Abdominal Transplant Surgery and Transplant Coordination University Hospitals Leuven 1997–2007: an Overview

Evaluation of Liver Quality after Circulatory Death Versus Brain Death: A Comparative Preclinical Pig Model Study

The current organ shortage in hepatic transplantation leads to increased use of marginal livers. New organ sources are needed, and deceased after circulatory death (DCD) donors present an interesting possibility. However, many unknown remains on these donors and their pathophysiology regarding ischemia reperfusion injury (IRI). Our hypothesis was that DCD combined with abdominal normothermic regional recirculation (ANOR) is not inferior to deceased after brain death (DBD) donors. We performed a mechanistic comparison between livers from DBD and DCD donors in a highly reproducible pig model, closely mimicking donor conditions encountered in the clinic. DCD donors were conditioned by ANOR. We determined that from the start of storage, pro-lesion pathways such as oxidative stress and cell death were induced in both donor types, but to a higher extent in DBD organs. Furthermore, pro-survival pathways, such as resistance to hypoxia and regeneration showed activation levels closer to healthy livers in DCD-ANOR rather than in DBD organs. These data highlight critical differences between DBD and DCD-ANOR livers, with an apparent superiority of DCD in terms of quality. This confirms our hypothesis and further confirms previously demonstrated benefits of ANOR. This encourages the expended use of DCD organs, particularly with ANOR preconditioning.

Simvastatin maintains function and viability of steatotic rat livers procured for transplantation

BACKGROUND & AIMS

Liver grafts obtained from healthy rat donors develop acute microcirculatory dysfunction due to cold-storage and warm-reperfusion injuries. These detrimental effects are avoided adding simvastatin to the cold-storage solution. Considering the importance of increasing organ donor pool for transplantation, we characterized whether simvastatin pretreatment can protect steatotic grafts from cold-storage and warm-reperfusion injuries.

METHODS

Rats fed with high-fat diet received a single dose of simvastatin, or its vehicle, 30 min before liver procurement. Grafts were then cold stored for 0 h (control group) or 16 h and warm reperfused. At the end of the reperfusion period, hepatic vascular resistance, endothelial function, nitric oxide pathway, cell death, oxidative stress, autophagy, and liver injury were evaluated. Hepatic vascular resistance and endothelial function were determined in a group of simvastatin-treated livers in the presence of the nitric oxide synthase inhibitor L-NNA.

RESULTS

Cold-stored rat steatotic livers exhibit increased hepatic vascular resistance and marked endothelial dysfunction, together with liver damage, oxidative stress, and low nitric oxide. Simvastatin markedly improved liver injury and prevented hepatic endothelial dysfunction. The beneficial effects of simvastatin were associated with cell death diminution, autophagy induction, and nitric oxide release. Statin-derived liver microcirculation protection was not observed when nitric oxide production was blunted.

CONCLUSIONS

Pretreatment of steatotic liver donors with simvastatin shortly before procurement of the liver graft strongly protects both parenchymal and endothelial components of the liver after warm reperfusion. Our data reinforce the use of statins to protect liver grafts undergoing transplantation.

Phosphoenolpyruvate, a glycolytic intermediate, as a cytoprotectant and antioxidant in ex-vivo cold-preserved mouse liver: a potential application for organ preservation

OBJECTIVES

The aim of this study was to examine the effect of phosphoenolpyruvate (PEP), a glycolytic intermediate, on organ damage during cold preservation of liver.

METHODS

An ex-vivo mouse liver cold-preservation model and an in-vitro liver injury model induced by hydrogen peroxide in HepG2 cells were leveraged.

KEY FINDINGS

PEP attenuated the elevation of aminotransferases and lactate dehydrogenase leakage during organ preservation, histological changes and changes in oxidative stress parameters (measured as thiobarbituric acid reactive substance and glutathione content) induced by 72 h of cold preservation of the liver. The effects were comparable with the University of Wisconsin solution, a gold standard organ preservation agent. The decrease in ATP content in liver during the cold preservation was attenuated by PEP treatment. PEP prevented the cellular injury and increases in intracellular reactive oxygen species in HepG2 cells. In addition, PEP scavenged hydroxyl radicals, but had no effect on superoxide anion as evaluated by an electron paramagnetic resonance spin-trapping technique.

CONCLUSIONS

PEP significantly attenuated the injury, oxidative stress and ATP depletion in liver during cold preservation. The antioxidative potential of PEP was confirmed by in-vitro examination. We suggest that PEP acts as a glycolytic intermediate and antioxidant, and is particularly useful as an organ preservation agent in clinical transplantation.

Notch-dependent expression of epithelial-mesenchymal transition markers in cholangiocytes after liver transplantation

AIM

  Epithelial-mesenchymal transition (EMT) has been identified in chronic cholestatic liver diseases, which are characterized by biliary proliferation and fibrosis. Activation of Notch signaling mediates EMT in a variety of epithelial cell types. In the present study, we investigated the role of Notch signaling in the regulation of EMT marker expression in cholangiocytes after liver transplantation.

METHODS

  Orthotopic liver transplantation was performed in Sprague-Dawley rats. Liver tissues and isolated cholangiocytes were collected 1 week after transplantation. The expression of mesenchymal and biliary epithelial markers was evaluated by immunohistochemistry, quantitative polymerase chain reaction (PCR) and western blotting in liver sections and isolated cholangiocytes. Quantitative real-time PCR and western blotting for Jagged1 and HES1 were utilized to evaluate the activation of Notch signaling. Proliferation and migration of cholangiocytes were assessed by 5-bromodeoxyuridine and transwell assays, respectively. Cholangiocyte proliferation, migration and expression of EMT markers were also evaluated following the inhibition of Notch signaling with N,(N-[3,5-difluorophenacetyl]-L-alanyl)-S-phenylglycine t-butylester (γ-secretase inhibitor) and a Jagged1-neutralizing antibody.

RESULTS

  Expression of EMT markers by cholangiocytes was observed in liver grafts and isolated cholangiocytes obtained 1 week after transplantation. Inhibition of Notch signaling prevented the expression of EMT markers in bile ducts of liver sections and isolated cholangiocytes. Cholangiocyte proliferative and migratory capacities were also suppressed by the inhibition of Notch signaling.

CONCLUSION

  Activation of Notch signaling promotes cholangiocyte proliferation and expression of EMT markers after liver transplantation.

Addition of simvastatin to cold storage solution prevents endothelial dysfunction in explanted rat livers

Pathophysiological alterations in the endothelial phenotype result in endothelial dysfunction. Flow cessation, occurring during organ procurement for transplantation, triggers the endothelial dysfunction characteristic of ischemia/reperfusion injury, partly due to a reduction in the expression of the vasoprotective transcription factor Kruppel-like Factor 2 (KLF2). We aimed at (1) characterizing the effects of flow cessation and cold storage on hepatic endothelial phenotype, and (2) ascertaining if the consequences of cold stasis on the hepatic endothelium can be pharmacologically modulated, improving liver graft function. Expression of KLF2 and its vasoprotective programs was determined in (i) hepatic endothelial cells (HEC) incubated under cold storage conditions with or without the KLF2-inducer simvastatin, and (ii) rat livers not cold stored or preserved in cold University of Wisconsin solution (UWS) supplemented with simvastatin or its vehicle. In addition, upon warm reperfusion hepatic vascular resistance, endothelial function, nitric oxide vasodilator pathway, apoptosis, inflammation, and liver injury were evaluated in not cold stored livers or livers preserved in cold UWS supplemented with simvastatin or vehicle. Expression of KLF2 and its vasoprotective programs decrease in HEC incubated under cold storage conditions. Cold-stored rat livers exhibit a time-dependent decrease in KLF2 and its target genes, liver injury, increased hepatic vascular resistance, and endothelial dysfunction. The addition of simvastatin to the storage solution, maintained KLF2-dependent vasoprotective programs, prevented liver damage, inflammation, and oxidative stress and improved endothelial dysfunction.

CONCLUSION

Our results provide a rationale to evaluate the beneficial effects of a vasoprotective preservation solution on human liver procurement for transplantation.

Hypothermic Liver Machine Perfusion With EKPS-1 Solution vs Aqix RS-I Solution: In Vivo Feasibility Study in a Pig Transplantation Model

OBJECTIVE

Hypothermic machine perfusion (HMP) is superior to simple cold storage for kidney preservation. We previous observed in a porcine liver transplantation model increased tumor necrosis factor-alpha (TNF-alpha) production eventually leading to poor recipient survival after HMP using standard kidney perfusion solution (KPS-1) compared with simple cold storage. We compared two solutions for HMP preservation of the liver: enriched KPS-1 (EKPS-1) and Aqix RS-I.

METHODS

Pig livers were obtained after cold flushing with histidine-tryptophan-ketoglutarate solution. Subsequently, the livers were subjected to dual-vessel perfusion with two preservation solutions: EKPS-1 (n = 6) and Aqix RS-I (n = 3). After HMP preservation and transplantation, graft and recipient survival, hepatocellular damage (aspartate aminotransferase concentration), TNF-alpha production, and endothelial cell damage (hyaluronic acid clearance) were recorded.

RESULTS

No primary graft nonfunction was observed. Recipient survival at postoperative day 3 was similar in both groups (33%). Aspartate aminotransferase concentration measured in serum samples after reperfusion was similar in both groups. After reperfusion, TNF-alpha concentration was higher and hyaluronic acid clearance was lower in the EKPS-1 group vs the Aqix RS-I group at 60, 120, and 180 minutes (all P < .05).

CONCLUSION

Hypothermic machine perfusion provided adequate longer term graft survival. After reperfusion, TNF-alpha production seems to be reduced, and endothelial cell dysfunction remains pronounced with Aqix RS-1 solution compared with EKPS-1 solution.

Amsacrine-induced lesions in DNA and their modulation by novobiocin and 2,4-dinitrophenol

The cancer chemotherapeutic agent amsacrine, 4'-(9-acridinylamino)-methanesulfon-m-anisidide (mAMSA), is thought to effect cytotoxicity by inhibiting the ATP-dependent enzyme topoisomerase II in the act of its duplex strand-passing action. Upon protein denaturation, the arrested "cleavable complex" that results gives rise to double- and single-strand breaks (dsbs and ssbs) and DNA-protein cross-links (dpcs). Simultaneous cotreatments with 2,4-dinitrophenol (DNP) or novobiocin (novo) abrogates mAMSA cytotoxicity in Chinese hamster cells (H. Utsumi et al., Cancer Res., 50:2577-2581, 1990). Pulsed-field gel electrophoresis was used to estimate dsbs, velocity sedimentation in alkaline sucrose gradients for ssbs, and alkaline elution without protease digestion for dpcs. Although cotreatment with DNP or novo modulated somewhat the yield of DNA lesions due to mAMSA, quantitatively these changes did not correlate at all with, and therefore could not account for, the reduced lethality that resulted from cotreatments. For example, DNA cotreatment markedly increased the yields of dsbs, ssbs, and dpcs, even though cell killing was appreciably reduced. Furthermore, neither DNP nor novo cotreatment affected the rate, or the completeness of, the repair of mAMSA-induced DNA damage, and neither cotreatment lowered total cellular ATP. Hence, the arresting of the cleavable complex by mAMSA, made evident by lesions in DNA, did not correlate with cytotoxicity. However, cotreatment with either DNP or novo resulted in an enhanced recovery of the mAMSA-induced inhibition of replicative DNA synthesis. Because DNP and novo (transiently) slow down DNA synthesis, it is proposed that these compounds abrogate mAMSA killing of S phase cells by reducing the disorganization of the processing of replicated DNA by topoisomerase II.