Chemical-based membrane sealants for dystrophic muscle

描述(申请人提供)：这项研究的长期目标是设计、测试和实施一种新的基于化学物质的膜修复疗法，以阻止、预防并可能逆转Duchenne肌营养不良症(DMD)明显的横纹肌恶化。大多数DMD患者在第二个十年有明显的心肌病，心力衰竭至少占DMD死亡的15%-30%。这项提议具有显著的健康相关性，因为它寻求一种新的治疗策略，其特点是系统地给予基于化学物质的膜密封剂泊洛沙姆，以保护营养不良的狗和小鼠的横纹肌。最近的工作证明了泊洛沙姆188(P188)对DMD MDX小鼠模型的心肌细胞和全心功能的急性保护作用。与MDX小鼠相比，营养不良的狗表现出明显的横纹肌疾病，在时间和严重程度上都与人类患者的营养不良症状的进展非常相似。P188已被证明是安全的，在啮齿动物、狗和人类身上都有良好的耐受性。指导这一建议的工作假设是：1)与营养不良小鼠相比，营养不良狗的心肌和骨骼肌细胞功能障碍更严重；2)与MDX小鼠相比，p188急性治疗营养不良狗的孤立横纹肌具有更大的益处；3)长期服用p188将对DMD小鼠和狗模型的横纹肌结构和功能产生长期益处。这项建议在确定p188在DMD动物模型中的作用机制和治疗潜力方面具有独特的地位。体外研究将利用一种独特的微碳纤维收缩试验来直接确定单个心肌细胞在生理负荷下的被动和主动作用力。体内急性和慢性研究将确定体内注射p188对DMD大小哺乳动物模型的疗效。目的：1.比较p188对膜完整的单个心肌细胞和Dystrophin缺陷小鼠、犬骨骼肌的被动和主动收缩行为的影响。假设：急性暴露于p188将立即纠正被动张力-伸展特性和主动等长力的缺陷，犬的恢复幅度明显大于小鼠心肌细胞。P188治疗对营养不良小鼠收缩损伤后的完整骨骼肌有保护作用。目的2：检测系统注射p188能否在体内阻止、预防或逆转dystrophin缺陷小鼠和犬的心肌功能障碍和衰竭。假设：注入p188对活体心肌功能有即刻和长期的有益影响，对dystrophin缺乏症的狗的影响比对小鼠的影响更大。

DESCRIPTION (provided by applicant): The long-range goal of this research is to design, test, and implement a new chemical-based membrane repair therapy to halt, prevent and possibly reverse the marked striated muscle deterioration in Duchenne muscular dystrophy (DMD). Most DMD patients have a pronounced cardiomyopathy by the second decade of life, with heart failure accounting for at least 15-30% of deaths in DMD. This proposal has marked health relevance as it seeks a new therapeutic strategy featuring systemic delivery of chemical-based membrane sealant poloxamers to protect striated muscles in dystrophic dogs and mice. Recent work demonstrates the acute protective effects of poloxamer 188 (P188) on cardiac myocyte and whole heart function in the mdx mouse model of DMD. Compared with the mdx mouse, the dystrophic dog displays overt striated muscle disease that parallels closely in both timing and severity the progression of the dystrophic symptoms of the human patients. P188 has been shown to be safe and well tolerated in rodents, dogs, and humans. The working hypotheses guiding this proposal are: 1) cellular dysfunction will be greater in cardiac and skeletal muscle from dystrophic dogs compared to dystrophic mice, 2) acute treatment with P188 to isolated striated muscle of dystrophic dogs will have greater beneficial effects as compared to mdx mice; and 3) chronically administered P188 will produce long-term benefits to striated muscle structure and function in both mouse and dog models of DMD. This proposal is uniquely positioned to determine the mechanism of action and therapeutic potential of P188 in animal models of DMD. In vitro studies will utilize a unique micro-carbon fiber contractile assay to directly determine single myocyte passive and active forces under physiological load. In vivo acute and chronic studies will determine the efficacy of P188 infusion in vivo in small and large mammalian models of DMD. The Specific Aims are: Aim 1. To compare the effects of P188 on passive and active contractile performance in membrane intact single cardiac myocytes and in skeletal muscles isolated from dystrophin-deficient mice and dogs. Hypothesis: Acute exposure to P188 will immediately correct deficits in passive tension-extension properties and active isometric force with the magnitude of restitution significantly greater in canine than in mouse cardiac myocytes. P188 treatment will protect intact skeletal muscle of dystrophic mice contraction-induced injury. Aim 2: To test whether systemic delivery of P188 will halt, prevent or reverse the myocardial dysfunction and failure in dystrophin-deficient mice and dogs in vivo. Hypothesis: Infusion of P188 will confer both immediate and long-term beneficial effects to myocardial performance in vivo with the effects being comparatively greater in dystrophin-deficient dogs than in mice.