Islet cell transplantation today.

INTRODUCTION: Long-term studies strongly suggest that tight control of blood glucose can prevent the development and retard the progression of chronic complications of type 1 diabetes mellitus. In contrast to conventional insulin treatment, replacement of a patient's islets of Langerhans either by pancreas organ transplantation or by isolated islet transplantation is the only treatment to achieve a constant normoglycemic state and avoiding hypoglycemic episodes, a typical adverse event of multiple daily insulin injections. However, the cost of this benefit is still the need for immunosuppressive treatment of the recipient with all its potential risks. MATERIALS AND METHODS: Islet cell transplantation offers the advantage of being performed as a minimally invasive procedure in which islets can be perfused percutaneously into the liver via the portal vein. Between January 1990 and December 2004, 458 pancreatic islet transplants worldwide have been reported to the International Islet Transplant Registry (ITR) at our Third Medical Department, University of Giessen/Germany. RESULTS: Data analysis of islet cell transplants performed in the last 5 years (1999-2004) shows at 1 year after adult islet transplantation a patient survival rate of 97%, a functioning islet graft in 82% of the cases, whereas insulin independence was meanwhile achieved in 43% of the cases. However, using a novel protocol established by the Edmonton Center/Canada, the insulin independence rates have improved significantly reaching meanwhile a 50-80% level. CONCLUSION: Finally, the concept of islet cell or stem cell transplantation is most attractive, as it offers many perspectives: islet cell availability could become unlimited and islet or stem cells my be transplanted without life-long immunosuppressive treatment of the recipient, just to mention two of them.

Characterization of somatostatin receptor subtype-specific regulation of insulin and glucagon secretion: an in vitro study on isolated human pancreatic islets.

INTRODUCTION: Pancreatic A- and B-cells express somatostatin receptors (SSTRs). Five pharmacologically distinct SSTR subtypes are known (SSTR1-SSTR5). In rodents, SSTR2 inhibits glucagon secretion, whereas SSTR5 suppresses the release of insulin. Human pancreatic A- and B-cells express SSTR1-3 and SSTR5; however, their contribution to the regulation of glucagon and insulin secretion is not well known. AIM OF THE STUDY: The goal of this study was to characterize the role of individual SSTR subtypes in regulating human glucagon and insulin secretion in vitro. METHODS: Human pancreatic islets were isolated from healthy donors and incubated with somatostatin, SSTR1-3-selective and SSTR5-selective agonists, or an SSTR2-selective antagonist (DC-41-33). Stimulation of insulin secretion was induced by glucose (10, 20 mm) alone or in combination with 10 nm exendin-4 or 10 mm L-arginine. Glucagon secretion was induced by 20 mm L-arginine. Basal secretion of insulin and glucagon was measured at 2.8 or 3.3 mm glucose. RESULTS: SSTR1-, SSTR2-, and SSTR5-selective agonists inhibited insulin secretion with the following order of potency: SSTR2 (EC50, 0.08 nm) > SSTR5 (EC50, 5.3 nm) > SSTR1 (EC50, 35 nm). Glucagon secretion was inhibited by SSTR-selective agonists with the following order of potency: SSTR2 (EC50, 0.05 nm) > SSTR1 (EC50, 1.8 nm) > SSTR5 (EC50, 28 nm). DC-41-33 dose-dependently reversed the effects of the SSTR2-selective agonist on insulin and glucagon secretion. CONCLUSION: Our study demonstrates that SSTR2-agonist is the most potent inhibitor of insulin and glucagon secretion from isolated human pancreatic islets. Furthermore, we identify SSTR1- and SSTR5-selective agonists as additional inhibitors of insulin and glucagon secretion from human pancreas.

Expression of transcription factor Oct-4 and other embryonic genes in CD133 positive cells from human umbilical cord blood.

A significant number of hematopoietic stem/progenitor cells (HSPC) in human umbilical cord blood could serve as a reservoir for the placental vasculature, yet, their morphological and functional features are not completely understood. Here, we describe the characterization of purified CD133(+) progenitor cells from umbilical cord blood, a subset of CD34(+) hematopoietic progenitors that were grown in proliferation medium containing Flt3-ligand, thrombopoietin and stem cell factor. Following isolation and enrichment of the CD133(+) cells by immunomagnetic cell sorting, they remained non-adherent for up to 40 days in culture and expressed different pluripotency markers including Sox-1, Sox-2, FGF-4, Rex-1 and Oct-4.Oct-4 expression was confirmed by laser-assisted single cell picking with subsequent quantitative real-time RT-PCR. The expression of Oct-4 indicates a pluripotent phenotype of CD133(+) cells and appears to be of functional relevance: After three weeks in endothelial differentiation medium, suspended cells became adherent, developed an endothelial cell-like morphology, bound fluoresceine isothiocyanate-labeled Ulex europaeus agglutinin-1, took up acetylated Di-LDL, and expressed other endothelial markers such as PECAM-1 or VEGFR-2. Concomitantly, Oct-4 expression was significantly reduced. Moreover, following treatment with retinoic acid, CD133(+) cells exhibited neural morphology associated with the expression of beta-III-tubulin. CD133(+) cells were found to express the luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor, detected by RT-PCR and immunocytochemistry. The recombinant human chorionic gonadotropin induced proliferation of the CD133(+) cells in a dose-specific manner. Our results indicate that CD133(+) HSPC from umbilical cord blood may have a greater differentiation potential than previously recognized and give rise to proliferative endothelial cells participating in placental vasculogenesis.

Successful single donor islet allotransplantation in the streptozotocin diabetes rat model.

The objective of this study was to define pretransplant islet culture conditions for optimum tissue engraftment in the rat islet allotransplantation model. Lewis rat islets were cultured in TCM 199/5% fetal calf serum for I day at 37 degrees C, followed by 1 day of culture at 22 degrees C. When islets from single donors were allotransplanted intraportally into single streptozotocin-diabetic Wistar-Furth rats, complete normoglycemia was restored within 1 day after transplantation in seven out of seven rats, and persisted up to immunological rejection about 1 week later. In five out of six rats receiving a posttransplant injection of antilymphocyte serum, plasma glucose was normalized for >100 days. These data demonstrate, for the first time, successful single-donor-to-single-recipient transplantation of allogeneic rat pancreatic islets. Because islet engraftment may still be regarded as a main problem for clinical islet transplantation, the pretransplant islet culture regimen outlined in this article may lead to a more efficient use of donor pancreatic islet tissue in the clinical setting, as well.