Engagement of alphavbeta3 integrin regulates proliferation and apoptosis of hepatic stellate cells

Depletion of Activated Hepatic Stellate Cells and Capillarized Liver Sinusoidal Endothelial Cells Using a Rationally Designed Protein for Nonalcoholic Steatohepatitis and Alcoholic Hepatitis Treatment

Nonalcoholic steatohepatitis (NASH) and alcoholic hepatitis (AH) affect a large part of the general population worldwide. Dysregulation of lipid metabolism and alcohol toxicity drive disease progression by the activation of hepatic stellate cells and the capillarization of liver sinusoidal endothelial cells. Collagen deposition, along with sinusoidal remodeling, alters sinusoid structure, resulting in hepatic inflammation, portal hypertension, liver failure, and other complications. Efforts were made to develop treatments for NASH and AH. However, the success of such treatments is limited and unpredictable. We report a strategy for NASH and AH treatment involving the induction of integrin αvβ3-mediated cell apoptosis using a rationally designed protein (ProAgio). Integrin αvβ3 is highly expressed in activated hepatic stellate cells (αHSCs), the angiogenic endothelium, and capillarized liver sinusoidal endothelial cells (caLSECs). ProAgio induces the apoptosis of these disease-driving cells, therefore decreasing collagen fibril, reversing sinusoid remodeling, and reducing immune cell infiltration. The reversal of sinusoid remodeling reduces the expression of leukocyte adhesion molecules on LSECs, thus decreasing leukocyte infiltration/activation in the diseased liver. Our studies present a novel and effective approach for NASH and AH treatment.

Advances in Noninvasive Molecular Imaging Probes for Liver Fibrosis Diagnosis

Liver fibrosis is a wound-healing response to chronic liver injury, which may lead to cirrhosis and cancer. Early-stage fibrosis is reversible, and it is difficult to precisely diagnose with conventional imaging modalities such as magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and ultrasound imaging. In contrast, probe-assisted molecular imaging offers a promising noninvasive approach to visualize early fibrosis changes in vivo, thus facilitating early diagnosis and staging liver fibrosis, and even monitoring of the treatment response. Here, the most recent progress in molecular imaging technologies for liver fibrosis is updated. We start by illustrating pathogenesis for liver fibrosis, which includes capillarization of liver sinusoidal endothelial cells, cellular and molecular processes involved in inflammation and fibrogenesis, as well as processes of collagen synthesis, oxidation, and cross-linking. Furthermore, the biological targets used in molecular imaging of liver fibrosis are summarized, which are composed of receptors on hepatic stellate cells, macrophages, and even liver collagen. Notably, the focus is on insights into the advances in imaging modalities developed for liver fibrosis diagnosis and the update in the corresponding contrast agents. In addition, challenges and opportunities for future research and clinical translation of the molecular imaging modalities and the contrast agents are pointed out. We hope that this review would serve as a guide for scientists and students who are interested in liver fibrosis imaging and treatment, and as well expedite the translation of molecular imaging technologies from bench to bedside.

Profibrogenic role of IL-15 through IL-15 receptor alpha-mediated trans-presentation in the carbon tetrachloride-induced liver fibrosis model

Background

Inflammatory cytokines play key pathogenic roles in liver fibrosis. IL-15 is a proinflammatory cytokine produced by myeloid cells. IL-15 promotes pathogenesis of several chronic inflammatory diseases. However, increased liver fibrosis has been reported in mice lacking IL-15 receptor alpha chain (IL-15Rα), suggesting an anti-fibrogenic role for IL-15. As myeloid cells are key players in liver fibrosis and IL-15 signaling can occur independently of IL-15Rα, we investigated the requirement of IL-15 and IL-15Rα in liver fibrosis.

Methods

We induced liver fibrosis in Il15-/- , Il15ra-/- and wildtype C57BL/6 mice by the administration of carbon tetrachloride (CCl4). Liver fibrosis was evaluated by Sirius red and Mason's trichrome staining and α-smooth muscle acting immunostaining of myofibroblasts. Gene expression of collagens, matrix modifying enzymes, cytokines and chemokines was quantified by RT-qPCR. The phenotype and the numbers of intrahepatic lymphoid and myeloid cell subsets were evaluated by flow cytometry.

Results

Both Il15-/- and Il15ra-/- mice developed markedly reduced liver fibrosis compared to wildtype control mice, as revealed by reduced collagen deposition and myofibroblast content. Il15ra-/- mice showed further reduction in collagen deposition compared to Il15-/- mice. However, Col1a1 and Col1a3 genes were similarly induced in the fibrotic livers of wildtype, Il15-/- and Il15ra-/- mice, although notable variations were observed in the expression of matrix remodeling enzymes and chemokines. As expected, Il15-/- and Il15ra-/- mice showed markedly reduced numbers of NK cells compared to wildtype mice. They also showed markedly less staining of CD45+ immune cells and CD68+ macrophages, and significantly reduced inflammatory cell infiltration into the liver, with fewer pro-inflammatory and anti-inflammatory monocyte subsets compared to wildtype mice.

Conclusion

Our findings indicate that IL-15 exerts its profibrogenic role in the liver by promoting macrophage activation and that this requires trans-presentation of IL-15 by IL-15Rα.

Integrins in biliary injury and fibrosis

PURPOSE OF REVIEW

Current treatment options for cholangiopathies are severely limited and there is thus a critical need to identify and develop therapies. This review discusses the role of integrins in biliary injury and fibrosis and their potential as therapeutic targets.

RECENT FINDINGS

There are a diverse set of roles that integrins play in biliary injury and fibrosis. Some integrins activate TGF-β signaling or are involved in sensing of the extracellular matrix, making them attractive targets for biliary fibrosis. In recent work, autoantibodies to α v β 6 were identified in patients with PSC, supporting the relevance of this integrin in the disease. In addition, a role for α 2 β 1 in cyst formation was identified in a mouse model of polycystic liver disease. Leukocyte integrins (e.g. α E β 7 and α 4 β 7 ) contribute to lymphocyte trafficking, making them potential targets for biliary inflammation; however, this has not yet translated to the clinic.

SUMMARY

While all members of the same family of proteins, integrins have diverse roles in the pathogenesis of biliary disease. Targeting one or multiple of these integrins may slow or halt the progression of biliary injury and fibrosis by simultaneously impacting different pathologic cells and processes.

Radiotracers for Imaging of Fibrosis: Advances during the Last Two Decades and Future Directions

Fibrosis accompanies various pathologies, and there is thus an unmet medical need for non-invasive, sensitive, and quantitative methods for the assessment of fibrotic processes. Currently, needle biopsy with subsequent histological analysis is routinely used for the diagnosis along with morphological imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). However, none of these imaging techniques are sufficiently sensitive and accurate to detect minor changes in fibrosis. More importantly, they do not provide information on fibrotic activity on the molecular level, which is critical for fundamental understanding of the underlying biology and disease course. Molecular imaging technology using positron emission tomography (PET) offers the possibility of imaging not only physiological real-time activity, but also high-sensitivity and accurate quantification. This diagnostic tool is well established in oncology and has exhibited exponential development during the last two decades. However, PET diagnostics has only recently been widely applied in the area of fibrosis. This review presents the progress of development of radiopharmaceuticals for non-invasive detection of fibrotic processes, including the fibrotic scar itself, the deposition of new fibrotic components (fibrogenesis), or the degradation of existing fibrosis (fibrolysis).

The extracellular matrix in hepatocellular carcinoma: Mechanisms and therapeutic vulnerability

The tumor microenvironment (TME) is influenced by a "disorganized" extracellular matrix (ECM) that sensitizes cancer cells toward mechanical stress, signaling, and structural alterations. In hepatocellular carcinoma (HCC), lack of knowledge about key ECM proteins driving the TME refractory to targeted therapies poses a barrier to the identification of new therapeutic targets. Herein, we discuss the contributions of various ECM components that impact hepatocytes and their surrounding support network during tumorigenesis. In addition, the underpinnings by which ECM proteins transduce mechanical signals to the liver TME are detailed. Finally, in view of the bidirectional feedback between the ECM, transformed hepatocytes, and immune cells, we highlight the potential role of the ECM disorganization process in shaping responses to immune checkpoint inhibitors and targeted therapies. Our comprehensive characterization of these ECM components may provide a roadmap for innovative therapeutic approaches to restrain HCC.

Evaluation of an Integrin αvβ3 Radiotracer, [18F]F-FPP-RGD2, for Monitoring Pharmacological Effects of Integrin αv siRNA in the NASH Liver

Purpose

Integrin αv is a key regulator in the pathophysiology of hepatic fibrosis. In this study, we evaluated the potential utility of an integrin αvβ3 positron emission tomography (PET) radiotracer, 18F-labeled cyclic arginine-glycine-aspartic acid penta-peptide ([18F]F-FPP-RGD2), for detecting hepatic integrin αv and function in nonalcoholic steatohepatitis (NASH) model rats using integrin αv siRNA.

Methods

NASH model rats were produced by feeding a choline-deficient, low-methionine, high-fat diet for 8 weeks. PET/computerized tomography imaging and quantification of integrin αv protein, serum aspartate aminotransferase, and alanine aminotransferase were performed 1 week after single intravenous injection of integrin αv siRNA.

Results

Integrin αv siRNA (0.1 and 0.5 mg/kg) dose-dependently decreased hepatic integrin αv protein concentrations in control and NASH model rats. The hepatic mean standard uptake value of [18F]F-FPP-RGD2 was decreased dose-dependently by integrin αv siRNA. The mean standard uptake value was positively correlated with integrin αv protein levels in control and NASH model rats. Serum aspartate aminotransferase and alanine aminotransferase concentrations were also decreased by siRNA injection and correlated with liver integrin αv protein expression levels in NASH model rats.

Conclusion

This study suggests that [18F]F-FPP-RGD2 PET imaging is a promising radiotracer for monitoring hepatic integrin αv protein levels and hepatic function in NASH pathology.

Cell Adhesion Molecules in Fibrotic Diseases

Mechanisms underlying the pathogenesis of tissue fibrosis remain incompletely understood. Emerging evidence suggests that cell adhesion molecules (CAMs) are critical in fibrotic progression in many organs, including lung, kidney, skin, and liver. CAMs promote cell-cell and cell-extracellular matrix (ECM) interactions to maintain tissue architecture and normal function in homeostasis. However, dysregulated expression and function of CAMs can lead to chronic inflammation and tissue fibrosis. The major families of CAMs include integrins, cadherins, selectins, and immunoglobulins. Here, we review the role of the CAMs in fibrosis development across various organs with a focus on integrins and cadherins, and discuss their respective roles in the development of pulmonary fibrosis.

Human milk oligosaccharide disialyllacto-n-tetraose protects human intestinal epithelium integrity and permeability against mast cell chymase-induced disruption by stabilizing ZO-1/FAK/P38 pathway of intestinal epithelial cell

CONTEXT

Inflammatory bowel disease (IBD) is a chronic gut disease with intestinal-epithelium disruption. Mast cell (MC) has been discussed in IBD studies, but its subset MC_TC (chymase/tryptase) and MC-chymase have not been well-explored extensively. Human-milk-oligosaccharide-Disialyllacto-N-Tetraose (DSLNT) was reported as an effective strategy to protect infants against IBD with unclear mechanism.

OBJECTIVE

This study was to examine the distribution of chymase-positive mast cells in the intestinal-epithelium-tissue of IBD infants, to explore the MC-chymase function on intestinal-epithelium, and to investigate the influences of DSLNT against MC-chymase-induced disruptions.

MATERIALS AND METHODS

The intestinal-biopsies (surgical-waste) of the infants with IBD or with intestinal-atresia (non-IBD) were paraffin-embedded for immunohistochemistry. In-situ intestinal-tissue model and in-vitro human-intestinal-epithelial-cell (Caco-2) model were established with or without the treatments of MC-chymase (50mU/mL), DSLNT (600 µM) and DSLNT + MC-chymase respectively. The tissue morphology analysis, cell proliferation assay, cell-gap-closure assessment, fluorescence-immunocytochemistry, western blot, trans-epithelial-electrical-resistance, cell-cycle and statistical analysis were applied.

RESULTS

There was an increased number of MC_TC subset around the inflamed intestinal area in-vivo; MC-chymase caused intestinal-epithelial-barrier damage in-situ, decreased trans-epithelial-electrical-resistance of caco-2 cell monolayer in-vitro; while DSLNT protected epithelium against MC-chymase induced disruptions. MC-chymase reduced cell-viability, proliferation and migration, altered cell-cycle, down-regulated ZO-1, FAK, and P38 expressions, while DSLNT protected cells by impairing MC-chymase-induced interruptions. DSLNT can rescue ZO-1, FAK and P38 expressions and restore epithelial-cell integrity and cell cycle.

CONCLUSIONS

Chymase-positive MCs are involved in IBD progress. MC-chymase disrupts intracellular ZO-1/FAK/P38 signal pathway and cell-cell/cell-matrix contacts, while DSLNT protects intestinal-epithelium against MC-chymase to maintain the intestinal epithelium integrity.

Structure-Based Discovery of a Novel Class of Small-Molecule Pure Antagonists of Integrin αVβ3

Inhibitors of integrin αVβ3 have therapeutic promise for a variety of diseases. Most αVβ3-targeting small molecules patterned after the RGD motif are partial agonists because they induce a high-affinity, ligand-binding conformation and prime the receptor to bind the ligand without an activating stimulus, in part via a charge-charge interaction between their aspartic acid carboxyl group and the metal ion in the metal-ion-dependent adhesion site (MIDAS). Building upon our previous studies on the related integrin αIIbβ3, we searched for pure αVβ3 antagonists that lack this typical aspartic acid carboxyl group and instead engage through direct binding to one of the coordinating residues of the MIDAS metal ion, specifically β3 E220. By in silico screening of two large chemical libraries for compounds interacting with β3 E220, we indeed discovered a novel molecule that does not contain an acidic carboxyl group and does not induce the high-affinity, ligand-binding state of the receptor. Functional and structural characterization of a chemically optimized version of this compound led to the discovery of a novel small-molecule pure αVβ3 antagonist that (i) does not prime the receptor to bind the ligand and does not induce hybrid domain swing-out or receptor extension as judged by antibody binding and negative-stain electron microscopy, (ii) binds at the RGD-binding site as predicted by metadynamics rescoring of induced-fit docking poses and confirmed by a cryo-electron microscopy structure of the compound-bound integrin, and (iii) coordinates the MIDAS metal ion via a quinoline moiety instead of an acidic carboxyl group.

Enhanced US/CT/MR imaging of integrin αvβ3 for liver fibrosis staging in rat

Liver fibrosis is a global health challenge with high morbidity and mortality rates, and diagnostic sensitivity of liver fibrosis tests can be increased using multimodal molecular agents. We designed cyclic arginine-glycine-aspartic acid (cRGD)-modified nanoparticles (NPs) using ultrasound (US)/computed tomography (CT)/magnetic resonance (MR) triple-modality imaging to evaluate liver fibrosis stages. In vitro and in vivo studies were conducted using primary hepatic stellate cells (HSCs) and a rat model of liver fibrosis induced by carbon tetrachloride (CCl4). Our results showed cRGD-poly(lactic-co-glycolic acid)-Fe3O4-perfluorocarbon bromide (cRGD-PLGA-Fe3O4-PFOB) NPs were preferentially internalised by activated HSCs (aHSCs). The main cell types expressing integrin αvβ3 during liver fibrogenesis were the aHSCs. The protein levels of αv and β3 expressed on aHSCs increased with the progression of liver fibrosis. After intravenous injection of cRGD-PLGA-Fe3O4-PFOB NPs, the echo intensity (EI) values, CT values, and T2 values of liver parenchyma correlated well with liver fibrosis severity. cRGD-PLGA-Fe3O4-PFOB NPs as multifunction contrast agents showed great potential to reflect the degree of HSC activation and distinguish among different liver fibrotic stages. The ligand-directed and integrin αvβ3-mediated accumulation provides active and passive targeting capabilities, permitting the targeted multimodal imaging of cRGD-PLGA-Fe3O4-PFOB NPs, which delivers accurate non-invasive diagnosis and real-time monitoring of liver fibrosis development.

Integrins as a drug target in liver fibrosis

As the worldwide prevalence of chronic liver diseases is high and continuing to increase, there is an urgent need for treatment to prevent cirrhosis-related morbidity and mortality. Integrins are heterodimeric cell-surface proteins that are promising targets for therapeutic intervention. αv integrins are central in the development of fibrosis as they activate latent TGFβ, a known profibrogenic cytokine. The αv subunit can form heterodimers with β1, β3, β5, β6 or β8 subunits and one or more of these integrins are central to the development of liver fibrosis, however, their relative importance is not understood. This review summarises the current knowledge of αv integrins and their respective β subunits in different organs, with a focus on liver fibrosis and the emerging preclinical and clinical data with regards to αv integrin inhibitors.

Dual inhibition of αvβ6 and αvβ1 reduces fibrogenesis in lung tissue explants from patients with IPF

RATIONALE

αv integrins, key regulators of transforming growth factor-β activation and fibrogenesis in in vivo models of pulmonary fibrosis, are expressed on abnormal epithelial cells (αvβ6) and fibroblasts (αvβ1) in fibrotic lungs.

OBJECTIVES

We evaluated multiple αv integrin inhibition strategies to assess which most effectively reduced fibrogenesis in explanted lung tissue from patients with idiopathic pulmonary fibrosis.

METHODS

Selective αvβ6 and αvβ1, dual αvβ6/αvβ1, and multi-αv integrin inhibitors were characterized for potency, selectivity, and functional activity by ligand binding, cell adhesion, and transforming growth factor-β cell activation assays. Precision-cut lung slices generated from lung explants from patients with idiopathic pulmonary fibrosis or bleomycin-challenged mouse lungs were treated with integrin inhibitors or standard-of-care drugs (nintedanib or pirfenidone) and analyzed for changes in fibrotic gene expression or TGF-β signaling. Bleomycin-challenged mice treated with dual αvβ6/αvβ1 integrin inhibitor, PLN-74809, were assessed for changes in pulmonary collagen deposition and Smad3 phosphorylation.

MEASUREMENTS AND MAIN RESULTS

Inhibition of integrins αvβ6 and αvβ1 was additive in reducing type I collagen gene expression in explanted lung tissue slices from patients with idiopathic pulmonary fibrosis. These data were replicated in fibrotic mouse lung tissue, with no added benefit observed from inhibition of additional αv integrins. Antifibrotic efficacy of dual αvβ6/αvβ1 integrin inhibitor PLN-74809 was confirmed in vivo, where dose-dependent inhibition of pulmonary Smad3 phosphorylation and collagen deposition was observed. PLN-74809 also, more potently, reduced collagen gene expression in fibrotic human and mouse lung slices than clinically relevant concentrations of nintedanib or pirfenidone.

CONCLUSIONS

In the fibrotic lung, dual inhibition of integrins αvβ6 and αvβ1 offers the optimal approach for blocking fibrogenesis resulting from integrin-mediated activation of transforming growth factor-β.

Targeting integrin αvβ3 by a rationally designed protein for chronic liver disease treatment

Chronic Liver Diseases (CLD) are characterized by abnormal accumulation of collagen fibrils, neo-angiogenesis, and sinusoidal remodeling. Collagen deposition along with intrahepatic angiogenesis and sinusoidal remodeling alters sinusoid structure resulting in portal hypertension, liver failure, and other complications. Efforts were made to develop treatments for CLDs. However, the success of such treatments is limited and unpredictable. We report a strategy for CLD treatment by induction of integrin αvβ3 mediated cell apoptosis using a rationally designed protein (ProAgio). ProAgio is designed to target integrin αvβ3 at a novel site. Integrin αvβ3 is highly expressed in activated Hepatic Stellate Cells (HSC), angiogenic endothelium, and capillarized Liver Sinusoidal Endothelial Cells (LSEC). ProAgio induces apoptosis of these disease causative cells. Tests with liver fibrosis mouse models demonstrate that ProAgio reverses liver fibrosis and relieves blood flow resistance by depleting activated HSC and capillarized LSEC. Our studies demonstrate an effective approach for CLD treatment.

Therapeutic targets, novel drugs, and delivery systems for diabetes associated NAFLD and liver fibrosis

Type 2 diabetes mellitus (T2DM) associated non-alcoholic fatty liver disease (NAFLD) is the fourth-leading cause of death. Hyperglycemia induces various complications, including nephropathy, cirrhosis and eventually hepatocellular carcinoma (HCC). There are several etiological factors leading to liver disease development, which involve insulin resistance and oxidative stress. Free fatty acid (FFA) accumulation in the liver exerts oxidative and endoplasmic reticulum (ER) stresses. Hepatocyte injury induces release of inflammatory cytokines from Kupffer cells (KCs), which are responsible for activating hepatic stellate cells (HSCs). In this review, we will discuss various molecular targets for treating chronic liver diseases, including homeostasis of FFA, lipid metabolism, and decrease in hepatocyte apoptosis, role of growth factors, and regulation of epithelial-to-mesenchymal transition (EMT) and HSC activation. This review will also critically assess different strategies to enhance drug delivery to different cell types. Targeting nanocarriers to specific liver cell types have the potential to increase efficacy and suppress off-target effects.

Integrin αVβ1 regulates procollagen I production through a non-canonical transforming growth factor β signaling pathway in human hepatic stellate cells

Hepatic stellate cells (HSCs) are thought to play key roles in the development of liver fibrosis. Extensive evidence has established the concept that αV integrins are involved in the activation of latent transforming growth factor β (TGF-β), a master regulator of the fibrotic signaling cascade. Based on mRNA and protein expression profiling data, we found that αVβ1 integrin is the most abundant member of the αV integrin family in either quiescent or TGF-β1-activated primary human HSCs. Unexpectedly, either a selective αVβ1 inhibitor, Compound 8 (C8), or a pan-αV integrin inhibitor, GSK3008348, decreased TGF-β1-activated procollagen I production in primary human HSCs, in which the role of β1 integrin was confirmed by ITGB1 siRNA. In contrast with an Activin receptor-like kinase 5 (Alk5) inhibitor, C8 and GSK3008348 failed to inhibit TGF-β1 induced SMAD3 and SMAD2 phosphorylation, but inhibited TGF-β-induced phosphorylation of ERK1/2 and STAT3, suggesting that αVβ1 integrin is involved in non-canonical TGF-β signaling pathways. Consistently, ITGB1 siRNA significantly decreased phosphorylation of ERK1/2. Furthermore, a selective inhibitor of MEK1/2 blocked TGF-β1 induced phosphorylation of ERK1/2 and decreased TGF-β1 induced procollagen I production, while a specific inhibitor of STAT3 had no effect on TGF-β1 induced procollagen I production. Taken together, current data indicate that αVβ1 integrin can regulate TGF-β signaling independent of its reported role in activating latent TGF-β. Our data further support that αVβ1 inhibition is a promising therapeutic target for the treatment of liver fibrosis.

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.

Changing our view of the Schistosoma granuloma to an ecological standpoint

Schistosomiasis, a neglected parasitic tropical disease that has plagued humans for centuries, remains a major public health burden. A primary challenge to understanding schistosomiasis is deciphering the most remarkable pathological feature of this disease, the granuloma - a highly dynamic and self-organized structure formed by both host and parasite components. Granulomas are considered a remarkable example of how parasites evolved with their hosts to establish complex and intimate associations. However, much remains unclear regarding life within the granuloma, and strategies to restrain its development are still lacking. Here we explore current information on the hepatic Schistosoma mansoni granuloma in the light of Ecology and propose that this intricate structure acts as a real ecosystem. The schistosomal granuloma is formed by cells (biotic component), protein scaffolds, fibres, and chemical compounds (abiotic components) with inputs/outputs of energy and matter, as complex as in classical ecosystems. We review the distinct cell populations ('species') within the granuloma and examine how they integrate with each other and interact with their microenvironment to form a multifaceted cell community in different space-time frames. The colonization of the hepatic tissue to form granulomas is explained from the point of view of an ecological succession whereby a community is able to modify its physical environment, creating conditions and resources for ecosystem construction. Remarkably, the granuloma represents a dynamic evolutionary system that undergoes progressive changes in the 'species' that compose its community over time. In line with ecological concepts, we examine the granuloma not only as a place where a community of cells is settled (spatial niche or habitat) but also as a site in which the functional activities of these combined populations occur in an orchestrated way in response to microenvironmental gradients such as cytokines and egg antigens. Finally, we assert how the levels of organization of cellular components in a granuloma as conventionally defined by Cell Biology can fit perfectly into a hierarchical structure of biological systems as defined by Ecology. By rethinking the granuloma as an integrating and evolving ecosystem, we draw attention to the inner workings of this structure that are central to the understanding of schistosomiasis and could guide its future treatment.

Transcriptional regulation of alcohol induced liver fibrosis in a translational porcine hepatocellular carcinoma model

Hepatocellular carcinoma (HCC) is the 5th most common and 2nd deadliest cancer worldwide. HCC risk factors include alcohol induced liver cirrhosis, which prompts hepatic inflammation, cell necrosis, and fibrosis deposition. As 25% of HCC cases are associated with alcohol induced liver disease, understanding the effects of the cirrhotic liver microenvironment on HCC tumor biology and therapeutic responses are critical. This study utilized the Oncopig Cancer Model-a transgenic pig model that recapitulates human HCC through induced expression of KRAS^G12D and TP53^R167H driver mutations-to investigate the molecular mechanisms underlying alcohol induced liver disease. Oncopigs (n = 5) underwent fibrosis induction via infusion of ethanol and ethiodized oil (1:3 v/v dosed at 0.75 mL/kg) into the hepatic arterial circulation. Eight-weeks post induction, liver tissue samples from fibrotic and age-matched control (n = 5) Oncopigs were collected for histological evaluation and transcriptional profiling. Increased hepatic inflammation and fibrosis was observed in fibrotic Oncopigs via pathological assessment. Transcriptional profiling (RNA-seq) resulted in the identification of 4387 differentially expressed genes between Oncopig fibrotic and control livers. GO term enrichment analysis identified pathway alterations associated with cirrhosis progression in humans, including cell proliferation, angiogenesis, extracellular matrix deposition, and oxidation-reduction. Key alterations include activation of hepatic stellate cells, increased matrix metalloproteinase production, and altered expression of ABC and SLC transporter genes involved in transport of anticancer drugs.These results demonstrate Oncopig liver fibrosis recapitulates transcriptional hallmarks of human cirrhosis, making the Oncopig an ideal model for studying the effects of the cirrhotic liver microenvironment on HCC tumor biology and therapeutic response.

Extracellular Matrix Remodeling in Chronic Liver Disease

PURPOSE OF THE REVIEW

This review aims to summarize the current knowledge of the extracellular matrix remodeling during hepatic fibrosis. We discuss the diverse interactions of the extracellular matrix with hepatic cells and the surrounding matrix in liver fibrosis, with the focus on the molecular pathways and the mechanisms that regulate extracellular matrix remodeling.

RECENT FINDINGS

The extracellular matrix not only provides structure and support for the cells, but also controls cell behavior by providing adhesion signals and by acting as a reservoir of growth factors and cytokines.

SUMMARY

Hepatic fibrosis is characterized by an excessive accumulation of extracellular matrix. During fibrogenesis, the natural remodeling process of the extracellular matrix varies, resulting in the excessive accumulation of its components, mainly collagens. Signals released by the extracellular matrix induce the activation of hepatic stellate cells, which are the major source of extracellular matrix and most abundant myofibroblasts in the liver.

GRAPHICAL ABSTRACT

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Quantitative evaluation of hepatic integrin αvβ3 expression by positron emission tomography imaging using 18F-FPP-RGD2 in rats with non-alcoholic steatohepatitis

Background

Integrin α_vβ₃, which are expressed by activated hepatic stellate cells in non-alcoholic steatohepatitis (NASH), play an important role in the fibrosis. Recently, we reported that an RGD peptide positron emission tomography (PET) probe is useful as a predictor of hepatic fibrosis. Kinetic analysis of the RGD PET probe has been performed in tumours, but not in hepatic fibrosis. Therefore, we aimed to quantify hepatic integrin α_vβ₃ in a model of NASH by kinetic analysis using ¹⁸F-FPP-RGD₂, an integrin α_vβ₃ PET probe.

Methods

¹⁸F-FPP-RGD₂ PET/CT scans were performed in control and NASH rats. Tissue kinetic analyses were performed using a one-tissue, two-compartment (1T2C) and a two-tissue, three-compartment (2T3C) model using an image-derived input function (IDIF) for the left ventricle. We then conducted correlation analysis between standard uptake values (SUVs) or volume of distribution (V_T), evaluated using compartment kinetic analysis and integrin α_v or β₃ protein expression.

Results

Biochemical and histological evaluation confirmed the development of NASH rats. Integrin α_vβ₃ protein expression and hepatic SUV were higher in NASH- than normal rats. The hepatic activity of ¹⁸F-FPP-RGD₂ peaked rapidly after administration and then gradually decreased, whereas left ventricular activity rapidly disappeared. The 2T3C model was found to be preferable for ¹⁸F-FPP-RGD₂ kinetic analysis in the liver. The V_{T (IDIF)} for ¹⁸F-FPP-RGD₂, calculated using the 2T3C model, was significantly higher in NASH- than normal rats and correlated strongly with hepatic integrin α_v and β₃ protein expression. The strengths of these correlations were similar to those between SUV_60–90 min and hepatic integrin α_v or β₃ protein expression.

Conclusions

We have demonstrated that the V_{T (IDIF)} of ¹⁸F-FPP-RGD₂, calculated using kinetic modelling, positively correlates with integrin α_v and β₃ protein in the liver of NASH rats. These findings suggest that hepatic V_{T (IDIF)} provides a quantitative assessment of integrin α_vβ₃ protein in liver.

Differential effects of olive oil, soybean oil, corn oil and lard oil on carbon tetrachloride-induced liver fibrosis in mice

Olive oil could attenuate carbon tetrachloride (CCl₄) induced liver fibrosis (LF) in mouse model. The present study aimed to evaluate the effects of other common oils on CCl₄ induced LF. Healthy male ICR mice were administered with CCl₄ intraperitoneally at 2.5 ml/kg twice a week for total 3 weeks. Mice were pre-treated with olive oil, soybean oil, corn oil or lard oil. After treatment, histopathological changes were observed using Masson trichrome staining, and alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), hydroxyproline (HYP) and triglyceride (TG) were measured by commercial kits. The expression of LF related genes was detected by quantitative real-time PCR. We found that soybean oil or olive oil significantly reduced ALT and AST levels in serum, and MDA, HYP and TG levels in the liver, compared with corn oil or lard oil. Moreover, Masson trichrome staining and real-time PCR showed that the mice treated with CCl₄ dissolved in soybean oil or olive oil had less fibrosis and apoptosis in the liver comparted to the mice treated with CCl₄ dissolved in corn oil or lard oil. In conclusion, soybean oil but not corn or lard oil exerts protective effects against CCl₄ induced LF in mice, possibly due to its antioxidant activity.

Advances in the clinical use of collagen as biomarker of liver fibrosis

INTRODUCTION

Hepatic fibrosis is the excessive synthesis and deposition of extracellular matrix including collagen in the tissue. Chronic liver insult leads to progressive parenchymal damage, portal hypertension, and cirrhosis. Determination of hepatic collagen by invasive liver biopsy is the gold standard to estimate severity and stage of fibrosis. However, this procedure is associated with pain, carries the risk of infection and bleeding, and is afflicted with a high degree of sampling error. Therefore, there is urgent need for serological collagen-derived markers to assess collagen synthesis/turnover.

AREAS COVERED

Biochemical properties of collagens, cellular sources of hepatic collagen synthesis, and regulatory aspects in collagen expression. Markers are discussed suitable to estimate hepatic collagen synthesis and/or turnover. Discussed studies were identified through a PubMed search done in May 2020 and the authors' topic knowledge.

EXPERT OPINION

Hepatic fibrosis is mainly characterized by accumulation of collagen-rich scar tissue. Although traditionally performed liver biopsy is still standard in estimating hepatic fibrosis, there is evidence that noninvasive diagnostic scores and collagen-derived neo-epitopes provide clinical useful information. These noninvasive tests are less expensive than liver biopsy, better tolerated, safer, and more acceptable to patients. Therefore, these tests will lead to dramatic changes in diagnosis.

Modulation of Cancer-Associated Fibrotic Stroma by An Integrin αvβ3 Targeting Protein for Pancreatic Cancer Treatment

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is resistant to most therapeutics owing to dense fibrotic stroma orchestrated by cancer-associated pancreatic stellate cells (CAPaSC). CAPaSC also support cancer cell growth, metastasis, and resistance to apoptosis. Currently, there is no effective therapy for PDAC that specifically targets CAPaSC. We previously reported a rationally designed protein, ProAgio, that targets integrin αvβ3 at a novel site and induces apoptosis in integrin αvβ3-expressing cells. Because both CAPaSC and angiogenic endothelial cells express high levels of integrin αvβ3, we aimed to analyze the effects of ProAgio in PDAC tumor.

METHODS

Expression of integrin αvβ3 was examined in both patient tissue and cultured cells. The effects of ProAgio on CAPaSC were analyzed using an apoptosis assay kit. The effects of ProAgio in PDAC tumor were studied in 3 murine tumor models: subcutaneous xenograft, genetic engineered (KrasG12D; p53R172H; Pdx1-Cre, GEM-KPC) mice, and an orthotopic KrasG12D; p53R172H; Pdx1-Cre (KPC) model.

RESULTS

ProAgio induces apoptosis in CAPaSC. ProAgio treatment significantly prolonged survival of a genetically engineered mouse-KPC and orthotopic KPC mice alone or in combination with gemcitabine (Gem). ProAgio specifically induced apoptosis in CAPaSC, resorbed collagen, and opened collapsed tumor vessels without an increase in angiogenesis in PDAC tumor, enabling drug delivery into the tumor. ProAgio decreased intratumoral insulin-like growth factor 1 levels as a result of depletion of CAPaSC and consequently decreased cytidine deaminase, a Gem metabolism enzyme in cancer cells, and thereby reduced resistance to Gem-induced apoptosis.

CONCLUSIONS

Our study suggests that ProAgio is an effective PDAC treatment agent because it specifically depletes CAPaSC and eliminates tumor angiogenesis, thereby enhancing drug delivery and Gem efficacy in PDAC tumors.

GNS561 acts as a potent anti-fibrotic and pro-fibrolytic agent in liver fibrosis through TGF-β1 inhibition

Background:

Hepatic fibrosis is the result of chronic liver injury that can progress to cirrhosis and lead to liver failure. Nevertheless, there are no anti-fibrotic drugs licensed for human use. Here, we investigated the anti-fibrotic activity of GNS561, a new lysosomotropic molecule with high liver tropism.

Methods:

The anti-fibrotic effect of GNS561 was determined in vitro using LX-2 hepatic stellate cells (HSCs) and primary human HSCs by studying cell viability, activity of caspases 3/7, autophagic flux, cathepsin maturation and activity, HSC activation and transforming growth factor-β1 (TGF-β1) maturation and signaling. The contribution of GNS561 lysosomotropism to its anti-fibrotic activity was assessed by increasing lysosomal pH. The potency of GNS561 on fibrosis was evaluated in vivo in a rat model of diethylnitrosamine-induced liver fibrosis.

Results:

GNS561 significantly decreased cell viability and promoted apoptosis. Disrupting the lysosomal pH gradient impaired its pharmacological effects, suggesting that GNS561 lysosomotropism mediated cell death. GNS561 impaired cathepsin activity, leading to defective TGF-β1 maturation and autophagic processes. Moreover, GNS561 decreased HSC activation and extracellular matrix deposition by downregulating TGF-β1/Smad and mitogen-activated proteine kinase signaling and inducing fibrolysis. Finally, oral administration of GNS561 (15 mg/kg per day) was well tolerated and attenuated diethylnitrosamine-induced liver fibrosis in this rat model (decrease of collagen deposition and of pro-fibrotic markers and increase of fibrolysis).

Conclusion:

GNS561 is a new potent lysosomotropic compound that could represent a valid medicinal option for hepatic fibrosis treatment through both its anti-fibrotic and its pro-fibrolytic effects. In addition, this study provides a rationale for targeting lysosomes as a promising therapeutic strategy in liver fibrosis.

Noninvasive Assessment of Liver Fibrosis: Current and Future Clinical and Molecular Perspectives

Liver fibrosis is one of the risk factors for hepatocellular carcinoma (HCC) development. The staging of liver fibrosis can be evaluated only via a liver biopsy, which is an invasive procedure. Noninvasive methods for the diagnosis of liver fibrosis can be divided into morphological tests such as elastography and serum biochemical tests. Transient elastography is reported to have excellent performance in the diagnosis of liver fibrosis and has been accepted as a useful tool for the prediction of HCC development and other clinical outcomes. Two-dimensional shear wave elastography is a new technique and provides a real-time stiffness image. Serum fibrosis markers have been studied based on the mechanism of fibrogenesis and fibrolysis. In the healthy liver, homeostasis of the extracellular matrix is maintained directly by enzymes called matrix metalloproteinases (MMPs) and their specific inhibitors, tissue inhibitors of metalloproteinases (TIMPs). MMPs and TIMPs could be useful serum biomarkers for liver fibrosis and promising candidates for the treatment of liver fibrosis. Further studies are required to establish liver fibrosis-specific markers based on further clinical and molecular research. In this review, we summarize noninvasive fibrosis tests and molecular mechanism of liver fibrosis in current daily clinical practice.

[18F]-Alfatide PET imaging of integrin αvβ3 for the non-invasive quantification of liver fibrosis

BACKGROUND & AIMS

The vitronectin receptor integrin αvβ3 drives fibrogenic activation of hepatic stellate cells (HSCs). Molecular imaging targeting the integrin αvβ3 could provide a non-invasive method for evaluating the expression and the function of the integrin αvβ3 on activated HSCs (aHSCs) in the injured liver. In this study, we sought to compare differences in the uptake of [18F]-Alfatide between normal and injured liver to evaluate its utility for assessment of hepatic fibrogenesis.

METHODS

PET with [18F]-Alfatide, non-enhanced CT, histopathology, immunofluorescence staining, immunoblotting and gene analysis were performed to evaluate and quantify hepatic integrin αvβ3 levels and liver fibrosis progression in mouse models of fibrosis (carbon tetrachloride [CCl4] and bile duct ligation [BDL]). The liver AUC divided by the blood AUC over 30 min was used as an integrin αvβ3-PET index to quantify fibrosis progression. Ex vivo analysis of frozen liver tissue from patients with fibrosis and cirrhosis verified the animal findings.

RESULTS

Fibrotic mouse livers showed enhanced [18F]-Alfatide uptake and retention compared to control livers. The radiotracer was demonstrated to bind specifically with integrin αvβ3, which is mainly expressed on aHSCs. Autoradiography and histopathology confirmed the PET imaging results. Further, the mRNA and protein level of integrin αvβ3 and its signaling complex were higher in CCl4 and BDL models than controls. The results obtained from analyses on human fibrotic liver sections supported the animal findings.

CONCLUSIONS

Imaging hepatic integrin αvβ3 with PET and [18F]-Alfatide offers a potential non-invasive method for monitoring the progression of liver fibrosis.

LAY SUMMARY

Integrin αvβ3 expression on activated hepatic stellate cells (aHSCs) is associated with HSC proliferation during hepatic fibrogenesis. Herein, we show that a radioactive tracer, [18F]-Alfatide, binds to integrin αvβ3 with high affinity and specificity. [18F]-Alfatide could thus be used as a non-invasive imaging biomarker to track hepatic fibrosis progression.

PET/SPECT Molecular Probes for the Diagnosis and Staging of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a significant public health challenge afflicting approximately 1 billion individuals both in the Western world and in the East world. While liver biopsy is considered as gold standard in the diagnosis and staging of liver fibrosis, noninvasive imaging technologies, including ultrasonography, computed tomography, single-photon emission computed tomography (SPECT), magnetic resonance imaging, and positron emission tomography (PET) could offer more sensitive, comprehensive, and quantitative measurement for NAFLD. In this review, we focus on recent development and applications of PET/SPECT molecular probes that enable multispatial/temporal visualization and quantification of physiopathological progress at the molecular level in the NAFLD. We shall also discuss the limitations of current radioligands and future direction for PET/SPECT probe development.

Matrix Metalloproteinases as Potential Biomarkers and Therapeutic Targets in Liver Diseases

Chronic liver diseases, characterized by an excessive accumulation of extracellular matrix (ECM) resulting in scar tissue formation, are a growing health problem causing increasing morbidity and mortality worldwide. Currently, therapeutic options for tissue fibrosis are severely limited, and organ transplantation is the only treatment for the end-stage liver diseases. During liver damage, injured hepatocytes release proinflammatory factors resulting in the recruitment and activation of immune cells that activate quiescent hepatic stellate cells (HSCs). Upon activation, HSCs transdifferentiate into highly proliferative, migratory, contractile and ECM-producing myofibroblasts. The disrupted balance between ECM deposition and degradation leads to the formation of scar tissue referred to as fibrosis. This balance can be restored either by reducing ECM deposition (by inhibition of HSCs activation and proliferation) or enhancing ECM degradation (by increased expression of matrix metalloproteinases (MMPs)). MMPs play an important role in ECM remodeling and represent an interesting target for therapeutic drug discovery. In this review, we present the current knowledge about ECM remodeling and role of the different MMPs in liver diseases. MMP expression patterns in different stages of liver diseases have also been reviewed to determine their role as biomarkers. Finally, we highlight MMPs as promising therapeutic targets for the resolution of liver diseases.

β-Sitosterol attenuates carbon tetrachloride-induced oxidative stress and chronic liver injury in rats

Chronic liver diseases are clinically silent and responsible for significant morbidity and mortality worldwide. β-Sitosterol (BSS), major phytosterol in plants, has a wide spectrum of protective effect against various chronic ailments. We investigated the hepatoprotective effect of BSS against carbon tetrachloride (CCl₄)-induced chronic liver injury in rats. Thirty rats were divided into five groups, with six animals in each group. Group I rats served as control while groups II, III, IV, and V rats were injected intraperitoneally with CCl₄ (0.2 mL/100 g b.w. in olive oil (1:1)) for 7 consecutive weeks. After 7 weeks, group II rats were left without any treatments and served as CCl₄ alone group, while groups III, IV, and V rats were treated with BSS 25 and 50 mg/kg b.w. and silymarin 100 mg/kg b.w. as oral post-treatments respectively, for the next 4 weeks. At the end of the experiment, hepatotoxicity marker enzymes in serum, oxidative stress, and fibrosis marker were analyzed. CCl₄ administration caused significant elevation of marker enzymes of hepatotoxicity in serum and increased lipid peroxidation and fibrosis markers such as hydroxyproline, collagen, α-smooth muscle actin, vimentin, desmin, and matrix metalloproteinases 9 in liver tissue of rats. This treatment also caused a significant diminution of intracellular enyzmic antioxidants such as SOD and CAT in the liver tissue of rats. All the above adversities were significantly mitigated by the BSS post-treatments. The results suggest that BSS could have a hepatoprotective effect against oxidative stress-mediated CLD induced by CCl₄.

Novel Pure αVβ3 Integrin Antagonists That Do Not Induce Receptor Extension, Prime the Receptor, or Enhance Angiogenesis at Low Concentrations

The integrin αVβ3 receptor has been implicated in several important diseases, but no antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit αVβ3-mediated cell adhesion to αVβ3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the αVβ3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC50, which correlates with cilengitide's enhancement of tumor growth in vivo.

The Many Roles of Cell Adhesion Molecules in Hepatic Fibrosis

Fibrogenesis is a progressive scarring event resulting from disrupted regular wound healing due to repeated tissue injury and can end in organ failure, like in liver cirrhosis. The protagonists in this process, either liver-resident cells or patrolling leukocytes attracted to the site of tissue damage, interact with each other by soluble factors but also by direct cell–cell contact mediated by cell adhesion molecules. Since cell adhesion molecules also support binding to the extracellular matrix, they represent excellent biosensors, which allow cells to modulate their behavior based on changes in the surrounding microenvironment. In this review, we focus on selectins, cadherins, integrins and members of the immunoglobulin superfamily of adhesion molecules as well as some non-classical cell adhesion molecules in the context of hepatic fibrosis. We describe their liver-specific contributions to leukocyte recruitment, cell differentiation and survival, matrix remodeling or angiogenesis and touch on their suitability as targets in antifibrotic therapies.

Targeting tumor cells and neovascularization using RGD-functionalized magnetoliposomes

Purpose

Magnetoliposomes (MLs) have shown great potential as magnetic resonance imaging contrast agents and as delivery vehicles for cancer therapy. Targeting the MLs towards the tumor cells or neovascularization could ensure delivery of drugs at the tumor site. In this study, we evaluated the potential of MLs targeting the αvβ3 integrin overexpressed on tumor neovascularization and different tumor cell types, including glioma and ovarian cancer.

Methods

MLs functionalized with a Texas Red fluorophore (anionic MLs), and with the fluorophore and the cyclic Arginine-Glycine-Aspartate (cRGD; cRGD-MLs) targeting the αvβ3 integrin, were produced in-house. Swiss nude mice were subcutaneously injected with 10⁷ human ovarian cancer SKOV-3 cells. Tumors were allowed to grow for 3 weeks before injection of anionic or cRGD-MLs. Biodistribution of MLs was followed up with a 7T preclinical magnetic resonance imaging (MRI) scanner and fluorescence imaging (FLI) right after injection, 2h, 4h, 24h and 48h post injection. Ex vivo intratumoral ML uptake was confirmed using FLI, electron paramagnetic resonance spectroscopy (EPR) and histology at different time points post injection.

Results

In vivo, we visualized a higher uptake of cRGD-MLs in SKOV-3 xenografts compared to control, anionic MLs with both MRI and FLI. Highest ML uptake was seen after 4h using MRI, but only after 24h using FLI indicating the lower sensitivity of this technique. Furthermore, ex vivo EPR and FLI confirmed the highest tumoral ML uptake at 4 h. Last, a Perl’s stain supported the presence of our iron-based particles in SKOV-3 xenografts.

Conclusion

Uptake of cRGD-MLs can be visualized using both MRI and FLI, even though the latter was less sensitive due to lower depth penetration. Furthermore, our results indicate that cRGD-MLs can be used to target SKOV-3 xenograft in Swiss nude mice. Therefore, the further development of this particles into theranostics would be of interest.

Emerging strategies to disrupt the central TGF-β axis in kidney fibrosis

Chronic kidney disease (CKD) affects more than 20 million people in the United States and the global burden of this disorder is increasing. Many affected individuals will progress to end stage kidney disease necessitating dialysis or transplantation. CKD is also a major independent contributor to the risk of cardiovascular morbidity and mortality. Tubulointerstitial fibrosis is a final common pathway for most causes of progressive CKD. Currently, there are no clinically available therapies targeting fibrosis that can slow the decline in kidney function. Although it has long been known that TGF-β signaling is a critical mediator of kidney fibrosis, translating this knowledge to the clinic has been challenging. In this review, we highlight some recent insights into the mechanisms of TGF-β signaling that target activation of this cytokine at the site of injury or selectively inhibit pro-fibrotic gene expression. Molecules directed at these targets hold the promise of attaining therapeutic efficacy while limiting toxicity seen with global inhibition of TGF-β. Kidney injury has profound epigenetic effects leading to altered expression of more than a thousand genes. We discuss how drugs targeting epigenetic modifications, some of which are in use for cancer therapy, have the potential to reprogram gene regulatory networks to favor adaptive repair and prevent fibrosis. The lack of reliable biomarkers of kidney fibrosis is a major limitation in designing clinical trials for testing CKD treatments. We conclude by reviewing recent advances in fibrosis biomarker development.

Adoptive Transfer of Bone Marrow-Derived Monocytes Ameliorates Schistosoma mansoni -Induced Liver Fibrosis in Mice

Liver diseases are a major health problem worldwide leading to high mortality rates and causing a considerable economic burden in many countries. Cellular therapies as potential treatments for liver diseases have proven beneficial in most of the conditions. In recent years, studies involving therapy with bone marrow cells have been implemented to promote liver regeneration and to reduce hepatic fibrosis, however identifying the cell population present in the bone marrow that is responsible for hepatic improvement after therapy is still necessary. The aim of the present study was the evaluation of the therapeutic efficacy of monocytes obtained from bone marrow in fibrosis resulting from S. mansoni infection in C57BL/6 mice. Monocytes were isolated by immunomagnetic separation and administered to the infected animals. The effects of treatment were evaluated through morphometric, biochemical, immunological and molecular analyzes. Monocyte therapy promoted reduction of liver fibrosis induced by S. mansoni infection, associated with a decrease in production of inflammatory and pro-fibrogenic mediators. In addition, monocyte infusion caused downregulation of factors associated with the M1 activation profile, as well as upregulation of M2reg markers. The findings altogether reinforce the hypothesis that the predominance of M2reg macrophages, producers of immunosuppressive cytokines, may favor the improvement of hepatic fibrosis in a preclinical model, through fibrous tissue remodeling, modulation of the inflammatory response and fibrogenesis.

Vitronectin deficiency attenuates hepatic fibrosis in a non-alcoholic steatohepatitis-induced mouse model

Vitronectin (VN), an extracellular matrix protein, is a promising immune biomarker of non-alcoholic steatohepatitis (NASH); however, its precise function remains unclear. This study investigated how VN deficiency contributes to the development of NASH. Towards this aim, wild-type (WT) and VN-/- mice were fed with a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) for 6 and 10 weeks to induce NASH, and the livers were isolated. In WT mice fed with CDAHFD for 6 and 10 weeks, the expression of Vn mRNA and protein was up-regulated compared with that in mice fed with the MF control diet, indicating that VN is regulated in NASH condition. VN-/- mice showed decreased picrosirius red staining in the liver area and Col1a2 mRNA expression levels, compared with WT mice, indicating that the severity of hepatic fibrosis is attenuated in the CDAHFD-fed VN-/- mice. In addition, VN deficiency did not affect the area of lipid droplets in haematoxylin-eosin staining and the mRNA expression levels of fatty acid synthases, Srebp, Acc and Fas in the CDAHFD-fed mice. Moreover, VN deficiency decreased the inflammation score and the mRNA expression levels of Cd11b and F4/80, macrophage markers, as well as Tnf-α and Il-1β, inflammatory cytokines in the CDAHFD-fed mice. Furthermore, VN deficiency decreased the protein and mRNA expression levels of α-smooth muscle actin in the CDAHFD-fed mice, suggesting that VN deficiency inhibits the activation of hepatic stellate cells (HSCs). Our findings indicate that VN contributes to the development of fibrosis in the NASH model mice via modulation of the inflammatory reaction and activation of HSCs.

Fibrosis and alcohol-related liver disease

Histological fibrosis stage is one of the most important prognostic factors in compensated and decompensated alcohol-related liver disease (ALD). Morphological assessment of fibrosis is useful for patient stratification, enabling individualised management, and for evaluation of treatment effects in clinical studies. In contrast to most chronic liver diseases where fibrosis is portal-based, fatty liver disease (FLD) of alcoholic or non-alcoholic aetiology (NAFLD) is associated with a centrilobular pattern of injury which leads to perivenular fibrosis and/or pericellular fibrosis. Progression of FLD drives expansive pericellular fibrosis, linking vascular structures and paving the way for the development of cirrhosis. At the cirrhotic stage, ongoing tissue damage leads to increasing fibrosis severity due to parenchymal loss and proliferation of fibrous scars. Histologic fibrosis staging systems have been devised, based on topography and the extent of fibrosis, for most chronic liver diseases. The utility of histological staging is reflected in different risks associated with individual fibrosis stages which cannot be reliably distinguished by non-invasive fibrosis assessment. In contrast to NAFLD, ALD-specific staging systems that enable the standardised prognostication required for clinical management and trials are lacking. Although morphological similarities between NAFLD and ALD exist, differences in clinical and histological features may substantially limit the utility of established NAFLD-specific staging systems for prognostication in ALD. This review summarises morphological features of fibrosis in ALD and compares them to other chronic liver diseases, particularly NAFLD. ALD-related fibrosis is examined in the context of pathogenetic mechanisms of fibrosis progression, regression and clinical settings that need to be considered in future prognostically relevant ALD staging approaches.

Molecular imaging of fibrosis: recent advances and future directions

Fibrosis, the progressive accumulation of connective tissue that occurs in response to injury, causes irreparable organ damage and may result in organ failure. The few available antifibrotic treatments modify the rate of fibrosis progression, but there are no available treatments to reverse established fibrosis. Thus, more effective therapies are urgently needed. Molecular imaging is a promising biomedical methodology that enables noninvasive visualization of cellular and subcellular processes. It provides a unique means to monitor and quantify dysregulated molecular fibrotic pathways in a noninvasive manner. Molecular imaging could be used for early detection, disease staging, and prognostication, as well as for assessing disease activity and treatment response. As fibrotic diseases are often molecularly heterogeneous, molecular imaging of a specific pathway could be used for patient stratification and cohort enrichment with the goal of improving clinical trial design and feasibility and increasing the ability to detect a definitive outcome for new therapies. Here we review currently available molecular imaging probes for detecting fibrosis and fibrogenesis, the active formation of new fibrous tissue, and their application to models of fibrosis across organ systems and fibrotic processes. We provide our opinion as to the potential roles of molecular imaging in human fibrotic diseases.

Ron Receptor Signaling Ameliorates Hepatic Fibrosis in a Diet-Induced Nonalcoholic Steatohepatitis Mouse Model

Liver fibrosis is commonly observed in the terminal stages of nonalcoholic steatohepatitis (NASH) and with no specific and effective antifibrotic therapies available, this disease is a major global health burden. The MSP/Ron receptor axis has been shown to have anti-inflammatory properties in a number of mouse models, due at least in part, to its ability to limit pro-inflammatory responses in tissue-resident macrophages and hepatocytes. In this study, we established the role of the Ron receptor in steatohepatitis-induced hepatic fibrosis using Ron ligand domain knockout mice on an apolipoprotein E knockout background (DKO). After 18 weeks of high-fat high-cholesterol feeding, loss of Ron activation resulted in exacerbated NASH-associated steatosis which is precedent to hepatocellular injury, inflammation and fibrosis. ¹H nuclear magnetic resonance (NMR)-based metabolomics identified significant changes in serum metabolites that can modulate the intrahepatic lipid pool in hepatic steatosis. Serum from DKO mice had higher concentrations of lipids, VLDL/LDL and pyruvate, whereas glycine levels were reduced. Parallel to the aggravated steatohepatitis, increased accumulation of collagen, inflammatory immune cells and collagen producing-myofibroblasts were seen in the livers of DKO mice. Gene expression profiling revealed that DKO mice exhibited elevated expression of genes encoding Ron receptor ligand MSP, collagens, ECM remodeling proteins and pro-fibrogenic cytokines in the liver. Our results demonstrate the protective effects of Ron receptor activation on NASH-induced hepatic fibrosis.

New Concepts on Reversibility and Targeting of Liver Fibrosis; A Review Article

Currently, liver fibrosis and its complications are regarded as critical health problems. With the studies showing the reversible nature of liver fibrogenesis, scientists have focused on understanding the underlying mechanism of this condition in order to develop new therapeutic strategies. Although hepatic stellate cells are known as the primary cells responsible for liver fibrogenesis, studies have shown contributing roles for other cells, pathways, and molecules in the development of fibrosis depending on the etiology of liver fibrosis. Hence, interventions could be directed in the proper way for each type of liver diseases to better address this complication. There are two main approaches in clinical reversion of liver fibrosis; eliminating the underlying insult and targeting the fibrosis process, which have variable clinical importance in the treatment of this disease. In this review, we present recent concepts in molecular pathways of liver fibrosis reversibility and their clinical implications.

Activation of Hepatic Stellate Cells During Liver Carcinogenesis Requires Fibrinogen/Integrin αvβ5 in Zebrafish

Hepatocellular carcinoma (HCC) is one of the most common cancers and it usually develops from a background of liver fibrosis or inflammation. The crosstalk between tumor cells and stromal cells plays an important and stimulating role during tumor progression. Previously we found in a krasV12-induced zebrafish HCC model that oncogenic hepatocytes activate hepatic stellate cells (HSCs) by up-regulation of serotonin and activate neutrophils and macrophages by up-regulation of cortisol. In the present study, we found a novel signaling transduction mechanism between oncogenic hepatocytes and HSCs. After krasV12 induction, fibrinogen was up-regulated in oncogenic hepatocytes. We reasoned that fibrinogen may bind to integrin αvβ5 on HSCs to activate HSCs. Consistent with this notion, pharmaceutical treatment using an antagonist of integrin αvβ5, cilengitide, significantly blocked HSC activation and function, accompanied by attenuated proliferation of oncogenic hepatocytes and progression of liver fibrosis. On the contrary, adenosine 5'-diphosphate, an agonist of αvβ5, activated HSCs significantly that further stimulated the tumor progression and liver fibrosis. Interestingly, in human liver disease samples, we detected an increased level of fibrinogen during tumor progression which indicated the potential role of fibrinogen signaling in HCC progression. Thus, we concluded a novel interaction between oncogenic hepatocytes and HSCs through the fibrinogen related pathway in both the zebrafish HCC model and human liver disease samples.

Integrins in wound healing, fibrosis and tumor stroma: High potential targets for therapeutics and drug delivery

Wound healing is a complex process, which ultimately leads to fibrosis if not repaired well. Pathologically very similar to fibrosis is the tumor stroma, found in several solid tumors which are regarded as wounds that do not heal. Integrins are heterodimeric surface receptors which control various physiological cellular functions. Additionally, integrins also sense ECM-induced extracellular changes during pathological events, leading to cellular responses, which influence ECM remodeling. The purpose and scope of this review is to introduce integrins as key targets for therapeutics and drug delivery within the scope of wound healing, fibrosis and the tumor stroma. This review provides a general introduction to the biology of integrins including their types, ligands, means of signaling and interaction with growth factor receptors. Furthermore, we highlight integrins as key targets for therapeutics and drug delivery, based on their biological role, expression pattern within human tissues and at cellular level. Next, therapeutic approaches targeting integrins, with a focus on clinical studies, and targeted drug delivery strategies based on ligands are described.

Targeting extracellular matrix stiffness to attenuate disease: From molecular mechanisms to clinical trials

Tissues stiffen during aging and during the pathological progression of cancer, fibrosis, and cardiovascular disease. Extracellular matrix stiffness is emerging as a prominent mechanical cue that precedes disease and drives its progression by altering cellular behaviors. Targeting extracellular matrix mechanics, by preventing or reversing tissue stiffening or interrupting the cellular response, is a therapeutic approach with clinical potential. Major drivers of changes to the mechanical properties of the extracellular matrix include phenotypically converted myofibroblasts, transforming growth factor β (TGFβ), and matrix cross-linking. Potential pharmacological interventions to overcome extracellular matrix stiffening are emerging clinically. Aside from targeting stiffening directly, alternative approaches to mitigate the effects of increased matrix stiffness aim to identify and inhibit the downstream cellular response to matrix stiffness. Therapeutic interventions that target tissue stiffening are discussed in the context of their limitations, preclinical drug development efforts, and clinical trials.

The diagnosis of hepatic fibrosis by magnetic resonance and near-infrared imaging using dual-modality nanoparticles

Hepatic fibrosis (HF), as the only reversible process of chronic liver disease, remains a big diagnostic challenge. Development of noninvasive and effective methods to assess quantitatively early-stage HF is of great clinical importance. Compared with conventional diagnostic methods, near-infrared fluorescence imaging (NIR) and magnetic resonance imaging (MRI) could offer highly sensitive and spatial resolution signals for HF detection. However, precise detection using contrast agents is not possible. Superparamagnetic iron oxide (SPIO) nanoparticles have low toxicity, high sensitivity and excellent biocompatibility. Integration of Fe₃O₄ nanoparticles and indocyanine green (ICG), coupled with targeting ligand of integrin α_vβ₃, arginine–glycine–aspartic acid (RGD) expressed on hepatic stellate cells (HSCs), were used to detect HF. Both in vivo and in vitro results showed that the SPIO@SiO₂–ICG–RGD had high stability and low cytotoxicity. The biodistribution of SPIO@SiO₂–ICG–RGD was significantly different between mice with HF and healthy controls. SPIO@SiO₂–ICG–RGD was characterized and the results of imaging in vitro and in vivo demonstrated the expression of integrin α_vβ₃ on activated HSCs. These data suggest that our SPIO@SiO₂–ICG–RGD probe could be used for the diagnosis of early-stage HF. This new nanoprobe with a dual-modality imaging approach holds great potential for the diagnosis and classification of HF.

Schematic diagram for the synthesis of SPIO@SiO₂–ICG–RGD.

CCN1/Cyr61 enhances the function of hepatic stellate cells in promoting the progression of hepatocellular carcinoma

Hepatic stellate cells (HSCs) are the main extracellular matrix (ECM)-producing cells in liver fibrosis. Activated HSCs stimulate the proliferation and migration of hepatocellular carcinoma (HCC) cells. Cysteine-rich 61 (CCN1/Cyr61) is an ECM protein. Our previous studies demonstrated that the expression of CCN1 was significantly higher in benign hepatic cirrhosis tissue and cancer-adjacent hepatic cirrhosis tissues. CCN1 is a target gene of β-catenin in HCC and promotes the proliferation of HCC cells. The present study aimed to examine whether CCN1 can activate HSCs and affect the function of activated HSCs in promoting the progression of HCC. CCN1 expression was determined during the progression of liver fibrosis in a mouse model. LX-2 cells, which were infected with adenoviruses AdCCN1 or AdRFP, and HepG2 cells were co-cultured or subcutaneously co-implanted into in nude mice. MTT assay, Crystal Violet staining, Boyden chamber, matrigel invasion and monolayer scratch assays were used to analyze the proliferation, migration and invasion capability of HepG2 cells. Xenograft sizes were measured and histological analyses were performed by hematoxylin and eosin, immunohistochemical, immunefluorescence and Sirius Red staining. It was demonstrated that the expression of CCN1 was continually increased in liver fibrosis and the that expression may be correlated with the progression of liver fibrosis. CCN1 affected the function of LX-2 and enhanced the effect of LX-2 on promoting the viability, migration and invasion of HepG2 cells in vitro. CCN1 enhanced the effect of LX-2 on promoting the growth of HepG2 xenografts in vivo. CCN1 also affected the function of activated HSCs and regulated the formation of the xenograft microenvironment, including fibrogenesis and angiogenesis, which are beneficial for the progression of HCC. These findings demonstrated that CCN1 may be involved in the progression of the hepatic cirrhosis-HCC axis through regulating HSCs.

Matrix metalloproteinases and liver fibrosis (translational aspects)

Liver fibrosis, a reversible wound-healing response to chronic cellular injury, reflects a balance between liver repair and progressive substitution of the liver parenchyma by scar tissue. Complex mechanisms that underlie liver fibrogenesis are summarized to provide the basis for generating targeted therapies to reverse fibrogenesis and improve the outcomes of patients with chronic liver disease. This minireview presents some pathophysiological aspects of liver fibrosis as a dynamic process and elucidates matrix metalloproteinases (MMPs) and their role within as well as beyond matrix degradation. Open questions remain, whether inhibition of fibrogenesis or induction of fibrolysis is the key mechanism to resolve fibrosis. And a point of principle might be whether regeneration of liver cirrhosis is possible. Will we ever cure fibrosis?

Matrix metalloproteinase functions in hepatic injury and fibrosis

Liver fibrosis is the most common final outcome for chronic liver diseases. The complex pathogenesis includes hepatic parenchymal damage as a result of a persistent noxe, activation and recruitment of immune cells, activation of hepatic stellate cells, and the synthesis of fibrotic extracellular matrix (ECM) components leading to scar formation. Clinical studies and animal models demonstrated that fibrosis can be reversible. In this regard matrix metalloproteinases (MMPs) have been focused as therapeutic targets due to their ability to modulate tissue turnover during fibrogenesis as well as regeneration and, of special interest, due to their influence on cellular behavior like proliferation, gene expression, and apoptosis that, in turn, impact fibrosis and regeneration. The current review aims to summarize and update the knowledge about expression pattern and the central roles of MMPs in hepatic fibrosis.

Ultrasound molecular imaging with cRGD-PLGA-PFOB nanoparticles for liver fibrosis staging in a rat model

Hepatic fibrosis is the only chronic liver disease process that can be reversed. Developing non-invasive and effective methods to quantitatively assess the degree of liver fibrosis is of great clinical significance and remains a major challenge. The key factors in hepatic fibrosis pathogenesis are the activation and proliferation of hepatic stellate cells that subsequently express integrin α_vβ₃. An ultrasound (US) agent combined with a targeting peptide may be used for the early and non-invasive diagnosis of hepatic fibrosis. Herein, we report the synthesis of core-shell nanoparticles (NPs) successfully engineered by conjugation with cyclic arginine-glycine-aspartic acid (cRGD) octapeptide, allowing hepatic integrin α_vβ₃ targeting for liver fibrosis staging. This system consists of a perfluorooctyl bromide (PFOB) liquid in the core that is stabilized with a Poly (lactic-co-glycolic acid) (PLGA) polymer shell and modified with a cRGD. These core-shell NPs (cRGD-PLGA-PFOB NPs) exhibited useful US molecular imaging features including high imaging contrast among liver fibrotic stages and the adjacent tissues. Our results indicate that the cRGD-PLGA-PFOB NPs have significant potential to distinguish different liver fibrotic stages and could be used in clinical applications.