Fig. 1

RH237 does not label hESC-CM graft tissue, but di-2-ANEPEQ does label graft. Still images acquired on the “red” RH237 (a) and “green” GCaMP3 (c) channels from the epicardial surface of a representative cryoinjured heart with GCaMP3+ hESC-CM graft (in this case, derived from the RUES2 line). b, d Corresponding fluorescence traces on each channel from the two indicated ROIs. The region labeled “G” is located in hESC-CM graft tissue (encircled by the yellow dotted line), while “H” is located in viable host myocardium outside of the cryoinjury zone (encircled by the white dotted line). While RH237-derived oAPs (red traces) from both ROIs occurred in 1:1 synchrony with QRS complexes of the simultaneously-acquired ECG (black) and applied stimulus (blue), GCaMP3 fluorescence transients (green) from graft tissue clearly activated independently from host myocardium. e When this heart was transversely sectioned, slices showed uniform staining of the host myocardium by RH237 (red fluorescence), but GCaMP3+ graft tissue (green) was completely devoid of RH237 staining. f By contrast, when an equivalently injured and transplanted heart was sectioned following perfusion with di-2-ANEPEQ, comparable dye staining of host and graft tissue was observed