Role of Skeletal Muscle Lymphatics in Duchenne Muscular Dystrophy Regulation

杜氏肌营养不良症（DMD）是一种无法治愈的X染色体连锁肌肉疾病， 骨骼肌消耗/虚弱以及相关的炎症和功能障碍。虽然现有数据显示， DMD患者和动物模型中的抗炎药物在减少炎症方面是有希望的， 促进患者的肌肉愈合，进一步了解炎症机制和DMD 发病机制是开发下一代DMD药物的关键。这些激进分子已经成为 在炎症过程中扮演重要角色，并在炎症的消退和进展中发挥积极作用。 这一建议为DMD的治疗带来了新的视角。由于淋巴系统在体内起着积极的作用， 无论是炎症的解决和进展，这个想法是，进一步增加淋巴管生成， 肌肉组织将增加淋巴运输，从而减轻炎症，改善肌肉健康 DMD肌肉初步数据表明：i）远端骨盆肢体的淋巴运输减少， 来自严重受影响的D2 mdx小鼠的胫骨前肌中的淋巴管密度增加; ii） 骨骼肌特异性血管内皮生长因子（VEGF）-D过表达增加 正常肌肉中的淋巴管生成，随着肌肉重量的增加， 前肢握力和iii）增强去神经肌肉中的淋巴转运。因此，中心假设 炎性淋巴管生成与淋巴管收缩活性的降低相结合， 淋巴转运减少，从而引起DMD动物肌肉中的慢性炎症状态，和2） VEGF-D过度表达进一步增强淋巴管生成， 在营养不良的肌肉中观察到的淋巴管生成将改善骨骼肌中的淋巴转运，并且 因此，在DMD动物中解决炎症并减轻肌肉无力和功能障碍。 具体目的：1）探讨DMD患者骨骼肌淋巴管结构和功能的变化 小鼠和犬模型和2）为了确定实验性增加骨骼中的淋巴管生成是否 肌肉改善D2.mdx小鼠和金毛猎犬肌营养不良症（GRMD）狗的肌肉健康。不同 将使用D2.mdx小鼠和野生型对照DBA/2 J小鼠的年龄组。GRMD犬和肌肉活检 还将使用来自各种狗品种的肌肉营养不良患者的收集物。VEGF-D过表达 在D2.mdx小鼠和GRMD中的表达将通过遗传或腺相关病毒方法实现。 淋巴管生成，炎症，淋巴收缩和淋巴运输，肌肉健康和功能将 在对照组和实验动物中进行评价。该提案将提供有关以下方面的新信息： 淋巴管生成在改善DMD动物模型中的肌肉健康中的治疗作用。

Duchenne muscular dystrophy (DMD) is an incurable, X chromosome-linked muscle disease that exhibits skeletal muscle wasting/weakness and the associated inflammation and dysfunction. Though available data on anti-inflammatory drugs in DMD patients and animal models are promising in diminishing inflammation and promoting muscle healing in patients, further understanding the inflammatory mechanisms and DMD pathogenesis is critical to develop the next generation of DMD drugs. The lymphatics have emerged as a central player in the process of inflammation and play active roles in both the resolution and progression of inflammation. This proposal brings a novel perspective for treatment of DMD. Since the lymphatic system plays active roles in both the resolution and progression of inflammation, the idea is that further increasing lymphangiogenesis in muscle tissues will augment lymph transport, and consequently, lessen inflammation and improve muscle health in DMD muscle. Preliminary data demonstrate: i) lymph transport in the distal pelvic limb is decreased while lymphatic vessel density is increased in tibialis anterior muscle from the severely affected, D2mdx mice; ii) skeletal muscle-specific overexpression of vascular endothelial growth factor (VEGF)-D increases lymphangiogenesis in normal muscle, with an increase in muscle weight and a positive trend in improving forelimb grip strength and iii) augments lymph transport in denervated muscle. Hence, central hypotheses are: 1) Inflammatory lymphangiogenesis combined with a decrease in lymphatic contractile activity cause a decrease in lymph transport, thereby causing chronic inflammatory status in muscles of DMD animals and 2) further augmenting lymphangiogenesis with VEGF-D overexpression beyond the level of inflammatory lymphangiogenesis observed in dystrophic muscle will improve lymph transport in skeletal muscle, and consequently, resolve the inflammation and attenuate muscle weakness and dysfunction in DMD animals. Specific Aims are: 1) To determine the changes in lymphatic structure and function in skeletal muscle of DMD mouse and canine models and 2) To determine whether experimentally increasing lymphangiogenesis in skeletal muscle improves muscle health in D2.mdx mice and golden retriever muscular dystrophy (GRMD) dogs. Different age groups of D2.mdx mice and wildtype control DBA/2J mice will be used. GRMD dogs and muscle biopsy collections from muscle dystrophy patients of various dog breeds will also be used. Overexpression of VEGF-D in D2.mdx mice and in GRMD will be achieved by genetic or adeno-associated virus approaches. Lymphangiogenesis, inflammation, lymphatic contractility and lymph transport, muscle health and function will be evaluated in controls and experimental animals. This proposal will provide novel information regarding the therapeutic role of lymphangiogenesis in improving muscle health in DMD animal models.