Recovery of pancreatic tissue perfusion and ATP tissue level after reperfusion in canine pancreas grafts preserved by the two-layer method

Ischemia-Reperfusion Injuries Assessment during Pancreas Preservation

Maintaining organ viability between donation and transplantation is of critical importance for optimal graft function and survival. To date in pancreas transplantation, static cold storage (SCS) is the most widely practiced method of organ preservation. The first experiments in ex vivo perfusion of the pancreas were performed at the beginning of the 20th century. These perfusions led to organ oedema, hemorrhage, and venous congestion after revascularization. Despite these early hurdles, a number of factors now favor the use of perfusion during preservation: the encouraging results of HMP in kidney transplantation, the development of new perfusion solutions, and the development of organ perfusion machines for the lung, heart, kidneys and liver. This has led to a resurgence of research in machine perfusion for whole organ pancreas preservation. This review highlights the ischemia-reperfusion injuries assessment during ex vivo pancreas perfusion, both for assessment in pre-clinical experimental models as well for future use in the clinic. We evaluated perfusion dynamics, oedema assessment, especially by impedance analysis and MRI, whole organ oxygen consumption, tissue oxygen tension, metabolite concentrations in tissue and perfusate, mitochondrial respiration, cell death, especially by histology, total cell free DNA, caspase activation, and exocrine and endocrine assessment.

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.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

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.

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.

Improved human islet isolation outcome from marginal donors following addition of oxygenated perfluorocarbon to the cold-storage solution

Last year, from the approximately 6,000 organ donors, only approximately 1,500 pancreata were used for clinical transplantation. Factors that contribute to this poor pancreas use include strict donor selection criteria and the requirement for short cold-ischemia time (CIT). Numerous pancreata have not been used because of long ischemia times postprocurement. Given the oxygen-rich environment of the islets in the native pancreas, it is conceivable that islets are highly susceptible to irreversible damage following prolonged ischemia. The use of continuously oxygenated perfluorohydrocarbons (PFCs), known for their high oxygen-solubility coefficients, in a two-layer culture with standard University of Wisconsin preservation media, has extended the acceptable range CIT, and, furthermore, there has been no evidence of adverse effects from PFCs on the outcome of transplanted cells, whereas they often enhance islet cell function. The purpose of this study was to use the two-layer culture method to improve donor-organ use from marginal donors. Fifteen organs were procured using the two-layer method, and 18 without using it, from donors greater than 50 years of age. Despite nonsignificant differences in age, weight of the donors, weight of the organ and CIT, the PFC group yielded an average of twofold more islet equivalents than those harvested from the control group. As a result, from the control group, only 2 of 18 organs were used for clinical islet transplantation, whereas 8 of 15 were used from the PFC group. To this end, the two-layer method may help clinicians overcome the problem of organ underuse.

Role of hepatocytes and bile duct cells in preservation-reperfusion injury of liver grafts

In liver transplantation, it is currently hypothesized that nonparenchymal cell damage and/or activation is the major cause of preservation-related graft injury. Because parenchymal cells (hepatocytes) appear morphologically well preserved even after extended cold preservation, their injury after warm reperfusion is ascribed to the consequences of nonparenchymal cell damage and/or activation. However, accumulating evidence over the past decade indicated that the current hypothesis cannot fully explain preservation-related liver graft injury. We review data obtained in animal and human liver transplantation and isolated perfused animal livers, as well as isolated cell models to highlight growing evidence of the importance of hepatocyte disturbances in the pathogenesis of normal and fatty graft injury. Particular attention is given to preservation time-dependent decreases in high-energy adenine nucleotide levels in liver cells, a circumstance that (1) sensitizes hepatocytes to various stimuli and insults, (2) correlates well with graft function after liver transplantation, and (3) may also underlie the preservation time-dependent increase in endothelial cell damage. We also review damage to bile duct cells, which is increasingly being recognized as important in the long-lasting phase of reperfusion injury. The role of hydrophobic bile salts in that context is particularly assessed. Finally, a number of avenues aimed at preserving hepatocyte and bile duct cell integrity are discussed in the context of liver transplantation therapy as a complement to reducing nonparenchymal cell damage and/or activation.