A Comparative Study of Single and Dual Perfusion During End-ischemic Subnormothermic Liver Machine Preservation

Protective mechanisms and current clinical evidence of hypothermic oxygenated machine perfusion (HOPE) in preventing post-transplant cholangiopathy

The development of cholangiopathies after liver transplantation impacts on the quality and duration of graft and patient survival, contributing to higher costs as numerous interventions are required to treat strictures and infections at the biliary tree. Prolonged donor warm ischaemia time in combination with additional cold storage are key risk factors for the development of biliary strictures. Based on this, the clinical implementation of dynamic preservation strategies is a current hot topic in the field of donation after circulatory death (DCD) liver transplantation. Despite various retrospective studies reporting promising results, also regarding biliary complications, there are only a few randomised-controlled trials on machine perfusion. Recently, the group from Groningen has published the first randomised-controlled trial on hypothermic oxygenated perfusion (HOPE), demonstrating a significant reduction of symptomatic ischaemic cholangiopathies with the use of a short period of HOPE before DCD liver implantation. The most likely mechanism for this important effect, also shown in several experimental studies, is based on mitochondrial reprogramming under hypothermic aerobic conditions, e.g. exposure to oxygen in the cold, with a controlled and slow metabolism of ischaemically accumulated succinate and simultaneous ATP replenishment. This unique feature prevents mitochondrial oxidative injury and further downstream tissue inflammation. HOPE treatment therefore supports livers by protecting them from ischaemia-reperfusion injury (IRI), and thereby also prevents the development of post-transplant biliary injury. With reduced IRI-associated inflammation, recipients are also protected from activation of the innate immune system, with less acute rejections seen after HOPE.

Delivering siRNA Compounds During HOPE to Modulate Organ Function: A Proof-of-Concept Study in a Rat Liver Transplant Model

BACKGROUND

Apoptosis contributes to the severity of ischemia-reperfusion injury (IRI), limiting the use of extended criteria donors in liver transplantation (LT). Machine perfusion has been proposed as a platform to administer specific therapies to improve graft function. Alternatively, the inhibition of genes associated with apoptosis during machine perfusion could alleviate IRI post-LT. The aim of the study was to investigate whether inhibition of an apoptosis-associated gene (FAS) using a small interfering RNA (siRNA) approach could alleviate IRI in a rat LT model.

METHODS

In 2 different experimental protocols, FASsiRNA (500 µg) was administered to rat donors 2 h before organ procurement, followed by 22 h of static cold storage, (SCS) or was added to the perfusate during 1 h of ex situ hypothermic oxygenated perfusion (HOPE) to livers previously preserved for 4 h in SCS.

RESULTS

Transaminase levels were significantly lower in the SCS-FASsiRNA group at 24 h post-LT. Proinflammatory cytokines (interleukin-2, C-X-C motif chemokine 10, tumor necrosis factor alpha, and interferon gamma) were significantly decreased in the SCS-FASsiRNA group, whereas the interleukin-10 anti-inflammatory cytokine was significantly increased in the HOPE-FASsiRNA group. Liver absorption of FASsiRNA after HOPE session was demonstrated by confocal microscopy; however, no statistically significant differences on the apoptotic index, necrosis levels, and FAS protein transcription between treated and untreated groups were observed.

CONCLUSIONS

FAS inhibition through siRNA therapy decreases the severity of IRI after LT in a SCS protocol; however the association of siRNA therapy with a HOPE perfusion model is very challenging. Future studies using better designed siRNA compounds and appropriate doses are required to prove the siRNA therapy effectiveness during liver HOPE liver perfusion.

Dual versus single vessel normothermic ex vivo perfusion of rat liver grafts using metamizole for vasodilatation

Background

Normothermic ex vivo liver perfusion (NEVLP) is a promising strategy to increase the donor pool in liver transplantation. Small animal models are essential to further investigate questions regarding organ preservation and reconditioning by NEVLP. A dual vessel small animal NEVLP (dNEVLP) model was developed using metamizole as a vasodilator and compared to conventional portovenous single vessel NEVLP (sNEVLP).

Methods

Livers of male Wistar rats were perfused with erythrocyte-supplemented culture medium for six hours by either dNEVLP via hepatic artery and portal vein or portovenous sNEVLP. dNEVLP was performed either with or without metamizole treatment. Perfusion pressure and flow rates were constantly monitored. Transaminase levels were determined in the perfusate at the start and after three and six hours of perfusion. Bile secretion was monitored and bile LDH and GGT levels were measured hourly. Histopathological analysis was performed using liver and bile duct tissue samples after perfusion.

Results

Hepatic artery pressure was significantly lower in dNEVLP with metamizole administration. Compared to sNEVLP, dNEVLP with metamizole treatment showed higher bile production, lower levels of transaminases during and after perfusion as well as significantly lower necrosis in liver and bile duct tissue. Biochemical markers of bile duct injury showed the same trend.

Conclusion

Our miniaturized dNEVLP system enables normothermic dual vessel rat liver perfusion. The administration of metamizole effectively ameliorates arterial vasospasm allowing for six hours of dNEVLP, with superior outcome compared to sNEVLP.