Intraportal Islet Transplantation Research Articles

Thrombin-Activatable Fibrinolysis Inhibitor Is Activated in an Instant Blood-Mediated Inflammatory Reaction After Intraportal Islet Transplant

Activated thrombin-activatable fibrinolysis inhibitor is a coagulation factor in some thrombotic diseases. However, available data on whether thrombin-activatable fibrinolysis inhibitor is activated in islet transplant are limited. In this study, changes of plasma-activated thrombin-activatable fibrinolysis inhibitor levels in instant blood-mediated inflammatory reaction after islet transplant were assessed. Plasma concentrations of thrombin-antithrombin complex, D-dimer, C-peptide, and activated thrombin-activatable fibrinolysis inhibitor were assessed at 0 minutes, 30 minutes, 1 hour, 6 hours, 12 hours, and 24 hours after an intraportal islet transplant using rats via an enzyme-linked immunosorbent assay, or solid-phase, 2-site chemiluminescent immunometric assay. We recovered the liver at 1 hour after the transplant for histologic examination. Thrombin-antithrombin complex, C-peptide, and activated thrombin-activatable fibrinolysis inhibitor levels increased immediately after we stopped islet infusion, and their peak levels occurred at 1 hour after islet infusion. D-dimer levels increased continually after islet infusion was stopped, and peaked 24 hours after infusion. Histologic examination of the liver 1 hour after islet infusion revealed frequent portal venous thrombi, with entrapped islets. The entrapped islets showed a disrupted morphology. Activated thrombin-activatable fibrinolysis inhibitor was generated and peaked 1 hour after islet transplant according with activating coagulation, indicating that thrombin-activatable fibrinolysis inhibitor is activated and accumulated at levels in instant blood-mediated inflammatory reaction was sufficient to affect fibrinolysis.

Benefits of PEGylation in the early post-transplant period of intraportal islet transplantation as assessed by magnetic resonance imaging of labeled islets

While a few studies have demonstrated the benefit of PEGylation in islet transplantation, most have employed renal subcapsular models and none have performed direct comparisons of islet mass in intraportal islet transplantation using islet magnetic resonance imaging (MRI). In this study, our aim was to demonstrate the benefit of PEGylation in the early post-transplant period of intraportal islet transplantation with a novel algorithm for islet MRI. Islets were PEGylated after ferucarbotran labeling in a rat syngeneic intraportal islet transplantation model followed by comparisons of post-transplant glycemic levels in recipient rats infused with PEGylated (n = 12) and non-PEGylated (n = 13) islets. The total area of hypointense spots and the number of hypointense spots larger than 1.758 mm2 of PEGylated and non-PEGylated islets were quantitatively compared. The total area of hypointense spots (P < 0.05) and the number of hypointense spots larger than 1.758 mm2 (P < 0.05) were higher in the PEGylated islet group 7 and 14 days post translation (DPT). These results translated into better post-transplant outcomes in the PEGylated islet group 28 DPT. In validation experiments, MRI parameters obtained 1, 7, and 14 DPT predicted normoglycemia 4 wk post-transplantation. We directly demonstrated the benefit of islet PEGylation in protection against nonspecific islet destruction in the early post-transplant period of intraportal islet transplantation using a novel algorithm for islet MRI. This novel algorithm could serve as a useful tool to demonstrate such benefit in future clinical trials of islet transplantation using PEGylated islets.

Strategy for clinical setting in intramuscular and subcutaneous islet transplantation

Intraportal islet transplantation has a long history as a procedure for clinical islet transplantation. However, many recent studies revealed that the intraportal procedure has some disadvantages in transplant efficiency and safety. Many candidates as an optimal transplant site for islets have been assessed, but further studies and clinical trials are still necessary. Intramuscular and subcutaneous spaces are important candidates, because the transplant and biopsy procedures are simple approaches with minimal invasion and few complications. Although they are sites with hypovascularity and hypoxia, which contribute to the poor transplant efficiency, many experimental trials for improving the outcome in intramuscular and subcutaneous islet transplantations have been performed, focusing on early angiogenesis and scaffolds for engrafting transplanted islets. We review current progress in intramuscular and subcutaneous islet transplantations and discuss ways to develop them as optimal transplant sites for islets.

Thioredoxin-1 Attenuates Early Graft Loss after Intraportal Islet Transplantation in Mice

AimsRecent studies suggest that decreasing oxidative stress is crucial to achieve successful islet transplantation. Thioredoxin-1 (TRX), which is a multifunctional redox-active protein, has been reported to suppress oxidative stress. Furthermore, it also has anti-inflammatory and anti-apoptotic effects. In this study, we investigated the effects of TRX on early graft loss after islet transplantation.MethodsIntraportal islet transplantation was performed for two groups of streptozotocin-induced diabetic mice: a control and a TRX group. In addition, TRX-transgenic (Tg) mice were alternately used as islet donors or recipients.ResultsThe changes in blood glucose levels were significantly lower in the TRX group compared with the TRX-Tg donor and control groups (p<0.01). Glucose tolerance and the residual graft mass were considerably better in the TRX group. TRX significantly suppressed the serum levels of interleukin-1β (p<0.05), although neither anti-apoptotic nor anti-chemotactic effects were observed. Notably, no increase in the 8-hydroxy-2′-deoxyguanosine level was observed after islet infusion, irrespective of TRX administration.ConclusionsThe present study demonstrates that overexpression of TRX on the islet grafts is not sufficient to improve engraftment. In contrast, TRX administration to the recipients exerts protective effects on transplanted islet grafts by suppressing the serum levels of interleukin-1β. However, TRX alone appears to be insufficient to completely prevent early graft loss after islet transplantation. We therefore propose that a combination of TRX and other anti-inflammatory treatments represents a promising regimen for improving the efficacy of islet transplantation.

Inhibition of alternative complement pathway prevents the immediate complement activation after intraportal adult porcine islet transplantation in non-human primates

Inhibition of alternative complement pathway prevents the immediate complement activation after intraportal adult porcine islet transplantation in non-human primates

Potential of Protein Phosphatase Inhibitor 1 As Biomarker of Pancreatic β-Cell Injury In Vitro and In Vivo

There is a need for plasma-based tests that can directly measure the extent of β-cell injury in vivo in patients receiving islet grafts and in animal models. In this study, we propose protein phosphatase 1, regulatory (inhibitor) subunit 1A (PPP1R1A) as a novel biomarker for acute β-cell destruction. Liquid chromatography–tandem mass spectrometry proteome analysis of fluorescence-activated cell sorter–purified β-cells, tissue-comparative Western blotting, and immunohistochemistry indicated relatively high molar abundance and selectivity of PPP1R1A in β-cells. PPP1R1A was discharged into the extracellular space of chemically injured rat and human islets in vitro, proportionate to the extent of β-cell death. Streptozotocin injection in rats led to a progressive PPP1R1A depletion from the cytoplasm of disintegrating β-cells and a marked surge in plasma levels detectable by an affinity-capture method. A similar massive PPP1R1A discharge in blood was also detected in three patients immediately after intraportal islet transplantation. Our findings provide first proof-of-principle for PPP1R1A as real-time biomarker of β-cell destruction in animal models and patients and warrant development of more sensitive methods for its further validation in clinical trials.

Inhibition of instant blood-mediated inflammatory responses by co-immobilization of sCR1 and heparin on islets

Intraportal transplantation of islets of Langerhans is followed by marked islet loss, mainly caused by instant blood-mediated inflammatory responses (IBMIR). We previously developed a method of co-immobilizing sCR1 and heparin on islets. Here we examined whether this process could reduce islet loss following intraportal islet transplantation in a syngeneic mouse model. sCR1-heparin islets or unmodified islet controls were transplanted into the livers of streptozotocin-induced diabetic mice. Transplantation of 100 and 125 sCR1-heparin islets normalized blood glucose levels in 8 of 9 (88.9%) and 9 of 9 diabetic mice (100%), respectively, whereas transplantation of 100 and 125 non-treated islets induced normoglycemia in 0 of 9 and 2 of 9 diabetic mice, respectively. Fibrin staining and plasma insulin measurements indicated that, compared to non-treated islets, sCR1-heparin islet transplantation was associated with fewer blood clots around islets, and significantly less insulin leakage from damaged islets at 1 h post-transplantation. Long-term follow-up of the sCR1-heparin islet group showed islet cells in the livers and insulin expression. In conclusion, co-immobilization of sCR1 and heparin on islets could effectively reduce islet damage by IBMIR, and might be useful to enable transplantation with only one donor and one recipient.

The Magnetic Appeal of Silencing Theranostics

Islet cell transplantation has recently emerged as a promising means to treat patients with type 1 diabetes. Despite significant success with the Edmonton protocol for intraportal naked islet transplantation (1), there is an active debate regarding whether or not the overall clinical success rates have met initial expectations (2,3). The next vital steps for improving islet cell transplantation protocols include developing a nontoxic and effective means to prevent graft rejection and islet cell death, as well as suitable imaging techniques to noninvasively probe islet engraftment and long-term survival. Although it is currently unknown how long and what percentage of grafted cells survive, estimates suggest that up to only 30% of the initial β-cell mass remains after 2 weeks (4). It is believed that, aside from immunorejection, rapid islet cell death may occur from lack of oxygen before and after transplantation. One way to increase islet cell survival is to store them in perfluorocarbon emulsions that can act as an oxygen sink, leading to improved oxygenation (5). Another approach is to prevent immunorejection by encapsulating islets in semipermeable alginate capsules (6) or a combination of the two approaches (7). Although monitoring of islet engraftment following intraportal injection is possible by prelabeling naked cells (8,9 …

Allogeneic Pancreatic Islet Transplantation Into the Bone Marrow Cavity in Diabetic Rhesus Monkey

Introduction: Liver is the general implantation site for clinical islet transplantation. but it has some disadvantages of physiologic and anatomic characterization for islet engraftment. Intraportal islet transplantation also has technical limitations and the risk of the instant blood-mediated inflammatory reaction (IBMIR) triggered by the islets. In recent years, bone marrow had been reported as an alternative site for islet transplantation in rats and mice. And these studies demonstrated that bone marrow cavity offers a widely distributed and well-vascularized microenvironment. In this study, we investigated whether the bone marrow cavity is a suitable site for islet transplantation in diabetic rhesus monkey. Methods: The monkey pancreas were digested with Collagenase P and purified by discontinued Ficoll density-gradient centrifugation. The glucose stimulated insulin secretion and cell viability of purified islets were assessed before transplantation. 3254±1140 IEQ/kg islets (5ml suspension) were transplanted into the bone marrow of 6 diabetic rhesus monkeys respectively through the medial tibial plateau. No immunosuppressant was used after transplantation. The recipients were evaluated by the following parameters: The general condition (body weight, food intake, behavioral activity, and etc.); Laboratory testing: blood biochemistry and routine blood examinations; and Glycemic control: fasting blood glucose (FBG), postprandial blood glucose (PBG). Results: Pancreatic islets can be successfully engrafted into the bone marrow of rhesus monkey. During the investigated 60 days, all the recipients were in good general health. Of the 6 receptors, 1 (17%) attained insulin independence with good glycemic control for 24 days, and little insulin dependence with good glycemic control until now; 5 (83%) reduced insulin dependence (18 vs. 6˜14 IU/day) with good glycemic control for mor than 45 days. Conclusions: These preliminary results show that, without immunosuppression treatment, the allogeneic islets can survive and remain functionally for a long period in bone marrow cavity in diabetic rhesus monkey. Further research the functional interaction between islet engraftment and bone marrow with nonhuman primate diabetic model, may provide experimental data for clinical application of bone marrow cavity islet transplant.Figure: [Extra Insulin Dose]Figure: [FBG Level]

Bone Marrow Cavity Is a Feasible Site for Islet Transplantation in Nonhuman Primates

Introduction: The liver, which is currently the only approved site for clinical islet transplantation, presents numerous immunologic and non-immunologic barriers to islet engraftment and survival. The bone marrow cavity represents an attractive alternative site: It avoids liver-specific first-pass metabolism, is easily accessed, and intraosseous delivery has successfully been used as an alternative to intravenous delivery for human bone marrow transplantation. In light of the successful transplantation of islets into the bone marrow of rodents, we hypothesized that the bone marrow could be a feasible site for islet transplantation in nonhuman primates. Methods: Five rhesus macaques were rendered diabetic with streptozotocin. A mean of 13,991 (±3,114) MHC-mismatched islet equivalents per kilogram were transplanted into the bone marrow cavity at five separate sites, including bilateral humeri, bilateral femurs and the iliac crest. Recipients were treated with an immunosuppression regimen that we have previously shown significantly prolongs islet allograft survival: induction therapy with TS1/22, a monoclonal antibody to LFA-1, and belatacept maintenance therapy. Rejection was defined as fasting blood glucose greater than 130mg/dL on two consecutive days. Results: Four of five recipients achieved immediate insulin-independent normoglycemia. The fifth recipient required insulin therapy to maintain normoglycemia; this rate of engraftment with insulin independence is similar to that seen with intraportal islet transplantation. Rejection-free survival for recipients with functional grafts is currently 80, >79, >51 and >29 days. Conclusion: The bone marrow cavity may be a feasible alternative to intraportal islet transplantation and provide an attractive option for clinical islet transplantation.

Thioredoxin-1 Attenuates Early Graft Loss after Intraportal Islet Transplantation in Mice

Thioredoxin-1 Attenuates Early Graft Loss after Intraportal Islet Transplantation in Mice

Quantification of Islet Loss During Immune Rejection Using Iron-Labeled Islet Cells by 3T MRI in the Rat Model

Background: Monitoring the fate of transplanted islets remains a major challenge in clinical islet transplantation (IT). We developed a MRI imaging protocol (3D difference ultra-short echo-time = dUTE), resulting in positive contrast images of superparamagnetic iron-oxide (SPIO) nanoparticles-labeled islets transplanted in rat. Our aim was to compare the evolution of the MRI signal in 3 types of IT in the rat model. Methods: Syngeneic and allogeneic SPIO-labeled islets (ferucarbotran, 280μg/ml iron) were injected intraportally into streptozotocin-induced diabetic Lewis rats. Xenogeneic human islets were transplanted into normoglycaemic rats and graft functionality was evaluated by serum human C-peptide levels. Images were performed on a 3T clinical scanner, from day 0 up to day 106. An intensity threshold was applied within the liver region, giving automatically the number of dUTE-enhanced pixels, allowing quantification. Histological studies included insulin, CD4 and CD8 staining and iron detection. Results: Decay rates for the 3 types of transplantation were different (Figure 1). The syngeneic graft signal showed a 20% decrease during the first 2 weeks and remained stable up thereafter. For allogeneic transplantation, islet rejection (G>20 mmol/l) occurred at day 7.7±0.5 and 41%±12 of the initial signal was lost. In the xenogeneic model, 43%±8 of the initial signal was lost by day 3, when significant basal and stimulated human C-peptide levels were not detected any longer. Islet rejection was confirmed by islet CD4+ and CD8+ cell infiltration and loss of insulin staining. When allogeneic transplanted rats are treated with anti-lymphocytic serum, glycemia remains normal but MRI signal shows a slight decrease corresponding to sub-clinical immune rejection. Conclusion: After intra-portal IT and during immune rejection, the loss of SPIO-labeled islets can be monitored with clinical-grade 3T MRI imaging using a semi-automatic quantification method. The decay of the signal is correlated with the graft function and histological findings.

Inhibitory Effect of Thrombomodulin on HMGB1-Stimulated IFN-γ Production of Hepatic NKT and Gr-1+ Cells, Facilitating to Prevent Early Loss of Transplanted Islets in the Liver of Mice

Currently, insulin independence in patients with IDDM has been hardly achieved after pancreatic islet transplantation (tx) from a single donor mainly due to early loss of transplanted islets. Previously, we have shown in mice that pancreatic islets contain abundant HMGB1, released into circulation and triggering NKT cell-dependent IFN-γ production of Gr-1+ cells (neutrophils) in the liver receiving islets (JCI 2010) which is an essential component of early loss of transplanted islets (JEM 2005). In the present study, we hypothesize that the beneficial effect of thrombomodulin (TM) on engraftments of islets in the liver might be mediated through inhibition of HMGB1-NKT-Gr-1+cell pathways since TM has been reported to produce sequestration of HMGB1 (JCI 2005). Hyperglycemia of STZ-diabetic mice (C57BL/6) receiving 200 syngenic islets from a single donor into the liver via the portal vein was ameliorated when TM was administered IV for 3 times (0, 12 and 24hrs, 200μg/injection/mouse, n=5), while those of mice (n=5) treated with saline did not. Morphologically, intact islet grafts with well granulated β cells were seen in the liver of normoglycemic recipients treated with TM, while in contrast, degenerated islets with de-granulated β cells were seen in hyperglycemic control mice. IPGTT (1g/kg glucose) at 60 days after tx revealed that the glucose tolerance of TM-treated mice receiving 200 islets (n=5) was superior to that of normoglycemic mice receiving 400 islets without TM treatment (n=5). FACS analysis showed that IFN-γ production of NKT cells and Gr-1+ cells accumulated in the liver of mice receiving islets and treated with saline was up-regulated at 6 hours after tx as reported previously, while in contrast, that in mice receiving 200 islets and treated with TM was down-regulated with reduction in number of infiltrating Gr-1+ cells. IFN-γ production of NKT cells and Gr-1+ cells accumulated in the liver of mice at 2 hours after the IV injection of HMGB1 (100 μg/injection/mouse) without islet transplantation was up-regulated, while in marked contrast, that in mice treated with TM (500μg, iv) prior to the HMGB1 injection was down-regulated with reduced number of infiltrated Gr-1+ cells. These findings indicate that TM prevents the early loss of transplanted islets in the liver of mice through inhibition of stimulatory effects of HMGB1. Importantly, recombinant TM has already been used in clinics with great impact on its efficacy for the treatment of sepsis with disseminated intravascular coagulation in Japan. Thus, the safety issue regarding the clinical use of TM has been cleared and it seems ready to apply this to clinical islet transplantation to improve the efficiency of intraportal islet transplantation.

A Novel Monoclonal Antibody to CD40 Prolongs Islet Allograft Survival

The importance of CD40/CD154 costimulatory pathway blockade in immunosuppression strategies is well-documented. Efforts are currently focused on monoclonal antibodies specific for CD40 because of thromboembolic complications associated with monoclonal antibodies directed towards CD154. Here we present the rational development and characterization of a novel antagonistic monoclonal antibody to CD40. Rhesus macaques were treated with the recombinant anti-CD40 mAb, 2C10, or vehicle before immunization with keyhole limpet hemocyanin (KLH). Treatment with 2C10 successfully inhibited T cell-dependent antibody responses to KLH without significant peripheral B cell depletion. Subsequently, MHC-mismatched macaques underwent intraportal allogeneic islet transplantation and received basiliximab and sirolimus with or without 2C10. Islet graft survival was significantly prolonged in recipients receiving 2C10 (graft survival time 304, 296, 265, 163 days) compared to recipients receiving basiliximab and sirolimus alone (graft survival time 8, 8, 10 days). The survival advantage conferred by treatment with 2C10 provides further evidence for the importance of blockade of the CD40/CD154 pathway in preventing alloimmune responses. 2C10 is a particularly attractive candidate for translation given its favorable clinical profile.

Three Aspects Are Critical for Carrying Out Intraportal Islet Transplants Successfully in a Diabetes Mouse Model

Three Aspects Are Critical for Carrying Out Intraportal Islet Transplants Successfully in a Diabetes Mouse Model

Counting Small Hypointense Spots Confounds the Quantification of Functional Islet Mass Based on Islet MRI

Iron-containing fragmented islets or free iron released from dying cells could confound the interpretation of MRI of iron nanoparticle-labeled islets. Exclusion of small hypointense spots could be a useful strategy to avoid such artifact. We investigated whether this strategy could improve the estimation of functioning islet mass after islet transplantation. Using a rat syngeneic intraportal islet transplantation model, we quantitatively assessed the relationships between total area, number of hypointense spots on MRI that belong to each size quartile and glycemic control of the recipients. The total area of hypointense spots on MRI was greater in the recipients that achieved diabetes reversal (p = 0.002), whereas the total number of hypointense spots was not different (p = 0.757). Exclusion of small hypointense spots improved the association between the number of hypointense spots and the blood glucose level of the recipients (p < 0.001). Ex-vivo imaging and histologic study confirmed that some small hypointense spots represent the phagocytosed free iron. Exclusion of small hypointense spots improved the quantification of the functional islet mass based on islet MRI. This would be a useful principle in the development of an algorithm to estimate functioning islet mass based on islet MRI.

Percutaneous transhepatic portal catheterization guided by ultrasound technology for islet transplantation in rhesus monkey

Pig islet xenotransplantation has the potential to overcome the shortage of donated human islets for islet cell transplantation in type 1 diabetes. Testing in non-human primate models is necessary before clinical application in humans. Intraportal islet transplantation in monkeys is usually performed by surgical infusion during laparotomy or laparoscopy. In this paper, we describe a new method of percutaneous transhepatic portal catheterization (PTPC) as an alternative to current methods of islet transplantation in rhesus monkeys. We performed ultrasound-guided PTPC in five adult rhesus monkeys weighing 7-8 kg, with portal vein catheterization confirmed by digital subtraction angiography. We monitored for complications in the thoracic and abdominal cavity. To evaluate the safety of ultrasound-guided PTPC, we recorded the changes in portal pressure throughout the microbead transplantation procedure. Ultrasound-guided PTPC and infusion of 16 000 microbeads/kg body weight into the portal vein was successful in all five monkeys. Differences in the hepatobiliary anatomy of rhesus monkeys compared to humans led to a higher initial complication rate. The first monkey died of abdominal hemorrhage 10 hours post-transplantation. The second suffered from a mild pneumothorax but recovered fully after taking only conservative measures. After gaining experience with the first two monkeys, we decreased both the hepatic puncture time and the number of puncture attempts required, with the remaining three monkeys experiencing no complications. Portal pressures initially increased proportional to the number of transplanted microbeads but returned to pre-infusion levels at 30 minutes post-transplantation. The changes in portal pressures occurring during the procedure were not significantly different. Ultrasound-guided PTPC is an effective, convenient, and minimally invasive method suitable for use in non-human primate models of islet cell transplantation provided that care is taken with hepatic puncture. Its advantages must be weighed against the risks of procedure-related complications.

Partial hepatectomy improves the outcome of intraportal islet transplantation by promoting revascularization

Revascularization of grafts is one of the important key factors for the success of islet transplantation. After partial hepatectomy, many growth factors such as hepatocyte growth factor and vascular endothelial growth factor are increased in the remnant liver. These growth factors have properties that promote angiogenesis. This might be an optimal environment for revascularization of islets transplanted intraportally. To verify this hypothesis, syngeneic islets (330 per recipient) were transplanted into the right hepatic lobes of streptozotocin-induced diabetic Balb/c mice with (hepatectomy group) or without (control group) left liver resection. Blood glucose was monitored for 28 d after transplantation. Glucose tolerance test was performed on post-operative day (POD) 30, and histological assessments were performed on POD 7 and 30 respectively. Analysis revealed that 36.7% of the control and 90.0% of the hepatectomy mice attained normoglycemia during the observation period (*p = 0.0142). Glucose tolerance was improved in the hepatectomy group (Area under the curve of intraperitoneal glucose tolerance tests on POD 30, Control; 47,700 ± 5,890 min*mg/dl, Hepatectomy; 26,000 ± 2,060 min*mg/dl: **p = 0.00314). Revascularization of grafted islets was more pronounced in the hepatectomy group (Vessel number per islet area on POD 7, Control; 3.20 ± 0.463 × 10−4/µm2, Hepatectomy; 7.08 ± 0.513 × 10−4/µm2: **p < 0.01). In the present study, partial hepatectomy (30%) improved the outcome of intraportal islet transplantation. Revascularization of islets transplanted into the liver may have been promoted by the induction of liver regeneration.

Nerve growth factor is associated with islet graft failure following intraportal transplantation

Nerve growth factor (NGF) has recently been recognized as an angiogenic factor with an important regulatory role in pancreatic β-cell function. We previously showed that treatment of pancreatic islets with NGF improved their quality and viability. Revascularization and survival of islets transplanted under the kidney capsule were improved by NGF. However, the usefulness of NGF in intraportal islet transplantation was not previously tested. To resolve this problem, we transplanted syngeneic islets (360 islet equivalents per recipient) cultured with or without NGF into the portal vein of streptozotocin-induced diabetic BALB/c mice. Analysis revealed that 44.4% (4/9) of control and 12.5% (1/8) of NGF-treated mice attained normoglycemia (≤ 200 mg/dL) (p = 0.195). NGF-treated islets led to worse graft function (area under the curve of intraperitoneal glucose tolerance tests (IPGTT) on post-operative day (POD) 30, control; 35,800 ± 3,960 min*mg/dl, NGF-treated; 47,900 ± 3,220 min*mg/dl: *p = 0.0348). NGF treatment of islets was also associated with increased graft failure [the percentage of TdT-mediated dUTP-biotin nick-end labeling (TUNEL)-positive and necrotic transplanted islets on POD 5, control; 23.8% (5/21), NGF-treated; 52.9% (9/17): p = 0.0650] following intraportal islet transplantation. Nonviable (TUNEL-positive and necrotic) islets in both groups expressed vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α). On the other hand, viable (TUNEL-negative and not necrotic) islets in both groups did not express VEGF and HIF-1α. In the present study, pre-transplant NGF treatment was associated with impaired survival and angiogenesis of intraportal islet grafts. The effect of NGF on islet transplantation may significantly vary according to the transplant site.

Portal Vein Thrombosis Is a Potentially Preventable Complication in Clinical Islet Transplantation

Percutaneous transhepatic portal access avoids surgery but is rarely associated with bleeding or portal venous thrombosis (PVT). We herein report our large, single-center experience of percutaneous islet implantation and evaluate risk factors of PVT and graft function. Prospective data were collected on 268 intraportal islet transplants (122 subjects). A portal venous Doppler ultrasound was obtained on Days 1 and 7 posttransplant. Therapeutic heparinization, complete ablation of the portal catheter tract with Avitene paste and limiting packed cell volume (PCV) to <5 mL completely prevented any portal thrombosis in the most recent 101 islet transplant procedures over the past 5 years. In the previous cumulative experience, partial thrombosis did not affect islet function. Standard liver volume correlated negatively (r =-0.257, p < 0.001) and PCV correlated positively with portal pressure rise (r = 0.463, p < 0.001). Overall, partial portal thrombosis occurred after 10 procedures (overall incidence 3.7%, most recent 101 patient incidence 0%). There were no cases of complete thrombosis and no patient developed sequelae of portal hypertension. In conclusion, portal thrombosis is a preventable complication in clinical islet transplantation, provided therapeutic anticoagulation is maintained and PCV is limited to <5 mL.