A human intestinal M-cell-like model for investigating particle, antigen and microorganism translocation

Utility of human induced pluripotent stem cell-derived small intestinal epithelial cells for pharmacokinetic, toxicological, and immunological studies

The small intestine, which plays a crucial role in the absorption and metabolism of drugs and foods, serves as a target organ for drug-induced toxicity and immune interactions with functional foods and intestinal bacteria. Current alternative models of the human small intestine, such as Caco-2 cells and experimental animals, have limitations due to variations in the expression levels of metabolic enzymes, transporters, and receptors. This study presents investigations into the utility of human induced pluripotent stem cell-derived small intestinal epithelial cells (hiSIECs) for pharmacokinetic, toxicological, and immunological studies, respectively. While hiSIECs displayed small intestinal epithelial cell characteristics and barrier function, they demonstrated pharmacokinetic properties such as cytochrome P450 3A4/5 activity equivalent to human primary enterocytes and stable P-glycoprotein activity. These cells also demonstrated potential for assessing two forms of intestinal toxicity caused by anticancer drugs and gamma-secretase inhibitors, displaying immune responses mediated by toll-like and fatty acid receptors while serving as an inflammatory gut model through the addition of tumor necrosis factor alpha and interferon gamma. Overall, hiSIECs hold promise as an in vitro model for assessing pharmacokinetics, toxicity, and effects on the intestinal immunity of pharmaceuticals, functional foods, supplements, and intestinal bacteria.

Enhancement of Oral Bioavailability of Protein and Peptide by Polysaccharide-based Nanoparticles

Oral drug delivery is a prevalent and cost-effective method due to its advantages, such as increased drug absorption surface area and improved patient compliance. However, delivering proteins and peptides orally remains a challenge due to their vulnerability to degradation by digestive enzymes, stomach acids, and limited intestinal membrane permeability, resulting in poor bioavailability. The use of nanotechnology has emerged as a promising solution to enhance the bioavailability of these vital therapeutic agents. Polymeric NPs, made from natural or synthetic polymers, are commonly used. Natural polysaccharides, such as alginate, chitosan, dextran, starch, pectin, etc., have gained preference due to their biodegradability, biocompatibility, and versatility in encapsulating various drug types. Their hydrophobic-hydrophilic properties can be tailored to suit different drug molecules.

Recent Advances in Cell-Based In Vitro Models to Recreate Human Intestinal Inflammation

Inflammatory bowel disease causes a major burden to patients and healthcare systems, raising the need to develop effective therapies. Technological advances in cell culture, allied with ethical issues, have propelled in vitro models as essential tools to study disease aetiology, its progression, and possible therapies. Several cell-based in vitro models of intestinal inflammation have been used, varying in their complexity and methodology to induce inflammation. Immortalized cell lines are extensively used due to their long-term survival, in contrast to primary cultures that are short-lived but patient-specific. Recently, organoids and organ-chips have demonstrated great potential by being physiologically more relevant. This review aims to shed light on the intricate nature of intestinal inflammation and cover recent works that report cell-based in vitro models of human intestinal inflammation, encompassing diverse approaches and outcomes.

Biocompatible smart micro/nanorobots for active gastrointestinal tract drug delivery

INTRODUCTION

Oral delivery is the most commonly used route of drug administration owing to good patient compliance. However, the gastrointestinal (GI) tract contains multiple physiological barriers that limit the absorption efficiency of conventional passive delivery systems resulting in a low drug concentration reaching the diseased sites. Micro/nanorobots can convert energy to self-propulsive force, providing a novel platform to actively overcome GI tract barriers for noninvasive drug delivery and treatment.

AREAS COVERED

In this review, we first describe the microenvironments and barriers in the different compartments of the GI tract. Afterward, the applications of micro/nanorobots to overcome GI tract barriers for active drug delivery are highlighted and discussed. Finally, we summarize and discuss the challenges and future prospects of micro/nanorobots for further clinical applications.

EXPERT OPINION

Micro/nanorobots with the ability to autonomously propel themselves and to load, transport, and release payloads on demand are ideal carriers for active oral drug delivery. Although there are many challenges to be addressed, micro/nanorobots have great potential to introduce a new era of drug delivery for precision therapy.

The Diagnostic Potential of the Human Blood Microbiome: Are We Dreaming or Awake?

Human blood has historically been considered a sterile environment. Recently, a thriving microbiome dominated by Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes phyla was detected in healthy blood. The localization of these microbes is restricted to some blood cell populations, particularly the peripheral blood mononuclear cells and erythrocytes. It was hypothesized that the blood microbiome originates from the skin-oral-gut axis. In addition, many studies have evaluated the potential of blood microbiome dysbiosis as a prognostic marker in cardiovascular diseases, cirrhosis, severe liver fibrosis, severe acute pancreatitis, type 2 diabetes, and chronic kidney diseases. The present review aims to summarize current findings and most recent evidence in the field.

Alginate-Based Oral Delivery Systems to Enhance Protection, Release, and Absorption of Catalase

Oxidative stress, overproduction of reactive oxygen species (ROS), plays an important role in the development of inflammatory bowel diseases. Catalase has great therapeutic potential by scavenging hydrogen peroxide, one of the ROSs produced in cellular metabolisms. However, in vivo application to scavenge ROS is currently limited especially in oral administrations. Here, we introduced an alginate-based oral drug delivery system that effectively protected catalase from the simulated harsh conditions of the gastrointestinal (GI) tract, released it in the small intestine mimicked condition, and enhanced its absorption via M cells, highly specialized epithelium cells in the small intestine. First of all, catalase was encapsulated in alginate-based microparticles with different amounts of polygalacturonic acid or pectin, which achieved an encapsulation efficiency of more than 90%. It was further shown that catalase was released from alginate-based microparticles in a pH-dependent manner. Results indicated that alginate-polygalacturonic acid microparticles (60 wt % Alg:40 wt % Gal) released 79.5 ± 2.4% of encapsulated catalase at pH 9.1 in 3 h, while they only released 9.2 ± 1.5% of encapsulated catalase at pH 2.0. Even when catalase was encapsulated in microparticles (60 wt % Alg:40 wt % Gal) and exposed to pH 2.0 followed by pH 9.1, it still retained 81.0 ± 11.3% enzyme activity compared to that in microparticles prior to the pH treatment. We then investigated the efficiency of RGD conjugation to catalase on the catalase uptake by M-like cells, the coculturing of human epithelial colorectal adenocarcinoma; Caco-2 cells and B lymphocyte; Raji cells. RGD-catalase protected M-cells more efficiently from the cytotoxicity of H₂O₂, a typical ROS. RGD conjugation to catalase enhanced the uptake by M-cells with 87.6 ± 0.8% RGD-catalase, whereas 11.5 ± 9.2% of RGD-free catalase passed across M-cells. From the results of protection, release, and absorption of model therapeutic proteins from the harsh pH conditions, alginate-based oral drug delivery systems will have numerous applications for the controlled release of drugs that are easily degradable in the GI tract.

Functional assays to evaluate antibody-mediated responses against Shigella: a review

Shigella is a major global pathogen and the etiological agent of shigellosis, a diarrheal disease that primarily affects low- and middle-income countries. Shigellosis is characterized by a complex, multistep pathogenesis during which bacteria use multiple invasion proteins to manipulate and invade the intestinal epithelium. Antibodies, especially against the O-antigen and some invasion proteins, play a protective role as titres against specific antigens inversely correlate with disease severity; however, the context of antibody action during pathogenesis remains to be elucidated, especially with Shigella being mostly an intracellular pathogen. In the absence of a correlate of protection, functional assays rebuilding salient moments of Shigella pathogenesis can improve our understanding of the role of protective antibodies in blocking infection and disease. In vitro assays are important tools to build correlates of protection. Only recently animal models to recapitulate human pathogenesis, often not in full, have been established. This review aims to discuss in vitro assays to evaluate the functionality of anti-Shigella antibodies in polyclonal sera in light of the multistep and multifaced Shigella infection process. Indeed, measurement of antibody level alone may limit the evaluation of full vaccine potential. Serum bactericidal assay (SBA), and other functional assays such as opsonophagocytic killing assays (OPKA), and adhesion/invasion inhibition assays (AIA), are instead physiologically relevant and may provide important information regarding the role played by these effector mechanisms in protective immunity. Ultimately, the review aims at providing scientists in the field with new points of view regarding the significance of functional assays of choice which may be more representative of immune-mediated protection mechanisms.

Twin-bioengine self-adaptive micro/nanorobots using enzyme actuation and macrophage relay for gastrointestinal inflammation therapy

A wide array of biocompatible micro/nanorobots are designed for targeted drug delivery and precision therapy largely depending on their self-adaptive ability overcoming complex barriers in vivo. Here, we report a twin-bioengine yeast micro/nanorobot (TBY-robot) with self-propelling and self-adaptive capabilities that can autonomously navigate to inflamed sites for gastrointestinal inflammation therapy via enzyme-macrophage switching (EMS). Asymmetrical TBY-robots effectively penetrated the mucus barrier and notably enhanced their intestinal retention using a dual enzyme-driven engine toward enteral glucose gradient. Thereafter, the TBY-robot was transferred to Peyer's patch, where the enzyme-driven engine switched in situ to macrophage bioengine and was subsequently relayed to inflamed sites along a chemokine gradient. Encouragingly, EMS-based delivery increased drug accumulation at the diseased site by approximately 1000-fold, markedly attenuating inflammation and ameliorating disease pathology in mouse models of colitis and gastric ulcers. These self-adaptive TBY-robots represent a safe and promising strategy for the precision treatment of gastrointestinal inflammation and other inflammatory diseases.

Cellular Uptake and Transport Mechanism of 6-Mercaptopurine Nanomedicines for Enhanced Oral Bioavailability

Background

Nanomedicines have significant advantages in enhancing the oral bioavailability of drugs, but a deeper understanding of the underlying mechanisms remains to be interpreted. Hence, the present study aims to explain the uptake and trafficking mechanism for 6-MP nanomedicines we previously constructed.

Methods

6-MP loaded poly(lactide-co-glycolide) (PLGA) nanomedicines (6-MPNs) were prepared by the multiple emulsion method. The transcytosis mechanism of 6-MPNs was investigated in Caco-2 cells, Caco-2 monolayers, follicle associated epithelium (FAE) monolayers and rats, including transmembrane pathway, intracellular trafficking, paracellular transport and the involvement of transporter.

Results

Pharmacokinetics in rats showed that the area under the curve (AUC) of 6-MP in the 6-MPNs group (147.3 ± 42.89 μg/L·h) was significantly higher than that in the 6-MP suspensions (6-MPCs) group (70.31 ± 18.24 μg/L·h). The uptake of 6-MPNs in Caco-2 cells was time-, concentration- and energy-dependent. The endocytosis of intact 6-MPNs was mediated mainly through caveolae/lipid raft, caveolin and micropinocytosis. The intracellular trafficking of 6-MPNs was affected by endoplasmic reticulum (ER)-Golgi complexes, late endosome-lysosome and microtubules. The multidrug resistance associated protein 4 (MRP4) transporter-mediated transport of free 6-MP played a vital role on the transmembrane of 6-MPNs. The trafficking of 6-MPNs from the apical (AP) side to the basolateral (BL) side in Caco-2 monolayers was obviously improved. Besides, 6-MPNs affected the distribution and expression of zona occludens-1 (ZO-1). The transport of 6-MPNs in FAE monolayers was concentration- and energy-dependent, while reaching saturation over time. 6-MPNs improved the absorption of the intestinal Peyer's patches (PPs) in rats.

Conclusion

6-MPNs improve the oral bioavailability through multiple pathways, including active transport, paracellular transport, lymphatic delivery and MRP4 transporter. The findings of current study may shed light on the cellular uptake and transcellular trafficking mechanism of oral nanomedicines.

Capturing and Quantifying Particle Transcytosis with Microphysiological Intestine-on-Chip Models

Understanding the intestinal transport of particles is critical in several fields ranging from optimizing drug delivery systems to capturing health risks from the increased presence of nano- and micro-sized particles in human environment. While Caco-2 cell monolayers grown on permeable supports are the traditional in vitro model used to probe intestinal absorption of dissolved molecules, they fail to recapitulate the transcytotic activity of polarized enterocytes. Here, an intestine-on-chip model is combined with in silico modeling to demonstrate that the rate of particle transcytosis is ≈350× higher across Caco-2 cell monolayers exposed to fluid shear stress compared to Caco-2 cells in standard "static" configuration. This relates to profound phenotypical alterations and highly polarized state of cells grown under mechanical stimulation and it is shown that transcytosis in the microphysiological model is energy-dependent and involves both clathrin and macropinocytosis mediated endocytic pathways. Finally, it is demonstrated that the increased rate of transcytosis through cells exposed to flow is explained by a higher rate of internal particle transport (i.e., vesicular cellular trafficking and basolateral exocytosis), rather than a change in apical uptake (i.e., binding and endocytosis). Taken together, the findings have important implications for addressing research questions concerning intestinal transport of engineered and environmental particles.

In vitro and in vivo implications of rationally designed bromelain laden core-shell hybrid solid lipid nanoparticles for oral administration in thrombosis management

Bromelain, a dietary supplement of cysteine protease family having promising results against thrombosis, is gaining attention. Yet poor mechanical stability, gastric instability, high oral dose and poor patient compliance restricted its clinical application. Therefore, acid stable bromelain loaded hybrid solid lipid nanoparticles (Br-HNPs) were fabricated and characterized for their contribution to in-vivo stability and therapeutic efficacy in thrombosis management. Comprehensive optimization of various process and formulation variables ensued the formation of nano-sized (120.56 ± 40.12 nm) Br-HNPs with entrapment efficiency of 86.32 ± 5.56%. Spherical core shell framework of Br-HNPs prolonged drug release and provided in-vivo and storage stability at room temperature. Br-HNPs significantly inhibited platelet aggregation without affecting bleeding time and dissolved thrombus at 1.91-fold higher efficacy compared to bromelain. Furthermore, Br-HNPs prevented hypercoagulation states and suppressed cytokines production significantly (P < .05) contributing to its antiplatelet activity. These findings indicated that Br-HNPs could serve as a promising alternative to commercial therapies for management of thrombotic disorders.

Engineered Nanoparticles inside a Microparticle Oral System for Enhanced Mucosal and Systemic Immunity

Antigen delivery through an oral route requires overcoming multiple challenges, including gastrointestinal enzymes, mucus, and epithelial tight junctions. Although each barrier has a crucial role in determining the final efficiency of the oral vaccination, transcytosis of antigens through follicle-associated epithelium (FAE) represents a major challenge. Most of the research is focused on delivering an antigen to the M-cell for FAE transcytosis because M-cells can easily transport the antigen from the luminal site. However, the fact is that the M-cell population is less than 1% of the total gastrointestinal cells, and most of the oral vaccines have failed to show any effect in clinical trials. To challenge the current dogma of M-cell targeting, in this study, we designed a novel tandem peptide with a FAE-targeting peptide at the front position and a cell-penetrating peptide at the back position. The tandem peptide was attached to a smart delivery system, which overcomes the enzymatic barrier and the mucosal barrier. The result showed that the engineered system could target the FAE (enterocytes and M-cells) and successfully penetrate the enterocytes to reach the dendritic cells located at the subepithelium dome. There was successful maturation and activation of dendritic cells in vitro confirmed by a significant increase in maturation markers such as CD40, CD86, presentation marker MHC I, and proinflammatory cytokines (TNF-α, IL-6, and IL-10). The in vivo results showed a high production of CD4+ T-lymphocytes (helper T-cell) and a significantly higher production of CD8+ T-lymphocytes (killer T-cell). Finally, the production of mucosal immunity (IgA) in the trachea, intestine, and fecal extracts and systemic immunity (IgG, IgG1, and IgG2a) was successfully confirmed. To the best of our knowledge, this is the first study that designed a novel tandem peptide to target the FAE, which includes M-cells and enterocytes rather than M-cell targeting and showed that a significant induction of both the mucosal and systemic immune response was achieved compared to M-cell targeting.

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.

Best practices in current models mimicking drug permeability in the gastrointestinal tract - an UNGAP review

The absorption of orally administered drug products is a complex, dynamic process, dependent on a range of biopharmaceutical properties; notably the aqueous solubility of a molecule, stability within the gastrointestinal tract (GIT) and permeability. From a regulatory perspective, the concept of high intestinal permeability is intrinsically linked to the fraction of the oral dose absorbed. The relationship between permeability and the extent of absorption means that experimental models of permeability have regularly been used as a surrogate measure to estimate the fraction absorbed. Accurate assessment of a molecule's intestinal permeability is of critical importance during the pharmaceutical development process of oral drug products, and the current review provides a critique of in vivo, in vitro and ex vivo approaches. The usefulness of in silico models to predict drug permeability is also discussed and an overview of solvent systems used in permeability assessments is provided. Studies of drug absorption in humans are an indirect indicator of intestinal permeability, but in vitro and ex vivo tools provide initial screening approaches are important tools for direct assessment of permeability in drug development. Continued refinement of the accuracy of in silico approaches and their validation with human in vivo data will facilitate more efficient characterisation of permeability earlier in the drug development process and will provide useful inputs for integrated, end-to-end absorption modelling.

An update on oral drug delivery via intestinal lymphatic transport

Orally administered drug entities have to survive the harsh gastrointestinal environment, penetrate the enteric epithelia and circumvent hepatic metabolism before reaching the systemic circulation. Whereas the gastrointestinal stability can be well maintained by taking proper measures, hepatic metabolism presents as a formidable barrier to drugs suffering from first-pass metabolism. The pharmaceutical academia and industries are seeking alternative pathways for drug transport to circumvent problems associated with the portal pathway. Intestinal lymphatic transport is emerging as a promising pathway to this end. In this review, we intend to provide an updated overview on the rationale, strategies, factors and applications involved in intestinal lymphatic transport. There are mainly two pathways for peroral lymphatic transport-the chylomicron and the microfold cell pathways. The underlying mechanisms are being unraveled gradually and nowadays witness increasing research input and applications.

An overview of in vitro, ex vivo and in vivo models for studying the transport of drugs across intestinal barriers

Oral administration is the most commonly used route for drug delivery owing to its cost-effectiveness, ease of administration, and high patient compliance. However, the absorption of orally delivered compounds is a complex process that greatly depends on the interplay between the characteristics of the drug/formulation and the gastrointestinal tract. In this contribution, we review the different preclinical models (in vitro, ex vivo and in vivo) from their development to application for studying the transport of drugs across intestinal barriers. This review also discusses the advantages and disadvantages of each model. Furthermore, the authors have reviewed the selection and validation of these models and how the limitations of the models can be addressed in future investigations. The correlation and predictability of the intestinal transport data from the preclinical models and human data are also explored. With the increasing popularity and prevalence of orally delivered drugs/formulations, sophisticated preclinical models with higher predictive capacity for absorption of oral formulations used in clinical studies will be needed.

Cellular Uptake Pathways of Nanoparticles: Process of Endocytosis and Factors Affecting Their Fate

BACKGROUND

Efficient and controlled internalization of NPs into the cells depends on their physicochemical properties and dynamics of the plasma membrane. NPs-cell interaction is a complex process that decides the fate of NPs internalization through different endocytosis pathways.

OBJECTIVE

The aim of this review is to highlight the physicochemical properties of synthesized nanoparticles (NPs) and their interaction with the cellular-dynamics and pathways like phagocytosis, pinocytosis, macropinocytosis, clathrin, and caveolae-mediated endocytosis and the involvement of effector proteins domain such as clathrin, AP2, caveolin, Arf6, Cdc42, dynamin and cell surface receptors during the endocytosis process of NPs.

METHOD

An electronic search was performed to explore the focused reviews and research articles on types of endocytosis and physicochemical properties of nanoparticles and their impact on cellular internalizations. The search was limited to peer-reviewed journals in the PubMed database.

RESULTS

This article discusses in detail how different types of NPs and their physicochemical properties such as size, shape, aspect ratio, surface charge, hydrophobicity, elasticity, stiffness, corona formation, surface functionalization changes the pattern of endocytosis in the presence of different pharmacological blockers. Some external forces like a magnetic field, electric field, and ultrasound exploit the cell membrane dynamics to permeabilize them for efficient internalization with respect to fundamental principles of membrane bending and pore formation.

CONCLUSION

This review will be useful to attract and guide the audience to understand the endocytosis mechanism and their pattern with respect to physicochemical properties of NPs to improve their efficacy and targeting to achieve the impactful outcome in drug-delivery and theranostics applications.

Challenges of peptide and protein drug delivery by oral route: Current strategies to improve the bioavailability

Advancement in biotechnology provided a notable expansion of peptide and protein therapeutics, used as antigens, vaccines, hormones. It has a prodigious potential to treat a broad spectrum of diseases such as cancer, metabolic disorders, bone disorders, and so forth. Protein and peptide therapeutics are administered parenterally due to their poor bioavailability and stability, restricting their use. Hence, research focuses on the oral delivery of peptides and proteins for the ease of self-administration. In the present review, we first address the main obstacles in the oral delivery system in addition to approaches used to enhance the stability and bioavailability of peptide/protein. We describe the physiochemical parameters of the peptides and proteins influencing bioavailability in the systemic circulation. It encounters, many barriers affecting its stability, such as poor cellular membrane permeability at the GIT site, enzymatic degradation (various proteases), and first-pass hepatic metabolism. Then describe the current approaches to overcome the challenges mentioned above by the use of absorption enhancers or carriers, structural modification, formulation and advance technology.

Mucosal immunity-mediated modulation of the gut microbiome by oral delivery of probiotics into Peyer's patches

Methods capable of maintaining gut microbiota homeostasis to prevent bacterial translocation and infection under external threats are critical for multiple facets of human health but have been rarely reported. Here, we describe the elicitation of mucosal immunity to modulate the gut microbiota by oral delivery of living probiotics into Peyer's patches. Probiotics are individually camouflaged within a yeast membrane, on which the embedded β-glucan can facilitate the phagocytosis of microfold cells that locate in the intestinal epithelium. The delivery of probiotics into lymphoid follicles after oral ingestion promotes robust mucosal immune responses and notably upgrades the production of secretory immunoglobulin A. The provoked immunity positively regulates the gut microflora, which, in turn, retains gut homeostasis and provides defense against environmental attacks. In two murine models of gut barrier impairment, oral administration with camouflaged probiotics effectively prevents the breakdown of intestinal barrier and evidences limited bacterial translocation and systemic inflammation.

New In Vitro Coculture Model for Evaluating Intestinal Absorption of Different Lipid Nanocapsules

Standard models used for evaluating the absorption of nanoparticles like Caco-2 ignore the presence of vascular endothelium, which is a part of the intestinal multi-layered barrier structure. Therefore, a coculture between the Caco-2 epithelium and HMEC-1 (Human Microvascular Endothelial Cell type 1) on a Transwell^® insert has been developed. The model has been validated for (a) membrane morphology by transmission electron microscope (TEM); (b) ZO-1 and β-catenin expression by immunoassay; (c) membrane integrity by trans-epithelial electrical resistance (TEER) measurement; and (d) apparent permeability of drugs from different biopharmaceutical classification system (BCS) classes. Lipid nanocapsules (LNCs) were formulated with different sizes (55 and 85 nm) and surface modifications (DSPE-mPEG (2000) and stearylamine). Nanocapsule integrity and particle concentration were monitored using the Förster resonance energy transfer (FRET) technique. The result showed that surface modification by DSPE-mPEG (2000) increased the absorption of 55-nm LNCs in the coculture model but not in the Caco-2. Summarily, the coculture model was validated as a tool for evaluating the intestinal absorption of drugs and nanoparticles. The new coculture model has a different LNCs absorption mechanism suggesting the importance of intestinal endothelium and reveals that the surface modification of LNCs can modify the in vitro oral absorption.

Gastrointestinal lipolysis and trans-epithelial transport of SMEDDS via oral route

Self-microemulsifying drug delivery systems (SMEDDSs) have recently returned to the limelight of academia and industry due to their enormous potential in oral delivery of biomacromolecules. However, information on gastrointestinal lipolysis and trans-epithelial transport of SMEDDS is rare. Aggregation-caused quenching (ACQ) fluorescent probes are utilized to visualize the in vivo behaviors of SMEDDSs, because the released probes during lipolysis are quenched upon contacting water. Two SMEDDSs composed of medium chain triglyceride and different ratios of Tween-80 and PEG-400 are set as models, meanwhile Neoral® was used as a control. The SMEDDS droplets reside in the digestive tract for as long as 24 h and obey first order kinetic law of lipolysis. The increased chain length of the triglyceride decreases the lipolysis of the SMEDDSs. Ex vivo imaging of main tissues and histological examination confirm the trans-epithelial transportation of the SMEDDS droplets. Approximately 2%-4% of the given SMEDDSs are transported via the lymph route following epithelial uptake, while liver is the main termination. Caco-2 cell lines confirm the cellular uptake and trans-epithelial transport. In conclusion, a fraction of SMEDDSs can survive the lipolysis in the gastrointestinal tract, permeate across the epithelia, translocate via the lymph, and accumulate mainly in the liver.

Development of an M cell targeted nanocomposite system for effective oral protein delivery: preparation, in vitro and in vivo characterization

Background

There is a strong need for non-invasive and patient-friendly delivery systems of protein drugs for long-term therapy. However, oral delivery of protein drugs is a big challenge due to many barriers including instability in the gastrointestinal (GI) tract and low permeability. To overcome the absorption barriers in GI tract and improve the patient compliance, this study aimed to develop an M cell targeted-nanocomposite delivery system of protein drugs.

Results

An aminoclay-protein core complex (AC-Ins) was prepared by using insulin as a model protein and then sequentially coated with Ulex europaeus agglutinin 1 (UEA-1) for M-cell targeting and the pH sensitive polymer, Eudragit® L100 (EUAC-Ins). All nanoparticles were obtained with a high entrapment efficiency (> 90%) and their structural characteristics were confirmed by Fourier transform-infrared spectroscopy, energy dispersive X-ray spectroscopy, and circular dichroism. Among the developed nanoparticles, EUAC-Ins effectively suppressed drug release at pH 1.2, while rapidly released drugs at pH 6.8 due to dissolution of the outer coating layer. The conformational stability of insulin entrapped in EUAC-Ins was well maintained in the presence of proteolytic enzymes. Compared to free insulin, EUAC-Ins increased the membrane transport of insulin by 4.4-fold in M cells. In parallel, oral administration of EUAC-Ins in mice enhanced insulin uptake by 4.1-fold in the intestinal Peyer’s patches and 2.6-fold in intestinal epithelium tissues with normal villi, compared to free insulin. Orally administered EUAC-Ins decreased significantly the blood glucose level in diabetic mice, while the effect of oral insulin solution was negligible.

Conclusion

An M cell targeted-ternary nanocomposite system obtained by dual coating of the aminoclay-protein core complex with UEA-1 and a pH dependent polymer is promising as an effective oral protein delivery carrier.

An ex vivo investigation of the intestinal uptake and translocation of nanoparticles targeted to Peyer's patches microfold cells

Diverse nanoparticulate systems have been engineered as vehicles towards enhancing the bioavailability of orally administrated vaccines. Substantial evidence suggests that targeting microfold cells (M cells) within Peyer's patches (PPs) is a prerequisite for vaccine-loaded nanocarriers to induce an effective antigen-specific immune response. Improved understanding of the contribution of M cells to sampling luminal nanoparticles into the underlying gut associated lymphoid tissues would accelerate the development of oral vaccine formulations. Herein, a novel clearing-based whole tissue mount/imaging technique was developed to enable the specific distribution of nanoparticles within ex vivo murine PPs to be quantitatively determined at the cellular level. This revealed that 200 nm nanoparticles modified with M cell targeting ligands (lectin Ulex europaeus agglutinin-1, UEA-1) were translocated into subepithelial domes 7.6 and 16.3 times greater than the non-targeted ones at 60 min and 120 min, respectively. This approach provides a new methodology to quantitatively investigate the transcytotic activity of M cells for particulate formulations, which may aid in the design of improved oral vaccines.

New and novel approaches for enhancing the oral absorption and bioavailability of protein and peptides therapeutics

The advancement of the oral route for macromolecules has gained a lot of attention due to its noninvasive nature, safe and challenging in active research but with limited success. Oral administration poses challenges due to poor solubility, short half-life, quick elimination and the physical, chemical and biological barriers of the gastrointestinal tract. Approaches of past for improving oral absorption, such as enhancers, mucoadhesive delivery and enzyme inhibitors have been taken over by novel approaches like advanced liposomes, self-nanoemulsifying drug delivery system, nanoparticles and targeted delivery. Eudratech™ Pep, Peptelligence, Rani Pill and Pharm Film are the emerging technologies for delivering oral proteins and peptide. Calcitonin, semaglutide and octreotide are the peptides available in the market for oral delivery as outcomes of these technologies.

A Tribute to Professor Per Artursson - Scientist, Explorer, Mentor, Innovator, and Giant in Pharmaceutical Research

This issue of the Journal of Pharmaceutical Sciences is dedicated to Professor Per Artursson and the groundbreaking contributions he has made and continues to make in the Pharmaceutical Sciences. Per is one of the most cited researchers in his field, with more than 30,000 citations and an h-index of 95 as of September 2020. Importantly, these citations are distributed over the numerous fields he has explored, clearly showing the high impact the research has had on the discipline. We provide a short portrait of Per, with emphasis on his personality, driving forces and the inspirational sources that shaped his career as a world-leading scientist in the field. He is a curious scientist who deftly moves between disciplines and has continued to innovate, expand boundaries, and profoundly impact the pharmaceutical sciences throughout his career. He has developed new tools and provided insights that have significantly contributed to today's molecular and mechanistic approaches to research in the fields of intestinal absorption, cellular disposition, and exposure-efficacy relationships of pharmaceutical drugs. We want to celebrate these important contributions in this special issue of the Journal of Pharmaceutical Sciences in Per's honor.

Screening, Safety Evaluation, and Mechanism of Two Lactobacillus fermentum Strains in Reducing the Translocation of Staphylococcus aureus in the Caco-2 Monolayer Model

Staphylococcus aureus is a common commensal of humans, and its translocation from gastrointestine to peripheral organs and tissues could cause severe diseases and complications. This study focuses on the screening and characterization of Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus through Caco-2 monolayers. First, strains with strong affinity for mucin and Caco-2 cells were obtained, via microtiter plate assay and adhesion assay, respectively. Obtained bacteria were further tested for their inhibitory effects on the growth of S. aureus by well diffusion assay. Subsequently, two strains preincubated with Caco-2 monolayers were found to inhibit the translocation of S. aureus CMCC26003 by 80.95 and 43.96%, respectively, via the transcellular translocation assay. These two strains were then identified to be Lactobacillus fermentum NCU3087 and L. fermentum NCU3088. Second, the mechanism of inhibition was investigated by analyzing the relative concentration of tight junction proteins and proinflammatory cytokines of Caco-2 cells, by Western blot and enzyme-linked immunosorbent assay, respectively. Results showed that both NCU3087 and NCU3088 significantly attenuated the degradation of occludin, claudin-1, ZO-1, and JAM-1 and suppressed the secretion of interleukin 6 and tumor necrosis factor-α induced by S. aureus, to different extent. Moreover, two Lactobacillus strains could barely translocate the Caco-2 monolayers, had no hemolytic activity, displayed strong resistance to gastrointestinal fluids, and were sensitive or moderate sensitive to nine clinically relevant antibiotics. Collectively, this study identified two Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus, and their safeness for application was evaluated, thereby providing potential solutions for prevention of S. aureus and prophylaxis of related diseases.

Ascorbyl-dipalmitate-stabilised nanoemulsions as a potential localised treatment of inflammatory bowel diseases

Current efforts on inflammatory bowel diseases (IBD) treatment are focused on strategies for localised drug delivery at the intestinal mucosa. Despite the potential of curcumin (CC) for IBD treatment, its low solubility and stability limit its application. Thus, the design of nanocarriers that focus CC delivery at the intestinal epithelium is an area of interest. This work proposes α-tocopherol nanoemulsions (NE) stabilised by ascorbyl-2,6-dipalmitate (ADP) as intestinal CC-carriers. The antioxidant capacity of α-tocopherol and ADP could have a synergistic effect on IBD-affected tissues, characterised by an oxidative environment. We obtained nanoemulsions (NE-ADP) with size below 200 nm, negative surface charge, stable in gastrointestinal media and no toxic in the Caco-2 cell model. Intracellular retention of NE-ADP in Caco-2 cells was observed by confocal microscopy. The extremely low P_app values obtained for CC and α-tocopherol indicated the lack of transport across the Caco-2 monolayer. Control nanoemulsion stabilised by lecithin (NE-L) was greatly transported across the Caco-2 cells monolayer, confirming the relevance of ADP on the cellular retention of NE-ADP. The therapeutic potential of NE-ADP was shown by the significant decrease of intracellular ROS levels. Altogether, these results indicate the potential of NE-ADP as a novel approach for the treatment of IBD.

Per Artursson's Major Contributions to the Caco-2 Cell Literature in Pharmaceutical Sciences

This edition of the Journal of Pharmaceutical Sciences is dedicated to the wonderful career of Per Artursson from the Uppsala University. My Commentary focusses on Per's major contributions to the Caco-2 cell literature over the past 30 years. Two especially influential papers have been cited more than 1000 times out of a total citation count of almost 30,000 and a h-index of 93 (Google Scholar), making Per one of the most cited and influential Pharmaceutical scientists of his generation. The Caco-2 field to which Per contributed so many advances has informed the community on key areas including predictive drug fluxes across the intestine, metabolism by intestinal epithelia, the role of transporters during flux, enantiomer-selective flux, excipient interaction with tight junctions, and nanoparticle uptake by enterocytes. In this pioneering work, Per has been careful to emphasise that Caco-2 monolayers have limitations and are a model of the human small intestine where observations must be backed up with in vitro tissue and in vivo work. Throughout, he has paid great attention to detail in methodology, as reflected by co-authorship of two Nature Protocols on Caco-2 assays. The article briefly assesses some of the most important milestones in Per's published Caco-2 research.

The construction of in vitro nasal cavity-mimic M-cell model, design of M cell-targeting nanoparticles and evaluation of mucosal vaccination by nasal administration

In order to better evaluate the transport effect of nanoparticles through the nasal mucosa, an in vitro nasal cavity-mimic model was designed based on M cells. The differentiation of M cells was induced by co-culture of Calu-3 and Raji cells in invert model. The ZO-1 protein staining and the transport of fluorescein sodium and dexamethasone showed that the inverted co-culture model formed a dense monolayer and possessed the transport ability. The differentiation of M cells was observed by up-regulated expression of Sialyl Lewis A antigen (SLAA) and integrin β1, and down-regulated activity of alkaline phosphatase. After targeting M cells with iRGD peptide (cRGDKGPDC), the transport of nanoparticles increased. In vivo, the co-administration of iRGD could result in the increase of nanoparticles transported to the brain through the nasal cavity after intranasal administration. In the evaluation of immune effect in vivo, the nasal administration of OVA-PLGA/iRGD led to more release of IgG, IFN-γ, IL-2 and secretory IgA (sIgA) compared with OVA@PLGA group. Collectively, the study constructed in vitro M cell model, and proved the enhanced effect of targeting towards M cell with iRGD on improving nasal immunity.

Advanced In Vitro Testing Strategies and Models of the Intestine for Nanosafety Research

There is growing concern about the potential adverse effects of oral exposure to engineered nanomaterials (ENM). Recent years have witnessed major developments in and advancement of intestinal in vitro models for nanosafety evaluation. The present paper reviews the key factors that should be considered for inclusion in nonanimal alternative testing approaches to reliably reflect the in vivo dynamics of the physicochemical properties of ENM as well the intestinal physiology and morphology. Currently available models range from simple cell line-based monocultures to advanced 3D systems and organoids. In addition, in vitro approaches exist to replicate the mucous barrier, digestive processes, luminal flow, peristalsis, and interactions of ENM with the intestinal microbiota. However, while the inclusion of a multitude of individual factors/components of particle (pre)treatment, exposure approach, and cell model approximates in vivo-like conditions, such increasing complexity inevitably affects the system's robustness and reproducibility. The selection of the individual modules to build the in vitro testing strategy should be driven and justified by the specific purpose of the study and, not least, the intended or actual application of the investigated ENM. Studies that address health hazards of ingested ENM likely require different approaches than research efforts to unravel the fundamental interactions or toxicity mechanisms of ENM in the intestine. Advanced reliable and robust in vitro models of the intestine, especially when combined in an integrated testing approach, offer great potential to further improve the field of nanosafety research.

Transcytosis subversion by M cell-to-enterocyte spread promotes Shigella flexneri and Listeria monocytogenes intracellular bacterial dissemination

Microfold (M) cell host-pathogen interaction studies would benefit from the visual analysis of dynamic cellular and microbial interplays. We adapted a human in vitro M cell model to physiological bacterial infections, expression of fluorescent localization reporters and long-term three-dimensional time-lapse microscopy. This approach allows following key steps of M cell infection dynamics at subcellular resolution, from the apical onset to basolateral epithelial dissemination. We focused on the intracellular pathogen Shigella flexneri, classically reported to transcytose through M cells to initiate bacillary dysentery in humans, while eliciting poorly protective immune responses. Our workflow was critical to reveal that S. flexneri develops a bimodal lifestyle within M cells leading to rapid transcytosis or delayed vacuolar rupture, followed by direct actin motility-based propagation to neighboring enterocytes. Moreover, we show that Listeria monocytogenes, another intracellular pathogen sharing a tropism for M cells, disseminates in a similar manner and evades M cell transcytosis completely. We established that actin-based M cell-to-enterocyte spread is the major dissemination pathway for both pathogens and avoids their exposure to basolateral compartments in our system. Our results challenge the notion that intracellular pathogens are readily transcytosed by M cells to inductive immune compartments in vivo, providing a potential mechanism for their ability to evade adaptive immunity.

Microfold (M) epithelial cells are important for the onset of infections and induction of immune responses in many mucosal diseases. We extended a human in vitro M cell model to apical infections, expression of fluorescent host and microbial reporters and real-time fluorescence microscopy. Focusing on the human intracellular pathogen S. flexneri, responsible for bacillary dysentery, this workflow allowed us to uncover that the bacterium can subvert the immunological sampling function of M cells by promoting a cytosolic lifestyle and spreading directly to neighboring enterocytes. This mechanism was shared with the etiologic agent of listeriosis, the intracellular pathogen L. monocytogenes and allowed both pathogens to avoid exposure to underlying immune compartments. These results may provide a mechanism for the ability of intracellular pathogens to evade adaptive immunity in vivo, emphasizing the importance of advanced studies of M cell host-pathogen interactions to understand early steps of mucosal invasion and their consequences on immunity.

Induction of Th2 response through TLR2-mediated MyD88-dependent pathway in human microfold cells stimulated with chitosan nanoparticles loaded with Brucella abortus Mdh

Drug delivery by the nasal or oral route is considered the preferred route of administration because it can induce systemic mucosal immunity. However, few studies have examined the immunogenicity and transport of antigen at the level of the microfold (M) cell, the epithelial cell that specializes in antigen sampling at mucosal surfaces. In our previous study, Brucella abortus malate dehydrogenase (Mdh) was loaded in chitosan nanoparticles (CNs), and it induced high production of proinflammatory cytokines in THP-1 cells and systemic IgA in BALB/C mice. In the present study, an in vitro M cell model was used in which Caco-2 cells and Raji B cells were co-cultured to investigate the impact of the uptake and immunogenicity of B. abortus Mdh on nanoparticle transport in human M cells. Our results showed that loaded CNs induced enhanced transport of Mdh in the M cell model. ELISAs showed significantly higher production of IL-1β and IL-6 in the CN-Mdh stimulation group than that seen in the Mdh stimulation group. The observed increase of gene expression of TLR2, MyD88, TRAF6, IRF4 and CD14 implied that MyD88-dependent TLR2 signaling was activated by stimulation with CNs-Mdh. These results suggest that Mdh and CNs may function synergistically to enhance Th2-related responses triggered by the MyD88-dependent TLR2 signaling pathway and could induce an inflammatory response in M cells as an M cell-targeted delivery system. This study will contribute to the development of not only effective antigens for intracellular bacteria, including B. abortus, but also vaccine delivery systems that target M cells.

Investigation of Twenty Metal, Metal Oxide, and Metal Sulfide Nanoparticles' Impact on Differentiated Caco-2 Monolayer Integrity

The use of engineered nanomaterials (ENMs) in foods and consumer products is rising, increasing the potential for unintentional ingestion. While the cytotoxicity of many ENMs has been investigated, less attention has been given to adverse impact on the intestinal barrier integrity. Chronical disruption of gastrointestinal integrity can have far reaching health implications. Using fully differentiated Caco-2 cells, the perturbation of intestinal barrier function and cytotoxicity were investigated for 20 metal, metal oxide, and metal sulfide ENMs. Caco-2 cells were exposed to 50 μg/mL ENMs for 24 hours. ENM formulations were characterized at 0 and 24 hours, and In Vitro Sedimentation, Diffusion and Dosimetry Modeling was applied to calculate the effective dose of exposure during 24 hours. The apparent permeability coefficient (P_app) was determined for fluorescent labeled dextran (3,000 Da) and tight junction integrity was evaluated by immunofluorescence microscopy. Cytotoxicity was investigated by determining lactate dehydrogenase release (LDH) and cell metabolic activity (tetrazolium based MTS) assays. Four ENMs led to significantly increased P_app, (15.8% w/w% Ag-SiO₂ nanoparticle (NP), 60 nm CdS NP, 100 nm V₂O₅ flakes, and 50 nm ZnO NP), while one ENM (20 nm MgO NP) decreased P_app. With the exception of CdS NP, significantly increased P_app was not connected with cell cytotoxicity. The calculated effective dose concentration was not correlated with increased P_app. Our results illustrate that while many metal, metal oxide, and metal sulfide ENMs do not adversely affect monolayer integrity or induce cytotoxicity in differentiated Caco-2 cells, a subset of ENMs may compromise the intestinal integrity. This study demonstrated the use of differentiated Caco-2 monolayer and P_app as an endpoint to identify and prioritize ENMs that should be investigated further. The interaction between ENMs and the intestinal epithelium needs to be evaluated to understand potential intestinal barrier dysfunction and resulting health implications.

Chips-on-a-plate device for monitoring cellular migration in a microchannel-based intestinal follicle-associated epithelium model

This paper describes a chips-on-a-plate (COP) device for monitoring the migration of Raji cells in the Caco-2/Raji coculture. To generate a model of the human intestinal follicle-associated epithelium (FAE), the coculture method using a conventional Transwell cell culture insert was established. Due to the structural limitations of the Transwell insert, live-cell tracking studies have not been performed previously using the existing FAE model. In this study, we designed a COP device to conduct long-term live-cell tracking of Raji cell migration using a microchannel-based FAE model. The COP device incorporates microfluidic chips integrated on a standard well plate, consistent humidity control to allow live-cell microscopy for 2 days, and microchannels connecting the two cell culture chambers of the COP device, which serve as a monitoring area for cellular migration. Using the COP device, we provide the first analysis of various migratory characteristics of Raji cells, including their chemotactic index in the microchannel-based FAE model. We showed that the migration of Raji cells could be controlled by modulating the geometry of the connecting microchannels. Cellular treatments with cytokines revealed that the cytokines increased the permeability of an FAE model with a detachment of Caco-2 cells. Live-cell monitoring of Raji cells treated with a fluorescent reagent also indicated exocytosis as a key agent of the Caco-2/Raji interaction. The COP device allows live-cell tracking analyses of cocultured cells in the microchannel-based FAE model, providing a promising tool for investigating cellular behavior associated with the recruitment of Raji to Caco-2 cells.

Striving Towards the Perfect In Vitro Oral Drug Absorption Model

Oral drug delivery systems have multiple goals, assessing and enabling intestinal absorption at efficacious doses being one of them. Here we highlight the in vitro advances in modeling drug absorption, which more faithfully reflect human intestinal physiology and reduce the reliance on animal models.

Induced Differentiation of M Cell-like Cells in Human Stem Cell-derived Ileal Enteroid Monolayers

M (microfold) cells of the intestine function to transport antigen from the apical lumen to the underlying Peyer's patches and lamina propria where immune cells reside and therefore contribute to mucosal immunity in the intestine. A complete understanding of how M cells differentiate in the intestine as well as the molecular mechanisms of antigen uptake by M cells is lacking. This is because M cells are a rare population of cells in the intestine and because in vitro models for M cells are not robust. The discovery of a self-renewing stem cell culture system of the intestine, termed enteroids, has provided new possibilities for culturing M cells. Enteroids are advantageous over standard cultured cell lines because they can be differentiated into several major cell types found in the intestine, including goblet cells, Paneth cells, enteroendocrine cells and enterocytes. The cytokine RANKL is essential in M cell development, and addition of RANKL and TNF-α to culture media promotes a subset of cells from ileal enteroids to differentiate into M cells. The following protocol describes a method for the differentiation of M cells in a transwell epithelial polarized monolayer system of the intestine using human ileal enteroids. This method can be applied to the study of M cell development and function.

Successful oral delivery of poorly water-soluble drugs both depends on the intraluminal behavior of drugs and of appropriate advanced drug delivery systems

Poorly water-soluble drugs continue to be a problematic, yet important class of pharmaceutical compounds for treatment of a wide range of diseases. Their prevalence in discovery is still high, and their development is usually limited by our lack of a complete understanding of how the complex chemical, physiological and biochemical processes that occur between administration and absorption individually and together impact on bioavailability. This review defines the challenge presented by these drugs, outlines contemporary strategies to solve this challenge, and consequent in silico and in vitro evaluation of the delivery technologies for poorly water-soluble drugs. The next steps and unmet needs are proposed to present a roadmap for future studies for the field to consider enabling progress in delivery of poorly water-soluble compounds.

Transferrin Functionization Elevates Transcytosis of Nanogranules across Epithelium by Triggering Polarity-Associated Transport Flow and Positive Cellular Feedback Loop

Overcoming the epithelial barriers to enhance drug transport is a focused topic for gastrointestinal, intratracheal, intranasal, vaginal, and intrauterine delivery. Nanomedicines with targeting functionization promote such a process owing to specific ligand-receptor interaction. However, compared to the cell uptake of targeting nanotherapies, currently few studies concentrate on their transcytosis including endocytosis for "in" and exocytosis for "out". In fact, the cellular regulatory mechanism for these pathways as well as the principle of ligand's effect on the transcytosis are almost ignored. Here, we fabricated transferrin (Tf) functionalized nanogranules (Tf-NG) as the nanomedicine model and confirmed the difference in polar distributions of Tf receptors (TfRs) between two epithelium models (bipolarity for Caco-2 and unipolarity for MDCK cells). Compared to the nonspecific reference, Tf-conjugation boosted the endocytosis by different pathways in two cell models and transformed the intracellular route of Tf-NG in both cells differently, affecting exocytosis, recycling, and degradation but not the secretion pathway. Only bipolar cells could establish a complete transport flow from "in" to "out", leading to the enhanced transcytosis of Tf-NG. Importantly, epithelia could make responses to Tf-NG transcytosis. Based on the quantitative proteomics, the intracellular trafficking of Tf-NG altered the protein expression profiles, in which the endocytosis- and transcytosis-related proteins were specifically upregulated. Particularly, only bipolar cells could positively feed back to such trafficking via accelerating the subsequent Tf-NG transcytosis. Here, all the cell transport of Tf-NG was polarity associated. In summary, Tf modification elevated the transcytosis of Tf-NG across the epithelium by triggering the polarity-associated transport flow and positive cell feedback loop. These findings provided an insight into the targeting nanodelivery for efficient transport through epithelial barriers.

Identifying human and murine M cells in vitro

IMPACT STATEMENT

The study of M cells, a specialized epithelial cell type found in the follicle-associated epithelium, is hampered by the lack of a universal M cell marker. As such, many studies lack reliable and universally recognized methods to identify M cells in their proposed models. As a result of this it is difficult to ascertain whether the effects observed are due to the presence of M cells or an unaccounted variable. The outcome of this review is the thorough evaluation of the many M cell markers that have been used in the literature thus far and a proposed criterion for the identification of M cells for future publications. This will hopefully lead to an improvement in the quality of future publications in this field.

Development of a host-microbiome model of the small intestine

The intestinal epithelium plays an essential role in the balance between tolerant and protective immune responses to infectious agents. In vitro models do not typically consider the innate immune response and gut microbiome in detail, so these models do not fully mimic the physiologic aspects of the small intestine. We developed and characterized a long-term in vitro model containing enterocyte, goblet, and immune-like cells exposed to a synthetic microbial community representative of commensal inhabitants of the small intestine. This model showed differential responses toward a synthetic microbial community of commensal bacterial inhabitants of the small intestine in the absence or presence of LPS from Escherichia coli O111:B4. Simultaneous exposure to LPS and microbiota induced impaired epithelial barrier function; increased production of IL-8, IL-6, TNF-α, and C-X-C motif chemokine ligand 16; and augmented differentiation and adhesion of macrophage-like cells and the overexpression of dual oxidase 2 and TLR-2 and -4 mRNA. In addition, the model demonstrated the ability to assess the adhesion of specific bacterial strains from the synthetic microbial community-more specifically, Veillonella parvula-to the simulated epithelium. This novel in vitro model may assist in overcoming sampling and retrieval difficulties when studying host-microbiome interactions in the small intestine.-Calatayud, M., Dezutter, O., Hernandez-Sanabria, E., Hidalgo-Martinez, S., Meysman, F. J. R., Van de Wiele, T. Development of a host-microbiome model of the small intestine.