Fig. 4: Graft automaticity.

A Fluorescence image of a slice with a small circular graft (blue circle) that was implanted with perpendicular injection. The remote pacing site (P) and the site of Vm recordings in (B, C) are indicated. B In the absence of pacing, the graft activated spontaneously at ~0.75 Hz (CaT), but activation did not spread to the host (Vm). C During remote pacing, the host activated (Vm), but activation did not spread to the graft (CaT). D(I), Immunohistological image with DAPI staining (blue) and human-specific KU80 labeling (red), which indicates human myocytes in the graft. (II), The same section with additional α-SA labeling (cyan) for cardiac myocytes. The circular demarcation between the implanted human cardiomyocytes and host myocardium (dotted line) is evident in both images. (III), The same section after de-staining and re-staining with DAPI and antibodies for CX43 (red), and in (IV), α-SA. The demarcation between host and graft is still evident. α-SA indicates α-sarcomeric actin; CX43, connexin-43; and DAPI, 4’,6-diamidino-2-phenylindole.