Induction of myocardial biglycan in heart failure in rats—an extracellular matrix component targeted by AT1 receptor antagonism

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Abstract
Objective: Cardiac remodelling associated with congestive heart failure typically involves dilatation of the ventricular cavities, cardiomyocyte hypertrophy and alterations of extracellular matrix. Biglycan is an extracellular proteoglycan with several recently appreciated functions including cell adhesion, collagen fibril assembly, and growth factor interactions. The aims of this study were to investigate the regulation of biglycan expression and to elucidate the site(s) of synthesis of biglycan in myocardial tissue in an experimental model of heart failure (HF). Methods: Myocardial tissue samples were obtained from rats with myocardial infarction (MI) subsequent to ligation of the left coronary artery. Northern blot analysis and real-time quantitative RT-PCR were employed to investigate mRNA levels. The cellular distribution of biglycan was analysed by in situ hybridisation and immunohistochemistry. Results: Myocardial biglycan mRNA levels in non-ischemic tissue of both left and right ventricles of heart failure rats were substantially elevated as compared to sham-operated rats. Although expression levels peaked 7 days after MI (13-fold increase compared to the sham group, P1 receptor antagonist losartan (12.5 mg·kg−1 b.i.d. per os, for 25 days) prevented the increase of myocardial biglycan as well as TGF-β1 mRNA. Conclusion: This report demonstrates global induction of myocardial biglycan mRNA in heart failure. Myocardial biglycan expression could be targeted by AT1 receptor antagonism, an intervention well documented to halt cardiac remodelling in heart failure. Furthermore, the study provides evidence that angiotensin II is a regulator of biglycan expression in cardiac fibroblasts.

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