Wnt5a Is Required for Endothelial Differentiation of Embryonic Stem Cells and Vascularization via Pathways Involving Both Wnt/β-Catenin and Protein Kinase Cα

In this study, we examined the signaling pathways activated by Wnt5a in endothelial differentiation of embryonic stem ( ES) cells and the function of Wnt5a during vascular development. We first found that Wnt5a (-/-) mouse embryonic stem ( mES) cells exhibited a defect in endothelial differentiation, which was rescued by addition of Wnt5a, suggesting that Wnt5a is required for endothelial differentiation of ES cells. Involvement of both beta-catenin and protein kinase (PK) C alpha pathways in endothelial differentiation of mES cells requiring Wnt5a was indicated by activation of both beta-catenin and PKC alpha in Wnt5a(+/-) but not in Wnt5a (-/-) mES cells. We also found that beta-catenin or PKC alpha knockdowns inhibited the Wnt5a- induced endothelial differentiation of ES cells. Moreover, the lack of endothelial differentiation of Wnt5a (-/-) mES cells was rescued only by transfection of both beta-catenin and PKC alpha, indicating that both genes are required for Wnt5a-mediated endothelial differentiation. Wnt5a was also found to be essential for the differentiation of mES cells into immature endothelial progenitor cells, which are known to play a role in repair of damaged endothelium. Furthermore, a defect in the vascularization of the neural tissue was detected at embryonic day 14.5 in Wnt5a (-/-) mice, implicating Wnt5a in vascular development in vivo. Thus, we conclude that Wnt5a is involved in the endothelial differentiation of ES cells via both Wnt/beta-catenin and PKC signaling pathways and regulates embryonic vascular development. ( Circ Res. 2009; 104: 372-379.)