Evaluation of the DBA/2J mouse as a potential background strain for genetic models of cardiomyopathy

The potential use of the D2.mdx mouse (the mdx mutation on the DBA/2J genetic background) as a preclinical model of the cardiac aspects of Duchenne muscular dystrophy (DMD) has been criticized based on speculation that the DBA/2J genetic background displays an inherent hypertrophic cardiomyopathy (HCM) phenotype. Accordingly, the goal of the current study was to further examine the cardiac status of this mouse strain over a 12-month period to determine if observable signs of HCM develop, including histopathology and pathological enlargement of the myocardium. Previous reports have documented heightened TGFβ signaling in the DBA2/J striated muscles, as compared to the C57 background, which, as expected, is manifested as increased cardiomyocyte size, wall thickness, and heart mass as compared to the C57 background. While normalized heart mass is larger in the DBA/2J mice, compared to age-matched C57/BL10 mice, both strains similarly increase in size from 4 to 12 months of age. We also report that DBA/2J mice contain equivalent amounts of left ventricular collagen as healthy canine and human samples. In a longitudinal echocardiography study, neither sedentary nor exercised DBA/2J mice demonstrated left ventricular wall thickening or cardiac functional deficits. In summary, we find no evidence of HCM, nor any other cardiac pathology, and thus propose that it is an appropriate background strain for genetic modeling of cardiac diseases, including the cardiomyopathy associated with DMD.