Clear mortality gap caused by graft macrosteatosis in Chinese patients after cadaveric liver transplantation

Outcomes and risk factors for liver transplantation using steatotic grafts for hepatocellular carcinoma: a multicenter study

INTRODUCTION

A growing number of steatotic grafts have been used in liver transplantation (LT), including hepatocellular carcinoma (HCC) patients. However, the impact of steatotic grafts on the prognosis of HCC recipients remains unclear. This study aims to evaluate the impact of steatotic graft in long-term prognosis for HCC recipients and development an algorithm for minimizing the risk of these grafts.

MATERIALS AND METHODS

The clinicopathologic data of HCC patients undergoing LT from 2003 to 2022 in the United Network for Organ Sharing database was analyzed. The disease-free survival (DFS) and overall survival (OS) of recipients were compared between non-steatotic (macrosteatosis <30 %) and steatotic (macrosteatosis ≥30 %) graft groups after propensity score matching (PSM). Interaction analysis was conducted to identify factors that amplified the negative impact of steatotic grafts on DFS.

RESULTS

A total of 8345 eligible HCC patients were included. Three factors exhibited significant interaction effect with steatotic grafts: cold ischemia time ≥6h (HR = 1.447; P = 0.023), donor body mass index ≥40 (HR = 1.771; P = 0.018) and recipient with non-alcoholic fatty liver disease (HR = 1.632; P = 0.032). Hazard Associated with Macrosteatotic Liver (HAML) score was created based on these three factors. In HAML ≥1 cohort, the DFS and OS of steatotic graft group were significantly reduced compared to non-steatotic graft group. But in HAML = 0 cohort, no significant differences in DFS and OS were observed between the two groups.

CONCLUSIONS

The risk of steatotic grafts in LT for HCC could be minimized through evaluating HAML score.

Molecular Mechanisms of Ischemia/Reperfusion Injury and Graft Dysfunction in Liver Transplantation: Insights from Multi-Omics Studies in Rodent Animal Models

Rodent ischemia-reperfusion injury (IRI) and liver transplantation (LT) models play crucial roles in mimicking graft injury and immune rejection, developing therapeutic approaches, and evaluating the efficacy of treatments. The application of integrated multi-omics data and advanced omics techniques like single-cell RNA sequencing in rodent models has expanded researchers' perspectives on pathophysiological processes in LT settings. This review summarizes key molecules and pathways associated with reperfusion injury and prognosis in LT models, highlighting the potential of omics data in understanding and improving transplant outcomes. In addition, we highlight the current challenges and future approaches for the application of omics data in rodent LT models. Cross-species validation with human data will improve therapeutic potential. Finally, further applications combining advanced single-cell, spatial omics technologies and machine learning algorithms will help to identify the key regulatory networks in specific cell populations underlying poor outcomes after LT.

Evaluation of Minimum-to-Severe Global and Macrovesicular Steatosis in Human Liver Specimens: A Portable Ambient Light-Compatible Spectroscopic Probe

BACKGROUND AND AIMS

Hepatic steatosis (HS), particularly macrovesicular steatosis (MaS), influences transplant outcomes. Accurate assessment of MaS is crucial for graft selection. While traditional assessment methods have limitations, non-invasive spectroscopic techniques like Raman and reflectance spectroscopy offer promise. This study aimed to evaluate the efficacy of a portable ambient light-compatible spectroscopic system in assessing global HS and MaS in human liver specimens.

METHODS

A two-stage approach was employed on thawed snap-frozen human liver specimens under ambient room light: biochemical validation involving a comparison of fat content from Raman and reflectance intensities with triglyceride (TG) quantifications and histopathological validation, contrasting Raman-derived fat content with evaluations by an expert pathologist and a "Positive Pixel Count" algorithm. Raman and reflectance intensities were combined to discern significant (≥ 10%) discrepancies in global HS and MaS.

RESULTS

The initial set of 16 specimens showed a positive correlation between Raman and reflectance-derived fat content and TG quantifications. The Raman system effectively differentiated minimum-to-severe global and macrovesicular steatosis in the subsequent 66 specimens. A dual-variable prediction algorithm was developed, effectively classifying significant discrepancies (> 10%) between algorithm-estimated global HS and pathologist-estimated MaS.

CONCLUSION

Our study established the viability and reliability of a portable spectroscopic system for non-invasive HS and MaS assessment in human liver specimens. The compatibility with ambient light conditions and the ability to address limitations of previous methods marks a significant advancement in this field. By offering promising differentiation between global HS and MaS, our system introduces an innovative approach to real-time and quantitative donor HS assessments. The proposed method holds the promise of refining donor liver assessment during liver recovery and ultimately enhancing transplantation outcomes.

Hypothermic oxygenated perfusion inhibits CLIP1-mediated TIRAP ubiquitination via TFPI2 to reduce ischemia‒reperfusion injury of the fatty liver

The use of fatty livers in liver transplantation has emerged as a crucial strategy to expand the pool of donor livers; however, fatty livers are more sensitive to ischemia‒reperfusion injury (IRI). Excessive congenital inflammatory responses are crucial in IRI. Hypothermic oxygenated perfusion (HOPE) is a novel organ preservation technique that may improve marginal donor liver quality by reducing the inflammatory response. Tissue factor pathway inhibitor-2 (TFPI2) and CAP-Gly domain-containing linker protein 1 (CLIP1) exhibit modulatory effects on the inflammatory response. However, the underlying mechanisms of HOPE in fatty liver and the effects of TFPI2 and CLIP1 in fatty liver IRI remain unclear. Here, we aimed to explore the impact of HOPE on the inflammatory response in a rat model of fatty liver IRI and the mechanisms of action of TFPI2 and CLIP1. HOPE significantly reduces liver injury, especially the inflammatory response, and alleviates damage to hepatocytes and endothelial cells. Mechanistically, HOPE exerts its effects by inhibiting TFPI2, and CLIP1 can rescue the damaging effects of TFPI2. Moreover, HOPE promoted the ubiquitination and subsequent degradation of Toll/interleukin-1 receptor domain-containing adapter protein (TIRAP) by regulating the binding of R24 of the KD1 domain of TFPI2 with CLIP1, thereby negatively regulating the TLR4/NF-κB-mediated inflammatory response and reducing IRI. Furthermore, TFPI2 expression increased and CLIP1 expression decreased following cold ischemia in human fatty livers. Overall, our results suggest that targeting the inflammatory response by modulating the TFPI2/CLIP1/TIRAP signaling pathway via HOPE represents a potential therapeutic approach to ameliorate IRI during fatty liver transplantation.

Dose-response relationship of serum ferritin and dietary iron intake with metabolic syndrome and non-alcoholic fatty liver disease incidence: a systematic review and meta-analysis

Aim

This study aims to assess the dose-response impact of iron load on systemic and hepatic metabolic disorders including metabolic syndrome (MetS) and non-alcoholic fatty liver disease (NAFLD).

Methods

Serum ferritin (SF) and dietary iron intake were selected to represent the indicators of iron load in the general population. PubMed, EMBASE and Web of Science databases were searched for epidemiological studies assessing the impact of SF/dietary iron intake on MetS/NAFLD occurrence. All literature was published before September 1st, 2023 with no language restrictions.

Results

Fifteen and 11 papers were collected with a focus on connections between SF and MetS/NAFLD, respectively. Eight papers focusing on dietary iron and MetS were included in the following meta-analysis. For the impact of SF on MetS, the pooled odds ratio (OR) of MetS was 1.88 (95% CI: 1.58-2.24) for the highest versus lowest SF categories. In males, the OR was 1.15 (95% CI: 1.10-1.21) per incremental increase in SF of 50 μg/L, while for females, each 50 μg/L increase in SF was associated with a 1.50-fold higher risk of MetS (95% CI: 1.15-1.94). For connections between SF and NAFLD, we found higher SF levels were observed in NAFLD patients compared to the control group [standardized mean difference (SMD) 0.71; 95% CI: 0.27-1.15], NASH patients against control group (SMD1.05; 95% CI:0.44-1.66), NASH patients against the NAFLD group (SMD 0.6; 95% CI: 0.31-1.00), each 50 μg/L increase in SF was associated with a 1.08-fold higher risk of NAFLD (95% CI: 1.07-1.10). For the impact of dietary iron on MetS, Pooled OR of MetS was 1.34 (95% CI: 1.10-1.63) for the highest versus lowest dietary iron categories.

Conclusion

Elevated SF levels is a linear relation between the incidence of MetS/NAFLD. In addition, there is a positive association between dietary iron intake and metabolic syndrome. The association between serum ferritin and metabolic syndrome may be confounded by body mass index and C-reactive protein levels.

Integrative analysis of the transcriptome and metabolome reveals the importance of hepatokine FGF21 in liver aging

Aging is a contributor to liver disease. Hence, the concept of liver aging has become prominent and has attracted considerable interest, but its underlying mechanism remains poorly understood. In our study, the internal mechanism of liver aging was explored via multi-omics analysis and molecular experiments to support future targeted therapy. An aged rat liver model was established with d-galactose, and two other senescent hepatocyte models were established by treating HepG2 cells with d-galactose and H2O2. We then performed transcriptomic and metabolomic assays of the aged liver model and transcriptome analyses of the senescent hepatocyte models. In livers, genes related to peroxisomes, fatty acid elongation, and fatty acid degradation exhibited down-regulated expression with aging, and the hepatokine Fgf21 expression was positively correlated with the down-regulation of these genes. In senescent hepatocytes, similar to the results found in aged livers, FGF21 expression was also decreased. Moreover, the expressions of cell cycle-related genes were significantly down-regulated, and the down-regulated gene E2F8 was the key cell cycle-regulating transcription factor. We then validated that FGF21 overexpression can protect against liver aging and that FGF21 can attenuate the declines in the antioxidant and regenerative capacities in the aging liver. We successfully validated the results from cellular and animal experiments using human liver and blood samples. Our study indicated that FGF21 is an important target for inhibiting liver aging and suggested that pharmacological prevention of the reduction in FGF21 expression due to aging may be used to treat liver aging-related diseases.

Multi-omics analysis reveals a crosstalk between ferroptosis and peroxisomes on steatotic graft failure after liver transplantation

To identify the mechanism underlying macrosteatosis (MaS)-related graft failure (GF) in liver transplantation (LT) by multi-omics network analysis. The transcriptome and metabolome were assayed in graft and recipient plasma in discovery (n = 68) and validation (n = 89) cohorts. Differentially expressed molecules were identified by MaS and GF status. Transcriptional regulatory networks were generated to explore the mechanism for MaS-related inferior post-transplant prognosis. The differentially expressed molecules associated with MaS and GF were enriched in ferroptosis and peroxisome-related pathways. Core features of MaS-related GF were presented on decreased transferrin and impaired anti-oxidative capacity dependent upon dysregulation of transcription factors hepatocyte nuclear factor 4A (HNF4A) and hypoxia-inducible factor 1A (HIF1A). Furthermore, miR-362-3p and miR-299-5p inhibited transferrin and HIF1A expression, respectively. Lower M2 macrophages but higher memory CD4 T cells were observed in MaS-related GF cases. These results were validated in clinical specimens and cellular models. Systemic analysis of multi-omics data depicted a panorama of biological pathways deregulated in MaS-related GF. Transcriptional regulatory networks centered on transferrin and anti-oxidant responses were associated with poor MaS graft quality, qualifying as potential targets to improve prognosis of patients after LT.

The biological mechanism and emerging therapeutic interventions of liver aging

Research on liver aging has become prominent and has attracted considerable interest in uncovering the mechanism and therapeutic targets of aging to expand lifespan. In addition, multi-omics studies are widely used to perform further mechanistic investigations on liver aging. In this review, we illustrate the changes that occur with aging in the liver, present the current models of liver aging, and emphasize existing multi-omics studies on liver aging. We integrated the multi-omics data of enrolled studies and reanalyzed them to identify key pathways and targets of liver aging. The results indicated that C-X-C motif chemokine ligand 9 (Cxcl9) was a regulator of liver aging. In addition, we provide a flowchart for liver aging research using multi-omics analysis and molecular experiments to help researchers conduct further research. Finally, we present emerging therapeutic treatments that prolong lifespan. In summary, using cells and animal models of liver aging, we can apply a multi-omics approach to find key metabolic pathways and target genes to mitigate the adverse effects of liver aging.

Multi-omics network analysis on samples from sequential biopsies reveals vital role of proliferation arrest for Macrosteatosis related graft failure in rats after liver transplantation

To investigate the molecular impact of graft MaS on post-transplant prognosis, based on multi-omics integrative analysis. Rats were fed by methionine-choline deficient diet (MCD) for MaS grafts. Samples were collected from grafts by sequential biopsies. Transcriptomic and metabolomic profilings were assayed. Post-transplant MaS status showed a close association with graft failure. Differentially expressed genes (DEGs) for in-vivo MaS were mainly enriched on pathways of cell cycle and DNA replication. Post-transplant MaS caused arrests of graft regeneration via inhibiting the E2F1 centered network, which was confirmed by an in vitro experiment. Data from metabolomics assays found insufficient serine/creatine which is located on one‑carbon metabolism was responsible for MaS-related GF. Pre-transplant MaS caused severe fibrosis in long-term survivors. DEGs for grafts from long-term survivors with pre-transplant MaS were mainly enriched in pathways of ECM-receptor interaction and focal adhesion. Transcriptional regulatory network analysis confirmed SOX9 as a key transcription factor (TF) for MaS-related fibrosis. Metabolomic assays found elevation of aromatic amino acid (AAA) was a major feature of fibrosis in long-term survivors. Graft MaS in vivo increased post-transplant GF via negative regulations on graft regeneration. Pre-transplant MaS induced severe fibrosis in long-term survivors via activations on ECM-receptor interaction and AAA metabolism.

Small extracellular vesicles from HO-1-modified bone marrow-derived mesenchymal stem cells attenuate ischemia-reperfusion injury after steatotic liver transplantation by suppressing ferroptosis via miR-214-3p

Donor shortage is a major problem that limits liver transplantation availability. Steatotic donor liver presents a feasible strategy to solve this problem. However, severe ischemia-reperfusion injury (IRI) is an obstacle to the adoption of steatotic transplanted livers. Evidence from our prior studies indicated that bone marrow mesenchymal stem cells modified with heme oxygenase-1 (HMSCs) can attenuate non-steatotic liver IRI. However, the contribution of HMSCs in transplanted steatotic liver IRI is unclear. Here, HMSCs and their derived small extracellular vesicles (HM-sEVs) alleviated IRI in transplanted steatotic livers. After liver transplantation, there was significant enrichment of the differentially expressed genes in the glutathione metabolism and ferroptosis pathways, accompanied by ferroptosis marker upregulation. The HMSCs and HM-sEVs suppressed ferroptosis and attenuated IRI in the transplanted steatotic livers. MicroRNA (miRNA) microarray and validation experiments indicated that miR-214-3p, which was abundant in the HM-sEVs, suppressed ferroptosis by targeting cyclooxygenase 2 (COX2). In contrast, COX2 overexpression reversed this effect. Knockdown of miR-214-3p in the HM-sEVs diminished its ability to suppress ferroptosis and protect liver tissues/cells. The findings suggested that HM-sEVs suppressed ferroptosis to attenuate transplanted steatotic liver IRI via the miR-214-3p-COX2 axis.

Graft-to-recipient weight ratio exerts nonlinear effects on prognosis by interacting with donor liver macrosteatosis

AIM

To investigate the interactions between the graft-to-recipient weight ratio (GWRWR) and other risk factors responsible for inferior allograft outcomes.

METHODS

A total of 362 patients who received liver transplantation (LT) were enrolled. Indicators such as graft/recipient weight and other prognostic factors were collected. Comparisons of indicators and survival analysis were performed in groups categorized by the GWRWR. Interactions of large-for-size grafts (LFSGs) with graft macrosteatosis (MaS) were evaluated in terms of relative excess risk caused by interaction (RERI) and attributable proportion (AP). Cytoscape visualized the role of LFSGs in the risk profile for poor prognosis.

RESULTS

Based on the GWRWR, LT cases can be categorized into three subgroups, standard (1%-2.5%), optimal (2.5%-3.0%), and inferior prognosis (>3.0%). Survival analysis confirmed clear separations in cases categorized by the above-defined limits on the GWRWR (P < 0.05). LFSGs caused inferior prognosis by initiating positive interactions with MaS severity.

CONCLUSION

The GWRWR exerted nonlinear effects on prognosis in deceased donor LT cases. LFSGs (GWRWR > 3.0%) caused inferior outcomes, while grafts sized within (2.5%-3.0%) had optimal post-transplant prognosis. MaS increased the risk of poor prognosis by exerting positive synergistic effects on LFSGs.

Recent Progress and Future Direction for the Application of Multiomics Data in Clinical Liver Transplantation

Omics data address key issues in liver transplantation (LT) as the most effective therapeutic means for end-stage liver disease. The purpose of this study was to review the current application and future direction for omics in LT. We reviewed the use of multiomics to elucidate the pathogenesis leading to LT and prognostication. Future directions with respect to the use of omics in LT are also described based on perspectives of surgeons with experience in omics. Significant molecules were identified and summarized based on omics, with a focus on post-transplant liver fibrosis, early allograft dysfunction, tumor recurrence, and graft failure. We emphasized the importance omics for clinicians who perform LTs and prioritized the directions that should be established. We also outlined the ideal workflow for omics in LT. In step with advances in technology, the quality of omics data can be guaranteed using an improved algorithm at a lower price. Concerns should be addressed on the translational value of omics for better therapeutic effects in patients undergoing LT.

Integrative Network Analysis Revealed Genetic Impact of Pyruvate Kinase L/R on Hepatocyte Proliferation and Graft Survival after Liver Transplantation

Background

Pyruvate kinase L/R (PKLR) has been suggested to affect the proliferation of hepatocytes via regulation of the cell cycle and lipid metabolism. However, its impact on the global metabolome and its clinical implications remain unclear.

Aims

We aimed to clarify the genetic impact of PKLR on the metabolomic profiles of hepatoma cells and its potential effects on grafts for liver transplantation (LT).

Methods

Nontargeted and targeted metabolomic assays were performed in human hepatoma cells transfected with lentiviral vectors causing PKLR overexpression and silencing, respectively. We then constructed a molecular network based on integrative analysis of transcriptomic and metabolomic data. We also assessed the biological functions of PKLR in the global metabolome in LT grafts in patients via a weighted correlation network model.

Results

Multiomic analysis revealed that PKLR perturbations significantly affected the pyruvate, citrate, and glycerophospholipid metabolism pathways, as crucial steps in de novo lipogenesis (DNL). We also confirmed the importance of phosphatidylcholines (PC) and its derivative lyso-PC supply on improved survival of LT grafts in patients. Coexpression analysis revealed beneficial effects of PKLR overexpression on posttransplant prognosis by alleviating arachidonic acid metabolism of the grafts, independent of operational risk factors.

Conclusion

This systems-level analysis indicated that PKLR affected hepatoma cell viability via impacts on the whole process of DNL, from glycolysis to final PC synthesis. PKLR also improved prognosis after LT, possibly via its impact on the increased genesis of beneficial glycerophospholipids.

Metabonomic Profile of Macrosteatotic Allografts for Orthotopic Liver Transplantation in Patients With Initial Poor Function: Mechanistic Investigation and Prognostic Prediction

BACKGROUND

Our previous study revealled amplified hazardous effects of macrosteatosis (MaS) on graft failure (GF) in recipients with severe liver damage in short post-operative days, with vague mechanism inside.

AIM

We aimed to uncover the molecular mechanism of donor MaS on GF, and construct the predictive model to monitor post-transplant prognosis based on "omics" perspective.

METHODS

Ultra-performance liquid chromatography coupled to mass spectrometry metabolomic analysis was performed in allograft tissues from 82 patients with initial poor function (IPF) from multi-liver transplant (LT) centers. Pathway analysis was performed by on-line toolkit Metaboanalyst (v 3.0). Predictive model was constructed based on combinative metabonomic and clinical data extracted by stepwised cox proportional analysis.

RESULTS

Principle component analysis (PCA) analysis revealled stratification on metabolic feature in organs classified by MaS status. Differential metabolits both associated with MaS and GF were significantly enriched on pathway of glycerophospholipid metabolism (P < 0.05). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) involved in glycerophospholipid metabolism was significantly decreased in cases with MaS donors and GF (P < 0.05). Better prediction was observed on graft survival by combinative model (area under the curve = 0.91) and confirmed by internal validation.

CONCLUSION

Metabonomic features of allografts can be clearly distinguished by MaS status in patients with IPF. Dysfunction on glycerophospholipid metabolism was culprit to link donor MaS and final GF. Decrement on PC and PE exerted the fatal effects of MaS on organ failure. Metabonomic data might help for monitoring long-term graft survival after LT.