Each year a disease known as Duchenne Muscular Dystrophy (DMD) strikes thousands of boys in the U.S. Indeed, DMD is considered the most common genetic disorder--and a particularly devastating one at that, causing progressive weakening of the muscles until the heart or those muscles that control breathing can no longer function. DMD patients usually die by their early twenties. No effective therapies exist currently, but the results of a study described today in the Proceedings of the National Academy of Sciences may eventually lead to one. According to the report, researchers have developed the most promising gene therapy yet to treat DMD.
DMD patients lack a protein dubbed dystrophin, which plays a critical role in muscle maintenance. Xiao Xiao of the University of Pittsburgh and his colleagues thus set out to develop a system by which they could deliver dystrophin to muscles. They created a pared-down version of the dystrophin gene--the minimal amount needed to express functional dystrophin protein--so that they could insert it into a genetically modified virus (the entire dystrophin gene exceeds the carrying capacity of the viral vector). When the team injected this construct into the calf muscles of dystrophic mice, it delivered the gene to the muscles, where it began producing dystrophin protein. In fact, the protein was expressed in nearly 90 percent of the muscle targeted. Moreover, the effects appear to be long-lasting: the mice were still producing dystrophin at the end of the experiment, a year later. "This gives us great hope that we can use this gene therapy strategy in a larger animal model of DMD," Xiao remarks, "and eventually treat patients within several years."