Stanford researchers have devised the first mouse model of Duchenne muscular dystrophy. (Previous attempts had resulted in mice that showed only minimal muscle weakness, rather than the severe wasting and early death that confronts humans with the disorder.) The research shows that, although the muscle damage is caused by a mutation in the dystrophin gene, symptoms occur because the muscle stem cells pegged to repair the damaged tissue run out of steam in humans much more quickly than they do in mice.
“The results suggest that treatments directed solely at the muscle fiber will not suffice and could even exacerbate the disease. The muscle stem cells must be taken into consideration,” said Blau. Former postdoctoral fellow Jason Pomerantz, MD, co-corresponding author and now an assistant professor at the University of California-San Francisco, said, “if a treatment does not replenish the stem cell compartment, it will likely fail; it would be like pushing the gas pedal to the floor when there is no reserve.”
Developing a good mouse model for the disorder gives researchers and clinicians a way to learn more about the disorder and test possible therapies.
As for the laboratory mice, the reason they seem impervious to the dystrophin gene mutation is because their chromosomes sport longer protective caps (called telomeres) than do human chromosomes. The longer telomeres allow the mouse muscle stem cells to divide more times - and generate more muscle tissue - than their human counterparts. So, despite what you may have heard, sometimes size does matter.