Figure 4

Pdx1 expressing ES cell-derived IPCs cause teratoma formation. (a) The long-term fate of the IPCs transplanted under the renal capsule in diabetic mice was monitored by real-time noninvasive bioluminescence imaging (BLI). Our ES cells were engineered using rat insulin promoter (RIP) driven luciferase reporter. Following differentiation of the ES cells, the transcriptional activation of the RIP leads to a selective robust expression of luciferase in the IPCs. In one of the IPC transplanted mouse, the BLI signal showed a progressive increase, especially beyond Day 40 post-transplantation with maximum BLI signal intensity at Day 50 post-transplantation. (b) The mouse transplanted with ES cell-derived IPCs was sacrificed and the internal organs were examined. The kidney bearing the transplanted IPCs revealed the presence of teratoma formation covering the dorsal and ventral sides of the kidney. (c) Histopathology following hematoxylin-eosin staining revealed the presence of epidermal, mucous secreting, ciliated epithelial as well as the neuronal tissues. However, there was no evidence of any metastatic lesions in any other organs. (d) Immunostaining using anti-GFP and anti-C-peptide antibodies revealed the presence of both AcGFP and insulin-positive transplanted cells.