Current status of adult liver transplantation: utilization of living donor versus deceased donor graft

GalNac-siRNA conjugate delivery technology promotes the treatment of typical chronic liver diseases

INTRODUCTION

Nucleic acid-based therapeutics have become a key pillar of the 'third wave' of modern medicine, following the eras of small molecule inhibitors and antibody drugs. Their rapid progress is heavily dependent on delivery technologies, with the development of N-acetylgalactosamine (GalNAc) conjugates marking a breakthrough in targeting liver diseases. This technology has gained significant attention for its role in addressing chronic conditions like chronic hepatitis B (CHB) and nonalcoholic steatohepatitis (NASH), which are challenging to treat with conventional methods.

AREAS COVERED

This review explores the origins, mechanisms, and advantages of GalNAc-siRNA delivery systems, highlighting their ability to target hepatocytes via the asialoglycoprotein receptor (ASGPR). The literature reviewed covers preclinical and clinical advancements, particularly in CHB and NASH. Key developments in stabilization chemistry and conjugation technologies are examined, emphasizing their impact on enhancing therapeutic efficacy and patient compliance.

EXPERT OPINION

GalNAc-siRNA technology represents a transformative advancement in RNA interference (RNAi) therapies, addressing unmet needs in liver-targeted diseases. While significant progress has been made, challenges remain, including restricted targeting scope and scalability concerns. Continued innovation is expected to expand applications, improve delivery efficiency, and overcome limitations, establishing GalNAc-siRNA as a cornerstone for future nucleic acid-based treatments.

Graft inflow modulation in recipients with portal hypertension

The extended application of living donor liver transplantation (LDLT) has revealed the problem of graft size mismatching, potentially leading to the "small-for-size syndrome" (SFSS). SFSS is a rare dysfunction that may affect a partial liver graft, characterized by coagulopathy, cholestasis, ascites, and encephalopathy. A key role in the physiopathology of SFSS is played by portal hypertension (PHT) to which a small allograft is submitted after reperfusion, resulting in sinusoidal congestion and hemorrhage. Portal overflow injures the liver directly through nutrient excess, endothelial activation, and sinusoidal shear stress, and indirectly through arterial vasoconstriction. Thus, SFSS prevention relies not only on increasing graft volume (implementing the use of larger grafts or auxiliary/dual liver transplantation), but also on the control of the increased portal vein pressure (PVP) and portal vein flow (PVF). To this aim, surgical graft inflow modulation techniques (GIM) such as splenic artery ligation (SAL), splenectomy and hemiportocaval shunts, can be considered when an imbalance between the PVP and the hepatic arterial flow (HAF) is acknowledged. However, such strategies have their pros and cons, and a deep knowledge of the indications and complications is needed. Furthermore, pharmacological modulation has also been proposed. This review is aimed to update available literature on the current knowledge and strategies for modulating portal vein flow in LDLT.

American perspectives for LDLT in 2024

Living donor liver transplantation (LDLT) was first performed in the US in 1989, primarily benefiting pediatric patients. Its adoption for adults faced setbacks after a donor death in 2001, causing widespread risk aversion. Despite ethical justification and demonstrated safety, LDLT remains underutilized, with fewer than 10% of liver transplants being LDLT. Recent trends indicate improved access to deceased donor liver transplantation (DDLT) due to increased organ donation and technological advances like Normothermic Regional Perfusion (NRP). However, LDLT remains critical, especially for pediatric patients and specific adult populations who benefit significantly from it. Barriers to LDLT include public and clinician apprehensions about donor risks, despite studies showing low-complication rates. Non-directed donations and broader social media engagement have increased donor pools, though the volume of LDLT in the US remains lower than in Asia due to limited training and experience. The A2ALL consortium has been pivotal in studying LDLT safety and outcomes. Currently, around 40 US centers perform LDLT, with high-volume centers leading by example. Training paradigms for LDLT are evolving, with initiatives like the ASTS LDLT master class aiming to enhance surgical expertise. While LDLT is embedded in US liver-transplant practices, its expansion is hampered by risk aversion and the availability of DDLT. Nonetheless, LDLT is essential for addressing the supply-demand mismatch in liver transplantation.

Older living liver donors can enlarge the donor pool: a systematic review and meta-analysis

BACKGROUND

Living donor liver transplantation (LDLT) is the best option for end-stage liver disease patients. Older potential donors are increasingly requesting donation. This study aims to systematically assess the differences in donor perioperative and postoperative complications, mortality, and quality of life (QoL) between younger and older living liver donors.

MATERIALS AND METHODS

Embase, Medline, and Cochrane were searched for studies published between 2002 and 2 June 2023. Donor complications, major complications, biliary complications, mortality, and QoL were systematically reviewed, including meta-analyses. Donors aged >50 years were considered older. The methodological quality of the studies was assessed using the Newcastle-Ottawa quality assessment Scale.

RESULTS

The search yielded 8320 studies, of which 17 were included. The risk ratio (RR) for complications in younger donors was 1.08 [0.90-1.31] ( P =0.41). RRs for major complications in younger donors were 0.98 [0.64, 1.48] and 0.89 [0.50, 1.57] using Clavien-Dindo ≥III and ≥IIIb as major complication. RR for biliary complications in younger donors was 1.59 [1.05-2.42] ( P =0.03). Mortality rate in younger donors was 47/13 238 (0.4%) and in older donors 13/989 (1.3%). Physical component summary (PCS) in younger donors was 51.87 and in older donors 51.29. Mental component summary (MCS) in younger donors was 52.93 and in older donors 55.40.

CONCLUSION

Older donors do not have a higher complication or mortality rate than younger donors after LDLT. They may have a lower rate of biliary complications. Additionally, older donors have a similar QoL after LDLT. With careful selection, older donors can be included in screening programs for living liver donation to expand the donor pool.

Chronological and Geographical Variations in the Incidence and Acceptance of COVID-19-Positive Donors and Outcomes Among Abdominal Transplant Patients

INTRODUCTION

Given the importance of understanding COVID-19-positive donor incidence and acceptance, we characterize chronological and geographic variations in COVID-19 incidence relative to COVID-19-positive donor acceptance.

METHODS

Data on deceased donors and recipients of liver and kidney transplants were obtained from the UNOS database between 2020 and 2023. Hierarchical cluster analysis was used to assess trends in COVID-19-positive donor incidence. Posttransplant graft and patient survival were assessed using Kaplan-Meier curves.

RESULTS

From among 38 429 deceased donors, 1517 were COVID-19 positive. Fewer kidneys (72.4% vs. 76.5%, p < 0.001) and livers (56.4% vs. 62.0%, p < 0.001) were used from COVID-19-positive donors versus COVID-19-negative donors. Areas characterized by steadily increased COVID-19 donor incidence exhibit the highest transplantation acceptance rates (92.33%), followed by intermediate (84.62%) and rapidly increased (80.00%) COVID-19 incidence areas (p = 0.016). Posttransplant graft and patient survival was comparable among recipients, irrespective of donor COVID-19 status.

CONCLUSIONS

Regions experiencing heightened rates of COVID-19-positive donors are associated with decreased acceptance of liver and kidney transplantation. Similar graft and patient survival is noted among recipients, irrespective of donor COVID-19 status. These findings emphasize the need for adaptive practices and unified medical consensus in navigating a dynamic pandemic.

Liver Transplantation for Hepatocellular Carcinoma: A Narrative Review and A Glimpse into The Future

Liver transplantation (LT) is a highly effective treatment for carefully selected patients with hepatocellular carcinoma (HCC). In this review, we explored the development of LT selection criteria and organ allocation policies, comparing original data to underscore their historical progression into the intricate task of quantitatively estimating pre- and post-LT survivals. We emphasized the role of biomarkers such as serum alpha-fetoprotein, Des-gamma-carboxy-prothrombin, circulating tumor cells, and circulating tumor DNA in predicting patient outcomes. Additionally, we examined the transplant-associated survival benefits and the difficulties in accurately calculating these benefits. We also reviewed recent advancements in targeted therapy and checkpoint inhibitors for advanced, inoperable HCC and projected their integration into LT for HCC. We further discussed the growing use of living donor liver transplants in the United States and compared its outcomes with those of deceased donor liver transplants. Furthermore, we examined the progress in machine perfusion techniques, which have shown potential in improving patient outcomes and enlarging the donor pool. These advancements present opportunities to enhance LT patient survivals, refine selection criteria, establish new priority metrics, develop innovative bridging and downstaging strategies, and formulate redesigned LT strategies for HCC treatments.

Comparing High- and Low-Model for End-Stage Liver Disease Living-Donor Liver Transplantation to Determine Clinical Efficacy: A Systematic Review and Meta-Analysis (CHALICE Study)

INTRODUCTION

Various studies have demonstrated that low-Model for End-Stage Liver Disease (MELD) living-donor liver transplant (LDLT) recipients have better outcomes with improved patient survival than deceased-donor liver transplantation (DDLT) recipients. LDLT recipients gain the most from being transplanted at MELD <25-30; however, some existing data have outlined that LDLT may provide equivalent outcomes in high-MELD and low-MELD patients, although the term "high" MELD is arbitrarily defined in the literature and various cut-off scores are outlined between 20 and 30, although most commonly, the dividing threshold is 25. The aim of this meta-analysis was to compare LDLT in high-MELD with that in low-MELD recipients to determine patient survival and graft survival, as well as perioperative and postoperative complications.

METHODS

Following PROSPERO registration CRD-42021261501, a systematic database search was conducted for the published literature between 1990 and 2021 and yielded a total of 10 studies with 2183 LT recipients; 490 were HM-LDLT recipients and 1693 were LM-LDLT recipients.

RESULTS

Both groups had comparable mortality at 1, 3 and 5 years post-transplant (5-year HR 1.19; 95% CI 0.79-1.79; p-value 0.40) and graft survival (HR 1.08; 95% CI 0.72, 1.63; p-value 0.71). No differences were observed in the rates of major morbidity, hepatic artery thrombosis, biliary complications, intra-abdominal bleeding, wound infection and rejection; however, the HM-LDLT group had higher risk for pulmonary infection, abdominal fluid collection and prolonged ICU stay.

CONCLUSIONS

The high-MELD LDLT group had similar patient and graft survival and morbidities to the low-MELD LDLT group, despite being at higher risk for pulmonary infection, abdominal fluid collection and prolonged ICU stay. The data, primarily sourced from high-volume Asian centers, underscore the feasibility of living donations for liver allografts in high-MELD patients. Given the rising demand for liver allografts, it is sensible to incorporate these insights into U.S. transplant practices.

Effect of dexmedetomidine on liver transplantation: a meta-analysis

Background: Dexmedetomidine (DEX), an adjuvant anesthetic, may improve the clinical outcomes of liver transplantation (LT). Methods: We summarized the relevant clinical trials of DEX in patients undergoing LT. As of 30 January 2023, we searched The Cochrane Library, MEDLINE, EMBASE, Clinical Trial.gov and the WHO ICTRP. The main outcomes were postoperative liver and renal function. The random effect model or fixed effect model was used to summarize the outcomes across centers based on the differences in heterogeneity. Results: The meta-analysis included nine studies in total. Compared with the control group, the DEX group had a reduced warm ischemia time (MD-4.39; 95% CI-6.74--2.05), improved postoperative liver (peak aspartate transferase: MD-75.77, 95% CI-112.81--38.73; peak alanine transferase: MD-133.51, 95% CI-235.57--31.45) and renal function (peak creatinine: MD-8.35, 95% CI-14.89--1.80), and a reduced risk of moderate-to-extreme liver ischemia-reperfusion injury (OR 0.28, 95% CI 0.14-0.60). Finally, the hospital stay of these patients was decreased (MD-2.28, 95% CI-4.00--0.56). Subgroup analysis of prospective studies showed that DEX may have better efficacy in living donors and adult recipients. Conclusion: DEX can improve short-term clinical outcomes and shorten the hospital stay of patients. However, the long-term efficacy of DEX and its interfering factors deserves further study. Systematic Review: identifier CRD42022351664.

Impact of Older Donor Age on Recipient and Graft Survival After LDLT: The US Experience

BACKGROUND

The impact of selecting older donors for living donor liver transplantation (LDLT) in the United States is incompletely studied, particularly in light of the recent expansion of LDLT nationally.

METHODS

Adult LDLTs from January 01, 2005 to December 31, 2019 were identified using the United Network for Organ Sharing database. Multivariable Cox models evaluated living donor (LD) age as a predictor of LDLT recipient and graft survival. The impact of increasing donor age on recipient outcomes was compared between LD and deceased donor recipients. Donor postoperative outcomes were evaluated.

RESULTS

There were 3539 LDLTs at 65 transplant centers during the study period. Despite the recent expansion of LDLT, the proportion of LDs aged ≥50 y was stable. There were no clinically significant differences in recipient or donor characteristics by LD age group. LD age ≥50 y was associated with an adjusted hazard ratio of 1.49 ( P = 0.012) for recipient survival and 1.61 ( P < 0.001) for graft survival (vs LDs aged 18-29 y). The negative impact of increasing donor age on graft survival was more profound after LDLT than deceased donor liver transplantation (interaction P = 0.019). There was a possible increased rate of early donor biliary complications for donors >55 y (7.1% versus 3.1% for age <40 y; P = 0.156).

CONCLUSIONS

Increasing LD age is associated with decreased recipient and graft survival, although older donors still largely yield acceptable outcomes. Donor outcomes were not clearly impacted by increasing age, though this warrants further study.

Bioelectrical Impedance Analysis for Preoperative Volemia Assessment in Living Donor Hepatectomy

Donor safety remains an important concern. We introduced preoperative bioelectrical impedance analysis (BIA) in living donor hepatectomy, as it is a practical method for volemia assessment with the advantages of noninvasiveness, rapid processing, easy handling, and it is relatively inexpensive. We analyzed 51 living donors who underwent right hemihepatectomy between July 2015 and May 2022. The ratio of extracellular water:total body water (ECW/TBW; an index of volemic status) was measured. ECT/TBW < 0.378 was correlated to central venous pressure (CVP) < 5 mm Hg in a previous study and we used this value for personalized preoperative management. In the BIA group (n = 21), donors with ECW/TBW ≥ 0.378 (n = 12) required whole-day nothing by mouth (NPO), whereas those with ECW/TBW < 0.378 (n = 9) required midnight NPO, similar to the control group (n = 30). In comparison with the control group, the BIA group had a significantly lower central venous pressure (p < 0.001) from the start of surgery to the end of surgery, leading to a better surgical field grade (p = 0.045) and decreased operative duration (240.5 ± 45.6 vs. 276.5 ± 54.0 min, p = 0.016). A cleaner surgical field (surgical field grade 1) was significantly associated with decreased operative duration (p = 0.001) and estimated blood loss (p < 0.001). Preoperative BIA was the only significant predictor of a cleaner surgical field (odds ratio, 6.914; 95% confidence interval, 1.6985−28.191, p = 0.007). In conclusion, preoperative volemia assessment using BIA can improve operative outcomes by creating a favorable surgical environment in living donor hepatectomy.

Marginal parental donors for pediatric living donor liver transplantation

PURPOSE OF REVIEW

Living donor liver transplantation (LT) has been increasingly recognized as an effective treatment modality with excellent patient survival. Indications for LT have evolved not only for cholestatic liver disease, but also metabolic liver diseases. Living donor selection, particularly for pediatric inherited disease, is essential to prevent morbidity, both in the donor and recipient.

RECENT FINDINGS

Based on 30 years of experience in pediatric living donor LT in Japan, we could identify marginal parental living donors who have potential risks following LT, including heterozygous mothers with ornithine transcarbamylase deficiency, heterozygous protein C deficiency, heterozygous hypercholesterolemia, heterozygous protoporphyria, asymptomatic parental donors with paucity of intrahepatic bile duct, and human leukocyte antigen-homozygous parental donors.

SUMMARY

Although these situations seem rare due to infrequency of the condition, careful living donor evaluation is required to optimize the outcomes for pediatric recipients. In the setting of an appropriate selection of a living donor, we should avoid any additional hazards, given that the procedure itself has risks for a healthy individual.

Outcomes in Elderly Patients Undergoing Liver Transplantation Compared with Liver-Directed Ablative Therapy in Early-Stage Hepatocellular Carcinoma

BACKGROUND

Orthotopic liver transplantation (OLT) is the accepted treatment in patients with unresectable, early-stage hepatocellular carcinoma (HCC) in the setting of cirrhosis. Due to increasing waitlist demand for OLT, determining optimal groups for transplant is critical. Elderly patients are known to have poorer postoperative outcomes. Considering the effectiveness of liver-directed therapies for HCC, we sought to determine whether elderly patients received survival benefit from OLT over liver-directed therapy alone.

STUDY DESIGN

The National Cancer Database participant use file was used to analyze data between 2004 and 2017. Only patients ≥70 years of age who received OLT or liver-directed therapy alone were included. Patients with alpha-fetoprotein >500 ng/mL or missing alpha-fetoprotein values were excluded. Baseline demographic variables, model for end-stage liver disease score, and overall survival from time of diagnosis were collected. Descriptive statistics, Kaplan-Meier survival, Cox proportional hazards model, and propensity score matching were used.

RESULTS

A total of 2,377 patients received ablative therapy alone, and 214 patients received OLT. Multivariable analysis and Kaplan-Meier showed that OLT conferred a significant survival benefit compared to liver-directed therapy alone. Age was also associated with a yearly 3% increase in risk of mortality. Propensity-matched analysis adjusting also demonstrated a significant survival benefit for elderly patients receiving OLT compared to liver-directed therapy alone.

CONCLUSION

Despite increased age and associated comorbidities being factors associated with poor outcomes, OLT confers a survival advantage compared to liver-directed ablative therapies alone in selected elderly patients with HCC. OLT should be offered in medically appropriate elderly patients with HCC.