Functional characterization of a novel 3D model of the epithelial-mesenchymal trophic unit

Guidelines for visualization and analysis of DC in tissues using multiparameter fluorescence microscopy imaging methods

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state-of-the-art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs and various non-lymphoid tissues. Here, we provide detailed procedures for a variety of multiparameter fluorescence microscopy imaging methods to explore the spatial organization of DC in tissues and to dissect how DC migrate, communicate, and mediate their multiple functional roles in immunity in a variety of tissue settings. The protocols presented here entail approaches to study DC dynamics and T cell cross-talk by intravital microscopy, large-scale visualization, identification, and quantitative analysis of DC subsets and their functions by multiparameter fluorescence microscopy of fixed tissue sections, and an approach to study DC interactions with tissue cells in a 3D cell culture model. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer-reviewed by leading experts and approved by all co-authors, making it an essential resource for basic and clinical DC immunologists.

Chemical Modification of Human Decellularized Extracellular Matrix for Incorporation into Phototunable Hybrid-Hydrogel Models of Tissue Fibrosis

Tissue fibrosis remains a serious health condition with high morbidity and mortality rates. There is a critical need to engineer model systems that better recapitulate the spatial and temporal changes in the fibrotic extracellular microenvironment and enable study of the cellular and molecular alterations that occur during pathogenesis. Here, we present a process for chemically modifying human decellularized extracellular matrix (dECM) and incorporating it into a dynamically tunable hybrid-hydrogel system containing a poly(ethylene glycol)-α methacrylate (PEGαMA) backbone. Following modification and characterization, an off-stoichiometry thiol-ene Michael addition reaction resulted in hybrid-hydrogels with mechanical properties that could be tuned to recapitulate many healthy tissue types. Next, photoinitiated, free-radical homopolymerization of excess α-methacrylates increased crosslinking density and hybrid-hydrogel elastic modulus to mimic a fibrotic microenvironment. The incorporation of dECM into the PEGαMA hydrogel decreased the elastic modulus and, relative to fully synthetic hydrogels, increased the swelling ratio, the average molecular weight between crosslinks, and the mesh size of hybrid-hydrogel networks. These changes were proportional to the amount of dECM incorporated into the network. Dynamic stiffening increased the elastic modulus and decreased the swelling ratio, average molecular weight between crosslinks, and the mesh size of hybrid-hydrogels, as expected. Stiffening also activated human fibroblasts, as measured by increases in average cellular aspect ratio (1.59 ± 0.02 to 2.98 ± 0.20) and expression of α-smooth muscle actin (αSMA). Fibroblasts expressing αSMA increased from 25.8 to 49.1% upon dynamic stiffening, demonstrating that hybrid-hydrogels containing human dECM support investigation of dynamic mechanosensing. These results improve our understanding of the biomolecular networks formed within hybrid-hydrogels: this fully human phototunable hybrid-hydrogel system will enable researchers to control and decouple the biochemical changes that occur during fibrotic pathogenesis from the resulting increases in stiffness to study the dynamic cell-matrix interactions that perpetuate fibrotic diseases.

Zonular and capsular bag disorders: a hypothetical perspective based on recent pathophysiological insights

The purpose of this article was to look at the pathophysiology behind and devise a classification system for the causes of zonular apparatus-capsular bag (ZACB) insufficiency. Also discussed is dystrophic bag syndrome, including clinical cases and addressing where it lies on the ZACB spectrum. There has been interest in the emergence of in-the-bag intraocular lens (IOL) subluxation, the prevalence of which is increasing. There has also been a recent report of dead bag syndrome, which the authors believe is part of the same disease spectrum. The authors put these phenomena into perspective and provide a classification system based on the possible causes of what they have termed ZACB insufficiency. The basic aspects of capsular bag-IOL ocular pathophysiology are summarized with a focus on functional aspects and the consequences for IOL fastening. Within this framework, dystrophic bag syndrome is a form of primary capsular ZACB insufficiency. The contribution of factors such as intraocular drugs may suggest a reconsideration of agents used and their mode of application.

A dynamic Air Liquid Interface system for in vitro mimicking of the nasal mucosa

The development of an in vitro 3D model for the growth of the nasal mucosa cells can improve the therapy and the study of pathological states for subjects with chronic airway conditions. We have previously characterized a system consisting of a scaffold with an internal channel and a perfusion bioreactor with two independent flows provided by an external and an internal circuit, respectively. In this paper, this system was designed as a model of the nasal cavity, in which cells, grown on the inner surface of the scaffold channel, would be in contact at the same time with both culture medium, supplied by the external circuit, and air, provided with the internal flow. To ensure adequate nutrient supply to the cells in the scaffold channel, the radial diffusion of the culture medium through the porous matrix was evaluated first in qualitative and, then, in quantitative terms, demonstrating the capability of the system to control the value and direction of this flux. As a preliminary study, the culture of epithelial cells in the scaffold channel is also discussed in static, maintaining the air-liquid-interface (ALI) condition for up to three weeks. Despite minor abnormalities, such as a gap between cell layers and some detachments from the scaffold, the scaffold ensured cell survival and growth during the experimental time. This article is protected by copyright. All rights reserved.

Replacement Strategies for Animal Studies in Inhalation Testing

Animal testing is mandatory in drug testing and is the gold standard for toxicity and efficacy evaluations. This situation is expected to change in the future as the 3Rs principle, which stands for the replacement, reduction, and refinement of the use of animals in science, is reinforced by many countries. On the other hand, technologies for alternatives to animal testing have increased. The need to develop and use alternatives depends on the complexity of the research topic and also on the extent to which the currently used animal models can mimic human physiology and/or exposure. The lung morphology and physiology of commonly used animal species differs from that of human lungs, and the realistic inhalation exposure of animals is challenging. In vitro and in silico methods can assess important aspects of the in vivo effects, namely particle deposition, dissolution, action at, and permeation through, the respiratory barrier, and pharmacokinetics. This review discusses the limitations of animal models and exposure systems and proposes in vitro and in silico techniques that could, when used together, reduce or even replace animal testing in inhalation testing in the future.

Extracellular Vesicles in Airway Homeostasis and Pathophysiology

The epithelial–mesenchymal trophic unit (EMTU) is a morphofunctional entity involved in the maintenance of the homeostasis of airways as well as in the pathogenesis of several diseases, including asthma and chronic obstructive pulmonary disease (COPD). The “muco-microbiotic layer” (MML) is the innermost layer of airways made by microbiota elements (bacteria, viruses, archaea and fungi) and the surrounding mucous matrix. The MML homeostasis is also crucial for maintaining the healthy status of organs and its alteration is at the basis of airway disorders. Nanovesicles produced by EMTU and MML elements are probably the most important tool of communication among the different cell types, including inflammatory ones. How nanovesicles produced by EMTU and MML may affect the airway integrity, leading to the onset of asthma and COPD, as well as their putative use in therapy will be discussed here.

Disease Models: Lung Models for Testing Drugs Against Inflammation and Infection

Lung diseases have increasingly attracted interest in the past years. The all-known fear of failing treatments against severe pulmonary infections and plans of the pharmaceutical industry to limit research on anti-infectives to a minimum due to cost reasons makes infections of the lung nowadays a "hot topic." Inhalable antibiotics show promising efficacy while limiting adverse systemic effects to a minimum. Moreover, in times of increased life expectancy in developed countries, the treatment of chronic maladies implicating inflammatory diseases, like bronchial asthma or chronic obstructive pulmonary disease, becomes more and more exigent and still lacks proper treatment.In this chapter, we address in vitro models as well as necessary in vivo models to help develop new drugs for the treatment of various severe pulmonary diseases with a strong focus on infectious diseases. By first presenting the essential hands-on techniques for the setup of in vitro models, we intend to combine these with already successful and interesting model approaches to serve as some guideline for the development of future models. The overall goal is to maximize time and cost-efficacy and to minimize attrition as well as animal trials when developing novel anti-infective therapeutics.

Responsiveness of human bronchial fibroblasts and epithelial cells from asthmatic and non-asthmatic donors to the transforming growth factor-β1 in epithelial-mesenchymal trophic unit model

BACKGROUND

The asthma-related airway wall remodeling is associated i.a. with a damage of bronchial epithelium and subepithelial fibrosis. Functional interactions between human bronchial epithelial cells and human bronchial fibroblasts are known as the epithelial-mesenchymal trophic unit (EMTU) and are necessary for a proper functioning of lung tissue. However, a high concentration of the transforming growth factor-β₁ (TGF-β₁) in the asthmatic bronchi drives the structural disintegrity of epithelium with the epithelial-to-mesenchymal transition (EMT) of the bronchial epithelial cells, and of subepithelial fibrosis with the fibroblast-to-myofibroblast transition (FMT) of the bronchial fibroblasts. Since previous reports indicate different intrinsic properties of the human bronchial epithelial cells and human bronchial fibroblasts which affect their EMT/FMT potential beetween cells derived from asthmatic and non-asthmatic patients, cultured separatelly in vitro, we were interested to see whether corresponding effects could be obtained in a co-culture of the bronchial epithelial cells and bronchial fibroblasts. In this study, we investigate the effects of the TGF-β₁ on the EMT markers of the bronchial epithelial cells cultured in the air-liquid-interface and effectiveness of FMT in the bronchial fibroblast populations in the EMTU models.

RESULTS

Our results show that the asthmatic co-cultures are more sensitive to the TGF-β₁ than the non-asthmatic ones, which is associated with a higher potential of the asthmatic bronchial cells for a profibrotic response, analogously to be observed in '2D' cultures. They also indicate a noticeable impact of human bronchial epithelial cells on the TGF-β₁-induced FMT, stronger in the asthmatic bronchial fibroblast populations in comparison to the non-asthmatic ones. Moreover, our results suggest the protective effects of fibroblasts on the structure of the TGF-β₁-exposed mucociliary differentiated bronchial epithelial cells and their EMT potential.

CONCLUSIONS

Our data are the first to demonstrate a protective effect of the human bronchial fibroblasts on the properties of the human bronchial epithelial cells, which suggests that intrinsic properties of not only epithelium but also subepithelial fibroblasts affect a proper condition and function of the EMTU in both normal and asthmatic individuals.

What Have In Vitro Co-Culture Models Taught Us about the Contribution of Epithelial-Mesenchymal Interactions to Airway Inflammation and Remodeling in Asthma?

As the lung develops, epithelial-mesenchymal crosstalk is essential for the developmental processes that drive cell proliferation, differentiation, and extracellular matrix (ECM) production within the lung epithelial-mesenchymal trophic unit (EMTU). In asthma, a number of the lung EMTU developmental signals have been associated with airway inflammation and remodeling, which has led to the hypothesis that aberrant activation of the asthmatic EMTU may lead to disease pathogenesis. Monoculture studies have aided in the understanding of the altered phenotype of airway epithelial and mesenchymal cells and their contribution to the pathogenesis of asthma. However, 3-dimensional (3D) co-culture models are needed to enable the study of epithelial-mesenchymal crosstalk in the setting of the in vivo environment. In this review, we summarize studies using 3D co-culture models to assess how defective epithelial-mesenchymal communication contributes to chronic airway inflammation and remodeling within the asthmatic EMTU.

Epithelial-mesenchymal crosstalk in COPD: An update from in vitro model studies

Chronic Obstructive Pulmonary disease (COPD) involves airway inflammation and remodeling leading to small airways disease and emphysema, which results in irreversible airflow obstruction. During lung development, reciprocal interactions between the endoderm and mesoderm (epithelial-mesenchymal trophic unit (EMTU)) are essential for morphogenetic cues that direct cell proliferation, differentiation, and extracellular (ECM) production. In COPD, a significant number of the inflammation and remodeling mediators resemble those released during lung development, which has led to the hypothesis that aberrant activation of the EMTU may occur in the disease. Studies assessing lung epithelial and fibroblast function in COPD, have been primarily focused on monoculture studies. To capture the in vivo environment of the human lung and aid in the understanding of mechanisms and mediators involved in abnormal epithelial-fibroblast communication in COPD, complex co-culture models are required. In this review, we describe the studies that have used co-culture models to assess epithelial-fibroblast interactions and their role in the pathogenesis of COPD.

Molecular mechanisms in chaperonopathies: clues to understanding the histopathological abnormalities and developing novel therapies

Molecular chaperones, many of which are heat shock proteins (Hsps), are components of the chaperoning system and when defective can cause disease, the chaperonopathies. Chaperone-gene variants cause genetic chaperonopathies, whereas in the acquired chaperonopathies the genes are normal, but their protein products are not, due to aberrant post-transcriptional mechanisms, e.g. post-translational modifications (PTMs). Since the chaperoning system is widespread in the body, chaperonopathies affect various tissues and organs, making these diseases of interest to a wide range of medical specialties. Genetic chaperonopathies are uncommon but the acquired ones are frequent, encompassing various types of cancer, and inflammatory and autoimmune disorders. The clinical picture of chaperonopathies is known. Much less is known on the impact that pathogenic mutations and PTMs have on the properties and functions of chaperone molecules. Elucidation of these molecular alterations is necessary for understanding the mechanisms underpinning the tissue and organ abnormalities occurring in patients. To illustrate this issue, we discuss structural-functional alterations caused by mutation in the chaperones CCT5 and HSPA9, and PTM effects on Hsp60. The data provide insights into what may happen when CCT5 and HSPA9 malfunction in patients, e.g. accumulation of cytotoxic protein aggregates with tissue destruction; or for Hsp60 with aberrant PTM, degradation and/or secretion of the chaperonin with mitochondrial damage. These and other possibilities are now open for investigation. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Establishment of rapid risk assessment model for cigarette smoke extract exposure in chronic obstructive pulmonary disease

Rapid risk assessment models for different types of cigarette smoke extract (CSE) exposure are critical to understanding the etiology of chronic obstructive pulmonary disease. The present study investigated inflammation of cultured tracheal tissues with CSE exposure. Rat trachea rings were isolated, cultured, then exposed to various concentrations of CSE from 3R4 F reference cigarettes for 4 h. Tissue/cellular morphology, ultrastructure, viability and damage, inflammatory cell infiltration, and inflammatory protein levels were measured and compared to untreated controls. Human bronchial epithelial cells (BEAS-2B) exposed to 0 or 300 μg/mL CSE were cocultured with macrophages to assess extent of mobilization and phagocytosis. Endotracheal epithelium cilia densities were significantly reduced with increasing CSE concentrations, while mucous membranes became increasingly disordered; both eventually disappeared. Macrophages became larger as the CSE concentration increased, with microvilli and extended pseudopodium covering their surface, and many primary and secondary lysosomes present in the cytoplasm. Inflammatory cell infiltration also increased with increasing CSE dose, as did intracellular adhesion molecule-1(ICAM-1), interleukin-6(IL-6). The method described here may be useful to qualitatively characterized the effects of the compound under study. Then, we use BEAS-2B cell line system to strength the observation made in the cultured tissues. Probably, an approach to integrate results from both experiments will facilitate its application. These results demonstrate that cultured rat tracheal rings have a whole-tissue structure that undergoes inflammatory processes similar to in vivo tissues upon CSE exposure.

Human primary macrophages scavenge AuNPs and eliminate it through exosomes. A natural shuttling for nanomaterials

The use of nanomaterials is increasing but the real risk associated with their use in humans has to be defined. In fact, nanomaterials tend to accumulate in organs over a long period of time and are slowly degraded or eliminated by the body. Exosomes are nanovesicles actively shuttle molecules, including chemical products and metals, through the body. Macrophages scavenge the body from both organic and inorganic substances, and they use to release high amounts of exosomes. We hypothesized that macrophages may have a role in eliminating nanomaterials through their exosomes. We treated human primary macrophages with 20 nm gold nanoparticles (AuNPs), analyzing the presence of AuNPs in both cells and the released exosomes by the implementation of different techniques, including SP-ICP-MS and NTA. We showed that macrophages endocytosed AuNPs and released them through exosomes. Our study on one hand provide the evidence for a new methodology in the early identification of the nanomaterials levels in exposed subjects. On the other hand we depict a way our body shuttle virtually intact nanoparticles through macrophage-released exosomes.

Tissue-informed engineering strategies for modeling human pulmonary diseases

Chronic pulmonary diseases, including idiopathic pulmonary fibrosis (IPF), pulmonary hypertension (PH), and chronic obstructive pulmonary disease (COPD), account for staggering morbidity and mortality worldwide but have limited clinical management options available. Although great progress has been made to elucidate the cellular and molecular pathways underlying these diseases, there remains a significant disparity between basic research endeavors and clinical outcomes. This discrepancy is due in part to the failure of many current disease models to recapitulate the dynamic changes that occur during pathogenesis in vivo. As a result, pulmonary medicine has recently experienced a rapid expansion in the application of engineering principles to characterize changes in human tissues in vivo and model the resulting pathogenic alterations in vitro. We envision that engineering strategies using precision biomaterials and advanced biomanufacturing will revolutionize current approaches to disease modeling and accelerate the development and validation of personalized therapies. This review highlights how advances in lung tissue characterization reveal dynamic changes in the structure, mechanics, and composition of the extracellular matrix in chronic pulmonary diseases and how this information paves the way for tissue-informed engineering of more organotypic models of human pathology. Current translational challenges are discussed as well as opportunities to overcome these barriers with precision biomaterial design and advanced biomanufacturing techniques that embody the principles of personalized medicine to facilitate the rapid development of novel therapeutics for this devastating group of chronic diseases.

Airway remodeling in asthma: update on mechanisms and therapeutic approaches

PURPOSE OF REVIEW

The term 'airway remodeling' reflects changes in the type, quantity, and nature of airway wall components and their organization. The purpose of this review is to look at recent publications on airway remodeling in asthma.

RECENT FINDINGS

Animal models and in-vitro studies have confirmed the involvement of airway epithelium, airway smooth muscle (ASM), and extracellular matrix components in asthma-related airway remodeling. They report influences on proliferation of ASM cells, and how their orientation or morphology, in addition to the heterogeneity of ASM mass at different levels of airways could influence their effects. Clinical benefits have been observed following reduction of ASM following bronchial thermoplasty. Asthmatic epithelial cell transcriptome alterations were found to involve metabolism and epigenetics, beyond epithelial mesenchymal trophic unit driven by injury and repair in chronic inflammation. New ways to explore airway remodeling such as imaging or endoscopic techniques have been evaluated. Finally, new data support the role of eosinophils and mast cells in remodeling and show the influence of new asthma drugs on this process.

SUMMARY

As recently stated by an American Thoracic Society task force, we need more research on airway remodeling, its determinants and clinical relevance, and on the effects of asthma drugs on its various components.

Fast-track development of an in vitro 3D lung/immune cell model to study Aspergillus infections

To study interactions of airborne pathogens, e.g. Aspergillus (A.) fumigatus with upper and lower respiratory tract epithelial and immune cells, we set up a perfused 3D human bronchial and small airway epithelial cell system. Culturing of normal human bronchial or small airway epithelial (NHBE, SAE) cells under air liquid interphase (ALI) and perfusion resulted in a significantly accelerated development of the lung epithelia associated with higher ciliogenesis, cilia movement, mucus-production and improved barrier function compared to growth under static conditions. Following the accelerated differentiation under perfusion, epithelial cells were transferred into static conditions and antigen-presenting cells (APCs) added to study their functionality upon infection with A. fumigatus. Fungi were efficiently sensed by apically applied macrophages or basolaterally adhered dendritic cells (DCs), as illustrated by phagocytosis, maturation and migration characteristics. We illustrate here that perfusion greatly improves differentiation of primary epithelial cells in vitro, which enables fast-track addition of primary immune cells and significant shortening of experimental procedures. Additionally, co-cultured primary DCs and macrophages were fully functional and fulfilled their tasks of sensing and sampling fungal pathogens present at the apical surface of epithelial cells, thereby promoting novel possibilities to study airborne infections under conditions mimicking the in vivo situation.