Background
The primary causes of the reduced life span of patients with Duchenne Muscular Dystrophy (DMD) are severe respiratory insufficiency, due to the weakening of the diaphragm, or cardiac failure, due to the TGF?-dependent myocardial fibrosis. Fibrosis is one of the principal resultants of muscle degeneration. D2.B10 mice show an early cardiac damage compared to the commonly used mdx mice, resulting in a more severe phenotype of DMD.
Objectives
This study was aimed at evaluating anatomy and function of left ventricle (LV) in conscious D2.B10 mice compared to wild type DBA/2J mice by echocardiography.
Approach
Transthoracic echocardiography (ARIETTA 50 – FUJIFILM Healthcare) was performed in 10 mice per group at baseline (15/17 weeks old mice) and after 4 + 4 weeks (23/25 weeks old mice). After the last echocardiographic evaluation, blood samples were drawn to measure high sensitivity cardiac troponin T (hs-cTnT) and N terminal-proatrial natriuretic peptide (NT-proANP) levels. Mice were euthanized, diaphragm and heart were excised. Fibrosis was measured in 0.1% Sirius Red stained sections of both muscles.
Results
After 8 weeks of follow-up, heart rate, LV end-systolic volume, LV ejection fraction, trans-mitral E wave velocity and pulmonary-arterial-acceleration time were significantly different in D2.B10 mice compared to wt mice. Hs-cTnT, but not NT-proANP plasma concentrations, were significantly higher in D2.B10 than in wt mice (p = 0.02). Cardiac fibrotic areas were distributed mostly in the epicardium of the right ventricle (RV) and in the rightward of the intraventricular septum. In diaphragm and heart the percentage of fibrosis was higher (p < 0.0001) in D2.B10 compared to wt mice.
Conclusions
The data obtained suggest that anatomical and functional pathological manifestation in LV and RV of D2.B10 mice were mild to moderate. D2.B10 mice represent a well characterized model of DMD cardiomyopathy.