Site-dependent pathological differences in smooth muscles and skeletal muscles of the adult mdx mouse

This study presents a survey of the morphometric characteristics, the regeneration rate, and the extent of muscle dystrophy in several smooth and skeletal muscles from adult mdx mice, an animal model of the Duchenne muscular dystrophy (DMD). Smooth muscles from adult mdx mice showed neither cell necrosis nor fibrosis. As compared to control C57 mice, the thickness of the mdx smooth muscle was normal in the vascular and urogenital layers but significantly reduced in the digestive layers, a finding relevant to clinical reports of gastrointestinal dilatation in DMD patients, and suggesting that gastrointestinal dysfunctions should be systemically searched for in DMD patients. Adult mdx skeletal muscles, however, presented different patterns of muscle suffering: either absent (esophagus); very mild (trunk and limb muscles); or severe (diaphragm). In these three conditions we studied the fiber diameters, the nuclei locations, and the regeneration rate. From this comparative study, it seems that severe dystrophy occurs in muscle tissues showing large fiber diameter and peripheral location of the nuclei. We showed that this combination occurs in the mouse diaphragm which is thus a realistic model for human DMD muscles.