formation in mdx mice, a mouse model for DMD. We thus propose this study to characterize the functions of muscle fibrocytes and their contribution to muscle scar formation in mdx mice. We will also determine which chemokines and chemokine receptors regulate muscle fibrocyte functions, and test whether inhibit these regulatory proteins can suppress fibrocyte functions and reduce muscle scar formation. Our long-term goal is to utilize the knowledge gained from these studies to develop novel therapies to reduce scar formation and improve muscle function for patients with DMD.