THE mdx MOUSE SKELETAL MUSCLE MYOPATHY: I. A HISTOLOGICAL, MORPHOMETRIC AND BIOCHEMICAL INVESTIGATION

TLDR

The study examined skeletal muscle in a colony of mdx myopathic mice. In 65 mdx mice aged 22–303 days, extensive necrosis, regeneration, and infiltration were observed, with abnormal fiber size and central nuclei, elevated serum muscle enzymes, cardiomyopathy in 13 animals, and a pattern resembling Duchenne muscular dystrophy but with greater regeneration and no fibro‑fatty replacement.

Abstract

Skeletal muscle has been examined in a colony of the mdx strain of myopathic mice. Sixty-five mice from 22 to 303 days of age, showed extensive and recurrent areas of necrosis and regeneration of muscle fibres, often accompanied by active cellular infiltration. Morphometry of the soleus muscle revealed an abnormal proportion of small and large muscle fibres; over half of the muscle fibres contained 'central' (non-peripheral) nuclei. No histochemical muscle fibre-type grouping was detected. Serum activities of muscle-derived enzymes were greatly elevated in all animals and probably reflect enzyme leakage from damaged muscle fibres. Histological evidence of a cardiomyopathy was found in 13 mice. The mdx myopathy thus shows features seen in Duchenne muscular dystrophy. Mdx differs from Duchenne dystrophy principally in that it exhibits a greater degree of compensatory muscle regeneration and an absence of fibro-fatty replacement of muscle fibres.