Short term preservation of porcine livers

Challenges With the Implementation of Machine Perfusion in Clinical Liver Transplantation

Dynamic organ preservation is a relatively old technique which has regained significant interest in the last decade. Machine perfusion (MP) techniques are applied in various fields of solid organ transplantation today. The first clinical series of ex situ MP in liver transplantation was presented in 2010. Since then, the number of research and clinical applications has substantially increased. Despite the notable beneficial effect on organ quality and recipient outcome, MP is still not routinely used in liver transplantation. Based on the enormous need to better preserve organs and the subsequent demand to continuously innovate and develop perfusion equipment further, this technology is also beneficial to test and deliver future therapeutic strategies to livers before implantation. This article summarizes the various challenges observed during the current shift from static to dynamic liver preservation in the clinical setting. The different organ perfusion strategies are discussed first, together with ongoing clinical trials and future study design. The current status of research and the impact of costs and regulations is highlighted next. Factors contributing to costs and other required resources for a worldwide successful implementation and reimbursement are presented third. The impact of research on cost-utility and effectivity to guide the tailored decision-making regarding the optimal perfusion strategy is discussed next. Finally, this article provides potential solutions to the challenging field of innovation in healthcare considering the various social and economic factors and the role of clinical, regulatory, and financial stakeholders worldwide.

Successful transplantation of porcine liver grafts following 48-hour normothermic preservation

Current cold storage organ preservation technique fails to preserve marginal donor grafts sufficiently. Evidence from large animal experiments suggests superiority of normothermic machine preservation of liver allografts. Long-term organ preservation using normothermic perfusion might not only allow organ viability assessment before transplantation, but also provide the means for further organ modifications under physiologic conditions. Previous research has shown that porcine livers can be transplanted successfully after normothermic preservation of 20 hours. In the present study we investigate whether similar methodology is capable of further extending the safe limit to 48 hours. In this study, livers from White Landrace pigs were preserved by normothermic, oxygenated sanguineous perfusion. After a 48-hour period of preservation, livers were transplanted into recipient pigs and followed for 5 days. Outcome parameters measured included markers of synthetic and metabolic liver function as well as hepatocellular injury and blood gas analysis during perfusion and follow-up. Histological assessment of morphological liver integrity was performed. All livers showed sustained bile production and metabolic activity throughout the preservation period. Low levels of hepatocellular damage were found. Following transplantation all liver grafts revealed excellent graft function and death-censored graft survival was 100%. Porcine livers were transplanted successfully following 48 hours normothermic machine preservation.

Liver ex situ machine perfusion preservation: A review of the methodology and results of large animal studies and clinical trials

Ex vivo machine perfusion (MP) is a promising way to better preserve livers prior to transplantation. Currently, no methodology has a verified benefit over simple cold storage. Before becoming clinically feasible, MP requires validation in models that reliably predict human performance. Such a model has been found in porcine liver, whose physiological, anatomical, and immunological characteristics closely resemble the human liver. Since the 1930s, researchers have explored MP as preservation, but only recently have clinical trials been performed. Making this technology clinically available holds the promise of expanding the donor pool through more effective preservation of extended criteria donor (ECD) livers. MP promises to decrease delayed graft function, primary nonfunction, and biliary strictures, which are all common failure modes of transplanted ECD livers. Although hypothermic machine perfusion (HMP) has become the standard for kidney ex vivo preservation, the precise settings and clinical role for liver MP have not yet been established. In research, there are 2 schools of thought: normothermic machine perfusion, closely mimicking physiologic conditions, and HMP, to maximize preservation. Here, we review the literature for porcine ex vivo MP, with an aim to summarize perfusion settings and outcomes pertinent to the clinical establishment of MP. Liver Transplantation 23 679-695 2017 AASLD.

Graft Reconditioning before Liver Transplantation

BACKGROUND

The high demand for livers for transplantation has led to organs of limited quality being accepted to expand the donor pool. This is associated with inferior outcomes due to more pronounced preservation injury. Accordingly, recent research has aimed to develop preservation modalities for improved preservation as well as strategies for liver viability assessment and liver reconditioning.

METHODS

The PubMed database was searched using the terms 'perfusion', 'liver', 'preservation', and 'reconditioning' in various combinations, and the according literature was reviewed.

RESULTS

Several perfusion techniques have been developed in recent years with the potential for liver reconditioning. Preclinical and first emerging clinical data suggest feasibility, safety, and superiority over the current gold standard of cold storage.

CONCLUSION

This review outlines current advances in the field of liver preservation with an emphasis on liver reconditioning methods.

Advances in the management of the explanted donor liver

Liver transplantation is the best therapy in end-stage liver disease. Donor organ shortage and efforts to expand the donor organ pool are permanent issues given that advances in perioperative management and immunosuppressive therapy have brought the procedure into widespread clinical use. The management of organ procurement, including donor preconditioning and adequate organ storage, has a key role in transplantation. However, the organ procurement process can differ substantially between transplant centres, depending on local and national preferences. Advances in the field have come from experimental and clinical research on dynamic storage systems, such as machine perfusion devices, as an alternative to static cold storage. Determination of the clinical significance of these new systems is a topic worthy of future investigations.

Flow Competition between Hepatic Arterial and Portal Venous flow during Hypothermic Machine Perfusion Preservation of Porcine Livers

Hypothermic machine perfusion (HMP) is regarded as a better preservation method for donor livers than cold storage. During HMP, livers are perfused through the inlet blood vessels, namely the hepatic artery (HA) and the portal vein (PV). In previous HMP feasibility studies of porcine and human livers, we observed that the PV flow decreased while the HA flow increased. This flow competition restored either spontaneously or by lowering the HA pressure (PHA). Since this phenomenon had never been observed before and because it affects the HMP stability, it is essential to gain more insight into the determinants of flow competition. To this end, we investigated the influence of the HMP boundary conditions on liver flows during controlled experiments. This paper presents the flow effects induced by increasing PHA and by obstructing the outlet blood vessel, which is the vena cava inferior (VCI).

Flow competition was evoked by increasing PHA to 55–70 mmHg, as well as by obstructing the VCI. Remarkably, a severe obstruction resulted in a repetitive and alternating tradeoff between the HA and PV flows. These phenomena could be related to intra-sinusoidal pressure alterations. Consequently, a higher PHA is most likely transmitted to the sinusoidal level. This increased sinusoidal pressure reduces the pressure drop between the PV and the sinusoids, leading to a decreased PV perfusion. Flow competition has not been encountered or evoked under physiological conditions and should be taken into account for the design of liver HMP protocols. Nevertheless, more research is necessary to determine the optimal parameters for stable HMP.

Organ Preservation: Current Concepts and New Strategies for the Next Decade

SUMMARY: Organ transplantation has developed over the past 50 years to reach the sophisticated and integrated clinical service of today through several advances in science. One of the most important of these has been the ability to apply organ preservation protocols to deliver donor organs of high quality, via a network of organ exchange to match the most suitable recipient patient to the best available organ, capable of rapid resumption of life-sustaining function in the recipient patient. This has only been possible by amassing a good understanding of the potential effects of hypoxic injury on donated organs, and how to prevent these by applying organ preservation. This review sets out the history of organ preservation, how applications of hypothermia have become central to the process, and what the current status is for the range of solid organs commonly transplanted. The science of organ preservation is constantly being updated with new knowledge and ideas, and the review also discusses what innovations are coming close to clinical reality to meet the growing demands for high quality organs in transplantation over the next few years.

Current state of hypothermic machine perfusion preservation of organs: The clinical perspective

This review focuses on the application of hypothermic perfusion technology as a topic of current interest with the potential to have a salutary impact on the mounting clinical challenges to improve the quantity and quality of donor organs and the outcome of transplantation. The ex vivo perfusion of donor organs on a machine prior to transplant, as opposed to static cold storage on ice, is not a new idea but is being re-visited because of the prospects of making available more and better organs for transplantation. The rationale for pursuing perfusion technology will be discussed in relation to emerging data on clinical outcomes and economic benefits for kidney transplantation. Reference will also be made to on-going research using other organs with special emphasis on the pancreas for both segmental pancreas and isolated islet transplantation. Anticipated and emerging benefits of hypothermic machine perfusion of organs are: (i) maintaining the patency of the vascular bed, (ii) providing nutrients and low demand oxygen to support reduced energy demands, (iii) removal of metabolic by-products and toxins, (iv) provision of access for administration of cytoprotective agents and/or immunomodulatory drugs, (v) increase of available assays for organ viability assessment and tissue matching, (vi) facilitation of a change from emergency to elective scheduled surgery with reduced costs and improved outcomes, (vii) improved clinical outcomes as demonstrated by reduced PNF and DGF parameters, (viii) improved stabilization or rescue of ECD kidneys or organs from NHBD that increase the size of the donor pool, (ix) significant economic benefit for the transplant centers and reduced health care costs, and (x) provision of a technology for ex vivo use of non-transplanted human organs for pharmaceutical development research.

Artificial circulation of the liver: machine perfusion as a preservation method in liver transplantation

Due to the sharp increase in liver transplant candidates and the subsequent shortage of suitable donor livers, an extension of the current donor criteria is necessary. Simple cold storage, the current standard in organ preservation has proven to be insufficient to preserve extended criteria donor livers. Therefore a renewed interest grew toward alternative methods for liver preservation, such as hypothermic machine perfusion and normothermic machine perfusion. These "new" preservation methods were primarily assessed in rat models, and only a few clinically relevant large animal models have been described so far. This review will elaborate on these alternative preservation methods.

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.

Hypothermic perfusion preservation: the future of organ preservation revisited?

Hypothermic perfusion preservation (HPP) was an integral step in the development of early clinical transplantation programmes, and considerable progress was made in understanding the basic principles underlying the technique. In subsequent years, the development of better preservation solutions for cold hypoxic storage, along with pragmatic choices made on grounds of costs and logistics, saw a fall in the application of HPP. More recently, the acute shortage of suitable organ donors and the inevitable pressure to use organs from sub-optimal (or expanded criteria) donors, has forced a re-evaluation of HPP, and the development of a new generation of HPP machines and associated perfusion solutions. This review sets out the historical development of HPP across the range of organs in which the method was originally investigated, describes the biological benefits and drawbacks associated with HPP, and sets out the most recent literature on the topic (including comments on the interest in use of higher temperatures in organ perfusion).

The Groningen Hypothermic Liver Perfusion Pump: Functional Evaluation of a New Machine Perfusion System

To improve preservation of donor livers, we have developed a portable hypothermic machine perfusion (HMP) system as an alternative for static cold storage. A prototype of the system was built and evaluated on functionality. Evaluation criteria included 24 h of adequate pressure controlled perfusion, sufficient oxygenation, a maintained 0-4 degrees C temperature and sterile conditions. Porcine livers were perfused with pump pressures that were set at 4 mmHg (continuous, portal vein) and 30/20 mmHg, at 60 BPM (pulsatile, hepatic artery). Control livers were preserved using the clinical golden standard: static cold storage. In the HMP group, pressure, flow and temperature were continuously monitored for 24 h. At time-points t = 0, 2, 4, 8, 12, and 24 h samples of University of Wisconsin machine preservation solution were taken for measurement of partial oxygen pressure (pO(2)) and lacto-dehydrogenase. Biopsies in every lobe were taken for histology and electron microscopy; samples of ice, preservation solution, liver surface, and bile were taken and cultured to determine sterility. Results showed that temperature was maintained at 0-4 degrees C; perfusion pressure was maintained at 4 mmHg and 30/20 mmHg for portal vein and hepatic artery, respectively. Flow was approximately 350 and 80 ml/min, respectively, but decreased in the portal vein, probably due to edema formation. Arterial pO(2) was kept at 100 kPa. Histology showed complete perfusion of the liver with no major damage to hepatocytes, bile ducts, and non-parenchymal cells compared to control livers. The machine perfusion system complied to the design criteria and will have to demonstrate the superiority of machine perfusion over cold storage in transplant experiments.

Twelve-hour liver preservation in the pig using hypothermia and hyperbaric oxygen

In an attempt to prolong successful storage of the pig liver beyond the 6–8 hours previously described from this laboratory, the addition of cell-membranestabilizing drugs to the preserving solution and the use of a potassium-rich solution were investigated. Using simple hypothermia alone, 10- and 12-hour storage was unsuccessful. Using the previously described hypothermic technique, but with the addition of hyperbaric oxygen at 3 atmospheres absolute (A.T.A.), consistently successful 12-hour preservation was achieved.

Numerical simulation of the hepatic circulation

Availability of donor livers and the relatively short preservation time limit the success of liver transplantation. The use of hypothermic machine perfusion could pave the way for expansion of the donor pool. To better define optimal settings of such a device, the feasibility of using a numerical simulation model of the hepatic circulation is determined. Hemodynamics in the hepatic arterial, portal venous and hepatic venous compartments of the hepatic vascular tree was modelled using an electrical analogue. Calculated pressure and flow profiles throughout the liver were in accordance with physiologic profiles in the total circulatory system. Comparison of calculated flow values with normal control values showed a discrepancy that was explained by inaccurate diameter input data. Until more precise methods for determining vascular dimensions become available, redefining vessel diameter makes the simulation model perfectly suitable for predicting influences of temperature and/or viscosity on hepatic hemodynamics and is thereby an excellent tool in defining optimal settings for our hypothermic liver perfusion system.

Advantages of normothermic perfusion over cold storage in liver preservation

BACKGROUND

To minimize the ischemia-reperfusion injury that occurs to the liver with the current method of preservation and transplantation, we have used an extracorporeal circuit to preserve the liver with normothermic, oxygenated, sanguineous perfusion. In this study, we directly compared preservation by the standard method of simple cold storage in University of Wisconsin (UW) solution with preservation by perfusion.

METHODS

Porcine livers were harvested from large white sows weighing between 30 and 50 kg by the standard procedure for human retrieval. The livers were preserved for 24 hr by either cold storage in UW solution (n=5) or by perfusion with oxygenated autologous blood at body temperature (n=5). The extracorporeal circuit used included a centrifugal pump, heat exchanger, and oxygenator. Both groups were then tested on the circuit for a 24 hr reperfusion phase, analyzing synthetic function, metabolic capacity, hemodynamics, markers of hepatocyte and reperfusion injury, and histology.

RESULTS

Livers preserved with normothermic perfusion were significantly superior (P=0.05) to cold-stored livers in terms of bile production, factor V production, glucose metabolism, and galactose clearance. Cold-stored livers showed significantly higher levels of hepatocellular enzymes in the perfusate and were found to have significantly more damage by a blinded histological scoring system.

CONCLUSIONS

Normothermic sanguineous oxygenated perfusion is a superior method of preservation compared with simple cold storage in UW solution. In addition, perfusion allows the possibility to assess viability of the graft before transplantation.

Liver and kidney preservation by perfusion

The clinical boundaries of transplantation have been set in an era of simple cold storage. Research in organ preservation has led to the development of flush solutions that buffer the harsh molecular conditions which develop during ischaemia, and provide stored organs that are fit to sustain life after transplantation. Although simple and efficient, this method might be reaching its limit with respect to the duration, preservation, and the quality of organs that can be preserved. In addition, flush preservation does not allow for adequate viability assessment. There is good evidence that preservation times will be extended by the provision of continuous cellular substrate. Stimulation of in-vivo conditions by ex-vivo perfusion could also mean that marginal organs will be salvaged for transplantation. Perfusion will also allow for assessing the viability of organs before transplantation in a continuous fashion. The cumulative effect of these benefits would include expansion of the donor pool, less risk of primary non-function, and extension of the safe preservation period. Use of non-heart-beating donors, international organ sharing, and precise calculation of the risk of primary organ failure could become standard.

Effects of a phosphate buffered extracellular (Ep4) solution in preservation and reperfusion injury in the canine liver

The Ep4 solution, a phosphate buffered extracellular-type solution, is effective in canine lung transplantation following a 96-hour hypothermic (4 degrees C) preservation. In this experiment, we used this solution for liver preservation followed by transplantation. We compared the Ep4 solution with the lactated Ringer's (LR) and the Collins' M (CM) solution (a phosphate buffered intracellular-type solution) in two studies, 1) 48-hour liver preservation, and 2) orthotopic liver transplantation after 5-hour preservation. In the preservation study, purine nucleoside phosphorylase (PNP) levels as a marker of endothelial damage, and alanine aminotransferase (ALT) levels were significantly lower in the livers immersed into the Ep4 solution than in those immersed into other solutions at 36 and 48 hours after preservation. Microscopically, the endothelial injury occurred 24 hours after preservation in the CM solution, and 36 hours after preservation in the LR and Ep4 solutions. In the transplantation study, serum PNP and ALT levels in the livers immersed in Ep4 solution showed a lower tendency compared with those in other solutions at the time of reperfusion, but the histological differences among three groups were not apparent. The present study suggests that the liver can be stored better for a longer time using Ep4 solution than using LR and CM solutions.

The evaluation of the isolated perfused liver as a model for the assessment of liver preservation

An ex vivo isolated perfused porcine liver model was tested to assess its suitability for rapid, reliable and relatively cheap testing of organ preservation solutions for liver transplantation. The model consists of a machine driven recirculating system incorporating an organ chamber, blood pump and membrane oxygenator. Autologous blood was used for perfusion for a period of 2 h at a temperature of 37 degrees C. The model was tested with five groups of livers which had sustained varying degrees of injury ranging from minimally damaged to those known to be incapable of sustaining life when used for liver transplantation. The groups of livers were: (i) controls; (ii) preserved in University of Wisconsin solution (UW) for 6 h; (iii) preserved in an albumin-based extracellular fluid (ALB) for 6 h; (iv) preserved in UW for 18 h; and (v) preserved in ALB for 18 h. Bile production was found to be a reliable parameter of preservation damage. Changes in perfusate levels of aspartate aminotransferase, potassium, glucose and calcium also occurred in relationship to preservation damage. In contrast, weight gain of the liver, sequestration of the white cells and platelets in the liver, urea production and oxygen consumption were unreliable predictors of liver damage. Histology of biopsy specimens revealed apparently well preserved livers in all cases after preservation but before perfusion, but serious abnormalities after perfusion in long preserved livers, with features in these suggestive of damage to the sinusoidal endothelium. We believe that the model is a worthwhile adjunct to research into liver preservation.

Review article: improved preservation of the liver for transplantation

This paper reviews the development of the techniques used for liver preservation and describes their clinical use. Recent advances with the introduction of lactobionate based solutions for simple cold storage are described and illustrated by their effect on the Cambridge/King's College Hospital transplant programmes. Better preservation of the liver has simplified the logistics of the transplant procedure, improving organ usage and allowing increased sharing of livers for urgent or paediatric cases.

Ultrastructural changes in rat liver sinusoids during storage in cold Euro-Collins solution

Changes in the sinusoids of rat livers stored in cold (2 degrees C) Euro-Collins solution for various periods were observed using combined scanning (SEM) and transmission electron microscopy (TEM). The sinusoidal endothelial cells were vulnerable to cold ischemia. Fenestrations of the endothelial cells were enlarged and became mesh-like after a 4-h preservation period. Following 8 h storage the sieve plates and cytoplasmic processes of the endothelial cells were destroyed and there was a tendency for the perikaryon to desquamate. Blebs derived from hepatocytes were seen after 4 h and these increased in number and size with prolonged preservation. Although the sinusoids were filled with blebs after 24 h preservation. no irreversible ultrastructural damage in the parenchymal cells was observed. Within 12 h storage, the liver had a mosaic pattern after perfusion fixation indicating uneven fixation and profound circulatory disturbance. These results suggest that endothelial cell destruction and/or numerous blebs may have unfavorable effects on the microcirculation of the transplanted liver after prolonged preservation.

Ultrastructural changes in the rat liver during Euro-Collins storage, compared with hypothermic in vitro ischemia

The ultrastructural alterations in liver tissue induced by in vitro ischemia at 4 degrees C under conditions commonly used for transplantation (Euro-Collins perfused and stored liver tissue) have been compared with changes due to hypothermic in vitro ischemia in non-perfused liver. It was found that the process of cell deterioration in non-perfused liver occurred very slowly; signs of irreversible damage appeared in sinusoidal lining cells before hepatocytes (after 24 and 96 h, respectively). Liver perfused with, and stored in Euro-Collins solution showed acceleration of the ischemical damage in both types of cell (irreversible damage to sinusoidal lining cells after 12 h and to hepatocytes after 52 h), compared with non-perfused liver. These findings indicate that the safe period for storage of rat liver in Euro-Collins before damage to the microcirculatory system is less than 12 h. It might also be questioned whether Euro-Collins treatment is the optimal procedure for tissue preservation before liver transplantation.

Liver preservation techniques for transplantation

The development of optimal methods for preservation is important for the advancement of liver transplantation. This study compares hypothermic storage (HS) and hypothermic pulsatile perfusion (HPP) with various solutions, using an isolated normothermic perfusion model (LIPM). Canine livers were removed from mongrel dogs without warm ischemia and flushed with either heparinized Ringer's lactate (control and HPP-preserved groups) or the solution used for hypothermic storage (TP-V or modified Collins). The type of preservation and solution for each of the experimental groups was as follows: group I (n = 7), no preservation, fresh; group II (n = 7), 24-h HS with TP-V (a hyperosmolar colloid solution containing sucrose, dextrose, and ATP-MgCl2); group III (n = 7), 24-h HS with modified Collins (C-2), an intracellular crystalloid solution; group IV (n = 5), 24-h HP with TP-V; group V (n = 6), 24-h HPP with Belzer solution, containing ATP-MgCl2; group VI (n = 3), 24-h HPP with albumin. After the preservation period, livers were placed on HPP at 37 degrees C with albumin-mannitol solution for 3-h testing in an LIPM. Perfusate samples were taken at 1-h intervals to assess liver function. LDH, SGOT, alkaline phosphatase, lactic acid, LAP, GGT, pO2, pCO2, pH, osmolarity, AMP, ADP, and ATP were studied. Histologic studies were performed, as were representative HIDA scans. Using the LIPM, livers preserved by HS and HPP with TP-V solution appeared to be superior to those preserved with modified Collins, Belzer, and albumin solutions. In these non-TP-V groups, the greatest cellular and organ damage was observed. TP-V HPP appeared to give the best overall liver functional response and histologic results and is recommended as the preferred method for 24-h liver preservation.

Effect of drug treatment on liver-slice function following 72-hour hypothermic perfusion

The viability of hypothermically perfused dog liver was evaluated with a tissue-slice technique. After being preserved for 72 hr, slices of liver were incubated at 30 degrees C for as long as 2 hr; then water content, K+/Na+ ratio, and ATP concentration were measured. Dog livers were assigned to the following experimental groups: Group 1 (no preservation; control); Group 2 (livers preserved for 72 hr); Group 3 (donor animals pretreated with 3.5 mg/kg of chlorpromazine (CPZ) and 20 mg/kg of methylprednisolone (MP), and livers preserved for 72 hr); Group 4 (livers pretreated with 2-deoxycoformycin (2-DOC), 50 mg/liter, and preserved for 72 hr); and Group 5 (combination of Group 3 and Group 4 treatments). Livers in Groups 2, 3, and 4 lost K+ during preservation, and the mean K+/Na+ ratio significantly decreased from a control value of 4.2 +/- 0.4 to 1.5-1.9 (P less than 0.05). Group 5 livers did not lose K+; mean K+/Na+ ratio was 3.9 +/- 0.5. Fresh livers (no preservation) rapidly reaccumulated K+ when the tissue slices were incubated for 2 hr at 30 degrees C; mean K+/Na+ ratio was 3.7 +/- 0.5. Tissue slices from Group 2 livers (72 hr preservation), and livers pretreated with CPZ-MP (Group 3) or pretreated with 2-DOC (Group 4) did not significantly reaccumulate K+ at 30 degrees C; mean K+/Na+ ratio was 1.7-2.1. Only slices prepared from liver pretreated with both CPZ-MP and 2-DOC reaccumulated K+; mean K+/Na+ ratio was 4.6 +/- 1.2.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of cold storage and perfusion of dog livers on function of tissue slices

We compared how two methods of hypothermic preservation affect physiological functions of tissue slices of dog liver. Livers were preserved by either (i) cold storage (CS) in Collins' solution or (ii) continuous perfusion (P) with a perfusate, containing hydroxyethyl starch, sodium gluconate, adenosine, and potassium phosphate, recently developed in our laboratory. Livers were cold stored for 6 to 8, 24, or 48 hr, and perfused for 24 or 72 hr. Tissue slices of preserved livers were incubated at 30 degrees C and analyzed for volume control, electrolyte-pump activity (K and Na), and adenine nucleotide concentration. Also, mitochondria were isolated after preservation to quantify respiratory activity. Slice functions of livers preserved for short periods (6 to 8 hr by CS and 24 hr by P) were similar to those for control livers. After normothermic incubation, the mean (+/- SD) water content of tissue (expressed per unit dry mass of tissue) was 2.3 +/- 0.3 kg/kg for control, 2.6 +/- 0.4 kg/kg for 6- to 8-hr CS, and 2.5 +/- 0.5 kg/kg for 24-hr P. Longer periods of preservation resulted in cell swelling, and water content was 3.3 +/- 0.4 kg/kg for 24- to 48-hr CS and 2.8 +/- 0.3 kg/kg for 72-hr P. The mean (+/- SD) K/Na ratio was nearly normal for livers preserved for short periods: 3.7 +/- 0.5 for control, 4.1 +/- 0.2 for 6- to 8-hr CS, and 3.3 +/- 0.4 for 24-hr P.(ABSTRACT TRUNCATED AT 250 WORDS)

Small bowel transplantation in the rat: the adverse effect of increased pressure during the flushing procedure of the graft

The influence of the pressure during the flushing procedure on the results of the subsequent transplantation was investigated in a model of heterotopic functional small bowel transplantation in the outbred Wistar rat. In this model insufficient small bowel preservation will result in a lethal shock, soon after revascularization. If the size of the small bowel graft was reduced to a 15-cm segment of the proximal jejunum, improper preservation did not lead to lethal shock, but to histological changes of the graft. The influence of high flushing pressure (80 cm), medium flushing pressure (50 cm), low flushing pressure (35 cm), and no flushing procedure at all, was investigated in different groups of rats. Flushing was performed by gravity using chilled Ringer's lactate solution (4 degrees C), buffered with NaHCO3 at a pH of 7.4. The results were evaluated histologically as well as clinically. Results indicated flushing of the graft to be superior to a nonflushing procedure. A flushing pressure of 80 cm and even 50 cm proved to be harmful to the jejunal graft. Flushing pressure of 35 cm resulted in successful segmental (jejunal) and subtotal (minus 5- to 7-cm distal ileum) small bowel transplantation. However, survival of a total small bowel graft could not be achieved with the optimal flushing procedure indicating that the functional integrity of a small bowel graft also depends on conditions other than the method of short-term preservation.

[Electron microscopic findings during hypothermic storage. Preservation of the liver. I. (author's transl)]

Porcine livers were preserved by simple hypothermic storage for 6 h using plasma-protein-fraction 5%, albumin 5%, Collins C2, and Ringer-lactate. Electron-microscopic alterations primarily consist of aggregations of nuclear chromatin, marginal chromatin condensation, swelling and destruction of cristae mitochondriales, swelling and degranulation of the endoplasmic reticulum. These signs of cell damage are of varying intensity depending on the different preservation methods. The best condition of hepatocytes on the whole is guaranteed by using Collins C2-solution.

Maintenance of rat liver viability enhanced by cold flushing with oxygenated perfluorochemicals

The possible benefit of oxygenation during initial cold flushing was investigated as means of improving the quality of live preservation in rats. In five group of animals (total 61 experiments), the lives were flushed with different perfusates. Non-oxygenated groups included controls, Collins' solution alone and Collins' solution containing perfluorotributylamine (FC-43). In the oxygenated groups, Collins' solution alone and collins' solution containing FC-43 were oxygenated by bubbling. The hepatic ATP level and histopathological changes were used to assess the quality of liver preservation. Oxygenation during the initial cooling process proved to be effective in maintaining energy metabolism and preventing the characteristic microscopic changes of ischemic damage. Oxygenated Collins' solution containing FC-43 showed a much longer lasting effect compared with oxygenated Collins' solution alone. Without FC-43. Under light microscopy, in integrity of the liver appeared to be well preserved up to eight hours with the former solution. It is concluded that enhanced oxygenation with FC-43 in the initial cold flushing period can improve the quality of liver preservation.

Successful preservation of pig's liver for 5-8 hours by simple ice storage

Successful preservation of pig's liver using simple ice storage is described. The liver is apparently stored well by this method for 5-8 hours.

The natural history of liver alloone and autotransplantation in the pig

A series of 40 pig liver transplants surviving for at least 5 days is presented. Twenty orthotopic allografts are compared with 20 autograft controls, and in each group biliary drainage by a cholecystoduodenostomy (gall-bladder to duodenum anastomosis) is compared with a choledochocholedochostomy (direct bile-duct to bile-duct anastomosis).

The pigs with liver allotransplants usually demonstrated low-grade liver rejection, maximal during the second week, which subsequently spontaneously subsided without immunosuppression. However, in 15 per cent of the pigs the rejection process was more intense with death from rejection between the fifth and seventh days. Although prolonged survival was achieved in the remaining allografts, the final outcome was invariably a fatal one, owing either to gastric ulceration with haemorrhage or to infection. The mean survival time in the autograft controls was similar, and even when gastric ulceration was virtually eliminated in this group by a bile-duct to bile-duct anastomosis, death owing to infection usually occurred in the third week.

The autograft controls demonstrated the superiority of a direct bile-duct to bile-duct anastomosis in the pig, and reduced the incidence of biliary stasis and cholangitis as well as gastric ulceration in this group.

Repeated liver biopsies in both groups revealed that biochemical changes suggestive of rejection did not always represent rejection, but merely cholestasis, which could be caused by rejection or by other factors such as a cholestatic biliary anastomosis (cholecystoduodenostomy). This has important implications in human liver transplantation.