Facilitated Engraftment of Isolated Islets Coated With Expanded Vascular Endothelial Cells for Islet Transplantation.

BACKGROUND: Diabetes is complex disease, which involves primary metabolic changes followed by immunological and vascular pathophysiological adjustments. However, it is mostly characterized by an unbalanced decreased number of the ß-cells unable to maintain the metabolic requirements and failure to further regenerate newly functional pancreatic islets. The objective of this study was to analyze the properties of the endothelial cells to facilitate the islet cells engraftment after islet transplantation. METHODS: We devised a co-cultured engineer system to coat isolated islets with vascular endothelial cells. To assess the cell integration of cell-engineered islets, we stained them for endothelial marker CD31 and nuclei counterstained with DAPI dye. We comparatively performed islet transplantations into streptozotocin-induced diabetic mice and recovered the islet grafts for morphometric analyses on days 3, 7, 10, and 30. Blood glucose levels were measured continuously after islet transplantation to monitor the functional engraftment and capacity to achieve metabolic control. RESULTS: Cell-engineered islets showed a well-defined rounded shape after co-culture when compared with native isolated islets. Furthermore, the number of CD31-positive cells layered on the islet surface showed a direct proportion with engraftment capacities and less TUNEL-positive cells on days 3 and 7 after transplantation. CONCLUSIONS: We observed that vascular endothelial cells could be functional integrated into isolated islets. We also found that islets that are coated with vascular endothelial cells increased their capacity to engraft. These findings indicate that islets coated with endothelial cells have a greater capacity of engraftment and thus establish a definitely vascular network to support the metabolic requirements.

Endothelial cells promote pancreatic stem cell activation during islet regeneration in mice.

OBJECTIVES: Diabetes is the clinical consequence of the loss of the majority of the ß-cell population and failure to regenerate new pancreatic ß cells. The current therapies based on ß-cell replacement have failed to achieve ß-cell renewal and thus, long-term insulin freedom. We have hypothesized that early rejection of endothelial elements within the islet grafts may seriously hamper islet regeneration in both native and islet grafts. METHODS: In the present study, we analyzed the role of endothelial cells to activate pancreatic stem cells during islet regeneration. Mice were pretreated with or without endothelial pharmacological ablation of endothelial cells, followed by an acute ß-cell injury using a single intraperitoneal injection of streptozotocin. We performed comparative morphometric analyses of recovered pancreata on days 3, 7, 10, and 30 after streptozotocin injury, staining with bromodeoxyuridine (BrdU) for representative cell types, ß cells, endothelial elements, and stem cells. Blood glucose levels were measured continuously after the injury to monitor the capacity for metabolic control. RESULTS: Morphometric analyses revealed an increasing number of cells over time to be stained with a stem cell and BrdU markers among animals only injured with streptozotocin but not with endothelial ablation. Notably, on day 10, stem cell markers were dramatically decrease nearly to basal levels, with appearance of numerous insulin-positive cells. Intact vessels with cobblestone-shaped endothelial elements were observed in direct proportion to the better outcomes, both by morphometric and by metabolic parameters. In contrast, fewer insulin-positive cells were observed in pancreata that had been ablated of endothelial cells showing extensive collapse of endocrine functions. CONCLUSIONS: We observed that endothelial elements promoted stem cell proliferation and islet regeneration after a ß-cell insult. We believe that preservation of endothelial cells positively affects the process of pancreatic regeneration.