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Expression of immune modulating mediators in human Islets of Langerhans could have important implications for development of autoimmunity in type 1 diabetes and influence the outcome of clinical islet transplantation. Islets obtained from five donors were analyzed at various times after isolation using cDNA array technology. The Atlas Human Cytokine/Receptor and Hematology/ Immunology nylon membranes representing 268 genes and 406, respectively, were used and the relative expression of each gene analyzed. Of the 51 gene products identified, high mRNA expression of MCP-1, MIF, VEGF, and thymosin b-10 was detected in all islet samples. IL-8, IL-1-b, IL-5R, and INF-c antagonist were expressed in islets cultured for 2 days. IL-2R was expressed in islets cultured for more than 6 days. In conclusion, several inflammatory mediators were expressed in isolated islets, particularly at an early stage after isolation, indicating that a few days of culture could be beneficial for the outcome of islet transplantation.

OBJECTIVE-Mesenchymal stem cells (MSCs) contribute to endothelial cell (EC) migration by producing proteases, thereby paving the way into the tissues for ECs. MSCs were added to our previously described composite EC islets as a potential means to improve their capacity for islet angiogenesis.RESEARCH DESIGN AND METHODS-Human islets were coated with primary human bone marrow-derived MSCs and dermal microvascular ECs. The capacity of ECs, with or without MSCs, to adhere to and grow into human islets was analyzed. The survival and functionality of these composite islets were evaluated in a dynamic perifusion assay, and their capacity for angiogenesis in vitro was assessed in a three-dimensional fibrin gel assay.RESULTS-ECs proliferated after culture in MSC-conditioned medium, and MSCs improved the EC coverage threefold compared with EC islets alone. Islet survival in vitro and the functionality of the composite islets after culture were equal to those of control islets. The EC-MSC islets showed a twofold increase in total sprout formation compared with EC islets, and vascular sprouts emanating from the EC-MSC-islet surface showed migration of ECs into the islets and also into the surrounding matrix, either alone or in concert with MSCs. T he islets of Langerhans are micro-organs, with afferent and efferent blood vessels connecting the capillary network of the islets to the circulation system (1). Intra-islet endothelial cells (ECs) are fenestrated, and the density of the capillary network in the islets is ϳ10 times higher than that of the surrounding exocrine tissue (2,3). During the process of islet isolation before transplantation, the ECs in the islets lose their external vascular support; this situation contributes to their dedifferentiation, apoptosis, and necrosis during subsequent in vitro culture (4). CONCLUSIONS-ECThe formation of new capillaries during revascularization is a complex process that involves digestion of the vascular wall by proteases and the migration, proliferation, and differentiation of ECs (5). When blood vessels are assembled, ECs produce platelet-derived growth factor, which attracts supportive cells, including mesenchymal stem cells (MSCs) that can differentiate into pericytes (6).We hypothesized that adding MSCs to our previously described composite EC islets (7) might improve the adherence of the ECs to the islets and subsequent vascularization because MSCs contribute to EC migration by producing proteases, thereby paving the way into the surrounding tissue for the immature EC sprouts (8). MSCs have also been shown to upregulate the expression of angiopoietin and vascular endothelial growth factor (VEGF) in ECs, contributing to an increase in angiogenesis and stabilization of the vasculature (9). Moreover, MSCs have been shown to possess important immune-modulating properties (10), and they do not trigger adaptive immune reactions, which could make them ideal in islet transplantation setting (11,12).The present study describes a gentle and reproducible technique for forming EC-MSC i...

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