For years, scientists have tried to understand why children with Duchenne muscular dystrophy experience severe muscle wasting and eventual death. After all, laboratory mice with the same mutation that causes the disease in humans display only a slight weakness. Now a new animal model of the disease points a finger squarely at the inability of human muscle stem cells to keep up with the ongoing damage caused by the disorder.
There are at least nine types of muscular dystrophy, the most well known of which is Duchenne's. Each causes a pattern of weakness and disability and is inherited. Weakness and disability are most severe in Duchenne's.
“Patients with muscular dystrophy experience chronic muscle damage, which initiates a never-ending cycle of repair and wasting,” said Helen Blau, PhD, Donald E. and Delia B. Baxter Professor at the Stanford School of Medicine and member of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine. “We found that in mice the muscle stem cells can keep up with the demands on them to cycle.”
Duchenne muscular dystrophy is the most prevalent form of the muscular dystrophies. It is caused by a mutation in the dystrophin gene, which connects the interior cytoskeleton of the muscle fiber to the extracellular matrix. Its absence leads to death of the muscle tissue and progressive weakness, which eventually affects a patient’s ability to breathe; 10-year-olds are often wheelchair-bound. Death usually occurs by the second or third decade as a result of respiratory and heart problems. The disorder affects about one of every 3,500 boys in the United States, whereas girls are generally spared because the gene lies on the X chromosome.
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