Comparing the effects of Dextran 70 and Hydroxyethyl starch in an intestinal storage solution

Introduction

Our lab has developed a novel strategy for intestinal preservation involving the intraluminal delivery of a nutrient-rich preservation solution. The aim of this study was to compare the effectiveness of two impermeant agents for use in our solution: Dextran 70 (D70; Mw = 70 kDa) and Hydroxyethyl starch (HES; Mw = 2200 kDa).

Methods

Rat intestines were procured, including an intravascular flush with University of Wisconsin solution followed by a ‘backtable’ intraluminal flush with: UW solution (group 1, UW), or an amino acid-based nutrient-rich preservation solution (AA solution) containing either 5% D70 (group 2, AA-D70) or HES (group 3, AA-HES). Tissue samples (n = 6) were taken at 2, 4, 8, and 12 h cold storage; histology, energetic, end-product, and oxidative parameters were assessed. In separate groups (n = 4), D70 and HES were fluorescently labeled with fluorescein isothiocyanate (FITC) in order to directly observe mucosal penetration of the starch and dextran.

Results

Over the 12 h storage time-course, direct visualization of the fluorescently labeled D70 showed penetration of the mucosal layer as early as 2 h and progressively continued to do so throughout the 12 h period. In contrast, HES did not cross the mucosal barrier and remained captive within the lumen. As time of storage progressed, grade of injury increased in all groups, however, at 4 and 12 h the AA-HES treated tissues exhibited significantly less injury compared to UW and AA-D70, P < 0.05. AA-HES group showed on moderate villus clefting (median grade 2; P < 0.05) while the AA-D70 group exhibited complete villus denudation (grade 4) and the UW group had extensive injury into the regenerative cryptal regions (grade 6). Metabolic parameters revealed a preferential maintenance of ATP and Energy Charge; increases in lactate, alanine and ammonium supported the involvement of aerobic and anaerobic pathways for energy production.

Conclusion

The results of this study challenge the idea that oncotic support is not a fundamental requirement of static organ storage. Furthermore, our data suggests that HES is an effective oncotic agent for use in our intraluminal nutrient-rich preservation solution, while Dextran 70 is not.     

Comparing the effects of Dextran 70 and Hydroxyethyl starch in an intestinal storage solution

IntroductionOur lab has developed a novel strategy for intestinal preservation involving the intraluminal delivery of a nutrient-rich preservation solution. The aim of this study was to compare the effectiveness of two impermeant agents for use in our solution: Dextran 70 (D70; Mw = 70 kDa) and Hydroxyethyl starch (HES; Mw = 2200 kDa).MethodsRat intestines were procured, including an intravascular flush with University of Wisconsin solution followed by a ‘backtable’ intraluminal flush with: UW solution (group 1, UW), or an amino acid-based nutrient-rich preservation solution (AA solution) containing either 5% D70 (group 2, AA-D70) or HES (group 3, AA-HES). Tissue samples (n = 6) were taken at 2, 4, 8, and 12 h cold storage; histology, energetic, end-product, and oxidative parameters were assessed. In separate groups (n = 4), D70 and HES were fluorescently labeled with fluorescein isothiocyanate (FITC) in order to directly observe mucosal penetration of the starch and dextran.ResultsOver the 12 h storage time-course, direct visualization of the fluorescently labeled D70 showed penetration of the mucosal layer as early as 2 h and progressively continued to do so throughout the 12 h period. In contrast, HES did not cross the mucosal barrier and remained captive within the lumen. As time of storage progressed, grade of injury increased in all groups, however, at 4 and 12 h the AA-HES treated tissues exhibited significantly less injury compared to UW and AA-D70, P < 0.05. AA-HES group showed on moderate villus clefting (median grade 2; P < 0.05) while the AA-D70 group exhibited complete villus denudation (grade 4) and the UW group had extensive injury into the regenerative cryptal regions (grade 6). Metabolic parameters revealed a preferential maintenance of ATP and Energy Charge; increases in lactate, alanine and ammonium supported the involvement of aerobic and anaerobic pathways for energy production.ConclusionThe results of this study challenge the idea that oncotic support is not a fundamental requirement of static organ storage. Furthermore, our data suggests that HES is an effective oncotic agent for use in our intraluminal nutrient-rich preservation solution, while Dextran 70 is not.     

Cold preservation of rat osteochondral tissues in two types of solid organ preservation solution, culture medium and saline

We compared Dulbecco’s modified Eagle’s medium (DMEM), saline, Euro-Collins (EC) solution and University of Wisconsin (UW) solution to determine which was best for cold preservation of rat osteochondral tissues (OCTs). After 7 days’ cold preservation, OCTs kept in UW solution had the highest relative viable cell number by the tetrazolium assay and the lowest activity of lactate dehydrogenase released from damaged cells. Histological evaluation revealed chondrocyte deformity, such as shrunken cytoplasm and pyknotic nuclei, particularly in the deeper layer of articular cartilage after preservation in saline and EC solution and predominantly in all layers if preserved in DMEM. In contrast, chondrocyte morphology in all layers of the articular cartilage preserved in UW solution was relatively unchanged and remained similar to fresh OCTs. It is therefore concluded that UW solution is the most suitable for cold preservation of rat OCTs as well as solid organs.     

Improvement of renal preservation by adding lidoflazine to University of Wisconsin solution. An experimental study in the rat.

The purpose of this study was to investigate the possibility of improving the organ preservation properties of the University of Wisconsin (UW) solution by adding the calcium entry blocker lidoflazine. We also investigated the possibility of decreasing the cold ischemia and reperfusion damage by pretreatment with lidoflazine of the donor and/or recipient. The protective effects of lidoflazine treatment were estimated by measuring the amount of trapped erythrocytes in the rat renal medulla after 48 h of cold storage, subsequent transplantation, and 20 min of reperfusion. Lidoflazine (20 mg/liter) added to the UW solution decreased the amount of erythrocyte trapping from 14.8 +/- 3.1% in controls to 8.6 +/- 1.7% (P less than 0.01). The flow rate of the flush-out solution during the harvesting procedure was also significantly (P less than 0.01) increased when lidoflazine was included in the UW solution (1.10 +/- 0.21 ml/min vs 0.75 +/- 0.22 ml/min). Administration of lidoflazine (0.28 mg/kg body wt) to the donor and/or the recipient did not further reduce the postischemia/reperfusion damage as estimated by the degree of erythrocyte trapping. In conclusion, the results indicate that the preservation properties of the UW solution can be significantly improved by adding lidoflazine to the solution.     

Influence of colloid, preservation medium and trimetazidine on renal medulla injury

In organ transplantation, preservation injury is an important factor which could influence short-term and long-term graft outcome. The renal medulla is particularly sensitive to oxidant stress and ischemia-reperfusion injury (IRI). Using an autotransplant pig kidney model, we investigated renal function and medullary damage determined between day 1 and week 2 after 24- or 48-h cold storage in different preservation solutions: University of Wisconsin solution (UW), Hopital Edouard Herriot solution (a high Na+ version of UW), ECPEG (high Na+ preservation solution with PEG) and ICPEG (a high K+ version of ECPEG) with or without trimetazidine (TMZ). TMZ improved renal preservation and increased renal function when added in each preservation solution (particularly HEH and ECPEG). Medullary damage led to the early appearance of trimethylamine-N-oxide (TMAO) followed by 1H-NMR in urine and plasma. TMZ and ECPEG is the most efficient association to reduce medullary damage. This study clarifies the role of colloid and polarity solution and the role of mitochondrial protection by TMZ.     

Effect of cold storage on tissue and cellular glutathione

One of the mechanisms thought to cause injury in preserved organs is the formation of oxygen free radicals. The cell is protected from oxidative stress by many defense mechanisms. A major defense mechanism involves glutathione and glutathione-dependent enzymes. During organ preservation by simple cold storage the loss of glutathione may sensitize the organ to free radical damage after transplantation. In this study we show that glutathione is depleted from the rabbit liver, kidney, and heart cold-stored (5 degrees C) for up to 72 h in the UW solution without glutathione. In the first 24 h kidney glutathione decreased to 84 +/- 3% of control values, liver glutathione decreased to 49 +/- 3% of control values, and heart glutathione decreased to 73 +/- 3% of control values. After 48 h of storage the kidney and liver lost an additional 30 and 20%, respectively, whereas heart glutathione changed very little. By 72 h all three organs had lost more than 50% of the glutathione found in freshly obtained tissue. To determine if glutathione added to the UW solution can effectively prevent this loss of glutathione during preservation, hepatocytes were cold-stored for up to 72 h in a preservation solution with and without glutathione. We found that adding glutathione to the preservation solution slowed the rate of loss of glutathione from the cells. These data suggest that at hypothermia the cell may be permeable to GSH. Methods to suppress the loss of glutathione during preservation of organs may be an important factor in suppressing oxygen free radical injury.     

The functional effects of suppression of hypothermia-induced cell swelling in liver preservation by cold storage

It is known that cellular edema and functional impairment develop during anaerobic cold storage of organs. The extent of both is related to the storage time and the composition of the preservation solution used. We studied hypothermia-induced cell swelling and its effect on liver function after cold storage preservation with either Eurocollins (EC), a number of modified EC solutions in which glucose was replaced by various concentrations of raffinose, or UW solution. After 24 h storage, tissue swelling as determined by total tissue water (TTW) in rat liver tissue slices was most pronounced in slices incubated in Eurocollins, whereas the TTW was only moderately increased in slices stored in modified Eurocollins containing 90 to 120 mM raffinose. In contrast, slices incubated in UW solution had a TTW equal to normal rat liver tissue. Furthermore, intact rabbit livers preserved with Eurocollins had an increase in the whole organ weight, while there was no weight change after preservation with the modified solution containing 120 mM raffinose (M120). In contrast, a pronounced weight loss was observed after preservation with UW solution. After cold storage, the livers were reperfused for 2 h at 38 degrees C in an isolated perfusion circuit (IPL) with an acellular perfusate. Bile flow was significantly greater in livers preserved in M120 than in those preserved with the conventional Eurocollins. However, the bile flow in the livers stored in M120 was inferior to that in the livers preserved with UW solution, which in turn was equal to that in control livers. The release of alanine-aspartate-aminotransferase into the perfusate was higher in livers preserved with Eurocollins, with or without modification, than in the livers preserved with UW solution.(ABSTRACT TRUNCATED AT 250 WORDS)     

From the freezer to the clinic: Antifreeze proteins in the preservation of cells,tissues, and organs

Understanding the mechanisms by which natural anti‐freeze proteins protect cells and tissues from cold could help to improve the availability of donor organs for transplantation.

The first successful organ transplant in humans was performed in 1954 by Joseph Murray, who used a patient’s twin as a kidney donor. Murrays’ breakthrough paved the way for organ transplantation and the number of transplanted organs has grown ever since. For example, in 2017, a total of 139.024 solid organs—mostly kidney, liver, heart, lung, pancreas, and small bowel—were transplanted (Fig 1A). But this number only reflects 10% of the worldwide need; many patients still die of end‐stage organ failure while on a waiting list. The limited number of donor organs contributes only partially to this shortage. Many donor organs are not transplanted eventually owing to inefficient preservation techniques that shorten their extracorporeal lifetime. In fact, the percentage of donor organs that are unused is estimated to range from around 25% for kidneys and livers up to 70–80% for hearts and lungs (Giwa et al, 2017); Fig 1B).Open in a separate windowFigure 1Organ transplantation and preservability statusStatistics show a positive correlation between the duration of ex vivo preservation and the number of organ transplants. Number of solid organs transplanted in 2017 (A). Percentage of organs failed to be transplanted (B). Duration of solid organ ex vivo preservation in static cold storage (C). Sources: Data from the Global Observatory on Donation and Transplantation and (Parsons et al, 2014), (Guibert et al, 2011) and (Editorial: Buying time for transplants (2017))

Many donor organs are not transplanted eventually owing to inefficient preservation techniques that shorten their extracorporeal lifetime.

To address the shortage of donor organs and decrease the number of organs that go to waste, biobanks could efficiently store viable tissues and organs until transplantation. Yet, the current standard for ex vivo preservation of donor organs is static cold storage (4–8°C) which, depending on the organ, ensures viable conservation for only some hours; hearts are typically viable for a maximum of only 4 h (Fig 1C). In addition, this approach leads to hypothermic damage and to ischemia/reperfusion injury.Hence, there is an urgent need for strategies that prolong the viable preservation of donor organs. Two main strategies have emerged for cryopreservation and subzero storage, both of which cool tissues below the freezing point. While subzero storage just below 0°C may suffice for short‐term preservation, cryopreservation at −80°C or even lower temperatures is required for long‐term storage in biobanks. A proof‐of‐principle study already demonstrated that subzero preservation extended the preservation of rat hearts up to 24 h after collection (Amir et al, 2004); cryopreservation of whole hearts is currently not possible. The main reason is that lowering the temperature below the freezing point of water leads to ice formation, which causes cell damage and destroys tissues. One of the main challenges in biomedical research for organ transplantation is therefore finding non‐toxic and biocompatible antifreeze compounds that enable subzero storage and cryopreservation without causing tissue damage. An additional benefit is a larger time window to perform evaluation in terms of organ size and human leukocyte antigens matching and preparing the recipient patient to increase the chance of a successful transplantation.     

Technique of Subnormothermic Ex Vivo Liver Perfusion for the Storage,Assessment, and Repair of Marginal Liver Grafts

The success of liver transplantation has resulted in a dramatic organ shortage. In most transplant regions 20-30% of patients on the waiting list for liver transplantation die without receiving an organ transplant or are delisted for disease progression. One strategy to increase the donor pool is the utilization of marginal grafts, such as fatty livers, grafts from older donors, or donation after cardiac death (DCD). The current preservation technique of cold static storage is only poorly tolerated by marginal livers resulting in significant organ damage. In addition, cold static organ storage does not allow graft assessment or repair prior to transplantation.These shortcomings of cold static preservation have triggered an interest in warm perfused organ preservation to reduce cold ischemic injury, assess liver grafts during preservation, and explore the opportunity to repair marginal livers prior to transplantation. The optimal pressure and flow conditions, perfusion temperature, composition of the perfusion solution and the need for an oxygen carrier has been controversial in the past.In spite of promising results in several animal studies, the complexity and the costs have prevented a broader clinical application so far. Recently, with enhanced technology and a better understanding of liver physiology during ex vivo perfusion the outcome of warm liver perfusion has improved and consistently good results can be achieved.This paper will provide information about liver retrieval, storage techniques, and isolated liver perfusion in pigs. We will illustrate a) the requirements to ensure sufficient oxygen supply to the organ, b) technical considerations about the perfusion machine and the perfusion solution, and c) biochemical aspects of isolated organs.     

Subzero nonfreezing cryopresevation of rat hearts using antifreeze protein I and antifreeze protein III

The purpose of the present study was to evaluate whether AFPs protect the heart from freezing and improve survival and viability in subzero cryopreservation. Hearts were subject to 5 preservation protocols; University of Wisconsin solution (UW) at 4 degrees C, UW at -1.3 degrees C without nucleation, UW at -1.3 degrees C with nucleation, UW AFP I (15 mg/cm(3)) at -1.3 degrees C with nucleation, and in UW AFP III (15 mg/cm(3)) at -1.3 degrees C with nucleation. Hearts were preserved for 24, 28, and 32 h, rewarmed and connected to the working isolated perfusion system. Data [heart rate (HR), coronary flow (CF), and developed pressure (dP)] was collected 30 and 60 min after reperfusion. Hearts preserved at -1.3 degrees C without AFPs froze, while hearts preserved with AFP did not freeze when nucleation was initiated and survived. Survival and dP of hearts preserved for 24h at -1.3 degrees C using AFP III was better than those preserved at 4 degrees C, (dP; 1.4 vs. 0.8, p<0.05). Four of six hearts and six of six hearts died when preserved at 4 degrees C for 28 and 32 h, respectively, all of the hearts that were preserved at -1.3 degrees C with or without AFPs survived after 28 h (n=18) and 32 h (n=18). CF was higher in UW -1.3 degrees C group without attempted nucleation than in AFP I and AFP III groups after 28 and 32 h (3.4 vs. 1.7, p<0.05, and 3.4 vs. 1.7, p<0.05, respectively). In conclusion, AFPs were found to protect the heart from freezing and improve survival and dP (AFP III) in prolonged subzero preservation.     

Preservation methods for kidney and liver

With the successful testing of the immunosuppressive effects of cyclosporine in transplant patients in 1978, the field of organ transplants began an exponential growth. With that, the field of organ preservation became increasingly important as the need to increase preservation time and improve graft function became paramount. However, for every patient that receives a transplanted organ, there are 4 more on the waiting list. In addition, a patient dies from the lack of a transplant almost every 1½ hour. To alleviate this donor crisis, there is a need to expand the donor pool to marginal donor organs. The main reason these organs are underutilized is because the current method of static preservation, simple cold storage, is ineffective. This article will provide a general review of the methods of preservation including simple cold storage, hypothermic machine perfusion, normothermic machine perfusion, and oxygen persufflation. In addition, the article will provide a review of how these dynamic preservation methods have improved the recovery and preservation of marginal donor organs including donation after cardiac death and fatty livers.     

Preservation methods for kidney and liver

With the successful testing of the immunosuppressive effects of cyclosporine in transplant patients in 1978, the field of organ transplants began an exponential growth. With that, the field of organ preservation became increasingly important as the need to increase preservation time and improve graft function became paramount. However, for every patient that receives a transplanted organ, there are four more on the waiting list. In addition, a patient dies from the lack of a transplant almost every 1½ hour. To alleviate this donor crisis, there is a need to expand the donor pool to marginal donor organs. The main reason these organs are underutilized is because the current method of static preservation, simple cold storage, is ineffective. This article will provide a general review of the methods of preservation including simple cold storage, hypothermic machine perfusion, normothermic machine perfusion, and oxygen persufflation. In addition, the article will provide a review of how these dynamic preservation methods have improved the recovery and preservation of marginal donor organs including Donation after Cardiac Death and Fatty livers.     

Endothelial cell preservation at hypothermic to normothermic conditions using clinical and experimental organ preservation solutions

Introduction

Endothelial barrier function is pivotal for the outcome of organ transplantation. Since hypothermic preservation (gold standard) is associated with cold-induced endothelial damage, endothelial barrier function may benefit from organ preservation at warmer temperatures. We therefore assessed endothelial barrier integrity and viability as function of preservation temperature and perfusion solution, and hypothesized that endothelial cell preservation at subnormothermic conditions using metabolism-supporting solutions constitute optimal preservation conditions.Methods: Human umbilical vein endothelial cells (HUVEC) were preserved at 4–37 °C for up to 20 h using Ringer's lactate, histidine–tryptophan–ketoglutarate solution, University of Wisconsin (UW) solution, Polysol, or endothelial cell growth medium (ECGM). Following preservation, the monolayer integrity, metabolic capacity, and ATP content were determined as positive parameters of endothelial cell viability. As negative parameters, apoptosis, necrosis, and cell activation were assayed. A viability index was devised on the basis of these parameters.Results: HUVEC viability and barrier integrity was compromised at 4 °C regardless of the preservation solution. At temperatures above 20 °C, the cells' metabolic demands outweighed the preservation solutions' supporting capacity. Only UW maintained HUVEC viability up to 20 °C. Despite high intracellular ATP content, none of the solutions were capable of sufficiently preserving HUVEC above 20 °C except for ECGM.Conclusion: Optimal HUVEC preservation is achieved with UW up to 20 °C. Only ECGM maintains HUVEC viability at temperatures above 20 °C.     

Supercooling as a Viable Non-Freezing Cell Preservation Method of Rat Hepatocytes

Supercooling preservation holds the potential to drastically extend the preservation time of organs, tissues and engineered tissue products, and fragile cell types that do not lend themselves well to cryopreservation or vitrification. Here, we investigate the effects of supercooling preservation (SCP at -4^oC) on primary rat hepatocytes stored in cryovials and compare its success (high viability and good functional characteristics) to that of static cold storage (CS at +4^oC) and cryopreservation. We consider two prominent preservation solutions a) Hypothermosol (HTS-FRS) and b) University of Wisconsin solution (UW) and a range of preservation temperatures (-4 to -10 ^oC). We find that there exists an optimum temperature (-4^oC) for SCP of rat hepatocytes which yields the highest viability; at this temperature HTS-FRS significantly outperforms UW solution in terms of viability and functional characteristics (secretions and enzymatic activity in suspension and plate culture). With the HTS-FRS solution we show that the cells can be stored for up to a week with high viability (~56%); moreover we also show that the preservation can be performed in large batches (50 million cells) with equal or better viability and no loss of functionality as compared to smaller batches (1.5 million cells) performed in cryovials.     

A subset of 26S proteasomes is activated at critically low ATP concentrations and contributes to myocardial injury during cold ischemia

Molecular mechanisms leading to myocardial injury during warm or cold ischemia are insufficiently understood. Although proteasomes are thought to contribute to myocardial ischemia-reperfusion injury, their roles during the ischemic period remain elusive. Because donor hearts are commonly exposed to prolonged global cold ischemia prior to cardiac transplantation, we evaluated the role and regulation of the proteasome during cold ischemic storage of rat hearts in context of the myocardial ATP content. When measured at the actual tissue ATP concentration, cardiac proteasome peptidase activity increased by 225% as ATP declined during cold ischemic storage of hearts in University of Wisconsin (UW) solution for up to 48 h. Addition of the specific proteasome inhibitor epoxomicin to the UW solution inhibited proteasome activity in the cardiac extracts, significantly reduced edema formation and preserved the ultrastructural integrity of the cardiomyocyte. Utilizing purified 20S/26S proteasome enzyme preparations, we demonstrate that this activation can be attributed to a subset of 26S proteasomes which are stable at ATP concentrations far below physiological levels, that ATP negatively regulates its activity and that maximal activation occurs at ATP concentrations in the low μmol/L range. These data suggest that proteasome activation is a pathophysiologically relevant mechanism of cold ischemic myocardial injury. A subset of 26S proteasomes appears to be a cell-destructive protease that is activated as ATP levels decline. Proteasome inhibition during cold ischemia preserves the ultrastructural integrity of the cardiomyocyte.     

The influence of short-term fasting on the quality of small bowel graft preservation

INTRODUCTION: Donor nutritional status may be a determinant of small bowel (SB) quality following storage. In this study, we investigated the effect of donor nutritional status and a proven nutrient-rich preservation solution on graft quality following cold storage. METHODS: Rats were fasted (12-14 h) or non-fasted. SB (n=6) was flushed vascularly with modified University of Wisconsin (UW) solution and flushed luminally with UW or an amino acid-rich (AA) solution as follows: Fasted. UWV, none; UWL, UW solution; AAL, AA solution. Non-fasted. UWV, none; UWL, UW solution; AAL, AA solution. Energetics, peroxidation (malondialdehyde; MDA), glutathione and histology were assessed over 24 h at 4 degrees C. RESULTS: Energetics (ATP, ATP/ADP, and energy charge) were significantly higher in AAL (fasted and non-fasted) groups than other groups. However, there were no differences in energetics parameters between fasted and non-fasted animals in all groups. MDA was higher in fasted groups than non-fasted tissues; interestingly, AAL values were up to 10-fold lower than other groups. Higher glutathione levels were detected in non-fasted AAL tissues. Mucosal integrity was markedly superior in luminally treated tissues (UWL and AAL) in fasted and non-fasted states. Most noteably, AAL tissues from fasted animals exhibited grade 2 injury (villus clefting), whereas normal mucosa was observed in non-fasted tissues (grade 0). CONCLUSION: Luminal flushing and a nutrient-rich preservation solution improve energetics, oxidative stress, and mucosal integrity during storage. Poorer donor nutritional status does not affect energetics throughout storage, but causes mucosal injury as a result of increased oxidative stress, even after a brief period of donor fasting.     

Optimizing the concentration of hydroxyethylstarch in a novel intestinal-specific preservation solution

Introduction

Our lab has developed an effective nutrient-rich solution that facilitates energy production and control of oxidative stress during static cold storage of the intestine; however, the requirement for oncotic agents, such as hydroxyethylstarch (HES), has not been evaluated. This study investigated the effectiveness and requirement for HES in an intraluminal preservation solution during a clinically relevant period of cold storage.

Methods

Rat intestines were procured, including an intravascular flush with University of Wisconsin solution followed by a ‘back table’ intraluminal flush with a nutrient-rich preservation solution containing varying amounts of HES (n = 6 per group): Group 1, 0%; Group 2, 2.5%; Group 3, 5%; Group 4, 10%. Energetics, oxidative stress, and morphology were assessed over a 24 h time-course of cold storage.

Results

Overall, the 5% HES solution, Group 3, demonstrated superior energetic status (ATP and total adenylates) compared to all groups, P < 0.05. Malondialdehyde levels indicated a reduction in oxidative stress in Groups 3 and 4 (P < 0.05). After 12 h, median modified Parks’ grades for Groups 2 and 3 were significantly lower than Groups 1 and 4, P < 0.05.

Conclusion

Our data suggests that when employing an intraluminal preservation solution for static organ storage, oncotic support is a fundamental requirement; 5% HES is optimal.     

Electrical bioimpedance measurement during hypothermic rat kidney preservation for assessing ischemic injury

Non-heart-beating donors sustain an ischemic insult of unknown severity and duration, which can compromise the viability of the graft. This preliminary study aimed to assess whether electrical bioimpedance monitoring of cold preserved organs could be useful to identify kidneys that have suffered previous warm ischemia (WI). Two rat groups were studied during 24 h of preservation in University of Wisconsin solution (UW): a control cold ischemia group and another group subjected previously to 45 min of WI. Multi-frequency bioimpedance was monitored during preservation by means of a miniaturized silicon probe and the results were modeled according to the Cole equation. Tissular ATP content, lactate dehydrogenase in UW solution and histological injury were assessed. Renal function and cell injury, evaluated during 3 h of ex vivo reperfusion using the isolated perfused rat kidney model, demonstrated differences between groups. Bioimpedance results showed that the time constant and the high frequency resistivity parameters derived from the Cole equation were able to discriminate between groups at the beginning of the preservation (Deltatau approximately 78%, DeltaRinfinity approximately 36%), but these differences tended to converge as preservation time advanced. Nevertheless, another of the Cole parameters, alpha, showed increasing significant differences until 24 h of preservation (Deltaalpha approximately 15%).