Abstract 1334: Wnt5a Modulates Cardiac Gene Expressions And Histone Modifications Of Adult Progenitor Cells Via A Pkcδ-dependent Pathway
Wnt signalling controls the balance between stem cell proliferation and differentiation and body patterning throughout development. Previous data demonstrated that non-canonical Wnts (Wnt5a, Wnt11) enhanced cardiac gene expression of endothelial progenitor cells (EPC) and mesenchymal stem cells in vitro. First, we tested whether pre-treatment of EPC with Wnt5a enhances cardiac commitment in vivo. Peripheral blood-derived EPC were incubated with recombinant Wnt5a for 24 hours. Then, cells were intravenously infused in nude mice model of acute myocardial infarction. Cardiac differentiation was determined by using human specific primers detecting troponin I (TnI). Hearts isolated from Wnt5a-pretreated mice showed a higher expression of human cardiac TnI compared to the control cell-treated mice. Furthermore, human cells, identified by a human specific Alu probe, which co-express cardiac actin, were preferentially detected in hearts from the Wnt5a-pretreated group. Next, we determined the signalling induced by Wnt5a. Since previous studies suggested a contribution of the protein kinase C (PKC) family, we used specific pharmacological inhibitors directed against different PKC isoforms. Inhibition of the novel PKC isoform, PKCδ, significantly blocked cardiac differentiation in vitro (77.3±9.3%), whereas other inhibitors directed against the classical Ca2+-dependent PKC isoforms or PKCϵ-inhibitors were not effective. In accordance, Wnt5a selectively activated phosphorylation and translocation of PKCδ. The specific involvement of PKCδ was additionally confirmed by using EPC isolated from PKCδ-deficient mice which showed a reduction in cardiac differentiation (33.2% of wild type control). To determine the downstream targets of Wnt/PKC, we performed microarray analysis. We identified that several enzymes, which modified histone acetylation and methylation such as HDACs, YY1, and PCGF2, were significantly increased by Wnt5a. Indeed, histone methylation patterns were changed by Wnt5a and this effect was suppressed by the PKCδ inhibitor. These data indicated that Wnt5a increased cardiac differentiation of adult progenitor cells via PKCδ. Wnt5a may sensitize cardiac commitment by changing epigenetic control mechanisms.