Cytoglobin is expressed in hepatic stellate cells, but not in myofibroblasts, in normal and fibrotic human liver

SIRT1 activation ameliorates rhesus monkey liver fibrosis by inhibiting the TGF-β/smad signaling pathway

TGF-β/Smad signaling pathway plays an important role in the pathogenesis and progression of liver fibrosis. Silent information regulator 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+) dependent enzyme and responsible for deacetylating the proteins. Increasing numbers of reports have shown that the molecular mechanism of SIRT1 as an effective therapeutic target for liver fibrosis but the transformation is not very clear. In the present study, liver fibrotic tissues were screened by staining with Masson, hematoxylin-eosin staining (H&E) and Immunohistochemistry (IHC) for histopathological observation from the liver biopsy of seventy-seven rhesus monkey, which fixed with 4% paraformaldehyde (PFA) after treatment with high-fat diet (HFD) for two years. And the liver function was further determined by serum biochemical tests. The mRNA levels and protein expression of rat hepatic stellate (HSC-T6) cells were determined after treatment with Resveratrol (RSV) and Nicotinamide (NAM), respectively. The results showed that with the increasing of hepatic fibrosis in rhesus monkeys, the liver function impaired, and the transforming growth factor-β1 (TGF-β1), p-Smad3 (p-Smad3) and alpha-smooth muscle actin (α-SMA) was up-regulated, while SIRT1 and Smad7 were down-regulated. Moreover, when stimulated the HSC-T6 with RSV to activate SIRT1 for 6, 12, and 24 h, the results showed that RSV promoted the expression of smad7, while the expression of TGF-β1, p-Smad3 and α-SMA were inhibited. In contrast, when the cells stimulated with NAM to inhibit SIRT1 for 6, 12, and 24 h, the Smad7 expression was decreased, while TGF-β1, p-Smad3, and α-SMA expressions were increased. These results indicate that SIRT1 acts as an important protective factor for liver fibrosis, which may be attributed to inhibiting the signaling pathway of TGF-β/Smad in hepatic fibrosis of the rhesus monkey.

Molecular analysis of the human cytoglobin mRNA isoforms

Multiple functions have been proposed for the ubiquitously expressed vertebrate globin cytoglobin (Cygb), including nitric oxide (NO) metabolism, lipid peroxidation/signalling, superoxide dismutase activity, reactive oxygen/nitrogen species (RONS) scavenging, regulation of blood pressure, antifibrosis, and both tumour suppressor and oncogenic effects. Since alternative splicing can expand the biological roles of a gene, we investigated whether this mechanism contributes to the functional diversity of Cygb. By mining of cDNA data and molecular analysis, we identified five alternative mRNA isoforms for the human CYGB gene (V-1 to V-5). Comprehensive RNA-seq analyses of public datasets from human tissues and cells confirmed that the canonical CYGB V-1 isoform is the primary CYGB transcript in the majority of analysed datasets. Interestingly, we revealed that isoform V-3 represented the predominant CYGB variant in hepatoblastoma (HB) cell lines and in the majority of analysed normal and HB liver tissues. CYGB V-3 mRNA is transcribed from an alternate upstream promoter and hypothetically encodes a N-terminally truncated CYGB protein, which is not recognized by some antibodies used in published studies. Little to no transcriptional evidence was found for the other CYGB isoforms. Comparative transcriptomics and flow cytometry on CYGB+/+ and gene-edited CYGB-/- HepG2 HB cells did not unveil a knockout phenotype and, thus, a potential function for CYGB V-3. Our study reveals that the CYGB gene is transcriptionally more complex than previously described as it expresses alternative mRNA isoforms of unknown function. Additional experimental data are needed to clarify the biological meaning of those alternative CYGB transcripts.

Transcriptomics of a cytoglobin knockout mouse: Insights from hepatic stellate cells and brain

The vertebrate respiratory protein cytoglobin (Cygb) is thought to exert multiple cellular functions. Here we studied the phenotypic effects of a Cygb knockout (KO) in mouse on the transcriptome level. RNA sequencing (RNA-Seq) was performed for the first time on sites of major endogenous Cygb expression, i.e. quiescent and activated hepatic stellate cells (HSCs) and two brain regions, hippocampus and hypothalamus. The data recapitulated the up-regulation of Cygb during HSC activation and its expression in the brain. Differential gene expression analyses suggested a role of Cygb in the response to inflammation in HSCs and its involvement in retinoid metabolism, retinoid X receptor (RXR) activation-induced xenobiotics metabolism, and RXR activation-induced lipid metabolism and signaling in activated cells. Unexpectedly, only minor effects of the Cygb KO were detected in the transcriptional profiles in hippocampus and hypothalamus, precluding any enrichment analyses. Furthermore, the transcriptome data pointed at a previously undescribed potential of the Cygb- knockout allele to produce cis-acting effects, necessitating future verification studies.

The knockout of cytoglobin 1 in zebrafish (Danio rerio) alters lipid metabolism, iron homeostasis and oxidative stress response

Cytoglobin (Cygb) is an evolutionary ancient heme protein with yet unclear physiological function(s). Mammalian Cygb is ubiquitously expressed in all tissues and is proposed to be involved in reactive oxygen species (ROS) detoxification, nitric oxide (NO) metabolism and lipid-based signaling processes. Loss-of-function studies in mouse associate Cygb with apoptosis, inflammation, fibrosis, cardiovascular dysfunction or oncogenesis. In zebrafish (Danio rerio), two cygb genes exist, cytoglobin 1 (cygb1) and cytoglobin 2 (cygb2). Both have different coordination states and distinct expression sites within zebrafish tissues. The biological roles of the cygb paralogs are largely uncharacterized. We used a CRISPR/Cas9 genome editing approach and generated a knockout of the penta-coordinated cygb1 for in vivo analysis. Adult male cygb1 knockouts develop phenotypic abnormalities, including weight loss. To identify the molecular mechanisms underlying the occurrence of these phenotypes and differentiate between function and effect of the knockout we compared the transcriptomes of cygb1 knockout at different ages to age-matched wild-type zebrafish. We found that immune regulatory and cell cycle regulatory transcripts (e.g. tp53) were up-regulated in the cygb1 knockout liver. Additionally, the expression of transcripts involved in lipid metabolism and transport, the antioxidative defense and iron homeostasis was affected in the cygb1 knockout. Cygb1 may function as an anti-inflammatory and cytoprotective factor in zebrafish liver, and may be involved in lipid-, iron-, and ROS-dependent signaling.

Extracellular matrix turnover: phytochemicals target and modulate the dual role of matrix metalloproteinases (MMPs) in liver fibrosis

Extracellular matrix (ECM) resolution by matrix metalloproteinases (MMPs) is a well-documented mechanism. MMPs play a dual and complex role in modulating ECM degradation at different stages of liver fibrosis, depending on the timing and levels of their expression. Increased MMP-1 combats disease progression by cleaving the fibrillar ECM. Activated hepatic stellate cells (HSCs) increase expression of MMP-2, -9, and -13 in different chemicals-induced animal models, which may alleviate or worsen disease progression based on animal models and the stage of liver fibrosis. In the early stage, elevated expression of certain MMPs may damage surrounding tissue and activate HSCs, promoting fibrosis progression. At the later stage, downregulation of MMPs can facilitate ECM accumulation and disease progression. A number of phytochemicals modulate MMP activity and ECM turnover, alleviating disease progression. However, the effects of phytochemicals on the expression of different MMPs are variable and may depend on the disease models and stage, and the dosage, timing and duration of phytochemicals used in each study. Here, we review the most recent advances in the role of MMPs in the effects of phytochemicals on liver fibrogenesis, which indicates that further studies are warranted to confirm and define the potential clinical efficacy of these phytochemicals.

Cytoglobin attenuates pancreatic cancer growth via scavenging reactive oxygen species

Pancreatic cancer is a highly challenging malignancy with extremely poor prognosis. Cytoglobin (CYGB), a hemeprotein involved in liver fibrosis and cancer development, is expressed in pericytes of all organs. Here, we examined the role of CYGB in the development of pancreatic cancer. CYGB expression appeared predominately in the area surrounding adenocarcinoma and negatively correlated with tumor size in patients with pancreatic cancer. Directly injecting 7, 12-dimethylbenz[a]anthracene into the pancreatic tail in wild-type mice resulted in time-dependent induction of severe pancreatitis, fibrosis, and oxidative damage, which was rescued by Cygb overexpression in transgenic mice. Pancreatic cancer incidence was 93% in wild-type mice but only 55% in transgenic mice. Enhanced CYGB expression in human pancreatic stellate cells in vitro reduced cellular collagen synthesis, inhibited cell activation, increased expression of antioxidant-related genes, and increased CYGB secretion into the medium. Cygb-overexpressing or recombinant human CYGB (rhCYGB) -treated MIA PaCa-2 cancer cells exhibited dose-dependent cell cycle arrest at the G1 phase, diminished cell migration, and reduction in colony formation. RNA sequencing in rhCYGB-treated MIA PaCa-2 cells revealed downregulation of cell cycle and oxidative phosphorylation pathways. An increase in MIA PaCa-2 cell proliferation and reactive oxygen species production by H₂O₂ challenge was blocked by rhCYGB treatment or Cygb overexpression. PANC-1, OCUP-A2, and BxPC-3 cancer cells showed similar responses to rhCYGB. Known antioxidants N-acetyl cysteine and glutathione also inhibited cancer cell growth. These results demonstrate that CYGB suppresses pancreatic stellate cell activation, pancreatic fibrosis, and tumor growth, suggesting its potential therapeutic application against pancreatic cancer.

Inhibition of Hepatic Stellate Cell Activation Suppresses Tumorigenicity of Hepatocellular Carcinoma in Mice

Transdifferentiation (or activation) of hepatic stellate cells (HSCs) to myofibroblasts is a key event in liver fibrosis. Activated HSCs in the tumor microenvironment reportedly promote tumor progression. This study analyzed the effect of an inhibitor of HSC activation, retinol-binding protein–albumin domain III fusion protein (R-III), on protumorigenic functions of HSCs. Although conditioned medium collected from activated HSCs enhanced the migration, invasion, and proliferation of the hepatocellular carcinoma cell line Hepa-1c1c7, this effect was not observed in Hepa-1c1c7 cells treated with conditioned medium from R-III–exposed HSCs. In a subcutaneous tumor model, larger tumors with increased vascular density were formed in mice transplanted with Hepa-1c1c7+HSC than in mice transplanted with Hepa-1c1c7 cells alone. Intriguingly, when Hepa-1c1c7+HSC–transplanted mice were injected intravenously with R-III, a reduction in vascular density and extended tumor necrosis were observed. In an orthotopic tumor model, co-transplantation of HSCs enhanced tumor growth, angiogenesis, and regional metastasis accompanied by increased peritumoral lymphatic vessel density, which was abolished by R-III. In vitro study showed that R-III treatment affected the synthesis of pro-angiogenic and anti-angiogenic factors in activated HSCs, which might be the potential mechanism underlying the R-III effect. These findings suggest that the inhibition of HSC activation abrogates HSC-induced tumor angiogenesis and growth, which represents an attractive therapeutic strategy.

Hexa Histidine-Tagged Recombinant Human Cytoglobin Deactivates Hepatic Stellate Cells and Inhibits Liver Fibrosis by Scavenging Reactive Oxygen Species

BACKGROUND AND AIMS

Antifibrotic therapy remains an unmet medical need in human chronic liver disease. We report the antifibrotic properties of cytoglobin (CYGB), a respiratory protein expressed in hepatic stellate cells (HSCs), the main cell type involved in liver fibrosis.

APPROACH AND RESULTS

Cygb-deficient mice that had bile duct ligation-induced liver cholestasis or choline-deficient amino acid-defined diet-induced steatohepatitis significantly exacerbated liver damage, fibrosis, and reactive oxygen species (ROS) formation. All of these manifestations were attenuated in Cygb-overexpressing mice. We produced hexa histidine-tagged recombinant human CYGB (His-CYGB), traced its biodistribution, and assessed its function in HSCs or in mice with advanced liver cirrhosis using thioacetamide (TAA) or 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). In cultured HSCs, extracellular His-CYGB was endocytosed and accumulated in endosomes through a clathrin-mediated pathway. His-CYGB significantly impeded ROS formation spontaneously or in the presence of ROS inducers in HSCs, thus leading to the attenuation of collagen type 1 alpha 1 production and α-smooth muscle actin expression. Replacement the iron center of the heme group with cobalt nullified the effect of His-CYGB. In addition, His-CYGB induced interferon-β secretion by HSCs that partly contributed to its antifibrotic function. Momelotinib incompletely reversed the effect of His-CYGB. Intravenously injected His-CYGB markedly suppressed liver inflammation, fibrosis, and oxidative cell damage in mice administered TAA or DDC mice without adverse effects. RNA-sequencing analysis revealed the down-regulation of inflammation- and fibrosis-related genes and the up-regulation of antioxidant genes in both cell culture and liver tissues. The injected His-CYGB predominantly localized to HSCs but not to macrophages, suggesting specific targeting effects. His-CYGB exhibited no toxicity in chimeric mice with humanized livers.

CONCLUSIONS

His-CYGB could have antifibrotic clinical applications for human chronic liver diseases.

Hepatic stellate cells - from past till present: morphology, human markers, human cell lines, behavior in normal and liver pathology

Hepatic stellate cell (HSC), initially analyzed by von Kupffer, in 1876, revealed to be an extraordinary mesenchymal cell, essential for both hepatocellular function and lesions, being the hallmark of hepatic fibrogenesis and carcinogenesis. Apart from their implications in hepatic injury, HSCs play a vital role in liver development and regeneration, xenobiotic response, intermediate metabolism, and regulation of immune response. In this review, we discuss the current state of knowledge regarding HSCs morphology, human HSCs markers and human HSC cell lines. We also summarize the latest findings concerning their roles in normal and liver pathology, focusing on their impact in fibrogenesis, chronic viral hepatitis and liver tumors.

Single-cell RNA sequencing of human liver reveals hepatic stellate cell heterogeneity

Background & Aims

The multiple vital functions of the human liver are performed by highly specialised parenchymal and non-parenchymal cells organised in complex collaborative sinusoidal units. Although crucial for homeostasis, the cellular make-up of the human liver remains to be fully elucidated. Here, single-cell RNA-sequencing was used to unravel the heterogeneity of human liver cells, in particular of hepatocytes (HEPs) and hepatic stellate cells (HSCs).

Method

The transcriptome of ~25,000 freshly isolated human liver cells was profiled using droplet-based RNA-sequencing. Recently published data sets and RNA in situ hybridisation were integrated to validate and locate newly identified cell populations.

Results

In total, 22 cell populations were annotated that reflected the heterogeneity of human parenchymal and non-parenchymal liver cells. More than 20,000 HEPs were ordered along the portocentral axis to confirm known, and reveal previously undescribed, zonated liver functions. The existence of 2 subpopulations of human HSCs with unique gene expression signatures and distinct intralobular localisation was revealed (i.e. portal and central vein-concentrated GPC3⁺ HSCs and perisinusoidally located DBH⁺ HSCs). In particular, these data suggest that, although both subpopulations collaborate in the production and organisation of extracellular matrix, GPC3⁺ HSCs specifically express genes involved in the metabolism of glycosaminoglycans, whereas DBH⁺ HSCs display a gene signature that is reminiscent of antigen-presenting cells.

Conclusions

This study highlights metabolic zonation as a key determinant of HEP transcriptomic heterogeneity and, for the first time, outlines the existence of heterogeneous HSC subpopulations in the human liver. These findings call for further research on the functional implications of liver cell heterogeneity in health and disease.

Lay summary

This study resolves the cellular landscape of the human liver in an unbiased manner and at high resolution to provide new insights into human liver cell biology. The results highlight the physiological heterogeneity of human hepatic stellate cells.

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A cell atlas from the near-native transcriptome of >25,000 human liver cells is presented.

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Hepatocytes were ordered along the portocentral axis to reveal previously undescribed gene expression patterns and zonated liver functions.

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Two subpopulations of human hepatic stellate cells (HSCs) are reported, characterised by different spatial distribution in the native tissue.

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Characteristic gene signatures of HSC subpopulations are suggestive of far-reaching functional differences.

The Tumor Microenvironment in Liver Metastases from Colorectal Carcinoma in the Context of the Histologic Growth Patterns

Colorectal carcinoma (CRC) is the third most common cancer. Likewise, it is a disease that has a long survival if it is prematurely detected. However, more than 50% of patients will develop metastases, mainly in the liver (LM-CRC), throughout the evolution of their disease, which accounts for most CRC-related deaths. Treatment it is certainly a controversial issue, since it has not been shown to increase overall survival in the adjuvant setting, although it does improve disease free survival (DFS). Moreover, current chemotherapy combinations are administered based on data extrapolated from primary tumors (PT), not considering that LM-CRC present a very particular tumor microenvironment that can radically condition the effectiveness of treatments designed for a PT. The liver has a particular histology and microenvironment that can determine tumor growth and response to treatments: double blood supply, vascularization through fenestrated sinusoids and the presence of different mesenchymal cell types, among other particularities. Likewise, the liver presents a peculiar immune response against tumor cells, a fact that correlates with the poor response to immunotherapy. All these aspects will be addressed in this review, putting them in the context of the histological growth patterns of LM-CRC, a particular pathologic feature with both prognostic and predictive repercussions.

Comprehensive analysis of liver and blood miRNA in precancerous conditions

Streptozotocin administration to mice (STZ-mice) induces type I diabetes and hepatocellular carcinoma (HCC). We attempted to elucidate the carcinogenic mechanism and the miRNA expression status in the liver and blood during the precancerous state. Serum and liver tissues were collected from STZ-mice and non-treated mice (CTL-mice) at 6, 10, and 12 W. The exosome enriched fraction extracted from serum was used. Hepatic histological examination and hepatic and exosomal miRNA expression analysis were serially performed using next-generation sequencing (NGS). Human miRNA expression analysis of chronic hepatitis liver tissue and exosomes, which were collected before starting the antiviral treatment, were also performed. No inflammation or fibrosis was found in the liver of CTL-mice during the observation period. In STZ-mice, regeneration and inflammation of hepatocytes was found at 6 W and nodules of atypical hepatocytes were found at 10 and 12 W. In the liver tissue, during 6-12 W, the expression levels of let-7f-5p, miR-143-3p, 148a-3p, 191-5p, 192-5p, 21a-5p, 22-3p, 26a-5p, and 92a-3p was significantly increased in STZ-mice, and anti-oncogenes of their target gene candidates were down-regulated. miR-122-5p was also significantly down-regulated in STZ-mice. Fifteen exosomal miRNAs were upregulated in STZ-mice. Six miRNAs (let-7f-5p, miR-10b-5p, 143-3p, 191-5p, 21a-5p, and 26a-5p) were upregulated, similarly to human HCC cases. From the precancerous state, aberrant expression of hepatic miRNAs has already occurred, and then, it can promote carcinogenesis. In exosomes, the expression pattern of common miRNAs between mice and humans before carcinogenesis was observed and can be expected to be developed as a cancer predictive marker.

TGF-β1-driven reduction of cytoglobin leads to oxidative DNA damage in stellate cells during non-alcoholic steatohepatitis

BACKGROUND & AIMS

Cytoglobin (CYGB) is a respiratory protein that acts as a scavenger of reactive oxygen species. The molecular role of CYGB in human hepatic stellate cell (HSC) activation and human liver disease remains uncharacterised. The aim of this study was to reveal the mechanism by which the TGF-β1/SMAD2 pathway regulates the human CYGB promoter and the pathophysiological function of CYGB in human non-alcoholic steatohepatitis (NASH).

METHODS

Immunohistochemical staining was performed using human NASH biopsy specimens. Molecular and biochemical analyses were performed by western blotting, quantitative PCR, and luciferase and immunoprecipitation assays. Hydroxyl radicals (^•OH) and oxidative DNA damage were measured using an ^•OH-detectable probe and 8-hydroxy-2'-deoxyguanosine (8-OHdG) ELISA.

RESULTS

In culture, TGF-β1-pretreated human HSCs exhibited lower CYGB levels - together with increased NADPH oxidase 4 (NOX4) expression - and were primed for H₂O₂-triggered ^•OH production and 8-OHdG generation; overexpression of human CYGB in human HSCs reversed these effects. Electron spin resonance demonstrated the direct ^•OH scavenging activity of recombinant human CYGB. Mechanistically, pSMAD2 reduced CYGB transcription by recruiting the M1 repressor isoform of SP3 to the human CYGB promoter at nucleotide positions ⁺2-⁺13 from the transcription start site. The same repression did not occur on the mouse Cygb promoter. TGF-β1/SMAD3 mediated αSMA and collagen expression. Consistent with observations in cultured human HSCs, CYGB expression was negligible, but 8-OHdG was abundant, in activated αSMA⁺pSMAD2⁺- and αSMA⁺NOX4⁺-positive hepatic stellate cells from patients with NASH and advanced fibrosis.

CONCLUSIONS

Downregulation of CYGB by the TGF-β1/pSMAD2/SP3-M1 pathway brings about ^•OH-dependent oxidative DNA damage in activated hepatic stellate cells from patients with NASH.

LAY SUMMARY

Cytoglobin (CYGB) is a respiratory protein that acts as a scavenger of reactive oxygen species and protects cells from oxidative DNA damage. Herein, we show that the cytokine TGF-β1 downregulates human CYGB expression. This leads to oxidative DNA damage in activated hepatic stellate cells. Our findings provide new insights into the relationship between CYGB expression and the pathophysiology of fibrosis in patients with non-alcoholic steatohepatitis.

Cytoglobin-expressing cells in the splenic cords contribute to splenic fibrosis in cirrhotic patients

BACKGROUND AND AIM

Among several noninvasive evaluation methods of portal hypertension (PH), the measurement of spleen stiffness is a reliable method for predicting esophageal variceal bleeding; however, the underlying mechanisms for increased stiffness remain unclear. We attempted to elucidate the pathological changes to the spleen and the underlying mechanisms in patients with PH.

METHODS

Histological examination was performed using splenic tissues from 42 patients with PH who underwent laparoscopic splenectomy, and the results were compared with those from patients without PH.

RESULTS

In addition to splenic sinus congestion, diffuse fibrosis was detected in the splenic cords in the red pulp of patients with PH. The degree of the fibrosis was well correlated with severity in thrombocytopenia and splenomegaly. Cells expressing α-smooth muscle actin dramatically increased in the splenic cord. Cytoglobin (Cygb) expression was detected in human splenic cords as reported in animal reticular cells, and fluorescent double immunostaining revealed that these cells expressed α-smooth muscle actin in patients with PH, suggesting transformation of Cygb-expressing cells to myofibroblastic cells. Expression levels of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 2, nitrotyrosine, and transforming growth factor-β were markedly upregulated in the red pulp of patients with PH, implying a significant role of oxidative stress in the mechanism for splenic fibrosis.

CONCLUSION

Splenic fibrosis progresses along with advancement of PH. Cygb-expressing cells in the splenic cord possibly participate in this process through mechanisms including oxidative stress.

Stellate Cells in the Tumor Microenvironment

As tumor microenvironments share many of the same qualities as chronic wounds, attention is turning to the wound-repair cells that support the growth of cancerous cells. Stellate cells are star-shaped cells that were first discovered in the perisinusoidal spaces in the liver and have been found to support wound healing by the secretion of growth factors and extracellular matrix. They have since been also found to serve a similar function in the pancreas. In both organs, the wound-healing process may become dysregulated and lead to pathological fibrosis (also known as cirrhosis in the liver). In recent years there has been increasing attention paid to the role of these cells in tumor formation and progression. They may be a factor in initiating the first steps of carcinogenesis such as with liver cirrhosis and hepatocellular carcinoma and also contribute to continued tumor growth, invasion, metastasis, evasion of the immune system, and resistance to chemotherapy, in cancers of both the liver and pancreas. In this chapter we aim to review the structure and function of hepatic and pancreatic stellate cells and their contributions to the tumor microenvironment in their respective cancers and also discuss potential new targets for cancer therapy based on our new understanding of these vital components of the tumor stroma.

The Hepatic Sinusoid in Aging and Disease: Update and Advances From the 20th Liver Sinusoid Meeting

This is a meeting report of the 2019 Liver Sinusoid Meeting, 20th International Symposium on Cells of the Hepatic Sinusoid, held in Sydney, Australia, in September 2019. The meeting, which was organized by the International Society for Hepatic Sinusoidal Research, provided an update on the recent advances in the field of hepatic sinusoid cells in relation to cell biology, aging, and liver disease, with particular focus on the molecular and cellular targets involved in hepatic fibrosis, nonalcoholic hepatic steatohepatitis, alcoholic liver disease, hepatocellular carcinoma, and cirrhosis. In addition, the meeting highlighted the recent advances in regenerative medicine, targeted nanotechnologies, therapeutics, and novel methodologies.

Role of cytoglobin, a novel radical scavenger, in stellate cell activation and hepatic fibrosis

Cytoglobin (Cygb), a stellate cell-specific globin, has recently drawn attention due to its association with liver fibrosis. In the livers of both humans and rodents, Cygb is expressed only in stellate cells and can be utilized as a marker to distinguish stellate cells from hepatic fibroblast-derived myofibroblasts. Loss of Cygb accelerates liver fibrosis and cancer development in mouse models of chronic liver injury including diethylnitrosamine-induced hepatocellular carcinoma, bile duct ligation-induced cholestasis, thioacetamide-induced hepatic fibrosis, and choline-deficient L-amino acid-defined diet-induced non-alcoholic steatohepatitis. This review focuses on the history of research into the role of reactive oxygen species and nitrogen species in liver fibrosis and discusses the current perception of Cygb as a novel radical scavenger with an emphasis on its role in hepatic stellate cell activation and fibrosis.

Human Liver-Derived Extracellular Matrix for the Culture of Distinct Human Primary Liver Cells

The lack of robust methods to preserve, purify and in vitro maintain the phenotype of the human liver’s highly specialized parenchymal and non-parenchymal cell types importantly hampers their exploitation for the development of research and clinical applications. There is in this regard a growing interest in the use of tissue-specific extracellular matrix (ECM) to provide cells with an in vitro environment that more closely resembles that of the native tissue. In the present study, we have developed a method that allows for the isolation and downstream application of the human liver’s main cell types from cryopreserved material. We also isolated and solubilized human liver ECM (HL-ECM), analyzed its peptidomic and proteomic composition by mass spectrometry and evaluated its interest for the culture of distinct primary human liver cells. Our analysis of the HL-ECM revealed proteomic diversity, type 1 collagen abundance and partial loss of integrity following solubilization. Solubilized HL-ECM was evaluated either as a coating or as a medium supplement for the culture of human primary hepatocytes, hepatic stellate cells and liver sinusoidal endothelial cells. Whereas the solubilized HL-ECM was suitable for cell culture, its impact on the phenotype and/or functionality of the human liver cells was limited. Our study provides a first detailed characterization of solubilized HL-ECM and a first report of its influence on the culture of distinct human primary liver cells.

Programmed death-ligand 1 expression is an unfavorable prognostic factor of hepatocellular carcinoma after archiving sustained virologic response for hepatitis C virus infection

The aim of the present study was to study the pathological prognostic factor of initial hepatocellular carcinoma (HCC) after archiving sustained virologic response (SVR) for hepatitis C virus (HCV) infection. A single-center retrospective analysis was performed for patients who underwent hepatectomy between 2003 and 2017. We studied clinico-pathological findings of resected liver tissues in 35 patients with HCC after SVR treated by interferon (IFN group) and 13 patients with HCC after SVR treated by direct acting antivirals (DAA group). We also performed immunohistochemical staining using antibodies against programmed death-ligand 1 (PD-L1), cytokeratin 19, epithelial cell adhesion molecule (EpCAM) and regulator of G-protein signaling 5 (RGS5). PD-L1 positive HCC was observed in 6 cases of the IFN group and 4 cases of the DAA group. In the IFN group, in univariate analysis of recurrence free survival after surgery (RFS), the PD-L1 expression had a statistically significant impact (HR=6.01; P=0.02). In the multivariate analysis of RFS, PD-L1 expression significantly remained (HR=5.01; P=0.03). For both RFS and overall survival, Kaplan-Meier curves confirmed that patients with PD-L1 expression showed significantly worse prognosis (log-rank test P<0.01). Nuclear grade, RGS5 expression, and EpCAM expression were significantly higher in the PD-L1-positive HCC group compared with the PD-L1-negative HCC group (P<0.05). Therefore, PD-L1 expression may be an independent prognostic factor of surgically resected HCC after achieving SVR.

Molecular characterization of a precision-cut rat lung slice model for the evaluation of antifibrotic drugs

The translation of novel pulmonary fibrosis therapies from preclinical models into the clinic represents a major challenge demonstrated by the high attrition rate of compounds that showed efficacy in preclinical models but demonstrated no significant beneficial effects in clinical trials. A precision-cut lung tissue slice (PCLS) contains all major cell types of the lung and preserves the original cell-cell and cell-matrix contacts. It represents a promising ex vivo model to study pulmonary fibrosis. In this study, using RNA sequencing, we demonstrated that transforming growth factor-β1 (TGFβ1) induced robust fibrotic responses in the rat PCLS model, as it changed the expression of genes functionally related to extracellular matrix remodeling, cell adhesion, epithelial-to-mesenchymal transition, and various immune responses. Nintedanib, pirfenidone, and sorafenib each reversed a subset of genes modulated by TGFβ1, and of those genes we identified 229 whose expression was reversed by all three drugs. These genes define a molecular signature characterizing many aspects of pulmonary fibrosis pathology and its attenuation in the rat PCLS fibrosis model. A panel of 12 genes and three secreted biomarkers, including procollagen I, hyaluronic acid, and WNT1-inducible signaling pathway protein 1 were validated as efficacy end points for the evaluation of antifibrotic activity of experimental compounds. Finally, we showed that blockade of αV-integrins suppressed TGFβ1-induced fibrotic responses in the rat PCLS fibrosis model. Overall, our results suggest that the TGFβ1-induced rat PCLS fibrosis model may represent a valuable system for target validation and to determine the efficacy of experimental compounds.

Selective overexpression of cytoglobin in stellate cells attenuates thioacetamide-induced liver fibrosis in mice

Cytoglobin (CYGB), discovered in hepatic stellate cells (HSCs), is known to possess a radical scavenger function, but its pathophysiological roles remain unclear. Here, for the first time, we generated a new transgenic (TG) mouse line in which both Cygb and mCherry reporter gene expression were under the control of the native Cygb gene promoter. We demonstrated that the expression of Cygb-mCherry was related to endogenous Cygb in adult tissues by tracing mCherry fluorescence together with DNA, mRNA, and protein analyses. Administration of a single dose (50 mg/kg) of thioacetamide (TAA) in Cygb-TG mice resulted in lower levels of alanine transaminase and oxidative stress than those in WT mice. After 10 weeks of TAA administration, Cygb-TG livers exhibited reduced neutrophil accumulation, cytokine expression and fibrosis but high levels of quiescent HSCs. Primary HSCs isolated from Cygb-TG mice (HSCCygb-TG) exhibited significantly decreased mRNA levels of α-smooth muscle actin (αSMA), collagen 1α1, and transforming growth factor β-3 after 4 days in culture relative to WT cells. HSCsCygb-TG were resistant to H2O2-induced αSMA expression. Thus, cell-specific overexpression of Cygb attenuates HSC activation and protects mice against TAA-induced liver fibrosis presumably by maintaining HSC quiescence. Cygb is a potential new target for antifibrotic approaches.

Immunohistochemical characterization of cancer-associated fibroblasts at the primary sites and in the metastatic lymph nodes of human intrahepatic cholangiocarcinoma

Cancer-associated fibroblasts (CAFs) are an important constituent of the cancer stroma. In intrahepatic cholangiocarcinoma (ICC), the features of CAFs at the primary site and in the metastatic lymph nodes (Met-LNs) and their origin have been unclear. In the present study, we characterized CAFs at the primary site (n = 42) and in the Met-LNs (n = 10) of human ICC by immunohistochemistry using potential molecular markers of CAFs, portal fibroblasts (PFs), hepatic stellate cells (HSCs), and bone marrow-derived fibrocytes (BMDFs). At the primary site, the stroma was strongly positive for α-smooth muscle actin (α-SMA; marker for CAFs), platelet-derived growth factor receptor-β (PDGFR-β) (common marker for HSCs and PFs), fibulin-2, and thymus cell antigen-1 (Thy-1; PF marker), whereas immunoreactivity for fascin (HSC marker) was scarce. Most of the α-SMA-positive cells were found to express PDGFR-β, Thy-1, and fibulin-2 by double immunostaining. A small population of BMDF marker-positive (α-SMA⁺CD45⁺CD34⁺) cells was found by triple immunostaining. In the micro-Met-LNs, α-SMA-positive cells were absent in cancer aggregates of the LN sinus, whereas they were present in the invasion area of cancer cells from the LN sinus to the LN parenchyma. In the macro-Met-LNs, there were abundant α-SMA-positive cells that were also positive for PDGFR-β and Thy-1 but negative for fibulin-2 and fascin. Thus, regarding the expression of molecular markers, CAFs at the primary site of ICC are similar to PFs and different from those of HSCs or CAFs in the Met-LNs. CAFs at the primary sites and in the Met-LN are thought to be derived from PFs/BMDFs and resident cells of LNs, respectively.

Epalrestat Stimulated Oxidative Stress, Inflammation, and Fibrogenesis in Mouse Liver

Epalrestat (EPS), an aldose reductase inhibitor, is widely prescribed to manage diabetic neuropathy. It is generally believed that EPS is beneficial to diabetic patients because it can protect endothelial cells, Schwann cells, or other neural cells from oxidative stress. However, several clinical studies revealed that EPS therapy led to liver dysfunction, which limited its clinical applications. Currently, the underlying mechanism by which EPS causes liver dysfunction is unknown. This study aimed to investigate the mechanism responsible for EPS-induced liver injury. In mouse liver, EPS 1) increased oxidative stress, indicated by increased expression of manganese superoxide dismutase, Ho-1, and Nqo1, 2) induced inflammation, indicated by infiltration of inflammatory cells, and induced expression of tumor necrosis factor-alpha, CD11b, and CD11c, as well as 3) predisposed to induce fibrosis, evidenced by increased mRNA and protein expression of early profibrotic biomarker genes procollagen I and alpha-smooth muscle actin, and by increased collagen deposition. In cultured mouse and human hepatoma cells, EPS treatment induced oxidative stress, decreased cell viability, and triggered apoptosis evidenced by increased Caspase-3 cleavage/activation. In addition, EPS increased mRNA and protein expression of cytoglobin in mouse liver, indicating that EPS activated hepatic stellate cells (HSCs). Furthermore, EPS treatment in cultured human HSCs increased cell viability. In summary, EPS administration induced oxidative stress and inflammation in mouse liver, and stimulated liver fibrogenesis. Therefore, cautions should be exercised during EPS therapy.

Bioprinting Perfusion-Enabled Liver Equivalents for Advanced Organ-on-a-Chip Applications

Many tissue models have been developed to mimic liver-specific functions for metabolic and toxin conversion in in vitro assays. Most models represent a 2D environment rather than a complex 3D structure similar to native tissue. To overcome this issue, spheroid cultures have become the gold standard in tissue engineering. Unfortunately, spheroids are limited in size due to diffusion barriers in their dense structures, limiting nutrient and oxygen supply. Recent developments in bioprinting techniques have enabled us to engineer complex 3D structures with perfusion-enabled channel systems to ensure nutritional supply within larger, densely-populated tissue models. In this study, we present a proof-of-concept for the feasibility of bioprinting a liver organoid by combining HepaRG and human stellate cells in a stereolithographic printing approach, and show basic characterization under static cultivation conditions. Using standard tissue engineering analytics, such as immunohistology and qPCR, we found higher albumin and cytochrome P₄₅₀ 3A4 (CYP3A4) expression in bioprinted liver tissues compared to monolayer controls over a two-week cultivation period. In addition, the expression of tight junctions, liver-specific bile transporter multidrug resistance-associated protein 2 (MRP2), and overall metabolism (glucose, lactate, lactate dehydrogenase (LDH)) were found to be stable. Furthermore, we provide evidence for the perfusability of the organoids’ intrinsic channel system. These results motivate new approaches and further development in liver tissue engineering for advanced organ-on-a-chip applications and pharmaceutical developments.

Stagnation of histopathological improvement is a predictor of hepatocellular carcinoma development after hepatitis C virus eradication

BACKGROUND

Hepatocellular carcinoma (HCC) develops in some patients who achieve sustained virological response (SVR) against hepatitis C virus (HCV) infection via anti-HCV therapy. To examine the pathogenesis of HCC development after HCV eradication, histopathological changes and clinical markers were evaluated in SVR patients.

METHODS

Of 654 SVR patients treated with interferon (IFN)-based therapies, 34 patients who had undergone liver biopsy before initiating IFN therapy and after SVR achievement were enrolled: 11 patients with HCC and 23 patients without HCC (male/female, 9/2 and 8/15, respectively: age, 58 ± 5 and 54 ± 11 years, respectively). We compared the clinical and histopathological factors between the two groups. Immunohistochemistry for Cytoglobin (CYGB) and α smooth muscle actin (α-SMA) was also performed.

RESULTS

At baseline, prior to initiating the IFN-based therapy, there were significant differences between the SVR-non-HCC and SVR-HCC groups in the male gender, HBc antibody positivity, prothrombin activity, and histological inflammatory grade. Histopathological evaluation, using the new Inuyama classification system, revealed an improvement in the inflammatory grade, from 2.1 ± 0.6 to 1.0 ± 0.6 (p < 0.0001), whereas the fibrosis stage remained unchanged, from 2.3 ± 0.9 to 2.0 ± 1.2 (p = 0.2749), during the 97 ± 72-month observation period in the SVR-HCC group. Both the grade and stage scores were significantly improved in the SVR-non-HCC group. The area of collagen deposition, evaluated using Sirius red staining, showed a marked decrease, from 18.6 ± 7.6% to 7.7 ± 4.6%, in the SVR-non-HCC group, with no change in the SVR-HCC group. CYGB- and α-SMA-positive hepatic stellate cells (HSCs), indicative of the HSC activated phenotype, remained in the fibrotic tissue of livers among patients in the SVR-HCC group.

CONCLUSION

Stagnation of fibrosis regression is associated with a high risk for HCC after SVR. HSC activation may inhibit improvement in fibrosis after SVR and potentially contribute to hepatocarcinogenesis.

Development of a peptide-modified siRNA nanocomplex for hepatic stellate cells

Insulin-like growth factor 2 receptor (IGF2R) is overexpressed in activated hepatic stellate cells (HSCs) and therefore can be utilized for HSC-specific drug delivery. We recently discovered an IGF2R-specific peptide using a novel biopanning. Here, we adopted biotin-conjugated IGF2R-specific peptide, cholesterol, and vitamin A as the targeting ligands for the neutravidin-based siRNA nanocomplex to deliver PCBP2 siRNA, a potentially antifibrotic agent, to HSCs. Compared to vitamin A and cholesterol, the IGF2R-specific peptide exhibited the highest targeting effect to human LX-2 HSC, rat HSC-T6 cell line, and activated primary rat HSCs. Accordingly, the IGF2R-specific peptide coupled nanocomplex demonstrated higher silencing activity of PCBP2 and better inhibition on the migration of activated HSCs. Compared to free siRNA and the nanocomplexes coupled with vitamin A and cholesterol, the IGF2R-specific peptide coupled nanocomplex showed the highest uptake in the liver and lowest uptake in the lung and kidney of the rats with CCl4-induced liver fibrosis.

Human hepatic stellate cell isolation and characterization

The hepatic stellate cells (HSCs) localize at the space of Disse in the liver and have multiple functions. They are identified as the major contributor to hepatic fibrosis. Significant understanding of HSCs has been achieved using rodent models and isolated murine HSCs; as well as investigating human liver tissues and human HSCs. There is growing interest and need of translating rodent study findings to human HSCs and human liver diseases. However, species-related differences impose challenges on the translational research. In this review, we focus on the current information on human HSCs isolation methods, human HSCs markers, and established human HSC cell lines.

Positive Feedback Regulation between Transglutaminase 2 and Toll-Like Receptor 4 Signaling in Hepatic Stellate Cells Correlates with Liver Fibrosis Post Schistosoma japonicum Infection

Liver fibrosis induced by Schistosoma japonicum (Sj) infection is characterized by the accumulation of extracellular matrix (ECM). The activated and differentiated hepatic stellate cells (HSCs) are the predominant ECM-producing cell type in the liver. Toll-like receptor (TLR) 4 pathway activation plays a key role in mice liver fibrosis models induced by alcohol, biliary ligation, and carbon tetrachloride 4. In this work, we found that TLR4 pathway activation correlated with the severity of liver fibrosis post Sj infection. The TLR4 receptor inhibitor TAK242 reduced the extent of liver fibrosis. The increased expression of TLR4, α-smooth muscle actin (α-SMA), and cytoglobin was observed in the HSCs of mouse liver after Sj infection. In response to stimulation with either lipopolysaccharide or Sj's soluble egg antigen (SEA), high levels of TLR4 and α-SMA were induced in HSCs and were inhibited by TAK242 treatment. In previous work, we had reported that a high level of transglutaminase 2 (TGM2) is crucial for liver fibrosis post Sj infection. Herein, we found that TLR4 signaling also controlled Tgm2 expression. Inhibition of TGM2 activity by cystamine (CTM) in Sj-infected mice or in HSCs induced with all-trans-retinoic acid (ATRA) stimulation led to a lowered activation of TLR4 signaling and a reduced α-SMA expression. These results were confirmed by downregulating the Tgm2 gene by specific siRNA. These observations implied the presence of a positive feedback regulation between TGM2 and TLR4 signaling in HSCs that correlated with liver fibrosis post Sj infection. This novel connection between TGM2 and TLR4 pathway activation in liver fibrosis induced by Sj infection enhances our understanding of liver diseases.

Fibroblast growth factor 2 (FGF2) regulates cytoglobin expression and activation of human hepatic stellate cells via JNK signaling

Cytoglobin (CYGB) belongs to the mammalian globin family and is exclusively expressed in hepatic stellate cells (HSCs) in the liver. In addition to its gas-binding ability, CYGB is relevant to hepatic inflammation, fibrosis, and cancer because of its anti-oxidative properties; however, the regulation of CYGB gene expression remains unknown. Here, we sought to identify factors that induce CYGB expression in HSCs and to clarify the molecular mechanism involved. We used the human HSC cell line HHSteC and primary human HSCs isolated from intact human liver tissues. In HHSteC cells, treatment with a culture supplement solution that included fibroblast growth factor 2 (FGF2) increased CYGB expression with concomitant and time-dependent α-smooth muscle actin (αSMA) down-regulation. We found that FGF2 is a key factor in inducing the alteration in both CYGB and αSMA expression in HHSteCs and primary HSCs and that FGF2 triggered the rapid phosphorylation of both c-Jun N-terminal kinase (JNK) and c-JUN. Both the JNK inhibitor PS600125 and transfection of c-JUN-targeting siRNA abrogated FGF2-mediated CYGB induction, and conversely, c-JUN overexpression induced CYGB and reduced αSMA expression. Chromatin immunoprecipitation analyses revealed that upon FGF2 stimulation, phospho-c-JUN bound to its consensus motif (5'-TGA(C/G)TCA), located -218 to -222 bases from the transcription initiation site in the CYGB promoter. Of note, in bile duct-ligated mice, FGF2 administration ameliorated liver fibrosis and significantly reduced HSC activation. In conclusion, FGF2 triggers CYGB gene expression and deactivation of myofibroblastic human HSCs, indicating that FGF2 has therapeutic potential for managing liver fibrosis.

The different expressed serum proteins in rhCygb treated rat model of liver fibrosis by the optimized two-dimensional gel electrophoresis

Liver fibrosis, a common pathological process of chronic liver diseases, is the final stage of liver dysfunction that has severely deleterious impact on human health. Cytoglobin was first discovered in 2001 by proteomic analysis in rat stellate cells and was reported to play an important role in controlling tissue fibrosis. However, the mechanism by which cytoglobin inhibits or reverses the progression of fibrosis remains unclear. The present study examines the effect of recombinant human cytoblobin (rhCygb) in a rat model of liver fibrosis. Proteomic approaches were employed to identify differentially expressed proteins in the fibrosis model. Optimized conditions for two-dimensional gel electrophoresis were developed to provide improved protein detection and separation. A total of 43 spots were obtained and, through the use of matrix-assisted laser desorption ionization time-of-flight mass spectrometry, 30 differentially expressed proteins were identified. Gene ontology term annotation and KEGG pathway analysis allowed us to explore the function of the represented proteins. Based on these results, we provide a theory of the molecular mechanism related to rhCygb reversion of fibrosis and which will assist in the identification of biomarkers in patient serum to improve early diagnosis of liver fibrosis.

Identification of markers for quiescent pancreatic stellate cells in the normal human pancreas

Pancreatic stellate cells (PSCs) play a central role as source of fibrogenic cells in pancreatic cancer and chronic pancreatitis. In contrast to quiescent hepatic stellate cells (qHSCs), a specific marker for quiescent PSCs (qPSCs) that can be used in formalin-fixed and paraffin embedded (FFPE) normal human pancreatic tissue has not been identified. The aim of this study was to identify a marker enabling the identification of qPSCs in normal human FFPE pancreatic tissue. Immunohistochemical (IHC), double-IHC, immunofluorescence (IF) and double-IF analyses were carried out using a tissue microarray consisting of cores with normal human pancreatic tissue. Cores with normal human liver served as control. Antibodies directed against adipophilin, α-SMA, CD146, CRBP-1, cytoglobin, desmin, GFAP, nestin, S100A4 and vinculin were examined, with special emphasis on their expression in periacinar cells in the normal human pancreas and perisinusoidal cells in the normal human liver. The immunolabelling capacity was evaluated according to a semiquantitative scoring system. Double-IF of the markers of interest together with markers for other periacinar cells was performed. Moreover, the utility of histochemical stains for the identification of human qPSCs was examined, and their ultrastructure was revisited by electron microscopy. Adipophilin, CRBP-1, cytoglobin and vinculin were expressed in qHSCs in the liver, whereas cytoglobin and adipophilin were expressed in qPSCs in the pancreas. Adipophilin immunohistochemistry was highly dependent on the preanalytical time interval (PATI) from removal of the tissue to formalin fixation. Cytoglobin, S100A4 and vinculin were expressed in periacinar fibroblasts (FBs). The other examined markers were negative in human qPSCs. Our data indicate that cytoglobin and adipophilin are markers of qPSCs in the normal human pancreas. However, the use of adipophilin as a qPSC marker may be limited due to its high dependence on optimal PATI. Cytoglobin, on the other hand, is a sensitive marker for qPSCs but is expressed in FBs as well.

Redox and Peroxidase Activities of the Hemoglobin Superfamily: Relevance to Health and Disease

SIGNIFICANCE

Erythrocyte hemoglobin (Hb) and myocyte myoglobin, although primarily oxygen-carrying proteins, have the capacity to do redox chemistry. Such redox activity in the wider family of globins now appears to have important associations with the mechanisms of cell stress response. In turn, an understanding of such mechanisms in vivo may have a potential in the understanding of cancer therapy resistance and neurodegenerative disorders such as Alzheimer's. Recent Advances: There has been an enhanced understanding of the redox chemistry of the globin superfamily in recent years, leading to advances in development of Hb-based blood substitutes and in hypotheses relating to specific disease mechanisms. Neuroglobin (Ngb) and cytoglobin (Cygb) have been linked to cell protection mechanisms against hypoxia and oxidative stress, with implications in the onset and progression of neurodegenerative diseases for Ngb and cancer for Cygb.

CRITICAL ISSUES

Despite advances in the understanding of redox chemistry of globins, the physiological roles of many of these proteins still remain ambiguous at best. Confusion over potential physiological roles may relate to multifunctional roles for globins, which may be modulated by surface-exposed cysteine pairs in some globins. Such roles may be critical in deciphering the relationships of these globins in human diseases.

FUTURE DIRECTIONS

Further studies are required to connect the considerable knowledge on the mechanisms of globin redox chemistry in vitro with the physiological and pathological roles of globins in vivo. In doing so, new therapies for neurodegenerative disorders and cancer therapy resistance may be targeted. Antioxid. Redox Signal. 26, 763-776.

CUG-binding protein 1 regulates HSC activation and liver fibrogenesis

Excessive activation of hepatic stellate cells (HSCs) is a key step in liver fibrogenesis. Here we report that CUG-binding protein 1 (CUGBP1) expression is elevated in HSCs and positively correlates with liver fibrosis severity in human liver biopsies. Transforming growth factor-beta (TGF-β) selectively increases CUGBP1 expression in cultured HSCs in a p38 mitogen-activated protein kinase (MAPK)-dependent manner. Knockdown of CUGBP1 inhibits alpha smooth muscle actin (α-SMA) expression and promotes interferon gamma (IFN-γ) production in HSCs in vitro. We further show that CUGBP1 specifically binds to the 3′ untranslated region (UTR) of human IFN-γ mRNA and promotes its decay. In mice, knockdown of CUGBP1 alleviates, whereas its overexpression exacerbates, bile duct ligation (BDL)-induced hepatic fibrosis. Therefore, CUGBP1-mediated IFN-γ mRNA decay is a key event for profibrotic TGF-β-dependent activation of HSCs, and inhibiting CUGBP1 to promote IFN-γ signalling in activated HSCs could be a novel strategy to treat liver fibrosis.

Activation of hepatic stellate cells is a critical event in the development of fibrosis, which is driven by TGF-beta and inhibited by IFN-gamma. Here Wu et al. show that the RNA binding protein CUGBP1 is increased by TGF-beta signalling and promotes IFN-gamma mRNA degradation.

Pathogenesis of Nonalcoholic Steatohepatitis: Interactions between Liver Parenchymal and Nonparenchymal Cells

Nonalcoholic fatty liver disease (NAFLD) is the most common type of chronic liver disease in the Western countries, affecting up to 25% of the general population and becoming a major health concern in both adults and children. NAFLD encompasses the entire spectrum of fatty liver disease in individuals without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) and cirrhosis. NASH is a manifestation of the metabolic syndrome and hepatic disorders with the presence of steatosis, hepatocyte injury (ballooning), inflammation, and, in some patients, progressive fibrosis leading to cirrhosis. The pathogenesis of NASH is a complex process and implicates cell interactions between liver parenchymal and nonparenchymal cells as well as crosstalk between various immune cell populations in liver. Lipotoxicity appears to be the central driver of hepatic cellular injury via oxidative stress and endoplasmic reticulum (ER) stress. This review focuses on the contributions of hepatocytes and nonparenchymal cells to NASH, assessing their potential applications to the development of novel therapeutic agents. Currently, there are limited pharmacological treatments for NASH; therefore, an increased understanding of NASH pathogenesis is pertinent to improve disease interventions in the future.

Doxazosin Treatment Attenuates Carbon Tetrachloride-Induced Liver Fibrosis in Hamsters through a Decrease in Transforming Growth Factor β Secretion

Background/Aims

The development of therapeutic strategies for the treatment of cirrhosis has become an important focus for basic and clinical researchers. Adrenergic receptor antagonists have been evaluated as antifibrotic drugs in rodent models of carbon tetrachloride (CCl4)-induced cirrhosis. The aim of the present study was to evaluate the effects of carvedilol and doxazosin on fibrosis/cirrhosis in a hamster animal model.

Methods

Cirrhotic-induced hamsters were treated by daily administration of carvedilol and doxazosin for 6 weeks. Hepatic function and histological evaluation were conducted by measuring biochemical markers, including total bilirubin, aspartate aminotransferase, alanine aminotransferase and albumin, and liver tissue slices. Additionally, transforming growth factor β (TGF-β) immunohistochemistry was analyzed.

Results

Biochemical markers revealed that hepatic function was restored after treatment with doxazosin and carvedilol. Histological evaluation showed a decrease in collagen type I deposits and TGF-β-secreting cells.

Conclusions

Taken together, these results suggest that the decrease in collagen type I following treatment with doxazosin or carvedilol is achieved by decreasing the profibrotic activities of TGF-β via the blockage of α1- and β-adrenergic receptor. Consequently, a diminution of fibrotic tissue in the CCl4-induced model of cirrhosis is achieved.

Absence of cytoglobin promotes multiple organ abnormalities in aged mice

Cytoglobin (Cygb) was identified in hepatic stellate cells (HSCs) and pericytes of all organs; however, the effects of Cygb on cellular functions remain unclear. Here, we report spontaneous and age-dependent malformations in multiple organs of Cygb(-/-) mice. Twenty-six percent of young Cygb(-/-) mice (<1 year old) showed heart hypertrophy, cystic disease in the kidney or ovary, loss of balance, liver fibrosis and lymphoma. Furthermore, 71.3% (82/115) of aged Cygb(-/-) mice (1-2 years old) exhibited abnormalities, such as heart hypertrophy and cancer development in multiple organs; by contrast, 5.8% (4/68) of aged wild-type (WT) mice had abnormalities (p < 0.0001). Interestingly, serum and urine analysis demonstrated that the concentration of nitric oxide metabolites increased significantly in Cygb(-/-) mice, resulting in an imbalance in the oxidative stress and antioxidant defence system that was reversed by N(G)-monomethyl-L-arginine treatment. A senescent phenotype and evidence of DNA damage were found in primary HSCs and the liver of aged Cygb(-/-) mice. Moreover, compared with HSC(+/+), HSC(-/-) showed high expression of Il-6 and chemokine mRNA when cocultured with mouse Hepa 1-6 cells. Thus, the absence of Cygb in pericytes provokes organ abnormalities, possibly via derangement of the nitric oxide and antioxidant defence system and through accelerated cellular senescence.

A novel comparative pattern analysis approach identifies chronic alcohol mediated dysregulation of transcriptomic dynamics during liver regeneration

BACKGROUND

Liver regeneration is inhibited by chronic ethanol consumption and this impaired repair response may contribute to the risk for alcoholic liver disease. We developed and applied a novel data analysis approach to assess the effect of chronic ethanol intake in the mechanisms responsible for liver regeneration. We performed a time series transcriptomic profiling study of the regeneration response after 2/3rd partial hepatectomy (PHx) in ethanol-fed and isocaloric control rats.

RESULTS

We developed a novel data analysis approach focusing on comparative pattern counts (COMPACT) to exhaustively identify the dominant and subtle differential expression patterns. Approximately 6500 genes were differentially regulated in Ethanol or Control groups within 24 h after PHx. Adaptation to chronic ethanol intake significantly altered the immediate early gene expression patterns and nearly completely abrogated the cell cycle induction in hepatocytes post PHx. The patterns highlighted by COMPACT analysis contained several non-parenchymal cell specific markers indicating their aberrant transcriptional response as a novel mechanism through which chronic ethanol intake deregulates the integrated liver tissue response.

CONCLUSIONS

Our novel comparative pattern analysis revealed new insights into ethanol-mediated molecular changes in non-parenchymal liver cells as a possible contribution to the defective liver regeneration phenotype. The results revealed for the first time an ethanol-induced shift of hepatic stellate cells from a pro-regenerative phenotype to that of an anti-regenerative state after PHx. Our results can form the basis for novel interventions targeting the non-parenchymal cells in normalizing the dysfunctional repair response process in alcoholic liver disease. Our approach is illustrated online at http://compact.jefferson.edu .

Cytoglobin as a Marker of Hepatic Stellate Cell-derived Myofibroblasts

Myofibroblasts play important roles in inflammation, fibrosis and tumorigenesis in chronically inflamed liver. Liver myofibroblasts originate from hepatic stellate cells, portal fibroblasts or mesothelial cells, and they are localized in and around fibrotic septum and portal tracts. Liver myofibroblasts are the source of extracellular matrix materials, including type I collagen and multiple fibrogenic growth factors, such as transforming growth factor-β and vascular endothelial growth factor. Although a detailed characterization of the function of individual myofibroblasts has not been conducted, owing to the lack of appropriate cell markers, recent lineage-tracing technology has revealed the limited contribution of myofibroblasts that are derived from portal fibroblasts to various types of liver fibrosis, as compared with the contribution of hepatic stellate cells. In addition, cytoglobin, which is the fourth globin in mammals and function as a local gas sensor, provides a new perspective on the involvement of stellate cells in fibrosis and carcinogenesis, possibly through its anti-oxidative properties and is a promising new marker that discriminates between myofibroblasts derived from stellate cells and those from portal fibroblasts.

All-In-One: Advanced preparation of Human Parenchymal and Non-Parenchymal Liver Cells

Background & Aims

Liver cells are key players in innate immunity. Thus, studying primary isolated liver cells is necessary for determining their role in liver physiology and pathophysiology. In particular, the quantity and quality of isolated cells are crucial to their function. Our aim was to isolate a large quantity of high-quality human parenchymal and non-parenchymal cells from a single liver specimen.

Methods

Hepatocytes, Kupffer cells, liver sinusoidal endothelial cells, and stellate cells were isolated from liver tissues by collagenase perfusion in combination with low-speed centrifugation, density gradient centrifugation, and magnetic-activated cell sorting. The purity and functionality of cultured cell populations were controlled by determining their morphology, discriminative cell marker expression, and functional activity.

Results

Cell preparation yielded the following cell counts per gram of liver tissue: 2.0±0.4×10⁷ hepatocytes, 1.8±0.5×10⁶ Kupffer cells, 4.3±1.9×10⁵ liver sinusoidal endothelial cells, and 3.2±0.5×10⁵ stellate cells. Hepatocytes were identified by albumin (95.5±1.7%) and exhibited time-dependent activity of cytochrome P450 enzymes. Kupffer cells expressed CD68 (94.5±1.2%) and exhibited phagocytic activity, as determined with 1μm latex beads. Endothelial cells were CD146⁺ (97.8±1.1%) and exhibited efficient uptake of acetylated low-density lipoprotein. Hepatic stellate cells were identified by the expression of α-smooth muscle actin (97.1±1.5%). These cells further exhibited retinol (vitamin A)-mediated autofluorescence.

Conclusions

Our isolation procedure for primary parenchymal and non-parenchymal liver cells resulted in cell populations of high purity and quality, with retained physiological functionality in vitro. Thus, this system may provide a valuable tool for determining liver function and disease.

Ancient Duplications and Expression Divergence in the Globin Gene Superfamily of Vertebrates: Insights from the Elephant Shark Genome and Transcriptome

Comparative analyses of vertebrate genomes continue to uncover a surprising diversity of genes in the globin gene superfamily, some of which have very restricted phyletic distributions despite their antiquity. Genomic analysis of the globin gene repertoire of cartilaginous fish (Chondrichthyes) should be especially informative about the duplicative origins and ancestral functions of vertebrate globins, as divergence between Chondrichthyes and bony vertebrates represents the most basal split within the jawed vertebrates. Here, we report a comparative genomic analysis of the vertebrate globin gene family that includes the complete globin gene repertoire of the elephant shark (Callorhinchus milii). Using genomic sequence data from representatives of all major vertebrate classes, integrated analyses of conserved synteny and phylogenetic relationships revealed that the last common ancestor of vertebrates possessed a repertoire of at least seven globin genes: single copies of androglobin and neuroglobin, four paralogous copies of globin X, and the single-copy progenitor of the entire set of vertebrate-specific globins. Combined with expression data, the genomic inventory of elephant shark globins yielded four especially surprising findings: 1) there is no trace of the neuroglobin gene (a highly conserved gene that is present in all other jawed vertebrates that have been examined to date), 2) myoglobin is highly expressed in heart, but not in skeletal muscle (reflecting a possible ancestral condition in vertebrates with single-circuit circulatory systems), 3) elephant shark possesses two highly divergent globin X paralogs, one of which is preferentially expressed in gonads, and 4) elephant shark possesses two structurally distinct α-globin paralogs, one of which is preferentially expressed in the brain. Expression profiles of elephant shark globin genes reveal distinct specializations of function relative to orthologs in bony vertebrates and suggest hypotheses about ancestral functions of vertebrate globins.

Portal myofibroblasts promote vascular remodeling underlying cirrhosis formation through the release of microparticles

Liver fibrosis expanding from portal tracts and vascular remodeling are determinant factors in the progression of liver diseases to cirrhosis. In the present study, we examined the potential contribution of portal myofibroblasts (PMFs) to the vascular changes leading to cirrhosis. The analyses of liver cells based on the transcriptome of rat PMFs, compared to hepatic stellate cell HSC-derived myofibroblasts in culture, identified collagen, type XV, alpha 1 (COL15A1) as a marker of PMFs. Normal liver contained rare COL15A1-immunoreactive cells adjacent to the bile ducts and canals of Hering in the portal area. A marked increase in COL15A1 expression occurred together with that of the endothelial marker, von Willebrand factor, in human and rat liver tissue, at advanced stages of fibrosis caused by either biliary or hepatocellular injury. In cirrhotic liver, COL15A1-expressing PMFs adopted a perivascular distribution outlining vascular capillaries proximal to reactive ductules, within large fibrotic septa. The effect of PMFs on endothelial cells (ECs) was evaluated by in vitro and in vivo angiogenesis assays. PMF-conditioned medium increased the migration and tubulogenesis of liver ECs as well as human umbilical vein ECs and triggered angiogenesis within Matrigel plugs in mice. In coculture, PMFs developed intercellular junctions with ECs and enhanced the formation of vascular structures. PMFs released vascular endothelial growth factor (VEGF)A-containing microparticles, which activated VEGF receptor 2 in ECs and largely mediated their proangiogenic effect. Cholangiocytes potentiated the angiogenic properties of PMFs by increasing VEGFA expression and microparticle shedding in these cells.

CONCLUSION

PMFs are key cells in hepatic vascular remodeling. They signal to ECs through VEGFA-laden microparticles and act as mural cells for newly formed vessels, driving scar progression from portal tracts into the parenchyma.

Cytoglobin deficiency promotes liver cancer development from hepatosteatosis through activation of the oxidative stress pathway

This study was conducted to clarify the role of cytoglobin (Cygb), a globin expressed in hepatic stellate cells (HSCs), in the development of liver fibrosis and cancer in nonalcoholic steatohepatitis (NASH). Cygb expression was assessed in patients with NASH and hepatocellular carcinoma. Mouse NASH model was generated in Cygb-deficient (Cygb(-/-)) or wild-type (WT) mice by giving a choline-deficient amino acid-defined diet and, in some of them, macrophage deletion and N-acetyl cysteine treatment were used. Primary-cultured mouse HSCs isolated from WT (HSCs(Cygb-wild)) or Cygb(-/-) (HSCs(Cygb-null)) mice were characterized. As results, the expression of CYGB was reduced in patients with NASH and hepatocellular carcinoma. Choline-deficient amino acid treatment for 8 weeks induced prominent inflammation and fibrosis in Cygb(-/-) mice, which was inhibited by macrophage deletion. Surprisingly, at 32 weeks, despite no tumor formation in the WT mice, all Cygb(-/-) mice developed liver cancer, which was ameliorated by N-acetyl cysteine treatment. Altered expression of 31 genes involved in the metabolism of reactive oxygen species was notable in Cygb(-/-) mice. Both HSCs(Cygb-null) and Cygb siRNA-transfected-HSCs(Cygb-wild) exhibited the preactivation condition. Our findings provide important insights into the role that Cygb, expressed in HSCs during liver fibrosis, plays in cancer development with NASH.

Function and evolution of vertebrate globins

Globins are haem-proteins that bind O2 and thus play an important role in the animal's respiration and oxidative energy production. However, globins may also have other functions such as the decomposition or production of NO, the detoxification of reactive oxygen species or intracellular signalling. In addition to the well-investigated haemoglobins and myoglobins, genome sequence analyses have led to the identification of six further globin types in vertebrates: androglobin, cytoglobin, globin E, globin X, globin Y and neuroglobin. Here, we review the present state of knowledge on the functions, the taxonomic distribution and evolution of vertebrate globins, drawing conclusions about the functional changes underlying present-day globin diversity.

Fibrogenesis and Carcinogenesis in Nonalcoholic Steatohepatitis (NASH): Involvement of Matrix Metalloproteinases (MMPs) and Tissue Inhibitors of Metalloproteinase (TIMPs)

Nonalcoholic steatohepatitis (NASH) is emerging worldwide because life-styles have changed to include much over-eating and less physical activity. The clinical and pathophysiological features of NASH are very different from those of HBV- and HCV-chronic liver diseases. The prognosis of NASH is worse among those with nonalcoholic fatty liver diseases (NAFLD), and some NASH patients show HCC with or without cirrhosis. In the present review we discuss fibrogenesis and the relationship between fibrosis and HCC occurrence in NASH to clarify the role of MMPs and TIMPs in both mechanisms. Previously we proposed MMP and TIMP expression in the multi-step occurrence of HCC from the literature based on viral-derived HCC. We introduce again these expressions during hepatocarcinogenesis and compare them to those in NASH-derived HCC, although the relationship with hepatic stem/progenitor cells (HPCs) invasion remains unknown. Signal transduction of MMPs and TIMPs is also discussed because it is valuable for the prevention and treatment of NASH and NASH-derived HCC.

Cytoglobin in tumor hypoxia: novel insights into cancer suppression

Emerging new and intriguing roles of cytoglobin (Cygb) have attracted considerable attention of cancer researchers in recent years. Hypoxic upregulation of Cygb as well as its altered expression in various human cancers suggest another possible role of this newly discovered globin in tumor cell response under low oxygen tension. Since tumor hypoxia is strongly associated with malignant progression of disease and poor treatment response, it constitutes an area of paramount importance for rational design of cancer selective therapies. However, the mechanisms involved during this process are still elusive. This review outlines the current understanding of Cygb's involvement in tumor hypoxia and discusses its role in tumorigenesis. A better perception of Cygb in tumor hypoxia response is likely to open novel perspectives for future tumor therapy.

Strategies to Detect Hepatic Myofibroblasts in Liver Cirrhosis of Different Etiologies

Liver cirrhosis, a late stage of hepatic fibrosis, is an increasing cause of morbidity and mortality worldwide. Hepatic fibrosis is mainly caused by alcoholic or non-alcoholic steatohepatitis, chronic viral hepatitis, or autoimmune and biliary diseases. Myofibroblasts, which are absent from the normal liver, are differentiated from heterogeneous cell populations in response to a liver injury of any etiology and produce the extracellular matrix. Hepatic stellate cells are considered the main source of myofibroblasts. However, the origin of hepatic myofibroblasts remains unresolved, and despite considerable research, only a limited success has been achieved by existing anti-fibrotic therapies. The question remains whether these limitations are caused by lack of attention to the critical targets, the myofibroblasts derived from cells of other mesenchymal origins. Therefore, identifying the origin of myofibroblasts may provide insight into the mechanisms underlying liver fibrosis, and may lead to the development of more effective therapies. This review will examine our current strategies for detecting hepatic myofibroblasts of different origins.