The muscular dystrophies

Chronic administration of a leupeptin-derived calpain inhibitor fails to ameliorate severe muscle pathology in a canine model of duchenne muscular dystrophy

Calpains likely play a role in the pathogenesis of Duchenne muscular dystrophy (DMD). Accordingly, calpain inhibition may provide therapeutic benefit to DMD patients. In the present study, we sought to measure benefit from administration of a novel calpain inhibitor, C101, in a canine muscular dystrophy model. Specifically, we tested the hypothesis that treatment with C101 mitigates progressive weakness and severe muscle pathology observed in young dogs with golden retriever muscular dystrophy (GRMD). Young (6-week-old) GRMD dogs were treated daily with either C101 (17 mg/kg twice daily oral dose, n = 9) or placebo (vehicle only, n = 7) for 8 weeks. A battery of functional tests, including tibiotarsal joint angle, muscle/fat composition, and pelvic limb muscle strength were performed at baseline and every 2 weeks during the 8-week study. Results indicate that C101-treated GRMD dogs maintained strength in their cranial pelvic limb muscles (tibiotarsal flexors) while placebo-treated dogs progressively lost strength. However, concomitant improvement was not observed in posterior pelvic limb muscles (tibiotarsal extensors). C101 treatment did not mitigate force drop following repeated eccentric contractions and no improvement was seen in the development of joint contractures, lean muscle mass, or muscle histopathology. Taken together, these data do not support the hypothesis that treatment with C101 mitigates progressive weakness or ameliorates severe muscle pathology observed in young dogs with GRMD.

Evidence of left ventricular dysfunction in children with merosin-deficient congenital muscular dystrophy

BACKGROUND

Deficiency of the sarcolemmal protein dystrophin has been linked to dilated cardiomyopathy. Some children with congenital muscular dystrophy have a deficiency of the laminin alpha2 chain of merosin, an extracellular matrix protein linked to dystrophin through a group of glycoproteins. It has been shown that deficiency in one of these glycoproteins is responsible for muscular dystrophy and dilated cardiomyopathy. Children with laminin alpha2 deficiency may be at risk for development of cardiomyopathy.

METHODS AND RESULTS

We studied the cardiac function of a cohort of 16 children with congenital muscular dystrophy by using 2-dimensional echocardiography. The expression of the laminin alpha2 of merosin in the patients was determined on a skin or muscle biopsy. Two of 6 merosin-deficient children had an ejection fraction <40%. The average ejection fraction of the merosin-deficient children was 43%+/-11%, which was significantly lower than the merosin-positive children (53%+/-5%, P=.03).

CONCLUSIONS

This study suggests that a deficiency of laminin alpha2 can give rise to dilated cardiomyopathy, supporting the idea that defects of dystrophin, or of associated proteins, can cause dilated cardiomyopathy in addition to muscular dystrophy.