Crypt-Villus Scaffold Architecture for Bioengineering Functional Human Intestinal Epithelium

An Array of Carbon Nanofiber Bundle_Based 3D In Vitro Intestinal Microvilli for Mimicking Functional and Physical Activities of the Small Intestine

Researchers have developed in vitro small intestine models of biomimicking microvilli, such as gut-on-a-chip devices. However, fabrication methods developed to date for 2D and 3D in vitro gut still have unsolved limitations. In this study, an innovative fabrication method of a 3D in vitro gut model is introduced for effective drug screening. The villus is formed on a patterned carbon nanofiber (CNF) bundle as a flexible and biocompatible scaffold. Mechanical properties of the fabricated villi structure are investigates. A microfluidic system is applied to induce the movement of CNFs villi. F-actin and Occludin staining of Caco-2 cells on a 2D flat-chip as a control and a 3D gut-chip with or without fluidic stress is observed. A permeability test of FD20 is performed. The proposed 3D gut-chip with fluidic stress achieve the highest value of Papp. Mechano-active stimuli caused by distinct structural and movement effects of CNFs villi as well as stiffness of the suggested CNFs villi not only can help accelerate cell differentiation but also can improve permeability. The proposed 3D gut-chip system further strengthens the potential of the platform to increase the accuracy of various drug tests.

Perfused In Vitro Intestine Tissue Model to Evaluate the Role of Stromal and Immune Cells in Epithelial Response to Inflammatory Cues and Drug Therapies

We establish an in vitro perfusion intestinal tissue bioreactor system tailored to study drug responses related to inflammatory bowel disease (IBD). The system includes key components including multiple human intestinal cell types (colonoids, myofibroblasts, and macrophages), a three-dimensional (3D) intestinal architecture, and fluid flow. Inclusion of myofibroblasts resulted in increased secretion of cytokines such as glypican-1 (GCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin 1-α (IL-1α), whereas inclusion of macrophages resulted in increased secretion of monocyte chemoattractant proteins (MCPs) demonstrating a significant role of both stromal and immune cell types in intestinal inflammation. The system is responsive to drug treatments, as reflected in the reduction of pro-inflammatory cytokine production in tissue in some treatment scenarios. While future studies are needed to evaluate more nuanced responses in an IBD context, the present study demonstrates the ability to establish a 3D intestinal model with multiple relevant cell types and flow that is responsive to both inflammatory cues and various drug treatment options.

A novel membrane-on-chip guides morphogenesis for the reconstruction of the intestinal crypt-villus axis

Reconstructing the microscale villous organisation and functionality of the small intestine is essential for developingin vitroplatforms tailored for absorption studies as well as for investigating intestinal morphogenesis in development and disease. However, the current fabrication techniques able to mimic the villus-crypt axis poses significant challenges in terms of reconstruction of the complex 3D microarchitecture. These challenges extend beyond mere structural intricacies to encompass the incorporation of diverse cell types and the management of intricate fluid dynamics within the system. Here, we introduce a novel microfluidic device calledIn-Crypts, which integrates a cell-instructive membrane aimed at inducing and guiding Caco-2 cells morphogenesis. Patterned topographical cues embossed onto the porous membrane induce the formation of a well-organized intestinal epithelium, characterized by proliferating crypt-like domains and differentiated villus-like regions. Notably, our cell-instructive porous membrane effectively sustains stem cells development, faithfully replicating the niche environment ofin vivointestinal crypts thus mirroring the cell biogeography observedin vivo. Moreover, by introducing dynamic fluid flow, we provide a faithful recapitulation of the native microenvironmental shear stress experienced by the intestinal epithelium. This stress plays a crucial role in influencing cell behaviour, differentiation, and overall functionality, thus offering a highly realistic model for studying intestinal physiology and pathology. The resulting intestinal epithelium exhibits significantly denser regions of mucus and microvilli, characteristic typically absent in static cultures, upregulating more than 1.5 of the amount expressed in the classical flattened configuration, enhanced epithelial cell differentiation and increased adsorptive surface area. Hence, the innovative design ofIn-Cryptsproves the critical role of employing a cell-instructive membrane in argument the physiological relevance of organs-on-chips. This aspect, among others, will contribute to a more comprehensive understanding of organism function, directly impacting drug discovery and development.

Bioengineered Silk Protein-Based 3D In Vitro Models for Tissue Engineering and Drug Development: From Silk Matrix Properties to Biomedical Applications

3D in vitro model has emerged as a valuable tool for studying tissue development, drug screening, and disease modeling. 3D systems can accurately replicate tissue microstructures and physiological features, mirroring the in vivo microenvironment departing from conventional 2D cell cultures. Various 3D in vitro models utilizing biomacromolecules like collagen and synthetic polymers have been developed to meet diverse research needs and address the complex challenges of contemporary research. Silk proteins, bearing structural and functional similarities to collagen, have been increasingly employed to construct advanced 3D in vitro systems, surpassing the limitations of 2D cultures. This review examines silk proteins' composition, structure, properties, and functions, elucidating their role in 3D in vitro models. Furthermore, recent advances in biomedical applications involving silk-based organoid models are discussed. In particular, the unique physiological attributes of silk matrix constituents in in vitro tissue constructs are highlighted, providing a meticulous evaluation of their importance. Additionally, it outlines the current research hurdles and complexities while contemplating future avenues, thereby paving the way for developing complex and biomimetic silk protein-based microtissues.

3D embedded bioprinting of large-scale intestine with complex structural organization and blood capillaries

Accurate reproduction of human intestinal structure and functionin vitrois of great significance for understanding the development and disease occurrence of the gut. However, mostin vitrostudies are often confined to 2D models, 2.5D organ chips or 3D organoids, which cannot fully recapitulate the tissue architecture, microenvironment and cell compartmentalization foundin vivo. Herein, a centimeter-scale intestine tissue that contains intestinal features, such as hollow tubular structure, capillaries and tightly connected epithelium with invivo-likering folds, crypt-villi, and microvilli is constructed by 3D embedding bioprinting. In our strategy, a novel photocurable bioink composed of methacrylated gelatin, methacrylated sodium alginate and poly (ethylene glycol) diacrylate is developed for the fabrication of intestinal model. The Caco-2 cells implanted in the lumen are induced by the topological structures of the model to derive microvilli, crypt-villi, and tight junctions, simulating the intestinal epithelial barrier. The human umbilical vein endothelial cells encapsulated within the model gradually form microvessels, mimicking the dense capillary network in the intestine. This intestine-like tissue, which closely resembles the structure and cell arrangement of the human gut, can act as a platform to predict the therapeutic and toxic side effects of new drugs on the intestine.

Effect of Porosity on the Colonization of Digital Light-Processed 3D Hydrogel Constructs toward the Development of a Functional Intestinal Model

With the rapid increase of the number of patients with gastrointestinal diseases in modern society, the need for the development of physiologically relevant in vitro intestinal models is key to improve the understanding of intestinal dysfunctions. This involves the development of a scaffold material exhibiting physiological stiffness and anatomical mimicry of the intestinal architecture. The current work focuses on evaluating the scaffold micromorphology of gelatin-methacryloyl-aminoethyl-methacrylate-based nonporous and porous intestinal 3D, intestine-like constructs, fabricated via digital light processing, on the cellular response. To this end, Caco-2 intestinal cells were utilized in combination with the constructs. Both porous and nonporous constructs promoted cell growth and differentiation toward enterocyte-like cells (VIL1, ALPI, SI, and OCLD expression showed via qPCR, ZO-1 via immunostaining). The porous constructs outperformed the nonporous ones regarding cell seeding efficiency and growth rate, confirmed by MTS assay, live/dead staining, and TEER measurements, due to the presence of surface roughness.

Animal and In Vitro Models as Powerful Tools to Decipher the Effects of Enteric Pathogens on the Human Gut Microbiota

Examining the interplay between intestinal pathogens and the gut microbiota is crucial to fully comprehend the pathogenic role of enteropathogens and their broader impact on human health. Valid alternatives to human studies have been introduced in laboratory practice to evaluate the effects of infectious agents on the gut microbiota, thereby exploring their translational implications in intestinal functionality and overall health. Different animal species are currently used as valuable models for intestinal infections. In addition, considering the recent advances in bioengineering, futuristic in vitro models resembling the intestinal environment are also available for this purpose. In this review, the impact of the main human enteropathogens (i.e., Clostridioides difficile, Campylobacter jejuni, diarrheagenic Escherichia coli, non-typhoidal Salmonella enterica, Shigella flexneri and Shigella sonnei, Vibrio cholerae, and Bacillus cereus) on intestinal microbial communities is summarized, with specific emphasis on results derived from investigations employing animal and in vitro models.

Challenges in Permeability Assessment for Oral Drug Product Development

Drug permeation across the intestinal epithelium is a prerequisite for successful oral drug delivery. The increased interest in oral administration of peptides, as well as poorly soluble and poorly permeable compounds such as drugs for targeted protein degradation, have made permeability a key parameter in oral drug product development. This review describes the various in vitro, in silico and in vivo methodologies that are applied to determine drug permeability in the human gastrointestinal tract and identifies how they are applied in the different stages of drug development. The various methods used to predict, estimate or measure permeability values, ranging from in silico and in vitro methods all the way to studies in animals and humans, are discussed with regard to their advantages, limitations and applications. A special focus is put on novel techniques such as computational approaches, gut-on-chip models and human tissue-based models, where significant progress has been made in the last few years. In addition, the impact of permeability estimations on PK predictions in PBPK modeling, the degree to which excipients can affect drug permeability in clinical studies and the requirements for colonic drug absorption are addressed.

Bio-Microfabrication of 2D and 3D Biomimetic Gut-on-a-Chip

Traditional goal of microfabrication was to limitedly construct nano- and micro-geometries on silicon or quartz wafers using various semiconductor manufacturing technologies, such as photolithography, soft lithography, etching, deposition, and so on. However, recent integration with biotechnologies has led to a wide expansion of microfabrication. In particular, many researchers studying pharmacology and pathology are very interested in producing in vitro models that mimic the actual intestine to study the effectiveness of new drug testing and interactions between organs. Various bio-microfabrication techniques have been developed while solving inherent problems when developing in vitro micromodels that mimic the real large intestine. This intensive review introduces various bio-microfabrication techniques that have been used, until recently, to realize two-dimensional and three-dimensional biomimetic experimental models. Regarding the topic of gut chips, two major review subtopics and two-dimensional and three-dimensional gut chips were employed, focusing on the membrane-based manufacturing process for two-dimensional gut chips and the scaffold-based manufacturing process for three-dimensional gut chips, respectively.

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.