Liver Sinusoidal Endothelial Cells Fenestrae Research Articles

Extra-corporeal non-liver transplant therapies for acute liver failure: Focus on plasma exchange and continuous renal replacement therapy.

The acute inflammatory milieu in patients with acute liver failure (ALF) results in 'toxic' blood in these patients. In vitro experiments have shown that the plasma obtained from ALF patients is toxic to rabbit hepatocytes and inhibits regeneration of rat hepatocytes. Treatments such as plasma exchange and continuous renal replacement therapy to cleanse the blood have improved survival in ALF patients. In the liver microcirculation, the exchange of fluid across fenestrae in liver sinusoidal endothelial cells (LSECs) is vital for proper functioning of hepatocytes. Clogging of the liver filter bed by inflammatory debris and cells ('traffic jam hypothesis') impeding blood flow in sinusoids may in turn reduce the exchange of fluid across LSEC fenestrae and cause dysfunction and necrosis of hepatocytes in ALF patients. In mouse model of paracetamol overdose, disturbances in microcirculation in the liver preceded the development of injury and necrosis of hepatocytes. This may represent a reversible pathophysiological mechanism in ALF which may be improved by the anti-inflammatory effect of plasma exchange. Wider access to urgent plasma exchange is a major advantage compared to urgent liver transplantation to treat ALF patients worldwide, especially so in resource constrained settings. Continuous hemo-filtration or dialysis is used toreduce ammonia levels and treat cerebral edema in ALF patients. In this review, we discuss the different modalities to cleanse the blood in ALF patients, with an emphasis on plasma exchange, from a hepatology perspective.

Nucleophagic Degradation of Progerin Ameliorates Defenestration in Liver Sinusoidal Endothelium Due to SIRT1-Mediated Deacetylation of Nuclear LC3

Progerin, a permanently farnesylated prelamin A protein in cell nuclei, is potentially implicated in the defenestration of liver sinusoidal endothelial cells (LSECs) and liver fibrogenesis. Autophagy regulates the degradation of nuclear components, called nucleophagy, in response to damage. However, little is known about the role of nucleophagy in LSEC defenestration. Herein, we aim to dissect the underlying mechanism of progerin and nucleophagy in LSEC phenotype. We found an abnormal accumulation of progerin and a loss of SIRT1 in the nucleus of intrahepatic cells in human fibrotic liver tissue. In vivo, nuclear progerin abnormally accumulated in defenestrated LSECs, along with a depletion of SIRT1 and Cav-1 during liver fibrogenesis, whereas these effects were reversed by the overexpression of SIRT1 with the adenovirus vector. In vitro, H2O2 induced the excessive accumulation of progeirn, with the depletion of Lamin B1 and Cav-1 to aggravate LSEC defenestration. NAC and mito-TEMPO, classical antioxidants, inhibited NOX2- and NOX4-dependent oxidative stress to improve the depletion of Lamin B1 and Cav-1 and promoted progerin-related nucleophagy, leading to a reverse in H2O2-induced LSEC defenestration. However, rapamycin aggravated the H2O2-induced depletion of Lamin B1 and Cav-1 due to excessive autophagy, despite promoting progerin nucleophagic degradation. In addition, overexpressing SIRT1 with the adenovirus vector inhibited oxidative stress to rescue the production of Lamin B1 and Cav-1. Moreover, the SIRT1-mediated deacetylation of nuclear LC3 promoted progerin nucleophagic degradation and subsequently inhibited the degradation of Lamin B1 and Cav-1, as well as improved F-actin remodeling, contributing to maintaining LSEC fenestrae. Hence, our findings indicate a new strategy for reversing LSEC defenestration by promoting progerin clearance via the SIRT1-mediated deacetylation of nuclear LC3.

Liver sinusoidal endothelial cell expressed vascular cell adhesion molecule 1 promotes liver fibrosis.

BackgroundDuring liver injury, liver sinusoidal endothelial cells (LSECs) dysfunction and capillarization promote liver fibrosis. We have previously reported that the LSEC vascular cell adhesion molecule 1 (VCAM1) plays a key role in liver inflammation in nonalcoholic steatohepatitis (NASH) and we now aim to uncover its role in LSEC capillarization and liver fibrosis.MethodsWild-type C57BL/6J mice were fed either chow or high fat, fructose and cholesterol diet to induce NASH and treated with either anti-VCAM1 neutralizing antibody or control isotype antibody. Inducible endothelial cell-specific Vcam1 deleted mice (Vcam1Δend ) and control mice (Vcam1fl/fl ) were fed choline-deficient high-fat diet (CD-HFD) to induce NASH or injected with carbon tetrachloride to induce liver fibrosis. LSECs isolated from Vcam1fl/fl or Vcam1Δend and hepatic stellate cells (HSCs) isolated from wild-type mice were cocultured in a 3-D system or a μ-Slide 2 well co-culture system.ResultsImmunostaining for Lyve1 (marker of differentiated LSECs) was reduced in Vcam1fl/fl mice and restored in Vcam1Δend mice in both NASH and liver fibrosis models. Co-immunostaining showed increased α-smooth muscle actin in the livers of Vcam1fl/fl mice in areas lacking Lyve1. Furthermore, scanning electron microscopy showed reduced LSEC fenestrae in the Vcam1fl/fl mice but not Vcam1Δend mice in both injury models, suggesting that VCAM1 promotes LSEC capillarization during liver injury. HSCs profibrogenic markers were reduced when cocultured with LSECs from CD-HFD fed Vcam1Δend mice compared to Vcam1fl/fl mice. Furthermore, recombinant VCAM1 activated the Yes-associated protein 1 pathway and induced a fibrogenic phenotype in HSCs in vitro, supporting the profibrogenic role of LSEC VCAM1.ConclusionVCAM1 is not just a scaffold for leukocyte adhesion during liver injury, but also a modulator of LSEC capillarization and liver fibrosis.

Cavin1 Deficiency Causes Disorder of Hepatic Glycogen Metabolism and Neonatal Death by Impacting Fenestrations in Liver Sinusoidal Endothelial Cells.

It has been reported that Cavin1 deficiency causes lipodystrophy in both humans and mice by affecting lipid metabolism. The ablation of Cavin1 in rodents also causes a significant deviation from Mendelian ratio at weaning in a background‐dependent manner, suggesting the presence of undiscovered functions of Cavin1. In the current study, the results show that Cavin1 deficiency causes neonatal death in C57BL/6J mice by dampening the storage and mobilization of glycogen in the liver, which leads to lethal neonatal hypoglycemia. Further investigation by electron microscopy reveals that Cavin1 deficiency impairs the fenestration in liver sinusoidal endothelial cells (LSECs) and impacts the permeability of endothelial barrier in the liver. Mechanistically, Cavin1 deficiency inhibits the RhoA‐Rho‐associated protein kinase 2‐LIM domain kinase‐Cofilin signaling pathway and suppresses the dynamics of the cytoskeleton, and eventually causes the reduction of fenestrae in LSECs. In addition, the defect of fenestration in LSECs caused by Cavin1 deficiency can be rescued by treatment with the F‐actin depolymerization reagent latrunculin A. In summary, the current study reveals a novel function of Cavin1 on fenestrae formation in LSECs and liver glycogen metabolism, which provide an explanation for the neonatal death of Cavin1 null mice and a potential mechanism for metabolic disorders in patients with Cavin1 mutation.

Effect of Curcumol on the Fenestrae of Liver Sinusoidal Endothelial Cells Based on NF-κB Signaling Pathway.

Objective To study the effect of curcumol on liver sinusoidal endothelial cells (LSECs) and to analyze the mechanism of antihepatic fibrosis. Methods The effects of drug intervention on cell proliferation rates were detected by MTT assay. The expression of NF-κB was detected by RT-PCR and WB. The NF-κB expression and entry into the nucleus were detected by immunofluorescence; scanning electron microscopy was used to observe the changes of LSECs fenestrae. Results MTT results showed that the interference of cell proliferation in each group was small. RT-PCR showed that the expression of NF-κB in the curcumol intervention group was significantly lower than that in the positive control group (P < 0.05). The WB detection found that, in the curcumol intervention group, the expression of pNF-κB in the NF-κB signaling pathway was significantly lower than that in the positive control group (P < 0.05). Scanning electron microscopy showed that the LSEC fenestrae were significantly improved compared with the positive control group. Conclusion Curcumol may be one of the mechanisms of antihepatic fibrosis by inhibiting the activity of the NF-κB signaling pathway and increasing the fenestrae of LSECs.

LSEC Fenestrae Are Preserved Despite Pro-inflammatory Phenotype of Liver Sinusoidal Endothelial Cells in Mice on High Fat Diet.

Healthy liver sinusoidal endothelial cells (LSECs) maintain liver homeostasis, while LSEC dysfunction was suggested to coincide with defenestration. Here, we have revisited the relationship between LSEC pro-inflammatory response, defenestration, and impairment of LSEC bioenergetics in non-alcoholic fatty liver disease (NAFLD) in mice. We characterized inflammatory response, morphology as well as bioenergetics of LSECs in early and late phases of high fat diet (HFD)-induced NAFLD. LSEC phenotype was evaluated at early (2–8 week) and late (15–20 week) stages of NAFLD progression induced by HFD in male C57Bl/6 mice. NAFLD progression was monitored by insulin resistance, liver steatosis and obesity. LSEC phenotype was determined in isolated, primary LSECs by immunocytochemistry, mRNA gene expression (qRT-PCR), secreted prostanoids (LC/MS/MS) and bioenergetics (Seahorse FX Analyzer). LSEC morphology was examined using SEM and AFM techniques. Early phase of NAFLD, characterized by significant liver steatosis and prominent insulin resistance, was related with LSEC pro-inflammatory phenotype as evidenced by elevated ICAM-1, E-selectin and PECAM-1 expression. Transiently impaired mitochondrial phosphorylation in LSECs was compensated by increased glycolysis. Late stage of NAFLD was featured by prominent activation of pro-inflammatory LSEC phenotype (ICAM-1, E-selectin, PECAM-1 expression, increased COX-2, IL-6, and NOX-2 mRNA expression), activation of pro-inflammatory prostaglandins release (PGE2 and PGF2α) and preserved LSEC bioenergetics. Neither in the early nor in the late phase of NAFLD, were LSEC fenestrae compromised. In the early and late phases of NAFLD, despite metabolic and pro-inflammatory burden linked to HFD, LSEC fenestrae and bioenergetics are functionally preserved. These results suggest prominent adaptive capacity of LSECs that might mitigate NAFLD progression.

Tracking Fenestrae Dynamics in Live Murine Liver Sinusoidal Endothelial Cells.

The fenestrae of liver sinusoidal endothelial cells (LSECs) allow passive transport of solutes, macromolecules, and particulate material between the sinusoidal lumen and the liver parenchymal cells. Until recently, fenestrae and fenestrae-associated structures were mainly investigated using electron microscopy on chemically fixed LSECs. Hence, the knowledge about their dynamic properties has remained to date largely elusive. Recent progress in atomic force microscopy (AFM) has allowed the study of live cells in three dimensions (X, Y, and Z) over a prolonged time (t) and this at unprecedented speeds and resolving power. Hence, we employed the latest advances in AFM imaging on living LSECs. As a result, we were able to monitor the position, size, and number of fenestrae and sieve plates using four-dimensional AFM (X, Y, Z, and t) on intact LSECs in vitro. During these time-lapse experiments, dynamic data were collected on the origin and morphofunctional properties of the filtration apparatus of LSECs. We present structural evidence on single laying and grouped fenestrae, thereby elucidating their dynamic nature from formation to disappearance. We also collected data on the life span of fenestrae. More especially, the formation and closing of entire sieve plates were observed, and how the continuous rearrangement of sieve plates affects the structure of fenestrae within them was recorded. We observed also the dawn and rise of fenestrae-forming centers and defenestration centers in LSECs under different experimental conditions. Conclusion: Utilizing a multimodal biomedical high-resolution imaging technique we collected fine structural information on the life span, formation, and disappearance of LSEC fenestrae; by doing so, we also gathered evidence on three different pathways implemented in the loss of fenestrae that result in defenestrated LSECs.

Actin Depolymerization in Dedifferentiated Liver Sinusoidal Endothelial Cells Promotes Fenestrae Re-Formation.

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, which are key for the exchange between blood and hepatocytes. Alterations in their number or diameter have important implications for hepatic function in liver diseases. They are lost early in the development of hepatic fibrosis through a process called capillarization. In this study, we aimed to demonstrate whether in vitro dedifferentiated LSECs that have lost fenestrae are able to re‐form these structures. Using stimulated emission depletion super‐resolution microscopy in combination with transmission electron microscopy, we analyzed fenestrae formation in a model mimicking the capillarization process in vitro. Actin is known to be involved in fenestrae regulation in differentiated LSECs. Using cytochalasin D, an actin‐depolymerizing agent, we demonstrated that dedifferentiated LSECs remain capable of forming fenestrae. Conclusion: We provide a new insight into the complex role of actin in fenestrae formation and in the control of their size and show that LSEC fenestrae re‐formation is possible, suggesting that this process could be used during fibrosis regression to try to restore exchanges and hepatocyte functions.

STED microscopy: A simplified method for liver sinusoidal endothelial fenestrae analysis.

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, open transcellular pores with an average diameter of 100nm. These fenestrae allow for the exchange between blood and hepatocytes. Alterations in their number or diameter in liver diseases have important implications for hepatic microcirculation and function. Although decades of studies, fenestrae are still observed into fixed cells and we have poor knowledge of their dynamics. Using stimulated emission depletion (STED) super-resolution microscopy, we have established a faster and simplest method to observe and quantify fenestrae. Indeed, using cytochalasin D, an actin depolymerising agent known to promote fenestrae formation, we measure the increase of fenestrae number. We adapted this methodology to develop an automated method to study fenestrae dynamics. Moreover, with two-colour STED analysis, we have shown that this approach could be useful to study LSECs fenestrae molecular composition. Our approach demonstrates that STED microscopy is suitable for LSEC fenestrae study. This new way of analysing LSEC fenestrae will allow for expedited investigation of their dynamics, molecular composition and functions to better understand their function in liver pathophysiology.

Autophagic degradation of caveolin-1 promotes liver sinusoidal endothelial cells defenestration

Autophagy, interacting with actin cytoskeleton and the NO-dependent pathway, may affect the phenotype and function of endothelial cells. Moreover, caveolin-1 (Cav-1), as a structure protein in liver sinusoidal endothelial cells (LSECs), is closely related to autophagy. Hence, we aim to explore the role of autophagic degradation of Cav-1 in LSECs defenestration. In vivo, we found the increase of autophagy in liver sinusoidal endothelium in human fibrotic liver. Furthermore, autophagy, degradation of Cav-1, and actin filament (F-actin) remodeling were triggered during the process of CCl4-induced LSECs defenestration; in contrast, autophagy inhibitor 3MA diminished the degradation of Cav-1 to maintain fenestrae and relieve CCl4-induced fibrosis. In vitro, during LSECs defenestration, the NO-dependent pathway was down-regulated through the reduction of the PI3K–AKT–MTOR pathway and initiation of autophagic degradation of Cav-1; while, these effects were aggravated by starvation. However, VEGF inhibited autophagic degradation of Cav-1 and F-actin remodeling to maintain LSECs fenestrae via activating the PI3K–AKT–MTOR pathway. Additionally, inhibiting autophagy, such as 3MA, bafilomycin, or ATG5-siRNA, could attenuate the depletion of Cav-1 and F-actin remodeling to maintain LSECs fenestrae and improve the NO-dependent pathway; in turn, eNOS-siRNA and L-NAME, for blocking the NO-dependent pathway, could elevate autophagic degradation of Cav-1 to aggravate defenestration. Finally, overexpressed Cav-1 rescued rapamycin-induced autophagic degradation of Cav-1 to maintain LSECs fenestrae; whereas knockdown of Cav-1 facilitated defenestration due to the activation of the AMPK-dependent autophagy. Consequently, autophagic degradation of Cav-1 promotes LSECs defenestration via inhibiting the NO-dependent pathway and F-actin remodeling.

Differential Effects of Kupffer Cell Inactivation on Inflammation and The Liver Sieve Following Caecal-Ligation and Puncture-Induced Sepsis in Mice.

Sepsis remains a common clinical problem with significant mortality. Activation of the Kupffer cells during sepsis is associated with systemic inflammatory response and multiple organ failure. Kupffer cell activation also leads to structural changes in the liver sinusoidal endothelial cells (LSECs) during endotoxemia. However, these effects remain to be elucidated in caecal-ligation and puncture (CLP)-induced polymicrobial sepsis. To investigate the role of Kupffer cells on LSECs fenestrae and inflammation during CLP-induced sepsis, sepsis was induced by CLP and mice were treated with gadolinium chloride (GdCl3) before CLP-induced sepsis, to inactivate Kupffer cells. Mice were sacrificed after 8 h. Blood, liver, and lung tissues were collected and processed to measure LSECs fenestration, myeloperoxidase (MPO) activity, alanine transaminase (ALT) and aspartate aminotransferase (AST) activity, histological examination, and various cytokines/chemokines levels. LSECs fenestrae was studied using scanning electron micrographs of the LSECs. Strikingly, CLP mice treated with GdCl3 were protected against liver injury as evidenced by decreased LSECs defenestration and damage, MPO, ALT and AST activities, liver tissue damage, and inflammatory cytokines TNF-α, IL-6 and IL-1β, and chemokines MCP-1 and MIP-2α. However, CLP mice treated with GdCl3 had no protection against increased lung MPO activity, tissue damage, inflammatory cytokines, and chemokines. Treatment with GdCl3 also had no effect on the systemic inflammatory response as shown by no change in the circulatory inflammatory cytokines and chemokines following CLP-induced sepsis. Collectively, these data suggest that inactivation of Kupffer cells by GdCl3 protects the liver but had no effect on lung injury or inflammation and systemic inflammatory response following CLP-induced sepsis.

The protective effect of Gan Shen Fu Fang on liver endothelial cells in common bile duct-ligated rats

Objective: To elucidate the protective effect of Gan Shen Fu Fang (GSFF) on liver endothelial cells in common bile duct-ligated (CBDL) rats. Materials and Methods: Cirrhosis was induced by common bile duct ligation. The rats were divided into three groups: sham group, CBDL group, and GSFF group. After 2 weeks of ligation, rats in the GSFF group were administered GSFF. After 4 weeks, the hydroxyproline (Hyp) content of liver tissues was spectrophotometrically determined. The histological changes were evaluated by H and E and Masson staining. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to observe the ultrastructural changes in the liver, especially in the liver sinusoidal endothelial cells (LSECs). Results: Hyp synthesis was significantly inhibited by GSFF, which agreed with the results from H and E and Masson staining for liver fibrosis. The TEM observations of CBDL rats revealed reduced hepatocyte microvilli and deposited fibrous tissue underneath LSECs. SEM confirmed the TEM findings and showed that the fenestrae of LSECs decreased and even disappeared in CBDL rats. The morphological results indicated hepatic sinusoid capillarization. GSFF promoted the restoration of fenestrae and reversed hepatic sinusoid capillarization. Conclusion: GSFF can inhibit Hyp synthesis, restore the fenestrae of LSECs, and reverse hepatic sinusoid capillarization in CBDL rats. These results provide a basis for future detailed investigations of the mechanism of action of GSFF in LSECs.

Cystathionine-Gamma-Lyase Gene Deletion Protects Mice against Inflammation and Liver Sieve Injury following Polymicrobial Sepsis.

BackgroundHydrogen sulfide (H2S), produced by the activity of cystathionine-gamma-lyase (CSE), is a key mediator of inflammation in sepsis. The liver sinusoidal endothelial cells (LSECs) are important target and mediator of sepsis. The aim of this study was to investigate the role of CSE-derived H2S on inflammation and LSECs fenestrae in caecal-ligation and puncture (CLP)-induced sepsis using CSE KO mice.MethodsSepsis was induced by CLP, and mice (C57BL/6J, male) were sacrificed after 8 hours. Liver, lung, and blood were collected and processed to measure CSE expression, H2S synthesis, MPO activity, NF-κB p65, ERK1/2, and cytokines/chemokines levels. Diameter, frequency, porosity and gap area of the liver sieve were calculated from scanning electron micrographs of the LSECs.ResultsAn increased CSE expression and H2S synthesizing activity in the liver and lung of wild-type mice following CLP-induced sepsis. This was associated with an increased liver and lung MPO activity, and increased liver and lung and plasma levels of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β, and the chemokines MCP-1 and MIP-2α. Conversely, CSE KO mice had less liver and lung injury and reduced inflammation following CLP-induced sepsis as evidenced by decreased levels of H2S synthesizing activity, MPO activity, and pro-inflammatory cytokines/chemokines production. Extracellular-regulated kinase (ERK1/2) and nuclear factor-κB p65 (NF-κB) became significantly activated after the CLP in WT mice but not in CSE KO mice. In addition, CLP-induced damage to the LSECs, as indicated by increased defenestration and gaps formation in the LSECs compared to WT sham control. CSE KO mice showed decreased defenestration and gaps formation following sepsis.ConclusionsMice with CSE (an H2S synthesising enzyme) gene deletion are less susceptible to CLP-induced sepsis and associated inflammatory response through ERK1/2-NF-κB p65 pathway as evidenced by reduced inflammation, tissue damage, and LSECs defenestration and gaps formation.

Increased Expression Of NGF In Hepatocytes Is An Early Event In Iron Overloaded Mouse By Transcriptome Analysis

The liver plays a central role in iron metabolism by storing and sensing the amounts of iron in the body. The dietary iron from duodenum and recycled-iron by reticuloendothelial system are the main source of body iron. When excess iron enters the liver, hepatocytes secrete hepcidin, an anti-microbial peptide which negatively regulates iron excretion from enterocytes and macrophages, and stores the excess iron as ferritin-bound iron. A dysfunction of this regulatory system causes iron overload in the liver. Aberrant iron accumulation in the liver is found in hereditary hemochromatosis and chronic liver disease, and this is considered to be an exacerbating factor in liver cirrhosis and hepatocellular carcinoma. It is therefore important to understand the precise molecular events that take place as a result of iron accumulation during the early stages of iron overload.In the present study, we performed transcriptome analysis on the liver of dietary iron overloaded mice. Transcriptome analysis using a high throughput sequencer is capable of comprehensive analysis with high sensitivity. We hypothesized that this method will be suitable in detecting the changes in gene expression induced by iron overload, even in slightly expressed genes. C57B1/6 mice were fed a normal diet, and a 2.5% iron diet for 8 weeks. Serum and liver tissue samples were then collected, and histological analysis showed the features of early stage iron overload without significant hepatic damage in the iron-fed mice.From the results of the transcriptome analysis, we found that nerve growth factor (NGF) was significantly expressed in the slightly iron overloaded liver. This observation was also confirmed by real time RT-PCR, Western blotting and immunohistochemistry. Similarly, NGF upregulation was induced in mice primary hepatocytes cultured in conditioned iron overloaded medium (with high concentration of holo-transferrin or ferric ammonium citrate). Furthermore, immunohistochemical analysis showed that TrkA, a high affinity NGF receptor, was expressed in liver sinusoidal endothelial cells (LSECs). Using scanning electron microscopy, we sought to examine any morphological changes in the sinusoids of the iron overloaded liver and observed that although sieve plate structures (so-called ‘fenestrae') were found in the LSECs of mice fed a normal diet, they were not visible in the iron-fed mice. The loss of fenestrae was also observed in the LSECs of mice that received intraperitoneal injections of NGF. In cultured isolated primary LSECs, treatment with NGF, or conditioned medium from iron overloaded primary hepatocytes reduced the fenestrae while the anti-NGF neutralization antibody or TrkA inhibitor K252a cancelled this effect. In addition, a fresh iron overloaded medium did not reduce the fenestrae in primary LSECs, indicating that iron itself has no direct effects on the fenestrae in LSECs.LSECs constitute the sinusoidal wall in the liver and can be regarded as unique capillaries which differ from other capillaries in the body due to the presence of fenestrae which lack a diaphragm, and are therefore open connections between the lumen of the sinusoid and the space of Disse. The fenestrae in LSECs therefore play an important role in the exchange of solutes between the lumen of the sinusoid and hepatocytes.The results of this study indicate that iron accumulation induces the expression of NGF in hepatoctyes, which in turn leads to the loss of fenestrae in LSECs via TrkA. This phenomenon may therefore contribute to the defensive machinery against iron accumulation in hepatocytes in the early stages of iron overload. These data further suggest a novel function of NGF in the regulation of iron transport. Disclosures:No relevant conflicts of interest to declare.

Relation between Ultrastructural Localization, Changes in Caveolin-1, and Capillarization of Liver Sinusoidal Endothelial Cells in Human Hepatitis C–Related Cirrhotic Liver

Most vascular endothelial cells are continuously exposed to shear stress in vivo. Caveolae are omega-shaped membrane invaginations in endothelial cells (ECs) and are enriched in cholesterol, caveolins, and signaling molecules. This study was designed to elucidate the ultrastructural localization and change in caveolin-1 expression within human liver sinusoidal endothelial cells (LSECs) during the progression of cirrhosis caused by hepatitis C, using tissue sections prepared via perfusion-fixation. Normal control liver specimens and hepatitis C-related Child-Pugh A and C cirrhotic liver specimens were studied. Caveolin-1 in the liver sinusoids was examined via immunohistochemistry, Western blotting, and immunoelectron microscopy. In control liver tissue, caveolin-1 was localized on caveolae mainly in arterial and portal endothelial cells of the portal tract and was also found on vesicles and some fenestrae in LSECs around the central vein. In cirrhotic liver tissue, aberrant caveolin-1 expression was observed on caveolae-like structures in LSECs. Caveolin-1 was especially overexpressed in late-stage cirrhosis. This study demonstrates that caveolin-1 is strongly expressed within caveolae-like structures and associated vesicles within LSECs of the hepatitis C-related cirrhotic liver. These findings suggest a direct association of caveolin-1 in the process of differentiation of LSECs in cirrhosis-mediated capillarization.