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

Optimization of dye solutions for detecting damaged pancreatic tissues during islet isolation procedures

We previously reported that dye was effective to prevent the leakage of enzyme solutions from pancreatic glands during an islet isolation procedure. However, the dye used for islet isolation has not yet been optimized. In this study, we focused on pyoktanin blue (PB), diagnogreen (DG), and indigo carmine (IC) as potential candidates among clinically established dyes. A serial dilution assay was performed to determine minimal effective concentrations of each dye for detecting damaged pancreatic tissues. According to the outcome of serial dilution assays, double minimum effective concentrations of each dye were used for in vitro toxicity assays on islets and used in the isolation procedure to investigate whether they adversely affect islet isolation efficiency. The evaluations included islet yield, ADP/ATP, ATP/DNA, glucose stimulation test, and insulin/DNA assays. Islet viability cultured with PB contained medium was significantly lower than the other dyes. DG and IC appeared to be non-toxic to the islets. In isolation experiments, the islet yield in the DG group was considerably lower than that in the Control group, suggesting that DG might inhibit enzyme activity. The present study demonstrates that IC could be a promising candidate for an effective dye to detect damaged pancreatic tissues without affecting the enzyme activity and islet quality.

Pancreatic Islet Purification from Large Mammals and Humans Using a COBE 2991 Cell Processor versus Large Plastic Bottles

The islet purification step in clinical islet isolation is important for minimizing the risks associated with intraportal infusion. Continuous density gradient with a COBE 2991 cell processor is commonly used for clinical islet purification. However, the high shear force involved in the purification method using the COBE 2991 cell processor causes mechanical damage to the islets. We and other groups have shown human/porcine islet purification using large cylindrical plastic bottles. Shear stress can be minimized or eliminated using large cylindrical plastic bottles because the bottles do not have a narrow segment and no centrifugation is required during tissue loading and the collection processes of islet purification. This review describes current advances in islet purification from large mammals and humans using a COBE 2991 cell processor versus large cylindrical plastic bottles.

Pancreatic islet transplantation: toward definitive treatment for diabetes mellitus

Since the late 20th century, advances in pancreatic islet transplantation have targeted improved glycemic control and fewer hypoglycemic events in patients with type 1 diabetes, and some important milestones have been reached. Following the Edmonton group's success in achieving insulin independence in all transplanted patients with type 1 diabetes, clinical islet transplantation is now performed worldwide. β cell replacement therapy for type 1 diabetes was established based on the favorable outcomes of a phase 3, prospective, open-label, single-arm, clinical study conducted at 8 centers in North America, in which 42 of 48 patients who underwent islet transplantation from 2008 to 2011 achieved HbA1c < 7.0% (53 mmol/mol) at day 365, which was maintained at 2 years in 34 patients. In Japan, a phase 2 multicenter clinical trial of islet transplantation for type 1 diabetes patients is currently ongoing and will end soon, but the interim results have already led to positive changes, with allogeneic islet transplantation being covered by the national health insurance system since April 2020. Current efforts are being made to solve the problem of donor shortage by studying alternative donor sources, such as porcine islets and pancreatic progenitor cells derived from pluripotent stem cells. The results of clinical trials in this area are eagerly awaited. It is hoped that they will contribute to establishing alternative sources for insulin-producing β cells in the near future.

Beneficial effects of the novel marine oxygen carrier M101 during cold preservation of rat and human pancreas

Ischaemia impairs organ quality during preservation in a time‐dependent manner, due to a lack of oxygen supply. Its impact on pancreas and islet transplantation outcome has been demonstrated by a correlation between cold ischaemia time and poor islet isolation efficiency. Our goal in the present study was to improve pancreas and islet quality using a novel natural oxygen carrier (M101, 2 g/L), which has been proven safe and efficient in other clinical applications, including kidney transplantation, and for several pre‐clinical transplantation models. When M101 was added to the preservation solution of rat pancreas during ischaemia, a decrease in oxidative stress (ROS), necrosis (HMGB1), and cellular stress pathway (p38 MAPK)activity was observed. Freshly isolated islets had improved function when M101 was injected in the pancreas. Additionally, human pancreases exposed to M101 for 3 hours had an increase in complex 1 mitochondrial activity, as well as activation of AKT activity, a cell survival marker. Insulin secretion was also up‐regulated for isolated islets. In summary, these results demonstrate a positive effect of the oxygen carrier M101 on rat and human pancreas during preservation, with an overall improvement in post‐isolation islet quality.

Strategy towards tailored donor tissue-specific pancreatic islet isolation

BACKGROUND

Optimizing the collagenase G (ColG):collagenase H (ColH) ratio is a key strategy for achieving tailored donor-tissue specific islet isolation. Collagen V (Col V) and collagen III (Col III) are crucial target matrices of ColG and ColH, respectively. We herein investigated the relevance between the expression of target matrices in pancreatic tissues and influence of ColG:ColH ratio on islet isolation outcome.

METHODS

Islet isolation was performed in Lewis and SD rats using different ColG:ColH ratios (5:1, 1:1 and 1:5; n = 7/group). The composition of Col III and Col V was examined using immunohistochemical staining, real-time polymerase chain reaction (PCR), Western blotting and mass spectrometry. Chain types in collagen I (Col I) were also assessed using mass spectrometry.

RESULTS

No beneficial effects were observed by increasing the ColG amount, irrespective of the rat strain. In contrast, the islet yield in Lewis rats was considerably increased by high amounts of ColH but decreased in SD rats, suggesting that Lewis pancreas contains more Col III than SD pancreas. Neither immunohistochemical nor real-time PCR showed correlation with isolation outcome. However, Western blotting revealed that Lewis contained considerably higher amount of Col III than SD (p = 0.10). Likewise, Col-I(α1)/Col-III(α1) and Col-I(α2)/Col-III(α1) were significantly lower in Lewis than in SD rats (p = 0.007, respectively). Furthermore, the isolation outcome was considerably correlated with the composition of homotrimeric Col I.

CONCLUSIONS

The Col III expression and the composition of homotrimeric Col I in pancreatic tissues determined using mass analyses appeared useful for optimizing the ColG:ColH ratio in islet isolation.

Mimicking oxygen delivery and waste removal functions of blood

In addition to immunological and wound healing cell and platelet delivery, ion stasis and nutrient supply, blood delivers oxygen to cells and tissues and removes metabolic wastes. For decades researchers have been trying to develop approaches that mimic these two immediately vital functions of blood. Oxygen is crucial for the long-term survival of tissues and cells in vertebrates. Hypoxia (oxygen deficiency) and even at times anoxia (absence of oxygen) can occur during organ preservation, organ and cell transplantation, wound healing, in tumors and engineering of tissues. Different approaches have been developed to deliver oxygen to tissues and cells, including hyperbaric oxygen therapy (HBOT), normobaric hyperoxia therapy (NBOT), using biochemical reactions and electrolysis, employing liquids with high oxygen solubility, administering hemoglobin, myoglobin and red blood cells (RBCs), introducing oxygen-generating agents, using oxygen-carrying microparticles, persufflation, and peritoneal oxygenation. Metabolic waste accumulation is another issue in biological systems when blood flow is insufficient. Metabolic wastes change the microenvironment of cells and tissues, influence the metabolic activities of cells, and ultimately cause cell death. This review examines advances in blood mimicking systems in the field of biomedical engineering in terms of oxygen delivery and metabolic waste removal.

Long-Term Glycemic Control in Adult Patients Undergoing Remote vs. Local Total Pancreatectomy With Islet Autotransplantation

OBJECTIVES

Total pancreatectomy with islet autotransplantation (TPIAT) is increasingly performed with remote islet cell processing and preparation, i.e., with islet cell isolation performed remotely from the primary surgical site at an appropriately equipped islet isolation facility. We aimed to determine whether TPIAT using remote islet isolation results in comparable long-term glycemic outcomes compared with TPIAT performed with standard local isolation.

METHODS

We performed a retrospective cohort study of adult patients who underwent TPIAT at three tertiary care centers from 2010 to 2013. Two centers performed remote isolation and one performed local isolation. Explanted pancreata in the remote cohort were transported ∼130 miles to and from islet isolation facilities. The primary outcome was insulin independence 1 year following transplant.

RESULTS

Baseline characteristics were similar between groups except the remote cohort had higher preoperative hemoglobin A1c (HbA1c; 5.43 vs. 5.25, P=0.02) and there were more females in the local cohort (58% vs. 76%, P=0.049). At 1 year, 27% of remote and 32% of local patients were insulin independent (P=0.48). Remote patients experienced a greater drop in fasting c-peptide (-1.66 vs. -0.64, P=0.006) and a greater rise in HbA1c (1.65 vs. 0.99, P=0.014) at 1-year follow-up. A preoperative c-peptide >2.7 (odds ratio (OR) 4.4, 95% confidence interval (CI) 1.6-14.3) and >3,000 islet equivalents/kg (OR 11.0, 95% CI 3.2-37.3) were associated with one-year insulin independence in the local group.

CONCLUSIONS

At 1 year after TPIAT, patients undergoing remote surgery have equivalent rates of long-term insulin independence compared with patients undergoing TPIAT locally, but metabolic control is superior with local isolation.

Islet Cell Yield Following Remote Total Pancreatectomy With Islet Autotransplant is Independent of Cold Ischemia Time

OBJECTIVES

Total pancreatectomy with islet autotransplantation is increasingly being performed remotely, that is, removing the pancreas in 1 location, isolating the islet cells in another location, then returning the islets to the original location for reimplantation into the patient. We determined the influence of extended cold ischemia time on key clinical outcomes in remote islet autotransplantation.

METHODS

We evaluated patients who underwent remote islet autotransplantation at 2 centers from 2011 to 2014. Patients were divided into 2 groups: those with and those without a decrease in C-peptide greater than 50% from baseline. The primary clinical outcome was the quantity of isolated islet equivalents per kilogram body weight (IEQs/kg).

RESULTS

Twenty-five patients met inclusion criteria; 15 had a decrease in C-peptide greater than 50% from baseline and had lower corresponding IEQs/kg compared with those without a decrease greater than 50% (4045 vs 6654 IEQs/kg, P = 0.01). There was no difference in cold ischemia time between the 2 groups (664 vs 600 minutes, P = 0.25). Daily insulin use at 1 year nearly met statistical significance (25.3 vs 8 U, P = 0.06), as did glycated hemoglobin (8.07 vs 6.69 mmol/L, P = 0.06).

CONCLUSIONS

Cold ischemia time does not influence islet yield in patients undergoing pancreatectomy with remote isolation.

Comparison of Purification Solutions With Different Osmolality for Porcine Islet Purification

The osmolality of the purification solution is one of the most critical variables in human islet purification during islet isolation. We previously reported the effectiveness of a combined continuous density/osmolality gradient for the supplemental purification of human islets. We herein applied a combined continuous density/osmolality gradient for regular purification. The islets were purified with a continuous density gradient without osmolality preparation [continuous density/normal osmolality (CD/NO)] or continuous density/osmolality solution with osmolality preparation by 10× Hank's balanced salt solution (HBSS) [continuous density/continuous osmolality (CD/CO)]. The osmolality of the low-density solution was 400 mOsm/kg in both groups and that of the high-density solution was 410 mOsm/kg in the CD/NO group and 500 mOsm/kg in the CD/CO group. Unexpectedly, we noted no significant differences between the two solutions in terms of the islet yield, rate of viability and purity, score, stimulation index, or the attainability and suitability of posttransplantation normoglycemia. Despite reports that the endocrine and exocrine tissues of pancreata have distinct osmotic sensitivities and that high-osmolality solutions result in greater purification efficiency, the isolation and transplant outcomes did not markedly differ between the two purification solutions with different osmolalities in this study.

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.

National Institutes of Health-Sponsored Clinical Islet Transplantation Consortium Phase 3 Trial: Manufacture of a Complex Cellular Product at Eight Processing Facilities

Eight manufacturing facilities participating in the National Institutes of Health-sponsored Clinical Islet Transplantation (CIT) Consortium jointly developed and implemented a harmonized process for the manufacture of allogeneic purified human pancreatic islet (PHPI) product evaluated in a phase 3 trial in subjects with type 1 diabetes. Manufacturing was controlled by a common master production batch record, standard operating procedures that included acceptance criteria for deceased donor organ pancreata and critical raw materials, PHPI product specifications, certificate of analysis, and test methods. The process was compliant with Current Good Manufacturing Practices and Current Good Tissue Practices. This report describes the manufacturing process for 75 PHPI clinical lots and summarizes the results, including lot release. The results demonstrate the feasibility of implementing a harmonized process at multiple facilities for the manufacture of a complex cellular product. The quality systems and regulatory and operational strategies developed by the CIT Consortium yielded product lots that met the prespecified characteristics of safety, purity, potency, and identity and were successfully transplanted into 48 subjects. No adverse events attributable to the product and no cases of primary nonfunction were observed.

Advances in organ preservation for transplantation

Organ transplantation provides the best available therapy for a myriad of medical conditions, including end-stage renal disease, hepatic failure and type I diabetes mellitus. The current clinical reality is, however, that there is a significant shortage of organs available for transplantation with respect to the number of patients on organ waiting lists. As such, methods to increase organ supply have been instituted, including improved donor management, organ procurement and preservation strategies, living organ donation, transplantation education and the increased utilization of donation after circulatory death and expanded criteria donors. In particular, especially over the last decade, we have witnessed a significant change in the way donor organs are preserved, away from static cold storage methods to more dynamic techniques centred on machine perfusion (MP). This review highlights the current state and future of organ preservation for transplantation, focusing on both abdominal and thoracic organs. In particular, we focus on MP preservation of renal, hepatic, pancreatic, cardiac and lung allografts, also noting relevant advances in Australasia. MP of organs after procurement holds considerable promise, and has the potential to significantly improve graft viability and function post-transplantation, especially in donors in whom acceptance criteria have been expanded.

A Multicenter Study: North American Islet Donor Score in Donor Pancreas Selection for Human Islet Isolation for Transplantation

Selection of an optimal donor pancreas is the first key task for successful islet isolation. We conducted a retrospective multicenter study in 11 centers in North America to develop an islet donor scoring system using donor variables. The data set consisting of 1,056 deceased donors was used for development of a scoring system to predict islet isolation success (defined as postpurification islet yield >400,000 islet equivalents). With the aid of univariate logistic regression analyses, we developed the North American Islet Donor Score (NAIDS) ranging from 0 to 100 points. The c index in the development cohort was 0.73 (95% confidence interval 0.70-0.76). The success rate increased proportionally as the NAIDS increased, from 6.8% success in the NAIDS < 50 points to 53.7% success in the NAIDS ≥ 80 points. We further validated the NAIDS using a separate set of data consisting of 179 islet isolations. A comparable outcome of the NAIDS was observed in the validation cohort. The NAIDS may be a useful tool for donor pancreas selection in clinical practice. Apart from its utility in clinical decision making, the NAIDS may also be used in a research setting as a standardized measurement of pancreas quality.

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.

Islet product characteristics and factors related to successful human islet transplantation from the Collaborative Islet Transplant Registry (CITR) 1999-2010

The Collaborative Islet Transplant Registry (CITR) collects data on clinical islet isolations and transplants. This retrospective report analyzed 1017 islet isolation procedures performed for 537 recipients of allogeneic clinical islet transplantation in 1999-2010. This study describes changes in donor and islet isolation variables by era and factors associated with quantity and quality of final islet products. Donor body weight and BMI increased significantly over the period (p<0.001). Islet yield measures have improved with time including islet equivalent (IEQ)/particle ratio and IEQs infused. The average dose of islets infused significantly increased in the era of 2007-2010 when compared to 1999-2002 (445.4±156.8 vs. 421.3±155.4×0(3) IEQ; p<0.05). Islet purity and total number of β cells significantly improved over the study period (p<0.01 and <0.05, respectively). Otherwise, the quality of clinical islets has remained consistently very high through this period, and differs substantially from nonclinical islets. In multivariate analysis of all recipient, donor and islet factors, and medical management factors, the only islet product characteristic that correlated with clinical outcomes was total IEQs infused. This analysis shows improvements in both quantity and some quality criteria of clinical islets produced over 1999-2010, and these parallel improvements in clinical outcomes over the same period.

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.

DCD for Islet Transplantation

Pancreatic islet transplantation has the potential to become the most physiologically advantageous and minimally invasive procedure for the treatment of type 1 diabetes mellitus. Since the first clinical islet transplantation was performed at the University of Minnesota in 1974 [1], the results have been far from ideal for more than two decades in spite of an improvement of islet isolation technique by Ricordi et al. [2–4]. The introduction of the Edmonton protocol, with a highly improved rate of insulin independency, encouraged us to promote clinical islet transplantation [5, 6]. In Japan, we organized the Working Group (The Japanese Islet Transplant Registry) in 1997 under the Japanese Society for Pancreas and Islet Transplantation for the purpose of starting clinical islet transplantation. The first issue of the Working Group was to construct a system of clinical islet transplantation in Japan including the registration of the recipients, procurement of the pancreas for islet isolation and transplantation of the isolated islets. In Japan, afterwards, various problems facing to a start of clinical islet transplantation have been discussed and we completed the guideline for clinical islet transplantation in Japan. The Japanese Organ Transplant Law was enforced in 1997 and organ transplantations using brain dead (DBD) donors were finally started. Since the islet transplantation was not included in the Japanese Organ Transplant Law because it was categorized as tissue transplantation, we were able to use the pancreas only from DCD donors for islet transplantation. The first islet isolation from the human pancreas was performed in 2003.9 and the first islet transplantation was performed in 2004.4 [7–9]. Sixty-five islet isolations and 34 islet transplantations were performed in our country from 2003.9.12 to 2007.3.11 [10].

In this chapter, we describe the current status of clinical islet transplantation using DCD donors in Japan.

Gene expression changes in rat pancreas transplant model after long-term cold storage of the graft in perfluorohexyloctane

BACKGROUND

Perfluorohexyloctane (PFH) is a promising storage solution that has been successfully used for pancreas preservation before islet isolation. This hyperoxygen carrier has been designed to prevent ischemic injury to the pancreas graft during cold storage. In our storage, we aimed to evaluate the impact of this solution on long-term cold storage in a rat whole pancreas transplantation model.

METHOD

Brown-Norway rats were used for syngeneic heterotopic pancreas transplantation. The procured organs were cold-stored for 18 hours in preoxygenated PFH (PFH group; n = 8) or in the University of Wisconsin solution (UW group; n = 8), or were transplanted immediately in the control group (n = 8). Two hours after reperfusion, we obtained blood and pancreas tissue samples for biochemistry and gene analyses (real-time polymerase chain reaction).

RESULTS

A significant difference between the UW and PFH group was observed in the tumor necrosis factor (TNF)β and endothelin 1 genes, which was overexpressed more than twofold in the UW group. In the blood samples, the UW group compared with the PFH group showed significantly higher levels of pancreatic amylase and lipase (94.2 ± 25.2 vs 67.7 ± 13.4 μkat/L and 5.5 ± 2.8 vs 3 ± 0.7 μkat/L, respectively; P < .05).

CONCLUSION

We found significantly lower expression levels of the endothelin 1 and TNFβ genes and lower concentrations of pancreatic amylase and lipase in the PFH group. All these findings suggest lower rate of ischemic reperfusion injury in the PFH group. These findings may result in better post-transplant outcomes after long-term cold storage in PFH compared with the UW solution. Further research in this area is required.

Automated digital image analysis of islet cell mass using Nikon's inverted eclipse Ti microscope and software to improve engraftment may help to advance the therapeutic efficacy and accessibility of islet transplantation across centers

Reliable assessment of islet viability, mass, and purity must be met prior to transplanting an islet preparation into patients with type 1 diabetes. The standard method for quantifying human islet preparations is by direct microscopic analysis of dithizone-stained islet samples, but this technique may be susceptible to inter-/intraobserver variability, which may induce false positive/negative islet counts. Here we describe a simple, reliable, automated digital image analysis (ADIA) technique for accurately quantifying islets into total islet number, islet equivalent number (IEQ), and islet purity before islet transplantation. Islets were isolated and purified from n = 42 human pancreata according to the automated method of Ricordi et al. For each preparation, three islet samples were stained with dithizone and expressed as IEQ number. Islets were analyzed manually by microscopy or automatically quantified using Nikon's inverted Eclipse Ti microscope with built-in NIS-Elements Advanced Research (AR) software. The AIDA method significantly enhanced the number of islet preparations eligible for engraftment compared to the standard manual method (p < 0.001). Comparisons of individual methods showed good correlations between mean values of IEQ number (r(2) = 0.91) and total islet number (r(2) = 0.88) and thus increased to r(2) = 0.93 when islet surface area was estimated comparatively with IEQ number. The ADIA method showed very high intraobserver reproducibility compared to the standard manual method (p < 0.001). However, islet purity was routinely estimated as significantly higher with the manual method versus the ADIA method (p < 0.001). The ADIA method also detected small islets between 10 and 50 µm in size. Automated digital image analysis utilizing the Nikon Instruments software is an unbiased, simple, and reliable teaching tool to comprehensively assess the individual size of each islet cell preparation prior to transplantation. Implementation of this technology to improve engraftment may help to advance the therapeutic efficacy and accessibility of islet transplantation across centers.

Addition of perfluorocarbons to alginate hydrogels significantly impacts molecular transport and fracture stress

Perfluorocarbons (PFCs) are used in biomaterial formulations to increase oxygen (O(2) ) tension and create a homogeneous O(2) environment in three-dimensional tissue constructs. It is unclear how PFCs affect mechanical and transport properties of the scaffold, which are critical for robustness, intracellular signaling, protein transport, and overall device efficacy. In this study, we investigate composite alginate hydrogels containing a perfluorooctyl bromide (PFOB) emulsion stabilized with Pluronic(®) F68 (F68). We demonstrate that PFC addition significantly affects biomaterial properties and performance. Solution and hydrogel mechanical properties and transport of representative hydrophilic (riboflavin), hydrophobic (methyl and ethyl paraben), and protein (bovine serum albumin, BSA) solutes were compared in alginate/F68 composite hydrogels with or without PFOB. Our results indicate that mechanical properties of the alginate/F68/PFOB hydrogels are not significantly affected under small strains, but a significant decrease fracture stress is observed. The effective diffusivity D(eff) of hydrophobic small molecules decreases with PFOB emulsion addition, yet the D(eff) of hydrophilic small molecules remained unaffected. For BSA, the D(eff) increased and the loading capacity decreased with PFOB emulsion addition. Thus, a trade-off between the desired increased O(2) supply provided by PFCs and the mechanical weakening and change in transport of cellular signals must be carefully considered in the design of biomaterials containing PFCs.

Improved pancreatic islet isolation outcome in autologous transplantation for chronic pancreatitis

Total or partial pancreatectomy followed by autologous islet transplantation is a therapeutic option for the treatment of refractory chronic pancreatitis (CP). Maximization of islet yields from fibrotic and inflamed organs is crucial for prevention of posttransplant diabetes. We adapted technical advancements developed for islet allotransplantation toward islet autotransplantation. Eight patients (two men, six women; ages 24-58 years) underwent total (n = 7) or partial (n = 1) pancreatectomy for the treatment of CP refractory to maximal medical management. Pancreata were preserved in UW solution (UW group) in initial three cases and the last five pancreata were preserved with pancreatic ductal injection followed by ET-Kyoto/oxygenated PFC solutions (DI+TLM group). Islets were isolated by modified Ricordi method and were purified only in one case. All islet infusions were performed under general anesthesia via direct vein injection into the portal venous system with pressure monitoring. Total islet yields (129,314 ± 51,627 vs. 572,841 ± 116,934 IEQ, p < 0.04), islet yield/pancreas weight (1,233 ± 359 vs. 6,848 ± 847 IEQ/g, p < 0.003), and islet yield/patient body weight (1,951 ± 762 vs. 7,305 ± 1,531 IEQ/kg, p < 0.05) were significantly higher in the DI+TLM group when compared to the UW group. Pellet size was also higher (5.3 ± 0.3 vs. 13.5 ± 3.4 ml) in the DI+TLM group, suggesting that this method of preservation effectively protected pancreatic tissue against autolysis. First month posttransplant basal C-peptide and the secretory unit of islet transplant objects (SUITO) index were also higher in the DI+TLM group when compared to the UW group (2.0 ± 0.3 vs. 1.4 ± 0.4 ng/ml and 42.6 ± 12.7 vs. 14.6 ± 5.6, respectively). There were no technical complications related to the infusion. Our results suggest that higher islet yields can be achieved even from chronically inflamed and fibrotic organs using DI+TLM. The techniques applied for islet isolations from normal pancreata are showing promise for fibrotic pancreata from CP patients.

Quality of isolated pig islets is improved using perfluorohexyloctane for pancreas storage in a split lobe model

Pancreas transportation between donor center and islet production facility is frequently associated with prolonged ischemia impairing islet isolation and transplantation outcomes. It is foreseeable that shipment of pig pancreases from distant centralized biosecure breeding facilities to institutes that have a long-term experience in porcine islet isolation is essentially required in future clinical islet xenotransplantation. Previously, we demonstrated that perfluorohexyloctan (F6H8) is significantly more efficient to protect rat and human pancreata from ischemically induced damage compared to perfluorodecalin (PFD). To evaluate the effect of F6H8 on long-term stored pig pancreases in a prospective study, we utilized the split lobe model to minimize donor variability. Retrieved pancreases were dissected into the connecting and splenic lobe, intraductally flushed with UW solution and immersed alternately in either preoxygenated F6H8 or PFD for 8-10 h. Prior to pancreas digestion, the intrapancreatic pO2 and the ratio of ATP-to-inorganic phosphate was compared utilizing 31P-NMR spectroscopy. Isolated islets were cultured for 2-3 days at 37°C and subjected to quality assessment. Pancreatic lobes stored in preoxygenated F6H8 had a significantly higher intrapancreatic pO2 compared to pancreata in oxygen-precharged PFD (10.11 ± 3.87 vs. 1.64 ± 1.13 mmHg, p < 0.05). This correlated with a higher ATP-to-inorganic phosphate ratio (0.30 ± 0.04 vs. 0.14 ± 0.01). No effect was observed concerning yield and purity of freshly isolated islets. Nevertheless, a significantly improved glucose-stimulated insulin response, increased viability and postculture survival (57.2 ± 5.7 vs. 39.3 ± 6.4%, p < 0.01) was measured in islets isolated from F6H8-preserved pancreata. The present data suggest that F6H8 does not increase islet yield but improves quality of pig islets isolated after prolonged cold ischemia.

The potential benefit of non-purified islets preparations for islet transplantation

Since the advent of islet transplantation, there has been a significant emphasis on the importance of islet purity despite an inevitable associated loss of islet mass during the purification process. One of the key elements of the 'Edmonton Protocol' for islet transplantation published in 2000 was an emphasis on the need for sequential transplants of highly purified islets (averaging 24% beta cell purity) and the close correlation between the numbers of islets transplanted and the success of the procedure. However, the emphasis on islet purity may warrant further consideration as auto transplantation of non-purified islets currently provides the most successful insulin independence rates within the field of islet transplantation. While the role of auto and allo immunity could contribute to the differences in the success rates it is clear that within the clinical setting, significant acinar and ductal contamination is well tolerated. However, one could go further and hypothesize that extra-insular tissue including acinar tissue, ductal tissue, peri-pancreatic lymph nodes and vascular tissue actually confer an advantage to islet survival/function and may even contribute to the insulin secreting capacity of the graft post transplant. As such this review will assess the influence of extra-insular pancreatic tissue on the results of islet transplantation based on published evidence and will also explore the possibility that non-islet pancreatic cells are capable of differentiating into a beta cell phenotype in vivo contributing to an ongoing regeneration of endocrine mass during the period following transplantation.

A Combined Continuous Density/Osmolality Gradient for Supplemental Purification of Human Islets

For islet transplantation, islet purification minimizes the risks associated with islet infusion through the portal vein. However, islet purification may result in decreased numbers of islets recovered from digested tissue. In this study, we evaluated the effectiveness of performing supplemental purification (SP) after regular purification (RP). We designed the densities of low- and high-density solutions based on the outcome of RP. Moreover, a combined continuous osmolality/continuous density gradient for the SP was used in this study. Low-density/osmolality (1.075-1.110 g/cm³/400-410 mOsm/kg) and high-density/osmolality (1.090-1.125 g/cm³/495-505 mOsm/kg) solutions were produced by changing the volumetric ratio of iodixanol, 10 × HBSS, and RP solutions. The percentage of islet recovery (postpurification IE/prepurification IE × 100) after RP was 77.3 ± 5.6%, and the percentage of islet recovery after addition of SP was 85.3 ± 5.4%. In vitro and in vivo assessments showed that islet viability and function were not altered by the additional purification step. These data suggest that the addition of SP could contribute approximately 8% to islet recovery with viability and potency comparable to that obtained by RP and, therefore, that usage of the combined continuous density and continuous osmolality gradient for SP could efficiently improve islet equivalents in the final preparation.

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.

Recent progress in pancreatic islet transplantation

Diabetes mellitus remains a major burden. More than 200 million people are affected worldwide, which represents 6% of the world’s population. Type 1 diabetes mellitus is an autoimmune disease, which induces the permanent destruction of the β-cells of the pancreatic islets of Langerhans. Although intensive insulin therapy has proven effective to delay and sometimes prevent the progression of complications such as nephropathy, neuropathy or retinopathy, it is difficult to achieve and maintain long term in most subjects. The successes achieved over the last few decades by the transplantation of whole pancreas and isolated islets suggest that diabetes can be cured by the replenishment of deficient β cells. However, islet transplantation efforts have various limitations, including the limited supply of donor pancreata, the paucity of experienced islet isolation teams, side effects of immunosuppressants and poor long term results. The purpose of this article is to review the recent progress in clinical islet transplantation for the treatment of diabetes and to describe the recent progress on pancreatic stem/progenitor cell research, which has opened up several possibilities for the development of new treatments for diabetes.

Improvement of pancreatic islet cell isolation for transplantation

Pancreatic islet transplantation is a promising treatment for diabetes but still faces several challenges. Poor islet isolation efficiency and poor long-term insulin independence are currently two major issues, although donor shortage and the need for immunosuppressants also need to be addressed. We established the Kyoto islet isolation method (KIIM), which has enabled us to isolate and transplant islets even from non-heart-beating donors. KIIM involves 1) cooling the donor pancreas in situ, 2) preserving the ducts with modified Kyoto solution, 3) using a modified two-layer pancreas preservation method, and 4) adjusting the density of the density gradient centrifugation and using an iodixanol-based solution for purification. KIIM has enabled us to transplant 17 islet preparations out of 21 isolations (an 81% success rate). All transplanted islets functioned, and all transplanted patients had improved glycemic control without hypoglycemic unawareness. Recently, we used KIIM for islet isolation from a brain-dead donor at Baylor, which resulted in a very high islet yield (789,984 IE) with high viability (100% by fluorescein diacetate/propidium iodide staining and a stimulation index of 4.7). This preliminary evidence suggests that KIIM may also be promising for islet isolation from brain-dead donors. In addition, to assess engrafted islet mass, we developed a secretory unit of islet transplant objects (SUITO) index: fasting C-peptide (ng/dL) / [fasting blood glucose (mg/dL) - 63] x 1500. This simple index has enabled us to monitor the engrafted islet mass. This index should be useful when deciding whether to perform additional islet transplantations to maintain insulin independence. Poor islet isolation efficacy and poor long-term results could be resolved with ongoing research.

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.

31-Phosphorus magnetic resonance spectroscopy for dynamic assessment of adenosine triphosphate levels in pancreas preserved by the two-layer method

Cold preservation injury influences islet graft function. Reliable tools for real-time assessment of pancreas viability before islet isolation are lacking. Phosphorus magnetic resonance spectroscopy ((31)P-MRS) was used immediately after organ harvest to study rat pancreases at 4 °C to 6 °C in five randomized preservation groups: Marshall's solution, static two-layer method (TLM), continuous TLM with oxygen perfused at 0.5 L/min, and static TLM or continuous TLM both the latter following 30 minutes of warm ischemia (WI). (31)P spectra were analyzed for phosphomonoesters, inorganic phosphate (Pi) and α-, β-and γ-nucleotide triphosphate. Intergroup rates of change of [γ-adenosine triphosphate (ATP)]/[Pi] and [β-ATP]/[Pi] throughout preservation period were significantly different. For continuous TLM there was an increase relative to baseline (0.043 (SD0.033) h(-1) and 0.029 (0.029) h(-1), respectively) but a decrease for both static TLM (-0.023 (0.016) h(-1) and 0.015 (0.026), P < .001 and < .05, respectively) and Marshall's (-0.049 (0.025) h(-1) and -0.036 (0.019) h(-1), respectively, both P < .001) with respect to continuous TLM. Rate of decrease was similar for the Marshall's and static TLM groups. [γ-ATP]/[Pi] and [β-ATP]/[Pi] increased with WI continuous TLM (0.008 [0.009] h(-1) and 0.007 [0.008] hr(-1), respectively) but decreased for WI static TLM (-0.018 (0.008) h(-1) and -0.014 (0.004) hr(-1), respectively, P < .001). (31)P-MRS is an effective tool for noninvasive assessment of pancreas bioenergetics. Continuous TLM preserves cellular bioenergetics and is superior to current non-perfluorocar bone based solutions for pancreas preservation.

Pancreas procurement and preservation for islet transplantation: personal considerations

Pancreatic islet transplantation is a promising option for the treatment of type 1 diabetic patients. After the successful demonstration of the Edmonton protocol, islet transplantation has advanced significantly on several fronts, including improved pancreas procurement and preservation systems. Since we frequently use pancreata from donors after cardiac death in Japan,we have applied the in situ regional organ cooling system for pancreas procurement to reduce the warm ischemic time. To reduce the apoptosis of pancreatic tissue during cold preservation, we have applied the ductal injection of preservation solution. For pancreas preservation, we use modified Kyoto solution, which is advantageous at trypsin inhibition and less collagenase inhibition. In this paper, we show pancreas procurement and preservation in our group for islet transplantation.

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.

Clinical allogeneic and autologous islet cell transplantation: update

Islet cell transplantation is categorized as a β-cell replacement therapy for diabetic patients who lack the ability to secrete insulin. Allogeneic islet cell transplantation is for the treatment of type 1 diabetes, and autologous islet cell transplantation is for the prevention of surgical diabetes after a total pancreatectomy. The issues of allogeneic islet cell transplantation include poor efficacy of islet isolation, the need for multiple donor pancreata, difficulty maintaining insulin independence and undesirable side effects of immunosuppressive drugs. Those issues have been solved step by step and allogeneic islet cell transplantation is almost ready to be the standard therapy. The donor shortage will be the next issue and marginal and/or living donor islet cell transplantation might alleviate the issue. Xeno-islet cell transplantation, β-cell regeneration from human stem cells and gene induction of the naïve pancreas represent the next generation of β-cell replacement therapy. Autologous islet cell transplantation after total pancreatectomy for the treatment of chronic pancreatitis with severe abdominal pain is the standard therapy, even though only limited centers are able to perform this treatment. Remote center autologous islet cell transplantation is an attractive option for hospitals performing total pancreatectomies without the proper islet isolation facilities.

Organ Preservation: Current Concepts and New Strategies for the Next Decade

SUMMARY: Organ transplantation has developed over the past 50 years to reach the sophisticated and integrated clinical service of today through several advances in science. One of the most important of these has been the ability to apply organ preservation protocols to deliver donor organs of high quality, via a network of organ exchange to match the most suitable recipient patient to the best available organ, capable of rapid resumption of life-sustaining function in the recipient patient. This has only been possible by amassing a good understanding of the potential effects of hypoxic injury on donated organs, and how to prevent these by applying organ preservation. This review sets out the history of organ preservation, how applications of hypothermia have become central to the process, and what the current status is for the range of solid organs commonly transplanted. The science of organ preservation is constantly being updated with new knowledge and ideas, and the review also discusses what innovations are coming close to clinical reality to meet the growing demands for high quality organs in transplantation over the next few years.

Persufflation improves pancreas preservation when compared with the two-layer method

Islet transplantation is emerging as a promising treatment for patients with type 1 diabetes. It is important to maximize viable islet yield for each organ due to scarcity of suitable human donor pancreata, high cost, and the large dose of islets required for insulin independence. However, organ transport for 8 hours using the two-layer method (TLM) frequently results in low islet yields. Since efficient oxygenation of the core of larger organs (eg, pig, human) in TLM has recently come under question, we investigated oxygen persufflation as an alternative way to supply the pancreas with oxygen during preservation. Porcine pancreata were procured from donors after cardiac death and preserved by either TLM or persufflation for 24 hours and subsequently fixed. Biopsies collected from several regions of the pancreas were sectioned, stained with hematoxylin and eosin, and evaluated by a histologist. Persufflated tissues exhibited distended capillaries and significantly less autolysis/cell death relative to regions not exposed to persufflation or to tissues preserved with TLM. The histology presented here suggests that after 24 hours of preservation, persufflation dramatically improves tissue health when compared with TLM. These results indicate the potential for persufflation to improve viable islet yields and extend the duration of preservation, allowing more donor organs to be utilized.

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.

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.

Experience of islet isolation without neutral protease supplementation

BACKGROUND

We have reported improved islet isolation outcomes using a new digestion protocol where the pancreas is perfused only with collagenase, and neutral protease (NP) is administered during the digestion phase. Since the inception of this protocol, we have had some cases where administration of NP was not required. Our new protocol was utilized in 94 islet isolations. The timing of adding NP was dependent on the progression of digestion but in 10 cases the progression was rapid and most islets in the assessment samples were free from the exocrine tissue. As a result NP was not added at all for these isolations (no-NP group). In the remaining 84 isolations, NP was added during digestion phase (control group).

RESULTS

Pancreata in the each group were digested with a similar collagenase dose. Digestion time was shorter in the no-NP (15.0±1.8 vs 19.5±0.6 min, P=0.004). At post-digestion, the no-NP had fewer trapped islets (10.9±2.8 vs 28.1±2.4%, P=0.009). Post-purification islet yield was similar (355±45 x10 ( 3) vs 318±17 x10 ( 3) IE, P=0.29). Five preparations in the no-NP were used for clinical transplantation, leading to a 64.3±15.2% reduction in insulin usage. Interestingly, cold ischemia time was longer in the no-NP (10.3±0.9 vs 7.9±0.4 h, P=0.04). One particular collagenase lot having the highest NP activity contamination was used in 7 isolations in the no-NP. Our experience indicates that supplementation of collagenase with NP is not always necessary for effective isolation. Cold ischemia time and NP contamination should be evaluated for optimal NP dosage.

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.

The role of perfluorocarbon in organ preservation

Perfluorocarbons (PFCs) are inert solutions that have a high capacity for dissolving oxygen. There has been a continuing level of research into the delivery of oxygen during solid organ preservation with the use of PFCs. The one- and two-layer methods have been used as static storage techniques, proving particularly successful for pancreas preservation. They can also be formulated as an emulsion for continual perfusion or as a simple flush solution. The success of PFCs in organ preservation seems to be somewhat organ and species dependant, and further experimental evidence is needed to establish their application.

Why do Japan's advanced medical treatments never get ahead?

Islet cell transplantation is a minimally invasive procedure which effectively controls blood glucose level for diabetic patients but is considered as experimental. After islet transplantation, type 1 diabetic patients could become insulin free with stable glycemic control. But for long term effects, only stable glycemic control was maintained and not insulin free status. In 2004 Kyoto University performed the first Japanese islet cell transplant using non-heart beating donor. Of note, due to the lack of cadaveric donors in Japan, the same group performed the world's first successful case of living donor islet transplantation in 2005. Both patients achieved transit insulin-independence; however excellent glycemic control was able to be maintained for a prolonged period. Even though the series of islet transplants at Kyoto University showed promising results, the leading scientist did not continue his research in Japan. This was because it is extremely difficult to implement newly developed treatment as a standard therapy in Japan.

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.

Islet isolation for clinical transplantation

Islet transplantation is emerging as a viable treatment option for selected patients with type 1 diabetes. Following the initial report in 2000 from Edmonton of insulin independence in seven out of seven consecutive recipients, there has been a huge expansion in clinical islet transplantation. The challenge we now face is the apparent decline in graft function over time. Isolating high-quality human islets which survive and function for a longer period will no doubt contribute to further improvement in long-term clinical outcome. This chapter reviews the selection of appropriate donors for islet isolation and transplantation, describes each step during islet isolation, and discusses the scope for further improvements.

Estimation of donor usability for islet transplantation in the United States with the kyoto islet isolation method

The quality of donor pancreata is important for successful islet isolation. However, in some countries like Japan, the number of donor pancreata is very low; therefore, marginal donors have been used with less restrictive donor criteria. In order to use marginal donor pancreata, we established the Kyoto islet isolation method (KIIM). According to United Network for Organ Sharing (UNOS) in 2005, more than 6,000 pancreata were not clinically used in the US. In this study, we applied the KIIM for brain-dead donors and reevaluated donor usability based on the Japanese islet donor criteria. Islets were isolated with the Ricordi method using pancreata stored in University of Wisconsin (UW) solution (UW group) or by the two-layer method (TLM group) or the TLM combined with ductal injection (DI group). We implemented the KIIM (KIIM group) to confirm the effect of the KIIM on brain-dead donors. Donor charts in Texas from 2005 to 2006 were reviewed. If pancreata were not used clinically, the reason was reviewed and donors were reevaluated based on Japanese criteria. There were no significant differences of islet yield, viability, and purity between the UW and TLM groups. The DI group significantly improved islet yields and isolations were further improved in the KIIM group [UW: 251,663 +/- 60,217 islet equivalent (IE); TLM: 243,738 +/- 54,170 IE; DI: 498,639 +/- 28,853 IE; KIIM: 678,286 +/- 55,853]. The KIIM provided high-quality islets in high numbers from islet isolations from brain-dead donors. A total of 236 donor charts were reviewed and 194 pancreata (82%) were not used. Of these, 185 cases identified the reasons that the pancreata were not used. When we applied the Japanese criteria, an additional 82 cases out of 185 (44%) seem to be suitable for islet isolations. With the KIIM, more than 2,500 additional donor pancreata can be used for islet isolation in the US every year when the Japanese criteria are applied.

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.

Seven consecutive successful clinical islet isolations with pancreatic ductal injection

Inconsistent islet isolation is one of the issues of clinical islet transplantation. In the current study, we applied ductal injection to improve the consistency of islet isolation. Seven islet isolations were performed with the ductal injection of ET-Kyoto solution (DI group) and eight islet isolations were performed without the ductal injection (standard group) using brain-dead donor pancreata. Isolated islets were evaluated based on the Edmonton protocol for transplantation. The DI group had significantly higher islet yields (588,566 +/- 64,319 vs. 354,836 +/- 89,649 IE, p < 0.01) and viability (97.3 +/- 1.2% vs. 92.6 +/- 1.2%, p < 0.02) compared with the standard group. All seven isolated islet preparations in the DI group (100%), versus only three out of eight isolated islet preparations (38%) in the standard group met transplantation criteria. The islets from the DI group were transplanted into three type 1 diabetic patients and all three patients became insulin independent. Ductal injection significantly improved quantity and quality of isolated islets and resulted in high success rate of clinical islet transplantation. This simple modification will reduce the risk of failure of clinical islet isolation.

Pancreatic duct: A suitable route to oxygenate tissue during pancreas hypothermic preservation?

The effectiveness of Two-Layer Method has been questioned recently. In this study we hypothesized that pancreatic duct might be an appropriate route to oxygenate the organ and prevent cold ischemic injury. Male Sprague-Dawley rats were employed for the pancreas procurement. Pancreata were removed after 20ml ductal injection of cold Hank's Balanced Salt Solution (HBSS), or pre-oxygenated solutions of HBSS (O-HBSS), perfluorocarbon (O-PFC), and emulsified PFC (O-ePFC) and then preserved in HBSS for 24h. Spectrophotometric analysis was performed to measure ATP, adenosine diphosphate (ADP), and adenosine monophosphate (AMP). To standardize metabolite data, values were reported in terms of 'per gram protein of pancreatic tissue'. Protein was measured according to Lowry et al. ADP/ATP ratio, total adenylates and energy charge (EC) were calculated. There was a significant decrease in tissue ATP after hypothermic preservation. Pancreatic tissues lost 47.8% of their ATP values just in the first hour of preservation and 98.5% of their ATP values within 12h of preservation and ductal oxygenation could not prevent the ischemia. Unlike the other groups, ductal injection of oxygenated PFC could slow the total adenylates reduction rate that no significant difference was detected (9.6+/-2.9 vs. 14.8+/-2.1mol/g protein, NS) after 12h of preservation. Ductal injection of oxygenated PFC significantly reduced ADP/ATP ratio (8.57+/-0.6 vs. 14.2+/-2.4, p<0.03) and improved intracellular energy charge (0.36+/-0.05 vs. 0.22+/-0.03, p<0.001) as compared to HBSS group. The findings indicate that the pancreatic duct might be a suitable route for pancreatic oxygenation.