Possible systemic smooth muscle layer dysfunction due to a deficiency of dystrophin in Duchenne muscular dystrophy

The localization of dystrophin was examined immunohistochemically in various tissues from mice and rats as well as from biopsied human muscle specimens, using polyclonal antibodies against dystrophin. Although dystrophin was completely absent in biopsied muscle specimens from 3 male DMD patients, it was faintly observed in the surface membrane of almost all muscle fibers examined in a female DMD patient. In all controls, human and animal, a strong dystrophin reaction was observed in the surface membrane of intrafusal muscle fibers and at the neuromuscular junctions, rather than in the surface membrane of skeletal and cardiac muscle fibers. In addition, dystrophin was clearly localized in the surface membrane of smooth muscle fibers in the viscera, bronchial system, ureter, and tunica media of blood vessels, including arteries and veins, in all examined animal tissues. In mdx mice, dystrophin was absent in almost all muscle and smooth muscle fibers in various tissues and blood vessels. These results suggested a possible systemic dysfunction of smooth muscle layers, especially those of blood vessels, as well as skeletal muscle fibers, due to a deficiency of dystrophin in Duchenne muscular dystrophy.