Rat precision-cut liver slices predict drug-induced cholestatic injury

Cholangiocyte organoids to study drug-induced injury

BACKGROUND

Drug induced bile duct injury is a frequently observed clinical problem leading to a wide range of pathological features. During the past decades, several agents have been identified with various postulated mechanisms of bile duct damage, however, mostly still poorly understood.

METHODS

Here, we investigated the mechanisms of chlorpromazine (CPZ) induced bile duct injury using advanced in vitro cholangiocyte cultures. Intrahepatic cholangiocyte organoids (ICOs) were driven into mature cholangiocyte like cells (CLCs), which were exposed to CPZ under cholestatic or non-cholestatic conditions through the addition of a bile acid cocktail.

RESULTS

CPZ caused loss of monolayer integrity by reducing expression levels of tight junction protein 1 (TJP1), E-cadherin 1 (CDH1) and lysyl oxidase homolog 2 (LOXL2). Loss of zonula occuludens-1 (ZO-1) and E-cadherin was confirmed by immunostaining after exposure to CPZ and rhodamine-123 leakage further confirmed disruption of the cholangiocyte barrier function. Furthermore, oxidative stress seemed to play a major role in the early damage response by CPZ. The drug also decreased expression of three main basolateral bile acid transporters, ABCC3 (ATP binding cassette subfamily C member 3), SLC51A/B (solute carrier family 51 subunit alpha/beta) and multidrug resistance transporter ABCB1 (ATP binding cassette subfamily B member 1), thereby contributing to bile acid accumulation. CPZ did not induce an inflammatory response by itself, but addition of TNFα revealed a synergistic effect.

CONCLUSION

These results show that ICOs present a model to identify toxic drugs affecting the bile ducts while providing mechanistic insights into hepatotoxicity.

Hepatic bile acid synthesis and secretion: Comparison of in vitro methods

Reliable hepatic in vitro systems are crucial for the safety assessment of xenobiotics. Certain xenobiotics decrease the hepatic bile efflux, which can ultimately result in cholestasis. Preclinical animal models and the currently available in vitro systems poorly predict a xenobiotic's cholestatic potential. Here, we compared the phenotype and capacity of three liver derived in vitro systems to emulate human functionality to synthesize and secrete bile acids (BAs). To this end, basal BA production of sandwich cultured human hepatocytes (SCHHs), HepaRG cells (HepaRGs) and hepatocyte-like intrahepatic cholangiocyte organoids (ICO-heps) were analysed, and the effect of the known BSEP (Bile Salt Export Pump)-inhibitors bosentan and lopinavir on BA disposition in SCHHs and HepaRGs was quantified. RT-qPCR of selected target genes involved in maturation status, synthesis, transport and conjugation of BAs was performed to mechanistically underpin the observed differences in BA homeostasis. ICO-heps produced a (very) low amount of BAs. SCHHs are a powerful tool in cholestasis-testing due to their high basal BA production and high transporter expression compared to the other models tested. HepaRGs were responsive to both selected BSEP-inhibitors and produced a BA profile that is most similar to the human in vivo situation, making them a suitable and practical candidate for cholestasis-testing.

Mouse precision-cut liver slices as an ex vivo model to study drug-induced cholestasis

Drugs are often withdrawn from the market due to the manifestation of drug-induced liver injury (DILI) in patients. Drug-induced cholestasis (DIC), defined as obstruction of hepatic bile flow due to medication, is one form of DILI. Because DILI is idiosyncratic, and the resulting cholestasis complex, there is no suitable in vitro model for early DIC detection during drug development. Our goal was to develop a mouse precision-cut liver slice (mPCLS) model to study DIC and to assess cholestasis development using conventional molecular biology and analytical chemistry methods. Cholestasis was induced in mPCLS through a 48-h-incubation with three drugs known to induce cholestasis in humans, namely chlorpromazine (15, 20, and 30 µM), cyclosporin A (1, 3, and 6 µM) or glibenclamide (25, 50, and 65 µM). A bile-acid mixture (16 µM) that is physiologically representative of the human bile-acid pool was added to the incubation medium with drug, and results were compared to incubations with no added bile acids. Treatment of PCLS with cholestatic drugs increased the intracellular bile-acid concentration of deoxycholic acid and modulated bile-transporter genes. Chlorpromazine led to the most pronounced cholestasis in 48 h, observed as increased toxicity; decreased protein and gene expression of the bile salt export pump; increased gene expression of multidrug resistance-associated protein 4; and accumulation of intracellular bile acids. Moreover, chlorpromazine-induced cholestasis exhibited some transition into fibrosis, evidenced by increased gene expression of collagen 1A1 and heatshock protein 47. In conclusion, we demonstrate that mPCLS can be used to study human DIC onset and progression in a 48 h period. We thus propose this model is suited for other similar studies of human DIC.

Best Practices and Progress in Precision-Cut Liver Slice Cultures

Thirty-five years ago, precision-cut liver slices (PCLS) were described as a promising tool and were expected to become the standard in vitro model to study liver disease as they tick off all characteristics of a good in vitro model. In contrast to most in vitro models, PCLS retain the complex 3D liver structures found in vivo, including cell–cell and cell–matrix interactions, and therefore should constitute the most reliable tool to model and to investigate pathways underlying chronic liver disease in vitro. Nevertheless, the biggest disadvantage of the model is the initiation of a procedure-induced fibrotic response. In this review, we describe the parameters and potential of PCLS cultures and discuss whether the initially described limitations and pitfalls have been overcome. We summarize the latest advances in PCLS research and critically evaluate PCLS use and progress since its invention in 1985.

Protective effects of phenolic acids on mercury-induced DNA damage in precision-cut kidney slices

Objective(s):

Precision-cut tissue slices are considered an organotypic 3D model widely used in biomedical research. The comet assay is an important screening test for early genotoxicity risk assessment that is mainly applied on in vitro models. The aim of the present study was to provide a 3D organ system for determination of genotoxicity using a modified method of the comet assay since the stromal components from the original tissue make this technique complicated.

Materials and Methods:

A modified comet assay technique was validated using precision-cut hamster kidney slices to analyze the antigenotoxic effect of the phenolic compounds caffeic acid, chlorogenic acid, and rosmarinic acid in tissue slices incubated with 15 µM HgCl₂. Cytotoxicity of the phenolic compounds was studied in Vero cells, and by morphologic analysis in tissue slices co-incubated with HgCl₂ and phenolic compounds.

Results:

A modification of the comet assay allows obtaining better and clear comet profiles for analysis. Non-cytotoxic concentrations of phenolic acids protected kidney tissue slices against mercury-induced DNA damage, and at the same time, were not nephrotoxic. The highest protection was provided by 3 µg/ml caffeic acid, although 6 µg/ml rosmarinic and 9 µg/ml chlorogenic acids also exhibited protective effects.

Conclusion:

This is the first time that a modification of the comet assay technique is reported as a tool to visualize the comets from kidney tissue slices in a clear and simple way. The phenolic compounds tested in this study provided protection against mercury-induced genotoxic damage in precision-cut kidney slices.

Mechanisms and in vitro models of drug-induced cholestasis

Cholestasis underlies one of the major manifestations of drug-induced liver injury. Drug-induced cholestatic liver toxicity is a complex process, as it can be triggered by a variety of factors that induce 2 types of biological responses, namely a deteriorative response, caused by bile acid accumulation, and an adaptive response, aimed at removing the accumulated bile acids. Several key events in both types of responses have been characterized in the past few years. In parallel, many efforts have focused on the development and further optimization of experimental cell culture models to predict the occurrence of drug-induced cholestatic liver toxicity in vivo. In this paper, a state-of-the-art overview of mechanisms and in vitro models of drug-induced cholestatic liver injury is provided.

Ex Vivo Model in Cholestasis Research

To mimic (human) cholestasis in vitro requires multiple triggers to establish a diseased phenotype. However, this is currently not simulated by existing in vitro models. Therefore, there is a high need for multicellular systems similar to the human physiology. In such an in vitro model, cell-cell interactions and intact bile canaliculi with functional bile flow should be present and preserved during long-term culture. Precision-cut liver slices represent an ex vivo tissue culture technique that replicates most of the multicellular characteristics of a whole liver in vivo. This chapter describes the preparation and culturing of (human) precision-cut liver slices. Furthermore, a protocol to use the precision-cut liver slices technique to predict drug-induced cholestatic liver injury is described.

Comparison of base-line and chemical-induced transcriptomic responses in HepaRG and RPTEC/TERT1 cells using TempO-Seq

The utilisation of genome-wide transcriptomics has played a pivotal role in advancing the field of toxicology, allowing the mapping of transcriptional signatures to chemical exposures. These activities have uncovered several transcriptionally regulated pathways that can be utilised for assessing the perturbation impact of a chemical and also the identification of toxic mode of action. However, current transcriptomic platforms are not very amenable to high-throughput workflows due to, high cost, complexities in sample preparation and relatively complex bioinformatic analysis. Thus, transcriptomic investigations are usually limited in dose and time dimensions and are, therefore, not optimal for implementation in risk assessment workflows. In this study, we investigated a new cost-effective, transcriptomic assay, TempO-Seq, which alleviates the aforementioned limitations. This technique was evaluated in a 6-compound screen, utilising differentiated kidney (RPTEC/TERT1) and liver (HepaRG) cells and compared to non-transcriptomic label-free sensitive endpoints of chemical-induced disturbances, namely phase contrast morphology, xCELLigence and glycolysis. Non-proliferating cell monolayers were exposed to six sub-lethal concentrations of each compound for 24 h. The results show that utilising a 2839 gene panel, it is possible to discriminate basal tissue-specific signatures, generate dose-response relationships and to discriminate compound-specific and cell type-specific responses. This study also reiterates previous findings that chemical-induced transcriptomic alterations occur prior to cytotoxicity and that transcriptomics provides in depth mechanistic information of the effects of chemicals on cellular transcriptional responses. TempO-Seq is a robust transcriptomic platform that is well suited for in vitro toxicity experiments.

Predicting drug-induced cholestasis: preclinical models

INTRODUCTION

In almost 50% of patients with drug-induced liver injury (DILI), the bile flow from the liver to the duodenum is impaired, a condition known as cholestasis. However, this toxic response only appears in a small percentage of the treated patients (idiosyncrasy). Prediction of drug-induced cholestasis (DIC) is challenging and emerges as a safety issue that requires attention by professionals in clinical practice, regulatory authorities, pharmaceutical companies, and research institutions. Area covered: The current synopsis focuses on the state-of-the-art in preclinical models for cholestatic DILI prediction. These models differ in their goal, complexity, availability, and applicability, and can widely be classified in experimental animals and in vitro models. Expert opinion: Drugs are a growing cause of cholestasis, but the progress made in explaining mechanisms and differences in susceptibility is not growing at the same rate. We need reliable models able to recapitulate the features of DIC, particularly its idiosyncrasy. The homogeneity and the species-specific differences move animal models away from a fair predictability. However, in vitro human models are improving and getting closer to the real hepatocyte phenotype, and they will likely be the choice in the near future. Progress in this area will not only need reliable predictive models but also mechanistic insights.