Study on skeletal muscle dystrophin and neuromuscular junction in adult and young mdx mice

Abstract

Objective To observe the skeletal muscle dystrophin expression and neuromuscular junction (NMJ) morphology in adult and young mdx mice.  Methods Select eight 8-week-old specific pathogen free (SPF) C57BL/6 mice, four 8-week-old adult mdx mice and four 2-week-old young mdx mice. Observe the histological features of myoctyes by HE staining, and detect the expression changes of gastrocnemius muscle dystrophin and morphology of NMJ by immunofluorescent staining.  Results The gastrocnemius muscle cells of C57BL/6 mice were almost uniform in size and polygonal. The nuclei were located in the peripheral of cells, while only a few were located in the center of myofiber. The sarcolemma expressed dystrophin uniformly and NMJ were intact. The gastrocnemius muscle cells of mdx mice were not consistent in size and had round shape. Part of nuclei were centralized. Only a few muscle cells expressed dystrophin. The acetylcholine receptor (AChR) on postsynaptic membrane of adult mdx mice were broken into small fragments, and the nerve terminal of presynaptic membrane had a great increase in the number of attenuated neurites. The morphology of NMJ in young mdx mice was similar to C57BL/6 mice. In both adult and young mdx mice, the number of NMJ had a great reduction, the cross-sectional area of presynaptic and postsynaptic membrane decreased obviously, and intercellular neural axons were thinned evidently.  Conclusions The absence of dystrophin in mdx mice is not the direct factor causing NMJ abnormities. The degeneration of muscle in the development of DMD may lead to the changes.

DOI: 10.3969/j.issn.1672-6731.2015.05.007