Liver sinusoidal endothelial cells: Physiology and role in liver diseases

Bevacizumab and near infrared probe conjugated iron oxide nanoparticles for vascular endothelial growth factor targeted MR and optical imaging

Vascular endothelial growth factor (VEGF) plays a pivotal role in the cascade of development and progression of cancers. Targeting this cancer hallmark is a logical strategy for imaging based cancer detection and monitoring the anti-angiogenesis treatment. Using Bevacizumab (Avastin®), which is a recombinant humanized monoclonal antibody directly against VEGF and an angiogenesis inhibitor, as a targeting ligand, a multimodal VEGF targeted molecular imaging probe was developed by conjugating near infrared dye (NIR830) labeled bevacizumab to magnetic iron oxide nanoparticles (IONP) for optical and magnetic resonance (MR) imaging of cancers over-expressing VEGF. The targeting effect of NIR830-bevacizumab-IONPs on VEGF over-expressing cells was investigated by receptor mediated cell uptake experiments and a blocking assay using VEGF over-expressing 4T1 breast cancer cells. Systemic administration of VEGF-targeted NIR830-bevacizumab-IONPs into mice bearing 4T1 breast tumors resulted in higher accumulation of targeting IONPs in tumors compared to non-targeted IONPs. Quantitative analysis of T2-weighted MRI at 48 h post-injection revealed that the averaged percentage of signal intensity change in tumors treated with NIR830-bevacizumab-IONPs was 52.4 ± 11.0% compared to 26.9 ± 12.4% in controls treated with non-targeted IONPs. The results demonstrated the feasibility and efficacy of NIR830-bevacizumab-IONPs as a VEGF targeting dual-modality molecular imaging probe that can be potentially used for imaging of cancers with VEGF over-expression and delivery of bevacizumab for imaging guided anti-cancer treatment.

Primary rat LSECs preserve their characteristic phenotype after cryopreservation

Liver disease is a leading cause of morbidity and mortality worldwide. Recently, the liver non-parenchymal cells have gained increasing attention for their potential role in the development of liver disease. Liver sinusoidal endothelial cells (LSECs), a specialized type of endothelial cells that have unique morphology and function, play a fundamental role in maintaining liver homeostasis. Current protocols for LSEC isolation and cultivation rely on freshly isolated cells which can only be maintained differentiated in culture for a few days. This creates a limitation in the use of LSECs for research and a need for a consistent and reliable source of these cells. To date, no LSEC cryopreservation protocols have been reported that enable LSECs to retain their functional and morphological characteristics upon thawing and culturing. Here, we report a protocol to cryopreserve rat LSECs that, upon thawing, maintain full LSEC-signature features: fenestrations, scavenger receptor expression and endocytic function on par with freshly isolated cells. We have confirmed these features by a combination of biochemical and functional techniques, and super-resolution microscopy. Our findings offer a means to standardize research using LSECs, opening the prospects for designing pharmacological strategies for various liver diseases, and considering LSECs as a therapeutic target.

Challenges and innovations of drug delivery in older age

Both drug delivery performance and various age-related physical, mental and physiological changes can affect drug effectiveness and safety in elderly patients. The many drug delivery systems developed over the years include recent novel transdermal, nasal, pulmonary and orally disintegrating tablets that provide consistent, precise, timely and more targeted drug delivery. Certain drug delivery systems may be associated with suboptimal outcomes in the elderly because of the nature of drug present, a lack of appreciation of the impact of age-related changes in drug absorption, distribution and clearance, the limited availability of pharmacokinetic, safety and clinical data. Polypharmacy, patient morbidity and poor adherence can also contribute to sub-optimal drug delivery systems outcomes in the elderly. The development of drug delivery systems for the elderly is a poorly realised opportunity, with each system having specific advantages and limitations. A key challenge is to provide the innovation that best meets the specific physiological, psychological and multiple drug requirements of individual elderly patients.

Non-parenchymal hepatic cell lipotoxicity and the coordinated progression of non-alcoholic fatty liver disease and atherosclerosis

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) appears to be independently associated with the development of atherosclerosis. The biological mechanisms underlying this association are complex, and likely involve liver-resident cell types other than hepatocytes. Thus, we review recent evidence that non-parenchymal hepatic cell responses to lipid excess contribute to the pathogenesis of both NAFLD and atherosclerosis.

RECENT FINDINGS

Significant independent associations between NAFLD and atherosclerosis have been identified through cross-sectional studies and meta-analyses. Mechanistic studies in cell cultures and in rodent models suggest that liver-resident macrophages, activated hepatic stellate cells (HSC) and liver sinusoidal endothelial cells (LSEC) mount lipotoxic responses under NAFLD conditions which can contribute to the progression of both NAFLD and atherosclerosis.

SUMMARY

Non-parenchymal hepatic cell types exhibit some similarity in their responses to lipid excess, and in their pathogenic mechanisms, which likely contribute to the coordinated progression of NAFLD and atherosclerosis. In response to lipotoxic conditions, macrophages, Kupffer cells and HSC initiate robust inflammatory responses, whereas LSEC generate excess reactive oxygen species (ROS). The extent to which inflammatory cytokines and ROS produced by non-parenchymal cells contribute to the progression of both NAFLD and atherosclerosis warrants further investigation.

Liver fibrosis: Pathophysiology, pathogenetic targets and clinical issues

The progression of chronic liver diseases (CLD), irrespective of etiology, involves chronic parenchymal injury, persistent activation of inflammatory response as well as sustained activation of liver fibrogenesis and wound healing response. Liver fibrogenesis, is a dynamic, highly integrated molecular, cellular and tissue process responsible for driving the excess accumulation of extracellular matrix (ECM) components (i.e., liver fibrosis) sustained by an eterogeneous population of hepatic myofibroblasts (MFs). The process of liver fibrogenesis recognizes a number of common and etiology-independent mechanisms and events but it is also significantly influenced by the specific etiology, as also reflected by peculiar morphological patterns of liver fibrosis development. In this review we will analyze the most relevant established and/or emerging pathophysiological issues underlying CLD progression with a focus on the role of critical hepatic cell populations, mechanisms and signaling pathways involved, as they represent potential therapeutic targets, to finally analyze selected and relevant clinical issues.

Microfluidic-based vascularized microphysiological systems

Microphysiological systems have emerged in the last decade to provide an alternative to in vivo models in basic science and pharmaceutical research. In the field of vascular biology, in particular, there has been a lack of a suitable in vitro model exhibiting a three-dimensional structure and the physiological function of vasculature integrated with organ-on-a-chip models. The rapid development of organ-on-a-chip technology is well positioned to fulfill unmet needs. Recently, functional integration of vasculature with diverse microphysiological systems has been increasing. This recent trend corresponds to emerging research interest in how the vascular system contributes to various physiological and pathological conditions. This innovative platform has undergone significant development, but adoption of this technology by end-users and researchers in biology is still a work in progress. Therefore, it is critical to focus on simplification and standardization to promote the distribution and acceptance of this technology by the end-users. In this review, we will introduce the latest developments in vascularized microphysiological systems and summarize their outlook in basic research and drug screening applications.

The contributions of mesoderm-derived cells in liver development

The liver is an indispensable organ for metabolism and drug detoxification. The liver consists of endoderm-derived hepatobiliary lineages and various mesoderm-derived cells, and interacts with the surrounding tissues and organs through the ventral mesentery. Liver development, from hepatic specification to liver maturation, requires close interactions with mesoderm-derived cells, such as mesothelial cells, hepatic stellate cells, mesenchymal cells, liver sinusoidal endothelial cells and hematopoietic cells. These cells affect liver development through precise signaling events and even direct physical contact. Through the use of new techniques, emerging studies have recently led to a deeper understanding of liver development and its related mechanisms, especially the roles of mesodermal cells in liver development. Based on these developments, the current protocols for in vitro hepatocyte-like cell induction and liver-like tissue construction have been optimized and are of great importance for the treatment of liver diseases. Here, we review the roles of mesoderm-derived cells in the processes of liver development, hepatocyte-like cell induction and liver-like tissue construction.

Transcriptional and epigenomic landscapes of CNS and non-CNS vascular endothelial cells

Vascular endothelial cell (EC) function depends on appropriate organ-specific molecular and cellular specializations. To explore genomic mechanisms that control this specialization, we have analyzed and compared the transcriptome, accessible chromatin, and DNA methylome landscapes from mouse brain, liver, lung, and kidney ECs. Analysis of transcription factor (TF) gene expression and TF motifs at candidate cis-regulatory elements reveals both shared and organ-specific EC regulatory networks. In the embryo, only those ECs that are adjacent to or within the central nervous system (CNS) exhibit canonical Wnt signaling, which correlates precisely with blood-brain barrier (BBB) differentiation and Zic3 expression. In the early postnatal brain, single-cell RNA-seq of purified ECs reveals (1) close relationships between veins and mitotic cells and between arteries and tip cells, (2) a division of capillary ECs into vein-like and artery-like classes, and (3) new endothelial subtype markers, including new validated tip cell markers.

Analyzing 2000 in Vivo Drug Delivery Data Points Reveals Cholesterol Structure Impacts Nanoparticle Delivery

Lipid nanoparticles (LNPs) are formulated using unmodified cholesterol. However, cholesterol is naturally esterified and oxidized in vivo, and these cholesterol variants are differentially trafficked in vivo via lipoproteins including LDL and VLDL. We hypothesized that incorporating the same cholesterol variants into LNPs-which can be structurally similar to LDL and VLDL-would alter nanoparticle targeting in vivo. To test this hypothesis, we quantified how >100 LNPs made with six cholesterol variants delivered DNA barcodes to 18 cell types in wild-type, LDLR-/-, and VLDLR-/- mice that were both age-matched and female. By analyzing ∼2000 in vivo drug delivery data points, we found that LNPs formulated with esterified cholesterol delivered nucleic acids more efficiently than LNPs formulated with regular or oxidized cholesterol when compared across all tested cell types in the mouse. We also identified an LNP containing cholesteryl oleate that efficiently delivered siRNA and sgRNA to liver endothelial cells in vivo. Delivery was as-or more-efficient as the same LNP made with unmodified cholesterol. Moreover, delivery to liver endothelial cells was 3 times more efficient than delivery to hepatocytes, distinguishing this oleate LNP from hepatocyte-targeting LNPs. RNA delivery can be improved by rationally selecting cholesterol variants, allowing optimization of nanoparticle targeting.

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.

C-type natriuretic peptide (CNP) in endothelial cells attenuates hepatic fibrosis and inflammation in non-alcoholic steatohepatitis

AIMS

Our previous study revealed that mice transgenic for endothelial-cell-specific overexpression of CNP (E-CNP Tg mice) are protected against the increased fat weight, inflammation, and insulin resistance associated with high-fat diet (HFD)-induced obesity. In addition, E-CNP overexpression prevented abnormal lipid profiles and metabolism and blocked inflammation in the livers of HFD-fed mice. Because obesity, dyslipidemia, and insulin resistance increase the risk of various liver diseases, including non-alcoholic steatohepatitis (NASH), we here studied the role of E-CNP overexpression in the livers of mice in which NASH was induced through feeding of either HFD or a choline-deficient defined l‑amino-acid diet (CDAA).

MAIN METHODS

Wild-type (Wt) and E-CNP Tg mice were fed either a standard diet or HFD for 25 weeks or CDAA for 10 weeks. We then assessed hepatic and serum biochemistry; measured blood glucose during glucose tolerance test (GTT) and insulin tolerance test (ITT); evaluated hepatic fibrosis and inflammation; and performed hepatic histology and gene expression analysis.

KEY FINDINGS

Serum triglycerides, total cholesterol, non-esterified fatty acids, asparagine transaminase, glucose tolerance, and insulin resistance were ameliorated by CNP overexpression in endothelial cells of HFD-fed E-CNP Tg mice. In addition, hepatic fibrosis and inflammation were decreased in HFD-fed E-CNP Tg mice compared with HFD-fed Wt mice. CDAA-fed E-CNP Tg mice showed improved glycemic control, but liver parameters, fibrosis, and inflammation were remained elevated and equivalent to those in CDAA-fed Wt mice.

SIGNIFICANCE

The overexpression of CNP in endothelial cells has anti-fibrotic and anti-inflammatory effects in liver during HFD-induced NASH in mice.

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).

Deoxynivalenol induces structural alterations in epidermoid carcinoma cells A431 and impairs the response to biomechanical stimulation

Morphology together with the capability to respond to surrounding stimuli are key elements governing the spatial interaction of living cells with the environment. In this respect, biomechanical stimulation can trigger significant physiological cascades that can potentially modulate toxicity. Deoxynivalenol (DON, vomitoxin) is one of the most prevalent mycotoxins produced by Fusarium spp. and it was used to explore the delicate interaction between biomechanical stimulation and cytotoxicity in A431 cells. In fact, in addition of being a food contaminant, DON is a relevant toxin for several organ systems. The combination between biomechanical stimulation and the mycotoxin revealed how DON can impair crucial functions affecting cellular morphology, tubulin and lysosomes at concentrations even below those known to be cytotoxic in routine toxicity studies. Sub-toxic concentrations of DON (0.1-1 μM) impaired the capability of A431 cells to respond to a biomechanical stimulation that normally sustains trophic effects in these cells. Moreover, the effects of DON (0.1-10 μM) were partially modulated by the application of uniaxial stretching (0.5 Hz, 24 h, 15% deformation). Ultimately, proteomic analysis revealed the potential of DON to alter several proteins necessary for cell adhesion and cytoskeletal modulation suggesting a molecular link between biomechanics and the cytotoxic potential of the mycotoxin.

Septins regulate junctional integrity of endothelial monolayers

Junctional integrity of endothelial monolayers is crucial to control movement of molecules and cells across the endothelium. Examining the structure and dynamics of cell junctions in endothelial monolayers, we discovered a role for septins. Contacts between adjacent endothelial cells were dynamic, with protrusions extending above or below neighboring cells. Vascular endothelial cadherin (VE-cadherin) was present at cell junctions, with a membrane-associated layer of F-actin. Septins localized at cell-junction membranes, in patterns distinct from VE-cadherin and F-actin. Septins assumed curved and scallop-shaped patterns at junctions, especially in regions of positive membrane curvature associated with actin-rich membrane protrusions. Depletion of septins led to disrupted morphology of VE-cadherin junctions and increased expression of VE-cadherin. In videos, septin-depleted cells displayed remodeling at cell junctions; regions with VE-cadherin were broader, and areas with membrane ruffling were wider. Septin depletion and junction disruption led to functional loss of junctional integrity, revealed by decreased transendothelial electric resistance and increased transmigration of immune cells. We conclude that septins, as cytoskeletal elements associated with the plasma membrane, are important for cell junctions and junctional integrity of endothelial monolayers, functioning at regions of positive curvature in support of actin-rich protrusions to promote cadherin-based cell junctions.

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

BACKGROUND INFORMATION

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, open transcellular pores with an average diameter of 100 nm. 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.

RESULTS

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.

CONCLUSIONS

Our approach demonstrates that STED microscopy is suitable for LSEC fenestrae study.

SIGNIFICANCE

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.

The effect of mechanosensitive channel MscL expression in cancer cells on 3D confined migration

Metastatic cancer cells migrate through constricted spaces and experience significant compressive stress, but mechanisms enabling migration in confined geometries remain unclear. Cancer cell migration within confined 3-dimensional (3D) microfluidic channels has been shown to be distinct from 2D cell migration. However, whether 3D confined migration can be manipulated by mechanosensory components has not been examined in detail. In this work, we exogenously introduced a mechanosensitive channel of large conductance (MscL) into metastatic breast cancer cells MDA-MB-231. We discovered that inducing expression of a gain-of-function G22S mutant of MscL in MDA-MB-231 cells significantly reduced spontaneous lung metastasis without affecting the growth of orthotopic tumor implants. To further investigate the effects of G22S MscL on cell migration, we designed a microfluidic device with channels of various cross-sections ranging from a 2D planar environment to narrow 3D constrictions. Both MscL G22S and control breast cancer cells migrated progressively slower in more constricted environments. Migration of cells expressing MscL G22S did not differ from control cells, even though MscL was activated in cells in constricted channels of 3 μm width. Interestingly, we found MscL expressing cells to be more frequently “stuck” at the entrance of the 3 μm channels and failed to migrate into the microchannel. Our work demonstrates the possibility of engineering mechanotransduction for controlling confined cell migration.

Hypothermic oxygenated perfusion (HOPE) attenuates ischemia/reperfusion injury in the liver through inhibition of the TXNIP/NLRP3 inflammasome pathway in a rat model of donation after cardiac death

Hypothermic oxygenated perfusion (HOPE) is a relatively new dynamic preservation procedure that has not been widely implemented in liver transplantation despite its advantages. Improved graft protection is one such advantage offered by HOPE and has been attributed to multiple mechanisms, one of which may be the modulation of the thioredoxin-interacting protein (TXNIP)/NOD-like receptor protein 3 (NLRP3) inflammasome pathway. The TXNIP/NLRP3 inflammasome pathway plays a critical role in sterile inflammation under oxidative stress as a result of ischemia/reperfusion injury (IRI). In the current study, we aimed to investigate the graft protection offered by HOPE and its impact on the TXNIP/NLRP3 inflammasome pathway. To simulate conditions of donation after cardiac death (DCD) liver transplantation, rat livers were exposed to 30 min of warm ischemia after cardiac arrest. Livers were then preserved under cold storage (CS) or with HOPE for 3 h. Livers were then subjected to 1 h of isolated reperfusion. Liver injuries were assessed on the isolated perfusion rat liver model system before and after reperfusion. Compared with the CS group, the HOPE group had a significant reduction in liver injury and improvement in liver function. Our findings also revealed that reperfusion injury induced liver damage and activated the TXNIP/NLRP3 inflammasome pathway in DCD rat livers. Pretreatment of DCD rat livers with HOPE inhibited the TXNIP/NLRP3 inflammasome pathway and attenuated liver IRI. Attenuation of oxidative stress as a result of HOPE led to the down-regulation of the TXNIP/NLRP3 inflammasome pathway and thus offered superior protection compared with the traditional CS method of organ preservation.-He, W., Ye, S., Zeng, C., Xue, S., Hu, X., Zhang, X., Gao, S., Xiong, Y., He, X., Vivalda, S., Li, L., Wang, Y., Ye, Q. Hypothermic oxygenated perfusion (HOPE) attenuates ischemia/reperfusion injury in the liver through inhibition of the TXNIP/NLRP3 inflammasome pathway in a rat model of donation after cardiac death.

Factors relating to the biodistribution & clearance of nanoparticles & their effects on in vivo application

Nanoparticles have promising biomedical applications for drug delivery, tumor imaging and tumor treatment. Pharmacokinetics are important for the in vivo application of nanoparticles. Biodistribution and clearance are largely defined as the key points of pharmacokinetics to maximize therapeutic efficacy and to minimize side effects. Different engineered nanoparticles have different biodistribution and clearance processes. The interactions of organs with nanoparticles, which are determined by the characteristics of the organs and the biochemical/physical properties of the nanoparticles, are a major factor influencing biodistribution and clearance. In this review, the clearance functions of organs and the properties related to pharmacokinetics, including nanoparticle size, shape, biodegradation and surface modifications are discussed.

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.

Development of the liver: Insights into organ and tissue morphogenesis

Recent development of improved tools and methods to analyse tissues at the three-dimensional level has expanded our capacity to investigate morphogenesis of foetal liver. Here, we review the key morphogenetic steps during liver development, from the prehepatic endoderm stage to the postnatal period, and consider several model organisms while focussing on the mammalian liver. We first discuss how the liver buds out of the endoderm and gives rise to an asymmetric liver. We next outline the mechanisms driving liver and lobe growth, and review morphogenesis of the intra- and extrahepatic bile ducts; morphogenetic responses of the biliary tract to liver injury are discussed. Finally, we describe the mechanisms driving formation of the vasculature, namely venous and arterial vessels, as well as sinusoids.

Pivotal roles of Kupffer cells in the progression and regression of DDC-induced chronic cholangiopathy

Kupffer cells (KCs) are key players in maintaining tissue homeostasis and are involved in various liver diseases. However, the roles of KCs in the pathogenesis of cholangiopathy are largely unknown. We aimed to investigate the precise roles of KCs in both the progression and regression phases of the 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-induced cholangiopathy model. In the early phase of DDC-induced cholangiopathy, the number of KCs significantly increased over time. Moreover, KCs were associated with abnormal phenotypic changes in other liver cells, such as hepatocytes, biliary epithelial cells, liver sinusoidal endothelial cells, and hepatic stellate cells. In contrast, KC depletion by clodronate administration suppressed the progression of the disease, and maintained the phenotypes of other cells. In the regression phase, the numbers of KCs significantly decreased, and the cells redifferentiated to their quiescent state. In contrast, KC depletion delayed the recovery of cells by maintaining other liver cells in an active state. These findings suggest that KCs play detrimental roles in the progression phase; however, they are beneficial in the regression phase by mediating interactions between other liver cells. Our data provide new insights into the roles of KCs in the pathogenesis of cholangiopathy.

Endothelial Dysfunction in Steatotic Human Donor Livers: A Pilot Study of the Underlying Mechanism During Subnormothermic Machine Perfusion

Supplemental digital content is available in the text.

Background

Steatosis is a major risk factor for primary nonfunction in liver transplantations. Steatotic livers recover poorly from ischemia reperfusion injury, in part due to alterations in the microcirculation, although the exact mechanism is unclear. In this study, we tested if there were any alterations in the shear stress sensing Kruppel-like factor 2 (KLF2) and its likely downstream consequences in the ex vivo perfused human liver endothelium, which would imply perturbations in microcirculatory flow in macrosteatotic livers disrupts laminar flow to evaluate if this is a potential therapeutic target for steatotic livers.

Methods

Using a subnormothermic machine perfusion system, 5 macrosteatotic and 4 nonsteatotic human livers were perfused for 3 hours. Flow, resistance, and biochemical profile were monitored. Gene expression levels of nitric oxide synthase 3 (eNOS), KLF2, and thrombomodulin were determined. Nitric oxide (NO) was measured in the perfusion fluid and activation of eNOS was measured with Western blotting.

Results

Flow dynamics, injury markers, and bile production were similar in both groups. Kruppel-like factor 2 expression was significantly higher in nonsteatotic livers. Western blotting analyses showed significantly higher levels of activated eNOS in nonsteatotic livers, consistent with an increase in NO production over time. Macrosteatotic livers showed decreased KLF2 upregulation, eNOS activity, and NO production during machine perfusion.

Conclusions

These results indicate a perturbed KLF2 sensing in steatotic livers, which aligns with perturbed microcirculatory state. This may indicate endothelial dysfunction and contribute to poor posttransplantation outcomes in fatty livers, and further studies to confirm by evaluation of flow and testing treatments are warranted.

Von Willebrand factor indicates bacterial translocation, inflammation, and procoagulant imbalance and predicts complications independently of portal hypertension severity

BACKGROUND

Elevated plasma von Willebrand factor antigen (vWF) has been shown to indicate the presence of clinically significant portal hypertension, and thus, predicts the development of clinical events in patients with cirrhosis.

AIM

To investigate the impact of bacterial translocation and inflammation on vWF, as well as the association between vWF and procoagulant imbalance. Moreover, we assessed whether vWF predicts complications of cirrhosis, independent of the severity of portal hypertension.

METHODS

Our study population comprised 225 patients with hepatic venous pressure gradient (HVPG) ≥ 10 mm Hg without active bacterial infections or hepatocellular carcinoma.

RESULTS

vWF correlated with markers of bacterial translocation (lipopolysaccharide-binding protein [LBP; ρ = 0.201; P = 0.021]), inflammation (interleukin 6 [IL-6; ρ = 0.426; P < 0.001] and C-reactive protein [CRP; ρ = 0.249; P < 0.001]), and procoagulant imbalance (factor VIII/protein C ratio; ρ = 0.507; P < 0.001). Importantly, the associations between vWF and these parameters were independent of HVPG. Moreover, vWF (per 10%) independently predicted variceal bleeding (hazard ratio [HR]: 1.08 [95% confidence interval (95% CI): 1.01-1.16]; P = 0.023), requirement of paracentesis (HR: 1.05 [95% CI: 1.01-1.1]; P = 0.023) and bacterial infections (HR: 1.04 [95% CI: 1-1.09]; P = 0.04) including spontaneous bacterial peritonitis (HR: 1.09 [95% CI: 0.999-1.18]; P = 0.053) on a trend-wise level. After backward elimination, vWF (HR: 1.05 [95% CI: 1.02-1.08]; P = 0.003) and CRP (per 10 mg/L; HR: 1.53 [95% CI: 1.14-2.05]; P = 0.005) remained in the final model for transplant-free mortality. Finally, the independent prognostic value of vWF/CRP groups for mortality was confirmed by competing risk analysis.

CONCLUSION

Our results demonstrate that vWF is not only a marker of portal hypertension but also independently linked to bacterial translocation, inflammation and procoagulant imbalance, which might explain its HVPG-independent association with most clinical events. Prognostic groups based on vWF/CRP efficiently discriminate between patients with a poor 5-year survival and patients with a favourable prognosis.

The Contribution of Non-Professional Antigen-Presenting Cells to Immunity and Tolerance in the Liver

The liver represents a unique organ biased toward a tolerogenic milieu. Due to its anatomical location, it is constantly exposed to microbial and food-derived antigens from the gut and thus equipped with a complex cellular network that ensures dampening T-cell responses. Within this cellular network, parenchymal cells (hepatocytes), non-parenchymal cells (liver sinusoidal endothelial cells and hepatic stellate cells), and immune cells contribute directly or indirectly to this process. Despite this refractory bias, the liver is capable of mounting efficient T-cell responses. How the various antigen-presenting cell (APC) populations contribute to this process and how they handle danger signals determine the outcome of the generated immune responses. Importantly, liver mounted responses convey consequences not only for the local but also to systemic immunity. Here, we discuss various aspects of antigen presentation and its consequences by the non-professional APCs in the liver microenvironment.

Origins of Portal Hypertension in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) advanced to cirrhosis is often complicated by clinically significant portal hypertension, which is primarily caused by increased intrahepatic vascular resistance. Liver fibrosis has been identified as a critical determinant of this process. However, there is evidence that portal venous pressure may begin to rise in the earliest stages of NAFLD when fibrosis is far less advanced or absent. The biological and clinical significance of these early changes in sinusoidal homeostasis remains unclear. Experimental and human observations indicate that sinusoidal space restriction due to hepatocellular lipid accumulation and ballooning may impair sinusoidal flow and generate shear stress, increasingly disrupting sinusoidal microcirculation. Sinusoidal endothelial cells, hepatic stellate cells, and Kupffer cells are key partners of hepatocytes affected by NAFLD in promoting endothelial dysfunction through enhanced contractility, capillarization, adhesion and entrapment of blood cells, extracellular matrix deposition, and neovascularization. These biomechanical and rheological changes are aggravated by a dysfunctional gut-liver axis and splanchnic vasoregulation, culminating in fibrosis and clinically significant portal hypertension. We may speculate that increased portal venous pressure is an essential element of the pathogenesis across the entire spectrum of NAFLD. Improved methods of noninvasive portal venous pressure monitoring will hopefully give new insights into the pathobiology of NAFLD and help efforts to identify patients at increased risk for adverse outcomes. In addition, novel drug candidates targeting reversible components of aberrant sinusoidal circulation may prevent progression in NAFLD.

Are we any closer to treating liver fibrosis (and if no, why not)?

This review provides a personal view on anti-fibrosis therapy in the liver. The worst clinical consequence of liver fibrosis is the development of liver cirrhosis and portal hypertension. Etiology is a decisive factor which determines patterns of fibrous septa and subsequent vascular remodeling, which is essential for the development of portal hypertension. Removing or controlling the disease-causing agent, i.e. anti-viral treatment for hepatitis, is the essential first step for treating chronic liver diseases and can reverse fibrosis in some settings. However, removing etiology is not always sufficient to prevent fibrosis from progressing towards cirrhosis and portal hypertension. In liver diseases such as severe alcoholic hepatitis and massive parenchymal loss, the formation of vascular anastomoses between portal to central veins based on bridging fibrosis results in cirrhosis and portal hypertension. For these patients, anti-fibrotic treatment is crucial and urgent. Unfortunately, a lack of understanding how fibrosis contributes to vascular remodeling caused by and combined with a lack of suitable experimental models that recapitulate human liver diseases, has hampered the development of successful anti-fibrotic drugs for clinical use to date.

Platelets as Modulators of Liver Diseases

Platelets are key players in thrombosis and hemostasis. Alterations in platelet count and function are common in liver disease, and may contribute to bleeding or thrombotic complications in liver diseases and during liver surgery. In addition to their hemostatic function, platelets may modulate liver diseases by mechanisms that are incompletely understood. Here, we present clinical evidence for a role of platelets in the progression of chronic and acute liver diseases, including cirrhosis, acute liver failure, and hepatocellular carcinoma. We also present clinical evidence that platelets promote liver regeneration following partial liver resection. Subsequently, we summarize studies in experimental animal models that support these clinical observations, and also highlight studies that are in contrast with clinical observations. The combined results of clinical and experimental studies suggest that platelets may be a therapeutic target in the treatment of liver injury and repair, but the gaps in our understanding of mechanisms involved in platelet-mediated modulation of liver diseases call for caution in clinical application of these findings.

Intentional Modulation of Portal Venous Pressure by Splenectomy Saves the Patient with Liver Failure and Portal Hypertension After Major Hepatectomy: Is Delayed Splenectomy an Acceptable Therapeutic Option for Secondary Portal Hypertension?

BACKGROUND Major or aggressively-extended hepatectomy (MAEH) may cause secondary portal hypertension (PH), and postoperative liver failure (POLF) and is often fatal. Challenges to prevent secondary PH and subsequent POLF, such as shunt creation and splenic arterial ligation, have been reported. However, these procedures have been performed simultaneously only during the initial MAEH. CASE REPORT A 58-year-old female with chronic hepatitis C developed a solitary hepatic cellular carcinoma with portal tumor thrombosis. Blood examination and imaging revealed a decreased platelet count and splenomegaly. Her liver viability was preserved, and collaterals did not develop, and her tumor thrombosis forced us to perform a right hepatectomy from an oncological standpoint. The estimated volume of her liver remnant was 51.8%. A large volume of ascites and pleural effusion were observed on post-operative day (POD) 3, and ascetic infection occurred on POD 14. Hepatic encephalopathy was observed on POD 16. According to the post-operative development of collaterals due to secondary PH, submucosal bleeding in the stomach occurred on POD 37. Though it is unclear whether delayed portal venous pressure (PVP) modulation after MAEH is effective, a therapeutic strategy for recovery from POLF may involve PVP modulation to resolve intractable PH. We performed a splenectomy on POD 41 to reduce PVP. The initial PVP value was 32 mm Hg, and splenectomy decreased PVP to 23 mm Hg. Thereafter, she had a complete recovery from POLF. CONCLUSIONS Our thought-provoking case is the first successfully-treated case of secondary PH and POLF after MAEH, achieved by delayed splenectomy for PVP modulation.

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.

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.

The Injury-Related Activation of Hedgehog Signaling Pathway Modulates the Repair-Associated Inflammation in Liver Fibrosis

Liver fibrosis is a wound healing response initiated by inflammation responding for different iterative parenchymal damages caused by diverse etiologies. Immune cells, which exert their ability of either inducing injury or promoting repair, have been regarded as crucial participants in the fibrogenic response. A characteristic feature of the fibrotic microenvironment associated with chronic liver injury is aberrant activation of hedgehog (Hh) signaling pathway. Growing evidence from a number of different studies in vivo and in vitro has indicated that immune-mediated events involved in liver fibrogenesis are regulated by Hh signaling pathway. In this review, we emphasize the impacts of injury-activated Hh signaling on liver fibrogenesis through modulating repair-related inflammation and focus on the regulatory action of aberrant Hh signaling on repair-related inflammatory responses mediated by hepatic classical and non-classical immune cell populations in the progression of liver fibrosis. Moreover, we also assess the potentiality of Hh pathway inhibitors as good candidates for anti-fibrotic therapeutic agents because of their immune regulation actions for fibrogenic liver repair. The identification of immune-modulatory mechanisms of Hh signaling pathway underlying the fibrotic process of chronic liver diseases might provide a basis for Hh-centered therapeutic strategies for liver fibrosis.

Liver Sinusoidal Endothelial Cell: An Update

This update focuses on two main topics. First, recent developments in our understanding of liver sinusoidal endothelial cell (LSEC) function will be reviewed, specifically elimination of blood-borne waste, immunological function of LSECs, interaction of LSECs with liver metastases, LSECs and liver regeneration, and LSECs and hepatic fibrosis. Second, given the current emphasis on rigor and transparency in biomedical research, the update discusses the need for standardization of methods to demonstrate identity and purity of isolated LSECs, pitfalls in methods that might lead to a selection bias in the types of LSECs isolated, and questions about long-term culture of LSECs. Various surface markers used for immunomagnetic selection are reviewed.

Hepatic stellate cells as key target in liver fibrosis

Progressive liver fibrosis, induced by chronic viral and metabolic disorders, leads to more than one million deaths annually via development of cirrhosis, although no antifibrotic therapy has been approved to date. Transdifferentiation (or "activation") of hepatic stellate cells is the major cellular source of matrix protein-secreting myofibroblasts, the major driver of liver fibrogenesis. Paracrine signals from injured epithelial cells, fibrotic tissue microenvironment, immune and systemic metabolic dysregulation, enteric dysbiosis, and hepatitis viral products can directly or indirectly induce stellate cell activation. Dysregulated intracellular signaling, epigenetic changes, and cellular stress response represent candidate targets to deactivate stellate cells by inducing reversion to inactivated state, cellular senescence, apoptosis, and/or clearance by immune cells. Cell type- and target-specific pharmacological intervention to therapeutically induce the deactivation will enable more effective and less toxic precision antifibrotic therapies.

Oroxylin A prevents angiogenesis of LSECs in liver fibrosis via inhibition of YAP/HIF-1α signaling

Angiogenesis of liver sinusoidal endothelial cells (LSECs) accompanies with hypoxia in liver fibrosis and they are of mutual promotion, which has raised wide concern. Here we established murine model of liver fibrosis and found that oroxylin A (40 mg/kg) could ameliorate angiogenesis in liver fibrosis may related to hypoxia inducible factor 1α (HIF-1α). The underlying mechanism was further investigated by isolating and culturing murine primary LSECs. Hypoxia induced vascular endothelial growth factor A (VEGF-A), angiopoietin 2 (Ang-2), and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) elevated in LSECs were reduced by oroxylin A or acriflavine (ACF, an HIF-1α inhibitor), indicating HIF-1α involved the angiogenesis of LSECs. Additionally, interference with Yes-associated protein (YAP) significant downregulated the protein expression of HIF-1α and VEGF-A, while YAP plasmid exhibited an opposite effect. We next found that oroxylin A inhibited hypoxia-induced nuclear translocation of YAP, which may influence the accumulation of HIF-1α and subsequently decrease transcription of downstream target gene including VEGF-A and Ang-2, thereby exerting an anti-angiogenic activity.

An in-depth review of chemical angiogenesis inhibitors for treating hepatocellular carcinoma

INTRODUCTION

Hepatocellular carcinoma (HCC) is a frequent and severe complication of cirrhosis. Most HCC patients initially present with or progress to advanced stage disease and require systemic treatment. As hypervascularization is a major characteristic of HCC, antiangiogenic drugs have been tested. Areas covered: In this review, we summarize data on the use of drugs targeting the angiogenesis. Despite many trials, in 2017 only 3 drugs, all antiangiogenic, have demonstrated efficacy in first (sorafenib, lenvatinib) or second line (regorafenib) treatment of advanced HCC. The heterogeneous mechanisms of action and the major reasons for failure of most trials are discussed. An English-language, abstract-based literature review was performed by a PubMed-based strategy. Expert opinion: Currently all trials based on purely antiangiogenic compounds (bevacizumab, linifanib, brivanib and ramucirumab) or drugs with strong antiangiogenic properties (sunitinib) have failed (increased toxicity, minor efficacy and/or flaws in trial design); sorafenib, lenvatinib and regorafenib are multityrosine kinase inhibitors and their efficacy can be partly related to another mechanism of action. We need to better refine future trials design (randomized phase 2, good stratification factors and marker-enriched patient selection) in order to progress toward customized treatment, perhaps in association with immunotherapy.

Vascular Endothelial Regulation of Obesity-Associated Insulin Resistance

Obesity is a worldwide epidemic that predisposes individuals to metabolic complications, such as type 2 diabetes mellitus and non-alcoholic fatty liver disease, all of which are related to an imbalance between food intake and energy expenditure. Identification of the pathogenic molecular mechanisms and effective therapeutic approaches are urgently needed. A well-accepted paradigm is that crosstalk between organs/tissues contributes to diseases. Endothelial dysfunction characterizes metabolic disorders and the related vascular complications. Over the past two decades, overwhelming studies have focused on mechanisms that lead to endothelial dysfunction. New investigations, however, have begun to appreciate the opposite direction of the crosstalk: endothelial regulation of metabolism, although the underlying mechanisms remain to be elucidated. This review summarizes the evidence that supports the concept of endothelial regulation of obesity and the associated insulin resistance in fat, liver, and skeletal muscles, the classic targets of insulin. Outstanding questions and future research directions are highlighted. Identification of the mechanisms of vascular endothelial regulation of metabolism may offer strategies for prevention and treatment of obesity and the related metabolic complications.

Plumbagin Alleviates Capillarization of Hepatic Sinusoids In Vitro by Downregulating ET-1, VEGF, LN, and Type IV Collagen

Critical roles for liver sinusoidal endothelial cells (LSECs) in liver fibrosis have been demonstrated, while little is known regarding the underlying molecular mechanisms of drugs delivered to the LSECs. Our previous study revealed that plumbagin plays an antifibrotic role in liver fibrosis. In this study, we investigated whether plumbagin alleviates capillarization of hepatic sinusoids by downregulating endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), laminin (LN), and type IV collagen on leptin-stimulated LSECs. We found that normal LSECs had mostly open fenestrae and no organized basement membrane. Leptin-stimulated LSECs showed the formation of a continuous basement membrane with few open fenestrae, which were the features of capillarization. Expression of ET-1, VEGF, LN, and type IV collagen was enhanced in leptin-stimulated LSECs. Plumbagin was used to treat leptin-stimulated LSECs. The sizes and numbers of open fenestrae were markedly decreased, and no basement membrane production was found after plumbagin administration. Plumbagin decreased the levels of ET-1, VEGF, LN, and type IV collagen in leptin-stimulated LSECs. Plumbagin promoted downregulation of ET-1, VEGF, LN, and type IV collagen mRNA. Altogether, our data reveal that plumbagin reverses capillarization of hepatic sinusoids by downregulation of ET-1, VEGF, LN, and type IV collagen.

Probing the unseen structure and function of liver cells through atomic force microscopy

With the arrival of atomic force microscopy (AFM) about thirty years ago, this new imaging tool opened up a new area for the exploration of biological samples, ranging from the tissue and cellular level down to the supramolecular scale. Commercial instruments of this new imaging technique began to appear in the five years following its discovery in 1986 by Binnig, Quate & Gerber. From that point onwards the AFM has attracted many liver biologists, and the number of publications describing structure-function relationships on the diverse set of liver cells has grown steadily ever since. It is therefore timely to reflect on the achievements of AFM in disclosing the cellular architecture of hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, stellate cells and liver-associated natural killer cells. In this thematic paper, we present new data and provide an in-depth overview of the current AFM literature on liver cell biology. We furthermore include a future outlook on how this scanning probe imaging tool and its latest developments can contribute to clarify various structural and functional aspects of cells in liver health and disease.

Hepatic Progenitor Cells: An Update

Liver regeneration is a fascinating and complex process with many medical implications. An important component of this regenerative process is the hepatic progenitor cell (HPC). These appealing cells are able to participate in the renewal of hepatocytes and cholangiocytes when the normal homeostatic regeneration is exhausted. Moreover, the HPC niche is of vital importance toward the activation, differentiation, and proliferation of the HPC. This niche provides a rich microenvironment for the regulation of the HPC, thanks to the intercellular secretion of molecules. New findings indicate that the regenerative possibilities in the liver could provide a diverse basis for therapeutic targets.

Endothelial microparticles released by activated protein C protect beta cells through EPCR/PAR1 and annexin A1/FPR2 pathways in islets

Islet transplantation is associated with early ischaemia/reperfusion, localized coagulation and redox‐sensitive endothelial dysfunction. In animal models, islet cytoprotection by activated protein C (aPC) restores islet vascularization and protects graft function, suggesting that aPC triggers various lineages. aPC also prompts the release of endothelial MP that bear EPCR, its specific receptor. Microparticles (MP) are plasma membrane procoagulant vesicles, surrogate markers of stress and cellular effectors. We measured the cytoprotective effects of aPC on endothelial and insulin‐secreting Rin‐m5f β‐cells and its role in autocrine and paracrine MP‐mediated cell crosstalk under conditions of oxidative stress. MP from aPC‐treated primary endothelial (EC) or β‐cells were applied to H₂O₂‐treated Rin‐m5f. aPC activity was measured by enzymatic assay and ROS species by dihydroethidium. The capture of PKH26‐stained MP and the expression of EPCR were probed by fluorescence microscopy and apoptosis by flow cytometry. aPC treatment enhanced both annexin A1 (ANXA1) and PAR‐1 expression in EC and to a lesser extent in β‐cells. MP from aPC‐treated EC (eM_aPC) exhibited high EPCR and annexin A1 content, protected β‐cells, restored insulin secretion and were captured by 80% of β cells in a phosphatidylserine and ANXA1‐dependent mechanism. eMP activated EPCR/PAR‐1 and ANXA1/FPR2‐dependent pathways and up‐regulated the expression of EPCR, and of FPR2/ALX, the ANXA1 receptor. Cytoprotection was confirmed in H₂O₂‐treated rat islets with increased viability (62% versus 48% H₂O₂), reduced apoptosis and preserved insulin secretion in response to glucose elevation (16 versus 5 ng/ml insulin per 10 islets). MP may prove a promising therapeutic tool in the protection of transplanted islets.

剪切力对肝脏切除术后肝窦内皮细胞的作用

肝切除术是肝脏疾病尤其是肝脏肿瘤的重要治疗手段, 并且在肝切除术后会出现肝脏血流动力学的改变. 肝窦内皮细胞是肝窦毛细血管内一类特殊的内皮细胞, 对血流变化十分敏感. 本文就肝脏切除术后血流产生的剪切力作用于肝窦内皮细胞, 从而调节肝细胞再生和肝组织恢复的作用及机制作一综述.