The Effect of Normothermic Machine Perfusion on the Immune Profile of Donor Liver

Haemoadsorption cartridge connected to the machine perfusion for donation after circulatory death porcine liver marginal grafts

BACKGROUND

Marginal donation after circulatory death (DCD) liver grafts are carefully used to combat the constant shortage of donors. Clinically, the worst outcomes are mainly related to severe ischemia-reperfusion-injury and the dangerous effect of various inflammatory cytokines (CK). The machine perfusion (MP) is a promising device to rescue these grafts.

AIM

To analyze the role of MP connected to a sorbent cartridge (PerSorb^®) and used for very damaged DCD pig livers.

METHODS

Seven grafts were procured from pigs from a slaughterhouse. Grafts were made very marginal with at least 60 minutes of donor warm ischemia time and 24 hours of static-cold ischemia time: (1) 3 grafts were perfused in hypothermic MP with PerSorb (Sorb); (2) 2 other grafts in hypothermic MP (HMP) without the cartridge (NoSorb); and (3) The other 2 livers stored in the ice box (NoTreat). The CK were measured at HMP start (T0) and at the end (Tend). Biopsies were taken at T0 and Tend.

RESULTS

All 5 grafts treated with HMP had a negative lactate trend after 3 hours of treatment (8.83 at T0 vs 6.4 at Tend of Sorb; 15 at T0 vs 5.45 at Tend for NoSorb, P value > 0.05). At Tend, both Sorb and NoSorb groups had better hemodynamic parameters, comparable between the two groups. Enzyme-linked immunosorbent assay analysis showed a reduction of monocyte chemotactic protein-1, tumor necrosis factor-alpha and interleukin-1β for NoSorb group at Tend and a complete downregulation to physiological levels of the same CK in Sorb livers after 3 hours of treatment. Biopsies showed a reduction of the perisinusoidal edema for the Sorb grafts compared with the NoSorb livers.

CONCLUSION

These data suggest a potential protective role of treatment of grafts with MP and sorbent cartridge in reducing the inflammatory response after a severe ischemic injury.

The Impact of Over Three Years Commercial Use of Ex Vivo Normothermic Machine Perfusion for Liver Transplantation in the USA: A UNOS/OPTN Database Analysis

BACKGROUND

Data to date using normothermic machine perfusion (NMP) devices to resuscitate and assess marginal livers such as donation after circulatory death (DCD) livers has shown impressive prevention of ischemic reperfusion injury and ischemic cholangiopathy (IC). We examined the impact of these NMP devices over 3 years after their release for commercial use on deceased donor liver transplantation (LT).

METHODS

We conducted a retrospective analysis of UNOS-SRTR data of livers recovered from DCD donors or older (≥ 60 years old) donation after brain death (DBD) donors for LT as well as the outcome of LT from DBD or DCD donors performed from 1/1/2016 to 6/30/2024 to compare differences with ischemic cold storage (ICS) versus NMP.

RESULTS

Among 10 778 donors of DCD livers, 1987 donors used NMP, and 8791 donors used ICS. In NMP group, the proportion of discarded livers was significantly less (7.25% vs. 30.52%), donors were older, donor BMI higher and more expanded criteria donor than those in ICS group (all, p < 0.001). For older donors, 416 cases used NMP and in 10 708 cases the liver was recovered via ICS. The discard rate of livers in NMP group was significantly less (4.33% vs. 12.18%, p < 0.001) and donors were older and donor BMI higher than that in ICS group. In DCD LT, the incidence of primary nonfunction (PNF), acute rejection within 1 year after LT as well as graft failure due to IC and hepatic artery thrombosis (HAT) in NMP group were significantly less than those in ICS group.

CONCLUSION

In conclusion, commercial use of NMP has expanded the donor pool by accelerated usage of marginal livers such as DCD and older donors by permitting longer preservation and functional assessment of the liver. In addition, the usage of NMP for DCD LTs was associate with a reduced incidence of rejection, PNF, graft failure due to IC and HAT.

Ex-situ machine perfusion in clinical liver transplantation: Current practices and future directions

Ex-situ machine perfusion of the liver has surmounted traditional limitations associated with static cold storage in the context of organ preservation. This innovative technology has changed the landscape of liver transplantation by mitigating ischemia perfusion injury, offering a platform for continuous assessment of organ quality, and providing an avenue for optimizing the use of traditionally marginal allografts. This review summarizes the contemporary clinical applications of machine perfusion devices and discusses potential future strategies for real-time viability assessment, therapeutic interventions, and modulation of organ function after recovery.

Perfusate Liver Arginase 1 Levels After End-Ischemic Machine Perfusion Are Associated with Early Allograft Dysfunction

Background/Objectives: The rising use of liver grafts from donation after circulatory death (DCD) has been enabled by advances in normothermic regional perfusion (NRP) and machine perfusion (MP) technologies. We aimed to identify predictive biomarkers in DCD grafts subjected to NRP, followed by randomization to either normothermic machine perfusion (NMP) or dual hypothermic oxygenated perfusion (D-HOPE). Methods: Among 57 DCD donors, 32 liver grafts were transplanted, and recipients were monitored for one week post-transplant. Biomarkers linked with oxidative stress, hepatic injury, mitochondrial dysfunction, inflammation, regeneration, and autophagy were measured during NRP, end-ischemic MP, and one week post-transplant. Results: Arginase-1 (ARG-1) levels were consistently higher in discarded grafts and in recipients who later developed early allograft dysfunction (EAD). Specifically, ARG-1 levels at the end of MP correlated with markers of hepatic injury. Receiver operating characteristic analysis indicated that ARG-1 at the end of MP had a good predictive accuracy for EAD (AUC = 0.713; p = 0.02). Lipid peroxidation (TBARS) elevated at the start of NRP, declined over time, with higher levels in D-HOPE than in NMP, suggesting a more oxidative environment in D-HOPE. Metabolites like flavin mononucleotide (FMN) and NADH exhibited significant disparities between perfusion types, due to differences in perfusate compositions. Inflammatory biomarkers rose during NRP and NMP but normalized post-transplantation. Regenerative markers, including osteopontin and hepatocyte growth factor, increased during NRP and NMP and normalized post-transplant. Conclusions: ARG-1 demonstrates strong potential as an early biomarker for assessing liver graft viability during perfusion, supporting timely and effective decision-making in transplantation.

Revolutionizing Liver Transplantation: Transitioning to an Elective Procedure Through Ex Situ Normothermic Machine Perfusion - A Benefit Analysis

OBJECTIVE

To assess the impact of normothermic machine perfusion (NMP) on patients, medical teams, and costs by gathering global insights and exploring current limitations.

BACKGROUND

NMP for ex situ liver graft perfusion is gaining increasing attention for its capability to extend graft preservation. It has the potential to transform liver transplantation (LT) from an urgent to a purely elective procedure, which could revolutionize LT logistics, reduce burden on patients and health care providers, and decrease costs.

METHODS

A 31-item survey was sent to international transplant directors to gather their NMP experiences and vision. In addition, we performed a systematic review on cost-analysis in LT and assessed studies on cost-benefit in converting urgent-to-elective procedures. We compared the costs of available NMPs and conducted a sensitivity analysis of NMP's cost benefits.

RESULTS

Of 120 transplant programs contacted, 64 (53%) responded, spanning North America (31%), Europe (42%), Asia (22%), and South America (5%). Of the total, 60% had adopted NMP, with larger centers (>100 transplants/year) in North America and Europe more likely to use it. The main NMP systems were OrganOx-metra (39%), XVIVO (36%), and TransMedics-OCS (15%). Despite NMP adoption, 41% of centers still perform >50% of LTs at nights/weekends. Centers recognized NMP's benefits, including improved work satisfaction and patient outcomes, but faced challenges like high costs and machine complexity. 16% would invest $100,000 to 500'000, 33% would invest $50,000 to 100'000, 38% would invest $10,000 to 50'000, and 14% would invest <$10,000 in NMP. These results were strengthened by a cost analysis for NMP in emergency-to-elective LT transition. Accordingly, while liver perfusions with disposables up to $10,000 resulted in overall positive net balances, this effect was lost when disposables' cost amounted to >$40,000/organ.

CONCLUSIONS

The adoption of NMP is hindered by high costs and operational complexity. Making LT elective through NMP could reduce costs and improve outcomes, but overcoming barriers requires national reimbursements and simplified, automated NMP systems for multiday preservation.

Impact of machine perfusion on transplant infectious diseases: New challenges and opportunities

Preservation techniques that maintain the viability of an organ graft between retrieval from the donor and implantation into the recipient remain a critical aspect of solid organ transplantation. While traditionally preservation is accomplished with static cold storage, advances in ex vivo dynamic machine perfusion, both hypothermic and normothermic, have allowed for prolongation of organ viability and recovery of marginal organs effectively increasing the usable donor pool. However, the use of these novel machine perfusion technologies likely exposes the recipient to additional infectious risk either through clonal expansion of pathogens derived during organ recovery or de novo exogenous acquisition of pathogens while the organ remains on the machine perfusion circuit. There is a paucity of high-quality studies that have attempted to quantify infection risk, although it appears that prolonging the time on the machine perfusion circuit and normothermic parameters increases the risk of infection. Conversely, the use of ex vivo machine perfusion unlocks new opportunities to detect and treat donor-derived infections before implantation into the recipient. This review seeks to reveal how the use of ex vivo machine perfusion strategies may augment the risk of infection in the organ recipient as well as outline ways that this technology could be leveraged to enhance our ability to manage donor-derived infections.

Improving liver transplant outcomes with transplant-omics and network biology

PURPOSE OF REVIEW

Molecular omics data is increasingly ubiquitous throughout medicine. In organ transplantation, recent large-scale research efforts are generating the 'transplant-ome' - the entire set of molecular omics data, including the genome, transcriptome, proteome, and metabolome. Importantly, early studies in anesthesiology have demonstrated how perioperative interventions alter molecular profiles in various patient populations. The next step for anesthesiologists and intensivists will be to tailor perioperative care to the transplant-ome of individual liver transplant patients.

RECENT FINDINGS

In liver transplant patients, elements of the transplant-ome predict complications and point to novel interventions. Importantly, molecular profiles of both the donor organ and recipient contribute to this risk, and interventions like normothermic machine perfusion influence these profiles. As we can now measure various omics molecules simultaneously, we can begin to understand how these molecules interact to form molecular networks and emerging technologies offer noninvasive and continuous ways to measure these networks throughout the perioperative period. Molecules that regulate these networks are likely mediators of complications and actionable clinical targets throughout the perioperative period.

SUMMARY

The transplant-ome can be used to tailor perioperative care to the individual liver transplant patient. Monitoring molecular networks continuously and noninvasively would provide new opportunities to optimize perioperative management.

Prolonged warm ischemia time increases mitogen-activated protein kinase activity and decreases perfusate cytokine levels in ex vivo rat liver machine perfusion

Introduction

Machine perfusion is increasingly being utilized in liver transplantation in lieu of traditional cold static organ preservation. Nevertheless, better understanding of the molecular mechanisms underlying the ischemia-reperfusion injury (IRI) during ex vivo perfusion is necessary to improve the viability of liver grafts after transplantation using machine perfusion technology. Since key cellular signaling pathways involved in hepatic IRI may allow a chance for designing a promising approach to improve the clinical outcomes from this technology, we determined how warm ischemia time (WIT) during procurement affects the activity of mitogen-activated protein kinase (MAPK) and perfusate concentration of cytokines in an ex vivo rat liver machine perfusion model.

Methods

Male Sprague-Dawley rats underwent in situ hepatic ischemia with varying WIT (0, 10, 20, 30 min, n = 5 each), and subsequently 3 h of cold ischemia time and 2 h of machine perfusion prior to determining the degree of MAPK activation-phosphorylation and cytokine concentration in liver tissue and perfusates, respectively.

Results

Our data revealed a strong correlation between incremental WIT and a series of liver injury markers, and that prolonged WIT increases ERK1/2 and p54 JNK phosphorylation during machine perfusion. Notably, specific cytokine levels (MCP-1, MIP-2, GRO/KC, IL-10, and IL-5) were inversely correlated with the phosphorylation levels of ERK1/2, p38 MAPK, and p46/p54 JNK.

Discussion

These results suggest that MAPK activation, specifically ERK1/2 and p54 JNK phosphorylation, have potential as a biomarker for hepatic IRI pathophysiology during machine perfusion. Elucidation of their functional significance may lead to designing a novel strategy to increase the clinical benefit of machine perfusion.

The Distinct Innate Immune Response of Warm Ischemic Injured Livers during Continuous Normothermic Machine Perfusion

Although normothermic machine perfusion (NMP) provides superior preservation of liver grafts compared to static cold storage and allows for viability testing of high-risk grafts, its effect on the liver immune compartment remains unclear. We investigated the innate immune response during 6 h of continuous NMP (cNMP) of livers that were directly procured (DP, n = 5) or procured after 60 min warm ischemia (WI, n = 5), followed by 12 h of whole blood (WB) reperfusion. WI livers showed elevated transaminase levels during cNMP but not after WB reperfusion. Perfusate concentrations of TNF-α were lower in WI livers during cNMP and WB reperfusion, whereas IL-8 concentrations did not differ significantly. TGF-β concentrations were higher in WI livers during NMP but not after WB reperfusion, whereas IL-10 concentrations were similar. Endoplasmic stress and apoptotic signaling were increased in WI livers during cNMP but not after WB reperfusion. Additionally, neutrophil mobilization increased to a significantly lesser extent in WI livers at the end of NMP. In conclusion, WI livers exhibit a distinct innate immune response during cNMP compared to DP livers. The cytokine profile shifted towards an anti-inflammatory phenotype during cNMP and WB reperfusion, and pro-apoptotic signaling was stronger during cNMP. During WB reperfusion, livers exhibited a blunted cytokine release, regardless of ischemic damage, supporting the potential reconditioning effect of cNMP.

Bioenergetic and Cytokine Profiling May Help to Rescue More DCD Livers for Transplantation

The majority of organs used for liver transplantation come from brain-dead donors (DBD). In order to overcome the organ shortage, increasingly donation after circulatory death (DCD) organs are also considered. Since normothermic machine perfusion (NMP) restores metabolic activity and allows for in-depth assessment of organ quality and function prior to transplantation, such organs may benefit from NMP. We herein compare the bioenergetic performance through a comprehensive evaluation of mitochondria by high-resolution respirometry in tissue biopsies and the inflammatory response in DBD and DCD livers during NMP. While livers were indistinguishable by perfusate biomarker assessment and histology, our findings revealed a greater impairment of mitochondrial function in DCD livers after static cold storage compared to DBD livers. During subsequent NMPs, DCD organs recovered and eventually showed a similar performance as DBD livers. Cytokine expression analysis showed no differences in the early phase of NMP, while towards the end of NMP, significantly elevated levels of IL-1β, IL-5 and IL-6 were found in the perfusate of DCD livers. Based on our results, we find it worthwhile to reconsider more DCD organs for transplantation to further extend the donor pool. Therefore, donor organ quality criteria must be developed, which may include an assessment of bioenergetic function and cytokine quantification.

Immune cell dynamics deconvoluted by single-cell RNA sequencing in normothermic machine perfusion of the liver

Normothermic machine perfusion (NMP) has emerged as an innovative organ preservation technique. Developing an understanding for the donor organ immune cell composition and its dynamic changes during NMP is essential. We aimed for a comprehensive characterization of immune cell (sub)populations, cell trafficking and cytokine release during liver NMP. Single-cell transcriptome profiling of human donor livers prior to, during NMP and after transplantation shows an abundance of CXC chemokine receptor 1⁺/2⁺ (CXCR1⁺/CXCR2⁺) neutrophils, which significantly decreased during NMP. This is paralleled by a large efflux of passenger leukocytes with neutrophil predominance in the perfusate. During NMP, neutrophils shift from a pro-inflammatory state towards an aged/chronically activated/exhausted phenotype, while anti-inflammatory/tolerogenic monocytes/macrophages are increased. We herein describe the dynamics of the immune cell repertoire, phenotypic immune cell shifts and a dominance of neutrophils during liver NMP, which potentially contribute to the inflammatory response. Our findings may serve as resource to initiate future immune-interventional studies.

The liver-resident immune cell repertoire - A boon or a bane during machine perfusion?

The liver has been proposed as an important “immune organ” of the body, as it is critically involved in a variety of specific and unique immune tasks. It contains a huge resident immune cell repertoire, which determines the balance between tolerance and inflammation in the hepatic microenvironment. Liver-resident immune cells, populating the sinusoids and the space of Disse, include professional antigen-presenting cells, myeloid cells, as well as innate and adaptive lymphoid cell populations. Machine perfusion (MP) has emerged as an innovative technology to preserve organs ex vivo while testing for organ quality and function prior to transplantation. As for the liver, hypothermic and normothermic MP techniques have successfully been implemented in clinically routine, especially for the use of marginal donor livers. Although there is evidence that ischemia reperfusion injury-associated inflammation is reduced in machine-perfused livers, little is known whether MP impacts the quantity, activation state and function of the hepatic immune-cell repertoire, and how this affects the inflammatory milieu during MP. At this point, it remains even speculative if liver-resident immune cells primarily exert a pro-inflammatory and hence destructive effect on machine-perfused organs, or in part may be essential to induce liver regeneration and counteract liver damage. This review discusses the role of hepatic immune cell subtypes during inflammatory conditions and ischemia reperfusion injury in the context of liver transplantation. We further highlight the possible impact of MP on the modification of the immune cell repertoire and its potential for future applications and immune modulation of the liver.