Drug Screening, Oral Bioavailability and Regulatory Aspects: A Need for Human Organoids

Comparative analysis of Caco-2 cells and human jejunal and duodenal enteroid-derived cells in gel- and membrane-based barrier models of intestinal permeability

Intestinal absorption is a key toxicokinetics parameter. Although the colon carcinoma cell line Caco-2 is the most used in vitro model to estimate human drug absorption, models representing other intestinal segments are available. We characterized the morphology, tissue-specific markers, and functionality of 3 human intestinal cell types: Caco-2, primary human enteroid-derived cells from jejunum (J2), and duodenum (D109) when cultured in the OrganoPlate 3-lane 40 microphysiological system (MPS) or static 24-well Transwells. In both conditions, J2 and D109 formed dome-like structures; Caco-2 formed uniform monolayers. In MPS, only Caco-2 formed tubules. Cells grown on Transwells formed a thicker monolayer. All cells and conditions exhibited expression of ZO-1 (tight junctions). Polarization markers Ezrin and Villin were highest in J2 and D109 in MPS, highest expression of Mucin was observed with J2. However, J2 and D109 exhibited poor barrier (70 kDa TRITC-dextran) in MPS, whereas robust barrier was recorded in Transwells. Barrier function and drug transport were evaluated using caffeine, indomethacin, and propranolol. The gel lane in MPS acted as a blockade; only a small fraction crossed, even without cells. The permeability ratios were used to parameterize the probabilistic compartmental absorption model to determine whether in vitro data could reduce uncertainty. The most accurate prediction of the fraction absorbed was achieved with Transwell-derived data from Caco-2, combined with the experimentally derived segment-specific absorption ratios. The impact of this study includes demonstration that enteroid-derived cells cultured in MPS show most physiological morphology, but that studies of drug permeability in this MPS are challenging.

Exploring organoid and assembloid technologies: a focus on retina and brain

BACKGROUND

The recent emergence of three-dimensional organoids and their utilization as in vitro disease models confirmed the complexities behind organ-specific functions and unravelled the importance of establishing suitable human models for various applications. Also, in light of persistent challenges associated with their use, researchers have been striving to establish more advanced structures (i.e. assembloids) that can help address the limitations presented in the current organoids.

METHODS

In this review, we discuss the distinct organoid types that are available to date, with a special focus on retinal and brain organoids, and highlight their importance in disease modelling.

RESULTS

We refer to published research to explore the extent to which retinal and brain organoids can serve as potential alternatives to organ/cell transplants and direct our attention to the topic of photostimulation in retinal organoids. Additionally, we discuss the advantages of incorporating microfluidics and organ-on-a-chip devices for boosting retinal organoid performance. The challenges of organoids leading to the subsequent development of assembloid fusion models are also presented.

CONCLUSION

In conclusion, organoid technology has laid the foundation for generating upgraded models that not only better replicate in vivo systems but also allow for a deeper comprehension of disease pathophysiology.

From gut to liver: organoids as platforms for next-generation toxicology assessment vehicles for xenobiotics

Traditional toxicological assessment relied heavily on 2D cell cultures and animal models of study, which were inadequate for the precise prediction of human response to chemicals. Researchers have now shifted focus on organoids for toxicological assessment. Organoids are 3D structures produced from stem cells that mimic the shape and functionality of human organs and have a number of advantages compared to traditional models of study. They have the capacity to replicate the intricate cellular microenvironment and in vivo interactions. They offer a physiologically pertinent platform that is useful for the researchers to monitor cellular responses in a more realistic manner and evaluate drug toxicity. Additionally, organoids can be created from cells unique to a patient, allowing for individualized toxicological research and providing understanding of the inter-individual heterogeneity in drug responses. Recent developments in the use of gut and liver organoids for assessment of the xenobiotics (environmental toxins and drugs) is reviewed in this article. Gut organoids can reveal potential damage to the digestive system and how xenobiotics affect nutrient absorption and barrier function. Liver is the primary site of detoxification and metabolism of xenobiotics, usually routed from the gut. Hence, these are linked and crucial for evaluating chemical or pollutant induced organ toxicity, forecasting their metabolism and pharmacokinetics. When incorporated into the drug development process, organoid models have the potential to improve the accuracy and efficiency of drug safety assessments, leading to safer and more effective treatments. We also discuss the limitations of using organoid-based toxicological assays, and future prospects, including the need for standardized protocols for overcoming reproducibility issues.

Opportunities of patient-derived organoids in drug development

Various model systems are utilised during drug development starting from basic research, moving to preclinical research and development for clinical applications in order to identify new drugs to improve human health. However, there are characteristics of humans that are not captured by established models. Such models include homogeneous two-dimensional (2D) cell lines, which lack cellular heterogeneity and physiological relevance, and species differences of animal models. Organoids can mitigate these differences by providing more physiologically relevant three-dimensional (3D) cell models that resemble the molecular state in healthy and pathological tissue. This review presents exemplary approaches using patient-derived organoids (PDOs) that have been developed and the new opportunities that are evolving in drug development with a focus on patient adult stem cell (ASC)-derived organoids. These demonstrate the potential of PDOs used alongside established cell and animal models to improve drug development from basic research to clinical applications such as personalised medicine.

Live-Cell Calcium Imaging in 3D Intestinal Organoids

Live-cell Ca2+ imaging is an important tool to detect activation of receptors by a putative ligand/drug and complements studies on transport processes, as intracellular Ca2+ changes provide direct evidence for substrate fluxes. Organoid-based systems offer numerous advantages over other in vitro systems such as cell lines, primary cells, or tissue explants, and in particular, intestinal organoid culture has revolutionized research on functional gastrointestinal processes. Calcium imaging using the fluorescent Ca2+ indicator Fura-2-AM can be applied to 3D intestinal organoids, which show an excellent dye-loading efficiency. Here we describe live-cell Ca2+ imaging in intestinal organoids, an important technique to improve research on malabsorption syndromes, secretory diarrhea, and metabolic disorders.

Current applications of intestinal organoids: a review

In the past decade, intestinal organoid technology has paved the way for reproducing tissue or organ morphogenesis during intestinal physiological processes in vitro and studying the pathogenesis of various intestinal diseases. Intestinal organoids are favored in drug screening due to their ability for high-throughput in vitro cultivation and their closer resemblance to patient genetic characteristics. Furthermore, as disease models, intestinal organoids find wide applications in screening diagnostic markers, identifying therapeutic targets, and exploring epigenetic mechanisms of diseases. Additionally, as a transplantable cellular system, organoids have played a significant role in the reconstruction of damaged epithelium in conditions such as ulcerative colitis and short bowel syndrome, as well as in intestinal material exchange and metabolic function restoration. The rise of interdisciplinary approaches, including organoid-on-chip technology, genome editing techniques, and microfluidics, has greatly accelerated the development of organoids. In this review, VOSviewer software is used to visualize hot co-cited journal and keywords trends of intestinal organoid firstly. Subsequently, we have summarized the current applications of intestinal organoid technology in disease modeling, drug screening, and regenerative medicine. This will deepen our understanding of intestinal organoids and further explore the physiological mechanisms of the intestine and drug development for intestinal diseases.

Intestinal Membrane Function in Inflammatory Bowel Disease

Inflammatory bowel disease is a set of chronic inflammatory diseases that mainly develop in the gastrointestinal mucosa, including ulcerative colitis and Crohn's disease. Gastrointestinal membrane permeability is an important factor influencing the pharmacological effects of pharmaceuticals administered orally for treating inflammatory bowel disease and other diseases. Understanding the presence or absence of changes in pharmacokinetic properties under a disease state facilitates effective pharmacotherapy. In this paper, we reviewed the gastrointestinal membrane function in ulcerative colitis and Crohn's disease from the perspective of in vitro membrane permeability and electrophysiological parameters. Information on in vivo permeability in humans is summarized. We also overviewed the inflammatory bowel disease research using gut-on-a-chip, in which some advances have recently been achieved. It is expected that these findings will be exploited for the development of therapeutic drugs for inflammatory bowel disease and the optimization of treatment options and regimens.

Advanced gut-on-chips for assessing carotenoid absorption, metabolism, and transport

Bioengineered strategies enable gut chips to faithfully replicate essential features of intestinal microsystems, encompassing geometric properties, peristalsis, intraluminal fluid flow, oxygen gradients, and the microbiome. This emerging technique serves as a powerful tool for nutrition studies by emulating the absorption and distribution processes in a manner highly relevant to human physiology. It offers unprecedented accessibility for investigating the mechanisms governing nutrition metabolism. While the application of gut-on-chip models in disease modeling and drug screening has been extensively explored, their potential in dietary nutrition research remains relatively unexplored. This comprehensive review provides an overview of the different approaches employed in constructing gut-on-chip platforms using diverse cell sources and niche mimics. Furthermore, it explores the applications and prospects of gut-on-chips in nutrition-related investigations, with a specific focus on carotenoid transport, absorption, and metabolism. Lastly, this review discusses the future development trajectory of this groundbreaking technology paradigm, highlighting its broad applicability in the field of food technology. By harnessing the capabilities of these state-of-the-art techniques within gut chip platforms, researchers can establish a robust scientific foundation for unraveling the intricate mechanisms that govern the behavior and functional properties of carotenoids.

The application of organ-on-chip models for the prediction of human pharmacokinetic profiles during drug development

Organ-on-chip (OoC) technology has led to in vitro models with many new possibilities compared to conventional in vitro and in vivo models. In this review, the potential of OoC models to improve the prediction of human oral bioavailability and intrinsic clearance is discussed, with a focus on the functionality of the models and the application in current drug development practice. Multi-OoC models demonstrating the application for pharmacokinetic (PK) studies are summarized and existing challenges are identified. Physiological parameters for a minimal viable platform of a multi-OoC model to study PK are provided, together with PK specific read-outs and recommendations for relevant reference compounds to validate the model. Finally, the translation to in vivo PK profiles is discussed, which will be required to routinely apply OoC models during drug development.

Magnetic resonance imaging and ultrasound elastography in the context of preclinical pharmacological research: significance for the 3R principles

The 3Rs principles-reduction, refinement, replacement-are at the core of preclinical research within drug discovery, which still relies to a great extent on the availability of models of disease in animals. Minimizing their distress, reducing their number as well as searching for means to replace them in experimental studies are constant objectives in this area. Due to its non-invasive character in vivo imaging supports these efforts by enabling repeated longitudinal assessments in each animal which serves as its own control, thereby enabling to reduce considerably the animal utilization in the experiments. The repetitive monitoring of pathology progression and the effects of therapy becomes feasible by assessment of quantitative biomarkers. Moreover, imaging has translational prospects by facilitating the comparison of studies performed in small rodents and humans. Also, learnings from the clinic may be potentially back-translated to preclinical settings and therefore contribute to refining animal investigations. By concentrating on activities around the application of magnetic resonance imaging (MRI) and ultrasound elastography to small rodent models of disease, we aim to illustrate how in vivo imaging contributes primarily to reduction and refinement in the context of pharmacological research.

A vascularized crypt-patterned colon model for high-throughput drug screening and disease modelling

The colon serves as a primary target for pharmaceutical compound screening and disease modelling. To better study colon diseases and develop treatments, engineered in vitro models with colon-specific physiological features are required. Existing colon models lack integration of colonic crypt structures with underlying perfusable vasculature, where vascular-epithelial crosstalk is affected by disease progression. We present a colon epithelium barrier model with vascularized crypts that recapitulates relevant cytokine gradients in both healthy and inflammatory conditions. Using our previously published IFlowPlate384 platform, we initially imprinted crypt topography and populated the patterned scaffold with colon cells. Proliferative colon cells spontaneously localized to the crypt niche and differentiated into epithelial barriers with a tight brush border. Toxicity of the colon cancer drug, capecitabine, was tested and showed a dose-dependent response and recovery from crypt-patterned colon epithelium exclusively. Perfusable microvasculature was then incorporated around the colon crypts followed by treatment with pro-inflammatory TNFα and IFNγ cytokines to simulate inflammatory bowel disease (IBD)-like conditions. We observed in vivo-like stromal basal-to-apical cytokine gradients in tissues with vascularized crypts and gradient reversals upon inflammation. Taken together, we demonstrated crypt topography integrated with underlying perfusable microvasculature has significant value for emulating colon physiology and in advanced disease modelling.

Experimental and computational models to investigate intestinal drug permeability and metabolism

Oral administration is the preferred route for drug administration that leads to better therapy compliance. The intestine plays a key role in the absorption and metabolism of oral drugs, therefore, new intestinal models are being continuously proposed, which contribute to the study of intestinal physiology, drug screening, drug side effects, and drug-drug interactions.Advances in pharmaceutical processes have produced more drug formulations, causing challenges for intestinal models. To adapt to the rapid evolution of pharmaceuticals, more intestinal models have been created. However, because of the complexity of the intestine, few models can take all aspects of the intestine into account, and some functions must be sacrificed to investigate other areas. Therefore, investigators need to choose appropriate models according to the experimental stage and other requirements to obtain the desired results.To help researchers achieve this goal, this review summarised the advantages and disadvantages of current commonly used intestinal models and discusses possible future directions, providing a better understanding of intestinal models.

Progress of research on tumor organoids: A bibliometric analysis of relevant publications from 2011 to 2021

Background

Research on tumor organoids has developed rapidly over the past 20 years, but a systematic analysis of current research trends is lacking. Researchers in the field need relevant references and knowledge of current research hot spots. Bibliometric analysis and visualization is a systematic method of acquiring an in-depth understanding of the status of research on tumor organoids.

Methods

CiteSpace, VOSviewer and the Bibliometric Online Analysis Platform from the Web of Science Core Collection were used to analyze and predict publishing trends and research hot spots worldwide in the field of tumor organoids.

Results

A total of 3,666 publications on tumor organoids were retrieved, and 2,939 eligible articles were included in the final analysis. The number of publications has grown significantly, with the United States of America as the leading country for research on tumor organoids. Among journals, Cancers published the largest number of articles. Harvard Medical School published the highest number of articles among all institutions. The Chinese Academy of Sciences was ranked highest among all contributing institutions on the importance of their publications. A trend in multi-disciplinary collaboration was observed in studies on tumor organoids. Keywords indicated that the current research largely concentrated on optimizing the construction of organoid models to use for medication development and screening in the clinical setting, and to provide patients with individualized treatment for gastric cancer and colorectal cancer, which are newly emerging research hotspots. Gastric and colorectal cancers were the top two tumors that have received increasing attention and have become the focal points of recent studies.

Conclusion

This study analyzed 2,939 publications covering the topic of tumor organoids. Although optimizing the construction of organoid models has always been a hot topic in this field, the application of tumor organoids to the development of medications and screenings will foster individualized treatment for patients, which is another emerging hot spot in this field of research.

Modeling mucus physiology and pathophysiology in human organs-on-chips

The surfaces of human internal organs are lined by a mucus layer that ensures symbiotic relationships with commensal microbiome while protecting against potentially injurious environmental chemicals, toxins, and pathogens, and disruption of this layer can contribute to disease development. Studying mucus biology has been challenging due to the lack of physiologically relevant human in vitro models. Here we review recent progress that has been made in the development of human organ-on-a-chip microfluidic culture models that reconstitute epithelial tissue barriers and physiologically relevant mucus layers with a focus on lung, colon, small intestine, cervix and vagina. These organ-on-a-chip models that incorporate dynamic fluid flow, air-liquid interfaces, and physiologically relevant mechanical cues can be used to study mucus composition, mechanics, and structure, as well as investigate its contributions to human health and disease with a level of biomimicry not possible in the past.

Unraveling the mystery of efficacy in Chinese medicine formula: New approaches and technologies for research on pharmacodynamic substances

Traditional Chinese medicine (TCM) is the key to unlock treasures of Chinese civilization. TCM and its compound play a beneficial role in medical activities to cure diseases, especially in major public health events such as novel coronavirus epidemics across the globe. The chemical composition in Chinese medicine formula is complex and diverse, but their effective substances resemble "mystery boxes". Revealing their active ingredients and their mechanisms of action has become focal point and difficulty of research for herbalists. Although the existing research methods are numerous and constantly updated iteratively, there is remain a lack of prospective reviews. Hence, this paper provides a comprehensive account of existing new approaches and technologies based on previous studies with an in vitro to in vivo perspective. In addition, the bottlenecks of studies on Chinese medicine formula effective substances are also revealed. Especially, we look ahead to new perspectives, technologies and applications for its future development. This work reviews based on new perspectives to open horizons for the future research. Consequently, herbal compounding pharmaceutical substances study should carry on the essence of TCM while pursuing innovations in the field.