Pancreatic endoderm derived from human embryonic stem cells generates glucose-responsive insulin-secreting cells in vivo

Development of a cell therapy for diabetes would be greatly aided by a renewable supply of human β-cells. Here we show that pancreatic endoderm derived from human embryonic stem (hES) cells efficiently generates glucose-responsive endocrine cells after implantation into mice. Upon glucose stimulation of the implanted mice, human insulin and C-peptide are detected in sera at levels similar to those of mice transplanted with ~3,000 human islets. Moreover, the insulin-expressing cells generated after engraftment exhibit many properties of functional β-cells, including expression of critical β-cell transcription factors, appropriate processing of proinsulin and the presence of mature endocrine secretory granules. Finally, in a test of therapeutic potential, we demonstrate that implantation of hES cell–derived pancreatic endoderm protects against streptozotocin-induced hyperglycemia. Together, these data provide definitive evidence that hES cells are competent to generate glucose-responsive, insulin-secreting cells. Development of a cellular therapy for the amelioration of diabetes requires a renewable source of human insulin–secreting cells that respond to glucose in a physiologic manner. Currently, cellular replacement is performed either by whole-pancreas transplant or by infusion of isolated primary islets into the portal vein 1 . These procedures, although effective, are not suitable for the general diabetes population, primarily because of the inadequate supply of organs and the necessity of chronic immunosuppression. One approach to overcoming the problem of insufficient supply is to generate islets from proliferative stem cell populations. Currently, the only stem cell population with sufficient proliferative capacity to achieve this goal is human embryonic stem (hES) cells, which proliferate in culture at a rate of >250 population doublings per year 2,3 . Of equal importance, hES cells are capable of efficiently and rapidly differentiating through a series of defined developmental transitions to generate cells of all somatic lineages. This competence has allowed us to produce definitive endoderm cells 4 , foregut, pancreatic and endocrine precursor cells 5 and ultimately insulin-secreting cells 5 . However, in previous studies, functional characterization of hES cells differentiated to endocrine populations showed insulin secretion in response to various secretagogues but not to glucose in vitro 5 or in vivo 6 . Fetal human pancreatic tissues at 14–20 weeks 7–9 or 6–9 weeks 10,11 of age have been shown to develop functionally after implantation in animals. At 6–9 weeks, only a few hormone-expressing endocrine cells, which do not respond to glucose, are present in the fetal human pancreatic anlagen. After implantation, these tissues differentiate