Type 1 Diabetes (T1D) is an autoimmune disease characterized by the destruction of insulin-producing beta cells in the pancreas. Amelioration of T1D and the prevention of its detrimental complications are possible through islet transplantation, wherein hormone-producing clusters of cells, islets of Langerhans (islets), are separated from the pancreas and transplanted into a diabetic patient. However, alterations due to the effects of organ recovery, cold ischemia time (CIT), and islet isolation may increase the inflammatory and immunogenic properties of these islets, thereby predisposing them to functional impairment and rejection in a transplant. Understanding the inflammatory properties of islets will allow for the development of strategies that decrease early islet loss and effectively enhance engraftment and long-term function. Therefore, the aims of this study were to 1) identify and characterize populations of antigen presenting cells (APC) and other immune cells in nonhuman primate (NHP) islets in situ and after isolation; and 2) characterize the expression and functional role of CD40 and the IFN alpha receptor in NHP islets, including their effects on islet immunogenicity. A surprising result of these studies was that half of the APC present in isolated NHP islets were B lymphocytes. We observed that the number of islet-resident immune cells increased with islet size, and described the localization pattern of these cells within islets. We characterized CD40 expression in NHP islets, demonstrating that multiple CD40 isoforms are expressed, and made the novel finding that functional CD40 is expressed on the somatostatin-producing δ cells. When CD40 was stimulated with its ligand, it induced downstream signaling changes, increased proinflammatory cytokine release, and increased islet immunogenicity. Based on our results, we have hypothesized a model of CD40 signaling in islet δ cells. Microarray analysis revealed expression changes in many inflammatory molecules integral to inflammation, the immune response, and apoptosis in islets that had endured increased CIT, demonstrating the unfavorable conditions created within islets following organ recovery, CIT, and islet isolation. Furthermore, we demonstrated that the IFN alpha receptor is present on isolated NHP islets, and that stimulation with IFN alpha leads to increased proinflammatory cytokine release, surface receptor upregulation, and a decrease in immunogenicity. In summary, in NHP islets we have defined the type and quantity of immune cells, the inflammatory molecules expressed, including CD40 and the IFN alpha receptor, and their downstream functional roles in an immune response.

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京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第22884号 / 医博第4678号 / 新制||医||1048(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 長船 健二, 教授 羽賀 博典, 教授 椛島 健治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21342号 / 医博第4400号 / 新制||医||1031(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 長船 健二, 教授 羽賀 博典, 教授 妹尾 浩 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13610号 / 論医博第2320号 / 新制||医||1073(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 川口 義弥, 教授 伊達 洋至, 教授 長船 健二 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Diabetes is a major health problem worldwide, and there is substantial interest in developing xenogeneic islet transplantation as a potential treatment. The potential to relieve the demand on an inadequate supply of human pancreata is dependent upon the efficiency of techniques for isolating and culturing islets from the source pancreata. Porcine islets are favored for xenotransplantation, but mature pigs (>2 years) present logistic and economic challenges, and young pigs (3-6 months) have not yet proven to be an adequate source. In this study, islets were isolated from 20 juvenile porcine pancreata (similar to 3 months; 25 kg Yorkshire pigs) immediately following procurement or after 24 h of hypothermic machine perfusion (HMP) preservation. The resulting islet preparations were characterized using a battery of tests during culture in silicone rubber membrane flasks. Islet biology assessment included oxygen consumption, insulin secretion, histopathology, and in vivo function. Islet yields were highest from HMP-preserved pancreata (2,242 +/- 449 IEQ/g). All preparations comprised a high proportion (>90%) of small islets (<100 mu m), and purity was on average 63 +/- 6%. Morphologically, islets appeared as clusters on day 0, loosely disaggregated structures at day 1, and transitioned to aggregated structures comprising both exocrine and endocrine cells by day 6. Histopathology confirmed both insulin and glucagon staining in cultures and grafts excised after transplantation in mice. Nuclear staining (Ki-67) confirmed mitotic activity consistent with the observed plasticity of these structures. Metabolic integrity was demonstrated by oxygen consumption rates=175 +/- 16 nmol/min/mg DNA, and physiological function was intact by glucose stimulation after 6-8 days in culture. In vivo function was confirmed with blood glucose control achieved in nearly 50% (8/17) of transplants. Preparation and culture of juvenile porcine islets as a source for islet transplantation require specialized conditions. These immature islets undergo plasticity in culture and form fully functional multicellular structures. Further development of this method for culturing immature porcine islets is expected to generate small pancreatic tissue-derived organoids termed "pancreatites," as a therapeutic product from juvenile pigs for xenotransplantation and diabetes research.

Diabetes is a debilitating disease affecting millions of people worldwide. The transplantation of insulin-producing, pancreatic islet cells has been an extensively explored approach for the treatment of Type 1 Diabetes. However, the need for a multi-donor source, the strong host immune responses, and a life-long immunosuppressive therapy regimen limits the widespread applicability of islet transplantation. Encapsulation of islet cells within a semi-permeable biomaterial as a means to mask transplanted cells from the host has been shown to be a viable option for the protection of islets upon transplantation. Recent advancements, incorporating additional knowledge of biomaterials, have revitalized the field of islet encapsulation. This thesis work focused on both micro- and nano-scale encapsulation techniques. Initially, a novel, covalently linked alginate-poly(ethylene glycol) (PEG), termed XAlginate-PEG, microcapsule was evaluated, and was shown to exhibit superior stability over traditional ionically bound alginate microcapsules. The XAlginate-PEG capsules exhibited a 5-fold decrease in osmotic swelling than traditional alginate microcapsules, and remained completely intact upon chelation of ionic interactions. In addition, in vitro study of the novel polymer matrix showed high compatibility with mouse insulinoma cell lines, rat and human islets. Furthermore, no disruption in islet function was observed upon encapsulation. The second study of this thesis work focused on the nano-scale encapsulation of islets with a single layer PEG coating. A PEG polymer was grafted directly on the collagen matrix of the islet capsule to form a stable amide bond. PEGylation of the islet cells was shown to camouflage inflammatory agents, such as tissue factor (TF), present on the surface of the islet, while maintaining islet morphology and function. In summary, PEG dampened coagulation cascade activation, and concealed activated factor X (afX) generation under pro-inflammatory culture conditions. The present findings contribute to the field of cellular encapsulation, both in the fabrication of novel encapsulation techniques and the evaluation of nano-scale coatings. The future potential of this research includes the attenuation of immune responses to transplanted cells, elimination of continuous immunosuppression, and provide flexibility in cell source. Furthermore, the platforms evaluated in this thesis are generalized for all cell types, thereby permitting translation of techniques to alternative cellular therapies.

Transplantation of insulin producing cells is currently the only cure for type 1 diabetes. However, even though the Edmonton protocol markedly increased the success rate of pancreatic islet transplantation, the long term insulin independence is still very poor. An adequate engraftment is critical for islet graft survival and function. In the present thesis, isolated islet endothelial cells were found to have a low proliferatory and migratory capacity towards vascular endothelial growth factor (VEGF), but this could be reversed by using neutralizing antibodies to the angiostatic factors thrombospondin-1, endostatin or alpha1-antitrypsin. In the adult islet endothelial cell, VEGF may act as a permeability inducer more than an inducer of angiogenesis. p38 MAP kinase activity has been shown to serve as a switch between these properties of VEGF. Inhibition of p38 MAP kinase by daily injections of SB203580 in the early posttransplantation phase lead to a redistribution of the islet graft blood vessels from the stroma into the endocrine tissue and this was accompanied by a higher oxygen tension. Besides transports of oxygen and nutrients, beta-cells may require signals from the endothelial cells for their growth and differentiation. It was demonstrated that islet endothelial cells secrete factors, including laminin, that have positive effects on beta-cell insulin release and insulin content. Our results suggest that improved revascularization of transplanted islets may be achieved by either inhibition of angiostatic factors, or by blocking p38 MAPkinase activity, in the implanted tissue. Islet endothelial cells have a supportive paracrine role for beta-cells that might be hampered by the normally poor revascularization.

Successful survival of large volume engineered tissues depends on the development of a vasculature to support the metabolic demands of donor tissue in vivo. Pancreatic islet transplantation is a cell therapy procedure to treat Type 1 diabetes that can potentially benefit from such a vascularization strategy. The treatment is limited as the majority of transplanted islets (60%) fail to engraft due to insufficient revascularization in the host(1, 2). Modular tissue engineering is a means of designing large volume functional tissues using micron sized tissues with an intrinsic vascularization. In this thesis, we explored the potential of endothelialized modules to drive vascularization in vivo and promote islet engraftment. Human endothelial cells (EC) covered modules were transplanted in the omental pouch of athymic rats and human EC formed vessels near implanted modules until 7 days when host macrophages were depleted. Rat endothelial cells covered modules were similarly transplanted in the omental pouch of allogeneic rats with and without immunosuppressants. When the drugs were administered, endothelialized modules significantly increased the vessel density. Moreover, donor GFP labelled EC formed vessels that integrated with the host vasculature and were perfusable until 60 days; this key result demonstrate for the first time that unmodified primary endothelial cells form stable vessels in an allograft model. Transplantation of islets in such endothelialized modules significantly improved the vessel density around transplanted islets. Donor endothelial cells formed vessels near transplanted islets in allogeneic immunesuppressed recipients. Meanwhile, there was an increase in islet viability with transplantation of endothelialized modules in syngeneic recipients but this difference was not significant. In summary, endothelialized modules were effective in promoting stable vascularization and improving transplanted islet vascularisation. Future work should promote faster maturity of donor vessels and modulate the host immune and inflammatory responses to significantly improve transplanted islet engraftment.