Xeno-Transplantation of macro-encapsulated islets and Pluripotent Stem Cell-Derived Pancreatic Progenitors without Immunosuppression

Islet transplantation effectively treats diabetes but relies on immune suppression and is practically limited by the number of cadaveric islets available. An alternative cellular source is insulin-producing cells derived from pluripotent cell sources. Three animal cohorts were used in the current study to evaluate whether an oxygen-providing macro-encapsulation device, 'βAIR', could function in conjunction with human embryonic stem cells (hESCs) and their derivatives. The first cohort received macro-encapsulated undifferentiated hESCs, a second cohort received hESCs differentiated to a pancreatic progenitor state with limited endocrine differentiation. A reference cohort received human islets. Macro-encapsulation devices were implanted subcutaneously and monitored for up to 4 months. Undifferentiated pluripotent stem cells did not form teratoma but underwent cell death following implantation. Human C-peptide (hC- peptide) was detectable in host serum one week after implantation for both other cohorts. hC-peptide levels decreasing over time but remained detectable up to the end of the study. Key factors associated with mature endocrine cells were observed in grafts recovered from cohorts containing islets and hESC-derivatives including C-peptide, insulin, glucagon and urocortin 3. We conclude that the 'βAIR' macroencapsulation device is compatible with both human islets and pluripotent derivatives, but has a limited capability of sustaining undifferentiated pluripotent cells.

Use of glucagon-like peptide-1 agonists to improve islet graft performance

Human islet transplantation is an effective and promising therapy for type I diabetes. However, long-term insulin independence is both difficult to achieve and inconsistent. De novo or early administration of incretin-based drugs is being explored for improving islet engraftment. In addition to its glucose-dependent insulinotropic effects, incretins also lower postprandial glucose excursion by inhibiting glucagon secretion, delaying gastric emptying, and can protect beta-cell function. Incretin therapy has so far proven clinically safe and tolerable with little hypoglycemic risk. The present review aims to highlight the new frontiers in research involving incretins from both in vitro and in vivo animal studies in the field of islet transplant. It also provides an overview of the current clinical status of incretin usage in islet transplantation in the management of type I diabetes.

Induction of differentiation of embryonic stem cells into insulin-secreting cells by fetal soluble factors

Cell signals produced during pancreas embryogenesis regulate pancreatic differentiation. We show that the developing pancreas releases soluble factors responsible for in vitro endocrine pancreatic differentiation from embryonic stem cells (ESCs). A mouse D3 ESC line was transfected with a human insulin promoter/betageo/phosphoglycerate kinase-hygromycin-resistant construct. To direct differentiation, cells were cultured for 7 days to form embryoid bodies and then plated for an additional 7 days. During this 14-day period, besides eliminating leukemia inhibitory factor, cells were cultured in low serum concentration with the addition of conditioned media from embryonic day-16.5 pancreatic buds. Islet cell differentiation was studied by the following: (a) X-gal staining after neomycin selection, (b) BrdU (bro-modeoxyuridine) studies, (c) simple and double immunohistochemistry for insulin, C-peptide, and glucose transporter 2 (Glut-2), (d) reverse transcription-polymerase chain reaction for insulin and pancreas duodenum homeobox 1 (PDX-1), (e) insulin and C-peptide content and secretion assays, (f) intraperitoneal glucose tolerance test, (g) electrophysiology (patch-clamp studies in inside-out configuration), and (h) transplantation of differentiated cells under the kidney capsule of streptozotocin-diabetic mice. The differentiated ESCs showed the following: changes in the mRNA levels of insulin and PDX-1; coexpression of insulin, C-peptide, and Glut-2; glucose and tolbutamide-dependent insulin and C-peptide release; K-channel activity regulated by ATP; and normalization of blood glucose levels after transplantation into diabetic mice and hyperglycemia after graft removal. In this study, we establish a battery of techniques that could be used together to properly characterize islet cell differentiation. Moreover, identification of factors released by the developing pancreas may be instrumental in engineering beta cells from stem cells.

Nicotinamide induces both proliferation and differentiation of embryonic stem cells into insulin-producing cells

In contrast to the consistent observation that methods that promote proliferation also dedifferentiate insulin-producing cells, useful in vitro differentiation protocols must drive both proliferation and differentiation. We herein describe an strategy in which the combination of nutrient restriction and nicotinamide supplementation results in a consistent increase in the mass of insulin-producing cells.