Ultrastructural analyses of pancreatic grafts preserved by the two-layer cold-storage method and by simple cold storage in University of Wisconsin solution

Acinar phenotype is preserved in human exocrine pancreas cells cultured at low temperature: implications for lineage-tracing of β-cell neogenesis

In vitro cultured pancreatic acinar cells rapidly differentiate. Low temperature exposure prevents this process and improves the efficiency of acinar cell labelling with adenovirus vectors. This may help in tracing β-cell neogenesis from human pancreatic acinar cells.

The regenerative medicine field is expanding with great successes in laboratory and preclinical settings. Pancreatic acinar cells in diabetic mice were recently converted into β-cells by treatment with ciliary neurotrophic factor (CNTF) and epidermal growth factor (EGF). This suggests that human acinar cells might become a cornerstone for diabetes cell therapy in the future, if they can also be converted into glucose-responsive insulin-producing cells. Presently, studying pancreatic acinar cell biology in vitro is limited by their high plasticity, as they rapidly lose their phenotype and spontaneously transdifferentiate to a duct-like phenotype in culture. We questioned whether human pancreatic acinar cell phenotype could be preserved in vitro by physico-chemical manipulations and whether this could be valuable in the study of β-cell neogenesis. We found that culture at low temperature (4°C) resulted in the maintenance of morphological and molecular acinar cell characteristics. Specifically, chilled acinar cells did not form the spherical clusters observed in controls (culture at 37°C), and they maintained high levels of acinar-specific transcripts and proteins. Five-day chilled acinar cells still transdifferentiated into duct-like cells upon transfer to 37°C. Moreover, adenoviral-mediated gene transfer evidenced an active Amylase promoter in the 7-day chilled acinar cells, and transduction performed in chilled conditions improved acinar cell labelling. Together, our findings indicate the maintenance of human pancreatic acinar cell phenotype at low temperature and the possibility to efficiently label acinar cells, which opens new perspectives for the study of human acinar-to-β-cell transdifferentiation.

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.

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.

Pancreas preservation for pancreas and islet transplantation

PURPOSE OF REVIEW

To summarize advances and limitations in pancreas procurement and preservation for pancreas and islet transplantation, and review advances in islet protection and preservation.

RECENT FINDINGS

Pancreases procured after cardiac death, with in-situ regional organ cooling, have been successfully used for islet transplantation. Colloid-free Celsior and histidine-tryptophan-ketoglutarate preservation solutions are comparable to University of Wisconsin solution when used for cold storage before pancreas transplantation. Colloid-free preservation solutions are inferior to University of Wisconsin solution for pancreas preservation prior to islet isolation and transplantation. Clinical reports on pancreas transplants suggest that the two-layer method may not offer significant benefits over cold storage with the University of Wisconsin solution: improved oxygenation may depend on the graft size; benefits in experimental models may not translate to human organs. Improvements in islet yield and quality occurred from pancreases treated with inhibitors of stress-induced apoptosis during procurement, storage, isolation or culture desirable before islet isolation and transplantation and may improve islet yield and quality. Methods for real-time, noninvasive assessment of pancreas quality during preservation have been implemented and objective islet-potency assays have been developed and validated. These innovations should contribute to objective evaluation and establishment of improved pancreas-preservation and islet-isolation strategies.

SUMMARY

Cold storage may be adequate for preservation before pancreas transplants, but insufficient when pancreases are processed for islets or when expanded donors are used. Supplementation of cold-storage solutions with cytoprotective agents and perfusion may improve pancreas and islet transplant outcomes.

Pancreas preservation for pancreas and islet transplantation

PURPOSE OF REVIEW

To summarize advances and limitations in pancreas procurement and preservation for pancreas and islet transplantation, and review advances in islet protection and preservation.

RECENT FINDINGS

Pancreases procured after cardiac death, with in-situ regional organ cooling, have been successfully used for islet transplantation. Colloid-free Celsior and histidine-tryptophan-ketoglutarate preservation solutions are comparable to University of Wisconsin solution when used for cold storage before pancreas transplantation. Colloid-free preservation solutions are inferior to University of Wisconsin solution for pancreas preservation prior to islet isolation and transplantation. Clinical reports on pancreas and islet transplants suggest that the two-layer method may not offer significant benefits over cold storage with the University of Wisconsin solution: improved oxygenation may depend on the graft size; benefits in experimental models may not translate to human organs. Improvements in islet yield and quality occurred from pancreases treated with inhibitors of stress-induced apoptosis during procurement, storage, isolation or culture. Pancreas perfusion may be desirable before islet isolation and transplantation and may improve islet yields and quality. Methods for real-time, noninvasive assessment of pancreas quality during preservation have been implemented and objective islet potency assays have been developed and validated. These innovations should contribute to objective evaluation and establishment of improved pancreas preservation and islet isolation strategies.

SUMMARY

Cold storage may be adequate for preservation before pancreas transplants, but insufficient when pancreases are processed for islets or when expanded donors are used. Supplementation of cold storage solutions with cytoprotective agents and perfusion may improve pancreas and islet transplant outcomes.

Molecular markers in stored kidneys using perfluorocarbon-based preservation solution: preliminary results

BACKGROUND

Delayed graft function (DGF) is a problem in kidney transplantation and cold ischemia has been identified as a risk factor. Perfluorocarbons (PFC) have an enhanced ability to dissolve and release oxygen. We evaluated histologically and a number of molecular changes induced by ischemia in stored kidneys with University of Wisconsin (UW) and PFC-based preservation solutions (PFC-UW).

MATERIALS AND METHODS

ACI rats were used as kidney donors. UW (control group) or PFC-UW (study group) preservation solutions were used for kidney perfusion. All kidneys were stored at 4 degrees C for 12, 24, and 36 hours. After this time, intragraft histologic evaluation as well as mRNA HO-1 and iNOS levels were also analyzed.

RESULTS

In the kidneys stored at 24 hours, mRNA HO-1 levels were elevated in the study group when compared with the control and mRNA iNOS was decreased.

CONCLUSION

We observed overexpression of HO-1 and underexpression of iNOS in the kidney tissue stored with PFC-UW solution at 24 hours. These preliminary data suggest that increasing oxygen delivery by PFC added to the perfusion solution triggers cytoprotective mechanism in kidney transplantation.

Pancreas Oxygenation Is Limited During Preservation With the Two-Layer Method

BACKGROUND

The two-layer method (TLM) for pancreas preservation reportedly improves islet yield and transplantation outcome relative to previous methods. Increased ATP concentrations support the hypothesis that these improvements are related to better oxygenation from the perfluorocarbon solution. However, there are limited direct measurements of oxygen partial pressure, (pO(2)) in pancreata preserved with the TLM. Theory predicts that only a small fraction of a human pancreas can be oxygenated externally. In this report we examine pancreas oxygenation with the TLM using theory and direct pO(2) measurements.

METHODS

pO(2) profiles in cylindrical pancreata were calculated at various temperatures with a diffusion-reaction model. The pO(2) was measured using fiber optic sensors in the core of porcine pancreatic tissue preserved with the TLM in media saturated with 100% oxygen.

RESULTS

The model predicts that at 8 degrees C, even in the absence of an external pO(2) gradient, oxygen penetration depth is about 1 mm and insensitive to pancreas diameter, while the oxygenated volume fraction is about 15% for a 2.5-cm-diameter pancreas. Experimental measurements verified that pO(2) is virtually zero in the core of a 1-cm-thick pancreatic piece preserved with the TLM. Penetration of solution around the sensor may be responsible for the observed lag and for the previously reported nonzero pO(2) measurements. Reoxygenation of heat-treated tissue took several hours.

CONCLUSIONS

The TLM can oxygenate only a small volume fraction of a human pancreas. Pancreas oxygenation through the native vasculature should be explored to further improve yield of viable islets.

Detailed analysis of mucosal restoration of the small intestine after the cavitary two-layer cold storage method

Small bowel transplantation (SBT) is associated with a high incidence of infectious complications because of ischemia/reperfusion (I/R) mucosal injury concomitant with potent immunosuppression. In this study, we evaluated whether the cavitary two-layer method (cTLM) could reduce I/R injury and allow early mucosal restoration, particularly after prolonged preservation and transplantation. Canine heterotopic segmental SBT was performed immediately without preservation (group 1), after 24-h preservation in UW solution (group 2) or by the cTLM (group 3). The graft samples were taken 1 h after reperfusion and on days 1, 4 and 7. We assessed graft mucosa with detailed microscopic and electromicroscopic analyses. In Group 3, histological injury and cell apoptosis after transplantation were significantly alleviated and rapidly recovered to a similar level of group 1. The mucosal restoration was morphologically completed within 4 days. In contrast, in group 2, more pronounced mucosal injury and delayed recovery were noted. Crypt cell proliferation activity was well maintained in groups 1 and 3 throughout the experimental period. Our ultrastructural analysis suggested that mitochondrial integrity achieved by the cTLM was a basal mechanism under the prompt mucosal restoration. The cTLM could reduce I/R injury, facilitate mucosal regeneration and restore the nearly normal structure early after SBT.

Clinical application of perfluorocarbons for organ preservation

Perfluorocarbons (PFC), which store and release high levels of oxygen, have been examined as oxygen carriers. PFC was first used in organ preservation as a component of the two-layer method (TLM). The TLM is comprised of University of Wisconsin solution [UW] and oxygenated PFC for pancreas preservation. Pancreata preserved in the TLM are oxygenated through the PFC and substrates are supplied by the UW. TLM has been shown to prolong the preservation period and repair pancreatic injury caused by warm ischemia. Currently the TLM was used for pancreas preservation prior to clinical whole organ transplant. In this first clinical trial, the morphologic quality of the human pancreas graft after reperfusion was excellent compared with the pancreas stored in UW. In addition, there was no acute rejection episode of pancreata preserved by the TLM. TLM preservation of human pancreata, without initial cold UW storage, prior to islet isolation, resulted in better isolation results and improved the success rate of islet transplantation. Thus preservation of human pancreata by the TLM has become an important process for successful islet transplantation. Nowadays, PFC is routinely used for pancreas preservation prior to islet isolation, which has had a significant impact on curing type 1 diabetes.

Evaluation of the viability and energy metabolism of canine pancreas graft subjected to significant warm ischemia damage during preservation by UW solution cold storage method

AIM: To evaluate the viability and energy metabolism of long warm ischemically damaged pancreas during preservation by the UW solution cold storage method.

METHODS: The pancreas grafts subjected to 30-120 min warm ischemia were preserved by the UW solution cold storage method for 24 h. The tissue concentrations of adenine nucleotides (AN) and adenosine triphosphate (ATP) and total adenine nucleotides (TAN) were determined by using high performance liquid chromatography (HPLC) and the viability of the pancreas graft was tested in the canine model of segmental pancreas autotransplantation.

RESULTS: The functional success rates of pancreas grafts of groups after 30 min, 60 min, 90 min, 120 min of warm ischemia were 100%, 100%, 67.7%, 0%, respectively. There was an excellent correlation between the posttransplant viability and tissue concentration of ATP and TAN at the end of preservation.

CONCLUSION: The UW solution cold storage method was effective for functional recovery of the pancreas suffering 60-min warm ischemia. The tissue concentration of ATP and TAN at the end of 24 h preservation by the UW solution cold storage method would predict the posttransplant outcome of pancreas graft subjected to significant warm ischemia.

Effect of the two-layer (University of Wisconsin solution-perfluorochemical plus O2) method of pancreas preservation on human islet isolation, as assessed by the Edmonton Isolation Protocol

BACKGROUND

Current techniques for isolating islets require that pancreata stored with University of Wisconsin solution (UW) are processed within 12 hours of cold storage. In this study, we hypothesized that the two-layer method (TLM) could extend the acceptable preservation period of pancreata before islet isolation and increase islet yields.

METHODS

In the first experimental set, eight pancreata were maintained for an average of 8.3+/-1.2 hours in UW and transferred into the TLM for an additional 14.3+/-1.1 hours for a total cold ischemic period of 22.6+/-1.6 hours (prolonged TLM). Four pancreata were maintained as a control group in UW alone for a total of 21.3+/-2.0 hours. In the second experimental set, six pancreata were maintained for an average of 6.4+/-1.8 hours in UW followed by 4.8+/-0.8 hours with the TLM for a total preservation time of 11.3+/-2.5 hours (short TLM). The control organs for the short TLM group were stored for an average of 9.5+/-1.3 hours in UW alone. Islets were isolated and evaluated according to the Edmonton protocol.

RESULTS

Between each group of the two experimental sets, there was no significant difference in donor-related factors (i.e. gender, age, body mass index [BMI], etc.). The TLM as compared with UW preservation resulted in a significant increase in islet yields postpurification for both short (3,353+/-394 islet equivalents [IE] vs. 2,027+/-415 IE; mean+/-SEM) and prolonged (2,404+/-503 IE vs. 514+/-180 IE) periods of storage. Furthermore, islet yields after prolonged storage with the TLM were not significantly different from organs maintained for only a short period with UW (P=0.17). The quality of islets as assessed by size, postculture viability, survival rates, insulin content, and insulin secretion were similar for each of the four groups.

CONCLUSION

In comparison with UW organ preservation, exposure of pancreata to the TLM result in greater islet yields and extended preservation times.