Phenotype of dystrophinopathy in old mdx mice.

BACKGROUND: Mdx mutant mice, like patients with Duchenne Muscular Dystrophy (DMD), lack dystrophin, a subsarcolemmal protein, that results in myofiber necrosis. However young mdx mice, in contrast to DMD children, exhibit a successful muscle regeneration and not an extensive fibrosis.
METHODS: Old mdx mice were monitored clinically up to their spontaneous death, and most of their organs were studied histologically to look for differences with those of the wild C57BL/10 mice strain.
RESULTS: In old mdx mice (at least 20 months of age), we report clinical and pathological features of muscular dystrophy, i.e., progressive motor weakness and loss of myofibers replaced by extensive connective tissue, similar to the phenotype of dystrophinopathy observed in DMD patients. Various degrees of dystrophic involvement were observed in cardiac, respiratory, postural, and hindlimb skeletal mdx muscles and also in smooth muscles of the digestive and urinary tracts. No gross histological abnormalities were found in other tissue than muscular tissue.
CONCLUSIONS: Late in life, mdx mice develop a muscular dystrophy close to DMD dystrophinopathy. We suggest that the study of the effects of ageing in mdx mice would give clues to better understand the pathophysiology of DMD.