Rejection is still a critical barrier to the long-term survival of graft after liver transplantation, requiring clinicians to unveil the underlying mechanism of liver transplant rejection. The cellular diversity and the interplay between immune cells in the liver graft microenvironment remain unclear. Herein, we performed single-cell RNA sequencing analysis to delineate the landscape of immune cells heterogeneity in liver transplantation. T cells, NK cells, B cells, and myeloid cell subsets in human liver and blood were enriched to characterize their tissue distribution, gene expression, and functional modules. The proportion of CCR6+CD4+ T cells increased within an allograft, suggesting that there are more memory CD4+ T cells after transplantation, in parallel with exhausted CTLA4+CD8+ T and actively proliferating MKI67+CD8+ T cells increased significantly, where they manifested heterogeneity, distinct function, and homeostatic proliferation. Remarkably, the changes of CD1c+ DC, CADM+ DC, MDSC, and FOLR3+ Kupffer cells increase significantly, but the proportion of CD163+ Kupffer, APOE+ Kupffer, and GZMA+ Kupffer decreased. Furthermore, we identified LDLR as a novel marker of activated MDSC to prevent liver transplant rejection. Intriguingly, a subset of CD4+CD8+FOXP3+ T cells included in CTLA4+CD8+ T cells was first detected in human liver transplantation. Furthermore, intercellular communication and gene regulatory analysis implicated the LDLR+ MDSC and CTLA4+CD8+ T cells interact through TIGIT-NECTIN2 signaling pathway. Taken together, these findings have gained novel mechanistic insights for understanding the immune landscape in liver transplantation, and it outlines the characteristics of immune cells and provides potential therapeutic targets in liver transplant rejection.

Rationale: Understanding the immune mechanisms associated with liver transplantation (LT), particularly the involvement of tissue-resident memory T cells (TRMs), represents a significant challenge.

Background: Sarcopenia is associated with unfavourable long‐term survival in patients undergoing liver transplantation (LT) for hepatocellular carcinoma (HCC). However, the impact of myosteatosis and muscle loss on patient prognosis has not been investigated.Methods: Seven hundred fifty‐six HCC patients who received LT at 3 transplant centres were included. Computed tomography (CT) images of recipients were collected to measure skeletal muscle index (SMI) and skeletal muscle radiodensity (SMRA). The impact of myosteatosis on the prognosis of sarcopenic and non‐sarcopenic patients was studied separately. Muscle status was evaluated based on the presence of sarcopenia and myosteatosis. The muscle loss of 342 males was calculated as the relative change of SMI between pre‐ and post‐LT evaluations. Cox regression models were used to identify predictors of overall survival (OS) and recurrence‐free survival (RFS).Results: The study comprised 673 males and 83 females. The median follow‐up time was 31 months (interquartile range, 19–43 months). Prior to LT, 267 (39.7%) and 187 (27.8%) males were defined as sarcopenic (low‐SMI) and myosteatotic (low‐SMRA), respectively. For sarcopenic recipients, the presence of myosteatosis was followed by a 23.6% decrease in 5 year OS (P < 0.001) and a 15.0% decrease in 5 year RFS (P = 0.014). Univariate and multivariate analyses revealed that muscle status was an independent predictor of OS [hazard ratio (HR), 1.569; 95% confidence interval (CI), 1.317–1.869; P < 0.001] and RFS (HR, 1.369; 95% CI, 1.182–1.586; P < 0.001). Postoperatively, a muscle loss >14.2% was an independent risk factor for poor OS (HR, 2.286; 95% CI, 1.358–3.849; P = 0.002) and RFS (HR, 2.219; 95% CI, 1.418–3.471; P < 0.001) in non‐sarcopenic recipients (N = 209).Conclusions: Pre‐transplant myosteatosis aggravated the adverse impact of sarcopenia on liver transplant outcomes in male HCC patients. Post‐transplant muscle loss might assist in prognostic stratification of recipients without pre‐existing sarcopenia, intriguing new insights into individualized management.

Background: The high incidence of early recurrence after liver resection (LR) for hepatocellular carcinoma (HCC) is the main obstacle in achieving good long-term survival outcomes. The aim of the present study is to develop a prognostic model in predicting the risk of very early (1-year) recurrence. Material and methods: Consecutive patients who underwent LR for HCC with curative intent at multicenters in China were enrolled in this study. The VERM-pre (the Preoperative Very Early Recurrence Model of HCC) with good performance was derived and validated by internal and external cohorts retrospectively and by another two-center cohort prospectively. Results: Seven thousand four hundred one patients were enrolled and divided randomly into three cohorts. Eight variables (tumor diameter, tumor number, macrovascular invasion, satellite nodule, alpha-fetoprotein, level of HBV-DNA, γ-GT, and prothrombin time) were identified as independent risk factors for recurrence-free survival on univariate and multivariate analyses. The VERM-pre model was developed which showed a high capacity of discrimination (C-index: 0.722; AUROC at 1-year: 0.722)) and was validated comprehensively by the internal, external, and prospective cohorts, retrospectively. Calibration plots showed satisfactory fitting of probability of early HCC recurrence in the cohorts. Three risk strata were derived to have significantly different recurrence-free survival rates (low-risk: 80.4–85.4%; intermediate-risk: 59.7–64.8%; high-risk: 32.6–42.6%). In the prospective validation cohort, the swimming plot illustrated consistent outcomes with the beginning predictive score. Conclusion: The VERM-pre model accurately predicted the 1-year recurrence rates of HCC after LR with curative intent. The model was retrospectively and prospectively validated and then developed as the online tool.