Liver transplantation as last-resort treatment for patients with bile duct injuries following cholecystectomy: a multicenter analysis.

BACKGROUND: Liver transplantation (LT) has been used as a last resort in patients with end-stage liver disease due to bile duct injuries (BDI) following cholecystectomy. Our study aimed to identify and evaluate factors that cause or contribute to an extended liver disease that requires LT as ultimate solution, after BDI during cholecystectomy. METHODS: Data from 8 high-volume LT centers relating to patients who underwent LT after suffering BDI during cholecystectomy were prospectively collected and retrospectively analyzed. RESULTS: Thirty-four patients (16 men, 18 women) with a median age of 45 (range 22-69) years were included in this study. Thirty of them (88.2%) underwent LT because of liver failure, most commonly as a result of secondary biliary cirrhosis. The median time interval between BDI and LT was 63 (range 0-336) months. There were 23 cases (67.6%) of postoperative morbidity, 6 cases (17.6%) of post-transplant 30-day mortality, and 10 deaths (29.4%) in total after LT. There was a higher probability that patients with concomitant vascular injury (hazard ratio 10.69, P=0.039) would be referred sooner for LT. Overall survival following LT at 1, 3, 5 and 10 years was 82.4%, 76.5%, 73.5% and 70.6%, respectively. CONCLUSION: LT for selected patients with otherwise unmanageable BDI following cholecystectomy yields acceptable long-term outcomes.

Immunosuppression in Liver Transplantation: State of the Art and Future Perspectives.

BACKGROUND: Novel drugs and combinations for immunosuppression (IS) after liver transplantation is one main reason for improved graft and patient survival seen in the last decades. The backbone of IS is still steroids and calcineurin inhibitors, although novel drugs are being introduced, such as the mammalian target of rapamycin inhibitors (mTOR inhibitor). The challenge today, along with increased patient survival, is the adverse effects of long-term use of immunosuppressive drugs, mainly nephrotoxicity and other serious adverse effects. Concepts: The ultimate outcome after liver transplantation would be achieving tolerance, a state where all IS can be withdrawn. In the meantime, different approaches to reduce and withdraw IS have been tested out in different clinical trials with the aim to reduce the adverse effects of steroids and calcineurin inhibitors. This has formed the basis of today's clinical practice. The different combinations of immunosuppressive drugs have included mTOR inhibitor such as everolimus and different induction drugs such as anti-interleukin 2 receptor antibodies. Regarding induction drugs, lymphocyte depleting (alemtuzumab and ATG) and non-depleting agents, such as basiliximab, have shown advantageous effects. SUMMARY: Alongside steroid and calcineurin inhibitors reduction or elimination, current strategies for post-liver transplantation immunosuppression explore combinations of novel agents. The gauge (or yardstick) here is the fine balance between the adverse effects of IS drugs and the risk of rejection. Long-term maintenance IS regimens, development of tolerance and antibody-mediated rejection are also discussed in this review.

Open Randomized Multicenter Study to Evaluate Safety and Efficacy of Low Molecular Weight Sulfated Dextran in Islet Transplantation.

BACKGROUND: When transplanted human pancreatic islets are exposed to blood during intraportal infusion, an innate immune response is triggered. This instant blood-mediated inflammatory reaction (IBMIR) activates the coagulation and complement cascades and leads to the destruction of 25% of all transplanted islets within minutes, contributing to the need, in most patients, for islets from more than 1 donor. Low molecular dextran sulfate (LMW-DS) has been shown in experimental settings to inhibit IBMIR. METHODS: The Clinical Islet Transplantation consortium 01 study was a phase II, multicenter, open label, active control, randomized study. Twenty-four subjects were randomized to peritransplant intraportal and systemic treatment with either LMW-DS or heparin, targeting an activated partial thromboplastin time of 150 ± 10 seconds and 50 ± 5 seconds, respectively. C-peptide response was measured with a mixed meal tolerance test at 75 and 365 days after transplant. RESULTS: Low molecular dextran sulfate was safe and well tolerated with similar observed adverse events (mostly attributed to immunosuppression) as in the heparin arm. There was no difference in the primary endpoint (stimulated C-peptide 75 ± 5 days after the first transplant) between the 2 arms (1.33 ± 1.10 versus 1.56 ± 1.36 ng/mL, P = 0.66). Insulin requirement, metabolic parameters, Clarke and HYPO score, quality of life, and safety were similar between the 2 treatments groups. CONCLUSIONS: Even with low dosing, LMW-DS showed similar efficacy in preventing IBMIR to promote islet engraftment when compared to "state-of-the art" treatment with heparin. Furthermore, no substantial differences in the efficacy and safety endpoints were detected, providing important information for future studies with more optimal dosing of LMW-DS for the prevention of IBMIR in islet transplantation.

First Scandinavian Protocol for Controlled Donation After Circulatory Death Using Normothermic Regional Perfusion.

BACKGROUND: Donation after circulatory death (DCD) can increase the pool of available organs for transplantation. This pilot study evaluates the implementation of a controlled DCD (cDCD) protocol using normothermic regional perfusion in Norway. METHODS: Patients aged 16 to 60 years that are in coma with documented devastating brain injury in need of mechanical ventilation, who would most likely attain cardiac arrest within 60 minutes after extubation, were eligible. With the acceptance from the next of kin and their wish for organ donation, life support was withdrawn and cardiac arrest observed. After a 5-minute no-touch period, extracorporeal membrane oxygenation for post mortem regional normothermic regional perfusion was established. Cerebral and cardiac reperfusion was prevented by an aortic occlusion catheter. Measured glomerular filtration rates 1 year postengraftment were compared between cDCD grafts and age-matched grafts donated after brain death (DBD). RESULTS: Eight cDCD were performed from 2014 to 2015. Circulation ceased median 12 (range, 6-24) minutes after withdrawal of life-sustaining treatment. Fourteen kidneys and 2 livers were retrieved and subsequently transplanted. Functional warm ischemic time was 26 (20-51) minutes. Regional perfusion was applied for 97 minutes (54-106 minutes). Measured glomerular filtration rate 1 year postengraftment was not significantly different between cDCD and donation after brain death organs, 75 (65-76) vs 60 (37-112) mL/min per 1.73 m2 (P = 0.23). No complications have been observed in the 2 cDCD livers. CONCLUSION: A protocol for cDCD is successfully established in Norway. Excellent transplant outcomes have encouraged us to continue this work addressing the shortage of organs for transplantation.

Human Adipose-Derived Mesenchymal Stem Cells Respond to Short-Term Hypoxia by Secreting Factors Beneficial for Human Islets In Vitro and Potentiate Antidiabetic Effect In Vivo.

Adipose-derived mesenchymal stem cells (ASCs) release factors beneficial for islets in vitro and protect against hyperglycemia in rodent models of diabetes. Oxygen tension has been shown to induce metabolic changes and alter ASCs' release of soluble factors. The effects of hypoxia on the antidiabetic properties of ASCs have not been explored. To investigate this, we incubated human ASCs for 48 h in 21% (normoxia) or 1% O2 (hypoxia) and compared viability, cell growth, surface markers, differentiation capability, and soluble factors in the conditioned media (CM). Human islets were exposed to CM from ASCs incubated in either normoxia or hypoxia, and islet function and apoptosis after culture with or without proinflammatory cytokines were measured. To test hypoxic preconditioned ASCs' islet protective effects in vivo, ASCs were incubated for 48 h in normoxia or hypoxia before being injected into Balb/c Rag 1-/- immunodeficient mice with streptozotocin-induced insulitis. Progression of diabetes and insulin content of pancreas were measured. We found that incubation in hypoxia was well tolerated by ASCs and that levels of VEGF-A, FGF-2, and bNGF were elevated in CM from ASCs incubated in hypoxia compared to normoxia, while levels of HGF, IL-8, and CXCL1 were reduced. CM from ASCs incubated in hypoxia significantly improved human islet function and reduced apoptosis after culture, and reduced cytokine-induced apoptosis. In our mouse model, pancreas insulin content was higher in both groups receiving ASCs compared to control, but the mice receiving preconditioned ASCs had lower random and fasting blood glucose, as well as improved oral glucose tolerance compared to untreated mice. In conclusion, our in vitro results indicate that the islet protective potential of ASCs improves in hypoxia, and we give insight into factors involved in this. Finally we show that hypoxic preconditioning potentiates ASCs' antidiabetic effect in vivo.

Glial cell-line derived neurotrophic factor protects human islets from nutrient deprivation and endoplasmic reticulum stress induced apoptosis.

One of the key limitations to successful human islet transplantation is loss of islets due to stress responses pre- and post-transplantation. Nutrient deprivation and ER stress have been identified as important mechanisms leading to apoptosis. Glial Cell-line Derived Neurotrophic Factor (GDNF) has recently been found to promote islet survival after isolation. However, whether GDNF could rescue human islets from nutrient deprivation and ER stress-mediated apoptosis is unknown. Herein, by mimicking those conditions in vitro, we have shown that GDNF significantly improved glucose stimulated insulin secretion, reduced apoptosis and proinsulin:insulin ratio in nutrient deprived human islets. Furthermore, GDNF alleviated thapsigargin-induced ER stress evidenced by reduced expressions of IRE1α and BiP and consequently apoptosis. Importantly, this was associated with an increase in phosphorylation of PI3K/AKT and GSK3B signaling pathway. Transplantation of ER stressed human islets pre-treated with GDNF under kidney capsule of diabetic mice resulted in reduced expressions of IRE1α and BiP in human islet grafts with improved grafts function shown by higher levels of human C-peptide post-transplantation. We suggest that GDNF has protective and anti-apoptotic effects on nutrient deprived and ER stress activated human islets and could play a significant role in rescuing human islets from stress responses.

Hepatic Epithelioid Hemangioendothelioma and Adult Liver Transplantation: Proposal for a Prognostic Score Based on the Analysis of the ELTR-ELITA Registry.

BACKGROUND: Hepatic epithelioid hemangioendothelioma (HEHE) is a rare vascular tumor which has an intermediate aggressive behavior. Although the value of liver transplantation (LT) is well established, its place in the management of HEHE is still unclear. The aim of this study is to confirm, based on a very large patient cohort, the value of LT in the management of HEHE and to identify risk factors for post-LT recurrence. METHODS: The outcome of 149 transplant recipients with HEHE recorded in the European Liver Transplant Registry during the period November 1984 to May 2014 was analyzed. Median post-LT follow-up was 7.6 years (interquartile range, 2.8-14.4). RESULTS: Cox regression analysis showed that macrovascular invasion (hazard ratio [HR], 4.8; P < 0.001), pre-LT waiting time of 120 days or less (HR, 2.6; P = 0.01) and hilar lymph node invasion (HR = 2.2; P = 0.03), but not pre-LT extrahepatic disease, were significant risk factors for recurrence. These findings, which were also confirmed in a propensity score analysis, allowed the development of a HEHE-LT score enabling stratification of patients in relation to their risk of tumor recurrence. Patients with a score of 2 or less had a much better 5-year disease-free survival compared to those having a score of 6 or higher (93.9% vs 38.5%; P < 0.001). CONCLUSIONS: The analysis of this (largest in the world) HEHE adult liver recipient cohort clearly confirms the value of LT in the treatment of this rare disorder and also permits identification of patients at risk of posttransplant recurrence. Posttransplant follow-up should take the HEHE-LT score into account. Extrahepatic disease localization is reconfirmed not to be a contraindication for LT.

Cost and clinical outcome of islet transplantation in Norway 2010-2015.

Islet transplantation is a minimally invasive ß-cell replacement strategy. Islet transplantation is a reimbursed treatment in Norway. Here, we summarize the cost and clinical outcome of 31 islet transplantations performed at Oslo University Hospital (OUS) from January 2010 to June 2015. Patients were retrospectively divided into three groups. Thirteen patients received either one or two islet transplantation alone (ITA), while five patients received islet transplantation after previous solid organ transplantation. For the group receiving 2 ITA, Kaplan-Meier estimates show an insulin independence of 20% more than 4 years after their last transplantation. An estimated 70% maintain at least partial graft function, defined as fasting C-peptide >0.1 nmol L-1 , and 47% maintain a HbA1c below 6.5% or 2 percent points lower than before ITA. For all groups combined, we estimate that 44% of the patients have a 50% reduction in insulin requirement 4 years after the initial islet transplantation. The average cost for an islet transplantation procedure was 347 297±60 588 NOK, or 35 424±6182 EUR, of which isolation expenses represent 34%. We hereby add to the common pool of growing experience with islet transplantation and also describe the cost of the treatment at our center.

Liver Transplantation for Hepatic Trauma: A Study From the European Liver Transplant Registry.

BACKGROUND: Liver transplantation is the most extreme form of surgical management of patients with hepatic trauma, with very limited literature data supporting its use. The aim of this study was to assess the results of liver transplantation for hepatic trauma. METHODS: This retrospective analysis based on European Liver Transplant Registry comprised data of 73 recipients of liver transplantation for hepatic trauma performed in 37 centers in the period between 1987 and 2013. Mortality and graft loss rates at 90 days were set as primary and secondary outcome measures, respectively. RESULTS: Mortality and graft loss rates at 90 days were 42.5% and 46.6%, respectively. Regarding general variables, cross-clamping without extracorporeal veno-venous bypass was the only independent risk factor for both mortality (P = 0.031) and graft loss (P = 0.034). Regarding more detailed factors, grade of liver trauma exceeding IV increased the risk of mortality (P = 0.005) and graft loss (P = 0.018). Moreover, a tendency above the level of significance was observed for the negative impact of injury severity score (ISS) on mortality (P = 0.071). The optimal cut-off for ISS was 33, with sensitivity of 60.0%, specificity of 80.0%, positive predictive value of 75.0%, and negative predictive value of 66.7%. CONCLUSIONS: Liver transplantation seems to be justified in selected patients with otherwise fatal severe liver injuries, particularly in whom cross-clamping without extracorporeal bypass can be omitted. The ISS cutoff less than 33 may be useful in the selection process.

Evaluation of Perfluorohexyloctane/Polydimethylsiloxane for Pancreas Preservation for Clinical Islet Isolation and Transplantation.

This study aimed to evaluate a 50:50 mix of perfluorohexyloctane/polydimethylsiloxane 5 (F6H8S5) preservation of pancreases in a clinical setting compared with standard solutions for 1) cold ischemia time (CIT) 10 h and 2) an extended CIT 20 h. Procured clinical-grade pancreases were shipped in either F6H8S5 or in standard preservation solutions, that is, University of Wisconsin (UW) or Custodiol. F6H5S5 was preoxygenated for at least 15 min. Included clinical-grade pancreases were procured in UW or Custodiol. Upon arrival at the islet isolation laboratory, the duodenum was removed followed by rough trimming while F6H8S5 was oxygenated for 1520 min. Trimmed pancreases were immersed into oxygenated F6H8S5 and stored at 4C overnight followed by subsequent islet isolation. Pancreas preservation using F6H8S5 proved as effective as UW and Custadiol when used within CIT up to 10 h, in terms of both isolation outcome and islet functionality. Preservation in F6H8S5 of pancreases with extended CIT gave results similar to controls with CIT 10 h for both isolated islet functionality and isolation outcome. This study of clinically obtained pancreases indicates a clear benefit of using F6H8S5 on pancreases with extended CIT as it seems to allow extended cold ischemic time without affecting islet function and islet numbers.

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids.

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 µg/L), sirolimus (30 µg/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 µg/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus.

Intracellular sirolimus concentration is reduced by tacrolimus in human pancreatic islets in vitro.

MAIN PROBLEM: Islet transplantation has become a promising treatment for type 1 diabetes. However, immunosuppressive drugs used today cause islet deterioration and modification strategies are necessary. But little is known about pharmacokinetics interactions and intracellular concentrations of immunosuppressive drugs in human islets. METHODS: We determined the pharmacokinetics of tacrolimus and sirolimus in islets by measuring intracellular concentration after exposure alone or in combination at two different doses up to 48 h. A quantification technique established in our laboratory using a Micromass Quattro micro API MS/MS-instrument with electrospray ionization was used. Islets function was measured by oxygen consumption rates. Presence of drug transporters OATP1B1 and ABCB1 and metabolizing enzyme CYP3A4 in islets were quantified using real-time quantitative PCR. RESULTS: Islets incubated with tacrolimus and sirolimus had a significant decrease in intracellular concentration of sirolimus compared to sirolimus alone. Reduced intracellular sirolimus concentration was followed by increased p70S6k phosphorylation suggesting preservation of the mTOR-signaling pathway. Drug transporters OATP1B1 and ABCB1 and enzyme CYP3A4 were expressed in human islets, but were not involved in the reduced sirolimus concentration by tacrolimus. CONCLUSION: These findings provide new knowledge of the drug interaction between tacrolimus and sirolimus, suggesting that tacrolimus has an inhibitory effect on the intracellular concentration of sirolimus in human islets.

Liver transplantation in the Nordic countries - An intention to treat and post-transplant analysis from The Nordic Liver Transplant Registry 1982-2013.

AIM AND BACKGROUND: The Nordic Liver Transplant Registry (NLTR) accounts for all liver transplants performed in the Nordic countries since the start of the transplant program in 1982. Due to short waiting times, donor liver allocation has been made without considerations of the model of end-stage liver disease (MELD) score. We aimed to summarize key outcome measures and developments for the activity up to December 2013. MATERIALS AND METHODS: The registry is integrated with the operational waiting-list and liver allocation system of Scandiatransplant (www.scandiatransplant.org) and accounted at the end of 2013 for 6019 patients out of whom 5198 were transplanted. Data for recipient and donor characteristics and relevant end-points retransplantation and death are manually curated on an annual basis to allow for statistical analysis and the annual report. RESULTS: Primary sclerosing cholangitis, acute hepatic failure, alcoholic liver disease, primary biliary cirrhosis and hepatocellular carcinoma are the five most frequent diagnoses (accounting for 15.3%, 10.8%, 10.6%, 9.3% and 9.0% of all transplants, respectively). Median waiting time for non-urgent liver transplantation during the last 10-year period was 39 days. Outcome has improved over time, and for patients transplanted during 2004-2013, overall one-, five- and 10-year survival rates were 91%, 80% and 71%, respectively. In an intention-to-treat analysis, corresponding numbers during the same time period were 87%, 75% and 66%, respectively. CONCLUSION: The liver transplant program in the Nordic countries provides comparable outcomes to programs with a MELD-based donor liver allocation system. Unique features comprise the diagnostic spectrum, waiting times and the availability of an integrated waiting list and transplant registry (NLTR).

Graft function 1 year after pregnancy in an islet-transplanted patient.

Pancreatic islet transplantation is a treatment option for patients with type 1 diabetes (T1D), but pregnancy has generally not been advised for women after receiving an islet allograft. We hereby describe what is to our knowledge the first successful pregnancy and persistent graft function in a woman 4 years after her initial islet transplantation. A 37-year-old woman with brittle type 1 diabetes was transplanted with two separate islet graft infusions, eventually becoming insulin independent. Ten months after her second transplantation, her immunosuppression was switched from tacrolimus and sirolimus to tacrolimus, azathioprine, and prednisolone, due to her wish to become pregnant. She became pregnant one year later, and after 38 weeks of uncomplicated pregnancy, she gave birth to a healthy child by C-section. The current report suggests that pregnancy and childbirth can be accomplished after islet transplantation without loss of islet graft function.

Transplantation With Livers From Deceased Donors Older Than 75 Years.

BACKGROUND: The availability of donor organs limits the number of patients in need who are offered liver transplantation. Measures to expand the donor pool are crucial to prevent on-list mortality. The aim of this study was to evaluate the use of livers from deceased donors who were older than 75 years. METHODS: Fifty-four patients who received a first liver transplant (D75 group) from 2001 to 2011 were included. Donor and recipient data were collected from the Nordic Liver Transplant Registry and medical records. The outcome was compared with a control group of 54 patients who received a liver graft from donors aged 20 to 49 years (D20-49 group). Median donor age was 77 years (range, 75-86 years) in the D75 group and 41 years (range, 20-49 years) in the D20-49 group. Median recipient age was 59 years (range, 31-73 years) in the D75 group and 58 years (range, 31-74 years) in the D20-49 group. RESULTS: The 1-, 3-, and 5-year patient/graft survival values were 87/87%, 81/81%, and 71/67% for the D75 group and 88/87%, 75/73%, and 75/73% for the D20-49 group, respectively. Patient (P = 0.89) and graft (P = 0.79) survival did not differ between groups. The frequency of biliary complications was higher in the D75 group (29.6/13%, P = 0.03). CONCLUSIONS: Selected livers from donors over age 75 years should not be excluded based on age, which does not compromise patient or graft survival despite a higher frequency of biliary complications.

Continuous molecular adsorbent recirculating system treatment in 69 patients listed for liver transplantation.

OBJECTIVE: The molecular adsorbent recirculating system (MARS) is used to purify blood from albumin-bound toxins in patients with liver failure. However, the application of MARS has not demonstrated improved survival in randomized clinical trials and the clinical utility has not been finally established. In our department, the use of MARS is now restricted to the most critically ill patients with acute or acute on chronic liver failure. MATERIAL AND METHODS: Since 2005, we have treated 69 patients (30 males/39 females with median age of 49 years ranging from 1 months to 70 years) listed for liver transplantation (LT) with MARS. Median model of end-stage liver disease score in patients older than 12 years of age (n = 56) was 33 (interquartile range 26-39). The flow rate was 35-40 mL/kg/h and treatment kits were changed every 8-12 h. The patients were treated for a median of 27 h (range 1-144 h). RESULTS: Fifty-six patients (81%) were transplanted. Nine died before they could be transplanted, and four patients recovered without transplantation. Forty-six (82%) of the transplanted patients were alive 30 days after transplantation. Ammonium decreased modestly from a median of 148 to 124 µM (p = 0.03) during MARS treatment. We detected worsening of coagulopathy with significant decreases in platelet count and fibrinogen concentrations, and increase in International Normalized Ratio. Phosphate and magnesium decreased significantly during MARS treatment. CONCLUSION: Continuous MARS therapy may bridge liver failure patients to LT under close observation and treatment of coagulopathy and electrolyte disturbances.

Liver transplantation with deceased ABO-incompatible donors is life-saving but associated with increased risk of rejection and post-transplant complications.

ABO-incompatible (ABOi) liver transplantation (LT) with deceased donor organs is performed occasionally when no ABO-compatible (ABOc) graft is available. From 1996 to 2011, 61 ABOi LTs were performed in Oslo and Gothenburg. Median patient age was 51 years (range 13-75); 33 patients were transplanted on urgent indications, 13 had malignancy-related indications, and eight received ABOi grafts for urgent retransplantations. Median donor age was 55 years (range 10-86). Forty-four patients received standard triple immunosuppression with steroids, tacrolimus, and mycophenolate mofetil, and forty-four patients received induction with IL-2 antagonist or anti-CD20 antibody. Median follow-up time was 29 months (range 0-200). The 1-, 3-, 5-, and 10-year Kaplan-Meier estimates of patient survival (PS) and graft survival (GS) were 85/71%, 79/57%, 75/55%, and 59/51%, respectively, compared to 90/87%, 84/79%, 79/73%, and 65/60% for all other LT recipients in the same period. The 1-, 3-, 5-, and 10-year GS for A2 grafts were 81%, 67%, 62%, and 57%, respectively. In conclusion, ABOi LT performed with non-A2 grafts is associated with inferior graft survival and increased risk of rejection, vascular and biliary complications. ABOi LT with A2 grafts is associated with acceptable graft survival and can be used safely in urgent cases.

The effects of exendin-4 treatment on graft failure: an animal study using a novel re-vascularized minimal human islet transplant model.

Islet transplantation has become a viable clinical treatment, but is still compromised by long-term graft failure. Exendin-4, a glucagon-like peptide 1 receptor agonist, has in clinical studies been shown to improve insulin secretion in islet transplanted patients. However, little is known about the effect of exendin-4 on other metabolic parameters. We therefore aimed to determine what influence exendin-4 would have on revascularized minimal human islet grafts in a state of graft failure in terms of glucose metabolism, body weight, lipid levels and graft survival. Introducing the bilateral, subcapsular islet transplantation model, we first transplanted diabetic mice with a murine graft under the left kidney capsule sufficient to restore normoglycemia. After a convalescent period, we performed a second transplantation under the right kidney capsule with a minimal human islet graft and allowed for a second recovery. We then performed a left-sided nephrectomy, and immediately started treatment with exendin-4 with a low (20µg/kg/day) or high (200µg/kg/day) dose, or saline subcutaneously twice daily for 15 days. Blood was sampled, blood glucose and body weight monitored. The transplanted human islet grafts were collected at study end point and analyzed. We found that exendin-4 exerts its effect on failing human islet grafts in a bell-shaped dose-response curve. Both doses of exendin-4 equally and significantly reduced blood glucose. Glucagon-like peptide 1 (GLP-1), C-peptide and pro-insulin were conversely increased. In the course of the treatment, body weight and cholesterol levels were not affected. However, immunohistochemistry revealed an increase in beta cell nuclei count and reduced TUNEL staining only in the group treated with a low dose of exendin-4 compared to the high dose and control. Collectively, these results suggest that exendin-4 has a potential rescue effect on failing, revascularized human islets in terms of lowering blood glucose, maintaining beta cell numbers, and improving metabolic parameters during hyperglycemic stress.