Progenitor Cell Heart Therapy Figure 1. Derivation and in vitro characterization of mouse ESC-derived CPCs. ESCs were induced to differentiate through 3D aggregation and embryoid body formation. Clusters of CPCs, located within the embryoid body, expressed GFP under the control of the Nkx2-5 enhancer element (a–b). GFP(+) CPCs isolated by FACS sorting differentiated exclusively into cardiomyocytes (a-Actinin) while retaining GFP expression (c–d). The CPCs differentiated in vitro into cardiomyocytes (a-Actinin), smooth muscle (Smooth muscle actin), and endothelial cells (Von Willebrand factor) (e–f). Temporal quantitative RT-PCR analysis for the nascent mesoderm marker Brachyury, the cardiac progenitor marker Nkx2-5, and a cardiomyocyte marker Mhc6 (g). The percentage of GFP(+) CPCs was determined temporally following induction of mouse ESC differentiation (h). doi:10.1371/journal.pone.0011536.g001 PLoS ONE | www.plosone.org 3 July 2010 | Volume 5 | Issue 7 | e11536