Qualitative analysis of striated skeletal muscles in thedystrophynopathy of mdx mice submitted to physical activity

ABSTRACT

Duchenne’s Muscular Dystrophy (DMD) is a recessive hereditary myopathy linked to the chromosome X,caused by a mutation in the dystrophin gene, which strengthens and stabilizes the sarcolemma during the stressof muscular contraction and, when absent, the sarcollema ruptures and allows calcium to enter, which causesthe muscle fiber to necrotize. The object of the present study was to perform the morphologic analysis of theanterior tibial and the gastrocnemius muscles with (w/pa) or without (n/pa) physical activity for five weeks.We used 72 mice, divided in 12 experimental groups – 6 of them mdx and 6 control groups (C57/10J) aged4, 7, and 10 weeks. The samples were collected, processed and stained with hematoxylin-eosin. They wereanalyzed by light microscopy, selected and photomicrographed. On the cross-sections of control animals aged4, 7 and 10 weeks w/pa and n/pa, polygonal muscle fibers of many different sizes, ellipse-shaped and withseveral peripheral nucleuses were observed. In the mdx mice w/pa aged 4, 7 and 10 weeks, the muscle fibersshowed different shapes, sizes and stain affinities, rounded edges, anuclear or centered nucleuses; hyalines andmyofibrillas were highly contracted. Muscular regeneration and nectrotic areas with inflammatory infiltrateswere identified in the mdx animals aged 4, 7 and 10 weeks w/pa, as well as in animals aged 10 weeks n/pa.With the progression of the disease in the animals submitted to physical activity, there was evidence of failurein the regeneration and muscular degeneration, intensified and characterized by the gradual replacement ofthe striated skeletal muscle tissue by fibroadipose connective tissue.