Prokineticins are secreted peptides that activate two receptors. We investigated the role of each receptor in heart by generating transgenic (TG) mice overexpressing PKR1 or PKR2 in cardiomyocytes. TG-PKR1 displayed an increased number of epicardial-derived progenitor cells (EPDCs), capillary density and vessels, without inducing any cardiomyocyte abnormalities. Coculturing EPDCs with H9c2 cardiomyoblasts overexpressing PKR1 upragulates prokineticin-2 as a paracrine factor that promotes EPDC differentiation into endothelial and smooth muscle cells, mimicking our transgenic model. Exogenous prokineticin-2 induces neonatal and adult EPDC differentiation. These prokineticin-2 effects were abolished in EPDCs from mice with PKR1-null mutation, indicating involvement of PKR1. This study provides a novel insight for possible therapeutic strategies aiming at restoring pluripotency of adult EPDCs to promote neovasculogenesis by induction of cardiomyocyte PKR1 signaling. TG-PKR2 exhibit increased hypertrophic gene expressions and increased left ventricular endsystolic and diastolic diameters without cardiac dysfunction at the age of 24 weeks. TG hearts exhibit abnormal endothelial cell shape and ultrastructure, changed cellular distribution of a tight junction protein ZO-1, and vascular leakage in heart. The application of media conditioned by H9c2 cardioblast cells overexpressing PKR2 disturbed ZO-1 localization in H5V endothelial cells, mimicking the TG model. These findings showed that cardiomyocyte PKR2 signalling leads to eccentric hypertrophy in an autocrine regulation and impaired endothelial integrity in a paracrine regulation.

Our findings should facilitate the discovery of specific agonist and antagonist targeting PKR1 and PKR2 for possible use of treatment of ischemic heart diseases.