Overexpression of angiopoietin-2 in rats and patients with liver fibrosis. Therapeutic consequences of its inhibition

Vascular heterogeneity of tight junction Claudins guides organotropic metastasis

Carcinomas are associated with metastasis to specific organs while sparing others. Breast cancer presents with lung metastasis but rarely kidney metastasis. Using this difference as an example, we queried the mechanism(s) behind the proclivity for organ-specific metastasis. We used spontaneous and implant models of metastatic mammary carcinoma coupled with inflammatory tissue fibrosis, single-cell sequencing analyses and functional studies to unravel the causal determinants of organ-specific metastasis. Here we show that lung metastasis is facilitated by angiopoietin 2 (Ang2)-mediated suppression of lung-specific endothelial tight junction protein Claudin 5, which is augmented by the inflammatory fibrotic microenvironment and prevented by anti-Ang2 blocking antibodies, while kidney metastasis is prevented by non-Ang2-responsive Claudins 2 and 10. Suppression of Claudins 2 and 10 was sufficient to induce the emergence of kidney metastasis. This study illustrates the influence of organ-specific vascular heterogeneity in determining organotropic metastasis, independent of cancer cell-intrinsic mechanisms.

Intrahepatic Transcriptomics Differentiate Advanced Fibrosis and Clinical Outcomes in Adults With Fontan Circulation

BACKGROUND

The molecular mechanisms underlying Fontan-associated liver disease (FALD) remain largely unknown.

OBJECTIVES

This study aimed to assess intrahepatic transcriptomic differences among patients with FALD according to the degree of liver fibrosis and clinical outcomes.

METHODS

This retrospective cohort study included adults with the Fontan circulation. Baseline clinical, laboratory, imaging, and hemodynamic data as well as a composite clinical outcome (CCO) were extracted from medical records. Patients were classified into early or advanced fibrosis. RNA was isolated from formalin-fixed paraffin-embedded liver biopsy samples; RNA libraries were constructed with the use of an rRNA depletion method and sequenced on an Illumina Novaseq 6000. Differential gene expression and gene ontology analyses were performed with the use of DESeq2 and Metascape.

RESULTS

A total of 106 patients (48% male, median age 31 years [IQR: 11.3 years]) were included. Those with advanced fibrosis had higher B-type natriuretic peptide levels and Fontan, mean pulmonary artery, and capillary wedge pressures. The CCO was present in 23 patients (22%) and was not predicted by advanced liver fibrosis, right ventricular morphology, presence of aortopulmonary collaterals, or Fontan pressures on multivariable analysis. Samples with advanced fibrosis had 228 upregulated genes compared with early fibrosis. Samples with the CCO had 894 upregulated genes compared with those without the CCO. A total of 136 upregulated genes were identified in both comparisons and were enriched in cellular response to cytokine stimulus or oxidative stress, VEGFA-VEGFR2 signaling pathway, TGF-β signaling pathway, and vasculature development.

CONCLUSIONS

Patients with FALD and advanced fibrosis or the CCO exhibited upregulated genes related to inflammation, congestion, and angiogenesis.

Serum Angiopoietin-2 Levels Predict the Development of Hepatocellular Carcinoma following Hepatitis C Virus Eradication Using Direct-Acting Antiviral Agents

INTRODUCTION

Our previous studies showed that serum angiopoietin-2 (Ang-2) and C-X-C motif chemokine ligand 10 (CXCL10) levels predicted improvement in liver fibrosis following sustained virological response (SVR) of hepatitis C virus (HCV) obtained with administration of with direct-acting antiviral agents (DAAs). These levels were evaluated retrospectively as predictive indicators of hepatocellular carcinoma (HCC) development following SVR.

METHODS

We enrolled individuals from a historical cohort of 89 chronic HCV patients without history of HCC at baseline and with SVR following DAA therapy and had baseline serum levels of Mac-2 binding protein glycosylation isomer ≥2.0 cut-off index (C.O.I.).

RESULTS

Multivariate analyses revealed that only the Ang-2 level at 24 weeks following the end of treatment (EOT24W) was significantly related to HCC development (hazard ratio 2.27; p = 0.003). This result was reproduced in individuals without history of HCC and with advanced liver fibrosis (M2BPGi level ≥3.3 C.O.I. at baseline). Time-dependent receiver operating characteristic curve analyses for the future risk of developing HCC within 5 years of follow-up (5y-HCC) showed the best cut-off Ang-2 level at the EOT24W was 2,780 pg/mL, and significantly stratified the cumulative incidence of HCC (≥2,780 vs. < 2,780 pg/mL, 5y-HCC: 45.5 vs. 8.2%, p < 0.001).

CONCLUSIONS

At the EOT24W, serum Ang-2 level predicts the likelihood of developing HCC following SVR to DAA therapy.

Serum Angiopoetin-2 Levels in Pediatric Patients After Fontan Operation

Angiopoietin-2 is associated with chronic inflammation and angiogenesis, but its activity after Fontan operation in pediatric patients remains uncertain. We compared serum angiopoietin-2 levels in pediatric patients after Fontan operation versus those with congenital heart disease as a control group. A total of 185 patients (median age 7 [3 to 12] years, 106 males) were included, consisting of 140 in the Fontan group and 45 in the control group. Serum angiopoietin-2 levels were significantly higher in the Fontan group (7,670 vs 2,351 pg/ml, p <0.001). In the Fontan group, a serum angiopoietin-2 level ≥3.9 of common logarithm was an independent risk factor for death or Fontan-related adverse events with an adjusted hazard ratio of 6.25 (95% confidence interval 1.64 to 23.9, p = 0.007). In preoperative variables, desaturation was independently associated with increased serum angiopoietin-2 levels after Fontan operation (p = 0.047). In conclusion, serum angiopoietin-2 levels were elevated in the pediatric phase after Fontan operation. In Fontan patients, a higher serum angiopoietin-2 level was an independent risk factor for death or Fontan-related adverse events. The clinical implication of measuring and monitoring serum angiopoietin-2 levels in this cohort requires further investigation.

Comparison the therapeutic effects of bone marrow CD144+ endothelial cells and CD146+ mesenchymal stem cells in POF rats

Introduction

Premature ovarian insufficiency (POI) is a challenging issue in terms of reproduction biology. In this study, therapeutic properties of bone marrow CD146+ mesenchymal stem cells (MSCs) and CD144+ endothelial cells (ECs) were separately investigated in rats with POI.

Methods

POI rats were classified into control POI, POI + CD146+ MSCs, and POI + CD144+ ECs groups. Enriched CD146+ MSCs and CD144+ ECs were directly injected into ovarian tissue (15 × 104 cells/10 μL) in relevant groups. After 4 weeks, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) levels were measured in blood samples. Ovarian tissues were collected and subjected to Hematoxylin-Eosin and Masson's trichrome staining. The expression of angp-2, vegfr-2, smad-2, -4, -6, and tgf-β1 was studied using qRT-PCR analysis. Histopathological examination indicated an increased pattern of atretic follicles in the POI group related to the control rats (P<0.0001).

Results

Data indicated that injection of POI + CD146+ MSCs and CD144+ ECs in POI rats reduced atretic follicles and increased the number of normal follicles (P<0.01). Along with these changes, the content of blue-colored collagen fibers was diminished after cell transplantation. Besides, cell transplantation in POI rats had the potential to reduce increased FSH, and LH levels (P<0.05). In contrast, E2 content was increased in POI + CD146+ MSCs and POI + CD144+ ECs groups compared to control POI rats, indicating restoration of follicular function. CD144+ (smad-2, and -4) and CD146+ (smad-6) cells altered the activity of genes belonging TGF-β signaling pathway. Unlike POI + CD146+ MSCs, aberrant angiogenesis properties were significantly down-regulated in POI + CD144+ ECs related to the control POI group (P<0.05).

Conclusion

The transplantation of bone marrow CD146+ and CD144+ cells can lead to the restoration of ovarian tissue function in POI rats via modulating different mechanisms associated with angiogenesis and fibrosis.

Monocyte-endothelial cell interactions in vascular and tissue remodeling

Monocytes are circulating leukocytes of innate immunity derived from the bone marrow that interact with endothelial cells under physiological or pathophysiological conditions to orchestrate inflammation, angiogenesis, or tissue remodeling. Monocytes are attracted by chemokines and specific receptors to precise areas in vessels or tissues and transdifferentiate into macrophages with tissue damage or infection. Adherent monocytes and infiltrated monocyte-derived macrophages locally release a myriad of cytokines, vasoactive agents, matrix metalloproteinases, and growth factors to induce vascular and tissue remodeling or for propagation of inflammatory responses. Infiltrated macrophages cooperate with tissue-resident macrophages during all the phases of tissue injury, repair, and regeneration. Substances released by infiltrated and resident macrophages serve not only to coordinate vessel and tissue growth but cellular interactions as well by attracting more circulating monocytes (e.g. MCP-1) and stimulating nearby endothelial cells (e.g. TNF-α) to expose monocyte adhesion molecules. Prolonged tissue accumulation and activation of infiltrated monocytes may result in alterations in extracellular matrix turnover, tissue functions, and vascular leakage. In this review, we highlight the link between interactions of infiltrating monocytes and endothelial cells to regulate vascular and tissue remodeling with a special focus on how these interactions contribute to pathophysiological conditions such as cardiovascular and chronic liver diseases.

Intrahepatic transcriptomics differentiate advanced fibrosis and clinical outcomes in adults with the Fontan circulation

Background

The molecular mechanisms underlying Fontan associated liver disease (FALD) remain largely unknown. We aimed to assess intrahepatic transcriptomic differences among patients with FALD according to the degree of liver fibrosis and clinical outcomes.

Methods

This retrospective cohort study included adults with the Fontan circulation at the Ahmanson/UCLA Adult Congenital Heart Disease Center. Clinical, laboratory, imaging and hemodynamic data prior to the liver biopsy were extracted from medical records. Patients were classified into early (F1-F2) or advanced fibrosis (F3-F4). RNA was isolated from formalin-fixed paraffin embedded liver biopsy samples; RNA libraries were constructed using rRNA depletion method and sequencing was performed on Illumina Novaseq 6000. Differential gene expression and gene ontology analyses were carried out using DESeq2 and Metascape. Medical records were comprehensively reviewed for a composite clinical outcome which included decompensated cirrhosis, hepatocellular carcinoma, liver transplantation, protein-losing enteropathy, chronic kidney disease stage 4 or higher, or death.

Results

Patients with advanced fibrosis had higher serum BNP levels and Fontan, mean pulmonary artery and capillary wedge pressures. The composite clinical outcome was present in 23 patients (22%) and was predicted by age at Fontan, right ventricular morphology and presence of aortopulmonary collaterals on multivariable analysis. Samples with advanced fibrosis had 228 up-regulated genes compared to early fibrosis. Samples with the composite clinical outcome had 894 up-regulated genes compared to those without it. A total of 136 up-regulated genes were identified in both comparisons and these genes were enriched in cellular response to cytokine stimulus, response to oxidative stress, VEGFA-VEGFR2 signaling pathway, TGF-beta signaling pathway, and vasculature development.

Conclusions

Patients with FALD and advanced liver fibrosis or the composite clinical outcome exhibit up-regulated genes including pathways related to inflammation, congestion, and angiogenesis. This adds further insight into FALD pathophysiology.

Serum Angiopoietin-2 Predicts the Occurrence and Recurrence of Hepatocellular Carcinoma after Direct-Acting Antiviral Therapy for Hepatitis C

Progressive liver fibrosis after anti-HCV treatment is a risk factor for HCC. Angiopoietin-2 (Ang2) is associated with non-regression of liver fibrosis after direct-acting antiviral (DAA). This study evaluated the predictive value of serum Ang2 levels for HCC occurrence or recurrence after DAA administration. In this retrospective study, 310 HCV-infected patients treated with DAAs in 2014-2020 were screened and evaluated for HCC occurrence or recurrence every three-six months. Multivariate Cox regression analysis revealed that age ≥ 75 years (HR: 2.92, 95% CI: 1.34-6.33; p = 0.007) and baseline Ang2 level ≥ 464 pg/mL (HR: 2.75, 95% CI: 1.18-6.37; p = 0.019) were significantly associated with HCC occurrence after DAA therapy. A high or low risk of HCC after DAA therapy could be distinguished by the combination of age and baseline Ang2 level. The cumulative incidences of de-novo HCC at two and four years were 0.8% and 3.8% in the low-risk group and 22.6% and 27.1% in the high-risk group, respectively. Baseline Ang2 level ≥ 402 pg/mL was significantly associated with HCC recurrence in patients who achieved sustained virological response with DAAs (HR: 3.68). In conclusion, serum Ang2 levels can predict HCC occurrence and recurrence after successful HCV eradication by DAAs.

Serum angiopoietin-2 levels predict regression of Mac-2 binding protein glycosylation isomer-based liver fibrosis after hepatitis C virus eradication by direct-acting antiviral agents

AIM

It is desirable to identify predictors of regression of liver fibrosis after achieving a sustained virologic response (SVR) by direct-acting antiviral agents (DAAs) to antihepatitis C virus (HCV) therapy. Here, we retrospectively investigated the serum angiopoietin-2 (Ang-2) level as a predictive indicator of regression of liver fibrosis after successful HCV eradication by DAA therapy.

METHODS

The study subjects were recruited from a historical cohort of 109 chronically HCV-infected patients who had achieved SVR by DAA therapy and whose serum Mac-2 binding protein glycosylation isomer (M2BPGi) levels at baseline (before DAA therapy) were ≥2.0 the cut-off index (COI). We defined patients with M2BPGi levels <1.76 and ≥1.76 COI at 2 years after the end of treatment (EOT) as the regression (R, n = 69) and nonregression (NR, n = 40) groups, respectively.

RESULTS

Multivariate analyses revealed that the Ang-2 level at baseline and the Ang-2 level, albumin-bilirubin score, and FIB-4 index at 24 weeks after the EOT were significantly associated with regression of M2BPGi-based liver fibrosis. Receiver operating characteristic curve analyses showed that the Ang-2 level at 24 weeks after the EOT had the largest area under the curve values (0.859). The same results were obtained even when the serum M2BPGi levels were aligned by propensity score matching and in patients with advanced M2BPGi-based liver fibrosis: M2BPGi levels ≥3.3 COI at baseline.

CONCLUSIONS

The serum Ang-2 level at 24 weeks after the EOT is a feasible predictor of regression of M2BPGi-based liver fibrosis after achieving SVR by DAA therapy.

Angiopoietin 2 levels decrease after HCV-cure and reflect the evolution of portal hypertension

BACKGROUND

Portal hypertension (PH) does not resolve in a considerable proportion of patients who achieved HCV-cure.

AIMS

To investigate (i)whether HCV-cure impacts cytokines that orchestrate angiogenesis (i.e.,Ang1/Ang2/VEGF) and fibrogenesis (i.e.,PDGF/TGF-β) and (ii)whether their changes reflect PH-evolution and its complications.

METHODS

We measured plasma levels of cytokines and von Willebrand factor (VWF) and assessed hepatic venous pressure gradient (HVPG) before/after HCV-cure in 66 patients with pre-treatment PH and 23 patients without advanced disease, who served as controls.

RESULTS

Following HCV-cure, we observed a decrease in Ang2/TGF-β, but no changes in the other cytokines. The differences in circulating cytokine profiles in PH patients persisted after removing the primary etiological factor. Patients with pre-treatment HVPG≥10 mmHg with HVPG-reduction≥10% had a more pronounced relative decrease in Ang2. Finally, post-treatment Ang2 predicted FU-HVPG≥16 mmHg/decompensation with AUROC-values of 0.804/0.835.

CONCLUSIONS

HCV-cure decreases circulating Ang2 - a mediator/indicator of dysangiogenesis/endothelial dysfunction, as well as TGF-β - a profibrogenic cytokine. The dynamics of Ang2 mirrored those of PH, rendering FU-Ang2 a non-invasive test for pronounced PH at FU that also predicts hepatic decompensation. The pathophysiological significance of the persistently altered cytokine levels for mechanisms that hinder the PH-regression warrants further study.

A strategy of vascular-targeted therapy for liver fibrosis

BACKGROUND AND AIMS

No effective treatments are available for liver fibrosis. Angiogenesis is deeply involved in liver fibrogenesis. However, current controversial results suggest it is difficult to treat liver fibrosis through vascular targeting. There are three different microvessels in liver: portal vessels, liver sinusoids, and central vessels. The changes and roles for each of the three different vessels during liver fibrogenesis are unclear. We propose that they play different roles during liver fibrogenesis, and a single vascular endothelial cell (EC) regulator is not enough to fully regulate these three vessels to treat liver fibrosis. Therefore, a combined regulation of multiple different EC regulatory signaling pathway may provide new strategies for the liver fibrosis therapy. Herein, we present a proof-of-concept strategy by combining the regulation of leukocyte cell-derived chemotaxin 2 (LECT2)/tyrosine kinase with immunoglobulin-like and epidermal growth factor-like domains 1 signaling with that of vascular endothelial growth factor (VEGF)/recombinant VEGF (rVEGF) signaling.

APPROACH AND RESULTS

The CCl₄ -induced mouse liver fibrosis model and NASH model were both used. During fibrogenesis, vascular changes occurred at very early stage, and different liver vessels showed different changes and played different roles: decreased portal vessels, increased sinusoid capillarization and the increased central vessels the increase of portal vessels alleviates liver fibrosis, the increase of central vessels aggravates liver fibrosis, and the increase of sinusoid capillarization aggravates liver fibrosis. The combinational treatment of adeno-associated viral vector serotype 9 (AAV9)-LECT2-short hairpin RNA (shRNA) and rVEGF showed improved therapeutic effects, but it led to serious side effects. The combination of AAV9-LECT2-shRNA and bevacizumab showed both improved therapeutic effects and decreased side effects.

CONCLUSIONS

Liver vascular changes occurred at very early stage of fibrogenesis. Different vessels play different roles in liver fibrosis. The combinational treatment of AAV9-LECT2-shRNA and bevacizumab could significantly improve the therapeutic effects on liver fibrosis.

The clinical value of angiopoietin-2 in liver diseases

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Angiopoietin-2 levels correlates with disease activity in children with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD), a chronic liver disease in children, ranges from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH). We investigated the role of Angiopoietin-2 (Ang-2) as a biomarker for pediatric NAFLD-related liver damage.

METHODS

We assessed the plasma levels of Ang-2 and cytokeratin-18 (CK18) fragments and their association with histologic activity in 76 children with NAFLD and 28 controls.

RESULTS

The mean plasma levels of Ang-2 and CK18 were higher in children with NAFLD than in age-matched controls (Ang-2 155.4 ± 72.5 vs 7.5 ± 2.3 ng/mL, p < 0.001; CK18 390.4 ± 145.6 vs 193.9 ± 30.8 IU/L, p < 0.001). Ang-2 was significantly increased (p < 0.0001) in children with NASH (N = 41) while CK18 was significantly increased (p = 0.002) in children with fibrosis (N = 47). Ang-2 levels accurately predicted NASH (AUROC 0.911; 95% CI 0.844-0.979; p < 0.0001), while CK18 predicted both NASH (AUROC 0.827; 95% CI 0.735-0.919; p < 0.0001) and fibrosis (AUROC 0.724; 95% CI 0.611-0.837; p = 0.001). Ang-2 and CK18 in combination were good predictors of NASH with a sensitivity of 71.4% and a specificity of 100%.

CONCLUSIONS

In conclusion, our data suggested Ang-2 as a suitable biomarker of NASH in the pediatric population. However, our findings need external validation in other cohorts.

IMPACT

Several circulating factors have been extensively studied as potential biomarkers for NASH. Angiopoietin-2 circulating levels are increased in children with NAFLD and are associated with NASH. Angiopoietin-2 levels are more efficient than CK18 levels at assessing the most severe form of disease, and the combining of these two biomarkers reached a positive predictive value of 100% for NASH.

Plasma angiopoietin 2 as a novel prognostic biomarker in alcohol-related cirrhosis and hepatitis

Background and aim

Severe alcoholic hepatitis (SAH), the most florid form of alcohol-related liver disease (ALD), has a mortality rate of 16% at 28 days. The angiopoietin-Tie 2 system regulates angiogenesis and inflammation, both of which are implicated in the pathogenesis of ALD. This study examined plasma and hepatic gene expression of angiopoietin 1 (ANG1) and angiopoietin 2 (ANG2) in patients with SAH and ALD and investigated their roles as prognostic biomarkers.

Methods

A case-control study was performed measuring plasma levels of ANG1 and ANG2 by enzyme-linked immunosorbent assay (ELISA) from 30 patients with SAH (Maddrey's discriminant function ≥32), 32 patients with ALD cirrhosis and 15 healthy controls (HC). RNA sequencing for ANG1, ANG2, TIE1 (codes for Tie1 receptor) and TEK (codes for Tie2 receptor) gene expression from a separate cohort study of 79 patients was also performed.

Results

Plasma levels of ANG1 were lower (P = 0.010) and ANG2 were higher (P < 0.0001) in patients with ALD/SAH compared to HC. The ANG2: ANG1 ratio was higher in those with ALD/SAH compared to HC (P < 0.0001). ANG2 levels were the highest in patients who developed sepsis (P = 0.030) and those dying within 90 days (P = 0.020). ANG2 levels correlated positively with model for end-stage liver disease (MELD) score (r = 0.30, P = 0.020), Child-Pugh score (r = 0.38, P = 0.003), international normalized ratio (r = 0.41, P = 0.001) and white blood cell count (r = 0.28, P = 0.040) and inversely correlated with albumin (r = -0.26, P = 0.040).ANG1 gene expression from liver biopsies was higher in SAH than that in HC (P < 0.0001), and greater in severe disease (P < 0.0001). ANG2 gene expression trended towards being lower in SAH than that in HC (P = 0.070) though was upregulated in severe disease (P = 0.0003).

Conclusions

Plasma ANG2 is raised in SAH and ALD and could be useful as a prognostic biomarker in this patient population.

Baseline elevated serum angiopoietin-2 predicts long-term non-regression of liver fibrosis after direct-acting antiviral therapy for hepatitis C

We previously revealed that Angiopoietin-2 (Ang2) predicts non-regression of liver fibrosis based on liver stiffness measurement (LSM) at 24 weeks after anti-hepatitis C virus (HCV) treatment. In this study, we extended the observational period to 96 weeks to investigate the factors associated with non-regression after treatment with direct-acting-antivirals (DAAs). Patients treated with DAAs who underwent transient elastography at baseline and 24 and 96 weeks after DAA therapy were included. Baseline and post-treatment serum Ang2 levels were measured. Liver fibrosis stages were defined based on LSM. Multivariate regression was used to evaluate factors associated with non-regression of liver fibrosis between various time points. In total, 110 patients were included. Of these, 11% showed non-regression of LSM-based fibrosis stage at 96 weeks after DAA therapy. In multivariate analysis, advanced liver fibrosis stage and high baseline Ang2 levels were significantly associated with non-regression at 96 weeks. In patients with advanced liver fibrosis (F3/4), baseline Ang2 levels were associated with non-regression of liver fibrosis stage. Between SVR24 and SVR96, post-treatment Ang2 levels and controlled attenuation parameter values at SVR24 were significantly associated with non-regression of liver fibrosis stage in patients with F3/4. Thus, serum Ang2 levels are an important target for monitoring and therapy.

Serum Angiopoietin 2 acts as a diagnostic and prognostic biomarker in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is typically accompanied by abundant arterial blood flow. Although angiogenic growth factors such as Angiopoietin 2 (Ang2) play a central role in tumor angiogenesis in HCC, the role of serum Ang2 as a biomarker in HCC remains unclear. In this study, we aimed to investigate the potential of Ang2 as a diagnostic and prognostic biomarker in HCC using a sandwich enzyme-linked immunosorbent assay (ELISA). The median Ang2 levels in controls (n=20), chronic liver disease patients (n=98), and HCC patients (n=275) were 1.58, 2.33, and 3.53 ng/mL, respectively. The optimal cut-off value of Ang2 was determined as 3.5 ng/mL by receiver operating curve analysis. The sensitivity, specificity, and accuracy of Ang2 for HCC detection were 50.9, 83.7, and 59.5%, respectively. Spearman's rank correlation coefficient analysis demonstrated only a weak correlation between Ang2 serum levels and alpha-fetoprotein (AFP) or des-gamma-carboxy prothrombin (DCP) serum levels. The diagnostic value of Ang2 was comparable to those of other existing markers. In addition, 24 out of 73 patients with normal AFP and DCP levels (32.9%) demonstrated abnormally high Ang2 levels (≥3.5 ng/mL). Although no significant difference in overall survival was found between Ang2^high and Ang2^low patients with curative ablation therapy, recurrence-free survival (RFS) in Ang2^high patients was observed to be significantly shorter than those in Ang2^low patients. Multivariate analysis demonstrated that high serum Ang2 levels (≥3.5 ng/mL) and the presence of multiple tumors were poor prognostic factors. In conclusion, our findings indicate that serum Ang2 is a potential novel biomarker for both diagnosis and prognosis in HCC.

Angiogenesis in the progression from liver fibrosis to cirrhosis and hepatocelluar carcinoma

Introduction: Persistent inflammation and hypoxia are strong stimulus for pathological angiogenesis and vascular remodeling, and are also the most important elements resulting in liver fibrosis. Sustained inflammatory process stimulates fibrosis to the end-point of cirrhosis and sinusoidal portal hypertension is an important feature of cirrhosis. Neovascularization plays a pivotal role in collateral circulation formation of portal vein, mesenteric congestion, and high perfusion. Imbalance of hepatic artery and portal vein blood flow leads to the increase of hepatic artery inflow, which is beneficial to the formation of nodules. Angiogenesis contributes to progression from liver fibrosis to cirrhosis and hepatocellular carcinoma (HCC) and anti-angiogenesis therapy can improve liver fibrosis, reduce portal pressure, and prolong overall survival of patients with HCC. Areas covers: This paper will try to address the difference of the morphological characteristics and mechanisms of neovascularization in the process from liver fibrosis to cirrhosis and HCC and further compare the different efficacy of anti-angiogenesis therapy in these three stages. Expert opinion: More in-depth understanding of the role of angiogenesis factors and the relationship between angiogenesis and other aspects of the pathogenesis and transformation may be the key to enabling future progress in the treatment of patients with liver fibrosis, cirrhosis, and HCC.

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.

Nonalcoholic fatty liver disease and portal hypertension

Nonalcoholic fatty liver disease (NAFLD) is a substantial and growing problem worldwide and has become the second most common indication for liver transplantation as it may progress to cirrhosis and develop complications from portal hypertension primarily caused by advanced fibrosis and erratic tissue remodeling. However, elevated portal venous pressure has also been detected in experimental models of fatty liver and in human NAFLD when fibrosis is far less advanced and cirrhosis is absent. Early increases in intrahepatic vascular resistance may contribute to the progression of liver disease. Specific pathophenotypes linked to the development of portal hypertension in NAFLD include hepatocellular lipid accumulation and ballooning injury, capillarization of liver sinusoidal endothelial cells, enhanced contractility of hepatic stellate cells, activation of Kupffer cells and pro-inflammatory pathways, adhesion and entrapment of recruited leukocytes, microthrombosis, angiogenesis and perisinusoidal fibrosis. These pathological events are amplified in NAFLD by concomitant visceral obesity, insulin resistance, type 2 diabetes and dysbiosis, promoting aberrant interactions with adipose tissue, skeletal muscle and gut microbiota. Measurement of the hepatic venous pressure gradient by retrograde insertion of a balloon-tipped central vein catheter is the current reference method for predicting outcomes of cirrhosis associated with clinically significant portal hypertension and guiding interventions. This invasive technique is rarely considered in the absence of cirrhosis where currently available clinical, imaging and laboratory correlates of portal hypertension may not reflect early changes in liver hemodynamics. Availability of less invasive but sufficiently sensitive methods for the assessment of portal venous pressure in NAFLD remains therefore an unmet need. Recent efforts to develop new biomarkers and endoscopy-based approaches such as endoscopic ultrasound-guided measurement of portal pressure gradient may help achieve this goal. In addition, cellular and molecular targets are being identified to guide emerging therapies in the prevention and management of portal hypertension.

An integrative method to predict signalling perturbations for cellular transitions

Induction of specific cellular transitions is of clinical importance, as it allows to revert disease cellular phenotype, or induce cellular reprogramming and differentiation for regenerative medicine. Signalling is a convenient way to accomplish such transitions without transfer of genetic material. Here we present the first general computational method that systematically predicts signalling molecules, whose perturbations induce desired cellular transitions. This probabilistic method integrates gene regulatory networks (GRNs) with manually-curated signalling pathways obtained from MetaCore from Clarivate Analytics, to model how signalling cues are received and processed in the GRN. The method was applied to 219 cellular transition examples, including cell type transitions, and overall correctly predicted experimentally validated signalling molecules, consistently outperforming other well-established approaches, such as differential gene expression and pathway enrichment analyses. Further, we validated our method predictions in the case of rat cirrhotic liver, and identified the activation of angiopoietins receptor Tie2 as a potential target for reverting the disease phenotype. Experimental results indicated that this perturbation induced desired changes in the gene expression of key TFs involved in fibrosis and angiogenesis. Importantly, this method only requires gene expression data of the initial and desired cell states, and therefore is suited for the discovery of signalling interventions for disease treatments and cellular therapies.

Vascular Endothelial Growth Factor Promotes Proliferation of Epithelial Cell Adhesion Molecule-Positive Cells in Nonalcoholic Steatohepatitis

AIM

An impaired hepatocyte proliferation during severe liver injury causes the proliferation of hepatic progenitor cells (HPCs), also called as the ductular reaction (DR). In the present study, we studied the role of key angiogenic factors in HPC-mediated DR in nonalcoholic steatohepatitis (NASH).

METHODS

Liver biopsies from patients with NASH (n = 14) were included in the study. Patients with NASH were divided in two groups, early and late fibrosis (based on fibrosis staging). Biopsies were used to analyze the gene expression by quantitative real-time polymerase chain reaction and immunohistochemical (IHC) staining for two markers of DR, viz, CK19 and epithelial cell adhesion molecule (EpCAM). Cocultures were performed between steatotic human umbilical vein endothelial cells (HUVECs) and LX2 and Huh7 cells. Enzyme-linked immunosorbent assays were performed to measure levels of vascular endothelial growth factor (VEGF) in coculture studies. Next, Huh7 cells were treated with VEGF, and proliferation was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assays. The number of EpCAM-positive cells was analyzed by flow cytometry.

RESULTS

Of all the angiogenic factors, the gene expression of VEGF and angiopoietin 2 (Ang2) was significantly different between patients with NASH in the early and late fibrosis groups (P < 0.05 for both). Both VEGF and Ang2 also correlated significantly with the IHC scores of CK19 and EpCAM in the study group. In the in vitro studies, VEGF levels were significantly increased when Huh7 cells were cocultured with steatotic HUVECs and LX2 cells. The proliferation and percentage of EpCAM-positive cells was increased when Huh7 cells were treated with VEGF.

CONCLUSION

Our study indicates an important contribution of VEGF toward the activation of HPC-mediated regeneration and DR in NASH.

Roles of the Hepatic Endocannabinoid and Apelin Systems in the Pathogenesis of Liver Fibrosis

Hepatic fibrosis is the consequence of an unresolved wound healing process in response to chronic liver injury and involves multiple cell types and molecular mechanisms. The hepatic endocannabinoid and apelin systems are two signalling pathways with a substantial role in the liver fibrosis pathophysiology-both are upregulated in patients with advanced liver disease. Endogenous cannabinoids are lipid-signalling molecules derived from arachidonic acid involved in the pathogenesis of cardiovascular dysfunction, portal hypertension, liver fibrosis, and other processes associated with hepatic disease through their interactions with the CB₁ and CB₂ receptors. Apelin is a peptide that participates in cardiovascular and renal functions, inflammation, angiogenesis, and hepatic fibrosis through its interaction with the APJ receptor. The endocannabinoid and apelin systems are two of the multiple cell-signalling pathways involved in the transformation of quiescent hepatic stellate cells into myofibroblast like cells, the main matrix-producing cells in liver fibrosis. The mechanisms underlying the control of hepatic stellate cell activity are coincident despite the marked dissimilarities between the endocannabinoid and apelin signalling pathways. This review discusses the current understanding of the molecular and cellular mechanisms by which the hepatic endocannabinoid and apelin systems play a significant role in the pathophysiology of liver fibrosis.

The Evaluation of Angiogenesis Markers in Hepatocellular Carcinoma and Precursor Lesions in Liver Explants From a Single Institution

Hepatocellular carcinoma (HCC) is a global health problem associated with chronic liver disease. Precursor lesions are described, and the correct diagnosis of liver nodules is paramount when considering liver transplantation. We evaluated the immunohistochemical expression of vascular endothelial growth factor (VEGF) and angiopoietin-2 in HCC and precursors lesion in a single institution series of whole liver explants between 2013 and 2015, evaluating morphologic and clinical variables. The study comprised 67 patients (32.8% female) and 107 nodules. The mean age of the patients was 52.7 years (29 to 70 y). There were no significant epidemiologic differences among malignant lesions, dysplastic nodules, and regenerative nodules. Angiopoietin-2 expression was significantly more expressed in carcinoma when compared with regenerative lesions (P<0.0001). A statistically significant relationship was noted between the expression of VEGF in hepatocytes and Ang-2 expression in the small vasculature (P=0.006). VEGF expression also correlated significantly with the number of nonpaired arteries (P=0.03), although it was not useful in separating benign from malignant cases. We identified a sensitivity of 54% and a specificity of 96% using angiopoietin-2, and a sensitivity of 68.7% and a specificity of 31.2% when using VEGF for the diagnosis of HCC. There was no significant correlation between the immunohistochemical parameters and the clinical staging, the number of gross lesions, and the histologic grade in cases of HCC. Angiopoietin-2 may be a candidate biomarker in assessing liver nodules in transplant patients, and may assist in the diagnosis of difficult lesions and in small biopsies pretransplant.

Angiopoietin-2 Promotes Pathological Angiogenesis and Is a Therapeutic Target in Murine Nonalcoholic Fatty Liver Disease

Angiogenesis contributes to the development of nonalcoholic steatohepatitis (NASH) and promotes inflammation, fibrosis, and progression to hepatocellular carcinoma (HCC). Angiopoietin-2 (Ang-2) is a key regulator of angiogenesis. We aimed to investigate the role of Ang-2 and its potential as a therapeutic target in NASH using human samples, in vivo mouse models, and in vitro assays. Serum Ang-2 levels were determined in 104 obese patients undergoing bariatric surgery and concomitant liver biopsy. The effect of the Ang-2/Tie2 receptor inhibiting peptibody L1-10 was evaluated in the methionine-choline deficient (MCD) and streptozotocin-western diet nonalcoholic fatty liver disease mouse models, and in vitro on endothelial cells and bone marrow-derived macrophages. The hepatic vasculature was visualized with µCT scans and scanning electron microscopy of vascular casts. Serum Ang-2 levels were increased in patients with histological NASH compared with patients with simple steatosis and correlated with hepatic CD34 immunoreactivity as a marker of hepatic angiogenesis. Serum and hepatic Ang-2 levels were similarly increased in mice with steatohepatitis. Both preventive and therapeutic L1-10 treatment reduced hepatocyte ballooning and fibrosis in MCD diet-fed mice and was associated with reduced hepatic angiogenesis and normalization of the vascular micro-architecture. Liver-isolated endothelial cells and monocytes from MCD-fed L1-10-treated mice showed reduced expression of leukocyte adhesion and inflammatory markers, respectively, compared with cells from untreated MCD diet-fed mice. In the streptozotocin-western diet model, therapeutic Ang-2 inhibition was able to reverse NASH and attenuate HCC progression. In vitro, L1-10 treatment mitigated increased cytokine production in lipopolysaccharide-stimulated endothelial cells but not in macrophages. Conclusion: Our findings provide evidence for Ang-2 inhibition as a therapeutic strategy to target pathological angiogenesis in NASH.

Serum Angiopoietin-2 Predicts Mortality and Kidney Outcomes in Decompensated Cirrhosis

Acute kidney injury in decompensated cirrhosis has limited therapeutic options, and novel mechanistic targets are urgently needed. Angiopoietin-2 is a context-specific antagonist of Tie2, a receptor that signals vascular quiescence. Considering the prominence of vascular destabilization in decompensated cirrhosis, we evaluated Angiopoietin-2 to predict clinical outcomes. Serum Angiopoietin-2 was measured serially in a prospective cohort of hospitalized patients with decompensated cirrhosis and acute kidney injury. Clinical characteristics and outcomes were examined over a 90-day period and analyzed according to Angiopoietin-2 levels. Primary outcome was 90-day mortality. Our study included 191 inpatients (median Angiopoietin-2 level 18.2 [interquartile range 11.8, 26.5] ng/mL). Median Model for End-Stage Liver Disease (MELD) score was 23 [17, 30] and 90-day mortality was 41%. Increased Angiopoietin-2 levels were associated with increased mortality (died 21.9 [13.9, 30.3] ng/mL vs. alive 15.2 [9.8, 23.0] ng/mL; P < 0.001), higher Acute Kidney Injury Network stage (stage I 13.4 [9.8, 20.1] ng/mL vs. stage II 20.0 [14.1, 26.2] ng/mL vs. stage III 21.9 [13.0, 29.5] ng/mL; P = 0.002), and need for renal replacement therapy (16.5 [11.3, 23.6] ng/mL vs. 25.1 [13.3, 30.3] ng/mL; P = 0.005). The association between Angiopoietin-2 and mortality was significant in unadjusted and adjusted Cox regression models (P ≤ 0.001 for all models), and improved discrimination for mortality when added to MELD score (integrated discrimination increment 0.067; P = 0.001). Conclusion: Angiopoietin-2 was associated with mortality and other clinically relevant outcomes in a cohort of patients with decompensated cirrhosis with acute kidney injury. Further experimental study of Angiopoietin/Tie2 signaling is warranted to explore its potential mechanistic and therapeutic role in this population.

Identification of proteins associated with clinical and pathological features of proliferative diabetic retinopathy in vitreous and fibrovascular membranes

Purpose

To identify the protein profiles in vitreous associated with retinal fibrosis, angiogenesis, and neurite formation in epiretinal fibrovascular membranes (FVMs) in patients with proliferative diabetic retinopathy (PDR).

Methods

Vitreous samples of 5 non-diabetic control patients with vitreous debris and 7 patients with PDR membranes were screened for 507 preselected proteins using the semi-quantitative RayBio® L-series 507 antibody array. From this array, 60 proteins were selected for a custom quantitative antibody array (Raybiotech, Human Quantibody® array), analyzing 7 control patients, 8 PDR patients with FVMs, and 5 PDR patients without FVMs. Additionally, mRNA levels of proteins of interest were measured in 10 PDR membranes and 11 idiopathic membranes and in retinal tissues and cells to identify possible sources of protein production.

Results

Of the 507 proteins screened, 21 were found to be significantly elevated in PDR patients, including neurogenic and angiogenic factors such as neuregulin 1 (NRG1), nerve growth factor receptor (NGFR), placental growth factor (PlGF) and platelet derived growth factor (PDGF). Angiopoietin-2 (Ang2) concentrations were strongly correlated to the degree of fibrosis and the presence of FVMs in patients with PDR. Protein correlation analysis showed PDGF to be extensively co-regulated with other proteins, including thrombospondin-1 and Ang2. mRNA levels of glial-derived and brain/derived neurotrophic factor (GDNF and BDNF) were elevated in PDR membranes. These results were validated in a second study of 52 vitreous samples of 32 PDR patients and 20 control patients.

Conclusions

This exploratory study reveals protein networks that potentially contribute to neurite outgrowth, angiogenesis and fibrosis in the formation of fibrovascular membranes in PDR. We identified a possible role of Ang2 in fibrosis and the formation of FVMs, and of the neurotrophic factors NRG1, PDGF and GDNF in neurite growth that occurs in all FVMs in PDR.

Therapeutic targeting of the angiopoietin-TIE pathway

The endothelial angiopoietin (ANG)-TIE growth factor receptor pathway regulates vascular permeability and pathological vascular remodelling during inflammation, tumour angiogenesis and metastasis. Drugs that target the ANG-TIE pathway are in clinical development for oncological and ophthalmological applications. The aim is to complement current vascular endothelial growth factor (VEGF)-based anti-angiogenic therapies in cancer, wet age-related macular degeneration and macular oedema. The unique function of the ANG-TIE pathway in vascular stabilization also renders this pathway an attractive target in sepsis, organ transplantation, atherosclerosis and vascular complications of diabetes. This Review covers key aspects of the function of the ANG-TIE pathway in vascular disease and describes the recent development of novel therapeutics that target this pathway.

Angiopoietin-2/angiopoietin-1 as non-invasive biomarker of cirrhosis in chronic hepatitis C

AIM

To evaluate the efficacy of peripheral blood concentrations of angiopoietins (Ang) as cirrhosis biomarkers of chronic hepatitis C (CHC).

METHODS

Ang1 and Ang2 serum levels were measured by enzyme-linked immunosorbent assays (ELISA) in samples from 179 cirrhotic and non-cirrhotic CHC patients, classified according to the METAVIR system. Groups were compared by non-parametric Mann-Whitney U test. Subsequently, the association of peripheral concentrations of angiopoietins with the stage of fibrosis was analyzed using Spearman correlation test. Finally, the accuracy, sensitivity and specificity of circulating angiopoietins for cirrhosis diagnosis were determined by the study of the respective area under the curve of receiver operator characteristics (AUC-ROC).

RESULTS

Peripheral blood concentrations of Ang1 and Ang2 in CHC patients were significantly related to fibrosis. While Ang1 was decreased in cirrhotic subjects compared to non-cirrhotic (P < 0.0001), Ang2 was significantly increased as CHC progressed to the end stage of liver disease (P < 0.0001). Consequently, Ang2/Ang1 ratio was notably amplified and significantly correlated with fibrosis (P < 0.0001). Interestingly, the individual performance of each angiopoietin for the diagnosis of cirrhosis reached notable AUC-ROC values (above 0.7, both), but the Ang2/Ang1 ratio was much better (AUC-ROC = 0.810) and displayed outstanding values of sensitivity (71%), specificity (84%) and accuracy (82.1%) at the optimal cut-off (10.33). Furthermore, Ang2/Ang1 ratio improved the performance of many other previously described biomarkers or scores of liver cirrhosis in CHC.

CONCLUSION

Ang2/Ang1 ratio might constitute a useful tool for monitoring the progression of chronic liver disease towards cirrhosis and play an important role as therapeutic target.

Mechanisms of adaptation of the hepatic vasculature to the deteriorating conditions of blood circulation in liver cirrhosis

PubMed, EMBASE, Orphanet, MIDLINE, Google Scholar and Cochrane Library were searched for articles published between 1983 and 2015. Relevant articles were selected by using the following terms: "Liver cirrhosis", "Endothelial dysfunction", "Sinusoidal remodeling", "Intrahepatic angiogenesis" and "Pathogenesis of portal hypertension". Then the reference lists of identified articles were searched for other relevant publications as well. Besides gross hepatic structural disorders related to diffuse fibrosis and formation of regenerative nodules, the complex morphofunctional rearrangement of the hepatic microvascular bed and intrahepatic angiogenesis also play important roles in hemodynamic disturbances in liver cirrhosis. It is characterized by endothelial dysfunction and impaired paracrine interaction between activated stellate hepatocytes and sinusoidal endotheliocytes, sinusoidal remodeling and capillarization, as well as development of the collateral microcirculation. In spite of the fact that complex morphofunctional rearrangement of the hepatic microvascular bed and intrahepatic angiogenesis in liver cirrhosis are the compensatory-adaptive reaction to the deteriorating conditions of blood circulation, they contribute to progression of disease and development of serious complications, in particular, related to portal hypertension.