Optimal cardioplegia and 24-hour heart storage with simplified UW solution containing polyethylene glycol

Shaping of Hepatic Ischemia/Reperfusion Events: The Crucial Role of Mitochondria

Hepatic ischemia reperfusion injury (HIRI) is a major hurdle in many clinical scenarios, including liver resection and transplantation. Various studies and countless surgical events have led to the observation of a strong correlation between HIRI induced by liver transplantation and early allograft-dysfunction development. The detrimental impact of HIRI has driven the pursuit of new ways to alleviate its adverse effects. At the core of HIRI lies mitochondrial dysfunction. Various studies, from both animal models and in clinical settings, have clearly shown that mitochondrial function is severely hampered by HIRI and that its preservation or restoration is a key indicator of successful organ recovery. Several strategies have been thus implemented throughout the years, targeting mitochondrial function. This work briefly discusses some the most utilized approaches, ranging from surgical practices to pharmacological interventions and highlights how novel strategies can be investigated and implemented by intricately discussing the way mitochondrial function is affected by HIRI.

Bardallo R, Calvo M, Folch-Puy E, Carbonell T, Palmeira C, Roselló Catafau J, Adam R. Polyethylene Glycol 35 as a Perfusate Additive for Mitochondrial and Glycocalyx Protection in HOPE Liver Preservation

Organ transplantation is a multifactorial process in which proper graft preservation is a mandatory step for the success of the transplantation. Hypothermic preservation of abdominal organs is mostly based on the use of several commercial solutions, including UW, Celsior, HTK and IGL-1. The presence of the oncotic agents HES (in UW) and PEG35 (in IGL-1) characterize both solution compositions, while HTK and Celsior do not contain any type of oncotic agent. Polyethylene glycols (PEGs) are non-immunogenic, non-toxic and water-soluble polymers, which present a combination of properties of particular interest in the clinical context of ischemia-reperfusion injury (IRI): they limit edema and nitric oxide induction and modulate immunogenicity. Besides static cold storage (SCS), there are other strategies to preserve the organ, such as the use of machine perfusion (MP) in dynamic preservation strategies, which increase graft function and survival as compared to the conventional static hypothermic preservation. Here we report some considerations about using PEG35 as a component of perfusates for MP strategies (such as hypothermic oxygenated perfusion, HOPE) and its benefits for liver graft preservation. Improved liver preservation is closely related to mitochondria integrity, making this organelle a good target to increase graft viability, especially in marginal organs (e.g., steatotic livers). The final goal is to increase the pool of suitable organs, and thereby shorten patient waiting lists, a crucial problem in liver transplantation.

Concentration and chain length of polyethylene glycol in islet isolation solution: evaluation in a pancreatic islet transplantation model

To improve graft preservation and consequently reduce conservation injuries, the composition of preservation solution is of outmost importance. It was demonstrated that the colloid polyethylene glycol (PEG), used in SCOT solution, has protective effects on cell membranes and immunocamouflage properties. The aim of this study was to optimize the concentration and chain length of PEG to improve pancreatic islet preservation and outcome. In a model of murine islet allotransplantation, islets were isolated with SCOT containing various concentrations of PEG 20 kDa or 35 kDa. Better islet yield (IEQ) was obtained with SCO +PEG at 15-30 g/L versus other PEG concentrations and control CMRL-1066 + 1% BSA solution (p < 0.05). Allograft survival was better prolonged (up to 20 days) in the groups SCOT + PEG 20 kDa 10-30 g/L compared to PEG 35 kDa (less than 17.8 days) and to control solutions (less than 17.5 days). In terms of graft function recovery, the use of PEG 20 kDa 15-30 g/L induced no primary nonfunction and delayed graft function contrary to CMRL-1066 and other PEG solutions. The use of the extracellular-type solution SCOT containing PEG 20 kDa 15 g/L as colloid could be a new way to optimize graft integrity preservation and allograft outcome.

Small bowel preservation for intestinal transplantation: a review

Intestinal transplantation has become the therapy of choice for patients with intestinal failure and life-threatening complications from total parenteral nutrition. Results, however, remain inferior as compared with other transplant types with the quality of the organ graft as the most important factor of outcome after transplantation. The intestine is extremely sensitive to ischemia. Unfortunately, a relatively long ischemic preservation period is inevitable. The current standard in organ preservation [cold storage (CS) with University of Wisconsin solution] was developed for kidney/liver preservation and is suboptimal for the intestinal graft despite good results for other organs. This review aimed at appraising the results from the use of previously applied and recently developed preservation solutions and techniques to identify key areas for improvement. As the studies available do not reveal the most effective method for intestinal preservation, an optimal strategy will result from a synergistic effect of different vital elements identified from a review of published material from the literature. A key factor is the composition of the solution using a low-viscosity solution to facilitate washout of blood, including amino acids to improve viability, impermeants and colloids to prevent edema, and buffer for pH-homeostasis. Optimizing conditions include a vascular flush before CS and luminal preservation. The most effective composition of the luminal solution and a practical, clinically applicable optimal technique are yet to reach finality. Short-duration oxygenated arterial and/or luminal perfusion have to be considered. Thus, a tailor-made approach to luminal preservation solution and technique need further investigation in transplant models and the human setting to develop the ultimate technique meeting the physiologic demands of the intestinal graft during preservation.

Perspectives in organ preservation

Maintaining organ viability after donation until transplantation is critically important for optimal graft function and survival. To date, static cold storage is the most widely used form of preservation in every day clinical practice. Although simple and effective, it is questionable whether this method is able to prevent deterioration of organ quality in the present era with increasing numbers of organs retrieved from older, more marginal, and even non-heart-beating donors. This review describes principles involved in effective preservation and focuses on some basic components and methods of abdominal organ preservation in clinical and experimental transplantation. Concepts and developments to reduce ischemia related injury are discussed, including hypothermic machine perfusion. Despite the fact that hypothermic machine perfusion might be superior to static cold storage preservation, organs are still exposed to hypothermia induced damage. Therefore, recently some groups have pointed at the beneficial effects of normothermic machine perfusion as a new perspective in organ preservation and transplantation.

Protective effect of PEG 35,000 Da on renal cells: paradoxical activation of JNK signaling pathway during cold storage

Polyethylene glycol (PEG), a high-molecular weight colloid, is added to preservation solutions in order to decrease cold- and ischemia-induced injuries of the grafted organ. We evaluated on LLC-PK1, a porcine proximal tubular epithelial cell line (1) the efficiency of several commercial preservation solutions (University of Wisconsin, Euro-Collins, Celsior, SCOT, IGL-1), and (2) whether adding PEG (400-35,000 Da) in a simple extracellular-type buffer modified cell integrity and mitogen-activated protein kinase (MAPK) signaling pathways. SCOT was the most efficient commercial solution. Moreover, only PEG 35,000 Da totally preserved cell viability, induced a decrease on reactive oxygen species production and a decrease on p38-MAPK activation. Furthermore PEG 35,000 Da stimulated c-Jun N-terminal kinase (JNK). However, the inhibition of JNK pathway, with the specific SP600125 inhibitor, in the presence of PEG 35,000 Da did not affect cell survival. We also confirmed on whole pig kidney the protective effect of PEG 35,000 Da on cold-induced tubular injuries. This study confirms PEG antioxidative properties, but we demonstrate that its effect on JNK signaling pathway had also a paradoxical effect on cell death. This sheds a new light on PEG effects during cell preservation, independently from the classical immuno-camouflaging hypothesis.

Optimization of a new preservation solution for machine perfusion of the liver: which is the preferred colloid?

AIMS

Machine perfusion (MP) has proven to be beneficial in experimental preservation of the liver. The modified University of Wisconsin solution (UW-Gluconate or UW-G) is used as the MP preservation solution of choice. We have developed Polysol, an enriched MP preservation solution based on a colloid. We sought to optimize Polysol by substituting the colloid hydroxyethylstarch (HES) with the colloids dextran and polyethylene glycol (PEG).

METHODS

In an isolated perfused rat liver model, hepatocellular damage and liver function were assessed during reperfusion with Krebs-Henseleit buffer after 24 hours hypothermic MP using Polysol-HES, Polysol-dextran, or Polysol-PEG. Control livers were preserved by MP using UW-G.

RESULTS

Compared to MP-UW-G, MP using Polysol resulted in significantly less damage and improved function during reperfusion. MP using Polysol-dextran or Polysol-PEG resulted in equal or less damage than Polysol-HES. Differences in ammonia clearance and bile production were not significant. Tissue edema was higher after MP using Polysol-HES as compared to Polysol-dextran and Polysol-PEG.

CONCLUSIONS

MP of rat livers for 24 hours using UW-G results in more extensive damage and reduced liver function compared to MP using Polysol. MP using Polysol-dextran or Polysol-PEG results in equal or even better preservation compared to Polysol-HES.

Cardioprotective effect of perfluorochemical emulsion for cardiac preservation after six-hour cold storage

Perfluoro-octyl bromide (PFOB) emulsion is capable of transferring oxygen to tissues even at 4 degrees C, suggesting an application in myocardial preservation. We evaluated the cardioprotective effect of PFOB emulsion added to the storage solution. Guinea pig hearts were isolated (n = 24) and perfused with Krebs-Henseleit solution (KHS) and then cooled and perfused with St. Thomas Hospital II solution (STS). The hearts were stored in three different solutions: STS (STS group), oxygenated (O2) STS (O2 STS group), and O2 STS with PFOB emulsion (30%) (O2 STS + PFOB group) for 6 hours at 4 degrees C. After storage, rewarming was performed, followed by reperfusion with KHS. Left ventricular developed pressure of O2 STS + PFOB group was significantly higher than that of the other groups during reperfusion (p < 0.01). There was no difference among the three groups in O2 extraction and cardiac efficiency; however, cardiac oxygen consumption in the O2 STS + PFOB group significantly improved during reperfusion. In the O2 STS + PFOB group, creatinine kinase, lactate dehydrogenase, and myocardial water content were significantly decreased (p < 0.01). This study suggests that PFOB emulsion is beneficial for the cardioprotection of donor hearts, allowing a prolonged cardiac storage time.

Beneficial effect of polyethylene glycol in lung preservation: early evaluation by proton nuclear magnetic resonance spectroscopy

BACKGROUND

Proton nuclear magnetic resonance spectroscopy can be used to measure organic molecules in biological fluids. In this study, proton nuclear magnetic resonance spectroscopy of bronchoalveolar lavage was assessed to detect cellular damage in lung transplants. Also we evaluated a polyethylene glycol solution in lung preservation.

METHODS

An isolated perfused and working pig lung was used to assess initial pulmonary function after in situ cold flush and cold storage for 6 hours in three preservation solutions: (1) Euro-Collins solution, (2) University of Wisconsin solution, and (3) low potassium solution with polyethylene glycol (PEG). Pulmonary vascular resistance and partial pressure of arterial oxygen were measured during reperfusion. Bronchoalveolar lavage was studied by proton nuclear magnetic resonance spectroscopy and a histologic study of the lungs was done at the harvest after ischemia and after reperfusion.

RESULTS

Partial pressure of arterial oxygen and pulmonary vascular resistance were significantly better in PEG compared with Euro-Collins solution (p = 0.011). Interstitial edema was significantly higher in Euro-Collins solution (2.4 +/- 0.24; p = 0.02) and University of Wisconsin solution (2.7 +/- 0.20; p = 0.0003) than PEG (2 +/- 0.16). Mitochondria scale was better in PEG (8.1 +/- 0.46) than in Euro-Collins solution (6.2 +/- 0.37; p = 0.0001) or University of Wisconsin solution (5.6 +/- 1.36; p = 0.0046). In bronchoalveolar lavage proton nuclear magnetic resonance spectroscopy spectra, lactate, pyruvate, citrate, and acetate were only detected after reperfusion, with a significantly reduced production of acetate in PEG. Pyruvate was reduced at the limit of significance in PEG versus University of Wisconsin solution.

CONCLUSIONS

Proton nuclear magnetic resonance spectroscopy seems to be a simple and suitable method for assessment of early injury to the lung transplant. In this experimental study, PEG preserved the lung better than University of Wisconsin solution and Euro-Collins solution in both the proton nuclear magnetic resonance spectroscopy study as well as the physiologic study.

A comparative study of the most widely used solutions for cardiac graft preservation during hypothermia

BACKGROUND

Reports conflict on the benefits of preservative solutions. We investigated the efficacy of the most widely used cardioplegic solutions by comparing extracellular solutions such as Celsior solution, St. Thomas Hospital solutions 1 and 2 (STH-1, STH-2), the modified University of Wisconsin solution (UW-1), Lyon Preservation solution (LYPS) from our laboratory, and intracellular solutions such as standard University of Wisconsin solution (UW), Bretschneider solution (HTK), Stanford solution (STF), and Euro-Collins solution (EC).

METHODS

Male rats (n = 110) were randomized into 11 groups: LYPS, Celsior, STH-1, STH-2, UW-1, UW, HTK, STF, EC, and normal saline solution groups, and a control group. All hearts, except controls, were preserved by cold storage (8 hours at 4 degrees C) in the various solutions. We used an isolated non-working-heart model and biopsy specimens to assess heart preservation (n = 5/group).

RESULTS

Hearts stored in the EC and saline solutions had poor left ventricular developed pressure (LVDP) x heart rate (HR) (1,407.5 +/- 154 and 1,390 +/- 439 mm Hg/mn, respectively). In contrast, hearts stored in LYPS and Celsior had a LVDP x HR close to control hearts (31,349 +/- 1,847, 27,620 +/- 1,207, and 36,627 +/- 1,322 mm Hg/mn, respectively), whereas hearts stored in STH-1, STH-2, UW-1, UW, HTK, and STF had intermediate functional response (14,278 +/- 2,176, 12,402 +/- 1,571, 11,428 +/- 1,629, 11,603 +/- 2,521, 7,045 +/- 537, and 7,086 +/- 1,206 mm Hg/mn, respectively). Hearts preserved with STH-2, UW, HTK, STF, EC, and saline solution showed significantly increased release of creatine kinase and lactate dehydrogenase than did control hearts or hearts preserved in Celsior, LYPS, STH-1, and UW-1. The energetic charge (EC = [(0.5 adenosine diphosphate + adenosine triphosphate) / (adenosine triphosphate + adenosine diphosphate + adenosine monophosphate)]) in STH-2, UW, HTK, STF, EC, and saline groups was significantly lower (p < 0.05) than in the other groups.

CONCLUSION

Extracellular-type solutions provided better preservation than did intracellular-type solutions. However, UW and UW-1 (intracellular- and extracellular-type solutions) provided equivalent preservation of cardiac function. Preservation quality may be attributed to calcium, often added to extracellular solutions. Among extracellular solutions, Celsior and LYPS solution showed comparable efficacy on left ventricular function and seemed to offer better preservation than the other solutions tested in this study.

Polyethylene glycol reduces early and long-term cold ischemia-reperfusion and renal medulla injury

Ischemia-reperfusion injury (IRI) after transplantation is a major cause of delayed graft function, which has a negative impact on early and late graft function and improve acute rejection. We have previously shown that polyethylene glycol (PEG) and particularly PEG 20M has a protective effect against cold ischemia and reperfusion injury in an isolated perfused pig and rat kidney model. We extended those observations to investigate the role of PEG using different doses (30g or 50g/l) added (ICPEG30 or ICPEG50) or not (IC) to a simplified preservation solution to reduce IRI after prolonged cold storage (48-h) of pig kidneys when compared with Euro-Collins and University of Wisconsin solutions. The study of renal function and medulla injury was performed with biochemical methods and proton NMR spectroscopy. Histological and inflammatory cell studies were performed after reperfusion (30-40 min) and on days 7 and 14 and weeks 4, 8, and 12. Peripheral-type benzodiazepine receptor (PBR), a mitochondrial protein involved in cholesterol homeostasis, was also studied. The results demonstrated that ICPEG30 improved renal function and reduced medulla injury. ICPEG30 also improved tubular function and strongly protect mitochondrial integrity. Post-IRI inflammation was strongly reduced in this group, particularly lymphocytes TCD4(+), PBR expression was influenced by IRI in the early period and during the development of chronic dysfunction. This study clearly shows that PEG has a beneficial effect in renal preservation and suggests a role of PBR as a marker IRI and repair processes.

Clinical impact of histidine-ketoglutarate-tryptophan (HTK) cardioplegic solution on the perioperative period in open heart surgery patients

BACKGROUND

Ischemia-reperfusion injury during open heart surgery related to unsuccessful myocardial protection may increase morbidity or mortality. We analyze the clinical outcome after cardiac surgery with a cardioplegic solution based on intracellular components added with histidine-ketoglutarate-tryptophan.

METHODS

Thirty patients programmed for elective open heart surgery were randomized into two groups. In group I (n = 15), myocardial protection was carried out with Bretschenider solution (HTK), and in group II (n = 15) with conventional crystalloid cardioplegia. The incidence of arrhythmias, inotropic support requirement, and length-of-stay in the intensive care unit were evaluated.

RESULTS

During reperfusion, there was no difference in incidence of arrhythmias; however, in the postoperative period group I had a lower incidence of arrhythmias (p = 0.001). Inotropic support (p = 0.003) and length-of-stay in the intensive care unit (p = 0.037) were lower in group I. There were no deaths in either group.

CONCLUSIONS

It was concluded that myocardial protection with Bretschneider solution effectively decreases incidence of arrhythmias, inotropic support, and length-of-stay in the intensive care unit.

Protection of autotransplanted pig kidneys from ischemia-reperfusion injury by polyethylene glycol

BACKGROUND

Ischemia-reperfusion injury (IRI) is often responsible for graft rejection and leads to delayed graft function of cadaveric kidneys. We have shown that adding polyethylene glycol (PEG 20M) to the preservation solutions helps protect isolated perfused pig kidneys against cold ischemia and reperfusion injury.

METHODS

We compared the effects of adding PEG to a simplified high-K+ perfusion solution of cold-stored kidneys to Euro-Collins or University of Wisconsin solutions on the function of reperfused autotransplanted pig kidneys. The left kidney was cold-flushed with the preservation solutions and stored for 48 hr at 4 degrees C before reimplantation. Creatinine clearance and fractional excretion of sodium were analyzed 2 days before surgery and over 7 days after transplantation. Histological sections were obtained 40 min after reperfusion and on day 7 after surgery.

RESULTS

Adding PEG to the perfusate significantly reduced IRI from autotransplanted pig kidneys. Creatinine clearance was significantly higher and fractional excretion of sodium was significantly lower in pigs transplanted with kidneys cold-flushed with PEG-supplemented perfusate than in those flushed with Euro-Collins or University of Wisconsin solutions. PEG supplementation also better preserved the integrity of kidney cells and markedly reduced interstitial cell infiltrates.

CONCLUSION

PEG protects against IRI and reduces early cellular inflammation. PEG may impair the recruitment and migration of leukocytes into retransplanted pig kidneys. Cold preservation of donor organs with PEG-supplemented solutions may therefore help limit IRI in human renal transplantation.

alpha-Galactosyl oligosaccharides conjugated with polyethylene glycol as potential inhibitors of hyperacute rejection upon xenotransplantation

Antibodies to an alpha-galactosyl saccharide structure are mainly responsible for hyperacute rejection after pig-to-primate xenotransplantation. The beneficial effect of alpha-galactosyl oligosaccharides has been shown on the inhibition of anti-pig natural antibodies. We synthesized polyethylene glycol (PEG)-conjugates of alpha-galactosyl disaccharide (Di) and trisaccharide (Tri) as potential inhibitors of the rejection reaction. The half lives of Di, Tri, PEG-conjugated Di (Di-PEG) and PEG-conjugated Tri (Tri-PEG) were 18.1 +/- 2.3 min, 20.2 +/- 0.9 min, 38.7 +/- 2.8 min and 35.8 +/- 1.6 min, respectively. Furthermore, Di-PEG and Tri-PEG showed biphasic clearance, and their half lives at the second phase were longer than 10 hours. PEG-conjugated oligosaccharides (Di-PEG, Tri-PEG) markedly inhibited cytotoxic action of human sera to pig kidney cell line (PK15) compared to unconjugated oligosaccharides (Di, Tri). The binding of IgM antibodies to PK15 cells, however, was more strongly blocked by unconjugated oligosaccharides than PEG-conjugated oligosaccharides. This phenomenon can be explained by the finding that PEG has anti-complement activity and masks antigenic sites of oligosaccharides. In conclusion, conjugation of PEG to oligosaccharides provided two beneficial effects; prolonged intravascular retention time and anti-complement activity, upon systemic application of the oligosaccharides. The present findings opened a new approach to treatment of hyperacute rejection after xenotransplantation.

Comparison of solutions for preservation of the rabbit liver as tested by isolated perfusion

The University of Wisconsin (UW) solution consists of a relatively complex mixture of agents. In this study we compared simpler preservation solutions, namely, histidine-tryptophan-ketoglutarate (HTK) and phosphate-buffered sucrose (PBS) with different compositions of UW solution in the isolated perfused rabbit liver model. Livers were stored cold for 24 and 48 h. After 24 h of preservation, the amount of bile produced in UW-preserved livers was significantly greater (P < 0.05) than that in HTK-preserved livers. Also, there was less LDH released into the perfusate in UW-preserved livers. There was more edema and lower K +/Na+rations in HTK-preserved livers than in UW-preserved livers (all data P < 0.05). After 48 h of preservation, the differences between livers preserved in UW or HTK solution were less noticeable than at 24 h and bile production was similar. LDH and AST release were greater in HTK-preserved livers than in UW livers, but these differences were not statistically significant. Preservation in PBS for 48 h was worse than in either UW or HTK solution. Substitution of polyethylene glycol (PEG) for hydroxyethyl starch (HES) in 48-h UW-preserved livers was not effective. We conclude that solutions simpler in composition than UW solution may be effective in kidney transplantation but do not appear suitable for successful liver preservation.

Resuscitation of cardiac energy metabolism in the rabbit heart by brief hypothermic reperfusion after preservation studied by 31P NMR spectroscopy

Rabbit hearts were subjected to 24-h cold ischaemic storage (at 0 degree-2 degrees C in melting ice) after initial flushing with either St Thomas' cardioplegic solution (STS) or modified lactobionate/raffinose solution (LR), and the status of phosphorylated energy metabolites was measured by 31phosphorus nuclear magnetic resonance (P NMR) spectroscopy. In both groups signals for ATP and phosphocreatine (PCr) were still detectable by 31P NMR after 24 h, and there was significantly more ATP in the LR group (P < 0.01). The hearts were then subjected to coronary reperfusion via an aortic cannula using the same storage solution (either STS or LR) at 6 degrees-8 degrees C, which was oxygenated. In both groups PCr recovered within 30 min of cold reperfusion, and by 60 min PCr was significantly higher in the LR group (P < 0.001). Also, levels of ATP were maintained at higher values during cold reperfusion i the LR group. These studies suggest two important points: (1) the general supply of phosphorylated high-energy intermediates of hearts during cold ischaemic storage is better preserved using LR, and (2) brief cold reperfusion may be used to restore energy metabolism in hearts before re-implantation.

Extended cardiopulmonary preservation: University of Wisconsin solution versus Bretschneider's cardioplegic solution

Application of the University of Wisconsin cold storage solution has rapidly expanded to include medium-term to long-term preservation of virtually all intraabdominal organs. Its use in intrathoracic organ transplantation has also been suggested. We therefore examined the efficacy of the University of Wisconsin solution in a primate allotransplantation model for preservation of hearts, and as a simple single-solution system for static preservation of heart-lung blocks, for periods of ischemia ranging from 6 to 24 hours. For comparison, we employed the histidine-tryptophane-ketoglutarate cardioplegic solution of Bretschneider. University of Wisconsin solution provided superior results with regard to clinical outcome and hemodynamic recovery of hearts after ischemic periods of up to 16 hours. This was in contrast to Bretschneider's solution, which allowed storage of hearts for periods of only up to 10 hours. Heart-lung blocks were equally well preserved with either University of Wisconsin or Bretschneider's solution after 6 to 12 hours, although the University of Wisconsin solution group exhibited a more notable increase in pulmonary water content. This was in accordance with histological data, which suggested that, although hemodynamic recovery of hearts stored for periods longer than 10 hours was poor, preservation of pulmonary ultrastructure was far superior using Bretschneider's solution as compared with University of Wisconsin solution after an ischemic period of up to 16 hours.

PEG-SOD and myocardial protection. Studies in the blood- and crystalloid-perfused rabbit and rat hearts

BACKGROUND

Polyethylene glycol, covalently linked to superoxide dismutase (PEG-SOD), has a long plasma half-life (greater than 30 hours) and has been proposed as an effective agent for reducing free radical-mediated injury ischemia and reperfusion.

METHODS AND RESULTS

Using an isolated rabbit heart perfused with arterial blood from a support rabbit, we have demonstrated that pretreatment with PEG-SOD (30,000 units/kg, intravenous bolus, 12-24 hours before 60 minutes of normothermic global ischemia), combined with addition of PEG-SOD to the blood perfusion circuit (30,000 units/kg to the support rabbit) and inclusion of PEG-SOD (150 micrograms/ml) in a cardioplegic solution, enhanced the postischemic recovery of left ventricular developed pressure (LVDP) from 51 +/- 6 to 74 +/- 9 mm Hg (p less than 0.05; n = 9 per group). In further studies we showed that, whereas maximum protection was obtained when PEG-SOD was given as a combined pretreatment and additive to both the cardioplegic and the reperfusate solutions (postischemic LVDP recovery increased from 44 +/- 4% in the control group to 70 +/- 3% in the PEG-SOD group), the administration of PEG-SOD during pretreatment plus cardioplegia or during reperfusion alone also resulted in a significant improvement in postischemic function (62 +/- 7% and 60 +/- 3%, respectively). However, the use of PEG-SOD as a cardioplegic additive alone failed to afford protection (47 +/- 4% recovery of LVDP). In dose-response studies (with 0, 3,000, 6,000, 12,000, 30,000, or 60,000 units/kg; n = 8 per group), maximum recovery of LVDP was obtained with the administration of 12,000 units/kg of PEG-SOD. Studies of the plasma activity of PEG-SOD confirmed its long half-life and showed that the treatment with PEG-SOD either 1 hour or 12-24 hours before the study resulted in similar levels of plasma activity. In an attempt to assess any involvement of blood-borne elements in the protection afforded by PEG-SOD, studies were also carried out in the crystalloid-perfused rabbit heart, and no protection was observed. Similarly, no protection was observed at any one of a variety of doses in the crystalloid-perfused rat heart.

CONCLUSIONS

PEG-SOD can afford protection in the blood-perfused rabbit heart; this protection is dose dependent and probably involves some action of PEG-SOD on blood-borne elements, possibly leukocytes.

Flow cytometric analysis of organ preservation-induced endothelial cell membrane damage

Organ preservation for transplantation is associated with endothelial cell damage. This vascular injury results in increased capillary permeability, graft edema, and early graft dysfunction. This damage may be the limiting factor in preservation of these organs. This study uses flow cytometric assessment of membrane integrity to examine the effects of various organ preservation solutions on human umbilical vein endothelial cell cultures. Confluent plates of human umbilical vein endothelial cells were incubated at 4 degrees C for 24, 48, and 72 hours in commonly used preservation solutions. After cold incubation, the cells were harvested and stained with propridium iodide and fluorescein diacetate. Cells were examined using a flow cytometer for membrane integrity and cytosolic activity. When examined after 24, 48, and 72 hours, cells stored at 4 degrees C in a 5% polyethylene glycol salt solution were significantly less damaged than those stored in any other solution (p less than 0.05). After 48 and 72 hours at 4 degrees C, cells stored in ViaSpan were significantly more intact than cells stored in EuroCollins and 0.9% saline solution (p less than 0.05). This study demonstrates that endothelial cell damage occurs during cold storage and that a polyethylene glycol-based solution showed superior cellular preservation.

Freezing preservation of the mammalian cardiac explant. II. Comparing the protective effect of glycerol and polyethylene glycol

We compared the cryoprotective ability of glycerol and polyethylene glycol (PEG) during freezing. Isolated rat hearts were flushed with one of three cardioplegic solutions (CP-14, CP-15, and CP-16), frozen at -1.4 degrees C, and reperfused after thawing to assess function. After 3 h freezing, cardiac output (CO) in CP-14-flushed hearts recovered to 58.1% of control. CP-16 (CP-14 with 5% PEG) improved CO to 77.5%. Five hours of freezing abolished recovery in CP-14 hearts, but CP-15 (CP-14 with 50 mM glycerol) and CP-16 hearts produced 40.0 and 49.0% CO, respectively. With 6 h freezing, CP-15 hearts did not recover, whereas CP-16 hearts recovered 37.5% CO. In CP-14 hearts frozen for 3 h, 37.4% of the tissue water was ice that increased to 44.7% with 5 h freezing. CP-15 and CP-16 hearts had 34.4 and 30.9% tissue ice, respectively, after 5 h freezing. Tissue water contents in CP-14 and CP-15 hearts (3.83 to 3.96 g H2O/g dry) were 14 to 24% higher than that in CP-16 hearts. Six hours of freezing elevated AMP and ADP contents and reduced ATP levels in CP-15 and CP-16 hearts. Total adenine nucleotide (TAN) content of CP-15 hearts was 72% of control, while that of CP-16 hearts was normal. In conclusion, both glycerol and PEG offered cryoprotection by reducing tissue ice formation. PEG was superior by reducing tissue ice content further via dehydration and by better preserving TAN content.

Viability and primary culture of rat hepatocytes after hypothermic preservation: the superiority of the Leibovitz medium over the University of Wisconsin solution for cold storage

Hepatocytes isolated from adult rat livers were hypothermically preserved for 24 or 48 hr before being plated under conventional culture conditions. They were stored either in the Leibovitz medium, a cell culture medium with and without polyethylene glycol (PEG), a compound known to suppress ischemia-induced cell swelling, or in the University of Wisconsin solution, the most effective solution for cold organ preservation. After 24 or 48 hr of storage at 4.5 degrees C in Leibovitz medium, cell viability and adherence efficiency to plastic dish, were only slightly reduced, whereas University of Wisconsin hepatocytes had a decreased viability and (especially after 48-hr storage) lost their adhesion ability; they did not survive in vitro. The metabolic competence of hepatocytes maintained in Leibovitz medium was retained over the 3 days of culture, as shown by low extracellular levels of the membrane-bound and cytosolic hepatic enzymes, as well as by intracellular glutathione content, albumin secretion rate and several phase I and phase II drug metabolic reactions very close to those found with fresh hepatocytes maintained under similar culture conditions. Addition of polyethylene glycol to the Leibovitz medium resulted in slightly higher viability and function of hepatocytes after cold storage. These results clearly demonstrate that viability of a transplanted liver does not correlate with long-term in vitro viability of isolated hepatocytes after hypothermic preservation in University of Wisconsin solution. They also suggest that nutritional and energy substrates as found in the Leibovitz medium are probably required to define a suitable solution for cold preservation of isolated parenchymal cells. The findings with Leibovitz medium favor the conclusion that hypothermically preserved hepatocytes could be used for various metabolic studies and for the treatment of liver insufficiency.

24-hour preservation of isolated rat hearts perfused with pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) solution at low temperature

We examined the effects of long-term perfusion with pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) solution on cardiac function of isolated rat hearts. Hearts were perfused with oxygenated Krebs-Henseleit (K-H) solution containing 3% PHP or hydroxyethyl starch (HES) at a constant pressure of 13 mm Hg for 24 h at 15 degrees C. After 24 h preservation, hearts were rewarmed with K-H solution. Heart rate (HR) in PHP-preserved hearts was almost the same as control and cardiac contractility was maintained at 70% of control, but coronary outflow decreased to about 50% of control. No edema developed in the PHP group. Addition of a Ca2+ antagonist, diltiazem, inhibited the elevation of the end-diastolic pressure significantly. In HES-preserved hearts, HR did not recover to control levels, but there was no significant difference in cardiac contractility between PHP- and HES-perfused hearts. The results demonstrate that isolated hearts can be preserved by perfusion with PHP solution under hypothermic conditions for 24 h and suggest that PHP solution would be useful for a perfusate of isolated organs and tissues for preservation.