Wnt inhibition promotes vascular specification of embryonic cardiac progenitors

Abstract

Several studies have demonstrated a multiphasic role for Wnt signaling during embryonic cardiogenesis (Naito et al., 2006; Qyang et al., 2007) and developed protocols that enrich for cardiac derivatives during in vitro differentiation of human pluripotent stem cells (hPSC) (Elliott et al., 2011; Iyer et al., 2016; Lian et al., 2012; Paige et al., 2010; Willems et al., 2011; Witty et al., 2014), however, few studies have investigated the role of Wnt signaling in specification of cardiac progenitor cells (CPC) toward downstream fates. Using transgenic mice and hPSCs, we tracked endothelial cells (EC) that originated from CPCs expressing Nkx2.5. Analysis of EC-fated CPCs at discrete phenotypic milestones during hPSC differentiation identified reduced Wnt activity as a hallmark of EC specification, and enforced activation or inhibition of Wnt reduced or increased, respectively, the degree of vascular commitment within the CPC population during both hPSC differentiation and mouse embryogenesis. Wnt5a, which has been shown to play an inhibitory role on Wnt during cardiac development, was dynamically expressed during vascular commitment of hPSC-derived CPCs and ectopic Wnt5a promoted vascular specification of hPSC-derived and mouse embryonic CPCs.