The Role of Osteopontin in Extracellular Matrix Remodeling Following Chronic Sympathetic Stimulation in The Aging Heart

Cardiovascular disease (CVD) is the leading cause of death in the United States. A common feature in most cardiac pathologies is the dysregulation of beta-adrenergic receptors (β-AR) and changes in the extracellular matrix (ECM). The ECM maintains strength and normal organization of cardiac tissue, while fibrosis (connective tissue scarring) is necessary for repair of damaged cardiac tissue. However, the dysregulation of the ECM leads to a number of cardiac disease pathologies. Osteopontin (OPN) is a protein with diverse biological functions in regulating the ECM such as bone resorption and calcification, wound healing, cell adhesion, cell survival, and apoptosis. OPN is expressed at low levels in the heart but increases with injury by promoting collagen synthesis, cardiac fibroblast growth, and adhesions to ECM proteins. Furthermore, as the heart ages, increases in ECM reorganization leads to cardiac damage and failure. Several studies have examined the role of OPN in the heart, but to date, no studies exist on the role of OPN in response to β-AR signaling and cardiac remodeling or the role that aging plays in this response. The goal of this study was to examine the effects of OPN on cardiac ECM remodeling following chronic beta-adrenergic stimulation. We proposed that OPN expression increases cardiac remodeling and dysfunction following ISO treatment in the aging heart evidenced by increased fibrosis. For this study, young (4 months) and middle age (14 months) mice with (WT) and without (KO) the OPN gene were treated with isoproterenol (ISO) for 28 days. Echocardiography was used to assess cardiac function. Mice were euthanized, and the hearts were analyzed for fibrosis using Masson’s Trichrome Staining. Results showed ISO increased fibrosis in the WT-ISO, but not KO-ISO compared to the respective controls (SHAM, no ISO treatment) for the middle age mice (p≤0.05). Furthermore, the aged WT-ISO group exhibited a 3-fold increase in fibrosis compared to the young WT-ISO group. Results from echocardiography will be analyzed and we expect to see compromised cardiac function in the WT-ISO groups compared to KO-ISO groups. OPN is currently being examined as a potential biomarker in heart failure. The results from this study will provide new insight on changes in the cardiac vasculature in the aging heart following injury and the role OPN plays in this process.