iPSC-derived Hepatocytes Research Articles

In vitro hepatic 3D cell models and their application in genetic toxicology: a systematic review

The rapid development of new chemicals and consumer products has raised concerns about their potential genotoxic effects on human health, including DNA damage leading to serious diseases. For such new chemicals and pharmaceutical products, international regulations require genotoxicity data, initially obtained through in vitro tests, followed by in vivo experiments, if needed. Traditionally, laboratory animals have been used for this purpose, however, they are costly, ethically problematic, and often unreliable due to species differences. Therefore, innovative more accurate in vitro testing approaches are rapidly being developed to replace, refine and reduce (3R) the use of animals for experimental purposes and to improve the relevance for humans in toxicology studies. One of such innovative approaches are in vitro three-dimensional (3D) cell models, which are already being highlighted as superior alternatives to the two-dimensional (2D) cell cultures that are traditionally used as in vitro models for the safety testing of chemicals and pharmaceuticals. 3D cell models provide physiologically relevant information and more predictive data for in vivo conditions. In the review article, we provide a comprehensive overview of 3D hepatic cell models, including HepG2, HepG2/C3A, HepaRG, human primary hepatocytes, and iPSC-derived hepatocytes, and their application in the field of genotoxicology. Through a detailed literature analysis, we identified 31 studies conducted between 2007 and April 2024 that used a variety of standard methods, such as the comet assay, the micronucleus assay, and the γH2AX assay, as well as new methodological approaches, including toxicogenomics, to assess the cytotoxic and genotoxic activity of chemicals, nanoparticles and natural toxins. Based on our search, we can conclude that the use of in vitro 3D cell models for genotoxicity testing has been increasing over the years and that 3D cell models have an even greater potential for future implementation and further refinement in genetic toxicology and risk assessment.

Thyroid hormone receptor beta (THRβ1) is the major regulator of T3 action in human iPSC-derived hepatocytes

ObjectiveThyroid hormone (TH) action is mediated by thyroid hormone receptor (THR) isoforms. While THRβ1 is likely the main isoform expressed in liver, its role in human hepatocytes is not fully understood. MethodsTo elucidate the role of THRβ1 action in human hepatocytes we used CRISPR/Cas9 editing to knock out THRβ1 in induced pluripotent stem cells (iPSC). Following directed differentiation to the hepatic lineage, iPSC-derived hepatocytes were then interrogated to determine the role of THRβ1 in ligand-independent and -dependent functions. ResultsWe found that the loss of THRβ1 promoted alterations in proliferation rate and metabolic pathways regulated by T3, including gluconeogenesis, lipid oxidation, fatty acid synthesis, and fatty acid uptake. We observed that key genes involved in liver metabolism are regulated through both T3 ligand-dependent and -independent THRβ1 signaling mechanisms. Finally, we demonstrate that following THRβ1 knockout, several key metabolic genes remain T3 responsive suggesting they are THRα targets. ConclusionsThese results highlight that iPSC-derived hepatocytes are an effective platform to study mechanisms regulating TH signaling in human hepatocytes.

Hepatitis B Virus-KMT2B Integration Drives Hepatic Oncogenic Processes in a Human Gene-edited Induced Pluripotent Stem Cells-derived Model

Background & AimsHepatitis B virus (HBV)-DNA integration into the host genome contributes to hepatocellular carcinoma (HCC) development. KMT2B is the second most frequent locus of HBV-DNA integration in HCC, however its role and function remain unclear. We aimed to clarify the impact of HBV-KMT2B integration in HCC development using a human genome-edited induced pluripotent stem cells (iPSCs) model. MethodsBased on the genetic information on HBV-KMT2B integration in HCC, we determined its complete DNA sequence and transcript variants. To exclude the effect of other oncogenic mutations, we reproduced HBV integration in healthy donor iPSCs with an intact genome and analyzed its effects using iPSC-derived hepatic progenitor cells (HPCs) and hepatocytes (iPS-Heps). ResultsThe reproduced HBV-KMT2B integration significantly upregulated the proliferation of hepatic cells. Comprehensive transcriptional and epigenetic analyses revealed enhanced expression of cell cycle-related genes in hepatic cells with HBV-KMT2B integration based on perturbation of histone 3 lysine 4 tri-methylation(H3K4me3), mimicking that in the original HCC sample. Long-read RNA-sequence detected the common KMT2B transcript variants in the HCC sample and HPCs. Overexpression of the truncated variant significantly enhanced proliferation of hepatic cells, whereas HBV-KMT2B fusion transcripts did not enhance proliferation. HBV-KMT2B-integrated HPCs exhibited replication stress and DNA damage, indicating that our model initiated the process of hepatocarcinogenesis due to abnormally promoted KMT2B function. ConclusionsOur disease model using genetically engineered iPSCs provides the first insight into both the KMT2B function in HCC development and the oncogenic processes by HBV-KMT2B integration. We clarified the novel oncogenic mechanism in HBV-related HCC due to aberrant KMT2B function.

P02-34 iPSC-derived hepatocytes from multiple donors capture the effects of population diversity in drug metabolism and response

P02-34 iPSC-derived hepatocytes from multiple donors capture the effects of population diversity in drug metabolism and response

P02-36 In vitro monogenic liver disease models using iPSC-derived hepatocytes demonstrate an altered CYP450 gene expression profile compared to wild-type cells

P02-36 In vitro monogenic liver disease models using iPSC-derived hepatocytes demonstrate an altered CYP450 gene expression profile compared to wild-type cells

P02-26 Optimized iPSC-derived hepatocytes offer a novel liver cell model for in vitro predictive toxicity and drug efficacy studies

P02-26 Optimized iPSC-derived hepatocytes offer a novel liver cell model for in vitro predictive toxicity and drug efficacy studies

A PNPLA3-Deficient iPSC-Derived Hepatocyte Screen Identifies Pathways to Potentially Reduce Steatosis in Metabolic Dysfunction-Associated Fatty Liver Disease.

The incidence of nonalcoholic fatty liver disease (NAFLD), or metabolic dysfunction-associated fatty liver disease (MAFLD), is increasing in adults and children. Unfortunately, effective pharmacological treatments remain unavailable. Single nucleotide polymorphisms (SNPs) in the patatin-like phospholipase domain-containing protein (PNPLA3 I148M) have the most significant genetic association with the disease at all stages of its progression. A roadblock to identifying potential treatments for PNPLA3-induced NAFLD is the lack of a human cell platform that recapitulates the PNPLA3 I148M-mediated onset of lipid accumulation. Hepatocyte-like cells were generated from PNPLA3-/- and PNPLA3I148M/M-induced pluripotent stem cells (iPSCs). Lipid levels were measured by staining with BODIPY 493/503 and were found to increase in PNPLA3 variant iPSC-derived hepatocytes. A small-molecule screen identified multiple compounds that target Src/PI3K/Akt signaling and could eradicate lipid accumulation in these cells. We found that drugs currently in clinical trials for cancer treatment that target the same pathways also reduced lipid accumulation in PNPLA3 variant cells.

Human-induced pluripotent stem cell-derived hepatocyte platform in modeling of SARS-CoV-2 infection.

Currently, SARS-CoV-2 is still spreading rapidly and globally. A large proportion of patients with COVID-19 developed liver injuries. The human-induced pluripotent stem cell (iPSC)-derived hepatocytes recapitulate primary human hepatocytes and have been widely used in studies of liver diseases. To explore the susceptibility of hepatocytes to SARS-CoV-2, we differentiated iPSCs to functional hepatocytes and tried infecting them with different MOI (1, 0.1, 0.01) of SARS-CoV-2. The iPSC-derived hepatocytes are highly susceptible to virus infection, even at 0.01 MOI. Other than the ancestral strain, iHeps also support the replication of SARS-CoV-2 variants including alpha, beta, theta, and delta. More interestingly, the ACE2 expression significantly upregulated after infection, suggesting a vicious cycle between virus infection and liver injury. The iPSC-derived hepatocytes can support the replication of SARS-CoV-2, and this platform could be used to investigate the SARS-CoV-2 hepatotropism and hepatic pathogenic mechanisms.

Hepatotoxicity of silver nanoparticles: Benchmark concentration modeling of an in vitro transcriptomics study in human iPSC-derived hepatocytes

Despite two decades of research on silver nanoparticle (AgNP) toxicity, a safe threshold for exposure has not yet been established, albeit being critically needed for risk assessment and regulatory decision-making. Traditionally, a point-of-departure (PoD) value is derived from dose response of apical endpoints in animal studies using either the no-observed-adverse-effect level (NOAEL) approach, or benchmark dose (BMD) modeling. To develop new approach methodologies (NAMs) to inform human risk assessment of AgNPs, we conducted a concentration response modeling of the transcriptomic changes in hepatocytes derived from human induced pluripotent stem cells (iPSCs) after being exposed to a wide range concentration (0.01–25 μg/ml) of AgNPs for 24 h. A plausible transcriptomic PoD of 0.21 μg/ml was derived for a pathway related to the mode-of-action (MOA) of AgNPs, and a more conservative PoD of 0.10 μg/ml for a gene ontology (GO) term not apparently associated with the MOA of AgNPs. A reference dose (RfD) could be calculated from either of the PoDs as a safe threshold for AgNP exposure. The current study illustrates the usefulness of in vitro transcriptomic concentration response study using human cells as a NAM for toxicity study of chemicals that lack adequate toxicity data to inform human risk assessment.

Formation of functional, extended bile canaliculi, and increased bile acid production in sandwich-cultured human cryopreserved hepatocytes using commercially available culture medium

Drug-induced cholestasis results in drug discontinuation and market withdrawal, and the prediction of cholestasis risk is critical in the early stages of drug development. Animal tests and membrane vesicle assay are currently being conducted to assess the risk of cholestasis in the preclinical stage. However, these methods have drawbacks, such as species differences with humans and difficulties in evaluating the effects of drug metabolism and other transporters, implying the need for a cholestasis risk assessment system using human hepatocytes. However, human hepatocytes hardly form functional, extended bile canaliculi, a requirement for cholestasis risk assessment. We previously established a culture protocol for functional, extended bile canaliculi formation in human iPSC-derived hepatocytes. In this study, we modified this culture protocol to support the formation of functional, extended bile canaliculi in human cryopreserved hepatocytes (cryoheps). The production of bile acids, which induces bile canaliculi extension, increased time-dependently during bile canaliculi formation using this protocol, suggesting that increased bile acid production may be involved in the extended bile canaliculi formation. We have also shown that our culture protocol can be applied to cryoheps from multiple donors and that bile canaliculi can be formed stably among different culture batches. Furthermore, this protocol enables long-term maintenance of bile canaliculi and scaling down to culture in 96-well plates. We expect our culture protocol to be a breakthrough for in vitro cholestasis risk assessment.

Oxidative DNA damage contributes to usnic acid-induced toxicity in human induced pluripotent stem cell-derived hepatocytes.

Dietary supplements containing usnic acid have been increasingly marketed for weight loss over the past decades, even though incidences of severe hepatotoxicity and acute liver failure due to their overuse have been reported. To date, the toxic mechanism of usnic acid-induced liver injury at the molecular level still remains to be fully elucidated. Here, we conducted a transcriptomic study on usnic acid using a novel in vitro hepatotoxicity model employing human induced pluripotent stem cell (iPSC)-derived hepatocytes. Treatment with 20 μM usnic acid for 24 h caused 4272 differentially expressed genes (DEGs) in the cells. Ingenuity Pathway Analysis (IPA) based on the DEGs and gene set enrichment analysis (GSEA) using the whole transcriptome expression data concordantly revealed several signaling pathways and biological processes that, when taken together, suggest that usnic acid caused oxidative stress and DNA damage in the cells, which further led to cell cycle arrest and eventually resulted in cell death through apoptosis. These transcriptomic findings were subsequently corroborated by a variety of cellular assays, including reactive oxygen species (ROS) generation and glutathione (GSH) depletion, DNA damage (pH2AX detection and 8-hydroxy-2'-deoxyguanosine [8-OH-dg] assay), cell cycle analysis, and caspase 3/7 activity. Collectively, the results of the current study accord with previous in vivo and in vitro findings, provide further evidence that oxidative stress-caused DNA damage contributes to usnic acid-induced hepatotoxicity, shed new light on molecular mechanisms of usnic acid-induced hepatotoxicity, and demonstrate the usefulness of iPSC-derived hepatocytes as an in vitro model for hepatotoxicity testing and prediction.

A patient-based iPSC-derived hepatocyte model of alcohol-associated cirrhosis reveals bioenergetic insights into disease pathogenesis.

Only ~20% of heavy drinkers develop alcohol cirrhosis (AC). While differences in metabolism, inflammation, signaling, microbiome signatures and genetic variations have been tied to the pathogenesis of AC, the key underlying mechanisms for this interindividual variability, remain to be fully elucidated. Induced pluripotent stem cell-derived hepatocytes (iHLCs) from patients with AC and healthy controls differ transcriptomically, bioenergetically and histologically. They include a greater number of lipid droplets (LDs) and LD-associated mitochondria compared to control cells. These pre-pathologic indicators are effectively reversed by Aramchol, an inhibitor of stearoyl-CoA desaturase. Bioenergetically, AC iHLCs have lower spare capacity, slower ATP production and their mitochondrial fuel flexibility towards fatty acids and glutamate is weakened. MARC1 and PNPLA3, genes implicated by GWAS in alcohol cirrhosis, show to correlate with lipid droplet-associated and mitochondria-mediated oxidative damage in AC iHLCs. Knockdown of PNPLA3 expression exacerbates mitochondrial deficits and leads to lipid droplets alterations. These findings suggest that differences in mitochondrial bioenergetics and lipid droplet formation are intrinsic to AC hepatocytes and can play a role in its pathogenesis.

IPSC-derived hepatocytes as a novel tool for Ornithine Transcarbamylase Deficiency (OTCD) modelling and drug screening

iPSC-derived hepatocytes as a novel tool for Ornithine Transcarbamylase Deficiency (OTCD) modelling and drug screening

Reproducibility and Robustness of a Liver Microphysiological System PhysioMimix LC12 under Varying Culture Conditions and Cell Type Combinations.

The liver is one of the key organs for exogenous and endogenous metabolism and is often a target for drug- and chemical-driven toxicity. A wide range of experimental approaches has been established to model and characterize the mechanisms of drug- and chemical-induced hepatotoxicity. A number of microfluidics-enabled in vitro models of the liver have been developed, but the unclear translatability of these platforms has hindered their adoption by the pharmaceutical industry; to achieve wide use for drug and chemical safety evaluation, demonstration of reproducibility and robustness under various contexts of use is required. One of these commercially available platforms is the PhysioMimix LC12, a microfluidic device where cells are seeded into a 3D scaffold that is continuously perfused with recirculating cell culture media to mimic liver sinusoids. Previous studies demonstrated this model's functionality and potential applicability to preclinical drug development. However, to gain confidence in PhysioMimix LC12's robustness and reproducibility, supplementary characterization steps are needed, including the assessment of various human hepatocyte sources, contribution of non-parenchymal cells (NPCs), and comparison to other models. In this study, we performed replicate studies averaging 14 days with either primary human hepatocytes (PHHs) or induced pluripotent stem cell (iPSC)-derived hepatocytes, with and without NPCs. Albumin and urea secretion, lactate dehydrogenase, CYP3A4 activity, and metabolism were evaluated to assess basal function and metabolic capacity. Model performance was characterized by different cell combinations under intra- and inter-experimental replication and compared to multi-well plates and other liver platforms. PhysioMimix LC12 demonstrated the highest metabolic function with PHHs, with or without THP-1 or Kupffer cells, for up to 10-14 days. iPSC-derived hepatocytes and PHHs co-cultured with additional NPCs demonstrated sub-optimal performance. Power analyses based on replicate experiments and different contexts of use will inform future study designs due to the limited throughput and high cell demand. Overall, this study describes a workflow for independent testing of a complex microphysiological system for specific contexts of use, which may increase end-user adoption in drug development.

Activation of cAMP (EPAC2) signaling pathway promotes hepatocyte attachment

Primary Human Hepatocyte (PHH) remains undefeated as the gold standard in hepatic studies. Despite its valuable properties, partial attachment loss due to the extraction process and cryopreservation remained the main hurdle in its application. We hypothesized that we could overcome the loss of PHH cell attachment through thawing protocol adjustment and medium composition. We reported a novel use of a medium designed for iPSC-derived hepatocytes, increasing PHH attachment on the collagen matrix. Delving further into the medium composition, we discovered that removing BSA and exposure to cAMP activators such as IBMX and Forskolin benefit PHH attachment. We found that activating EPAC2, the cAMP downstream effector, by S-220 significantly increased PHH attachment. We also found that EPAC2 activation induced bile canaliculi formation in iPS-derived hepatocytes. Combining these factors in studies involving PHH or iPS-hepatocyte culture provides promising means to improve cell attachment and maintenance of hepatic function.

Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages

Hepatic insulin resistance is recognized as a driver of type 2 diabetes and fatty liver disease but specific therapies are lacking. Here we explore the potential of human induced pluripotent stem cells (iPSCs) for modeling hepatic insulin resistance in vitro, with a focus on resolving the controversy about the impact of inflammation in the absence of steatosis. For this, we establish the complex insulin signaling cascade and the multiple inter-dependent functions constituting hepatic glucose metabolism in iPSC-derived hepatocytes (iPSC-Heps). Co-culture of these insulin-sensitive iPSC-Heps with isogenic iPSC-derived pro-inflammatory macrophages induces glucose output by preventing insulin from inhibiting gluconeogenesis and glycogenolysis and activating glycolysis. Screening identifies TNFα and IL1β as the mediators of insulin resistance in iPSC-Heps. Neutralizing these cytokines together restores insulin sensitivity in iPSC-Heps more effectively than individual inhibition, reflecting specific effects on insulin signaling and glucose metabolism mediated by NF-κB or JNK. These results show that inflammation is sufficient to induce hepatic insulin resistance and establish a human iPSC-based in vitro model to mechanistically dissect and therapeutically target this metabolic disease driver.

1588-P: Translatable Modeling of Glucagon Actions in Human iPSC-Derived Hepatocytes Uniquely Predicts Differential Clinical Responses to Glucagon Analog Agonist Molecules

As the development of clinically efficacious glucagon receptor (GCGR) agonists for the treatment of metabolic diseases evolves, the challenge to identify physiologically relevant preclinical models that predict glucagon receptor actions in humans becomes ever more important. While many hepatocyte models are available, most fail to recapitulate fundamental metabolic regulatory responses to key physiologic stimuli including integration of glucagon and insulin actions that govern hepatic carbohydrate or lipid metabolism. We developed and optimized a human induced pluripotent stem cell (iPSC)-derived hepatocyte model to mimic physiologic insulin and glucagon signaling and counter-regulation of metabolic pathways. We leveraged the model to evaluate functional responses of different glucagon receptor agonist molecules to regulate carbohydrate and lipid metabolism. Unlike assays conducted in several other cell line and primary isolated hepatocyte systems, hepatic glucose output assays in the human IPSC hepatocyte model demonstrated substantial potency differences between two novel soluble glucagon analog agonists. These findings predicted differential dose-dependent blood glucose excursions in response to these agonists when administered in a single ascending dose study in healthy human volunteers. Modeling physiologic integration of insulin and glucagon signaling in a clinically translatable human iPSC hepatocyte model can advance understanding of the regulation of nutrient metabolism by glucagon receptor agonists in humans and support the development of novel therapeutic approaches to address metabolic disorders, including type 2 diabetes, obesity, and nonalcoholic fatty liver disease. Disclosure W.Roell: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. A.Regmi: Employee; Eli Lilly and Company. C.T.Benson: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. T.Coskun: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. J.S.Moyers: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. J.Alsina-fernandez: Employee; Eli Lilly and Company. M.K.Thomas: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company.

Label-Free Evaluation of Maturation and Hepatotoxicity of Human iPSC-Derived Hepatocytes Using Hyperspectral Raman Imaging.

To promote the clinical application of human induced pluripotent stem cell (hiPSC)-derived hepatocytes, a method capable of monitoring regenerative processes and assessing differentiation efficiency without harming or modifying these cells is important. Raman microscopy provides a powerful tool for this as it enables label-free identification of intracellular biomolecules in live samples. Here, we used label-free Raman microscopy to assess hiPSC differentiation into hepatocyte lineage based on the intracellular chemical content. We contrasted these data with similar phenotypes from the HepaRG and from commercially available hiPSC-derived hepatocytes (iCell hepatocytes). We detected hepatic cytochromes, lipids, and glycogen in hiPSC-derived hepatocyte-like cells (HLCs) but not biliary-like cells (BLCs), indicating intrinsic differences in biomolecular content between these phenotypes. The data show significant glycogen and lipid accumulation as early as the definitive endoderm transition. Additionally, we explored the use of Raman imaging as a hepatotoxicity assay for the HepaRG and iCell hepatocytes, with data displaying a dose-dependent reduction of glycogen accumulation in response to acetaminophen. These findings show that the nondestructive and high-content nature of Raman imaging provides a promising tool for both quality control of hiPSC-derived hepatocytes and hepatotoxicity screening.

A human iPSC-derived hepatocyte screen identifies compounds that inhibit production of Apolipoprotein B

Familial hypercholesterolemia (FH) patients suffer from excessively high levels of Low Density Lipoprotein Cholesterol (LDL-C), which can cause severe cardiovascular disease. Statins, bile acid sequestrants, PCSK9 inhibitors, and cholesterol absorption inhibitors are all inefficient at treating FH patients with homozygous LDLR gene mutations (hoFH). Drugs approved for hoFH treatment control lipoprotein production by regulating steady-state Apolipoprotein B (apoB) levels. Unfortunately, these drugs have side effects including accumulation of liver triglycerides, hepatic steatosis, and elevated liver enzyme levels. To identify safer compounds, we used an iPSC-derived hepatocyte platform to screen a structurally representative set of 10,000 small molecules from a proprietary library of 130,000 compounds. The screen revealed molecules that could reduce the secretion of apoB from cultured hepatocytes and from humanized livers in mice. These small molecules are highly effective, do not cause abnormal lipid accumulation, and share a chemical structure that is distinct from any known cholesterol lowering drug.

A tiered testing strategy based on in vitro phenotypic and transcriptomic data for selecting representative petroleum UVCBs for toxicity evaluation in vivo.

Hazard evaluation of substances of "unknown or variable composition, complex reaction products and biological materials" (UVCBs) remains a major challenge in regulatory science because their chemical composition is difficult to ascertain. Petroleum substances are representative UVCBs and human cell-based data have been previously used to substantiate their groupings for regulatory submissions. We hypothesized that a combination of phenotypic and transcriptomic data could be integrated to make decisions as to selection of group-representative worst-case petroleum UVCBs for subsequent toxicity evaluation in vivo. We used data obtained from 141 substances from 16 manufacturing categories previously tested in 6 human cell types (induced pluripotent stem cell [iPSC]-derived hepatocytes, cardiomyocytes, neurons, and endothelial cells, and MCF7 and A375 cell lines). Benchmark doses for gene-substance combinations were calculated, and both transcriptomic and phenotype-derived points of departure (PODs) were obtained. Correlation analysis and machine learning were used to assess associations between phenotypic and transcriptional PODs and to determine the most informative cell types and assays, thus representing a cost-effective integrated testing strategy. We found that 2 cell types-iPSC-derived-hepatocytes and -cardiomyocytes-contributed the most informative and protective PODs and may be used to inform selection of representative petroleum UVCBs for further toxicity evaluation in vivo. Overall, although the use of new approach methodologies to prioritize UVCBs has not been widely adopted, our study proposes a tiered testing strategy based on iPSC-derived hepatocytes and cardiomyocytes to inform selection of representative worst-case petroleum UVCBs from each manufacturing category for further toxicity evaluation in vivo.