Localization of caspase 12 in masseter muscle of mdx mice during regeneration

Abstract

The mdx mouse, a model of muscular dystrophy, lacks dystrophin, a cell membrane protein. It is known that this lack of dystrophin results in muscle fiber necrosis from 2 weeks after birth, and the majority of necrotic fibers are replaced by regenerated fibers by 4 weeks of age. Recent studies reported the detection of mitochondrial and endoplasmic reticulum stress proteins during muscle fiber necrosis in mdx mice, but did not histologically localize them to determine the timing of their expression during the process from cell necrosis to regeneration. Therefore, in this study, we investigated histological localization and gene-level expression in the mdx mouse masseter muscle of caspase-12 protein (among the caspases, which are cell stress-related genes) involved in the endoplasmic reticulum stress pathway. We observed caspase-12 expression in muscle cells that seemed to be in the process of necrosis in the mdx mouse masseter muscle at 2 weeks after birth, but not in regenerated muscle cells with centrally located nuclei observed at 3 to 4 weeks of age. These results suggest that due to the lack of dystrophin, it becomes difficult for muscle cells to maintain their morphology, and endoplasmic reticulum stress occurs to maintain cell morphology during the process of cell necrosis.