Chemical-based membrane sealants for dystrophic muscle

描述（由申请人提供）：本研究的长期目标是设计、测试和实施一种新的基于化学的膜修复疗法，以停止、预防并可能逆转杜氏肌营养不良症（DMD）中显著的横纹肌退化。大多数DMD患者在生命的第二个十年有明显的心肌病，心力衰竭至少占DMD死亡人数的15-30%。该建议具有显著的健康相关性，因为它寻求一种新的治疗策略，该策略以系统递送化学基膜密封剂poloxamers来保护营养不良犬和小鼠的横纹肌。最近的研究表明，poloxam188 （P188）对mdx小鼠DMD模型的心肌细胞和整个心脏功能具有急性保护作用。与mdx小鼠相比，营养不良犬表现出明显的横纹肌疾病，在时间和严重程度上与人类患者营养不良症状的进展密切相似。P188在啮齿类动物、狗和人类中已被证明是安全且耐受性良好的。指导这一提议的工作假设是：1)与营养不良小鼠相比，营养不良犬的心脏和骨骼肌细胞功能障碍更大；2)与mdx小鼠相比，P188急性治疗营养不良犬的分离横纹肌会有更大的有益效果；3)长期给药P188对DMD小鼠和狗的横纹肌结构和功能都有长期的益处。该方案在确定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优势。体外研究将利用独特的微碳纤维收缩试验来直接确定生理负荷下单个肌细胞的被动和主动力量。体内急性和慢性研究将确定P188输注在小型和大型DMD哺乳动物模型中的有效性。具体目标是：目标1。比较P188对肌营养不良蛋白缺乏小鼠和犬分离的完整膜单个心肌细胞和骨骼肌被动和主动收缩性能的影响。假设：急性暴露于P188会立即纠正被动张力-伸展特性和主动等距力的缺陷，犬心肌细胞的恢复幅度明显大于小鼠。P188可保护收缩性损伤小鼠完整的骨骼肌。目的2：在体内测试P188是否会停止、预防或逆转肌营养不良蛋白缺陷小鼠和犬的心肌功能障碍和衰竭。假设：输注P188对体内心肌功能有即时和长期的有益影响，且在肌营养不良蛋白缺陷犬中的作用相对大于小鼠。

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.