Severe mechanical dysfunction in pharyngeal muscle from adult mdx mice.
The mdx mouse is a widely used animal model of human muscular dystrophy. Although diaphragm muscle exhibits severe muscle weakness throughout the life of the animal, the limb muscle function of mdx mice spontaneously recovers by 6 mo of age. Pharyngeal dilator muscles such as sternohyoid (SH) contribute to upper airway patency during breathing. We hypothesized that SH muscle function was impaired in 6-mo-old mdx mice. Mechanical properties and myosin heavy chain (MHC) composition were investigated in isolated SH from 6-mo-old control (C, n = 10) and mdx (n = 10) mice. As compared with C, peak tetanic tension (Pmax) and maximum shortening velocity were 50% and 16% lower in mdx mice (p < 0.001 and p < 0.05, respectively). Peak mechanical power was lower in mdx than in C (19.0 +/- 3.2 versus 57.4 +/- 5.1 mW g(-)(1), p < 0.001). Both C and mdx SH were composed exclusively of fast myosin isoforms. As compared with C, mdx SH presented a higher proportion of IIX-MHC and a reduction in IIB-MHC (each p < 0.001). In conclusion, our results demonstrated severe SH muscle dysfunction in 6-mo-old mdx mice, that is, at a time when limb muscle function has recovered. Thus, SH muscle of the mdx mouse may be an excellent muscle for studying Duchenne muscular dystrophy.
Attal
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P
Service d'Oto-Rhyno-Laryngologie et de Chirurgie Cervico-Faciale, Hôpital de Bicêtre; INSERM U451-Loa-ENSTA-Ecole Polytechnique, Palaiseau Cedex, France.
Lambert
F
F
Marchand-Adam
S
S
Bobin
S
S
Pourny
J C
JC
Chemla
D
D
Lecarpentier
Y
Y
Coirault
C
C
D000367:Age Factors; D000818:Animals; D051379:Mice; D018101:Mice, Inbred mdx; D009119:Muscle Contraction; D009136:Muscular Dystrophies / Q000503:physiopathology; D009218:Myosins / Q000096:biosynthesis; D010609:Pharyngeal Muscles / Q000503:physiopathology*; D020033:Protein Isoforms / Q000096:biosynthesis; D012720:Severity of Illness Index
D020033:Protein Isoforms; D009218:Myosins