Generation of expandable human pluripotent stem cell-derived hepatocyte-like liver organoids

Polystyrene microplastics induce hepatotoxicity and disrupt lipid metabolism in the liver organoids

Microplastic particles (MP) has been detected in the environment widespread. Human beings are inevitably exposed to MP via multiple routines. However, the hazard identifications, as direct evidence of exposure and health risk, have not been fully characterized in human beings. Many studies suggest the liver is a potential target organ, but currently no study regarding the MP on human liver has been reported. In this study, we used a novel in vitro 3D model, the liver organoids (LOs) generated from human pluripotent stem cells, as an alternative model to the human liver, to explore the adverse biological effect of 1 μm polystyrene-MP (PS-MP) microbeads applying a non-static exposure approach. When the LOs were exposed to 0.25, 2.5 and 25 μg/mL PS-MP (the lowest one was relevant to the environmental concentrations, calculated to be 102 ± 7 items/mL). The potential mechanisms of PS-MP induced hepatotoxicity and lipotoxicity, in aspects of cytotoxicity, levels of key molecular markers, ATP production, alteration in lipid metabolism, ROS generation, oxidative stress and inflammation response, were determined. Specifically, it has been firstly observed that PS-MP could increase the expression of hepatic HNF4A and CYP2E1. Based on these findings, the potential adverse outcome pathways (AOPs) relevant to PS-MP were proposed, and the potential risks of PS-MP on liver steatosis, fibrosis and cancer were implicated. The combined application of novel LOs model and AOPs framework provides a new insight into the risk assessment of MP. Further studies are anticipated to validate the hepatotoxic molecular mechanism of PS-MP based on HNF4A or CYP2E1, and to investigate the MP-induced physical damage and its relationship to hepatic adverse effect for human beings. CAPSULE: Microplastics cause hepatotoxicity and disrupt lipid metabolism in the human pluripotent stem cells-derived liver organoids, providing evidence for human implication.

Induced Pluripotent Stem Cells for the Treatment of Liver Diseases: Novel Concepts

Millions of people worldwide with incurable liver disease die because of inadequate treatment options and limited availability of donor organs for liver transplantation. Regenerative medicine as an innovative approach to repairing and replacing cells, tissues, and organs is undergoing a major revolution due to the unprecedented need for organs for patients around the world. Induced pluripotent stem cells (iPSCs) have been widely studied in the field of liver regeneration and are considered to be the most promising candidate therapies. This review will conclude the current state of efforts to derive human iPSCs for potential use in the modeling and treatment of liver disease.

Organoids as research models for hepatocellular carcinoma

Organoid culture is an emerging research tool that has proved tremendously useful in a multitude of aspects, one of which is cancer research. They largely overcome the limitations of previous cancer models by their faithful recapitulation of the in vivo biology, while still remaining amenable to perturbations. Using a cocktail of biologicals that mimic the stem cell niche signaling, hepatocellular carcinoma (HCC) organoids could be generated from tissue samples of both human and murine origin. Existing reports show that HCC organoids retain key characteristics of their parental tumor tissue, including the histological architecture, genomic landscape, expression profile and intra-tumor heterogeneity. There is ongoing effort to establish living biobanks of patient-derived cancer organoids, annotated with multi-omics data and clinical data, and they can be particularly valuable in stratification of HCC subtypes, pre-clinical drug discovery and personalized medicine. In the future, efforts in the standardization of procedures and nomenclature, refinement of protocols, as well as engineering of the culture systems will enable scientists to unleash the full potential of organoid technology.

Induction and Maturation of Hepatocyte-Like Cells In Vitro: Focus on Technological Advances and Challenges

Limited by the poor proliferation and restricted sources of adult hepatocytes, there is an urgent need to find substitutes for proliferation and cultivation of mature hepatocytes in vitro for use in disease treatment, drug approval, and toxicity testing. Hepatocyte-like cells (HLCs), which originate from undifferentiated stem cells or modified adult cells, are considered good candidates because of their advantages in terms of cell source and in vitro expansion ability. However, the majority of induced HLCs are in an immature state, and their degree of differentiation is heterogeneous, diminishing their usability in basic research and limiting their clinical application. Therefore, various methods have been developed to promote the maturation of HLCs, including chemical approaches, alteration of cell culture systems, and genetic manipulation, to meet the needs of in vivo transplantation and in vitro model establishment. This review proposes different cell types for the induction of HLCs, and provide a comprehensive overview of various techniques to promote the generation and maturation of HLCs in vitro.

Generation of human induced pluripotent stem cell line, KRIBBi003-A, from urinary cells of a patient with glycogen storage disease type IXa

Glycogen storage disease type IXa (GSD IXa) is a rare genetic disorder characterized by phosphorylase kinase (PhK) deficiency, which leads to excessive glycogen accumulation in the liver. Urinary cells (UCs) were isolated from a GSD IXa patient and reprogrammed into induced pluripotent stem cells (iPSCs) using Sendai virus. The established iPSC line, KRIBBi003-A, exhibited pluripotency marker expression and a normal karyotype. The differentiation capacity of the cell line was confirmed by the differentiation of the three germ layers in vitro. The established iPSC line is a potential useful resource for disease modeling of GSD IXa.

Advanced preclinical models for evaluation of drug-induced liver injury - consensus statement by the European Drug-Induced Liver Injury Network [PRO-EURO-DILI-NET]

Drug-induced liver injury (DILI) is a major cause of acute liver failure (ALF) and one of the leading indications for liver transplantation in Western societies. Given the wide use of both prescribed and over the counter drugs, DILI has become a major health issue for which there is a pressing need to find novel and effective therapies. Although significant progress has been made in understanding the molecular mechanisms underlying DILI, our incomplete knowledge of its pathogenesis and inability to predict DILI is largely due to both discordance between human and animal DILI in preclinical drug development and a lack of models that faithfully recapitulate complex pathophysiological features of human DILI. This is exemplified by the hepatotoxicity of acetaminophen (APAP) overdose, a major cause of ALF because of its extensive worldwide use as an analgesic. Despite intensive efforts utilising current animal and in vitro models, the mechanisms involved in the hepatotoxicity of APAP are still not fully understood. In this expert Consensus Statement, which is endorsed by the European Drug-Induced Liver Injury Network, we aim to facilitate and outline clinically impactful discoveries by detailing the requirements for more realistic human-based systems to assess hepatotoxicity and guide future drug safety testing. We present novel insights and discuss major players in APAP pathophysiology, and describe emerging in vitro and in vivo pre-clinical models, as well as advanced imaging and in silico technologies, which may improve prediction of clinical outcomes of DILI.

Human Pluripotent Stem Cell-Derived Hepatocyte-Like Cells and Organoids for Liver Disease and Therapy

Liver disease is a global health issue that has caused an economic burden worldwide. Organ transplantation is the only effective therapy for end-stage liver disease; however, it has been hampered by a shortage of donors. Human pluripotent stem cells (hPSCs) have been widely used for studying liver biology and pathology as well as facilitating the development of alternative therapies. hPSCs can differentiate into multiple types of cells, which enables the generation of various models that can be applied to investigate and recapitulate a range of biological activities in vitro. Here, we summarize the recent development of hPSC-derived hepatocytes and their applications in disease modeling, cell therapy, and drug discovery. We also discuss the advantages and limitations of these applications and critical challenges for further development.

Organoid Models for Cancer Research-From Bed to Bench Side and Back

Organoids are a new 3D ex vivo culture system that have been applied in various fields of biomedical research. First isolated from the murine small intestine, they have since been established from a wide range of organs and tissues, both in healthy and diseased states. Organoids genetically, functionally and phenotypically retain the characteristics of their tissue of origin even after multiple passages, making them a valuable tool in studying various physiologic and pathophysiologic processes. The finding that organoids can also be established from tumor tissue or can be engineered to recapitulate tumor tissue has dramatically increased their use in cancer research. In this review, we discuss the potential of organoids to close the gap between preclinical in vitro and in vivo models as well as clinical trials in cancer research focusing on drug investigation and development.

Cell-Based Regeneration and Treatment of Liver Diseases

The liver, in combination with a functional biliary system, is responsible for maintaining a great number of vital body functions. However, acute and chronic liver diseases may lead to irreversible liver damage and, ultimately, liver failure. At the moment, the best curative option for patients suffering from end-stage liver disease is liver transplantation. However, the number of donor livers required by far surpasses the supply, leading to a significant organ shortage. Cellular therapies play an increasing role in the restoration of organ function and can be integrated into organ transplantation protocols. Different types and sources of stem cells are considered for this purpose, but highly specific immune cells are also the focus of attention when developing individualized therapies. In-depth knowledge of the underlying mechanisms governing cell differentiation and engraftment is crucial for clinical implementation. Additionally, novel technologies such as ex vivo machine perfusion and recent developments in tissue engineering may hold promising potential for the implementation of cell-based therapies to restore proper organ function.

Organoid Technology: A Reliable Developmental Biology Tool for Organ-Specific Nanotoxicity Evaluation

Engineered nanomaterials are bestowed with certain inherent physicochemical properties unlike their parent materials, rendering them suitable for the multifaceted needs of state-of-the-art biomedical, and pharmaceutical applications. The log-phase development of nano-science along with improved "bench to beside" conversion carries an enhanced probability of human exposure with numerous nanoparticles. Thus, toxicity assessment of these novel nanoscale materials holds a key to ensuring the safety aspects or else the global biome will certainly face a debacle. The toxicity may span from health hazards due to direct exposure to indirect means through food chain contamination or environmental pollution, even causing genotoxicity. Multiple ways of nanotoxicity evaluation include several in vitro and in vivo methods, with in vitro methods occupying the bulk of the "experimental space." The underlying reason may be multiple, but ethical constraints in in vivo animal experiments are a significant one. Two-dimensional (2D) monoculture is undoubtedly the most exploited in vitro method providing advantages in terms of cost-effectiveness, high throughput, and reproducibility. However, it often fails to mimic a tissue or organ which possesses a defined three-dimensional structure (3D) along with intercellular communication machinery. Instead, microtissues such as spheroids or organoids having a precise 3D architecture and proximate in vivo tissue-like behavior can provide a more realistic evaluation than 2D monocultures. Recent developments in microfluidics and bioreactor-based organoid synthesis have eased the difficulties to prosper nano-toxicological analysis in organoid models surpassing the obstacle of ethical issues. The present review will enlighten applications of organoids in nanotoxicological evaluation, their advantages, and prospects toward securing commonplace nano-interventions.

Drug-Induced Liver Injury: Highlights and Controversies in the Recent Literature

Drug-induced liver injury (DILI) remains an important, yet challenging diagnosis for physicians. Each year, additional drugs are implicated in DILI and this year was no different, with more than 1400 articles published on the subject. This review examines some of the most significant highlights and controversies in DILI-related research over the past year and their implications for clinical practice. Several new drugs were approved by the US Food and Drug Administration including a number of drugs implicated in causing DILI, particularly among the chemotherapeutic classes. The COVID-19 pandemic was also a major focus of attention in 2020 and we discuss some of the notable aspects of COVID-19-related liver injury and its implications for diagnosing DILI. Updates in diagnostic and causality assessments related to DILI such as the Roussel Uclaf Causality Assessment Method are included, mindful that there is still no single biomarker or diagnostic tool to unequivocally diagnose DILI. Glutamate dehydrogenase received renewed attention as being more specific than alanine aminotransferase. There were a few new reports of previously unrecognized hepatotoxins, including immune modulators and novel gene therapy drugs that we highlight. Updates and new developments of previously described hepatotoxins, such as immune checkpoint inhibitors and anti-tuberculosis drugs are reviewed. Finally, novel technologies such as organoid culture systems to better predict DILI preclinically may be coming of age and determinants of hepatocyte loss, such as calculating P_ALT are poised to improve our current means of estimating DILI severity and the risk of acute liver failure.

Generating Self-Assembling Human Heart Organoids Derived from Pluripotent Stem Cells

The ability to study human cardiac development in health and disease is highly limited by the capacity to model the complexity of the human heart in vitro. Developing more efficient organ-like platforms that can model complex in vivo phenotypes, such as organoids and organs-on-a-chip, will enhance the ability to study human heart development and disease. This paper describes a protocol to generate highly complex human heart organoids (hHOs) by self-organization using human pluripotent stem cells and stepwise developmental pathway activation using small molecule inhibitors. Embryoid bodies (EBs) are generated in a 96-well plate with round-bottom, ultra-low attachment wells, facilitating suspension culture of individualized constructs. The EBs undergo differentiation into hHOs by a three-step Wnt signaling modulation strategy, which involves an initial Wnt pathway activation to induce cardiac mesoderm fate, a second step of Wnt inhibition to create definitive cardiac lineages, and a third Wnt activation step to induce proepicardial organ tissues. These steps, carried out in a 96-well format, are highly efficient, reproducible, and produce large amounts of organoids per run. Analysis by immunofluorescence imaging from day 3 to day 11 of differentiation reveals first and second heart field specifications and highly complex tissues inside hHOs at day 15, including myocardial tissue with regions of atrial and ventricular cardiomyocytes, as well as internal chambers lined with endocardial tissue. The organoids also exhibit an intricate vascular network throughout the structure and an external lining of epicardial tissue. From a functional standpoint, hHOs beat robustly and present normal calcium activity as determined by Fluo-4 live imaging. Overall, this protocol constitutes a solid platform for in vitro studies in human organ-like cardiac tissues.

Organoid engineering with microfluidics and biomaterials for liver, lung disease, and cancer modeling

As life expectancy improves and the number of people suffering from various diseases increases, the need for developing effective personalized disease models is rapidly rising. The development of organoid technology has led to better recapitulation of the in vivo environment of organs, and can overcome the constraints of existing disease models. However, for more precise disease modeling, engineering approaches such as microfluidics and biomaterials, that aid in mimicking human physiology, need to be integrated with the organoid models. In this review, we introduce key elements for disease modeling and recent engineering advances using both liver and lung organoids. Due to the importance of personalized medicine, we also emphasize patient-derived cancer organoid models and their engineering approaches. These organoid-based disease models combined with microfluidics, biomaterials, and co-culture systems will provide a powerful research platform for understanding disease mechanisms and developing precision medicine; enabling preclinical drug screening and drug development. STATEMENT OF SIGNIFICANCE: The development of organoid technology has led to better recapitulation of the in vivo environment of organs, and can overcome the constraints of existing disease models. However, for more precise disease modeling, engineering approaches such as microfluidics and biomaterials, that aid in mimicking human physiology, need to be integrated with the organoid models. In this review, we introduce liver, lung, and cancer organoids integrated with various engineering approaches as a novel platform for personalized disease modeling. These engineered organoid-based disease models will provide a powerful research platform for understanding disease mechanisms and developing precision medicine.

An Individual Patient's "Body" on Chips-How Organismoid Theory Can Translate Into Your Personal Precision Therapy Approach

The first concepts for reproducing human systemic organismal biology in vitro were developed over 12 years ago. Such concepts, then called human- or body-on-a-chip, claimed that microphysiological systems would become the relevant technology platform emulating the physiology and morphology of human organisms at the smallest biologically acceptable scale in vitro and, therefore, would enable the selection of personalized therapies for any patient at unprecedented precision. Meanwhile, the first human organoids-stem cell-derived complex three-dimensional organ models that expand and self-organize in vitro-have proven that in vitro self-assembly of minute premature human organ-like structures is feasible, once the respective stimuli of ontogenesis are provided to human stem cells. Such premature organoids can precisely reflect a number of distinct physiological and pathophysiological features of their respective counterparts in the human body. We now develop the human-on-a-chip concepts of the past into an organismoid theory. We describe the current concept and principles to create a series of organismoids-minute, mindless and emotion-free physiological in vitro equivalents of an individual's mature human body-by an artificially short process of morphogenetic self-assembly mimicking an individual's ontogenesis from egg cell to sexually mature organism. Subsequently, we provide the concept and principles to maintain such an individual's set of organismoids at a self-sustained functional healthy homeostasis over very long time frames in vitro. Principles how to perturb a subset of healthy organismoids by means of the natural or artificial induction of diseases are enrolled to emulate an individual's disease process. Finally, we discuss using such series of healthy and perturbed organismoids in predictively selecting, scheduling and dosing an individual patient's personalized therapy or medicine precisely. The potential impact of the organismoid theory on our healthcare system generally and the rapid adoption of disruptive personalized T-cell therapies particularly is highlighted.

Heart Organoids and Engineered Heart Tissues: Novel Tools for Modeling Human Cardiac Biology and Disease

Organoids are three-dimensional in vitro cell constructs that recapitulate organ properties and structure to a significant extent. They constitute particularly useful models to study unapproachable states in humans, such as embryonic and fetal development, or early disease progression in adults. In recent years organoids have been implemented to model a wide range of different organs and disease conditions. However, the technology for their fabrication and application to cardiovascular studies has been lagging significantly when compared to other organoid types (e.g., brain, pancreas, kidney, intestine). This is a surprising fact since cardiovascular disease (CVD) and congenital heart disease (CHD) constitute the leading cause of mortality and morbidity in the developed world, and the most common birth defect in humans, respectively, and collectively constitute one of the largest unmet medical needs in the modern world. There is a critical need to establish in vitro models of the human heart that faithfully recapitulate its biology and function, thus enabling basic and translational studies to develop new therapeutics. Generating heart organoids that truly resemble the heart has proven difficult due to its complexity, but significant progress has been made recently to overcome this obstacle. In this review, we will discuss progress in novel heart organoid generation methods, the advantages and disadvantages of each approach, and their translational applications for advancing cardiovascular studies and the treatment of heart disorders.

Hepatitis B virus infection modeling using multi-cellular organoids derived from human induced pluripotent stem cells

Chronic infection with hepatitis B virus (HBV) remains a global health concern despite the availability of vaccines. To date, the development of effective treatments has been severely hampered by the lack of reliable, reproducible, and scalable in vitro modeling systems that precisely recapitulate the virus life cycle and represent virus-host interactions. With the progressive understanding of liver organogenesis mechanisms, the development of human induced pluripotent stem cell (iPSC)-derived hepatic sources and stromal cellular compositions provides novel strategies for personalized modeling and treatment of liver disease. Further, advancements in three-dimensional culture of self-organized liver-like organoids considerably promote in vitro modeling of intact human liver tissue, in terms of both hepatic function and other physiological characteristics. Combined with our experiences in the investigation of HBV infections using liver organoids, we have summarized the advances in modeling reported thus far and discussed the limitations and ongoing challenges in the application of liver organoids, particularly those with multi-cellular components derived from human iPSCs. This review provides general guidelines for establishing clinical-grade iPSC-derived multi-cellular organoids in modeling personalized hepatitis virus infection and other liver diseases, as well as drug testing and transplantation therapy.

Bioengineered Liver Models for Investigating Disease Pathogenesis and Regenerative Medicine

Owing to species-specific differences in liver pathways, in vitro human liver models are utilized for elucidating mechanisms underlying disease pathogenesis, drug development, and regenerative medicine. To mitigate limitations with de-differentiated cultures, bioengineers have developed advanced techniques/platforms, including micropatterned cocultures, spheroids/organoids, bioprinting, and microfluidic devices, for perfusing cell cultures and liver slices. Such techniques improve mature functions and culture lifetime of primary and stem-cell human liver cells. Furthermore, bioengineered liver models display several features of liver diseases including infections with pathogens (e.g., malaria, hepatitis C/B viruses, Zika, dengue, yellow fever), alcoholic/nonalcoholic fatty liver disease, and cancer. Here, we discuss features of bioengineered human liver models, their uses for modeling aforementioned diseases, and how such models are being augmented/adapted for fabricating implantable human liver tissues for clinical therapy. Ultimately, continued advances in bioengineered human liver models have the potential to aid the development of novel, safe, and efficacious therapies for liver disease.

Development of a quantitative prediction algorithm for target organ-specific similarity of human pluripotent stem cell-derived organoids and cells

Human pluripotent stem cell (hPSC)-derived organoids and cells have similar characteristics to human organs and tissues. Thus, in vitro human organoids and cells serve as a superior alternative to conventional cell lines and animal models in drug development and regenerative medicine. For a simple and reproducible analysis of the quality of organoids and cells to compensate for the shortcomings of existing experimental validation studies, a quantitative evaluation method should be developed. Here, using the GTEx database, we construct a quantitative calculation system to assess similarity to the human organs. To evaluate our system, we generate hPSC-derived organoids and cells, and detected organ similarity. To facilitate the access of our system by researchers, we develop a web-based user interface presenting similarity to the appropriate organs as percentages. Thus, this program could provide valuable information for the generation of high-quality organoids and cells and a strategy to guide proper lineage-oriented differentiation.

Quantitative methods to assess the quality of hPSC-derived organoids have not been developed. Here they present a prediction algorithm to assess the transcriptomic similarity between hPSC-derived organoids and the corresponding human target organs and perform validation on lung bud organoids, antral gastric organoids, and cardiomyocytes.

Engineering the Vasculature of Stem-Cell-Derived Liver Organoids

The vasculature of stem-cell-derived liver organoids can be engineered using methods that recapitulate embryonic liver development. Hepatic organoids with a vascular network offer great application prospects for drug screening, disease modeling, and therapeutics. However, the application of stem cell-derived organoids is hindered by insufficient vascularization and maturation. Here, we review different theories about the origin of hepatic cells and the morphogenesis of hepatic vessels to provide potential approaches for organoid generation. We also review the main protocols for generating vascularized liver organoids from stem cells and consider their potential and limitations in the generation of vascularized liver organoids.

Developing liver organoids from induced pluripotent stem cells (iPSCs): An alternative source of organoid generation for liver cancer research

Primary liver cancer (PLC) represents a significant proportion of all human cancers and constitutes a substantial health and economic burden to society. Traditional therapeutic approaches such as surgical resection and chemotherapy often fail due to tumour relapse or innate tumour chemoresistance. There is a dearth of efficient treatments for PLC in part due to the poor capacity of current laboratory models to reflect critical features of the native tumour in vivo. The increasing incorporation of organoid systems has led to a resurgence of interest in liver cancer research. Organoid systems show promise as the gold standard for recapitulating tumours in vitro. Further, developments in culturing techniques will improve the various shortcomings of the current systems. Induced pluripotent stem cell (iPSC)-derived liver organoids are a promising alternative to the conventional liver organoid model as it circumvents the need to rely on primary resections which are often scarce. In this concise review, we will discuss novel techniques for organoid culture with a focus on organoid co-cultures and their advantages over traditional organoid systems. A detailed technical protocol for the generation of iPSC-derived liver organoids is provided as an appendix.

Liver Organoids: Formation Strategies and Biomedical Applications

The liver is the most important digestive organ in the body. Several studies have explored liver biology and diseases related to the liver. However, most of these studies have only explored liver development, mechanism of liver regeneration and pathophysiology of liver diseases mainly based on two-dimensional (2D) cell lines and animal models. Traditional 2D cell lines do not represent the complex three-dimensional tissue architecture whereas animal models are limited by inter-species differences. These shortcomings limit understanding of liver biology and diseases. Liver organoid technology is effective in elucidating structural and physiological characteristics and basic tissue-level functions of liver tissue. In this review, formation strategies and a wide range of applications in biomedicine of liver organoid are summarized. Liver organoids are derived from single type cell culture, such as induced pluripotent stem cells (iPSCs), adult stem cells, primary hepatocytes, and primary cholangiocytes and multi-type cells co-culture, such as iPSC-derived hepatic endoderm cells co-cultured with mesenchymal stem cells and umbilical cord-derived endothelial cells. In vitro studies report that liver organoids are a promising model for regenerative medicine, organogenesis, liver regeneration, disease modelling, drug screening and personalized treatment. Liver organoids are a promising in vitro model for basic research and for development of clinical therapeutic interventions for hepatopathy.

Human Pluripotent Stem-Cell-Derived Models as a Missing Link in Drug Discovery and Development

Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and human-induced pluripotent stem cells (hiPSCs), have the potential to accelerate the drug discovery and development process. In this review, by analyzing each stage of the drug discovery and development process, we identified the active role of hPSC-derived in vitro models in phenotypic screening, target-based screening, target validation, toxicology evaluation, precision medicine, clinical trial in a dish, and post-clinical studies. Patient-derived or genome-edited PSCs can generate valid in vitro models for dissecting disease mechanisms, discovering novel drug targets, screening drug candidates, and preclinically and post-clinically evaluating drug safety and efficacy. With the advances in modern biotechnologies and developmental biology, hPSC-derived in vitro models will hopefully improve the cost-effectiveness and the success rate of drug discovery and development.

Next-Generation Human Liver Models for Antimalarial Drug Assays

Advances in malaria prevention and treatment have significantly reduced the related morbidity and mortality worldwide, however, malaria continues to be a major threat to global public health. Because Plasmodium parasites reside in the liver prior to the appearance of clinical manifestations caused by intraerythrocytic development, the Plasmodium liver stage represents a vulnerable therapeutic target to prevent progression. Currently, a small number of drugs targeting liver-stage parasites are available, but all cause lethal side effects in glucose-6-phosphate dehydrogenase-deficient individuals, emphasizing the necessity for new drug development. Nevertheless, a longstanding hurdle to developing new drugs is the availability of appropriate in vitro cultures, the crucial conventional platform for evaluating the efficacy and toxicity of drugs in the preclinical phase. Most current cell culture systems rely primarily on growing immortalized or cancerous cells in the form of a two-dimensional monolayer, which is not very physiologically relevant to the complex cellular architecture of the human body. Although primary human cells are more relevant to human physiology, they are mainly hindered by batch-to-batch variation, limited supplies, and ethical issues. Advances in stem cell technologies and multidimensional culture have allowed the modelling of human infectious diseases. Here, current in vitro hepatic models and toolboxes for assaying the antimalarial drug activity are summarized. Given the physiological potential of pluripotent and adult stem cells to model liver-stage malaria, the opportunities and challenges in drug development against liver-stage malaria is highlighted, paving the way to assess the efficacy of hepatic plasmodicidal activity.

Advances in 3D cell culture for liver preclinical studies

The 3D cell culture model is an indispensable tool in the study of liver biology in the field of health and disease and the development of clinically relevant products for liver therapies. The 3D culture model captures critical factors of the microenvironmental niche required by hepatocytes for exhibiting optimal phenotypes, thus enabling the pursuit of a range of preclinical studies that are not entirely feasible in conventional 2D cell models. In this review, we highlight the major attributes associated with and the components needed for the development of a functional 3D liver culture model for a range of applications.

Challenges in Studying Stem Cell Metabolism

The expanding field of stem cell metabolism has been supported by technical advances in metabolite profiling and novel functional analyses. While use of these methodologies has been fruitful, many challenges are posed by the intricacies of culturing stem cells in vitro, along with the distinctive scarcity of adult tissue stem cells and the complexities of their niches in vivo. This review provides an examination of the methodologies used to characterize stem cell metabolism, highlighting their utility while placing a sharper focus on their limitations and hurdles the field needs to overcome for the optimal study of stem cell metabolic networks.

The Combination of Cell Cultured Technology and In Silico Model to Inform the Drug Development

Human-derived in vitro models can provide high-throughput efficacy and toxicity data without a species gap in drug development. Challenges are still encountered regarding the full utilisation of massive data in clinical settings. The lack of translated methods hinders the reliable prediction of clinical outcomes. Therefore, in this study, in silico models were proposed to tackle these obstacles from in vitro to in vivo translation, and the current major cell culture methods were introduced, such as human-induced pluripotent stem cells (hiPSCs), 3D cells, organoids, and microphysiological systems (MPS). Furthermore, the role and applications of several in silico models were summarised, including the physiologically based pharmacokinetic model (PBPK), pharmacokinetic/pharmacodynamic model (PK/PD), quantitative systems pharmacology model (QSP), and virtual clinical trials. These credible translation cases will provide templates for subsequent in vitro to in vivo translation. We believe that synergising high-quality in vitro data with existing models can better guide drug development and clinical use.

Integrated Isogenic Human Induced Pluripotent Stem Cell-Based Liver and Heart Microphysiological Systems Predict Unsafe Drug-Drug Interaction

Three-dimensional (3D) microphysiological systems (MPSs) mimicking human organ function in vitro are an emerging alternative to conventional monolayer cell culture and animal models for drug development. Human induced pluripotent stem cells (hiPSCs) have the potential to capture the diversity of human genetics and provide an unlimited supply of cells. Combining hiPSCs with microfluidics technology in MPSs offers new perspectives for drug development. Here, the integration of a newly developed liver MPS with a cardiac MPS—both created with the same hiPSC line—to study drug–drug interaction (DDI) is reported. As a prominent example of clinically relevant DDI, the interaction of the arrhythmogenic gastroprokinetic cisapride with the fungicide ketoconazole was investigated. As seen in patients, metabolic conversion of cisapride to non-arrhythmogenic norcisapride in the liver MPS by the cytochrome P450 enzyme CYP3A4 was inhibited by ketoconazole, leading to arrhythmia in the cardiac MPS. These results establish integration of hiPSC-based liver and cardiac MPSs to facilitate screening for DDI, and thus drug efficacy and toxicity, isogenic in the same genetic background.

Building consensus on definition and nomenclature of hepatic, pancreatic, and biliary organoids

Hepatic, pancreatic, and biliary (HPB) organoids are powerful tools for studying development, disease, and regeneration. As organoid research expands, the need for clear definitions and nomenclature describing these systems also grows. To facilitate scientific communication and consistent interpretation, we revisit the concept of an organoid and introduce an intuitive classification system and nomenclature for describing these 3D structures through the consensus of experts in the field. To promote the standardization and validation of HPB organoids, we propose guidelines for establishing, characterizing, and benchmarking future systems. Finally, we address some of the major challenges to the clinical application of organoids.

A Combined Model of Human iPSC-Derived Liver Organoids and Hepatocytes Reveals Ferroptosis in DGUOK Mutant mtDNA Depletion Syndrome

Mitochondrial DNA depletion syndrome (MDS) is a group of severe inherited disorders caused by mutations in genes, such as deoxyribonucleoside kinase (DGUOK). A great majority of DGUOK mutant MDS patients develop iron overload progressing to severe liver failure. However, the pathological mechanisms connecting iron overload and hepatic damage remains uncovered. Here, two patients' skin fibroblasts are reprogrammed to induced pluripotent stem cells (iPSCs) and then corrected by CRISPR/Cas9. Patient-specific iPSCs and corrected iPSCs-derived high purity hepatocyte organoids (iHep-Orgs) and hepatocyte-like cells (iHep) are generated as cellular models for studying hepatic pathology. DGUOK mutant iHep and iHep-Orgs, but not control and corrected one, are more sensitive to iron overload-induced ferroptosis, which can be rescued by N-Acetylcysteine (NAC). Mechanically, this ferroptosis is a process mediated by nuclear receptor co-activator 4 (NCOA4)-dependent degradation of ferritin in lysosome and cellular labile iron release. This study reveals the underlying pathological mechanisms and the viable therapeutic strategies of this syndrome, and is the first pure iHep-Orgs model in hereditary liver diseases.

Liver organoid as a 3D in vitro model for drug validation and toxicity assessment

The past decade has seen many advancements in the development of three-dimensional (3D) in vitro models in pharmaceutical sciences and industry. Specifically, organoids present a self-organising, self-renewing and more physiologically relevant model than conventional two-dimensional (2D) cell cultures. Liver organoids have been developed from a variety of cell sources, including stem cells, cell lines and primary cells. They have potential for modelling patient-specific disease and establishing personalised therapeutic approaches. Additionally, liver organoids have been used to test drug efficacy and toxicity. Herein we summarise cell sources for generating liver organoids, the advantages and limitations of each cell type, as well as the application of the organoids in modelling liver diseases. We focus on the use of liver organoids as tools for drug validation and toxicity assessment.

Liver organoids in domestic animals: an expected promise for metabolic studies

The liver is one of the most important organs, both in terms of the different metabolic processes (energy, lipid, ferric, uric, etc.) and of its central role in the processes of detoxification of substances of food origin or noxious substances (alcohol, drugs, antibiotics, etc.). The development of a relevant model that reproduces some of the functions of this tissue has become a challenge, in particular for human medicine. Thus, in recent years, most studies aimed at producing hepatocytes in vitro with the goal of developing hepatic 3D structures have been carried out in the human model. However, the tools and protocols developed using this unique model can also be considered to address physiological questions specific to this tissue in other species, such as the pig, chicken, and duck. Different strategies are presently being considered to carry out in vitro studies of the hepatic metabolism of these agronomic species.

Phenotypic screening with target identification and validation in the discovery and development of E3 ligase modulators

The use of phenotypic screening was central to the discovery and development of novel thalidomide analogs, the IMiDs (immunomodulatory drugs) agents. With the discovery that these agents bind the E3 ligase, CRL4^CRBN, and alter its substrate specificity, there has been a great deal of endeavor to discover other small molecules that can modulate alternative E3 ligases. Furthermore, the chemical properties necessary for drug discovery and the rules by which neo-substrates are selected for degradation are being defined in the context of phenotypic alterations in specific cellular systems. This review gives a detailed summary of these recent advances and the methodologies being exploited to understand the mechanism of action of emerging protein degradation therapies.

Production of Functional Hepatobiliary Organoids from Human Pluripotent Stem Cells

The research on human hepatobiliary development and disorders has been constrained by minimal access to human fetal tissue, and low accuracy of animal models. To overcome this problem, we have established a system for the differentiation of human pluripotent stem cells (hPSCs) into functional hepatobiliary organoids (HBOs). We have previously reported that our 45-d approach closely mimics key stages of hepatobiliary development, starting with the differentiation of hiPSC into endoderm and a small part of mesoderm, and subsequently into hepatoblast-like cells, followed by the parallel generation of hepatocyte-like cells and cholangiocyte-like cells, formation of immature HBO expressing early hepatic and biliary markers, and mature HBO displaying hepatobiliary functionality. In this study, we present an updated version of our previous protocol, which only needs 35 days to achieve maturation in vitro. Furthermore, a hepatobiliary culture medium is developed to functionally maintain the HBOs for more than 1.5 months. The capacity of this approach for producing large amounts of functional HBOs and enabling long-term culture in vitro holds promise for applications on developmental research, disease modeling, as well as screening of therapeutic agents.

Robust expansion and functional maturation of human hepatoblasts by chemical strategy

Background

Chemically strategies to generate hepatic cells from human pluripotent stem cells (hPSCs) for the potential clinical application have been improved. However, producing high quality and large quantities of hepatic cells remain challenging, especially in terms of step-wise efficacy and cost-effective production requires more improvements.

Methods

Here, we systematically evaluated chemical compounds for hepatoblast (HB) expansion and maturation to establish a robust, cost-effective, and reproducible methodology for self-renewal HBs and functional hepatocyte-like cell (HLC) production.

Results

The established chemical cocktail could enable HBs to proliferate nearly 3000 folds within 3 weeks with preserved bipotency. Moreover, those expanded HBs could be further efficiently differentiated into homogenous HLCs which displayed typical morphologic features and functionality as mature hepatocytes including hepatocyte identity marker expression and key functional activities such as cytochrome P450 metabolism activities and urea secretion. Importantly, the transplanted HBs in the injured liver of immune-defect mice differentiated as hepatocytes, engraft, and repopulate in the injured loci of the recipient liver.

Conclusion

Together, this chemical compound-based HLC generation method presents an efficient and cost-effective platform for the large-scale production of functional human hepatic cells for cell-based therapy and drug discovery application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02233-9.

Advancements in stem cell-derived hepatocyte-like cell models for hepatotoxicity testing

Drug-induced liver injury (DILI) is one of the leading causes of clinical trial failures and high drug attrition rates. Currently, the commonly used hepatocyte models include primary human hepatocytes (PHHs), animal models, and hepatic cell lines. However, these models have disadvantages that include species-specific differences or inconvenient cell extraction methods. Therefore, a novel, inexpensive, efficient, and accurate model that can be applied to drug screening is urgently needed. Owing to their self-renewable ability, source abundance, and multipotent competence, stem cells are stable sources of drug hepatotoxicity screening models. Because 3D culture can mimic the in vivo microenvironment more accurately than can 2D culture, the former is commonly used for hepatocyte culture and drug screening. In this review, we introduce the different sources of stem cells used to generate hepatocyte-like cells and the models for hepatotoxicity testing that use stem cell-derived hepatocyte-like cells.

Convergence of human pluripotent stem cell, organoid, and genome editing technologies

The last decade has seen many exciting technological breakthroughs that greatly expanded the toolboxes for biological and biomedical research, yet few have had more impact than induced pluripotent stem cells and modern-day genome editing. These technologies are providing unprecedented opportunities to improve physiological relevance of experimental models, further our understanding of developmental processes, and develop novel therapies. One of the research areas that benefit greatly from these technological advances is the three-dimensional human organoid culture systems that resemble human tissues morphologically and physiologically. Here we summarize the development of human pluripotent stem cells and their differentiation through organoid formation. We further discuss how genetic modifications, genome editing in particular, were applied to answer basic biological and biomedical questions using organoid cultures of both somatic and pluripotent stem cell origins. Finally, we discuss the potential challenges of applying human pluripotent stem cell and organoid technologies for safety and efficiency evaluation of emerging genome editing tools.

Effect of Microbial Short-Chain Fatty Acids on CYP3A4-Mediated Metabolic Activation of Human Pluripotent Stem Cell-Derived Liver Organoids

The early and accurate prediction of the hepatotoxicity of new drug targets during nonclinical drug development is important to avoid postmarketing drug withdrawals and late-stage failures. We previously established long-term expandable and functional human-induced pluripotent stem cell (iPSC)-derived liver organoids as an alternative source for primary human hepatocytes. However, PSC-derived organoids are known to present immature fetal characteristics. Here, we treated these liver organoids with microbial short-chain fatty acids (SCFAs) to improve metabolic maturation based on microenvironmental changes in the liver during postnatal development. The effects of the three main SCFA components (acetate, propionate, and butyrate) and their mixture on liver organoids were determined. Propionate (1 µM) significantly promoted the CYP3A4/CYP3A7 expression ratio, and acetate (1 µM), propionate (1 µM), and butyrate (1 µM) combination treatment, compared to no treatment (control), substantially increased CYP3A4 activity and albumin secretion, as well as gene expression. More importantly, mixed SCFA treatment accurately revealed troglitazone-induced hepatotoxicity, which was redeemed on a potent CYP3A4 inhibitor ketoconazole treatment. Overall, we determined, for the first time, that SCFA mixture treatment might contribute to the accurate evaluation of the CYP3A4-dependent drug toxicity by improving metabolic activation, including CYP3A4 expression, of liver organoids.

Human liver model systems in a dish

The human adult liver has a multi-cellular structure consisting of large lobes subdivided into lobules containing portal triads and hepatic cords lined by specialized blood vessels. Vital hepatic functions include filtering blood, metabolizing drugs, and production of bile and blood plasma proteins like albumin, among many other functions, which are generally dependent on the location or zone in which the hepatocyte resides in the liver. Due to the liver's intricate structure, there are many challenges to design differentiation protocols to generate more mature functional hepatocytes from human stem cells and maintain the long-term viability and functionality of primary hepatocytes. To this end, recent advancements in three-dimensional (3D) stem cell culture have accelerated the generation of a human miniature liver system, also known as liver organoids, with polarized epithelial cells, supportive cell types and extra-cellular matrix deposition by translating knowledge gained in studies of animal organogenesis and regeneration. To facilitate the efforts to study human development and disease using in vitro hepatic models, a thorough understanding of state-of-art protocols and underlying rationales is essential. Here, we review rapidly evolving 3D liver models, mainly focusing on organoid models differentiated from human cells.

Generation of immune cell containing adipose organoids for in vitro analysis of immune metabolism

Adipose tissue is an organized endocrine organ with important metabolic and immunological functions and immune cell-adipocyte crosstalk is known to drive various disease pathologies. Suitable 3D adipose tissue organoid models often lack resident immune cell populations and therefore require the addition of immune cells isolated from other organs. We have created the first 3D adipose tissue organoid model which could contain and maintain resident immune cell populations of the stromal vascular fraction (SVF) and proved to be effective in studying adipose tissue biology in a convenient manner. Macrophage and mast cell populations were successfully confirmed within our organoid model and were maintained in culture without the addition of growth factors. We demonstrated the suitability of our model for monitoring the lipidome during adipocyte differentiation in vitro and confirmed that this model reflects the physiological lipidome better than standard 2D cultures. In addition, we applied mass spectrometry-based lipidomics to track lipidomic changes in the lipidome upon dietary and immunomodulatory interventions. We conclude that this model represents a valuable tool for immune-metabolic research.

The Microfluidic Environment Reveals a Hidden Role of Self-Organizing Extracellular Matrix in Hepatic Commitment and Organoid Formation of hiPSCs

The specification of the hepatic identity during human liver development is strictly controlled by extrinsic signals, yet it is still not clear how cells respond to these exogenous signals by activating secretory cascades, which are extremely relevant, especially in 3D self-organizing systems. Here, we investigate how the proteins secreted by human pluripotent stem cells (hPSCs) in response to developmental exogenous signals affect the progression from endoderm to the hepatic lineage, including their competence to generate nascent hepatic organoids. By using microfluidic confined environment and stable isotope labeling with amino acids in cell culture-coupled mass spectrometry (SILAC-MS) quantitative proteomic analysis, we find high abundancy of extracellular matrix (ECM)-associated proteins. Hepatic progenitor cells either derived in microfluidics or exposed to exogenous ECM stimuli show a significantly higher potential of forming hepatic organoids that can be rapidly expanded for several passages and further differentiated into functional hepatocytes. These results prove an additional control over the efficiency of hepatic organoid formation and differentiation for downstream applications.

Chitosan 3D cell culture system promotes naïve-like features of human induced pluripotent stem cells: A novel tool to sustain pluripotency and facilitate differentiation

A simplified and cost-effective culture system for maintaining the pluripotency of human induced pluripotent stem cells (hiPSCs) is crucial for stem cell applications. Although recombinant protein-based feeder-free hiPSC culture systems have been developed, their manufacturing processes are expensive and complicated, which hinders hiPSC technology progress. Chitosan, a versatile biocompatible polysaccharide, has been reported as a biomaterial for three-dimensional (3D) cell culture system that promotes the physiological activities of mesenchymal stem cells and cancer cells. In the current study, we demonstrated that chitosan membranes sustained proliferation and pluripotency of hiPSCs in long-term culture (up to 365 days). Moreover, using vitronectin as the comparison group, the pluripotency of hiPSCs grown on the membranes was altered into a naïve-like state, which, for pluripotent stem cells, is an earlier developmental stage with higher stemness. On the chitosan membranes, hiPSCs self-assembled into 3D spheroids with an average diameter of ~100 μm. These hiPSC spheroids could be directly differentiated into lineage-specific cells from the three germ layers with 3D structures. Collectively, chitosan membranes not only promoted the naïve pluripotent features of hiPSCs but also provided a novel 3D differentiation platform. This convenient biomaterial-based culture system may enable the effective expansion and accessibility of hiPSCs for regenerative medicine, disease modeling, and drug screening.

Establishment of human fetal hepatocyte organoids and CRISPR-Cas9-based gene knockin and knockout in organoid cultures from human liver

The liver is composed of two epithelial cell types: hepatocytes and liver ductal cells. Culture conditions for expansion of human liver ductal cells in vitro as organoids were previously described in a protocol; however, primary human hepatocytes remained hard to expand, until recently. In this protocol, we provide full details of how we overcame this limitation, establishing culture conditions that facilitate long-term expansion of human fetal hepatocytes as organoids. In addition, we describe how to generate (multi) gene knockouts using CRISPR-Cas9 in both human fetal hepatocyte and adult liver ductal organoid systems. Using a CRISPR-Cas9 and homology-independent organoid transgenesis (CRISPR-HOT) approach, efficient gene knockin can be achieved in these systems. These gene knockin and knockout approaches, and their multiplexing, should be useful for a variety of applications, such as disease modeling, investigating gene functions and studying processes, such as cellular differentiation and cell division. The protocol to establish human fetal hepatocyte organoid cultures takes ~1-2 months. The protocols to genome engineer human liver ductal organoids and human fetal hepatocyte organoids take 2-3 months.

Differentiation of Human Parthenogenetic Embryonic Stem Cells into Functional Hepatocyte-like Cells

Stem cell and tissue engineering-based therapies for acute liver failure (ALF) have been limited by the lack of an optimal cell source. We aimed to determine the suitability of human parthenogenetic embryonic stem cells (hPESCs) for the development of strategies to treat ALF. We studied the ability of human parthenogenetic embryonic stem cells (hPESCs) with high whole-genome SNP homozygosity, which were obtained by natural activation during in vitro fertilization (IVF), to differentiate into functional hepatocyte-like cells in vitro by monolayer plane orientation. hPESCs were induced on a single-layer flat plate for 21 d in complete medium with the inducers activin A, FGF-4, BMP-2, HGF, OSM, DEX, and B27. Polygonal cell morphology and binuclear cells were observed after 21 d of induction by using an inverted microscope. RT-qPCR results showed that the levels of hepatocyte-specific genes such as AFP, ALB, HNF4a, CYP3A4, SLCO1B3, and ABCC2 significantly increased after induction. Immunocytochemical assay showed CK18 and Hepa expression in the induced cells. Indocyanine green (ICG) staining showed that the cells had the ability to absorb and metabolize dyes. Detection of marker proteins and urea in cell culture supernatants showed that the cells obtained after 21 d of induction had synthetic and secretory functions. The typical ultrastructure of liver cells was observed using TEM after 21 d of induction. The results indicate that naturally activated hPESCs can be induced to differentiate into hepatocellular cells by monolayer planar induction.

Generation of uniform liver spheroids from human pluripotent stem cells for imaging-based drug toxicity analysis

Recent advances in pluripotent stem cell technology provide an alternative source of human hepatocytes to overcome the limitations of current toxicity tests. However, this approach requires optimization and standardization before it can be used as a fast and reliable toxicity screening system. Here, we designed and tested microwell culture platforms with various diameters. We found that large quantities of uniformly-sized hepatocyte-like cell (HLC) spheroids (3D-uniHLC-Ss) could be efficiently and reproducibly generated in a short period time from a small number of differentiating human pluripotent stem cells (hPSCs). The hPSC-3D-uniHLC-Ss that were produced in 500-μm diameter microwells consistently exhibited high expressions of hepatic marker genes and had no significant signs of cell death. Importantly, a hepatic master gene hepatocyte nuclear factor 4α (HNF4α) was maintained at high levels, and the epithelial-mesenchymal transition was significantly attenuated in hPSC-3D-uniHLC-Ss. Additionally, when compared with 3D-HLC-Ss that were produced in other 3D platforms, hPSC-3D-uniHLC-Ss showed significantly higher hepatic gene expressions and drug-metabolizing activity of the enzyme, CYP3A4. Imaging-based drug toxicity studies demonstrated that hPSC-3D-uniHLC-Ss exhibited enhanced sensitivity to various hepatotoxicants, compared to HLCs, which were differentiated under 2D conditions. Precise prediction of drug-induced hepatotoxicity is a crucial step in the early phases of drug discovery. Thus, the hPSC-3D-uniHLC-Ss produced using our microwell platform could be used as an imaging-based toxicity screening system to predict drug hepatotoxicity.

EZH2 as a Potential Target for NAFLD Therapy

Non-alcoholic fatty liver disease (NAFLD) is a complex disease that is affected by genetic predisposition and epigenetic modification. Deregulation of epigenetic pathways is now recognized as a frequent event in NAFLD, and understanding the mechanistic roles of these epigenetic factors may lead to new strategies for NAFLD treatment. Enhancer of zeste homolog 2 (EZH2) catalyzes methylation on Lys 27 of histone H3, which leads to chromatin compaction and gene silencing. EZH2 regulates embryonic development and cell lineage determination and is related to many human diseases. Recent studies show that EZH2 has critical roles in liver development, homeostasis, and regeneration. Moreover, aberrant activation of EZH2 promotes NAFLD progression. Several EZH2 inhibitors have been developed and studied both in vitro and in clinical trials. In this review, we summarize our current understanding of the role of EZH2 in NAFLD and highlight its potential as a novel therapeutic target for NAFLD treatment.

Organoids to model liver disease

The organoid model represents a major breakthrough in cell biology that has revolutionised biomedical research. Organoids are 3D physiological in vitro structures that recapitulate morphological and functional features of in vivo tissues and offer significant advantages over traditional cell culture methods. Liver organoids are of particular interest because of the pleiotropy of functions exerted by the human liver, their utility to model different liver diseases, and their potential application as cell-based therapies in regenerative medicine. Moreover, because they can be derived from patient tissues, organoid models offer new perspectives in personalised medicine and drug discovery. In this review, we discuss the current liver organoid models for the study of liver disease.

Generation of human liver organoids from pluripotent stem cell-derived hepatic endoderms

Background

The use of a personalized liver organoid derived from human-induced pluripotent stem cells (HuiPSCs) is advancing the use of in vitro disease models for the design of specific, effective therapies for individuals. Collecting patient peripheral blood cells for HuiPSC generation is preferable because it is less invasive; however, the capability of blood cell-derived HuiPSCs for hepatic differentiation and liver organoid formation remains uncertain. Moreover, the currently available methods for liver organoid formation require a multistep process of cell differentiation or a combination of hepatic endodermal, endothelial and mesenchymal cells, which is a major hurdle for the application of personalized liver organoids in high-throughput testing of drug toxicity and safety. To demonstrate the capability of blood cell-derived HuiPSCs for liver organoid formation without support from endothelial and mesenchymal cells.

Methods

The peripheral blood-derived HuiPSCs first differentiated into hepatic endoderm (HE) in two-dimensional (2D) culture on Matrigel-coated plates under hypoxia for 10 days. The HE was then collected and cultured in 3D culture using 50% Matrigel under ambient oxygen. The maturation of hepatocytes was further induced by adding hepatocyte growth medium containing HGF and oncostatin M on top of the 3D culture and incubating the culture for an additional 12–17 days. The function of the liver organoids was assessed using expression analysis of hepatocyte-specific gene and proteins. Albumin (ALB) synthesis, glycogen and lipid storage, and metabolism of indocyanine were evaluated. The spatial distribution of albumin was examined using immunofluorescence and confocal microscopy.

Results

CD34+ hematopoietic cell-derived HuiPSCs were capable of differentiating into definitive endoderm expressing SOX17 and FOXA2, hepatic endoderm expressing FOXA2, hepatoblasts expressing AFP and hepatocytes expressing ALB. On day 25 of the 2D culture, cells expressed SOX17, FOXA2, AFP and ALB, indicating the presence of cellular heterogeneity. In contrast, the hepatic endoderm spontaneously formed a spherical, hollow structure in a 3D culture of 50% Matrigel, whereas hepatoblasts and hepatocytes could not form. Microscopic observation showed a single layer of polygonal-shaped cells arranged in a 3D structure. The hepatic endoderm-derived organoid synthesis ALB at a higher level than the 2D culture but did not express definitive endoderm-specific SOX17, indicating the greater maturity of the hepatocytes in the liver organoids. Confocal microscopic images and quantitative ELISA confirmed albumin synthesis in the cytoplasm of the liver organoid and its secretion. Overall, 3D culture of the hepatic endoderm is a relatively fast, simple, and less laborious way to generate liver organoids from HuiPSCs that is more physiologically relevant than 2D culture.

A potential ex vivo infection model of human induced pluripotent stem cell-3D organoids beyond coronavirus disease 2019

The novel coronavirus disease 2019 (COVID-19) outbreak began in the city of Wuhan, whereupon it rapidly spread throughout China and subsequently across the world. Rapid transmission of COVID-19 has caused wide-spread panic. Many established medications have been used to treat the disease symptoms; however, no specific drugs or vaccines have been developed. Organoids derived from human induced pluripotent stem cells (iPSCs) may serve as suitable infection models for ex vivo mimicking of the viral life cycle and drug screening. Human iPSC-3D organoids, self-organised tissues with multiple cell environments, have a similar structure and function as real human organs; hence, these organoids allow greater viral infection efficiency, mimic the natural host-virus interactions, and are suitable for long-term experimentation. Here, we suggest the use of a functional human iPSC-organoid that could act as a reliable and feasible ex vivo infection model for investigation of the virus. This approach will provide much needed insight into the underlying molecular dynamics of COVID-19 for the development of novel treatment and prevention strategies.

The science and engineering of stem cell-derived organoids-examples from hepatic, biliary, and pancreatic tissues

The field of organoid engineering promises to revolutionize medicine with wide-ranging applications of scientific, engineering, and clinical interest, including precision and personalized medicine, gene editing, drug development, disease modelling, cellular therapy, and human development. Organoids are a three-dimensional (3D) miniature representation of a target organ, are initiated with stem/progenitor cells, and are extremely promising tools with which to model organ function. The biological basis for organoids is that they foster stem cell self-renewal, differentiation, and self-organization, recapitulating 3D tissue structure or function better than two-dimensional (2D) systems. In this review, we first discuss the importance of epithelial organs and the general properties of epithelial cells to provide a context and rationale for organoids of the liver, pancreas, and gall bladder. Next, we develop a general framework to understand self-organization, tissue hierarchy, and organoid cultivation. For each of these areas, we provide a historical context, and review a wide range of both biological and mathematical perspectives that enhance understanding of organoids. Next, we review existing techniques and progress in hepatobiliary and pancreatic organoid engineering. To do this, we review organoids from primary tissues, cell lines, and stem cells, and introduce engineering studies when applicable. We discuss non-invasive assessment of organoids, which can reveal the underlying biological mechanisms and enable improved assays for growth, metabolism, and function. Applications of organoids in cell therapy are also discussed. Taken together, we establish a broad scientific foundation for organoids and provide an in-depth review of hepatic, biliary and pancreatic organoids.