Treatment of Muscular Dystrophy by Increased Angiogenesis

 描述（由申请人提供）：杜氏肌营养不良症（DMD）是一种进行性神经退行性肌肉疾病，由肌营养不良蛋白缺失引起。目前，DMD没有治愈方法，治疗仅限于类固醇和姑息治疗。虽然肌营养不良蛋白是骨骼肌的主要成分，但其在血管系统中的作用直到最近才被认识到。本项目的长期目标是阐明血管和肌肉干细胞的作用及其相互作用，因为它涉及DMD的肌肉病理学。我们以前已经表明，通过删除血管内皮生长因子（VEGF）受体Flt-1基因的一个等位基因，在DMD模型mdx小鼠中发育性增加血管生成和毛细血管密度。有趣的是，这导致了肌肉干细胞（卫星细胞）的增加，并改善了组织学和收缩功能。[这些数据表明，增加血管系统可以增加卫星细胞池，并改善mdx小鼠中观察到的营养不良表型。然而，这种相互作用背后的机制仍不清楚。本提案将试图填补这一知识空白。首先，我们将鉴定肌肉干细胞上表达的VEGF受体，并确定外源性VEGF对这些细胞的体外作用。其次，我们将利用内皮细胞/肌肉干细胞共培养系统，以确定是否内皮细胞可以调节肌肉干细胞的静止，增殖和分化。最后，我们将利用Cre-loxP介导的条件性Flt-1基因敲除小鼠来检查出生后Flt-1基因的完全切除是否导致骨骼肌中毛细血管密度增加和mdx小鼠中营养不良表型的改善。这将作为一个概念验证，看看Flt-1是否可以用作治疗DMD的药物靶点。这一信息可以具有DMD以外的应用，因为VEGF及其受体也正在研究用于治疗外周动脉疾病、缺血性损伤以及抗癌治疗。这三个独立目标的结果将直接导致DMD促血管生成治疗方案的开发，因此反映了NIAMS的使命。

 DESCRIPTION (provided by applicant): Duchenne muscular dystrophy (DMD) is a progressive neurodegenerative muscle disease caused by the absence of the dystrophin protein. Currently, there is no cure for DMD, and treatment is confined to steroids and palliative therapy. Although dystrophin is a major component of the skeletal muscle, its role in the vasculature has only recently been appreciated. The long-term goal of this project is to elucidate the role of the vasculature and muscle stem cells and their interactions as it pertains to muscle pathology in DMD. We have previously shown that developmentally increased angiogenesis and capillary density in DMD model mdx mice by deleting one allele for the Vascular Endothelial Growth Factor (VEGF) receptor, Flt-1 gene. Interestingly, this led to an increase in muscle stem cells (satellite cells) and improved histological and contractile function. [These data suggest tha increasing the vasculature can increase the satellite cell pool and ameliorate the dystrophic phenotype seen in mdx mice. However, the mechanism behind this interaction remains unclear. This proposal will attempt to fill this gap in knowledge. First, we will identify the VEGF receptor expressed on muscle stem cells and determine the effects of exogenous VEGF on these cells in vitro. Second, we will utilize endothelial cell/muscle stem cell co-culture systems to determine whether endothelial cells can modulate quiescence, proliferation, and differentiation in muscle stem cells. Lastly, we will utilize Cre-loxP-mediated conditional Flt-1 gene knockout mice to examine whether complete post-natal excision of Flt-1 gene results in increased capillary density in the skeletal muscle and an improvement in the dystrophic phenotype in the mdx mice. ] This will serve as a proof of concept to see whether Flt-1 can be used as a drug target for the treatment of DMD. This information can have applications beyond DMD as VEGF and its receptors are also under investigation for the treatment of peripheral artery disease, ischemic injury, as well as anti-cancer therapy. Outcomes from these three independent Aims will directly lead to the development of pro-angiogenic treatment options for DMD and therefore reflects the mission of NIAMS.