Endodermal cells differentiate to form the gastrointestinal tract, the endocrine glands and organs (liver, pancreas, and gallbladder), and the respiratory tract. The pancreas develops following budding from the embryonic endoderm. Specifically, the pancreas develops from multipotent populations of endoderm cells in the paired lateral domains (ventral pancreas) and a medial dorsal domain (dorsal pancreas). In human embryos pancreatic cells are believed to respond to glucose and secrete insulin after 14-20 weeks of age. Development of the pancreas is thought to be dependent on interactions with the notochord, formed from the mesoderm. Earliest markers of endormermal cells differentiating in a pancreatic direction include the expression of the pancreatic and duodenal homeobox gene 1 (PDX-1/IPF-1).
Current research is attempting to elucidate the signaling pathways that govern the differentiation of definitive endoderm cells into pancreatic progenitors. Advances in this research topic are important for developing cell-based therapies for diabetes, which are centered on the implantation of a renewable supply of insulin-secreting pancreatic beta cells.