Abstract 196: Cardiotrophin-1 Promotes Physiologic Cardiac Hypertrophy

Abstract

The post-natal heart retains a remarkable adaptive capacity, which matches growth of the myocardium to increased physical demands. The beneficial form of myocardial growth is referred to as physiologic hypertrophy, and derives from a compensatory response to conditions that require increased blood volumes such as pregnancy and chronic exercise training. Despite the clear benefits associated with this form of adaptation, the molecular mechanism(s) that initiate or sustain such cardiac remodeling remain obscure. As such, identification of factors that promote physiologic hypertrophy will be of considerable interest to both cardiac biologists and clinicians. Here, we have begun to explore the role of the cytokine, cardiotrophin 1 (CT-1) as a central mediator of physiologic hypertrophy. We demonstrate that primary cardiomyocytes treated with recombinant human CT-1 protein engage a physiologic growth response, adding sarcomeres in series, a cellular/molecular change that is fully reversible with the removal of CT-1. This physiologic hypertrophy response to CT-1 is dominant, as CT-1 administration overrides the pathologic hypertrophy associated with agonists such as phenylephrine. In vivo delivery of human CT-1 protein leads to a rapid (14 days) alteration in the structure of the rat heart, with volume and wall dimension increases characteristic of exercise adaptation, changes that are fully reversible upon cessation of CT-1 treatment. In addition, CT-1 administration mitigates right heart failure in a model of pulmonary arterial hypertension, and sustains cardiac function in the post infarct rat heart. Finally, gene expression analysis revealed that CT-1 treatment leads to up-regulation of angiogenic factors within cardiomyocytes, suggesting that this cytokine engages a paracrine signaling mechanism to ensure that myocardial growth is matched by a robust angiogenesis.