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Pathological analysis of muscle hypertrophy and degeneration in muscular dystrophy in gamma-sarcoglycan-deficient mice.

Authors
Type
Published Article
Journal
Neuromuscular Disorders
0960-8966
Publisher
Elsevier
Publication Date
Volume
13
Issue
3
Pages
193–206
Identifiers
PMID: 12609501
Source
Medline
License
Unknown

Abstract

While calf muscle hypertrophy is a striking diagnostic finding in sarcoglycanopathy, as it is in Duchenne and Becker muscular dystrophies, its pathogenetic mechanism remains unknown. gamma-Sarcoglycan, one of the subunits of the sarcoglycan complex, is the protein responsible for gamma-sarcoglycanopathy. To elucidate the pathogenetic mechanisms of muscle hypertrophy and degeneration in muscular dystrophy, we utilized a mutant mouse as a model animal. In this study, we generated gamma-sarcoglycan-deficient (gsg-/-) mice by gene targeting. The gsg-/- mice described here, similar to the gsg-/- mice reported previously (J Cell Biol 142 (1998) 1279), demonstrated skeletal and cardiac muscle degeneration. The limb, shoulder, and pelvic muscles of the gsg-/- mice exhibited progressive muscle hypertrophy and weakness with age, and the findings were similar to those seen in other mouse models for limb-girdle and Duchenne muscular dystrophy. We found that the number of muscle fibers increased with age, and most of the fibers in the hypertrophic muscle were centrally nucleated regenerating fibers. Therefore, muscle hypertrophy of the gsg-/- mice may result from an increase of the number of muscle fibers and probable fiber branching and may not be due to the pseudohypertrophy caused by fibrous and fat tissue replacement, as has been long supposed in muscular dystrophy. The muscle pathology became more 'dystrophic' in mice over 1 year of age when there was a marked variation in fiber size with interstitial fibrosis.

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