Strategies to Improve the Utilization and Function of DCD Livers

A Novel Machine Perfusion System for Enhancing Hepatic Microcirculation Perfusion

BACKGROUND

Machine perfusion is a promising strategy for safeguarding liver transplants donated after cardiac death (DCD). In this study, we developed and validated a novel machine perfusion approach for mitigating risk factors and salvaging severe DCD livers.

METHODS

A novel hypothermic oxygenated perfusion (HOPE) system was developed, incorporating two pumps and an elastic water sac to emulate the functionality of the cardiac cycle. Compared to conventional systems (HOPE S1 and S2), the novel HOPE system (HOPE S3) was evaluated in rats, utilizing healthy livers perfused with methylene blue diluted using Histidine-tryptophan-ketoglutarate (HTK) solution or DCD livers subjected to 60 min of warm ischemia without heparin administration. Liver perfusion outcomes were assessed through macroscopic and microscopic evaluations, molecular analyses, and orthotopic liver transplantation (OLT).

RESULTS

DCD livers subjected to HOPE systems' perfusion exhibited decreased injury and enhanced survival rates compared to static cold storage following 60 min of warm ischemia (DCD + SCS). The 4-week post-transplantation survival rates were 0%, 20%, and 33% in the DCD + SCS, HOPE S1, and HOPE S2 groups, respectively. HOPE S3 conferred protection against hepatocyte and non-parenchymal cell injury, resulting in a 67% animal survival rate following 60 min of warm donor ischemia (HOPE S3). Assessments of hepatic sinusoidal microcirculation, morphological changes, and molecular alterations in preserved livers further confirmed these findings.

CONCLUSIONS

The newly devised machine perfusion system can enhance and uniform liver perfusion and may become a promising tool for revitalizing DCD liver grafts afflicted with severe warm ischemic injuries.

Does Time to Asystole in Donors After Circulatory Death Impact Recipient Outcome in Liver Transplantation?

BACKGROUND

The agonal phase can vary following treatment withdrawal in donor after circulatory death (DCD). There is little evidence to support when procurement teams should stand down in relation to donor time to death (TTD). We assessed what impact TTD had on outcomes following DCD liver transplantation.

METHODS

Data were extracted from the UK Transplant Registry on DCD liver transplant recipients from 2006 to 2021. TTD was the time from withdrawal of life-sustaining treatment to asystole, and functional warm ischemia time was the time from donor systolic blood pressure and/or oxygen saturation falling below 50 mm Hg and 70%, respectively, to aortic perfusion. The primary endpoint was 1-y graft survival. Potential predictors were fitted into Cox proportional hazards models. Adjusted restricted cubic spline models were generated to further delineate the relationship between TTD and outcome.

RESULTS

One thousand five hundred fifty-eight recipients of a DCD liver graft were included. Median TTD in the entire cohort was 13 min (interquartile range, 9-17 min). Restricted cubic splines revealed that the risk of graft loss was significantly greater when TTD ≤14 min. After 14 min, there was no impact on graft loss. Prolonged hepatectomy time was significantly associated with graft loss (hazard ratio, 1.87; 95% confidence interval, 1.23-2.83; P  = 0.003); however, functional warm ischemia time had no impact (hazard ratio, 1.00; 95% confidence interval, 0.44-2.27; P  > 0.9).

CONCLUSIONS

A very short TTD was associated with increased risk of graft loss, possibly because of such donors being more unstable and/or experiencing brain stem death as well as circulatory death. Expanding the stand down times may increase the utilization of donor livers without significantly impairing graft outcome.

Cell-specific Extracellular Vesicles and Their miRNA Cargo Released Into the Organ Preservation Solution During Cold Ischemia Storage as Biomarkers for Liver Transplant Outcomes

BACKGROUND

Liver transplantation (LT) is crucial for end-stage liver disease patients, but organ shortages persist. Donation after circulatory death (DCD) aims to broaden the donor pool but presents challenges. Complications like acute rejection, hepatic artery thrombosis, and biliary issues still impact posttransplant prognosis. Biomarkers, including extracellular vesicles (EVs) and microRNAs (miRNAs), show promise in understanding and monitoring posttransplant events. This study explores the role of EVs and their miRNA cargo in LT, including their potential as diagnostic tools.

METHODS

EVs from intrahepatic end-ischemic organ preservation solution (eiOPS) in 79 donated livers were detected using different techniques (nanosight tracking analysis, transmission electron microscopy, and flow cytometry). EV-derived miRNAs were identified by quantitative real time-polymerase chain reaction. Bioinformatics analysis was performed using the R platform.

RESULTS

Different-sized and origin-specific EVs were found in eiOPS, with significantly higher concentrations in DCD compared with donation after brain death organs. Additionally, several EV-associated miRNAs, including let-7d-5p , miR-28-5p , miR-200a-3p , miR-200b-3p , miR-200c-3p , and miR-429 , were overexpressed in DCD-derived eiOPS. These miRNAs also exhibited differential expression patterns in liver tissue biopsies. Pathway analysis revealed enrichment in signaling pathways involved in extracellular matrix organization and various cellular processes. Moreover, specific EVs and miRNAs correlated with clinical outcomes, including survival and early allograft dysfunction. A predictive model combining biomarkers and clinical variables showed promise in acute rejection detection after LT.

CONCLUSIONS

These findings provide new insights into the use of EVs and miRNAs as biomarkers and their possible influence on posttransplantation outcomes, potentially contributing to improved diagnostic approaches and personalized treatment strategies in LT.

Return of the cold: How hypothermic oxygenated machine perfusion is changing liver transplantation

Hypothermic Oxygenated machine PErfusion (HOPE) has recently emerged as a preservation technique which can reduce ischemic injury and improve clinical outcomes following liver transplantation. First developed with the advent solid organ transplantation techniques, hypothermic machine perfusion largely fell out of favour following the development of preservation solutions which can satisfactorily preserve grafts using the cheap and simple method, static cold storage (SCS). However, with an increasing need to develop techniques to reduce graft injury and better utilise marginal and donation after circulatory death (DCD) grafts, HOPE has emerged as a relatively simple and safe technique to optimise clinical outcomes following liver transplantation. Perfusing the graft with cold, acellular, oxygenated perfusate either via the portal vein (PV) alone, or via both the PV and hepatic artery (HA), HOPE is generally commenced for a period of 1-2 h immediately prior to implantation. The technique has been validated by multiple randomised control trials, and pre-clinical evidence suggests HOPE primarily reduces graft injury by decreasing the accumulation of harmful mitochondrial intermediates, and subsequently, the severity of post-reperfusion injury. HOPE can also facilitate real time graft assessment, most notably via the measurement of flavin mononucleotide (FMN) in the perfusate, allowing transplant teams to make better informed clinical decisions prior to transplantation. HOPE may also provide a platform to administer novel therapeutic agents to ex situ organs without risk of systemic side effects. As such, HOPE is uniquely positioned to revolutionise how liver transplantation is approached and facilitate optimised clinical outcomes for liver transplant recipients.

Current role and perspectives of living donor liver transplantation for hepatocellular carcinoma: systematic review of the past 20 years

Hepatocellular carcinoma (HCC) poses a significant global health challenge, and liver transplantation (LT) remains the best curative option. Living donor liver transplantation (LDLT) emerged as a potential solution to organ scarcity, reducing waitlist times. This comprehensive review explores LDLT practices, focusing on patient selection criteria and oncologic outcomes. A systematic review following PRISMA guidelines included 50 studies (2004-2023) with 8062 patients. Data encompassed baseline characteristics, HCC features, and oncologic outcomes. Further analysis categorized results by geography and publication year. Heterogeneity in patient demographics, tumor burden, and transplant characteristics was observed. Recent LDLT series demonstrated a shift towards refined selection criteria, increased neoadjuvant treatment, and improved oncologic outcomes. Geographic disparities revealed unique challenges in Eastern and Western practices. LDLT proves effective for HCC, addressing donor shortages. Evolving practices highlight the importance of refining inclusion criteria and optimizing tumor management. While geographic differences exist, LDLT, when judiciously applied, offers promising outcomes.