Key result
Dystrophin-deficient fast-twitch muscles from 22-month-old mdx mice lost ~92% of their maximum force after one eccentric contraction compared to ~16% in controls, correlating with increased fiber branching.
Why the study?
Duchenne muscular dystrophy is characterized by progressive cycles of necrosis and regeneration, prompting investigation into the morphological and contractile chronology of dystrophic skeletal muscle pathology across the lifespan in dystrophin-deficient mdx mice.
Does aging and eccentric contraction reduce contractile function in mdx mice compared to littermate controls?
Population
Dystrophin-deficient mdx mice 4–22 months of age
Comparison
Fast-twitch Extensor Digitorum Longus muscles across different age groups (4–22 months)
Design
Preclinical animal study
Authors
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Supports branched-fiber mechanism in aged mdx muscle; leaves open translation to human DMD.
Does aging and eccentric contraction reduce contractile function in mdx mice compared to littermate controls?
Mean Difference: 76.29 (95% CI 68.05–84.54)
Absolute Event Rate: 92% vs 16%
p-value: p=<0.0001
In dystrophic mdx mice, aging leads to a dramatic increase in branched muscle fibers, which irrevocably rupture upon eccentric contraction and cause catastrophic force loss.
Kiriaev et al. (2021) studied Duchenne muscular dystrophy (n=71). Dystrophin deficiency (mdx genotype) vs. Littermate controls was evaluated on Force loss after first eccentric contraction in 22-month-old mice (MD 76.29, 95% CI 68.05-84.54, p=<0.0001). Dystrophin-deficient fast-twitch muscles from 22-month-old mdx mice lost ~92% of their maximum force after one eccentric contraction compared to ~16% in controls, correlating with increased fiber branching.
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