Altered microvasculature in pancreatic islets from subjects with type 1 diabetes

Abstract

Aims The transcriptome of different dissociated pancreatic islet cells has been described in enzymatically isolated islets in both health and disease. However, the isolation, culturing, and dissociation procedures likely affect the transcriptome profiles, distorting the biological conclusions. The aim of the current study was to characterize the cells of the islets of Langerhans from subjects with and without type 1 diabetes in a way that reflects the in vivo situation to the highest possible extent. Methods Islets were excised using laser capture microdissection directly from frozen pancreatic tissue sections obtained from organ donors with (n = 7) and without (n = 8) type 1 diabetes. Transcriptome analysis of excised samples was performed using AmpliSeq. Consecutive pancreatic sections were used to estimate the proportion of beta-, alpha-, and delta cells using immunofluorescence and to examine the presence of CD31 positive endothelial regions using immunohistochemistry. Results The proportion of beta cells in islets from subjects with type 1 diabetes was reduced to 0% according to both the histological and transcriptome data, and several alterations in the transcriptome were derived from the loss of beta cells. In total, 473 differentially expressed genes were found in the islets from subjects with type 1 diabetes. Functional enrichment analysis showed that several of the most upregulated gene sets were related to vasculature and angiogenesis, and histologically, vascular density was increased in subjects with type 1 diabetes. Downregulated in type 1 diabetes islets was the gene set epithelial mesenchymal transition. Conclusion A number of transcriptional alterations are present in islets from subjects with type 1 diabetes. In particular, several gene sets related to vasculature and angiogenesis are upregulated and there is an increased vascular density, suggesting an altered microvasculature in islets from subjects with type 1 diabetes. By studying pancreatic islets extracted directly from snap-frozen pancreatic tissue, this study reflects the in vivo situation to a high degree and gives important insights into islet pathophysiology in type 1 diabetes.

Pericyte dysfunction and impaired vasomotion are hallmarks of islets during the pathogenesis of type 1 diabetes

“…Vascular alterations were accompanied by metabolic changes indicated by significant upregulation of PDK4 and LDHA in endocrine alpha and beta cells in T1D pancreata. These data show that transcriptional alterations related to the vasculature are present in the pancreas of single Aab+ donors, similarly to what had been described for T1D (45).…”

Replenishable prevascularized cell encapsulation devices increase graft survival and function in the subcutaneous space

“…Our results confirm other studies reporting that implantation within the subcutaneous space does not allow for the survival of beta cells, which are typically highly vascularized in their native environment 5,19,40,48,49 . Low oxygen tension and lack of nutrient supply caused by insufficient vasculature often lead to ischemia and necrosis of the highly metabolic beta cells 2,4,24,25,39,50,51 .…”

“…We next asked whether prevascularization, with or without removal of the device, affects the survival of stem cell‐derived insulin‐producing beta cell clusters. These luciferase‐labeled cell clusters were generated using a previously established protocol 47,48 . For cell survival studies, two different stages of stem cell‐derived insulin‐producing beta cell clusters were used.…”

“…Given the viability data, we hypothesized that RPVIM devices would show greater glucose‐stimulated insulin secretion than SIM or SPVIM devices. Since the d20 cells are immature and do not respond significantly to glucose challenge, we conducted functional tests on d28 cells that more closely resemble mature beta‐cell‐like clusters and demonstrate glucose‐stimulate insulin secretion 47,48 . To assess the function of the encapsulated cells, after 28 days of implantation, we performed an intraperitoneal glucose tolerance test (IPGTT), in which mice were fasted overnight (“fasting”) and then challenged with a bolus intraperitoneal injection of 20 mM glucose (“fed”).…”

“…Immunofluorescence staining of von Willebrand Factor Our results confirm other studies reporting that implantation within the subcutaneous space does not allow for the survival of beta cells, which are typically highly vascularized in their native environment. 5,19,40,48,49 Low oxygen tension and lack of nutrient supply caused by insufficient vasculature often lead to ischemia and necrosis of the highly metabolic beta cells. 2,4,24,25,39,50,51 It has also been shown that beta cell function and insulin secretion are severely impacted by the dense vascular network through blood flowdependent and independent pathways.…”