Primary hepatocytes and their cultures in liver apoptosis research

Combining human liver ECM with topographically featured electrospun scaffolds for engineering hepatic microenvironment

Liver disease cases are rapidly expanding worldwide, and transplantation remains the only effective cure for end-stage disease. There is an increasing demand for developing potential drug treatments, and regenerative therapies using in-vitro culture platforms. Human decellularized extracellular matrix (dECM) is an appealing alternative to conventional animal tissues as it contains human-specific proteins and can serve as scaffolding materials. Herein we exploit this with human donor tissue from discarded liver which was not suitable for transplant using a synergistic approach to combining biological and topographical cues in electrospun materials as an in-vitro culture platform. To realise this, we developed a methodology for incorporating human liver dECM into electrospun polycaprolactone (PCL) fibres with surface nanotopographies (230-580 nm). The hybrid scaffolds were fabricated using varying concentrations of dECM; their morphology, mechanical properties, hydrophilicity and stability were analysed. The scaffolds were validated using HepG2 and primary mouse hepatocytes, with subsequent results indicating that the modified scaffolds-maintained cell growth and influenced cell attachment, proliferation and hepatic-related gene expression. This work demonstrates a novel approach to harvesting the potential from decellularized human tissues in the form of innovative in-vitro culture platforms for liver.

Enhanced apoptotic index in hepatocytes, Kupffer cells, and inflammatory infiltrate showed positive correlation with hepatic lesion intensity, parasite load, and clinical status in naturally Leishmania-infected dogs

It is unknown if Leishmania amastigote infections affect hepatocytes and Kupffer cell apoptosis, and the role played by apoptosis in liver lesions in leishmaniasis is still unclear. Clinically affected and subclinically infected dogs with leishmaniosis and uninfected controls were assessed. Parasite load, biochemical markers for evaluation of liver damage, morphometry (area, perimeter, number of inflammatory focus, major and minor diameters), apoptosis in hepatic tissue (hepatocytes, Kupffer cells, and inflammatory infiltrates) and cellularity in inflammatory foci were quantified. The parasite load in clinically affected dogs proved to be higher than in the other groups. All morphometric parameters (area, perimeter, number of inflammatory focus, major and minor diameters) from clinically affected were higher than the values found in the subclinically infected and uninfected control dogs. Only clinically affected dogs presented high levels of ALT, FA, GGT and cholesterol in serum. Strong positive correlation was observed between biochemical markers for evaluation of liver damage (ALT, FA, GGT and cholesterol) and hepatic apoptosis (hepatocytes, Kupffer cells, and inflammation). Clinically affected dogs showed a more intense hepatic lesion. Hepatocytes showed a higher rate of apoptosis in Leishmania-infected dogs than in uninfected control dogs. The Kupffer cell apoptotic index and apoptosis within the inflammatory infiltrates were higher in clinically affected dogs. The apoptotic index evaluated in hepatocytes, Kupffer cells, and inflammatory infiltrates showed a positive correlation with the intensity of the hepatic lesion, parasite load, and clinical status. Apoptotic cells also showed positive immunostaining for TUNEL, Bcl2, and Bax. Our data showed that hepatic apoptosis was related to the severity of liver damage, the progression of infection, and the parasite load in leishmaniasis. Apoptotic regulated cell recruitment modulated the inflammatory response and favored the survival and dissemination of parasites, depending on the clinical status of the Leishmania-infected dogs.

A robust reprogramming strategy for generating hepatocyte-like cells usable in pharmaco-toxicological studies

BACKGROUND

High-throughput pharmaco-toxicological testing frequently relies on the use of established liver-derived cell lines, such as HepG2 cells. However, these cells often display limited hepatic phenotype and features of neoplastic transformation that may bias the interpretation of the results. Alternate models based on primary cultures or differentiated pluripotent stem cells are costly to handle and difficult to implement in high-throughput screening platforms. Thus, cells without malignant traits, optimal differentiation pattern, producible in large and homogeneous amounts and with patient-specific phenotypes would be desirable.

METHODS

We have designed and implemented a novel and robust approach to obtain hepatocytes from individuals by direct reprogramming, which is based on a combination of a single doxycycline-inducible polycistronic vector system expressing HNF4A, HNF1A and FOXA3, introduced in human fibroblasts previously transduced with human telomerase reverse transcriptase (hTERT). These cells can be maintained in fibroblast culture media, under standard cell culture conditions.

RESULTS

Clonal hTERT-transduced human fibroblast cell lines can be expanded at least to 110 population doublings without signs of transformation or senescence. They can be easily differentiated at any cell passage number to hepatocyte-like cells with the simple addition of doxycycline to culture media. Acquisition of a hepatocyte phenotype is achieved in just 10 days and requires a simple and non-expensive cell culture media and standard 2D culture conditions. Hepatocytes reprogrammed from low and high passage hTERT-transduced fibroblasts display very similar transcriptomic profiles, biotransformation activities and show analogous pattern behavior in toxicometabolomic studies. Results indicate that this cell model outperforms HepG2 in toxicological screening. The procedure also allows generation of hepatocyte-like cells from patients with given pathological phenotypes. In fact, we succeeded in generating hepatocyte-like cells from a patient with alpha-1 antitrypsin deficiency, which recapitulated accumulation of intracellular alpha-1 antitrypsin polymers and deregulation of unfolded protein response and inflammatory networks.

CONCLUSION

Our strategy allows the generation of an unlimited source of clonal, homogeneous, non-transformed induced hepatocyte-like cells, capable of performing typical hepatic functions and suitable for pharmaco-toxicological high-throughput testing. Moreover, as far as hepatocyte-like cells derived from fibroblasts isolated from patients suffering hepatic dysfunctions, retain the disease traits, as demonstrated for alpha-1-antitrypsin deficiency, this strategy can be applied to the study of other cases of anomalous hepatocyte functionality.

Cellular microarrays for assessing single-cell phenotypic changes in vascular cell populations

Microengineering technologies provide bespoke tools for single-cell studies, including microarray approaches. There are many challenges when culturing adherent single cells in confined geometries for extended periods, including the ability of migratory cells to overcome confining cell-repellent surfaces with time. Following studies suggesting clonal expansion of only a few vascular smooth muscle cells (vSMCs) contributes to plaque formation, the investigation of vSMCs at the single-cell level is central to furthering our understanding of atherosclerosis. Herein, we present a medium throughput cellular microarray, for the tracking of single, freshly-isolated vSMCs as they undergo phenotypic modulation in vitro. Our solution facilitates long-term cell confinement (> 3 weeks) utilising novel application of surface functionalisation methods to define individual culture microwells. We demonstrate successful tracking of hundreds of native vSMCs isolated from rat aortic and carotid artery tissue, monitoring their proliferative capacity and uptake of oxidised low-density lipoprotein (oxLDL) by live-cell microscopy. After 7 days in vitro, the majority of viable SMCs remained as single non-proliferating cells (51% aorta, 78% carotid). However, a sub-population of vSMCs demonstrated high proliferative capacity (≥ 10 progeny; 18% aorta, 5% carotid), in line with reports that a limited number of medial SMCs selectively expand to populate atherosclerotic lesions. Furthermore, we show that, when exposed to oxLDL, proliferative cells uptake higher levels of lipoproteins, whilst also expressing greater levels of galectin-3. Our microwell array approach enables long-term characterisation of multiple phenotypic characteristics and the identification of new cellular sub-populations in migratory, proliferative adherent cell types.

Upgrading Hepatic Differentiation and Functions on 3D Printed Silk-Decellularized Liver Hybrid Scaffolds

We developed hybrid liver-specific three-dimensional (3D) printed scaffolds using a solubilized native decellularized liver (DCL) matrix and silk fibroin (SF) and investigated their ability to support functional cultures of hepatic cells. Rat livers were decellularized by perfusing detergents via the portal vein, solubilized using pepsin to form DCL, and characterized. SF blended with gelatin (8% w/v) was optimized with varying percentages of DCL to obtain silk gelatin-DCL bioink (SG-DCL). Different compositions of SG-DCL were studied by rheology for optimum versatility and print fidelity. 3D printed six-layered scaffolds were fabricated using a sophisticated direct-write 3D bioprinter. Huh7 cells were cultured on the 3D printed scaffolds for 3 weeks. 3D printed SG scaffolds without DCL along with 2D films (SG and SG-DCL) and 2D culture on tissue culture Petri dish control were used for comparative studies. The DCL matrix showed the absence of cells in histology and SEM. The combined SG-DCL ink at all of the studied DCL percentages (1-10%) revealed shear-thinning behavior in the printable range. The storage modulus value for the SG-DCL ink at all DCL percentages was higher than the loss modulus. In comparison to 2D controls, hepatic cells cultured on 3D SG-DCL revealed increased proliferation until 2 weeks and an upregulated expression of hepatocyte markers, including asialoglycoprotein receptor 1 (ASGR1). The Wnt pathway gene β-catenin was upregulated by more than 4-fold in 3D SG-DCL on day 3, while it showed a decline on day 7 as compared to 3D SG and also 2D controls. The expression of the epithelial cell adhesion molecule (EpCAM) was however lower in both 2D SG-DCL (2-fold) and 3D SG-DCL (2.5-fold) as compared to that in 2D controls. Immunofluorescence studies validated the protein expression of ASGR1 in 3D SG-DCL. Albumin (ALB) was not identified on SG scaffolds but prominently expressed in 3D SG-DCL constructs. In comparison to 2D SG, both ALB (1.8-fold) and urea (5-fold) were enhanced in cells cultured on 3D SG-DCL on day 7 of culture. Hence, the SG-DCL 3D printed scaffolds provide a conducive microenvironment for elevating differentiation and functions of hepatic cells possibly through an involvement of the Wnt/β-catenin signaling pathway.

In Vitro Liver Toxicity Testing of Chemicals: A Pragmatic Approach

The liver is among the most frequently targeted organs by noxious chemicals of diverse nature. Liver toxicity testing using laboratory animals not only raises serious ethical questions, but is also rather poorly predictive of human safety towards chemicals. Increasing attention is, therefore, being paid to the development of non-animal and human-based testing schemes, which rely to a great extent on in vitro methodology. The present paper proposes a rationalized tiered in vitro testing strategy to detect liver toxicity triggered by chemicals, in which the first tier is focused on assessing general cytotoxicity, while the second tier is aimed at identifying liver-specific toxicity as such. A state-of-the-art overview is provided of the most commonly used in vitro assays that can be used in both tiers. Advantages and disadvantages of each assay as well as overall practical considerations are discussed.

The human vault RNA enhances tumorigenesis and chemoresistance through the lysosome in hepatocellular carcinoma

The small non-coding VTRNA1-1 (vault RNA 1–1) is known to confer resistance to apoptosis in several malignant cell lines and to also modulate the macroautophagic/autophagic flux in hepatocytes, thus highlighting its pro-survival role. Here we describe a new function of VTRNA1-1 in regulating in vitro and in vivo tumor cell proliferation, tumorigenesis and chemoresistance. Knockout (KO) of VTRNA1-1 in human hepatocellular carcinoma cells reduced nuclear localization of TFEB (transcription factor EB), leading to a downregulation of the coordinated lysosomal expression and regulation (CLEAR) network genes and lysosomal compartment dysfunction. We demonstrate further that impaired lysosome function due to loss of VTRNA1-1 potentiates the anticancer effect of conventional chemotherapeutic drugs. Finally, loss of VTRNA1-1 reduced drug lysosomotropism allowing higher intracellular compound availability and thereby significantly reducing tumor cell proliferation in vitro and in vivo. These findings reveal a so far unknown role of VTRNA1-1 in the intracellular catabolic compartment and describe its contribution to lysosome-mediated chemotherapy resistance.

Abbreviations: ATP6V0D2: ATPase H+ transporting V0 subunit d2; BafA: bafilomycin A1; CLEAR: coordinated lysosomal expression and regulation; CQ: chloroquine; DMSO: dimethyl sulfoxide; GST-BHMT: glutathionine S-transferase N-terminal to betaine–homocysteine S-methyltransferase; HCC: hepatocellular carcinoma; LAMP1: lysosomal associated membrane protein 1; LLOMe: L-leucyl-L-leucine methyl ester; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MAPK: mitogen-activated protein kinase; MITF: melanocyte inducing transcription factor; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; ncRNA: non-coding RNA; RNP: ribonucleoprotein; SF: sorafenib; SQSTM1/p62: sequestosome 1; STS: staurosporine; tdRs: tRNA-derived RNAs; TFE3: transcription factor binding to IGHM enhancer 3; TFEB: transcription factor EB; vtRNA: vault RNA transcript.

Response differences of HepG2 and Primary Mouse Hepatocytes to morphological changes in electrospun PCL scaffolds

Liver disease cases are rapidly expanding across the globe and the only effective cure for end-stage disease is a transplant. Transplant procedures are costly and current supply of donor livers does not satisfy demand. Potential drug treatments and regenerative therapies that are being developed to tackle these pressing issues require effective in-vitro culture platforms. Electrospun scaffolds provide bio-mimetic structures upon which cells are cultured to regulate function in-vitro. This study aims to shed light on the effects of electrospun PCL morphology on the culture of an immortalised hepatic cell line and mouse primary hepatocytes. Each cell type was cultured on large 4-5 µm fibres and small 1-2 µm fibres with random, aligned and highly porous cryogenically spun configurations. Cell attachment, proliferation, morphology and functional protein and gene expression was analysed. Results show that fibre morphology has a measurable influence on cellular morphology and function, with the alteration of key functional markers such as CYP1A2 expression.

In vitro effects of Type I interferons (IFNτ and IFNα) on bovine hepatocytes cultured with or without Kupffer cells

In cattle, maternal recognition of early pregnancy depends on the effects of the embryonic signal interferon (IFN)-τ. IFN-stimulated genes have been upregulated in the maternal liver during early pregnancy. In this study, primary hepatocyte cell culture models were evaluated for their suitability to test Type I IFN effects invitro. The expression of target genes (interferon-stimulated gene 15 (ISG-15), interferon-induced GTP-binding protein (MX-1), C-X-C motif chemokine 10 (CXCL-10), CXCL-5, insulin-like growth factor 1 (IGF-1), IGF binding protein 2 (IGFBP-2)) was measured using reverse transcription-quantitative polymerase chain reaction in hepatocytes from monoculture or in indirect coculture with Kupffer cells (HKCid) on Days 1, 2, 3 and 4 of culture (n=21 donor cows). Gene expression was also measured on Day 4 after challenging the cultures with recombinant IFNτ, IFNα, progesterone (P4), IFNτ+IFNα or IFNτ+P4 for 6h. A significant increase in the mRNA expression of target genes in hepatocytes was shown in response to stimulation with IFNτ. The Kupffer cells in coculture did not influence the effects of IFNτ in hepatocytes. In conclusion, primary bovine hepatocyte cultures are suitable for stimulation experiments with Type I IFNs and as an extrauterine model for embryo-maternal communication. The proposed endocrine action of IFNτ in the liver may affect maternal metabolism and immune function in the liver.

Tm7sf2 Disruption Alters Radial Gene Positioning in Mouse Liver Leading to Metabolic Defects and Diabetes Characteristics

Tissue-specific patterns of radial genome organization contribute to genome regulation and can be established by nuclear envelope proteins. Studies in this area often use cancer cell lines, and it is unclear how well such systems recapitulate genome organization of primary cells or animal tissues; so, we sought to investigate radial genome organization in primary liver tissue hepatocytes. Here, we have used a NET47/Tm7sf2^–/– liver model to show that manipulating one of these nuclear membrane proteins is sufficient to alter tissue-specific gene positioning and expression. Dam-LaminB1 global profiling in primary liver cells shows that nearly all the genes under such positional regulation are related to/important for liver function. Interestingly, Tm7sf2 is a paralog of the HP1-binding nuclear membrane protein LBR that, like Tm7sf2, also has an enzymatic function in sterol reduction. Fmo3 gene/locus radial mislocalization could be rescued with human wild-type, but not TM7SF2 mutants lacking the sterol reductase function. One central pathway affected is the cholesterol synthesis pathway. Within this pathway, both Cyp51 and Msmo1 are under Tm7sf2 positional and expression regulation. Other consequences of the loss of Tm7sf2 included weight gain, insulin sensitivity, and reduced levels of active Akt kinase indicating additional pathways under its regulation, several of which are highlighted by mispositioning genes. This study emphasizes the importance for tissue-specific radial genome organization in tissue function and the value of studying genome organization in animal tissues and primary cells over cell lines.

Current progress in hepatic tissue regeneration by tissue engineering

Liver, as a vital organ, is responsible for a wide range of biological functions to maintain homeostasis and any type of damages to hepatic tissue contributes to disease progression and death. Viral infection, trauma, carcinoma, alcohol misuse and inborn errors of metabolism are common causes of liver diseases are a severe known reason for leading to end-stage liver disease or liver failure. In either way, liver transplantation is the only treatment option which is, however, hampered by the increasing scarcity of organ donor. Over the past years, considerable efforts have been directed toward liver regeneration aiming at developing new approaches and methodologies to enhance the transplantation process. These approaches include producing decellularized scaffolds from the liver organ, 3D bio-printing system, and nano-based 3D scaffolds to simulate the native liver microenvironment. The application of small molecules and micro-RNAs and genetic manipulation in favor of hepatic differentiation of distinct stem cells could also be exploited. All of these strategies will help to facilitate the application of stem cells in human medicine. This article reviews the most recent strategies to generate a high amount of mature hepatocyte-like cells and updates current knowledge on liver regenerative medicine.

Cross-species comparison of CAR-mediated procarcinogenic key events in a 3D liver microtissue model

Characterisation of the mode of action (MOA) of constitutive androstane receptor (CAR)-mediated rodent liver tumours involves measurement 5 key events including activation of the CAR receptor, altered gene expression, hepatocellular proliferation, clonal expansion and increased hepatocellular adenomas/carcinomas. To test whether or not liver 3D microtissues (LiMTs) recapitulate CAR- mediated procarcinogenic key events in response to the prototypical CAR activator phenobarbital (PB) we performed hepatocyte proliferation (LI%) analysis in rat and human LiMTs using a microTMA technology in conjunction with integrated transcriptomics (microarray) and proteomics analysis. The rationale for this approach was that LiMTs containing parenchymal and non-parenchymal cells (NPCs) are more physiologically representative of liver and thus would generate data more relevant to the in vivo situation. Rat and human LiMTs were treated with PB over a range of concentrations (500 uM - 2000 uM) and times (24 h - 96 h) in a dose-response/time-course analysis. There was a dose-dependent induction of LI% in rat LiMTs, however there was little or no effect of PB on LI% in human LiMTs. ATP levels in the rat and human LiMTs were similar to control in all of the PB treatments. There was also a dose- and time-dependent PB-mediated RNA induction of CAR regulated genes CYP2B6/Cyp2b2, CYP3A7/Cyp3a9 and UGT1A6/Ugt1a6 in human and rat LiMTs, respectively. These CAR regulated genes were also upregulated at the protein level. Ingenuity pathways analysis (IPA) indicated that there was a significant (Z score >2.0;-log p value >) activation of CAR by PB in both human and rat LiMTs. These results indicate that human and rat LiMTs showed the expected responses at the level of PB-induced hepatocyte proliferation and enzyme induction with rat LiMTs showing significant dose-dependent effects while human LiMTs showed no proliferation response but did show dose-dependent enzyme induction at the RNA and protein levels. In conclusion LiMTs serve as a model to provide mechanistic data for 3 of the 5 key events considered necessary to establish a CAR-mediated MOA for liver tumourigenesis and thus can potentially reduce the use of animals when compiling mechanistic data packages.

Optimization of DamID for use in primary cultures of mouse hepatocytes

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DamID adaptation to primary hepatocytes may preserve tissue 3D genome architecture.

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Growth factors, vector tropism and enhancers are needed for DamID in primary cells.

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Mitochondrial contamination can yield high background signal in primary cells.

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Signal intensity comparisons can increase calling of interesting differential LADs.

DamID, a method to identify DNA associating with a particular protein, was originally developed for use in immortalized tissue culture lines. The power of this technique has led to its adaptation for a number of additional systems. Here we report adaptations for its use in primary cells isolated from rodents with emphasis on the challenges this presents. Specifically, we present several modifications that allow the method to be performed in mouse acutely isolated primary hepatocytes while seemingly maintaining tissue genome architecture. We also describe the downstream bioinformatic analysis necessary to identify LADs and discuss some of the parameters and their effects with regards to the sensitivity of the method.

Cellular Mechanisms of Hepatoprotection Mediated by M2-Like Macrophages

Background

Acute liver injury in the setting of hepatic fibrosis is an intriguing and still unsettled issue. We previously have demonstrated the protective effects conferred by M2-like macrophages in the fibrotic liver. In the present work, we further decipher the cellular mechanisms governing this hepatoprotection.

Material/Methods

Macrophages were isolated from control mice (M0 macrophages), then polarized into M1 or M2 phenotype using IFN-γ or IL-4, respectively. Conditioned media (CM) from M0, M1, and M2 macrophages were harvested and applied to M1 macrophages. Cell apoptosis was evaluated by immunostaining and real-time PCR. Similarly, human monocyte-derived macrophages were isolated and polarized, then M0, M1, and M2 CM were applied to HL-7702 or HepG2 cells followed by apoptosis induction. Cell apoptosis was assessed by flow cytometry.

Results

For the mouse conditioned medium experiment, stronger expression of cleaved caspase 3 and higher Bax/Bcl-2 mRNA ratio were found in M1 macrophages pretreated with M2 CM compared to those in M1 macrophages pretreated with M0 or M1 CM. Similarly, exposure of HL-7702 and HepG2 cells to either M0 or M1 CM had no significant effect on cell apoptosis. Nevertheless, the frequency of hepatocyte apoptosis was substantially reduced in HL-7702 (from 32.23±2.99 to 15.37±0.69 for Annexin V+/PI+ staining, p<0.01) and HepG2 cells (from 36.1±7.26 to 15.2±1.2 for Annexin V+/PI+ staining, p<0.01) with M2 CM pretreatment.

Conclusions

M2-like macrophages exert their hepatoprotective effect by promoting M1-like macrophage apoptosis but protecting against hepatocyte apoptosis.

Prolongation of liver-specific function for primary hepatocytes maintenance in 3D printed architectures

Isolated primary hepatocytes from the liver are very similar to in vivo native liver hepatocytes, but they have the disadvantage of a limited lifespan in 2D culture. Although a sandwich culture and 3D organoids with mesenchymal stem cells (MSCs) as an attractive assistant cell source to extend lifespan can be used, it cannot fully reproduce the in vivo architecture. Moreover, long-term 3D culture leads to cell death because of hypoxic stress. Therefore, to overcome the drawback of 2D and 3D organoids, we try to use a 3D printing technique using alginate hydrogels with primary hepatocytes and MSCs. The viability of isolated hepatocytes was more than 90%, and the cells remained alive for 7 days without morphological changes in the 3D hepatic architecture with MSCs. Compared to a 2D system, the expression level of functional hepatic genes and proteins was higher for up to 7 days in the 3D hepatic architecture. These results suggest that both the 3D bio-printing technique and paracrine molecules secreted by MSCs supported long-term culture of hepatocytes without morphological changes. Thus, this technique allows for widespread expansion of cells while forming multicellular aggregates, may be applied to drug screening and could be an efficient method for developing an artificial liver.

Transcriptomic characterization of bovine primary cultured hepatocytes; a cross-comparison with a bovine liver and the Madin-Darby bovine kidney cells

Bovine primary cultured hepatocytes (CHs) are widely used in vitro models for liver toxicity testing. However, little is known about their whole-transcriptome profile and its resemblance to the normal liver tissue. In the present study, we profiled - by microarray - the whole-transcriptome of bovine CHs (n=4) and compared it with the transcriptomic landscape of control liver samples (n=8), as well the Madin-Darby bovine kidney (MDBK) cells (n=4). Compared with liver tissue, the bovine CHs relatively expressed (fold change >2, P<0.05) about 2155 and 2073 transcripts at a lower and higher abundance, respectively. Of those expressed at a lower abundance, many were drug biotransformation enzyme-coding genes, such as the cytochrome P450 family (CYPs), sulfotransferases, methyltransferases, and glutathione S-transferases. Also, several drug transporters and solute carriers were expressed at a lower abundance in bovine CHs. 'Drug metabolism', 'PPAR signaling', and 'metabolism of xenobiotics by CYPs' were among the most negatively-enriched pathways in bovine CHs compared with liver. A qPCR cross-validation using 8 selected genes evidenced a high correlation (r=0.95, P=0.001) with the corresponding microarray results. Although from a kidney origin, and albeit to a lower extent compared to bovine CHs, the MDBK cells showed a basal expression of many CYP-coding genes. Our study provides a whole-transcriptome-based evidence for the bovine CHs and hepatic tissue resemblance. Overall, the bovine CHs' transcriptomic profile might render it unreliable as an in vitro model to study drug metabolism.

Three-dimensional (3D) printing of mouse primary hepatocytes to generate 3D hepatic structure

Purpose

The major problem in producing artificial livers is that primary hepatocytes cannot be cultured for many days. Recently, 3-dimensional (3D) printing technology draws attention and this technology regarded as a useful tool for current cell biology. By using the 3D bio-printing, these problems can be resolved.

Methods

To generate 3D bio-printed structures (25 mm × 25 mm), cells-alginate constructs were fabricated by 3D bio-printing system. Mouse primary hepatocytes were isolated from the livers of 6–8 weeks old mice by a 2-step collagenase method. Samples of 4 × 10⁷ hepatocytes with 80%–90% viability were printed with 3% alginate solution, and cultured with well-defined culture medium for primary hepatocytes. To confirm functional ability of hepatocytes cultured on 3D alginate scaffold, we conducted quantitative real-time polymerase chain reaction and immunofluorescence with hepatic marker genes.

Results

Isolated primary hepatocytes were printed with alginate. The 3D printed hepatocytes remained alive for 14 days. Gene expression levels of Albumin, HNF-4α and Foxa3 were gradually increased in the 3D structures. Immunofluorescence analysis showed that the primary hepatocytes produced hepatic-specific proteins over the same period of time.

Conclusion

Our research indicates that 3D bio-printing technique can be used for long-term culture of primary hepatocytes. It can therefore be used for drug screening and as a potential method of producing artificial livers.

Isolation and cultivation of adult primary bovine hepatocytes from abattoir derived liver

The aim was to establish a cell culture of adult primary bovine hepatocytes obtained from liver following slaughter and to cultivate the cells in a sandwich culture. Cells and medium samples were taken after separation of cells (day 0), during monolayer (days 1, 2 and 3) and during sandwich culture (days 1, 2, 3, 4, 7, 10 and 14). The mRNA expression of BAX, BCL2L, FAS, IGF-1 and GHR1A was measured as well as urea and LDH. Hepatocytes were obtained by using a two-step collagenase perfusion and were purified thereafter by density gradient centrifugation. The viability was 68.2 ± 9.5 %. In sandwich culture, cells have a typical polygonal hepatocyte-like shape, build cell-cell contacts, and show irregularity of cell borders suggesting bile canaliculi generation. The BAX mRNA expression increased on day 1 as well but decreased steadily until day 3 and remained constant for 14 days. Urea- and LDH-concentrations increased from day 4 to day 7. In conclusion, we found that it is possible to gather viable primary hepatocytes from adult bovine liver after slaughter, and that cells gathered this way show typical morphologies, urea-production and low LDH-leakage especially at day 4 in a sandwich system.

In vitro testing of basal cytotoxicity: Establishment of an adverse outcome pathway from chemical insult to cell death

In this paper, an in vitro basal cytotoxicity testing strategy is described for new chemical entities that lack any pre-existing information on potential toxicity. Special attention is paid to the selection of the cellular system, cytotoxicity assay and exposure conditions. This approach is based on a newly proposed generic adverse outcome pathway from chemical insult to cell death that consists of 3 steps, including initial cell injury, mitochondrial dysfunction and cell demise. The suggested strategy to consider in vitro basal cytotoxicity as a first step in evaluating the toxicity of new chemical entities can be placed in a tiered strategy that could be continued by evaluating more specific types of toxicity.

The pseudokinase MLKL mediates programmed hepatocellular necrosis independently of RIPK3 during hepatitis

Although necrosis and necroinflammation are central features of many liver diseases, the role of programmed necrosis in the context of inflammation-dependent hepatocellular death remains to be fully determined. Here, we have demonstrated that the pseudokinase mixed lineage kinase domain-like protein (MLKL), which plays a key role in the execution of receptor-interacting protein (RIP) kinase-dependent necroptosis, is upregulated and activated in human autoimmune hepatitis and in a murine model of inflammation-dependent hepatitis. Using genetic and pharmacologic approaches, we determined that hepatocellular necrosis in experimental hepatitis is driven by an MLKL-dependent pathway that occurs independently of RIPK3. Moreover, we have provided evidence that the cytotoxic activity of the proinflammatory cytokine IFN-γ in hepatic inflammation is strongly connected to induction of MLKL expression via activation of the transcription factor STAT1. In summary, our results reveal a pathway for MLKL-dependent programmed necrosis that is executed in the absence of RIPK3 and potentially drives the pathogenesis of severe liver diseases.

Basic fibroblast growth factor-treated adipose tissue-derived mesenchymal stem cell infusion to ameliorate liver cirrhosis via paracrine hepatocyte growth factor

BACKGROUND AND AIM

Recent studies show that adipose tissue-derived mesenchymal stem cells have potential clinical applications. However, the mechanism has not been fully elucidated yet. Here, we investigated the effect of basic fibroblast growth factor-treated adipose tissue-derived mesenchymal stem cells infusion on a liver fibrosis rat model and elucidated the underlying mechanism.

METHODS

Adipose tissue-derived mesenchymal stem cells were infused into carbon tetrachloride-induced hepatic fibrosis rats through caudal vein. Liver functions and pathological changes were assessed. A co-culture model was used to clarify the potential mechanism.

RESULTS

Basic fibroblast growth factor treatment markedly improved the proliferation, differentiation, and hepatocyte growth factor expression ability of adipose tissue-derived mesenchymal stem cells. Although adipose tissue-derived mesenchymal stem cells infusion alone slightly ameliorated liver functions and suppressed fibrosis progression, basic fibroblast growth factor-treatment significantly enhanced the therapeutic effect in association with elevated hepatocyte growth factor expression. Moreover, double immunofluorescence staining confirmed that the infused cells located in fibrosis area. Furthermore, co-culture with adipose tissue-derived mesenchymal stem cell led to induction of hepatic stellate cell apoptosis and enhanced hepatocyte proliferation. However, these effects were significantly weakened by knockdown of hepatocyte growth factor. Mechanism investigation revealed that co-culture with adipose tissue-derived mesenchymal stem cells activated c-jun N-terminal kinase-p53 signaling in hepatic stellate cell and promoted apoptosis.

CONCLUSIONS

Basic fibroblast growth factor treatment enhanced the therapeutic effect of adipose tissue-derived mesenchymal stem cells, and secretion of hepatocyte growth factor from adipose tissue-derived mesenchymal stem cells plays a critical role in amelioration of liver injury and regression of fibrosis.

Measurement of Apoptotic and Necrotic Cell Death in Primary Hepatocyte Cultures

Hepatotoxicity, including drug-induced liver injury, is frequently accompanied by cell death. The latter is typically driven by apoptosis or necrosis, which substantially differ based upon biochemical and morphological criteria. This chapter describes two commonly used methods to probe apoptotic and necrotic activities in adherent monolayer cultures of primary hepatocytes. The apoptosis assay uses a prototypical substrate of caspase 3, the main executor of apoptotic cell death, which can be cleaved, yielding a product that can be measured fluorimetrically. The second assay relies on the disruption of the cell plasma membrane, which typically occurs in necrotic cell death and that results in the extracellular release of cytoplasmic enzymes, such as lactate dehydrogenase. The latter can be indirectly assessed by spectrophotometrically measuring the consumption of reduced nicotinamide adenine dinucleotide.

Epigenetic Modifications as Antidedifferentiation Strategy for Primary Hepatocytes in Culture

A well-known problem of cultured primary hepatocytes is their rapid dedifferentiation. During the last years, several strategies to counteract this phenomenon have been developed, of which changing the in vitro environment is the most popular one. However, mimicking the in vivo setting in vitro by adding soluble media additives or the restoration of both cell-cell and cell-extracellular matrix contacts is not sufficient and only delays the dedifferentiation process instead of counteracting it. In this chapter, new strategies to prevent the deterioration of the liver-specific phenotype of primary hepatocytes in culture by targeting the (epi)genetic mechanisms that drive hepatocellular gene expression are described.