ABSTRACT
Duchenne muscular dystrophy is a lethal X-linked recessive disorder caused by mutations in the dystrophin gene. Delivery of functionally effective levels of dystrophin to immunocompetent, adult mdx (dystrophin-deficient) mice has been challenging because of the size of the gene, immune responses against viral vectors, and inefficient infection of mature muscle. Here we show that high titer stocks of three different gutted adenoviral vectors carrying full-length, muscle-specific, dystrophin expression cassettes are able to efficiently transduce muscles of 1-yr-old mdx mice. Single i.m. injections of viral vector restored dystrophin production to 25-30% of mouse limb muscle 1 mo after injection. Furthermore, functional tests of virally transduced muscles revealed almost 40% correction of their high susceptibility to contraction-induced injury. Our results show that functional abnormalities of dystrophic muscle can be corrected by delivery of full-length dystrophin to adult, immunocompetent mdx mice, raising the prospects for gene therapy of muscular dystrophies.
Subject(s)
Dystrophin/biosynthesis , Mice, Inbred mdx/genetics , Muscles/metabolism , Adenoviridae/genetics , Animals , Electrophoresis, Polyacrylamide Gel , Gene Transfer Techniques , Humans , Mice , Mice, Inbred C57BL , Mice, Inbred mdx/metabolism , Mice, Transgenic , Microscopy, Fluorescence , Models, GeneticABSTRACT
Attempts to develop gene therapy for Duchenne muscular dystrophy (DMD) have been complicated by the enormous size of the dystrophin gene. We have performed a detailed functional analysis of dystrophin structural domains and show that multiple regions of the protein can be deleted in various combinations to generate highly functional mini- and micro-dystrophins. Studies in transgenic mdx mice, a model for DMD, reveal that a wide variety of functional characteristics of dystrophy are prevented by some of these truncated dystrophins. Muscles expressing the smallest dystrophins are fully protected against damage caused by muscle activity and are not morphologically different from normal muscle. Moreover, injection of adeno-associated viruses carrying micro-dystrophins into dystrophic muscles of immunocompetent mdx mice results in a striking reversal of histopathological features of this disease. These results demonstrate that the dystrophic pathology can be both prevented and reversed by gene therapy using micro-dystrophins.
