Update on implications and mechanisms of angiogenesis in liver fibrosis

Reversal of fibrosis and portal hypertension by Empagliflozin treatment of CCl4-induced liver fibrosis: Emphasis on gal-1/NRP-1/TGF-β and gal-1/NRP-1/VEGFR2 pathways

To date, liver fibrosis has no clinically approved treatment. Empagliflozin (EMPA), a highly selective sodium-glucose-cotransporter-2 (SGLT2) inhibitor, has shown ameliorative potential in liver diseases without revealing its full mechanisms. Neuropilin-1 (NRP-1) is a novel regulator of profibrogenic signaling pathways related to hepatic stellate cells (HSCs) and hepatic sinusoidal endothelial cells (HSECs) that modulates intrahepatic profibrogenic and angiogenic pathways. Herein, EMPA's antifibrotic potentials and effects on galactin-1 (Gal-1)/NRP-1 signaling pathways have been evaluated in an experimental liver fibrosis rat model by testing different EMPA dose regimens. EMPA treatment brought a dose-dependent decrease in Gal-1/NRP-1 hepatic expression. This was coupled with suppression of major HSCs pro-fibrotic pathways; transforming growth factor-β (TGF-β)/TGF-βRI/Smad2 and platelet-derived growth factor-beta (PDGF-β) with a diminution of hepatic Col 1A1 level. In addition, EMPA prompted a protuberant suppression of the angiogenic pathway; vascular endothelial growth factor (VEGF)/VEGF-receptor-2 (VEGFR-2)/SH2-Domain Containing Adaptor Protein-B (Shb), and reversal of altered portal hypertension (PHT) markers; endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS). The amelioration of liver fibrosis was coupled with a remarkable improvement in liver aminotransferases and histologic hepatic fibrosis Ishak scores. The highest EMPA dose showed a good safety profile with minimal changes in renal function and glycemic control. Thus, the current study brought about novel findings for a potential liver fibrosis treatment modality via targeting NRP-1 signaling pathways by EMPA.

Angiogenesis induction as a key step in cardiac tissue Regeneration: From angiogenic agents to biomaterials

Cardiovascular diseases are the leading cause of death worldwide. After myocardial infarction, the vascular supply of the heart is damaged or blocked, leading to the formation of scar tissue, followed by several cardiac dysfunctions or even death. In this regard, induction of angiogenesis is considered as a vital process for supplying nutrients and oxygen to the cells in cardiac tissue engineering. The current review aims to summarize different approaches of angiogenesis induction for effective cardiac tissue repair. Accordingly, a comprehensive classification of induction of pro-angiogenic signaling pathways through using engineered biomaterials, drugs, angiogenic factors, as well as combinatorial approaches is introduced as a potential platform for cardiac regeneration application. The angiogenic induction for cardiac repair can enhance patient treatment outcomes and generate economic prospects for the biomedical industry. The development and commercialization of angiogenesis methods often involves collaboration between academic institutions, research organizations, and biomedical companies.

Anti-Fibrotic Efficacy of Apigenin in a Mice Model of Carbon Tetrachloride-Induced Hepatic Fibrosis by Modulation of Oxidative Stress, Inflammation, and Fibrogenesis: A Preclinical Study

BACKGROUND

Hepatic fibrosis is a major health problem all over the world, and there is no effective treatment to cure it. Hence, the current study sought to assess the anti-fibrotic efficacy of apigenin against CCl₄-induced hepatic fibrosis in mice.

METHODS

Forty-eight mice were put into six groups. G1: Normal Control, G2: CCl₄ Control, G3: Silymarin (100 mg/kg), G4 and G5: Apigenin (2 &20 mg/Kg), G6: Apigenin alone (20 mg/Kg). Groups 2, 3, 4, and 5 were given CCl₄ (0.5 mL/kg. i.p.) twice/week for six weeks. The level of AST, ALT, TC, TG, and TB in serum and IL-1β, IL-6, and TNF-α in tissue homogenates were assessed. Histological studies by H&E staining and Immunostaining of liver tissues were also performed.

RESULTS

The CCl₄-challenged group showed increased serum AST (4-fold), ALT (6-fold), and TB (5-fold). Both silymarin and apigenin treatments significantly improved these hepatic biomarkers. The CCl₄-challenged group showed reduced levels of CAT (89%), GSH (53%), and increased MDA (3-fold). Both silymarin and apigenin treatments significantly altered these oxidative markers in tissue homogenates. The CCl₄-treated group showed a two-fold increase in IL-1β, IL-6, and TNF-α levels. Silymarin and apigenin treatment considerably decreased the IL-1β, IL-6, and TNF-α levels. Apigenin treatment inhibited angiogenic activity, as evidenced by a decrease in VEGF (vascular endothelial growth factor) expression in liver tissues, and a decline in vascular endothelial cell antigen expression (CD34).

CONCLUSIONS

Finally, these data collectively imply that apigenin may have antifibrotic properties, which may be explained by its anti-inflammatory, antioxidant, and antiangiogenic activities.

Collagenase-I decorated co-delivery micelles potentiate extracellular matrix degradation and hepatic stellate cell targeting for liver fibrosis therapy

Liver fibrosis is a pathological process of multiple chronic liver diseases progressing to cirrhosis for which there are currently no effective treatment options. During fibrosis progression, the overproduction of extracellular matrix (ECM) collagen secreted by hepatic stellate cells (HSCs) greatly impedes drug delivery and reduces drug therapeutic effects. In this study, a glycyrrhetinic acid (GA)-conjugated prodrug micellar system with collagenase I (COL) decoration (COL-HA-GA, abbreviated as CHG) was designed to codelivery sorafenib (Sora/CHG, abbreviated as S/CHG) for potentiating ECM degradation and HSCs targeting on liver fibrosis therapy. In ECM barrier models established in vitro or in vivo, CHG micelles efficiently degraded pericellular collagen and demonstrated enormous ECM penetration abilities as well as superior HSCs internalization. Moreover, CHG micelles exhibited more Sora & GA accumulations and activated HSCs targeting efficiencies in the fibrotic livers than those in the normal livers. More importantly, S/CHG micelles were more effective in anti-liver fibrosis by lowering the collagen content, inhibiting the HSCs activation, as well as down-regulating the fibrosis-related factors, leading to reverse the fibrotic liver to normal liver through the multi-mechanisms including angiogenesis reduction, liver fibrosis microenvironment regulation, and epithelial-mesenchymal transition inhibition. In conclusion, the developed COL decorated nano-codelivery system with fibrotic ECM collagen degradation and activated HSCs targeting dual-functions exhibited great potential for liver fibrosis therapy. STATEMENT OF SIGNIFICANCE: A glycyrrhetinic acid (GA)-conjugated prodrug with collagenase I (COL) decoration (CHG) was designed for codelivery with sorafenib (S/CHG), potentiating extracellular matrix (ECM) degradation-penetration and hepatic stellate cells (HSCs) targeting on liver fibrosis therapy. In ECM barrier models, CHG micelles efficiently degraded pericellular collagen and demonstrated ECM penetration abilities, as well as displayed superior HSCs internalization. Moreover, S/CHG micelles were more effective in anti-liver fibrosis by lowering the collagen content, inhibiting the HSCs activation, as well as down-regulating cytokines, reversing the fibrotic liver to normal through various mechanisms. In conclusion, the developed fibrotic ECM degradation and HSCs targeting dual-functional nano-codelivery system provided a prospective potentiality in liver fibrosis therapy.

Stimulation of the atypical chemokine receptor 3 (ACKR3) by a small-molecule agonist attenuates fibrosis in a preclinical liver but not lung injury model

Atypical chemokine receptor 3 (ACKR3, formerly CXC chemokine receptor 7) is a G protein-coupled receptor that recruits β-arrestins, but is devoid of functional G protein signaling after receptor stimulation. In preclinical models of liver and lung fibrosis, ACKR3 was previously shown to be upregulated after acute injury in liver sinusoidal and pulmonary capillary endothelial cells, respectively. This upregulation was linked with a pro-regenerative and anti-fibrotic role for ACKR3. A recently described ACKR3-targeting small molecule agonist protected mice from isoproterenol-induced cardiac fibrosis. Here, we aimed to evaluate its protective role in preclinical models of liver and lung fibrosis. After confirming its in vitro pharmacological activity (i.e., ACKR3-mediated β-arrestin recruitment and receptor binding), in vivo administration of this ACKR3 agonist led to increased mouse CXCL12 plasma levels, indicating in vivo interaction of the agonist with ACKR3. Whereas twice daily in vivo administration of the ACKR3 agonist lacked inhibitory effect on bleomycin-induced lung fibrosis, it had a modest, but significant anti-fibrotic effect in the carbon tetrachloride (CCl4)-induced liver fibrosis model. In the latter model, ACKR3 stimulation affected the expression of several fibrosis-related genes and led to reduced collagen content as determined by picro-sirius red staining and hydroxyproline quantification. These data confirm that ACKR3 agonism, at least to some extent, attenuates fibrosis, although this effect is rather modest and heterogeneous across various tissue types. Stimulating ACKR3 alone without intervening in other signaling pathways involved in the multicellular crosstalk leading to fibrosis will, therefore, most likely not be sufficient to deliver a satisfactory clinical outcome.

Combination therapy based on targeted nano drug co-delivery systems for liver fibrosis treatment: A review

Liver fibrosis is the hallmark of liver disease and occurs prior to the stages of cirrhosis and hepatocellular carcinoma. Any type of liver damage or inflammation can result in fibrosis. Fibrosis does not develop overnight, but rather as a result of the long-term action of injury factors. At present, however, there are no good treatment methods or specific drugs other than removing the pathogenic factors. Drug application is still limited, which means that drugs with good performance in vitro cannot achieve good therapeutic effects in vivo, owing to various factors such as poor drug targeting, large side effects, and strong hydrophobicity. Hepatic stellate cells (HSC) are the primary effector cells in liver fibrosis. The nano-drug delivery system is a new and safe drug delivery system that has many advantages which are widely used in the field of liver fibrosis. Drug resistance and side effects can be reduced when two or more drugs are used in combination drug delivery. Combination therapy of drugs with different targets has emerged as a novel approach to treating liver fibrosis, and the nano co-delivery system enhances the benefits of combination therapy. While nano co-delivery systems can maximize benefits while avoiding drug side effects, this is precisely the advantage of the nano co-delivery system. This review briefly described the pathogenesis and current treatment strategies, the different co-delivery systems of combination drugs in the nano delivery system, and targeting strategies for nano delivery systems on liver fibrosis therapy. Because of their superior performance, nano delivery systems and targeting drug delivery systems have received a lot of attention in the new drug delivery system. The new delivery systems offer a new pathway in the treatment of liver fibrosis, and it is believed that it can be a new treatment for fibrosis in the future. Nano co-delivery system of combination drugs and targeting strategies has proven the effectiveness of anti-fibrosis at the experimental level.

Endothelial angiogenic activity and adipose angiogenesis is controlled by extracellular matrix protein TGFBI

Several studies have suggested that extracellular matrix (ECM) remodeling and the microenvironment are tightly associated with adipogenesis and adipose angiogenesis. In the present study, we demonstrated that transforming growth factor-beta induced (TGFBI) suppresses angiogenesis stimulated by adipocyte-conditioned medium (Ad-CM), both in vitro and in vivo. TGFBI knockout (KO) mice exhibited increased numbers of blood vessels in adipose tissue, and blood vessels from these mice showed enhanced infiltration into Matrigel containing Ad-CM. The treatment of Ad-CM-stimulated SVEC-10 endothelial cells with TGFBI protein reduced migration and tube-forming activity. TGFBI protein suppressed the activation of the Src and extracellular signaling-related kinase signaling pathways of these SVEC-10 endothelial cells. Our findings indicated that TGFBI inhibited adipose angiogenesis by suppressing the activation of Src and ERK signaling pathways, possibly because of the stimulation of the angiogenic activity of endothelial cells.

The roles and mechanisms of hypoxia in liver fibrosis

Liver fibrosis occurs in response to any etiology of chronic liver injury. Lack of appropriate clinical intervention will lead to liver cirrhosis or hepatocellular carcinoma (HCC), seriously affecting the quality of life of patients, but the current clinical treatments of liver fibrosis have not been developed yet. Recent studies have shown that hypoxia is a key factor promoting the progression of liver fibrosis. Hypoxia can cause liver fibrosis. Liver fibrosis can, in turn, profoundly further deepen the degree of hypoxia. Therefore, exploring the role of hypoxia in liver fibrosis will help to further understand the process of liver fibrosis, and provide the theoretical basis for its diagnosis and treatment, which is of great significance to avoid further deterioration of liver diseases and protect the life and health of patients. This review highlights the recent advances in cellular and molecular mechanisms of hypoxia in developments of liver fibrosis.

Interaction of non‑parenchymal hepatocytes in the process of hepatic fibrosis (Review)

Hepatic fibrosis (HF) is the process of fibrous scar formation caused by chronic liver injury of different etiologies. Previous studies have hypothesized that the activation of hepatic stellate cells (HSCs) is the central process in HF. The interaction between HSCs and surrounding cells is also crucial. Additionally, hepatic sinusoids capillarization, inflammation, angiogenesis and fibrosis develop during HF. The process involves multiple cell types that are highly connected and work in unison to maintain the homeostasis of the hepatic microenvironment, which serves a key role in the initiation and progression of HF. The current review provides novel insight into the intercellular interaction among liver sinusoidal endothelial cells, HSCs and Kupffer cells, as well as the hepatic microenvironment in the development of HF.

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.

Autophagy-induced p62 accumulation is required for curcumol to regulate KLF5-mediated angiogenesis in liver sinusoidal endothelial cells

Liver pathological angiogenesis is considered to be one of the key events in the development of liver fibrosis. Autophagy is a defense and stress regulation mechanism. However, whether autophagy regulates pathological angiogenesis in liver fibrosis is still questionable. Here, we aimed to study how curcumol regulated liver sinusoidal endothelial cells (LSECs) angiogenesis through autophagy. We found that curcumol (10, 20 and 40 μM) could inhibit the expression of angiogenesis markers in the LSECs. Importantly, we showed that curcumol might influence LSEC pathological angiogenesis by regulating autophagy level. Furthermore, we indicated that the transcription factor Krüppel-like factor 5 (KLF5) was considered as a key target for curcumol to regulate LSEC angiogenesis. Interestingly, we also suggested that autophagy was as a potential mechanism for curcumol to restrain KLF5 expression. Increased autophagy level could impair the suppression effect of curcumol on KLF5. Fascinatingly, our results indicated that curcumol inhibited autophagy and led to p62 accumulation, which might be a regulation mechanism of KLF5 degradation. Finally, in mice liver fibrosis model, we unanimously showed that curcumol (30 mg/kg) inhibited pathological angiogenesis by reducing LSEC autophagy level and suppressing KLF5 expression. Collectively, these results provided a deeper insight into the molecular mechanism of curcumol to inhibit LSEC pathological angiogenesis during liver fibrosis.

Curcumol inhibits KLF5-dependent angiogenesis by blocking the ROS/ERK signaling in liver sinusoidal endothelial cells

AIMS

Liver fibrosis is a difficult problem in the medical field. We previously reported that curcumol, a bioactive substance, may inhibit the pathological angiogenesis of liver sinusoidal endothelial cells (LSECs) and play a good anti-hepatic fibrosis effect. However, the mechanism of curcumol inhibiting angiogenesis in LSEC needs to be further clarified. Here, we focus on how curcumol inhibits LSEC angiogenesis in liver fibrosis.

MATERIALS AND METHODS

Primary rat LSECs were cultured in vitro, and various molecular experiments including real-time PCR, western blot, immunofluorescence, tube formation assay and transwell migration assay were used to clarify the potential mechanism of curcumol. Carbon tetrachloride (CCl4) was applied to create a mouse liver fibrosis model. Blood and livers were taken to elucidate the efficacy of curcumol in vivo.

KEY FINDINGS

We found that curcumol could effectively inhibit LSEC angiogenesis in vitro. Interestingly, this process may depend on curcumol's inhibition of the expression of transcription factor KLF5. Mice experiment also showed that curcumol could alleviate chronic liver injury by reducing KLF5 expression. In addition, we suggested that curcumol could reduce the production of mitochondrial ROS and improve mitochondrial morphology in LSEC. More importantly, we proved that curcumol could suppress KLF5-mediated LSEC angiogenesis by inhibiting ROS/ERK signaling.

SIGNIFICANCE

We suggested that transcription factor KLF5 could be considered as a new target molecule of curcumol in improving liver fibrosis, and pointed out that curcumol targeted ROS/ERK-mediated KLF5 expression could inhibit LSEC angiogenesis. This provided a new theoretical basis for curcumol to ameliorate liver fibrosis.

The Role of Sinusoidal Endothelial Cells in the Axis of Inflammation and Cancer Within the Liver

Liver sinusoidal endothelial cells (LSEC) form a unique barrier between the liver sinusoids and the underlying parenchyma, and thus play a crucial role in maintaining metabolic and immune homeostasis, as well as actively contributing to disease pathophysiology. Whilst their endocytic and scavenging function is integral for nutrient exchange and clearance of waste products, their capillarisation and dysfunction precedes fibrogenesis. Furthermore, their ability to promote immune tolerance and recruit distinct immunosuppressive leukocyte subsets can allow persistence of chronic viral infections and facilitate tumour development. In this review, we present the immunological and barrier functions of LSEC, along with their role in orchestrating fibrotic processes which precede tumourigenesis. We also summarise the role of LSEC in modulating the tumour microenvironment, and promoting development of a pre-metastatic niche, which can drive formation of secondary liver tumours. Finally, we summarise closely inter-linked disease pathways which collectively perpetuate pathogenesis, highlighting LSEC as novel targets for therapeutic intervention.

Remote Ischemic Preconditioning in a Cirrhotic Patient Undergoing Major Hepatectomy

Remote ischemic preconditioning (RIPC) has been shown to reduce ischemic reperfusion injury for patients undergoing hepatectomy for colorectal liver metastasis. We present a case of a 69-year-old male who underwent right hepatectomy for a multifocal hepatocellular carcinoma of the right liver and concomitant liver cirrhosis (Child-Pugh stage A). We performed portal vein embolization prior to surgery and intraoperative RIPC of the iliac vessels. The postoperative course after major hepatectomy went uneventful.

Genetic algorithms identify individuals with high risk of severe liver disease caused by schistosomes

Schistosomes induce severe hepatic disease, which is fatal in 2-10% of cases, mortality being higher in cases of co-infection with HBV or HCV. Hepatic disease occurs as a consequence of the chronic inflammation caused by schistosome eggs trapped in liver sinusoids. In certain individuals, the repair process leads to a massive accumulation of fibrosis in the periportal spaces. We and others have shown that genetic variants play a crucial role in disease progression from mild to severe fibrosis and explain why hepatic fibrosis progresses rapidly in certain subjects only. We will review here published findings concerning the strategies that have been used in the analysis of hepatic fibrosis in schistosome-infected individuals, the genetic variants that have associated with fibrosis, and variants in new pathways crucial for fibrosis progression. Together, these studies show that the development of fibrosis is under the tight genetic control of various common variants with moderate effects. This polygenic control has made it possible to develop models that identify schistosome-infected individual at risk of severe hepatic disease. We discuss the performances and limitations of these models.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSION

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

Neovascularization is a key feature of liver fibrosis progression: anti-angiogenesis as an innovative way of liver fibrosis treatment

Liver fibrosis affects over 100 million people in the world; it represents a multifactorial, fibro-inflammatory disorder characterized by exacerbated production of extracellular matrix with consequent aberration of hepatic tissue. The aetiology of this disease is very complex and seems to involve a broad spectrum of factors including the lifestyle, environment factors, genes and epigenetic changes. More evidences indicate that angiogenesis, a process consisting in the formation of new blood vessels from pre-existing vessels, plays a crucial role in the progression of liver fibrosis. Central to the pathogenesis of liver fibrosis is the hepatic stellate cells (HSCs) which represent a crossroad among inflammation, fibrosis and angiogenesis. Quiescent HSCs can be stimulated by a host of growth factors, pro-inflammatory mediators produced by damaged resident liver cell types, as well as by hypoxia, contributing to neoangiogenesis, which in turn can be a bridge between acute and chronic inflammation. As matter of fact, studies demonstrated that neutralization of vascular endothelial growth factor as well as other proangiogenic agents can attenuate the progression of liver fibrosis. With this review, our intent is to discuss the cause and the role of angiogenesis in liver fibrosis focusing on the current knowledge about the impact of anti-angiogenetic therapies in this pathology.

Serum Vascular Endothelial Growth Factor in Patients with Hepatocellular Carcinoma and its Validity as a Tumor Biomarker

Background:

Hepatocellular Carcinoma (HCC) is one of the most common cancers associated with deaths worldwide and the presence of valid biomarkers for early diagnosis in high-risk patients can ameliorate the outcome of HCC. Vascular Endothelial Growth Factor (VEGF) has been found to play an essential role in the process of HCC growth and progression.

Objectives:

Therefore, we evaluated the serum VEGF levels in patients with HCC and liver cirrhosis and estimated its significant value for differentiating HCC patients from liver cirrhosis patients.

Material and methods:

Eighty-one subjects were enrolled in the study, 30 patients had HCC, 31 patients had liver cirrhosis and 20 were healthy control subjects. VEGF and AFP were measured using ELIZA. Abdominal ultrasound and triphasic abdominal computed tomography were performed in all subjects. Receiver Operating Characteristics curve analysis was performed for serum VEGF to determine its validity as a tumor biomarker.

Results:

The median levels of the serum VEGF were highly expressed in the HCC group (418 pg/ml) and the liver cirrhosis group (308 pg/ml) with no significant difference (P = 0.767); however both groups showed a significant increase compared to the control group (0.8 pg/ml, P <0.000). Serum VEGF showed high sensitivity (100%) and high specificity (100%) in differentiating HCC patients from controls with a cut-off value of ≥ 64.2 pg/ml, although it showed low sensitivity (29.2%) and specificity (85.7%) for differentiating HCC patients from liver cirrhosis patients.

Conclusion:

VEGF can be used as a reliable biomarker for differentiating HCC patients from healthy subjects but it can't be used as a reliable biomarker for differentiating HCC patients from high-risk patients as liver cirrhosis. The elevated serum VEGF levels in HCC and liver cirrhosis patients can elucidate the crucial role of angiogenesis in HCC and liver cirrhosis.

Emerging Roles of Vascular Endothelium in Metabolic Homeostasis

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

Distribution of Connective Tissue in the Male and Female Porcine Liver: Histological Mapping and Recommendations for Sampling

The pig is a large animal model that is often used in experimental medicine. The aim of this study was to assess, in normal pig livers, sexual dimorphism in the normal fraction of hepatic interlobular and intralobular connective tissue (CT) in six hepatic lobes and in three macroscopical regions of interest (ROIs) with different positions relative to the liver vasculature. Using stereological point grids, the fractions of CT were quantified in histological sections stained with aniline blue and nuclear fast red. Samples (415 tissue blocks) were collected from healthy piglets, representing paracaval, paraportal and peripheral ROIs. There was considerable variability in the CT fraction at all sampling levels. In males the mean fraction of interlobular CT was 4.7 ± 2.4% (mean ± SD) and ranged from 0% to 11.4%. In females the mean fraction of the interlobular CT was 3.6 ± 2.2% and ranged from 0% to 12.3%. The mean fraction of intralobular (perisinusoidal summed with pericentral) CT was <0.2% in both sexes. The interlobular CT represented >99.8% of the total hepatic CT and the fractions were highly correlated (Spearman r = 0.998, P <0.05). The smallest CT fraction was observed in the left medial lobe and in the paracaval ROI and the largest CT fraction was detected in the quadrate lobe and in the peripheral ROI. For planning experiments involving the histological quantification of liver fibrosis and requiring comparison between the liver lobes, these data facilitate the power analysis for sample size needed to detect the expected relative increase or decrease in the fraction of CT.

Cellular senescence and liver disease: Mechanisms and therapeutic strategies

Cellular senescence is a fundamental cell fate caused by several cellular injuries which results in irreversible cell cycle arrest yet remaining metabolically active across all species. Cellular senescence not only can prevent tumor occurrence by inhibiting the proliferation of injured cells, but also can affect the surrounding cells through the senescence-associated secretory phenotype (SASP). Attractively, accumulating evidence shows that cellular senescence is closely related to various liver diseases. Therapeutic opportunities based on targeting senescent cells and the SASP are considered to be potential strategy for liver diseases. However, although research on cell senescence has attracted widespread attention, the overview on detailed mechanism and biological function of cell senescence in liver disease is still largely unknown. The present review summarizes the specific role of cell senescence in various liver diseases, and updates the molecular mechanisms underlying cell senescence. Moreover, the review also explores new strategies for prevention and treatment of liver disease through promoting senescence or counteracting excessive pathological senescence.

Lipophagy and liver disease: New perspectives to better understanding and therapy

Intracellular lipid droplets (LDs) are remarkably dynamic and complex organelles that enact regulated storage and release of lipids to fulfil their fundamental roles in energy metabolism, membrane synthesis and provision of lipid-derived signaling molecules. The recent finding that LDs can be selectively degraded by the lysosomal pathway of autophagy through a process termed lipophagy has opened up a new understanding of how lipid metabolism regulates cellular physiology and pathophysiology. Many new functions for autophagic lipid metabolism have now been defined in various diseases including liver disease. Lipophagy was originally described in hepatocytes, where it is critical for maintaining cellular energy homeostasis in obesity and metabolic syndrome. In vitro and in vivo studies have demonstrated the selective uptake of LDs by autophagosomes, and inhibition of autophagy has been shown to reduce the β-oxidation of free fatty acids due to the increased accumulation of lipids and LDs. The identification of lipophagy as a new process dedicated to cellular lipid removal has mapped autophagy as an emerging player in cellular lipid metabolism. Pharmacological or genetic modulation of lipophagy might point to possible therapeutic strategies for combating a broad range of liver diseases. This review summarizes recent work focusing on lipophagy and liver disease as well as highlighting challenges and future directions of research. On the other hand, it also offers a glimpse into different strategies that have been used in experimental models to counteract excessive pathological lipophagy in the prevention and treatment of liver disease.

Diagnostic efficacy of noninvasive liver fibrosis indexes in predicting portal hypertension in patients with cirrhosis

Background

Recent data suggest that noninvasive liver fibrosis indexes could be useful for predicting esophageal varices (EV) in cirrhotic patients. However, thus far, the diagnostic efficacy of these indexes in predicting portal hypertension (PH) in cirrhotic patients has been poorly evaluated.

Aims

To evaluate the diagnostic efficacy of noninvasive liver fibrosis indexes in the diagnosis of PH.

Methods

A total of 238 cirrhotic patients underwent hepatic venous pressure gradient (HVPG) evaluation and relevant serum tests to analyze the variables associated with PH grade. Then, the diagnostic performances of seven fibrosis indexes, the aspartate aminotransferase (AST)-to-alanine aminotransferase (ALT) ratio (AAR), AST-to-platelet (PLT) ratio index (APRI), fibrosis index (FI), FIB-4, Forns index, King’s score and the Lok index, were evaluated to determine their efficacy in predicting clinically significant PH (CSPH) and severe PH (SPH). In addition, the performances of these fibrosis indexes in different subgroups were investigated.

Results

The results of a multivariate analysis of serum markers showed that AST values, platelet (PLT) count and albumin (ALB) were associated with PH grade. Among the seven—fibrosis indexes, King’s score, APRI and the Lok index showed modest diagnostic accuracy in predicting CSPH and SPH, as indicated by AUC of 0.755 and 0.742, 0.740 and 0.742, and 0.722 and 0.717, respectively. In addition, combination of King’s score (cutoff 23.47) and Lok index (cutoff 1.30) predicted presence of CSPH, with the highest PPV (95.38%) and +LR (5.49). A subgroup analysis indicated that the noninvasive screening model may be more applicable to patients with cirrhosis of viral etiology.

Conclusions

Serum liver fibrosis indexes exhibited modest diagnostic accuracy for PH in cirrhotic patients. These indexes may not be able to replace HVPG measurements for the diagnosis of PH but may be used as a first-line screening method for CSPH in liver cirrhosis patients.

Remote Ischemic Preconditioning: A Novel Strategy in Rescuing Older Livers From Ischemia-reperfusion Injury in a Rodent Model

OBJECTIVES

The aim of this study was to determine whether remote ischemic preconditioning (RIPC) protects aged liver against ischemia reperfusion (IR).

SUMMARY OF BACKGROUND DATA

The demands for liver surgery in an aging population are growing. Clamping of vessels to prevent blood loss is integral to liver surgery, but the resulting IR injury (IRI) augments postoperative complications. More so, sensitivity to hepatic IRI increases with age; however, no strategies have been developed that specifically protect old liver. RIPC, a novel protective approach, was performed distant to the surgical site. Whether RIPC may also protect old liver from IRI is unknown.

METHODS

RIPC to the femoral vascular bundle was compared against direct ischemic preconditioning (IPC) and the standard of care intermittent clamping (IC) using a model of partial hepatic ischemia in mice aged 20 to 24 months. Liver injury was measured 6 hours after reperfusion. Protective signaling (serotonin-Vegf-Il10/Mmp8 axis, Kupffer cell polarization) was assessed immediately after preconditioning. Neutralizing antibody was used to test the role of Vegf. Hepatic vasculature was examined by electron microscopy.

RESULTS

RIPC was superior over other strategies in protecting old liver from IRI, with standard IPC approaches being ineffective. RIPC induced the strongest elevations in circulating Vegf, and Vegf inhibition dampened protective signaling and abrogated the protective effects. RIPC was further associated with improvements in vascular functionality.

CONCLUSIONS

RIPC is highly effective in protecting old liver from ischemic insults, mainly owing to its ability to induce circulating Vegf. These findings warrant efforts toward clinical translation.

Intrahepatic angiogenesis increases portal hypertension in hepatitis B patients with cirrhosis

AIM

It remains unclear whether intrahepatic angiogenesis increases portal hypertension (PH) in hepatitis B with cirrhosis. We aim to investigate the relationship between intrahepatic angiogenesis and PH in hepatitis B patients with cirrhosis.

METHODS

Sixty hepatitis B patients with cirrhosis and 40 healthy subjects were included in this study. Angiogenesis markers vascular endothelial growth factor receptor-2 (VEGFR2), von Willebrand factor (vWF), and fibrosis marker α-smooth muscle actin (α-SMA) were observed by immunohistochemistry. Sirius Red staining was also used to determine liver fibrosis. Correlations between levels of intrahepatic angiogenesis and Child-Pugh classes, liver fibrosis degree, and portal vein pressure were examined. We also analyzed the relationship between levels of intrahepatic angiogenesis and complications of PH, including esophageal varices (EV), ascites, and hypersplenism.

RESULTS

Correlation was observed between the levels of VEGFR2 (r = 0.590, P < 0.01), vWF (r = 0.524, P < 0.01) in tissue, and Child-Pugh classes. Significant correlations were observed between levels of VEGFR2 and α-SMA (r = 0.710, P < 0.01), VEGFR2 and Sirius Red (r = 0.841, P < 0.01), vWF and α-SMA (r = 0.768, P < 0.01), and vWF and Sirius Red (r = 0.825, P < 0.01). Patients with hepatic venous pressure gradient (HVPG) ≥12 mmHg showed higher levels of VEGFR2 and vWF expression compared to those with (HVPG) <12 mmHg (2.60 ± 1.28% vs. 1.09 ± 0.73%; 5.85 ± 2.45% vs. 2.31 ± 1.34%, P < 0.01), respectively. Moreover, complications of PH, including size of esophageal varices (P < 0.01), presence of ascites (P < 0.01), and spleen volume (P < 0.01) were significantly affected by the levels of intrahepatic angiogenesis.

CONCLUSION

Intrahepatic angiogenesis increases PH in hepatitis B patients with cirrhosis. The study provides the potential ways to intervene in the progresses for therapeutic benefits in cirrhosis and PH.

Advances in Hypoxia-Mediated Mechanisms in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common and the third most deadly malignant tumor worldwide. Hypoxia and related oxidative stress are heavily involved in the process of HCC development and its therapies. However, direct and accurate measurement of oxygen concentration and evaluation of hypoxic effects in HCC prove difficult. Moreover, the hypoxia-mediated mechanisms in HCC remain elusive. Here, we summarize recent major evidence of hypoxia in HCC lesions shown by measuring partial pressure of oxygen (pO₂), the clinical importance of hypoxic markers in HCC, and recent advances in hypoxia-related mechanisms and therapies in HCC. For the mechanisms, we focus mainly on the roles of oxygen-sensing proteins (i.e., hypoxia-inducible factor and neuroglobin) and hypoxia-induced signaling proteins (e.g., matrix metalloproteinases, high mobility group box 1, Beclin 1, glucose metabolism enzymes, and vascular endothelial growth factor). With respect to therapies, we discuss mainly YQ23, sorafenib, 2-methoxyestradiol, and celastrol. This review focuses primarily on the results of clinical and animal studies.

Dual-Functional Nanoparticles Targeting CXCR4 and Delivering Antiangiogenic siRNA Ameliorate Liver Fibrosis

The progression of liver fibrosis, an intrinsic response to chronic liver injury, is associated with hepatic hypoxia, angiogenesis, abnormal inflammation, and significant matrix deposition, leading to the development of cirrhosis and hepatocellular carcinoma (HCC). Due to the complex pathogenesis of liver fibrosis, antifibrotic drug development has faced the challenge of efficiently and specifically targeting multiple pathogenic mechanisms. Therefore, CXCR4-targeted nanoparticles (NPs) were formulated to deliver siRNAs against vascular endothelial growth factor (VEGF) into fibrotic livers to block angiogenesis during the progression of liver fibrosis. AMD3100, a CXCR4 antagonist that was incorporated into the NPs, served dual functions: it acted as a targeting moiety and suppressed the progression of fibrosis by inhibiting the proliferation and activation of hepatic stellate cells (HSCs). We demonstrated that CXCR4-targeted NPs could deliver VEGF siRNAs to fibrotic livers, decrease VEGF expression, suppress angiogenesis and normalize the distorted vessels in the fibrotic livers in the carbon tetrachloride (CCl4) induced mouse model. Moreover, blocking SDF-1α/CXCR4 by CXCR4-targeted NPs in combination with VEGF siRNA significantly prevented the progression of liver fibrosis in CCl4-treated mice. In conclusion, the multifunctional CXCR4-targeted NPs delivering VEGF siRNAs provide an effective antifibrotic therapeutic strategy.

Selective portal vein injection for the design of syngeneic models of liver malignancy

Liver metastases are the most frequent cause of death due to colorectal cancer (CRC). Syngeneic orthotopic animal models, based on the grafting of cancer cells or tissue in host liver, are efficient systems for studying liver tumors and their (patho)physiological environment. Here we describe selective portal vein injection as a novel tool to generate syngeneic orthotopic models of liver tumors that avoid most of the weaknesses of existing syngeneic models. By combining portal vein injection of cancer cells with the selective clamping of distal liver lobes, tumor growth is limited to specific lobes. When applied on MC-38 CRC cells and their mouse host C57BL6, selective portal vein injection leads with 100% penetrance to MRI-detectable tumors within 1 wk, followed by a steady growth until the time of death (survival ∼7 wk) in the absence of extrahepatic disease. Similar results were obtained using CT-26 cells and their syngeneic Balb/c hosts. As a proof of principle, lobe-restricted liver tumors were also generated using Hepa1-6 (C57BL6-syngeneic) and TIB-75 (Balb/c-syngeneic) hepatocellular cancer cells, demonstrating the general applicability of selective portal vein injection for the induction of malignant liver tumors. Selective portal vein injection is technically straightforward, enables liver invasion via anatomical routes, preserves liver function, and provides unaffected liver tissue. The tumor models are reproducible and highly penetrant, with survival mainly dependent on the growth of lobe-restricted liver malignancy. These models enable biological studies and preclinical testing within short periods of time.

Differential Roles of Angiogenesis in the Induction of Fibrogenesis and the Resolution of Fibrosis in Liver

Liver fibrosis is a wound healing process that includes inflammation, deposition of extracellular matrix molecules, and pathological neovascularization. Angiogenesis, which is defined by the formation of new blood vessels from pre-existing vessels, is a complex and dynamic process under both physiological and pathological conditions. Although whether angiogenesis can induce or occur in parallel with the progression of hepatic fibrosis has not yet been determined, intrahepatic sinusoidal formation and remodeling are key features of liver fibrosis. Some recent evidence has suggested that experimental inhibition of angiogenesis ameliorates the development of liver fibrosis, while other recent studies indicate that neutralization or genetic ablation of vascular endothelial growth factor (VEGF) in myeloid cells can delay tissue repair and fibrosis resolution in damaged liver. In this review, we briefly summarize the current knowledge about the differential roles of angiogenesis in the induction of fibrogenesis and the resolution of fibrosis in damaged livers. Possible strategies for the prevention and treatment of liver fibrosis are also discussed.

von Willebrand factor as a novel noninvasive predictor of portal hypertension and esophageal varices in hepatitis B patients with cirrhosis

OBJECTIVE

At present, there is no perfect noninvasive method to assess portal hypertension and esophageal varices. Early predicting esophageal varices can provide evidence for managing cirrhotic patients. We aimed to further investigate von Willebrand factor (vWF) as a noninvasive predictor of portal hypertension, especially of esophageal varices.

MATERIAL AND METHODS

A total of 60 hepatitis B patients with cirrhosis and 45 healthy subjects were enrolled in this study. Levels of six markers were examined. All patients underwent hepatic venous pressure gradient (HVPG) and esophagogastroduodenoscopy. We evaluated the performance of six factors for diagnosis of portal hypertension and esophageal varices. The vWF levels in liver tissues were observed by immunohistochemistry. Correlations between the level of vWF in liver tissues and HVPG and between levels of vWF in tissues and plasma were examined.

RESULTS

Cutoff values of plasma vWF (1510.5 mU/mL and 1701 mU/mL) showed high positive predictive value (PPV, 90.2% and 87.5%) in predicting clinically significant portal hypertension and severe portal hypertension. Cutoff values of vWF (1414 mU/ml and 1990 mU/mL, PPV 90.3% and 86.3%, respectively) were provided to detect the presence and degree of esophageal varices. Linear correlations were observed between levels of vWF in liver tissues and HVPG (r(2) = 0.552, p < 0.001) and between the level of vWF in liver tissues and in plasma (r(2) = 0.461, p < 0.001).

CONCLUSION

The vWF is a noninvasive predictor of portal hypertension and esophageal varices in hepatitis B patients with cirrhosis. Increased levels of vWF in liver tissues may induce the elevated plasma vWF levels, but molecular mechanism is needed for further study.

Hepatic erythropoietin response in cirrhosis

BACKGROUND

Erythropoietin (EPO) is produced in the liver during fetal life, but after birth the production shifts to the kidneys. The liver maintains a production capacity of 10% of the total EPO-production, but can be up-regulated to 100%. Previous studies have demonstrated both elevated and reduced concentrations of EPO in cirrhosis. Increased EPO concentrations could be expected due to anemia, hypoxia, renal hypoperfusion, or EPO-mediated hepatoprotective mechanisms. In contrast, poor hepatic production capacity may cause reduced EPO concentrations in cirrhosis. In the present paper we aimed to study hepatic and renal venous concentrations of EPO in relation to the severity of the disease.

MATERIALS AND METHODS

We included 24 patients with alcoholic cirrhosis and eight age-matched healthy controls. All had a full catheterization performed with the determination of EPO concentrations in the hepatic, renal and femoral veins and artery. All patients were clinically, biochemically, and hemodynamically characterized.

RESULTS

The median arterial EPO concentrations in the cirrhotic patients and controls were 7.1 mIU/mL (range 3.5-179) and 7.2 mIU/mL (range 3.8-15.3), respectively. In the patient group we found no significant correlations to stage of disease of hemodynamic derangement.

CONCLUSION

We found no significant differences in EPO concentrations across the liver, kidney, or peripheral circulation in the patient or control groups; and no significant correlations to clinical, biochemical, or hemodynamic characteristics. This suggests that hepatic EPO synthesis is not enhanced in cirrhosis, but larger scale studies are needed to clarify this question.

Hepatic erythropoietin response in cirrhosis. A contemporary review

The main function of erythropoietin (EPO) is to maintain red blood cell mass, but in recent years, increasing evidence has suggested a wider biological role not solely related to erythropoiesis, e.g. angiogenesis and tissue protection. EPO is produced in the liver during fetal life, but the main production shifts to the kidney after birth. The liver maintains a production capacity of up to 10% of the total EPO synthesis in healthy controls, but can be up-regulated to 90-100%. However, the hepatic EPO synthesis has been shown not to be adequate for correction of anemia in the absence of renal-derived EPO. Elevated circulating EPO has been reported in a number of diseases, but data from cirrhotic patients are sparse and the level of plasma EPO in patients with cirrhosis is controversial. Cirrhosis is characterized by liver fibrosis, hepatic dysfunction and the release of proinflammatory cytokines, which lead to arterial hypotension, hepatic nephropathy and anemia. An increase in EPO due to renal hypoperfusion, hypoxia and anemia or an EPO-mediated hepato-protective and regenerative mechanism is plausible. However, poor hepatic synthesis capacity, a decreasing co-factor level and inflammatory feedback mechanisms may explain a potential insufficient EPO response in end-stage cirrhosis. Finally, the question remains as to whether a potential increase in EPO production in certain stages of cirrhosis originates from the kidney or liver. This paper aims to review contemporary aspects of EPO relating to chronic liver disease.

Angiogenesis and Fibrogenesis in Chronic Liver Diseases

Pathologic angiogenesis appears to be intrinsically associated with the fibrogenic progression of chronic liver diseases, which eventually leads to the development of cirrhosis and related complications, including hepatocellular carcinoma. Several laboratories have suggested that this association is relevant for chronic liver disease progression, with angiogenesis proposed to sustain fibrogenesis. This minireview offers a synthesis of relevant findings and opinions that have emerged in the last few years relating liver angiogenesis to fibrogenesis. We discuss liver angiogenesis in normal and pathophysiologic conditions with a focus on the role of hypoxia and hypoxia-inducible factors and assess the evidence supporting a clear relationship between angiogenesis and fibrogenesis. A section is dedicated to the critical interactions between liver sinusoidal endothelial cells and either quiescent hepatic stellate cells or myofibroblast-like stellate cells. Finally, we introduce the unusual, dual (profibrogenic and proangiogenic) role of hepatic myofibroblasts and emerging evidence supporting a role for specific mediators like vasohibin and microparticles and microvesicles.

Kruppel-like factor 2 inhibit the angiogenesis of cultured human liver sinusoidal endothelial cells through the ERK1/2 signaling pathway

Kruppel-like factor 2 (KLF2) is a crucial anti-angiogenic factor. However, its precise role in hepatic angiogenesis induced by liver sinusoidal endothelial cells (LSECs) remain unclear. This study was aimed to evaluate the effect of KLF2 on angiogenesis of LSECs and to explore the corresponding mechanism. Cultured human LSECs were infected with different lentiviruses to overexpress or suppress KLF2 expression. The CCK-8 assay, transwell migration assay and tube formation test, were used to investigate the roles of KLF2 in the proliferation, migration and vessel tube formation of LSECs, respectively. The expression and phosphorylation of ERK1/2 were detected by western blot. We discovered that the up-regulation of KLF2 expression dramatically inhibited proliferation, migration and tube formation in treated LSECs. Correspondingly, down-regulation of KLF2 expression significantly promoted proliferation, migration and tube formation in treated LSECs. Additionally, KLF2 inhibited the phosphorylation of ERK1/2 pathway, followed by the function of KLF2 in the angiogenesis of LSECs disrupted. In conclusion, KLF2 suppressed the angiogenesis of LSECs through inhibition of cell proliferation, migration, and vessel tube formation. These functions of KLF2 may be mediated through the ERK1/2 signaling pathway.

Strategies to prevent and reverse liver fibrosis in humans and laboratory animals

Liver fibrosis results from chronic damage to the liver in conjunction with various pathways and is mediated by a complex microenvironment. Based on clinical observations, it is now evident that fibrosis is a dynamic, bidirectional process with an inherent capacity for recovery and remodeling. The major mechanisms involved in liver fibrosis include the repetitive injury of hepatocytes, the activation of the inflammatory response after injury stimulation, and the activation and proliferation of hepatic stellate cells (HSCs), which represents the major extracellular matrix (ECM)-producing cells, stimulated by hepatocyte injury and inflammation. The microenvironment in the liver is synergistically regulated abnormal ECM deposition, scar formation, angiogenesis, and fibrogenesis. Moreover, recent studies have clarified novel mechanism in fibrosis such as epigenetic regulation of HSCs, the leptin and PPARγ pathways, the coagulation system, and even autophagy. Uncovering the mechanisms of liver fibrogenesis provides a basis to develop potential therapies to reverse and treat the fibrotic response, thereby improving the outcomes of patients with chronic liver disease. Although both scientific and clinical challenges remain, emerging studies attempt to reveal the ideal anti-fibrotic drug that could be easily delivered to the liver with high specificity and low toxicity. This review highlights the mechanisms, including novel pathways underlying fibrogenesis that may be translated into preventive and treatment strategies, reviews both current and novel agents that target specific pathways or multiple targets, and discusses novel drug delivery systems such as nanotechnology that can be applied in the treatment of liver fibrosis. In addition, we also discuss some current treatment strategies that are being applied in animal models and in clinical trials.