Utrophin up-regulation helps maintain normal cardiac geometry in a gene therapy model for Duhenne muscular dystrophy heart disease [abstract]

Duchenne muscular dystrophy (DMD) is the most common childhood muscle wasting disease. DMD sufferers rarely survive past their mid-twenties succumbing to respiratory or heart failure. Skeletal and heart muscle pathology in DMD are caused by mutations in the dystrophin gene. Gene therapy strategies to restore dystrophin expression bring the hope of a cure for DMD. Unfortunately, treatment of the heart remains largely unexplored. A critical question for heart gene therapy is the percentage of cells which must be repaired. We have previously shown that expressing a mosaic pattern of dystrophin in 50% of cardiomyocytes prevents heart disease (Bostick et al 2008 Cir Res102:121-130). A surprising finding from this study was up-regulation of a dystrophin homolog, utrophin, strictly in dystrophinnegative cardiomyocytes. This finding implicates a role for utrophin in modulating DMD heart disease. To answer this question, we developed a mouse model expressing 50% mosaic dystrophin in the heart with utrophin expression knocked out. We then analyzed cardiac physiology, anatomical/histological morphology and dystrophin/utrophin expression. We found that 50% mosaic dystrophin in the absence of utrophin normalized electrocardiographic parameters of the heart. Left ventricular catheterization revealed normal stroke volume, cardiac output and markers of contractility. Additionally, dobutamine stress response and mouse survival were normalized. Interestingly, utrophin knockout mice exhibited increased end-diastolic and end-systolic volumes. Our findings support the previous hypothesis that 50% mosaic dystrophin expression in the heart ameliorates DMD heart disease. However, the increased end-diastolic and end-systolic volumes indicate a potential role for utrophin in strengthening the integrity of the heart

Gene therapy for Duchenne muscular dystrophy heart disease requires treating both heart and skeletal muscle

Abstract only availableDuchenne muscular dystrophy (DMD) is a lethal muscle wasting disease caused by mutations in the dystrophin gene. Affected children are wheelchair bound by the age of ten and die in their mid-twenties from respiratory and/or cardiac failure. Gene therapy represents a promising avenue for curing DMD. While significant progress has been made for treatment of skeletal muscle disease, few studies have investigated the potential of gene therapy to treat heart disease. A cure for DMD requires rescuing both skeletal and heart muscles. Gene therapy aims to deliver a functional copy of the dystrophin gene to affected muscle cells. However, the dystrophin gene is the largest gene in the body and cannot be effectively delivered with any currently available methods. This led researchers to develop abbreviated versions of the dystrophin gene. The most promising of these genes is a 7 kb mini-dystrophin gene which can completely restore skeletal muscle in the mdx mouse model of DMD. The potential of the mini-dystrophin gene for treating heart disease is uncertain. Cardiac specific mini-dystrophin gene expression improved but did not normalize heart function. To investigate whether the incomplete cardiac rescue is due to skeletal muscle disease, we generated double transgenic male mdx mice which expressed the mini-dystrophin gene in both heart and skeletal muscle. We performed comprehensive skeletal and cardiac muscle testing at 6 months of age. Restoration of skeletal muscle function was confirmed by the grip strength assay. Next, we performed an uphill treadmill assay to gauge overall cardiac performance. Double transgenic mice ran significantly farther than cardiac transgenic mice. Finally, we performed electrocardiographic (ECG) analysis to examine the function of the cardiac conduction system. ECG analysis revealed an improved heart rate for double transgenic mice when compared to heart-only transgenic mice. Taken together, these results support a role for skeletal muscle disease in modulating heart function. Furthermore, these findings highlight the importance of tailoring gene therapy approaches to treat both the heart and skeletal muscle.Life Sciences Undergraduate Research Opportunity Progra

Development of gene therapy for Duchenne muscular dystrophy heart disease in the MDX mouse model

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on March 11, 2011).Vita.Thesis advisor: Dongsheng Duan."December 2010"Ph. D. University of Missouri-Columbia 2010.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Duchenne muscular dystrophy (DMD) is a fatal genetic muscle disease with no cure. DMD results from mutations in a critical muscle protein called dystrophin. Children born with DMD suffer severe muscle wasting leading to progressive weakness and paralysis. Patients usually die of respiratory or heart failure before the age of thirty. Gene therapy raises the hope of a cure for DMD heart disease. While significant strides have been made towards therapy for skeletal muscle disease, development of heart gene therapy lags behind. The seminal questions for realization of heart gene therapy of DMD include; developing an animal model, determining dosage, finding the correct gene, developing the vehicle for gene therapy and optimizing gene delivery. This dissertation details critical advancements towards gene therapy for DMD heart disease. First, we developed an animal model of DMD heart disease in the mdx mouse. We then determined that 50% mosaic dystrophin expression was sufficient to prevent DMD heart disease in this model. Next, we established that the truncated mini-dystrophin gene was capable of ameliorating DMD heart disease in the mdx mouse through cardiac specific transgenic expression. Then, we established the adeno-associated virus (AAV) as a vehicle for DMD heart gene therapy regardless of mouse age or the route of administration. Finally, we discovered that AAV-mediated truncated dystrophin gene therapy prevented DMD heart disease in neonatal mdx mice and ameliorated heart disease in symptomatic mdx mice. This work represents significant progress towards realization of an effective therapy for DMD heart disease.Includes bibliographical reference