Figure 4: Assessing pluripotency of hESCs maintained under the defined culture with teratoma formation. Undifferentiated hESCs after prolonged propagation in the defined system were injected into SCID mice. Histological analysis of the resulting teratomas confirmed the presence of tissues of all three embryonic germ layers (A-C), including pigmented and neural tissue (D) (ectoderm); gut epithelium (E) (endoderm); adipose cells and vascular endothelium (F), cartilage (G), smooth muscle and connective tissue (H) (mesoderm). Magnification: (A) and (B), 4X; (C), 10X; (D-H), 20X.