Insulin expressing hepatocytes not destroyed in transgenic NOD mice

BACKGROUND: The liver has been suggested as a suitable target organ for gene therapy of Type 1 diabetes. However, the fundamental issue whether insulin-secreting hepatocytes in vivo will be destroyed by the autoimmune processes that kill pancreatic β cells has not been fully addressed. It is possible that the insulin secreting liver cells will be destroyed by the immune system because hepatocytes express major histocompatibility complex (MHC) class I molecules and exhibit constitutive Fas expression; moreover the liver has antigen presenting activity. Together with previous reports that proinsulin is a possible autoantigen in the development of Type 1 diabetes, the autoimmune destruction of insulin producing liver cells is a distinct possibility. METHODS: To address this question, transgenic Non-Obese Diabetic (NOD) mice which express insulin in the liver were made using the Phosphoenolpyruvate Carboxykinase (PEPCK) promoter to drive the mouse insulin I gene (Ins). RESULTS: The liver cells were found to possess preproinsulin mRNA, translate (pro)insulin in vivo and release it when exposed to 100 nmol/l glucagon in vitro. The amount of insulin produced was however significantly lower than that produced by the pancreas. The transgenic PEPCK-Ins NOD mice became diabetic at 20–25 weeks of age, with blood glucose levels of 24.1 ± 1.7 mmol/l. Haematoxylin and eosin staining of liver sections from these transgenic NOD PEPCK-Ins mice revealed the absence of an infiltrate of immune cells, a feature that characterised the pancreatic islets of these mice. CONCLUSIONS: These data show that hepatocytes induced to produce (pro)insulin in NOD mice are not destroyed by an ongoing autoimmune response; furthermore the expression of (pro)insulin in hepatocytes is insufficient to prevent development of diabetes in NOD mice. These results support the use of liver cells as a potential therapy for type 1 diabetes. However it is possible that a certain threshold level of (pro)insulin production might have to be reached to trigger the autoimmune response

Definitive endoderm derived from human embryonic stem cells highly express the integrin receptors αV and β5

Human embryonic stem cells (hESCs) can be directed to differentiate into a number of endoderm cell types, however mature functional cells have yet to be produced in vitro. This suggests that there may be important factors that have yet to be described, which may be essential for the proper derivation of these cells. One such factor is the integrin mediated interactions between a cell and the extracellular matrix (ECM). On this basis, the present study investigated the role of the ECM in the directed differentiation of hESCs to definitive endoderm via analysis of integrin gene expression. The results showed that definitive endoderm can be efficiently and effectively derived from hESCs in a feeder free, single defined ECM of laminin. Analysis of integrin expression also showed that definitive endoderm highly express the integrins αV and β5, which have the ability to bind to vitronectin, whilst expression of the pluripotency related laminin binding integrins α3, α6 and β4 were downregulated. This suggested a potential role of vitronectin binding integrins in the development of definitive endoderm. © 2010 Landes Bioscience

「アドミッションセンター」の多機能化―国立大学における位置づけと高大接続改革―

While working as an Admission Coordinator at Gunma University from June 2019, we became aware of the issue of the role and position of the Admission Center at various national universities. The purpose of this paper is to clarify the current role and position of the Admission Center, which was established at a national university in the 2000s. Under these circumstances, it was found that the government's recent High School/University Articulation Reforms have affected the operations of the Admission Center, and its role has been expanding

Noninvasive Tracking of Encapsulated Insulin Producing Cells Labelled with Magnetic Microspheres by Magnetic Resonance Imaging

Microencapsulated islets are usually injected free-floating into the peritoneal cavity, so the position of the grafts remains elusive after transplantation. This study aims to assess magnetic resonance imaging (MRI) as a noninvasive means to track microencapsulated insulin producing cells following transplantation. Encapsulated insulin producing cells (MIN6 and human islets) were labelled with magnetic microspheres (MM), assessed for viability and insulin secretion, and imaged in vitro using a clinical grade 3 T MRI and in vivo using both clinical grade 3 T and research grade 11.7 T MRI. Fluorescent imaging demonstrated the uptake of MM by both MIN6 and human islets with no changes in cell morphology and viability. MM labelling did not affect the glucose responsiveness of encapsulated MIN6 and islets in vitro. In vivo encapsulated MM-labelled MIN6 normalized sugar levels when transplanted into diabetic mice. In vitro MRI demonstrated that single microcapsules as well as clusters of encapsulated MM-labelled cells could be visualised clearly in agarose gel phantoms. In vivo encapsulated MM-labelled MIN6 could be visualised more clearly within the peritoneal cavity as discrete hypointensities using the high power 11.7 T but not the clinical grade 3 T MRI. This study demonstrates a method to noninvasively track encapsulated insulin producing cells by MM labelling and MRI

Islet Transplantation and Encapsulation: An Update on Recent Developments

Human islet transplantation can provide good glycemic control in diabetic recipients without exogenous insulin. However, a major factor limiting its application is the recipient's need to adhere to life-long immunosuppression, something that has serious side effects. Microencapsulating human islets is a strategy that should prevent rejection of the grafted tissue without the need for anti-rejection drugs. Despite promising studies in various animal models, the encapsulated human islets so far have not made an impact in the clinical setting. Many non-immunological and immunological factors such as biocompatibility, reduced immunoprotection, hypoxia, pericapsular fibrotic overgrowth, effects of the encapsulation process and post-transplant inflammation hamper the successful application of this promising technology. In this review, strategies are discussed to overcome the above-mentioned factors and to enhance the survival and function of encapsulated insulin-producing cells, whether in islets or surrogate β-cells. Studies at our center show that barium alginate microcapsules are biocompatible in rodents, but not in humans, raising concerns over the use of rodents to predict outcomes. Studies at our center also show that the encapsulation process had little or no effect on the cellular transcriptome of human islets and on their ability to function either in vitro or in vivo. New approaches incorporating further modifications to the microcapsule surface to prevent fibrotic overgrowth are vital, if encapsulated human islets or β-cell surrogates are to become a viable therapy option for type 1 diabetes in humans

Bioengineering approaches to islet transplantation for management of diabetes

Human islet transplantation, as currently carried out by portal vein infusion in the liver, can provide good glycaemic control in diabetic patients and can significantly reduce the need to inject exogenous insulin. Perhaps the main challenge in islet transplantation is the need for life long immunosuppression which is highly undesirable due to side effects resulting in poor quality of life. Unquestionably, there has been significant progress in clinical islet transplantation, but many challenges are yet to be overcome. This calls for novel approaches to make islet based therapies more practical, sustainable and economical. By preventing adverse immune reaction and creating an environment that would reduce death of the grafted cells islet transplantation strategies can be vastly improved. Here we discuss various bioengineering approaches that are currently in development to achieve desirable outcome in islet transplantation within a clinical setting

The Humanized NOD/SCID Mouse as a Preclinical Model to Study the Fate of Encapsulated Human Islets

Despite encouraging results in animal models, the transplantation of microencapsulated islets into humans has not yet reached the therapeutic level. Recent clinical trials using microencapsulated human islets in barium alginate showed the presence of dense fibrotic overgrowth around the microcapsules with no viable islets. The major reason for this is limited understanding of what occurs when encapsulated human islets are allografted. This warrants the need for a suitable small animal model. In this study, we investigated the usefulness of NOD/SCID mice reconstituted with human PBMCs (called humanized NOD/SCID mice) as a preclinical model. In this model, human T cell engraftment could be achieved, and CD45+ cells were observed in the spleen and peripheral blood. Though the engrafted T cells caused a small fibrotic overgrowth around the microencapsulated human islets, this failed to stop the encapsulated islets from functioning in the diabetic recipient mice. The ability of encapsulated islets to survive in this mouse model might partly be attributed to the presence of Th2 cytokines IL-4 and IL-10, which are known to induce graft tolerance. In conclusion, this study showed that the hu-NOD/SCID mouse is not a suitable preclinical model to study the allograft rejection mechanisms of encapsulated human islets. As another result, the maintained viability of transplanted islets on the NOD/SCID background emphasized a critical role of protective mechanisms in autoimmune diabetes transplanted subjects due to specific immunoregulatory effects provided by IL-4 and IL-10