Capillarization of hepatic sinusoid by liver endothelial cell-reactive autoantibodies in patients with cirrhosis and chronic hepatitis

Angiocrine signaling in sinusoidal homeostasis and liver diseases

The hepatic sinusoids are composed of liver sinusoidal endothelial cells (LSECs), which are surrounded by hepatic stellate cells (HSCs) and contain liver-resident macrophages called Kupffer cells, and other patrolling immune cells. All these cells communicate with each other and with hepatocytes to maintain sinusoidal homeostasis and a spectrum of hepatic functions under healthy conditions. Sinusoidal homeostasis is disrupted by metabolites, toxins, viruses, and other pathological factors, leading to liver injury, chronic liver diseases, and cirrhosis. Alterations in hepatic sinusoids are linked to fibrosis progression and portal hypertension. LSECs are crucial regulators of cellular crosstalk within their microenvironment via angiocrine signaling. This review discusses the mechanisms by which angiocrine signaling orchestrates sinusoidal homeostasis, as well as the development of liver diseases. Here, we summarise the crosstalk between LSECs, HSCs, hepatocytes, cholangiocytes, and immune cells in health and disease and comment on potential novel therapeutic methods for treating liver diseases.

Dynamics of Endothelial Cell Diversity and Plasticity in Health and Disease

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity.

Targeting chronic liver diseases: Molecular markers, drug delivery strategies and future perspectives

Chronic liver inflammation, a pervasive global health issue, results in millions of annual deaths due to its progression from fibrosis to the more severe forms of cirrhosis and hepatocellular carcinoma (HCC). This insidious condition stems from diverse factors such as obesity, genetic conditions, alcohol abuse, viral infections, autoimmune diseases, and toxic accumulation, manifesting as chronic liver diseases (CLDs) such as metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic dysfunction-associated steatohepatitis (MASH), alcoholic liver disease (ALD), viral hepatitis, drug-induced liver injury, and autoimmune hepatitis. Late detection of CLDs necessitates effective treatments to inhibit and potentially reverse disease progression. However, current therapies exhibit limitations in consistency and safety. A potential breakthrough lies in nanoparticle-based drug delivery strategies, offering targeted delivery to specific liver cell types, such as hepatocytes, Kupffer cells, and hepatic stellate cells. This review explores molecular targets for CLD treatment, ongoing clinical trials, recent advances in nanoparticle-based drug delivery, and the future outlook of this research field. Early intervention is crucial for chronic liver disease. Having a comprehensive understanding of current treatments, molecular biomarkers and novel nanoparticle-based drug delivery strategies can have enormous impact in guiding future strategies for the prevention and treatment of CLDs.

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.

Role of liver sinusoidal endothelial cell in metabolic dysfunction-associated fatty liver disease

Liver sinusoidal endothelial cells (LSECs) are highly specialized endothelial cells that represent the interface between blood cells on one side and hepatocytes on the other side. LSECs not only form a barrier within the hepatic sinus, but also play important physiological functions such as regulating hepatic vascular pressure, anti-inflammatory and anti-fibrotic. Pathologically, pathogenic factors can induce LSECs capillarization, that is, loss of fenestra and dysfunction, which are conducive to early steatosis, lay the foundation for the progression of metabolic dysfunction-associated fatty liver disease (MAFLD), and accelerate metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis. The unique localization, phenotype, and function of LSECs make them potential candidates for reducing liver injury, inflammation, and preventing or reversing fibrosis in the future.

Protein disulfide isomerase A1 regulates fenestration dynamics in primary mouse liver sinusoidal endothelial cells (LSECs)

Protein disulfide isomerases (PDIs) are involved in many intracellular and extracellular processes, including cell adhesion and cytoskeletal reorganisation, but their contribution to the regulation of fenestrations in liver sinusoidal endothelial cells (LSECs) remains unknown. Given that fenestrations are supported on a cytoskeleton scaffold, this study aimed to investigate whether endothelial PDIs regulate fenestration dynamics in primary mouse LSECs. PDIA3 and PDIA1 were found to be the most abundant among PDI isoforms in LSECs. Taking advantage of atomic force microscopy, the effects of PDIA1 or PDIA3 inhibition on the fenestrations in LSECs were investigated using a classic PDIA1 inhibitor (bepristat) and novel aromatic N-sulfonamides of aziridine-2-carboxylic acid derivatives as PDIA1 (C-3389) or PDIA3 (C-3399) inhibitors. The effect of PDIA1 inhibition on liver perfusion was studied in vivo using dynamic contrast-enhanced magnetic resonance imaging. Additionally, PDIA1 inhibitors were examined in vitro in LSECs for effects on adhesion, cytoskeleton organisation, bioenergetics, and viability. Inhibition of PDIA1 with bepristat or C-3389 significantly reduced the number of fenestrations in LSECs, while inhibition of PDIA3 with C-3399 had no effect. Moreover, the blocking of free thiols by the cell-penetrating N-ethylmaleimide, but not by the non-cell-penetrating 4-chloromercuribenzenesulfonate, resulted in LSEC defenestration. Inhibition of PDIA1 did not affect LSEC adhesion, viability, and bioenergetics, nor did it induce a clear-cut rearrangement of the cytoskeleton. However, PDIA1-dependent defenestration was reversed by cytochalasin B, a known fenestration stimulator, pointing to the preserved ability of LSECs to form new pores. Importantly, systemic inhibition of PDIA1 in vivo affected intra-parenchymal uptake of contrast agent in mice consistent with LSEC defenestration. These results revealed the role of intracellular PDIA1 in the regulation of fenestration dynamics in LSECs, and in maintaining hepatic sinusoid homeostasis.

Single-Cell Transcriptomics Reveals the Ameliorative Effect of Oridonin on Septic Liver Injury

Sepsis is a life-threatening syndrome leading to hemodynamic instability and potential organ dysfunction. Oridonin, commonly used in Traditional Chinese Medicine (TCM), exhibits significant anti-inflammation activity. To explore the protective mechanisms of oridonin against the pathophysiological changes, the authors conducted single-cell transcriptome (scRNA-seq) analysis on septic liver models induced by cecal ligation and puncture (CLP). They obtained a total of 63,486 cells, distributed across 11 major cell clusters, and concentrated their analysis on four specific clusters (hepatocytes/Heps, macrophages, endothelial/Endos and T/NK) based on their changes in proportion during sepsis and under oridonin treatment. Firstly, biological changes in Hep, which are related to metabolic dysregulation and pro-inflammatory signaling, are observed during sepsis. Secondly, they uncovered the dynamic profiles of macrophage's phenotype, indicating that a substantial number of macrophages exhibited a M1-skewed phenotype associated with pro-inflammatory characteristics in septic model. Thirdly, they detected an upregulation of both inflammatory cytokines and transcriptomic factor Nfkb1 expression within Endo, along with slight capillarization during sepsis. Moreover, excessive accumulation of cytotoxic NK led to an immune imbalance. Though, oridonin ameliorated inflammatory-related responses and improved the liver dysfunction in septic mice. This study provides fundamental evidence of the protective effects of oridonin against sepsis-induced cytokine storm.

Senescence of Hepatic Stellate Cells by Specific Delivery of Manganese for Limiting Liver Fibrosis

Senescence of activated hepatic stellate cells (HSCs) is crucial for the regression of liver fibrosis. However, impaired immune clearance can result in the accumulation of senescent HSCs, exacerbating liver fibrosis. The activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway is essential for both senescence and the innate immune response. Additionally, the specific delivery to activated HSCs is hindered by their inaccessible anatomical location, capillarization of liver sinusoidal endothelial cells (LSECs), and loss of substance exchange. Herein, we propose an antifibrotic strategy that combines prosenescence with enhanced immune clearance through targeted delivery of manganese (a cGAS-STING stimulator) via albumin-mediated transcytosis, specifically aimed at inducing senescence and eliminating activated HSCs in liver fibrosis. Our findings demonstrate that only albumin efficiently transfers manganese to activated HSCs from LSECs via transcytosis compared to liposomes, resulting in significant antifibrotic effects in vivo while exhibiting negligible toxicity.

27-Hydroxycholesterol induces liver fibrosis via down-regulation of trimethylation of histone H3 at lysine 27 by activating oxidative stress; effect of nutrient interventions

BACKGROUND

Chronic liver injury caused by activation of hepatic stellate cells (HSCs) is a key event in the development of liver fibrosis (LF). A high-cholesterol diet can prompt accumulation of free cholesterol in HSCs, which promotes HSC activation and progression of LF.

OBJECTIVE

27-Hydroxycholesterol (27HC) is the most abundant cholesterol metabolite. Here, we investigated whether the HSC activation and LF induced by high cholesterol is caused by its metabolite 27HC, and whether TGFβ classical signaling were involved in these processes.

METHODS

In vitro, LX2 and HSC-T6 cells were used to explore the effects of 27HC on activation of HSCs, while LSECs were used to observe the effects of 27HC on capillarization. In vivo, zebrafish were used to assess the effect of 27HC on LF.

RESULTS

The cholesterol metabolite 27HC promoted the proliferation of HSCs and up-regulated expression of COL-1 and α-SMA as well as CTGF and TIMP1. Also, 27HC up-regulated expression of Smad2/3 and phosphorylated Smad2/3 in HSCs. Furthermore, 27HC-induced up-regulation of COL-1, α-SMA, CTGF, and TIMP1 protein levels was inhibited by Smad2/3 knockout. In addition, 27HC down-regulated H3K27me3 by inhibition of EZH2 and promotion of UTX and JMJD3 expression via the TGFβ signaling, thereby inducing activation of HSCs. Notably, 27HC significantly aggravated the pathological damage induced by DEN, and induced deposition of collagen fibers in zebrafish liver. Folic acid (FA) and resveratrol (RES) both reduced 27HC-induced production of reactive oxygen species (ROS) and inhibited the effects of TGFβ signaling on EZH2, UTX, and JMJD3, thereby increasing H3K27me3, and finally jointly inhibiting LF.

CONCLUSION

Cholesterol is metabolized to 27HC, which mediates activation of HSCs and onset of LF. Reduced expression of H3k27me3 by TGFβ signaling is crucial to 27HC-induced LF. FA and RES ameliorated activation of HSCs and LF by reducing 27HC-induced production of ROS and regulating of H3K27me3.

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

Decellularization Techniques for Tissue Engineering: Towards Replicating Native Extracellular Matrix Architecture in Liver Regeneration

The process of tissue regeneration requires the utilization of a scaffold, which serves as a structural framework facilitating cellular adhesion, proliferation, and migration within a physical environment. The primary aim of scaffolds in tissue engineering is to mimic the structural and functional properties of the extracellular matrix (ECM) in the target tissue. The construction of scaffolds that accurately mimic the architecture of the extracellular matrix (ECM) is a challenging task, primarily due to the intricate structural nature and complex composition of the ECM. The technique of decellularization has gained significant attention in the field of tissue regeneration because of its ability to produce natural scaffolds by removing cellular and genetic components from the extracellular matrix (ECM) while preserving its structural integrity. The present study aims to investigate the various decellularization techniques employed for the purpose of isolating the extracellular matrix (ECM) from its native tissue. Additionally, a comprehensive comparison of these methods will be presented, highlighting their respective advantages and disadvantages. The primary objective of this study is to gain a comprehensive understanding of the anatomical and functional features of the native liver, as well as the prevalence and impact of liver diseases. Additionally, this study aims to identify the limitations and difficulties associated with existing therapeutic methods for liver diseases. Furthermore, the study explores the potential of tissue engineering techniques in addressing these challenges and enhancing liver performance. By investigating these aspects, this research field aims to contribute to the advancement of liver disease treatment and management.

Optimization of Statin-Loaded Delivery Nanoparticles for Treating Chronic Liver Diseases by Targeting Liver Sinusoidal Endothelial Cells

In this study, we developed functionalized polymeric micelles (FPMs) loaded with simvastatin (FPM-Sim) as a drug delivery system to target liver sinusoidal endothelial cells (LSECs) for preserving liver function in chronic liver disease (CLD). Polymeric micelles (PMs) were functionalized by coupling peptide ligands of LSEC membrane receptors CD32b, CD36 and ITGB3. Functionalization was confirmed via spectroscopy and electron microscopy. In vitro and in vivo FPM-Sim internalization was assessed by means of flow cytometry in LSECs, hepatocytes, Kupffer and hepatic stellate cells from healthy rats. Maximum tolerated dose assays were performed in healthy mice and efficacy studies of FPM-Sim were carried out in bile duct ligation (BDL) and thioacetamide (TAA) induction rat models of cirrhosis. Functionalization with the three peptide ligands resulted in stable formulations with a greater degree of in vivo internalization in LSECs than non-functionalized PMs. Administration of FPM-Sim in BDL rats reduced toxicity relative to free simvastatin, albeit with a moderate portal-pressure-lowering effect. In a less severe model of TAA-induced cirrhosis, treatment with FPM-CD32b-Sim nanoparticles for two weeks significantly decreased portal pressure, which was associated with a reduction in liver fibrosis, lower collagen expression as well as the stimulation of nitric oxide synthesis. In conclusion, CD32b-FPM stands out as a good nanotransporter for drug delivery, targeting LSECs, key inducers of liver injury.

Oxidative Stress-Induced Liver Damage and Remodeling of the Liver Vasculature

As an organ critically important for targeting and clearing viruses, bacteria, and other foreign material, the liver operates via immune-tolerant, anti-inflammatory mechanisms indispensable to the immune response. Stress and stress-induced factors disrupt the homeostatic balance in the liver, inflicting tissue damage, injury, and remodeling. These factors include oxidative stress (OS) induced by viral infections, environmental toxins, drugs, alcohol, and diet. A recurrent theme seen among stressors common to multiple liver diseases is the induction of mitochondrial dysfunction, increased reactive oxygen species expression, and depletion of ATP. Inflammatory signaling additionally exacerbates the condition, generating a proinflammatory, immunosuppressive microenvironment and activation of apoptotic and necrotic mechanisms that disrupt the integrity of liver morphology. These pathways initiate signaling pathways that significantly contribute to the development of liver steatosis, inflammation, fibrosis, cirrhosis, and liver cancers. In addition, hypoxia and OS directly enhance angiogenesis and lymphangiogenesis in chronic liver diseases. Late-stage consequences of these conditions often narrow the outcomes for liver transplantation or result in death. This review provides a detailed perspective on various stress-induced factors and the specific focus on role of OS in different liver diseases with special emphasis on different molecular mechanisms. It also highlights how resultant changes in the liver vasculature correlate with pathogenesis.

An idiosyncratic zonated stroma encapsulates desmoplastic liver metastases and originates from injured liver

A perimetastatic capsule is a strong positive prognostic factor in liver metastases, but its origin remains unclear. Here, we systematically quantify the capsule's extent and cellular composition in 263 patients with colorectal cancer liver metastases to investigate its clinical significance and origin. We show that survival improves proportionally with increasing encapsulation and decreasing tumor-hepatocyte contact. Immunostaining reveals the gradual zonation of the capsule, transitioning from benign-like NGFRhigh stroma at the liver edge to FAPhigh stroma towards the tumor. Encapsulation correlates with decreased tumor viability and preoperative chemotherapy. In mice, chemotherapy and tumor cell ablation induce capsule formation. Our results suggest that encapsulation develops where tumor invasion into the liver plates stalls, representing a reparative process rather than tumor-induced desmoplasia. We propose a model of metastases growth, where the efficient tumor colonization of the liver parenchyma and a reparative liver injury reaction are opposing determinants of metastasis aggressiveness.

Proteomic Analysis of Dysfunctional Liver Sinusoidal Endothelial Cells Reveals Substantial Differences in Most Common Experimental Models of Chronic Liver Diseases

Molecular markers of dedifferentiation of dysfunctional liver sinusoidal endothelial cells (LSEC) have not been fully elucidated. We aimed at deciphering the molecular profile of dysfunctional LSEC in different pathological scenarios. Flow cytometry was used to sort CD11b-/CD32b+ and CD11b-/CD32b- LSEC from three rat models of liver disease (bile duct ligation-BDL; inhaled carbon tetrachloride-CCl4; and high fat glucose/fructose diet-HFGFD). A full proteomic profile was performed applying nano-scale liquid chromatography tandem mass spectrometry (nLC-MS) and analyzed with PEAKS software. The percentage of CD32b- LSEC varied across groups, suggesting different capillarization processes. Both CD32+ and CD32b- LSEC from models are different from control LSEC, but differently expressed proteins in CD32b- LSEC are significantly higher. Heatmaps evidenced specific protein expression patterns for each model. Analysis of biological significance comparing dysfunctional CD32b- LSEC with specialized CD32b+ LSEC from controls showed central similarities represented by 45 common down-regulated proteins involved in the suppression of the endocytic machinery and 63 common up-regulated proteins associated with the actin-dependent cytoskeleton reorganization. In summary; substantial differences but also similarities in dysfunctional LSEC from the three most common models of liver disease were found, supporting the idea that LSEC may harbor different protein expression profiles according to the etiology or disease stage.

Novel fluorescence biosensor custom-made for protein tyrosine phosphatase 1B detection based on titanium dioxide-decorated single-walled carbon nanohorn nanocomposite

This paper presents a new fluorescent approach for the detection of protein tyrosine phosphatase 1B (PTP1B) based on titanium dioxide-decorated single-wall carbon nanohorns (TiO₂-SWCNHs). The novel TiO₂-SWCNHs nanocomposite was synthesized and characterized for the first time and the phosphorylated peptide as the substrate of PTP1B was designed. Properties of SWCNHs and TiO₂ were combined by growing nano-sized TiO₂ particles on SWCNHs, resulting in TiO₂-SWCNHs. TiO₂ provides SWCNHs a large adsorption surface area and can specifically bind to phosphopeptide substrate. TiO₂-SWCNHs effectively quenched the fluorescence of the phosphorylated peptide substrate labeled by the fluorophore, and the system had a low fluorescence background. In the presence of PTP1B, dephosphorylation of the peptide occurred owing to the reaction between PTP1B and the peptide, causing the separation of the dye-labeled peptide from TiO₂-SWCNHs, which resulted in fluorescence enhancement of the reaction system. Thus, a simple and rapid strategy for the detection of PTP1B activity was developed, with a detection limit of 0.01 ng/mL and linear range of 0-10 ng/mL. The system can be used to detect PTP1B in serum using the standard addition method. This system provides a new approach for screening PTP1B inhibitors.

Defenestrated endothelium delays liver-directed gene transfer in hemophilia A mice

Hemophilia A is an inherited bleeding disorder caused by defective or deficient coagulation factor VIII (FVIII) activity. Until recently, the only treatment for prevention of bleeding involved IV administration of FVIII. Gene therapy with adeno-associated vectors (AAVs) has shown some efficacy in patients with hemophilia A. However, limitations persist due to AAV-induced cellular stress, immunogenicity, and reduced durability of gene expression. Herein, we examined the efficacy of liver-directed gene transfer in FVIII knock-out mice by AAV8-GFP. Surprisingly, compared with control mice, FVIII knockout (F8TKO) mice showed significant delay in AAV8-GFP transfer in the liver. We found that the delay in liver-directed gene transfer in F8TKO mice was associated with absence of liver sinusoidal endothelial cell (LSEC) fenestration, which led to aberrant expression of several sinusoidal endothelial proteins, causing increased capillarization and decreased permeability of LSECs. This is the first study to link impaired liver-directed gene transfer to liver-endothelium maladaptive structural changes associated with FVIII deficiency in mice.

Intercellular crosstalk of liver sinusoidal endothelial cells in liver fibrosis, cirrhosis and hepatocellular carcinoma

Intercellular crosstalk among various liver cells plays an important role in liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Capillarization of liver sinusoidal endothelial cells (LSECs) precedes fibrosis and accumulating evidence suggests that the crosstalk between LSECs and other liver cells is critical in the development and progression of liver fibrosis. LSECs dysfunction, a key event in the progression from fibrosis to cirrhosis, and subsequently obstruction of hepatic sinuses and increased intrahepatic vascular resistance (IHVR) contribute to development of portal hypertension (PHT) and cirrhosis. More importantly, immunosuppressive tumor microenvironment (TME), which is closely related to the crosstalk between LSECs and immune liver cells like CD8+ T cells, promotes advances tumorigenesis, especially HCC. However, the connections within the crosstalk between LSECs and other liver cells during the progression from liver fibrosis to cirrhosis to HCC have yet to be discussed. In this review, we first summarize the current knowledge of how different crosstalk between LSECs and other liver cells, including hepatocytes, hepatic stellate cells (HSCs), macrophoges, immune cells in liver and extra cellular matrix (ECM) contribute to the physiological function and the progrssion from liver fibrosis to cirrhosis, or even to HCC. Then we examine current treatment strategies for LSECs crosstalk in liver fibrosis, cirrhosis and HCC.

A review of hepatic fibrosis-associated histopathology in aged cadavers

This article reviews hepatic fibrosis-associated histopathology of aged cadavers (mean age 82 years). A study of 68 livers identified steatosis in 35.5%, central vein fibrosis in 49.2%, perisinusoidal fibrosis in 63.2%, portal tract fibrosis in 47.7%, septa formation in 44.1%, bridging fibrosis in 30.8%, and cirrhosis in 4.4% of the samples as well as one hepatocellular carcinoma and six metastatic tumors. Other studies have revealed that collagens I, III, IV, V, and VI and fibronectin constitute the matrices of fibrous central veins, perisinusoidal space, portal tracts, and septa. Elastin is rich in portal tracts and fibrous septa but absent from the perisinusoidal space. Hepatic stellate cells are ubiquitous in the liver parenchyma while myofibroblasts localize in fibrotic foci. Factor VIII-related antigen expression signals sinusoidal to systemic vascular endothelium transformation while collagen IV and laminin codistribution indicates formation of perisinusoidal membranes. Their coincidence reflects focalized capillarization of sinusoids in the aged liver. In response to fibrogenesis, hepatic progenitor cells residing in the canal of Hering in the periportal parenchyma undergo expansion and migration deep into the lobule. Concomitantly, intermediate hepatocyte-like cells increase in advanced fibrosis stages, which is possibly related to hepatic regeneration. Metabolic zonation of glutamine synthetase expands from the perivenous to non-perivenous parenchyma in fibrosis progression but its expression is lost in cirrhosis, while cytochrome P-4502E1 expression is maintained in centrilobular and midlobular zones in fibrosis progression and expressed in cirrhosis. Hence, cadaveric livers provide a platform for further investigation of hepatic histopathologies associated with the aging liver.

Immunomodulation by endothelial cells - partnering up with the immune system?

Blood vessel endothelial cells (ECs) have long been known to modulate inflammation by regulating immune cell trafficking, activation status and function. However, whether the heterogeneous EC populations in various tissues and organs differ in their immunomodulatory capacity has received insufficient attention, certainly with regard to considering them for alternative immunotherapy. Recent single-cell studies have identified specific EC subtypes that express gene signatures indicative of phagocytosis or scavenging, antigen presentation and immune cell recruitment. Here we discuss emerging evidence suggesting a tissue-specific and vessel type-specific immunomodulatory role for distinct subtypes of ECs, here collectively referred to as 'immunomodulatory ECs' (IMECs). We propose that IMECs have more important functions in immunity than previously recognized, and suggest that these might be considered as targets for new immunotherapeutic approaches.

Alcohol-associated capillarization of sinusoids: A critique since the discovery by Schaffner and Popper in 1963

This article reviews the literature on capillarization of hepatic sinusoids since its discovery in 1963. Liver sinusoidal endothelial cells are uniquely fenestrated and lack an underlying basement membrane. In chronic liver disease, the sinusoids capillarize and transform into systemic capillaries, a process termed capillarization of sinusoids. The histopathology is marked by defenestration, basement membrane formation, and space of Disse fibrogenesis. Capillarized sinusoids compromise the bidirectional exchange of materials between sinusoids and hepatocytes, leading to hepatocellular dysfunction. Sinusoidal capillarization was first described in active cirrhosis of alcoholics in 1963. Since then, it has been found in early and progressive stages of alcoholic hepatic fibrosis before the onset of cirrhosis. The sinusoidal structure is not altered in alcoholic steatosis without fibrosis. Defenestration impairs the ability of the endothelium to filter chylomicron remnants from sinusoids into the Disse's space, contributing to alcohol-induced postprandial hyperlipidemia and possibly atherosclerosis. Ethanol also modulates the fenestration dynamics in animals. In baboons, chronic alcohol consumption diminishes endothelial porosity in concomitance with hepatic fibrogenesis and in rats defenestrates the endothelium in the absence of fibrosis, and sometimes capillarizes the sinusoids. Acute ethanol ingestion enlarges fenestrations in rats and contracts fenestrations in rabbits. In sinusoidal endothelial cell culture, ethanol elicits fenestration dilation, which is likely related to its interaction with fenestration-associated cytoskeleton. Ethanol potentiates sinusoidal injury caused by cocaine, acetaminophen or lipopolysaccharide in mice and rats. Understanding ethanol's mechanisms on pathogenesis of sinusoidal capillarization and fenestration dynamics will lead to development of methods to prevent risks for atherosclerosis in alcoholism.

Gene Signatures Detect Damaged Liver Sinusoidal Endothelial Cells in Chronic Liver Diseases

Liver sinusoidal endothelial cells have a gatekeeper function in liver homeostasis by permitting substrates from the bloodstream into the space of Disse and regulating hepatic stellate cell activation status. Maintenance of LSEC's highly specialized phenotype is crucial for liver homeostasis. During liver fibrosis and cirrhosis, LSEC phenotype and functions are lost by processes known as capillarization and LSEC dysfunction. LSEC capillarization can be demonstrated by the loss of fenestrae (cytoplasmic pores) and the manifestation of a basement membrane. Currently, no protein or genetic markers can clearly distinguish healthy from damaged LSECs in acute or chronic liver disease. Single cell (sc)RNA sequencing efforts have identified several LSEC populations in mouse models for liver disease and in human cirrhotic livers. Still, there are no clearly defined genesets that can identify LSECs or dysfunctional LSEC populations in transcriptome data. Here, we developed genesets that are enriched in healthy and damaged LSECs which correlated very strongly with healthy and early stage- vs. advanced human liver diseases. A damaged LSEC signature comprised of Fabp4/5 and Vwf/a1 was established which could efficiently identify damaged endothelial cells in single cell RNAseq data sets. In LSECs from an acute CCl₄ liver injury mouse model, Fabp4/5 and Vwf/a1 expression is induced within 1-3 days while in cirrhotic human livers these 4 genes are highly enriched in damaged LSECs. In conclusion, our newly developed gene signature of damaged LSECs can be applicable to a wide range of liver disease etiologies, implicating a common transcriptional alteration mechanism in LSEC damage.

Liver Sinusoidal Endothelial Cells at the Crossroad of Iron Overload and Liver Fibrosis

Significance: Liver fibrosis results from different etiologies and represents one of the most serious health issues worldwide. Fibrosis is the outcome of chronic insults on the liver and is associated with several factors, including abnormal iron metabolism. Recent Advances: Multiple mechanisms underlying the profibrogenic role of iron have been proposed. The pivotal role of liver sinusoidal endothelial cells (LSECs) in iron-level regulation, as well as their morphological and molecular dedifferentiation occurring in liver fibrosis, has encouraged research on LSECs as prime regulators of very early fibrotic events. Importantly, normal differentiated LSECs may act as gatekeepers of fibrogenesis by maintaining the quiescence of hepatic stellate cells, while LSECs capillarization precedes the onset of liver fibrosis. Critical Issues: In the present review, the morphological and molecular alterations occurring in LSECs after liver injury are addressed in an attempt to highlight how vascular dysfunction promotes fibrogenesis. In particular, we discuss in depth how a vicious loop can be established in which iron dysregulation and LSEC dedifferentiation synergize to exacerbate and promote the progression of liver fibrosis. Future Directions: LSECs, due to their pivotal role in early liver fibrosis and iron homeostasis, show great promises as a therapeutic target. In particular, new strategies can be devised for restoring LSECs differentiation and thus their role as regulators of iron homeostasis, hence preventing the progression of liver fibrosis or, even better, promoting its regression. Antioxid. Redox Signal. 35, 474-486.

Pathophysiology and Treatment Options for Hepatic Fibrosis: Can It Be Completely Cured?

Hepatic fibrosis is a dynamic process that occurs as a wound healing response against liver injury. During fibrosis, crosstalk between parenchymal and non-parenchymal cells, activation of different immune cells and signaling pathways, as well as a release of several inflammatory mediators take place, resulting in inflammation. Excessive inflammation drives hepatic stellate cell (HSC) activation, which then encounters various morphological and functional changes before transforming into proliferative and extracellular matrix (ECM)-producing myofibroblasts. Finally, enormous ECM accumulation interferes with hepatic function and leads to liver failure. To overcome this condition, several therapeutic approaches have been developed to inhibit inflammatory responses, HSC proliferation and activation. Preclinical studies also suggest several targets for the development of anti-fibrotic therapies; however, very few advanced to clinical trials. The pathophysiology of hepatic fibrosis is extremely complex and requires comprehensive understanding to identify effective therapeutic targets; therefore, in this review, we focus on the various cellular and molecular mechanisms associated with the pathophysiology of hepatic fibrosis and discuss potential strategies to control or reverse the fibrosis.

Targeting Liver Sinusoidal Endothelial Cells: An Attractive Therapeutic Strategy to Control Inflammation in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), especially its advanced stage nonalcoholic steatohepatitis (NASH), has become a threatened public health problem worldwide. However, no specific drug has been approved for clinical use to treat patients with NASH, though there are many promising candidates against NAFLD in the drug development pipeline. Recently, accumulated evidence showed that liver sinusoidal endothelial cells (LSECs) play an essential role in the occurrence and development of liver inflammation in patients with NAFLD. LSECs, as highly specialized endothelial cells with unique structure and anatomical location, contribute to the maintenance of liver homeostasis and could be a promising therapeutic target to control liver inflammation of NAFLD. In this review, we outline the pathophysiological roles of LSECs related to inflammation of NAFLD, highlight the pro-inflammatory and anti-inflammatory effects of LSECs, and discuss the potential drug development strategies against NAFLD based on targeting to LSECs.

The endothelial dysfunction blocker CU06-1004 ameliorates choline-deficient L-amino acid diet-induced non-alcoholic steatohepatitis in mice

Non-alcoholic steatohepatitis (NASH) is a severe, advanced form of non-alcoholic fatty liver disease (NAFLD) that is associated with features of metabolic syndrome and characterized by hepatic steatosis, inflammation, and fibrosis. In addition, NASH is associated with endothelial dysfunction within the hepatic vasculature. Treatment with CU06-1004 (previously called Sac-1004) ameliorates endothelial dysfunction by inhibiting hyperpermeability and inflammation. In this study, we investigated the protective effects of CU06-1004 in a choline-deficient L-amino acid (CDAA)-induced mouse model of NASH for 3 or 6 weeks. Specifically, we evaluated the effects of CU06-1004 on lipid accumulation, inflammation, hepatic fibrosis, and liver sinusoidal endothelial cell (LSEC) capillarization through biochemical analysis, immunohistochemistry, and real-time PCR. We found that the administration of CU06-1004 to mice improved liver triglyceride (TG) and serum alanine aminotransferase (ALT) in this CDAA-induced model of NASH for 6 weeks. In groups of NASH induced mice for both 3 and 6 weeks, CU06-1004 significantly reduced the hepatic expression of genes related to lipogenesis, inflammation, and cell adhesion. However, expression of genes related to hepatic fibrosis and vascular endothelial changes were only decreased in animals with mild NASH. These results suggest that the administration of CU06-1004 suppresses hepatic steatosis, inflammation, fibrosis, and LSEC capillarization in a CDAA-induced mouse model of NASH. This suggests that CU06-1004 has therapeutic potential for the treatment of mild NASH.

A glitch in the matrix: Age-dependent changes in the extracellular matrix facilitate common sites of metastasis

People over 55 years old represent the majority of cancer patients and suffer from increased metastatic burden compared to the younger patient population. As the aging population increases globally, it is prudent to understand how the intrinsic aging process contributes to cancer progression. As we age, we incur aberrant changes in the extracellular matrix (ECM) of our organs, which contribute to numerous pathologies, including cancer. Notably, the lung, liver, and bone represent the most common sites of distal metastasis for all cancer types. In this review, we describe how age-dependent changes in the ECM of these organs influence cancer progression. Further, we outline how these alterations prime the premetastatic niche and why these may help explain the disparity in outcome for older cancer patients.

Upregulation of C-Reactive Protein by Placenta-Derived Mesenchymal Stem Cells Promotes Angiogenesis in A Rat Model with Cirrhotic Liver

Background and Objectives

Liver cirrhosis is accompanied by abnormal vascular shunts. The Wnt pathway is essential for endothelial cell survival and proliferation. C-reactive protein (CRP), which is produced by hepatocyte, activates angiogenesis in cardiovascular diseases.

Methods and Results

The expression of CRP in CCl₄-injured rat livers was detected using qRT-PCR and Western blotting after transplantation of placenta-derived mesenchymal stem cells (PD-MSCs) into rats. To determine whether CRP functions in hepatic regeneration by promoting angiogenesis through the Wnt pathway, we detected VEGF and β-catenin in liver tissues and BrdU and β-catenin in hepatocytes by immunofluorescence. The expression levels of CRP, Wnt pathway-related and angiogenic factors were increased in CCl₄-injured and PD-MSCs transplanted rat livers. In vitro, the expression levels of Wnt signaling and angiogenic factors were decreased in siRNA-CRP-transfected rat hepatocytes.

Conclusions

CRP upregulation by PD-MSCs participates in vascular remodeling to promote liver regeneration via the Wnt signaling pathway during hepatic failure.

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.

Prominent Receptors of Liver Sinusoidal Endothelial Cells in Liver Homeostasis and Disease

Liver sinusoidal endothelial cells (LSECs) are the most abundant non-parenchymal cells lining the sinusoidal capillaries of the hepatic system. LSECs are characterized with numerous fenestrae and lack basement membrane as well as a diaphragm. These unique morphological characteristics of LSECs makes them the most permeable endothelial cells of the mammalian vasculature and aid in regulating flow of macromolecules and small lipid-based structures between sinusoidal blood and parenchymal cells. LSECs have a very high endocytic capacity aided by scavenger receptors (SR), such as SR-A, SR-B (SR-B1 and CD-36), SR-E (Lox-1 and mannose receptors), and SR-H (Stabilins). Other high-affinity receptors for mediating endocytosis include the FcγRIIb, which assist in the antibody-mediated removal of immune complexes. Complemented with intense lysosomal activity, LSECs play a vital role in the uptake and degradation of many blood borne waste macromolecules and small (<280 nm) colloids. Currently, seven Toll-like receptors have been investigated in LSECs, which are involved in the recognition and clearance of pathogen-associated molecular pattern (PAMPs) as well as damage associated molecular pattern (DAMP). Along with other SRs, LSECs play an essential role in maintaining lipid homeostasis with the low-density lipoprotein receptor-related protein-1 (LRP-1), in juxtaposition with hepatocytes. LSECs co-express two surface lectins called L-Specific Intercellular adhesion molecule-3 Grabbing Non-integrin Receptor (L-SIGN) and liver sinusoidal endothelial cell lectin (LSECtin). LSECs also express several adhesion molecules which are involved in the recruitment of leukocytes at the site of inflammation. Here, we review these cell surface receptors as well as other components expressed by LSECs and their functions in the maintenance of liver homeostasis. We further discuss receptor expression and activity and dysregulation associated with the initiation and progression of many liver diseases, such as hepatocellular carcinoma, liver fibrosis, and cirrhosis, alcoholic and non-alcoholic fatty liver diseases and pseudocapillarization with aging.

An integrated biomimetic array chip for high-throughput co-culture of liver and tumor microtissues for advanced anticancer bioactivity screening

The integration of liver metabolism and hepatotoxicity evaluation for anticancer bioactivity assays in vitro is of fundamental importance to better predict the efficacy and safety of anticancer drugs. In particular, there is a lack of co-culture techniques that can fully mimic the physiological microenvironment at speeds consistent with high-throughput screening. Herein, an integrated Biomimetic Array Chip (iBAC) that enables co-culture of three-dimensional (3D) liver and tumor microtissues was developed for advanced anticancer bioactivity screening at throughputs. The iBAC consisted of two functional chips, a liver chip and a tumor chip containing a cross-shaped protrusion on the tip of a pillar array for co-culture. First, the 3D biomimetic liver microtissue on the liver chip was optimized to mimic superior liver function. Next, the constructed iBAC was evaluated for metabolism-induced anticancer bioactivity by using model prodrugs and for the effect of drug-drug interactions. Finally, the functionality of the iBAC for simultaneous evaluation of anticancer bioactivity and hepatotoxicity was verified. The iBAC exhibits superior performance in biomimetic and integrated functions as well as operationally simple and high-throughput co-culture that makes a good balance between functionality and throughput. Overall, the iBAC provides an integrated, biomimetic and high-throughput co-culture platform to complement the conventional bioactivity assay in tiered screening strategies and could be used as a secondary screening tool at the early phase of drug development.

Immune Cell Trafficking to the Liver

The human liver is an organ with a diverse array of immunologic functions. Its unique anatomic position that leads to it receiving all the mesenteric venous blood, combined with its unique micro anatomy, allows it to serve as a sentinel for the body's immune system. Hepatocytes, biliary epithelial cells, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells express key molecules that recruit and activate innate and adaptive immunity. Additionally, a diverse array of lymphoid and myeloid immune cells resides within and traffics to the liver in specific circumstances. Derangement of these trafficking mechanisms underlies the pathophysiology of autoimmune liver diseases, nonalcoholic steatohepatitis, and liver transplantation. Here, we review these pathways and interactions along with potential targets that have been identified to be exploited for therapeutic purposes.

Asparaginyl endopeptidase may promote liver sinusoidal endothelial cell angiogenesis via PI3K/Akt pathway

BACKGROUND AND AIMS

pathological angiogenesis plays an important role in the progression of chronic liver diseases. Asparaginyl endopeptidase (AEP) participates in tumor angiogenesis and was recently shown to be associated with liver fibrosis. This study aimed to explore the effect of AEP on liver sinusoidal endothelial cell (LSECs) angiogenesis and determine the underlying mechanism.

METHODS

cultured LSECs were infected with lentiviruses in order to suppress AEP expression (AEP-KD1, AEP-KD2). The effect of AEP on LSECs proliferation, apoptosis and migration were subsequently determined by a CCK8 assay, flow cytometry and wound-healing and Transwell assays, respectively, in AEP knocked-down and control LSECs. The expression of the endothelial cell surface markers CD31, CD34 and von Willebrand factor (vWF) were detected by immunofluorescence assay and western blot. The angiogenic factors, vascular endothelial growth factor receptor 2 (VEGFR2) and interleukin 8 (IL 8) were detected by real-time PCR and western blot. The effect of AEP on vessel tube formation by LSECs was examined by Matrigel™ tube-formation assay. Phosphoinositide 3-kinase (PI3K)/Akt expression and phosphorylation were detected by western blot.

RESULTS

AEP was effectively knocked down by lentivirus infection in LSECs. Down-regulation of AEP expression significantly decreased proliferation and migration and increased apoptosis of LSECs. Moreover, expression levels of the endothelial cell surface markers CD31, CD34 and vWF, as well as angiogenic factors VEGFR2 and IL 8, were also reduced after AEP was knocked-down. The vessel tube formation abilities of AEP-KD1 and AEP-KD2 LSECs were significantly inhibited compared with LSECs without AEP knocked-down. Down-regulation of AEP also inhibited the phosphorylation of PI3K and Akt.

CONCLUSION

AEP promotes LSECs angiogenesis in vitro, possibly via the PI3K/Akt pathway. AEP may therefore be a potential therapeutic target for preventing the progression of liver fibrosis.

Antifibrotic Effects of Amyloid-Beta and Its Loss in Cirrhotic Liver

The function and regulation of amyloid-beta (Aβ) in healthy and diseased liver remains unexplored. Because Aβ reduces the integrity of the blood-brain barrier we have examined its potential role in regulating the sinusoidal permeability of normal and cirrhotic liver. Aβ and key proteins that generate (beta-secretase 1 and presenilin-1) and degrade it (neprilysin and myelin basic protein) were decreased in human cirrhotic liver. In culture, activated hepatic stellate cells (HSC) internalized Aβ more efficiently than astrocytes and HSC degraded Aβ leading to suppressed expression of α-smooth muscle actin (α-SMA), collagen 1 and transforming growth factor β (TGFβ). Aβ also upregulated sinusoidal permeability marker endothelial NO synthase (eNOS) and decreased TGFβ in cultured human liver sinusoidal endothelial cells (hLSEC). Liver Aβ levels also correlate with the expression of eNOS in transgenic Alzheimer’s disease mice and in human and rodent cirrhosis/fibrosis. These findings suggest a previously unexplored role of Aβ in the maintenance of liver sinusoidal permeability and in protection against cirrhosis/fibrosis via attenuation of HSC activation.

Curcumol may reverse early and advanced liver fibrogenesis through downregulating the uPA/uPAR pathway

Previous studies have suggested strong antifibrotic activity of curcumol in the liver; the underlying mechanisms of which, however, remain largely unknown. Aiming to investigate the role of curcumol in regulating early and advanced liver fibrosis, we designed a rat model with advanced liver fibrosis and cell model with an initial fibrotic stage. Model rats induced by CCl₄ and alcohol presented advanced liver fibrosis with complete fibrous septa. The administration of curcumol (25 mg/kg or 50 mg/kg) resulted in reversal of liver fibrosis. Leptin-administrated liver sinusoidal endothelial cells presented defenestration and basement membrane components deposition, including laminin (LN) and type IV collagen (Col IV), the characteristics of capillarization by scanning electron microscopy and immunofluorescence assays. After treatment with curcumol (12.5, 25, or 50 mg/L), defenestration was restored and the levels of LN and Col IV were decreased, consistent with the rat model. Quantitative polymerase chain reaction and Western blot results revealed that increased levels of urokinase plasminogen activator (uPA)/ uPA receptor (uPAR) were observed both in vivo and in vitro, curcumol significantly reduced uPA/uPAR at both the mRNA and protein levels. Reduction of uPA/uPAR may be synergistic with matrix metallopeptidase 13 to reverse liver fibrogenesis. In conclusion, curcumol protects liver from phenotypic changes in the early and advanced fibrogenesis, possibly through uPA/uPAR pathway.

Restoration of liver sinusoidal cell phenotypes by statins improves portal hypertension and histology in rats with NASH

Non-alcoholic steatohepatitis (NASH) is a common chronic liver disorder in developed countries, with the associated clinical complications driven by portal hypertension (PH). PH may precede fibrosis development, probably due to endothelial dysfunction at early stages of the disease. Our aim was to characterize liver sinusoidal endothelial cell (LSEC) dedifferentiation/capillarization and its contribution to PH in NASH, together with assessing statins capability to revert endothelial function improving early NASH stages. Sprague-Dawley rats were fed with high fat glucose-fructose diet (HFGFD), or control diet (CD) for 8 weeks and then treated with simvastatin (sim) (10 mg·kg⁻¹·day⁻¹), atorvastatin (ato) (10 mg·kg⁻¹·day⁻¹) or vehicle during 2 weeks. Biochemical, histological and hemodynamic determinations were carried out. Sinusoidal endothelial dysfunction was assessed in individualized sorted LSEC and hepatic stellate cells (HSC) from animal groups and in whole liver samples. HFGFD rats showed full NASH features without fibrosis but with significantly increased portal pressure compared with CD rats (10.47 ± 0.37 mmHg vs 8.30 ± 0.22 mmHg; p < 0.001). Moreover, HFGFD rats showed a higher percentage of capillarized (CD32b⁻/CD11b⁻) LSEC (8% vs 1%, p = 0.005) showing a contractile phenotype associated to HSC activation. Statin treatments caused a significant portal pressure reduction (sim: 9.29 ± 0.25 mmHg, p < 0.01; ato: 8.85 ± 0.30 mmHg, p < 0.001), NASH histology reversion, along with significant recovery of LSEC differentiation and a regression of HSC activation to a more quiescent phenotype. In an early NASH model without fibrosis with PH, LSEC transition to capillarization and HSC activation are reverted by statin treatment inducing portal pressure decrease and NASH features improvement.

Emerging Roles of Vascular Endothelium in Metabolic Homeostasis

Our understanding of the role of the vascular endothelium has evolved over the past 2 decades, with the recognition that it is a dynamically regulated organ and that it plays a nodal role in a variety of physiological and pathological processes. Endothelial cells (ECs) are not only a barrier between the circulation and peripheral tissues, but also actively regulate vascular tone, blood flow, and platelet function. Dysregulation of ECs contributes to pathological conditions such as vascular inflammation, atherosclerosis, hypertension, cardiomyopathy, retinopathy, neuropathy, and cancer. The close anatomic relationship between vascular endothelium and highly vascularized metabolic organs/tissues suggests that the crosstalk between ECs and these organs is vital for both vascular and metabolic homeostasis. Numerous reports support that hyperlipidemia, hyperglycemia, and other metabolic stresses result in endothelial dysfunction and vascular complications. However, how ECs may regulate metabolic homeostasis remains poorly understood. Emerging data suggest that the vascular endothelium plays an unexpected role in the regulation of metabolic homeostasis and that endothelial dysregulation directly contributes to the development of metabolic disorders. Here, we review recent studies about the pivotal role of ECs in glucose and lipid homeostasis. In particular, we introduce the concept that the endothelium adjusts its barrier function to control the transendothelial transport of fatty acids, lipoproteins, LPLs (lipoprotein lipases), glucose, and insulin. In addition, we summarize reports that ECs communicate with metabolic cells through EC-secreted factors and we discuss how endothelial dysregulation contributes directly to the development of obesity, insulin resistance, dyslipidemia, diabetes mellitus, cognitive defects, and fatty liver disease.

Role of liver sinusoidal endothelial cells in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) and its complications are an expanding health problem associated with the metabolic syndrome. Liver sinusoidal endothelial cells (LSECs) are highly specialized endothelial cells localized at the interface between the blood derived from the gut and the adipose tissue on the one side, and other liver cells on the other side. In physiological conditions, LSECs are gatekeepers of liver homeostasis. LSECs display anti-inflammatory and anti-fibrogenic properties by preventing Kupffer cell and hepatic stellate cell activation and regulating intrahepatic vascular resistance and portal pressure. This review focusses on changes occurring in LSECs in NAFLD and on their consequences on NAFLD progression and complications. Capillarization, namely the loss of LSEC fenestrae, and LSEC dysfunction, namely the loss of the ability of LSECs to generate vasodilator agents in response to increased shear stress both occur early in NAFLD. These LSEC changes favour steatosis development and set the stage for NAFLD progression. At the stage of non-alcoholic steatohepatitis, altered LSECs release inflammatory mediators and contribute to the recruitment of inflammatory cells, thus promoting liver injury and inflammation. Altered LSECs also fail to maintain hepatic stellate cell quiescence and release fibrogenic mediators, including Hedgehog signalling molecules, promoting liver fibrosis. Liver angiogenesis is increased in NAFLD and contributes to liver inflammation and fibrosis, but also to hepatocellular carcinoma development. Thus, improving LSEC health appears to be a promising approach to prevent NAFLD progression and complications.

Scintigraphic liver function and transient elastography in the assessment of patients with resectable hepatocellular carcinoma

BACKGROUND

Hepatobiliary scintigraphy (HBS) is used to quantify total and regional liver function. Transient elastography (TE) provides a non-invasive alternative to percutaneous biopsy to assess liver fibrosis and cirrhosis. This study aims to determine the correlation between HBS and histopathology of liver parenchyma, and to compare these with TE in patients with resectable hepatocellular carcinoma (HCC).

METHODS

Patients who underwent surgery for HCC between 2000 and 2016 after preoperative HBS were included. Non-tumorous liver tissue was evaluated for inflammation, steatosis, ballooning, siderosis and fibrosis. Correlation analysis was performed between HBS results and histopathological scoring. These were also compared with TE and surgical outcomes.

RESULTS

71 patients underwent preoperative HBS of whom 24 also had TE. HBS correlated with portal and lobular inflammation as well as fibrosis. TE correlated with portal and lobular inflammation, ballooning and fibrosis. A significant correlation was found between HBS and TE. No association was found with overall postoperative morbidity and mortality.

CONCLUSION

HBS and TE show a moderate to strong correlation. HBS and TE share discriminatory features of histopathological scoring and show a weak to moderate correlation with hepatic inflammation and fibrosis.

Fc gamma RIIb expression levels in human liver sinusoidal endothelial cells during progression of non-alcoholic fatty liver disease

Liver sinusoidal endothelial cells (LSECs) play a pivotal role in hepatic function and homeostasis. LSEC dysfunction has been recognized to be closely involved in various liver diseases, including non-alcoholic steatohepatitis (NASH), but not much is known about the fate of the scavenger receptors in LSECs during NASH. Fc gamma receptor IIb (FcγRIIb), known as a scavenger receptor, contributes to receptor-mediated endocytosis and immune complexes clearance. In this study, to elucidate the fate of FcγRIIb in the progression of non-alcoholic fatty liver disease (NAFLD), we examined FcγRIIb levels in NAFLD biopsy specimens by immunohistochemistry, and investigated their correlation with the exacerbation of biological indexes and clinicopathological scores of NASH. The FcγRIIb expression levels indicated significant negative correlations with serum levels of blood lipids (triglyceride, total cholesterol, high-density lipoprotein-cholesterol), type 4 collagen and hyaluronic acid, which are involved in hepatic lipid metabolism disorder, fibrosis, and inflammation, respectively. However, there was no significant difference of FcγRIIb expression levels among the pathological grades of NAFLD. During NAFLD progression, inflammation and fibrosis may influence the expression of FcγRIIb and their scavenger functions to maintain hepatic homeostasis.

Gastrodin induced HO-1 and Nrf2 up-regulation to alleviate H2O2-induced oxidative stress in mouse liver sinusoidal endothelial cells through p38 MAPK phosphorylation

Nuclear factor erythroid-related factor 2 (Nrf2) has been implicated in several detoxifying and antioxidant defense processes. Nrf2-mediated heme oxygenase-1 (HO-1) expression was demonstrated to play a key role against oxidative stress. Gastrodin (GSTD) is a well-known active compound isolated from the roots of Rhizoma gastrodiae, a plant used in ancient Chinese traditional medicine. The aim of this work was to investigate whether GSTD could alleviate H₂O₂-induced oxidative stress in mouse liver sinusoidal endothelial cells (LSECs). In LSECs exposed to 1 mM H₂O₂, treatment with GSTD (1, 10, or 50 µM) resulted in higher cell viability than the untreated control. Treated cells maintained a higher Bcl2/Bax ratio and suppressed caspase-9 expression compared with untreated cells, reducing cell apoptosis. GSTD was protective for H₂O₂-induced oxidative injury by reducing the generation of intracellular reactive oxygen species and malondialdehyde. HO-1 and Nrf2 expressions were synergistically upregulated by GSTD. Inhibition of HO-1 by 10 µM zinc protoporphyrin resulted in less protective effects on cell viability and malondialdehyde reduction by GSTD treatment in H₂O₂-exposed LSECs. Additionally, phosphorylated p38 in LSECs exposed to H₂O₂ was elevated by GSTD. Inhibition of p38 phosphorylation by SB203580 did not induce Nrf2 and HO-1 expression after 1 or 10 µM GSTD treatment and the protective effect on cell viability and malondialdehyde reduction in H₂O₂-exposed LSECs was reduced. The data conclusively demonstrated that GSTD-induced HO-1 and Nrf2 expression is involved in protection of LSECs from H₂O₂-induced oxidative injury, which may be regulated by p38 phosphorylation.

Endothelial Notch activation reshapes the angiocrine of sinusoidal endothelia to aggravate liver fibrosis and blunt regeneration in mice

Liver sinusoidal endothelial cells (LSECs) critically regulate liver homeostasis and diseases through angiocrine factors. Notch is critical in endothelial cells (ECs). In the current study, Notch signaling was activated by inducible EC-specific expression of the Notch intracellular domain (NIC). We found that endothelial Notch activation damaged liver homeostasis. Notch activation resulted in decreased fenestration and increased basement membrane, and a gene expression profile with decreased LSEC-associated genes and increased continuous EC-associated genes, suggesting LSEC dedifferentiation. Consistently, endothelial Notch activation enhanced hepatic fibrosis (HF) induced by CCl₄ . Notch activation attenuated endothelial nitric oxide synthase (eNOS)/soluble guanylate cyclase (sGC) signaling, and activation of sGC by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) reversed the dedifferentiation phenotype. In addition, Notch activation subverted the hepatocyte-supporting angiocrine profile of LSECs by down-regulating critical hepatocyte mitogens, including Wnt2a, Wnt9b, and hepatocyte growth factor (HGF). This led to compromised hepatocyte proliferation under both quiescent and regenerating conditions. Whereas expression of Wnt2a and Wnt9b was dependent on eNOS-sGC signaling, HGF expression was not rescued by the sGC activator, suggesting heterogeneous mechanisms of LSECs to maintain hepatocyte homeostasis.

CONCLUSION

Endothelial Notch activation results in LSEC dedifferentiation and accelerated liver fibrogenesis through eNOS-sGC signaling, and alters the angiocrine profile of LSECs to compromise hepatocyte proliferation and liver regeneration (LR). (Hepatology 2018).

Evaluation of high-fat high-fructose diet treatment in factor VIII (coagulation factor)-deficient mouse model

Non-alcoholic fatty liver disease (NAFLD)-like conditions enhance the production and action of clotting factors in humans. However, studies examining the effect of NAFLD due to high-fat high-fructose (HFHF) diet in factor VIII-deficient (haemophilia A) animals or patients have not been reported previously. In this study, we investigated the individual role of factor VIII in the progression of diet-induced NAFLD in the factor 8^-/- (F8^-/- ) mouse model system and its consequences on the haemophilic status of the mice. The F8^-/- mice were fed with HFHF diet for 14 weeks. Physiological, biochemical, haematological, molecular, pathological, and immune histochemical analyses were performed to evaluate the effect of this diet. The F8^-/- mice developed hepatic steatosis after 14 weeks HFHF diet and displayed lower energy metabolism, higher myeloid cell infiltration in the liver, decreased platelet count, upregulated de novo fatty acid synthesis, lipid accumulation, and collagen deposition. This study helps to understand the role of factor VIII in NAFLD pathogenesis and to analyse the severity and consequences of steatosis in haemophilic patients as compared to normal population. This study suggests that haemophilic animals (F8^-/- mice) are highly prone to hepatic steatosis and thrombocytopenia.

Changes in Expression of Bile Canalicular CD10 and Sinusoidal CD105 (Endoglin) in Peritumoral Hepatic Tissue

Aims and background

Hepatic tissues, including bile canaliculi and sinusoids, around primary or metastatic tumors are destructed and regenerate associated with tumor growth, and may show some phenotypic changes. The present study was undertaken to examine the expression of CD10 in bile canaliculi [CD10(BC)] and CD105 (endoglin) along hepatic sinusoids [CD105(HS)] in peritumoral hepatic tissue (PTH).

Methods

Fifty samples of resected liver bearing hepatocellular carcinoma (HCC) or metastatic carcinoma were immunostained for CD10 and CD105. The immunoreactivity for CD10(BC) and CD105(HS) in the background hepatic tissue of tumors and PTH was scored separately.

Results

CD10(BC) was moderately or markedly expressed in the background hepatic tissue without chronic hepatitis or cirrhosis in most of the cases, and was significantly downregulated in chronic hepatitis and cirrhosis. CD105(HS) was negative or minimally positive in most of the cases of hepatic tissue bearing metastatic carcinoma, and showed a significant increase in chronic hepatitis and cirrhosis. Compared with the background, PTH revealed significantly decreased CD10(BC) staining irrespective of HCC or metastatic carcinoma, and showed belt-like CD105(HS) expression in 66.7% of the cases of metastatic carcinoma and in 88.6% of those with HCC.

Conclusions

These data indicate that the expression patterns of CD10(BC) and CD105(HS) in PTH are similar to those in chronic hepatitis and cirrhosis, which may be caused by persistent injury and resultant regeneration of hepatic tissue.

Liver sinusoidal endothelial cells - gatekeepers of hepatic immunity

Liver sinusoidal endothelial cells (LSECs) line the low shear, sinusoidal capillary channels of the liver and are the most abundant non-parenchymal hepatic cell population. LSECs do not simply form a barrier within the hepatic sinusoids but have vital physiological and immunological functions, including filtration, endocytosis, antigen presentation and leukocyte recruitment. Reflecting these multifunctional properties, LSECs display unique structural and phenotypic features that differentiate them from the capillary endothelium present within other organs. It is now clear that LSECs have a critical role in maintaining immune homeostasis within the liver and in mediating the immune response during acute and chronic liver injury. In this Review, we outline how LSECs influence the immune microenvironment within the liver and discuss their contribution to immune-mediated liver diseases and the complications of fibrosis and carcinogenesis.

Role of canonical Hedgehog signaling pathway in liver

Hedgehog (Hh) signaling pathway plays an important role in embryonic development. It becomes reactivated in many types of acute and chronic liver injuries. Hh signaling is required for liver regeneration, regulates capillarisation, controls the fates of hepatic stellate cells, promotes liver fibrosis and liver cancers. In this review, we summarize the current knowledge of the role of canonical Hh signaling pathway in adult liver. This help to understand the pathogenesis of liver diseases and find out the new effective targeted therapeutic strategies for liver diseases treatments.

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.