Abstract P274: Cardiac-Specific Knockout of Capn4 Attenuates Myocardial Remodeling and Improves Function After Myocardial Infarction in Mice
Background - Calpain has been implicated in myocardial injury after myocardial infarction (MI). However, no direct evidence is available on the role of calpain in post-MI myocardial remodelling and dysfunction. The present study investigated the effects of cardiomyocyte-specific deletion of Capn4, essential for calpain-1 and calpain-2 activities on myocardial remodelling and dysfunction following MI.
Methods and Results - A novel mouse model with cardiomyocyte-specific deletion of Capn4(Capn4-ko) was generated. MI was induced by left coronary artery ligation. Deficiency of Capn4 significantly reduced the protein levels and activities of calpain-1 and calpain-2 in the Capn4-ko heart. In vivo cardiac function was relatively improved in Capn4-ko mice at 7 and 30 days after MI compared with their wild-type littermates. Deletion of Capn4 reduced cardiac apoptosis, limited infarct expansion and infarct zone thinning, and prevented left ventricle dilation in Capn4-ko mice. Furthermore, myocardial collagen deposition and cardiomyocyte cross-sectional areas were significantly attenuated in Capn4-ko mice, which were accompanied by down-regulation of pro-fibrotic genes and hypertrophic genes. These effects of Capn4 knockout correlated with down-regulation of inflammatory mediators and normalization of matrix metalloproteinase (MMP)-9 activity in the non-infarct area of Capn4-ko mice after MI. In vivo mouse model of endotoxemia confirmed that calpain activation resulted in inflammatory gene expression and MMP-9 activity in the heart.
Conclusions - Cardiomyocyte-specific knockout of calpain attenuates myocardial adverse remodelling and improves myocardial function after MI. These beneficial effects of calpain disruption may result from inhibition of cardiac apoptosis, inflammation and MMP-9 activity.
- © 2011 by American Heart Association, Inc.