Fig 4.

Histological analyses of hearts from non-graft subgroup (a–c) and engraftment subgroup (d–g). Fluc (green) and PB (blue particles) double staining revealed a few double positive cells (arrows in a) in the heart but no substantial graft was formed. SPIO-containing macrophages were identified by CD68 (red) and PB double staining (arrows in b and e). Combination of PB and MT staining (c) revealed SPIO-containing cells in the scar tissue. The majority of cells inside the teratoma were Fluc positive but PB negative (d). The dashed line in (e) marks the boundary of a cardiac teratoma. a & b & c, and d & e were adjacent sections. H&E staining of the teratoma in which tissue from three germ layers was identified (f): squamous cells with keratin pearl originated from ectoderm (small arrow head), osteoid of mesoderm origin (large arrow head) and columnar gland of endoderm origin (arrow). Cardiomyocytes inside the teratoma were identified by striations positive for sarcomeric α-actinin (brown color in g). The images in d-g were obtained from hearts harvested 4 weeks after injection of cells. Scale bar =50 μm in all panels except for panel f.