Reprogramming of enteroendocrine K cells to pancreatic β-cells through the combined expression of Nkx6.1 and Neurogenin3, and reaggregation in suspension culture. 
Recent studies have demonstrated that adult cells such as pancreatic exocrine cells can be converted to pancreatic β-cells in a process called cell reprogramming.  Enteroendocrine cells and β-cells share similar pathways of differentiation during embryonic development.  Notably, enteroendocrine K cells express many of the key proteins found in β-cells.  Thus, K cells could be reprogrammed to β-cells under certain conditions.  However, there is no clear evidence on whether these cells convert to β-cells.  K cells were selected from STC-1 cells, an enteroendocrine cell line expressing multiple hormones.  K cells were found to express many genes of transcription factors crucial for islet development and differentiation except for Nkx6.1 and Neurogenin3.  A K cell clone stably expressing Nkx6.1 (Nkx6.1(+)-K cells) was established.  Induction of Neurogenin3 expression in Nkx6.1(+)-K cells, by either treatment with a γ-secretase inhibitor or infection with a recombinant adenovirus expressing Neurogenin3, led to a significant increase in Insulin1 mRNA expression.  After infection with the adenovirus expressing Neurogenin3 and reaggregation in suspension culture, about 50% of Nkx6.1(+)-K cells expressed insulin as determined by immunostaining.  The intracellular insulin content was increased markedly.  Electron microscopy revealed the presence of insulin granules.  However, glucose-stimulated insulin secretion was defective, and there was no glucose lowering effect after transplantation of these cells in diabetic mice.  In conclusion, we demonstrated that K cells could be reprogrammed partially to β-cells through the combined expression of Nkx6.1 and Neurogenin3, and reaggregation in suspension culture.