Identification of insulin-producing cells derived from embryonic stem cells by zinc-chelating dithizone

Embryonic stem (ES) cells have a pluripotent ability to differentiate into a variety of cell lineages in vitro. We have recently identified the emergence of cellular clusters within differentiated ES cell cultures by staining with dithizone (DTZ). DTZ is a zinc-chelating agent known to selectively stain pancreatic beta cells because of their high zinc content. The aim of the present study was to investigate the characteristics of DTZ-stained cellular clusters originating from ES cells.

Embryoid bodies (EBs), formed by a 5-day hanging drop culture of ES cells, were allowed to form outgrowths in the culture. The outgrowths were incubated in DTZ solution (final concentration, 100 microg/ml ) for 15 minutes before being examined microscopically. The gene expression of endocrine pancreatic markers was also analyzed by reverse transcriptase-polymerase chain reaction. In addition, insulin production was examined immunohistochemically, and its secretion was examined using enzyme-linked immunosorbent assay.

DTZ-stained cellular clusters appeared after approximately 16 days in the EB culture and became more apparent by day 23. They were found to be immunoreactive to insulin and expressed pancreatic-duodenal homeobox 1 (PDX1), proinsulin 1, proinsulin 2, glucagon, pancreatic polypeptide, glucose transporter-2 (GLUT2), and islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) mRNA. They were also able to secrete detectable amounts of insulin.

ES cell-derived DTZ-positive cellular clusters possess characteristics of the endocrine pancreas, including insulin secretion. Further, DTZ staining is a useful method for the identification of differentiated pancreatic islets developed from EBs in vitro.