Current status and perspective of liver preservation solutions

BACKGROUND: A safe and effective preservation solution is a precondition for liver transplantation, which is accepted as the radical treatment for patients with end- stage liver disease. The increasing use of marginal donors and non-heart beating donors as well as the establishment of a national organ allocation network call for better preservation. New preservation solutions like histidine- tryptophan-ketoglutarate (HTK) solution and Celsior solution have been introduced to liver preservation, and protective gene intervention and other modifications have also been investigated. In this article, we review recent advances in liver preservation solutions. DATA SOURCES: An English-language literature search was conducted using MEDLINE (1990-2005) on liver preservation solution, biliary complication, protective gene and other related subjects. RESULTS: Although the high viscosity of the University of Wisconsin (UW) solution proved harmful to the hepatic microcirculation, three solutions showed equivalent preservation effects. When the cold ischemia time was short, there were no significant differences among the three solutions in the incidence of biliary complications. So far, modifications of preservation solutions have achieved great success. Several types of protective genes like A20, Bcl-2, Bcl-XL and HO-1 were reported to have definite liver protective effects. The addition of other substrates like TNF-α antibody, tacrolimus (FK506) and fructose-1, 6-bisphosphate (FBP) can also improve the preservation effect. However, addition of insulin to UW solution is harmful to the graft. CONCLUSIONS: In centers with highly-developed transplantation techniques, HTK and Celsior solutions are acceptable in liver preservation. Protective genemodification and addition of substrates like TNF-α antibody, FK506 and FBP are prominent approaches to improve liver preservation.

Relevance of proteolysis and proteasome activation in fatty liver graft preservation: An Institut Georges Lopez-1 vs University of Wisconsin appraisal

To compare liver proteolysis and proteasome activation in steatotic liver grafts conserved in University of Wisconsin (UW) and Institut Georges Lopez-1 (IGL-1) solutions.METHODSFatty liver grafts from male obese Zücker rats were conserved in UW and IGL-1 solutions for 24 h at 4 °Cand subjected to “ex vivo” normo-thermic perfusion (2 h; 37 °C). Liver proteolysis in tissue specimens and perfusate was measured by reverse-phase high performance liquid chromatography. Total free amino acid release was correlated with the activation of the ubiquitin proteasome system (UPS: measured as chymotryptic-like activity and 20S and 19S proteasome), the prevention of liver injury (transaminases), mitochondrial injury (confocal microscopy) and inflammation markers (TNF 1 alpha, high mobility group box-1 (HGMB-1) and PPAR gamma), and liver apoptosis (TUNEL assay, cytochrome c and caspase 3).RESULTSProfiles of free AA (alanine, proline, leucine, isoleucine, methionine, lysine, ornithine, and threonine, among others) were similar for tissue and reperfusion effluent. In all cases, the IGL-1 solution showed a significantly higher prevention of proteolysis than UW (P < 0.05) after cold ischemia reperfusion. Livers conserved in IGL-1 presented more effective prevention of ATP-breakdown and more inhibition of UPS activity (measured as chymotryptic-like activity). In addition, the prevention of liver proteolysis and UPS activation correlated with the prevention of liver injury (AST/ALT) and mitochondrial damage (revealed by confocal microscopy findings) as well as with the prevention of inflammatory markers (TNF1alpha and HMGB) after reperfusion. In addition, the liver grafts preserved in IGL-1 showed a significant decrease in liver apoptosis, as shown by TUNEL assay and the reduction of cytochrome c, caspase 3 and P62 levels.CONCLUSIONOur comparison of these two preservation solutions suggests that IGL-1 helps to prevent ATP breakdown more effectively than UW and subsequently achieves a higher UPS inhibition and reduced liver proteolysis.

Liver graft preservation methods during cold ischemia phase and normothermic machine perfusion

The growing demand for donor organs requires measures to expand donor pool.Those include extended criteria donors, such as elderly people, steatotic livers,donation after cardiac death, etc. Static cold storage to reduce metabolic requirements developed by Collins in late 1960 s is the mainstay and the golden standard for donated organ protection. Hypothermic machine perfusion provides dynamic organ preservation at 4°C with protracted infusion of metabolic substrates to the graft during the ex vivo period. It has been used instead of static cold storage or after it as short perfusion in transplant center. Normothermic machine perfusion(NMP) delivers oxygen, and nutrition at physiological temperature mimicking regular environment in order to support cellular function. This would minimize effects of ischemia/reperfusion injury.Potentially, NMP may help to estimate graft functionality before implantation into a recipient. Clinical studies demonstrated at least its non-inferiority or better outcomes vs static cold storage. Regular grafts donated after brain death could be safely preserved with convenient static cold storage. Except for prolonged ischemia time where hypothermic machine perfusion started in transplant center could be estimated to provide possible positive reconditioning effect. Use of hypothermic machine perfusion in regular donation instead of static cold storage or in extended criteria donors requires further investigation. Multicenter randomized clinical trial supposed to be completed in December 2021. Extended criteria donors need additional measures for graft storage and assessment until its implantation. NMP is actively evaluating promising method for this purpose.Future studies are necessary for precise estimation and confirmation to issue clinical practice recommendations.

Machine perfusion of the liver:Putting the puzzle pieces together

The realm of extended criteria liver transplantation created the'adjacent possible'for dynamic organ preservation.Machine perfusion of the liver greatly expanded donor organ preservation possibilities,reaching before unattainable goals,including the mitigation of ischemia-reperfusion injury,viability assessment,and organ reconditioning prior to transplantation.However,current scientific evidence lacks uniformity between studies,perfusion protocols,and acceptance criteria.Construction of collaborative research networks for sharing knowledge should,therefore,enable the development of high-level evidence and guidelines for machine perfusion utilization,including donor acceptance criteria.Finally,this approach shall guarantee conditions for further progress to occur.

STUDY ON MODIFIED COLD STORAGE METHOD OF RAT LIVERS WITH SELF-MADE HYD SOLUTION

To investigate the cold preservation effect of rat livers by modified storage method with self made HYD solution. Methods. The modified method was that the vascular bed of rat livers was expanded with an additional 20 to 40ml self made HYD solution/100g liver. After removing the liver, the extra HYD solution expressed as % liver weight was entrapped via portal infusion by tying off the supra and infra hepatic inferior vena cava. According to the amount of extra HYD solution, 40 rats were randomly divided into four groups including: control group with conventional storage method, 20% group, 30% group and 40% group. The preservation effect of modified storage method with that of conventional storage method by using isolated perfused rat liver model was compared. [WT5”BX] Results.[WT5”BZ] Bile production and all the indices of hepatic microcirculation including portal perfusion pressure, endothelin 1 in the effluent, trypan blue distribution time and histology in modified method groups were significantly superior to those in control group (P<0.05). The liver enzymes in 30% group were markedly lower than those in control group (P<0.05). The preservation effect of rat liver in 30% group was the best among the modified method groups. Conclusion. The modified cold storage method is effective and may have potential for clinical application for liver preservation.

Modified cold storage of rat livers with self-made HYD solution

Objective To investigate the cold preservation effect on rat livers of a modified storage method with self-made HYD solution.Methods The vascular bed of rat livers was expanded with an additional 20 to 40?ml self-made HYD solution/100?g liver. After resection of the liver, the extra HYD solution (expressed as % liver weight) was entrapped via portal infusion by tying off the supra- and infra-hepatic inferior vena cava. Forty rats were randomly divided into four groups including control group with conventional storage method, and 20%, 30% and 40% groups according to the amount of extra HYD solution. We compared the preservation effect of the modified storage method with that of the conventional storage method using an isolated perfused rat liver model.Results Bile production and all the indices of hepatic microcirculation including portal perfusion pressure, endothelin-1 in the effluent, trypan blue distribution time and histology were significantly superior in the modified method groups compared to those in the control group (P<0.05). The contents of dihydroxybenzoic acid (DHBA) in the modified method groups were significantly lower than those in the control group (P<0.05). Liver enzymes activities in the 30% group were markedly lower than those in the control group (P<0.05). The preservation effect on rat liver in the 30% group was the best among the modified method groups.Conclusion The modified cold storage method is effective and may have potential for clinical application in liver preservation.