Intramuscular islet transplantation promotes restored islet vascularity

In a recent publication, we reported that islets transplanted to mouse striated muscle became revascularized with intra-islet vessel densities comparable to native islets. Revascularization of islet grafts was completely dependent on recruited Gr-1+ leukocytes. Diabetic mice cured by transplantation of 300 islets into muscle handled glucose tolerance tests as healthy controls, whereas mice cured by intraportal islet transplantation into the liver had increased blood glucose values during the load. The translational impact of these observations were confirmed by magnetic resonance imaging of autotransplanted islets in the forearm muscle of pancreactomized patients, and higher blood perfusion of the grafts compared to adjacent muscle were found. In summary, the striated muscle is a promising site for islet transplantation which promotes full revascularization of implanted grafts. The proangiogenic role of recruited leukocytes during engraftment needs to be further characterized, and considered for immune suppression treatments.     

Intramuscular islet transplantation promotes restored islet vascularity

In a recent publication, we reported that islets transplanted to mouse striated muscle became revascularized with intra-islet vessel densities comparable to native islets. Revascularization of islet grafts was completely dependent on recruited Gr-1+ leukocytes. Diabetic mice cured by transplantation of 300 islets into muscle handled glucose tolerance tests as healthy controls, whereas mice cured by intraportal islet transplantation into the liver had increased blood glucose values during the load. The translational impact of these observations were confirmed by magnetic resonance imaging of autotransplanted islets in the forearm muscle of pancreactomized patients, and higher blood perfusion of the grafts compared to adjacent muscle were found. In summary, the striated muscle is a promising site for islet transplantation which promotes full revascularization of implanted grafts. The proangiogenic role of recruited leukocytes during engraftment needs to be further characterized, and considered for immune suppression treatments.     

Assessment of islet function following islet and pancreas transplantation

Pancreas and islet transplant recipients are monitored using various metabolic and imaging methods. The inaccessibility of the transplanted whole pancreas and of the isolated islets poses specific problems (eg, all assessment techniques are indirect). Although successful pancreas transplantation typically restores normal glucose homeostasis, islet transplantation into the liver does not completely normalize islet hormone secretion and glucose metabolism. Development of better testing strategies, such as direct islet imaging, will significantly advance the field.     

Pancreatic islet plasticity: Interspecies comparison of islet architecture and composition

The pancreatic islet displays diverse patterns of endocrine cell arrangement. The prototypic islet, with insulin-secreting β-cells forming the core surrounded by other endocrine cells in the periphery, is largely based on studies of normal rodent islets. Recent reports on large animals including humans show a difference in islet architecture, in which the endocrine cells are randomly distributed throughout the islet. This particular species difference has raised concerns regarding the interpretation of data based on rodent studies to humans. On the other hand, further variations have been reported in marsupials and some nonhuman primates, which possess an inverted ratio of β-cells to other endocrine cells. This review discusses the striking plasticity of islet architecture and cellular composition among various species including changes in response to metabolic states within a single species. We propose that this plasticity reflects evolutionary acquired adaptation induced by altered physiological conditions, rather than inherent disparities between species.     

Optimising islet engraftment is critical for successful clinical islet transplantation

Clinical islet transplantation is currently being explored as a treatment for persons with type 1 diabetes and hypoglycaemia unawareness. Although ‘proof-of-principle’ has been established in recent clinical studies, the procedure suffers from low efficacy. At the time of transplantation, the isolated islets are allowed to embolise the liver after injection in the portal vein, a procedure that is unique in the area of transplantation. A novel view on the engraftment of intraportally transplanted islets is presented that could explain the low efficacy of the procedure.     

糖尿病胰岛纤维化分子机制研究进展

大量病理研究发现,在1型和2型糖尿病患者及各种动物模型中,均可观察到胰岛纤维化现象.胰岛纤维化过程进一步破坏了胰岛的正常组织结构并导致胰岛功能恶化、β细胞数量减少、胰岛素分泌量降低.     

History of islet transplantation

Patients with a diagnosis of type 1 diabetes mellitus endure stringent life-long medical therapy through the use of insulin to prevent end organ complications and maintain normoglycemia. However, some patients still suffer from hypoglycemic unawareness, even under intensive therapy. Within the past decade, noble efforts have been attempted to provide normoglycemia through cadaveric islet of Langerhans transplantation in order to reach a physiologic response. This effort, which has evolved for more than a century, actually predates the discovery of insulin.     

Clinical islet transplantation

Type 1 diabetes affects over 1 million persons in the United States, with over 30,000 new cases diagnosed annually. Transplantation of new insulin-producing β cells, in the form of the whole pancreas or isolated islets, has been shown to ameliorate the disease by eliminating the need for exogenous insulin and normalizing glycosylated hemoglobin levels. Islet transplants are a particularly attractive form of therapy because they are a minimally invasive procedure and are more likely to be scaled-up to treat the large numbers of people affected by diabetes. Currently, only a handful of programs have been successful in the endeavor. Nevertheless, the early clinical experience strongly demonstrates that islet transplantation is an effective treatment strategy in select patients with type 1 diabetes. To scale up this therapy and use it earlier in the disease and for more people, the shortage of suitable donor tissue must be solved and the requirement of lifelong immunosuppression must be minimized.     

Clinical islet transplantation

Achieving stable metabolic control in patients with type 1 diabetes mellitus (T1DM) is highly desirable and may contribute to delaying and/or preventing the development of secondary complications. Transplantation of pancreatic islets represents a viable option for the treatment of patients with unstable T1DM with frequent severe hypoglycemia and hypoglycemia unawareness. The benefits of the transplant include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. The success of future clinical trials will depend on the implementation of an integrated therapeutic approach combining strategies to maximize islet availability and engraftment with those aiming at safely modulating the recipients' immunity to afford long-term function. The steady progress of recent years in islet cell processing and patient management after transplantation justify great optimism for the years to come.     

胰岛淀粉样纤维对体外胰岛细胞膜的毒性作用

目的探讨胰岛淀粉样多肽（IAPP,也称胰淀素Amylin）的纤维状态胰岛淀粉样纤维（IAf）对胰岛细胞膜的毒性作用及可能机制。方法比较用可溶性IAPP和IAf孵化培养的胰岛细胞膜流动性的变化,并在黏附细胞仪570记录各组[Ca^2＋]i的动态变化;以10μmol/LIAf组为对照组,分别比较Ca^2＋通道阻断剂组、无Ca^2＋培养液组、胆固醇干预组[Ca^2＋]i的动态变化,了解[Ca^2＋]i变化与钙离子通道的关系。结果细胞膜流动性和[Ca^2＋]i在IAf组中呈剂量依赖性升高,与可溶性IAPP组及空白对照组比较差异有统计学意义（P〈0.01）;而可溶性IAPP组与空白对照组间差异无统计学意义（P〉0.05）。Ca^2＋通道阻断剂预处理组加10μmol/LIAf刺激后[Ca^2＋]i变化与对照组相比差异无统计学意义（P〉0.05）,而无Ca^2＋培养液组和胆固醇预处理组加10μmol/LIAf刺激后[Ca^2＋]i变化均明显低于对照组（P〈0.01）。结论IAf可能通过改变胰岛细胞膜流动性和细胞内钙超载而导致细胞损伤,钙超载是由于外钙内流所致,其途径可能并非经过钙离子通道,可能与“淀粉样通道”形成有关。胆固醇具有拮抗此毒性的作用。     

FGF-21 enhances islet engraftment in mouse syngeneic islet transplantation model

To clarify the effect of fibroblast growth factor-21 (FGF-21) on islet transplantation, a suboptimal number of islets were transplanted into streptozotocin (STZ)-induced diabetic mice with or without FGF-21 treatment. Three-day treatment with FGF-21 contributed to restoration of normoglycemia by suppressing islet graft loss. The FGF-21-treated mice showed lower glycemic levels despite similar insulin content in the graft than that in untreated mice on day 3, indicating that FGF-21 not only has a cytoprotective effect but also decreases β-cell load by increasing insulin sensitivity. These results suggest that FGF-21 may be useful as a treatment to improve islet engraftment rates in clinical islet transplantation.     

Unaltered pancreatic islet blood perfusion in islet amyloid polypeptide-deficient mice.

OBJECTIVE: Several biological activities have been ascribed to islet amyloid polypeptide (IAPP). However, their physiological relevance remains unclear. Previous studies in rats with exogenous administration of IAPP suggest that the peptide may increase splanchnic vascular resistance and redistribute the blood flow within the pancreas to the islets. In this study, the use of IAPP-deficient mice allowed us to evaluate possible effects of the lack of IAPP on splanchnic blood perfusion and we could thereby circumvent the potentially pharmacological actions of exogenously administered IAPP. DESIGN: Regional splanchnic blood flow was measured after exogenous administration of IAPP and in IAPP-deficient mice. METHODS: Blood flow values were determined using a non-radioactive microsphere technique in anesthetized animals. RESULTS: No differences in whole pancreatic blood flow or islet blood flow could be detected in IAPP-deficient mice when compared with control mice; neither did IAPP deficiency affect the glucose-induced increase in islet blood flow. Duodenal, ileal and colonic blood flows were similar in IAPP-deficient and control mice. Exogenous administration of IAPP selectively increased islet blood flow in wild-type control mice. CONCLUSIONS: The present findings in the IAPP-deficient mice suggest that the vascular effects seen in the islets after exogenous administration of IAPP to normal mice reflect pharmacological, rather than physiological effects of the peptide. We conclude that the lack of endogenous IAPP within the splanchnic vascular system does not alter the blood perfusion of pancreatic islets or other splanchnic organs.     

FGF-21 enhances islet engraftment in mouse syngeneic islet transplantation model

To clarify the effect of fibroblast growth factor-21 (FGF-21) on islet transplantation, a suboptimal number of islets were transplanted into streptozotocin (STZ)-induced diabetic mice with or without FGF-21 treatment. Three-day treatment with FGF-21 contributed to restoration of normoglycemia by suppressing islet graft loss. The FGF-21-treated mice showed lower glycemic levels despite similar insulin content in the graft than that in untreated mice on day 3, indicating that FGF-21 not only has a cytoprotective effect but also decreases β-cell load by increasing insulin sensitivity. These results suggest that FGF-21 may be useful as a treatment to improve islet engraftment rates in clinical islet transplantation.     

Subcellular localization and preliminary characterization of islet hormone-degrading activities in anglerfish islet tissue

The degradation of [125I]iodoinsulin in anglerfish islet tissue was studied in a trichloroacetic acid solubilization assay system. The pH optima for insulin breakdown by acidic and neutral enzymes were determined in fish islets and compared with mammalian tissues (rat liver, pancreas, and islets of Langerhans). Two major insulinolytic activities of anglerfish islet tissue were partially characterized: 1) An acidic (pH 3.5) activity showing marked sensitivity to pepstatin, some sensitivity to antipain, leupeptin, phenylmethanesulfonyl fluoride (PMSF), and thiol proteinase inhibitors, but no inhibition by EDTA; and 2) a neutral (pH 7.3) activity showing marked sensitivity to thiol proteinase inhibitors, sensitivity to antipain and leupeptin, but no sensitivity to PMSF, EDTA, or pepstatin. Glucagonolytic activities were also observed at the same acidic and neutral pH optima. Following cell fractionation of anglerfish islet homogenates, acidic (pH 3.5) insulinolytic activities were distributed with the lysosome-rich, microsome, and cytosol fractions, whereas neutral (pH 7.3) activities were found chiefly in cytosol and microsomes. Little or no insulinolysis was observed in secretory granule fractions. The data suggest that insulin is degraded in islet tissue by at least two enzyme systems. Lysosomal insulinolysis was due principally to cathepsin D-like activity. Neutral insulinolysis, partially characterized in the cytosol fraction, was due to thiol proteinase activity. The activity profile indicates that islet tissue resembles other insulin-responsive tissues in its subcellular distribution of insulin-degrading activities. The cellular heterogeneity of islet tissue, and the presence of high concentrations of endogenous islet hormones require further efforts at purification before insulinolytic enzymes are fully characterized in this tissue.     

Analysis of islet cell antibodies reactivity to a human islet cell line.

A human pancreatic beta cell line (HP62) was tested for reactivity with islet cell antibodies (ICA) as compared with previously-established methods. Using indirect immunofluorescence test, we found that HP62 cell line failed to react in a specific way with ICA from type 1 (insulin-dependent) diabetic patients since sera from normal controls showed a reactivity similar to that found in the patients. So, the usefulness of this human beta cell line as a tool of immunological purpose is questioned when indirect immunofluorescence procedures are used.     

Enterovirus infection in human pancreatic islet cells,islet tropism in vivo and receptor involvement in cultured islet beta cells

Aims/hypothesis It is thought that enterovirus infections cause beta-cell damage and contribute to the development of Type 1 diabetes by replicating in the pancreatic islets. We sought evidence for this through autopsy studies and by investigating known enterovirus receptors in cultured human islets.Methods Autopsy pancreases from 12 newborn infants who died of fulminant coxsackievirus infections and from 65 Type 1 diabetic patients were studied for presence of enteroviral ribonucleic acid by in situ hybridisation. Forty non-diabetic control pancreases were included in the study. The expression and role of receptor candidates in cultured human islets were investigated with receptor-specific antibodies using immunocytochemistry and functional assays.Results Enterovirus-positive islet cells were found in some of both autopsy specimen collections, but not in control pancreases. No infected cells were seen in exocrine tissue. The cell surface molecules, poliovirus receptor and integrin v₃, which act as enterovirus receptors in established cell lines, were expressed in beta cells. Antibodies to poliovirus receptor, human coxsackievirus and adenovirus receptor and integrin v₃ protected islets and beta cells from adverse effects of poliovirus, coxsackie B viruses, and several of the arginine-glycine-aspartic acid motifs containing enteroviruses and human parechovirus 1 respectively. No evidence was found for expression of the decay-accelerating factor which acts as a receptor for several islet-cell-replicating echoviruses in established cell lines.Conclusions/interpretation The results show a definite islet-cell tropism of enteroviruses in the human pancreas. Some enteroviruses seem to use previously identified cell surface molecules as receptors in beta cells, whereas the identity of receptors used by other enteroviruses remains unknown.Abbreviations A-549 Human lung carcinoma cell line - CAV coxsackie A virus - CBV coxsackie B virus - DAF decay-accelerating factor - EV echovirus - HBSS Hanks balanced salt solution - FITC fluorescein isothiocyanate - GMK a green monkey kidney cell line - HCAR human coxsackievirus and adenovirus receptor - HPEV-1 human parechovirus 1 - PV-1 poliovirus type 1 - PVR poliovirus receptor - RGD arginine-glycine-aspartic acid - RNA ribonucleic acid P. Ylipaasto and K. Klingel contributed equally to the study