TGFßR1 inhibition drives hepatocellular carcinoma proliferation through induction of toll-like-receptor signalling.

Transforming growth factor (TGF)-ß and toll-like receptors (TLRs) have been shown to independently modulate the proliferation of hepatocellular carcinoma (HCC). Since a direct cross-talk between these two signalling pathways in HCC has not been clearly described before, we aimed here to explore the possibility of such interaction. A human HCC tissue array (n = 20 vs. four control samples), human HCC samples (n = 10) and steatohepatitis-driven murine HCC samples (control, NASH and HCC; n = 6/group) were immunostained for TGFßR1, pSMAD2, TRAF6, IRAK1 and PCNA. The results were confirmed by immunoblotting. Effects of constant activation of the SMAD pathway by constitutive expression of ALK5 or knockdown of mediators of TLR signalling, IRAK1 and MyD88, on HCC proliferation, were investigated in the HCC cell line (HUH-7) after treatment with TGFß1 cytokine or TGFßR1 kinase inhibitor (LY2157299) using PCNA and MTS assay. TGFßR1 expression is decreased in human and murine HCC and associated with downregulated pSMAD2, but increased IRAK1, TRAF6 and PCNA staining. TGFßR1 kinase inhibition abolished the cytostatic effects of TGFß1 and led to the induction of IRAK1, pIRAK1 and elevated mRNA levels of TLR-9. Overexpression of ALK5 and knockdown of MyD88 or IRAK1 augmented the cytostatic effects of TGFß1 on HUH-7. In another epithelial HCC cell line, that is, HepG2, TGFßR1 kinase inhibitor similarly elevated cellular proliferation. There is a balance between the canonical SMAD-driven tumour-suppressing arm and the non-canonical tumour-promoting arm of TGFß signalling. Disruption of this balance, by inhibition of the canonical pathway, induces HCC proliferation through TLR signalling.

Targeting of Scavenger Receptors Stabilin-1 and Stabilin-2 Ameliorates Atherosclerosis by a Plasma Proteome Switch Mediating Monocyte/Macrophage Suppression.

BACKGROUND: Scavenger receptors Stabilin-1 (Stab1) and Stabilin-2 (Stab2) are preferentially expressed by liver sinusoidal endothelial cells. They mediate the clearance of circulating plasma molecules controlling distant organ homeostasis. Studies suggest that Stab1 and Stab2 may affect atherosclerosis. Although subsets of tissue macrophages also express Stab1, hematopoietic Stab1 deficiency does not modulate atherogenesis. Here, we comprehensively studied how targeting Stab1 and Stab2 affects atherosclerosis. METHODS: ApoE-KO mice were interbred with Stab1-KO and Stab2-KO mice and fed a Western diet. For antibody targeting, Ldlr-KO mice were also used. Unbiased plasma proteomics were performed and independently confirmed. Ligand binding studies comprised glutathione-S-transferase-pulldown and endocytosis assays. Plasma proteome effects on monocytes were studied by single-cell RNA sequencing in vivo, and by gene expression analyses of Stabilin ligand-stimulated and plasma-stimulated bone marrow-derived monocytes/macrophages in vitro. RESULTS: Spontaneous and Western diet-associated atherogenesis was significantly reduced in ApoE-Stab1-KO and ApoE-Stab2-KO mice. Similarly, inhibition of Stab1 or Stab2 by monoclonal antibodies significantly reduced Western diet-associated atherosclerosis in ApoE-KO and Ldlr-KO mice. Although neither plasma lipid levels nor circulating immune cell numbers were decisively altered, plasma proteomics revealed a switch in the plasma proteome, consisting of 231 dysregulated proteins comparing wildtype with Stab1/2-single and Stab1/2-double KO, and of 41 proteins comparing ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO. Among this broad spectrum of common, but also disparate scavenger receptor ligand candidates, periostin, reelin, and TGFBi (transforming growth factor, ß-induced), known to modulate atherosclerosis, were independently confirmed as novel circulating ligands of Stab1/2. Single-cell RNA sequencing of circulating myeloid cells of ApoE-, ApoE-Stab1-, and ApoE-Stab2-KO mice showed transcriptomic alterations in patrolling (Ccr2-/Cx3cr1++/Ly6Clo) and inflammatory (Ccr2+/Cx3cr1+/Ly6Chi) monocytes, including downregulation of proatherogenic transcription factor Egr1. In wildtype bone marrow-derived monocytes/macrophages, ligand exposure alone did not alter Egr1 expression in vitro. However, exposure to plasma from ApoE-Stab1-KO and ApoE-Stab2-KO mice showed a reverted proatherogenic macrophage activation compared with ApoE-KO plasma, including downregulation of Egr1 in vitro. CONCLUSIONS: Inhibition of Stab1/Stab2 mediates an anti-inflammatory switch in the plasma proteome, including direct Stabilin ligands. The altered plasma proteome suppresses both patrolling and inflammatory monocytes and, thus, systemically protects against atherogenesis. Altogether, anti-Stab1- and anti-Stab2-targeted therapies provide a novel approach for the future treatment of atherosclerosis.

Liver Sinusoidal Endothelial Cells Suppress Bone Morphogenetic Protein 2 Production in Response to TGFß Pathway Activation.

BACKGROUND AND AIMS: TGFß/bone morphogenetic protein (BMP) signaling in the liver plays a critical role in liver disease. Growth factors, such as BMP2, BMP6, and TGFß1, are released from LSECs and signal in a paracrine manner to hepatocytes and hepatic stellate cells to control systemic iron homeostasis and fibrotic processes, respectively. The misregulation of the TGFß/BMP pathway affects expression of the iron-regulated hormone hepcidin, causing frequent iron overload and deficiency diseases. However, whether LSEC-secreted factors can act in an autocrine manner to maintain liver homeostasis has not been addressed so far. APPROACH AND RESULTS: We analyzed publicly available RNA-sequencing data of mouse LSECs for ligand-receptor interactions and identified members of the TGFß family (BMP2, BMP6, and TGFß1) as ligands with the highest expression levels in LSECs that may signal in an autocrine manner. We next tested the soluble factors identified through in silico analysis in optimized murine LSEC primary cultures and mice. Exposure of murine LSEC primary cultures to these ligands shows that autocrine responses to BMP2 and BMP6 are blocked despite high expression levels of the required receptor complexes partially involving the inhibitor FK-506-binding protein 12. By contrast, LSECs respond efficiently to TGFß1 treatment, which causes reduced expression of BMP2 through activation of activin receptor-like kinase 5. CONCLUSIONS: These findings reveal that TGFß1 signaling is functionally interlinked with BMP signaling in LSECs, suggesting druggable targets for the treatment of iron overload diseases associated with deficiency of the BMP2-regulated hormone hepcidin, such as hereditary hemochromatosis, ß-thalassemia, and chronic liver diseases.

MicroRNA-124 Alleviates Retinal Vasoregression via Regulating Microglial Polarization.

Microglial activation is implicated in retinal vasoregression of the neurodegenerative ciliopathy-associated disease rat model (i.e., the polycystic kidney disease (PKD) model). microRNA can regulate microglial activation and vascular function, but the effect of microRNA-124 (miR-124) on retinal vasoregression remains unclear. Transgenic PKD and wild-type Sprague Dawley (SD) rats received miR-124 at 8 and 10 weeks of age intravitreally. Retinal glia activation was assessed by immunofluorescent staining and in situ hybridization. Vasoregression and neuroretinal function were evaluated by quantitative retinal morphometry and electroretinography (ERG), respectively. Microglial polarization was determined by immunocytochemistry and qRT-PCR. Microglial motility was examined via transwell migration assays, wound healing assays, and single-cell tracking. Our data showed that miR-124 inhibited glial activation and improved vasoregession, as evidenced by the reduced pericyte loss and decreased acellular capillary formation. In addition, miR-124 improved neuroretinal function. miR-124 shifted microglial polarization in the PKD retina from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype by suppressing TNF-α, IL-1ß, CCL2, CCL3, MHC-II, and IFN-γ and upregulating Arg1 and IL-10. miR-124 also decreased microglial motility in the migration assays. The transcriptional factor of C/EBP-α-PU.1 signaling, suppressed by miR-124 both in vivo (PKD retina) and in vitro (microglial cells), could serve as a key regulator in microglial activation and polarization. Our data illustrate that miR-124 regulates microglial activation and polarization. miR-124 inhibits pericyte loss and thereby alleviates vasoregression and ameliorates neurovascular function.

TGF-ß2 silencing to target biliary-derived liver diseases.

OBJECTIVE: TGF-ß2 (TGF-ß, transforming growth factor beta), the less-investigated sibling of TGF-ß1, is deregulated in rodent and human liver diseases. Former data from bile duct ligated and MDR2 knockout (KO) mouse models for human cholestatic liver disease suggested an involvement of TGF-ß2 in biliary-derived liver diseases. DESIGN: As we also found upregulated TGFB2 in liver tissue of patients with primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), we now fathomed the positive prospects of targeting TGF-ß2 in early stage biliary liver disease using the MDR2-KO mice. Specifically, the influence of TgfB2 silencing on the fibrotic and inflammatory niche was analysed on molecular, cellular and tissue levels. RESULTS: TgfB2-induced expression of fibrotic genes in cholangiocytes and hepatic stellate cellswas detected. TgfB2 expression in MDR2-KO mice was blunted using TgfB2-directed antisense oligonucleotides (AON). Upon AON treatment, reduced collagen deposition, hydroxyproline content and αSMA expression as well as induced PparG expression reflected a significant reduction of fibrogenesis without adverse effects on healthy livers. Expression analyses of fibrotic and inflammatory genes revealed AON-specific regulatory effects on Ccl3, Ccl4, Ccl5, Mki67 and Notch3 expression. Further, AON treatment of MDR2-KO mice increased tissue infiltration by F4/80-positive cells including eosinophils, whereas the number of CD45-positive inflammatory cells decreased. In line, TGFB2 and CD45 expression correlated positively in PSC/PBC patients and localised in similar areas of the diseased liver tissue. CONCLUSIONS: Taken together, our data suggest a new mechanistic explanation for amelioration of fibrogenesis by TGF-ß2 silencing and provide a direct rationale for TGF-ß2-directed drug development.

ECM1 Prevents Activation of Transforming Growth Factor ß, Hepatic Stellate Cells, and Fibrogenesis in Mice.

BACKGROUND & AIMS: Activation of TGFB (transforming growth factor ß) promotes liver fibrosis by activating hepatic stellate cells (HSCs), but the mechanisms of TGFB activation are not clear. We investigated the role of ECM1 (extracellular matrix protein 1), which interacts with extracellular and structural proteins, in TGFB activation in mouse livers. METHODS: We performed studies with C57BL/6J mice (controls), ECM1-knockout (ECM1-KO) mice, and mice with hepatocyte-specific knockout of EMC1 (ECM1Δhep). ECM1 or soluble TGFBR2 (TGFB receptor 2) were expressed in livers of mice after injection of an adeno-associated virus vector. Liver fibrosis was induced by carbon tetrachloride (CCl4) administration. Livers were collected from mice and analyzed by histology, immunohistochemistry, in situ hybridization, and immunofluorescence analyses. Hepatocytes and HSCs were isolated from livers of mice and incubated with ECM1; production of cytokines and activation of reporter genes were quantified. Liver tissues from patients with viral or alcohol-induced hepatitis (with different stages of fibrosis) and individuals with healthy livers were analyzed by immunohistochemistry and in situ hybridization. RESULTS: ECM1-KO mice spontaneously developed liver fibrosis and died by 2 months of age without significant hepatocyte damage or inflammation. In liver tissues of mice, we found that ECM1 stabilized extracellular matrix-deposited TGFB in its inactive form by interacting with αv integrins to prevent activation of HSCs. In liver tissues from patients and in mice with CCl4-induced liver fibrosis, we found an inverse correlation between level of ECM1 and severity of fibrosis. CCl4-induced liver fibrosis was accelerated in ECM1Δhep mice compared with control mice. Hepatocytes produced the highest levels of ECM1 in livers of mice. Ectopic expression of ECM1 or soluble TGFBR2 in liver prevented fibrogenesis in ECM1-KO mice and prolonged their survival. Ectopic expression of ECM1 in liver also reduced the severity of CCl4-induced fibrosis in mice. CONCLUSIONS: ECM1, produced by hepatocytes, inhibits activation of TGFB and its activation of HSCs to prevent fibrogenesis in mouse liver. Strategies to increase levels of ECM1 in liver might be developed for treatment of fibrosis.

Modulating Portal Hemodynamics With Vascular Ring Allows Efficient Regeneration After Partial Hepatectomy in a Porcine Model.

OBJECTIVE: To investigate safety and efficacy of temporary portal hemodynamics modulation with a novel percutaneously adjustable vascular ring (MID-AVR) onto a porcine model of 75% hepatectomy. BACKGROUND: Postoperative liver failure is a leading cause of mortality after major hepatectomy. Portal flow modulation is an increasingly accepted concept to prevent postoperative liver failure. Nonetheless, the current strategies have shortcomings. METHODS: Resection was performed under hemodynamic monitoring in 17 large, white pigs allocated into 2 groups. Eight pigs had ring around the portal vein for 3 days with the aim of reducing changes in hemodynamics due to hepatectomy. Analysis of hemodynamics, laboratory, and histopathological parameters was performed. RESULTS: Percutaneous inflation, deflation, and removal of the MID-AVR were safe. Two (25%) pigs in the MID-AVR group and 4 (45%) controls died before day 3 (P = NS). A moderate increase of portal flow rate per liver mass after resection was associated with better survival (P = 0.017). The portocaval pressure gradient was lower after hepatectomy in the MID-AVR group (P = 0.001). Postoperative serum bilirubin levels were lower in the MID-AVR group (P = 0.007 at day 5). In the MID-AVR group, the Ki67 index was significantly higher on day 3 (P = 0.043) and the architectural derangement was lower (P < 0.05). Morphometric quantification of the bile canaliculi revealed a significantly lower number of intersection branches (P < 0.05) and intersection nodes (P < 0.001) on day 7 compared with the preoperative specimen, in the control group. These differences were not found in the ring group. CONCLUSIONS: MID-AVR is safe for portal hemodynamics modulation. It might improve liver regeneration by protecting liver microarchitecture.

Characterization of a Fetal Liver Cell Population Endowed with Long-Term Multiorgan Endothelial Reconstitution Potential.

Stable reconstitution of vascular endothelial beds upon transplantation of progenitor cells represents an important challenge due to the paucity and generally limited integration/expansion potential of most identified vascular related cell subsets. We previously showed that mouse fetal liver (FL) hemato/vascular cells from day 12 of gestation (E12), expressing the Stem Cell Leukaemia (SCL) gene enhancer transgene (SCL-PLAP+ cells), had robust endothelial engraftment potential when transferred to the blood stream of newborns or adult conditioned recipients, compared to the scarce vascular contribution of adult bone marrow cells. However, the specific SCL-PLAP+ hematopoietic or endothelial cell subset responsible for the long-term reconstituting endothelial cell (LTR-EC) activity and its confinement to FL developmental stages remained unknown. Using a busulfan-treated newborn transplantation model, we show that LTR-EC activity is restricted to the SCL-PLAP+ VE-cadherin+ CD45- cell population, devoid of hematopoietic reconstitution activity and largely composed by Lyve1+ endothelial-committed cells. SCL-PLAP+ Ve-cadherin+ CD45- cells contributed to the liver sinusoidal endothelium and also to the heart, kidney and lung microvasculature. LTR-EC activity was detected at different stages of FL development, yet marginal activity was identified in the adult liver, revealing unknown functional differences between fetal and adult liver endothelial/endothelial progenitors. Importantly, the observations that expanding donor-derived vascular grafts colocalize with proliferating hepatocyte-like cells and participate in the systemic circulation, support their functional integration into young livers. These findings offer new insights into the engraftment, phonotypical, and developmental characterization of a novel endothelial/endothelial progenitor cell subtype with multiorgan LTR-EC activity, potentially instrumental for the treatment/genetic correction of vascular diseases. Stem Cells 2017;35:507-521.

Bone morphogenetic protein 9 as a key regulator of liver progenitor cells in DDC-induced cholestatic liver injury.

BACKGROUND & AIMS: Bone morphogenetic protein 9 (BMP9) interferes with liver regeneration upon acute injury, while promoting fibrosis upon carbon tetrachloride-induced chronic injury. We have now addressed the role of BMP9 in 3,5 diethoxicarbonyl-1,4 dihydrocollidine (DDC)-induced cholestatic liver injury, a model of liver regeneration mediated by hepatic progenitor cell (known as oval cell), exemplified as ductular reaction and oval cell expansion. METHODS: WT and BMP9KO mice were submitted to DDC diet. Livers were examined for liver injury, fibrosis, inflammation and oval cell expansion by serum biochemistry, histology, RT-qPCR and western blot. BMP9 signalling and effects in oval cells were studied in vitro using western blot and transcriptional assays, plus functional assays of DNA synthesis, cell viability and apoptosis. Crosslinking assays and short hairpin RNA approaches were used to identify the receptors mediating BMP9 effects. RESULTS: Deletion of BMP9 reduces liver damage and fibrosis, but enhances inflammation upon DDC feeding. Molecularly, absence of BMP9 results in overactivation of PI3K/AKT, ERK-MAPKs and c-Met signalling pathways, which together with an enhanced ductular reaction and oval cell expansion evidence an improved regenerative response and decreased damage in response to DDC feeding. Importantly, BMP9 directly targets oval cells, it activates SMAD1,5,8, decreases cell growth and promotes apoptosis, effects that are mediated by Activin Receptor-Like Kinase 2 (ALK2) type I receptor. CONCLUSIONS: We identify BMP9 as a negative regulator of oval cell expansion in cholestatic injury, its deletion enhancing liver regeneration. Likewise, our work further supports BMP9 as an attractive therapeutic target for chronic liver diseases.

Galunisertib modifies the liver fibrotic composition in the Abcb4Ko mouse model.

Transforming growth factor (TGF)-ß stimulates extracellular matrix (ECM) deposition during development of liver fibrosis and cirrhosis, the most important risk factor for the onset of hepatocellular carcinoma. In liver cancer, TGF-ß is responsible for a more aggressive and invasive phenotype, orchestrating remodeling of the tumor microenvironment and triggering epithelial-mesenchymal transition of cancer cells. This is the scientific rationale for targeting the TGF-ß pathway via a small molecule, galunisertib (intracellular inhibitor of ALK5) in clinical trials to treat liver cancer patients at an advanced disease stage. In this study, the hypothesis that galunisertib modifies the tissue microenvironment via inhibition of the TGF-ß pathway is tested in an experimental preclinical model. At the age of 6 months, Abcb4ko mice-a well-established model for chronic liver disease development and progression-are treated twice daily with galunisertib (150 mg/kg) via oral gavage for 14 consecutive days. Two days after the last treatment, blood plasma and livers are harvested for further assessment, including fibrosis scoring and ECM components. The reduction of Smad2 phosphorylation in both parenchymal and non-parenchymal liver cells following galunisertib administration confirms the treatment effectiveness. Damage-related galunisertib does not change cell proliferation, macrophage numbers and leucocyte recruitment. Furthermore, no clear impact on the amount of fibrosis is evident, as documented by PicroSirius red and Gomori-trichome scoring. On the other hand, several fibrogenic genes, e.g., collagens (Col1α1 and Col1α2), Tgf-ß1 and Timp1, mRNA levels are significantly downregulated by galunisertib administration when compared to controls. Most interestingly, ECM/stromal components, fibronectin and laminin-332, as well as the carcinogenic ß-catenin pathway, are remarkably reduced by galunisertib-treated Abcb5ko mice. In conclusion, TGF-ß inhibition by galunisertib interferes, to some extent, with chronic liver progression, not by reducing the stage of liver fibrosis as measured by different scoring systems, but rather by modulating the biochemical composition of the deposited ECM, likely affecting the fate of non-parenchymal cells.

Confounding influence of tamoxifen in mouse models of Cre recombinase-induced gene activity or modulation.

Tamoxifen (TAM) is commonly used for cell type specific Cre recombinase-induced gene inactivation and in cell fate tracing studies. Inducing a gene knockout by TAM and using non-TAM exposed mice as controls lead to a situation where differences are interpreted as consequences of the gene knockout but in reality result from TAM-induced changes in hepatic metabolism. The degree to which TAM may compromise the interpretation of animal experiments with inducible gene expression still has to be elucidated. Here, we report that TAM strongly attenuates CCl4-induced hepatotoxicity in male C57Bl/6N mice, even after a 10 days TAM exposure-free period. TAM decreased (p < 0.0001) the necrosis index and the level of aspartate- and alanine transaminases in CCl4-treated compared to vehicle-exposed mice. TAM pretreatment also led to the downregulation of CYP2E1 (p = 0.0045) in mouse liver tissue, and lowered its activity in CYP2E1 expressing HepG2 cell line. Furthermore, TAM increased the level of the antioxidant ascorbate, catalase, SOD2, and methionine, as well as phase II metabolizing enzymes GSTM1 and UGT1A1 in CCl4-treated livers. Finally, we found that TAM increased the presence of resident macrophages and recruitment of immune cells in necrotic areas of the livers as indicated by F4/80 and CD45 staining. In conclusion, we reveal that TAM increases liver resistance to CCl4-induced toxicity. This finding is of high relevance for studies using the tamoxifen-inducible expression system particularly if this system is used in combination with hepatotoxic compounds such as CCl4.

Cholestasis-induced adaptive remodeling of interlobular bile ducts.

UNLABELLED: Cholestasis is a common complication in liver diseases that triggers a proliferative response of the biliary tree. Bile duct ligation (BDL) is a frequently used model of cholestasis in rodents. To determine which changes occur in the three-dimensional (3D) architecture of the interlobular bile duct during cholestasis, we used 3D confocal imaging, surface reconstructions, and automated image quantification covering a period up to 28 days after BDL. We show a highly reproducible sequence of interlobular duct remodeling, where cholangiocyte proliferation initially causes corrugation of the luminal duct surface, leading to an approximately five-fold increase in surface area. This is analogous to the function of villi in the intestine or sulci in the brain, where an expansion of area is achieved within a restricted volume. The increase in surface area is further enhanced by duct branching, branch elongation, and loop formation through self-joining, whereby an initially relatively sparse mesh surrounding the portal vein becomes five-fold denser through elongation, corrugation, and ramification. The number of connections between the bile duct and the lobular bile canalicular network by the canals of Hering decreases proportionally to the increase in bile duct length, suggesting that no novel connections are established. The diameter of the interlobular bile duct remains constant after BDL, a response that is qualitatively distinct from that of large bile ducts, which tend to enlarge their diameters. Therefore, volume enhancement is only due to net elongation of the ducts. Because curvature and tortuosity of the bile duct are unaltered, this enlargement of the biliary tree is caused by branching and not by convolution. CONCLUSION: BDL causes adaptive remodeling that aims at optimizing the intraluminal surface area by way of corrugation and branching.

Effect of a bradykinin-potentiating factor isolated from scorpion venom (Leiurus quinquestriatus) on some blood indices and lipid profile in irradiated rats.

Bradykinin appears to be an important regulator of cardiovascular function. It is also being increasingly noted as a participant in actions of drugs that affect the liver, kidney, and circulation. In our previous studies, bradykinin-potentiating factor (BPF) isolated from scorpion venom (Leiurus quinquestriatus) has been shown to be protective against hepato- and nephrotoxicity as well as healing skin burns by reducing oxidative stress in hyperglycemic conditions. Therefore, we aim to evaluate the ability of BPF in treating irradiated rats. A group of rats was exposed to γ-irradiation and subsequently treated with BPF injections aiming to elucidate the possibility of BPF to rescue γ-irradiation harmful effects. As controls, we used γ-irradiation exposed, BPF-injected, and untreated rats. The data obtained showed that the irradiated animals suffered from marked changes of many important blood parameters including red blood cells, leukocytes, platelets, hemoglobin, packed cell volume, high-density cholesterol, total cholesterol, triglycerides, and low-density cholesterol. Interestingly, BPF was able to rescue the deleterious effects of irradiation in rats and normalized their blood parameters to the basal levels. We conclude that BPF could ameliorate irradiation damaging effects.

A frequent misinterpretation in current research on liver fibrosis: the vessel in the center of CCl4-induced pseudolobules is a portal vein.

Carbon tetrachloride-induced liver injury is a thoroughly studied model for regeneration and fibrosis in rodents. Nevertheless, its pattern of liver fibrosis is frequently misinterpreted as portal type. To clarify this, we show that collagen type IV+ "streets" and α-SMA+ cells accumulate pericentrally and extend to neighbouring central areas of the liver lobule, forming a 'pseudolobule'. Blood vessels in the center of such pseudolobules are portal veins as indicated by the presence of bile duct cells (CK19+) and the absence of pericentral hepatocytes (glutamine synthetase+). It is critical to correctly describe this pattern of fibrosis, particulary for metabolic zonation studies.

Comparative analysis of 3D culture methods on human HepG2 cells.

Human primary hepatocytes represent a gold standard in in vitro liver research. Due to their low availability and high costs alternative liver cell models with comparable morphological and biochemical characteristics have come into focus. The human hepatocarcinoma cell line HepG2 is often used as a liver model for toxicity studies. However, under two-dimensional (2D) cultivation conditions the expression of xenobiotic-metabolizing enzymes and typical liver markers such as albumin is very low. Cultivation for 21 days in a three-dimensional (3D) Matrigel culture system has been reported to strongly increase the metabolic competence of HepG2 cells. In our present study we further compared HepG2 cell cultivation in three different 3D systems: collagen, Matrigel and Alvetex culture. Cell morphology, albumin secretion, cytochrome P450 monooxygenase enzyme activities, as well as gene expression of xenobiotic-metabolizing and liver-specific enzymes were analyzed after 3, 7, 14, and 21 days of cultivation. Our results show that the previously reported increase of metabolic competence of HepG2 cells is not primarily the result of 3D culture but a consequence of the duration of cultivation. HepG2 cells grown for 21 days in 2D monolayer exhibit comparable biochemical characteristics, CYP activities and gene expression patterns as all 3D culture systems used in our study. However, CYP activities did not reach the level of HepaRG cells. In conclusion, the increase of metabolic competence of the hepatocarcinoma cell line HepG2 is not due to 3D cultivation but rather a result of prolonged cultivation time.

TiQuant: software for tissue analysis, quantification and surface reconstruction.

MOTIVATION: TiQuant is a modular software tool for efficient quantification of biological tissues based on volume data obtained by biomedical image modalities. It includes a number of versatile image and volume processing chains tailored to the analysis of different tissue types which have been experimentally verified. TiQuant implements a novel method for the reconstruction of three-dimensional surfaces of biological systems, data that often cannot be obtained experimentally but which is of utmost importance for tissue modelling in systems biology. AVAILABILITY AND IMPLEMENTATION: TiQuant is freely available for non-commercial use at msysbio.com/tiquant. Windows, OSX and Linux are supported. CONTACT: hoehme@uni-leipzig.de SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Gene network activity in cultivated primary hepatocytes is highly similar to diseased mammalian liver tissue.

It is well known that isolation and cultivation of primary hepatocytes cause major gene expression alterations. In the present genome-wide, time-resolved study of cultivated human and mouse hepatocytes, we made the observation that expression changes in culture strongly resemble alterations in liver diseases. Hepatocytes of both species were cultivated in collagen sandwich and in monolayer conditions. Genome-wide data were also obtained from human NAFLD, cirrhosis, HCC and hepatitis B virus-infected tissue as well as mouse livers after partial hepatectomy, CCl4 intoxication, obesity, HCC and LPS. A strong similarity between cultivation and disease-induced expression alterations was observed. For example, expression changes in hepatocytes induced by 1-day cultivation and 1-day CCl4 exposure in vivo correlated with R = 0.615 (p < 0.001). Interspecies comparison identified predominantly similar responses in human and mouse hepatocytes but also a set of genes that responded differently. Unsupervised clustering of altered genes identified three main clusters: (1) downregulated genes corresponding to mature liver functions, (2) upregulation of an inflammation/RNA processing cluster and (3) upregulated migration/cell cycle-associated genes. Gene regulatory network analysis highlights overrepresented and deregulated HNF4 and CAR (Cluster 1), Krüppel-like factors MafF and ELK1 (Cluster 2) as well as ETF (Cluster 3) among the interspecies conserved key regulators of expression changes. Interventions ameliorating but not abrogating cultivation-induced responses include removal of non-parenchymal cells, generation of the hepatocytes' own matrix in spheroids, supplementation with bile salts and siRNA-mediated suppression of key transcription factors. In conclusion, this study shows that gene regulatory network alterations of cultivated hepatocytes resemble those of inflammatory liver diseases and should therefore be considered and exploited as disease models.

Gene networks and transcription factor motifs defining the differentiation of stem cells into hepatocyte-like cells.

BACKGROUND & AIMS: The differentiation of stem cells to hepatocyte-like cells (HLC) offers the perspective of unlimited supply of human hepatocytes. However, the degree of differentiation of HLC remains controversial. To obtain an unbiased characterization, we performed a transcriptomic study with HLC derived from human embryonic and induced stem cells (ESC, hiPSC) from three different laboratories. METHODS: Genome-wide gene expression profiles of ESC and HLC were compared to freshly isolated and up to 14days cultivated primary human hepatocytes. Gene networks representing successful and failed hepatocyte differentiation, and the transcription factors involved in their regulation were identified. RESULTS: Gene regulatory network analysis demonstrated that HLC represent a mixed cell type with features of liver, intestine, fibroblast and stem cells. The "unwanted" intestinal features were associated with KLF5 and CDX2 transcriptional networks. Cluster analysis identified highly correlated groups of genes associated with mature liver functions (n=1057) and downregulated proliferation associated genes (n=1562) that approach levels of primary hepatocytes. However, three further clusters containing 447, 101, and 505 genes failed to reach levels of hepatocytes. Key TF of two of these clusters include SOX11, FOXQ1, and YBX3. The third unsuccessful cluster, controlled by HNF1, CAR, FXR, and PXR, strongly overlaps with genes repressed in cultivated hepatocytes compared to freshly isolated hepatocytes, suggesting that current in vitro conditions lack stimuli required to maintain gene expression in hepatocytes, which consequently also explains a corresponding deficiency of HLC. CONCLUSIONS: The present gene regulatory network approach identifies key transcription factors which require modulation to improve HLC differentiation.