Extracellular Matrix Remodeling in Heart Failure

Abstract

Heart failure is a major health problem worldwide. In the United States, it represents the number one hospital discharge diagnosis among elderly persons each year. It appears most commonly in patients with previous MI.1,2 The chronically failing heart of ischemic origin is characterized by iterations in tissue structure, particularly fibrous tissue formation, that appear in infarcted and noninfarcted myocardium of both right and left ventricles.3,4 In other words, fibrosis appears at the site of MI as well as remote from it. Fibrosis remote from the infarct site is considered “the major cause of ventricular remodeling” in ischemic cardiomyopathy.4 Such an adverse accumulation of extracellular matrix initially raises myocardial stiffness; its continued accumulation further increases stiffness and impairs contractile behavior.5–10 Elucidating cellular and molecular mechanisms responsible for accumulation of extracellular matrix is essential to designing cardioprotective and reparative strategies that could prevent or regress fibrosis, respectively, after infarction.11,12 ACE inhibition has proved effective in reducing mortal and morbid events, improving symptomatic status, and attenuating the progressive nature of cardiac failure in symptomatic patients with ventricular diastolic and/or systolic dysfunction in whom activation of the circulating RAAS is present.1,13,14 ACE inhibitor–mediated reductions in circulating Ang II and aldosterone no doubt contribute to this salutary response. This would include an attenuation of well-recognized endocrine properties of these hormones, such as altered sodium homeostasis and vascular tonicity, and their adverse influence on matrix structure of atria and ventricles.15–20 Collectively, these adverse responses to RAAS effector hormones contribute to the progressive nature of chronic cardiac failure, which includes recurring bouts of symptomatic failure1,2,21 and reentrant arrhythmias originating in either atria or ventricles.22,23 ACEIs have also proved effective in asymptomatic patients with equivalent levels of ventricular systolic dysfunction but in whom chronic RAAS activation is not present. …