| 1. |
- Barbu, Andreea, et al.
(author)
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The use of hydrogen gas clearance for blood flow measurements in single endogenous and transplanted pancreatic islets
- 2015
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In: Microvascular Research. - : Elsevier BV. - 0026-2862 .- 1095-9319. ; 97, s. 124-129
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Journal article (peer-reviewed)abstract
- The blood perfusion of pancreatic islets is regulated independently from that of the exocrine pancreas, and is of importance for multiple aspects of normal islet function, and probably also during impaired glucose tolerance. Single islet blood flow has been difficult to evaluate due to technical limitations. We therefore adapted a hydrogen gas washout technique using microelectrodes to allow such measurements. Platinum micro-electrodes monitored hydrogen gas clearance from individual endogenous and transplanted islets in the pancreas of male Lewis rats and in human and mouse islets implanted under the renal capsule of male athymic mice. Both in the rat endogenous pancreatic islets as well as in the intra-pancreatically transplanted islets, the vascular conductance and blood flow values displayed a highly heterogeneous distribution, varying by factors 6-10 within the same pancreas. The blood flow of human and mouse islet grafts transplanted in athymic mice was approximately 30% lower than that in the surrounding renal parenchyma. The present technique provides unique opportunities to study the islet vascular dysfunction seen after transplantation, but also allows for investigating the effects of genetic and environmental perturbations on islet blood flow at the single islet level in vivo. (C) 2014 The Authors. Published by Elsevier Inc.
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| 2. |
- Biglarnia, Alireza, et al.
(author)
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The free radical scavenger S-PBN significantly prolongs DSG-mediated graft survival in experimental xenotransplantation
- 2012
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In: Xenotransplantation. - : Wiley. - 0908-665X .- 1399-3089. ; 19:3, s. 166-176
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Journal article (peer-reviewed)abstract
- Background: Nitrones such as 2-sulfo-phenyl-N-tert-butyl nitrone (S-PBN) are known to trap and stabilize free radicals and to reduce inflammation. Recently, S-PBN was shown to reduce infiltration of T lymphocytes and the expression of adhesion molecules on the endothelium in experimental traumatic brain injury. We hypothesized that S-PBN could reduce infiltration of T lymphocytes during cell-mediated xenograft rejection and thereby increase graft survival. The concordant mouse-to-rat heart transplantation model was used to test the hypothesis. In this model, grafts undergo acute humoral xenograft rejection (AHXR) almost invariably on day 3 and succumb to cell-mediated rejection on approximately day 8 if AHXR is inhibited by treatment with 15-deoxyspergualin (DSG). Material and methods: Hearts from Naval Medical Research Institute (NMRI) mice were transplanted to the neck vessels of Lewis rats. Recipients were treated with S-PBN (n = 9), DSG (n = 9), S-PBN and DSG in combination (n = 10) or left untreated (n = 9) for survival studies. S-PBN was given daily intraperitoneally at a dose of 150 mg/kg body weight (BW) on day -1 to 30, and DSG was given daily intraperitoneally at a dose of 10 mg/kg BW on day -1 to 4 and 5 mg/kg BW on day 5 to 21. Nine additional recipients were given S-PBN only on days -1 and 0 in combination with continuous DSG treatment. Grafts were monitored until they stopped beating. Additional recipients were treated with S-PBN (n = 5), DSG (n = 5), S-PBN and DSG in combination (n = 6) or left untreated (n = 5) for morphological, immunohistochemical and flow cytometry analyses on days 2 and 6 after transplantation. Results: S-PBN treatment in combination with DSG resulted in increased median graft survival compared to DSG treatment alone (14 vs. 7 days; P = 0.019). Lower number of T lymphocytes on day 6 (P = 0.019) was observed by ex vivo propagation and flow cytometry when combining S-PBN with DSG, whereas immunohistochemical analyses demonstrated a significant reduction in the number of infiltrated CD4+, but not TCR+, cells. S-PBN treatment alone had no impact on graft survival compared to untreated rats (3 vs. 3 days). No differences were seen in ICAM-1 and VCAM-1 expression or in morphology between the groups. Conclusion: The combination of S-PBN and DSG treatment increases xenograft survival. The main effect of S-PBN appears to be in direct connection with the transplantation. Because of its low toxicity, S-PBN could become useful in combination with other immunosuppressants to reduce cell-mediated xenograft rejection.
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| 3. |
- Chu, Xia, et al.
(author)
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Multiple Microvascular Alterations in Pancreatic Islets and Neuroendocrine Tumors of a Men1 Mouse Model
- 2013
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In: American Journal of Pathology. - : Elsevier BV. - 0002-9440 .- 1525-2191. ; 182:6, s. 2355-2367
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Journal article (peer-reviewed)abstract
- Vascular therapeutic targeting requires thorough evaluation of the mechanisms activated in the specific context of each particular tumor type. We highlight structural, molecular, and functional microvascular aberrations contributing to development and maintenance of pancreatic neuroendocrine tumors (NETs), with special reference to multiple endocrine neoplasia 1 (MEN1) syndrome, using a Men1 mouse model. Tissue samples were analyzed by immunofluorescence to detect vessel density and pericyte distribution within the endocrine pancreas; expression of angiogenic factors was assessed by immunohistochemistry and quantitative real-time PCR in isolated islets and adenomas cultured under normoxic or hypoxic conditions. The increased vascular density of pancreatic NETs developed in Men1 mice was paralleled by an early and extensive redistribution of pericytes within endocrine tissue. These morphological alterations are supported by, and in some cases preceded by, fine-tuned variations in expression of several angiogenic regulators and are further potentiated by hypoxia. By combining two novel ex vivo and in vivo single-islet and tumor perfusion techniques, we demonstrated that both vascular reactivity and blood perfusion of tumor arterioles are significantly altered in response to glucose and L-nitro-arginine methyl ester. Our findings unravel multiple potential molecular and physiological targets differentially activated in the endocrine pancreas of Men1 mice and highlight the need for in-depth functional studies to fully understand the contribution of each component to development of pancreatic NETs in MEN1 syndrome.
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| 4. |
- Espes, Daniel, et al.
(author)
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Cotransplantation of Polymerized Hemoglobin Reduces β-Cell Hypoxia and Improves β-Cell Function in Intramuscular Islet Grafts
- 2015
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In: Transplantation. - 0041-1337 .- 1534-6080. ; 99:10, s. 2077-2082
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Journal article (peer-reviewed)abstract
- Background. Muscle is a promising alternative site for islet transplantation that facilitates rapid restoration of islet vascularization. However, the development of fibrosis suggests massive cellular death after transplantation. This study tested the hypothesis that islet graft function is limited by hypoxia-related death early after intramuscular transplantation, but that this can be overcome by cotransplantation of an oxygen carrier, that is, polymerized bovine hemoglobin (PolyHb). Methods. Two hundred islets were transplanted with or without different doses of PolyHb intramuscularly to nondiabetic C57BL/6 and diabetic C57BL/6 nu/nu mice. beta-cell hypoxia and apoptosis were evaluated by immunohistochemistry after injection of the biochemical marker pimonidazole or by staining for caspase-3, respectively. Blood glucose concentrations were monitored for 30 days after islet transplantation and animals were then subjected to an intravenous glucose tolerance test. Results. Substantial hypoxia was observed in control islet grafts during the first 4 days after transplantation. Cotransplantation of PolyHb resulted in a dose-dependent reduction of beta-cell hypoxia, but beta-cell apoptosis was only reduced by cotransplantation of low-dose PolyHb (0.03 mg/g body weight) due to the inflammatory effects of higher PolyHb concentrations. Cotransplantation of low-dose PolyHb resulted in improved islet graft function 30 days after transplantation in diabetic mice, with a glucose tolerance comparable to transplantation of 50% more islets. Conclusion. We conclude that cotransplantation of islets with PolyHb can be used to effectively bridge the critical hypoxic phase immediately after transplantation, improve islet graft function, and reduce the number of islets needed for successful intramuscular transplantation.
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| 5. |
- Espes, Daniel, 1985-, et al.
(author)
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Function and Gene Expression of Islets Experimentally Transplanted to Muscle and Omentum
- 2020
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In: Cell Transplantation. - THOUSAND OAKS, CA USA : SAGE Publications. - 0963-6897 .- 1555-3892. ; 29, s. 1-10
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Journal article (peer-reviewed)abstract
- Islet transplantation to the liver is a potential curative treatment for patients with type 1 diabetes. Muscle and the greater omentum are two alternative implantation sites, which can provide excellent engraftment and hold potential as future sites for stem-cell-derived beta-cell replacement. We evaluated the functional outcome after islet transplantation to muscle and omentum and found that alloxan-diabetic animals were cured with a low number of islets (200) at both sites. The cured animals had a normal area under the curve blood glucose response to intravenous glucose, albeit animals with intramuscular islet grafts had increased 120-min blood glucose levels. They also demonstrated an exaggerated counter regulatory response to hypoglycemia. The expression of genes important for beta-cell function was, at both implantation sites, comparable to that in native pancreatic islets. The gene expression of insulin (INS1 and INS2) and glucose transporter-2 was even increased, and the expression of lactate dehydrogenase decreased, at both sites when compared to native islets. We conclude that muscle and omentum provide excellent conditions for engraftment of transplanted islets. When compared to control, 200 islets implanted to the omentum displayed a restored glucose tolerance, whereas animals with intramuscular islet grafts of similar size displayed mild glucose intolerance.
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| 6. |
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| 7. |
- Espes, Daniel, et al.
(author)
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Rapid Restoration of Vascularity and Oxygenation in Mouse and Human Islets Transplanted to Omentum May Contribute to Their Superior Function Compared to Intraportally Transplanted Islets
- 2016
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In: American Journal of Transplantation. - : Elsevier BV. - 1600-6135 .- 1600-6143. ; 16:11, s. 3246-3254
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Journal article (peer-reviewed)abstract
- Transplantation of islets into the liver confers several site-specific challenges, including a delayed vascularization and prevailing hypoxia. The greater omentum has in several experimental studies been suggested as an alternative implantation site for clinical use, but there has been no direct functional comparison to the liver. In this experimental study in mice, we characterized the engraftment of mouse and human islets in the omentum and compared engraftment and functional outcome with those in the intraportal site. The vascularization and innervation of the islets transplanted into the omentum were restored within the first month by paralleled ingrowth of capillaries and nerves. The hypoxic conditions in the islets early posttransplantation were transient and restricted to the first days. Newly formed blood vessels were fully functional, and the blood perfusion and oxygenation of the islets became similar to that of endogenous islets. Furthermore, islet grafts in the omentum showed at 1 month posttransplantation functional superiority to intraportally transplanted grafts. We conclude that in contrast to the liver the omentum provides excellent engraftment conditions for transplanted islets. Future studies in humans will be of great interest to investigate the capability of this site to also harbor larger grafts without interfering with islet functionality.
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| 8. |
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| 9. |
- Gao, Xiang, et al.
(author)
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Effects of Mn-DPDP and manganese chloride on hemodynamics and glucose tolerance in anesthetized rats
- 2014
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In: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 55:3, s. 328-334
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Journal article (peer-reviewed)abstract
- Background Previous studies have demonstrated that magnetic resonance imaging may be a method of choice to visualize transplanted pancreatic islets. However, contrast agents may interfere with microcirculation and affect graft function. Purpose To evaluate the effects manganese-containing contrast media on regional blood flow and glucose tolerance. Material and Methods Anesthetized rats were injected intravenously with MnCl2 (10 mu M/kg body weight) or Mn-DPDP (Teslascan; 5 mu M/kg body weight). Blood flow measurements were made with a microsphere technique 10min later. In separate animals vascular arteriolar reactivity in isolated, perfused islets was examined. Furthermore, an intraperitoneal glucose tolerance test was performed in separate rats. Results Glucose tolerance was unaffected by both agents. No changes in regional blood flow were seen after administration of Mn-DPDP, except for an increase in arterial liver blood flow. MnCl2 increased all blood flow values except that of the kidney. MnCl2, but not Mn-DPDP, caused a vasoconstriction in isolated rat islet arterioles but only at very high doses. Conclusion Mn-DPDP administration does not affect glucose tolerance or regional blood flow, besides an increase in arterial hepatic blood flow, and may therefore be suitable for visualization of islets.
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| 10. |
- Jansson, Leif, et al.
(author)
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Pancreatic islet blood flow and its measurement
- 2016
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In: Upsala Journal of Medical Sciences. - : Uppsala Medical Society. - 0300-9734 .- 2000-1967. ; 121:2, s. 81-95
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Research review (peer-reviewed)abstract
- Pancreatic islets are richly vascularized, and islet blood vessels are uniquely adapted to maintain and support the internal milieu of the islets favoring normal endocrine function. Islet blood flow is normally very high compared with that to the exocrine pancreas and is autonomously regulated through complex interactions between the nervous system, metabolites from insulin secreting beta-cells, endothelium derived mediators, and hormones. The islet blood flow is normally coupled to the needs for insulin release and is usually disturbed during glucose intolerance and overt diabetes. The present review provides a brief background on islet vascular function and especially focuses on available techniques to measure islet blood perfusion. The gold standard for islet blood flow measurements in experimental animals is the microsphere technique, and its advantages and disadvantages will be discussed. In humans there are still no methods to measure islet blood flow selectively, but new developments in radiological techniques hold great hopes for the future.
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