Insulin expression and teratoma formation/tumorigenicity assay of the pancreatic stem cell line D#22. A. Immunofluorescence analysis of differentiated cells derived from D#22 cells. Insulin and C-peptide staining of D#22 stage 5 cells was performed. Scale bars = 200 μm. B. Insulin release assay. D#22 stage 5 cells and iPS stage 5 cells were stimulated with D-glucose at 2.8 mM and 20 mM, and the amount of insulin released into the culture supernatant was measured using ELISA. Error bars represent standard error. C. In total, 1 × 107 of D#22 cells were injected into the thigh of nude mice. As a positive control, we transplanted 1 × 107 iPS cells into the contralateral thigh.