Dystrophic pathology in the intrinsic and extrinsic laryngeal muscles in the mdx mouse

In Duchenne muscular dystrophy (DMD) a deficiency in the dystrophin protein causes widespread skeletal muscle breakdown and eventual loss of function. However, some muscle groups, such as the extraocular muscles, are spared from damage despite the dystrophin deficiency. Identifying and characterising spared muscle groups may form the basis for developing new therapies to alleviate muscle breakdown in DMD. This study analysed the pathology in the intrinsic and extrinsic laryngeal muscles in dystrophin-deficient mdx mice. The mdx cricothyroid and extrinsic laryngeal muscles were characterised by similar levels of necrosis and centrally nucleated muscle fibres to the diaphragm and hind limb muscles, while the remaining intrinsic laryngeal muscles showed an extremely mild pathology. Expression of dystrophin, '-dystroglycan, and utrophin did not differ between mdx muscle groups. However, while caveolin-3 was upregulated in all mdx muscles compared with those from normal mice, this upregulation was significantly higher in the mdx extraocular muscles. This implies that high caveolin-3 levels may help protect the extraocular muscles, but that in other muscle groups levels of this protein do not correlate with the extent of dystrophic pathology.