HISTOLOGICAL STUDY OF MASSETER MUSCLE IN A MOUSE MUSCULAR DYSTROPHY MODEL (mdx mouse)

• Published in: Bulletin of Tokyo Dental College Vol. 41; no. 3; pp. 119 - 122
• Main Authors: ABE, SHINICHI, KASAHARA, NORIO, AMANO, MAKITO, YOSHII, MASATOSHI, WATANABE, HIROKI, IDE, YOSHINOBU
• Format: Journal Article
• Language: English
• Published: Japan Tokyo Dental College, Japan 2000; Japan Science and Technology Agency
• Subjects: Aging - pathology; Animals; Cell Nucleus - ultrastructure; Dentistry; Disease Models, Animal; Masseter Muscle - pathology; Mastication; Mastication - physiology; mdx mouse; Mice; Mice, Inbred mdx; Microscopy, Electron; Moth-eaten fiber; Muscle Fibers, Skeletal - ultrastructure; Muscular Dystrophies - pathology; Myofibrils - ultrastructure; Necrosis; Regenerated muscle; Regeneration - physiology; Sucking Behavior - physiology; Weaning
• ISSN: 0040-8891
• DOI: 10.2209/tdcpublication.41.119

Histological changes in the masseter muscle were observed over time in mdx mice, a muscular dystrophy model. It was found that marked necrosis occurs about the time of weaning at around 4 weeks of age; then the tissue actively regenerates at 8 weeks and stabilizes as regenerated muscle with centronuclei at 15 weeks old. This study examined the centronucleus in regenerated muscle. The process from necrosis to regeneration in muscle fibers occurs a little later in the masseter muscle than in other limbic muscles. Regenerated muscles observed around 15 weeks after birth showed a moth-eaten appearance. Transmission Erectron Microscope (TEM) observation of transverse sections of muscle fibers revealed that myofibrils surrounded lost regions in the area showing a moth-eaten appearance. Thus, some defensive mechanism may affect the ability of muscle fibers to maintain a function close to normal in mdx mice even though the muscle fibers develop muscular dystrophy. The function of the masseter muscle drastically changes from sucking to mastication behavior at around 4 weeks, and this was considered to influence the morphological changes in the muscle tissue. The moth-eaten appearance seen at 15 weeks may represent an appropriate myofibril reconstruction preventing invasion of the lost regions.