Influence of pancreas preservation on human islet isolation outcomes: impact of the two-layer method

Liraglutide Protects Pancreatic Islet From Ischemic Injury by Reducing Oxidative Stress and Activating Akt Signaling During Cold Preservation to Improve Islet Transplantation Outcomes

BACKGROUND

Islet transplantation is a promising therapy for patients with type 1 diabetes. However, ischemic injury to the donor islets during cold preservation leads to reduced islet quality and compromises transplant outcome. Several studies imply that liraglutide, a glucagon-like peptide-1 receptor agonist, has a positive effect on promoting islet survival, but its impact on islet cold-ischemic injury remains unexplored. Therefore, the aim of this study was to investigate whether liraglutide can improve islet transplantation efficacy by inhibiting cold-ischemic injury and to explore the underlying mechanisms.

METHODS

Liraglutide was applied in a mouse pancreas preservation model and a human islets cold-preservation model, and islet viability, function, oxidative stress levels were evaluated. Furthermore, islet transplantation was performed in a syngeneic mouse model and a human-to-nude mouse islet xenotransplantation model.

RESULTS

The supplementation of liraglutide in preservation solution improved islet viability, function, and reduced cell apoptosis. Liraglutide inhibited the oxidative stress of cold-preserved pancreas or islets through upregulating the antioxidant enzyme glutathione levels, inhibiting reactive oxygen species accumulation, and maintaining the mitochondrial membrane integrity, which is associated with the activation of Akt signaling. Furthermore, the addition of liraglutide during cold preservation of donor pancreas or donor islets significantly improved the subsequent transplant outcomes in both syngeneic mouse islet transplantation model and human-to-nude mouse islet xenotransplantation model.

CONCLUSIONS

Liraglutide protects islets from cold ischemia-related oxidative stress during preservation and hence improved islet transplantation outcomes, and this protective effect of liraglutide in islets is associated with the activation of Akt signaling.

Current issues in allogeneic islet transplantation

PURPOSE OF REVIEW

Transplantation of allogenic pancreatic islets is a minimally invasive treatment option to control severe hypoglycemia and dependence on exogenous insulin among type 1 diabetes (T1D) patients. This overview summarizes the current issues and progress in islet transplantation outcomes and research.

RECENT FINDINGS

Several clinical trials from North America and other countries have documented the safety and efficacy of clinical islet transplantation for T1D patients with impaired hypoglycemia awareness. A recently completed phase 3 clinical trial allows centres in the United States to apply for a Food and Drug Administration Biologics License for the procedure. Introduction of anti-inflammatory drugs along with T-cell depleting induction therapy has significantly improved long-term function of transplanted islets. Research into islet biomarkers, immunosuppression, extrahepatic transplant sites and potential alternative beta cell sources is driving further progress.

SUMMARY

Allogeneic islet transplantation has vastly improved over the past two decades. Success in restoration of glycemic control and hypoglycemic awareness after islet transplantation has been further highlighted by clinical trials. However, lack of effective strategies to maintain long-term islet function and insufficient sources of donor tissue still impose limitations to the widespread use of islet transplantation. In the United States, wide adoption of this technology still awaits regulatory approval and, importantly, a financial mechanism to support the use of this technology.

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 15-20 min. Trimmed pancreases were immersed into oxygenated F6H8S5 and stored at 4°C 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.

Influence of the Two-Layer Preservation Method on Human Pancreatic Islet Isolation: A Meta-Analysis

Introduction

There has been continuous debate on whether the Two-Layer Method (TLM) is superior to the University of Wisconsin solution (UW) for preserving human pancreas prior to islet isolation. The objective of the current meta-analysis is to assess which method is superior.

Methods

We searched electronic databases (MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials) for relevant human trials published in the English language from January 2000 to October 2013. Data on donor characteristics and islet isolation outcomes were extracted.

Results

14 articles containing 18 human studies were included in this meta-analysis. In comparison to UW alone, TLM alone produced a significantly higher islet yield (weighted mean difference, 776.32; 95% confidence interval; 370.82-1181.82; P = .0002). TLM alone also yielded higher proportion of transplantable preparations (odds ratio, 1.60; 95% confidence interval; 1.15-2.23; P = .005). The following measures did not differ: islet viability (weighted mean difference, 2.10; −2.41-6.60; P = .360), purity (weighted mean difference, −0.92; −3.75-1.91; P = .520) and function assessed by measuring the stimulation index (weighted mean difference, 0.17; −0.21-0.55; P = .380). When comparing TLM following UW storage with UW alone, the results were similar to the previous ones.

Conclusions

This data indicates that the TLM can improve islet yield and increase the opportunities of human pancreatic islet transplantation. Therefore, the TLM should be recommended for preserving human pancreas prior to islet isolation.

Effects of Donor-, Pancreas-, and Isolation-Related Variables on Human Islet Isolation Outcome: A Systematic Review

Different factors have been reported to influence islet isolation outcome, but their importance varies between studies and are hampered by the small sample sizes in most studies. The purpose of this study was to perform a systematic review to assess the impact of donor-, pancreas-, and isolation-related variables on successful human islet isolation outcome. PubMed, Embase, and Web of Science were searched electronically in April 2009. All studies reporting on donor-, pancreas-, and isolation-related factors relating to prepurification and postpurification islet isolation yield and proportion of successful islet isolations were selected. Seventy-four retrospective studies had sufficient data and were included in the analyses. Higher pre- and postpurification islet yields and a higher proportion of successful islet isolations were obtained when pancreata were preserved with the two-layer method rather than University of Wisconsin solution in donors with shorter cold ischemia times (CITs) [1 h longer CIT resulted in an average decline of prepurification and postpurification yields and proportion of successful isolations of 59 islet equivalents (IEQs)/g, 54 IEQs/g, and 21%, respectively]. Higher prepurification yields and higher percentage of successful islet isolations were found in younger donors with higher body mass index. Lower yields were found in donation after brain death donors compared to donation after cardiac death donors. Higher postpurification yields were found for isolation with Serva collagenase. This review identified donor-, pancreas-, and isolation-related factors that influence islet isolation yield. Standardized reports of these factors in all future studies may improve the power and identify additional factors and thereby contribute to improving islet isolation yield.

Establishment of a stringent large animal model of insulin-dependent diabetes for islet autotransplantation: combination of pancreatectomy and streptozotocin

OBJECTIVE

A stringent porcine islet autograft diabetes model was developed to enable the assessment of autoislet safety and efficacy in either portal vein or an extrahepatic site.

METHODS

A 95% pancreatectomy was performed preserving the pancreaticoduodenal arcade; however, glycemic control was still maintained at 3.3 ± 0.3 days (mean ± SEM), shown by euglycemic fasting blood glucose levels of 4.9 ± 0.8 mmol/L (mean ± SEM, n = 3). To reduce surgical complications and eliminate remaining islets, pigs were dosed intravenously after a modified 90% pancreatectomy, with 150-mg/kg streptozotocin, producing a diabetic state (18.9 ± 1.8 mmol/L [mean ± SEM], n = 8; P < 0.001) within 2.0 ± 0.9 days (mean ± SEM).

RESULTS

Animals presented with sustained hyperglycemia, failing a glucose challenge test 12 weeks after diabetic induction, and showed no stimulated C-peptide secretion compared to nondiabetic controls (baseline: 0.479 ± 0.080 ng/mL [mean ± SEM] vs after procedure: 0.219 ± 0.055 ng/mL [mean ± SEM], P = 0.02). Diabetic animals were maintained on daily insulin. Despite an initial decline in body weight acutely after pancreatectomy and streptozotocin administration, the mean body weight increased after induction over the approximately 88-day study, indicating that the animals were in good health.

CONCLUSION

This stringent porcine model of diabetic induction should be used to assess autograft transplantation safety and efficacy.

The islet size to oxygen consumption ratio reliably predicts reversal of diabetes posttransplant

β-Cell replacement therapy by either whole-organ pancreas or islets of Langerhans transplantation can restore carbohydrate control to diabetic patients and reduces complications associated with the disease. One of the variables inherent in islet transplantation is the isolation of functional islets from donor pancreata. Islet isolations fail to consistently produce good-quality functional islets. A rapid pretransplant assay to determine posttransplant function of islets would be an invaluable tool. We have tested the novel hypothesis that modified oxygen consumption rates (OCR), standardized to DNA quantity (nmol/min-mg DNA), would serve as a pretransplant assessment of the metabolic potency of the islets postisolation. This study compares the ability of current in vitro assays to predict in vivo restoration of normoglycemia in a diabetic nude mouse posttransplantation of adult pig islets. There is known to be a diversity of islet sizes within each preparation. This parameter has not heretofore been effectively considered a critical factor in islet engraftment. Our results suggest a surprising finding that islet size influences the probability of restoring carbohydrate control. Based on this observation, we thus developed a novel predictor of islet graft function that combines the effects of both islet OCR and size. When OCR was divided by the islet index (size), a highly significant predictor of graft function was established (p = 0.0002, n = 75). Furthermore, when OCR/islet index values exceeded 70.0 nmol/min-mg DNA/islet index, an effective threshold of diabetes reversal was observed. This assay can be performed with as few as 1,000 islet equivalents (IEQ) and conducted in less than 60 min. Our data suggest that, using this novel method to assess islet cell function prior to transplantation, OCR/islet index thresholds provide a valuable tool in identifying which islet preparations are most likely to restore glycemic control posttransplant.

Implication of mitochondrial cytoprotection in human islet isolation and transplantation

Islet transplantation is a promising therapy for type 1 diabetes mellitus; however, success rates in achieving both short- and long-term insulin independence are not consistent, due in part to inconsistent islet quality and quantity caused by the complex nature and multistep process of islet isolation and transplantation. Since the introduction of the Edmonton Protocol in 2000, more attention has been placed on preserving mitochondrial function as increasing evidences suggest that impaired mitochondrial integrity can adversely affect clinical outcomes. Some recent studies have demonstrated that it is possible to achieve islet cytoprotection by maintaining mitochondrial function and subsequently to improve islet transplantation outcomes. However, the benefits of mitoprotection in many cases are controversial and the underlying mechanisms are unclear. This article summarizes the recent progress associated with mitochondrial cytoprotection in each step of the islet isolation and transplantation process, as well as islet potency and viability assays based on the measurement of mitochondrial integrity. In addition, we briefly discuss immunosuppression side effects on islet graft function and how transplant site selection affects islet engraftment and clinical outcomes.

Pancreatic islets from non-heart-beating donor pig: two-layer preservation method in an in vitro porcine model

PURPOSE

Pancreata from non-heart beating donors could represent an unlimited source of islets if their cell viability can be efficiently preserved during the time necessary to process the organs by the use of a better solution of preservation compared to the classic University of Wisconsin solution. The aim of this study was to determine whether it is possible to obtain functioning "alive islets" from non-heart-beating donors by comparing, on a porcine model, the classic "UW ice-store" method with a two-layer cold storage method (TLM) using oxygenated Perfluorocarbons (PFC) and UW.

METHODS

Whole pancreata were harvested from 20 NHBDs female pigs with similar characteristics and preserved for 4 h in UW solution (n = 10) or TLM (UW/PFC) solution (n=10). The isolated islets were then evaluated for number, viability, purity, and insulin secretion, also estimated after 8 weeks of cryopreservation.

RESULTS

The total number of islets obtained from isolation, and their function assayed by the insulin stimulation index, before and after cryopreservation, showed a higher value in the TLM group. No significative differences in terms of purity and viability before and after cryopreservation were found when comparing the two groups.

CONCLUSIONS

TLM solution for NHBDs porcine pancreata with cold ischemia time lower than 4 h offers significant advantages over UW solution storage, thereby increasing the isolation yield and isolation success rate of the pancreatic porcine islets.

A Meta-Analysis for Comparison of the Two-Layer and University of Wisconsin Pancreas Preservation Methods in Islet Transplantation

Conflicting results have been reported on the effectiveness of the two-layer method (TLM) compared with the University of Wisconsin (UW) method for preserving pancreata. The objective of this study was to compile the evidence for or against any difference in human islet yield and viability between these two. PubMed (January 2000 to May 2008) and Cochran Library searches were performed and 17 studies were included for the meta-analysis. Data on donor characteristics, preservation time, and outcomes were abstracted. Studies were subgrouped based on how TLM was used (UW + TLM or TLM alone), on mean cold ischemic time (CIT) (>20 h or <20 h), and on whether special chemical was used (yes or no). Meta-analysis of all studies and subgroups was performed and the pooled standardized mean differences (SMD) with 95% confidence intervals (CI) were reported. Overall, the use of TLM significantly increased islet yield [SMD, 0.74 (0.44–1.04)] and viability [SMD, 0.63 (0.14–1.12)]. The beneficial effects of TLM on islet yield were more evident when TLM was used following UW storage or when prolonged CIT was used. TLM used alone, shorter CIT, and no chemical use all resulted in similar islet viability between TLM and UW groups. Beneficial effects of TLM on islet viability were demonstrated only when TLM was used following UW storage, or with prolonged CIT, or with chemical use. In conclusion, the TLM was beneficial for prolonged pancreas preservation before human islet isolation; however, benefit of the TLM for short-term preservation was not clear.

Pancreas oxygen persufflation increases ATP levels as shown by nuclear magnetic resonance

BACKGROUND

Islet transplantation is a promising treatment for type 1 diabetes. Due to a shortage of suitable human pancreata, high cost, and the large dose of islets presently required for long-term diabetes reversal; it is important to maximize viable islet yield. Traditional methods of pancreas preservation have been identified as suboptimal due to insufficient oxygenation. Enhanced oxygen delivery is a key area of improvement. In this paper, we explored improved oxygen delivery by persufflation (PSF), ie, vascular gas perfusion.

METHODS

Human pancreata were obtained from brain-dead donors. Porcine pancreata were procured by en bloc viscerectomy from heparinized donation after cardiac death donors and were either preserved by either two-layer method (TLM) or PSF. Following procurement, organs were transported to a 1.5-T magnetic resonance (MR) system for (31)P nuclear magnetic resonance spectroscopy to investigate their bioenergetic status by measuring the ratio of adenosine triphosphate to inorganic phosphate (ATP:P(i)) and for assessing PSF homogeneity by MRI.

RESULTS

Human and porcine pancreata can be effectively preserved by PSF. MRI showed that pancreatic tissue was homogeneously filled with gas. TLM can effectively raise ATP:P(i) levels in rat pancreata but not in larger porcine pancreata. ATP:P(i) levels were almost undetectable in porcine organs preserved with TLM. When human or porcine organs were preserved by PSF, ATP:P(i) was elevated to levels similar to those observed in rat pancreata.

CONCLUSION

The methods developed for human and porcine pancreas PSF homogeneously deliver oxygen throughout the organ. This elevates ATP levels during preservation and may improve islet isolation outcomes while enabling the use of marginal donors, thus expanding the usable donor pool.

Islet transplantation using donors after cardiac death: report of the Japan Islet Transplantation Registry

BACKGROUND

This report summarizes outcomes of islet transplantation employing donors after cardiac death (DCD) between 2004 and 2007 as reported to the Japan Islet Transplantation Registry.

METHOD

Sixty-five islet isolations were performed for 34 transplantations in 18 patients with insulin-dependent diabetes mellitus, including two patients who had prior kidney transplantation. All but one donor (64/65) was DCD at the time of harvesting.

RESULTS

Factors influencing criteria for islet release included duration of low blood pressure of the donor, cold ischemic time, and usage of Kyoto solution for preservation. Multivariate analysis selected usage of Kyoto solution as most important. Of the 18 recipients, 8, 4, and 6 recipients received 1, 2, and 3 islet infusions, respectively. Overall graft survival defined as C-peptide level more than or equal to 0.3 ng/mL was 76.5%, 47.1%, and 33.6% at 1, 2, and 3 years, respectively, whereas corresponding graft survival after multiple transplantations was 100%, 80.0%, and 57.1%, respectively. All recipients remained free of severe hypoglycemia while three achieved insulin independence for 14, 79, and 215 days. HbA1c levels and requirement of exogenous insulin were significantly improved in all patients.

CONCLUSION

Islet transplantation employing DCD can ameliorate severe hypoglycemic episodes, significantly improve HbA1c levels, sustain significant levels of C-peptide, and achieve insulin independence after multiple transplantations. Thus, DCD can be an important resource for islet transplantation if used under strict releasing criteria and in multiple transplantations, particularly in countries where heart-beating donors are not readily available.

Preoxygenation of different preservation solutions for porcine pancreas preservation

INTRODUCTION

Organ preservation quality impacts porcine islet cell isolation and transplantation success. Among several preservation methods, the two-layer method is promising, but technically demanding and fails to deliver sufficient oxygen. The use of hyperbaric oxygenation may be an easier, more effective method to supply high partial pressure of oxygen (pO(2)) for organ storage. Therefore, the aim of this study was to test the capability of preoxygenation of various preservation solutions with HBO to maintain high pO(2) levels.

METHODS

University of Wisconsin (UW), Custodiol, Perfadex, or Celsior solutions were preoxygenated in a pressure chamber. NaCl served as the control. pO(2) levels were measured at defined times. The oxygen storage capability was evaluated by leaving the storage bottles open for 2 minutes.

RESULTS

It was feasible to preoxygenate preservation solutions. The best solution to maintain high pO(2) tensions was Perfadex, followed by Celsior, and UW.

DISCUSSION

The greater the amount of oxygen in the preservation solution, the more oxygen can be delivered to the preserved pancreas. Further studies on the influence of preoxygenated preservation solutions on the porcine pancreas are warranted to improve organ quality, porcine islet cell isolation, and transplantation success.

Limited beneficial effects of perfluorocarbon emulsions on encapsulated cells in culture: experimental and modeling studies

Due to the high solubility of oxygen in perfluorocarbons (PFCs), these compounds have been explored for improved cell and tissue oxygenation. The goal of this study is to investigate the effects of a PFC emulsion on cellular growth and function in a tissue engineered construct. A perfluorotributylamine (PFTBA) emulsion was co-encapsulated at 10 vol% with mouse βTC-tet insulinoma cells in calcium alginate beads and cultured under normoxic and severely hypoxic conditions. The number of metabolically active cells and the induced insulin secretion rate were measured over time for up to 16 days. Results showed no significant effect of PFTBA relative to the PFTBA-free control. The alginate-PFC-cell system was also modeled mathematically, and simulations tracked the number of viable cells over time under the same conditions used experimentally. Simulations revealed only a small, likely experimentally undetectable difference in cell density between the PFC-containing and PFC-free control beads. It is concluded that PFTBA up to 10 vol% has no significant effect on the growth and function of encapsulated βTC-tet cells under normoxic and hypoxic conditions.

Limited Penetration of Perfluorocarbon in Porcine Pancreas Preserved by Two-Layer Method with 19Fluorine Magnetic Resonance Spectroscopy and Headspace Gas Chromatography

The mechanism of the two-layer method (TLM) of pancreas preservation is unclear. Facilitating oxygen diffusion into preserved pancreas has been suggested, but direct measurements of tissue pO2 have yielded conflicting results. The degree of penetration of perfluorocarbon (PFC) into the pancreas during TLM storage is unknown. Segments of porcine pancreas (7.5 cm in length) were preserved either in University of Wisconsin solution (UW) alone ( n = 6) or in TLM for 24 h ( n = 6). Pancreatic samples were analyzed using Varian INOVA 9.4T MR scanner. External PFC standard was introduced for quantification. Four consecutive transverse images of 4 mm thickness were obtained using a spin-echo sequence. 19Fluorine magnetic resonance spectroscopy (19F MRS) was performed with the same parameters except with more averages. MR data were confirmed by headspace chromatography. PFC standard was readily detected in 19F MR images. There was no signal from pancreas in 19F MR images following either UW or TLM storage. 19F MR spectra typical of PFC were not obtained from either UW- or TLM-preserved pancreas with nonlocalized 19F MRS. Mean concentration of PFC in TLM pancreas measured by head space chromatography was 0.011 nl/g (SD ±0.006), not significantly different from background concentration (0.012 nl/g, SD ±0.006) in UW pancreas ( p = 0.42). There was no evidence of penetration of PFC into pancreas tissues investigated either by MR or chromatography in organs preserved at hypothermia by TLM, and mechanisms of TLM remain speculative.

Multicenter analysis of novel and established variables associated with successful human islet isolation outcomes

Islet transplantation is a promising therapy used to achieve glycometabolic control in a select subgroup of individuals with type I diabetes. However, features that characterize human islet isolation success prior to transplantation are not standardized and lack validation. We conducted a retrospective analysis of 806 isolation records from 14 pancreas-processing laboratories, considering variables from relevant studies in the last 15 years. The outcome was defined as post-purification islet equivalent count, dichotomized into yields > or =315 000 or < or =220 000. Univariate analysis showed that donor cause of death and use of hormonal medications negatively influenced outcome. Conversely, pancreata from heavier donors and those containing elevated levels of surface fat positively influence outcome, as did heavier pancreata and donors with normal amylase levels. Multivariable logistic regression analysis identified the positive impact on outcome of surgically intact pancreata and donors with normal liver function, and confirmed that younger donors, increased body mass index, shorter cold ischemia times, no administration of fluid/electrolyte medications, absence of organ edema, use of University of Wisconsin preservation solution and a fatty pancreas improves outcome. In conclusion, this multicenter analysis highlights the importance of carefully reviewing all donor, pancreas and processing parameters prior to isolation and transplantation.

Pancreas preservation by the two-layer method: does it have a beneficial effect compared with simple preservation in University of Wisconsin solution?

A large number of reports have shown that the two-layer method (TLM), which employs oxygenated perfluorochemical (PFC) and University of Wisconsin (UW) solution, is superior to simple cold storage in UW in islet transplantation. However, two recent large-scale studies showed no beneficial effect of TLM compared with UW storage in human islet transplantation. We reevaluated the effect of TLM by following three groups: group 1: UW simple storage; group 2: TLM performed by multiorgan procurement teams (not specialists of islet isolation); and group 3: TLM performed by specialists of islet isolation (Noguchi and Matsumoto). There were no significant differences between groups 1 and 2, whereas islet yields were significantly higher in group 3 compared with either group 1 or 2. Our data suggest that exact, complete performance of TLM could improve the outcome of islet isolation and transplantation. In this review, we describe the mechanisms of the TLM, the procedure of preoxygenated TLM, and the several possibilities for the reasons of the discrepancy.

The effect of perfluorocarbon-based artificial oxygen carriers on tissue-engineered trachea

The biological effect of the perfluorocarbon-based artificial oxygen carrier (Oxygent) was investigated in tissue-engineered trachea (TET) construction. Media supplemented with and without 10% Oxygent were compared in all assessments. Partial tissue oxygen tension (PtO(2)) was measured with polarographic microprobes; epithelial metabolism was monitored by microdialysis inside the TET epithelium perfused with the medium underneath. Chondrocyte-DegraPol constructs were cultured for 1 month with the medium before glycosaminoglycan assessment and histology. Tissue reaction of TET epithelial scaffolds immersed with the medium was evaluated on the chick embryo chorioallantoic membrane. Oxygent perfusion medium increased the TET epithelial PtO(2) (51.2 +/- 0.3 mm Hg vs. 33.4 +/- 0.3 mm Hg at 200 microm thickness; 12.5 +/- 0.1 mm Hg vs. 3.1 +/- 0.1 mm Hg at 400 microm thickness, p < 0.01) and decreased the lactate concentration (0.63 +/- 0.08 vs. 0.80 +/- 0.06 mmol/L, p < 0.05), lactate/pyruvate (1.87 +/- 0.26 vs. 3.36 +/- 10.13, p < 0.05), and lactate/glucose ratios (0.10 +/- 0.00 vs. 0.29 +/- 0.14, p < 0.05). Chondrocyte-DegraPol in Oxygent group presented lower glycosaminoglycan value (0.03 +/- 0.00 vs. 0.13 +/- 0.00, p < 0.05); histology slides showed poor acid mucopolysaccharides formation. Orthogonal polarization spectral imaging showed no difference in functional capillary density between the scaffolds cultured on chorioallantoic membranes. The foreign body reaction was similar in both groups. We conclude that Oxygent increases TET epithelial PtO(2), improves epithelial metabolism, does not impair angiogenesis, and tends to slow cartilage tissue formation.

The effect of isolation methods and the use of different enzymes on islet yield and in vivo function

The ability to isolate high-yield pure and viable islets from human cadaver pancreas donors is dependent on donor factor as well as isolation factors. The aim of this study was to examine factors influencing islets recovery and in vivo function with an emphasis on donor and isolation methods as well as to compare the effectiveness of Liberase, widely used in clinical islet isolation, with Serva for the isolation of pure functional islets. The results of 123 islet isolations using Liberase for digestion were compared with those of 113 isolations with Serva. Islet equivalents per gram of tissue were similar between Liberase and Serva (3620 +/- 1858 vs. 4132 +/- 2104, p < 0.2) as well as the percent purity (75 +/- 16 vs. 74 +/- 15, p < 0.9). In vivo function of islets from 71 isolations (Liberase = 45, Serva = 26) were further tested by transplantation into NOD-SCID mice following short-term culture (< 6 days, n = 71). Our data show that both Liberase- and Serva-isolated islets showed similar function results following short-term culture. These data demonstrate that there is no difference in islet yield, purity, and function between the two enzymes. However, when these 71 isolations were analyzed for in vivo function with emphasis on donor factors, cold ischemia time (12.0 +/- 5.3 vs. 15.0 +/- 5.7, p < 0.04), islet integrity (1.6 +/- 0.7 vs. 1.3 +/- 0.5, p < 0.05), and female gender were the only factors that correlated with in vivo function. We also compared the mechanical-shaking method for islets isolation with hand-shaking methods. Our results show that although there is no different in islet yield, purity, and integrity between different enzymes using the same method, hand-shaking method yields more islets with better integrity than mechanical-shaking method.

A Meta-Analysis of the Impact of the Two-Layer Method of Preservation on Human Pancreatic Islet Transplantation

There are conflicting reports about the effectiveness of perfluorocarbons used in the two-layer method (TLM) of pancreas preservation for human islet transplantation. The mechanism of action is unclear and the optimal role of this method uncertain. The study design was a meta-analysis of the evidence that TLM improves islet isolation outcomes. Pubmed, CENTRAL, EMBASE, Science Citation Index, and BIOSIS were searched electronically in January 2008. After selecting the relevant human trials for meta-analysis data relating to donor variables, study design, primary and secondary islet isolation outcomes were extracted. Electronic searches identified eight unique citations, describing 11 human studies that were eligible for the meta-analysis. When comparing TLM with preservation in University of Wisconsin (UW) solution, there was a statistically significant higher islet yield [WMD 711.55, 95% confidence interval (CI) 140.03–1283.07] in the TLM group. The proportion of transplantable preparations obtained was not significantly different (OR 1.30, 95% CI 0.89–1.88) between the two groups. The rate of successful islet isolations for marginal organs was higher in the TLM group (OR 6.69, 95% CI 1.80–24.87). Improved oxygenation and preservation of cellular bioengertics is thought to be the main underlying mechanism, although no single mechanism has yet been confirmed. There is currently no clear evidence that the TLM is beneficial in human islet transplantation. It may improve the preservation of marginal organs.

Organ preservation in pancreas and islet transplantation

PURPOSE OF REVIEW

Organ preservation aims at reducing ischemia-reperfusion injury and maintains or even improves its function, and, therefore, increases transplant safety and efficiency. With the chronic lack of organs for transplantation, marginal donors are more and more frequently used in Western countries. New challenges, therefore, have to be met in organ preservation.

RECENT FINDINGS

We summarize the effects of cold preservation on various organ grafts, with particular emphasis on the pancreas. We review the different preservation solutions currently available in the clinic, and we present the current knowledge and clinical experience in pancreas and islet transplantation.

SUMMARY

Overall, in whole pancreas and islet transplantation, current cold preservation solutions (University of Wisconsin solution, Celsior, histidine-tryptophan-ketoglutarate) seem to be equivalent, with only few studies showing better results with University of Wisconsin solution. Regarding preservation with the two-layer method, conflicting results have been reported, and proper prospective controlled studies have yet to be performed to gather evidence on its impact on islet yield and function. Some recent developments and future strategies in general organ preservation not yet applied to pancreas preservation are reviewed at the end of the article.

Chromatin-bound mitogen-activated protein kinases transmit dynamic signals in transcription complexes in beta-cells

MAPK pathways regulate transcription through phosphorylation of transcription factors and other DNA-binding proteins. In pancreatic beta-cells, ERK1/2 are required for transcription of the insulin gene and several other genes in response to glucose. We show that binding of glucose-sensitive transcription activators and repressors to the insulin gene promoter depends on ERK1/2 activity. We also find that glucose and NGF stimulate the binding of ERK1/2 to the insulin gene and other promoters. An ERK1/2 cascade module, including MEK1/2 and Rsk, are found in complexes bound to these promoters. These findings imply that MAPK-containing signaling complexes are positioned on sensitive promoters with their protein substrates to modulate transcription in situ in response to incoming signals.

Real-time noninvasive assessment of pancreatic ATP levels during cold preservation

31P-NMR spectroscopy was utilized to investigate rat and porcine pancreatic ATP:P(i) ratios to assess the efficacy of existing protocols for cold preservation (CP) in maintaining organ quality. Following sacrifice, rat pancreata were immediately excised or left enclosed in the body for 15 minutes of warm ischemia (WI). After excision, rat pancreata were stored at 6 degrees C to 8 degrees C using histidine-tryptophan-ketoglutarate solution (HTK) presaturated with air (S1), HTK presaturated with O2 (S2), or the HTK/perfluorodecalin two-layer method (TLM) with both liquids presaturated with O2 (S3). 31P-NMR spectra were sequentially collected at 3, 6, 9, 12, and 24 hours of CP from pancreata stored with each of the three protocols examined. The ATP:Pi ratio for rat pancreata exposed to 15 minutes of WI and stored with S3 increased during the first 9 hours of CP, approaching values observed for organs procured with no WI. A marked reduction in the ATP:Pi ratio was observed beyond 12 hours of CP with S3. After 6 hours of CP, the ATP:Pi ratio was highest for S3, substantially decreased for S2, and below detection for S1. In sharp contrast to the rat model, ATP was barely detectable in porcine pancreata exposed to minimal warm ischemia (<15 minutes) stored with the TLM regardless of CP time. We conclude that 31P-NMR spectroscopy is a powerful tool that can be used to (1) noninvasively evaluate pancreata prior to islet isolation, (2) assess the efficacy of different preservation protocols, (3) precisely define the timing of reversible versus irreversible damage, and (4) assess whether intervention will extend this timing.

The caspase selective inhibitor EP1013 augments human islet graft function and longevity in marginal mass islet transplantation in mice

OBJECTIVE

Clinical islet transplantation can provide insulin independence in patients with type 1 diabetes, but chronic graft failure has been observed. This has been attributed in part to loss of >or=60% of the transplanted islets in the peritransplant period, resulting in a marginal implant mass. Strategies designed to maximize survival of the initial islet mass are likely to have major impact in enhancing long-term clinical outcomes. EP1013 (N-benzyloxycabonyl-Val Asp-fluoromethyl ketone [zVD-FMK]), is a broad-spectrum caspase selective inhibitor with no observed toxicity in rodents.

RESEARCH DESIGN AND METHODS

The therapeutic benefit of EP1013 was examined in a syngeneic rodent islet transplant model using deceased donor human islets to determine whether the amount of tissue required to restore euglycemia in diabetic animals could be reduced.

RESULTS

EP1013 (combined pretransplant islet culture for 2 h and in vivo treatment for days 0-5 posttransplant) significantly improved marginal islet mass function following syngeneic islet transplantation in mice, even at lower doses, compared with previous studies using the pan-caspase inhibitor N-benzyloxycabonyl-Val Ala-Asp-fluoromethyl ketone (zVAD-FMK). EP1013 supplementation in vitro improved human islet yields following prolonged culture and reversed diabetes following implantation of a marginal human islet mass (80-90% reduction) into mice.

CONCLUSIONS

Our data suggest that EP1013 therapy will markedly reduce the islet mass required in clinical islet transplantation, improving insulin independence rates following single-donor infusion.

Cold preservation of the liver with oxygenation by a two-layer method

BACKGROUND

The two-layer method (TLM) has recently been found to be superior to simple cold storage in University of Wisconsin (UW) solution as a means of pancreas preservation for islet transplantation. In this study, we investigated whether TLM would result in better hepatocyte function over UW cold storage and if it could be applied to hepatocyte transplantation.

MATERIALS AND METHODS

Hepatocytes from male Sprague Dawley rat livers were isolated and divided into three groups: a non-preservation group (group 1), a 10-h preservation group (group 2), and a 24-h preservation group (group 3). Groups 2 and 3 were then divided into three subgroups: a group preserved by the TLM (subgroup a), a group preserved in UW solution (subgroup b), and a group preserved in water (subgroup c). Isolated hepatocytes were evaluated for cell yield, viability, and adenosine triphosphate level after preservation. Hepatocytes were either cultured or transplanted.

RESULTS

Although no differences in cell yield or morphological findings were observed between any of the groups, TLM significantly improved hepatocyte viability and adenosine triphosphate levels in comparison with UW cold storage. Albumin production or urea synthesis were significantly higher in subgroup 3a than in subgroup 3b at almost all time points. Surprisingly, after hepatocyte transplantation, the serum albumin level in subgroup 2a was significantly higher than in subgroup 2b at every time point.

CONCLUSIONS

The results of this study demonstrated that liver preservation by the TLM before hepatocyte isolation might be beneficial and will be useful in the field of hepatotocyte transplantation.

The role of total pancreatectomy and islet autotransplantation for chronic pancreatitis

Total pancreatectomy and islet autotransplantation are done for chronic pancreatitis with intractable pain when other treatment measures have failed, allowing insulin secretory capacity to be preserved, minimizing or preventing diabetes, while at the same time removing the root cause of the pain. Since the first case in 1977, several series have been published. Pain relief is obtained in most patients, and insulin independence preserved long term in about a third, with another third having sufficient beta cell function so that the surgical diabetes is mild. Islet autotransplantation has been done with partial or total pancreatectomy for benign and premalignant conditions. Islet autotransplantation should be used more widely to preserve beta cell mass in major pancreatic resections.

Intramuscular autotransplantation of pancreatic islets in a 7-year-old child: a 2-year follow-up

A 7-year-old girl with severe hereditary pancreatitis underwent total pancreatectomy. A total of 160,000 islet equivalents (6400 islet/kg) were transplanted to the brachioradialis muscle of the right forearm. Her plasma C-peptide level was undetectable after pancreatectomy but increased to 1.37 ng/mL after 17 days; at this time point, her insulin requirement was 0.75 units of insulin/kg/day. At 5- and 27-months, her hemoglobin A1c (HbA1c) and insulin requirements were 4.5 and 5.3% and 0.3 and 0.18 units/kg/day, respectively. Basal and stimulated C-peptide levels were 0.67 +/- 0.07 and 3.36 +/- 1.37 ng/mL, respectively. Stimulated insulin levels were 30% higher in the islet-bearing arm compared to the contralateral arm after glucagon stimulation. After surgery and islet transplantation, the quality of life improved dramatically and she gained 8 kg of weight. In summary, a normal HbA1c, a low insulin requirement and the absence of recurrent hypoglycemia and the gradient of insulin between the arms indicate that the intramuscularly transplanted islets contribute to a long-term clinically significant metabolic control.

Toward maximizing the success rates of human islet isolation: influence of donor and isolation factors

In order to make islet transplantation a therapeutic option for patients with diabetes there is an urgent need for more efficient islet cell processing to maximize islet recovery. Improved donor management, organ recovery techniques, implementation of more stringent donor criteria, and improved islet cell processing techniques may contribute to enhance organ utilization for transplantation. We have analyzed the effects of donor and islet processing factors on the success rate of human islet cell processing for transplantation performed at a single islet cell processing center. Islet isolation outcomes improved when vasopressors, and in particular pitressin, and steroids were used for the management of multiorgan donors. Higher islet yields were obtained from adult male donors, BMI >25 kg/m2, adequate glycemic control during hospital stay, and when the pancreas was retrieved by a local surgical team. Successful isolations were obtained in 58% of the cases when > or = 4 donor criteria were met, and even higher success rates (69%) were observed when considering > or = 5 criteria. Our data suggest that a sequential, integrated approach is highly desirable to improve the success rate of islet cell processing.

Availability of suitable islet donors in the United States

BACKGROUND

We characterize donor utilization for islet transplantation and estimate the number of recipients who could achieve normoglycemia through islet transplantation if the current donor pool were used.

METHODS

Potential islet donors from all United Network for Organ Sharing donors (1/00-5/04) were identified and categorized into "optimal" islet donors (16-40 yr, body mass index >27 kg/m, hemodynamically stable) or "standard" donors (as traditionally described).

RESULTS

Of 27,552 potential donors during this period, 6,140 donor pancreata were used for whole organ transplant. Of the remaining 21,412 donors, 10,417 potential islet donors were identified (9260 [88.9%] standard and 1157 [11.1%] optimal donors). Islets from only 218 donors were used for transplant, representing 8.7% of optimal donors and 2.1% of all potential islet donors.

CONCLUSION

The widespread use of isolated islets could provide insulin independence for approximately 1000 type I diabetics a year, but at current rates of islet transplant, all recipients could be transplanted with islets from ideal donors.

Perspectives in organ preservation

Maintaining organ viability after donation until transplantation is critically important for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in every day clinical practice. Although simple and effective, it is questionable whether this method is able to prevent deterioration of organ quality in the present era with increasing numbers of organs retrieved from older, more marginal, and even non-heart-beating donors. This review describes principles involved in effective preservation and focuses on some basic components and methods of abdominal organ preservation in clinical and experimental transplantation. Concepts and developments to reduce ischemia related injury are discussed, including hypothermic machine perfusion. Despite the fact that hypothermic machine perfusion might be superior to static cold storage preservation, organs are still exposed to hypothermia induced damage. Therefore, recently some groups have pointed at the beneficial effects of normothermic machine perfusion as a new perspective in organ preservation and transplantation.

Differential regulation of CHOP-10/GADD153 gene expression by MAPK signaling in pancreatic beta-cells

CHOP-10 (GADD153/DDIT-3) is a bZIP protein involved in differentiation and apoptosis. Its expression is induced in response to stresses such as nutrient deprivation, perturbation of the endoplasmic reticulum, redox imbalance, and UV exposure. Here we show that CHOP expression is induced in cultured pancreatic beta-cells maintained in a basal glucose concentration of 5.5 mM and repressed by stimulatory glucose (>or=11 mM). Both induction and repression of CHOP are dependent on the MAPKs ERK1 and ERK2. Two regulatory composite sites containing overlapping MafA response elements (MARE) and CAAT enhancer binding (CEB) elements regulate transcription in an ERK1/2-dependent manner. One site (MARE-CEB), from -320 to -300 bp in the promoter, represses transcription. The other site (CEB-MARE), from +2,628 to +2,641 bp in the first intron of the CHOP gene, activates it. MafA can influence transcription of both sites. The MARE-CEB is repressed by MafA, whereas the CEB-MARE site, which is homologous to the A2C1 component of the glucose-sensitive RIPE3b region of the insulin gene promoter, is activated by MafA. These results indicate that ERK1/2 have dual roles in regulating CHOP gene expression via both promoter and intronic regions, depending on environmental and metabolic stresses imposed on pancreatic beta-cells.

The rationale for the new deceased donor pancreas allocation schema

BACKGROUND

To ensure the continued success of whole organ pancreas and islet transplantation, deceased donor pancreas allocation policy must continue to evolve.

METHODS

To assess the existing system, the Organ Procurement and Transplantation Network (OPTN)/United Network for Organ Sharing Kidney and Pancreas Transplant Committee retrospectively analyzed the disposition and outcomes of deceased donor pancreata in the United States between January 1, 2000 and December 31, 2003.

RESULTS

During the time period studied, consent was obtained but the pancreas was not recovered in 48% (11,820) of organ donors. The most common reasons given for nonrecovery were poor quality of the pancreas and difficulty in placement. Of whole organ pancreata that were transplanted, 90% were from donors with a body mass index (BMI) <or=30 kg/m and age <or=50 years. Pancreata from older and more obese donors were used more often for islet transplantation or research. For simultaneous pancreas-kidney transplants, the 1- and 3-year pancreas graft survival was lower when the donor was age >50 years (P=0.04), and there were trends toward lower graft survival with donor BMI >30 (P=0.06) and increasing cold-ischemia time.

CONCLUSIONS

Based on these data, the OPTN adopted a new allocation algorithm in which pancreata from donors >30 kg/m or >50 years of age are, unless accepted for a local whole organ pancreas transplant candidate, preferentially allocated for islet transplantation. These data also suggest that many good quality pancreata are not procured, emphasizing the need for improved communication and cooperation between organ procurement organizations and pancreas and islet transplant programs.

Factors influencing the loss of beta-cell mass in islet transplantation

Recent advances in clinical islet transplantation have clearly demonstrated that this procedure can provide excellent glycemic control and often insulin independence in a population of patients with type 1 diabetes. A key limitation in the widespread application of clinical islet transplantation is the requirement of 10,000 islet equivalents/kg in most recipients, generally derived from two or more cadaveric donors. It has been determined that a majority of the transplanted islets fail to engraft and become fully functional. In this review article, the factors that contribute to this early loss of islets following transplantation are discussed in depth.

Islet cell transplantation

People with type 1 diabetes have normal exocrine pancreatic function, making islet cell rather than whole organ transplantation an attractive option. Achieving insulin independence in type 1 diabetes was the perceived goal of islet cell transplantation. The success of the Edmonton group in achieving this in a selected group of type 1 patients has led to renewed optimism that this treatment could eventually replace whole organ pancreas transplantation. However the long-term results of this treatment indicate that insulin independence is lost with time in a significant proportion of patients, although they may retain glycaemic stability. In this context, the indications for islet cell transplantation, which have evolved over the last 5 years, indicate that the patients who benefit most are those who experience severe hypoglycaemic reactions despite optimal insulin therapy. This review will summarise the history of islet cell transplantation, islet isolation techniques, the transplant procedure, immunosuppressive therapy, indications for islet cell transplantation, current clinical trials, the early UK islet cell transplant experience using the Edmonton protocol, and some of the challenges that lie ahead.

Estado actual del trasplante de islotes pancreáticos

Due to the numerous advances in islet transplantation in the last few years, clinical outcomes following this procedure are continually improving. Novel immunosuppression protocols, improved donor and recipient selection, and careful attention to the process of organ extraction, preservation and islet isolation have contributed to long-term success. The present article reviews the results of clinical islet transplantation and their relationship with the different advances introduced. The use of new islet sources such as living and non-heart-beating donors, as well as recent advances in our knowledge of the mechanisms of rejection and its prevention, are also reviewed.

Shipment of human islets for transplantation

The use of regional human islet cell processing centers (ICPC) supporting distant clinical islet transplantation programs (CITP) has proven successful in recent clinical trials. Standardization of islet shipping protocols is needed to preserve cell product identity, quantity, quality and sterility, and to meet criteria for transplantation. We evaluated the use of gas-permeable bags for human islet preparation shipment from a single ICPC to two remote CITPs. Product release tests (counts, purity, viability, sterility and potency) were performed at both centers using identical protocols to determine adequacy for transplantation.Thirty-five islet preparations were shipped either immediately after isolation (n = 20) or following culture (n = 15). Islet recovery rate after shipment was higher in cultured preparations, when compared to those not cultured (91.2 +/- 4.9% vs. 72.9 +/- 4.7%, respectively; p < 0.05), though the overall recovery rate based on isolation and pre-transplant counts was comparable (72.9 +/- 4.7% vs. 70.4 +/- 3.5%, respectively; p = N.S.). All preparations met product release criteria for transplantation. Additional experiments showed that gas-permeable bags led to improved recovery and potency, when compared to 50-mL conical tubes or to non-gas-permeable bags for shipment.Collectively, our data demonstrate that the use of gas-permeable bags is efficient for clinical-grade and should be preferred also for the shipment of research-grade islet preparations.

Validation of the scoring system for standardization of the pancreatic donor for islet isolation as used in a new islet isolation center

BACKGROUND

The aim of this study was to evaluate the effectiveness of the Edmonton Donor Scoring System for use in our much less active islet center. Because the ability to recognize an appropriate donor may help to achieve consistent and predictable success of pancreatic islet isolation, it should lead to increased effectiveness and lower cost.

MATERIAL AND METHODS

Charts of 36 consecutive pancreas donors were reviewed to assess the donor points (DP). DP ranged from 0 to 100 based on donor age, body mass index, cause of death, social and medical history, hospital stay, vasopressor dosages, laboratory tests, cold ischemia time and procurement team, as well as pancreas size, consistency, fat content, damage, and quality of procurement and packing.

RESULTS

Successful isolation was achieved in 39% of donors (14 of 36), a value similar to that achieved in Edmonton (40%). We used the optimal cutoff value (DP = 79) proposed by the Edmonton group. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 66%, 75%, 57%, 82% and 72%, respectively. Successful islet isolation from poor or marginal donors (DP < 49.5 and 50 to 59.5) was 0% and 28.6% respectively; it was 63% and 100% in optimal donors (DP = 80 to 89.5 and 90 to 100). We concluded that islet isolation success correlated with the previously proposed donor scoring system.

CONCLUSIONS

The Donor Scoring System can be successfully implemented regardless of the level of activity of an experienced isolation center. This system permits identification of a suitable donor prior to organ processing. It may guide a center's donor selection strategy based on its goals and its budget.

Influence of Preservation Solution on Human Islet Isolation Outcome

BACKGROUND

The influence of the preservation solution used for in situ perfusion of the donor and pancreas storage on islet isolation has received little attention.

METHODS

In this prospective controlled trial, we compared the outcome of human islet isolation from pancreata perfused with University of Wisconsin (UW) solution or Celsior, an alternative colloid-free extracellular solution.

RESULTS

At the 1-year interim analysis, the viability and insulin secretion of islets isolated from donors perfused with UW (n=19) or Celsior (n=5) were identical. However, total islet recovery (IEQ) and isolation yield (IEQ/g) were 1.8-fold and 2.1-fold inferior in the Celsior group (P<0.05 vs. UW). Overall, 13 (68%) of islet preparations were effectively transplanted from the UW group vs. none from the Celsior group (P=0.01). The clinical study was discontinued and the causes of these differences were further explored in the pig (n=14). In contrast to UW, Celsior induced cell swelling and pancreas edema after only four hours of cold storage. These abnormalities were delayed when the donor was perfused with Solution de Conservation d'Organes et de Tissus (SCOT), an extracellular solution containing polyethylene glycol.

CONCLUSIONS

Our results suggest that colloid-free preservation solutions might be suboptimal for pancreas perfusion and cold storage prior to islet isolation and transplantation. Because pancreata are now frequently recovered for islet transplantation, preliminary experimental and clinical data about islet isolation should be obtained prior to the routine implementation of new preservation solutions for abdominal perfusion during multiorgan recovery.

Improved outcomes in islet isolation and transplantation by the use of a novel hemoglobin-based O2 carrier

During isolation, islets are exposed to warm ischemia. In this study, intraductal administration of oxygenated polymerized, stroma-free hemoglobin-pyridoxalated (Poly SFH-P) was performed to improve O2 delivery. Rat pancreata subjected to 30-min warm ischemia were perfused intraductally with collagenase in oxygenated Poly SFH-P/RPMI or RPMI (control). PO2 was increased by Poly SFH-P (381.7 +/- 35.3 mmHg vs. 202.3 +/- 28.2, p = 0.01) and pH maintained within physiological range (7.4-7.2 vs. 7.1-6.6, p = 0.009). Islet viability (77% +/- 4.6 vs. 63% +/- 4.7, p = 0.04) was improved and apoptosis lower with Poly SFH-P (caspase-3: 34,714 +/- 2167 vs. 45,985 +/- 1382, respectively, p = 0.01). Poly SFH-P improved islet responsiveness to glucose as determined by increased intracellular Ca2+ levels and improved insulin secretion (SI 5.4 +/- 0.1 vs. 3.1 +/- 0.2, p = 0.03). Mitochondrial integrity was improved in Poly SFH-P-treated islets, which showed higher percentage change in membrane potential after glucose stimulation (14.7% +/- 1.8 vs. 9.8 +/- 1.4, respectively, p < 0.05). O2 delivery by Poly SFH-P did not increase oxidative stress (GSH 7.1 +/- 2.9 nm/mg protein for Poly SFH-P vs. 6.8 +/- 2.4 control, p = 0.9) or oxidative injury (MDA 1.8 +/- 0.9 nmol/mg protein vs. 6.2 +/- 2.4, p = 0.19). Time to reach normoglycemia in transplanted diabetic nude mice was shorter (1.8 +/- 0.4 vs. 7 +/- 2.5 days, p = 0.02), and glucose tolerance improved in the Poly SFH-P group (AUC 8106 +/- 590 vs. 10,863 +/- 946, p = 0.03). Oxygenated Poly SFH-P improves islet isolation and transplantation outcomes by preserving mitochondrial integrity.

Islet isolation and transplantation outcomes of pancreas preserved with University of Wisconsin solution versus two-layer method using preoxygenated perfluorocarbon

BACKGROUND

Previous small clinical trials indicate that the two-layer method (TLM) for pancreas preservation improves islet isolation outcome. However, the effect of TLM has not been evaluated in large-scale study. In addition, a direct benefit of TLM on islet transplantation outcome has not been addressed in the setting of any randomized controlled trials.

METHODS

Between April 2003 and October 2005, human pancreata from brain-dead donors were preserved by TLM using preoxygenated perfluorocarbon (n = 75) or in University of Wisconsin (UW) solution (n = 91) prior to islet isolation. Islet isolation and transplantation outcomes were compared between the two groups.

RESULTS

We did not find any significant differences in adenosine triphosphate content in pancreatic tissue after preservation, pre and postpurification islet yields, in vitro insulin secretory function, or utilization ratio of transplantation between the two groups. Transplanted mass and functional viability of islet isolated from TLM-preserved pancreas were similar to those from UW-preserved pancreas. Patients receiving the TLM-islet or the UW-islet showed a marked decrease in insulin requirement after transplantation. However, no significant difference was observed in a decrease in insulin requirement between patients receiving the TLM-islet and the UW-islet.

CONCLUSIONS

No beneficial effect of TLM on islet isolation and transplantation outcomes was observed. Our findings bring into question the true merit of routine use of TLM prior to islet isolation.

Neonatal porcine islets exhibit natural resistance to hypoxia-induced apoptosis

BACKGROUND

Despite the success of the Edmonton protocol for human islet transplantation, an alternate source of islet tissue must be developed if beta-cell replacement therapy is to see widespread application. Neonatal porcine islets (NPI) represent one potential source of tissue. When human or rodent islets are transplanted, the majority of cells undergo hypoxia-induce apoptosis soon after the grafts are placed in the recipient. In the present study, we investigated whether NPI were similarly sensitive to hypoxia.

METHODS

NPI were exposed to hypoxia and hypoxia/reoxygenation using an in vitro hypoxic chamber. Afterwards, viability, frequency of apoptosis, and beta-cell function were evaluated. NPI and adult porcine islets were transplanted into chemically diabetic, immunodeficient mice and graft apoptosis was assessed 24 hours and seven days posttransplant.

RESULTS

NPI demonstrated a remarkable capacity to resist apoptosis and maintain insulin secretion despite severe stresses such as hypoxia/reoxygenation. One day after transplantation, NPI grafts showed limited apoptosis, confined to rare strongly insulin positive cells. In contrast, adult porcine islet grafts underwent widespread apoptosis. Western blotting revealed that NPI express high levels of at least one potent endogenous antiapoptotic protein (XIAP).

CONCLUSIONS

The majority of cells within transplanted human islets undergo apoptosis soon after portal infusion. In contrast, NPI have the capacity to resist this early posttransplant apoptosis, with likely reduced antigen release and diminished immune stimulation. NPI appear to contain a population of insulin-low to insulin-negative pre-beta-cells, which are resistant to hypoxia-induced apoptosis and still capable of differentiating into mature beta-cells.

The ADP/ATP ratio: A novel predictive assay for quality assessment of isolated pancreatic islets

The current standard assays for islet product release criteria are unable to predict the outcome after clinical islet transplantation. Therefore, establishment of reliable and rapid assays enabling pre-transplantation prediction of islet potency is warranted. In the present study, we have evaluated the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) test, the glucose-stimulated insulin release, the loss of islets during the first 24 h in culture, and the insulin/deoxyribonucleic acid as predictive assays for the ability of isolated porcine islets to cure athymic mice with streptozotocin-induced diabetes. From the results presented, it is concluded that the measurement of the ADP/ATP ratio was the only test that correlated with transplantation outcome. In summary, we propose that the ADP/ATP assay is worthwhile as applied to human islet transplantation and seek to validate it as a rapid and potent predictor of transplant outcome.

Overcoming the Challenges Now Limiting Islet Transplantation: A Sequential, Integrated Approach

Steady improvements in islet cell processing technology and immunosuppressive protocols have made pancreatic islet transplantation a clinical reality for the treatment of patients with Type 1 diabetes mellitus (T1DM). Recent trials are showing that improved glycemic metabolic control, prevention of severe hypoglycemia, and better quality of life can be reproducibly achieved after transplantation of allogeneic islets in patients with unstable T1DM. Despite these encouraging results, challenges ahead comprise obtaining adequate islet cells for transplant, enhancing islets engraftment, sustaining beta cell mass and function over time, and defining effective immune interventions, among others. In order to overcome the current hurdles to the widespread application of islet transplantation there is a need for implementation of integrated, sequential therapeutic approaches.

Improved human islet isolation using nicotinamide

We investigated the effects of nicotinamide (NA) supplementation of the processing medium during islet isolation. One hundred and two human pancreata were processed for clinical transplantation after preservation either in the University of Wisconsin (UW) or using the two-layer method (TLM). Pancreata were then divided into four groups and retrospectively analyzed. Group I: UW preservation followed by processing without NA, Group II: UW preservation and processing with NA, Group III: TLM preservation without NA, Group IV: TLM preservation with NA. We observed a significant increase in islet yield in Group II (4343+/-348 IEQ/g) [mean+/-SEM], compared to Group I (2789+/-348 IEQ/g) (p=0.005). Similarly, a significant increase in islet yield was observed when NA was used in the processing of organs preserved with TLM (Group IV: 5538+/-413 vs. Group III: 3500+/-629; p=0.02). Furthermore islet yield was higher in Group IV than in Group II (p<0.05). The percentages of preparations that qualified for transplantation were 25, 47, 45, 69% in Groups I, II, III, IV, respectively. Addition of NA to the processing medium significantly improved islet yields in both the UW and TLM preservation protocols, allowing for a higher percentage of islet preparations to qualify for clinical transplantation.

Sequential kidney/islet transplantation: efficacy and safety assessment of a steroid-free immunosuppression protocol

The aim of this study was to assess the efficiency and safety of the Edmonton immunosuppression protocol in recipients of islet-after-kidney (IAK) grafts. Fifteen islet infusions were administered to 8 patients with type 1 diabetes and a functioning kidney graft. Immunosuppression was switched on the day of transplantation to a regimen associating sirolimus-tacrolimus-daclizumab. Insulin-independence was achieved in all patients for at least 3 months, with an actual rate of 71% at 1 year after transplantation (5 of 7 patients). After 24-month mean follow-up, five have ongoing insulin independence, 11-34 months after transplantation, with normal HbA1c, fructosamine and mean amplitude of glycemic excursions (MAGE) values. Results of arginine-stimulation tests improved over time, mostly after the second islet infusion. Severe adverse events included bleeding after percutaneous portal access (n=2), severe pneumonia attributed to sirolimus toxicity (n=1), kidney graft loss after immunosuppression discontinuation (n=1), reversible humoral kidney rejection (n=1) and fever of unknown origin (n=1). These data indicate that the Edmonton approach can be successfully applied to the IAK setting. This procedure is associated with significant side effects and only patients with stable function of the kidney graft should be considered. The net harm versus benefit has not yet been established and will require further studies with larger numbers of enrolled subjects.