Drug-induced liver injury (DILI) is a major clinical and regulatory challenge, with cholestasis representing a frequent mechanism of hepatotoxicity. Conventional two-dimensional (2D) hepatocyte cultures often fail to predict such effects, underscoring the need for advanced models that better replicate liver architecture and function. In this study, a three-dimensional (3D) model was developed by encapsulating HepaRG cells within type I collagen hydrogels to enhance functional maturation and reduce differentiation time compared to standard 2D cultures. The 3D HepaRG model maintained long-term viability and exhibited improved hepatic functions, including urea and albumin production, xenobiotic metabolism, and antioxidant defense, particularly after 14 days of culture with a reduced amount of DMSO (1

This study reproduces the complex relationships between tumour plasma cells and their bone marrow microenvironment in multiple myeloma in vitro. These relationships are established both with other cells and with the extracellular matrix and are key factors in tumour progression, generating resistance to antitumour drugs in the cellular and non-cellular environments. This paper proposes a 3D microenvironment model designed to capture the main components of the multiple myeloma tumour microenvironment. Multiple myeloma cells (MMCs) were dispersed in a microgel medium formed by gel-textured microspheres. The proteins and polysaccharides considered important in the interaction of the MMCs with their non-cellular environment were successfully grafted onto the surface of the microspheres, while human mesenchymal stem cells (MSCs) were cultured in a pellet with non-functionalised microspheres. The MSCs pellet was placed in the well plate together with the microgel and the MMCs and orbitally shaken to maintain them in suspension. The viability, cell cycle and proliferation of the RPMI8226, MM1S and U266 multiple myeloma cell lines and the direct adhesion of MMCs to the MSC pellet were quantified. The results revealed that all three cell lines are able to grow satisfactorily. In addition, the normal behaviour of the MMCs is not modified in any of the culture conditions studied.

Liver extracellular matrix-based models that precisely reproduce liver physiology and functions are required as 3D culture microenvironments for multiple applications in toxicology and metabolism, or for understanding the mechanisms implicated in liver disease. We introduced injectable gelatin-chondroitin sulphate (Gel/CS) hydrogels for culturing HepG2 cells, and evaluated the mechanical properties and functionality of cells in different Gel/CS compositions. The Gel/CS hydrogels exhibited soft mechanical properties and allowed the HepG2 culture. The characterisation and comparison of 3D cultures to standard monolayer systems revealed the regulation of key hepatic markers (i.e. CYP3A4, GSTA1) when cells were cultured in the Gel/CS hydrogels compared to 2D cultures, and also enhanced urea and albumin production, which would indicate increased cells functionality. This study underpins 3D in vitro models based on the Gel/CS hydrogels that can be used for different hepatology applications by offering increased predictivity and physiological relevance compared to current in vitro models.

Drug-induced cholestasis is one of the major mechanisms implicated in drug-induced hepatotoxicity that poses a serious problem in terms of patient morbidity and mortality, healthcare system expenses and efficacy of newly developed drugs. Impaired bile acid homeostasis due to transporter alterations, hepatocellular injury or canalicular abnormalities is the most characteristic feature of cholestasis. Given the complexity of cholestasis and the different underlying mechanisms, new models and technologies that span a variety of biological processes are needed to accurately predict drugs' cholestatic potential. This review outlines the main triggering mechanisms of drug-induced cholestasis and summarizes the currently available in vitro systems and techniques that attempt to forecast and provide mechanistic details of cholestasis caused by drugs.

Liver fibrosis has been proposed as the most important predictive indicator affecting prognosis of patients with chronic liver disease. It is defined by an abnormal accumulation of extracellular matrix components that results from necrotic and inflammatory processes and eventually impairs organ function. With no approved therapy, comprehensive cellular models directly derived from patient’s cells are necessary to understand the mechanisms behind fibrosis and the response to anti-fibrotic therapies. Primary human cells, human hepatic cell lines and human stem cells-derived hepatic stellate-like cells have been widely used for studying fibrosis pathogenesis. In this paper, we depict the cellular crosstalk and the role of extracellular matrix during fibrosis pathogenesis and summarize different in vitro models from simple monolayers to multicellular 3D cultures used to gain deeper mechanistic understanding of the disease and the therapeutic response, discussing their major advantages and disadvantages for liver fibrosis modelling.

This study evaluated the anti-hypernociceptive interaction between morphine and the neuroprotective compound 3-ethoxycarbonyl-2-methyl-4-(2-nitrophenyl)-4,11-dihydro-1H-pyrido[2,3-b][1,5]benzodiazepine (JM-20) in neuropathic rats. Single and repeated co-administration of both drugs was assessed using the chronic constriction injury (CCI) model, via subcutaneous and oral routes. Isobolographic analysis was performed to determine the nature of the pharmacological interaction. In addition, in silico pharmacokinetic and toxicological profiling was conducted, and JM-20's effects on human UDP-glucuronosyltransferase (UGT) and cytochrome P450 (CYP) enzyme systems were evaluated in vitro. Morphine, JM-20, and their 1:1 fixed-ratio combinations significantly attenuated mechanical hypersensitivity in a dose-dependent manner. The observed ED50 for the combination (2.15 ± 0.07 mg/kg) was significantly lower than the theoretical additive ED50 (8.05 ± 0.58 mg/kg), indicating a synergistic interaction. Repeated morphine administration led to tolerance, while the morphine:JM-20 combination maintained efficacy for 14 days and prevented morphine-induced facilitation of neuropathic hypersensitivity. JM-20 did not alter UGT activity, suggesting no interference with morphine glucuronidation or active metabolite formation. However, JM-20 strongly inhibited CYP3A4 and other major CYP isoforms (1A, 2C9, 2D6, 2A6), potentially relevant for interactions with co-administered drugs, though not with morphine. JM-20 may also inhibit P-glycoprotein, possibly enhancing morphine's central bioavailability. In silico and in vitro analyses indicated a potential risk of cardiotoxicity and hepatotoxicity. Overall, JM-20 enhances morphine analgesia in neuropathic pain, but further in vivo studies are required to evaluate the long-term safety of this combination.

The evolving landscape of chemical risk assessment is increasingly focused on developing tiered, mechanistically driven approaches that avoid the use of animal experiments. In this context, adverse outcome pathways have gained importance for evaluating various types of chemical-induced toxicity. Using hepatic steatosis as a case study, this review explores the use of diverse computational techniques, such as structure–activity relationship models, quantitative structure–activity relationship models, read-across methods, omics data analysis, and structure-based approaches to fill data gaps within adverse outcome pathway networks. Emphasizing the regulatory acceptance of each technique, we examine how these methodologies can be integrated to provide a comprehensive understanding of chemical toxicity. This review highlights the transformative impact of in silico techniques in toxicology, proposing guidelines for their application in evidence gathering for developing and filling data gaps in adverse outcome pathway networks. These guidelines can be applied to other cases, advancing the field of toxicological risk assessment.

Hepatotoxicity poses a significant concern in drug design due to the potential liver damage that can be caused by new drugs. Among common manifestations of hepatotoxic damage is lipid accumulation in hepatic tissue, resulting in liver steatosis or phospholipidosis. Carboxylic derivatives are prone to interfere with fatty acid metabolism and cause lipid accumulation in hepatocytes. This study investigates the toxic behaviour of 24 structurally related carboxylic acids in hepatocytes, specifically their ability to cause accumulation of fatty acids and phospholipids. Using high-content screening (HCS) assays, we identified two distinct lipid accumulation patterns. Subsequently, we developed structure-activity relationship (SAR) and quantitative structure-activity relationship (QSAR) models to determine relevant molecular substructures and descriptors contributing to these adverse effects.Additionally, we calculated physicochemical properties associated with lipid accumulation in hepatocytes and examined their correlation with our chemical structure characteristics. To assess the applicability of our findings to a wide range of chemical compounds, we employed two external datasets to evaluate the distribution of our QSAR descriptors. Our study highlights the significance of subtle molecular structural variations in triggering hepatotoxicity, such as the presence of nitrogen or the specific arrangement of substitutions within the carbon chain. By employing our comprehensive approach, we pinpointed specific molecules and elucidated their mechanisms of toxicity, thus offering valuable insights to guide future toxicology investigations.

Liver tissue engineering offers a remarkable tool for toxicological screening and an approach to disease modeling, and provides an alternative solution to liver transplantation in treating end-stage liver diseases. As the liver is a highly specialized multicellular organ, distinctive features such as diversity of cell types, extracellular matrix composition, and three-dimensional architecture must be taken into consideration in recapitulating its physiology. Here, we review the current developments in liver tissue engineering approaches, focusing on their application to liver disease modeling and treatment, with special emphasis on bioprinting for high-throughput analysis. We also discuss the challenges encountered and the likely future developments in the area.

Cell-based liver therapies based on retrieving and steadying failed metabolic function(s) for acute and chronic diseases could be a valuable substitute for liver transplants, even though they are limited by the low engraftment capability and reduced functional quality of primary human hepatocytes (PHH). In this paper we propose the use of gelatin-hyaluronic acid (Gel-HA) scaffolds seeded with PHH for the treatment of liver failure. We first optimized the composition using Gel-HA hydrogels, looking for the mechanical properties closer to the human liver and determining HepG2 cells functionality. Gel-HA scaffolds with interconnected porosity (pore size 102 μm) were prepared and used for PHH culture and evaluation of key hepatic functions. PHH cultured in Gel-HA scaffolds exhibited increased albumin and urea secretion and metabolic capacity (CYP and UGT activity levels) compared to standard monolayer cultures. The transplant of the scaffold containing PHH led to an improvement in liver function (transaminase levels, necrosis) and ameliorated damage in a mouse model of acetaminophen (APAP)-induced liver failure. The study provided a mechanistic understanding of APAP-induced liver injury and the impact of transplantation by analyzing cytokine production and oxidative stress induction to find suitable biomarkers of cell therapy effectiveness.

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. 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. 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. 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.

Hazard assessment requires toxicity tests to allow deriving protective points of departure (PoDs) for risk assessment irrespective of a compound's mode of action (MoA). The scope of in vitro test batteries (ivTB) needed to assess systemic toxicity is still unclear. We explored the protectiveness regarding systemic toxicity of an ivTB with a scope that was guided by previous findings from rodent studies, where examining six main targets, including liver and kidney, was sufficient to predict the guideline scope -based PoD with high probability. The ivTB comprises human in vitro models representing liver, kidney, lung, and the neuronal system covering transcriptome, mitochondrial dysfunction, and neuronal outgrowth. Additionally, 32 CALUX (R)- and 10 HepG2 BAC-GFP reporters cover a broad range of disturbance mechanisms. Eight compounds were chosen for causing adverse effects such as immunotoxicity or anemia in vivo, i.e., effects not directly covered by assays in the ivTB. PoDs derived from the ivTB and from oral repeated dose studies in rodents were extrapolated to maximum unbound plasma concentrations for comparison. The ivTB-based PoDs were one to five orders of magnitude lower than in vivo PoDs for six of eight compounds, implying that they were protective. The extent of in vitro response varied across test compounds. Especially for hematotoxic substances, the ivTB showed either no response or only cytotoxicity. Assays better capturing this type of hazard would be needed to complement the ivTB. This study highlights the potentially broad applicability of ivTBs for deriving protective PoDs of compounds with unknown MoA. Plain language summary Animal tests are used to determine how much of a chemical is toxic ("threshold of toxicity") and which organs are affected. In principle, the threshold can also be derived solely from tests with cultured cells. However, only a limited number of cell types can practically be tested, so one challenge is to determine how many and which types shall be tested. In animal tests, only few organs including liver and kidney are regularly among those most sensitively affected. We explored whether a cellbased test battery representing these sensitive organs and covering important mechanisms of toxicity can be used to derive protective human thresholds. To challenge this approach, eight chemicals were tested that primarily cause effects in organs not directly represented in our test battery. Results provided protective thresholds for most of the investigated compounds and gave indications how to further improve the approach towards a full-fledged replacement of animal tests.

Hepatotoxicity or drug-induced liver injury (DILI) is a major safety issue in drug development as a primary reason for drug failure in clinical trials and the main cause for post-marketing regulatory measures like drug withdrawal. Idiosyncratic DILI (iDILI) is a patient-specific, multifactorial, and multicellular process that cannot be recapitulated in current in vitro models; thus, our major goal is to develop and fully characterize a co-culture system and to evaluate its suitability for predicting iDILI. For this purpose, we used human hepatoma HepG2 cells and macrophages differentiated from a monocyte cell line (THP-1) and established the appropriate co-culture conditions for mimicking an inflammatory environment. Then, mono-cultures and co-cultures were treated with model iDILI compounds (trovafloxacin, troglitazone) and their parent non-iDILI compounds (levofloxacin, rosiglitazone), and the effects on viability and the mechanisms implicated (i.e., oxidative stress induction) were analyzed. Our results show that co-culture systems including hepatocytes (HepG2) and other cell types (THP-1-derived macrophages) help to enhance the mechanistic understanding of iDILI, providing better hepatotoxicity predictions.

Typical protocols to differentiate induced pluripotent stem cells (iPSCs) from hepatocyte-like cells (HLCs) imply complex strategies that include transfection with key hepatic transcription factors and the addition to culture media of nutrients, growth factors, and cytokines. A main constraint to evaluate the hepatic phenotype achieved arises from the way the grade of differentiation is determined. Currently, it relies on the assessment of the expression of a limited number of hepatic gene transcripts, less frequently by assessing certain hepatic metabolic functions, and rarely by the global metabolic performance of differentiated cells. We envisaged a new strategy to assess the extent of differentiation achieved, based on the analysis of the cellular metabolome along the differentiation process and its quantitative comparison with that of primary human hepatocytes (PHHs). To validate our approach, we examined the changes in the metabolome of three iPSC progenies (transfected with/without key transcription factors), cultured in three differentiation media, and compared them to PHHs. Results revealed consistent metabolome changes along differentiation and evidenced the factors that more strongly promote changes in the metabolome. The integrated dissimilarities between the PHHs and HLCs retrieved metabolomes were used as a numerical reference for quantifying the degree of iPSCs differentiation. This newly developed metabolome-analysis approach evidenced its utility in assisting us to select a cell's source, culture conditions, and differentiation media, to achieve better-differentiated HLCs.

Nonalcoholic fatty liver disease (NAFLD) is now the leading cause of chronic liver disease in western countries. The molecular mechanisms leading to NAFLD are only partially understood, and effective therapeutic interventions are clearly needed. Therefore, preclinical research is required to improve knowledge about NAFLD physiopathology and to identify new therapeutic targets. Primary human hepatocytes, human hepatic cell lines, and human stem cell-derived hepatocyte-like cells exhibit different hepatic phenotypes and have been widely used for studying NAFLD pathogenesis. In this paper, apart from employing the different in vitro cell models for the in vitro assessment of NAFLD, we also reviewed other approaches (metabolomics, transcriptomics, and high-content screening). We aimed to summarize the characteristics of different cell types and methods and to discuss their major advantages and disadvantages for NAFLD modeling.

Multiple myeloma (MM) is a hematological malignancy in which the patient's drug resistance is one of the main clinical problems. As 2D cultures do not recapitulate the cellular microenvironment, which has a key role in drug resistance, there is an urgent need for better biomimetic models. Here, a novel 3D platform is used to model MM. The semi-solid culture consists of a dynamic suspension of microspheres and MM cells, termed as microgel. Microspheres are synthesized with acrylic polymers of different sizes, compositions, and functionalities (fibronectin or hyaluronic acid). Optimal conditions for the platform in terms of agitation speed and microsphere size have been determined. With these parameters the system allows good proliferation of the MM cell lines RPMI8226, U226, and MM1.S. Interestingly, when used for drug resistance studies, culture of the three MM cell lines in microgels showed close agreement in revealing the role of acrylic acid in resistance to anti-MM drugs such as dexamethasone and bortezomib. This work presents a unique platform for the in vitro modeling of non-solid tumors since it allows keeping non-adherent cells in suspension conditions but in a 3D context that can be easily tuned with different functionalizations.

Mesenchymal stem cells (MSCs) osteogenic commitment before injection enhances bone regeneration therapy results. Piezoelectric stimulation may be an effective cue to promote MSCs pre-differentiation, and poly(vinylidene) fluoride (PVDF) cell culture supports, when combined with CoFe2O4 (CFO), offer a wireless in vitro stimulation strategy. Under an external magnetic field, CFO shift and magnetostriction deform the polymer matrix varying the polymer surface charge due to the piezoelectric effect. To test the effect of piezoelectric stimulation on MSCs, our approach is based on a gelatin hydrogel with embedded MSCs and PVDF-CFO electroactive microspheres. Microspheres were produced by electrospray technique, favouring CFO incorporation, crystallisation in β-phase (85%) and a crystallinity degree of around 55%. The absence of cytotoxicity of the 3D construct was confirmed 24 h after cell encapsulation. Cells were viable, evenly distributed in the hydrogel matrix and surrounded by microspheres, allowing local stimulation. Hydrogels were stimulated using a magnetic bioreactor, and no significant changes were observed in MSCs proliferation in the short or long term. Nevertheless, piezoelectric stimulation upregulated RUNX2 expression after 7 days, indicating the activation of the osteogenic differentiation pathway. These results open the door for optimising a stimulation protocol allowing the application of the magnetically activated 3D electroactive cell culture support for MSCs pre-differentiation before transplantation.