The role of liver sinusoidal cells in local hepatic immune surveillance

Endothelial POFUT1 controls injury-induced liver fibrosis by repressing fibrinogen synthesis

BACKGROUND & AIMS

NOTCH signaling in liver sinusoidal endothelial cells (LSECs) regulates liver fibrosis, a pathological feature of chronic liver diseases. POFUT1 is an essential regulator of NOTCH signaling. Here, we investigated the role of LSEC-expressed POFUT1 in liver fibrosis.

METHODS

Endothelial-specific Pofut1 knockout mice were generated and experimental liver fibrosis was induced by chronic carbon tetrachloride exposure or common bile duct ligation. Liver samples were assessed by ELISA, histology, electron microscopy, immunostaining and RNA in situ hybridization. LSECs and hepatic stellate cells (HSCs) were isolated for gene expression analysis by RNA sequencing, qPCR, and western blotting. Signaling crosstalk between LSECs and HSCs was investigated by treating HSCs with supernatant from LSEC cultures. Liver single-cell RNA sequencing datasets from patients with cirrhosis and healthy individuals were analyzed to evaluate the clinical relevance of gene expression changes observed in mouse studies.

RESULTS

POFUT1 loss promoted injury-induced LSEC capillarization and HSC activation, leading to aggravated liver fibrosis. RNA sequencing analysis revealed that POFUT1 deficiency upregulated fibrinogen expression in LSECs. Consistently, fibrinogen was elevated in LSECs of patients with cirrhosis. HSCs treated with supernatant from LSECs of Pofut1 null mice showed exacerbated activation compared to those treated with supernatant from control LSECs, and this effect was attenuated by knockdown of fibrinogen or by pharmacological inhibition of fibrinogen receptor signaling, altogether suggesting that LSEC-derived fibrinogen induced the activation of HSCs. Mechanistically, POFUT1 loss augmented fibrinogen expression by enhancing NOTCH/HES1/STAT3 signaling.

CONCLUSIONS

Endothelial POFUT1 prevents injury-induced liver fibrosis by repressing the expression of fibrinogen, which functions as a profibrotic paracrine signal to activate HSCs. Therapies targeting the POFUT1/fibrinogen axis offer a promising strategy for the prevention and treatment of fibrotic liver diseases.

IMPACT AND IMPLICATIONS

Paracrine signals produced by liver vasculature play a major role in the development of liver fibrosis, which is a pathological hallmark of most liver diseases. Identifying those paracrine signals is clinically relevant in that they may serve as therapeutic targets. In this study, we discovered that genetic deletion of Pofut1 aggravated experimental liver fibrosis in mouse models. Moreover, fibrinogen was identified as a downstream target repressed by Pofut1 in liver endothelial cells and functioned as a novel paracrine signal that drove liver fibrosis. In addition, fibrinogen was found to be relevant to cirrhosis and may serve as a potential therapeutic target for this devastating human disease.

Liver fibrosis pathologies and potentials of RNA based therapeutics modalities

Liver fibrosis (LF) occurs when the liver tissue responds to injury or inflammation by producing excessive amounts of scar tissue, known as the extracellular matrix. This buildup stiffens the liver tissue, hinders blood flow, and ultimately impairs liver function. Various factors can trigger this process, including bloodborne pathogens, genetic predisposition, alcohol abuse, non-steroidal anti-inflammatory drugs, non-alcoholic steatohepatitis, and non-alcoholic fatty liver disease. While some existing small-molecule therapies offer limited benefits, there is a pressing need for more effective treatments that can truly cure LF. RNA therapeutics have emerged as a promising approach, as they can potentially downregulate cytokine levels in cells responsible for liver fibrosis. Researchers are actively exploring various RNA-based therapeutics, such as mRNA, siRNA, miRNA, lncRNA, and oligonucleotides, to assess their efficacy in animal models. Furthermore, targeted drug delivery systems hold immense potential in this field. By utilizing lipid nanoparticles, exosomes, nanocomplexes, micelles, and polymeric nanoparticles, researchers aim to deliver therapeutic agents directly to specific biomarkers or cytokines within the fibrotic liver, increasing their effectiveness and reducing side effects. In conclusion, this review highlights the complex nature of liver fibrosis, its underlying causes, and the promising potential of RNA-based therapeutics and targeted delivery systems. Continued research in these areas could lead to the development of more effective and personalized treatment options for LF patients.

Endothelial cells adopt a pro-reparative immune responsive signature during cardiac injury

Modulation of the heart's immune microenvironment is crucial for recovery after ischemic events such as myocardial infarction (MI). Endothelial cells (ECs) can have immune regulatory functions; however, interactions between ECs and the immune environment in the heart after MI remain poorly understood. We identified an EC-specific IFN responsive and immune regulatory gene signature in adult and pediatric heart failure (HF) tissues. Single-cell transcriptomic analysis of murine hearts subjected to MI uncovered an EC population (IFN-ECs) with immunologic gene signatures similar to those in human HF. IFN-ECs were enriched in regenerative-stage mouse hearts and expressed genes encoding immune responsive transcription factors (Irf7, Batf2, and Stat1). Single-cell chromatin accessibility studies revealed an enrichment of these TF motifs at IFN-EC signature genes. Expression of immune regulatory ligand genes by IFN-ECs suggests bidirectional signaling between IFN-ECs and macrophages in regenerative-stage hearts. Our data suggest that ECs may adopt immune regulatory signatures after cardiac injury to accompany the reparative response. The presence of these signatures in human HF and murine MI models suggests a potential role for EC-mediated immune regulation in responding to stress induced by acute injury in MI and chronic adverse remodeling in HF.

The Role of microRNAs in Hepatocellular Cancer: A Narrative Review Focused on Tumor Microenvironment and Drug Resistance

Globally, hepatic cancer ranks fourth in terms of cancer-related mortality and is the sixth most frequent kind of cancer. Around 80% of liver cancers are hepatocellular carcinomas (HCC), which are the leading cause of cancer death. It is well known that HCC may develop resistance to the available chemotherapy treatments very fast. One of the biggest obstacles in providing cancer patients with appropriate care is drug resistance. According to reports, more than 90% of cancer-specific fatalities are caused by treatment resistance. By binding to the 3'-untranslated region of target messenger RNAs (mRNAs), microRNAs (miRNAs), a group of noncoding RNAs which are around 17 to 25 nucleotides long, regulate target gene expression. Moreover, they play role in the control of signaling pathways, cell proliferation, and cell death. As a result, miRNAs play an important role in the microenvironment of HCC by changing immune phenotypes, hypoxic conditions, and acidification, as well as angiogenesis and extracellular matrix components. Moreover, changes in miRNA levels in HCC can effectively resist cancer cells to chemotherapy by affecting various cellular processes such as autophagy, apoptosis, and membrane transporter activity. In the current work, we narratively reviewed the role of miRNAs in HCC, with a special focus on tumor microenvironment and drug resistance.

New and Old Key Players in Liver Cancer

Liver cancer represents a major health problem worldwide with growing incidence and high mortality, hepatocellular carcinoma (HCC) being the most frequent. Hepatocytes are likely the cellular origin of most HCCs through the accumulation of genetic alterations, although hepatic progenitor cells (HPCs) might also be candidates in specific cases, as discussed here. HCC usually develops in a context of chronic inflammation, fibrosis, and cirrhosis, although the role of fibrosis is controversial. The interplay between hepatocytes, immune cells and hepatic stellate cells is a key issue. This review summarizes critical aspects of the liver tumor microenvironment paying special attention to platelets as new key players, which exert both pro- and anti-tumor effects, determined by specific contexts and a tight regulation of platelet signaling. Additionally, the relevance of specific signaling pathways, mainly HGF/MET, EGFR and TGF-β is discussed. HGF and TGF-β are produced by different liver cells and platelets and regulate not only tumor cell fate but also HPCs, inflammation and fibrosis, these being key players in these processes. The role of C3G/RAPGEF1, required for the proper function of HGF/MET signaling in HCC and HPCs, is highlighted, due to its ability to promote HCC growth and, regulate HPC fate and platelet-mediated actions on liver cancer.

Identification of Risk Factors and Phenotypes of Surgical Site Infection in Patients After Abdominal Surgery

OBJECTIVES

We aimed to determine the current incidence rate and risk factors for surgical site infection (SSI) after abdominal surgery in China and to further demonstrate the clinical features of patients with SSI.

BACKGROUND

Contemporary epidemiology and clinical features of SSI after abdominal surgery remain poorly characterized.

METHODS

A prospective multicenter cohort study was conducted from March 2021 to February 2022; the study included patients who underwent abdominal surgery at 42 hospitals in China. Multivariable logistic regression analysis was performed to identify risk factors for SSI. Latent class analysis (LCA) was used to explore the population characteristics of SSI.

RESULTS

In total, 23,982 patients were included in the study, of whom 1.8% developed SSI. There was a higher SSI incidence in open surgery (5.0%) than in laparoscopic or robotic surgeries (0.9%). Multivariable logistic regression indicated that the independent risk factors for SSI after abdominal surgery were older age, chronic liver disease, mechanical bowel preparation, oral antibiotic bowel preparation, colon or pancreas surgery, contaminated or dirty wounds, open surgery, and colostomy/ileostomy. LCA revealed 4 subphenotypes in patients undergoing abdominal surgery. Types α and β were mild subclasses with a lower SSI incidence; whereas types γ and δ were the critical subgroups with a higher SSI incidence, but their clinical features were different.

CONCLUSIONS

LCA identified 4 subphenotypes in patients who underwent abdominal surgery. Types γ and δ were critical subgroups with a higher SSI incidence. This phenotype classification can be used to predict SSI after abdominal surgery.

Recent updates on the role of the gut-liver axis in the pathogenesis of NAFLD/NASH, HCC, and beyond

The gut and the liver are anatomically and physiologically connected, and this connection is called the "gut-liver axis," which exerts various influences on liver physiology and pathology. The gut microbiota has been recognized to trigger innate immunity and modulate the liver immune microenvironment. Gut microbiota influences the physiological processes in the host, such as metabolism, by acting on various signaling receptors and transcription factors through their metabolites and related molecules. The gut microbiota has also been increasingly recognized to modulate the efficacy of immune checkpoint inhibitors. In this review, we discuss recent updates on gut microbiota-associated mechanisms in the pathogenesis of chronic liver diseases such as NAFLD and NASH, as well as liver cancer, in light of the gut-liver axis. We particularly focus on gut microbial metabolites and components that are associated with these liver diseases. We also discuss the role of gut microbiota in modulating the response to immunotherapy in liver diseases.

Remodeling the hepatic fibrotic microenvironment with emerging nanotherapeutics: a comprehensive review

Liver fibrosis could be the last hope for treating liver cancer and remodeling of the hepatic microenvironment has emerged as a strategy to promote the ablation of liver fibrosis. In recent years, especially with the rapid development of nanomedicine, hepatic microenvironment therapy has been widely researched in studies concerning liver cancer and fibrosis. In this comprehensive review, we summarized recent advances in nano therapy-based remodeling of the hepatic microenvironment. Firstly, we discussed novel strategies for regulatory immune suppression caused by capillarization of liver sinusoidal endothelial cells (LSECs) and macrophage polarization. Furthermore, metabolic reprogramming and extracellular matrix (ECM) deposition are caused by the activation of hepatic stellate cells (HSCs). In addition, recent advances in ROS, hypoxia, and impaired vascular remodeling in the hepatic fibrotic microenvironment due to ECM deposition have also been summarized. Finally, emerging nanotherapeutic approaches based on correlated signals were discussed in this review. We have proposed novel strategies such as engineered nanotherapeutics targeting antigen-presenting cells (APCs) or direct targeting T cells in liver fibrotic immunotherapy to be used in preventing liver fibrosis. In summary, this comprehensive review illustrated the opportunities in drug targeting and nanomedicine, and the current challenges to be addressed.

Liver angiocrine factors

Endothelial cells secrete growth factors, chemokines, and extracellular matrix components, including angiocrine factors or angiokines, involved in the regulation of organ morphogenesis, homeostasis, and regeneration. The concepts of angiocrine signaling have been demonstrated in the liver, pancreas, brain, lung, heart, kidney, skin, bone marrow, as well as in pathological conditions, including cancer. The aim of this review article is to analyze the role of angiocrine factors in the liver in physiological as well as in pathological conditions.

Role of immune responses for development of NAFLD-associated liver cancer and prospects for therapeutic modulation

The liver is the central metabolic organ of the body regulating energy and lipid metabolism and at the same time has potent immunological functions. Overwhelming the metabolic capacity of the liver by obesity and sedentary lifestyle leads to hepatic lipid accumulation, chronic necro-inflammation, enhanced mitochondrial/ER-stress and development of non-alcoholic fatty liver disease (NAFLD), with its pathologic form nonalcoholic steatohepatitis (NASH). Based on knowledge on pathophysiological mechanisms, specifically targeting metabolic diseases to prevent or slow down progression of NAFLD to liver cancer will become possible. Genetic/environmental factors contribute to development of NASH and liver cancer progression. The complex pathophysiology of NAFLD-NASH is reflected by environmental factors, particularly the gut microbiome and its metabolic products. NAFLD-associated HCC occurs in most of the cases in the context of a chronically inflamed liver and cirrhosis. Recognition of environmental alarmins or metabolites derived from the gut microbiota and the metabolically injured liver create a strong inflammatory milieu supported by innate and adaptive immunity. Several recent studies indicate that the chronic hepatic microenvironment of steatosis induces auto-aggressive CD8+CXCR6+PD1+ T cells secreting TNF and upregulating FasL to eliminate parenchymal and non-parenchymal cells in an antigen independent manner. This promotes chronic liver damage and a pro-tumorigenic environment. CD8+CXCR6+PD1+ T cells possess an exhausted, hyperactivated, resident phenotype and trigger NASH to HCC transition, and might be responsible for a less efficient treatment response to immune-check-point inhibitors - in particular atezolizumab/bevacizumab. Here, we provide an overview of NASH-related inflammation/pathogenesis focusing on new discoveries on the role of T cells in NASH-immunopathology and therapy response. This review discusses preventive measures to halt disease progression to liver cancer and therapeutic strategies to manage NASH-HCC patients.

Passive, active and endogenous organ-targeted lipid and polymer nanoparticles for delivery of genetic drugs

Genetic drugs based on nucleic acid biomolecules are a rapidly emerging class of medicines that directly reprogramme the central dogma of biology to prevent and treat disease. However, multiple biological barriers normally impede the intracellular delivery of nucleic acids, necessitating the use of a delivery system. Lipid and polymer nanoparticles represent leading approaches for the clinical translation of genetic drugs. These systems circumnavigate biological barriers and facilitate the intracellular delivery of nucleic acids in the correct cells of the target organ using passive, active and endogenous targeting mechanisms. In this Review, we highlight the constituent materials of these advanced nanoparticles, their nucleic acid cargoes and how they journey through the body. We discuss targeting principles for liver delivery, as it is the organ most successfully targeted by intravenously administered nanoparticles to date, followed by the expansion of these concepts to extrahepatic (non-liver) delivery. Ultimately, this Review connects emerging materials and biological insights playing key roles in targeting specific organs and cells in vivo.

A roadmap for serum biomarkers for hepatitis B virus: current status and future outlook

Globally, 296 million people are infected with hepatitis B virus (HBV), and approximately one million people die annually from HBV-related causes, including liver cancer. Although there is a preventative vaccine and antiviral therapies suppressing HBV replication, there is no cure. Intensive efforts are under way to develop curative HBV therapies. Currently, only a few biomarkers are available for monitoring or predicting HBV disease progression and treatment response. As new therapies become available, new biomarkers to monitor viral and host responses are urgently needed. In October 2020, the International Coalition to Eliminate Hepatitis B Virus (ICE-HBV) held a virtual and interactive workshop on HBV biomarkers endorsed by the International HBV Meeting. Various stakeholders from academia, clinical practice and the pharmaceutical industry, with complementary expertise, presented and participated in panel discussions. The clinical utility of both classic and emerging viral and immunological serum biomarkers with respect to the course of infection, disease progression, and response to current and emerging treatments was appraised. The latest advances were discussed, and knowledge gaps in understanding and interpretation of HBV biomarkers were identified. This Roadmap summarizes the strengths, weaknesses, opportunities and challenges of HBV biomarkers.

Mitochondria, mitophagy, and the role of deubiquitinases as novel therapeutic targets in liver pathology

Liver diseases such as nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma (HCC) have increased over the past few decades due to the absence or ineffective therapeutics. Recently, it has been shown that inappropriate regulation of hepatic mitophagy is linked to the pathogenesis of the above-mentioned liver diseases. As mitophagy maintains cellular homeostasis by removing damaged and nonfunctional mitochondria from the cell, the proper function of the molecules involved are of utmost importance. Thereby, mitochondrial E3 ubiquitin ligases as well as several deubiquitinases (DUBs) appear to play a unique role for the degradation of mitochondrial proteins and for proper execution of the mitophagy process by either adding or removing ubiquitin chains from target proteins. Therefore, these enzymes could be considered as valuable liver disease biomarkers and also as novel targets for therapy. In this review, we focus on the role of different DUBs on mitophagy and their contribution to NAFLD, NASH, alcohol-related liver disease, and especially HCC.

HBeAg Is Indispensable for Inducing Liver Sinusoidal Endothelial Cell Activation by Hepatitis B Virus

Background and Aims

Liver sinusoidal endothelial cells (LSECs) serve as sentinel cells to detect microbial infection and actively contribute to regulating immune responses for surveillance against intrahepatic pathogens. We recently reported that hepatitis B e antigen (HBeAg) stimulation could induce LSEC maturation and abrogate LSEC-mediated T cell suppression in a TNF-α and IL27 dependent manner. However, it remains unclear how HBeAg deficiency during HBV infection influences LSEC immunoregulation function and intrahepatic HBV-specific CD8 T cell responses.

Methods

The function of LSECs in regulating effector T cell response, intrahepatic HBV-specific CD8 T cell responses and HBV viremia were characterized in both HBeAg-deficient and -competent HBV hydrodynamic injection (HDI) mouse models.

Results

LSECs isolated from HBeAg-deficient HBV HDI mice showed a reduced capacity to promote T cell immunity in vitro compared with those isolated from wild-type HBV HDI mice. HBeAg expression replenishment in HBeAg-deficient HBV HDI mice restored the HBV-induced LSEC maturation, and resulted in potent intrahepatic anti-HBV CD8 T cell responses and efficient control of HBV replication. Moreover, in vivo TNF-α, but not IL27 blockade in HBV HDI mice impaired HBV-specific CD8 T cell immunity and delayed HBV clearance.

Conclusion

Our study underlines that HBeAg is indispensable for HBV-induced LSEC maturation to trigger intrahepatic HBV-specific T cell activation, and provides a new mechanism to elucidate the intrahepatic immune microenvironment regulation upon HBV exposure.

Immunotherapy for Hepatocellular Carcinoma: New Prospects for the Cancer Therapy

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. HCC patients may benefit from liver transplantation, hepatic resection, radiofrequency ablation, transcatheter arterial chemoembolization, and targeted therapies. The increased infiltration of immunosuppressive immune cells and the elevated expression of immunosuppressive factors in the HCC microenvironment are the main culprits of the immunosuppressive nature of the HCC milieu. The immunosuppressive tumor microenvironment can substantially attenuate antitumoral immune responses and facilitate the immune evasion of tumoral cells. Immunotherapy is an innovative treatment method that has been promising in treating HCC. Immune checkpoint inhibitors (ICIs), adoptive cell transfer (ACT), and cell-based (primarily dendritic cells) and non-cell-based vaccines are the most common immunotherapeutic approaches for HCC treatment. However, these therapeutic approaches have not generally induced robust antitumoral responses in clinical settings. To answer to this, growing evidence has characterized immune cell populations and delineated intercellular cross-talk using single-cell RNA sequencing (scRNA-seq) technologies. This review aims to discuss the various types of tumor-infiltrating immune cells and highlight their roles in HCC development. Besides, we discuss the recent advances in immunotherapeutic approaches for treating HCC, e.g., ICIs, dendritic cell (DC)-based vaccines, non-cell-based vaccines, oncolytic viruses (OVs), and ACT. Finally, we discuss the potentiality of scRNA-seq to improve the response rate of HCC patients to immunotherapeutic approaches.

Mechanisms of immune checkpoint inhibitor-mediated liver injury

The immune checkpoints, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed cell death protein-1/ligand-1 (PD-1/PD-L1) are vital contributors to immune regulation and tolerance. Recently immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy; however, they come with the cost of immune related adverse events involving multiple organs such as the liver. Due to its constant exposure to foreign antigens, the liver has evolved a high capacity for immune tolerance, therefore, blockade of the immune checkpoints can result in aberrant immune activation affecting the liver in up to 20% of patients depending on the agent(s) used and underlying factors. This type of hepatotoxicity is termed immune mediated liver injury from checkpoint inhibitors (ILICI) and is more common when CTLA4 and PD-1/PD-L1 are used in combination. The underlying mechanisms of this unique type of hepatotoxicity are not fully understood; however, the contribution of CD8+ cytotoxic T lymphocytes, various CD4+ T cells populations, cytokines, and the secondary activation of the innate immune system leading to liver injury have all been suggested. This review summarizes our current understanding of the underlying mechanisms of liver injury in immunotherapy using animal models of ILICI and available patient data from clinical studies.

How to get away with liver innate immunity? A viruses' tale

In their never-ending quest towards persistence within their host, hepatitis viruses have developed numerous ways to counteract the liver innate immunity. This review highlights the different and common mechanisms employed by these viruses to (i) establish in the liver (passive entry or active evasion from immune recognition) and (ii) actively inhibit the innate immune response (ie modulation of pattern recognition receptor expression and/or signalling pathways, modulation of interferon response and modulation of immune cells count or phenotype).

How Physical Factors Coordinate Virus Infection: A Perspective From Mechanobiology

Pandemics caused by viruses have threatened lives of thousands of people. Understanding the complicated process of viral infection provides significantly directive implication to epidemic prevention and control. Viral infection is a complex and diverse process, and substantial studies have been complemented in exploring the biochemical and molecular interactions between viruses and hosts. However, the physical microenvironment where infections implement is often less considered, and the role of mechanobiology in viral infection remains elusive. Mechanobiology focuses on sensation, transduction, and response to intracellular and extracellular physical factors by tissues, cells, and extracellular matrix. The intracellular cytoskeleton and mechanosensors have been proven to be extensively involved in the virus life cycle. Furthermore, innovative methods based on micro- and nanofabrication techniques are being utilized to control and modulate the physical and chemical cell microenvironment, and to explore how extracellular factors including stiffness, forces, and topography regulate viral infection. Our current review covers how physical factors in the microenvironment coordinate viral infection. Moreover, we will discuss how this knowledge can be harnessed in future research on cross-fields of mechanobiology and virology.

Roles of TLR7 in Schistosoma japonicum Infection-Induced Hepatic Pathological Changes in C57BL/6 Mice

S. japonicum infection can induce granulomatous inflammation in the liver of the host. Granulomatous inflammation limits the spread of infection and plays a role in host protection. Toll-like receptor 7 (TLR7) is an endosomal TLR that recognizes single-stranded RNA (ssRNA). In this study, the role of TLR7 in S. japonicum infection-induced hepatitis was investigated in both normal and TLR7 knockout (KO) C57BL/6 mice. The results indicated that TLR7 KO could aggravate S. japonicum infection-induced damage in the body, with less granuloma formation in the tissue, lower WBCs in blood, and decreased ALT and AST in the serum. Then, the expression of TLR7 was detected in isolated hepatic lymphocytes. The results indicated that the percentage of TLR7⁺ cells was increased in the infected mice. Hepatic macrophages, DCs, and B cells could express TLR7, and most of the TLR7-expressing cells in the liver of infected mice were macrophages. The percentage of TLR7-expressing macrophages was also increased after infection. Moreover, macrophages, T cells, and B cells showed significant changes in the counts, activation-associated molecule expression, and cytokine secretion between S. japonicum-infected WT and TLR7 KO mice. Altogether, this study indicated that TLR7 could delay the progression of S. japonicum infection-induced hepatitis mainly through macrophages. DCs, B cells, and T cells were involved in the TLR7-mediated immune response.

Experimental liver models: From cell culture techniques to microfluidic organs-on-chip

The liver is one of the most studied organs of the human body owing to its central role in xenobiotic and drug metabolism. In recent decades, extensive research has aimed at developing in vitro liver models able to mimic liver functions to study pathophysiological clues in high-throughput and reproducible environments. Two-dimensional (2D) models have been widely used in screening potential toxic compounds but have failed to accurately reproduce the three-dimensionality (3D) of the liver milieu. To overcome these limitations, improved 3D culture techniques have been developed to recapitulate the hepatic native microenvironment. These models focus on reproducing the liver architecture, representing both parenchymal and nonparenchymal cells, as well as cell interactions. More recently, Liver-on-Chip (LoC) models have been developed with the aim of providing physiological fluid flow and thus achieving essential hepatic functions. Given their unprecedented ability to recapitulate critical features of the liver cellular environments, LoC have been extensively adopted in pathophysiological modelling and currently represent a promising tool for tissue engineering and drug screening applications. In this review, we discuss the evolution of experimental liver models, from the ancient 2D hepatocyte models, widely used for liver toxicity screening, to 3D and LoC culture strategies adopted for mirroring a more physiological microenvironment for the study of liver diseases.

Role of liver sinusoidal endothelial cells in liver diseases

Liver sinusoidal endothelial cells (LSECs) form the wall of the hepatic sinusoids. Unlike other capillaries, they lack an organized basement membrane and have cytoplasm that is penetrated by open fenestrae, making the hepatic microvascular endothelium discontinuous. LSECs have essential roles in the maintenance of hepatic homeostasis, including regulation of the vascular tone, inflammation and thrombosis, and they are essential for control of the hepatic immune response. On a background of acute or chronic liver injury, LSECs modify their phenotype and negatively affect neighbouring cells and liver disease pathophysiology. This Review describes the main functions and phenotypic dysregulations of LSECs in liver diseases, specifically in the context of acute injury (ischaemia-reperfusion injury, drug-induced liver injury and bacterial and viral infection), chronic liver disease (metabolism-associated liver disease, alcoholic steatohepatitis and chronic hepatotoxic injury) and hepatocellular carcinoma, and provides a comprehensive update of the role of LSECs as therapeutic targets for liver disease. Finally, we discuss the open questions in the field of LSEC pathobiology and future avenues of research.

Tumor Immune Microenvironment and Immunosuppressive Therapy in Hepatocellular Carcinoma: A Review

Liver cancer has the fourth highest mortality rate of all cancers worldwide, with hepatocellular carcinoma (HCC) being the most prevalent subtype. Despite great advances in systemic therapy, such as molecular-targeted agents, HCC has one of the worst prognoses due to drug resistance and frequent recurrence and metastasis. Recently, new therapeutic strategies such as cancer immunosuppressive therapy have prolonged patients' lives, and the combination of an immune checkpoint inhibitor (ICI) and VEGF inhibitor is now positioned as the first-line therapy for advanced HCC. Since the efficacy of ICIs depends on the tumor immune microenvironment, it is necessary to elucidate the immune environment of HCC to select appropriate ICIs. In this review, we summarize the findings on the immune microenvironment and immunosuppressive approaches focused on monoclonal antibodies against cytotoxic T lymphocyte-associated protein 4 and programmed cell death protein 1 for HCC. We also describe ongoing treatment modalities, including adoptive cell transfer-based therapies and future areas of exploration based on recent literature. The results of pre-clinical studies using immunological classification and animal models will contribute to the development of biomarkers that predict the efficacy of immunosuppressive therapy and aid in the selection of appropriate strategies for HCC treatment.

Stabilin-1 is required for the endothelial clearance of small anionic nanoparticles

Clearance of nanoparticles (NPs) after intravenous injection - mainly by the liver - is a critical barrier for the clinical translation of nanomaterials. Physicochemical properties of NPs are known to influence their distribution through cell-specific interactions; however, the molecular mechanisms responsible for liver cellular NP uptake are poorly understood. Liver sinusoidal endothelial cells and Kupffer cells are critical participants in this clearance process. Here we use a zebrafish model for liver-NP interaction to identify the endothelial scavenger receptor Stabilin-1 as a non-redundant receptor for the clearance of small anionic NPs. Furthermore, we show that physiologically, Stabilin-1 is required for the removal of bacterial lipopolysaccharide (LPS/endotoxin) from circulation and that Stabilin-1 cooperates with its homolog Stabilin-2 in the clearance of larger (~100 nm) anionic NPs. Our findings allow optimization of anionic nanomedicine biodistribution and targeting therapies that use Stabilin-1 and -2 for liver endothelium-specific delivery.

Translation of IRF-1 Restricts Hepatic Interleukin-7 Production to Types I and II Interferons: Implications for Hepatic Immunity

Interleukin-7 (IL-7) is an important cytokine with pivotal pro-survival functions in the adaptive immune system. However, the role of IL-7 in innate immunity is not fully understood. In the present study, the impact of hepatic IL-7 on innate immune cells was assessed by functional experiments as well as in patients with different stages of liver cirrhosis or acute-on-chronic liver failure (ACLF). Human hepatocytes and liver sinusoidal endothelial cells secreted IL-7 in response to stimulation with interferons (IFNs) of type I and II, yet not type III. De novo translation of interferon-response factor-1 (IRF-1) restricted IL-7 production to stimulation with type I and II IFNs. LPS-primed human macrophages were identified as innate immune target cells responding to IL-7 signaling by inactivation of Glycogen synthase kinase-3 (GSK3). IL-7-mediated GSK3 inactivation augmented LPS-induced secretion of pro-inflammatory cytokines and blunted LPS tolerance of macrophages. The IFN-IRF-1-IL-7 axis was present in liver cirrhosis patients. However, liver cirrhosis patients with or without ACLF had significantly lower concentrations of IL-7 in serum compared to healthy controls, which might contribute to LPS-tolerance in these patients. In conclusion, we propose the presence of an inflammatory cascade where IFNs of type I/II induce hepatocellular IL-7 in an IRF-1-restriced way. Beyond its role in adaptive immune responses, IL-7 appears to augment the response of macrophages to LPS and to ameliorate LPS tolerance, which may improve innate immune responses against invading pathogens.

Changes in and effects of Kupffer cells on residual tumor after cryoablation in rabbit hepatic VX2 tumor

OBJECTIVE

Cryoablation can directly kill tumor cells through sudden changes in temperature. It can also enhance lymphocyte function and cause distant tumor regression far from the ablation treatment area. In order to further explore the changes of immune function after cryoablation, the changes of Kupffer cells (KCs), the main immune cells in the liver, and their effects on untreated tumors in vivo were studied.

METHODS

Rabbit VX2 liver cancer models were constructed. The growth of liver tumors was confirmed by ultrasound after transplantation for 3 weeks. Fifteen Japanese white rabbits were divided into a tumor control group and cryoablation group. Cryoablation group was treated with cryoablation of a single or partial tumor. Histologic and immunohistochemical changes of the treatment area and untreated tumor area before and after cryoablation were observed, and the phagocytic function changes of KCs around the untreated area and treatment area were observed by electron microscopy.

RESULTS

Cryoablation areas showed necrosis, infiltration of inflammatory cells (including KCs), and fibrosis of tissue. The number of inflammatory cells in the unfrozen tumor area was increased in the same treated rabbit. There was a significant difference in the maximum diameter of unfrozen tumors between the frozen group and control group at 15th days after cryoablation (P<0.05), while the difference was not obvious at the 3rd and 7th day (P>0.05). Electron microscopy showed that the number of debris fragments engulfed by KCs around the tumor after cryoablation was significantly higher than that of the control group. In the same rabbit, we compared the amount of debris between tissue surrounding the unfrozen area and around the cryoablation area. There was a significant difference on the 3rd day after cryoablation, P=0.043, while there was no significant difference on the 7th day, P=0.348.

CONCLUSION

After cryoablation, inflammatory cells aggregated around the cryoablated area. The activity of KCs had been increased and the function of phagocytosis enhanced. KCs had a certain inhibitory effect on the untreated tumor in the same animal at the early stage (within 15 days), but it was not enough to restrain the growth of the untreated tumors.

Emerging Role of Immunotherapy for Colorectal Cancer with Liver Metastasis

Colorectal cancer (CRC) is the third most common malignant tumor in the world and the second leading cause of cancer-related deaths, with the liver as the most common site of distant metastasis. The prognosis of CRC with liver metastasis is poor, and most patients cannot undergo surgery. In addition, conventional antitumor approaches such as chemotherapy, radiotherapy, targeted therapy, and surgery result in unsatisfactory outcomes. In recent years, immunotherapy has shown good prospects in the treatment of assorted tumors by enhancing the host's antitumor immune function, and it may become a new effective treatment for liver metastasis of CRC. However, challenges remain in applying immunotherapy to CRC with liver metastasis. This review examines how the microenvironment and immunosuppressive landscape of the liver favor tumor progression. It also highlights the latest research advances in immunotherapy for colorectal liver metastasis and identifies immunotherapy as a treatment regimen with a promising future in clinical applications.

Tumor microenvironment conditions that favor vessel co-option in colorectal cancer liver metastases: A theoretical model

Vessel co-option is an alternative strategy by which tumour cells vascularize and gain access to nutrients to support tumour growth, survival and metastasis. In vessel co-option, the cancer cells move towards the pre-existing vasculature and hijack them. Vessel co-option is adopted by a wide range of human tumours including colorectal cancer liver metastases (CRCLM) and is responsible for the effectiveness of treatment in CRCLM. Furthermore, vessel co-option is an intrinsic feature and an acquired mechanism of resistance to anti-angiogenic treatment. In this review, we describe the microenvironment, the molecular players, discovered thus far of co-opting CRCLM lesions and propose a theoretical model. We also highlight key unanswered questions that are critical to improving our understanding of CRCLM vessel co-option and for the development of effective approaches for the treatment of co-opting tumours.

Tumor microenvironment in primary liver tumors: A challenging role of natural killer cells

In the last years, several studies have been focused on elucidate the role of tumor microenvironment (TME) in cancer development and progression. Within TME, cells from adaptive and innate immune system are one of the main abundant components. The dynamic interactions between immune and cancer cells lead to the activation of complex molecular mechanisms that sustain tumor growth. This important cross-talk has been elucidate for several kind of tumors and occurs also in patients with liver cancer, such as hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA). Liver is well-known to be an important immunological organ with unique microenvironment. Here, in normal conditions, the rich immune-infiltrating cells cooperate with non-parenchymal cells, such as liver sinusoidal endothelial cells and Kupffer cells, favoring self-tolerance against gut antigens. The presence of underling liver immunosuppressive microenvironment highlights the importance to dissect the interaction between HCC and iCCA cells with immune infiltrating cells, in order to understand how this cross-talk promotes tumor growth. Deeper attention is, in fact, focused on immune-based therapy for these tumors, as promising approach to counteract the intrinsic anti-tumor activity of this microenvironment. In this review, we will examine the key pathways underlying TME cell-cell communications, with deeper focus on the role of natural killer cells in primary liver tumors, such as HCC and iCCA, as new opportunities for immune-based therapeutic strategies.

The Role of Sinusoidal Endothelial Cells in the Axis of Inflammation and Cancer Within the Liver

Liver sinusoidal endothelial cells (LSEC) form a unique barrier between the liver sinusoids and the underlying parenchyma, and thus play a crucial role in maintaining metabolic and immune homeostasis, as well as actively contributing to disease pathophysiology. Whilst their endocytic and scavenging function is integral for nutrient exchange and clearance of waste products, their capillarisation and dysfunction precedes fibrogenesis. Furthermore, their ability to promote immune tolerance and recruit distinct immunosuppressive leukocyte subsets can allow persistence of chronic viral infections and facilitate tumour development. In this review, we present the immunological and barrier functions of LSEC, along with their role in orchestrating fibrotic processes which precede tumourigenesis. We also summarise the role of LSEC in modulating the tumour microenvironment, and promoting development of a pre-metastatic niche, which can drive formation of secondary liver tumours. Finally, we summarise closely inter-linked disease pathways which collectively perpetuate pathogenesis, highlighting LSEC as novel targets for therapeutic intervention.

Kupffer cells promote T-cell hepatitis by producing CXCL10 and limiting liver sinusoidal endothelial cell permeability

Rationale: Kupffer cells (KCs) play a crucial role in liver immune homeostasis through interacting with other immune cells and liver sinusoidal endothelial cells (LSECs). However, how KCs exactly interact with these cells for maintaining the homeostasis still require the further investigation. CXCL10 is a chemokine that has been implicated in chemoattraction of monocytes, T cells, NK cells, and dendritic cells, and promotion of T cell adhesion to endothelial cells. Although CXCL10 is also known to participate in the pathogenesis of hepatic inflammation, the degree to which it is functionally involved in the crosstalk between immune cells and regulation of immune response is still unclear.

Methods: To dynamically investigate the function of KCs, we used our recently developed rapid cell ablation model, intermedilysin (ILY)/human CD59 (hCD59)-mediated cell ablation tool, to selectively ablate KC pool under normal condition or concanavalin A (Con A)- induced hepatitis. At certain time points after KCs ablation, we performed flow cytometry to monitor the amount of hepatic infiltrating immune cells. mRNA array was used to detect the change of hepatic cytokines and chemokines levels. Cytokines and chemokines in the serum were further measured by LEGENDplex^TM mouse proinflammatory chemokine panel and inflammation panel. Evans blue staining and transmission electron microscopy were used to investigate the interaction between KCs and LSECs in steady condition. CXCL10 neutralizing antibody and CXCL10 deficient mouse were used to study the role of CXCL10 in immune cell migration and pathogenesis of Con A-induced hepatitis.

Results: At steady state, elimination of KCs results in a reduction of hepatic infiltrating monocytes, T, B, and NK cells and a list of cytokines and chemokines at transcriptional level. In the meantime, the depletion of KCs resulted in increased sinusoidal vascular permeability. In the pathological condition, the KCs elimination rescues Con A-induced acute hepatitis through suppressing proinflammatory immune responses by down-regulation of hepatitis-associated cytokines/chemokines in serum such as CXCL10, and recruitment of infiltrating immune cells (monocytes, T, B, and NK cells). We further documented that deficiency or blockade of CXCL10 attenuated the development of Con A-induced hepatitis associated with reduction of the infiltrating monocytes, especially inflammatory Ly6C^hi monocytes.

Conclusions: This study supports the notion that KCs actively interact with immune cells and LSECs for maintaining immune response and liver homeostasis. Our data indicate that the interplay between KCs and infiltrated monocytes via CXCL10 contribute to Con A-induced hepatitis.

The Emerging Jamboree of Transformative Therapies for Autoimmune Diseases

Standard treatments for autoimmune and autoinflammatory disorders rely mainly on immunosuppression. These are predominantly symptomatic remedies that do not affect the root cause of the disease and are associated with multiple side effects. Immunotherapies are being developed during the last decades as more specific and safer alternatives to small molecules with broad immunosuppressive activity, but they still do not distinguish between disease-causing and protective cell targets and thus, they still have considerable risks of increasing susceptibility to infections and/or malignancy. Antigen-specific approaches inducing immune tolerance represent an emerging trend carrying the potential to be curative without inducing broad immunosuppression. These therapies are based on antigenic epitopes derived from the same proteins that are targeted by the autoreactive T and B cells, and which are administered to patients together with precise instructions to induce regulatory responses capable to restore homeostasis. They are not personalized medicines, and they do not need to be. They are precision therapies exquisitely targeting the disease-causing cells that drive pathology in defined patient populations. Immune tolerance approaches are truly transformative options for people suffering from autoimmune diseases.

Sensitivity of Kupffer cells and liver sinusoidal endothelial cells to ricin toxin and ricin toxin-Ab complexes

Ricin toxin is a plant-derived, ribosome-inactivating protein that is rapidly cleared from circulation by Kupffer cells (KCs) and liver sinusoidal endothelial cells (LSECs)-with fatal consequences. Rather than being inactivated, ricin evades normal degradative pathways and kills both KCs and LSECs with remarkable efficiency. Uptake of ricin by these 2 specialized cell types in the liver occurs by 2 parallel routes: a "lactose-sensitive" pathway mediated by ricin's galactose/N-acetylgalactosamine-specific lectin subunit (RTB), and a "mannose-sensitive" pathway mediated by the mannose receptor (MR; CD206) or other C-type lectins capable of recognizing the mannose-side chains displayed on ricin's A (RTA) and B subunits. In this report, we investigated the capacity of a collection of ricin-specific mouse MAb and camelid single-domain (VH H) antibodies to protect KCs and LSECs from ricin-induced killing. In the case of KCs, individual MAbs against RTA or RTB afforded near complete protection against ricin in ex vivo and in vivo challenge studies. In contrast, individual MAbs or VH Hs afforded little (<40%) or even no protection to LSECs against ricin-induced death. Complete protection of LSECs was only achieved with MAb or VH H cocktails, with the most effective mixtures targeting RTA and RTB simultaneously. Although the exact mechanisms of protection of LSECs remain unknown, evidence indicates that the Ab cocktails exert their effects on the mannose-sensitive uptake pathway without the need for Fcγ receptor involvement. In addition to advancing our understanding of how toxins and small immune complexes are processed by KCs and LSECs, our study has important implications for the development of Ab-based therapies designed to prevent or treat ricin exposure should the toxin be weaponized.

Chronic Hepatitis C Virus Infection Impairs M1 Macrophage Differentiation and Contributes to CD8+ T-Cell Dysfunction

Chronic hepatitis C virus (HCV) infection causes generalized CD8+ T cell impairment, not limited to HCV-specific CD8+ T-cells. Liver-infiltrating monocyte-derived macrophages (MDMs) contribute to the local micro-environment and can interact with and influence cells routinely trafficking through the liver, including CD8+ T-cells. MDMs can be polarized into M1 (classically activated) and M2a, M2b, and M2c (alternatively activated) phenotypes that perform pro- and anti-inflammatory functions, respectively. The impact of chronic HCV infection on MDM subset functions is not known. Our results show that M1 cells generated from chronic HCV patients acquire M2 characteristics, such as increased CD86 expression and IL-10 secretion, compared to uninfected controls. In contrast, M2 subsets from HCV-infected individuals acquired M1-like features by secreting more IL-12 and IFN-γ. The severity of liver disease was also associated with altered macrophage subset differentiation. In co-cultures with autologous CD8+ T-cells from controls, M1 macrophages alone significantly increased CD8+ T cell IFN-γ expression in a cytokine-independent and cell-contact-dependent manner. However, M1 macrophages from HCV-infected individuals significantly decreased IFN-γ expression in CD8+ T-cells. Therefore, altered M1 macrophage differentiation in chronic HCV infection may contribute to observed CD8+ T-cell dysfunction. Understanding the immunological perturbations in chronic HCV infection will lead to the identification of therapeutic targets to restore immune function in HCV+ individuals, and aid in the mitigation of associated negative clinical outcomes.

Transient liver dysfunction increases surgical site infections after coronary surgery

Background

Surgical site infections can have a significant impact on cardiac surgical outcome. The liver plays an important role in infection prevention. This study aimed to retrospectively determine whether transient postoperative liver dysfunction after coronary bypass surgery increased surgical site infections.

Methods

A modified version of the Schindl scoring scale for liver dysfunction was adapted to objectively quantify transient liver dysfunction in the first 7 days after on-pump coronary artery bypass grafting. A retrospective analysis of clinical outcomes at 30 months postoperatively was performed on data of 575 patients who underwent coronary artery bypass between 2014 and 2016. The patients were categorized into a liver dysfunction group (Schindl score ≥ 4) and a non-liver dysfunction group (Schindl score < 4).

Results

The liver dysfunction group (47.3%) had significantly more patients who were obese, current smokers, and had diabetes, renal impairment, and peripheral vascular disease. Surgical site infections occurred predominantly in the liver dysfunction group (12.1% vs. 0.3%, p < 0.001). The independent predictors of surgical site infection were liver dysfunction, body mass index > 30 kg m−2, and coronary bypass surgery combined with other cardiac procedures.

Conclusions

Surgical wound infections can be precipitated by multiple factors before, during, and after coronary bypass surgery. Transient liver dysfunction in the perioperative period is associated with an increased rate of surgical infections even after adjusting for known risk factors. Considering this factor as well as other known risks may help to identify and stratify patients with a potentially higher risk of surgical site infections.

Dysfunctional phagocytosis capacity, granulocyte recruitment and inflammatory factor secretion of Kupffer cells in diabetes mellitus reversed by Lidocaine

PURPOSE

Kupffer cells (KCs) present dysfunctional immunity capacity among the diabetes mellitus patients. This study aims to investigate whether Lidocaine could reverse dysfunctions of KCs, in terms of phagocytosis, granulocyte recruitment and inflammatory mediator secretion.

METHODS

db/db and C57BL/6 mice were employed to establish diabetic and nondiabetic models. Upon intravenous injection of Lidocaine, KCs were isolated and cultured ex vivo. The functions of phagocytosis, recruiting granulocytes and inflammatory mediator secretion in KCs were compared between Lidocaine-treated and untreated (control) groups.

RESULTS

Comparing with nondiabetic mice, KCs in diabetic mice presented reduced phagocytosis, activated granulocyte recruitment, increased expression of intercellular cell adhesion molecule-1 (ICAM-1) and activated levels of inflammatory mediators. With Lidocaine injection, phagocytic functions of KCs in diabetic mice were improved significantly; in contrast, recruitment of granulocytes, expression of ICAM-1 and secretion of inflammatory mediators were reduced markedly. However, Lidocaine intervention did not alter KC functions in phagocytosis, granulocyte recruitment, ICAM-1 expression or inflammatory mediator secretion among nondiabetic mice.

CONCLUSION

Lidocaine reversed diabetes-related dysfunctions of KCs in terms of phagocytosis, granulocyte recruitment, ICAM-1 expression or inflammatory mediator secretion.

Pathological process of liver sinusoidal endothelial cells in liver diseases

Cirrhosis develops from liver fibrosis and is the severe pathological stage of all chronic liver injury. Cirrhosis caused by hepatitis B virus and hepatitis C virus infection is especially common. Liver fibrosis and cirrhosis involve excess production of extracellular matrix, which is closely related to liver sinusoidal endothelial cells (LSECs). Damaged LSECs can synthesize transforming growth factor-beta and platelet-derived growth factor, which activate hepatic stellate cells and facilitate the synthesis of extracellular matrix. Herein, we highlight the angiogenic cytokines of LSECs related to liver fibrosis and cirrhosis at different stages and focus on the formation and development of liver fibrosis and cirrhosis. Inhibition of LSEC angiogenesis and antiangiogenic therapy are described in detail. Targeting LSECs has high therapeutic potential for liver diseases. Further understanding of the mechanism of action will provide stronger evidence for the development of anti-LSEC drugs and new directions for diagnosis and treatment of liver diseases.