Figure 2.

Engraftment of human ES cell-derived cardiomyocytes (hESC-CMs) in athymic rat hearts. hESC-CMs were injected directly into the athymic rat heart and histological analysis was performed at 2, 4, or 12 weeks after transplantation. (a–c) Hematoxylin–eosin (H&E) staining of grafted hESC-CMs in the host hearts. (d–f) Human grafted cardiomyocytes identified by the cardiac marker, β-myosin heavy chain (β-MHC, arrowheads). Note that β-MHC was exclusively expressed in grafted human cardiomyocytes but not in host rat cardiomyocytes. Black squares indicate the area where pictures below (g–l) were taken from. (g–l) Quadruple staining against cTNT (green), β-MHC (red), KI-67 (white), and DAPI (blue) in the graft area. Grafted cardiomyocytes at 12 weeks post transplantation (i,l) showed a mature appearance characterised by formation of an aligned sarcomere structure and serried deposition of cardiomyocytes, as well as rare expression of the proliferative marker KI-67. (m) Percentage of grafted area divided by total left-ventricular area (n = 5 per group). LV left ventricle. (n) Percentage of KI-67 positive graft cells at 2, 4, and 12 weeks post transplantation. *P = 0.0019 vs. 2 weeks, + P = 0.0019 vs. 4 weeks by ANOVA with Tukey’s post hoc test. See also SI Figure S3.