Generation of intestinal organoids derived from human pluripotent stem cells for drug testing

Exploring the potential of human intestinal organoids: Applications, challenges, and future directions

The complex and dynamic environment of the gastrointestinal tract shapes one of the fastest renewing tissues in the human body, the intestinal epithelium. Considering the lack of human preclinical studies, reliable models that mimic the intestinal environment are increasingly explored. Patient-derived intestinal organoids are powerful tools that recapitulate in vitro many pathophysiological features of the human intestine. In this review, the possible applications of human intestinal organoids in different research fields are highlighted. From physiologically relevant to intestinal disease modeling, regenerative medicine, and toxicology studies, the potential of intestinal organoids will be here presented and discussed. Despite the remarkable opportunities offered, limitations related to ethical concerns, tissue collection, reproducibility, and methodologies may hinder the full exploitation of this cell-based model into high throughput studies and clinical practice. Currently, distinct approaches can be used to overcome the numerous challenges found along the way and to allow the full implementation of this ground-breaking technology.

Translational Utility of Organoid Models for Biomedical Research on Gastrointestinal Diseases

Organoid models have recently been utilized to study 3D human-derived tissue systems to uncover tissue architecture and adult stem cell biology. Patient-derived organoids unambiguously provide the most suitable in vitro system to study disease biology with the actual genetic background. With the advent of much improved and innovative approaches, patient-derived organoids can potentially be used in regenerative medicine. Various human tissues were explored to develop organoids due to their multifold advantage over the conventional in vitro cell line culture approach and in vivo models. Gastrointestinal (GI) tissues have been widely studied to establish organoids and organ-on-chip for screening drugs, nutraceuticals, and other small molecules having therapeutic potential. The function of channel proteins, transporters, and transmembrane proteins was also explained. The successful application of genome editing in organoids using the CRISPR-Cas approach has been reported recently. GI diseases such as Celiac disease (CeD), Inflammatory bowel disease (IBD), and common GI cancers have been investigated using several patient-derived organoid models. Recent advancements on organoid bio-banking and 3D bio-printing contributed significantly in personalized disease management and therapeutics. This article reviews the available literature on investigations and translational applications of patient-derived GI organoid models, notably on elucidating gut-microbial interaction and epigenetic modifications.

Recommendations on fit-for-purpose criteria to establish quality management for microphysiological systems and for monitoring their reproducibility

Cell culture technology has evolved, moving from single-cell and monolayer methods to 3D models like reaggregates, spheroids, and organoids, improved with bioengineering like microfabrication and bioprinting. These advancements, termed microphysiological systems (MPSs), closely replicate tissue environments and human physiology, enhancing research and biomedical uses. However, MPS complexity introduces standardization challenges, impacting reproducibility and trust. We offer guidelines for quality management and control criteria specific to MPSs, facilitating reliable outcomes without stifling innovation. Our fit-for-purpose recommendations provide actionable advice for achieving consistent MPS performance.

Engineered Synthetic Matrices for Human Intestinal Organoid Culture and Therapeutic Delivery

Human intestinal organoids (HIOs) derived from pluripotent stem cells or adult stem cell biopsies represent a powerful platform to study human development, drug testing, and disease modeling in vitro, and serve as a cell source for tissue regeneration and therapeutic advances in vivo. Synthetic hydrogels can be engineered to serve as analogs of the extracellular matrix to support HIO growth and differentiation. These hydrogels allow for tuning the mechanical and biochemical properties of the matrix, offering an advantage over biologically derived hydrogels such as Matrigel. Human intestinal organoids have been used for repopulating transplantable intestinal grafts and for in vivo delivery to an injured intestinal site. The use of synthetic hydrogels for in vitro culture and for in vivo delivery is expected to significantly increase the relevance of human intestinal organoids for drug screening, disease modeling, and therapeutic applications.

Functional intestinal monolayers from organoids derived from human iPS cells for drug discovery research

BACKGROUND

Human induced pluripotent stem (iPS) cell-derived enterocyte-like cells (ELCs) are expected to be useful for evaluating the intestinal absorption and metabolism of orally administered drugs. However, it is difficult to generate large amounts of ELCs with high quality because they cannot proliferate and be passaged.

METHODS

To solve the issue above, we have established intestinal organoids from ELCs generated using our protocol. Furthermore, monolayers were produced from the organoids. We evaluated the usefulness of the monolayers by comparing their functions with those of the original ELCs and the organoids.

RESULTS

We established organoids from ELCs (ELC-org) that could be passaged and maintained for more than a year. When ELC-org were dissociated into single cells and seeded on cell culture inserts (ELC-org-mono), they formed a tight monolayer in 3 days. Both ELC-org and ELC-org-mono were composed exclusively of epithelial cells. Gene expressions of many drug-metabolizing enzymes and drug transporters in ELC-org-mono were enhanced, as compared with those in ELC-org, to a level comparable to those in adult human small intestine. The CYP3A4 activity level in ELC-org-mono was comparable or higher than that in primary cryopreserved human small intestinal cells. ELC-org-mono had the efflux activities of P-gp and BCRP. Importantly, ELC-org-mono maintained high intestinal functions without any negative effects even after long-term culture (for more than a year) or cryopreservation. RNA-seq analysis showed that ELC-org-mono were more mature as intestinal epithelial cells than ELCs or ELC-org.

CONCLUSIONS

We have successfully improved the function and convenience of ELCs by utilizing organoid technology.

Validating Enteroid-Derived Monolayers from Murine Gut Organoids for Toxicological Testing of Inorganic Particles: Proof-of-Concept with Food-Grade Titanium Dioxide

Human exposure to foodborne inorganic nanoparticles (NPs) is a growing concern. However, identifying potential hazards linked to NP ingestion often requires long-term exposure in animals. Owing these constraints, intestinal organoids are a promising alternative to in vivo experiments; as such, an in vitro approach should enable a rapid and reliable assessment of the effects of ingested chemicals on the gut. However, this remains to be validated for inorganic substances. In our study, a transcriptomic analysis and immunofluorescence staining were performed to compare the effects of food-grade TiO2 (fg-TiO2) on enteroid-derived monolayers (EDMs) from murine intestinal organoids to the known impacts of TiO2 on intestinal epithelium. After their ability to respond to a pro-inflammatory cytokine cocktail was validated, EDMs were exposed to 0, 0.1, 1, or 10 µg fg-TiO2/mL for 24 h. A dose-related increase of the muc2, vilin 1, and chromogranin A gene markers of cell differentiation was observed. In addition, fg-TiO2 induced apoptosis and dose-dependent genotoxicity, while a decreased expression of genes encoding for antimicrobial peptides, and of genes related to tight junction function, was observed. These results validated the use of EDMs as a reliable model for the toxicity testing of foodborne NPs likely to affect the intestinal barrier.

Unlocking the Potential of Human-Induced Pluripotent Stem Cells: Cellular Responses and Secretome Profiles in Peptide Hydrogel 3D Culture

Human-induced pluripotent stem cells (hiPSCs) have shown great potential for human health, but their growth and properties have been significantly limited by the traditional monolayer (2D) cell culture method for more than 15 years. Three-dimensional (3D) culture technology has demonstrated tremendous advantages over 2D. In particular, the 3D PGmatrix hiPSC derived from a peptide hydrogel offers a breakthrough pathway for the maintenance and expansion of physiologically relevant hiPSC 3D colonies (spheroids). In this study, the impact of 3D culture conditions in PGmatrix hiPSC on cell performance, integrity, and secretome profiles was determined across two commonly used hiPSC cell lines derived from fibroblast cells (hiPSC-F) and peripheral blood mononuclear cells (hiPSC-P) in the two most popular hiPSC culture media (mTeSR1 and essential eight (E8)). The 3D culture conditions varied in hydrogel strength, 3D embedded matrix, and 3D suspension matrix. The results showed that hiPSCs cultured in 3D PGmatrix hiPSC demonstrated the ability to maintain a consistently high cell viability that was above 95% across all the 3D conditions with cell expansion rates of 10-20-fold, depending on the 3D conditions and cell lines. The RT-qPCR analysis suggested that pluripotent gene markers are stable and not significantly affected by the cell lines or 3D PGmatrix conditions tested in this study. Mass spectrometry-based analysis of secretome from hiPSCs cultured in 3D PGmatrix hiPSC revealed a significantly higher quantity of unique proteins, including extracellular vesicle (EV)-related proteins and growth factors, compared to those in the 2D culture. Moreover, this is the first evidence to identify that hiPSCs in a medium with a rich supplement (i.e., mTeSR1) released more growth-regulating factors, while in a medium with fewer supplements (i.e., E8) hiPSCs secreted more survival growth factors and extracellular proteins. These findings offer insights into how these differences may impact hiPSC behavior, and they deepen our understanding of how hiPSCs respond to 3D culture conditions, aiding the optimization of hiPSC properties in translational biomedical research toward clinical applications.

Advances in iPSC Technology in Neural Disease Modeling, Drug Screening, and Therapy

Neurodegenerative disorders (NDs) including Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease are all incurable and can only be managed with drugs for the associated symptoms. Animal models of human illnesses help to advance our understanding of the pathogenic processes of diseases. Understanding the pathogenesis as well as drug screening using appropriate disease models of neurodegenerative diseases (NDs) are vital for identifying novel therapies. Human-derived induced pluripotent stem cell (iPSC) models can be an efficient model to create disease in a dish and thereby can proceed with drug screening and identifying appropriate drugs. This technology has many benefits, including efficient reprogramming and regeneration potential, multidirectional differentiation, and the lack of ethical concerns, which open up new avenues for studying neurological illnesses in greater depth. The review mainly focuses on the use of iPSC technology in neuronal disease modeling, drug screening, and cell therapy.

Quantitative Prediction of Intestinal Absorption of Drugs from In Vitro Study: Utilization of Differentiated Intestinal Epithelial Cells Derived from Intestinal Stem Cells at Crypts

Prediction of intestinal absorption of drugs in humans is one of the critical elements in the development process for oral drugs. However, it remains challenging, because intestinal absorption of drugs is influenced by multiple factors, including the function of various metabolic enzymes and transporters, and large species differences in drug bioavailability hinder the prediction of human bioavailability directly from in vivo animal experiments. For the screening of intestinal absorption properties of drugs, a transcellular transport assay with Caco-2 cells is still routinely used by pharmaceutical companies because of its convenience, but the predictability of the fraction of the oral dose that goes to the portal vein of metabolic enzyme/transporter substrate drugs was not always good because the cellular expression of metabolic enzymes and transporters is different from that in the human intestine. Recently, various novel in vitro experimental systems have been proposed such as the use of human-derived intestinal samples, transcellular transport assay with induced pluripotent stem-derived enterocyte-like cells, or differentiated intestinal epithelial cells derived from intestinal stem cells at crypts. Crypt-derived differentiated epithelial cells have an excellent potential to characterize species differences and regional differences in intestinal absorption of drugs because a unified protocol can be used for the proliferation of intestinal stem cells and their differentiation into intestinal absorptive epithelial cells regardless of the animal species and the gene expression pattern of differentiated cells is maintained at the site of original crypts. The advantages and disadvantages of novel in vitro experimental systems for characterizing intestinal absorption of drugs are also discussed. SIGNIFICANCE STATEMENT: Among novel in vitro tools for the prediction of human intestinal absorption of drugs, crypt-derived differentiated epithelial cells have many advantages. Cultured intestinal stem cells are rapidly proliferated and easily differentiated into intestinal absorptive epithelial cells simply by changing the culture media. A unified protocol can be used for the establishment of intestinal stem cell culture from preclinical species and humans. Region-specific gene expression at the collection site of crypts can be reproduced in differentiated cells.

Current screening, design, and delivery approaches to address low permeability of chemically synthesized modalities in drug discovery and early clinical development

A drug's permeability across biological membranes is a key property associated with the successful development of an orally absorbed drug candidate. Although a variety of methods are available for predicting and assessing permeability, some are more preferred than others at specific stages of drug discovery and development across the pharmaceutical industry. Permeability measurements may be interpreted differently depending on the chosen method. Herein, we present a refreshed perspective on the screening approaches and philosophy in permeability evaluation, from early drug discovery to early clinical development. Additionally, we review and discuss chemical design and drug delivery technologies that can be leveraged to overcome permeability challenges, which are increasingly being used with emerging modalities.

Development of rat duodenal monolayer model with effective barrier function from rat organoids for ADME assay

The in-depth analysis of the ADME profiles of drug candidates using in vitro models is essential for drug development since a drug's exposure in humans depends on its ADME properties. In contrast to efforts in developing human in vitro absorption models, only a limited number of studies have explored models using rats, the most frequently used species in in vivo DMPK studies. In this study, we developed a monolayer model with an effective barrier function for ADME assays using rat duodenal organoids as a cell source. At first, we developed rat duodenal organoids according to a previous report, but they were not able to generate a confluent monolayer. Therefore, we modified organoid culture protocols and developed cyst-enriched organoids; these strongly promoted the formation of a confluent monolayer. Furthermore, adding valproic acid to the culture accelerated the differentiation of the monolayer, which possessed an effective barrier function and apicobasal cell polarity. Drug transporter P-gp function as well as CYP3A activity and nuclear receptor function were confirmed in the model. We expect our novel monolayer model to be a useful tool for elucidating drug absorption processes in detail, enabling the development of highly absorbable drugs.

Challenges and Opportunities in the Oral Delivery of Recombinant Biologics

Recombinant biological molecules are at the cutting-edge of biomedical research thanks to the significant progress made in biotechnology and a better understanding of subcellular processes implicated in several diseases. Given their ability to induce a potent response, these molecules are becoming the drugs of choice for multiple pathologies. However, unlike conventional drugs which are mostly ingested, the majority of biologics are currently administered parenterally. Therefore, to improve their limited bioavailability when delivered orally, the scientific community has devoted tremendous efforts to develop accurate cell- and tissue-based models that allow for the determination of their capacity to cross the intestinal mucosa. Furthermore, several promising approaches have been imagined to enhance the intestinal permeability and stability of recombinant biological molecules. This review summarizes the main physiological barriers to the oral delivery of biologics. Several preclinical in vitro and ex vivo models currently used to assess permeability are also presented. Finally, the multiple strategies explored to address the challenges of administering biotherapeutics orally are described.

Comparison of human biopsy-derived and human iPS cell-derived intestinal organoids established from a single individual

Rodent-derived intestinal tissues or human colon cancer-derived Caco-2 cells are widely used for in vitro pharmacokinetic tests. However, both entail problems such as species differences from humans and low expression levels of specific pharmacokinetic-related factors, respectively. To solve these problems, many groups, including ours, have been focusing on human biopsy-derived intestinal organoids (b-IOs) and human iPS cell-derived intestinal organoids (i-IOs). However, no reports directly compare the two. Therefore, we established both from a single individual and conducted a comparative study. b-IOs had a shorter doubling time than i-IOs: about 59 h vs 148 h. b-IOs also had higher gene expression levels of major drug transporters and drug-metabolizing enzymes than i-IOs. To evaluate their applicability to pharmacokinetics, both organoids were two-dimensionally cultured. Although the b-IO monolayer had a lower transepithelial electrical resistance than the i-IO monolayer, it had higher gene expression levels of many drug transporters and major drug-metabolizing enzymes than the i-IO monolayer. RNA-seq analysis showed that the i-IOs monolayer had a more complex structure than the b-IOs monolayer because the former contained neuronal and vascular endothelial cells. This study provides basic information for pharmacokinetic applications of human biopsy-derived and human iPS cell-derived intestinal organoids.

Tumor organoid biobank-new platform for medical research

Organoids are a new type of 3D model for tumor research, which makes up for the shortcomings of cell lines and xenograft models, and promotes the development of personalized precision medicine. Long-term culture, expansion and storage of organoids provide the necessary conditions for the establishment of biobanks. Biobanks standardize the collection and preservation of normal or pathological specimens, as well as related clinical information. The tumor organoid biobank has a good quality control system, which is conducive to the clinical transformation and large-scale application of tumor organoids, such as disease modeling, new drug development and high-throughput drug screening. This article summarized the common tumor types of patient-derived organoid (PDO) biobanks and the necessary information for biobank construction, such as the number of organoids, morphology, success rate of culture and resuscitation, pathological types. In our results, we found that patient-derived tumor organoid (PDTO) biobanks were being established more and more, with the Netherlands, the United States, and China establishing the most. Biobanks of colorectal, pancreas, breast, glioma, and bladder cancers were established more, which reflected the relative maturity of culture techniques for these tumors. In addition, we provided insights on the precautions and future development direction of PDTO biobank building.

Culture of organoids with vestibular cell-derived factors promotes differentiation of embryonic stem cells into inner ear vestibular hair cells

Vestibular hair cells (V-HCs) residing in the inner ear have important roles related to balance. Although differentiation of pluripotent stem cells into HCs has been shown, an effective method has yet to be established. We previously reported that use of vestibular cell-derived conditioned medium (V-CM) was helpful to induce embryonic stem (ES) cells to differentiate into V-HC-like cells in two-dimensional (2D) cultures of ES-derived embryoid bodies (EBs). In the present report, V-CM was used with three-dimensional (3D) cultures of EBs, which resulted in augmented expression of V-HC-related markers (Math1, Myosin6, Brn3c, Dnah5), but not of the cochlear HC-related marker Lmod3. Gene expression analyses of both 2D and 3D EBs cultured for two weeks revealed a greater level of augmented induction of HC-related markers in the 3D-cultured EBs. These results indicate that a 3D culture in combination with use of V-CM is an effective method for producing V-HCs.

Investigating nanoplastics toxicity using advanced stem cell-based intestinal and lung in vitro models

Plastic particles in the nanometer range-called nanoplastics-are environmental contaminants with growing public health concern. As plastic particles are present in water, soil, air and food, human exposure via intestine and lung is unavoidable, but possible health effects are still to be elucidated. To better understand the Mode of Action of plastic particles, it is key to use experimental models that best reflect human physiology. Novel assessment methods like advanced cell models and several alternative approaches are currently used and developed in the scientific community. So far, the use of cancer cell line-based models is the standard approach regarding in vitro nanotoxicology. However, among the many advantages of the use of cancer cell lines, there are also disadvantages that might favor other approaches. In this review, we compare cell line-based models with stem cell-based in vitro models of the human intestine and lung. In the context of nanoplastics research, we highlight the advantages that come with the use of stem cells. Further, the specific challenges of testing nanoplastics in vitro are discussed. Although the use of stem cell-based models can be demanding, we conclude that, depending on the research question, stem cells in combination with advanced exposure strategies might be a more suitable approach than cancer cell lines when it comes to toxicological investigation of nanoplastics.

Single-Cell and Spatial Analysis of Emergent Organoid Platforms

Organoids have emerged as a promising advancement of the two-dimensional (2D) culture systems to improve studies in organogenesis, drug discovery, precision medicine, and regenerative medicine applications. Organoids can self-organize as three-dimensional (3D) tissues derived from stem cells and patient tissues to resemble organs. This chapter presents growth strategies, molecular screening methods, and emerging issues of the organoid platforms. Single-cell and spatial analysis resolve organoid heterogeneity to obtain information about the structural and molecular cellular states. Culture media diversity and varying lab-to-lab practices have resulted in organoid-to-organoid variability in morphology and cell compositions. An essential resource is an organoid atlas that can catalog protocols and standardize data analysis for different organoid types. Molecular profiling of individual cells in organoids and data organization of the organoid landscape will impact biomedical applications from basic science to translational use.

Effects of human induced pluripotent stem cell-derived intestinal organoids on colitis-model mice

Introduction

Ulcerative colitis (UC) is an inflammatory bowel disease characterized by repeated remissions and relapses. Immunosuppressive drugs have facilitated the induction and maintenance of remission in many patients with UC. However, immunosuppressive drugs cannot directly repair impaired intestinal mucosa and are insufficient for preventing relapse. Therefore, new treatment approaches to repair the damaged epithelium in UC have been attempted through the transplantation of intestinal organoids, which can be differentiated into mucosa by embedding in Matrigel, generated from patient-derived intestinal stem cells. The method, however, poses the challenge of yielding sufficient cells for UC therapy, and patient-derived cells might already have acquired pathological changes. In contrast, human induced pluripotent stem (iPS) cells generated from healthy individuals are infinitely proliferated and can be differentiated into target cells. Recently developed human iPS cell-derived intestinal organoids (HIOs) aim to generate organoids that closely resemble the adult intestine. However, no study till date has reported HIOs injected into in vivo inflammatory models, and it remains unclear whether HIOs with cells that closely resemble the adult intestine or with intestinal stem cells retain the better ability to repair tissue in colitis.

Methods

We generated two types of HIOs via suspension culture with and without small-molecule compounds: HIOs that include predominantly more intestinal stem cells [HIO (A)] and those that include predominantly more intestinal epithelial and secretory cells [HIO (B)]. We examined whether the generated HIOs engrafted in vivo and compared their ability to accelerate recovery of the damaged tissue.

Results

Findings showed that the HIOs expressed intestinal-specific markers such as caudal-type homeobox 2 (CDX2) and villin, and HIOs engrafted under the kidney capsules of mice. We then injected HIOs into colitis-model mice and found that the weight and clinical score of the mice injected with HIO (A) recovered earlier than that of the mice in the sham group. Further, the production of mucus and the expression of cell proliferation markers and tight junction proteins in the colon tissues of the HIO (A) group were restored to levels similar to those observed in healthy mice. However, neither HIO (A) nor HIO (B) could be engrafted into the colon.

Conclusions

Effective cell therapy should directly repair tissue by engraftment at the site of injury. However, the difference in organoid property impacting the rate of tissue repair in transplantation without engraftment observed in the current study should be considered a critical consideration in the development of regenerative medicine using iPS-derived organoids.

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Human iPS cell-derived intestinal organoids were generated via suspension culture.

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The effects of two types of intestinal organoids in vivo were compared.

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Intestinal organoids were engrafted under mouse kidney capsules.

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Intestinal organoids promoted mucosal healing in acute colitis-model mice.

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Organoids with a higher gene expression of intestinal stem cell had higher effects.

3D organ-on-a-chip: The convergence of microphysiological systems and organoids

Medicine today faces the combined challenge of an increasing number of untreatable diseases and fewer drugs reaching the clinic. While pharmaceutical companies have increased the number of drugs in early development and entering phase I of clinical trials, fewer actually successfully pass phase III and launch into the market. In fact, only 1 out of every 9 drugs entering phase I will launch. In vitro preclinical tests are used to predict earlier and better the potential of new drugs and thus avoid expensive clinical trial phases. The most recent developments favor 3D cell culture and human stem cell biology. These 3D humanized models known as organoids better mimic the 3D tissue architecture and physiological cell behavior of healthy and disease models, but face critical issues in production such as small-scale batches, greater costs (when compared to monolayer cultures) and reproducibility. To become the gold standard and most relevant biological model for drug discovery and development, organoid technology needs to integrate biological culture processes with advanced microtechnologies, such as microphysiological systems based on microfluidics technology. Microphysiological systems, known as organ-on-a-chip, mimic physiological conditions better than conventional cell culture models since they can emulate perfusion, mechanical and other parameters crucial for tissue and organ physiology. In addition, they reduce labor cost and human error by supporting automated operation and reduce reagent use in miniaturized culture systems. There is thus a clear advantage in combining organoid culture with microsystems for drug development. The main objective of this review is to address the recent advances in organoids and microphysiological systems highlighting crucial technologies for reaching a synergistic strategy, including bioprinting.

Organoid Technologies for SARS-CoV-2 Research

Purpose of Review

Organoids are an emerging technology utilizing three-dimensional (3D), multi-cellular in vitro models to represent the function and physiological responses of tissues and organs. By using physiologically relevant models, more accurate tissue responses to viral infection can be observed, and effective treatments and preventive strategies can be identified. Animals and two-dimensional (2D) cell culture models occasionally result in inaccurate disease modeling outcomes. Organoids have been developed to better represent human organ and tissue systems, and accurately model tissue function and disease responses. By using organoids to study SARS-Cov-2 infection, researchers have now evaluated the viral effects on different organs and evaluate efficacy of potential treatments. The purpose of this review is to highlight organoid technologies and their ability to model SARS-Cov-2 infection and tissue responses.

Recent Findings

Lung, cardiac, kidney, and small intestine organoids have been examined as potential models of SARS-CoV-2 infection. Lung organoid research has highlighted that SARS-CoV-2 shows preferential infection of club cells and have shown value for the rapid screening and evaluations of multiple anti-viral drugs. Kidney organoid research suggests human recombinant soluble ACE2 as a preventative measure during early-stage infection. Using small intestine organoids, fecal to oral transmission has been evaluated as a transmission route for the virus. Lastly in cardiac organoids drug evaluation studies have found that drugs such as bromodomain, external family inhibitors, BETi, and apabetalone may be effective treatments for SARs-CoV-2 cardiac injury.

Summary

Organoids are an effective tool to study the effects of viral infections and for drug screening and evaluation studies. By using organoids, more accurate disease modeling can be performed, and physiological effects of infection and treatment can be better understood.

Role of in vitro two-dimensional (2D) and three-dimensional (3D) cell culture systems for ADME-Tox screening in drug discovery and development: a comprehensive review

Drug discovery and development have become a very time-consuming and expensive process. Preclinical animal models have become the gold standard for studying drug pharmacokinetic and toxicity parameters. However, the involvement of a huge number of animal subjects and inter-species pathophysiological variations between animals and humans has provoked a lot of debate, particularly because of ethical concerns. Although many efforts are being established by biotech and pharmaceutical companies for screening new chemical entities in vitro before preclinical trials, failures during clinical trials are still involved. Currently, a large number of two- dimensional (2D) in vitro assays have been developed and are being developed by researchers for the screening of compounds. Although these assays are helpful in screening a huge library of compounds and have shown perception, there is a significant lack in predicting human Absorption, Distribution, Metabolism, Excretion and Toxicology (ADME-Tox). As a result, these assays cannot completely replace animal models. The recent inventions in three-dimensional (3D) cell culture-based assays like organoids and micro-physiological systems have shown great potential alternative tools for predicting the compound pharmacokinetic and pharmacodynamic fate in humans. In this comprehensive review, we have summarized some of the most commonly used 2D in vitro assays and emphasized the achievements in next-generation 3D cell culture-based systems for predicting the compound ADME-Tox.

Aggregation of cryopreserved mid-hindgut endoderm for more reliable and reproducible hPSC-derived small intestinal organoid generation

A major technical limitation hindering the widespread adoption of human pluripotent stem cell (hPSC)-derived gastrointestinal (GI) organoid technologies is the need for de novo hPSC differentiation and dependence on spontaneous morphogenesis to produce detached spheroids. Here, we report a method for simple, reproducible, and scalable production of small intestinal organoids (HIOs) based on the aggregation of cryopreservable hPSC-derived mid-hindgut endoderm (MHE) monolayers. MHE aggregation eliminates variability in spontaneous spheroid production and generates HIOs that are comparable to those arising spontaneously. With a minor modification to the protocol, MHE can be cryopreserved, thawed, and aggregated, facilitating HIO production without de novo hPSC differentiation. Finally, aggregation can also be used to generate antral stomach organoids and colonic organoids. This improved method removes significant barriers to the implementation and successful use of hPSC-derived GI organoid technologies and provides a framework for improved dissemination and increased scalability of GI organoid production.

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hPSC-derived HIO production requires highly variable spontaneous spheroid formation

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hPSC-derived MHE can be aggregated to reliably increase HIO production ∼10-fold

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MHE can be cryopreserved before aggregation and subsequent HIO production

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Antral stomach and colonic organoids can also be generated by aggregation

Automated high-speed 3D imaging of organoid cultures with multi-scale phenotypic quantification

Current imaging approaches limit the ability to perform multi-scale characterization of three-dimensional (3D) organotypic cultures (organoids) in large numbers. Here, we present an automated multi-scale 3D imaging platform synergizing high-density organoid cultures with rapid and live 3D single-objective light-sheet imaging. It is composed of disposable microfabricated organoid culture chips, termed JeWells, with embedded optical components and a laser beam-steering unit coupled to a commercial inverted microscope. It permits streamlining organoid culture and high-content 3D imaging on a single user-friendly instrument with minimal manipulations and a throughput of 300 organoids per hour. We demonstrate that the large number of 3D stacks that can be collected via our platform allows training deep learning-based algorithms to quantify morphogenetic organizations of organoids at multi-scales, ranging from the subcellular scale to the whole organoid level. We validated the versatility and robustness of our approach on intestine, hepatic, neuroectoderm organoids and oncospheres.

Transcytosis of IgA Attenuates Salmonella Invasion in Human Enteroids and Intestinal Organoids

Secretory IgA (SIgA) is the most abundant antibody type in intestinal secretions where it contributes to safeguarding the epithelium from invasive pathogens like the Gram-negative bacterium, Salmonella enterica serovar Typhimurium (STm). For example, we recently reported that passive oral administration of the recombinant monoclonal SIgA antibody, Sal4, to mice promotes STm agglutination in the intestinal lumen and restricts bacterial invasion of Peyer's patch tissues. In this report, we sought to recapitulate Sal4-mediated protection against STm in human Enteroids and human intestinal organoids (HIOs) as models to decipher the molecular mechanisms by which antibodies function in mucosal immunity in the human gastrointestinal tract. We confirm that Enteroids and HIO-derived monolayers are permissive to STm infection, dependent on HilD, the master transcriptional regulator of the SPI-I type three secretion system (T3SS). Stimulation of M-like cells in both Enteroids and HIOs by the addition of RANKL further enhanced STm invasion. The apical addition of Sal4 mouse IgA, as well as recombinant human Sal4 dimeric IgA (dIgA) and SIgA resulted a dose-dependent reduction in bacterial invasion. Moreover, basolateral application of Sal4 dIgA to Enteroid and HIO monolayers gave rise to SIgA in the apical compartment via a pathway dependent on expression of the polymeric immunoglobulin receptor (pIgR). The resulting Sal4 SIgA was sufficient to reduce STm invasion of Enteroid and HIO epithelial cell monolayers by ~20-fold. Recombinant Sal4 IgG was also transported in the Enteroid and HIOs, but to a lesser degree and via a pathway dependent on the neonatal Fc receptor (FCGRT). The models described lay the foundation for future studies into detailed mechanisms of IgA and IgG protection against STm and other pathogens.

4D Materials with Photoadaptable Properties Instruct and Enhance Intestinal Organoid Development

Intestinal organoids are self-organized tissue constructs, grown in vitro, that resemble the structure and function of the intestine and are often considered promising as a prospective platform for drug testing and disease modeling. Organoid development in vitro is typically instructed by exogenous cues delivered from the media, but cellular responses also depend on properties of the surrounding microenvironmental niche, such as mechanical stiffness and extracellular matrix (ECM) ligands. In recent years, synthetic hydrogel platforms have been engineered to resemble the in vivo niche, with the goal of generating physiologically relevant environments that can promote mature and reproducible organoid development. However, a few of these approaches consider the importance of intestinal organoid morphology or how morphology changes during development, as cues that may dictate organoid functionality. For example, intestinal organoids grown in vitro often lack the physical boundary conditions found in vivo that are responsible for shaping a collection of cells into developmentally relevant morphologies, resulting in organoids that often differ in structure and cellular organization from the parent organ. This disconnect relates, in part, to a lack of appropriate adaptable and programmable materials for cell culture, especially those that enable control over colony growth and differentiation in space and time (i.e., 4D materials). We posit that the future of organoid culture platforms may benefit from advances in photoadaptable chemistries and integration into biomaterials scaffolds, thereby allowing greater user-directed control over both the macro- and microscale material properties. In this way, synthetic materials can begin to better replicate changes in the ECM during development or regeneration in vivo. Recapitulation of cellular and tissue morphological changes, along with an appreciation for the appropriate developmental time scales, should help instruct the next generation of organoid models to facilitate predictable outcomes.

Mechanisms of uptake and transport of particulate formulations in the small intestine

Micro- and nano-scale particulate formulations are widely investigated towards improving the oral bioavailability of both biologics and drugs with low solubility and/or low intestinal permeability. Particulate formulations harnessing physiological intestinal transport pathways have recently yielded remarkably high oral bioavailabilities, illustrating the need for better understanding the specific pathways underpinning particle small intestinal absorption and the relative role of intestinal cells. Mechanistic knowledge has been hampered by the well acknowledged limitations of current in vitro, in vivo and ex vivo models relevant to the human intestinal physiology and the lack of standardization in studies reporting absorption data. Here we review the relevant literature and critically discusses absorption pathways with a focus on the role of specific intestinal epithelial and immune cells. We conclude that while Microfold (M) cells are a valid target for oral vaccines, enterocytes play a greater role in the systemic bioavailability of orally administrated particulate formulations, particularly within the sub-micron size range. We also comment on less-reported mechanisms such as paracellular permeability of particles, persorption due to cell damage and uptake by migratory immune cells.

Gutsy science: In vitro systems of the human intestine to model oral drug disposition

The intestine has important gate-keeping functions that can profoundly affect the systemic blood exposure of orally administered drugs. Thus, characterizing a new molecular entity's (NME) disposition within the intestine is of utmost importance in drug development. While currently used in vitro systems, such as Ussing chamber, precision-cut intestinal slices, immortalized cell lines, and primary enterocytes provide substantial knowledge about drug absorption and the intestinal first-pass effect, they remain sub-optimal for quantitatively predicting this process and the oral bioavailability of many drugs. Use of novel in vitro systems such as intestinal organoids and intestinal microphysiological systems have provided substantial advances over the past decade, expanding our understanding of intestinal physiology, pathology, and development. However, application of these emerging in vitro systems in the pharmaceutical science is in its infancy. Preliminary work has demonstrated that these systems more accurately recapitulate the physiology and biochemistry of the intact intestine, as it relates to oral drug disposition, and thus they hold considerable promise as preclinical testing platforms of the future. Here we review currently used and emerging in vitro models of the human intestine employed in pharmaceutical science research. We also highlight aspects of these emerging tools that require further study.

Organotypic and Microphysiological Human Tissue Models for Drug Discovery and Development-Current State-of-the-Art and Future Perspectives

The number of successful drug development projects has been stagnant for decades despite major breakthroughs in chemistry, molecular biology, and genetics. Unreliable target identification and poor translatability of preclinical models have been identified as major causes of failure. To improve predictions of clinical efficacy and safety, interest has shifted to three-dimensional culture methods in which human cells can retain many physiologically and functionally relevant phenotypes for extended periods of time. Here, we review the state of the art of available organotypic culture techniques and critically review emerging models of human tissues with key importance for pharmacokinetics, pharmacodynamics, and toxicity. In addition, developments in bioprinting and microfluidic multiorgan cultures to emulate systemic drug disposition are summarized. We close by highlighting important trends regarding the fabrication of organotypic culture platforms and the choice of platform material to limit drug absorption and polymer leaching while supporting the phenotypic maintenance of cultured cells and allowing for scalable device fabrication. We conclude that organotypic and microphysiological human tissue models constitute promising systems to promote drug discovery and development by facilitating drug target identification and improving the preclinical evaluation of drug toxicity and pharmacokinetics. There is, however, a critical need for further validation, benchmarking, and consolidation efforts ideally conducted in intersectoral multicenter settings to accelerate acceptance of these novel models as reliable tools for translational pharmacology and toxicology. SIGNIFICANCE STATEMENT: Organotypic and microphysiological culture of human cells has emerged as a promising tool for preclinical drug discovery and development that might be able to narrow the translation gap. This review discusses recent technological and methodological advancements and the use of these systems for hit discovery and the evaluation of toxicity, clearance, and absorption of lead compounds.

Navigating Through Cell-Based In vitro Models Available for Prediction of Intestinal Permeability and Metabolism: Are We Ready for 3D?

Traditionally, in vitro studies to quantify the intestinal permeability of drugs have relied on two-dimensional cell culture models using human colorectal carcinoma cell lines, namely Caco-2, HT 29 and T84 cells. Although these models have been commonly used for high-throughput screening of xenobiotics in preclinical studies, they do not fully recapitulate the morphology and functionality of enterocytes found in the human intestine in vivo. Efforts to improve the physiological and functional relevance of in vitro intestinal models have led to the development of enteroids/intestinal organoids and microphysiological systems. These models leverage advances in three-dimensional cell culture techniques and stem cell technology (in addition to microfluidics for microphysiological systems), to mimic the architecture and microenvironment of the in vivo intestine more accurately. In this commentary, we will discuss the advantages and limitations of these established and emerging intestinal models, as well as their current and potential future applications for the pre-clinical assessment of oral therapies.

HOPX+ injury-resistant intestinal stem cells drive epithelial recovery after severe intestinal ischemia

Intestinal ischemia is a life-threatening emergency with mortality rates of 50%-80% due to epithelial cell death and resultant barrier loss. Loss of the epithelial barrier occurs in conditions including intestinal volvulus and neonatal necrotizing enterocolitis. Survival depends on effective epithelial repair; crypt-based intestinal epithelial stem cells (ISCs) are the source of epithelial renewal in homeostasis and after injury. Two ISC populations have been described: 1) active ISC [aISC; highly proliferative; leucine-rich-repeat-containing G protein-coupled receptor 5 (LGR5⁺)-positive or sex-determining region Y-box 9 -antigen Ki67-positive (SOX9⁺Ki67⁺)] and 2) reserve ISC [rISC; less proliferative; homeodomain-only protein X positive (HOPX⁺)]. The contributions of these ISCs have been evaluated both in vivo and in vitro using a porcine model of mesenteric vascular occlusion to understand mechanisms that modulate ISC recovery responses following ischemic injury. In our previously published work, we observed that rISC conversion to an activated state was associated with decreased HOPX expression during in vitro recovery. In the present study, we wanted to evaluate the direct role of HOPX on cellular proliferation during recovery after injury. Our data demonstrated that during early in vivo recovery, injury-resistant HOPX⁺ cells maintain quiescence. Subsequent early regeneration within the intestinal crypt occurs around 2 days after injury, a period in which HOPX expression decreased. When HOPX was silenced in vitro, cellular proliferation of injured cells was promoted during recovery. This suggests that HOPX may serve a functional role in ISC-mediated regeneration after injury and could be a target to control ISC proliferation.NEW & NOTEWORTHY This paper supports that rISCs are resistant to ischemic injury and likely an important source of cellular renewal following near-complete epithelial loss. Furthermore, we have evidence that HOPX controls ISC activity state and may be a critical signaling pathway during ISC-mediated repair. Finally, we use multiple novel methods to evaluate ISCs in a translationally relevant large animal model of severe intestinal injury and provide evidence for the potential role of rISCs as therapeutic targets.

Biobanking of human gut organoids for translational research

The development of human organoid culture models has led to unprecedented opportunities to generate self-organizing, three-dimensional miniature organs that closely mimic in vivo conditions. The ability to expand, culture, and bank such organoids now provide researchers with the opportunity to generate next-generation living biobanks, which will substantially contribute to translational research in a wide range of areas, including drug discovery and testing, regenerative medicine as well as the development of a personalized treatment approach. However, compared to traditional tissue repositories, the generation of a living organoid biobank requires a much higher level of coordination, additional resources, and scientific expertise. In this short review, we discuss the opportunities and challenges associated with the generation of a living organoid biobank. Focusing on human intestinal organoids, we highlight some of the key aspects that need to be considered and provide an outlook for future development in this exciting field.

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.

Biomaterial-guided stem cell organoid engineering for modeling development and diseases

Organoids are miniature models of organs to recapitulate spatiotemporal cellular organization and tissue functionality. The production of organoids has revolutionized the field of developmental biology, providing the possibility to study and guide human development and diseases in a dish. More recently, novel biomaterial-based culture systems demonstrated the feasibility and versatility to engineer and produce the organoids in a consistent and reproducible manner. By engineering proper tissue microenvironment, functional organoids have been able to exhibit spatial-distinct tissue patterning and morphogenesis. This review focuses on enabling technologies in the field of organoid engineering, including the control of biochemical and biophysical cues via hydrogels, as well as size and geometry control via microwell and microfabrication techniques. In addition, this review discusses the enhancement of organoid systems for therapeutic applications using biofabrication and organoid-on-chip platforms, which facilitate the assembly of complex organoid systems for in vitro modeling of development and diseases. STATEMENT OF SIGNIFICANCE: Stem cell organoids have revolutionized the fields of developmental biology and tissue engineering, providing the opportunity to study human organ development and disease progression in vitro. Various works have demonstrated that organoids can be generated using a wide variety of engineering tools, materials, and systems. Specific culture microenvironment is tailored to support the formation, function, and physiology of the organ of interest. This review highlights the importance of cellular microenvironment in organoid culture, the versatility of organoid engineering techniques, and future perspectives to build better organoid systems.

Monolayer platform using human biopsy-derived duodenal organoids for pharmaceutical research

The human small intestine is the key organ for absorption, metabolism, and excretion of orally administered drugs. To preclinically predict these reactions in drug discovery research, a cell model that can precisely recapitulate the in vivo human intestinal monolayer is desired. In this study, we developed a monolayer platform using human biopsy-derived duodenal organoids for application to pharmacokinetic studies. The human duodenal organoid-derived monolayer was prepared by a simple method in 3-8 days. It consisted of polarized absorptive cells and had tight junctions. It showed much higher cytochrome P450 (CYP)3A4 and carboxylesterase (CES)2 activities than did the existing models (Caco-2 cells). It also showed efflux activity of P-glycoprotein (P-gp) and inducibility of CYP3A4. Finally, its gene expression profile was closer to the adult human duodenum, compared to the profile of Caco-2 cells. Based on these findings, this monolayer assay system using biopsy-derived human intestinal organoids is likely to be widely adopted.

The Gut-Brain Axis in Inflammatory Bowel Disease-Current and Future Perspectives

The gut–brain axis is a bidirectional communication system driven by neural, hormonal, metabolic, immunological, and microbial signals. Signaling events from the gut can modulate brain function and recent evidence suggests that the gut–brain axis may play a pivotal role in linking gastrointestinal and neurological diseases. Accordingly, accumulating evidence has suggested a link between inflammatory bowel diseases (IBDs) and neurodegenerative, as well as neuroinflammatory diseases. In this context, clinical, epidemiological and experimental data have demonstrated that IBD predisposes a person to pathologies of the central nervous system (CNS). Likewise, a number of neurological disorders are associated with changes in the intestinal environment, which are indicative for disease-mediated gut–brain inter-organ communication. Although this axis was identified more than 20 years ago, the sequence of events and underlying molecular mechanisms are poorly defined. The emergence of precision medicine has uncovered the need to take into account non-intestinal symptoms in the context of IBD that could offer the opportunity to tailor therapies to individual patients. The aim of this review is to highlight recent findings supporting the clinical and biological link between the gut and brain, as well as its clinical significance for IBD as well as neurodegeneration and neuroinflammation. Finally, we focus on novel human-specific preclinical models that will help uncover disease mechanisms to better understand and modulate the function of this complex system.

Synthetic scaffolds for 3D cell cultures and organoids: applications in regenerative medicine

Three-dimensional (3D) cell cultures offer an unparalleled platform to recreate spatial arrangements of cells in vitro. 3D cell culture systems have gained increasing interest due to their evident advantages in providing more physiologically relevant information and more predictive data compared to their two-dimensional (2D) counterpart. Design and well-established fabrication of organoids (a particular type of 3D cell culture system) are nowadays considered a pivotal achievement for their ability to replicate in vitro cytoarchitecture and the functionalities of an organ. In this condition, pluripotent stem cells self-organize into 3D structures mimicking the in vivo microenvironments, architectures and multi-lineage differentiation. Scaffolds are key supporting elements in these 3D constructs, and Matrigel is the most commonly used matrix despite its relevant translation limitations including animal-derived sources, non-defined composition, batch-to-batch variability and poorly tailorable properties. Alternatively, 3D synthetic scaffolds, including self-assembling peptides, show promising biocompatibility and biomimetic properties, and can be tailored on specific target tissue/cells. In this review, we discuss the recent advances on 3D cell culture systems and organoids, promising tools for tissue engineering and regenerative medicine applications. For this purpose, we will describe the current state-of-the-art on 3D cell culture systems and organoids based on currently available synthetic-based biomaterials (including tailored self-assembling peptides) either tested in in vivo animal models or developed in vitro with potential application in the field of tissue engineering, with the aim to inspire researchers to take on such promising platforms for clinical applications in the near future.

Resolving cell state in iPSC-derived human neural samples with multiplexed fluorescence imaging

Human induced pluripotent stem cell-derived (iPSC) neural cultures offer clinically relevant models of human diseases, including Amyotrophic Lateral Sclerosis, Alzheimer’s, and Autism Spectrum Disorder. In situ characterization of the spatial-temporal evolution of cell state in 3D culture and subsequent 2D dissociated culture models based on protein expression levels and localizations is essential to understanding neural cell differentiation, disease state phenotypes, and sample-to-sample variability. Here, we apply PRobe-based Imaging for Sequential Multiplexing (PRISM) to facilitate multiplexed imaging with facile, rapid exchange of imaging probes to analyze iPSC-derived cortical and motor neuron cultures that are relevant to psychiatric and neurodegenerative disease models, using over ten protein targets. Our approach permits analysis of cell differentiation, cell composition, and functional marker expression in complex stem-cell derived neural cultures. Furthermore, our approach is amenable to automation, offering in principle the ability to scale-up to dozens of protein targets and samples.

Tomov et al. utilize DNA-PRISM to allow for multiplexed imaging of cultured cells using antibodies modified with oligonucleotide probes. The differentiation of iPSCs to cortical and motor neurons is characterized in model cultures, relevant for use in disease research and drug screening.

In vitro models replicating the human intestinal epithelium for absorption and metabolism studies: A systematic review

Absorption, distribution, metabolism and excretion (ADME) studies represent a fundamental step in the early stages of drug discovery. In particular, the absorption of orally administered drugs, which occurs at the intestinal level, has gained attention since poor oral bioavailability often led to failures for new drug approval. In this context, several in vitro preclinical models have been recently developed and optimized to better resemble human physiology in the lab and serve as an animal alternative to accomplish the 3Rs principles. However, numerous models are ineffective in recapitulating the key features of the human small intestine epithelium and lack of prediction potential for drug absorption and metabolism during the preclinical stage. In this review, we provide an overview of in vitro models aimed at mimicking the intestinal barrier for pharmaceutical screening. After briefly describing how the human small intestine works, we present i) conventional 2D synthetic and cell-based systems, ii) 3D models replicating the main features of the intestinal architecture, iii) micro-physiological systems (MPSs) reproducing the dynamic stimuli to which cells are exposed in the native microenvironment. In this review, we will highlight the benefits and drawbacks of the leading intestinal models used for drug absorption and metabolism studies.

Impact of dietary fibers in infant formulas on gut microbiota and the intestinal immune barrier

Human milk (HM) is the gold standard for the nutrition of infants. An important component of HM is human milk oligosaccharides (hMOs), which play an important role in gut microbiota colonization and gut immune barrier establishment, and thereby contribute to the maturation of the immune system in early life. Guiding these processes is important as disturbances have life-long health effects and can lead to the development of allergic diseases. Unfortunately, not all infants can be exclusively fed with HM. These infants are routinely fed with infant formulas that contain hMO analogs and other non-digestible carbohydrates (NDCs) to mimic the effects of hMOs. Currently, the hMO analogs 2'-fucosyllactose (2'-FL), galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS), and pectins are added to infant formulas; however, these NDCs cannot mimic all hMO functions and therefore new NDCs and NDC mixtures need to become available for specific groups of neonates like preterm and disease-prone neonates. In this review, we discuss human data on the beneficial effects of infant formula supplements such as the specific hMO analog 2'-FL and NDCs as well as their mechanism of effects like stimulation of microbiota development, maturation of different parts of the gut immune barrier and anti-pathogenic effects. Insights into the structure-specific mechanisms by which hMOs and NDCs exert their beneficial functions might contribute to the development of new tailored NDCs and NDC mixtures. We also describe the needs for new in vitro systems that can be used for research on hMOs and NDCs. The current data suggest that "tailored infant formulas" for infants of different ages and healthy statuses are needed to ensure a healthy development of the microbiota and the gut immune system of infants.

Engineered Matrices Enable the Culture of Human Patient-Derived Intestinal Organoids

Human intestinal organoids from primary human tissues have the potential to revolutionize personalized medicine and preclinical gastrointestinal disease models. A tunable, fully defined, designer matrix, termed hyaluronan elastin-like protein (HELP) is reported, which enables the formation, differentiation, and passaging of adult primary tissue-derived, epithelial-only intestinal organoids. HELP enables the encapsulation of dissociated patient-derived cells, which then undergo proliferation and formation of enteroids, spherical structures with polarized internal lumens. After 12 rounds of passaging, enteroid growth in HELP materials is found to be statistically similar to that in animal-derived matrices. HELP materials also support the differentiation of human enteroids into mature intestinal cell subtypes. HELP matrices allow stiffness, stress relaxation rate, and integrin-ligand concentration to be independently and quantitatively specified, enabling fundamental studies of organoid-matrix interactions and potential patient-specific optimization. Organoid formation in HELP materials is most robust in gels with stiffer moduli (G' ≈ 1 kPa), slower stress relaxation rate (t1/2 ≈ 18 h), and higher integrin ligand concentration (0.5 × 10-3-1 × 10-3 m RGD peptide). This material provides a promising in vitro model for further understanding intestinal development and disease in humans and a reproducible, biodegradable, minimal matrix with no animal-derived products or synthetic polyethylene glycol for potential clinical translation.

Stem Cells for Next Level Toxicity Testing in the 21st Century

The call for a paradigm change in toxicology from the United States National Research Council in 2007 initiates awareness for the invention and use of human-relevant alternative methods for toxicological hazard assessment. Simple 2D in vitro systems may serve as first screening tools, however, recent developments infer the need for more complex, multicellular organotypic models, which are superior in mimicking the complexity of human organs. In this review article most critical organs for toxicity assessment, i.e., skin, brain, thyroid system, lung, heart, liver, kidney, and intestine are discussed with regards to their functions in health and disease. Embracing the manifold modes-of-action how xenobiotic compounds can interfere with physiological organ functions and cause toxicity, the need for translation of such multifaceted organ features into the dish seems obvious. Currently used in vitro methods for toxicological applications and ongoing developments not yet arrived in toxicity testing are discussed, especially highlighting the potential of models based on embryonic stem cells and induced pluripotent stem cells of human origin. Finally, the application of innovative technologies like organs-on-a-chip and genome editing point toward a toxicological paradigm change moves into action.

Current challenges and future perspectives in oral absorption research: An opinion of the UNGAP network

Although oral drug delivery is the preferred administration route and has been used for centuries, modern drug discovery and development pipelines challenge conventional formulation approaches and highlight the insufficient mechanistic understanding of processes critical to oral drug absorption. This review presents the opinion of UNGAP scientists on four key themes across the oral absorption landscape: (1) specific patient populations, (2) regional differences in the gastrointestinal tract, (3) advanced formulations and (4) food-drug interactions. The differences of oral absorption in pediatric and geriatric populations, the specific issues in colonic absorption, the formulation approaches for poorly water-soluble (small molecules) and poorly permeable (peptides, RNA etc.) drugs, as well as the vast realm of food effects, are some of the topics discussed in detail. The identified controversies and gaps in the current understanding of gastrointestinal absorption-related processes are used to create a roadmap for the future of oral drug absorption research.

Vinblastine treatment decreases the undifferentiated cell contamination of human iPSC-derived intestinal epithelial-like cells

Human induced pluripotent stem cell-derived intestinal epithelial cells (hiPSC-IECs) are expected to be utilized in regenerative medicine. To perform a safe transplantation without the risk of tumor formation, residual undifferentiated hiPSCs must be removed from hiPSC-IECs. In this study, we examined whether vinblastine (a multiple drug resistance 1 [MDR1] substrate) could remove residual undifferentiated hiPSCs in hiPSC-IECs and attempted to generate hiPSC-IECs applicable to transplantation medicine. We found that the expression levels of pluripotent markers were largely decreased and those of intestinal markers were increased by vinblastine treatment. The treatment of undifferentiated hiPSCs with vinblastine significantly decreased their viability. These results suggested that undifferentiated hiPSCs can be eliminated from hiPSC-IECs by vinblastine treatment. We hypothesized that MDR1-negative cells (such as undifferentiated hiPSCs) die upon vinblastine treatment because they are unable to excrete vinblastine. As expected, the cell viability of MDR1-knockout hiPSC-IECs was significantly decreased by vinblastine treatment. Furthermore, teratomas were formed by subcutaneous transplantation of hiPSC-IECs mixed with undifferentiated hiPSCs into mice, but they were not observed when the transplanted cells were pre-treated with vinblastine. Vinblastine-treated hiPSC-IECs would be an effective cell source for safe regenerative medicine.

Electromembrane Extraction and Mass Spectrometry for Liver Organoid Drug Metabolism Studies

Liver organoids are emerging tools for precision drug development and toxicity screening. We demonstrate that electromembrane extraction (EME) based on electrophoresis across an oil membrane is suited for segregating selected organoid-derived drug metabolites prior to mass spectrometry (MS)-based measurements. EME allowed drugs and drug metabolites to be separated from cell medium components (albumin, etc.) that could interfere with subsequent measurements. Multiwell EME (parallel-EME) holding 100 μL solutions allowed for simple and repeatable monitoring of heroin phase I metabolism kinetics. Organoid parallel-EME extracts were compatible with ultrahigh-performance liquid chromatography (UHPLC) used to separate the analytes prior to detection. Taken together, liver organoids are well-matched with EME followed by MS-based measurements.

Nanocomposite systems for precise oral delivery of drugs and biologics

Oral delivery is considered the favoured route of administration for both local and systemic delivery of active molecules. Formulation of drugs in conventional systems and nanoparticles has provided opportunities for targeting the gastrointestinal (GI) tract, increasing drug solubility and bioavailability. Despite the achievements of these delivery approaches, the development of a product with the ability of delivering drug molecules at a specific site and according to patients' needs remains a challenging endeavour. The complexity of the physicochemical properties of colloidal systems, their stability in different regions of the gastrointestinal tract, and interaction with the restrictive biological barriers hampered their success for oral precise medicine. To overcome these issues, nanoparticles have been combined with polymers to create hybrid nanosystems, namely nanocomposites. They offer enormous possibilities of structural and mechanical modifications to both nanoparticles and polymeric matrixes to generate systems with new properties, functions, and applications for oral delivery. In this review, nanocomposites' physicochemical and functional properties intended to target specific regions of the GI tract-oral cavity, stomach, small bowel, and colon-are analysed. In parallel, it is provided an insight in the nanocomposite solutions for oral delivery intended for systemic and local absorption, together with a focus on inflammatory bowel diseases (IBDs). Additional difficulties in managing IBD related to the alteration in the physiology of the intestine are described. Finally, future perspectives and opportunities for advancement in this field are discussed.

Extracellular Matrix Mechanical Properties and Regulation of the Intestinal Stem Cells: When Mechanics Control Fate

Intestinal stem cells (ISC) are crucial players in colon epithelium physiology. The accurate control of their auto-renewal, proliferation and differentiation capacities provides a constant flow of regeneration, maintaining the epithelial intestinal barrier integrity. Under stress conditions, colon epithelium homeostasis in disrupted, evolving towards pathologies such as inflammatory bowel diseases or colorectal cancer. A specific environment, namely the ISC niche constituted by the surrounding mesenchymal stem cells, the factors they secrete and the extracellular matrix (ECM), tightly controls ISC homeostasis. Colon ECM exerts physical constraint on the enclosed stem cells through peculiar topography, stiffness and deformability. However, little is known on the molecular and cellular events involved in ECM regulation of the ISC phenotype and fate. To address this question, combining accurately reproduced colon ECM mechanical parameters to primary ISC cultures such as organoids is an appropriated approach. Here, we review colon ECM physical properties at physiological and pathological states and their bioengineered in vitro reproduction applications to ISC studies.

The Past, Present and Future of Intestinal In Vitro Cell Systems for Drug Absorption Studies

The intestinal epithelium acts as a selective barrier for the absorption of water, nutrients and orally administered drugs. To evaluate the gastrointestinal permeability of a candidate molecule, scientists and drug developers have a multitude of cell culture models at their disposal. Static transwell cultures constitute the most extensively characterized intestinal in vitro system and can accurately categorize molecules into low, intermediate and high permeability compounds. However, they lack key aspects of intestinal physiology, including the cellular complexity of the intestinal epithelium, flow, mechanical strain, or interactions with intestinal mucus and microbes. To emulate these features, a variety of different culture paradigms, including microfluidic chips, organoids and intestinal slice cultures have been developed. Here, we provide an updated overview of intestinal in vitro cell culture systems and critically review their suitability for drug absorption studies. The available data show that these advanced culture models offer impressive possibilities for emulating intestinal complexity. However, there is a paucity of systematic absorption studies and benchmarking data and it remains unclear whether the increase in model complexity and costs translates into improved drug permeability predictions. In the absence of such data, conventional static transwell cultures remain the current gold-standard paradigm for drug absorption studies.