OP9 stroma cells increase intra-teratoma hematopoiesis. (A) OP9-GFP⁺ cells were injected with iPS cells to generate teratomas. After 8 weeks, teratomas showed the presence of GFP⁺ cells in the parenchyma. (B) FACS analysis reveals the presence of blood progenitor/stem cells, myeloid cells, B, T cells, and glycophorin⁺ erythroid cells in the teratoma parenchyma. The percentage of each population is indicated for a representative teratoma derived by co-injection of iPS cells with OP9D. The glycophorin⁺ population shown as the percentage compared with the total teratoma cell number. (C) Quantitative FACS analysis of different blood populations during teratoma formation when iPS were injected in NSG mice or co-injected with OP9 cells or OP9 ectopically expressing Delta-like1 (OP9D) or Wnt3A (OP9W3a). Error bars represent SD.