Muscle disease represents an important health threat to the general population. There is essentially no cure. Gene therapy holds great promise to correct the genetic defects and eventually achieve full recovery in these diseases. Significant progresses have been made in the field of muscle gene therapy over the last few years. The development of novel gene delivery vectors has substantially enhanced specificity and efficiency of muscle gene delivery. The new knowledge on the immune response to viral vectors has added new insight in overcoming the immune obstacles. Most importantly, the field has finally moved from small experimental animal models to human patients. This book will bring together the leaders in the field of muscle gene transfer to provide an updated overview on the progress of muscle gene therapy. It will also highlight important clinical applications of muscle gene therapy.
Gene therapy offers many conceptual advantages to treat muscle diseases, especially various forms of muscular dystrophies; however, it faces a number of unique challenges, including the need to deliver a therapeutic vector to all muscles throughout the body. In Muscle Gene Therapy: Methods and Protocols, expert researchers in the field present a collection of techniques aimed at bridging the translational gap in muscle gene therapy between the prevalent rodent models and vitally important larger animal models. Divided into three sections, this volume examines basic protocols for optimizing the muscle gene expression cassette and for evaluating the therapeutic outcomes, new developments in muscle gene therapy technology such as adeno-associated viral vector (AAV), oligonucleotide-mediated exon-skipping, and novel RNA-based strategies, and step-by-step guidance on muscle gene delivery in swine, ovine, canine, and non-human primates. Written in the highly successful Methods in Molecular BiologyTM series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, detailed, readily reproducible laboratory protocols, and tips on troubleshooting and avoiding known pitfalls. Authoritative and cutting-edge, Muscle Gene Therapy: Methods and Protocols serves as an invaluable resource for graduate students, post-doctoral fellows, and principle investigators pursuing the crucial advancement of muscle disease gene therapy in the hope of someday curing these debilitating disorders.
Duchenne Muscular Dystrophy (DMD) is one of the most prevalent genetic disorders of childhood and currently stands as an incurable condition. This authoritative guide provides a clear overview of the latest current and experimental approaches to the treatment of DMD and examines the clinical, genetic, and pathophysiological aspects of the disease i
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.
In gene therapy, engineered gene products are delivered directly to muscle fibers as transgenes carried by viral vectors, such as Adeno Associated Viruses (AAVs). Viral- mediated delivery of a normal copy of the mutated genes into dystrophic muscle fibers holds big promise as a therapeutic avenue for Muscular Dystrophies. However, considering the indispensible role of satellite cells in muscle regeneration, an effective and long-term therapy for genetic muscle diseases requires restoration of gene expression in both dystrophic muscle fibers and satellite cells. Conventional gene therapy approaches lack the potential for long-term restoration of the mutated gene expression in satellite cells. In order to address this limitation, this study provides the proof of concept evidence for the use of a novel gene editing approach, which allows irreversible correction of the mutations in both dystrophic skeletal muscle fibers and satellite cells.
Duchenne Muscular Dystrophy, an inherited and progressive muscle wasting disease, is one of the most common single gene disorders found in the developed world. In this fourth edition of the classic monograph on the topic, Alan Emery and Francesco Muntoni are joined by Rosaline Quinlivan, Consultant in Neuromuscular Disorders, to provide a thorough update on all aspects of the disorder. Recent understanding of the nature of the genetic defect responsible for Duchenne Muscular Dystrophy and isolation of the protein dystrophin has led to the development of new theories for the disease's pathogenesis. This new edition incorporates these advances from the field of molecular biology, and describes the resultant opportunities for screening, prenatal diagnosis, genetic counselling and from recent pioneering work with anti-sense oligonucleotides, the possibility of effective RNA therapy. Although there is still no cure for the disorder, there have been significant developments concerning the gene basis, publication of standards of care guidelines, and improvements in management leading to significantly longer survival, particularly with cardio-pulmonary care. The authors also investigate other forms of pharmacological, cellular and gene therapies. Duchenne Muscular Dystrophy will be essential reading not only for scientists and clinicians, but will also appeal to therapists and other professionals involved in the care of patients with muscular dystrophy.
Abstract: Facioscapulohumeral muscular dystrophy is the most common inherited muscular dystrophy though no treatment exists. The lack of therapeutic development for FSHD is directly linked to insufficient understanding of how the disease is caused. The goals of the studies presented here were to gain a better understanding of the pathogenic mechanisms of FSHD and to develop targeted translational therapies to treat the disease. FSHD is associated with D4Z4 repeat contraction on human chromosome 4q35, which does not result in complete loss or mutation of any gene. Consequently, the major obstacle to discerning the underlying pathogenic mechanism is to identify the cause. Although no gene was conclusively linked to FSHD development, evidence supported a role for the D4Z4-encoded DUX4 gene. In Chapter 3, our objective was to test the in vivo myopathic potential of DUX4. We delivered DUX4 to zebrafish and mouse muscle by transposon-mediated transgenesis and adeno-associated viral vectors, respectively. We found over-expression of DUX4 caused abnormalities associated with muscular dystrophy in both animal models. This toxicity required DNA binding, since a DUX4 DNA binding domain mutant produced no abnormalities. We also found the toxic effects of DUX4 were p53-dependent. This study demonstrated the myopathic potential of DUX4 in animal muscle and provided a p53-dependent mechanism for DUX4-induced toxicity. Considering previous studies showed DUX4 was elevated in FSHD patient muscles, our data support the hypothesis that DUX4 over-expression contributes to FSHD development. With DUX4 as a potential target, gene silencing approaches could provide treatment for FSHD. With as many as 29 different gene mutations responsible for other dominant myopathies, gene silencing approaches could have a broad impact. Feasible mechanisms to silence dominant disease genes have lagged behind gene replacement strategies, but with the discovery of RNA interference (RNAi) and its subsequent development into a promising new gene silencing tool, the landscape has changed. In Chapter 4, our objective was to demonstrate proof-of-principle for RNAi therapy of a dominant myopathy in vivo. We tested the potential of AAV-delivered therapeutic microRNAs, targeting the human Facioscapulohumeral muscular dystrophy (FSHD) Region Gene 1 (FRG1), to correct myopathic features in mice expressing toxic levels of human FRG1 (FRG1-high mice). We found that FRG1 gene silencing improved muscle mass, strength, and histopathological abnormalities associated with muscular dystrophy in FRG1-high mice, thereby demonstrating therapeutic promise for treatment of FSHD and other dominantly inherited myopathies using RNAi. Next we applied this therapeutic strategy to FSHD by targeting DUX4. Several recent studies support an FSHD pathogenesis model involving over-expression of the myopathic DUX4 gene making it the most promising therapeutic target. In Chapter 5, we tested a pre-clinical RNAi-based DUX4 gene silencing approach as a prospective treatment for FSHD. We found that AAV vector-delivered therapeutic microRNAs corrected DUX4-associated myopathy in mouse muscle. These results provide proof-of-principle for RNAi therapy of FSHD through DUX4 inhibition. Together these studies have helped define the main pathogenic insult in FSHD and laid out a plausible, targeted therapy to treat the disease.
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Muscular dystrophies are a group of inherited disorders characterized by progressive muscle weakness, and degeneration. One approach to treatment would be the replacement of the deficient protein via gene therapy. For effective gene therapy, both efficiency of gene delivery and stable expression of the transferred gene are important factors. Our goal was to determine which of the following mammalian expression vectors would be more useful (more stable) for muscle gene therapy; pAcGFP1-C1 and pEPito. We were also interested in switching/substituting both vectors' CMV promoter/enhancer region with the muscle specific promoter, Desmin (DES), to increase their stability for muscle gene therapy. This was accomplished by transfecting C2C12 myotubes with the aforementioned vectors. Both vectors showed relatively continuous GFP expression. Myotubes transfected with pEPito continued to express GFP till day 8. Cells transfected with pACGFP1-C1 also showed continuous GFP expression till day 6. Our results show that both vectors are promising candidates for gene therapy in muscle cells as they maintained stable gene expression of the GFP reporter gene for at least 6 days. Further studies should be done in order to determine the maximum duration that the myotubes would be able to maintain the plasmids and show continuous expression. Future studies could be done to assess stability of these vectors in mice which may lead to future gene therapy trials for muscle disorders and improving gene therapy strategies for other disorders.