Abstract
Owing to the beneficial properties of amniotic fluid-derived stem cells (AFSCs), including pluripotency and the lack of ethical issues associated with embryonic stem cells (ESCs), they should be a promising cell source for regenerative medicine. However, how to differentiate AFSCs into contracting cardiomyocytes has not been established. In this study, a well-established, direct cardiac differentiation protocol involving the modulation of Wnt signaling was used to differentiate Oct 3/4+ AFSCs into cardiomyocytes. By day 14 of cardiomyocyte differentiation, these AFSCs expressed cardiac-specific genes (i.e., cardiac troponin T and myosin light chain 2v) and proteins but could not spontaneously contract. Using the patch-clamp technique, we further characterized the electrophysiological properties of human ESC-derived cardiomyocytes (hESC-CMs) and differentiated AFSCs. We used different configurations to investigate membrane potentials and ion currents in differentiated AFSCs and hESC-CMs. Under cell-attached voltage- or whole-cell current-clamp modes, we recorded spontaneous action currents (ACs) or action potentials (APs) in hESC-CMs but not in differentiated AFSCs. Compared to hESC-CMs, differentiated AFSCs showed significantly diminished activity of both BKCa and IKCa channels, which might lead to a lack of spontaneous ACs and APs in differentiated AFSCs. These results indicated that this well-established Wnt signaling modulating cardiac differentiation protocol was insufficient to induce the differentiation of functional cardiomyocytes from Oct 3/4+ AFSCs. Therefore, AFSC may not be an ideal candidate for cardiomyocyte differentiation.