Aberrant differentiation and proliferation of hepatocytes in chronic liver injury and liver tumors.

Chronic liver injury induces liver cirrhosis and facilitates hepatocarcinogenesis. However, the effects of this condition on hepatocyte proliferation and differentiation are unclear. We showed that rodent hepatocytes display a ductular phenotype when they are cultured within a collagenous matrix. This process involves transdifferentiation without the emergence of hepatoblastic features and is at least partially reversible. During the ductular reaction in chronic liver diseases with progressive fibrosis, some hepatocytes, especially those adjacent to ectopic ductules, demonstrate ductular transdifferentiation, but the majority of increased ductules originate from the existing bile ductular system that undergoes extensive remodeling. In chronic injury, hepatocyte proliferation is weak but sustained, and most regenerative nodules in liver cirrhosis are composed of clonally proliferating hepatocytes, suggesting that a small fraction of hepatocytes maintain their proliferative capacity in chronic injury. In mouse hepatocarcinogenesis models, hepatocytes activate the expression of various fetal/neonatal genes, indicating that these cells undergo dedifferentiation. Hepatocyte-specific somatic integration of various oncogenes in mice demonstrated that hepatocytes may be the cells of origin for a broad spectrum of liver tumors through transdifferentiation and dedifferentiation. In conclusion, the phenotypic plasticity and heterogeneity of mature hepatocytes are important for understanding the pathogenesis of chronic liver diseases and liver tumors.

[Study on mitigating effect and mechanism of Cichorium glandulosum n-butanol extraction site on CCl_4-induced chronic liver injury in rats].

This study aims to investigate the mitigating effect and mechanism of Cichorium glandulosum n-butanol extraction site(CGE) on the disease in carbon tetrachloride(CCl_4)-induced chronic liver injury model in rats. A chronic liver injury model was constructed by subcutaneous injection of CCl_4 olive oil solution, and after four weeks of CGE treatment, serum levels of aspartate aminotransferase(AST), alanine aminotransferase(ALT), alkaline phosphatase(AKP), hydroxyproline(HYP), interleukin-4(IL-4), interleukin-6(IL-6), malondialdehyde(MDA), superoxide dismutase(SOD), and tumor necrosis factor-α(TNF-α) were detected. Liver tissue was processed by hematoxylin-eosin(HE) staining and Masson staining to observe the structure of the rat liver. qPCR and Western blot were used to examine the expression of transforming growth factor-ß1(TGF-ß1)/small mothers against decapentaplegic(Smad), Toll-like receptor 4(TLR4), α-smooth muscle actin(α-SMA), and fibronectin(Fn) in rat liver tissue and hepatic stellate-T6(HSC-T6) and evaluate the inhibitory effect of CGE on HSC activation. The results showed that CGE could significantly reduce the serum levels of AST, ALT, AKP, HYP, and affect the levels of related inflammatory indexes including IL-4, IL-6, and TNF-α, and MDA in CCl_4-induced chronic liver injury in rats and had no effect on SOD activity, which could delay the process of liver injury, alleviate the hepatic collagen deposition and inflammatory infiltration, and had significant efficacy in mitigating chronic liver injury in rats. CGE could inhibit α-SMA and TLR4 protein expression in the liver tissue and reverse the increased TGF-ß1/Smad, Fn, and TLR4-related expression in HSC-T6 in vitro. The above results indicated that CGE exerted hepatoprotective effects in rats by inhibiting HSC activation and alleviated CCl_4-induced chronic liver injury in rats and could ameliorate inflammatory response and slight liver fibrosis in rat liver tissue. Its pharmacodynamic mechanism might be related to TGF-ß1/Smad and TLR4-related expression.

Endothelial dysfunction in pathological processes of chronic liver disease during aging.

Aging is associated with gradual changes in liver structure and physiological/pathological functions in hepatic cells including hepatocytes, cholangiocytes, Kupffer cells, hepatic stellate cells (HSCs), and liver sinusoidal endothelial cells (LSECs). LSECs are specialized hepatic endothelial cells that regulate liver homeostasis. These cells actively impact the hepatic microenvironment as they have fenestrations and a thin morphology to allow substance exchange between circulating blood and the liver tissue. As aging occurs, LSECs have a reduction in both the number and size of fenestrations, which is referred to as pseudocapillarization. This along with the aging of the liver leads to increased oxidative stress, decreased availability of nitric oxide, decreased hepatic blood flow, and increased inflammatory cytokines in LSECs. Vascular aging can also lead to hepatic hypoxia, HSC activation, and liver fibrosis. In this review, we described the basic structure of LSECs, and the effect of LSECs on hepatic inflammation and fibrosis during aging process. We briefly summarized the changes of hepatic microcirculation during liver inflammation, the effect of aging on the clearance function of LSECs, the interactions between LSECs and immunity, hepatocytes or other hepatic nonparenchymal cells, and the therapeutic intervention of liver diseases by targeting LSECs and vascular system. Since LSECs play an important role in the development of liver fibrosis and the changes of LSEC phenotype occur in the early stage of liver fibrosis, the study of LSECs in the fibrotic liver is valuable for the detection of early liver fibrosis and the early intervention of fibrotic response.

(Pro)renin receptor inhibition attenuated liver steatosis, inflammation, and fibrosis in mice with steatohepatitis.

The (Pro)renin receptor (PRR) is reportedly involved in hepatic lipid metabolism and hepatocyte PRR knockdown protects mice against hepatosteatosis. However, the impact of PRR inhibition on liver inflammation and fibrosis in nonalcoholic steatohepatitis (NASH) remains unclear. Herein, C57BL/6 mice were fed a normal chow diet or fast food diet (FFD) for 24 weeks. Lentivirus-mediated PRR short hairpin RNA (shRNA) or handle region peptide (HRP), a PRR blocker, was administered for PRR inhibition. Mouse primary hepatocytes were cultured with palmitic acid, prorenin, siRNA-targeted PRR, and HRP. In FFD-fed mice, PRR inhibition via lentivirus-mediated PRR knockdown or HRP significantly attenuated liver steatosis, inflammation, and fibrosis. Mechanistically, PRR knockdown or HRP decreased hepatic acetyl-CoA carboxylase (ACC) abundance and upregulated peroxisome proliferator-activated receptor-alpha (PPARα). HRP treatment also decreased hepatic PRR expression. In addition, intrahepatic oxidative stress, apoptosis and inflammatory cell recruitment were ameliorated by PRR knockdown or HRP treatment, along with suppression of proinflammatory cytokine expression. PRR inhibition downregulated the hepatic expression of profibrotic factors, as well as TGF-ß1/SMAD3 pathway. In primary mouse hepatocytes, PRR knockdown with siRNA or HRP downregulated cellular ACC and increased PPARα expression. In conclusion, our findings revealed that PRR inhibition attenuated hepatic steatosis, inflammation, and fibrosis in mice with NASH. Accordingly, targeting PRR signaling may serve as a potential treatment for NASH.

Clinical features of patients with chronic liver disease in Japan related to alcohol use: Nationwide examination using alcohol use disorders identification test.

AIM: Patients often do not respond truthfully to physicians' interviews concerning alcohol. Few reports regarding the level of alcohol dependence in patients with chronic liver disease (CLD) have been presented. This study aimed to elucidate severity distribution in patients with CLD using the alcohol use disorders identification test (AUDIT). METHODS: From March to June 2022, 2034 Japanese outpatients with CLD, including 415 cases associated with hepatitis C virus, 436 with hepatitis B virus, 173 with alcohol-related liver disease (ARLD), and 1010 with other factors, were interviewed using AUDIT. Clinical features related to alcohol use in these patients were then retrospectively evaluated. RESULTS: In all patients, an AUDIT score 8-14 (harmful use) was noted in 5.8% of hepatitis C virus, 8.9% of hepatitis B virus, 24.3% of ARLD, and 4.4% of other groups, respectively (P < 0.001), while a score ≥15 (dependency) was noted in 3.4%, 3.0%, 27.7%, and 1.9%, respectively (P < 0.001). When the country was divided into regions, the percentages remained similar. Comparisons between patients with and without an AUDIT score ≥8 (n = 1412), performed after exclusion of those without related data (n = 622), showed no significant differences for hepatic reserve function, while those with harmful alcohol use were significantly younger (66 vs. 70 years, P = 0.006) and had a larger percentage of men (80.4% vs. 45.1%, P < 0.001). CONCLUSION: Harmful alcohol and alcohol dependency were observed in approximately 10% of patients with viral or non-viral CLD, after excluding patients with ARLD. Assessment of alcohol intake by use of the AUDIT questionnaire as well as adequate intervention should be considered necessary.

Effect of 4-hydroxychalcone as preventive and curative treatment in Wistar rats with liver injury.

The increasing prevalence and complications related to liver diseases (caused by infection, toxic agents, or metabolic syndrome), together with insufficient existence of treatments, make evident the need for better therapeutic alternatives. Therefore, the aim of this study was to determine the effect of 4-hydroxychalcone (4-HC) as preventive and curative treatment in acute and chronic liver injury, respectively. Liver damage was induced with carbon tetrachloride (CCl4) in Wistar rats. Rats were divided into two groups: (1) acute liver injury and (2) chronic liver injury. In turn, each group was divided into four subgroups: (i) control (water); (ii) dimethyl sulfoxide 10%; (iii) CCl4; and (iv) 4-HC. The pre-treatment with 4-HC decreased transaminases, IL-6 serum levels, and hepatic malondialdehyde, increased IL-10 serum levels and hepatic glutathione, and decreased liver damage (necrosis, steatosis, and inflammatory infiltrate). In contrast, treatment with 4-HC after the induction of chronic liver injury decreased IL-6 serum levels and liver damage (steatosis, inflammatory infiltrate, ballooning cells, steatofibrosis, and fibrosis degree). Thus, the 4-HC treatment is proposed as a preventive treatment against acute liver injury; moreover, these results suggested the potential of 4-HC as a curative treatment against chronic liver injury, but other scheme treatments must be evaluated in future.

The role of alcohol consumption on acetaminophen induced liver injury: Implications from a mathematical model.

Acetaminophen (APAP) overdose is one of the predominant causes of drug induced acute liver injury in the U.S and U.K. Clinical studies show that ingestion of alcohol may increase the risk of APAP induced liver injury. Chronic alcoholism may potentiate APAP hepatotoxicity and this increased risk of APAP toxicity is observed when APAP is ingested even shortly after alcohol is cleared from the body. However, clinical reports also suggest that acute alcohol consumption may have a protective effect against hepatotoxicity by inhibiting microsomal acetaminophen oxidation and thereby reducing N-acetyl-p-benzoquinone imine (NAPQI) production. The aim of this study is to model this dual role of alcohol to determine how the timing of alcohol ingestion affects APAP metabolism and resulting liver injury and identify mechanisms of APAP induced liver injury. The mathematical model is developed to capture condition of a patient of single time APAP overdose who may be an acute or chronic alcohol user. The analysis suggests that the risk of APAP-induced hepatotoxicity is increased if APAP is ingested shortly after alcohol is cleared from the body in chronic alcohol users. A protective effect of acute consumption of alcohol is also observed in patients with APAP overdose. For example, simultaneous ingestion of alcohol and APAP overdose or alcohol intake after or before few hours of APAP overdose may result in less APAP-induced hepatotoxicity when compared to a single time APAP overdose. The rate of hepatocyte damage in APAP overdose patients depends on trade-off between induction and inhibition of CYP enzyme.

MicroRNA 223 3p Negatively Regulates the NLRP3 Inflammasome in Acute and Chronic Liver Injury.

The granulocyte-specific microRNA-223 (miR-223) has recently emerged as a negative regulator of NOD-like receptor 3 (NLRP3) expression, a central key player in chronic hepatic injuries such as fibrotic nonalcoholic steatohepatitis (NASH), as well as in other liver conditions including acute hepatitis. In this study, we evaluated the therapeutic effect of the synthetic miR-223 analog miR-223 3p in a murine model of lipopolysaccharide (LPS)/D-GalN-induced endotoxin acute hepatitis (EAH) or fibrotic NASH resultant of long-term feeding with a high-fat, fructose, and cholesterol (FFC) diet. miR-223 3p ameliorated the infiltration of monocytes, neutrophils, and early activated macrophages and downregulated the transcriptional expression of the pro-inflammatory cytokines Il6 and Il12 and the chemokines Ccl2, Ccl3, Cxcl1, and Cxcl2 in EAH. In fibrotic NASH, treatment with miR-223 3p led to a remarkable mitigation of fibrosis development and activation of hepatic stellate cells (HSCs). miR-223 3p disrupted the activation of the NLRP3 inflammasome by impairing the synthesis of cleaved interleukin-1ß (IL-1ß), mature IL-1ß, and NLRP3, and the activation of caspase-1 p10 in both EAH and fibrotic NASH. Our data enlightens miR-223 3p as a post-transcriptional approach to treat acute and chronic hepatitis by silencing the activation of the NLRP3 inflammasome.

Smad7 Deficiency in Myeloid Cells Does Not Affect Liver Injury, Inflammation or Fibrosis after Chronic CCl4 Exposure in Mice.

Myeloid cells play an essential role in the maintenance of liver homeostasis, as well as the initiation and termination of innate and adaptive immune responses. In chronic hepatic inflammation, the production of transforming growth factor beta (TGF-ß) is pivotal for scarring and fibrosis induction and progression. TGF-ß signalling is tightly regulated via the Smad protein family. Smad7 acts as an inhibitor of the TGF-ß-signalling pathway, rendering cells that express high levels of it resistant to TGF-ß-dependent signal transduction. In hepatocytes, the absence of Smad7 promotes liver fibrosis. Here, we examine whether Smad7 expression in myeloid cells affects the extent of liver inflammation, injury and fibrosis induction during chronic liver inflammation. Using the well-established model of chronic carbon tetrachloride (CCl4)-mediated liver injury, we investigated the role of Smad7 in myeloid cells in LysM-Cre Smadfl/fl mice that harbour a myeloid-specific knock-down of Smad7. We found that the chronic application of CCl4 induces severe liver injury, with elevated serum alanine transaminase (ALT)/aspartate transaminase (AST) levels, centrilobular and periportal necrosis and immune-cell infiltration. However, the myeloid-specific knock-down of Smad7 did not influence these and other parameters in the CCl4-treated animals. In summary, our results suggest that, during long-term application of CCl4, Smad7 expression in myeloid cells and its potential effects on the TGF-ß-signalling pathway are dispensable for regulating the extent of chronic liver injury and inflammation.

Liver Injury and the Macrophage Issue: Molecular and Mechanistic Facts and Their Clinical Relevance.

The liver is an essential immunological organ due to its gatekeeper position to bypassing antigens from the intestinal blood flow and microbial products from the intestinal commensals. The tissue-resident liver macrophages, termed Kupffer cells, represent key phagocytes that closely interact with local parenchymal, interstitial and other immunological cells in the liver to maintain homeostasis and tolerance against harmless antigens. Upon liver injury, the pool of hepatic macrophages expands dramatically by infiltrating bone marrow-/monocyte-derived macrophages. The interplay of the injured microenvironment and altered macrophage pool skews the subsequent course of liver injuries. It may range from complete recovery to chronic inflammation, fibrosis, cirrhosis and eventually hepatocellular cancer. This review summarizes current knowledge on the classification and role of hepatic macrophages in the healthy and injured liver.

Purified anthocyanins from Zea mays L. cob ameliorates chronic liver injury in mice via modulating of oxidative stress and apoptosis.

BACKGROUND: Purple corn (Zea mays L.) is one of the main economic crops in China and has been used in the treatment of cystitis, urinary infections and obesity. However, purple corncobs, the by-product remaining after processing and having an intense purple-black color, are normally disposed of as waste or used as animal feed. Therefore, to further expand the medicinal value of purple corncob, its content was analyzed and, after purification, the effect and mechanism of purified purple corncob anthocyanins (PPCCA) on CCl4 -induced chronic liver injury in mice were investigated. RESULTS: It was observed that the total anthocyanin content (TAC) from PPCCA (317.51 ± 9.30 mg cyanidin 3-O-glucoside (C-3-G) g-1 dry weight) was significantly higher than that from the purified purple corn seed anthocyanin (266.73 ± 3.67 mg C-3-G g-1 dry weight), of which C-3-G accounted for 90.6% and 90.4% of the TAC, respectively. Furthermore, compared with the CCl4 group, PPCCA treatment significantly reduced liver index, serum total bilirubin, alanine transaminase, aspartate transaminase and liver malondialdehyde levels, but increased liver superoxide dismutase activity. The pathological changes were also improved, such as more regular arrangement of hepatocytes, less swelling, and fewer vacuoles and apoptotic cells. Additionally, mechanistic studies showed that PPCCA downregulated the expression of Caspase-3, Bax and cytochrome P450 2E1 proteins in the liver and upregulated the expression of Bcl-2. CONCLUSION: These results demonstrated that PPCCA could ameliorate CCl4 -induced chronic liver injury by regulating oxidative stress and hepatocyte apoptosis pathways. © 2021 Society of Chemical Industry.

[Research progress on the protective effect of Ghrelin on acute and chronic liver injury].

Ghrelin has been discovered as a kind of gastrointestinal hormone in recent years, which poses a variety of biological functions and has a wide range of functional effects on the body. Numerous studies have revealed that ghrelin are actively engaged to protect the liver by improving inflammatory response, reducing oxidative stress, and apoptosis in acute and chronic liver injury. This article summarizes the research progress of the protective effect of ghrelin for acute and chronic liver injury.

Liver Regeneration: Different Sub-Populations of Parenchymal Cells at Play Choreographed by an Injury-Specific Microenvironment.

Liver regeneration is crucial for the maintenance of liver functional mass during homeostasis and diseases. In a disease context-dependent manner, liver regeneration is contributed to by hepatocytes or progenitor cells. As long as they are replicatively competent, hepatocytes are the main cell type responsible for supporting liver size homeostasisand regeneration. The concept that all hepatocytes within the lobule have the same proliferative capacity but are differentially recruited according to the localization of the wound, or whether a yet to be defined sub-population of hepatocytes supports regeneration is still debated. In a chronically or severely injured liver, hepatocytes may enter a state of replicative senescence. In such conditions, small biliary cells activate and expand, a process called ductular reaction (DR). Work in the last few decades has demonstrated that DR cells can differentiate into hepatocytes and thereby contribute to parenchymal reconstitution. In this study we will review the molecular mechanisms supporting these two processes to determine potential targets that would be amenable for therapeutic manipulation to enhance liver regeneration.

miR-223 represents a biomarker in acute and chronic liver injury.

BACKGROUND: Dysregulation of miRNAs has been described in tissue and serum from patients with acute and chronic liver diseases. However, only little information on the role of miR-223 in the pathophysiology of acute liver failure (ALF) and liver cirrhosis is available. METHODS: We analysed cell and tissue specific expression levels as well as serum concentrations of miR-223 in mouse models of acute (hepatic ischaemia and reperfusion, single CCl4 injection) and chronic (repetitive CCl4 injection, bile duct ligation (BDL)) liver diseases. Results were validated in patients and correlated with clinical data. The specific hepatic role of miR-223 was analysed by using miR-223-/- mice in these models. RESULTS: miR-223 expression was significantly dysregulated in livers from mice after induction of acute liver injury and liver fibrosis as well as in liver samples from patients with ALF or liver cirrhosis. In acute and chronic models, hepatic miR-223 up-regulation was restricted to hepatocytes and correlated with degree of liver injury and hepatic cell death. Moreover, elevated miR-223 expression was reflected by significantly higher serum levels of miR-223 during acute liver injury. However, functional in vitro and in vivo experiments revealed no differences in the degree of liver cell death and liver fibrosis as miR-223-/- mice behaved identical with wild-type (wt) mice in all tested models. CONCLUSION: miR-223 represents a promising diagnostic marker in a panel of serum markers of liver injury. Together with previously published data, our results highlight that the role of miR-223 in the pathophysiology of the liver is complex and needs further analysis.

Chronic liver injury in mice promotes impairment of skin barrier function via tumor necrosis factor-alpha.

CONTEXT: Alcohol is frequently used to induce chronic liver injury in laboratory animals. Alcohol causes oxidative stress in the liver and increases the expression of inflammatory mediators that cause hepatocellular damage. However, during chronic liver injury, it is unclear if/how these liver-derived factors affect distal tissues, such as the skin. OBJECTIVE: The purpose of this study was to evaluate skin barrier function during chronic liver injury. MATERIALS AND METHODS: Hairless mice were administered 5% or 10% ethanol for 8 weeks, and damages to the liver and skin were assessed using histological and protein-analysis methods, as well as by detecting inflammatory mediators in the plasma. RESULTS: After alcohol administration, the plasma concentration of the aspartate and alanine aminotransferases increased, while albumin levels decreased. In mice with alcohol-induced liver injury, transepidermal water loss was significantly increased, and skin hydration decreased concurrent with ceramide and type I collagen degradation. The plasma concentrations of [Formula: see text]/[Formula: see text] and tumor necrosis factor-alpha (TNF-α) were significantly increased in mice with induced liver injury. TNF receptor (TNFR) 2 expression was upregulated in the skin of alcohol-administered mice, while TNFR1 levels remained constant. Interestingly, the impairment of skin barrier function in mice administered with 10% ethanol was ameliorated by administering an anti-TNF-α antibody. CONCLUSIONS: We propose a novel mechanism whereby plasma TNF-α, via TNFR2 alone or with TNFR1, plays an important role in skin barrier function during chronic liver disease in these mouse models.

Extrahepatic platelet-derived growth factor-ß, delivered by platelets, promotes activation of hepatic stellate cells and biliary fibrosis in mice.

BACKGROUND & AIMS: Platelet-derived growth factor-ß (PDGFB) is a mitogen for hepatic stellate cells (HSCs). We studied the cellular sources of PDGFB and the effects of a high-affinity monoclonal antibody against PDGFB (MOR8457) in mouse models of biliary fibrosis. METHODS: Cellular sources of PDGFB were identified using quantitative reverse-transcription polymerase chain reaction, biochemical, and immunohistologic methods. Mice with advanced biliary fibrosis, MDR2(Abcb4)-null mice, and C57Bl/6 (control) mice were placed on 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-supplemented diets and were given weekly intraperitoneal injections of MOR8457. Platelets were depleted from MDR2-null mice by injection of an antibody against CD41, or inhibited with diets containing low-dose aspirin. Liver tissues were collected and analyzed by quantitative reverse-transcription PCR and histologic and biochemical analyses. RESULTS: Levels of PDGFB protein, but not messenger RNA, were increased in fibrotic livers of MDR2-null mice, compared with control mice. Platelet clusters were detected in the hepatic endothelium, in close proximity to HSCs, and were identified as a source of PDGFB protein in MDR2-null mice. Levels of the PDGFB were increased in serum samples from patients with early stages of liver fibrosis of various etiologies (F1-2, n = 16; P < .05), compared with nonfibrotic liver tissue (F0, n = 12). Depletion of platelets from MDR2-null mice normalized hepatic levels of PDGFB within 48 hours, reducing levels of a marker of HSC activation (α-smooth muscle actin) and expression of genes that promote fibrosis. Diets supplemented with low-dose aspirin reduced circulating serum and hepatic levels of PDGFB and significantly reduced progression of fibrosis in MDR2-null mice over 1 year. MOR8457 produced a dose-dependent decrease in liver fibrosis in MDR2-null mice, reducing collagen deposition by 45% and expression of fibrosis-associated genes by 50%, compared with mice given a control antibody. In vitro, platelets activated freshly isolated HSCs (induction of α-smooth muscle actin and fibrosis-associated genes) via a PDGFB-dependent mechanism. MOR8457 also reduced liver fibrosis in mice placed on DDC-supplemented diets. CONCLUSIONS: Platelets produce PDGFB to activate HSC and promote fibrosis in MDR2-null mice and mice on DDC-supplemented diets. Antiplatelet therapy or selective inhibition of PDGFB might reduce biliary fibrosis in patients with liver disease.

Alcoholic hepatitis and HCV interactions in the modulation of liver disease.

Most HCV-infected patients regularly consume alcohol. Alcoholic liver disease (ALD) and chronic hepatitis C virus (HCV) infection together are the most common causes of liver disease worldwide. Although both factors independently cause liver disease, they synergistically promote rapid liver disease progression with devastating outcomes for patients. This review focuses on the prevalence, clinical characteristics and molecular pathophysiologic mechanisms of HCV infection associated with alcohol abuse. Recent findings have centred on the synergistic effect of alcohol and HCV on viral replication, hepatocyte apoptosis, oxidative stress, alcohol-induced 'leaky gut', miR-122 and immune dysregulation. Clinical and basic research findings presented here summarize key scientific findings with the aim of highlighting potential areas for new therapies and identifying ways of optimizing current treatments for alcoholics with HCV infection.

Biomarkers of liver cell death.

Hepatocyte cell death during liver injury was classically viewed to occur by either programmed (apoptosis), or accidental, uncontrolled cell death (necrosis). Growing evidence from our increasing understanding of the biochemical and molecular mechanisms involved in cell demise has provided an expanding view of various modes of cell death that can be triggered during both acute and chronic liver damage such as necroptosis, pyroptosis, and autophagic cell death. The complexity of non-invasively assessing the predominant mode of cell death during a specific liver insult in either experimental in vivo models or in humans is highlighted by the fact that in many instances there is significant crosstalk and overlap between the different cell death pathways. Nevertheless, the realization that during cell demise triggered by a specific mode of cell death certain intracellular molecules such as proteins, newly generated protein fragments, or MicroRNAs are released from hepatocytes into the extracellular space and may appear in circulation have spurred a significant interest in the development of non-invasive markers to monitor liver cell death. This review focuses on some of the most promising markers, and their potential role in assessing the presence and severity of liver damage in humans.

Hematopoietic stem cells and liver regeneration: differentially acting hematopoietic stem cell mobilization agents reverse induced chronic liver injury.

Bone marrow (BM) could serve as a source of cells facilitating liver repopulation in case of hepatic damage. Currently available hematopoietic stem cell (HSC) mobilizing agents, were comparatively tested for healing potential in liver fibrosis. Carbon tetrachloride (CCl4)-injured mice previously reconstituted with Green Fluorescent Protein BM were mobilized with Granulocyte-Colony Stimulating Factor (G-CSF), Plerixafor or G-CSF+Plerixafor. Hepatic fibrosis, stellate cell activation and oval stem cell frequency were measured by Gomori and by immunohistochemistry for a-Smooth Muscle Actin and Cytokeratin-19, respectively. Angiogenesis was evaluated by ELISA and immunohistochemistry. Quantitative real-time PCR was used to determine the mRNA levels of liver Peroxisome Proliferator-Activated Receptor gamma (PPAR-γ), Interleukin-6 (IL-6) and Tumor Necrosis-alpha (TNFα). BM-derived cells were tracked by double immunofluorescence. The spontaneous migration of mobilized HSCs towards injured liver and its cytokine secretion profile was determined in transwell culture systems. Either single-agent mobilization or the combination of agents significantly ameliorated hepatic damage by decreasing fibrosis and restoring the abnormal vascular network in the liver of mobilized mice compared to CCl4-only mice. The degree of fibrosis reduction was similar among all mobilized mice despite that G-CSF+Plerixafor yielded significantly higher numbers of circulating HSCs over other agents. The liver homing potential of variously mobilized HSCs differed among the agents. An extended G-CSF treatment provided the highest anti-fibrotic effect over all tested modalities, induced by the proliferation of hepatic stem cells and decreased hepatic inflammation. Plerixafor-mobilized HSCs, despite their reduced liver homing potential, reversed fibrosis mainly by increasing hepatic PPAR-γ and VEGF expression. In all groups, BM-derived mature hepatocytes as well as liver-committed BM stem cells were detected only at low frequencies, further supporting the concept that alternative mechanisms rather than direct HSC effects regulate liver recovery. Overall, our data suggest that G-CSF, Plerixafor and G-CSF+Plerixafor act differentially during the wound healing process, ultimately providing a potent anti-fibrotic effect.

Cellular and molecular mechanisms in liver fibrogenesis.

Liver fibrogenesis is a dynamic and highly integrated molecular, tissue and cellular process, potentially reversible, that drives the progression of chronic liver diseases (CLD) towards liver cirrhosis and hepatic failure. Hepatic myofibroblasts (MFs), the pro-fibrogenic effector cells, originate mainly from activation of hepatic stellate cells and portal fibroblasts being characterized by a proliferative and survival attitude. MFs also contract in response to vasoactive agents, sustain angiogenesis and recruit and modulate activity of cells of innate or adaptive immunity. Chronic activation of wound healing and oxidative stress as well as derangement of epithelial-mesenchymal interactions are "major" pro-fibrogenic mechanisms, whatever the etiology. However, literature has outlined a complex network of pro-fibrogenic factors and mediators proposed to modulate CLD progression, with some of them being at present highly debated in the field, including the role of epithelial to mesenchymal transition and Hedgehog signaling pathways. Hypoxia and angiogenesis as well as inflammasomes are recently emerged as ubiquitous pro-inflammatory and pro-fibrogenic determinants whereas adipokines are mostly involved in CLD related to metabolic disturbances (metabolic syndrome and/or obesity and type 2 diabetes). Finally, autophagy as well as natural killer and natural killer-T cells have been recently proposed to significantly affect fibrogenic CLD progression.