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

BACKGROUND: Previous small clinical trials indicate that the two-layer method (TLM) for pancreas preservation improves islet isolation outcome. However, the effect of TLM has not been evaluated in large-scale study. In addition, a direct benefit of TLM on islet transplantation outcome has not been addressed in the setting of any randomized controlled trials. METHODS: Between April 2003 and October 2005, human pancreata from brain-dead donors were preserved by TLM using preoxygenated perfluorocarbon (n = 75) or in University of Wisconsin (UW) solution (n = 91) prior to islet isolation. Islet isolation and transplantation outcomes were compared between the two groups. RESULTS: We did not find any significant differences in adenosine triphosphate content in pancreatic tissue after preservation, pre and postpurification islet yields, in vitro insulin secretory function, or utilization ratio of transplantation between the two groups. Transplanted mass and functional viability of islet isolated from TLM-preserved pancreas were similar to those from UW-preserved pancreas. Patients receiving the TLM-islet or the UW-islet showed a marked decrease in insulin requirement after transplantation. However, no significant difference was observed in a decrease in insulin requirement between patients receiving the TLM-islet and the UW-islet. CONCLUSIONS: No beneficial effect of TLM on islet isolation and transplantation outcomes was observed. Our findings bring into question the true merit of routine use of TLM prior to islet isolation.     

The effect of two-layer (University of Wisconsin solution/perfluorochemical) preservation method on clinical grade pancreata prior to islet isolation and transplantation

BACKGROUND: Research-grade pancreata preserved by the two-layer method (TLM) compared to organs stored with University of Wisconsin (UW) solution prior to islet isolation result in significantly better islet yields. However, it is unknown whether the TLM improves islet yields from pancreata that meet the criteria for the selection of clinical-grade organs. METHODS: Six clinical-grade pancreata were preserved for 4.8 +/- 0.5 hour in UW and three clinical-grade pancreata were preserved by the TLM for 11.7 +/- 2.0 hour. The local team procured all pancreata. All donors were hemodynamically stable without norepinephrine usage and length of hospitalization was less than 96 hour. Causes of death were either head trauma or cerebrovascular accident. Islets were isolated and evaluated according to the Edmonton protocol. RESULTS: The TLM as compared to UW resulted in a significant increase in islet yields (3415 +/- 227 vs 2006 +/- 337 IE/g pancreas, P <.03). The quality of islets as assessed by visual score was significantly better in the TLM group (8.7 +/- 0.2 vs 7.3 +/- 0.3, P <.02) but other parameters (viability, survival rate after culture, insulin content, stimulation index) were similar between the two groups. We transplanted all three islet preparations in the TLM group but only two of six preparations from the UW group. CONCLUSION: Compared to UW, exposure of pancreata to the TLM resulted in greater islet yields and extended preservation times with clinical grade pancreas. Pancreata should be preserved by the TLM prior to islet isolation even for donors that meet clinical grade organ selection criteria. The Human Islet Transplantation in Seattle (HITS) Consortium is supported in part by a grant from the Juvenile Diabetes Research Foundation International. The HITS consortium is an islet transplant program involving the University of Washington, Pacific Northwest Research Institute, the Puget Sound Blood Center, Fred Hutchinson Cancer Research Center, Swedish Hospital, and the Virginia Mason Research Center.     

Successful islet transplantation from nonheartbeating donor pancreata using modified Ricordi islet isolation method

BACKGROUND: Current success of islet transplantation has led to donor shortage and the need for marginal donor utilization to alleviate this shortage. The goal of this study was to improve the efficacy of islet transplantation using nonheartbeating donors (NHBDs). METHODS: First, we used porcine pancreata for the implementation of several strategies and applied to human pancreata. These strategies included ductal injection with trypsin inhibitor for protection of pancreatic ducts, ET-Kyoto solution for pancreas preservation, and Iodixanol for islet purification. RESULTS: These strategies significantly improved both porcine and human islet isolation efficacy. Average 399,469+/-36,411 IE human islets were obtained from NHBDs (n=13). All islet preparations met transplantation criteria and 11 out of 13 cases (85%) were transplanted into six type 1 diabetic patients for the first time in Japan. All islets started to secrete insulin and all patients showed better blood glucose control without hypoglycemic loss of consciousness. The average HbA1c levels of the six recipients significantly improved from 7.5+/-0.4% at transplant to 5.1+/-0.2% currently (P<0.0003). The average insulin amounts of the six recipients significantly reduced from 49.2+/-3.3 units at transplant to 11+/-4.4 units (P<0.0005) and five out of six patients reduced to less than half dose. The first patient is now insulin free, the first such case in Japan. CONCLUSION: This demonstrates that our current protocol makes it feasible to use NHBDs for islet transplant into type 1 diabetic patients efficiently.     

Pulsatile pump perfusion of pancreata before human islet cell isolation

Machine pulsatile perfusion for whole pancreas preservation might improve yield, viability, and function of human islets recovered after prolonged cold ischemia times. Four human pancreata were procured from cadaver donors (1 non-heart-beating donor) and stored in cold University of Wisconsin (UW) solution for a mean 13 hours prior to placement on a machine pulsatile perfusion device. The four pancreata were perfused for 4 hours with UW solution before undergoing islet isolation. Islets were quantified, viability was assessed, and insulin secretion was measured. Results were compared with nonpumped islet isolations stratified for cold ischemia time (CIT) <8 hours or cold ischemia time >8 hours. The islet yield for the four pumped pancreata was 3435 (+/-1951) islet equivalents/gram pancreas tissue (IEQ/g), compared with a mean yield of 5134 (+/-2700) IEQ/g and 2640 (+/-1000) IEQ/g from pancreas with <8 hours and >8 hours CIT, respectively. The mean viability after machine pulsatile perfusion was 86% (vs 74% and 74% for the <8 hour and >8 hour CIT groups). The mean viable yield (total yield x viability) was 2937 IEQ/g for machine perfusion, compared with 3799 IEQ/g and 1937 IEQ/g from pancreata with <8 hours and >8 hours CIT, respectively. The insulin secretion index of islets after machine perfusion was 6.4, compared with indices of 1.9 and 1.8 for the <8 hour and >8 hour CIT groups. This preliminary data indicates that low-flow machine pulsatile perfusion of pancreata with prolonged cold ischemia time can result in excellent yield, viability, and function.     

New class of oxygen carriers improves islet isolation from long-term stored rat pancreata

OBJECTIVE: Pancreas shipment is frequently associated with prolonged ischemia deteriorating islet graft function. The strategy to prevent ischemic damage utilizing perfluorodecalin (PFD) for human pancreas oxygenation does not seem to improve isolation outcome. The present study investigated the efficiency of perfluorohexyloctane (F6H8), a hyperoxygen carrier characterized by low specific density (1.33 g/cm3) and lipophilic qualities, to facilitate islet isolation from long-term stored rat pancreata. MATERIALS AND METHODS: Prior to islet isolation, pancreata were intraductally flushed in situ with Kyoto solution (KS) and stored for 24 hours in KS, oxygenated PFD, or F6H8. RESULTS: Islet isolation performed after 24-hour storage in KS failed completely. The intrapancreatic pO2 in PFD- and F6H8-incubated pancreata was almost the same. In correspondence, the ATP content and viability of isolated islets were similar as well. In contrast, islet yield and in vitro function were significantly reduced after storage in PFD compared with F6H8. CONCLUSION: This study suggested that islet isolation performed after long-term pancreas preservation can be significantly improved utilizing semifluorinated alkanes as oxygen carriers.     

Functional and histological comparison of rat liver preserved in University of Wisconsin solution compared with tissue preserved in a novel solution

An isolated perfused rat liver model was used to investigate biochemical and histologic changes during 2 hours of reperfusion after 24 hours of cold storage to compare Leeds solution (LS) with University of Wisconsin solution (UW). Compared with livers stored in UW, those perfused with LS showed significantly higher bile flow and lower enzyme production (P < .05 by 1-way analysis of variance). For example, after 120 minutes, alanine aminotransferase results were: LS 38.9 U/L vs UW 66.8 U/L and bile flows were LS 10.3 μg/15 min/g liver vs UW 9.2 μg/15 min/g liver. Histologically the reticulin breakdown was greater and its reformation slower in UW-preserved livers. Liver tissue was viable in both groups, as shown by the increased glycogen content after reperfusion in both groups, but seen at a higher rate among LS, perfused livers. In conclusion, LS compared favorably with UW to prevent ischemic damage and so could offer an alternative perfusion medium to UW.     

Perfluorohexyloctane improves long-term storage of rat pancreata for subsequent islet isolation

Pancreas oxygenation by means of the hyperoxygen carrier perfluorodecalin (PFD) has been established to prevent ischemically induced damage from cold-stored pancreata. However, large-scale studies did not confirm the promising results that had been observed in smaller donor populations. This study assessed whether islet isolation from pancreata stored for prolonged periods can be improved by utilizing the new oxygen carrier perfluorohexyloctane (F6H8) characterized by lower gravity and higher lipophilicity than PFD. Subsequent to 24 h of storage in either oxygenated PFD or F6H8, the rat pancreata were assessed for the intrapancreatic partial oxygen pressure (pO₂) and subsequently processed with current standard procedures. The intrapancreatic pO₂ was nearly identical in rat pancreata stored either in PFD or F6H8. Nevertheless, rat islet isolation outcome was significantly increased in terms of yield, integrity, in vitro function and post-transplant outcome after transplantation in diabetic nude mice when F6H8 was used as oxygen carrier. This proof-of-concept study demonstrated in rats that islet isolation performed after long-term storage of oxygenated pancreatic tissue can be significantly improved if PFD was replaced by F6H8.     

University of Wisconsin solution versus Celsior solution in clinical pancreas transplantation

INTRODUCTION: This study compared the safety and efficacy of University of Wisconsin solution (UW) and Celsior solution (C) in pancreas transplantation (PTx). METHODS: A retrospective review of 154 PTx performed over a 61-month period included 77 grafts preserved with UW and 77 with C. The two groups were comparable for both donor and recipient characteristics. RESULTS: After a mean cold ischemia time of 624 minutes (range 360 to 945 minutes) for UW versus 672 minutes (range 415 to 1005 minutes) for C (P = NS), no primary endocrine nonfunction occurred. Delayed endocrine function was diagnosed in two grafts in the UW group (2.6%) versus none in the C group (P = NS). After a minimum follow-up of 4 months (mean 26.5 +/- 15.2 months), 22 recipients (UW = 11 vs C = 11; P = NS) required relaparotomy. Overall, 18 pancreata were lost due to either patient death with functioning graft (UW = 4 vs C = 1; P = NS) or graft loss due to other reasons (UW = 8 vs C = 5; P = NS). Actuarial 1- and 5-year patient survival rates were 93.5% and 86.8% for UW compared with 98.7% and 98.7% for C (P = .04). Actuarial graft survival rates at the same times were 88.3% and 75.0% for UW compared with 90.4% and 90.4% for C (P = NS). CONCLUSIONS: Within the range of cold ischemia times reported in this study, UW and C show similar safety and efficacy profiles for PTx.     

Decrease in renal vascular resistance in University of Wisconsin solution preserved kidney transplants

Renal vascular resistance was compared in 2 groups of renal grafts: group 1-16 kidneys perfused with University of Wisconsin solution and group 2-16 kidneys perfused with Euro-Collins solution. Both groups had comparable donors and recipient criteria. Renal blood flow was measured by a miniaturized pulsed Doppler probe fixed on the graft renal artery. Renal vascular resistance was calculated either according to the formula: renal vascular resistance (mm. Hg/ml. per second) = systemic arterial pressure (P)/renal blood flow or through the renal vascular resistive index (RVRI): RVRI = systolic flow velocity - diastolic flow velocity/systolic flow velocity = (S-D)/S. Renal vascular resistance estimation seems to be more contributory than renal blood flow in assessment of renal graft reperfusion disorders. Our results show that University of Wisconsin solution seems to preserve intrarenal arterial caliber better with a decrease in intrarenal vascular resistance, thus, allowing for a higher arterial graft perfusion flow.     

Improved islet yield and function with ductal injection of University of Wisconsin solution before pancreas preservation

BACKGROUND: Ensuring sufficient islet yield from preserved pancreases is a critical step in clinical islet transplantation. The aim of this study was to investigate whether pancreatic ductal injection, performed at procurement, using a small volume of preservation solution before cold storage (ductal preservation method) would improve islet yield and function from rat pancreases preserved for 6 and 24 hr. MATERIALS AND METHODS: Islets were isolated from Lewis rats. Pancreases were classified into five groups: fresh (group 1); preserved for 6 hr in University of Wisconsin solution without and with ductal preservation (groups 2 and 3); and preserved for 24 hr in University of Wisconsin solution without and with ductal preservation (groups 4 and 5). We assessed islet yield, function, and viability of pancreatic ductal cells. RESULTS: Islet yields per pancreas in groups 1 to 5 were 2010+/-774, 674+/-450, 1418+/-528, 527+/-263, and 1655+/-618 (islet equivalent) (+/-SD), respectively. Stimulation indices in groups 1 to 5 were 11.97+/-3.17, 6.48+/-4.04, 12.44+/-5.65, 2.56+/-2.03, and 5.55+/-2.71. Functional success rates in groups 1 to 5 were 100%, 0%, 100%, 0%, and 66.7%. Percentages of nonviable pancreatic duct cells in groups 1 to 5 were 3.8+/-2.7%, 59.7+/-4.4%, 19.5+/-7.3%, 64.7+/-4.5%, and 17.2+/-2.6%. In all experiments, the differences were significant between the groups without versus the groups with ductal preservation (P<0.05, group 2 vs. group 3 and group 4 vs. group 5). CONCLUSIONS: Ductal preservation improved islet yield and function after 6 and 24 hr of preservation. Well-preserved pancreatic ducts maintained good distribution of collagenase solution.     

Successful islet transplantation from the pancreata of non-heart-beating donors

We performed 6 islet transplantations in 4 type 1 diabetes mellitus patients. From September 2003 to April 2007, 23 islet isolations were performed from pancreata of non-heart-beating donors. The pancreata preserved using a 2-layer method or simple cold storage in University of Wisconsin solution were transferred to our cell processing center. The islet isolation was performed according to the Edmonton protocol with some modifications. The immunosuppressive protocol was achieved using sirolimus, tacrolimus, and anti-CD25 antibody (basiliximab). Islet yield was 400 to 491,040 IEQ and purity was 1% to 70%. Stimulation indices upon static incubation were 1.38 to 11.69. All patients who underwent islet transplantation showed positive serum C-peptide levels immediately after transplantation. Although insulin independence was not achieved, they displayed stabilized blood glucose levels, reduced insulin doses, and disappearance of hypoglycemic unawareness. Although stomatitis and diarrhea due to the side effects of sirolimus were observed in 2 patients, there were no severe complications. In patient 1, serum C-peptide levels decreased gradually from 1 year after transplantation. In conclusion, successful islet transplantation was possible using islets isolated from the pancreata of non-heart-beating donors. Further improvements are needed to achieve prolonged graft survival.     

Importance of pH in resuspension media on viability of hepatocytes preserved in University of Wisconsin solution

The effect of different pH of resuspension media on the viability of hepatocytes preserved (for 96 h at 4°C) in University of Wisconsin solution (UW solution) was analyzed. After this cold resuspension media storage, we evaluated the rewarming step (incubation time 120 min at 37°C) using different pH levels (6.80, 7.00, 7.20, and 7.40). Cell viability assessed by trypan blue exclusion (TBE) showed a significant difference (p < 0.05) for cells incubated at pH = 7.20. For instance, TBE expressed as percent of change was 78.1 ± 1.4 compared with cells tested at other pH (pH = 6.80, TBE = 44.2 ±9.5; pH = 7.00, TBE = 66.5 ±1.1 and pH = 7.40, TBE = 62.0 ± 1.4). We also evaluated the capacity of these cells both to maintain potassium content (0.509± 0.230 μEq). K⁺/10⁶ cells) and to synthesize urea (5.36 ± 1.81μmol Urea/10⁶ cells). These results were compared with those obtained from freshly isolated non preserved hepatocytes (0.518 ± 0.060 μEq. K⁺/10⁶ cells and 5.91 ± 0.43 μmol Urea/10⁶ cells). The results show that viability is pH dependent and suggest that when resuspension media were used, the viability of hepatocytes was improved after 96 h of cold storage.     

Comparative study of the University of Wisconsin solution versus Eurocollins in kidney transplant

UW (University of Wisconsin) solution, formulated by Belzer's team in Madison, has already been proved to increase cold ischemia time in liver and pancreas preservation. A multicentre clinical trial is being conducted to compare renal preservation in human transplantation using two different solutions: UW and Eurocollins (EC). This paper, whose results will be included in the multicentre trial, reports local comparative results between UW and EC perfused Kidneys. The two donor populations UW (28 cases) and EC (47 cases) were not randomized. They were however comparable in renal function prior to harvesting but not in age (35 +/- 13.4 years EC versus 27.7 +/- 12.4 years UW). The two recipient populations (48 EC versus 48 UW) were more homogeneous. Comparative results were significant with better graft function in the UW group: creatinine at one week: 499.2 +/- 296.3 EC versus 277.6 +/- 226.2 mumol/l, p less than 0.0001; creatinine at one month: 228.7 +/- 135 EC versus 159.7 +/- 135.6 mumol/l, p less than 0.02 and a decrease in acute tubular necrosis (39.5% EC versus 14.5% UW) and hospital stay. These results justify the use of UW solution by intraaortic flush especially during multi-organ procurement.     

Storage of human pancreatic digest in University of Wisconsin solution significantly improves subsequent islet purification.

Density-gradient purification of human pancreatic islets from the collagenase-digested pancreas relies on the exocrine tissue being denser than the islets. Cold storage of the pancreas before and after digestion causes cell swelling, which can decrease the density of pancreatic exocrine tissue and adversely affect subsequent purification. Using 14 human pancreata (seven perfused in situ with hyperosmolar citrate (HOC) and seven with University of Wisconsin solution (UW)), it is shown that storage of the pancreatic digest in UW significantly increases the density of pancreatic exocrine tissue compared with storage in minimal essential medium (MEM) (P = 0.009). This results in an improvement in islet purity (P = 0.036) for HOC- but not UW-perfused pancreata. Storage in UW for 1 h not only prevented the deterioration that occurred in MEM, but resulted in an improvement in islet purity for five of the seven HOC-perfused pancreata. Most pancreata in the UK are perfused with HOC, but storage of the digest in UW results in significantly better islet purity and, when islets cannot be purified immediately, a period of storage will often improve separation and allow islets to be purified.     

Preservation of donor livers with University of Wisconsin solution

The University of Wisconsin-solution extends the cold storage time of liver grafts over 20 hours. The early function is equal or better than with Eurocollins solution. Due to the extended preservation time, logistical advantages are present. However, deliberate extension of cold ischemia over the limit of 20 to 24 hours seems not yet indicated, since primary non-functioning grafts have a higher incidence after extended preservation.