Urologic complications after transplantation of 225 en bloc kidneys from small pediatric donors ≤20 kg: Incidence,management, and impact on graft survival

Pediatric en bloc kidney transplants (EBKs) from small deceased pediatric donors are associated with increased early graft loss and morbidity. Yet, urologic complications post‐EBK and their potential impact on graft survival have not been systematically studied. We retrospectively studied urological complications requiring intervention for 225 EBKs performed at our center January 2005 to September 2017 from donors ≤20 kg into recipients ≥18 years. Overall ureteral complication incidence after EBK was 9.8% (n = 22) (12% vs 2% for EBK donors 10 vs 10 kg, respectively [P = .031]). The most common post‐EBK urologic complication was a stricture (55%), followed by urine leak (41%). In all, 95% of all urologic complications occurred early within 5 months posttransplant (median, 138 days). Urologic complications could be successfully managed nonoperatively in 50% of all cases and had no impact on graft or patient survival. In summary, urologic complications after EBK were common, associated with lower donor weights, occurred early posttransplant, and were often amenable to nonoperative treatment, without adversely affecting survival. We conclude that the higher urologic complication rate after EBK (1) should not prevent increased utilization of small pediatric donor en bloc kidneys for properly selected recipients, and (2) warrants specific discussion with EBK recipients during the preoperative consent process.     

Unmethylated Insulin DNA Is Elevated After Total Pancreatectomy With Islet Autotransplantation: Assessment of a Novel Beta Cell Marker

Beta cell death may occur both after islet isolation and during infusion back into recipients undergoing total pancreatectomy with islet autotransplantation (TPIAT) for chronic pancreatitis. We measured the novel beta cell death marker unmethylated insulin (INS) DNA in TPIAT recipients before and immediately after islet infusion (n = 21) and again 90 days after TPIAT, concurrent with metabolic functional assessments (n = 25). As expected, INS DNA decreased after pancreatectomy (p = 0.0002). All TPIAT recipients had an elevated unmethylated INS DNA ratio in the first hours following islet infusion. In four samples (three patients), INS DNA was also assessed immediately after islet isolation and again before islet infusion to assess the impact of the isolation process: Unmethylated and methylated INS DNA fractions both increased over this interval, suggesting death of beta cells and exocrine tissue before islet infusion. Higher glucose excursion with mixed‐meal tolerance testing was associated with persistently elevated INS DNA at day 90. In conclusion, we observed universal early elevations in the beta cell death marker INS DNA after TPIAT, with pronounced elevations in the islet supernatant before infusion, likely reflecting beta cell death induced by islet isolation. Persistent posttransplant elevation of INS DNA predicted greater hyperglycemia at 90 days.     

Validation of the BETA‐2 Score: An Improved Tool to Estimate Beta Cell Function After Clinical Islet Transplantation Using a Single Fasting Blood Sample

The beta score, a composite measure of beta cell function after islet transplantation, has limited sensitivity because of its categorical nature and requires a mixed‐meal tolerance test (MMTT). We developed a novel score based on a single fasting blood sample. The BETA‐2 score used stepwise forward linear regression incorporating glucose (in millimoles per liter), C‐peptide (in nanomoles per liter), hemoglobin A1c (as a percentage) and insulin dose (U/kg per day) as continuous variables from the original beta score data set (n = 183 MMTTs). Primary and secondary analyses assessed the score's ability to detect glucose intolerance (90‐min MMTT glucose ≥8 mmol/L) and insulin independence, respectively. A validation cohort of islet transplant recipients (n = 114 MMTTs) examined 12 mo after transplantation was used to compare the score's ability to detect these outcomes. The BETA‐2 score was expressed as follows (range 0–42): A score <20 and ≥15 detected glucose intolerance and insulin independence, respectively, with >82% sensitivity and specificity. The BETA‐2 score demonstrated greater discrimination than the beta score for these outcomes (p < 0.05). Using a fasting blood sample, the BETA‐2 score estimates graft function as a continuous variable and shows greater discrimination of glucose intolerance and insulin independence after transplantation versus the beta score, allowing frequent assessments of graft function. Studies examining its utility to track long‐term graft function are required.     

Islet Heparan Sulfate but Not Heparan Sulfate Proteoglycan Core Protein Is Lost During Islet Isolation and Undergoes Recovery Post‐Islet Transplantation

Islet beta cells in situ express intracellular heparan sulfate (HS), a property previously shown in vitro to be important for their survival. We report that HS levels inside islet beta cells correlate with the novel intracellular localization of the HSPG core proteins for collagen type XVIII (Col18), a conventional extracellular matrix component. Syndecan‐1 (Sdc1) and CD44 core proteins were similarly localized inside beta cells. During isolation, mouse islets selectively lose HS to 11–27% of normal levels but retain their HSPG core proteins. Intra‐islet HS failed to recover substantially during culture for 4 days and was not reconstituted in vitro using HS mimetics. In contrast, significant recovery of intra‐islet HS to ～40–50% of normal levels occurred by 5–10 days after isotransplantation. Loss of islet HS during the isolation procedure is independent of heparanase (a HS‐degrading endoglycosidase) and due, in part, to oxidative damage. Treatment with antioxidants reduced islet cell death by ～60% and increased the HS content of isolated islets by ～twofold compared to untreated islets, preserving intra‐islet HS to ～60% of the normal HS content of islets in situ. These findings suggest that the preservation of islet HS during the islet isolation process may optimize islet survival posttransplant.     

De Novo Donor‐Specific HLA Antibodies Are Associated With Rapid Loss of Graft Function Following Islet Transplantation in Type 1 Diabetes

Outcomes after islet transplantation continue to improve but etiology of graft failure remains unclear. De novo donor‐specific human leukocyte antigen (HLA) antibodies (DSA) posttransplant are increasingly recognized as a negative prognostic marker. Specific temporal associations between DSA and graft function remain undefined particularly in programs undertaking multiple sequential transplants. Impact of de novo DSA on graft function over 12 months following first islet transplant was determined prospectively in consecutive recipients taking tacrolimus/mycophenolate immunosuppression at a single center. Mixed‐meal tolerance test was undertaken in parallel with HLA antibody assessment pretransplant and 1–3 months posttransplant. Sixteen participants received a total of 26 islet transplants. Five (19%) grafts were associated with de novo DSA. Five (31%) recipients were affected: three post–first transplant; two post–second transplant. DSA developed within 4 weeks of all sensitizing grafts and were associated with decreased stimulated C‐peptide (median [interquartile range]) at 3 months posttransplant (DSA negative: 613(300–1090); DSA positive 106(34–235) pmol/L [p = 0.004]). De novo DSA directed against most recent islet transplant were absolutely associated with loss of graft function despite maintained immunosuppression at 12 months in the absence of a rescue nonsensitizing transplant. Alemtuzumab induction immunosuppression was associated with reduced incidence of de novo DSA formation (p = 0.03).     

Immunity to varicella,measles, and mumps in patients evaluated for lung transplantation

Vaccine-preventable viral infections are associated with increased risk of morbidity and mortality in post-transplant patients on immunosuppression regimens. Therefore, we studied rates of immunity against vaccine-preventable viruses in lung transplantation (LTx) candidates and their associations with underlying lung disease and clinical characteristics. We retrospectively studied 1025 consecutive adult patients who underwent first-time evaluation for LTx at a single center between January 2016 and October 2018. Viruses studied included varicella zoster (VZV), measles, and mumps. Young age (17–48 years old) was negatively associated with immunity for VZV (OR 4.54, p < .001), measles (OR 15.45, p < .001) and mumps (OR 3.1, p < .001), as compared to those 65+. Many LTx candidates with cystic fibrosis (CF) had undetectable virus-specific antibody titers including: 13.5% for VZV, 19.1% for measles, and 15.7% for mumps with significant odds of undetectable titers for VZV (OR 4.54, p < .001) and measles (OR 2.32, p = .010) as compared to those without CF. Therefore, a substantial number of patients undergoing LTx evaluation had undetectable virus-specific antibody titers. Our results emphasize the importance of screening for immunity to vaccine-preventable infections in this population and the need for revaccination in selected patients to boost their humoral immunity prior to transplantation.

     

A randomized controlled trial of liposomal cyclosporine A for inhalation in the prevention of bronchiolitis obliterans syndrome following lung transplantation

Long-term survival after lung transplantation is limited by chronic allograft dysfunction. The aim of this study was to investigate the effect of locally augmented immunosuppression with liposomal cyclosporine A for inhalation (L-CsA-i) for the prevention of bronchiolitis obliterans syndrome (BOS). In a randomized, double-blind, placebo-controlled, multi-center Phase 3 study, 180 LT recipients in BOS grade 0 were planned to receive L-CsA-i or placebo in addition to triple-drug immunosuppression. L-CsA-i was administered twice daily via an Investigational eFlow nebulizer to recipients of single (SLT) and bilateral lung transplants (BLT) within 6–32 weeks posttransplant, and continued for 2 years. The primary endpoint was BOS-free survival. 130 patients were enrolled before the study was prematurely terminated for business reasons. Despite a 2-year actuarial difference in BOS-free survival of 14.1% in favor of L-CsA-i in the overall study population, the primary endpoint was not met (p = .243). The pre-defined per protocol analysis of SLT recipients (n = 24) resulted in a treatment difference of 58.2% (p = .053). No difference was observed in the BLT (n = 48) subpopulation (p = .973). L-CsA-i inhalation was well tolerated. Although this study failed to meet its primary endpoint, the results warrant additional investigation of L-CsA-i in lung transplant recipients.

     

Joint modeling of liver transplant candidates outperforms the model for end-stage liver disease: The effect of disease development over time on patient outcome

Liver function is measured regularly in liver transplantation (LT) candidates. Currently, these previous disease development data are not used for survival prediction. By constructing and validating joint models (JMs), we aimed to predict the outcome based on all available data, using both disease severity and its rate of change over time. Adult LT candidates listed in Eurotransplant between 2007 and 2018 (n = 16 283) and UNOS between 2016 and 2019 (n = 30 533) were included. Patients with acute liver failure, exception points, or priority status were excluded. Longitudinal MELD(-Na) data were modeled using spline-based mixed effects. Waiting list survival was modeled with Cox proportional hazards models. The JMs combined the longitudinal and survival analysis. JM 90-day mortality prediction performance was compared to MELD(-Na) in the validation cohorts. MELD(-Na) score and its rate of change over time significantly influenced patient survival. The JMs significantly outperformed the MELD(-Na) score at baseline and during follow-up. At baseline, MELD-JM AUC and MELD AUC were 0.94 (0.92–0.95) and 0.87 (0.85–0.89), respectively. MELDNa-JM AUC was 0.91 (0.89–0.93) and MELD-Na AUC was 0.84 (0.81–0.87). The JMs were significantly (p < .001) more accurate than MELD(-Na). After 90 days, we ranked patients for LT based on their MELD-Na and MELDNa-JM survival rates, showing that MELDNa-JM-prioritized patients had three times higher waiting list mortality.

     

Modeling the Iatrogenic Pancreatic Cancer Risk After Islet Autotransplantation in Mouse

Iatrogenic pancreatic cancer metastasis after islet infusion is a potential risk of islet autotransplantation performed after pancreatectomy. To model this risk, islets and/or pancreatic exocrine clusters obtained from a genetically engineered mouse model for pancreatic ductal adenocarcinoma (the LSL‐Kras^G12D/+;LSL‐Trp53^R172H/+;Pdx‐1‐Cre, termed KPC mouse) were transplanted via the portal vein in syngeneic wild type (WT) severely diabetic recipients in the following treatment groups: group A (n = 11) received KPC exocrine clusters in volume equal to 250 islet equivalents (IEQs); group B (n = 12) received 250 WT IEQs mixed with KPC exocrine clusters (1:1 volume ratio); group C (n = 5) received 250 KPC IEQs, and group D (n = 7) received 250 WT IEQs. The incidence of hepatic metastasis was assessed by magnetic resonance imaging and histology over the 13 months of follow‐up. Overall survival was not different in the four groups. No mice developed liver metastases during the follow‐up. Two mice developed spontaneous tumors: a liver hepatocellular tumor in group A and a malignant lymphoma in group D. Islets and/or exocrine clusters obtained by KPC mouse, a model that develops pancreatic cancer with 100% penetrance, do not retain the same risk of tumor development when transplanted via the portal vein in a syngeneic diabetic recipient.     

Graft-versus-host disease after liver transplantation is associated with bone marrow failure,hemophagocytosis, and DNMT3A mutations

Graft-versus-host disease after liver transplantation (LT-GVHD) is rare, frequently fatal, and associated with bone marrow failure (BMF), cytopenias, and hyperferritinemia. Given hyperferritinemia and cytopenias are present in hemophagocytic lymphohistiocytosis (HLH), and somatic mutations in hematopoietic cells are associated with hyperinflammatory responses (clonal hematopoiesis of indeterminate potential, CHIP), we identified the frequency of hemophagocytosis and CHIP mutations in LT-GVHD. We reviewed bone marrow aspirates and biopsies, quantified blood/marrow chimerism, and performed next-generation sequencing (NGS) with a targeted panel of genes relevant to myeloid malignancies, CHIP, and BMF. In all, 12 marrows were reviewed from 9 LT-GVHD patients. In all, 10 aspirates were evaluable for hemophagocytosis; 7 had adequate DNA for NGS. NGS was also performed on marrow from an LT cohort (n = 6) without GVHD. Nine of 10 aspirates in LT-GVHD patients showed increased hemophagocytosis. Five (71%) of 7 with LT-GVHD had DNMT3A mutations; only 1 of 6 in the non-GVHD LT cohort demonstrated DNMT3A mutation (p = .04). Only 1 LT-GVHD patient survived. BMF with HLH features was associated with poor hematopoietic recovery, and DNMT3A mutations were over-represented, in LT-GVHD patients. Identification of HLH features may guide prognosis and therapeutics. Further studies are needed to clarify the origin and impact of CHIP mutations on the hyperinflammatory state.

     

Parameters favouring successful adult pig islet isolations for xenotransplantation in pig-to-primate models

Dufrane D, D'hoore W, Goebbels R‐M, Saliez A, Guiot Y, Gianello P. Parameters favouring successful adult pig islet isolations for xenotransplantation in pig‐to‐primate models.
Xenotransplantation 2006; 13: 204–214. © Blackwell Munksgaard, 2006 Abstract: Background: In the near future, adult porcine islets of Langerhans appear as an unlimited source of insulin‐producing cells which could play a major role for treating diabetes mellitus. There is, however, an obvious lack of pre‐clinical results and data in the pig‐to‐primate model. One of the main hurdles of this model is certainly related to the difficulty of reproducing regularly successful porcine islet isolation. This experimental work was designed to provide guidelines applicable in pig pancreas procurement and islet isolation for successful islet xenotransplantation into primates. Methods: Pancreases were harvested from adult Belgium Landrace pigs (n = 79) in a single centre. The impact on islet yield of (1) pancreas procurement (blood exsanguination and warm ischaemia time (WIT)), (2) cold storage solutions (classic UW and modified UW (without hydroxyethyl starch and inverse K⁺/Na⁺ concentration)), (3) a dynamic or static method of pancreas digestion, and (4) the endotoxin content and enzymatic activity from five different batches of Liberase PI was studied. In addition, pancreatic biopsies (n = 18), performed before isolation, were retrospectively analyzed to study the impact of histomorphometry on porcine islet yield. Finally, two diabetic cynomolgus monkeys were transplanted without immunosuppression with 15 000 pig islet equivalents/kg body weight of recipient to assess in vivo the function of freshly isolated islets. Univariate and multivariate analyses were performed. Results: By multiple linear regression, the most significant variables that significantly improved islet yield were, firstly, the presence of <30 EU (endotoxin units) of endotoxin in Liberase batches, followed by a WIT under 10 min and the use of blood exsanguination before pancreas harvesting (P<0.005). In contrast, isolation method (dynamic vs. static) and the solution used for storage (short‐term) (UW vs. modified UW) did not significantly influence islet yield. The correlation of retrospective histomorphometry analysis of native pancreas and extemporaneous biopsy before isolation clearly determined a positive relationship between isolated islet number and the number of islets/cm² (r = 0.708, P<0.01) or with the percentage of large islets (r = 0.680, P<0.01) found in pancreas biopsies. Pig pancreases containing more than 82 islets/cm² and more than 42% of large islets (>100 μm) thus enabled more than 120 000 islet equivalents to be obtained in 90% of the cases, which is an ideal amount of islets to transplant into a primate of 4 to 5 kg. In vivo, a reduction of blood glucose (<200 mg/dl), associated with porcine C‐peptide production, was observed in two primates after transplantation with adult pig islets. At day 7 post‐transplantation, however, loss of islet function was associated with graft destruction and immune reaction. Conclusions: Morphological screening of the pig pancreas before isolation, optimal blood exsanguination, WIT <10 min, and an endotoxin content <30 EU/mg in Liberase PI batches determine successful pig islet isolation for xenotransplantation in primates.     

Anti‐huCD20 Antibody Therapy for Antibody‐Mediated Rejection of Renal Allografts in a Mouse Model

We have reported that B6.CCR5^?/? mice reject renal allografts with high serum donor‐specific antibody (DSA) titers and marked C4d deposition in grafts, features consistent with antibody‐mediated rejection (AMR). B6.huCD20/CCR5^?/? mice, where human CD20 expression is restricted to B cells, rejected A/J renal allografts by day 26 posttransplant with DSA first detected in serum on day 5 posttransplant and increased thereafter. Recipient treatment with anti‐huCD20 mAb prior to the transplant and weekly up to 7 weeks posttransplant promoted long‐term allograft survival (>100 days) with low DSA titers. To investigate the effect of B cell depletion at the time serum DSA was first detected, recipients were treated with anti‐huCD20 mAb on days 5, 8, and 12 posttransplant. This regimen significantly reduced DSA titers and graft inflammation on day 15 posttransplant and prolonged allograft survival >60 days. However, DSA returned to the titers observed in control treated recipients by day 30 posttransplant and histological analyses on day 60 posttransplant indicated severe interstitial fibrosis. These results indicate that anti‐huCD20 mAb had the greatest effect as a prophylactic treatment and that the distinct kinetics of DSA responses accounts for acute renal allograft failure versus the development of fibrosis.

     

Islet damage during isolation as assessed by miRNAs and the correlation of miRNA levels with posttransplantation outcome in islet autotransplantation

High‐quality pancreatic islets are essential for better posttransplantation endocrine function in total pancreatectomy with islet autotransplantation (TPIAT), yet stress during the isolation process affects quality and yield. We analyzed islet‐enriched microRNAs (miRNAs) ‐375 and ‐200c released during isolation to assess damage and correlated the data with posttransplantation endocrine function. The absolute concentration of miR‐375, miR‐200c, and C‐peptide was measured in various islet isolation steps, including digestion, dilution, recombination, purification, and bagging, in 12 cases of TPIAT. Posttransplantation glycemic control was monitored through C‐peptide, hemoglobin A_1c, insulin requirement, and SUITO index. The amount of miR‐375 released was significantly higher during enzymatic digestion followed by the islet bagging (P < .001). Mir‐200c mirrored these changes, albeit at lower concentrations. In contrast, the C‐peptide amount was significantly higher in the purification and bagging steps (P < .001). Lower amounts of miR‐375 were associated with a lower 6‐month insulin requirement (P = .01) and lower hemoglobin A_1c (P = .04). Measurement of the absolute quantity of miRNA‐375 and ‐200c released during islet isolation is a useful tool to assess islet damage. The quantity of released miRNA is indicative of posttransplantation endocrine function in TPIAT patients.     

Islet isolation from adult designated pathogen-free pigs: use of the newer bovine nervous tissue-free enzymes and a revised donor selection strategy would improve the islet graft function

Jin S‐M, Shin JS, Kim KS, Gong C‐H, Park SK, Kim J‐S, Yeom S‐C, Hwang ES, Lee CT, Kim S‐J, Park C‐G. Islet isolation from adult designated pathogen‐free pigs: use of the newer bovine nervous tissue–free enzymes and a revised donor selection strategy would improve the islet graft function. Xenotransplantation 2011; 18: 369–379. © 2011 John Wiley & Sons A/S. Abstract: Background: In clinical trials using adult porcine islet products, islets should be isolated from the designated pathogen‐free (DPF) pigs under the current good manufacturing practice (GMP) regulations. Our previous studies suggested that male DPF pigs are better donors than retired breeder pigs and histomorphometrical parameters of donor pancreas predict the porcine islet quality. We aimed to investigate whether the use of the newer bovine nervous tissue–free enzymes and a revised donor selection strategy could improve the islet graft function in the context of islet isolation with DPF pigs. Methods: Using 30 DPF pigs within a closed herd, we compared the islet yield of porcine islets isolated with Liberase PI (n = 11, as a historical control group), Liberase MTF C/T, which is a GMP‐grade enzyme (n = 12), and CIzyme collagenase MA/BP protease (n = 7). We analyzed the relationship between the diabetes reversal rate of recipient NOD/SCID mice (n = 75) and histomorphometric parameters of each donor pancreas as well as donor characteristics. Results: Proportion of islets larger than 200 μm from the biopsied donor pancreas (P = 0.006) better predicted islet yield than age (P = 0.760) or body weight (P = 0.371) of donor. The proportion of islets larger than 200 μm from the biopsied donor pancreas was not related to the sex of the donor miniature pig (P = 0.358). The islet yield obtained with the three enzymes did not differ, even after stratification of the donor with the histomorphometric parameters of the biopsied donor pancreas and the sex of donor. The use of the newer bovine nervous tissue–free enzymes (P < 0.001), a higher proportion of large islets in donor pancreas (P = 0.006), and a male sex of the donor (P = 0.025) were independent predictors of earlier diabetes reversal. Conclusions: Use of the newer bovine nervous tissue–free enzymes including a GMP‐grade enzyme resulted in better islet quality than that of islet isolated using Liberase PI. To obtain high‐quality islet from DPF pigs, the donor should be male pig and histomorphometrical parameters from donor pancreas should be considered.     

Preservation of pancreas in the University of Wisconsin solution supplemented with AP39 reduces reactive oxygen species production and improves islet graft function

Ischemia-reperfusion injury (IRI) results in increased rates of delayed graft function and early graft loss. It has recently been reported that hydrogen sulfide (H₂S) protects organ grafts against prolonged IRI. Here, we investigated whether the preservation of pancreas in University of Wisconsin (UW) solution supplemented with AP39, which is a mitochondrial-targeted H₂S donor, protected pancreatic islets against IRI and improved islet function. Porcine pancreata were preserved in the UW solution with AP39 (UW + AP39) or the vehicle (UW) for 18 h, followed by islet isolation. The islet yields before and after purification were significantly higher in the UW + AP39 group than in the UW group. The islets isolated from the pancreas preserved in UW + AP39 exhibited significantly decreased levels of reactive oxygen species (ROS) production and a significantly increased mitochondrial membrane potential as compared to the islets isolated from the pancreas preserved in the vehicle. We found that the pancreas preserved in UW + AP39 improved the outcome of islet transplantation in streptozotocin-induced diabetic mice. These results suggest that the preservation of pancreas in UW + AP39 protects the islet grafts against IRI and could thus serve as a novel clinical strategy for improving islet transplantation outcomes.     

Inpatient COVID-19 outcomes in solid organ transplant recipients compared to non-solid organ transplant patients: A retrospective cohort

Immunosuppression and comorbidities might place solid organ transplant (SOT) recipients at higher risk from COVID-19, as suggested by recent case series. We compared 45 SOT vs. 2427 non-SOT patients who were admitted with COVID-19 to our health-care system (March 1, 2020 - August 21, 2020), evaluating hospital length-of-stay and inpatient mortality using competing-risks regression. We compared trajectories of WHO COVID-19 severity scale using mixed-effects ordinal logistic regression, adjusting for severity score at admission. SOT and non-SOT patients had comparable age, sex, and race, but SOT recipients were more likely to have diabetes (60% vs. 34%, p < .001), hypertension (69% vs. 44%, p = .001), HIV (7% vs. 1.4%, p = .024), and peripheral vascular disorders (19% vs. 8%, p = .018). There were no statistically significant differences between SOT and non-SOT in maximum illness severity score (p = .13), length-of-stay (sHR: _0.91.1_1.4, p = .5), or mortality (sHR: _0.10.4_1.6, p = .19), although the severity score on admission was slightly lower for SOT (median [IQR] 3 [3, 4]) than for non-SOT (median [IQR] 4 [3–4]) (p = .042) Despite a higher risk profile, SOT recipients had a faster decline in disease severity over time (OR = _0.760.81_0.86, p < .001) compared with non-SOT patients. These findings have implications for transplant decision-making during the COVID-19 pandemic, and insights about the impact of SARS-CoV-2 on immunosuppressed patients.

     

Failure to prolong pancreatic islet allograft survival in rats with donor-specific blood transfusions and immunosuppression

The effects on pancreatic islet allograft survival of donor-specific blood transfusions (DST) in combination with pre- and posttransplant immunosuppression were studied. A total of 12 groups of rats (n=105) with chemically induced diabetes underwent islet allotransplantation. Multiple DST or third-party blood transfusions (TPT) were given prior to transplantation. Pretransplant immunosuppression consisted of azathioprine and prednisolone, and low-dose cyclosporin A was used for posttransplant immunosuppression. TPT, as well as separate or combined pre- and posttransplant immunosuppression without blood transfusions, did not prolong islet allograft survival. DST resulted in either primary nonfunction of the islet allografts or a markedly decreased islet allograft survival. These findings contrast with the beneficial effect of DST on whole-organ allograft survival in rats previously described by others.     

Prolonged Insulin Independence After Islet Allotransplants in Recipients with Type 1 Diabetes

We sought to determine the long‐term outcomes in type 1 diabetic recipients of intraportal alloislet transplants on a modified immunosuppressive protocol. Six recipients with hypoglycemia unawareness received one to two islet infusions. Induction therapy was with antithymocyte globulin (ATG) plus etanercept for tumor necrosis factor‐α blockade. Recipients received cyclosporine and everolimus for maintenance immunosuppression for the first year posttransplant, with mycophenolic acid or mycophenolate mofetil subsequently substituted for everolimus. Recipients have been followed for 1173 ± 270 days since their last infusion for islet graft function (insulin independence, hemoglobin A_1c levels and C‐peptide production) and for adverse events associated with the study protocol. Of the six recipients, five were insulin‐independent at 1 year, and four continue to be insulin‐independent at a mean of 3.4 ± 0.4 years posttransplant. None of the six recipients experienced recurrence of severe hypoglycemia. Measured glomerular filtration rate decreased from 110.5 ± 21.2 mL/min/1.73 m² pretransplant to 82.6 ±19.1 mL/min/1.73 m² at 1 year posttransplant. In conclusion, islet transplants restored insulin independence for a mean of >3 years in four of six recipients treated with ATG and etanercept induction therapy and with cyclosporine and, initially, everolimus for maintenance. Our results suggest this immunosuppressive protocol may allow long‐term graft survival.     

Loss of end‐differentiated β‐cell phenotype following pancreatic islet transplantation

Replacement of pancreatic β‐cells through deceased donor islet transplantation is a proven therapy for preventing recurrent life‐threatening hypoglycemia in type 1 diabetes. Although near‐normal glucose levels and insulin independence can be maintained for many years following successful islet transplantation, restoration of normal functional β‐cell mass has remained elusive. It has recently been proposed that dedifferentiation/plasticity towards other endocrine phenotypes may play an important role in stress‐induced β‐cell dysfunction in type 2 diabetes. Here we report loss of end‐differentiated β‐cell phenotype in 2 intraportal islet allotransplant recipients. Despite excellent graft function and sustained insulin independence, all examined insulin‐positive cells had lost expression of the end‐differentiation marker, urocortin‐3, or appeared to co‐express the α‐cell marker, glucagon. In contrast, no insulin⁺/urocortin‐3^? cells were seen in nondiabetic deceased donor control pancreatic islets. Loss of end‐differentiated phenotype may facilitate β‐cell survival during the stresses associated with islet isolation and culture, in addition to sustained hypoxia following engraftment. As further refinements in islet isolation and culture are made in parallel with exploration of alternative β‐cell sources, graft sites, and ultimately fully vascularized bioengineered insulin‐secreting microtissues, differentiation status immunostaining provides a novel tool to assess whether fully mature β‐cell phenotype has been maintained.