Gene therapy in large animal models of muscular dystrophy

The muscular dystrophies are a group of genetically and phenotypically heterogeneously inherited diseases characterized by progressive muscle wasting, which can lead to premature death in severe forms such as Duchenne muscular dystrophy (DMD). In many cases they are caused by the absence of proteins that are critical components of the dystrophin-glycoprotein complex, which links the cytoskeleton and the basal lamina. There is no effective treatment for these disorders at present, but several novel strategies for replacing or repairing the defective gene are in development, with early encouraging results from animal models. We review these strategies, which include the use of stem cells of different tissue origins, gene replacement therapies mediated by various viral vectors, and transcript repair treatments using exon skipping strategies. We comment on their advantages and on limitations that must be overcome before successful application to human patients. Our focus is on studies in a clinically relevant large canine model of DMD. Recent advances in the field suggest that effective therapies for muscular dystrophies are on the horizon. Because of the complex nature of these diseases, it may be necessary to combine multiple approaches to achieve a successful treatment.