Abstract: Congestive heart failure is a disease of epidemic proportions with 4.6 million patients in the U.S. and in nearly half of these patients the etiology of their disease is unknown. It is generally viewed as a progressive disease in which initial myocardial damage is followed by cardiac remodeling and progressive dilation of the left ventricle. Cardiac compensation is followed by progressive de-compensation and patients present with worsening symptoms including fatigue, shortness of breath, and edema. Recent investigation has focused on the role of the proinflammatory cytokine TNF-alpha in the development of heart failure and in particular in the transition from compensated to decompensated heart failure. Although TNF-alpha can modulate the function of a group of potentially important cardiac proteins, recent evidence suggests that TNF-alpha modulates the expression of the two families of proteins that regulate the homeostatic balance within the extracellular matrix, the matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs). Furthermore, transgenic mice harboring cardiac restricted overexpression of TNF-alpha develop matrix remodeling, progressive fibrosis, and collagen denaturation that are associated with up-regulation of MMP activity. Anti-TNF-alpha therapy using adenovirus-mediated gene therapy significantly inhibited MMP activity, prevented myocardial fibrosis and collagen denaturation. These preliminary studies led us to hypothesize that the development of end-stage heart failure is due in large part to cytokine-induced matrix remodeling and fibrosis, and that the development of fibrosis marks the irreversibility of the disease. This proposal includes three specific aims: Specific Aim 1 will test the hypothesis that the expression of cytokines is required for structural remodeling of the extracellular matrix and the remodeling is facilitated by interaction with specific cytokine receptors. In Specific Aim 2, we will test the hypothesis that anti-cytokine therapy will prevent matrix remodeling but not ameliorate existing fibrosis. Finally, in Specific Aim 3 we will test the hypothesis that therapies designed to regulate matrix remodeling will prevent and /or reverse maladaptive changes in heart failure. These studies will utilize three experimental models: 1) transgenic mice with cardiac-restricted overexpression of TNF-alpha; and 2) mice with myocardial infarcts secondary to coronary ligation. The aims of this application will be further supported the availability of mice harboring mutations in selected cytokine receptors as well as recombinant AAV vectors expressing MMPs and TIMPs. These studies should enhance our understanding of the role of TNF-alpha and MMPs in the development of heart failure, and provide invaluable information for designing heart failure gene therapy strategies.