Intraportal Transplantation Research Articles

Study on MR tracking of magnetically labeled swine mesenchymal stem cells after autologous transplantation into acute injured liver in vivo

Objective To evaluate in vivo tracking of swine mesenchymal stem cells (MSCs) la-beled with super paramagnetic iron oxide (SPIO) in intraportal transplantation by a clinical 1.5T MR.Methods MSCs were isolated from swine and cultured as well as expanded, which were then incuba-ted with SPIO (Feridex I. V.). Prussian blue staining was performed for showing intracelluar irons.To establish a swine model of acute liver necrosis, 0.5 g/kg of D-galactosamine was administrated to 10 pigs. MSCs(labeled cells in six, unlabeled cells in four)were injected into liver via portal veins. MR imaging was performed with a clinical 1.5T MR immediately before and at 6 h, 3 d, 7 d, 14 d after transplantation, respectively. Results Prussian blue staining of SPIO labeled MSCs could be effec-tively labeled and the labeling efficiency was almost 100%. Signal intensity loss in liver by SPIO labe-ling on FFE sequence persisted until 14 days after transplantation. Histological analysis by Prussian blue staining showed homing of labeled MSCs in liver after 14 days, primarily distributing in hepatic sinusoids and liver parenchyma. Conclusion MSCs can be labeled with SPIO in vitro successfully.MRI can monitor magnetically labeled MSCs transplanted into liver. Key words: Stem cell transplantation; Mesenchymal stem cell; Super paramagnetic iron ox-ide; Feridex; Magnetic resonance imaging

Hyperbaric oxygen therapy improves early posttransplant islet function.

This study investigates the therapeutic potential of hyperbaric oxygen therapy (HBO) in reducing hypoxia and improving engraftment of intraportal islet transplants by promoting angiogenesis. Diabetic BALB/c mice were transplanted with 500 syngeneic islets intraportally and received six consecutive twice-daily HBO treatments (n = 9; 100% oxygen for 1 h at 2.5 atmospheres absolute) after transplantation. Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) was used to assess new vessel formation at postoperative days (POD) 3, 7, and 14. Liver tissue was recovered at the same time points for correlative histology, including: hematoxylin and eosin, hypoxia-inducible factor (HIF1α), Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL), vascular endothelial growth factor (VEGF), and von Willebrand Factor immunohistochemistry. HBO therapy significantly reduced HIF-1α, TUNEL and VEGF expression in islets at POD 7. In the non-HBO transplants, liver enhancement on DCE MRI peaked at POD 7 consistent with less mature vasculature but this enhancement was suppressed at POD 7 in the HBO-treated group. The number of new peri-islet vessels at POD 7 was not significantly different between HBO and control groups. These results are consistent with a hyperbaric oxygen-mediated decrease in hypoxia that appeared to enhance vessel maturation in the critical days following intraportal islet transplantation.

Pancreatic Islet Transplantation Using Vascularised Chambers Containing Nerve Growth Factor Ameliorates Hyperglycaemia in Diabetic Mice

Intraportal islet transplantation has shown initial promise for the treatment of type 1 diabetes. However, the portal vein site is associated with complications such as thrombosis and hepatic steatosis, leading to transplant failure. The aims of this study were to (1) test the feasibility of an alternative islet transplantation method that utilises a FDA-approved gelatin sponge as a novel islet carrier and (2) assess if exogenous addition of nerve growth factor (NGF) has any additional beneficial effects on graft performance in diabetic mice. Mice were rendered diabetic by a single intraperitoneal injection of streptozotocin. Five hundred syngeneic islets were seeded onto a Gelitaspon® disc in the presence or absence of NGF, and placed into a silicone chamber surrounding the femoral neurovascular pedicle. Islet function was assessed by weekly monitoring of blood glucose levels and an intraperitoneal glucose tolerance test performed at the end of the study. Chambers were harvested for further histological analysis. Four of five mice transplanted with islets seeded onto Gelitaspon with NGF showed a significant reduction in blood glucose levels by 4 weeks after transplantation, and demonstrated a response similar to non-diabetic mice when tested with an intraperitoneal glucose tolerance test. Chamber tissue from this group contained islets with insulin-producing β cells adjacent to the vascular pedicle. Islets seeded onto Gelitaspon with NGF and sited on femoral vessels using a tissue-engineering chamber offer an alternative method for islet transplantation in diabetic mice. This may have potential as a method for clinical islet transplantation.

Bilirubin protects grafts against nonspecific inflammation-induced injury in syngeneic intraportal islet transplantation

Nonspecific inflammatory response is the major cause for failure of islet grafts at the early phase of intraportal islet transplantation (IPIT). Bilirubin, a natural product of heme catabolism, has displayed anti-oxidative and anti-inflammatory activities. The present study has demonstrated that bilirubin protected islet grafts by inhibiting nonspecific inflammatory response in a syngeneic rat model of IPIT. The inflammation-induced cell injury was mimicked by exposing cultured rat insulinoma INS-1 cells to cytokines (IL-1β, TNF-α and IFN-γ) in in vitro assays. At appropriate lower concentrations, bilirubin significantly attenuated the reduced cell viability and enhanced cell apoptosis induced by cytokines, and protected the insulin secretory function of INS-1 cells. Diabetic inbred male Lewis rats induced by streptozotocin underwent IPIT at different islet equivalents (IEQs) (optimal dose of 1000, and suboptimal doses of 750 or 500), and bilirubin was administered to the recipients every 12 h, starting from one day before transplantation until 5 days after transplantation. Administration of bilirubin improved glucose control and enhanced glucose tolerance in diabetic recipients, and reduced the serum levels of inflammatory mediators including IL-1β, TNF-α, soluble intercellular adhesion molecule 1, monocyte chemoattractant protein-1 and NO, and inhibited the infiltration of Kupffer cells into the islet grafts, and restored insulin-producing ability of transplanted islets.

Anchoring of Vascular Endothelial Growth Factor to Surface-Immobilized Heparin on Pancreatic Islets: Implications for Stimulating Islet Angiogenesis

In pancreatic islet transplantation, early revascularization is necessary for long-term graft function. We have shown in in vitro and in vivo models that modification with surface-attached heparin protects the islets from acute attack by the innate immune system of the blood following intraportal islet transplantation. In this study, we have investigated the ability of an immobilized conjugate composed of heparin to bind the angiogenic growth factor vascular endothelial growth factor-A (VEGF-A) as a means of attracting endothelial cells (ECs) to induce angiogenesis and revascularization. We analyzed the capacity of VEGF-A to bind to immobilized heparin and how this affected the proliferation and adherence of ECs to both artificial glass surfaces and islets. Quartz crystal microbalance with dissipation monitoring and slot-blot demonstrated the binding of VEGF-A to heparin-coated surfaces upon which ECs showed protein-dependent proliferation. Also, ECs cultured on heparin-coated glass surfaces exhibited effects upon focal contacts. Heparinized islets combined with VEGF-A demonstrated unaffected insulin release. Further, covering islets with heparin also increased the adhesion of ECs to the islet surface. Immobilized heparin on the islet surface may be a useful anchor molecule for achieving complete coverage of islets with angiogenic growth factors, ultimately improving islet revascularization and engraftment in pancreatic islet transplantation.

Histologic Graft Assessment After Clinical Islet Transplantation

An accurate monitoring would help understanding the fate of islet grafts after transplantation. This work assessed the feasibility of needle biopsy monitoring after intraportal islet transplantation (n=16), and islet graft morphology was studied with the addition of autopsy samples (n=2). Pancreas autopsy samples from two nondiabetic individuals were used as control. Islet tissue was found in five needle samples (31%). Sampling success was related to size (100% sampling for the four biopsies of 1.8 cm in length or higher, P<or=0.01). Mild liver abnormalities included localized steatosis (n=8), mild nodular regenerative hyperplasia and mild portal venopathy (n=3), and hepatocyte swelling (n=2). Endocrine cell composition and distribution were similar between islet grafts and normal islets within the native pancreas. There was no or minimal immune cell infiltrate in patients on and off exogenous insulin, including two patients with ongoing negative metabolic events (increasing HbA1c or insulin requirement). The infiltrate was mainly composed of CD4- and CD8-positive cells. This study demonstrates that needle biopsy is feasible after clinical islet transplantation but with a limited practical value because of its low islet sampling rate using current sampling and analysis methods. Both biopsy and autopsy samples demonstrated the well-preserved islet endocrine composition after transplantation and the presence of focal areas of steatosis. Islet grafts showed no or minimal immune cell infiltration, even in the case of ongoing islet loss. On the basis of the findings, possible reasons for allograft islet loss are discussed.

Positron Emission Tomography in Clinical Islet Transplantation

The fate of islets in clinical transplantation is unclear. To elude on this positron emission tomography combined with computed tomography (PET/CT) was performed for 60 min during islet transplantation in five patients receiving six transplants. A fraction of the islets (23%) were labeled with 18F-fluorodeoxyglucose ([(18)F]FDG) and carefully mixed with unlabeled islets just prior to intraportal transplantation. The peak radioactivity concentration in the liver was found at 19 min after start of islet infusion and corresponded to only 75% of what was expected, indicating that islets are lost during the transplantation procedure. No accumulation of radioactivity was found in the lungs. A nonphysiological peak of C-peptide was found in plasma during and immediately after transplantation in all subjects. Distribution in the liver was heterogeneous with wide variations in location and concentration. Islets found in areas with concentrations of >400 IEQ/cc liver tissue varied between 1% and 32% of the graft in different subjects. No side effects attributed to the PET/CT procedure were found. Clinical outcome in all patients was comparable to that previously observed indicating that the [(18)F]FDG labeling procedure did not harm the islets. The technique has potential to be used to assess approaches to enhance islet survival and engraftment in clinical transplantation.

Surface Modification of Islets With PEG-Lipid for Improvement of Graft Survival in Intraportal Transplantation

Transplantation of islets of Langerhans (islets) is a promising technique for treating insulin-dependent diabetes mellitus (type I). One unsolved issue is the early graft loss due to inflammatory reactions triggered by blood coagulation and complement activation that occurs immediately after transplantation into the liver through the portal vein. Several proposed approaches for improvement of the graft survival include heparin coating and covalent poly(ethylene glycol) (PEG) conjugation. We previously have studied the improvement of graft survival by modification of islet surfaces using amphiphilic PEG-conjugated phospholipid and bioactive molecules. Here, we analyzed the effect of PEG-modification on the improvement of graft survival immediately after intraportal transplantation into streptozotocin-induced diabetic mice. The surface of hamster islets was modified with PEG-lipid. PEG-lipid modified islets (PEG-islets) were transplanted into the liver through the portal vein of streptozotocin-induced diabetic mice. We measured the graft survival periods and blood insulin levels immediately after intraportal transplantation to determine the cell damage to islets. Histocytochemical analyses of liver were also performed postintraportal transplantation. The graft survival of PEG-islets was significantly prolonged compared with bare islets in livers of diabetic mice. Reduction of blood insulin level within 60 min after transplantation of PEG-islets suggests that the cell damage observed immediately after transplantation could be suppressed by surface modification with PEG in comparison with bare islets. Our approach for the improvement of graft survival will be useful in the clinical setting.

Reinnervation of pancreatic islets and regulation of insulin secretion by hepatic sympathetic nerves after intraportal transplantation of islets into livers of diabetic rats.

It was the aim of this study to elucidate whether intraportally transplanted pancreatic islets were reinnervated after transplantation and whether the secretion of insulin from pancreatic islets might be modulated by the vegetative innervation of recipient livers. Two weeks after intraportal transplantation of 2000 neonatal pancreatic islets recipient rats completely recovered from streptozotocin-induced diabetes. Predominantly catecholaminergic, but also cholinergic nerve fibers were detected in islet cell complexes between beta-cells. Corresponding electron micrographs showed beta-cells in close contact with axons of nonmyelinated nerve fibers. Perfusion studies with livers of recipient rats revealed that the inhibition by hepatic sympathetic nerves of insulin secretion was mediated via alpha 2-receptors as in normal pancreatic islets.

Islet transplantation. The connection of experiment and clinic exemplified by the transplantation of islets of Langerhans.

Since approximately 25 years islet transplantation as a mean for the treatment of diabetes has been developed from early attempts in rodents to first clinical applications in man in recent years. The review describes the results obtained in diabetic rats including metabolic effects as well as prevention of late complications. In the syngeneic system (Lewis-rats) the intraportal transplantation of 1,000-2,000 isolated islets may cure streptozotocin-induced diabetes for the whole lifespan of the animal. In the allogeneic system (across a major histocompatibility barrier), however, isolated islets are highly immunogenic. According to present knowledge, mainly class-II antigen bearing cells are responsible while the role of the endocrine cells seems to be less important. By various in vitro methods (e.g. low temperature culture at 24 degrees C) it was possible to induce immunoalteration of allogeneic islets which was followed by long-term acceptance by the host in rodents. Whether the same technique is effective in larger animals and in man remains open. New technologies for the isolation of high numbers of pure islets from human pancreatic glands have been the key for the use of islet transplantation in man in several centers. The review describes the details regarding institutions as well as results in patients on the basis of the International Islet Transplant Registry which is located at Giessen University. Although longer lasting insulin independency (longest lasting effect 2 1/2 years) has been observed only in a few patients, islet transplantation has been proven to be a very safe procedure for the patient. It is hoped that with increasing experiences regarding the factors which at present limit the function as number and quality of islets, immunosuppressive protocols etc. islet transplantation will develop to a definite alternative to whole-organ transplantation. One of the most important challenges for modern medicine is the fact of a worldwide increase of diabetic long-term complications such as kidney failure, coronary and peripheral vascular disease, blindness and neuropathy. Although intensified insulin treatment in a small percentage of patients may moderate morbidity and mortality, from experimental work there is sufficient evidence suggesting that only the restoration of normoglycemia early in the course of the disease may prevent complications. This, however, can only be achieved by the replacement of the destroyed islets of Langerhans either by transplantation of an intact vascularised pancreas or by isolated islets.(ABSTRACT TRUNCATED AT 400 WORDS)

Hyperproliferative state of liver acini and pancreatic islets after intraportal transplantation of a small mass of islets of Langerhans in streptozotocininduced diabetic rats.

After the portal-embolic transplantation of a low number of isologous islets of Langerhans into streptozotocin-diabetic rats altered liver acini emerge down-stream to the islet grafts. The hepatocytes of these altered liver acini store high amounts of glycogen and/or fat. The proliferation of the hepatocytes of such altered acini and simultaneously their apoptotic elimination were increased strongly, compared with the surrounding unaltered liver acini. After transplantation of a high number of islets, altered liver acini were not observed. The reason for these focal phenomena was supposed to be the persistent systemic hyperglycemic diabetic state which stimulates the beta cells to produce insulin and to secrete it in maximal amounts. This hypothesis has been supported by electron-microscopical examination of the transplanted islets in a former publication, but the proliferative activity of the transplanted islet epithelial cells has not so far been examined. Furthermore, the period of observation has been only three weeks, and it seemed of interest to determine whether the locally increased hepatocytic proliferation and the stimulation of the beta-cells would persist for a longer time. 450-500 (group I, n = 14) or 1500-2000 (group II, n = 8) isologous pancreatic islets were transplanted to adult male Lewis-rats made diabetic by streptozotocin. Group I animals stayed hyperglycemic after transplantation, group II animals became normoglycemic. 5-bromo-2'-desoxyuridine (BrdU) was applied by osmotic minipumps for 6 days before death (6, 13, 21 and 67-77 days after islet transplantation). In group I animals the mitotic index (number of mitotic figures per 1000 hepatocytic nuclei), the apoptotic index (number of apoptotic bodies per 1000 hepatocytic nuclei) and the immunohistochemical-labeling index for BrdU (BrdU-labeled hepatocytic nuclei per 100 hepatocytic nuclei) of these altered acini (A) were compared with the adjacent non-altered acini (NA). The mitotic index in A was 40-fold to 100-fold increased compared with NA (for the whole period of observation). The apoptotic index in A was 6-fold to 20-fold increased compared with NA. The BrdU-LI in A was 20-fold to 80-fold increased compared with NA. In group II animals altered liver acini did not emerge. Furthermore, BrdU-LI of epithelial cells of group I islets were significantly higher compared with group II islets (28.4 vs. 6.3 at day 6, 28.8 vs. 4.2 at day 13, 23.2 vs. 2.9 at day 21, 15.3 vs. 0.1 at days 67 to 77, respectively). It is supposed that two different types of proliferative stimuli were active in this model of low number islet transplantation: 1) The chronic hyperglycemia induces endocrine epithelial cell proliferation in the grafts. 2) The local chronic hyperinsulinism induces glycogen and fat storage, proliferation and apoptotic elimination of the hepatocytes in the liver acini down-stream to the stimulated islets.

Factors affecting islet graft embolization in the liver of diabetic mice

Background: Embolic occlusion of the portal vein due to islet transplantation is one of the major reasons for reduced survival of transplanted islets. In this study, we examined the location of islets as well as the correlation between islet and portal vein size after intraportal islet transplantation, and evaluated liver and islet pathology. Methods: BALB/c mice were intraportally transplanted with 800 islets and the liver was examined at postoperative day (POD) 0 (n=7), POD 2 (n=4) and POD 28 (n=3). Liver specimens were stained for hematoxylin and eosin (necrosis), insulin, and TUNEL (apoptosis). We evaluated distance from liver surface to islets, islet and portal vein diameter, embolic ratio (islet diameter/portal vein diameter), apoptosis/necrosis of islets and apoptosis/necrosis of the liver tissue surrounding the islet. Results: The liver was divided into peripheral and central sites. Islet and liver apoptosis/necrosis were significantly higher at peripheral sites. In regions without liver apoptosis or necrosis, portal vein diameter was significantly larger and embolic ratios were significantly lower. Conclusion: Transplanted islets and liver tissue exhibited more injury at peripheral sites, in part, due to smaller diameters of portal venules that result in more frequent emboli following islet transplantation.

An In Vitro Model of Cell Transplantation for Evaluation of Cell Engraftment Enhancers

The limited availability of organs for liver transplantation has focused interest on the use of cell transplants to restore hepatic function. Advances have been made in rodent models, but efficacy is limited in humans due to low engraftment efficiency. In rodents, pretransplantation treatment of the liver with engraftment enhancers (EE) shows that repopulation is feasible, although the toxicity of the substances impedes their application in humans. Evaluation of low-toxicity engraftment enhancers for human use requires testing in animal models, a time-consuming, expensive process that also raises ethical issues. To reduce animal use in the preliminary evaluation of a new EE, we designed an easily quantitated in vitro method that mimics an intraportal cell transplant. It is based on EE-mediated disruption of intercellular adhesion in confluent endothelial cell cultures.

Thrombomodulin Improves Early Outcomes After Intraportal Islet Transplantation

Primary islet nonfunction due to an instant blood mediated inflammatory reaction (IBMIR) leads to an increase in donor islet mass required to achieve euglycemia. In the presence of thrombin, thrombomodulin generates activated protein C (APC), which limits procoagulant and proinflammatory responses. In this study, we postulated that liposomal formulations of thrombomodulin (lipo-TM), due to its propensity for preferential uptake in the liver, would enhance intraportal engraftment of allogeneic islets by inhibiting the IBMIR. Diabetic C57BL/6J mice underwent intraportal transplantation with B10.BR murine islets. In the absence of treatment, conversion to euglycemia was observed among 29% of mice receiving 250 allo-islets. In contrast, a single infusion of lipo-TM led to euglycemia in 83% of recipients (p = 0.0019). Fibrin deposition (p < 0.0001), neutrophil infiltration (p < 0.0001), as well as expression TNF-alpha and IL-beta (p < 0.03) were significantly reduced. Significantly, thrombotic responses mediated by human islets in contact with human blood were also reduced by this approach. Lipo-TM improves the engraftment of allogeneic islets through a reduction in local thrombotic and inflammatory processes. As an enzyme-based pharmacotherapeutic, this strategy offers the potential for local generation of APC at the site of islet infusion, during the initial period of elevated thrombin production.

Intraperitoneal Insulin Infusion Versus Islet Transplantation: Comparative Study in Patients with Type 1 Diabetes

The purpose of this article was to compare two strategies for insulin delivery in brittle type 1 diabetic patients: intraperitoneal insulin infusion (IPII) through an implantable pump and intraportal islet transplantation (IIT). Thirteen consecutive patients (6 islet after kidney and 7 islet transplantation alone), treated with IIT according to the Edmonton protocol, were compared with 17 patients treated with IPII in the same center in a nonrandomized study. Both groups of patients were assessed for clinical profile, metabolic results, and adverse events during the 3-year period after implantation. Sex ratio, mean age, body mass index, diabetes duration, daily insulin need (DIN), blood creatinine, lipid and HbA1c levels, and frequency of diabetic complications did not differ significantly between the two groups before inclusion. The comparison of metabolic results 3, 6, and 12 months after IIT or IPII showed that while mean HbA1c significantly decreased over time in both groups, mean DIN, glycemia, and number of hypoglycemias less than 3.3 mmol/L per patient per week (Hypo) only significantly decreased in the IIT group versus baseline. At 12 months, mean DIN, HbA1c, and Hypo were significantly lower in the IIT versus IPII group. After 24 and 36 months, mean DIN, HbA1c, and Hypo remained significantly lower in the IIT group versus baseline, and mean HbA1c and DIN versus IPII. Adverse events were, however, fourfold more frequent with IIT versus IPII, though their numbers decreased over time. These results suggest that metabolic results improve with both methods, but were significantly better with IIT versus IPII, though with more frequent side effects.

False aneurysm of a hepatic artery branch complicating intrahepatic islet transplantation

Islet transplantation, an innovative treatment strategy for type 1 diabetes mellitus, is a relatively safe procedure, with less morbidity than pancreas transplantation. Vascular injuries have not been reported to date. We report a percutaneous transhepatic intraportal islet transplant infusion that was followed by bleeding from a false aneurysm of an intrahepatic branch of the hepatic artery. The bleeding was controlled by selective embolization. Despite the complication and its treatment, the patient gained insulin independence, which was sustained for 285 days. She is currently on a small dose of insulin with good glycemic control.

MRI Assessment of Ischemic Liver After Intraportal Islet Transplantation

There is a recent focus on embolization of the portal vein by transplanted islets as a major cause of early graft loss. The resultant ischemia causes necrosis or apoptosis of cells within the liver. Thus, noninvasive assessment of the liver receiving the islet transplant is important to evaluate the status islet grafts. This study used noninvasive magnetic resonance imaging (MRI) for assessment of the posttransplant ischemic liver. Syngeneic islets in streprozotocin-induced diabetic mice were used. MRI and morphological liver assessments were performed at 0, 2, and 28 days after transplantation. Histologic assessment of insulin, hypoxia induced factor 1-alpha, and apoptosis were undertaken at similar time points. Ischemic/necrotic regions in the liver were detected by MRI at 2 days but not at 28 days after transplantation and were confirmed histologically. Liver injury was quantified from high intensity areas on T2-weighted images. Insulin release peaked 2 days after transplantation. Onset and reversal of liver ischemia due to intraportal islet transplantation are detectable using T2-weighted MRI. These changes coincide with periods of maximum insulin release likely due to partial islet destruction. We propose that MRI, as a noninvasive monitor of graft-related ischemia, may be useful in assessment of liver and islet engraftment after intraportal islet transplantation in a clinical setting.

Efficacy Comparison Between Intraportal and Subcapsular Islet Transplants in a Murine Diabetic Model

Background It is important to determine the efficacy of intraportal (IP) islet transplantation in comparison with other transplant sites. In this study, we sought to determine the optimal number of islets to achieve normoglycemia following transplantation into the liver versus the kidney using a mouse model. Methods Streptozotocin-induced diabetic mice (Balb/C) were transplanted with syngeneic islets via the IP versus renal subcapsular (SC) routes. The transplanted islet numbers were 0 to 800 ( n = 3–5). We assessed the correlation between parameters and islet numbers, comparing IP versus SC groups. The parameters were: (1) percentage of normoglycemia; (2) postoperative days to normoglycemia; (3) mean blood glucose levels at various points from pretransplantation to the end of the study (postoperative day 28); (4) mean serum insulin; and (5) area under the curve of blood glucose levels after glucose injection. Results Two hundred islets yielded normoglycemia in renal subcapsular grafts, while 800 islets were the minimum required for normoglycemia with IP transplantation. The transplant efficacy in SC transplantation was 2 to 5 times greater than that of IP transplantation. The days to normoglycemia were significantly different between IP versus renal SC islets (13.25 ± 4.38 days vs 4.50 ± 0.81 days; P = .007). Conclusion The efficacy of islet transplantation in murine diabetic models was significantly greater under the kidney capsule. Clinical islet transplantation could benefit from trials of alternative transplant sites.

Effect of nicotinamide on early graft failure following intraportal islet transplantation

Intraportal islet transplantation (IPIT) may potentially cure Type 1 diabetes mellitus; however, graft failure in the early post-transplantation period presents a major obstacle. In this study, we tested the ability of nicotinamide to prevent early islet destruction in a syngeneic mouse model. Mice (C57BL/6) with chemically-induced diabetes received intraportal transplants of syngeneic islet tissue in various doses. Islets were cultured for 24 h in medium with or without 10 mM nicotinamide supplementation. Following IPIT, islet function was confirmed by an intraperitoneal glucose tolerance test (IPGTT) and hepatectomy. The effects of nicotinamide were evaluated by blood glucose concentration, serum monocyte chemoattractant protein-1 (MCP-1) concentration, and immunohistology at 3 h and 24 h after IPIT. Among the various islet doses, an infusion of 300 syngeneic islets treated with nicotinamide exhibited the greatest differences in glucose tolerance between recipients of treated and untreated (i.e., control) islets. One day after 300 islet equivalent (IEQ) transplantation, islets treated with nicotinamide were better granulated than the untreated islets (P=0.01), and the recipients displayed a slight decrease in serum MCP-1 concentration, as compared to controls. After 15 days, recipients of nicotinamide-pretreated islets showed higher levels of graft function (as measured by IPGTT) than controls. The pretreatment also prolonged graft survival (>100 days) and function; these were confirmed by partial hepatectomy, which led to the recurrence of diabetes. Pretreatment of islet grafts with nicotinamide may prevent their deterioration on the early period following IPIT in a syngeneic mouse model.

Superiority of Fresh Islets Compared With Cultured Islets

Introduction It has recently been reported that the outcomes of islet transplantation with short periods of culture are comparable with those of freshly isolated islets. To clarify the influence of culture, fresh islets were compared with cultured islets in terms of quality. Materials and Methods The quality of freshly isolated islets was compared with that of cultured islets with CMRL 1066 including 10% allogeneic serum, CMRL 1066 including 0.5% human serum albumin, or Miami medium. We evaluated static glucose stimulation tests, insulin/DNA contents, ADP/ATP ratios, and an intraportal transplantation model into syngeneic diabetic rats. The expression of inflammatory mediators in the islets was examined using Western blotting for tissue factor (TF), which is the initiator of detrimental instant, blood-mediated, inflammatory reactions (IBMIR). Results Although the survival rate was similar in all groups, the stimulation index upon glucose challenge and the insulin/DNA ratio were significantly higher among fresh islets. Most importantly, the expression of TF on islets was significantly lower in fresh islets, suggesting that culture enhanced TF-dependent IBMIR after transplantation. In an in vivo transplantation model, the curative rate and insulin production by the recipient liver was considerably greater in the fresh islet group. Conclusions Isolated islets without prior culture showed results superior to cultured islets.