Ductular reaction in hereditary hemochromatosis: the link between hepatocyte senescence and fibrosis progression

Can serum ferritin serve as a biomarker for the prognosis of gynecological malignant tumors? A retrospective cohort study

PURPOSE

It is widely accepted that there is a strong relationship between iron levels and cancer. This study aimed to investigate the relationship between serum ferritin levels and the severity and prognosis of gynecological malignant tumors.

METHODS

This retrospective study included patients with gynecological malignant tumors at Sir Run Run Shaw Hospital in the Department of Obstetrics and Gynecology from January 2013 to June 2019. Patients were grouped according to their serum ferritin level: low (< 13 μg/L), normal (13-150 μg/L), and high (> 150 μg/L). Correlation analyses were performed between serum ferritin level and other factors. Cox univariable and multivariable analysis and Kaplan-Meier survival curves were used to assess the impact of ferritin on survival in patients with gynecologic tumors.

RESULTS

The 402 total patients were divided into a low (n= 37), normal (n= 182), and high (n= 183) ferritin level group. Correlation analyses were performed that WBC, MCV, CRP, CA125, and CA153 were significantly positively correlated with serum ferritin level. The Kaplan-Meier survival curves revealed that of the three groups analyzed, the high serum ferritin level group had a significantly shorter survival time versus the normal and low serum ferritin level groups (log-rank P= 0.003). Univariable Cox regression analysis identified that patients with high serum ferritin levels had a significant correlation with risk of death compared to the patients with lower and normal serum ferritin levels. Serum ferritin was not found to be significant (HR = 0.792, 95% CI: 0.351-1.787, P= 0.574) in the multivariable Cox analysis.

CONCLUSION

Although this study did not find serum ferritin to be a significant independent prognosis indicator in gynecological malignant tumors, this study did identify that gynecological malignant tumor patients with high serum ferritin levels have significantly less survival time than patients with low or normal serum ferritin levels.

Deep learning quantification reveals a fundamental prognostic role for ductular reaction in biliary atresia

BACKGROUND

We aimed to quantify ductular reaction (DR) in biliary atresia using a neural network in relation to underlying pathophysiology and prognosis.

METHODS

Image-processing neural network model was applied to 259 cytokeratin-7-stained native liver biopsies of patients with biliary atresia and 43 controls. The model quantified total proportional DR (DR%) composed of portal biliary epithelium (BE%) and parenchymal intermediate hepatocytes (PIH%). The results were related to clinical data, Sirius Red-quantified liver fibrosis, serum biomarkers, and bile acids.

RESULTS

In total, 2 biliary atresia biopsies were obtained preoperatively, 116 at Kasai portoenterostomy (KPE) and 141 during post-KPE follow-up. DR% (8.3% vs. 5.9%, p=0.045) and PIH% (1.3% vs. 0.6%, p=0.004) were increased at KPE in patients remaining cholestatic postoperatively. After KPE, patients with subsequent liver transplantation or death showed an increase in DR% (7.9%-9.9%, p = 0.04) and PIH% (1.6%-2.4%, p = 0.009), whereas patients with native liver survival (NLS) showed decreasing BE% (5.5%-3.0%, p = 0.03) and persistently low PIH% (0.9% vs. 1.3%, p = 0.11). In Cox regression, high DR predicted inferior NLS both at KPE [DR% (HR = 1.05, p = 0.01), BE% (HR = 1.05, p = 0.03), and PIH% (HR = 1.13, p = 0.005)] and during follow-up [DR% (HR = 1.08, p<0.0001), BE% (HR = 1.58, p = 0.001), and PIH% (HR = 1.04, p = 0.008)]. DR% correlated with Sirius red-quantified liver fibrosis at KPE (R = 0.47, p<0.0001) and follow-up (R = 0.27, p = 0.004). A close association between DR% and serum bile acids was observed at follow-up (R = 0.61, p<0.001). Liver fibrosis was not prognostic for NLS at KPE (HR = 1.00, p = 0.96) or follow-up (HR = 1.01, p = 0.29).

CONCLUSIONS

DR predicted NLS in different disease stages before transplantation while associating with serum bile acids after KPE.

Stem cell pathology: histogenesis of malignant fibrous histiocytoma and characterization of myofibroblasts appearing in fibrotic lesions

The concept of "stem cell pathology" is to establish the role of the stem cells by exploring their contribution to lesion development. The somatic stem cells are present in the body. Malignant fibrous histiocytoma (MFH; recently named "undifferentiated pleomorphic sarcoma") includes pluripotential undifferentiated mesenchymal stem cells as a cell element. An antibody (A3) generated by using rat MFH cells as the antigen labels somatic stem cells such as bone marrow stem cells and immature endothelial cells and pericytes, as well as immature epithelial cells in epithelialization. By using A3 and other antibodies recognizing somatic stem cells, it is considered that myofibroblasts appearing in rat fibrotic lesions are developed partly from immature hepatic stellate cells in hepatic fibrosis, immature pancreatic stellate cells in pancreatic fibrosis, pericytes/endothelial cells in neovascularization in injured tissues, as well as via the epithelial-mesenchymal transition. These progenitors may be in the stem cell lineage. In this review, the author introduces the histogenesis of MFH and the characteristics of myofibroblasts appearing in fibrosis, based mainly on the author's studies.

Hepatocyte-specific damage in acute toxicity of sodium ferrous citrate: Presentation of a human autopsy case and experimental results in mice

Acute iron overload is known to exert deleterious effects in the liver, but detailed pathology has yet to be documented. Here, we report pathological findings in an autopsy case of acute iron toxicity and validation of the findings in mouse experiments. In a 39-year-old woman who intentionally ingested a large amount of sodium ferrous citrate (equivalent to 7.5 g of iron), severe disturbance of consciousness and fulminant hepatic failure rapidly developed. Liver failure was refractory to treatment and the patient died on Day 13. Autopsy revealed almost complete loss of hepatocytes, while bile ducts were spared. To examine the detailed pathologic processes induced by excessive iron, mice were orally administered equivalent doses of ferrous citrate. Plasma aminotransferase levels markedly increased after 6 h, which was preceded by increased plasma iron levels. Hepatocytes were selectively damaged, with more prominent damage in the periportal area. Phosphorylated c-Jun was detected in hepatocyte nuclei after 3 h, which was followed by the appearance of γ-H2AX expression. Hepatocyte injury in mice was associated with the expression of Myc and p53 after 12 and 24 h, respectively. Even at lethal doses, the bile ducts were morphologically intact and fully viable. Our findings indicate that acute iron overload induces hepatocyte-specific liver injury, most likely through hydroxyl radical-mediated DNA damage and subsequent stress responses.

Update on Hepatobiliary Plasticity

The liver field has been debating for decades the contribution of the plasticity of the two epithelial compartments in the liver, hepatocytes and biliary epithelial cells (BECs), to derive each other as a repair mechanism. The hepatobiliary plasticity has been first observed in diseased human livers by the presence of biphenotypic cells expressing hepatocyte and BEC markers within bile ducts and regenerative nodules or budding from strings of proliferative BECs in septa. These observations are not surprising as hepatocytes and BECs derive from a common fetal progenitor, the hepatoblast, and, as such, they are expected to compensate for each other's loss in adults. To investigate the cell origin of regenerated cell compartments and associated molecular mechanisms, numerous murine and zebrafish models with ability to trace cell fates have been extensively developed. This short review summarizes the clinical and preclinical studies illustrating the hepatobiliary plasticity and its potential therapeutic application.

Emerging role of aging in the progression of NAFLD to HCC

With the aging of global population, the incidence of nonalcoholic fatty liver disease (NAFLD) has surged in recent decades. NAFLD is a multifactorial disease that follows a progressive course, ranging from simple fatty liver, nonalcoholic steatohepatitis (NASH) to liver cirrhosis and hepatocellular carcinoma (HCC). It is well established that aging induces pathological changes in liver and potentiates the occurrence and progression of NAFLD, HCC and other age-related liver diseases. Studies of senescent cells also indicate a pivotal engagement in the development of NAFLD via diverse mechanisms. Moreover, nicotinamide adenine dinucleotide (NAD⁺), silence information regulator protein family (sirtuins), and mechanistic target of rapamycin (mTOR) are three vital and broadly studied targets involved in aging process and NAFLD. Nevertheless, the crucial role of these aging-associated factors in aging-related NAFLD remains underestimated. Here, we reviewed the current research on the roles of aging, cellular senescence and three aging-related factors in the evolution of NAFLD to HCC, aiming at inspiring promising therapeutic targets for aging-related NAFLD and its progression.

EASL Clinical Practice Guidelines on haemochromatosis

Haemochromatosis is characterised by elevated transferrin saturation (TSAT) and progressive iron loading that mainly affects the liver. Early diagnosis and treatment by phlebotomy can prevent cirrhosis, hepatocellular carcinoma, diabetes, arthropathy and other complications. In patients homozygous for p.Cys282Tyr in HFE, provisional iron overload based on serum iron parameters (TSAT >45% and ferritin >200 μg/L in females and TSAT >50% and ferritin >300 μg/L in males and postmenopausal women) is sufficient to diagnose haemochromatosis. In patients with high TSAT and elevated ferritin but other HFE genotypes, diagnosis requires the presence of hepatic iron overload on MRI or liver biopsy. The stage of liver fibrosis and other end-organ damage should be carefully assessed at diagnosis because they determine disease management. Patients with advanced fibrosis should be included in a screening programme for hepatocellular carcinoma. Treatment targets for phlebotomy are ferritin <50 μg/L during the induction phase and <100 μg/L during the maintenance phase.

Prominent Pseudoacini in Focal Nodular Hyperplasia: A Potential Diagnostic Pitfall

Pseudoacini are generally a morphologic feature of hepatocellular carcinoma (HCC), being absent or rare in benign hepatocytic tumors, such as hepatocellular adenoma. However, rarely these can be seen in focal nodular hyperplasia (FNH) and may pose diagnostic challenges, especially when prominent. The study was aimed to evaluate the occurrence of pseudoacini in FNH and their clinicopathologic correlations. A total of 95 FNH cases diagnosed from 2005 to 2020 were included in the study. A pseudoacinus was defined as a circular arrangement of hepatocytes around a central dilated lumen present within the lobular parenchyma of the lesion with or without inspissated bile. Among the 95 FNH cases, 28 (29.5%) showed pseudoacini, which were prominent in 12 (12.6%) cases. Of these 3 occurred in patients above 50 years old. The pseudoacini were numerous in 3 cases, leading to an initial consideration of HCC in the differential diagnosis, and 1 case was diagnosed as well-differentiated hepatocellular neoplasm on initial biopsy. All 12 cases showed map-like staining pattern for glutamine synthetase. The hepatocytes forming the pseudoacini were positive for CK7 and HepPar1, while the inner lumina were highlighted by CD10 and bile salt export pump immunostains similar to adjacent canaliculi. The presence of prominent pseudoacini was not significantly associated with any clinical or pathologic features. The findings suggest that pseudoacini are likely manifestation of hepatocyte biliary transdifferentiation associated with chronic cholestasis in the lesion. This feature may pose a potential diagnostic pitfall especially on needle biopsies and awareness is needed to avoid misdiagnosing this as HCC.

Sesamol protects against liver fibrosis induced in rats by modulating lysophosphatidic acid receptor expression and TGF-β/Smad3 signaling pathway

The present study aimed to investigate the hepatoprotective effect of sesamol (SML), a nutritional phenolic compound obtained from sesame seeds, in liver fibrosis induced by thioacetamide (TAA) in rats and to explore the underlying mechanisms. Thirty-two male Sprague–Dawley rats were equally divided into four groups: control, TAA, TAA + SML 50 mg/kg, and TAA + SML 100 mg/kg groups. Liver functions and hepatic contents of glutathione (GSH) and malondialdehyde (MDA) were measured colorimetrically. Gene expressions of lysophosphatidic acid receptor (LPAR)-1 and -3, connective tissue growth factor (CTGF), transforming growth factor (TGF)-β1, small mothers against decapentaplegic (Smad)-3 and -7, α-smooth muscle actin (α-SMA), and cytokeratin 19 (CK19) were analyzed by qRT-PCR. Moreover, phosphorylated Smad3 (pSmad3) was quantified by ELISA. Additionally, TGF-β1, α-SMA, CK19, and vascular endothelial growth factor (VEGF) protein concentrations were semi-quantitatively analyzed by immunostaining of liver sections. SML treatment markedly improved liver index and liver functions. Moreover, SML protected against liver fibrosis in a dose-dependent manner as indicated by down-regulation of LPAR1, LPAR3, CTGF, TGF-β1/Smad3, and α-SMA expressions and a decrease in pSmad3 level, as well as an up-regulation of Smad7 expression. In addition, SML suppressed ductular reaction hinted by the decrease in CK19 expression. These results reveal the anti-fibrotic effect of SML against liver fibrosis that might be attributed to down-regulation of LPAR1/3 expressions, inhibition of TGF-β1/Smad3 pathway, and ductular reaction.

The CD38 glycohydrolase and the NAD sink: implications for pathological conditions

Nicotinamide adenine dinucleotide (NAD) acts as a cofactor in several oxidation-reduction (redox) reactions and is a substrate for a number of nonredox enzymes. NAD is fundamental to a variety of cellular processes including energy metabolism, cell signaling, and epigenetics. NAD homeostasis appears to be of paramount importance to health span and longevity, and its dysregulation is associated with multiple diseases. NAD metabolism is dynamic and maintained by synthesis and degradation. The enzyme CD38, one of the main NAD-consuming enzymes, is a key component of NAD homeostasis. The majority of CD38 is localized in the plasma membrane with its catalytic domain facing the extracellular environment, likely for the purpose of controlling systemic levels of NAD. Several cell types express CD38, but its expression predominates on endothelial cells and immune cells capable of infiltrating organs and tissues. Here we review potential roles of CD38 in health and disease and postulate ways in which CD38 dysregulation causes changes in NAD homeostasis and contributes to the pathophysiology of multiple conditions. Indeed, in animal models the development of infectious diseases, autoimmune disorders, fibrosis, metabolic diseases, and age-associated diseases including cancer, heart disease, and neurodegeneration are associated with altered CD38 enzymatic activity. Many of these conditions are modified in CD38-deficient mice or by blocking CD38 NADase activity. In diseases in which CD38 appears to play a role, CD38-dependent NAD decline is often a common denominator of pathophysiology. Thus, understanding dysregulation of NAD homeostasis by CD38 may open new avenues for the treatment of human diseases.

Liver regeneration and inflammation: from fundamental science to clinical applications

Liver regeneration is a complex process involving the crosstalk of multiple cell types, including hepatocytes, hepatic stellate cells, endothelial cells and inflammatory cells. The healthy liver is mitotically quiescent, but following toxic damage or resection the cells can rapidly enter the cell cycle to restore liver mass and function. During this process of regeneration, epithelial and non-parenchymal cells respond in a tightly coordinated fashion. Recent studies have described the interaction between inflammatory cells and a number of other cell types in the liver. In particular, macrophages can support biliary regeneration, contribute to fibrosis remodelling by repressing hepatic stellate cell activation and improve liver regeneration by scavenging dead or dying cells in situ. In this Review, we describe the mechanisms of tissue repair following damage, highlighting the close relationship between inflammation and liver regeneration, and discuss how recent findings can help design novel therapeutic approaches.

The role of mitochondria dysfunction and hepatic senescence in NAFLD development and progression

Senescence is a crucial player in several metabolic disorders and chronic inflammatory diseases. Recent data prove the involvement of hepatocyte senescence in the development of NAFLD (non-alcoholic fatty liver disease). As the main energy and ROS (reactive oxygen species) producing organelle, mitochondria play the central role in accelerated senescence and diseases development. In this review, we focus on the role of regulation of mitochondrial Ca²⁺ homeostasis, NAD+/NADH ratio, UPR^mt (mitochondrial unfolded protein response), phospholipids and fatty acid oxidation in hepatic senescence, lifespan and NAFLD disease susceptibility. Additionally, the involvement of mitochondrial and nuclear mutations in lifespan-modulation and NAFLD development is discussed. While nuclear and mitochondria DNA mutations and SNPs (single nucleotide polymorphisms) can be used as effective diagnostic markers and targets for treatments, advanced age should be considered as an independent risk factor for NAFLD development.

Aged-related Function Disorder of Liver is Reversed after Exposing to Young Milieu via Conversion of Hepatocyte Ploidy

Previous study showed that senescent hepatocytes from aged liver could be rejuvenated after repopulated in the young recipient liver. The proliferative capacity of hepatocytes was restored with the senescence reversal. However, it is unknown whether metabolic and homeostatic function of aged liver, as well as age-dependent liver steatosis could be rejuvenated or alleviated. Here, we found that senescent hepatocytes from aged liver were rejuvenated after exposing to young blood. An autonomous proliferation of senescent hepatocytes which resulting in ploidy reversal might be the underlying mechanism of senescent reversal. After performing 2/3 partial hepatectomy (2/3PHx) in young blood exposed old liver, delayed DNA synthesis of senescent hepatocytes was rescued and the number of BrdU positive hepatocytes was restored from 4.39±2.30% to 17.85±3.21%, similarly to that in the young mice at 36 hours post 2/3PHx. Moreover, Cyclin A2 and Cyclin E1 overexpression of hepatocytes in aged liver facilitating the G1/S phase transition was contributed to enhance liver regeneration. Furthermore, lipid droplet spread widely in the elderly human liver and old mouse liver, but this aged-associated liver steatosis was alleviated as senescence reversal. Collectively, our study provides new thoughts for effectively preventing age-related liver diseases.

Previous liver regeneration induces fibro-protective mechanisms during thioacetamide-induced chronic liver injury

Chronic liver injury is characterised by continuous or repeated epithelial cell loss and inflammation. Hepatic wound healing involves matrix deposition through activated hepatic stellate cells (HSCs) and the expansion of closely associated Ductular Reactions and liver progenitor cells (LPCs), which are thought to give rise to new epithelial cells. In this study, we used the murine thioacetamide (TAA) model to reliably mimic these injury and regeneration dynamics and assess the impact of a recovery phase on subsequent liver injury and fibrosis. Age-matched naïve or 6-week TAA-treated/4-week recovered mice (C57BL/6 J, n = 5-9) were administered TAA for six weeks (C57BL/6 J, n = 5-9). Sera and liver tissues were harvested at key time points to assess liver injury biochemically, by real-time PCR for fibrotic mediators, Sirius Red staining and hydroxyproline assessment for collagen deposition as well as immunofluorescence for inflammatory, HSC and LPC markers. In addition, primary HSCs and the HSC cell line LX-2 were co-cultured with the well-characterised LPC line BMOL and analysed for potential changes in expression of fibrogenic mediators. Our data demonstrate that recovery from a previous TAA insult, with LPCs still present on day 0 of the second treatment, led to a reduced TAA-induced disease progression with less severe fibrosis than in naïve TAA-treated animals. Importantly, primary activated HSCs significantly reduced pro-fibrogenic gene expression when co-cultured with LPCs. Taken together, previous TAA injury established a fibro-protective molecular and cellular microenvironment. Our proof-of principle HSC/LPC co-culture data demonstrate that LPCs communicate with HSCs to regulate fibrogenesis, highlighting a key role for LPCs as regulatory cells during chronic liver disease.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Cellular Senescence in Liver Disease and Regeneration

Cellular senescence is an irreversible cell cycle arrest implemented by the cell as a result of stressful insults. Characterized by phenotypic alterations, including secretome changes and genomic instability, senescence is capable of exerting both detrimental and beneficial processes. Accumulating evidence has shown that cellular senescence plays a relevant role in the occurrence and development of liver disease, as a mechanism to contain damage and promote regeneration, but also characterizing the onset and correlating with the extent of damage. The evidence of senescent mechanisms acting on the cell populations of the liver will be described including the role of markers to detect cellular senescence. Overall, this review intends to summarize the role of senescence in liver homeostasis, injury, disease, and regeneration.

Cellular senescence and hepatitis B-related hepatocellular carcinoma: An intriguing link

Chronic hepatitis B is mainly responsible for the morbidity and mortality from hepatitis B virus (HBV)-related complications, including hepatocellular carcinoma (HCC) and decompensated cirrhosis. Hepatocellular carcinoma remains the main challenge in the management of not only undiagnosed and/or untreated but also diagnosed and treated patients with chronic HBV infection, as its incidence decreases but is not eliminated even after many years of effective anti-HBV therapy. The exact mechanisms used by HBV to cause malignant transformation remain uncertain, although much of the available data are in favour of a pathogenetic role of HBx protein. Senescence is a cellular state, in which cells lose their ability to proliferate. This biological mechanism may function in a dual mode, namely being both cancer-protective as a result of reduced cellular proliferation, but also cancer-enhancing as a result of modulation of the tissular microenvironment by immune cells during persistent accumulation of senescent cells. Protein X of HBV protein exhibits many similarities in terms of the implemented mechanisms of action and pathways related to the biological process of cellular senescence. Concurrently, insufficient clearance of both senescent and precancerous hepatocytes combined with inadequate immune surveillance as a result of immunosenescence caused by chronic HBV infection may lead to hepatocarcinogenesis. Thus, the effect of HBV seems to be critical as a connecting link between cellular senescence and development of HCC. An ongoing research is underway towards identifying and validating markers of hepatocyte senescence, which could improve the landscape for evaluation of chronic liver disease, thereby providing valuable information in terms of HBV-related carcinogenesis.

Senolytic Drugs: Reducing Senescent Cell Viability to Extend Health Span

Senescence is the consequence of a signaling mechanism activated in stressed cells to prevent proliferation of cells with damage. Senescent cells (Sncs) often develop a senescence-associated secretory phenotype to prompt immune clearance, which drives chronic sterile inflammation and plays a causal role in aging and age-related diseases. Sncs accumulate with age and at anatomical sites of disease. Thus, they are regarded as a logical therapeutic target. Senotherapeutics are a new class of drugs that selectively kill Sncs (senolytics) or suppress their disease-causing phenotypes (senomorphics/senostatics). Since 2015, several senolytics went from identification to clinical trial. Preclinical data indicate that senolytics alleviate disease in numerous organs, improve physical function and resilience, and suppress all causes of mortality, even if administered to the aged. Here, we review the evidence that Sncs drive aging and disease, the approaches to identify and optimize senotherapeutics, and the current status of preclinical and clinical testing of senolytics.

Epithelial Plasticity during Liver Injury and Regeneration

Following injury, the liver's epithelial cells regenerate efficiently with rapid proliferation of hepatocytes and biliary cells. However, when proliferation of resident epithelial cells is impaired, alternative regeneration mechanisms can occur. Intricate lineage-tracing strategies and experimental models of regenerative stress have revealed a degree of plasticity between hepatocytes and biliary cells. New technologies such as single-cell omics, in combination with functional studies, will be instrumental to uncover the remaining unknowns in the field. In this review, we evaluate the experimental and clinical evidence for epithelial plasticity in the liver and how this influences the development of therapeutic strategies for chronic liver disease.

TCDD promotes liver fibrosis through disordering systemic and hepatic iron homeostasis

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is a toxic environmental pollutant which can cause severe health problems, such as fibrosis. However, the toxic effects and related mechanism of TCDD on the liver remain largely unknown. In this study, we established a liver fibrosis mouse model upon exposure of TCDD, as evidenced by increased collagen I, tumor growth factor β1 (TGFβ1), α-smooth muscle actin (α-SMA), and Masson staining. Meanwhile, there was also a significant increase of inflammatory factors and TUNEL-positive hepatocytes in liver, indicating that liver inflammation and hepatic cell apoptosis occurred. In addition, increased serum and liver iron were concomitant with liver injury induced by TCDD. We further investigated the mechanism underlying TCDD-induced hepatocyte apoptosis through apoptosis polymerase chain reaction array, and found that a crucial apoptosis-related gene, cell death-inducing DFF45-like effector b (Cideb), was significantly increased in primary hepatocytes from TCDD-exposed mice, and accompanied by liver iron deposition in hepcidin knockout mice. Therefore, Cideb depletion could effectively attenuated TCDD or iron induced cell death related genes expression. In conclusion, our results showed that iron-induced Cideb expression played a critical role in promoting TCDD-induced hepatocyte apoptosis and liver fibrosis, which provide a novel mechanism for understanding TCDD-induced liver injury.

Complex Cell Type-Specific Roles of Autophagy in Liver Fibrosis and Cirrhosis

The lysosomal degradation pathway, or autophagy, plays a fundamental role in cellular, tissue, and organismal homeostasis. A correlation between dysregulated autophagy and liver fibrosis (including end-stage disease, cirrhosis) is well-established. However, both the up and downregulation of autophagy have been implicated in fibrogenesis. For example, the inhibition of autophagy in hepatocytes and macrophages can enhance liver fibrosis, whereas autophagic activity in hepatic stellate cells and reactive ductular cells is permissive towards fibrogenesis. In this review, the contributions of specific cell types to liver fibrosis as well as the mechanisms underlying the effects of autophagy are summarized. In view of the functional effects of multiple cell types on the complex process of hepatic fibrogenesis, integrated approaches that consider the role of autophagy in each liver cell type should be a focus of future research.

Hepatocyte Injury and Hepatic Stem Cell Niche in the Progression of Non-Alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease characterized by lipid accumulation in hepatocytes in the absence of excessive alcohol consumption. The global prevalence of NAFLD is constantly increasing. NAFLD is a disease spectrum comprising distinct stages with different prognoses. Non-alcoholic steatohepatitis (NASH) is a progressive condition, characterized by liver inflammation and hepatocyte ballooning, with or without fibrosis. The natural history of NAFLD is negatively influenced by NASH onset and by the progression towards advanced fibrosis. Pathogenetic mechanisms and cellular interactions leading to NASH and fibrosis involve hepatocytes, liver macrophages, myofibroblast cell subpopulations, and the resident progenitor cell niche. These cells are implied in the regenerative trajectories following liver injury, and impairment or perturbation of these mechanisms could lead to NASH and fibrosis. Recent evidence underlines the contribution of extra-hepatic organs/tissues (e.g., gut, adipose tissue) in influencing NASH development by interacting with hepatic cells through various molecular pathways. The present review aims to summarize the role of hepatic parenchymal and non-parenchymal cells, their mutual influence, and the possible interactions with extra-hepatic tissues and organs in the pathogenesis of NAFLD.

A critical role of autophagy in regulating the mesenchymal transition of ductular cells in liver cirrhosis

Our previous studies have shown that autophagy mediates the link between ductular reaction (DR) and liver cirrhosis. Whether the subsequent fibrogenic response is regulated by increased autophagy in DR remains unclear. Here, using both human liver specimens and a rat model of liver cirrhosis induced by 2-acetylaminofluorene (AAF) and carbon tetrachloride (CCL4), we explored the involvement of autophagy in regulating mesenchymal transition of ductular cells. Ductular cells from AAF/CCL4 livers exhibited increased autophagy compared to those of normal livers. These cells showed morphological and functional characteristics of mesenchymal cells. Blocking autophagy using bafilomycin A1 or siRNA targeting ATG7 reduced the expression of mesenchymal markers in these ductular cells from AAF/CCL4 livers, indicating a role for autophagy in regulating the mesenchymal phenotype of ductular cells. Furthermore, we show that the mesenchymal transition in DR requires the activation of transforming growth factor-β (TGF-β) signaling in an autophagy-dependent manner. Importantly, in cirrhotic human livers, ductular cells that are positive for LC3B also showed increased expression of TGF-β and fibroblast-specific protein-1. Our data suggest activation of autophagy in ductular cells, and also demonstrate that it is required for the mesenchymal transition during the DR, processes that are critically involved in the pathogenesis of cirrhosis.

Hepatocellular Carcinoma Arising in a Non-cirrhotic Liver with Secondary Hemochromatosis

A 70-year-old man was admitted for treatment of a single liver nodule that was detected by contrast-enhanced computed tomography. Twenty years earlier, the patient had been diagnosed with myelodysplastic syndrome-refractory anemia and secondary hemochromatosis but had not received erythrocyte transfusions. The current histological, computed tomography, and magnetic resonance imaging findings revealed hepatocellular carcinoma (HCC) and non-cirrhotic liver hemochromatosis. The liver tumor was treated using radiofrequency ablation therapy. Secondary hemochromatosis may be a risk factor for HCC, even if the liver is not cirrhotic. In such cases, additional surveillance may be required to detect the development of HCC.

Iron and liver fibrosis: Mechanistic and clinical aspects

Liver fibrosis is characterised by excessive deposition of extracellular matrix that interrupts normal liver functionality. It is a pathological stage in several untreated chronic liver diseases such as the iron overload syndrome hereditary haemochromatosis, viral hepatitis, alcoholic liver disease, non-alcoholic fatty liver disease, non-alcoholic steatohepatitis and diabetes. Interestingly, regardless of the aetiology, iron-loading is frequently observed in chronic liver diseases. Excess iron can feed the Fenton reaction to generate unquenchable amounts of free radicals that cause grave cellular and tissue damage and thereby contribute to fibrosis. Moreover, excess iron can induce fibrosis-promoting signals in the parenchymal and non-parenchymal cells, which accelerate disease progression and exacerbate liver pathology. Fibrosis regression is achievable following treatment, but if untreated or unsuccessful, it can progress to the irreversible cirrhotic stage leading to organ failure and hepatocellular carcinoma, where resection or transplantation remain the only curative options. Therefore, understanding the role of iron in liver fibrosis is extremely essential as it can help in formulating iron-related diagnostic, prognostic and treatment strategies. These can be implemented in isolation or in combination with the current approaches to prepone detection, and halt or decelerate fibrosis progression before it reaches the irreparable stage. Thus, this review narrates the role of iron in liver fibrosis. It examines the underlying mechanisms by which excess iron can facilitate fibrotic responses. It describes the role of iron in various clinical pathologies and lastly, highlights the significance and potential of iron-related proteins in the diagnosis and therapeutics of liver fibrosis.

High-throughput sequencing identifies aetiology-dependent differences in ductular reaction in human chronic liver disease

Ductular reaction (DR) represents the activation of hepatic progenitor cells (HPCs) and has been associated with features of advanced chronic liver disease; yet it is not clear whether these cells contribute to disease progression and how the composition of their micro-environment differs depending on the aetiology. This study aimed to identify HPC-associated signalling pathways relevant in different chronic liver diseases using a high-throughput sequencing approach. DR/HPCs were isolated using laser microdissection from patient samples diagnosed with HCV or primary sclerosing cholangitis (PSC), as models for hepatocellular or biliary regeneration. Key signals were validated at the protein level for a cohort of 56 patients (20 early and 36 advanced stage). In total, 330 genes were significantly differentially expressed between the HPCs in HCV and PSC. Recruitment and homing of inflammatory cells were distinctly different depending on the aetiology. HPCs in PSC were characterised by a response to oxidative stress (e.g. JUN, VNN1) and neutrophil-attractant chemokines (CXCL5, CXCL6, IL-8), whereas HPCs in HCV were identified by T- and B-lymphocyte infiltration. Moreover, we found that communication between HPCs and macrophages was aetiology driven. In PSC, a high frequency of CCL28-positive macrophages was observed in the portal infiltrate, already in early disease in the absence of advanced fibrosis, while in HCV, HPCs showed a strong expression of the macrophage scavenger receptor MARCO. Interestingly, DR/HPCs in PSC showed more deposition of ECM (e.g. FN1, LAMC2, collagens) compared to HCV, where an increase of pro-invasive genes (e.g. PDGFRA, IGF2) was observed. Additionally, endothelial cells in the vicinity of DR/HPCs showed differential immunopositivity (e.g. IGF2 and INHBA expression). In conclusion, our data shine light on the role of DR/HPCs in immune signalling, fibrogenesis and angiogenesis in chronic liver disease. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Ductular Reaction in Liver Diseases: Pathological Mechanisms and Translational Significances

Ductular reaction (DR) is characterized by the proliferation of reactive bile ducts induced by liver injuries. DR is pathologically recognized as bile duct hyperplasia and is commonly observed in biliary disorders. It can also be identified in various liver disorders including nonalcoholic fatty liver disease. DR is associated with liver fibrosis and damage, and the extent of DR parallels to patient mortality. DR raises scientific interests because it is associated with transdifferentiation of liver cells and may play an important role in hepatic regeneration. The origin of active cells during DR can be cholangiocytes, hepatocytes, or hepatic progenitor cells, and associated signaling pathways could differ depending on the specific liver injury or animal models used in the study. Although further studies are needed to elucidate detailed mechanisms and the functional roles in liver diseases, DR can be a therapeutic target to inhibit liver fibrosis and to promote liver regeneration. This review summarizes previous studies of DR identified in patients and animal models as well as currently understood mechanisms of DR.

Immunohistochemical characterization of myofibroblasts appearing in isoproterenol-induced rat myocardial fibrosis

Fibrotic lesion is formed by myofibroblasts capable of producing collagens. The myofibroblasts are characterized by immunoexpressions of vimentin, desmin and α-smooth muscle actin (α-SMA) in varying degrees. The cellular characteristics remain investigated in myocardial fibrosis. We analyzed immunophenotypes of myofibroblasts appearing in isoproterenol-induced myocardial fibrosis in rats until 28 days after injection (10 mg/kg body weight); the lesions developed as interstitial edema and inflammatory cell reaction on 8 hr and days 1 and 3, and fibrosis occurred on days 1, 3, 7, 14, and 21 by gradual deposition of collagens, showing the greatest grade on day 14; the lesions gradually reduced with sporadic scar until day 28. Myofibroblasts expressing vimentin and α-SMA increased with a peak on day 3, and then, gradually decreased onwards. Interestingly, Thy-1 expressing cells appeared in the affected areas, apparently being corresponding to the grade similar to vimentin- and α-SMA-positive cells. Thy-1 is expressed in immature mesenchymal cells such as pericytes with pluripotent nature. The immunoreactivity for A3-antigen, a marker for immature mesenchymal cells, was seen in some surrounding cells. There were no cells reacting with antibodies to nestin or glial fibrillary acidic protein, although hepatic myofibroblats have been reported to react with these antibodies. Collectively, myofibroblasts appearing in rat myocardial fibrosis may have been derived from immature mesenchymal cells positive for Thy-1 or A3-antigen, with thereafter showing expressions of vimentin and α-SMA in differentiation.

Contribution of Resident Stem Cells to Liver and Biliary Tree Regeneration in Human Diseases

Two distinct stem/progenitor cell populations of biliary origin have been identified in the adult liver and biliary tree. Hepatic Stem/progenitor Cells (HpSCs) are bipotent progenitor cells located within the canals of Hering and can be differentiated into mature hepatocytes and cholangiocytes; Biliary Tree Stem/progenitor Cells (BTSCs) are multipotent stem cells located within the peribiliary glands of large intrahepatic and extrahepatic bile ducts and able to differentiate into hepatic and pancreatic lineages. HpSCs and BTSCs are endowed in a specialized niche constituted by supporting cells and extracellular matrix compounds. The actual contribution of these stem cell niches to liver and biliary tree homeostatic regeneration is marginal; this is due to the high replicative capabilities and plasticity of mature parenchymal cells (i.e., hepatocytes and cholangiocytes). However, the study of human liver and biliary diseases disclosed how these stem cell niches are involved in the regenerative response after extensive and/or chronic injuries, with the activation of specific signaling pathways. The present review summarizes the contribution of stem/progenitor cell niches in human liver diseases, underlining mechanisms of activation and clinical implications, including fibrogenesis and disease progression.

Senescence mirrors the extent of liver fibrosis in chronic hepatitis C virus infection

BACKGROUND

Chronic viral hepatitis is linked to fibrotic liver injury that can progress to liver cirrhosis with its associated complications. Recent evidence suggests a role of senescence in liver fibrosis, although the senescence regulators contributing to fibrosis progression remain unclear.

AIM

To investigate the role of senescence and different senescence markers for fibrosis progression in patients with chronic hepatitis C virus (HCV) infection.

METHODS

The expression of the cell cycle inhibitors p21, p27 and p16 as well as the senescence markers p-HP1γ and γ-H2AX was analysed in liver tissue with different fibrosis stages. Senescence-associated chitotriosidase activity was measured in sera of HCV patients (n = 61) and age-matched healthy individuals (n = 22).

RESULTS

We found a remarkable up-regulation of the cell cycle inhibitors and senescence markers in chronic HCV infection compared to healthy liver tissue. Liver tissue with relevant fibrosis stages (F2-3) or cirrhosis (F4) revealed a significant increase in senescent cells compared to livers with no or minimal fibrosis (F0-1). In cirrhotic livers, a significantly higher number of p-HP1γ, p21 and p27 positive cells was detected compared to liver tissue with F2-3 fibrosis. Importantly, we identified T-cells as the dominant cell type contributing to increased senescence during fibrosis progression. Compared to healthy individuals, serum chitotriosidase was significantly elevated and correlated with histological fibrosis stages and liver stiffness as assessed by transient elastography.

CONCLUSIONS

Senescence of hepatic T-cells is enhanced in chronic viral hepatitis and increases with fibrosis progression. Serological detection of senescence-associated chitotriosidase might allow for the non-invasive detection of relevant fibrosis stages.

Differential expression of Lutheran/BCAM regulates biliary tissue remodeling in ductular reaction during liver regeneration

Under chronic or severe liver injury, liver progenitor cells (LPCs) of biliary origin are known to expand and contribute to the regeneration of hepatocytes and cholangiocytes. This regeneration process is called ductular reaction (DR), which is accompanied by dynamic remodeling of biliary tissue. Although the DR shows apparently distinct mode of biliary extension depending on the type of liver injury, the key regulatory mechanism remains poorly understood. Here, we show that Lutheran (Lu)/Basal cell adhesion molecule (BCAM) regulates the morphogenesis of DR depending on liver disease models. Lu⁺ and Lu^- biliary cells isolated from injured liver exhibit opposite phenotypes in cell motility and duct formation capacities in vitro. By overexpression of Lu, Lu^- biliary cells acquire the phenotype of Lu⁺ biliary cells. Lu-deficient mice showed severe defects in DR. Our findings reveal a critical role of Lu in the control of phenotypic heterogeneity of DR in distinct liver disease models.

Bile is a green to yellow liquid that the body uses to break down and digest fatty molecules. The substance is produced by the liver, and then it is collected and transported to the small bowel by a series of tubes known as the bile duct.

When the liver is damaged, the ‘biliary’ cells that line the duct orchestrate the repair of the organ. In fact, the duct often reorganizes itself differently depending on the type of disease the liver is experiencing. For example, the biliary cells can form thin tube-like structures that deeply invade liver tissues, or they can grow into several robust pipes near the existing bile duct. However, it remains largely unknown which protein – or proteins – drive these different types of remodeling.

Miura et al. find that, in mice, the biliary cells which invade an injured liver have a large amount of a protein called Lutheran at their surface, but that the cells that form robust ducts do not. This protein helps a cell attach to its surroundings. In addition, the biliary cells can adopt different types of repairing behaviors depending on the amount of Lutheran in their environment.

Further experiments show that it is difficult for genetically modified mice without the protein to reshape their bile duct after liver injury. Finally, Miura et al. also detect Lutheran in the remodeling livers of patients with liver disease. Taken together, these results suggest that Lutheran plays an important role in tailoring the repairing roles of the biliary cells to a particular disease. The next step would be to clarify how different liver conditions coordinate the amount of Lutheran in biliary cells to create the right type of remodeling.

Immunophenotypical analysis of pancreatic interstitial cells in the developing rat pancreas and myofibroblasts in the fibrotic pancreas in dogs and cats

Pancreatic fibrosis develops as the results of the activity of myofibroblasts capable of producing collagens. The myofibroblasts derive from pancreatic interstitial cells, including pancreatic stellate cells (PSCs), which can express glial fibrillary acidic protein (GFAP). First, we investigated the expression patterns of vimentin, desmin, α-smooth muscle actin (α-SMA), Thy-1 and GFAP in the developing rat pancreas (in fetuses at 18 and 20 days, neonates from 1 to 21 days, and adults). Interstitial cells in the developing pancreas expressed vimentin, desmin, GFAP and Thy-1 at varying degrees; interestingly, the reactivity for desmin and vimentin was the highest in fetuses. GFAP expression was consistent between fetuses and neonates, and Thy-1 reactivity transiently increased after birth; however, α-SMA-positive interstitial cells were rarely seen. Next, we analyzed the immunophenotypical characteristics of myofibroblasts appearing in pancreatic fibrosis in dogs and cats. With increasing fibrotic grade, myofibroblasts showed increased expression of vimentin, desmin and α-SMA, in addition to increased GFAP expression. Collectively, pancreatic interstitial cells and myofibroblasts may have similar immunophenotypes, and myofibroblasts might originate partly from GFAP-expressing PSCs.

Taurocholate Induces Biliary Differentiation of Liver Progenitor Cells Causing Hepatic Stellate Cell Chemotaxis in the Ductular Reaction: Role in Pediatric Cystic Fibrosis Liver Disease

Cystic fibrosis liver disease (CFLD) in children causes progressive fibrosis leading to biliary cirrhosis; however, its cause(s) and early pathogenesis are unclear. We hypothesized that a bile acid-induced ductular reaction (DR) drives fibrogenesis. The DR was evaluated by cytokeratin-7 immunohistochemistry in liver biopsies, staged for fibrosis, from 60 children with CFLD, and it demonstrated that the DR was significantly correlated with hepatic fibrosis stage and biliary taurocholate levels. To examine the mechanisms involved in DR induction, liver progenitor cells (LPCs) were treated with taurocholate, and key events in DR evolution were assessed: LPC proliferation, LPC biliary differentiation, and hepatic stellate cell (HSC) chemotaxis. Taurocholate induced a time-dependent increase in LPC proliferation and expression of genes associated with cholangiocyte differentiation (cytokeratin 19, connexin 43, integrin β4, and γ-glutamyltranspeptidase), whereas the hepatocyte specification marker HNF4α was suppressed. Functional cholangiocyte differentiation was demonstrated via increased acetylated α-tubulin and SOX9 proteins, the number of primary cilia⁺ LPCs, and increased active γ-glutamyltranspeptidase enzyme secretion. Taurocholate induced LPCs to release MCP-1, MIP1α, and RANTES into conditioned medium causing HSC chemotaxis, which was inhibited by anti-MIP1α. Immunofluorescence confirmed chemokine expression localized to CK7⁺ DR and LPCs in CFLD liver biopsies. This study suggests that taurocholate is involved in initiating functional LPC biliary differentiation and the development of the DR, with subsequent induction of chemokines that drive HSC recruitment in CFLD.

Serum ferritin concentration predicts hepatic fibrosis better than hepatic iron concentration in human HFE-Haemochromatosis

BACKGROUND & AIMS

Ferritin is purported to have proinflammatory and profibrogenic effects on hepatic stellate cells. Thus, rather than acting as a passive indicator of hepatic iron concentration (HIC) in haemochromatosis, ferritin may directly influence fibrosis. This study evaluated whether serum ferritin is a better predictor of hepatic fibrosis compared to variables previously associated with increased fibrosis risk in haemochromatosis.

METHODS

We identified 291 C282Y HFE-homozygous patients who had undergone liver biopsy for histological fibrosis staging and measurement of HIC. Ordinal logistic regression determined the best model for fibrosis stage not including serum ferritin. Then, serum ferritin was introduced into this model to assess whether the predictive power of the model was significantly increased and to evaluate the effect on other predictors of fibrosis.

RESULTS

Ordinal logistic regression analyses without serum ferritin demonstrated that log HIC (OR 2.89; P < .001), male gender (OR 2.93; P = .005), alcohol consumption (g/day) (OR 1.01; P = .004), steatosis (OR 2.86; P = .01), arthritis (OR 2.46; P = .01) predicted increasing fibrosis stage (n=217). Addition of serum ferritin in multivariate analysis substantially improved the predictive power of the model (χ²  = 37.15; P < .01) and was highly predictive of fibrosis stage (OR 5.44; P < .001). Inclusion of serum ferritin in this model rendered the effects of HIC, gender, alcohol and steatosis to non-significance.

CONCLUSIONS

In haemochromatosis, serum ferritin is a better predictor of fibrosis stage than HIC, gender, steatosis and alcohol. These data support a hypothesis that ferritin may play a role in fibrosis rather than simply acting as a passive indicator of iron storage.

Ductular reaction correlates with fibrogenesis but does not contribute to liver regeneration in experimental fibrosis models

Background and aims

Ductular reaction is a standard component of fibrotic liver tissue but its function is largely unknown. It is supposed to interact with the matrix producing myofibroblasts and compensate the declining regenerative capacity of hepatocytes. The relationship between the extent of fibrosis—ductular reaction, proliferative activity of hepatocytes and ductular reaction were studied sequentially in experimental hepatic fibrosis models.

Methods

Liver fibrosis/cirrhosis was induced in wild type and TGFβ overproducing transgenic mice by carbon tetrachloride and thioacetamide administration. The effect of thioacetamide was modulated by treatment with imatinib and erlotinib. The extent of ductular reaction and fibrosis was measured by morphometry following cytokeratin 19 immunofluorescent labeling and Picro Sirius staining respectively. The proliferative activity of hepatocytes and ductular reaction was evaluated by BrdU incorporation. The temporal distribution of the parameters was followed and compared within and between different experimental groups.

Results

There was a strong significant correlation between the extent of fibrosis and ductular reaction in each experimental group. Although imatinib and erlotinib temporarily decreased fibrosis this effect later disappeared. We could not observe negative correlation between the proliferation of hepatocytes and ductular reaction in any of the investigated models.

Conclusions

The stringent connection between ductular reaction and fibrosis, which cannot be influenced by any of our treatment regimens, suggests that there is a close mutual interaction between them instead of a unidirectional causal relationship. Our results confirm a close connection between DR and fibrogenesis. However, since the two parameters changed together we could not establish a causal relationship and were unable to reveal which was the primary event. The lack of inverse correlation between the proliferation of hepatocytes and ductular reaction questions that ductular reaction can compensate for the failing regenerative activity of hepatocytes. No evidences support the persistent antifibrotic property of imatinib or erlotinib.

The histological quantification of alpha-smooth muscle actin predicts future graft fibrosis in pediatric liver transplant recipients

Activated hepatic stellate cells express cytoplasmic ASMA prior to secreting collagen and consequent liver fibrosis. We hypothesized that quantifying ASMA could predict severity of future fibrosis after LT. For this, 32 pairs of protocol biopsies, that is, "baseline" and "follow-up" biopsies taken at 1- to 2-year intervals from 18 stable pediatric LT recipients, transplanted between 2006 and 2012 were selected. Morphometric quantification of "ASMA-positive area percentage" was performed on the baseline biopsy. Histological and fibrosis assessment using Metavir and LAFSc was performed on all biopsies. The difference of fibrosis severity between the "baseline" and "follow-up" was termed "prospective change in fibrosis." Significant association was seen between extent of ASMA positivity on baseline biopsy and "prospective change in fibrosis" using Metavir (P=.02), cumulative LAFSc (P=.02), and portal LAFSc (P=.01) values. ASMA-positive area percentage >1.05 predicted increased fibrosis on next biopsy with 90.0% specificity. Additionally, an association was observed between extent of ASMA positivity and concomitant ductular reaction (P=.06), but not with histological inflammation in the portal tract or lobular area. Hence, ASMA quantification can predict the future course of fibrosis.

Cytokeratin19 positive hepatocellular carcinoma is associated with increased peritumoral ductular reaction

BACKGROUND AND AIMS

Cytokeratin19 positive (CK19+) hepatocellular carcinoma (HCC) is thought to derive from liver progenitor cells (LPC). However, whether peritumoralductular reaction (DR) differs between CK19+ and CK19 negative (CK19-) HCC patients remains unclear.

MATERIAL AND METHODS

One hundred and twenty HBV-related HCC patients were enrolled in this study. Clinicopathological variables were collected, and immunohistochemistry staining for CK19, proliferating cell nuclear antigen (PCNA), interleukin-6 (IL-6) and β-catenin were performed in tumor and peritumor liver tissues.

RESULTS

CK19+ HCC patients had higher grade of peritumoral DR and proportion of proliferative DR than the CK19- group. The mean number or the proportion of cytoplasmic β-catenin+ DR was higher in the CK19+ group than in the CK19- group. Furthermore, there were more patients with nuclear β-catenin+ peritumoral DR in the CK19+ group as compared to the CK19- group.

CONCLUSION

Peritumoral DR was more abundant and proliferative in CK19+ HCC patients, with higher level of nuclear translocation of β-catenin. However, it is unclear whether peritumoral DR is the cause or result of poor prognosis in these patients.

Members of the Cyr61/CTGF/NOV Protein Family: Emerging Players in Hepatic Progenitor Cell Activation and Intrahepatic Cholangiocarcinoma

Hepatic stem/progenitor cells (HPC) reside quiescently in normal biliary trees and are activated in the form of ductular reactions during severe liver damage when the replicative ability of hepatocytes is inhibited. HPC niches are full of profibrotic stimuli favoring scarring and hepatocarcinogenesis. The Cyr61/CTGF/NOV (CCN) protein family consists of six members, CCN1/CYR61, CCN2/CTGF, CCN3/NOV, CCN4/WISP1, CCN5/WISP2, and CCN6/WISP3, which function as extracellular signaling modulators to mediate cell-matrix interaction during angiogenesis, wound healing, fibrosis, and tumorigenesis. This study investigated expression patterns of CCN proteins in HPC and cholangiocarcinoma (CCA). Mouse HPC were induced by the biliary toxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). Differential expression patterns of CCN proteins were found in HPC from DDC damaged mice and in human CCA tumors. In addition, we utilized reporter mice that carried Ccn2/Ctgf promoter driven GFP and detected strong Ccn2/Ctgf expression in epithelial cell adhesion molecule (EpCAM)⁺ HPC under normal conditions and in DDC-induced liver damage. Abundant CCN2/CTGF protein was also found in cytokeratin 19 (CK19)⁺ human HPC that were surrounded by α-smooth muscle actin (α-SMA)⁺ myofibroblast cells in intrahepatic CCA tumors. These results suggest that CCN proteins, particularly CCN2/CTGF, function in HPC activation and CCA development.

Senescence in chronic liver disease: Is the future in aging?

Cellular senescence is a fundamental, complex mechanism with an important protective role present from embryogenesis to late life across all species. It limits the proliferative potential of damaged cells thus protecting against malignant change, but at the expense of substantial alterations to the microenvironment and tissue homeostasis, driving inflammation, fibrosis and paradoxically, malignant disease if the process is sustained. Cellular senescence has attracted considerable recent interest with recognition of pathways linking aging, malignancy and insulin resistance and the current focus on therapeutic interventions to extend health-span. There are major implications for hepatology in the field of fibrosis and cancer, where cellular senescence of hepatocytes, cholangiocytes, stellate cells and immune cells has been implicated in chronic liver disease progression. This review focuses on cellular senescence in chronic liver disease and explores therapeutic opportunities.

Stem/progenitor cells in liver regeneration

In severely or chronically injured livers where the proliferative capacity of hepatocytes is compromised, putative stem/progenitor cells are supposed to be activated. These cells are generally characterized as biliary epithelial cell marker-positive cells that emerge ectopically in the parenchymal region of the liver, as determined by histopathological examination of various liver diseases in humans and animal models. Whereas the biliary system indeed harbors cells with stem/progenitor activity that can be defined ex vivo, genetic lineage tracing studies in mice have casted doubt on their exact contribution as the genuine stem/progenitor cell population that differentiates in situ into hepatocytes. Here, I briefly review recent advances in the characterization and certification of the stem/progenitor cells in the adult liver and discuss the ongoing and future challenges to further our understanding of the cellular basis of liver regeneration. (Hepatology 2016;64:663-668).

The role of liver progenitor cells during liver regeneration, fibrogenesis, and carcinogenesis

The growing worldwide challenge of cirrhosis and hepatocellular carcinoma due to increasing prevalence of excessive alcohol consumption, viral hepatitis, obesity, and the metabolic syndrome has sparked interest in stem cell-like liver progenitor cells (LPCs) as potential candidates for cell therapy and tissue engineering, as an alternative approach to whole organ transplantation. However, LPCs always proliferate in chronic liver diseases with a predisposition to cancer; they have been suggested to play major roles in driving fibrosis, disease progression, and may even represent tumor-initiating cells. Hence, a greater understanding of the factors that govern their activation, communication with other hepatic cell types, and bipotential differentiation as opposed to their potential transformation is needed before their therapeutic potential can be harnessed.

Stem/Progenitor Cell Niches Involved in Hepatic and Biliary Regeneration

Niches containing stem/progenitor cells are present in different anatomical locations along the human biliary tree and within liver acini. The most primitive stem/progenitors, biliary tree stem/progenitor cells (BTSCs), reside within peribiliary glands located throughout large extrahepatic and intrahepatic bile ducts. BTSCs are multipotent and can differentiate towards hepatic and pancreatic cell fates. These niches' matrix chemistry and other characteristics are undefined. Canals of Hering (bile ductules) are found periportally and contain hepatic stem/progenitor cells (HpSCs), participating in the renewal of small intrahepatic bile ducts and being precursors to hepatocytes and cholangiocytes. The niches also contain precursors to hepatic stellate cells and endothelia, macrophages, and have a matrix chemistry rich in hyaluronans, minimally sulfated proteoglycans, fetal collagens, and laminin. The microenvironment furnishes key signals driving HpSC activation and differentiation. Newly discovered third niches are pericentral within hepatic acini, contain Axin2+ unipotent hepatocytic progenitors linked on their lateral borders to endothelia forming the central vein, and contribute to normal turnover of mature hepatocytes. Their relationship to the other stem/progenitors is undefined. Stem/progenitor niches have important implications in regenerative medicine for the liver and biliary tree and in pathogenic processes leading to diseases of these tissues.

Spatiotemporal Characterization of the Cellular and Molecular Contributors to Liver Fibrosis in a Murine Hepatotoxic-Injury Model

The interplay between the inflammatory infiltrate and tissue resident cell populations invokes fibrogenesis. However, the temporal and mechanistic contributions of these cells to fibrosis are obscure. To address this issue, liver inflammation, ductular reaction (DR), and fibrosis were induced in C57BL/6 mice by thioacetamide administration for up to 12 weeks. Thioacetamide treatment induced two phases of liver fibrosis. A rapid pericentral inflammatory infiltrate enriched in F4/80(+) monocytes co-localized with SMA(+) myofibroblasts resulted in early collagen deposition, marking the start of an initial fibrotic phase (1 to 6 weeks). An expansion of bone marrow-derived macrophages preceded a second phase, characterized by accelerated progression of fibrosis (>6 weeks) after DR migration from the portal tracts to the centrilobular site of injury, in association with an increase in DR/macrophage interactions. Although chemokine (C-C motif) ligand 2 (CCL2) mRNA was induced rapidly in response to thioacetamide, CCL2 deficiency only partially abrogated fibrosis. In contrast, colony-stimulating factor 1 receptor blockade diminished C-C chemokine receptor type 2 [CCR2(neg) (Ly6C(lo))] monocytes, attenuated the DR, and significantly reduced fibrosis, illustrating the critical role of colony-stimulating factor 1-dependent monocyte/macrophage differentiation and linking the two phases of injury. In response to liver injury, colony-stimulating factor 1 drives early monocyte-mediated myofibroblast activation and collagen deposition, subsequent macrophage differentiation, and their association with the advancing DR, the formation of fibrotic septa, and the progression of liver fibrosis to cirrhosis.

Increased Autophagy Markers Are Associated with Ductular Reaction during the Development of Cirrhosis

Autophagy is a regulatory pathway in liver fibrosis. We investigated the roles of autophagy in human cirrhotic livers. Cirrhotic and noncirrhotic liver tissues were obtained from patients with hepatocellular carcinoma, and liver tissues from live donors served as control. Patients with cirrhotic livers had significantly increased levels of various essential autophagy-related genes compared with noncirrhotic livers. In addition, colocalization of autophagy marker microtubule-associated protein 1 light chain 3B (LC3B) with lysosome-associated membrane protein-1, increased levels of lysosome-associated membrane protein-2, and increased maturation of lysosomal cathepsin D were observed in cirrhotic livers. By using dual-immunofluorescence staining, we demonstrated that increased LC3B was located mainly in the cytokeratin 19-labeled ductular reaction (DR) in human cirrhotic livers and in an experimental cirrhosis induced by 2-acetylaminofluorene (AAF) with carbon tetrachloride (CCl4), indicating a conserved response to chronic liver damage. Furthermore, an AAF/CCl4-mediated increase in DR and fibrosis were attenuated after chloroquine treatment, suggesting that the autophagy-lysosome pathway was essential for AAF/CCl4-induced DR-fibrosis. In conclusion, we demonstrated that increased autophagy marker positively correlated with DR during the development of cirrhosis. Therefore, targeting autophagy may hold therapeutic value for liver cirrhosis.

Osteopontin neutralisation abrogates the liver progenitor cell response and fibrogenesis in mice

BACKGROUND

Chronic liver injury triggers a progenitor cell repair response, and liver fibrosis occurs when repair becomes deregulated. Previously, we reported that reactivation of the hedgehog pathway promotes fibrogenic liver repair. Osteopontin (OPN) is a hedgehog-target, and a cytokine that is highly upregulated in fibrotic tissues, and regulates stem-cell fate. Thus, we hypothesised that OPN may modulate liver progenitor cell response, and thereby, modulate fibrotic outcomes. We further evaluated the impact of OPN-neutralisation on murine liver fibrosis.

METHODS

Liver progenitors (603B and bipotential mouse oval liver) were treated with OPN-neutralising aptamers in the presence or absence of transforming growth factor (TGF)-β, to determine if (and how) OPN modulates liver progenitor function. Effects of OPN-neutralisation (using OPN-aptamers or OPN-neutralising antibodies) on liver progenitor cell response and fibrogenesis were assessed in three models of liver fibrosis (carbon tetrachloride, methionine-choline deficient diet, 3,5,-diethoxycarbonyl-1,4-dihydrocollidine diet) by quantitative real time (qRT) PCR, Sirius-Red staining, hydroxyproline assay, and semiquantitative double-immunohistochemistry. Finally, OPN expression and liver progenitor response were corroborated in liver tissues obtained from patients with chronic liver disease.

RESULTS

OPN is overexpressed by liver progenitors in humans and mice. In cultured progenitors, OPN enhances viability and wound healing by modulating TGF-β signalling. In vivo, OPN-neutralisation attenuates the liver progenitor cell response, reverses epithelial-mesenchymal-transition in Sox9+ cells, and abrogates liver fibrogenesis.

CONCLUSIONS

OPN upregulation during liver injury is a conserved repair response, and influences liver progenitor cell function. OPN-neutralisation abrogates the liver progenitor cell response and fibrogenesis in mouse models of liver fibrosis.

Two sides of one coin: massive hepatic necrosis and progenitor cell-mediated regeneration in acute liver failure

Massive hepatic necrosis is a key event underlying acute liver failure, a serious clinical syndrome with high mortality. Massive hepatic necrosis in acute liver failure has unique pathophysiological characteristics including extremely rapid parenchymal cell death and removal. On the other hand, massive necrosis rapidly induces the activation of liver progenitor cells, the so-called "second pathway of liver regeneration." The final clinical outcome of acute liver failure depends on whether liver progenitor cell-mediated regeneration can efficiently restore parenchymal mass and function within a short time. This review summarizes the current knowledge regarding massive hepatic necrosis and liver progenitor cell-mediated regeneration in patients with acute liver failure, the two sides of one coin.

Hepatocyte buds derived from progenitor cells repopulate regions of parenchymal extinction in human cirrhosis

Repair of cirrhotic livers occurs, in part, by repopulation with hepatocytes through the stem/progenitor pathway. There remain many uncertainties regarding this pathway. Hepatocyte "buds" occurring in broad septa are hypothesized to be the anatomic manifestation of this pathway. Our purpose was to define a morphologic sequence of bud maturation to allow a quantitative measure of the importance of the stem/progenitor pathway in humans. Histologic sections from 37 liver resection specimens were stained with trichrome, epithelial cell adhesion molecule (EpCAM), K19, CD34, glutamine synthetase (GS), and Ki-67. Specimens were stratified by etiology (10 biliary, 22 nonbiliary, five controls) and stage. Buds were defined as clusters of hepatocytes within septa. Five levels of bud maturation (0-4) were defined by the progressive increase in hepatocyte progeny relative to cholangiocytes. Level 0 single-cell buds are K19(+) /GS(+) /EpCAM(+) /Heppar1(-) . In level 1, the progeny are morphologically hepatocytes (K19(-) /GS(+) /EpCAM(+) /Heppar1(+) ). In level 2-4 buds, hepatocytes increase and become progressively GS(-) and EpCAM(-) . Associated endothelium is CD34(+) in level 1-2 buds and becomes CD34(-) near hepatic veins in level 3-4 buds. Progeny of the bud sequence may represent up to 70% of hepatocytes (immaturity index of 70%). In biliary disease, bud number is reduced in association with duct loss and cholestatic destruction of nascent buds.

CONCLUSIONS

The stem/progenitor pathway, manifested anatomically by the bud sequence, is a major mechanism for repopulation of cirrhotic livers. The bud sequence reveals some critical features of hepatic morphogenesis, including that 1) the majority of distal cholangiocytes have stem-like properties, and 2) availability of bile ducts and/or venous drainage are limiting factors for regeneration.