The pancreatic islets are collections of endocrine cells, spread through the pancreas. In adult islets, endocrine cells are tightly related to capillary endothelial cells and get a high blood perfusion. Transplanted pancreatic islets, on the contrary, have a vascular disturbance, manifested as reduced blood vessel density. Apart from impaired islet blood perfusion and oxygenation, this means that the normal proximity between endothelial cells and ß-cell in adult islets is interrupted. The purpose of the dissertation was to examine if, and to what extent, ß-cells and islet endothelial cells can connect with each other. This hypothesis was looked into during physiological growth of pancreatic islets, following transplantation and in vitro. We noticed that islet endothelial and endocrine cell replication coincided soon after birth, and also in pregnancy….
Contents: Role of Islet Endothelial Cells in β-cell Function and Growth
Introduction
Islet anatomy
Cellular composition of pancreatic islets
ȕ-cell proliferation
Islet microvasculature
Islet vasculature and blood perfusion
Endothelial cells
Pericytes
Lymphatic vessels
Angiogenesis
Interactions between endothelial and endocrine cells in the pancreas
Early fetal development
Late fetal development
Interactions in adult tissues
Interactions after transplantation
Aims
Methods
Animals
Fetal and newborn rats (Paper I)
Pregnant rats (Paper II)
Chemical
In vivo protocols
H-Thymidine treatment (I-II)
Partial pancreatectomy (IV)
Islet isolation (II-IV)
Human islets (Paper IV)
Islet transplantation (III-IV)
Isolation of islet endothelial cells (II)
Oxygen tension measurements (III-IV)
Blood flow measurements (III-IV)
Measurements of blood parameters (III-IV)
Perfusion of graft bearing kidneys (IV)
Minimal islet mass model (III)
Histological protocols
Visualization of endothelial cells (I-IV)
Insulin staining (I-IV)
Cell proliferation
Thrombospondin-1 staining (II)
Double fluorescence staining for HGF and endothelium (II)
Morphological evaluations
Islet endothelial, ȕ-cell and endocrine cell proliferation (I-II, IV)
Islet mass and islet fraction (I-II)
Endocrine graft volume (III-IV)
Islet vascular density (I-IV)
Tsp-1 expression in endocrine cells (II)
Distance from endocrine cells to islet capillaries (I)
In vitro studies
In vitro stimulation with ovine PRL (II-III)
Islet-conditioned medium (II)
Endothelium-conditioned medium (II)
Islet incubation in conditioned medium (II)
Semi-quantitative real time RT- PCR (III)
Statistical analysis
Results and Discussion
Aim 1 – is physiological islet growth associated with endothelial cell replication?
Perinatal growth (I)
Growth during pregnancy (II)
Aim 2 – do native pancreatic islets become more pro-angiogenic when -cell growth is stimulated?
Aim 3 – can islet endothelial cells stimulate ȕ-cell growth and function
through paracrine interactions? (II)
Aim 4 – does ȕ-cell growth result in improved revascularization and function of transplanted pancreatic islets?
Endocrine graft volume (III-IV)
Islet revascularization (III-IV)….
Source: Uppsala University Library
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