Utility of spherical human liver microtissues for prediction of clinical drug-induced liver injury

Engineering a three-dimensional liver steatosis model

Liver transplantation is the key treatment for liver failure, yet organ scarcity, exacerbated by high discard rates of steatotic livers, leads to high waitlist mortality. Preclinical models of steatosis are necessary to understand the pathophysiology of the disease and to develop pharmacological interventions to decrease disease burden and liver discard rate. In this paper, we develop an expedited 3D steatotic organoid model containing primary human hepatocytes and non-parenchymal cells. We present our iterative approach as we transition from 2D to 3D models and from immortalized to primary cells to optimize conditions for the development of a 3D human steatosis model. Both primary cell aggregation and steatosis induction time were reduced from the standard, 5-7 days, to 2 days. Our 3D model incorporates human primary hepatocytes from discarded liver tissues, which have not been used in organoids previously due to their rapid loss of phenotype in culture. After optimizing our steatosis induction media there was a mix of macro- and micro-steatosis in these primary hepatocytes which is consistent with the human pathology. Our approach achieves a model reflective of the liver pathology, preserving cellular phenotypes and viability while exhibiting markers of oxidative stress, a key factor contributing to complications in the transplantation of steatotic livers.

Application of new approach methodologies for nonclinical safety assessment of drug candidates

The development of new approach methodologies (NAMs) and advances with in vitro testing systems have prompted revisions in regulatory guidelines and inspired dedicated in vitro/ex vivo studies for nonclinical safety assessment. This Review by a safety reflection initiative subgroup of the European Federation of Pharmaceutical Industries and Associations (EFPIA)/Preclinical Development Expert Group (PDEG) summarizes the current state and potential application of in vitro studies using human-derived material for safety assessment in drug development. It focuses on case studies from recent projects in which animal models alone proved to be limited or inadequate for safety testing. It further highlights four categories of drug candidates for which alternative in vitro approaches are applicable and discusses progress in using in vitro testing solutions for safety assessment in these categories. Finally, the article highlights new risk assessment strategies, initiatives and consortia promoting the advancement of NAMs. This collective work is meant to encourage the use of NAMs for more human-relevant safety assessment, which should ultimately result in reduced animal testing for drug development.

Evaluating the synergistic use of advanced liver models and AI for the prediction of drug-induced liver injury

INTRODUCTION

Drug-induced liver injury (DILI) is a leading cause of acute liver failure. Hepatotoxicity typically occurs only in a subset of individuals after prolonged exposure and constitutes a major risk factor for the termination of drug development projects.

AREAS COVERED

We provide an overview of available human liver models for DILI research and discuss how they have been used to aid in early risk assessments and to mitigate the risk of project closures due to DILI in clinical stages. We summarize the different data that can be provided by such models and illustrate how these diverse data types can be interfaced with machine learning strategies to improve predictions of liver safety liabilities.

EXPERT OPINION

Advanced human liver models closely mimic human liver phenotypes and functions for many weeks, allowing for the recapitulation of hepatotoxicity events in vitro. Integration of the biochemical, histological, and toxicogenomic output data from these models with physicochemical compound properties using different machine learning architectures holds promise to enhance preclinical DILI predictions. However, to realize this aim, it is important to benchmark the available liver models on test sets of DILI positive and negative compounds and to carefully annotate and share the resulting data.

Multi-organ model assessment of neurotoxicity following exposure of liver spheroids to drugs

Accurate prediction of drug toxicity is a major challenge for therapeutic development. The use of animal models for predicting toxicity has been a longstanding practice, but often falls short in accurately predicting human-specific responses. Human in vitro models, such as organoids and spheroids, provide alternative approaches to animal models. In this study, we employed primary human-derived liver spheroids (hLiSps) and human induced pluripotent stem cells (iPSC)-derived brain organoids (hiBOs) to create a combined Liver+Brain model for neurotoxicity assessment, to investigate the potential influence of incorporating a liver preconditioning component on toxic responses in the brain. Comparing the effect of six example drugs that are known to cause adverse clinical neurological effects, we observed that troglitazone (Trgl), tested at clinically relevant doses in the Liver+Brain model, caused a significantly greater reduction in cell viability compared to similar treatments in the Brain-only model. This was further confirmed across multiple donors and various stages of brain organoid development. In contrast, we found that high dose valproic acid treatment increased cell viability in the Liver+Brain model. Transcriptome analysis using RNA-seq revealed that liver-preconditioned Trgl elicited a more pronounced transcriptional response in hiBOs, identifying a 7-fold increase in the number of affected genes and over a 10-fold increase in affected pathways containing gene set components specifically associated with cell division and neurogenesis, which were not observed in the Brain model. Taken together, our data suggest that the addition of hLiSps to hiBOs is critical to accurately assess neurotoxicity using a comprehensive human in vitro model.

DILI prediction in drug development: present and future

INTRODUCTION

Idiosyncratic drug-induced liver injury (iDILI) results in significant patient morbidity and significantly increases the risk of drug development. The current methods to screen for iDILI risk are inadequate.

AREAS COVERED

The general mechanism of iDILI and the current methods to screen for iDILI are reviewed. Then the potential for new biomarkers is explored.

EXPERT OPINION

Better biomarkers of iDILI risk should be based on the mechanism of iDILI. In general, it is an adaptive immune response, specifically CD8+ cytotoxic T cells, that is responsible for hepatocyte cell death, not direct toxicity of the drug. Therefore, in vitro cytotoxicity assays represent an artifact not the mechanism of iDILI. Activation of the adaptive immune response leading to iDILI requires an innate immune response, in particular activation of antigen presenting cells. The innate immune response is immediate and unlikely to be idiosyncratic. For example, studies have found that incubation of hepatocytes with drugs causes the release of molecules that activate THP-1-derived macrophages. The response of hepatocytes, the release of damage-associated molecular pattern molecules (DAMPs), especially in extracellular vesicles, and the response of antigen presenting cells (APCs) are likely to provide better biomarkers of iDILI risk.

Studying the intracellular bile acid concentration and toxicity in drug-induced cholestasis: Comprehensive LC-MS/MS analysis with human liver slices

Drug-induced cholestasis (DIC) is a leading cause of drug-induced liver injury post-drug marketing, characterized by bile flow obstruction and toxic bile constituent accumulation within hepatocytes. This study investigates the toxicity associated with intracellular bile acid (BA) accumulation during DIC development. Using liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis, we examined intracellular BA concentrations in human precision-cut liver slices (PCLS) following the administration of cyclosporin A and chlorpromazine, both with and without an established BA mixture. Our findings indicate toxicity of cyclosporin A upon BA addition, while chlorpromazine's toxicity remained unaffected. Although neither drug led to the accumulation of all BAs intracellularly, BA mixture addition resulted in the accumulation of unconjugated BAs associated with DIC, such as deoxycholic acid (DCA) and cholic acid (CA). Additionally, cyclosporin A increased taurolithocholic acid (TLCA) concentrations. In the absence of the BA mixture, a decrease in conjugated BAs was observed, suggesting inhibition of BA metabolism by cholestatic drugs and warranting further investigation. The evident increase in CA and DCA for both drugs (and TLCA for cyclosporin A), despite not exacerbating toxicity with chlorpromazine, suggests these increases may be related to DIC development and possible toxicity. In conclusion, the current human PCLS model is appropriate for investigating and detecting essential contributors to DIC and can be used in future studies elucidating DIC ex vivo.

TAK-994 mechanistic investigation into drug-induced liver injury

The frequency of drug-induced liver injury (DILI) in clinical trials remains a challenge for drug developers despite advances in human hepatotoxicity models and improvements in reducing liver-related attrition in preclinical species. TAK-994, an oral orexin receptor 2 agonist, was withdrawn from phase II clinical trials due to the appearance of severe DILI. Here, we investigate the likely mechanism of TAK-994 DILI in hepatic cell culture systems examined cytotoxicity, mitochondrial toxicity, impact on drug transporter proteins, and covalent binding. Hepatic liabilities were absent in rat and nonhuman primate safety studies, however, murine studies initiated during clinical trials revealed hepatic single-cell necrosis following cytochrome P450 induction at clinically relevant doses. Hepatic cell culture experiments uncovered wide margins to known mechanisms of intrinsic DILI, including cytotoxicity (>100× Cmax/IC50), mitochondrial toxicity (>100× Cmax/IC50), and bile salt efflux pump inhibition (>20× Css, avg/IC50). A potential covalent binding liability was uncovered with TAK-994 following hepatic metabolism consistent with idiosyncratic DILI and the delayed-onset clinical toxicity. Although idiosyncratic DILI is challenging to detect preclinically, reductions in total daily dose and covalent binding can reduce the covalent body binding burden and, subsequently, the clinical incidence of idiosyncratic DILI.

Transcriptomic analysis in liver spheroids identifies a dog-specific mechanism of hepatotoxicity for amcenestrant

Therapeutic drugs can sometimes cause adverse effects in a nonclinical species that do not translate to other species, including human. Species-specific (rat, dog, and human) in vitro liver spheroids were employed to understand the human relevance of cholestatic liver injury observed with a selective estrogen receptor degrader (amcenestrant) in dog, but not in rat, during preclinical development. Amcenestrant showed comparable cytotoxicity in liver spheroids from all 3 species; however, its M5 metabolite (RA15400562) showed dog preferential cytotoxicity after 7 days of treatment. Whole genome transcript profiles generated from liver spheroids revealed downregulation of genes related to bile acid synthesis and transport indicative of strong farnesoid X receptor (FXR) antagonism following treatment with both amcenestrant and its M5 metabolite in the dog but not in rat or human. In human spheroids, upregulation of genes for detoxification enzymes indicative of pregnane X receptor (PXR) agonism was observed following amcenestrant treatment, whereas in the dog these genes were downregulated. The M5 metabolite showed gene dysregulation indicating PXR agonism in both rat and human, and antagonism in dog. Analysis of liver samples from a 3-mo dog toxicity study conducted with amcenestrant showed downregulation of several genes associated with PXR and FXR, corroborating the in vitro results. These results support the hypothesis that dogs are uniquely susceptible to cholestatic hepatotoxicity following administration of amcenestrant due to species-specific antagonism of FXR and highlight the value of in vitro liver spheroids to investigating mechanisms of toxicity and possible species differences.

Protocol for generating liver metastasis microtissues to decipher cellular interactions between metastatic intestinal cancer and liver tissue

Cell competition is a quality control mechanism that promotes elimination of suboptimal cells relative to fitter neighbors. Cancer cells exploit these mechanisms for expansion, but the underlying molecular pathways remain elusive. Here, we present a protocol for generating matrix-free microtissues recapitulating cellular interactions between intestinal cancer and hepatocyte-like cells using microscopy or transcriptomics/proteomics. We describe steps for generating and differentiating liver progenitor organoids and microtissue formation. We then detail procedures for immunofluorescence staining, mounting microtissues, and sorting cells. For complete details on the use and execution of this protocol, please refer to Krotenberg Garcia et al.1.

In vitro liver models for toxicological research

Drug-induced liver injury (DILI) presents a major challenge not only in new drug development but also in post-marketing withdrawals and the safety of food, cosmetics, and chemicals. Experimental model organisms such as the rodents have been widely used for preclinical toxicological testing. However, the tension exists associated with the ethical and sustainable use of animals in part because animals do not necessarily inform the human-specific ADME (adsorption, dynamics, metabolism and elimination) profiling. To establish alternative models in humans, in vitro hepatic tissue models have been proposed, ranging from primary hepatocytes, immortal hepatocytes, to the development of new cell resources such as stem cell-derived hepatocytes. Given the evolving number of novel alternative methods, understanding possible combinations of cell sources and culture methods will be crucial to develop the context-of-use assays. This review primarily focuses on 3D liver organoid models for conducting. We will review the relevant cell sources, bioengineering methods, selection of training compounds, and biomarkers towards the rationale design of in vitro toxicology testing.

A guide to pathophysiology, signaling pathways, and preclinical models of liver fibrosis

Liver fibrosis is potentially a reversible form of liver disease that evolved from the early stage of liver scarring as a consequence of chronic liver injuries. Recurrent injuries in the liver without any appropriate medication cause the injuries to get intense and deeper, which gradually leads to the progression of irreversible cirrhosis or carcinoma. Unfortunately, there are no approved treatment strategies for reversing hepatic fibrosis, making it one of the significant risk factors for developing advanced liver disorders and liver disease-associated mortality. Consequently, the interpretation of the fundamental mechanisms, etiology, and pathogenesis is crucial for identifying the potential therapeutic target as well as evaluating novel anti-fibrotic therapy. However, despite innumerable research, the functional mechanism and disease characteristics are still obscure. To accelerate the understanding of underlying disease pathophysiology, molecular pathways and disease progression mechanism, it is crucial to mimic human liver disease through the formation of precise disease models. Although various in vitro and in vivo liver fibrotic models have emerged and developed already, a perfect clinical model replicating human liver diseases is yet to be established, which is one of the major challenges in discovering proper therapeutics. This review paper will shed light on pathophysiology, signaling pathways, preclinical models of liver fibrosis, and their limitations.

Concentration-dependent effects of the nerve agents cyclosarin and VX on cytochrome P450 in a HepaRG cell-based liver model

The exposure to highly toxic organophosphorus (OP) compounds, including pesticides and nerve agents, is an ongoing medical challenge. OP can induce the uncontrolled overstimulation of the cholinergic system through inhibition of the enzyme acetylcholinesterase (AChE). The cytochrome P450 (CYP) enzymes in the liver play a predominant role in the metabolism of xenobiotics and are involved in the oxidative biotransformation of most clinical drugs. Previous research concerning the interactions between OP and CYP has usually focused on organothiophosphate pesticides that require CYP-mediated bioactivation to their active oxon metabolites to act as inhibitors of AChE. Since there has been little data available concerning the effect of nerve agents on CYP, we performed a study with cyclosarin (GF) and O-ethyl-S-[2-(diisopropylamino)-ethyl]-methylphosphonothioate (VX) by using a well-established, metabolically competent in vitro liver model (HepaRG cells). The inhibitory effect of the nerve agents GF and VX on the CYP3A4 enzyme was investigated showing a low CYP3A4 inhibitory potency. Changes on the transcription level of CYP and associated oxygenases were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR) using the two nerve agent concentrations 250 nM and 250 μM. In conclusion, the results demonstrated various effects on oxygenase-associated genes in dependence of the concentration and the structure of the nerve agent. Such information might be of relevance for potential interactions between nerve agents, antidotes or other clinically administered drugs, which are metabolized by the affected CYP, for example, for the therapy with benzodiazepines, that are used for the symptomatic treatment of OP poisoning and that require CYP-mediated biotransformation.

Opportunities for microphysiological systems from the view of Japanese industries

Regulatory authorities and pharmaceutical companies in Europe and the United States have paid attention to microphysiological systems (MPS), and various consortia and academic societies have been established. They are actively working toward their implementation under individual company or regulatory acceptance. In Japan, some AMED projects, academic societies, and consortia have also been established and activities have begun. This article focuses on domestic and international trends regarding MPS, especially on Japanese industries related to MPS, and describes the current status, challenges, and prospects of Japanese pharmaceutical companies, CROs, Food company, and MPS-related product development companies including the results of a survey conducted by CSAHi-MPS, an industrial MPS consortium in Japan.

The differentiation state of small intestinal organoid models influences prediction of drug-induced toxicity

Drug-induced intestinal toxicity (GIT) is a frequent dose-limiting adverse event that can impact patient compliance and treatment outcomes. In vivo, there are proliferative and differentiated cell types critical to maintaining intestinal homeostasis. Traditional in vitro models using transformed cell lines do not capture this cellular complexity, and often fail to predict intestinal toxicity. Primary tissue-derived intestinal organoids, on the other hand, are a scalable Complex in vitro Model (CIVM) that recapitulates major intestinal cell lineages and function. Intestinal organoid toxicity assays have been shown to correlate with clinical incidence of drug-induced diarrhea, however existing studies do not consider how differentiation state of the organoids impacts assay readouts and predictivity. We employed distinct proliferative and differentiated organoid models of the small intestine to assess whether differentiation state alone can alter toxicity responses to small molecule compounds in cell viability assays. In doing so, we identified several examples of small molecules which elicit differential toxicity in proliferative and differentiated organoid models. This proof of concept highlights the need to consider which cell types are present in CIVMs, their differentiation state, and how this alters interpretation of toxicity assays.

Integrating machine learning and structure-based approaches for repurposing potent tyrosine protein kinase Src inhibitors to treat inflammatory disorders

Tyrosine-protein kinase Src plays a key role in cell proliferation and growth under favorable conditions, but its overexpression and genetic mutations can lead to the progression of various inflammatory diseases. Due to the specificity and selectivity problems of previously discovered inhibitors like dasatinib and bosutinib, we employed an integrated machine learning and structure-based drug repurposing strategy to find novel, targeted, and non-toxic Src kinase inhibitors. Different machine learning models including random forest (RF), k-nearest neighbors (K-NN), decision tree, and support vector machine (SVM), were trained using already available bioactivity data of Src kinase targeting compounds. The performance evaluation of these models demonstrated SVM as the best model, which was further utilized to shortlist 51 highly potent compounds by screening an FDA-approved library of 1040 drugs. Molecular docking and molecular dynamic simulation were subsequently employed to evaluate the binding affinity and stability of the proposed compounds. Orlistat, acarbose and afatinib were identified as the potent leads, demonstrating stable conformations and stronger interactions, validated by root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (RoG), and hydrogen bond analyses. Molecular Mechanics/Generalized Born Surface Area (MMGBSA) analysis validated their binding affinities by providing comparably lower binding free energies for orlistat (- 33.4743 ± 3.8908), acarbose (- 19.5455 ± 5.4702), and afatinib (- 36.4944 ± 5.4929) than the control, dasatinib (- 13.7785 ± 5.8058). Finally, toxicity analysis revealed orlistat and acarbose as the possible safer therapeutics by eliminating afatinib as it showed significant toxicity concerns. Our investigation supports the advance computational methods utilization in the field of drug discovery and suggest further experimental validation of proposed inhibitors of Src kinase for their safer use against inflammatory diseases. The ultimate aim of this study is to advance the development of effective treatments for inflammatory diseases, linked with Src overexpression.

Design of optimal concentrations for in vitro cytotoxicity experiments

Concentration-dependent cytotoxicity experiments are frequently used in toxicology. Although it has been reported that an adequate choice of concentrations improves the quality of the statistical inference substantially, a recent literature review of three major toxicological journals has shown that the corresponding methods are rarely used in toxicological practice. In this study the performance of different sets of concentrations, also called designs, are analyzed, while the overall goal is to promote the advantages of optimal design procedures and to present a user-friendly guideline for planning new cytotoxicity concentration-response experiments. We compare the frequently used log-equidistant design to a Bayesian design, which is constructed by methods of optimum design theory. Using both a dense data set of concentration-cytotoxicity data of valproic acid (VPA) and regular assay data of 104 substances, the performance of the different designs is analyzed in two scenarios, where detailed previous knowledge on VPA is available or not. The results show that it is critical to apply a specific design strategy to determine optimal concentrations for cytotoxicity testing. In particular, the Bayesian design technique with and without incorporating pre-existing knowledge of a specific test substance resulted in a more precise statistical inference than the other used designs. Finally, we present a guideline for upcoming experiments and an accessible user-friendly Shiny app (see http://shiny.statistik.tu-dortmund.de:8080/app/occe ).

Physiological liver microtissue 384-well microplate system for preclinical hepatotoxicity assessment of therapeutic small molecule drugs

Hepatotoxicity can lead to the discontinuation of approved or investigational drugs. The evaluation of the potential hepatoxicity of drugs in development is challenging because current models assessing this adverse effect are not always predictive of the outcome in human beings. Cell lines are routinely used for early hepatotoxicity screening, but to improve the detection of potential hepatotoxicity, in vitro models that better reflect liver morphology and function are needed. One such promising model is human liver microtissues. These are spheroids made of primary human parenchymal and nonparenchymal liver cells, which are amenable to high throughput screening. To test the predictivity of this model, the cytotoxicity of 152 FDA (US Food & Drug Administration)-approved small molecule drugs was measured as per changes in ATP content in human liver microtissues incubated in 384-well microplates. The results were analyzed with respect to drug label information, drug-induced liver injury (DILI) concern class, and drug class. The threshold IC50ATP-to-Cmax ratio of 176 was used to discriminate between safe and hepatotoxic drugs. "vMost-DILI-concern" drugs were detected with a sensitivity of 72% and a specificity of 89%, and "vMost-DILI-concern" drugs affecting the nervous system were detected with a sensitivity of 92% and a specificity of 91%. The robustness and relevance of this evaluation were assessed using a 5-fold cross-validation. The good predictivity, together with the in vivo-like morphology of the liver microtissues and scalability to a 384-well microplate, makes this method a promising and practical in vitro alternative to 2D cell line cultures for the early hepatotoxicity screening of drug candidates.

Lower hepatotoxicity risk in Xelaglifam, a novel GPR40 agonist, compared to Fasiglifam for type 2 diabetes therapy

Fasiglifam, a candidate targeting GPR40, showed efficacy in clinical trials for type 2 diabetes but exerted liver toxicity. This study investigated the drug-induced liver injury (DILI) risk of Xelaglifam, a new GPR40 agonist, based on the potential toxicity mechanism of Fasiglifam; transporter inhibition, mitochondrial dysfunction, reactive metabolite formation, and covalent binding to proteins. In the hepatobiliary transporter assay, Xelaglifam showed a broader safety margin (>10-fold) against bile acid transporters, suggesting its less likelihood to cause bile acids accumulation, unlike Fasiglifam (<10-fold safety margin). Moreover, Xelaglifam showed no effect on glycocholic acid accumulation at higher concentrations than the estimated Cmax in the 3D human liver model, whereas Fasiglifam affected the accumulation. In the HepaRG spheroids 3D model, the AC50 values of Xelaglifam for mitochondrial function-related parameters were higher than Fasiglifam. Unlike Fasiglifam, none of the cell parameters for Xelaglifam were below the estimated 5x Cmax. Additionally, the glucuronide metabolite of Xelaglifam was negligible (<1 % of the parent) in the Safety Testing, indicating a limited contribution to DILI. Fasiglifam activated genes related to liver disease, whereas Xelaglifam had no effect; instead, it increased FXR activity, a bile acid regulator. Notably, toxicity studies in rats and monkeys showed no adverse liver effects at higher exposure levels than the effective human blood concentration. Overall, these results support a low risk of DILI for Xelaglifam treatment and the justification for its long-term use for treating type 2 diabetes.

Toxicological Assessment of 2-Hydroxychalcone-Mediated Photodynamic Therapy: Comparative In Vitro and In Vivo Approaches

BACKGROUND

Photodynamic therapy (PDT) is a treatment modality that uses light to activate a photosensitizing agent, destroying target cells. The growing awareness of the necessity to reduce or eliminate the use of mammals in research has prompted the search for safer toxicity testing models aligned with the new global guidelines and compliant with the relevant regulations.

OBJECTIVE

The objective of this study was to assess the impact of PDT on alternative models to mammals, including in vitro three-dimensional (3D) cultures and in vivo, in invertebrate animals, utilizing a potent photosensitizer, 2-hydroxychalcone.

METHODS

Cytotoxicity was assessed in two cellular models: monolayer (2D) and 3D. For this purpose, spheroids of two cell lines, primary dermal fibroblasts (HDFa) and adult human epidermal cell keratinocytes (HaCat), were developed and characterized following criteria on cell viability, shape, diameter, and number of cells. The survival percentages of Caenorhabditis elegans and Galleria mellonella were evaluated at 1 and 7 days, respectively.

RESULTS

The findings indicated that all the assessed platforms are appropriate for investigating PDT toxicity. Furthermore, 2-hydroxychalcone demonstrated low toxicity in the absence of light and when mediated by PDT across a range of in vitro (2D and 3D cultures) and in vivo (invertebrate animal models, including G. mellonella and C. elegans) models.

CONCLUSION

There was a strong correlation between the in vitro and in vivo tests, with similar toxicity results, particularly in the 3D models and C. elegans, where the concentration for 50% viability was approximately 100 µg/mL.

Advances in drug-induced liver injury research: in vitro models, mechanisms, omics and gene modulation techniques

Drug-induced liver injury (DILI) refers to drug-mediated damage to the structure and function of the liver, ranging from mild elevation of liver enzymes to severe hepatic insufficiency, and in some cases, progressing to liver failure. The mechanisms and clinical symptoms of DILI are diverse due to the varying combination of drugs, making clinical treatment and prevention complex. DILI has significant public health implications and is the primary reason for post-marketing drug withdrawals. The search for reliable preclinical models and validated biomarkers to predict and investigate DILI can contribute to a more comprehensive understanding of adverse effects and drug safety. In this review, we examine the progress of research on DILI, enumerate in vitro models with potential benefits, and highlight cellular molecular perturbations that may serve as biomarkers. Additionally, we discuss omics approaches frequently used to gather comprehensive datasets on molecular events in response to drug exposure. Finally, three commonly used gene modulation techniques are described, highlighting their application in identifying causal relationships in DILI. Altogether, this review provides a thorough overview of ongoing work and approaches in the field of DILI.

Control compounds for preclinical drug-induced liver injury assessment: Consensus-driven systematic review by the ProEuroDILI network

BACKGROUND & AIMS

Idiosyncratic drug-induced liver injury (DILI) is a complex and unpredictable event caused by drugs, and herbal or dietary supplements. Early identification of human hepatotoxicity at preclinical stages remains a major challenge, in which the selection of validated in vitro systems and test drugs has a significant impact. In this systematic review, we analyzed the compounds used in hepatotoxicity assays and established a list of DILI-positive and -negative control drugs for validation of in vitro models of DILI, supported by literature and clinical evidence and endorsed by an expert committee from the COST Action ProEuroDILI Network (CA17112).

METHODS

Following 2020 PRISMA guidelines, original research articles focusing on DILI which used in vitro human models and performed at least one hepatotoxicity assay with positive and negative control compounds, were included. Bias of the studies was assessed by a modified 'Toxicological Data Reliability Assessment Tool'.

RESULTS

A total of 51 studies (out of 2,936) met the inclusion criteria, with 30 categorized as reliable without restrictions. Although there was a broad consensus on positive compounds, the selection of negative compounds lacked clarity. 2D monoculture, short exposure times and cytotoxicity endpoints were the most tested, although there was no consensus on drug concentrations.

CONCLUSIONS

Extensive analysis highlighted the lack of agreement on control compounds for in vitro DILI assessment. Following comprehensive in vitro and clinical data analysis together with input from the expert committee, an evidence-based consensus-driven list of 10 positive and negative control drugs for validation of in vitro models of DILI is proposed.

IMPACT AND IMPLICATIONS

Prediction of human toxicity early in the drug development process remains a major challenge, necessitating the development of more physiologically relevant liver models and careful selection of drug-induced liver injury (DILI)-positive and -negative control drugs to better predict the risk of DILI associated with new drug candidates. Thus, this systematic study has crucial implications for standardizing the validation of new in vitro models of DILI. By establishing a consensus-driven list of positive and negative control drugs, the study provides a scientifically justified framework for enhancing the consistency of preclinical testing, thereby addressing a significant challenge in early hepatotoxicity identification. Practically, these findings can guide researchers in evaluating safety profiles of new drugs, refining in vitro models, and informing regulatory agencies on potential improvements to regulatory guidelines, ensuring a more systematic and efficient approach to drug safety assessment.

Enhanced hepatotoxicity assessment through encapsulated HepG2 spheroids in gelatin hydrogel matrices: Bridging the gap from 2D to 3D culture

Conventional 2D drug screening often fails to accurately predict clinical outcomes. We present an innovative approach to improve hepatotoxicity assessment by encapsulating HepG2 spheroids in gelatin hydrogel matrices with different mechanical properties. Encapsulated spheroids exhibit sustained liver-specific functionality, enhanced expression of drug-metabolizing enzymes, and increased drug sensitivity compared to 2D cultures. The platform detects critical variations in drug response, with significant differences in IC50 values between 2D and spheroid cultures ranging from 1.3-fold to > 13-fold, particularly for acetaminophen. Furthermore, drug-metabolizing enzyme expression varies across hydrogel concentrations, suggesting a role for matrix mechanical properties in modulating hepatocyte function. This novel spheroid-hydrogel platform offers a transformative approach to hepatotoxicity assessment, providing increased sensitivity, improved prediction, and a more physiologically relevant environment. The use of such advanced in vitro models can accelerate drug development, reduce animal testing, and contribute to improved patient safety and clinical outcomes.

Complexin vitromodels positioned for impact to drug testing in pharma: a review

Recent years have seen the creation and popularization of various complexin vitromodels (CIVMs), such as organoids and organs-on-chip, as a technology with the potential to reduce animal usage in pharma while also enhancing our ability to create safe and efficacious drugs for patients. Public awareness of CIVMs has increased, in part, due to the recent passage of the FDA Modernization Act 2.0. This visibility is expected to spur deeper investment in and adoption of such models. Thus, end-users and model developers alike require a framework to both understand the readiness of current models to enter the drug development process, and to assess upcoming models for the same. This review presents such a framework for model selection based on comparative -omics data (which we term model-omics), and metrics for qualification of specific test assays that a model may support that we term context-of-use (COU) assays. We surveyed existing healthy tissue models and assays for ten drug development-critical organs of the body, and provide evaluations of readiness and suggestions for improving model-omics and COU assays for each. In whole, this review comes from a pharma perspective, and seeks to provide an evaluation of where CIVMs are poised for maximum impact in the drug development process, and a roadmap for realizing that potential.

Peptide-mimetic treatment of Pseudomonas aeruginosa in a mouse model of respiratory infection

The rise of drug resistance has become a global crisis, with >1 million deaths due to resistant bacterial infections each year. Pseudomonas aeruginosa, in particular, remains a serious problem with limited solutions due to complex resistance mechanisms that now lead to more than 32,000 multidrug-resistant (MDR) infections and over 2000 deaths in the U.S. annually. While the emergence of resistant bacteria has become ominously common, identification of useful new drug classes has been limited over the past over 40 years. We found that a potential novel therapeutic, the peptide-mimetic TM5, is effective at killing P. aeruginosa and displays sufficiently low toxicity in mammalian cells to allow for use in treatment of infections. Interestingly, TM5 kills P. aeruginosa more rapidly than traditional antibiotics, within 30-60 min in vitro, and is effective against a range of clinical isolates, including extensively drug resistant strains. In vivo, TM5 significantly reduced bacterial load in the lungs within 24 h compared to untreated mice and demonstrated few adverse effects. Taken together, these observations suggest that TM5 shows promise as an alternative therapy for MDR P. aeruginosa respiratory infections.

Liver organoids: updates on generation strategies and biomedical applications

The liver is the most important metabolic organ in the body. While mouse models and cell lines have further deepened our understanding of liver biology and related diseases, they are flawed in replicating key aspects of human liver tissue, particularly its complex structure and metabolic functions. The organoid model represents a major breakthrough in cell biology that revolutionized biomedical research. Organoids are in vitro three-dimensional (3D) physiological structures that recapitulate the morphological and functional characteristics of tissues in vivo, and have significant advantages over traditional cell culture methods. In this review, we discuss the generation strategies and current advances in the field focusing on their application in regenerative medicine, drug discovery and modeling diseases.

A Pillar and Perfusion Plate Platform for Robust Human Organoid Culture and Analysis

Human organoids have the potential to revolutionize in vitro disease modeling by providing multicellular architecture and function that are similar to those in vivo. This innovative and evolving technology, however, still suffers from assay throughput and reproducibility to enable high-throughput screening (HTS) of compounds due to cumbersome organoid differentiation processes and difficulty in scale-up and quality control. Using organoids for HTS is further challenged by the lack of easy-to-use fluidic systems that are compatible with relatively large organoids. Here, these challenges are overcome by engineering "microarray three-dimensional (3D) bioprinting" technology and associated pillar and perfusion plates for human organoid culture and analysis. High-precision, high-throughput stem cell printing, and encapsulation techniques are demonstrated on a pillar plate, which is coupled with a complementary deep well plate and a perfusion well plate for static and dynamic organoid culture. Bioprinted cells and spheroids in hydrogels are differentiated into liver and intestine organoids for in situ functional assays. The pillar/perfusion plates are compatible with standard 384-well plates and HTS equipment, and thus may be easily adopted in current drug discovery efforts.

Beyond the hype and toward application: liver complex in vitro models in preclinical drug safety

INTRODUCTION

Drug induced Liver-Injury (DILI) is a leading cause of drug attrition and complex in vitro models (CIVMs), including three dimensional (3D) spheroids, 3D bio printed tissues and flow-based systems, could improve preclinical prediction. Although CIVMs have demonstrated good sensitivity and specificity in DILI detection their adoption remains limited.

AREAS COVERED

This article describes DILI, the challenges with its prediction and the current strategies and models that are being used. It reviews data from industry-FDA collaborations and strategic partnerships and finishes with an outlook of CIVMs in preclinical toxicity testing. Literature searches were performed using PubMed and Google Scholar while product information was collected from manufacturer websites.

EXPERT OPINION

Liver CIVMs are promising models for predicting DILI although, a decade after their introduction, routine use by the pharmaceutical industry is limited. To accelerate their adoption, several industry-regulator-developer partnerships or consortia have been established to guide the development and qualification. Beyond this, liver CIVMs should continue evolving to capture greater immunological mimicry while partnering with computational approaches to deliver systems that change the paradigm of predicting DILI.

3D-Bioprinted Hepar-on-a-Chip Implanted in Graphene-Based Plasmonic Sensors

Precise three-dimensional (3D) bioprinting designs enable the fabrication of unique structures for 3D-cell culture models. There is still an absence of real-time detection tools to effectively track in situ 3D-cell performance, hindering a comprehensive understanding of disease progression and drug efficacy assessment. While numerous bioinks have been developed, few are equipped with internal sensors capable of accurate detection. This study addresses these challenges by constructing a 3D-bioprinted hepar-on-a-chip embedded with graphene quantum dot-capped gold nanoparticle-based plasmonic sensors, featuring strong surface-enhanced Raman scattering (SERS) enhancement, biostability, and signal consistency. Such an integrated hepar-on-a-chip demonstrates excellent capability in the secretion of liver function-related proteins and the expression of drug metabolism and transport-related genes. Furthermore, the on-site detection of cell-secreted biomarker glutathione transferase α (GST-α) was successfully achieved using the plasmonic probe, with a dynamic linear detection range of 20-500 ng/mL, showcasing high anti-interference and specificity for GST-α. Ultimately, this integrated hepar-on-a-chip system offers a high-quality platform for monitoring liver injury.

A 3D spheroid model of quadruple cell co-culture with improved liver functions for hepatotoxicity prediction

Drug-induced liver injury (DILI) is one of the major concerns during drug development. Wide acceptance of the 3 R principles and the innovation of in-vitro techniques have introduced various novel model options, among which the three-dimensional (3D) cell spheroid cultures have shown a promising prospect in DILI prediction. The present study developed a 3D quadruple cell co-culture liver spheroid model for DILI prediction via self-assembly. Induction by phorbol 12-myristate 13-acetate at the concentration of 15.42 ng/mL for 48 hours with a following 24-hour rest period was used for THP-1 cell differentiation, resulting in credible macrophagic phenotypes. HepG2 cells, PUMC-HUVEC-T1 cells, THP-1-originated macrophages, and human hepatic stellate cells were selected as the components, which exhibited adaptability in the designated spheroid culture conditions. Following establishment, the characterization demonstrated the competence of the model in long-term stability reflected by the maintenance of morphology, viability, cellular integration, and cell-cell junctions for at least six days, as well as the reliable liver-specific functions including superior albumin and urea secretion, improved drug metabolic enzyme expression and CYP3A4 activity, and the expression of MRP2, BSEP, and P-GP accompanied by the bile acid efflux transport function. In the comparative testing using 22 DILI-positive and 5 DILI-negative compounds among the novel 3D co-culture model, 3D HepG2 spheroids, and 2D HepG2 monolayers, the 3D culture method significantly enhanced the model sensitivity to compound cytotoxicity compared to the 2D form. The novel co-culture liver spheroid model exhibited higher overall predictive power with margin of safety as the classifying tool. In addition, the non-parenchymal cell components could amplify the toxicity of isoniazid in the 3D model, suggesting their potential mediating role in immune-mediated toxicity. The proof-of-concept experiments demonstrated the capability of the model in replicating drug-induced lipid dysregulation, bile acid efflux inhibition, and α-SMA upregulation, which are the key features of liver steatosis and phospholipidosis, cholestasis, and fibrosis, respectively. Overall, the novel 3D quadruple cell co-culture spheroid model is a reliable and readily available option for DILI prediction.

Cell competition promotes metastatic intestinal cancer through a multistage process

Cell competition plays an instrumental role in quality control during tissue development and homeostasis. Nevertheless, cancer cells can exploit this process for their own proliferative advantage. In our study, we generated mixed murine organoids and microtissues to explore the impact of cell competition on liver metastasis. Unlike competition at the primary site, the initial effect on liver progenitor cells does not involve the induction of apoptosis. Instead, metastatic competition manifests as a multistage process. Initially, liver progenitors undergo compaction, which is followed by cell-cycle arrest, ultimately forcing differentiation. Subsequently, the newly differentiated liver cells exhibit reduced cellular fitness, rendering them more susceptible to outcompetition by intestinal cancer cells. Notably, cancer cells leverage different interactions with different epithelial populations in the liver, using them as scaffolds to facilitate their growth. Consequently, tissue-specific mechanisms of cell competition are fundamental in driving metastatic intestinal cancer.

Individualized Pharmacotherapy Utilizing Genetic Biomarkers and Novel In Vitro Systems As Predictive Tools for Optimal Drug Development and Treatment

In the area of drug development and clinical pharmacotherapy, a profound understanding of the pharmacokinetics and potential adverse reactions associated with the drug under investigation is paramount. Essential to this endeavor is a comprehensive understanding about interindividual variations in absorption, distribution, metabolism, and excretion (ADME) genetics and the predictive capabilities of in vitro systems, shedding light on metabolite formation and the risk of adverse drug reactions (ADRs). Both the domains of pharmacogenomics and the advancement of in vitro systems are experiencing rapid expansion. Here we present an update on these burgeoning fields, providing an overview of their current status and illuminating potential future directions. SIGNIFICANCE STATEMENT: There is very rapid development in the area of pharmacogenomics and in vitro systems for predicting drug pharmacokinetics and risk for adverse drug reactions. We provide an update of the current status of pharmacogenomics and developed in vitro systems on these aspects aimed to achieve a better personalized pharmacotherapy.

The use of a selective, nontoxic dual-acting peptide for breast cancer patients with brain metastasis

Triple-negative breast cancer (TNBC) is an aggressive subtype characterized by the absence of commonly targeted receptors. Unspecific chemotherapy is currently the main therapeutic option, with poor results. Another major challenge is the frequent appearance of brain metastasis (BM) associated with a significant decrease in patient overall survival. The treatment of BM is even more challenging due to the presence of the blood-brain barrier (BBB). Here, we present a dual-acting peptide (PepH3-vCPP2319) designed to tackle TNBC/BM, in which a TNBC-specific anticancer peptide (ACP) motif (vCPP2319) is joined to a BBB peptide shuttle (BBBpS) motif (PepH3). PepH3-vCPP2319 demonstrated selectivity and efficiency in eliminating TNBC both in monolayers (IC50≈5.0 µM) and in spheroids (IC50≈25.0 µM), with no stringent toxicity toward noncancerous cell lines and red blood cells (RBCs). PepH3-vCPP2319 was also able to cross the BBB in vitro and penetrate the brain in vivo, and was stable in serum with a half-life above 120 min. Tumor cell-peptide interaction is fast, with quick peptide internalization via clathrin-mediated endocytosis without membrane disruption. Upon internalization, the peptide is detected in the nucleus and the cytoplasm, indicating a multi-targeted mechanism of action that ultimately induces irreversible cell damage and apoptosis. In conclusion, we have designed a dual-acting peptide capable of brain penetration and TNBC cell elimination, thus expanding the drug arsenal to fight this BC subtype and its BM.

Exploiting the predictive power of educated spheroids to detect immune-mediated idiosyncratic drug-induced liver injury: the case of troglitazone

Idiosyncratic drug-induced liver injury (iDILI) is a major concern in drug development because its occurrence is unpredictable. Presently, iDILI prediction is a challenge, and cell toxicity is observed only at concentrations that are much higher than the therapeutic doses in preclinical models. Applying a proprietary cell educating technology, we developed a person-dependent spheroid system that contains autologous educated immune cells that can detect iDILI risk at therapeutic concentrations. Integrating this system into a high-throughput screening platform will help pharmaceutical companies accurately detect the iDILI risk of new molecules de-risking drug development.

Proteomic workflows for deep phenotypic profiling of 3D organotypic liver models

Organotypic human tissue models constitute promising systems to facilitate drug discovery and development. They allow to maintain native cellular phenotypes and functions, which enables long-term pharmacokinetic and toxicity studies, as well as phenotypic screening. To trace relevant phenotypic changes back to specific targets or signaling pathways, comprehensive proteomic profiling is the gold-standard. A multitude of proteomic workflows have been applied on 3D tissue models to quantify their molecular phenotypes; however, their impact on analytical results and biological conclusions in this context has not been evaluated. The performance of twelve mass spectrometry-based global proteomic workflows that differed in the amount of cellular input, lysis protocols and quantification methods was compared for the analysis of primary human liver spheroids. Results differed majorly between protocols in the total number and subcellular compartment bias of identified proteins, which is particularly relevant for the reliable quantification of transporters and drug metabolizing enzymes. Using a model of metabolic dysfunction-associated steatotic liver disease, we furthermore show that critical disease pathways are robustly identified using a standardized high throughput-compatible workflow based on thermal lysis, even using only individual spheroids (1500 cells) as input. The results increase the applicability of proteomic profiling to phenotypic screens in organotypic microtissues and provide a scalable platform for deep phenotyping from limited biological material.

The Current Status and Use of Microphysiological Systems by the Pharmaceutical Industry: The International Consortium for Innovation and Quality Microphysiological Systems Affiliate Survey and Commentary

Microphysiological systems (MPS) are comprised of one or multiple cell types of human or animal origins that mimic the biochemical/electrical/mechanical responses and blood-tissue barrier properties of the cells observed within a complex organ. The goal of incorporating these in vitro systems is to expedite and advance the drug discovery and development paradigm with improved predictive and translational capabilities. Considering the industry need for improved efficiency and the broad challenges of model qualification and acceptance, the International Consortium for Innovation and Quality (IQ) founded an IQ MPS working group in 2014 and Affiliate in 2018. This group connects thought leaders and end users, provides a forum for crosspharma collaboration, and engages with regulators to qualify translationally relevant MPS models. To understand how pharmaceutical companies are using MPS, the IQ MPS Affiliate conducted two surveys in 2019, survey 1, and 2021, survey 2, which differed slightly in the scope of definition of the complex in vitro models under question. The surveys captured demographics, resourcing, rank order for organs of interest, compound modalities tested, and MPS organ-specific questions, including nonclinical species needs and cell types. The major focus of this manuscript is on results from survey 2, where we specifically highlight the context of use for MPS within safety, pharmacology, or absorption, disposition, metabolism, and excretion and discuss considerations for including MPS data in regulatory submissions. In summary, these data provide valuable insights for developers, regulators, and pharma, offering a view into current industry practices and future considerations while highlighting key challenges impacting MPS adoption. SIGNIFICANCE STATEMENT: The application of microphysiological systems (MPS) represents a growing area of interest in the drug discovery and development framework. This study surveyed 20+ pharma companies to understand resourcing, current areas of application, and the key challenges and barriers to internal MPS adoption. These results will provide regulators, tech providers, and pharma industry leaders a starting point to assess the current state of MPS applications along with key learnings to effectively realize the potential of MPS as an emerging technology.

Organoids and organoids-on-a-chip as the new testing strategies for environmental toxicology-applications & advantages

An increasing number of harmful environmental factors are causing serious impacts on human health, and there is an urgent need to accurately identify the toxic effects and mechanisms of these harmful environmental factors. However, traditional toxicity test methods (e.g., animal models and cell lines) often fail to provide accurate results. Fortunately, organoids differentiated from stem cells can more accurately, sensitively and specifically reflect the effects of harmful environmental factors on the human body. They are also suitable for specific studies and are frequently used in environmental toxicology nowadays. As a combination of organoids and organ-on-a-chip technology, organoids-on-a-chip has great potential in environmental toxicology. It is more controllable to the physicochemical microenvironment and is not easy to be contaminated. It has higher homogeneity in the size and shape of organoids. In addition, it can achieve vascularization and exchange the nutrients and metabolic wastes in time. Multi-organoids-chip can also simulate the interactions of different organs. These advantages can facilitate better function and maturity of organoids, which can also make up for the shortcomings of common organoids to a certain extent. This review firstly discussed the limitations of traditional toxicology testing platforms, leading to the introduction of new platforms: organoids and organoids-on-a-chip. Next, the applications of different organoids and organoids-on-a-chip in environmental toxicology were summarized and prospected. Since the advantages of the new platforms have not been sufficiently considered in previous literature, we particularly emphasized them. Finally, this review also summarized the opportunities and challenges faced by organoids and organoids-on-a-chip, with the expectation that readers will gain a deeper understanding of their value in the field of environmental toxicology.

The choice of ultra-low attachment plates impacts primary human and primary canine hepatocyte spheroid formation, phenotypes, and function

Organotypic three-dimensional liver spheroid cultures in which hepatic cells retain their molecular phenotype and functionality have emerged as powerful tools for preclinical drug development. In recent years a multitude of culture systems have been developed; however, a thorough side-by-side benchmarking of the different methods is lacking. Here, we compared the performance of ten different 96- and 384-well microplate types to support spheroid formation and long-term culture. Specifically, we evaluated differences in spheroid formation kinetics, viability, functionality, expression patterns, and their utility for hepatotoxicity assessments using primary human hepatocytes (PHH) and primary canine hepatocytes (PCH). All 96-well plates enabled formation of PHH liver spheroids, albeit with differences between plates in spheroid size, geometry, and reproducibility. Performance of different 384-wells was less consistent. Only 6/10 microplates supported the formation of PCH aggregates. Interestingly, even if PCH aggregates in these six microplates were more loosely packed than PHH spheroids, they maintained their function and were compatible with long-term pharmacological and toxicological assays. Overall, Corning and Biofloat plates showed the best performance in the formation of both human and canine liver spheroids with highest viability, most physiologically relevant phenotypes, superior CYP activity and lowest coefficient of variation in toxicity assays. The presented data constitutes a valuable resource that demonstrates the impacts of current ultra-low attachment plates on liver spheroid metrics and can guide evidence-based plate selection. Combined, these results have important implications for the cross-comparison of different studies and can facilitate the standardization and reproducibility of three-dimensional liver culture experiments.

Novel Strategy to Assess the Neurotoxicity of Organic Solvents Such as Glycol Ethers: Protocol for Combining In Vitro and In Silico Methods With Human-Controlled Exposure Experiments

BACKGROUND

Chemicals are not required to be tested systematically for their neurotoxic potency, although they may contribute to the development of several neurological diseases. The absence of systematic testing may be partially explained by the current Organisation for Economic Co-operation and Development (OECD) Test Guidelines, which rely on animal experiments that are expensive, laborious, and ethically debatable. Therefore, it is important to understand the risks to exposed workers and the general population exposed to domestic products. In this study, we propose a strategy to test the neurotoxicity of solvents using the commonly used glycol ethers as a case study.

OBJECTIVE

This study aims to provide a strategy that can be used by regulatory agencies and industries to rank solvents according to their neurotoxicity and demonstrate the use of toxicokinetic modeling to predict air concentrations of solvents that are below the no observed adverse effect concentrations (NOAECs) for human neurotoxicity determined in in vitro assays.

METHODS

The proposed strategy focuses on a complex 3D in vitro brain model (BrainSpheres) derived from human-induced pluripotent stem cells (hiPSCs). This model is accompanied by in vivo, in vitro, and in silico models for the blood-brain barrier (BBB) and in vitro models for liver metabolism. The data are integrated into a toxicokinetic model. Internal concentrations predicted using this toxicokinetic model are compared with the results from in vivo human-controlled exposure experiments for model validation. The toxicokinetic model is then used in reverse dosimetry to predict air concentrations, leading to brain concentrations lower than the NOAECs determined in the hiPSC-derived 3D brain model. These predictions will contribute to the protection of exposed workers and the general population with domestic exposures.

RESULTS

The Swiss Centre for Applied Human Toxicology funded the project, commencing in January 2021. The Human Ethics Committee approval was obtained on November 16, 2022. Zebrafish experiments and in vitro methods started in February 2021, whereas recruitment of human volunteers started in 2022 after the COVID-19 pandemic-related restrictions were lifted. We anticipate that we will be able to provide a neurotoxicity testing strategy by 2026 and predicted air concentrations for 6 commonly used propylene glycol ethers based on toxicokinetic models incorporating liver metabolism, BBB leakage parameters, and brain toxicity.

CONCLUSIONS

This study will be of great interest to regulatory agencies and chemical industries needing and seeking novel solutions to develop human chemical risk assessments. It will contribute to protecting human health from the deleterious effects of environmental chemicals.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/50300.

The Material World of 3D-Bioprinted and Microfluidic-Chip Models of Human Liver Fibrosis

Biomaterials are extensively used to mimic cell-matrix interactions, which are essential for cell growth, function, and differentiation. This is particularly relevant when developing in vitro disease models of organs rich in extracellular matrix, like the liver. Liver disease involves a chronic wound-healing response with formation of scar tissue known as fibrosis. At early stages, liver disease can be reverted, but as disease progresses, reversion is no longer possible, and there is no cure. Research for new therapies is hampered by the lack of adequate models that replicate the mechanical properties and biochemical stimuli present in the fibrotic liver. Fibrosis is associated with changes in the composition of the extracellular matrix that directly influence cell behavior. Biomaterials could play an essential role in better emulating the disease microenvironment. In this paper, the recent and cutting-edge biomaterials used for creating in vitro models of human liver fibrosis are revised, in combination with cells, bioprinting, and/or microfluidics. These technologies have been instrumental to replicate the intricate structure of the unhealthy tissue and promote medium perfusion that improves cell growth and function, respectively. A comprehensive analysis of the impact of material hints and cell-material interactions in a tridimensional context is provided.

A comprehensive review on 3D tissue models: Biofabrication technologies and preclinical applications

The limitations of traditional two-dimensional (2D) cultures and animal testing, when it comes to precisely foreseeing the toxicity and clinical effectiveness of potential drug candidates, have resulted in a notable increase in the rate of failure during the process of drug discovery and development. Three-dimensional (3D) in-vitro models have arisen as substitute platforms with the capacity to accurately depict in-vivo conditions and increasing the predictivity of clinical effects and toxicity of drug candidates. It has been found that 3D models can accurately represent complex tissue structure of human body and can be used for a wide range of disease modeling purposes. Recently, substantial progress in biomedicine, materials and engineering have been made to fabricate various 3D in-vitro models, which have been exhibited better disease progression predictivity and drug effects than convention models, suggesting a promising direction in pharmaceutics. This comprehensive review highlights the recent developments in 3D in-vitro tissue models for preclinical applications including drug screening and disease modeling targeting multiple organs and tissues, like liver, bone, gastrointestinal tract, kidney, heart, brain, and cartilage. We discuss current strategies for fabricating 3D models for specific organs with their strengths and pitfalls. We expand future considerations for establishing a physiologically-relevant microenvironment for growing 3D models and also provide readers with a perspective on intellectual property, industry, and regulatory landscape.

An original donor-dependent spheroid system for the prediction of idiosyncratic drug-induced liver injury risk

One major drawback of preclinical models to test drug-induced liver injury (DILI) is their inability to predict the interindividual difference of DILI effect in a population. Consequently, a high number of molecules that passed preclinical phases, fail clinical trials, and many FDA-approved drugs were removed from the market due to idiosyncratic DILI. We use a proprietary-depleted human serum-based cell educating technology to generate donor-dependent spheroids with distinct morphology and functionality. We demonstrate that educated spheroids could capture the large variations in susceptibility to drug-induced liver injury between donors. We show that the model could predict clinical apparent DILI risk with a high specificity and sensitivity. We provide evidence that the model could address non-genetic factor-associated DILI risk and severity such as age or sex. Our study supports the benefit of using donor-dependent educated spheroids for hepatotoxicity evaluation in preclinical phase or in an exploratory study clinical trial phase 2 to provide a robust safety profile to a drug.

3D bioprinting of dECM-incorporated hepatocyte spheroid for simultaneous promotion of cell-cell and -ECM interactions

The cell spheroid technology, which greatly enhances cell-cell interactions, has gained significant attention in the development of in vitro liver models. However, existing cell spheroid technologies still have limitations in improving hepatocyte-extracellular matrix (ECM) interaction, which have a significant impact on hepatic function. In this study, we have developed a novel bioprinting technology for decellularized ECM (dECM)-incorporated hepatocyte spheroids that could enhance both cell-cell and -ECM interactions simultaneously. To provide a biomimetic environment, a porcine liver dECM-based cell bio-ink was developed, and a spheroid printing process using this bio-ink was established. As a result, we precisely printed the dECM-incorporated hepatocyte spheroids with a diameter of approximately 160-220 μm using primary mouse hepatocyte (PMHs). The dECM materials were uniformly distributed within the bio-printed spheroids, and even after more than 2 weeks of culture, the spheroids maintained their spherical shape and high viability. The incorporation of dECM also significantly improved the hepatic function of hepatocyte spheroids. Compared to hepatocyte-only spheroids, dECM-incorporated hepatocyte spheroids showed approximately 4.3- and 2.5-fold increased levels of albumin and urea secretion, respectively, and a 2.0-fold increase in CYP enzyme activity. These characteristics were also reflected in the hepatic gene expression levels of ALB, HNF4A, CPS1, and others. Furthermore, the dECM-incorporated hepatocyte spheroids exhibited up to a 1.8-fold enhanced drug responsiveness to representative hepatotoxic drugs such as acetaminophen, celecoxib, and amiodarone. Based on these results, it can be concluded that the dECM-incorporated spheroid printing technology has great potential for the development of highly functional in vitro liver tissue models for drug toxicity assessment.

Peptide-mimetic treatment of Pseudomonas aeruginosa in a mouse model of respiratory infection

The rise of drug resistance has become a global crisis, with >1 million deaths due to resistant bacterial infections each year. Pseudomonas aeruginosa, in particular, remains a serious problem with limited solutions due to complex resistance mechanisms that now lead to more than 32,000 multidrug-resistant (MDR) infections and over 2,000 deaths annually. While the emergence of resistant bacteria has become concerningly common, identification of useful new drug classes has been limited over the past 40+ years. We found that a potential novel therapeutic, the peptide-mimetic TM5, is effective at killing P. aeruginosa and displays sufficiently low toxicity for mammalian cells to allow for use in treatment of infections. Interestingly, TM5 kills P. aeruginosa more rapidly than traditional antibiotics, within 30-60 minutes in vitro , and is effective against a range of clinical isolates. In vivo , TM5 significantly reduced bacterial load in the lungs within 24 hours compared to untreated mice and demonstrated few adverse effects. Taken together, these observations suggest that TM5 shows promise as an alternative therapy for MDR P. aeruginosa respiratory infections.

Gelatin-Based Hybrid Hydrogel Scaffolds: Toward Physicochemical Liver Mimicry

There exists a clear need to develop novel materials that could serve liver tissue engineering purposes. Those materials need to be researched for the development of bioengineered liver tissue as an alternative to donor livers, as well as for materials that could be applied for scaffolds to develop an in vitro model for drug-induced liver injury (DILI) detection . In this paper, the hydrogels oxidized dextran-gelatin (Dexox-Gel) and norbornene-modified dextran-thiolated gelatin (DexNB-GelSH) were developed, and their feasibility toward processing via indirect 3D-printing was investigated with the aim to develop hydrogel scaffolds that physicochemically mimic native liver tissue. Furthermore, their in vitro biocompatibility was assessed using preliminary biological tests using HepG2 cells. Both materials were thoroughly physicochemically characterized and benchmarked to the methacrylated gelatin (GelMA) reference material. Due to inferior properties, Dexox-gel was not further processed into 3D-hydrogel scaffolds. This research revealed that DexNB-GelSH exhibited physicochemical properties that were in excellent agreement with the properties of natural liver tissue in contrast to GelMA. In combination with an equally good biological evaluation of DexNB-GelSH in comparison with GelMA based on an MTS proliferation assay and an albumin quantification assay, DexNB-GelSH can be considered promising in the field of liver tissue engineering.

Perspectives of data science in preclinical safety assessment

The data landscape in preclinical safety assessment is fundamentally changing because of not only emerging new data types, such as human systems biology, or real-world data (RWD) from clinical trials, but also technological advancements in data-processing software and analytical tools based on deep learning approaches. The recent developments of data science are illustrated with use cases for the three factors: predictive safety (new in silico tools), insight generation (new data for outstanding questions); and reverse translation (extrapolating from clinical experience to resolve preclinical questions). Further advances in this field can be expected if companies focus on overcoming identified challenges related to a lack of platforms and data silos and assuring appropriate training of data scientists within the preclinical safety teams.

Microphysiological Models for Mechanistic-Based Prediction of Idiosyncratic DILI

Drug-induced liver injury (DILI) is a major contributor to high attrition rates among candidate and market drugs and a key regulatory, industry, and global health concern. While acute and dose-dependent DILI, namely, intrinsic DILI, is predictable and often reproducible in preclinical models, the nature of idiosyncratic DILI (iDILI) limits its mechanistic understanding due to the complex disease pathogenesis, and recapitulation using in vitro and in vivo models is extremely challenging. However, hepatic inflammation is a key feature of iDILI primarily orchestrated by the innate and adaptive immune system. This review summarizes the in vitro co-culture models that exploit the role of the immune system to investigate iDILI. Particularly, this review focuses on advancements in human-based 3D multicellular models attempting to supplement in vivo models that often lack predictability and display interspecies variations. Exploiting the immune-mediated mechanisms of iDILI, the inclusion of non-parenchymal cells in these hepatoxicity models, namely, Kupffer cells, stellate cells, dendritic cells, and liver sinusoidal endothelial cells, introduces heterotypic cell-cell interactions and mimics the hepatic microenvironment. Additionally, drugs recalled from the market in the US between 1996-2010 that were studies in these various models highlight the necessity for further harmonization and comparison of model characteristics. Challenges regarding disease-related endpoints, mimicking 3D architecture with different cell-cell contact, cell source, and the underlying multi-cellular and multi-stage mechanisms are described. It is our belief that progressing our understanding of the underlying pathogenesis of iDILI will provide mechanistic clues and a method for drug safety screening to better predict liver injury in clinical trials and post-marketing.

From vision toward best practices: Evaluating in vitro transcriptomic points of departure for application in risk assessment using a uniform workflow

The growing number of chemicals in the current consumer and industrial markets presents a major challenge for regulatory programs faced with the need to assess the potential risks they pose to human and ecological health. The increasing demand for hazard and risk assessment of chemicals currently exceeds the capacity to produce the toxicity data necessary for regulatory decision making, and the applied data is commonly generated using traditional approaches with animal models that have limited context in terms of human relevance. This scenario provides the opportunity to implement novel, more efficient strategies for risk assessment purposes. This study aims to increase confidence in the implementation of new approach methods in a risk assessment context by using a parallel analysis to identify data gaps in current experimental designs, reveal the limitations of common approaches deriving transcriptomic points of departure, and demonstrate the strengths in using high-throughput transcriptomics (HTTr) to derive practical endpoints. A uniform workflow was applied across six curated gene expression datasets from concentration-response studies containing 117 diverse chemicals, three cell types, and a range of exposure durations, to determine tPODs based on gene expression profiles. After benchmark concentration modeling, a range of approaches was used to determine consistent and reliable tPODs. High-throughput toxicokinetics were employed to translate in vitro tPODs (µM) to human-relevant administered equivalent doses (AEDs, mg/kg-bw/day). The tPODs from most chemicals had AEDs that were lower (i.e., more conservative) than apical PODs in the US EPA CompTox chemical dashboard, suggesting in vitro tPODs would be protective of potential effects on human health. An assessment of multiple data points for single chemicals revealed that longer exposure duration and varied cell culture systems (e.g., 3D vs. 2D) lead to a decreased tPOD value that indicated increased chemical potency. Seven chemicals were flagged as outliers when comparing the ratio of tPOD to traditional POD, thus indicating they require further assessment to better understand their hazard potential. Our findings build confidence in the use of tPODs but also reveal data gaps that must be addressed prior to their adoption to support risk assessment applications.

The assessment of the potential hepatotoxicity of new drugs by in vitro metabolomics

Drug hepatotoxicity assessment is a relevant issue both in the course of drug development as well as in the post marketing phase. The use of human relevant in vitro models in combination with powerful analytical methods (metabolomic analysis) is a promising approach to anticipate, as well as to understand and investigate the effects and mechanisms of drug hepatotoxicity in man. The metabolic profile analysis of biological liver models treated with hepatotoxins, as compared to that of those treated with non-hepatotoxic compounds, provides useful information for identifying disturbed cellular metabolic reactions, pathways, and networks. This can later be used to anticipate, as well to assess, the potential hepatotoxicity of new compounds. However, the applicability of the metabolomic analysis to assess the hepatotoxicity of drugs is complex and requires careful and systematic work, precise controls, wise data preprocessing and appropriate biological interpretation to make meaningful interpretations and/or predictions of drug hepatotoxicity. This review provides an updated look at recent in vitro studies which used principally mass spectrometry-based metabolomics to evaluate the hepatotoxicity of drugs. It also analyzes the principal drawbacks that still limit its general applicability in safety assessment screenings. We discuss the analytical workflow, essential factors that need to be considered and suggestions to overcome these drawbacks, as well as recent advancements made in this rapidly growing field of research.