An ex vivo model of severe asthma using reconstituted human bronchial epithelium

Effect of cyclosporin A on respiratory viral replication in fully differentiated ex vivo human airway epithelia

Cyclosporin A (CsA), an immunosuppressive drug used in transplant recipients, inhibits graft rejection by binding to cyclophilins and competitively inhibiting calcineurin. While concerns about respiratory infections in immunosuppressed patients exist, contradictory data emerged during the COVID-19 pandemic, prompting investigations into CsA's impact on viral infections. This study explores CsA's antiviral effects on SARS-CoV-2 Omicron BA.1, Delta variants, and human parainfluenza virus 3 (HPIV3) using an ex vivo model of human airway epithelium (HAE). CsA exhibited a dose-dependent antiviral effect against the SARS-CoV-2 Delta variant, reducing viral load over 10 days. However, no significant impact was observed against SARS-CoV-2 Omicron or HPIV3, indicating a virus-specific effect. At high concentrations, CsA was associated with an increase of IL-8 and a decrease of IFNλ expression in infected and noninfected HAE. This study highlights the complexity of CsA's antiviral mechanisms, more likely involving intricate inflammatory pathways and interactions with specific viral proteins. The research provides novel insights into CsA's effects on respiratory viruses, emphasizing the need for understanding drug-virus interactions in optimizing therapeutic approaches for transplant recipients and advancing knowledge on immunosuppressive treatments' implications on respiratory viral infections. Limitations include the model's inability to assess T lymphocyte activation, suggesting the necessity for further comprehensive studies to decipher the intricate dynamics of immunosuppressive treatments on respiratory viral infections.

Factors influencing airway smooth muscle tone: a comprehensive review with a special emphasis on pulmonary surfactant

A thin film of pulmonary surfactant lines the surface of the airways and alveoli, where it lowers the surface tension in the peripheral lungs, preventing collapse of the bronchioles and alveoli and reducing the work of breathing. It also possesses a barrier function for maintaining the blood-gas interface of the lungs and plays an important role in innate immunity. The surfactant film covers the epithelium lining both large and small airways, forming the first line of defense between toxic airborne particles/pathogens and the lungs. Furthermore, surfactant has been shown to relax airway smooth muscle (ASM) after exposure to ASM agonists, suggesting a more subtle function. Whether surfactant masks irritant sensory receptors or interacts with one of them is not known. The relaxant effect of surfactant on ASM is absent in bronchial tissues denuded of an epithelial layer. Blocking of prostanoid synthesis inhibits the relaxant function of surfactant, indicating that prostanoids might be involved. Another possibility for surfactant to be active, namely through ATP-dependent potassium channels and the cAMP-regulated epithelial chloride channels [cystic fibrosis transmembrane conductance regulators (CFTRs)], was tested but could not be confirmed. Hence, this review discusses the mechanisms of known and potential relaxant effects of pulmonary surfactant on ASM. This review summarizes what is known about the role of surfactant in smooth muscle physiology and explores the scientific questions and studies needed to fully understand how surfactant helps maintain the delicate balance between relaxant and constrictor needs.

Murine Alox8 versus the human ALOX15B ortholog: differences and similarities

Human arachidonate 15-lipoxygenase type B is a lipoxygenase that catalyzes the peroxidation of arachidonic acid at carbon-15. The corresponding murine ortholog however has 8-lipoxygenase activity. Both enzymes oxygenate polyunsaturated fatty acids in S-chirality with singular reaction specificity, although they generate a different product pattern. Furthermore, while both enzymes utilize both esterified fatty acids and fatty acid hydro(pero)xides as substrates, they differ with respect to the orientation of the fatty acid in their substrate-binding pocket. While ALOX15B accepts the fatty acid "tail-first," Alox8 oxygenates the free fatty acid with its "head-first." These differences in substrate orientation and thus in regio- and stereospecificity are thought to be determined by distinct amino acid residues. Towards their biological function, both enzymes share a commonality in regulating cholesterol homeostasis in macrophages, and Alox8 knockdown is associated with reduced atherosclerosis in mice. Additional roles have been linked to lung inflammation along with tumor suppressor activity. This review focuses on the current knowledge of the enzymatic activity of human ALOX15B and murine Alox8, along with their association with diseases.

A gel-coated air-liquid-interface culture system with tunable substrate stiffness matching healthy and diseased lung tissues

Since its invention in the late 1980s, the air-liquid-interface (ALI) culture system has been the standard in vitro model for studying human airway biology and pulmonary diseases. However, in a conventional ALI system, cells are cultured on a porous plastic membrane that is much stiffer than human airway tissues. Here, we develop a gel-ALI culture system by simply coating the plastic membrane with a thin layer of hydrogel with tunable stiffness matching that of healthy and fibrotic airway tissues. We determine the optimum gel thickness that does not impair the transport of nutrients and biomolecules essential to cell growth. We show that the gel-ALI system allows human bronchial epithelial cells (HBECs) to proliferate and differentiate into pseudostratified epithelium. Furthermore, we discover that HBECs migrate significantly faster on hydrogel substrates with stiffness matching that of fibrotic lung tissues, highlighting the importance of mechanical cues in human airway remodeling. The developed gel-ALI system provides a facile approach to studying the effects of mechanical cues in human airway biology and in modeling pulmonary diseases.NEW & NOTEWORTHY In a conventional ALI system, cells are cultured on a plastic membrane that is much stiffer than human airway tissues. We develop a gel-ALI system by coating the plastic membrane with a thin layer of hydrogel with tunable stiffness matching that of healthy and fibrotic airway tissues. We discover that human bronchial epithelial cells migrate significantly faster on hydrogel substrates with pathological stiffness, highlighting the importance of mechanical cues in human airway remodeling.

A Fast Scoring of Human Primary Respiratory Epithelia Grown at Air-Liquid Interface (ALI) to Assess Epithelial Morphology in Research and Personalized Medicine Settings

BACKGROUND

In recent years, increasingly complex ALI protocols involving specialized, albeit laboratory-specific media have been established, while at the same time, many studies compile the data of only a few ALI donors in spite of site-, protocol- and donor-specific differentiation.

METHODS

We describe a simple morphology scoring protocol using histology material derived from epithelia grown on ALI inserts in parallel to other, more complex readouts.

RESULTS

Among more than 100 ALI inserts derived from different donors, significant differences in layer score (p = 0.001) and goblet cell score (p = 0.002) were observed when ALI epithelia derived from explanted lung material were compared to trachea-derived ALI cultures. Cortisol withdrawal for the final 2 days of ALI cultures influenced goblet cell density (p = 0.001).

CONCLUSIONS

While the histology score provides less resolution than FACS- or OMICs- based single cell analyses, the use of a subportion of the ALI epithelia grown on inserts makes it feasible to combine morphology assessment and other readouts of the same insert. This allows us to control for basic ALI morphology in research and personalized medicine settings in order to assess and, if desired, control for the impact of ALI culture protocols, site- and donor-specific influences on outcome of studies of ALI-derived epithelia.

Combination of CRISPR-Cas9-RNP and Single-Cell RNAseq to Identify Cell State-Specific FOXJ1 Functions in the Human Airway Epithelium

The study of the airway epithelium in vitro is routinely performed using air-liquid culture (ALI) models from nasal or bronchial basal cells. These 3D experimental models allow to follow the regeneration steps of fully differentiated mucociliary epithelium and to study gene function by performing gene invalidation. Recent progress made with CRISPR-based techniques has overcome the experimental difficulty of this approach, by a direct transfection of ribonucleoprotein complexes combining a mix of synthetic small guide RNAs (sgRNAs) and recombinant Cas9. The approach shows more than 95% efficiency and does not require any selection step. A limitation of this approach is that it generates cell populations that contain heterogeneous deletions, which makes the evaluation of invalidation efficiency difficult. We have successfully used Flongle sequencing (Nanopore) to quantify the number of distinct deletions. We describe the use of CRISPR-Cas9 RNP in combination with single-cell RNA sequencing to functionally characterize the impact of gene invalidation in ALI cultures. The complex ecosystem of the airway epithelium, composed of many cell types, makes single-cell approaches particularly relevant to study cell type, or cell state-specific events. This protocol describes the invalidation of FOXJ1 in ALI cultures through the following steps: (1) Establishment of basal cell cultures from nasal turbinates, (2) CRISPR-Cas9 RNP invalidation of FOXJ1, (3) Quantification of FOXJ1 invalidation efficiency by Nanopore sequencing, (4) Dissociation of ALI cultures and single-cell RNAseq, (5) Analysis of single-cell RNAseq data from FOXJ1-invalidated cells.We confirm here that FOXJ1 invalidation impairs the final differentiation step of multiciliated cells and provides a framework to explore other gene functions.

Multiomics Analysis of a DNAH5-Mutated PCD Organoid Model Revealed the Key Role of the TGF-β/BMP and Notch Pathways in Epithelial Differentiation and the Immune Response in DNAH5-Mutated Patients

Dynein axonemal heavy chain 5 (DNAH5) is the most mutated gene in primary ciliary dyskinesia (PCD), leading to abnormal cilia ultrastructure and function. Few studies have revealed the genetic characteristics and pathogenetic mechanisms of PCD caused by DNAH5 mutation. Here, we established a child PCD airway organoid directly from the bronchoscopic biopsy of a patient with the DNAH5 mutation. The motile cilia in the organoid were observed and could be stably maintained for an extended time. We further found abnormal ciliary function and a decreased immune response caused by the DNAH5 mutation through single-cell RNA sequencing (scRNA-Seq) and proteomic analyses. Additionally, the directed induction of the ciliated cells, regulated by TGF-β/BMP and the Notch pathway, also increased the expression of inflammatory cytokines. Taken together, these results demonstrated that the combination of multiomics analysis and organoid modelling could reveal the close connection between the immune response and the DNAH5 gene.

Arachidonate 15-lipoxygenase type B: Regulation, function, and its role in pathophysiology

As a lipoxygenase (LOX), arachidonate 15-lipoxygenase type B (ALOX15B) peroxidizes polyenoic fatty acids (PUFAs) including arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and linoleic acid (LA) to their corresponding fatty acid hydroperoxides. Distinctive to ALOX15B, fatty acid oxygenation occurs with positional specificity, catalyzed by the non-heme iron containing active site, and in addition to free PUFAs, membrane-esterified fatty acids serve as substrates for ALOX15B. Like other LOX enzymes, ALOX15B is linked to the formation of specialized pro-resolving lipid mediators (SPMs), and altered expression is apparent in various inflammatory diseases such as asthma, psoriasis, and atherosclerosis. In primary human macrophages, ALOX15B expression is associated with cellular cholesterol homeostasis and is induced by hypoxia. Like in inflammation, the role of ALOX15B in cancer is inconclusive. In prostate and breast carcinomas, ALOX15B is attributed a tumor-suppressive role, whereas in colorectal cancer, ALOX15B expression is associated with a poorer prognosis. As the biological function of ALOX15B remains an open question, this review aims to provide a comprehensive overview of the current state of research related to ALOX15B.

Mobilisation of HLA-F on the surface of bronchial epithelial cells and platelets in asthmatic patients

Uncontrolled inflammation of the airways in chronic obstructive lung diseases leads to exacerbation, accelerated lung dysfunction and respiratory insufficiency. Among these diseases, asthma affects 358 million people worldwide. Human bronchial epithelium cells (HBEC) express both anti-inflammatory and activating molecules, and their deregulated expression contribute to immune cell recruitment and activation, especially platelets (PLT) particularly involved in lung tissue inflammation in asthma context. Previous results supported that HLA-G dysregulation in lung tissue is associated with immune cell activation. We investigated here HLA-F expression, reported to be mobilised on immune cell surface upon activation and displaying its highest affinity for the KIR3DS1-activating NK receptor. We explored HLA-F transcriptional expression in HBEC; HLA-F total expression in PBMC and HBEC collected from healthy individuals at rest and upon chemical activation and HLA-F membrane expression in PBMC, HBEC and PLT collected from healthy individuals at rest and upon chemical activation. We compared HLA-F transcriptional expression in HBEC from healthy individuals and asthmatic patients and its surface expression in HBEC and PLT from healthy individuals and asthmatic patients. Our results support that HLA-F is expressed by HBEC and PLT under healthy physiological conditions and is retained in cytoplasm, barely expressed on the surface, as previously reported in immune cells. In both cell types, HLA-F reaches the surface in the inflammatory asthma context whereas no effect is observed at the transcriptional level. Our study suggests that HLA-F surface expression is a ubiquitous post-transcriptional process in activated cells. It may be of therapeutic interest in controlling lung inflammation.

Asthmatic bronchial smooth muscle increases rhinovirus replication within the bronchial epithelium

Rhinovirus (RV) infection of the bronchial epithelium is implicated in the vast majority of severe asthma exacerbations. Interestingly, the susceptibility of bronchial epithelium to RV infection is increased in persons with asthma. Bronchial smooth muscle (BSM) remodeling is an important feature of severe asthma pathophysiology, and its reduction using bronchial thermoplasty has been associated with a significant decrease in the exacerbation rate. We hypothesized that asthmatic BSM can play a role in RV infection of the bronchial epithelium. Using an original co-culture model between bronchial epithelium and BSM cells, we show that asthmatic BSM cells increase RV replication in bronchial epithelium following RV infection. These findings are related to the increased production of CCL20 by asthmatic BSM cells. Moreover, we demonstrate an original downregulation of the activity of the epithelial protein kinase RNA-activated (PKR) antiviral pathway. Finally, we identify a direct bottom-up effect of asthmatic BSM cells on bronchial epithelium susceptibility to RV infection.

Using intracellular SCGB1A1-sorted, formalin-fixed club cells for successful transcriptomic analysis

As opposed to surface marker staining, certain cell types can only be recognized by intracellular markers. Intracellular staining for use in cell sorting remains challenging. Fixation and permeabilization steps for intracellular staining and the presence of RNases notably affect preservation of high-quality mRNA. We report the work required for the optimization of a successful protocol for microarray analysis of intracellular target-sorted, formalin-fixed human bronchial club cells. Cells obtained from differentiated air-liquid interface cultures were stained with the most characteristic intracellular markers for club cell (SCGB1A1⁺) sorting. A benchmarked intracellular staining protocol was carried out before flow cytometry. The primary outcome was the extraction of RNA sufficient quality for microarray analysis as assessed by Bioanalyzer System. Fixation with 4% paraformaldehyde coupled with 0.1% Triton/0.1% saponin permeabilization obtained optimal results for SCGB1A1 staining. Addition of RNase inhibitors throughout the protocol and within the appropriate RNA extraction kit (Formalin-Fixed-Paraffin-Embedded) dramatically improved RNA quality, resulting in samples eligible for microarray analysis. The protocol resulted in successful cell sorting according to specific club cell intracellular marker without using cell surface marker. The protocol also preserved RNA of sufficient quality for subsequent microarray transcriptomic analysis, and we were able to generate transcriptomic signature of club cells.

Methods of Sputum and Mucus Assessment for Muco-Obstructive Lung Diseases in 2022: Time to “Unplug” from Our Daily Routine!

Obstructive lung diseases, such as chronic obstructive pulmonary disease, asthma, or non-cystic fibrosis bronchiectasis, share some major pathophysiological features: small airway involvement, dysregulation of adaptive and innate pulmonary immune homeostasis, mucus hyperproduction, and/or hyperconcentration. Mucus regulation is particularly valuable from a therapeutic perspective given it contributes to airflow obstruction, symptom intensity, disease severity, and to some extent, disease prognosis in these diseases. It is therefore crucial to understand the mucus constitution of our patients, its behavior in a stable state and during exacerbation, and its regulatory mechanisms. These are all elements representing potential therapeutic targets, especially in the era of biologics. Here, we first briefly discuss the composition and characteristics of sputum. We focus on mucus and mucins, and then elaborate on the different sample collection procedures and how their quality is ensured. We then give an overview of the different direct analytical techniques available in both clinical routine and more experimental settings, giving their advantages and limitations. We also report on indirect mucus assessment procedures (questionnaires, high-resolution computed tomography scanning of the chest, lung function tests). Finally, we consider ways of integrating these techniques with current and future therapeutic options. Cystic fibrosis will not be discussed given its monogenic nature.

Rhinovirus infection of bronchial epithelium induces specific bronchial smooth muscle cell migration of severe asthmatic patients

BACKGROUND

Patients with severe asthma show an increase in both exacerbation frequency and bronchial smooth muscle (BSM) mass. Rhinovirus (RV) infection of the bronchial epithelium (BE) is the main trigger of asthma exacerbations. Histological analysis of biopsies shows that a close connection between BE and hypertrophic BSM is a criterion for severity of asthma.

OBJECTIVE

We hypothesized that RV infection of BE specifically increases asthmatic BSM cell migration.

METHODS

Serum samples, biopsies or BSM cells were obtained from 86 patients with severe asthma and 31 non-asthmatic subjects. BE cells from non-asthmatic subjects were cultured in an air-liquid interface and exposed to RV-16. Migration of BSM cells was assessed in response to BE supernatant using chemotaxis assays. Chemokine concentrations were analyzed by transcriptomics and ELISAs. Immunocytochemistry, western blotting and flow cytometry were used to quantify CXCR3 isoform distribution. CXCR3 downstream signaling pathways were assessed by calcium imaging and western blots.

RESULTS

BSM cells from severe asthmatic patients specifically migrated toward RV-infected BE, whereas those from non-asthmatic subjects did not. This specific migration is driven by BE CXCL10, which was increased in vitro in response to RV infection as well as in vivo in serum from exacerbating patients with severe asthma. The mechanism is related to both decreased expression and activation of the CXCR3-B-specific isoform in severe asthmatic BSM cells.

CONCLUSION

We have demonstrated a novel mechanism of BSM remodeling in severe asthmatic patients following RV exacerbation. This study highlights the CXCL10/CXCR3-A axis as a potential therapeutic target in severe asthma.

Vulnerability to acid reflux of the airway epithelium in severe asthma

BACKGROUND

Severe asthma is associated with multiple co-morbidities, including gastro-oesophageal reflux disease (GORD) which can contribute to exacerbation frequency and poor quality of life. Since epithelial dysfunction is an important feature in asthma, we hypothesised that in severe asthma the bronchial epithelium is more susceptible to the effects of acid reflux.

METHODS

We developed an in vitro model of GORD using differentiated bronchial epithelial cells (BECs) from normal or severe asthmatic donors exposed to a combination of pepsin, acid pH, and bile acids using a multiple challenge protocol (MCP-PAB). We also analysed bronchial biopsies and undertook RNA-sequencing of bronchial brushings from controls and severe asthmatics without or with GORD.

RESULTS

Exposure of BECs to the MCP-PAB caused structural disruption, increased permeability, IL-33 expression, inflammatory mediator release and changes in gene expression for multiple biological processes. Cultures from severe asthmatics were significantly more affected than those from healthy donors. Analysis of bronchial biopsies confirmed increased IL-33 expression in severe asthmatics with GORD. RNA-sequencing of bronchial brushings from this group identified 15 of the top 37 dysregulated genes found in MCP-PAB treated BECs, including genes involved in oxidative stress responses.

CONCLUSIONS

By affecting epithelial permeability, GORD may increase exposure of the airway submucosa to allergens and pathogens, resulting in increased risk of inflammation and exacerbations.

CLINICAL IMPLICATION

These results suggest the need for research into alternative therapeutic management of GORD in severe asthma.

Airway epithelial dysfunction and mesenchymal transition in chronic obstructive pulmonary disease: Role of Oct-4

The airway epithelium is a dynamic tissue that undergoes slow but constant renewal. Dysregulation of airway epithelial function related to cigarette smoke exposure plays an important role in the pathophysiology of COPD. Oct4 is a transcription factor responsible for maintaining cellular self-renewal and regeneration, and CD146 and CD105/Endoglin are adhesion molecules involved in cell proliferation, differentiation, epithelial-mesenchymal-transition and tissue remodeling. Bronchial biopsy specimens (BBs) were obtained from 7 healthy controls (HC) and 10 COPD and subjected to paraffin embedding; BBs from HC were also used for epithelial cell expansion and pHBEC/ALI (air-liquid interface) culture. pHBEC/ALI were exposed to cigarette smoke extract (CSE) for 7, 14 and 21 days. In BBs, Oct4, CD146 and CD105 were evaluated by immunohistochemistry. In pHBEC/ALI, the expression of Oct4, CD146, CD105 and acetyl-αtubulin was evaluated by Western Blot, MUC5AC and IL-8 measurements by ELISA. The Oct4 epithelial immunoreactivity was lower in COPD than in HC, whilst CD146 and CD105 expression was higher in COPD than in HC. In pHBEC/ALI, Transepithelial Electrical Resistance values, measured over 7 to 21 days of differentiation, decreased by 18% (2.5% CSE) and 29% (5% CSE) compared to untreated samples. Oct4 and acetyl-αtubulin were induced after one-week differentiation and downregulated by CSE in reconstituted epithelium; CD146, CD105, MUC5AC and IL-8 were increased by CSE. Oct4 de-regulation and CD146 and CD105 overexpression, induced by cigarette smoke exposure, might play a role in airway epithelial dysfunction by causing changes in self-renewal and mesenchymal transition mechanisms, leading to alteration of epithelium homeostasis and abnormal tissue remodeling involved in progression of COPD.

Transcriptome-wide profiling discover: PM2.5 aggravates airway dysfunction through epithelial barrier damage regulated by Stanniocalcin 2 in an OVA-induced model

BACKGROUND

Epidemiologic evidence suggests that PM2.5 exposure aggravates asthma, but the molecular mechanisms are not fully discovered.

METHODS

Ovalbumin (OVA)-induced mice exposed to PM2.5 were constructed. Pathological staining and immunofluorescence were performed in in vivo study. Gene set enrichment analysis (GSEA) was performed to identify the pathway involved in asthma severity by using U-BIOPRED data (human bronchial biopsies) and RNA-seq data (Beas-2B cells treated with PM2.5). Lentiviruses transfection, Real-time qPCR, immunofluorescence staining and trans-epithelial electrical resistance (TEER) measurement were performed for mechanism exploration in vitro.

RESULTS

PM2.5 exposure aggravated airway inflammation and mucus secretion in OVA-induced mice. Based on transcriptome analysis of mild-to-severe asthma from human bronchial biopsies, gene set enrichment analysis (GSEA) showed that up-regulated reactive oxygen species (ROS) pathway gene set and down-regulated apical junction gene set correlated with asthma severity. Consistent with the analysis of mild-to-severe asthma, after PM2.5 exposure, the ROS pathway in Beas-2B cells was up-regulated with the down-regulation of apical junction. The expression levels of genes involved in the specific gene sets were validated by using qPCR. The mRNA levels of junction genes, ZO-1, E-cadherin and Occludin, were significantly decreased in cells exposed to PM2.5. Moreover, it confirmed that inhibition of ROS recovered the expression levels of E-cadherin, Occludin and ZO-1, and ameliorated inflammation and mucus secretion in airway in OVA-induced mice exposed to PM2.5. Meanwhile, ROS level was elevated by PM2.5. By checking trans-epithelial electrical resistance (TEER) value, we also found that epithelial barrier was damaged after PM2.5 exposure. Importantly, Stanniocalcin 2 (STC2) was identified as a key gene in regulation of epithelial barrier. It showed that STC2 expression was up-regulated by PM2.5, which was recovered by NAC as well. Over-expression of STC2 could decrease the expression levels of ZO-1, Occludin and E-cadherin. Contrarily, suppression of STC2 could increase the expression levels of ZO-1, Occludin and E-cadherin reduced by PM2.5.

CONCLUSIONS

By using transcriptome analysis, we revealed that STC2 played a key role in PM2.5 aggravated airway dysfunction through regulation of epithelial barrier in OVA-induced mice.

Air-liquid interface cultures of the healthy and diseased human respiratory tract: promises, challenges and future directions

Air-liquid interface (ALI) culture models currently represent a valid instrument to recreate the typical aspects of the respiratory tract in vitro in both healthy and diseased state. They can help reducing the number of animal experiments, therefore, supporting the 3R principle. This review discusses ALI cultures and co-cultures derived from immortalized as well as primary cells, which are used to study the most common disorders of the respiratory tract, in terms of both pathophysiology and drug screening. The article displays ALI models used to simulate inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, lung cancer, and viral infections. It also includes a focus on ALI cultures described in literature studying respiratory viruses such as SARS-CoV-2 causing the global Covid-19 pandemic at the time of writing this review. Additionally, commercially available models of ALI cultures are presented. Ultimately, the aim of this review is to provide a detailed overview of ALI models currently available and to critically discuss them in the context of the most prevalent diseases of the respiratory tract.

Long-term differentiating primary human airway epithelial cell cultures: how far are we?

BACKGROUND

Human airway epithelial (HAE) cellular models are widely used in applicative studies of the airway physiology and disease. In vitro expanded and differentiated primary HAE cells collected from patients seem to be an accurate model of human airway, offering a quicker and cheaper alternative to the induced pluripotent stem cell (iPSCs) models. However, the biggest drawback of primary HAE models is their limited proliferative lifespan in culture. Much work has been devoted to understand the factors, which govern the HAE cell proliferation and differentiation, both in vivo and in vitro. Here, I have summarized recent achievements in primary HAE culture, with the special emphasis on the models of conditionally reprogrammed cells (CRC), which allow longer in vitro proliferation and differentiation of HAE cells. The review compares the CRC HAE technique variants (feeder culture or HAE mono-culture), based on recently published studies exploiting this model. The advantages and limitations of each CRC HAE model variant are summarized, along with the description of other factors affecting the CRC HAE culture success (tissue type, sampling method, sample quality).

CONCLUSIONS

CRC HAE cultures are a useful technique in respiratory research, which in many cases exceeds the iPSCs and organoid culture methods. Until the current limitations of the iPSCs and organoid culture methods will be alleviated, the primary CRC HAE cultures might be a useful model in respiratory research. Airway epithelium (AE) is a type of tissue, which lines the whole length of human airways, from the nose to the bronchi. Improper functioning of AE causes several human airway disorders, such as asthma, chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF). Much work has been devoted to finding the best scientific model of human AE, in order to learn about its functioning in health and disease. Among the popular AE models are the primary in vitro cultured AE cells collected from human donors. Unfortunately, such human AE (HAE) cells do not easily divide (expand) in vitro; this poses a large logistic and ethical problem for the researchers. Here, I summarize recent achievements in the methods for in vitro culture of human AE cells, with special emphasis on the conditionally reprogrammed cell (CRC) models, which allow longer and more effective expansion of primary human AE cells in vitro. The review describes how the specific chemicals used in the CRC models work to allow the increased HAE divisions and compares the effects of the different so-far developed variants of the CRC HAE culture. The review also pinpoints the areas which need to be refined, in order to maximize the usefulness of the CRC AE cultures from human donors in research on human airway disorders. Video abstract.

Oxygenation as a driving factor in epithelial differentiation at the air-liquid interface

Culture at the air-liquid interface is broadly accepted as necessary for differentiation of cultured epithelial cells towards an in vivo-like phenotype. However, air-liquid interface cultures are expensive, laborious and challenging to scale for increased throughput applications. Deconstructing the microenvironmental parameters that drive these differentiation processes could circumvent these limitations, and here we hypothesize that reduced oxygenation due to diffusion limitations in liquid media limits differentiation in submerged cultures; and that this phenotype can be rescued by recreating normoxic conditions at the epithelial monolayer, even under submerged conditions. Guided by computational models, hyperoxygenation of atmospheric conditions was applied to manipulate oxygenation at the monolayer surface. The impact of this rescue condition was confirmed by assessing protein expression of hypoxia-sensitive markers. Differentiation of primary human bronchial epithelial cells isolated from healthy patients was then assessed in air-liquid interface, submerged and hyperoxygenated submerged culture conditions. Markers of differentiation, including epithelial layer thickness, tight junction formation, ciliated surface area and functional capacity for mucociliary clearance, were assessed and found to improve significantly in hyperoxygenated submerged cultures, beyond standard air-liquid interface or submerged culture conditions. These results demonstrate that an air-liquid interface is not necessary to produce highly differentiated epithelial structures, and that increased availability of oxygen and nutrient media can be leveraged as important strategies to improve epithelial differentiation for applications in respiratory toxicology and therapeutic development.

From Submerged Cultures to 3D Cell Culture Models: Evolution of Nasal Epithelial Cells in Asthma Research and Virus Infection

Understanding the response to viral infection in the context of respiratory diseases is of significant importance. Recently, there has been more focus on the role of the nasal epithelium in disease modeling. Here, we provide an overview of different submerged, organotypic 3D and spheroid cell culture models of nasal epithelial cells, which were used to study asthma and allergy with a special focus on virus infection. In detail, this review summarizes the importance, benefits, and disadvantages of patient-derived cell culture models of nasal- and bronchial epithelial cells, including a comparison of these cell culture models and a discussion on why investigators should consider using nasal epithelial cells in their research. Exposure experiments, simple virus transduction analyses as well as genetic studies can be performed in these models, which may provide first insights into the complexity of molecular signatures and may open new doors for drug discovery and biomarker research.

Metabolic differences between bronchial epithelium from healthy individuals and patients with asthma and the effect of bronchial thermoplasty

BACKGROUND

Asthma is a heterogeneous disease with differences in onset, severity, and inflammation. Bronchial epithelial cells (BECs) contribute to asthma pathophysiology.

OBJECTIVE

We determined whether transcriptomes of BECs reflect heterogeneity in inflammation and severity in asthma, and whether this was affected in BECs from patients with severe asthma after their regeneration by bronchial thermoplasty.

METHODS

RNA sequencing was performed on BECs obtained by bronchoscopy from healthy controls (n = 16), patients with mild asthma (n = 17), patients with moderate asthma (n = 5), and patients with severe asthma (n = 17), as well as on BECs from treated and untreated airways of the latter (also 6 months after bronchial thermoplasty) (n = 23). Lipidome and metabolome analyses were performed on cultured BECs from healthy controls (n = 7); patients with severe asthma (n = 9); and, for comparison, patients with chronic obstructive pulmonary disease (n = 7).

RESULTS

Transcriptome analysis of BECs from patients showed a reduced expression of oxidative phosphorylation (OXPHOS) genes, most profoundly in patients with severe asthma but less profoundly and more heterogeneously in patients with mild asthma. Genes related to fatty acid metabolism were significantly upregulated in asthma. Lipidomics revealed enhanced levels of lipid species (phosphatidylcholines, lysophosphatidylcholines. and bis(monoacylglycerol)phosphate), whereas levels of OXPHOS metabolites were reduced in BECs from patients with severe asthma. BECs from patients with mild asthma characterized by hyperresponsive production of mediators implicated in neutrophilic inflammation had decreased expression of OXPHOS genes compared with that in BECs from patients with mild asthma with normoresponsive production. BECs obtained after thermoplasty had significantly increased expression of OXPHOS genes and decreased expression of fatty acid metabolism genes compared with BECs obtained from untreated airways.

CONCLUSION

BECs in patients with asthma are metabolically different from those in healthy individuals. These differences are linked with inflammation and asthma severity, and they can be reversed by bronchial thermoplasty.

Experimental Models to Study COVID-19 Effect in Stem Cells

The new strain of coronavirus (severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2)) emerged in 2019 and hence is often referred to as coronavirus disease 2019 (COVID-19). This disease causes hypoxic respiratory failure and acute respiratory distress syndrome (ARDS), and is considered as the cause of a global pandemic. Very limited reports in addition to ex vivo model systems are available to understand the mechanism of action of this virus, which can be used for testing of any drug efficacy against virus infectivity. COVID-19 induces tissue stem cell loss, resulting inhibition of epithelial repair followed by inflammatory fibrotic consequences. Development of clinically relevant models is important to examine the impact of the COVID-19 virus in tissue stem cells among different organs. In this review, we discuss ex vivo experimental models available to study the effect of COVID-19 on tissue stem cells.

Resolution-Based Therapies: The Potential of Lipoxins to Treat Human Diseases

Inflammation is an a physiological response instead an essential response of the organism to injury and its adequate resolution is essential to restore homeostasis. However, defective resolution can be the precursor of severe forms of chronic inflammation and fibrosis. Nowadays, it is known that an excessive inflammatory response underlies the most prevalent human pathologies worldwide. Therefore, great biomedical research efforts have been driven toward discovering new strategies to promote the resolution of inflammation with fewer side-effects and more specificity than the available anti-inflammatory treatments. In this line, the use of endogenous specialized pro-resolving mediators (SPMs) has gained a prominent interest. Among the different SPMs described, lipoxins stand out as one of the most studied and their deficiency has been widely associated with a wide range of pathologies. In this review, we examined the current knowledge on the therapeutic potential of lipoxins to treat diseases characterized by a severe inflammatory background affecting main physiological systems, paying special attention to the signaling pathways involved. Altogether, we provide an updated overview of the evidence suggesting that increasing endogenously generated lipoxins may emerge as a new therapeutic approach to prevent and treat many of the most prevalent diseases underpinned by an increased inflammatory response.

Utilizing Organoid and Air-Liquid Interface Models as a Screening Method in the Development of New Host Defense Peptides

Host defense peptides (HDPs), also known as antimicrobial peptides, are naturally occurring polypeptides (~12–50 residues) composed of cationic and hydrophobic amino acids that adopt an amphipathic conformation upon folding usually after contact with membranes. HDPs have a variety of biological activities including immunomodulatory, anti-inflammatory, anti-bacterial, and anti-biofilm functions. Although HDPs have the potential to address the global threat of antibiotic resistance and to treat immune and inflammatory disorders, they have yet to achieve this promise. Indeed, there are several challenges associated with bringing peptide-based drug candidates from the lab bench to clinical practice, including identifying appropriate indications, stability, toxicity, and cost. These challenges can be addressed in part by the development of innate defense regulator (IDR) peptides and peptidomimetics, which are synthetic derivatives of HDPs with similar or better efficacy, increased stability, and reduced toxicity and cost of the original HDP. However, one of the largest gaps between basic research and clinical application is the validity and translatability of conventional model systems, such as cell lines and animal models, for screening HDPs and their derivatives as potential drug therapies. Indeed, such translation has often relied on animal models, which have only limited validity. Here we discuss the recent development of human organoids for disease modeling and drug screening, assisted by the use of omics analyses. Organoids, developed from primary cells, cell lines, or human pluripotent stem cells, are three-dimensional, self-organizing structures that closely resemble their corresponding in vivo organs with regards to immune responses, tissue organization, and physiological properties; thus, organoids represent a reliable method for studying efficacy, formulation, toxicity and to some extent drug stability and pharmacodynamics. The use of patient-derived organoids enables the study of patient-specific efficacy, toxicogenomics and drug response predictions. We outline how organoids and omics data analysis can be leveraged to aid in the clinical translation of IDR peptides.

Can PBDEs affect the pathophysiologic complex of epithelium in lung diseases?

Brominated flame-retardant (BFRs) exposure promotes multiple adverse health outcomes involved in oxidative stress, inflammation, and tissues damage. We investigated BFR effects, known as polybrominated diphenyl ethers (PBDEs) (47, 99 and 209) in an air-liquid-interface (ALI) airway tissue derived from A549 cell line, and compared with ALI culture of primary human bronchial epithelial cells (pHBEC). The cells, exposed to PBDEs (47, 99 and 209) (0.01-1 μM) for 24 h, were studied for IL-8, Muc5AC and Muc5B (mRNAs and proteins) production, as well as NOX-4 (mRNA) expression. Furthermore, we evaluated tight junction (TJ) integrity by Trans-Epithelial Electrical Resistance (TEER) measurements, and zonula occludens-1 (ZO-1) expression in the cells, and pH variations and rheological properties (elastic G', and viscous G″, moduli) in apical washes of ALI cultures. N-acetylcysteine (NAC) (10 mM) effects were tested in our experimental model of A549 cells. PBDEs (47, 99 and 209) exposure decreased TEER, ZO-1 and pH values, and increased IL-8, Muc5AC, Muc5B (mRNAs and proteins), NOX-4 (mRNA), and rheological parameters (G', G″) in ALI cultures of A549 cell line and pHBEC. NAC inhibited PBDE effects in A549 cells. PBDE inhalation might impairs human health of the lungs inducing oxidative stress, inflammatory response, loss of barrier integrity, unchecked mucus production, as well as altered physicochemical and biological properties of the fluids in airway epithelium. The treatment with anti-oxidants restored the negative effects of PBDEs in epithelial cells.

HLA-H: Transcriptional Activity and HLA-E Mobilization

Little attention is paid to pseudogenes from the highly polymorphic HLA genetic region. The pseudogene HLA-H is defined as a non-functional gene because it is deleted at different frequencies in humans and because it encodes a potentially non-functional truncated protein. However, different studies have shown HLA-H transcriptional activity. We formerly identified 13 novel HLA-H alleles, including the H*02:07 allele, which reaches 19.6% in East Asian populations and encodes a full-length HLA protein. The aims of this study were to explore the expression and possible function of the HLA-H molecule. HLA-H may act as a transmembrane molecule and/or indirectly via its signal peptide by mobilizing HLA-E to the cell surface. We analyzed HLA-H RNA expression in Peripheral Blood Mononuclear Cells (PBMC), Human Bronchial Epithelial Cells (HBEC), and available RNA sequencing data from lymphoblastoid cell lines, and we looked to see whether HLA-E was mobilized at the cell surface by the HLA-H signal peptide. Our data confirmed that HLA-H is transcribed at similar levels to HLA-G. We characterized a hemizygous effect in HLA-H expression, and expression differed according to HLA-H alleles; most interestingly, the HLA-H*02:07 allele had the highest level of mRNA expression. We showed that HLA-H signal peptide incubation mobilized HLA-E molecules at the cell surface of T-Lymphocytes, monocytes, B-Lymphocytes, and primary epithelial cells. Our results suggest that HLA-H may be functional but raises many biological issues that need to be addressed.

Altered generation of ciliated cells in chronic obstructive pulmonary disease

In COPD, epithelial changes are prominent features in the airways, such as goblet cell hyperplasia and squamous metaplasia. In contrast, it remains unclear whether ciliated cells are reduced and which pathways dysregulate epithelial differentiation. We hypothesized that bronchial epithelial cell lineage specification is dysregulated in COPD because of an aberrant reprogramming through transforming growth factor (TGF)-β1. Surgical lung tissue from 81 COPD and 61 control (smokers and non-smokers) patients was assessed for bronchial epithelial cell phenotyping by immunohistochemistry, both in situ and in vitro in reconstituted air-liquid interface (ALI) cultures. The role of TGF-β1 was studied in vitro. COPD epithelium in large airways, when compared to controls, showed decreased β-tubulin IV + ciliated cells (4.4%, 2.5–8.8% versus 8.5%, 6.3–11.8% of surface staining, median and IQR, p = 0.0009) and increased MUC5AC + goblet cells (34.8%, 24.4–41.9% versus 10.3%, 5.1–17.6%, p < 0.0001). Both features were recapitulated in the ALI-cultured epithelium from COPD patients. Exogenous TGF-β1 reduced mucociliary differentiation while neutralizing TGF-β1 during ALI increased both specialized cell types. The COPD airway epithelium displays altered differentiation for ciliated cells, which recapitulates in vitro, at least in part through TGF-β1.

Bronchial Epithelial IgA Secretion Is Impaired in Asthma. Role of IL-4/IL-13

RATIONALE

Asthma is associated with increased lung IgE production, but whether the secretory IgA system is affected in this disease remains unknown.

OBJECTIVES

We explored mucosal IgA transport in human asthma and its potential regulation by T-helper cell type 2 inflammation.

METHODS

Bronchial biopsies from asthma and control subjects were assayed for bronchial epithelial polymeric immunoglobulin receptor (pIgR) expression and correlated to T-helper cell type 2 biomarkers. Bronchial epithelium reconstituted in vitro from these subjects, on culture in air-liquid interface, was assayed for pIgR expression and regulation by IL-4/IL-13.

MEASUREMENTS AND MAIN RESULTS

Downregulation of pIgR protein was observed in the bronchial epithelium from patients with asthma (P = 0.0002 vs. control subjects). This epithelial defect was not observed ex vivo in the cultured epithelium from patients with asthma. Exogenous IL-13 and IL-4 could inhibit pIgR expression and IgA transcytosis. Mechanistic experiments showed that autocrine transforming growth factor-β mediates the IL-4/IL-13 effect on the pIgR, with a partial contribution of upregulated transforming growth factor-α/epidermal growth factor receptor.

CONCLUSIONS

This study shows impaired bronchial epithelial pIgR expression in asthma, presumably affecting secretory IgA-mediated frontline defense as a result of type 2 immune activation of the transforming growth factor pathway.

CCSP counterbalances airway epithelial-driven neutrophilic chemotaxis

Club cell secretory protein (CCSP) knockout mice exhibit increased airway neutrophilia, as found in chronic obstructive pulmonary disease (COPD). We therefore investigated whether treating COPD airway epithelia with recombinant human CCSP (rhCCSP) could dampen exaggerated airway neutrophilia.

Control, smoker and COPD air–liquid interface (ALI) cultures exposed to cigarette smoke extract (CSE) were treated with and without rhCCSP. The chemotactic properties of the supernatants were assessed using Dunn chambers. Neutrophil chemotaxis along recombinant human interleukin 8 (rhIL8) gradients (with and without rhCCSP) was also determined. rhCCSP–rhIL8 interactions were tested through co-immunoprecipitation, Biacore surface plasmon resonance (SPR) andin silicomodelling. The relationship between CCSP/IL8 concentration ratios in the supernatant of induced sputum from COPD patientsversusneutrophilic airway infiltration assessed in lung biopsies was assessed.

Increased neutrophilic chemotactic activity of CSE-treated ALI cultures followed IL8 concentrations and returned to normal when supplemented with rhCCSP. rhIL8-induced chemotaxis of neutrophils was reduced by rhCCSP. rhCCSP and rhIL8 co-immunoprecipitated. SPR confirmed thisin vitrointeraction (equilibrium dissociation constant=8 µM).In silicomodelling indicated that this interaction was highly likely. CCSP/IL8 ratios in induced sputum correlated well with the level of small airway neutrophilic infiltration (r2=0.746, p<0.001).

CCSP is a biologically relevant counter-balancer of neutrophil chemotactic activity. These different approaches used in this study suggest that, among the possible mechanisms involved, CCSP may directly neutralise IL8.

A lung/liver-on-a-chip platform for acute and chronic toxicity studies

The merging of three-dimensional in vitro models with multi-organ-on-a-chip (MOC) technology has taken in vitro assessment of chemicals to an unprecedented level. By connecting multiple organotypic models, MOC allows for the crosstalk between different organs to be studied to evaluate a compound's safety and efficacy better than with single cultures. The technology could also improve the toxicological assessment of aerosols that have been implicated in the development of chronic obstructive pulmonary disease, asthma, or lung cancer. Here we report the development of a lung/liver-on-a-chip, connecting in a single circuit, normal human bronchial epithelial (NHBE) cells cultured at the air-liquid interface (ALI), and HepaRG™ liver spheroids. Maintenance of the individual tissues in the chip increased NHBE ALI tissue transepithelial electrical resistance and decreased HepaRG™ spheroid adenosine triphosphate content as well as cytochrome P450 (CYP) 1A1/1B1 inducibility. CYP inducibility was partly restored when HepaRG™ spheroids were cocultured with NHBE ALI tissues. Both tissues remained viable and functional for 28 days when cocultured in the chip. The capacity of the HepaRG™ spheroids to metabolize compounds present in the medium and to modulate their toxicity was proven using aflatoxin B1 (AFB1). AFB1 toxicity in NHBE ALI tissues decreased when HepaRG™ spheroids were present in the same chip circuit, proving that the HepaRG™-mediated detoxification is protecting/decreasing from AFB1-mediated cytotoxicity. The lung/liver-on-a-chip platform presented here offers new opportunities to study the toxicity of inhaled aerosols or to demonstrate the safety and efficacy of new drug candidates targeting the human lung.

Optimising experimental research in respiratory diseases: an ERS statement

Experimental models are critical for the understanding of lung health and disease and are indispensable for drug development. However, the pathogenetic and clinical relevance of the models is often unclear. Further, the use of animals in biomedical research is controversial from an ethical perspective.The objective of this task force was to issue a statement with research recommendations about lung disease models by facilitating in-depth discussions between respiratory scientists, and to provide an overview of the literature on the available models. Focus was put on their specific benefits and limitations. This will result in more efficient use of resources and greater reduction in the numbers of animals employed, thereby enhancing the ethical standards and translational capacity of experimental research.The task force statement addresses general issues of experimental research (ethics, species, sex, age, ex vivo and in vitro models, gene editing). The statement also includes research recommendations on modelling asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, lung infections, acute lung injury and pulmonary hypertension.The task force stressed the importance of using multiple models to strengthen validity of results, the need to increase the availability of human tissues and the importance of standard operating procedures and data quality.

Spatiotemporal organization of cilia drives multiscale mucus swirls in model human bronchial epithelium

Mucociliary clearance is a biomechanical mechanism of airway protection. It consists of the active transport along the bronchial tree of the mucus, a fluid propelled by the coordinated beating of a myriad of cilia on the epithelial surface of the respiratory tract. The physics of mucus transport is poorly understood because it involves complex phenomena such as long-range hydrodynamic interactions, active collective ciliary motion, and the complex rheology of mucus. We propose a quantitative physical analysis of the ciliary activity and mucus transport on a large panel of human bronchial cultures from control subjects, patients with asthma and chronic obstructive pulmonary disease obtained from endobronchial biopsies. Here we report on the existence of multiple ciliary domains with sizes ranging from the tens of a micron to the centimeter, where ciliary beats present a circular orientational order. These domains are associated with circular mucus flow patterns, whose size scales with the average cilia density. In these domains, we find that the radial increase of the ciliated cell density coupled with the increase in the orientational order of ciliary beats result in a net local force proportional to the mucus velocity. We propose a phenomenological physical model that supports our results.

Human lung epithelial cell cultures for analysis of inhaled toxicants: Lessons learned and future directions

The epithelium that covers the conducting airways and alveoli is a primary target for inhaled toxic substances, and therefore a focus in inhalation toxicology. The increasing concern about the use of animal models has stimulated the development of in vitro cell culture models for analysis of the biological effects of inhaled toxicants. However, the validity of the current in vitro models and their acceptance by regulatory authorities as an alternative to animal models is a reason for concern, and requires a critical review. In this review, focused on human lung epithelial cell cultures as a model for inhalation toxicology, we discuss the choice of cells for these models, the cell culture system used, the method of exposure as well as the various read-outs to assess the cellular response. We argue that rapid developments in the 3D culture of primary epithelial cells, the use of induced pluripotent stem cells for generation of lung epithelial cells and the development of organ-on-a-chip technology are among the important developments that will allow significant advances in this field. Furthermore, we discuss the various routes of application of inhaled toxicants by air-liquid interface models as well as the vast array of read-outs that may provide essential information. We conclude that close collaboration between researchers from various disciplines is essential for development of valid methods that are suitable for replacement of animal studies for inhalation toxicology.

Expression of polycomb protein BMI-1 maintains the plasticity of basal bronchial epithelial cells

The airway epithelium is altered in respiratory disease and is thought to contribute to disease etiology. A caveat to disease research is that the technique of isolation of bronchial epithelial cells from patients is invasive and cells have a limited lifespan. The aim of this study was to extensively characterize the plasticity of primary human bronchial epithelial cells that have been engineered to delay cell senescence including the ability of these cells to differentiate. Cells were engineered to express BMI‐1 or hTERT using viral vector systems. Cells were characterized at passage (p) early (p5), mid (p10), and late (p15) stage for: BMI‐1, p16, and CK14 protein expression, viability and the ability to differentiate at air–liquid interface (ALI), using a range of techniques including immunohistochemistry (IHC), immunofluorescence (IF), transepithelial electrical resistance (TEER), scanning electron microscopy (SEM), MUC5AC and beta tubulin (BTUB) staining. BMI‐1‐expressing cells maintained elevated levels of the BMI‐1 protein and the epithelial marker CK14 and showed a suppression of p16. BMI‐1‐expressing cells had a viability advantage, differentiated at ALI, and had a normal karyotype. In contrast, hTERT‐expressing cells had a reduced viability, showed limited differentiation, and had an abnormal karyotype. We therefore provide extensive characterization of the plasticity of BMI‐1 expressing cells in the context of the ALI model. These cells retain properties of wild‐type cells and may be useful to characterize respiratory disease mechanisms in vitro over sustained periods.

Lung development, regeneration and plasticity: From disease physiopathology to drug design using induced pluripotent stem cells

Lungs have a complex structure composed of different cell types that form approximately 17 million airway branches of gas-delivering bronchioles connected to 500 million gas-exchanging alveoli. Airways and alveoli are lined by epithelial cells that display a low rate of turnover at steady-state, but can regenerate the epithelium in response to injuries. Here, we review the key points of lung development, homeostasis and epithelial cell plasticity in response to injury and disease, because this knowledge is required to develop new lung disease treatments. Of note, canonical signaling pathways that are essential for proper lung development during embryogenesis are also involved in the pathophysiology of most chronic airway diseases. Moreover, the perfect control of these interconnected pathways is needed for the successful differentiation of induced pluripotent stem cells (iPSC) into lung cells. Indeed, differentiation of iPSC into airway epithelium and alveoli is based on the use of biomimetics of normal embryonic and fetal lung development. In vitro iPSC-based models of lung diseases can help us to better understand the impaired lung repair capacity and to identify new therapeutic targets and new approaches, such as lung cell therapy.

Effect of nintedanib on airway inflammation and remodeling in a murine chronic asthma model

INTRODUCTION

Nintedanib is a multi-tyrosine kinase receptor inhibitor recently approved for treatment of idiopathic pulmonary fibrosis. Although angiogenesis is a key process involved in airway structural changes in patients with bronchial asthma, the effect of nintedanib targeting the angiokinase pathway on airway inflammation and remodeling has not been evaluated.

METHODS

We used a 3-month ovalbumin (OVA) challenge mouse model of airway remodeling. Nintedanib was orally administrated during the challenge period, and the effects were examined based on the percentage of airway inflammatory cells, airway hyper-reactivity (AHR), peribronchial goblet cell hyperplasia, total lung collagen and smooth muscle area. The expression of growth factor receptors was analyzed in mice lung tissues.

RESULTS

The OVA challenged group showed a significant increase in airway eosinophilic inflammation, elevated Th2 cytokines, AHR, and airway remodeling compared to those in the control group. The airway remodeling process, as evaluated by goblet cell hyperplasia, total lung collagen level, and airway smooth muscle area, was suppressed by nintedanib compared to that by OVA. Nintedanib effectively suppressed the phosphorylation of vascular endothelial growth factor/ platelet derived growth factor subunit2/fibroblast growth factor3 receptors in the mice lung.

CONCLUSIONS

Nintedanib effectively ameliorated airway inflammation and remodeling in an OVA-induced chronic asthma model. These results suggest that nintedanib could be a new treatment agent targeting airway remodeling in patients with severe asthma.

Epithelial ciliated beating cells essential for ex vivo ALI culture growth

Background

Bronchial epithelium plays a key role in orchestrating innate and adaptive immunity. The fate of ex vivo airway epithelial cultures growing at the air liquid interface (ALI) derived from human endobronchial biopsies or brushings is not easy to predict. Calibrating and differentiating these cells is a long and expensive process requiring rigorous expertise. Pinpointing factors associated with ALI culture success would help researchers gain further insight into epithelial progenitor behavior.

Methods

A successful ALI culture was defined as one in which a pseudostratified epithelium has formed after 28 days in the presence of all differentiated epithelial cell types. A 4-year prospective bi-center study was conducted with adult subjects enrolled in different approved research protocols.

Results

463 consecutive endobronchial biopsies were obtained from normal healthy volunteers, healthy smokers, asthmatic patients and smokers with COPD. All demographic variables, the different fiber optic centers and culture operators, numbers of endo-bronchial biopsies and the presence of ciliated cells were carefully recorded. Univariate and multivariate models were developed. A stepwise procedure was used to select the final logistic regression model. ALI culture success was independently associated with the presence of living ciliated cells within the initial biopsy (OR = 2.18 [1.50–3.16], p < 0.001).

Conclusion

This finding highlights the properties of the cells derived from the epithelium dedifferentiation process. The preferential selection of samples with ciliated beating cells would probably save time and money. It is still unknown whether successful ALI culture is related to indicators of general cell viability or a purported stem cell state specifically associated with ciliated beating cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-017-0423-5) contains supplementary material, which is available to authorized users.

Human bronchial epithelium orchestrates dendritic cell activation in severe asthma

The innate immune response is impaired in asthma, with increased epithelial release of C-X-C motif chemokine ligand (CXCL)8, interleukin (IL)-33 and thymic stromal lymphopoietin (TSLP). We hypothesised that dendritic cells might modulate the hyperresponsive epithelium in severe asthma.

For this purpose, we investigated epithelial–dendritic crosstalk in normal and diseased conditions, and because ultrafine particulate matter may affect asthmatic airways, we investigated its impact on this crosstalk. Air–liquid interface cultures of human bronchial epithelial cells (HBEC) of control subjects (cHBEC) or severe asthma patients (saHBEC) were co-cultured with monocyte-derived dendritic cells (moDC).

Increased release of CXCL8, TSLP and IL-33 from saHBEC contrasted with cHBEC producing CXCL10 and CCL2. Regarding moDC activation, saHBEC co-cultures induced only upregulation of CD86 expression, while cHBEC yielded full moDC maturation with HLA-DR, CD80, CD86 and CD40 upregulation. Particulate matter stimulation of HBEC had no effect on cHBEC but stimulated CXCL8 and IL-33 release in saHBEC. Particulate matter impaired epithelium signalling (TSLP, IL-33 and CXCL8) in saHBEC co-cultures despite C-C chemokine ligand 2 induction.

Crosstalk between HBEC and moDC can be establishedin vitro, driving a T1-type response with cHBEC and a T2-type response with saHBEC. Normal or asthmatic status of HBEC differentially shapes the epithelial–dendritic responses. We conclude that control moDC cannot rescue the hyperresponsive airway epithelium of severe asthmatics.

Bronchial Epithelial Cells from Asthmatic Patients Display Less Functional HLA-G Isoform Expression

Not all asthmatic patients adequately respond to current available treatments, such as inhaled corticosteroids or omalizumab^®. New treatments will aim to target the bronchial epithelium-immune response interaction using different pathways. HLA-G is involved in immunomodulation and may promote epithelial cell differentiation and proliferation. HLA-G protein has several isoforms generated by alternative splicing that might have differential functionalities. HLA-G protein expression and genetic polymorphisms have been reported to be associated with asthma. Our hypothesis is that bronchial epithelium from asthmatic patients displays less functional HLA-G isoforms. HLA-G transcriptional isoforms were quantified by real-time PCR in human bronchial epithelium cells (HBEC) grown in air-liquid interface culture obtained from five healthy controls (HC), seven patients with mild asthma (MA), and seven patients with severe asthma (SA). They were re-differentiated, and IL-13 exposure was used as a proxy for a pro-inflammatory cytokine. HLA-G protein expression was assessed by western blot analysis. HLA-G allele was typed by direct sequencing. Our results showed that both MA and SA display less functional HLA-G isoforms than HC (p < 0.05); in vitro HBEC re-differentiation from SA displays a particular isoform expression profile compared to MA and HC (p = 0.03); HLA-G*01:06 frequency in MA and SA was significantly higher than in the healthy population (p = 0.03 and p < 0.001, respectively); and IL-13 exposure had no impact on HLA-G expression. Our results support that an impaired expression of HLA-G isoforms in asthmatic patients could contribute to the loss of inflammation control and epithelium structural remodeling. Therefore, HLA-G might be an interesting alternative target for asthmatic patients not adequately responding to current drugs.

Astragalus polysaccharide modulates ER stress response in an OVA-LPS induced murine model of severe asthma

Endoplasmic reticulum (ER) stress has been recently revealed to play a pivotal role in the pathogenesis of severe asthma. Astragalus polysaccharide (APS), a major bioactive component from Astragalus membranaceus, exerts immunomodulatory and anti-inflammatory effects and has been shown to suppress ER stress in chronic diseases such as type-2 diabetes. However, the pharmaceutical application of APS in the treatment of severe asthma is unknown. The results obtained here indicate that APS significantly attenuates eosinophils and neutrophil-dominant airway inflammation by reducing the mRNA levels of Cxcl5, Il8, and chemokine (C-C motif) ligand 20 (Ccl20) and the protein levels of IL13RA and IL17RA. APS also inhibits the activation of unfolded protein response by decreasing the levels of ER stress markers such as C/EBP homologous protein (CHOP), which was associated with a reduction of PERK phosphorylation. Moreover, APS substantially blocks the nuclear translocation of ATF6 and NF-κB p65. Interestingly, we observed that APS markedly suppresses mucus hypersecretion by decreasing the levels of mucin (MUC) 5AC and MUC5B, which might be due to inhibition of goblet cells differentiation by suppressing the expression of IRE1β-correlated genes. In summary, APS can have potential pharmaceutical application in treatment of severe asthma.

KCa3.1 K+ Channel Expression and Function in Human Bronchial Epithelial Cells

The K_Ca3.1 K⁺ channel has been proposed as a novel target for pulmonary diseases such as asthma and pulmonary fibrosis. It is expressed in epithelia but its expression and function in primary human bronchial epithelial cells (HBECs) has not been described. Due to its proposed roles in the regulation of cell proliferation, migration, and epithelial fluid secretion, inhibiting this channel might have either beneficial or adverse effects on HBEC function. The aim of this study was to assess whether primary HBECs express the K_Ca3.1 channel and its role in HBEC function. Primary HBECs from the airways of healthy and asthmatic subjects, SV-transformed BEAS-2B cells and the neoplastic H292 epithelial cell line were studied. Primary HBECs, BEAS-2B and H292 cells expressed K_Ca3.1 mRNA and protein, and robust K_Ca3.1 ion currents. K_Ca3.1 protein expression was increased in asthmatic compared to healthy airway epithelium in situ, and K_Ca3.1 currents were larger in asthmatic compared to healthy HBECs cultured in vitro. Selective K_Ca3.1 blockers (TRAM-34, ICA-17043) had no effect on epithelial cell proliferation, wound closure, ciliary beat frequency, or mucus secretion. However, several features of TGFβ1-dependent epithelial-mesenchymal transition (EMT) were inhibited by K_Ca3.1 blockade. Treatment with K_Ca3.1 blockers is likely to be safe with respect to airway epithelial biology, and may potentially inhibit airway remodelling through the inhibition of EMT.

15-Lipoxygenases regulate the production of chemokines in human lung macrophages

BACKGROUND AND PURPOSE

15-Lipoxygenase (15-LOX) activity is associated with inflammation and immune regulation. The objectives of the present study were to investigate the expression of 15-LOX-1 and 15-LOX-2 and evaluate the enzymes' roles in the polarization of human lung macrophages (LMs) in response to LPS and Th2 cytokines (IL-4/-13).

EXPERIMENTAL APPROACH

LMs were isolated from patients undergoing surgery for carcinoma. The cells were cultured with a 15-LOX inhibitor (PD146176 or ML351), a COX inhibitor (indomethacin), a 5-LOX inhibitor (MK886) or vehicle and then stimulated with LPS (10 ng · mL(-1)), IL-4 (10 ng · mL(-1)) or IL-13 (50 ng · mL(-1)) for 24 h. Levels of ALOX15 (15-LOX-1) and ALOX15B (15-LOX-2) transcripts were determined by real-time quantitative PCR. Immunoassays were used to measure levels of LPS-induced cytokines (TNF-α, CCL2, CCL3, CCL4, CXCL1, CXCL8 and CXCL10) and Th2 cytokine-induced chemokines (CCL13, CCL18 and CCL22) in the culture supernatant.

KEY RESULTS

Stimulation of LMs with LPS was associated with increased expression of ALOX15B, whereas stimulation with IL-4/IL-13 induced the expression of ALOX15. PD146176 and ML351 (10 μM) reduced the release of the chemokines induced by LPS and Th2 cytokines. The effects of these 15-LOX inhibitors were maintained in the presence of indomethacin and MK886. Furthermore, indomethacin revealed the inhibitory effect of PD146176 on TNF-α release.

CONCLUSIONS AND IMPLICATIONS

Inhibition of the 15-LOX pathways is involved in the down-regulation of the in vitro production of chemokines in LMs. Our results suggest that the 15-LOX pathways have a role in the pathogenesis of inflammatory lung disorders and may thus constitute a potential drug target.

Analysis of a Panel of 48 Cytokines in BAL Fluids Specifically Identifies IL-8 Levels as the Only Cytokine that Distinguishes Controlled Asthma from Uncontrolled Asthma, and Correlates Inversely with FEV1

We sought to identify cells and cytokines in bronchoalveolar lavage (BAL) fluids that distinguish asthma from healthy control subjects and those that distinguish controlled asthma from uncontrolled asthma. Following informed consent, 36 human subjects were recruited for this study. These included 11 healthy control subjects, 15 subjects with controlled asthma with FEV1≥80% predicted and 10 subjects with uncontrolled asthma with FEV1 <80% predicted. BAL fluid was obtained from all subjects. The numbers of different cell types and the levels of 48 cytokines were measured in these fluids. Compared to healthy control subjects, patients with asthma had significantly more percentages of eosinophils and neutrophils, IL-1RA, IL-1α, IL-1β, IL-2Rα, IL-5, IL-6, IL-7, IL-8, G-CSF, GROα (CXCL1), MIP-1β (CCL4), MIG (CXCL9), RANTES (CCL5) and TRAIL in their BAL fluids. The only inflammatory markers that distinguished controlled asthma from uncontrolled asthma were neutrophil percentage and IL-8 levels, and both were inversely correlated with FEV1. We examined whether grouping asthma subjects on the basis of BAL eosinophil % or neutrophil % could identify specific cytokine profiles. The only differences between neutrophil-normal asthma (neutrophil≤2.4%) and neutrophil-high asthma (neutrophils%>2.4%) were a higher BAL fluid IL-8 levels, and a lower FEV1 in the latter group. By contrast, compared to eosinophil-normal asthma (eosinophils≤0.3%), eosinophil-high asthma (eosinophils>0.3%) had higher levels of IL-5, IL-13, IL-16, and PDGF-bb, but same neutrophil percentage, IL-8, and FEV1. Our results identify neutrophils and IL-8 are the only inflammatory components in BAL fluids that distinguish controlled asthma from uncontrolled asthma, and both correlate inversely with FEV1.

House dust mites induce proliferation of severe asthmatic smooth muscle cells via an epithelium-dependent pathway

RATIONALE

Asthma is a frequent airway disease, and asthma control determinants have been associated with indoor allergen sensitization. The most frequent allergens are house dust mites (HDM), which act in vivo on the bronchial epithelial layer. Severe asthma has also been associated with bronchial remodeling and more specifically with increased mass of bronchial smooth muscle (BSM). However, the relationship between HDM stimulation of the bronchial epithelial layer and BSM remodeling is unknown.

OBJECTIVES

To evaluate whether epithelial stimulation with HDM induces BSM cell proliferation in subjects with severe asthma.

METHODS

A total of 22 subjects with severe asthma and 27 subjects with no asthma were recruited. We have developed an in vitro culture model combining an epithelium layer in air-liquid interface (ALI) interacting with BSM. We assessed BSM proliferation using BrdU incorporation. We explored the role of epithelium-derived mediators using reverse-transcriptase polymerase chain reaction (RT-PCR) and ELISA in vitro and in vivo. Finally, leukotrienes receptor expression was assessed in vitro by flow cytometry and RT-PCR and ex vivo by laser microdissection and RT-PCR.

MEASUREMENTS AND MAIN RESULTS

We found that epithelial stimulation by HDM selectively increased the proliferation of asthmatic BSM cells and not that of nonasthmatic cells. The mechanism involved epithelial protease-activated receptor-2-dependent production of leukotrienes C4 associated with an overexpression of leukotrienes receptor CysLTR1 by asthmatic BSM cells in vitro and ex vivo.

CONCLUSIONS

This work demonstrates the selective role of HDM on BSM remodeling in patients with severe asthma and points out different therapeutic targets at epithelial and smooth muscle levels.

Airway epithelium interactions with aeroallergens: role of secreted cytokines and chemokines in innate immunity

Airway epithelial cells are the first line of defense against the constituents of the inhaled air, which include allergens, pathogens, pollutants, and toxic compounds. The epithelium not only prevents the penetration of these foreign substances into the interstitium, but also senses their presence and informs the organism’s immune system of the impending assault. The epithelium accomplishes the latter through the release of inflammatory cytokines and chemokines that recruit and activate innate immune cells at the site of assault. These epithelial responses aim to eliminate the inhaled foreign substances and minimize their detrimental effects to the organism. Quite frequently, however, the innate immune responses of the epithelium to inhaled substances lead to chronic and high level release of pro-inflammatory mediators that may mediate the lung pathology seen in asthma. The interactions of airway epithelial cells with allergens will be discussed with particular focus on interactions-mediated epithelial release of cytokines and chemokines and their role in the immune response. As pollutants are other major constituents of inhaled air, we will also discuss how pollutants may alter the responses of airway epithelial cells to allergens.

Human FAM154A (SAXO1) is a microtubule-stabilizing protein specific to cilia and related structures

Cilia and flagella are microtubule-based organelles present at the surface of most cells, ranging from protozoa to vertebrates, in which these structures are implicated in processes from morphogenesis to cell motility. In vertebrate neurons, microtubule-associated MAP6 proteins stabilize cold-resistant microtubules through their Mn and Mc modules, and play a role in synaptic plasticity. Although centrioles, cilia and flagella have cold-stable microtubules, MAP6 proteins have not been identified in these organelles, suggesting that additional proteins support this role in these structures. Here, we characterize human FAM154A (hereafter referred to as hSAXO1) as the first human member of a widely conserved family of MAP6-related proteins specific to centrioles and cilium microtubules. Our data demonstrate that hSAXO1 binds specifically to centriole and cilium microtubules. We identify, in vivo and in vitro, hSAXO1 Mn modules as responsible for microtubule binding and stabilization as well as being necessary for ciliary localization. Finally, overexpression and knockdown studies show that hSAXO1 modulates axoneme length. Taken together, our findings suggest a fine regulation of hSAXO1 localization and important roles in cilium biogenesis and function.

Transcription factors and miRNAs that regulate fetal to adult CFTR expression change are new targets for cystic fibrosis

The CFTR gene displays a tightly regulated tissue-specific and temporal expression. Mutations in this gene cause cystic fibrosis (CF). In this study we wanted to identify trans-regulatory elements responsible for CFTR differential expression in fetal and adult lung, and to determine the importance of inhibitory motifs in the CFTR-3'UTR with the aim of developing new tools for the correction of disease-causing mutations within CFTR. We show that lung development-specific transcription factors (FOXA, C/EBP) and microRNAs (miR-101, miR-145, miR-384) regulate the switch from strong fetal to very low CFTR expression after birth. By using miRNome profiling and gene reporter assays, we found that miR-101 and miR-145 are specifically upregulated in adult lung and that miR-101 directly acts on its cognate site in the CFTR-3'UTR in combination with an overlapping AU-rich element. We then designed miRNA-binding blocker oligonucleotides (MBBOs) to prevent binding of several miRNAs to the CFTR-3'UTR and tested them in primary human nasal epithelial cells from healthy individuals and CF patients carrying the p.Phe508del CFTR mutation. These MBBOs rescued CFTR channel activity by increasing CFTR mRNA and protein levels. Our data offer new understanding of the control of the CFTR gene regulation and new putative correctors for cystic fibrosis.