Spontaneous differentiation of the measles virus (MV)-derived induced pluripotent stem cell (iPSC)-like clones and teratoma formation. (A) Three MV- and one lentiviral vector (LV)-derived iPSC clone (#1, #2, #3, and 4LV) were analyzed by immunofluorescence for lineage markers for three germ layers (endoderm, mesoderm, and ectoderm). iPSC clones were spontaneously differentiated through embryoid body formation (top row). Pluripotency of derived iPSC clones was verified by generation of cells of ectoderm (β-III tubulin, green, second row), endoderm (FOXA2, red, third row), and mesoderm (CD31, green, bottom row) upon spontaneous differentiation. Nuclei were counterstained by 4′,6-diamidino-2-phenylindole (DAPI) (blue). Scale bars: 50 μm. (B) Transplant of iPSC clones into the kidney capsule of severe combined immunodeficiency (SCID)-beige mice resulted in teratoma formation. Pictures of harvested kidneys with iPSC transplant are shown for all clones. (C) Representative hematoxylin-and-eosin staining demonstrated multiple lineages within the complex architecture of the tumor, including cells of ectoderm (neuronal rosette-like structures, indicated by an asterisk), endoderm (gut tube-like structures, intestinal epithelial cells), and mesoderm (muscle-like tissue). Magnifications: 20× (top) and 40× (lower).