Hypothermic Oxygenated New Machine Perfusion System in Liver and Kidney Transplantation of Extended Criteria Donors:First Italian Clinical Trial

Normothermic and hypothermic machine perfusion preservation versus static cold storage for deceased donor kidney transplantation

BACKGROUND

Kidney transplantation is the optimal treatment for kidney failure. Donation, transport and transplant of kidney grafts leads to significant ischaemia reperfusion injury. Static cold storage (SCS), whereby the kidney is stored on ice after removal from the donor until the time of implantation, represents the simplest preservation method. However, technology is now available to perfuse or "pump" the kidney during the transport phase ("continuous") or at the recipient centre ("end-ischaemic"). This can be done at a variety of temperatures and using different perfusates. The effectiveness of these treatments manifests as improved kidney function post-transplant.

OBJECTIVES

To compare machine perfusion (MP) technologies (hypothermic machine perfusion (HMP) and (sub) normothermic machine perfusion (NMP)) with each other and with standard SCS.

SEARCH METHODS

We contacted the information specialist and searched the Cochrane Kidney and Transplant Register of Studies until 15 June 2024 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs comparing machine perfusion techniques with each other or versus SCS for deceased donor kidney transplantation were eligible for inclusion. All donor types were included (donor after circulatory death (DCD) and brainstem death (DBD), standard and extended/expanded criteria donors). Both paired and unpaired studies were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

The results of the literature search were screened, and a standard data extraction form was used to collect data. Both of these steps were performed by two independent authors. Dichotomous outcome results were expressed as risk ratios (RR) with 95% confidence intervals (CI). Survival analyses (time-to-event) were performed with the generic inverse variance meta-analysis of hazard ratios (HR). Continuous scales of measurement were expressed as a mean difference (MD). Random effects models were used for data analysis. The primary outcome was the incidence of delayed graft function (DGF). Secondary outcomes included graft survival, incidence of primary non-function (PNF), DGF duration, economic implications, graft function, patient survival and incidence of acute rejection. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Twenty-two studies (4007 participants) were included. The risk of bias was generally low across all studies and bias domains. The majority of the evidence compared non-oxygenated HMP with standard SCS (19 studies). The use of non-oxygenated HMP reduces the rate of DGF compared to SCS (16 studies, 3078 participants: RR 0.78, 95% CI 0.69 to 0.88; P < 0.0001; I2 = 31%; high certainty evidence). Subgroup analysis revealed that continuous (from donor hospital to implanting centre) HMP reduces DGF (high certainty evidence). In contrast, this benefit over SCS was not seen when non-oxygenated HMP was not performed continuously (low certainty evidence). Non-oxygenated HMP reduces DGF in both DCD and DBD settings in studies performed in the 'modern era' and when cold ischaemia times (CIT) were short. The number of perfusions required to prevent one episode of DGF was 7.69 and 12.5 in DCD and DBD grafts, respectively. Continuous non-oxygenated HMP versus SCS also improves one-year graft survival (3 studies, 1056 participants: HR 0.46, 0.29 to 0.75; P = 0.002; I2 = 0%; high certainty evidence). Assessing graft survival at maximal follow-up confirmed a benefit of continuous non-oxygenated HMP over SCS (4 studies, 1124 participants (follow-up 1 to 10 years): HR 0.55, 95% CI 0.40 to 0.77; P = 0.0005; I2 = 0%; high certainty evidence). This effect was not seen in studies where HMP was not continuous. The effect of non-oxygenated HMP on our other outcomes (PNF, incidence of acute rejection, patient survival, hospital stay, long-term graft function, duration of DGF) remains uncertain. Studies performing economic analyses suggest that HMP is either cost-saving (USA and European settings) or cost-effective (Brazil). One study investigated continuous oxygenated HMP versus non-oxygenated HMP (low risk of bias in all domains); the simple addition of oxygen during continuous HMP leads to additional benefits over non-oxygenated HMP in DCD donors (> 50 years), including further improvements in graft survival, improved one-year kidney function, and reduced acute rejection. One large, high-quality study investigated end-ischaemic oxygenated HMP versus SCS and found end-ischaemic oxygenated HMP (median machine perfusion time 4.6 hours) demonstrated no benefit compared to SCS. The impact of longer periods of end-ischaemic HMP is unknown. One study investigated NMP versus SCS (low risk of bias in all domains). One hour of end ischaemic NMP did not improve DGF compared with SCS alone. An indirect comparison revealed that continuous non-oxygenated HMP (the most studied intervention) was associated with improved graft survival compared with end-ischaemic NMP (indirect HR 0.31, 95% CI 0.11 to 0.92; P = 0.03). No studies investigated normothermic regional perfusion (NRP) or included any donors undergoing NRP.

AUTHORS' CONCLUSIONS

Continuous non-oxygenated HMP is superior to SCS in deceased donor kidney transplantation, reducing DGF, improving graft survival and proving cost-effective. This is true for both DBD and DCD kidneys, both short and long CITs, and remains true in the modern era (studies performed after 2008). In DCD donors (> 50 years), the simple addition of oxygen to continuous HMP further improves graft survival, kidney function and acute rejection rate compared to non-oxygenated HMP. Timing of HMP is important, and benefits have not been demonstrated with short periods (median 4.6 hours) of end-ischaemic HMP. End-ischaemic NMP (one hour) does not confer meaningful benefits over SCS alone and is inferior to continuous HMP in an indirect comparison of graft survival. Further studies assessing NMP for viability assessment and therapeutic delivery are warranted and in progress.

Liver Graft Machine Perfusion: From History Perspective to Modern Approaches in Transplant Surgery

The shortage of donor organs remains an unresolved issue in livertransplantation worldwide. Consequently, strategies for expanding the donor pool are currently being developed. Donors meeting extended criteria undergo thorough evaluation, as livers obtained from marginal donors yield poorer outcomes in recipients, including exacerbated reperfusion injury, acute kidney injury, early graft dysfunction, and primary nonfunctioning graft. However, the implementation of machine perfusion has shown excellent potential in preserving donor livers and improving their characteristics to achieve better outcomes for recipients. In this review, we analyzed the global experience of using machine perfusion in livertransplantation through the history ofthe development ofthis method to the latest trends and possibilities for increasing the number of liver transplants.

The role of cold ischemia time and hypothermic perfusion in predicting early hepatocellular carcinoma recurrences after liver transplantation

AIM

The aim of the study was to identify predictors of early tumor recurrence in patients with hepatocellular carcinoma (HCC) after liver transplantation (LT).

METHODS

Retrospective cohort study in 237 consecutive liver recipients with HCC between 2016 and 2021. Multivariate logistic analysis was performed to identify predictors of early HCC recurrences. The impact of hypothermic-oxygenated perfusion (HOPE) on outcome was analyzed after propensity score weighting.

RESULTS

Early recurrences were observed in 15 cases. Microvascular invasion (OR 3.737, 95% CI 1.246-11.206, p = 0.019) and cold ischemia time (OR 1.155, 95% CI 1.001-1.333, p = 0.049) were independently associated with a lower risk of HCC recurrences. After balancing for relevant variables, patients in the HOPE group had lower rates of tumor recurrence (weighted OR 0.126, 95% CI 0.016-0.989, p = 0.049) and higher recurrence free survival (weighted HR 0.132, 95% CI 0.017-0.999, p = 0.050).

CONCLUSION

Reducing cold ischemia time and graft perfusion with HOPE can lead to lower rates of early HCC recurrences and higher recurrence-free survival.

Benefits of Hypothermic Oxygenated Perfusion Versus Static Cold Storage in Liver Transplant: A Comprehensive Systematic Review and Meta-analysis

Background

The magnitude of potential benefits that hypothermic oxygenated perfusion (HOPE) may provide for liver transplantation (LT) patients compared to static cold storage (SCS) remains uncertain. In this systematic review and meta-analysis, we aimed to investigate the therapeutic effect that HOPE can offer LT recipients relative to SCS by synthesizing available evidence.

Methods

A literature search was conducted in Embase, Medline, Web of Science, and the Cochrane database up to 1 June, 2023. The included studies were pooled for meta-analysis to synthesize their findings. Subgroup analysis was performed to investigate potential differences between HOPE and SCS for specific subgroups.

Results

A total of 11 studies comprising 1765 patients were included. Compared with SCS, HOPE was associated with a significant reduction in the incidence of early allograft dysfunction (EAD) (OR: 0.36, 95% CI: 0.26-0.50), as well as a noteworthy decrease in graft loss rate within one year (OR: 0.57, 95% CI: 0.33-0.97) and a lower occurrence of Clavien-Dindo grade IIIa or higher complications (OR: 0.62, 95% CI: 0.43-0.89). Subgroup analysis revealed that HOPE significantly reduced the one-year mortality rate, any biliary complications incidence, and acute rejection of transplanted liver rate in patients who received organs from donation after cardiac death (DCD).

Conclusions

HOPE has demonstrated efficacy in reducing the incidence of EAD after LT and shows some potential in diminishing postoperative complications such as biliary complications and acute rejection. This ultimately leads to improved patient prognosis, particularly among those receiving DCD grafts.

Hypothermic machine perfusion reduces donation after circulatory death liver ischemia-reperfusion injury through the SERPINA3-mediated PI3Kδ/Akt pathway

Hypothermic machine perfusion (HMP) has been demonstrated to be more effective in mitigating ischemia-reperfusion injury (IRI) of donation after circulatory death (DCD) organs than cold storage (CS), yet the underlying mechanism remains obscure. We aimed to propose a novel therapeutic approach to ameliorate IRI in DCD liver transplantation. Twelve clinical liver samples were randomly assigned to HMP or CS treatment and subsequent transcriptomics analysis was performed. By combining in vivo HMP models, we discovered that HMP attenuated inflammation, oxidative stress, and apoptosis in DCD liver through a SEPRINA3-mediated PI3Kδ/AKT signaling cascade. Moreover, in the hypoxia/reoxygenation (H/R) model of BRL-3A, overexpression of SERPINA3 mitigated H/R-induced apoptosis, while SERPINA3 knockdown exacerbated cell injury. Idelalisib (IDE) treatment also reversed the protective effect of SERPINA3 overexpression. Overall, our research provided new insights into therapeutic strategies and identified potential novel molecular targets for therapeutic intervention against DCD liver.

Hypothermic oxygenated perfusion in liver transplantation: a meta-analysis of randomized controlled trials and matched studies

BACKGROUND

Hypothermic oxygenated machine perfusion (HOPE) is a novel organ-preservation technology designed to optimize organ quality. However, the effects of HOPE on morbidity and mortality after liver transplantation remain unclear. This meta-analysis evaluated the potential benefits of HOPE in liver transplantation.

MATERIALS AND METHODS

The Embase, Web of Science, PubMed, Cochrane Library, and Scopus databases were searched for articles published up to 15 June 2023 (updated on 12 August 2023). Mean differences (MDs), risk ratios (RRs), and 95% confidence intervals were calculated.

RESULTS

Eleven studies encompassing five randomized controlled trials and six matched studies were included, with a total of 1000 patients. HOPE did not reduce the incidence of major postoperative complications (RR 0.80), primary non-function (PNF) (RR 0.54), reperfusion syndrome (RR 0.92), hepatic artery thrombosis (RR 0.92), renal replacement therapy (RR 0.98), length of hospital stay (MD, -1.38 days), 1-year recipient death (RR 0.67), or intensive care unit stay (MD, 0.19 days) after liver transplantation. HOPE reduced the incidence of biliary complications (RR 0.74), non-anastomotic biliary strictures (NAS) (RR 0.34), early allograft dysfunction (EAD) (RR 0.54), and acute rejection (RR 0.54). In addition, HOPE improved the retransplantation (RR 0.42) and 1-year graft loss rates (RR 0.38).

CONCLUSIONS

Compared with static cold storage (SCS), HOPE can reduce the incidence of biliary complications, NAS, EAD, and acute rejection and retransplantation rate after liver transplantation and improve the 1-year graft loss rate. These findings suggest that HOPE, when compared to SCS, can contribute to minimizing complications and enhancing graft survival in liver transplantation. Further research is needed to investigate long-term outcomes and confirm the promising advantages of HOPE in liver transplantation settings.

Effects of machine perfusion strategies on different donor types in liver transplantation: a systematic review and meta-analysis

BACKGROUND

The increasing use of extended criteria donors (ECD) sets higher requirements for graft preservation. Machine perfusion (MP) improves orthotopic liver transplantation (OLT) outcomes, but its effects on different donor types remains unclear. The authors' aim was to assess the effects of hypothermic machine perfusion (HMP), normothermic machine perfusion (NMP), or normothermic regional perfusion (NRP) versus static cold storage (SCS) on different donor types.

MATERIALS AND METHODS

A literature search comparing the efficacy of MP versus SCS in PubMed, Cochrane, and EMBASE database was conducted. A meta-analysis was performed to obtain pooled effects of MP on ECD, donation after circulatory death (DCD), and donor after brainstem death.

RESULTS

Thirty nine studies were included (nine randomized controlled trials and 30 cohort studies). Compared with SCS, HMP significantly reduced the risk of non-anastomotic biliary stricture (NAS) [odds ratio (OR) 0.43, 95% confidence interval (CI) 0.26-0.72], major complications (OR 0.55, 95% CI 0.39-0.78), and early allograft dysfunction (EAD) (OR 0.46, 95% CI 0.32-0.65) and improved 1-year graft survival (OR 2.36, 95% CI 1.55-3.62) in ECD-OLT. HMP also reduced primary non-function (PNF) (OR 0.40, 95% CI 0.18-0.92) and acute rejection (OR 0.62, 95% CI 0.40-0.97). NMP only reduced major complications in ECD-OLT (OR 0.56, 95% CI 0.34-0.94), without favorable effects on other complications and survival. NRP lowered the overall risk of NAS (OR 0.27, 95% CI 0.11-0.68), PNF (OR 0.43, 95% CI 0.22-0.85), and EAD (OR 0.58, 95% CI 0.42-0.80) and meanwhile improved 1-year graft survival (OR 2.40, 95% CI 1.65-3.49) in control DCD-OLT.

CONCLUSIONS

HMP might currently be considered for marginal livers as it comprehensively improves ECD-OLT outcomes. NMP assists some outcomes in ECD-OLT, but more evidence regarding NMP-ECD is warranted. NRP significantly improves DCD-OLT outcomes and is recommended where longer non-touch periods exist.

Routine End-ischemic Hypothermic Oxygenated Machine Perfusion in Liver Transplantation From Donors After Brain Death: A Randomized Controlled Trial

OBJECTIVE

To assess whether end-ischemic hypothermic oxygenated machine perfusion (HOPE) is superior to static cold storage (SCS) in preserving livers procured from donors after brain death (DBD).

BACKGROUND

There is increasing evidence of the benefits of HOPE in liver transplantation, but predominantly in the setting of high-risk donors.

METHODS

In this randomized clinical trial, livers procured from DBDs were randomly assigned to either end-ischemic dual HOPE for at least 2 hours or SCS (1:3 allocation ratio). The Model for Early Allograft Function (MEAF) was the primary outcome measure. The secondary outcome measure was 90-day morbidity (ClinicalTrials. gov, NCT04812054).

RESULTS

Of the 104 liver transplantations included in the study, 26 were assigned to HOPE and 78 to SCS. Mean MEAF was 4.94 and 5.49 in the HOPE and SCS groups ( P =0.24), respectively, with the corresponding rates of MEAF >8 of 3.8% (1/26) and 15.4% (12/78; P =0.18). Median Comprehensive Complication Index was 20.9 after transplantations with HOPE and 21.8 after transplantations with SCS ( P =0.19). Transaminase activity, bilirubin concentration, and international normalized ratio were similar in both groups. In the case of donor risk index >1.70, HOPE was associated with significantly lower mean MEAF (4.92 vs 6.31; P =0.037) and lower median Comprehensive Complication Index (4.35 vs 22.6; P =0.050). No significant differences between HOPE and SCS were observed for lower donor risk index values.

CONCLUSION

Routine use of HOPE in DBD liver transplantations does not seem justified as the clinical benefits are limited to high-risk donors.

Beyond the Concepts of Elder and Marginal in DCD Liver Transplantation: A Prospective Observational Matched-Cohort Study in the Italian Clinical Setting

Donation after circulatory determination of death (DCD) is a valuable strategy to increase the availability of grafts for liver transplantation (LT). As the average age of populations rises, the donor pool is likely to be affected by a potential increase in DCD donor age in the near future. We conducted a prospective cohort study to evaluate post-transplantation outcomes in recipients of grafts from elderly DCD donors compared with younger DCD donors, and elderly donors after brainstem determination of death (DBD). From August 2020 to May 2022, consecutive recipients of deceased donor liver-only transplants were enrolled in the study. DCD recipients were propensity score matched 1:3 to DBD recipients. One-hundred fifty-seven patients were included, 26 of whom (16.6%) were transplanted with a DCD liver graft. After propensity score matching and stratification, three groups were obtained: 15 recipients of DCD donors ≥75 years, 11 recipients of DCD donors <75 years, and 28 recipients of DBD donors ≥75 years. Short-term outcomes, as well as 12 months graft survival rates (93.3%, 100%, and 89.3% respectively), were comparable among the groups. LT involving grafts retrieved from very elderly DCD donors was feasible and safe in an experienced high-volume center, with outcomes comparable to LTs from younger DCD donors and age-matched DBD donors.

VA-ECMO Cardiac Support During Liver Transplant: A Case Report

Extracorporeal membrane oxygenation (ECMO) is a rescue therapy for cardiovascular collapse during and after liver transplantation (LT). According to the most recent guidelines, patients with severe cardiomyopathy are excluded from LT because of high-mortality risk during surgery. Intraoperative ECMO support could give these patients the opportunity to undergo LT by reducing the risk of heart failure and reperfusion syndrome. In this case report, we present a case of veno-arterial ECMO (VA-ECMO) support started before LT surgery in a patient with severe pulmonary hypertension, mitral valve steno-insufficiency, and right heart dysfunction. The presence of severe heart disease would have contraindicated LT, but simultaneous liver cirrhosis contraindicated mitral valve surgery, leaving the patient locked in a "Catch-22" state. The best solution was to perform LT with VA-ECMO support before, during, and after the surgery to reduce cardiac load and possible heart failure. LT was performed with good hemodynamic stability and the patient was successfully weaned from ECMO a few hours after surgery. At the 6 month follow-up, normal liver and kidney functions were recorded as well as an overall improvement of heart function; the patient successfully underwent mitral valve replacement and tricuspid annuloplasty 10 months after transplant and is now in good condition.

Acute rejection after liver transplantation with machine perfusion versus static cold storage: A systematic review and meta-analysis

BACKGROUND AND AIMS

Acute cellular rejection (ACR) is a frequent complication after liver transplantation. By reducing ischemia and graft damage, dynamic preservation techniques may diminish ACR. We performed a systematic review to assess the effect of currently tested organ perfusion (OP) approaches versus static cold storage (SCS) on post-transplant ACR-rates.

APPROACH AND RESULTS

A systematic search of Medline, Embase, Cochrane Library, and Web of Science was conducted. Studies reporting ACR-rates between OP and SCS and comprising at least 10 liver transplants performed with either hypothermic oxygenated perfusion (HOPE), normothermic machine perfusion, or normothermic regional perfusion were included. Studies with mixed perfusion approaches were excluded. Eight studies were identified (226 patients in OP and 330 in SCS). Six studies were on HOPE, one on normothermic machine perfusion, and one on normothermic regional perfusion. At meta-analysis, OP was associated with a reduction in ACR compared with SCS [OR: 0.55 (95% CI, 0.33-0.91), p =0.02]. This effect remained significant when considering HOPE alone [OR: 0.54 (95% CI, 0.29-1), p =0.05], in a subgroup analysis of studies including only grafts from donation after cardiac death [OR: 0.43 (0.20-0.91) p =0.03], and in HOPE studies with only donation after cardiac death grafts [OR: 0.37 (0.14-1), p =0.05].

CONCLUSIONS

Dynamic OP techniques are associated with a reduction in ACR after liver transplantation compared with SCS. PROSPERO registration: CRD42022348356.

Successful transplantation of LUCAS device assisted uncontrolled DCD kidneys with prolonged relative warm ischemia time: An underutilized option in North America

Approximately 25% of deceased donors in the United States are procured in a donation after circulatory death (DCD) setting. Successful transplant outcomes from uncontrolled DCD (uDCD) practices have been reported in multiple European programs. They utilize established protocols for uDCD procurement with normo-thermic or hypothermic regional perfusion to reduce ischemic damage. Further, manual or mechanical chest compressions using extrinsic devices, such as the LUCAS device, are implemented to maintain circulation before organ retrieval. Currently, uDCDs are not a major part of DCD organ utilization in the United States. We report our experience with utilization of kidneys from uDCD with the use of the LUCAS device without normothermic or hypothermic regional perfusion. We transplanted four kidneys from three uDCD donors without utilization of in situ regional perfusion and with prolonged relative warm ischemia time (rWIT) (>100 min). All recipients had functional renal allografts and improved renal function after the transplant. To our knowledge, this is the 1st successful series reported in the United States of the utilization of kidneys from uDCDs without the utilization of in situ perfusion to maintain organ preservation with prolonged rWIT.

Hypothermic oxygenated perfusion attenuates DCD liver ischemia-reperfusion injury by activating the JAK2/STAT3/HAX1 pathway to regulate endoplasmic reticulum stress

BACKGROUND

Hepatic ischemia-reperfusion injury (IRI) in donation after cardiac death (DCD) donors is a major determinant of transplantation success. Endoplasmic reticulum (ER) stress plays a key role in hepatic IRI, with potential involvement of the Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway and the antiapoptotic protein hematopoietic-lineage substrate-1-associated protein X-1 (HAX1). In this study, we aimed to investigate the effects of hypothermic oxygenated perfusion (HOPE), an organ preservation modality, on ER stress and apoptosis during hepatic IRI in a DCD rat model.

METHODS

To investigate whether HOPE could improve IRI in DCD livers, levels of different related proteins were examined by western blotting and quantitative real-time polymerase chain reaction. Further expression analyses, immunohistochemical analyses, immunofluorescence staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and transmission electron microscopy were conducted to analyze the effects of HOPE on ER stress and apoptosis. To clarify the role of the JAK2/STAT3 pathway and HAX1 in this process, AG490 inhibitor, JAX1 plasmid transfection, co-immunoprecipitation (CO-IP), and flow cytometry analyses were conducted.

RESULTS

HOPE reduced liver injury and inflammation while alleviating ER stress and apoptosis in the DCD rat model. Mechanistically, HOPE inhibited unfolded protein responses by activating the JAK2/STAT3 pathway, thus reducing ER stress and apoptosis. Moreover, the activated JAK2/STAT3 pathway upregulated HAX1, promoting the interaction between HAX1 and SERCA2b to maintain ER calcium homeostasis. Upregulated HAX1 also modulated ER stress and apoptosis by inhibiting the inositol-requiring enzyme 1 (IRE1) pathway.

CONCLUSIONS

JAK2/STAT3-mediated upregulation of HAX1 during HOPE alleviates hepatic ER stress and apoptosis, indicating the JAK2/STAT3/HAX1 pathway as a potential target for IRI management during DCD liver transplantation.

How to Preserve Steatotic Liver Grafts for Transplantation

Liver allograft steatosis is a significant risk factor for postoperative graft dysfunction and has been associated with inferior patient and graft survival, particularly in the case of moderate or severe macrovesicular steatosis. In recent years, the increasing incidence of obesity and fatty liver disease in the population has led to a higher proportion of steatotic liver grafts being used for transplantation, making the optimization of their preservation an urgent necessity. This review discusses the mechanisms behind the increased susceptibility of fatty livers to ischemia-reperfusion injury and provides an overview of the available strategies to improve their utilization for transplantation, with a focus on preclinical and clinical evidence supporting donor interventions, novel preservation solutions, and machine perfusion techniques.

Outcomes of Kidney Perfusion Techniques in Transplantation from Deceased Donors: A Systematic Review and Meta-Analysis

The high demand for organs in kidney transplantation and the expansion of the donor pool have led to the widespread implementation of machine perfusion technologies. In this study, we aim to provide an up-to-date systematic review of the developments in this expanding field over the past 10 years, with the aim of answering the question: "which perfusion technique is the most promising technique in kidney transplantation?" A systematic review of the literature related to machine perfusion in kidney transplantation was performed. The primary outcome measure was delayed graft function (DGF), and secondary outcomes included rates of rejection, graft survival, and patient survival rates after 1 year. Based on the available data, a meta-analysis was performed. The results were compared with data from static cold storage, which is still the standard of care in many centers worldwide. A total of 56 studies conducted in humans were included, and 43 studies reported outcomes of hypothermic machine perfusion (HMP), with a DGF rate of 26.4%. A meta-analysis of 16 studies showed significantly lower DGF rates in the HMP group compared to those of static cold storage (SCS). Five studies reported outcomes of hypothermic machine perfusion + O₂, with an overall DGF rate of 29.7%. Two studies explored normothermic machine perfusion (NMP). These were pilot studies, designed to assess the feasibility of this perfusion approach in the clinical setting. Six studies reported outcomes of normothermic regional perfusion (NRP). The overall incidence of DGF was 71.5%, as it was primarily used in uncontrolled DCD (Maastricht category I-II). Three studies comparing NRP to in situ cold perfusion showed a significantly lower rate of DGF with NRP. The systematic review and meta-analysis provide evidence that dynamic preservation strategies can improve outcomes following kidney transplantation. More recent approaches such as normothermic machine perfusion and hypothermic machine perfusion + O₂ do show promising results but need further results from the clinical setting. This study shows that the implementation of perfusion strategies could play an important role in safely expanding the donor pool.

Intermittent Surface Oxygenation Results in Similar Mitochondrial Protection and Maintenance of Aerobic Metabolism as Compared to Continuous Oxygenation during Hypothermic Machine Kidney Machine Perfusion

Short bubble and subsequent surface oxygenation is an innovative oxygenation technique and alternative for membrane oxygenation during hypothermic machine perfusion (HMP). The metabolic effect of the interruption of surface oxygenation for 4 h (mimicking organ transport) during HMP was compared to continuous surface and membrane oxygenation in a pig kidney ex situ preservation model. After 30 min of warm ischemia by vascular clamping, a kidney of a ±40 kg pig was procured and subsequently preserved according to one of the following groups: (1) 22-h HMP + intermittent surface oxygenation (n = 12); (2) 22-h HMP + continuous membrane oxygenation (n = 6); and (3) 22-h HMP + continuous surface oxygenation (n = 7). Brief perfusate O₂ uploading before kidney perfusion was either obtained by direct bubble (groups 1, 3) or by membrane (group 2) oxygenation. Bubble oxygenation during minimum 15 min was as efficient as membrane oxygenation in achieving supraphysiological perfusate pO₂ levels before kidney perfusion. Metabolic tissue analysis (i.e., lactate, succinate, ATP, NADH, and FMN) during and at the end of the preservation period demonstrated similar mitochondrial protection between all study groups. Short bubble and subsequent intermittent surface oxygenation of the perfusate of an HMP-kidney might be an effective and cheap preservation strategy to protect mitochondria, eliminating the need/costs of a membrane oxygenator and oxygen source during transport.

Machine perfusion and the prevention of ischemic type biliary lesions following liver transplant: What is the evidence?

The widespread uptake of different machine perfusion (MP) strategies for liver transplant has been driven by an effort to minimize graft injury. Damage to the cholangiocytes during the liver donation, preservation, or early posttransplant period may result in stricturing of the biliary tree and inadequate biliary drainage. This problem continues to trouble clinicians, and may have catastrophic consequences for the graft and patient. Ischemic injury, as a result of compromised hepatic artery flow, is a well-known cause of biliary strictures, sepsis, and graft failure. However, very similar lesions can appear with a patent hepatic artery and these are known as ischemic type biliary lesions (ITBL) that are attributed to microcirculatory dysfunction rather than main hepatic arterial compromise. Both the warm and cold ischemic period duration appear to influence the onset of ITBL. All of the commonly used MP techniques deliver oxygen to the graft cells, and therefore may minimize the cholangiocyte injury and subsequently reduce the incidence of ITBL. As clinical experience and published evidence grows for these modalities, the impact they have on ITBL rates is important to consider. In this review, the evidence for the three commonly used MP strategies (abdominal normothermic regional perfusion [A-NRP], hypothermic oxygenated perfusion [HOPE], and normothermic machine perfusion [NMP] for ITBL prevention has been critically reviewed. Inconsistencies with ITBL definitions used in trials, coupled with variations in techniques of MP, make interpretation challenging. Overall, the evidence suggests that both HOPE and A-NRP prevent ITBL in donated after circulatory death grafts compared to cold storage. The evidence for ITBL prevention in donor after brain death grafts with any MP technique is weak.

Current Evidence and Future Perspectives to Implement Continuous and End-Ischemic Use of Normothermic and Oxygenated Hypothermic Machine Perfusion in Clinical Practice

The use of high-risk renal grafts for transplantation requires the optimization of pretransplant assessment and preservation reconditioning strategies to decrease the organ discard rate and to improve short- and long-term clinical outcomes. Active oxygenation is increasingly recognized to play a central role in dynamic preservation strategies, independent of preservation temperature, to recondition mitochondria and to restore the cellular energy profile. The oxygen-related decrease in mitochondrial succinate accumulation ameliorates the harmful effects of ischemia-reperfusion injury. The differences between normothermic and hypothermic machine perfusion with regard to organ assessment, preservation, and reconditioning, as well as the logistic and economic implications, are factors to take into consideration for implementation at a local level. Therefore, these different techniques should be considered complementary to the perfusion strategy selected depending on functional intention and resource availability. This review provides an overview of the current clinical evidence of normothermic and oxygenated hypothermic machine perfusion, either as a continuous or end-ischemic preservation strategy, and future perspectives.

Impact of Hypothermic Oxygenated Machine Perfusion on Hepatocellular Carcinoma Recurrence after Liver Transplantation

BACKGROUND

Machine perfusion may be able to mitigate ischemia-reperfusion injury (IRI), which increases hepatocellular carcinoma (HCC) recurrence after liver transplantation (LT). This study aimed to investigate the impact of dual-hypothermic oxygenated machine perfusion (D-HOPE) on HCC recurrence in LT.

METHODS

A single-center retrospective study was conducted from 2016 to 2020. Pre- and postoperative data of HCC patients undergoing LT were analyzed. Recipients of a D-HOPE-treated graft were compared to those of livers preserved using static cold storage (SCS). The primary endpoint was recurrence-free survival (RFS).

RESULTS

Of 326 patients, 246 received an SCS-preserved liver and 80 received a D-HOPE-treated graft (donation after brain death (DBD), n = 66; donation after circulatory death (DCD), n = 14). Donors of D-HOPE-treated grafts were older and had higher BMI. All DCD donors were treated by normothermic regional perfusion and D-HOPE. The groups were comparable in terms of HCC features and estimated 5-year RFS according to the Metroticket 2.0 model. D-HOPE did not reduce HCC recurrence (D-HOPE 10%; SCS 8.9%; p = 0.95), which was confirmed using Bayesian model averaging and inverse probability of treatment weighting-adjusted RFS analysis. Postoperative outcomes were comparable between groups, except for lower AST and ALT peak in the D-HOPE group.

CONCLUSIONS

In this single-center study, D-HOPE did not reduce HCC recurrence but allowed utilizing livers from extended criteria donors with comparable outcomes, improving access to LT for patients suffering from HCC.

Untargeted metabolomics of perfusate and their association with hypothermic machine perfusion and allograft failure

Although hypothermic machine perfusion (HMP) is associated with improved kidney graft viability and function, the underlying biological mechanisms are unknown. Untargeted metabolomic profiling may identify potential metabolites and pathways that can help assess allograft viability and contribute to organ preservation. Therefore, in this multicenter study, we measured all detectable metabolites in perfusate collected at the beginning and end of deceased-donor kidney perfusion and evaluated their associations with graft failure. In our cohort of 190 kidney transplants, 33 (17%) had death-censored graft failure over a median follow-up of 5.0 years (IQR 3.0-6.1 years). We identified 553 known metabolites in perfusate and characterized their experimental and biological consistency through duplicate samples and unsupervised clustering. After perfusion-time adjustment and false discovery correction, six metabolites in post-HMP perfusate were significantly associated with death-censored graft failure, including alpha-ketoglutarate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, 1-carboxyethylphenylalanine, and three glycerol-phosphatidylcholines. All six metabolites were associated with an increased risk of graft failure (Hazard Ratio per median absolute deviation range 1.04-1.45). Four of six metabolites also demonstrated significant interaction with donation after cardiac death with notably greater risk in the donation after cardiac death group (Hazard Ratios up to 1.69). Discarded kidneys did not have significantly different levels of any death-censored graft failure-associated metabolites. On interrogation of pathway analysis, production of reactive oxygen species and increased metabolism of fatty acids were upregulated in kidneys that subsequently developed death-censored graft failure. Thus, further understanding the role of these metabolites may inform the HMP process and help improve the objective evaluation of allograft offers, thereby reducing the discard of potentially viable organs.

Predictive value of portal fibrosis and inflammation in transplanted liver grafts treated with hypothermic oxygenated perfusion

BACKGROUND

Hypothermic oxygenated perfusion (HOPE) has become widespread for the preservation of liver grafts, making tangled the relationship among the use of extended criteria donors (ECD), graft histology and transplant outcome.

AIMS

To prospectively validate the impact of the graft histology on transplant outcome in recipient receiving liver grafts from ECD after HOPE.

METHODS

Ninety-three ECD grafts were prospectively enrolled; 49 (52.7 %) were perfused with HOPE according to our protocols. All clinical, histological and follow-up data were collected.

RESULTS

Grafts with portal fibrosis stage ≥ 3 according to Ishak's (evaluated with Reticulin stain) had a significantly higher incidence of early allograft dysfunction (EAD) and 6-month-dysfunction (p = 0.026 and p = 0.049), with more days in Intensive Care Unit (p = 0.050). Lobular fibrosis correlated with post-liver transplant kidney function (p = 0.019). Moderate-to-severe chronic portal inflammation was correlated with graft survival on both multivariate and univariate analyses (p < 0.001), but this risk factor is sensibly reduced by the execution of HOPE.

CONCLUSIONS

The use of liver grafts with portal fibrosis stage ≥ 3 implies a higher risk of post-transplant complications. Portal inflammation represents an important prognostic factor as well, but the execution of HOPE represents a valid tool to improve graft survival.

Solid Phase Microextraction—A Promising Tool for Graft Quality Monitoring in Solid Organ Transplantation

Solid organ transplantation is a life-saving intervention for patients suffering from end-stage organ failure. Although improvements in surgical techniques, standards of care, and immunosuppression have been observed over the last few decades, transplant centers have to face the problem of an insufficient number of organs for transplantation concerning the growing demand. An opportunity to increase the pool of organs intended for transplantation is the more frequent use of organs from extended criteria and the development of analytical methods allowing for a better assessment of the quality of organs to minimize the risk of post-transplant organ injury and rejection. Therefore, solid-phase microextraction (SPME) has been proposed in various studies as an effective tool for determining compounds of significance during graft function assessment or for the chemical profiling of grafts undergoing various preservation protocols. This review summarizes how SPME addresses the analytical challenges associated with different matrices utilized in the peri-transplant period and discusses its potential as a diagnostic tool in future work.

Renal Vessel Extension With Cryopreserved Vascular Grafts: Overcoming Surgical Pitfalls in Living Donor Kidney Transplant

In LDKT, right kidneys and kidneys with anomalous vascularization are often deferred because of concerns on complications and vascular reconstructions. To date, only few reports have examined renal vessel extension with cryopreserved vascular grafts in LDKT. The aim of this study is to investigate the effect of renal vessel extension on short-term outcomes and ischemia times in LDKT. From 2012 to 2020, recipients of LDKT with renal vessels extension were compared with standard LDKT recipients. Subset analysis of rights grafts and grafts with anomalous vascularization, with or without renal vessel extension, was performed. Recipients of LDKT with (n = 54) and without (n = 91) vascular extension experienced similar hospital stays, surgical complications and DGF rates. For grafts with multiple vessels, renal vessel extension granted a faster implantation time (44±5 vs. 72±14 min), which resulted comparable to that of standard anatomy grafts. Right kidney grafts with vascular extension had a faster implantation time compared to right kidney grafts without vascular lengthening (43±5 vs. 58±9 min), and a comparable implantation time to left kidney grafts. Renal vessel extension with cryopreserved vascular grafts allows faster implantation time in right kidney grafts or grafts with anomalous vascularization, maintaining similar surgical and functional outcomes.

A Narrative Review of the Applications of Ex-vivo Human Liver Perfusion

Ex-vivo perfusion describes the extra-corporeal delivery of fluid to an organ or tissue. Although it has been widely studied in the context of organ preservation and transplantation, it has also proven to be an invaluable tool in the development of novel models for translational pre-clinical research. Here, we review the literature reporting ex-vivo human liver perfusion experiments to further understand current perfusion techniques and protocols together with their applications. A computerised search was made of Ovid, MEDLINE, and Embase using the search words "ex-vivo liver or hepatic perfusion". All relevant studies in English describing experiments using ex-vivo perfusion of human livers between 2016 and 2021, inclusive, were included. Of 21 reviewed studies, 19 used ex-vivo human liver perfusion in the context of allogeneic liver transplantation. The quality and size of the studies varied considerably. Human liver perfusion was almost exclusively limited to whole organs and "split" livers, although one study did describe the successful perfusion of tissue sections following a partial hepatectomy. This review of recent literature involving ex-vivo human liver perfusion demonstrates that the technique is not limited to whole liver perfusion. Split-liver perfusion is extremely valuable allowing one lobe to act as a control and increasing the number available for research. This review also highlights the present lack of any reports of segmental liver perfusion. The discarded donor liver is a scarce resource, and the successful use of segmental perfusion has the potential to expand the available experimental models to facilitate pre-clinical experimentation.

A Review of Defatting Strategies for Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease is a huge cause of chronic liver failure around the world. This condition has become more prevalent as rates of metabolic syndrome, type 2 diabetes, and obesity have also escalated. The unfortunate outcome for many people is liver cirrhosis that warrants transplantation or being unable to receive a transplant since many livers are discarded due to high levels of steatosis. Over the past several years, however, a great deal of work has gone into understanding the pathophysiology of this disease as well as possible treatment options. This review summarizes various defatting strategies including in vitro use of pharmacologic agents, machine perfusion of extracted livers, and genomic approaches targeting specific proteins. The goal of the field is to reduce the number of necessary transplants and expand the pool of organs available for use.

Hypothermic oxygenated perfusion in extended criteria donor liver transplantation-A randomized clinical trial

Hypothermic Oxygenated Perfusion (HOPE) of the liver can reduce the incidence of early allograft dysfunction (EAD) and failure in extended criteria donors (ECD) grafts, although data from prospective studies are very limited. In this monocentric, open-label study, from December 2018 to January 2021, 110 patients undergoing transplantation of an ECD liver graft were randomized to receive a liver after HOPE or after static cold storage (SCS) alone. The primary endpoint was the incidence of EAD. The secondary endpoints included graft and patient survival, the EASE risk score, and the rate of graft or other graft-related complications. Patients in the HOPE group had a significantly lower rate of EAD (13% vs. 35%, p = .007) and were more frequently allocated to the intermediate or higher risk group according to the EASE score (2% vs. 11%, p = .05). The survival analysis confirmed that patients in the HOPE group were associated with higher graft survival one year after LT (p = .03, log-rank test). In addition, patients in the SCS group had a higher re-admission and overall complication rate at six months, in particular cardio-vascular adverse events (p = .04 and p = .03, respectively). HOPE of ECD grafts compared to the traditional SCS preservation method is associated with lower dysfunction rates and better graft survival.

Viability testing during liver preservation

PURPOSE OF REVIEW

Viability assessment is one of the main indications for machine perfusion (MP) in liver transplantation. This review summarizes the rationale, evolution and limitations of proposed viability criteria and suggests a framework for future studies.

RECENT FINDINGS

Liver viability is most frequently assessed during normothermic MP by combining parameters relative to perfusate and bile composition, vascular flows and macroscopic aspect. Assessment protocols are largely heterogeneous and have significantly evolved over time, also within the same group, reflecting the ongoing evolution of the subject. Several recent preclinical studies using discarded human livers or animal models have explored other approaches to viability assessment. During hypothermic MP, perfusate flavin mononucleotide has emerged as a promising biomarker of mitochondrial injury and function. Most studies on the subject suffer from limitations, including low numbers, lack of multicenter validation, and subjective interpretation of some viability parameters.

SUMMARY

MP adds a further element of complexity in the process of assessing the quality of a liver graft. Understanding the physiology of the parameters included in the different assessment protocols is necessary for their correct interpretation. Despite the possibility of assessing liver viability during MP, the importance of donor-recipient matching and operational variables should not be disregarded.

How useful is the machine perfusion in liver transplantation? An answer from a national survey

Machine perfusion (MP) has been shown worldwide to offer many advantages in liver transplantation, but it still has some gray areas. The purpose of the study is to evaluate the donor risk factors of grafts, perfused with any MP, that might predict an ineffective MP setting and those would trigger post-transplant early allograft dysfunction (EAD). Data from donors of all MP-perfused grafts at six liver transplant centers have been analyzed, whether implanted or discarded after perfusion. The first endpoint was the negative events after perfusion (NegE), which is the number of grafts discarded plus those that were implanted but lost after the transplant. A risk factor analysis for NegE was performed and marginal grafts for MP were identified. Finally, the risk of EAD was analyzed, considering only implanted grafts. From 2015 to September 2019, 158 grafts were perfused with MP: 151 grafts were implanted and 7 were discarded after the MP phase because they did not reach viability criteria. Of 151, 15 grafts were lost after transplant, so the NegE group consisted of 22 donors. In univariate analysis, the donor risk index >1.7, the presence of hypertension in the medical history, static cold ischemia time, and the moderate or severe macrovesicular steatosis were the significant factors for NegE. Multivariate analysis confirmed that macrosteatosis >30% was an independent risk factor for NegE (odd ratio 5.643, p = 0.023, 95% confidence interval, 1.27–24.98). Of 151 transplanted patients, 34% experienced EAD and had worse 1- and 3-year-survival, compared with those who did not face EAD (NoEAD), 96% and 96% for EAD vs. 89% and 71% for NoEAD, respectively (p = 0.03). None of the donor/graft characteristics was associated with EAD even if the graft was moderately steatotic or fibrotic or from an aged donor. For the first time, this study shows that macrovesicular steatosis >30% might be a warning factor involved in the risk of graft loss or a cause of graft discard after the MP treatment. On the other hand, the MP seems to be useful in reducing the donor and graft weight in the development of EAD.

Trophism and Homeostasis of Liver Sinusoidal Endothelial Graft Cells during Preservation, with and without Hypothermic Oxygenated Perfusion

The aim of the present study was to evaluate the homeostasis and trophism of liver sinusoidal endothelial cells (LSECs) in vivo in different stages of liver graft donation, in order to understand the effects of graft ischemia and perfusion on LSEC activity in liver grafts. Special attention was paid to grafts that underwent hypothermic oxygenated perfusion (HOPE). Forty-seven donors were prospectively enrolled, and two distinct biopsies were performed in each case: one allocation biopsy (at the stage of organ allocation) and one post-perfusion biopsy, performed after graft implant in the recipients. In all biopsies, immunohistochemistry and RT-PCR analyses were carried out for the endothelial markers CD34, ERG, Nestin, and VEGFR-2. We observed an increase in CD34 immunoreactivity in LSEC during the whole preservation/perfusion period (p < 0.001). Nestin and ERG expression was low in allocation biopsies, but increased in post-perfusion biopsies, in both immunohistochemistry and RT-PCR (p < 0.001). An inverse correlation was observed between ERG positivity and donor age. Our results indicate that LSEC trophism is severely depressed in liver grafts, but it is restored after reperfusion in standard conditions. The execution of HOPE seems to improve this recovery, confirming the effectiveness of this machine perfusion technique in restoring endothelial functions.

Liver perfusion strategies: what is best and do ischemia times still matter?

PURPOSE OF REVIEW

This review describes recent developments in the field of liver perfusion techniques.

RECENT FINDINGS

Dynamic preservation techniques are increasingly tested due to the urgent need to improve the overall poor donor utilization. With their exposure to warm ischemia, livers from donors after circulatory death (DCD) transmit additional risk for severe complications after transplantation. Although the superiority of dynamic approaches compared to static-cold-storage is widely accepted, the number of good quality studies remains limited. Most risk factors, particularly donor warm ischemia, and accepted thresholds are inconsistently reported, leading to difficulties to assess the impact of new preservation technologies. Normothermic regional perfusion (NRP) leads to good outcomes after DCD liver transplantation, with however short ischemia times. While randomized controlled trials (RCT) with NRP are lacking, results from the first RCTs with ex-situ perfusion were reported. Hypothermic oxygenated perfusion was shown to protect DCD liver recipients from ischemic cholangiopathy. In contrast, endischemic normothermic perfusion seems to not impact on the development of biliary complications, although this evidence is only available from retrospective studies.

SUMMARY

Dynamic perfusion strategies impact posttransplant outcomes and are increasingly commissioned in various countries along with more evidence from RCTs. Transparent reporting of risk and utilization with uniform definitions is required to compare the role of different preservation strategies in DCD livers with prolonged ischemia times.

Impact of Machine Perfusion on the Immune Response After Liver Transplantation – A Primary Treatment or Just a Delivery Tool

The frequent use of marginal livers forces transplant centres to explore novel technologies to improve organ quality and outcomes after implantation. Organ perfusion techniques are therefore frequently discussed with an ever-increasing number of experimental and clinical studies. Two main approaches, hypothermic and normothermic perfusion, are the leading strategies to be introduced in clinical practice in many western countries today. Despite this success, the number of studies, which provide robust data on the underlying mechanisms of protection conveyed through this technology remains scarce, particularly in context of different stages of ischemia-reperfusion-injury (IRI). Prior to a successful clinical implementation of machine perfusion, the concept of IRI and potential key molecules, which should be addressed to reduce IRI-associated inflammation, requires a better exploration. During ischemia, Krebs cycle metabolites, including succinate play a crucial role with their direct impact on the production of reactive oxygen species (ROS) at mitochondrial complex I upon reperfusion. Such features are even more pronounced under normothermic conditions and lead to even higher levels of downstream inflammation. The direct consequence appears with an activation of the innate immune system. The number of articles, which focus on the impact of machine perfusion with and without the use of specific perfusate additives to modulate the inflammatory cascade after transplantation is very small. This review describes first, the subcellular processes found in mitochondria, which instigate the IRI cascade together with proinflammatory downstream effects and their link to the innate immune system. Next, the impact of currently established machine perfusion strategies is described with a focus on protective mechanisms known for the different perfusion approaches. Finally, the role of such dynamic preservation techniques to deliver specific agents, which appear currently of interest to modulate this posttransplant inflammation, is discussed together with future aspects in this field.

PO2 21% oxygenated hypothermic machine perfusion in kidney transplantation: Any clinical benefit?

BACKGROUND

In deceased donor kidney transplantation (KT), the use of hypothermic machine perfusion (HMP) has been acquiring the status of best practice in the pre-transplant management of kidney grafts. Two types of HMP are currently available, oxygenated HMP and non-oxygenated HMP. However, data on the real clinical impact of oxygenation on KT outcome are still heterogeneous.

METHODS

Retrospective study on a cohort of 103 patients transplanted with a single kidney graft that was managed either with end-ischemic oxygenated (O₂ group, Waves Machine, n = 51, 49.5%) or non-oxygenated HMP (no-O₂ group, Life Port Kidney Transporter Machine, n = 52, 50.5%), during the period January 2016-December 2020. Oxygenation was performed at pO₂ 21%.

RESULTS

The median cold ischemia time was 29 h:40 min [IQR 26 h:55 min-31 h:10 min] and the prevalence of grafts from extended criteria donors (ECD) was 46.7%, with a median kidney donor profile index (KDPI) of 72 [41-94]. The study groups were homogeneous in terms of recipient characteristics, ischemia times and donor characteristics. O₂ and no-O₂ groups showed comparable outcomes in terms of delayed graft function (O₂ vs no-O₂, 21.5% vs 25%, p = 0.58), vascular (0.2% vs 0.2%, p > 0.99) and urologic (13.7% vs 11.5%, p = 0.77) complications, and episodes of graft rejection (11.7% vs 7.7%, p = 0.52). At 1 year follow up, even creatinine serum levels were comparable between the groups (1.27 mg/dL [1.09 and 1.67] vs 1.4 mg/dL [1.9-1.78], p = 0.319), with similar post-transplant trend (p = 0.870). No significant benefit was either observed in ECD or KDPI > 60 subgroups, respectively.

CONCLUSIONS

Oxygenation at pO₂ 21% during HMP seems not to significantly enhance the KT outcomes in terms of postoperative complications or graft function.

Outcome of liver transplantation with grafts from brain-dead donors treated with dual hypothermic oxygenated machine perfusion, with particular reference to elderly donors

Prompted by the utilization of extended criteria donors, dual hypothermic oxygenated machine perfusion (D-HOPE) was introduced in liver transplantation to improve preservation. When donors after neurological determination of death (DBD) are used, D-HOPE effect on graft outcomes is unclear. To assess D-HOPE value in this setting and to identify ideal scenarios for its use, data on primary adult liver transplant recipients from January 2014 to April 2021 were analyzed using inverse probability of treatment weighting, comparing outcomes of D-HOPE-treated grafts (n = 121) with those preserved by static cold storage (n = 723). End-ischemic D-HOPE was systematically applied since November 2017 based on donor and recipient characteristics and transplant logistics. D-HOPE use was associated with a significant reduction of early allograft failure (OR: 0.24; 0.83; p = .024), grade ≥3 complications (OR: 0.57; p = .046), comprehensive complication index (-7.20 points; p = .003), and improved patient and graft survival. These results were confirmed in the subset of elderly donors (>75-year-old). Although D-HOPE did not reduce the incidence of biliary complications, its use was associated with a reduced severity of ischemic cholangiopathy. In conclusion, D-HOPE improves postoperative outcomes and reduces early allograft loss in extended criteria DBD grafts.

Mesenchymal Stem/Stromal Cells in Organ Transplantation

Organ transplantation is essential and crucial for saving and enhancing the lives of individuals suffering from end-stage organ failure. Major challenges in the medical field include the shortage of organ donors, high rates of organ rejection, and long wait times. To address the current limitations and shortcomings, cellular therapy approaches have been developed using mesenchymal stem/stromal cells (MSC). MSC have been isolated from various sources, have the ability to differentiate to important cell lineages, have anti-inflammatory and immunomodulatory properties, allow immunosuppressive drug minimization, and induce immune tolerance towards the transplanted organ. Additionally, rapid advances in the fields of tissue engineering and regenerative medicine have emerged that focus on either generating new organs and organ sources or maximizing the availability of existing organs. This review gives an overview of the various properties of MSC that have enabled its use as a cellular therapy for organ preservation and transplant. We also highlight emerging fields of tissue engineering and regenerative medicine along with their multiple sub-disciplines, underlining recent advances, widespread clinical applications, and potential impact on the future of tissue and organ transplantation.

Extracellular Vesicles Derived from Mesenchymal Stromal Cells Delivered during Hypothermic Oxygenated Machine Perfusion Repair Ischemic/Reperfusion Damage of Kidneys from Extended Criteria Donors

Simple Summary

In this study, we explore for the first time an innovative tool for organ preservation aimed to preventing ischemia reperfusion injury (IRI) in marginal kidneys from expanded criteria donors (ECD) unsuitable for transplantation. Ex vivo hypothermic oxygenated perfusion (HOPE) with and without MSC-derived EV and normothermic reperfusion (NR) with artificial blood composed of bovine hemoglobin were applied on kidneys to evaluate global renal ischemic damage score, renal ultrastructure, mitochondrial distress, apoptosis, cell proliferation index, and the mediators of energy metabolism. Our study demonstrates that kidney conditioning with HOPE+EV arrests the ischemic damage, prevents reoxygenation-dependent injury, and preserves tissue integrity. EV delivery during HOPE can be considered a new organ preservation strategy to increase the donor pool and improving transplant outcome. The originality of our study lies an EV and HOPE combined novel setting use in kidneys from ECD, but also in any condition for graft dysfunction such as ischemia/reperfusion.

Abstract

The poor availability of kidney for transplantation has led to a search for new strategies to increase the donor pool. The main option is the use of organs from extended criteria donors. We evaluated the effects of hypothermic oxygenated perfusion (HOPE) with and without extracellular vesicles (EV) derived from mesenchymal stromal cells on ischemic/reperfusion injury of marginal kidneys unsuitable for transplantation. For normothermic reperfusion (NR), we used artificial blood as a substitute for red blood cells. We evaluated the global renal ischemic dam-age score (GRS), analyzed the renal ultrastructure (RU), cytochrome c oxidase (COX) IV-1 (a mitochondrial distress marker), and caspase-3 renal expression, the tubular cell proliferation index, hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) tissue levels, and effluent lactate and glucose levels. HOPE+EV kidneys had lower GRS and better RU, higher COX IV-1 expression and HGF and VEGF levels and lower caspase-3 expression than HOPE kidneys. During NR, HOPE+EV renal effluent had lower lactate release and higher glucose levels than HOPE renal effluent, suggesting that the gluconeogenesis system in HOPE+EV group was pre-served. In conclusion, EV delivery during HOPE can be considered a new organ preservation strategy for increasing the donor pool and improving transplant outcome.

Liver transplant outcomes after ex vivo machine perfusion: a meta-analysis

BACKGROUND

The pressure on liver-transplant programmes has expanded the usage of extended-criteria allografts. Machine perfusion may be better than conventional static cold storage (SCS) in alleviating ischaemia-reperfusion injury in this setting. Recipient outcomes with hypothermic or normothermic machine perfusion were assessed against SCS here.

METHODS

A search in MEDLINE, EMBASE and Scopus was conducted in February 2021. Primary studies investigating ex vivo machine perfusion were assessed for the following outcomes: morbidity, ICU and hospital stay, graft and patient survival rates and relative costs. Meta-analysis was performed to obtain pooled summary measures.

RESULTS

Thirty-four articles involving 1742 patients were included, of which 20 were used for quantitative synthesis. Odds ratios favoured hypothermic machine perfusion (over SCS) with less early allograft dysfunction, ischaemic cholangiopathy, non-anastomotic strictures and graft loss. Hypothermic machine perfusion was associated with a shorter hospital stay and normothermic machine perfusion with reduced graft injury. Two randomized clinical trials found normothermic machine perfusion reduced major complication risks.

CONCLUSION

Machine perfusion assists some outcomes with potential cost savings.

Advances in Hypothermic and Normothermic Perfusion in Kidney Transplantation

Hypothermic and normothermic machine perfusion in kidney transplantation are purported to exert a beneficial effect on post-transplant outcomes compared to the traditionally used method of static cold storage. Kidney perfusion techniques provide a window for organ reconditioning and quality assessment. However, how best to deliver these preservation methods or improve organ quality has not yet been conclusively defined. This review summarises the promising advances in machine perfusion science in recent years, which have the potential to further improve early graft function and prolong graft survival.

Machine Perfusion in Liver Transplantation: A Systematic Review and Meta-Analysis

Background

Liver transplantation (LTx) is the only treatment option for patients with end-stage liver disease. Novel organ preservation techniques such as hypothermic machine perfusion (HMP) or normothermic machine perfusion (NMP) are under investigation in order to improve organ quality from extended criteria donors and donors after circulatory death. The aim of this study was to systematically review the literature reporting LTx outcomes using NMP or HMP compared to static cold storage (SCS).

Methods

The following data were retrieved: graft primary nonfunction rate, early allograft dysfunction (EAD) rate, biliary complication rate, and 12-month graft and patient survival. A total of 15 studies were included (6 NMP and 9 HMP studies), and meta-analysis was performed only for HMP studies because NMP had considerable differences.

Results

The systematic review showed the potential of NMP to reduce graft injury and lower the liver graft discard rate. The performed quantitative analyses showed that the use of HMP reduces the rate of EAD (odds ratio [OR] 0.51; 95% confidence interval [CI] 0.34–0.76; p = 0.001; I² = 0%) and non-anastomotic biliary strictures (OR 0.34; 95% CI 0.17–0.67; p = 0.002; I² = 0%) compared to SCS.

Conclusion

Our systematic review and meta-analysis revealed that the use of HMP reduces the rate of EAD and non-anastomotic biliary strictures compared to SCS.

Advances in Kidney Preservation Techniques and Their Application in Clinical Practice

The use of cold preservation solutions to rapidly flush and cool the kidney followed by static cold storage in ice has been the standard kidney preservation technique for the last 50 y. Nonetheless, changing donor demographics that include organs from extended criteria donors and donation after circulatory death donors have led to the adoption of more diverse techniques of preservation. Comparison of hypothermic machine perfusion and static cold storage techniques for deceased donor kidneys has long been debated and is still contested by some. The recent modification of hypothermic machine perfusion techniques with the addition of oxygen or perfusion at subnormothermic or near-normothermic temperatures are promising strategies that are emerging in clinical practice. In addition, the use of normothermic regional perfusion to resuscitate abdominal organs of donation after circulatory death donors in situ before cold flushing is also increasingly being utilized. This review provides a synopsis of the different types of preservation techniques including their mechanistic effects and the outcome of their application in clinical practice for different types of donor kidney.

The Relationship between Timing of Pretransplant Kidney Biopsy, Graft Loss, and Survival in Kidney Transplantation: An Italian Cohort Study

INTRODUCTION

Kidney biopsy is performed to assess if an extended criteria graft can be used for transplantation. It may be performed before or after cross-clamping during organ procurement. This study aims to evaluate whether the timing of biopsy may modify cold ischemia times (CIT) and/or graft outcomes.

METHODS

Kidney transplants performed in our center from January 2007 to December 2017 were analyzed. Grafts with preimplantation kidney biopsy were included. Biopsies were performed during surgical back table (ex situ kidney biopsy [ESKB]) until 2012 and since then before the aortic cross-clamping (in situ kidney biopsy [ISKB]). To overcome biases owing to different distributions, a propensity score model was developed. The study population consists in 322 patients, 115 ESKB, and 207 ISKB.

RESULTS

CIT was significantly lower for ISKB (730 min ISKB vs. 840 min ESKB, p value = 0.001). In both crude (OR 0.27; 95% confidence interval, 95% CI 0.12-0.60; p value = 0.002) and adjusted analyses (OR 0.37; 95% CI 0.14-0.94; p value = 0.039), ISKB was associated with a reduced odd of graft loss when compared to ESKB.

DISCUSSION/CONCLUSION

Performing preimplantation kidney biopsy during the recovery, prior to the aortic cross-clamping, may be a strategy to reduce CIT and improve transplant outcomes.

The use of normothermic machine perfusion to rescue liver allografts from expanded criteria donors

The use of expanded criteria donors is one of the strategies used to overcome the gap between the demand for organs and the number of donors. Physicians debate the extent to which marginal grafts can be used. In recent years, normothermic machine perfusion (NMP) has been used to test liver viability before transplantation. Grafts underwent NMP whenever histological steatosis was > 40% or there were at least three Eurotransplant criteria for expanded criteria donor (ECD). We used NMP to test 19 grafts, 3 from donation after type 3 controlled cardiac death (DCD), and 16 from donation after brain death (DBD). Only two grafts from DBD were not transplanted, because perfusion proved they were not suitable (total of 17 transplanted grafts of 19 tested grafts). Kaplan-Meier survival estimates at 30, 90, 180, and 1 year after transplant were all 94% (95% CI 84-100%); estimated 3-years survival was 82% (95% CI 62-100%). Overall survival rates did not differ from those of patients transplanted with non-perfused grafts from an ECD. In our experience, the use of very marginal grafts preventively tested by NMP does not negatively influence the patient's outcome, and increases the number of transplants in low donation areas.

Clinical assessment of liver metabolism during hypothermic oxygenated machine perfusion using microdialysis

Background

While growing evidence supports the use of hypothermic oxygenated machine perfusion (HOPE) in liver transplantation, its effects on liver metabolism are still incompletely understood.

Methods

To assess liver metabolism during HOPE using microdialysis (MD), we conducted an open‐label, observational pilot study on 10 consecutive grafts treated with dual‐HOPE (D‐HOPE). Microdialysate and perfusate levels of glucose, lactate, pyruvate, glutamate, and flavin mononucleotide (FMN) were measured during back table preparation and D‐HOPE and correlated to graft function and patient outcome.

Results

Median (IQR) MD and D‐HOPE time was 228 (210, 245) and 116 (103, 143) min. Three grafts developed early allograft dysfunction (EAD), with one requiring retransplantation. During D‐HOPE, MD glucose and lactate levels increased (ANOVA = 9.88 [p = 0.01] and 3.71 [p = 0.08]). Their 2nd‐hour levels were higher in EAD group and positively correlated with L‐GrAFT score. 2nd‐hour MD glucose and lactate were also positively correlated with cold ischemia time, macrovesicular steatosis, weight gain during D‐HOPE, and perfusate FMN. These correlations were not apparent when perfusate levels were considered. In contrast, MD FMN levels invariably dropped steeply after D‐HOPE start, whereas perfusate FMN was higher in dysfunctioning grafts.

Conclusion

MD glucose and lactate during D‐HOPE are markers of hepatocellular injury and could represent additional elements of the viability assessment.

Heterogeneous indications and the need for viability assessment: An international survey on the use of machine perfusion in liver transplantation

Although machine perfusion (MP) is being increasingly adopted in liver transplantation, indications, timing, and modality are debated. To investigate current indications for MP a web‐based Google Forms survey was launched in January 2021 and addressed to 127 experts in the field, identified among first and corresponding Authors of MP literature in the last 10 years. The survey presented 10 real‐life cases of donor–recipient matching, asking whether the liver would be accepted (Q1), whether MP would be used in that particular setting (Q2) and, if so, by which MP modality (Q3) and at what timing during preservation (Q4). Respondents could also comment on each case. The agreement was evaluated using Krippendorff's alpha coefficient. Answers from 39 (30.1%) participants disclosed significant heterogeneity in graft acceptance, MP indications, technique, and timing. Agreement between respondents was generally poor (Q1, α = 0.11; Q2, α = 0.14; Q3, α = 0.12, Q4, α = 0.11). Overall, respondents preferred hypothermic MP and an end‐ischemic approach in 56.3% and 81.1% of cases, respectively. A total of 18 (46.2%) participants considered only one MP approach, whereas 17 (43.6%) and 3 (7.7%) considered using alternatively 2 or 3 different techniques. Of 38 comments, 17 (44.7%) were about the use of MP for graft viability assessment before implantation. This survey shows considerable variability in MP indications, emphasizing the need to identify scenarios of optimal utilization for each technique. Viability assessment emerges as a fundamental need of transplant professionals when considering the use of MP.

Perfluorocarbon-Based Oxygen Carriers and Subnormothermic Lung Machine Perfusion Decrease Production of Pro-Inflammatory Mediators

The quality of marginal donor lungs is clinically assessed with normothermic machine perfusion. Although subnormothermic temperature and perfluorocarbon-based oxygen carriers (PFCOC) have proven favourable for other organ transplants, their beneficial use for ex vivo lung perfusion (EVLP) still requires further investigation. In a rat model, we evaluated on a 4 h EVLP time the effects of PFCOC with either 28 °C or 37 °C perfusion temperatures. During EVLP at 28 °C with PFCOC, we recorded significantly lower lung pulmonary vascular resistance (PVR), higher dynamic compliance (Cdyn), significantly lower potassium and lactate levels, higher lung tissue ATP content, and significantly lower myeloperoxidase tissue activity when compared to the 37 °C EVLP with PFCOC. In the subnormothermic EVLP with or without PFCOC, the pro-inflammatory mediator TNFα, the cytokines IL-6 and IL-7, the chemokines MIP-3α, MIP-1α, MCP-1, GRO/KC as well as GM-CSF, G-CSF and the anti-inflammatory cytokines IL-4 and IL-10 were significantly lower. The 28 °C EVLP improved both Cdyn and PVR and decreased pro-inflammatory cytokines and pCO2 levels compared to the 37 °C EVLP. In addition, the 28 °C EVLP with PFCOC produced a significantly lower level of myeloperoxidase activity in lung tissue. Subnormothermic EVLP with PFCOC significantly improves lung donor physiology and ameliorates lung tissue biochemical and inflammatory parameters.

Simply Adding Oxygen during Hypothermic Machine Perfusion to Combat the Negative Effects of Ischemia-Reperfusion Injury: Fundamentals and Current Evidence for Kidneys

The use of high-risk renal grafts for transplantation requires optimization of pretransplant preservation and assessment strategies to improve clinical outcomes as well as to decrease organ discard rate. With oxygenation proposed as a resuscitative measure during hypothermic machine preservation, this review provides a critical overview of the fundamentals of active oxygenation during hypothermic machine perfusion, as well as the current preclinical and clinical evidence and suggests different strategies for clinical implementation.

NORMOTHERMIC WITH OR WITHOUT HYPOTHERMIC OXYGENATED PERFUSION FOR DCD BEFORE LIVER TRANSPLANTATION: EUROPEAN MULTI-CENTRIC EXPERIENCE

Grafts from donors with cardiac death (DCD) are subject to warm ischemia time (WIT) due to the no-touch-period (20 min. in Italy and 5 min. in France). These livers (LT) have higher rates of early allograft dysfunction (EAD), primary non-function (PNF), and ischemic cholangiopathy (IC) compared to LT from brain dead donors (DBD). Normothermic regional perfusion (NRP) is a beneficial strategy to mitigate organ damage; a further approach is the application of ex-vivo hypothermic oxygenated perfusion (HOPE) after cold storage (CS). We retrospectively analyzed LTs performed from 2016 to 2019 at three transplant centers using NRP-DCD grafts: Bologna and Milan treated with HOPE (group A), Rennes preserved using CS (group B). No-flow period, total and functional WIT were significantly higher in group A than in group B (30.5±7.7 vs. 20.5±4.1; 56.5±20.4 vs. 39.1±21.6; 41.9±12.5 vs. 25.5±3.7; respectively, p<0.05), without differences in the postoperative course. In particular, the two groups had similar rates of EAD (21.1%vs.25.0%), PNF (5.3%vs.6.3%), IC (0%vs.12.5%, p = 0.112) and non-IC biliary complications (0%vs.6.3%, p = 0.457), re-LT (10.5%vs.12.5%). This occurred despite a high rate of UK DCD risk score >10 (63.2% A vs.17.6% B, p = 0.000) which theoretically would make a large number of these transplants "futile". In conclusion, Italian and French groups had similar post-LT outcomes, probably related to the use of HOPE after CS in the case of long WIT. This article is protected by copyright. All rights reserved.