Pluripotent stem cells have demonstrated the potential to generate large numbers of functional cardiomyocytes (CMs) from different cell sources. Besides Wnt signaling, additional pathways are involved in early cardiac development and function. To date however, no study exists showing the effects of perturbing the canonical Wnt pathway using nonhuman primate embryonic stem (ES) cells. In this study, we investigated the effect of canonical Wnt inhibition during differentiation of nonhuman primate ES cell-derived CMs under defined, growth factor conditions. Rhesus monkey ES (rES) cells were differentiated into spontaneously beating CMs in the absence (control) or presence (treated) of Wnt inhibitor Dickkopf1 (DKK1), vascular endothelial growth factor, and basic fibroblast growth factor combined or added in a sequential manner during differentiation. Quantification and functional characterization of CMs were assessed by molecular and electrophysiological techniques. Analysis revealed no difference in average ratio of spontaneously beating clusters in both control and treated groups. However, the percentage of CMs was significantly reduced and the expressions of specific cardiac markers tested were also decreased in the treated group. Interestingly, we found that in CMs obtained from treated group, β-adrenergic receptors (β-ARs) were less expressed, their function was altered and electrophysiological studies revealed differences in action potential responsiveness to β-AR stimulation. We demonstrated that the Wnt/β-catenin pathway inhibitor, DKK1 associated with other growth factors repressed functional expression of β-ARs in rES cell-derived CMs. Thus, control of this pathway in each cell line and source is important for proper basic research and further cell therapy applications.
Keywords: WNT signaling pathway; cardiomyocytes; electrophysiology; embryonic stem cells; rhesus; β-adrenergic receptors.