Targeting fibrocytes in Duchenne muscular dystrophy

描述（由申请人提供）：肌肉纤维化是慢性肌肉疾病（包括肌营养不良症）的显著病理特征。它直接导致肌肉功能障碍和临床肌无力。杜氏肌营养不良症（DMD）是最常见和致命的肌肉疾病，目前尚无治愈方法。我们实验室和其他人以前的研究已经证明，改善肌肉纤维化是一种可行的治疗方法，可以改善mdx小鼠（DMD的小鼠模型）的肌营养不良表型。纤维化是由细胞外基质（ECM）蛋白的过度沉积引起的，其主要由组织效应成纤维细胞产生。在非肌肉组织的纤维化疾病模型中的广泛研究已经表明，循环来源的纤维细胞通过产生ECM蛋白和促纤维化细胞因子以及分化成组织效应成纤维细胞而成为组织纤维发生的重要细胞介质。趋化因子系统对于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mdx隔膜，mdx小鼠中唯一经历进行性纤维化的肌肉。我们进一步发现mdx膈纤维细胞表达趋化因子受体CCR1、CCR2、CCR5和CXCR4。本研究旨在阐明我们的中心假设，即纤维细胞在DMD相关的骨骼肌纤维化中起致病作用，趋化因子及其受体参与骨骼肌募集和纤维细胞的纤维化功能，阻断相关趋化因子受体及其配体可抑制纤维细胞募集和纤维化功能，改善营养不良肌肉的纤维化。我们将通过三个具体目标来解决我们的假设。具体目标1将表征mdx隔膜纤维细胞的肌肉募集和效应器特性。具体目标2将表征参与mdx隔膜纤维细胞募集和纤维化功能的趋化因子受体和配体。具体目标3将测试治疗干预，以抑制目标2中鉴定的趋化因子受体和配体，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DMD的新型抗纤维化疗法。 公共卫生相关性：杜氏肌营养不良症（DMD）是最常见和致命的肌肉疾病，目前尚无治愈方法。在DMD患者的肌肉中，瘢痕形成是明显的和渐进的，其导致肌肉功能障碍和无力。纤维细胞是已显示在肺、肾和肝的疾病小鼠模型中促成瘢痕形成的细胞。我们已经发现纤维细胞也存在于mdx小鼠（DMD的小鼠模型）中经历进行性瘢痕形成的肌肉中。因此，我们提出这项研究的特点肌肉纤维细胞的功能和他们的贡献肌肉瘢痕形成mdx小鼠。我们还将确定哪些调节蛋白，趋化因子和趋化因子受体，调节肌肉纤维细胞功能，并测试抑制这些蛋白质是否可以抑制纤维细胞功能并减少肌肉瘢痕形成。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疗法，以改善DMD患者的瘢痕形成和改善肌肉功能。

DESCRIPTION (provided by applicant): 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 and lethal 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 mdx diaphragm, the only 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: 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 which 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 also present 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 regulatory proteins, chemokines and chemokine receptors, regulate muscle fibrocyte functions, and test whether inhibit these 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 ameliorate scar formation and improve muscle functions for patients with DMD.