Differentiation of embryonic stem cells into insulin-producing cells promoted by Nkx2.2 gene transfer

AIM: To investigate the ability of a genetically altered embryonic stem (ES) cell line to generate insulin-producing cells in vitro following transfer of the Nkx2.2 gene. METHODS: Hamster Nkx2.2 genes were transferred into mouse ES cells. Parental and Nkx2.2-transfected ES cells were initiated toward differentiation in embryoid body (EB) culture for 5 d and the resulting EBs were transferred to an attached culture system. Dithizone (DTZ), a zinc-chelating agent known to selectively stain pancreatic beta cells, was used to detect insulin-producing cells. The outgrowths were incubated in DTZ solution (final concentration, 100 mu g/mL) for 15 min before being examined microscopically. Gene expression of the endocrine pancreatic markers was also analyzed by RT-PCR. In addition, insulin production was determined immunohistochemically and its secretion was examined using an ELISA. RESULTS: DTZ-stained cellular clusters appeared after approximately 14 d in the culture of Nkx2.2-transfected ES cells (Nkx-ES cells), which was as much as 2 wk earlier, than those in the culture of parental ES cells (wt-ES). The frequency of DTZ-positive cells among total cultured cells on day 28 accounted for approximately 1.0% and 0.1% of the Nkx-ES- and wt-ES-derived EB outgrowths, respectively. The DTZ-positive cellular clusters were found to be immunoreactive to insulin, while the gene expressions of pancreatic-duodenal homeobox 1 (PDX1), proinsulin 1 and proinsulin 2 were observed in the cultures that contained DTZ-positive cellular clusters. Insulin secretion was also confirmed by ELISA, whereas glucose-dependent secretion was not demonstrated. CONCLUSION: Nkx2.2-transfected ES cells showed an ability to differentiate into insulin-producing cells. (C) 2005 The WJG Press and Elsevier Inc. All rights reserved.