Dynamic Ultrastructure of Smooth Muscle Cells in Dystrophin-Deficient mdx or Normal scn Mice

Abstract

Duodenal smooth muscle cells of normal scn mice and dystrophin-deficient mdx mice were prepared by the in vivo cryotechnique (IVCT). The IVCT revealed more realistic ultrastructures of functional smooth muscle cells in both scn and mdx mice. In the scn mice, they were surrounded by compact extracellular matrix and had large gap junctions and closed caveolae with electron-dense contents. In the dystrophic mdx mice, however, the extracellular matrix was often torn off from the surface of the smooth muscle cells. The dystrophic mdx mouse had smooth muscle cells equipped with small gap junctions and uneven dense plaques in comparison with the normal scn mouse. They were surrounded with some incomplete basal lamina. The dystrophic smooth muscle cells also represented the atypical arrangement of caveolae, which were fusing together with neighboring caveolae. Such ultrastructural changes were mainly seen in the regions of caveolae, suggesting that a primary cause of the smooth muscle injury might be induced by the lack of normal arrangements of functional cell membranes.