Comparison of nasal and bronchial epithelial cells obtained from patients with COPD

Upper Airway Alarmin Cytokine Expression in Asthma of Different Severities

Background: The secretion of alarmin cytokines by epithelial cells, including thymic stromal lymphopoietin (TSLP), interleukin (IL)-25, and IL-33, initiates inflammatory cascades in asthma. However, alarmin cytokine expression in the upper airways in asthma remains largely unknown. Methods: We recruited 40 participants with asthma into four groups as per the Global Initiative for Asthma (GINA) steps (10 in each group of GINA 1/2, 3, 4, and 5). Cells were derived from nasal, buccal, and throat brushings. Intracellular cytokine expression (TSLP, IL-25, and IL-33) was assessed by flow cytometry in cytokeratin 8+ (Ck8+) epithelial cells immediately following collection. Results: TSLP was significantly increased (p < 0.001) in GINA 5 patients across nasal, buccal, and throat Ck8+ epithelial cells, while IL-25 was elevated in nasal and throat samples (p < 0.003), and IL-33 levels were variable, compared with GINA 1-4 patients. Individual GINA subgroup comparison showed that TSLP levels in nasal samples from GINA 5 patients were significantly (p = 0.03) elevated but did not differ between patients with and without nasal comorbidities. IL-25 and IL-33 (obtained from nasal, buccal, and throat samples) were not significantly different in individual groups. Conclusions: Our study demonstrates for the first time that Ck8+ nasal epithelial cells from GINA 5 asthma patients express elevated levels of TSLP.

Differential interferon responses to influenza A and B viruses in primary ferret respiratory epithelial cells

Influenza B viruses (IBV) cocirculate with influenza A viruses (IAV) and cause periodic epidemics of disease, yet antibody and cellular responses following IBV infection are less well understood. Using the ferret model for antisera generation for influenza surveillance purposes, IAV resulted in robust antibody responses following infection, whereas IBV required an additional booster dose, over 85% of the time, to generate equivalent antibody titers. In this study, we utilized primary differentiated ferret nasal epithelial cells (FNECs) which were inoculated with IAV and IBV to study differences in innate immune responses which may result in differences in adaptive immune responses in the host. FNECs were inoculated with IAV (H1N1pdm09 and H3N2 subtypes) or IBV (B/Victoria and B/Yamagata lineages) and assessed for 72 h. Cells were analyzed for gene expression by quantitative real-time PCR, and apical and basolateral supernatants were assessed for virus kinetics and interferon (IFN), respectively. Similar virus kinetics were observed with IAV and IBV in FNECs. A comparison of gene expression and protein secretion profiles demonstrated that IBV-inoculated FNEC expressed delayed type-I/II IFN responses and reduced type-III IFN secretion compared to IAV-inoculated cells. Concurrently, gene expression of Thymic Stromal Lymphopoietin (TSLP), a type-III IFN-induced gene that enhances adaptive immune responses, was significantly downregulated in IBV-inoculated FNECs. Significant differences in other proinflammatory and adaptive genes were suppressed and delayed following IBV inoculation. Following IBV infection, ex vivo cell cultures derived from the ferret upper respiratory tract exhibited reduced and delayed innate responses which may contribute to reduced antibody responses in vivo.IMPORTANCEInfluenza B viruses (IBV) represent nearly one-quarter of all human influenza cases and are responsible for significant clinical and socioeconomic impacts but do not pose the same pandemic risks as influenza A viruses (IAV) and have thus received much less attention. IBV accounts for greater severity and deaths in children, and vaccine efficacy remains low. The ferret can be readily infected with human clinical isolates and demonstrates a similar course of disease and immune responses. IBV, however, generates lower antibodies in ferrets than IAV following the challenge. To determine whether differences in initial innate responses following infection may affect the development of robust adaptive immune responses, ferret respiratory tract cells were isolated, infected with IAV/IBV, and compared. Understanding the differences in the initial innate immune responses to IAV and IBV may be important in the development of more effective vaccines and interventions to generate more robust protective immune responses.

Genomic attributes of airway commensal bacteria and mucosa

Microbial communities at the airway mucosal barrier are conserved and highly ordered, in likelihood reflecting co-evolution with human host factors. Freed of selection to digest nutrients, the airway microbiome underpins cognate management of mucosal immunity and pathogen resistance. We show here the initial results of systematic culture and whole-genome sequencing of the thoracic airway bacteria, identifying 52 novel species amongst 126 organisms that constitute 75% of commensals typically present in heathy individuals. Clinically relevant genes encode antimicrobial synthesis, adhesion and biofilm formation, immune modulation, iron utilisation, nitrous oxide (NO) metabolism and sphingolipid signalling. Using whole-genome content we identify dysbiotic features that may influence asthma and chronic obstructive pulmonary disease. We match isolate gene content to transcripts and metabolites expressed late in airway epithelial differentiation, identifying pathways to sustain host interactions with microbiota. Our results provide a systematic basis for decrypting interactions between commensals, pathogens, and mucosa in lung diseases of global significance.

Fusobacterium nucleatum putatively affects the alveoli by disrupting the alveolar epithelial cell tight junction, enlarging the alveolar space, and increasing paracellular permeability

Fusobacterium nucleatum (Fn) is abundant in the human oral cavity and has been associated with periodontal disease, which in-turn has been linked to respiratory disease development. Tight junctions (TJs) line the airway and alveoli surfaces serving as a first line of defense against multiple pathogens. Fn has already been linked to respiratory diseases, however, how Fn affects the alveolar TJ was not fully elucidated. Here, we designed and analyzed a TJ network, grew Fn cells and inoculated it in vitro (16HBE and primary cells) and in vivo (mice lung), measured transepithelial electrical resistance, performed RT-PCR, checked for in vitro cell and mice lung permeability, and determined air space size through morphometric measurements. We found that Fn can potentially affect TJs proteins that are directly exposed to the alveolar surface. Additionally, Fn could possibly cause neutrophil accumulation and an increase in alveolar space. Moreover, Fn putatively may cause an increase in paracellular permeability in the alveoli.

Culture expansion of primary human nasal epithelial cells (NEC) isolated with a nasal scraping spoon

OBJECTIVE

To obtain high-purity nasal epithelial cells (NEC) while avoiding the irritation experienced by patients during nasal biopsies.

METHODS

This prospective, observational study enrolled patients undergoing surgical treatment for nasal septum deviation. After general anaesthesia, a novel nasal scraping spoon was used to collect epithelial cells from the mid-part of the inferior turbinate. The cells were evenly plated on six-well plates coated with rat tail collagen. The morphology and growth of the cells were observed at different time-points using an inverted phase-contrast microscope. Immunofluorescent staining of cytokeratin 18 was used to identify NEC. Ki67 staining was used to check cell viability.

RESULTS

This study collected samples from 19 patients during a short procedure. No postoperative complications were observed. Cell samples ranging from 8.31 × 105 to 2.04 × 106 cells/sample were obtained. The culture model was suitable for primary NEC culture as demonstrated by the faster proliferation (5-7 days). There was no fungal or bacterial contamination. Immunofluorescent staining confirmed the presence and proliferative activity of NEC in the cultures.

CONCLUSION

A novel nasal scraping spoon provided an easy sampling method, avoided nasal injuries and psychological barriers to sampling and sufficient viable NEC to establish primary cultures.

Infection of Primary Nasal Epithelial Cells Grown at an Air-Liquid Interface to Characterize Human Coronavirus-Host Interactions

Three highly pathogenic human coronaviruses (HCoVs) - SARS-CoV (2002), MERS-CoV (2012), and SARS-CoV-2 (2019) - have emerged and caused significant public health crises in the past 20 years. Four additional HCoVs cause a significant portion of common cold cases each year (HCoV-NL63, -229E, -OC43, and -HKU1), highlighting the importance of studying these viruses in physiologically relevant systems. HCoVs enter the respiratory tract and establish infection in the nasal epithelium, the primary site encountered by all respiratory pathogens. We use a primary nasal epithelial culture system in which patient-derived nasal samples are grown at an air-liquid interface (ALI) to study host-pathogen interactions at this important sentinel site. These cultures recapitulate many features of the in vivo airway, including the cell types present, ciliary function, and mucus production. We describe methods to characterize viral replication, host cell tropism, virus-induced cytotoxicity, and innate immune induction in nasal ALI cultures following HCoV infection, using recent work comparing lethal and seasonal HCoVs as an example1. An increased understanding of host-pathogen interactions in the nose has the potential to provide novel targets for antiviral therapeutics against HCoVs and other respiratory viruses that will likely emerge in the future.

In Vitro Effect of Combined Hypertonic Saline and Salbutamol on Ciliary Beating Frequency and Mucociliary Transport in Human Nasal Epithelial Cells of Healthy Volunteers and Patients with Cystic Fibrosis

Background: Inhalation of hypertonic saline (HS) is standard of care in patients with cystic fibrosis (CF). However, it is unclear if adding salbutamol has-besides bronchodilation-further benefits, for example, on the mucociliary clearance. We assessed this in vitro by measuring the ciliary beating frequency (CBF) and the mucociliary transport rate (MCT) in nasal epithelial cells (NECs) of healthy volunteers and patients with CF. Aims: To investigate the effect of HS, salbutamol, and its combination on (muco)ciliary activity of NECs in vitro, and to assess potential differences between healthy controls and patients with CF. Methods: NECs obtained from 10 healthy volunteers and 5 patients with CF were differentiated at the air-liquid interface and aerosolized with 0.9% isotonic saline ([IS] control), 6% HS, 0.06% salbutamol, or combined HS and salbutamol. CBF and MCT were monitored over 48-72 hours. Results: In NECs of healthy controls, the absolute CBF increase was comparable for all substances, but CBF dynamics were different: HS increased CBF slowly and its effect lasted for an extended period, salbutamol and IS increased CBF rapidly and the effect subsided similarly fast, and HS and salbutamol resulted in a rapid and long-lasting CBF increase. Results for CF cells were comparable, but less pronounced. Similar to CBF, MCT increased after the application of all the tested substances. Conclusion: CBF and MCT of NECs of healthy participants and CBF of patients with CF increased upon treatment with aerosolized IS, HS, salbutamol, or HS and salbutamol, showing a relevant effect for all tested substances. The difference in the CBF dynamics can be explained by the fact that the properties of the mucus are changed differently by different saline concentrations.

Infection of primary nasal epithelial cells differentiates among lethal and seasonal human coronaviruses

The nasal epithelium is the initial entry portal and primary barrier to infection by all human coronaviruses (HCoVs). We utilize primary human nasal epithelial cells grown at air-liquid interface, which recapitulate the heterogeneous cellular population as well as mucociliary clearance functions of the in vivo nasal epithelium, to compare lethal [Severe acute respiratory syndrome (SARS)-CoV-2 and Middle East respiratory syndrome-CoV (MERS-CoV)] and seasonal (HCoV-NL63 and HCoV-229E) HCoVs. All four HCoVs replicate productively in nasal cultures, though replication is differentially modulated by temperature. Infections conducted at 33 °C vs. 37 °C (reflective of temperatures in the upper and lower airway, respectively) revealed that replication of both seasonal HCoVs (HCoV-NL63 and -229E) is significantly attenuated at 37 °C. In contrast, SARS-CoV-2 and MERS-CoV replicate at both temperatures, though SARS-CoV-2 replication is enhanced at 33 °C late in infection. These HCoVs also diverge significantly in terms of cytotoxicity induced following infection, as the seasonal HCoVs as well as SARS-CoV-2 cause cellular cytotoxicity as well as epithelial barrier disruption, while MERS-CoV does not. Treatment of nasal cultures with type 2 cytokine IL-13 to mimic asthmatic airways differentially impacts HCoV receptor availability as well as replication. MERS-CoV receptor DPP4 expression increases with IL-13 treatment, whereas ACE2, the receptor used by SARS-CoV-2 and HCoV-NL63, is down-regulated. IL-13 treatment enhances MERS-CoV and HCoV-229E replication but reduces that of SARS-CoV-2 and HCoV-NL63, reflecting the impact of IL-13 on HCoV receptor availability. This study highlights diversity among HCoVs during infection of the nasal epithelium, which is likely to influence downstream infection outcomes such as disease severity and transmissibility.

Air-liquid interface (ALI) impact on different respiratory cell cultures

The intranasal route has been receiving greater attention from the scientific community not only for systemic drug delivery but also for the treatment of pulmonary and neurological diseases. Along with it, drug transport and permeability studies across the nasal mucosa have exponentially increased. Nevertheless, the translation of data from in vitro cell lines to in vivo studies is not always reliable, due to the difficulty in generating an in vitro model that resembles respiratory human physiology. Among all currently available methodologies, the air-liquid interface (ALI) method is advantageous to promote cell differentiation and optimize the morphological and histological characteristics of airway epithelium cells. Cells grown under ALI conditions, in alternative to submerged conditions, appear to provide relevant input for inhalation and pulmonary toxicology and complement in vivo experiments. Different methodologies and a variety of materials have been used to induce ALI conditions in primary cells and numerous cell lines. Until this day, with only exploratory results, no consensus has been reached regarding the validation of the ALI method, hampering data comparison. The present review describes the most adequate cell models of airway epithelium and how these models are differently affected by ALI conditions. It includes the evaluation of cellular features before and after ALI, and the application of the method in primary cell cultures, commercial 3D primary cells, cell lines and stem-cell derived models. A variety of these models have been recently applied for pharmacological studies against severe acute respiratory syndrome-coronavirus(-2) SARS-CoV(-2), namely primary cultures with alveolar type II epithelium cells and organotypic 3D models. The herein compiled data suggest that ALI conditions must be optimized bearing in mind the type of cells (nasal, bronchial, alveolar), their origin and the objective of the study.

Nasal biomarkers of immune function differ based on smoking and respiratory disease status

Respiratory biomarkers have the potential to identify airway injury by revealing inflammatory processes within the respiratory tract. Currently, there are no respiratory biomarkers suitable for clinical use to identify patients that warrant further diagnostic work-up, counseling, and treatment for toxic inhalant exposures or chronic airway disease. Using a novel, noninvasive method of sampling the nasal epithelial lining fluid, we aimed to investigate if nasal biomarker patterns could distinguish healthy nonsmoking adults from active smokers and those with chronic upper and lower airway disease in this exploratory study. We compared 28 immune mediators from healthy nonsmoking adults (n = 32), former smokers with COPD (n = 22), chronic rhinosinusitis (CRS) (n = 22), and smoking adults without airway disease (n = 13). Using ANOVA, multinomial logistic regressions, and weighted gene co-expression network analysis (WGCNA), we determined associations between immune mediators and each cohort. Six mediators (IL-7, IL-10, IL-13, IL-12p70, IL-15, and MCP-1) were lower among disease groups compared to healthy controls. Participants with lower levels of IL-10, IL-12p70, IL-13, and MCP-1 in the nasal fluid had a higher odds of being in the COPD or CRS group. The cluster analysis identified groups of mediators that correlated with disease status. Specifically, the cluster of IL-10, IL-12p70, and IL-13, was positively correlated with healthy and negatively correlated with COPD groups, and two clusters were correlated with active smoking. In this exploratory study, we preliminarily identified groups of nasal mucosal mediators that differed by airway disease and smoking status. Future prospective, age-matched studies that control for medication use are needed to validate these patterns and determine if nasosorption has diagnostic utility for upper and lower airway disease or injury.

Organotypic sinonasal airway culture systems are predictive of the mucociliary phenotype produced by bronchial airway epithelial cells

Differentiated air-liquid interface models are the current standard to assess the mucociliary phenotype using clinically-derived samples in a controlled environment. However, obtaining basal progenitor airway epithelial cells (AEC) from the lungs is invasive and resource-intensive. Hence, we applied a tissue engineering approach to generate organotypic sinonasal AEC (nAEC) epithelia to determine whether they are predictive of bronchial AEC (bAEC) models. Basal progenitor AEC were isolated from healthy participants using a cytological brushing method and differentiated into epithelia on transwells until the mucociliary phenotype was observed. Tissue architecture was assessed using H&E and alcian blue/Verhoeff-Van Gieson staining, immunofluorescence (for cilia via acetylated α-tubulin labelling) and scanning electron microscopy. Differentiation and the formation of tight-junctions were monitored over the culture period (day 1-32) by quantifying trans-epithelial electrical resistance. End point (day 32) tight junction protein expression was assessed using Western blot analysis of ZO-1, Occludin-1 and Claudin-1. Reverse transcription qPCR-array was used to assess immunomodulatory and autophagy-specific transcript profiles. All outcome measures were assessed using R-statistical software. Mucociliary architecture was comparable for nAEC and bAEC-derived cultures, e.g. cell density P = 0.55, epithelial height P = 0.88 and cilia abundance P = 0.41. Trans-epithelial electrical resistance measures were distinct from day 1-14, converged over days 16-32, and were statistically similar over the entire culture period (global P < 0.001). This agreed with end-point (day 32) measures of tight junction protein abundance which were non-significant for each analyte (P > 0.05). Transcript analysis for inflammatory markers demonstrated significant variation between nAEC and bAEC epithelial cultures, and favoured increased abundance in the nAEC model (e.g. TGFβ and IL-1β; P < 0.05). Conversely, the abundance of autophagy-related transcripts were comparable and the range of outcome measures for either model exhibited a considerably more confined uncertainty distribution than those observed for the inflammatory markers. Organotypic air-liquid interface models of nAEC are predictive of outcomes related to barrier function, mucociliary architecture and autophagy gene activity in corresponding bAEC models. However, inflammatory markers exhibited wide variation which may be explained by the sentinel immunological surveillance role of the sinonasal epithelium.

Infection of primary nasal epithelial cells differentiates among lethal and seasonal human coronaviruses

The nasal epithelium is the initial entry portal and primary barrier to infection by all human coronaviruses (HCoVs). We utilize primary nasal epithelial cells grown at air-liquid interface, which recapitulate the heterogeneous cellular population as well as mucociliary clearance functions of the in vivo nasal epithelium, to compare lethal (SARS-CoV-2 and MERS-CoV) and seasonal (HCoV-NL63 and HCoV-229E) HCoVs. All four HCoVs replicate productively in nasal cultures but diverge significantly in terms of cytotoxicity induced following infection, as the seasonal HCoVs as well as SARS-CoV-2 cause cellular cytotoxicity as well as epithelial barrier disruption, while MERS-CoV does not. Treatment of nasal cultures with type 2 cytokine IL-13 to mimic asthmatic airways differentially impacts HCoV replication, enhancing MERS-CoV replication but reducing that of SARS-CoV-2 and HCoV-NL63. This study highlights diversity among HCoVs during infection of the nasal epithelium, which is likely to influence downstream infection outcomes such as disease severity and transmissibility.

NAM-based Prediction of Point-of-contact Toxicity in the Lung: A Case Example With 1,3-dichloropropene

Time, cost, ethical, and regulatory considerations surrounding in vivo testing methods render them insufficient to meet existing and future chemical safety testing demands. There is a need for the development of in vitro and in silico alternatives to replace traditional in vivo methods for inhalation toxicity assessment. Exposures of differentiated airway epithelial cultures to gases or aerosols at the air-liquid interface (ALI) can assess tissue responses and in vitro to in vivo extrapolation can align in vitro exposure levels with in-life exposures expected to give similar tissue exposures. Because the airway epithelium varies along its length, with various regions composed of different cell types, we have introduced a known toxic vapor to five human-derived, differentiated, in vitro airway epithelial cell culture models-MucilAir of nasal, tracheal, or bronchial origin, SmallAir, and EpiAlveolar-representing five regions of the airway epithelium-nasal, tracheal, bronchial, bronchiolar, and alveolar. We have monitored toxicity in these cultures 24hours after acute exposure using an assay for transepithelial conductance (for epithelial barrier integrity) and the lactate dehydrogenase (LDH) release assay (for cytotoxicity). Our vapor of choice in these experiments was 1,3-dichloropropene (1,3-DCP). Finally, we have developed an airway dosimetry model for 1,3-DCP vapor to predict in vivo external exposure scenarios that would produce toxic local tissue concentrations as determined by in vitro experiments. Measured in vitro points of departure (PoDs) for all tested cell culture models were similar. Calculated rat equivalent inhaled concentrations varied by model according to position of the modeled tissue within the airway, with nasal respiratory tissue being the most proximal and most sensitive tissue, and alveolar epithelium being the most distal and least sensitive tissue. These predictions are qualitatively in accordance with empirically determined in vivo PoDs. The predicted PoD concentrations were close to, but slightly higher than, PoDs determined by in vivo subchronic studies.

TLR Signals in Epithelial Cells in the Nasal Cavity and Paranasal Sinuses

The respiratory tract is constantly at risk of invasion by microorganisms such as bacteria, viruses, and fungi. In particular, the mucosal epithelium of the nasal cavity and paranasal sinuses is at the very forefront of the battles between the host and the invading pathogens. Recent studies have revealed that the epithelium not only constitutes a physical barrier but also takes an essential role in the activation of the immune system. One of the mechanisms equipped in the epithelium to fight against microorganisms is the Toll-like receptor (TLR) response. TLRs recognize common structural components of microorganisms and activate the innate immune system, resulting in the production of a plethora of cytokines and chemokines in the response against microbes. As the epithelia-derived cytokines are deeply involved in the pathogenesis of inflammatory conditions in the nasal cavity and paranasal sinuses, such as chronic rhinosinusitis (CRS) and allergic rhinitis (AR), the molecules involved in the TLR response may be utilized as therapeutic targets for these diseases. There are several differences in the TLR response between nasal and bronchial epithelial cells, and knowledge of the TLR signals in the upper airway is sparse compared to that in the lower airway. In this review, we provide recent evidence on TLR signaling in the upper airway, focusing on the expression, regulation, and responsiveness of TLRs in human nasal epithelial cells (HNECs). We also discuss how TLRs in the epithelium are involved in the pathogenesis of, and possible therapeutic targeting, for CRS and AR.

Susceptibility of Human Airway Tissue Models Derived From Different Anatomical Sites to Bordetella pertussis and Its Virulence Factor Adenylate Cyclase Toxin

To study the interaction of human pathogens with their host target structures, human tissue models based on primary cells are considered suitable. Complex tissue models of the human airways have been used as infection models for various viral and bacterial pathogens. The Gram-negative bacterium Bordetella pertussis is of relevant clinical interest since whooping cough has developed into a resurgent infectious disease. In the present study, we created three-dimensional tissue models of the human ciliated nasal and tracheo-bronchial mucosa. We compared the innate immune response of these models towards the B. pertussis virulence factor adenylate cyclase toxin (CyaA) and its enzymatically inactive but fully pore-forming toxoid CyaA-AC^-. Applying molecular biological, histological, and microbiological assays, we found that 1 µg/ml CyaA elevated the intracellular cAMP level but did not disturb the epithelial barrier integrity of nasal and tracheo-bronchial airway mucosa tissue models. Interestingly, CyaA significantly increased interleukin 6, interleukin 8, and human beta defensin 2 secretion in nasal tissue models, whereas tracheo-bronchial tissue models were not significantly affected compared to the controls. Subsequently, we investigated the interaction of B. pertussis with both differentiated primary nasal and tracheo-bronchial tissue models and demonstrated bacterial adherence and invasion without observing host cell type-specific significant differences. Even though the nasal and the tracheo-bronchial mucosa appear similar from a histological perspective, they are differentially susceptible to B. pertussis CyaA in vitro. Our finding that nasal tissue models showed an increased innate immune response towards the B. pertussis virulence factor CyaA compared to tracheo-bronchial tissue models may reflect the key role of the nasal airway mucosa as the first line of defense against airborne pathogens.

Impact of inhaled pollutants on response to viral infection in controlled exposures

Air pollutants are a major source of increased risk of disease, hospitalization, morbidity, and mortality worldwide. The respiratory tract is a primary target of potential concurrent exposure to both inhaled pollutants and pathogens, including viruses. Although there are various associative studies linking adverse outcomes to co- or subsequent exposures to inhaled pollutants and viruses, knowledge about causal linkages and mechanisms by which pollutant exposure may alter human respiratory responses to viral infection is more limited. In this article, we review what is known about the impact of pollutant exposure on antiviral host defense responses and describe potential mechanisms by which pollutants can alter the viral infection cycle. This review focuses on evidence from human observational and controlled exposure, ex vivo, and in vitro studies. Overall, there are a myriad of points throughout the viral infection cycle that inhaled pollutants can alter to modulate appropriate host defense responses. These alterations may contribute to observed increases in rates of viral infection and associated morbidity and mortality in areas of the world with high ambient pollution levels or in people using tobacco products. Although the understanding of mechanisms of interaction is advancing through controlled in vivo and in vitro exposure models, more studies are needed because emerging infectious pathogens, such as severe acute respiratory syndrome coronavirus 2, present a significant threat to public health.

Validation of in vitro models for smoke exposure of primary human bronchial epithelial cells

RATIONALE

The bronchial epithelium is constantly challenged by inhalative insults including cigarette smoke (CS), a key risk factor for lung disease. In vitro exposure of bronchial epithelial cells using CS extract (CSE) is a widespread alternative to whole CS (wCS) exposure. However, CSE exposure protocols vary considerably between studies, precluding direct comparison of applied doses. Moreover, they are rarely validated in terms of physiological response in vivo and the relevance of the findings is often unclear.

METHODS

We tested six different exposure settings in primary human bronchial epithelial cells (phBECs), including five CSE protocols in comparison with wCS exposure. We quantified cell-delivered dose and directly compared all exposures using expression analysis of 10 well-established smoke-induced genes in bronchial epithelial cells. CSE exposure of phBECs was varied in terms of differentiation state, exposure route, duration of exposure, and dose. Gene expression was assessed by quantitative Real-Time PCR (qPCR) and Western Blot analysis. Cell type-specific expression of smoke-induced genes was analyzed by immunofluorescent analysis.

RESULTS

Three surprisingly dissimilar exposure types, namely chronic CSE treatment of differentiating phBECs, acute CSE treatment of submerged basal phBECs, and wCS exposure of differentiated phBECs performed best, resulting in significant upregulation of seven (chronic CSE) and six (acute wCS, acute submerged CSE exposure) out of 10 genes. Acute apical or basolateral exposure of differentiated phBECs with CSE was much less effective despite similar doses used.

CONCLUSIONS

Our findings provide guidance for the design of human in vitro CS exposure models in experimental and translational lung research.

Airway microbial communities, smoking and asthma in a general population sample

BACKGROUND

Normal airway microbial communities play a central role in respiratory health but are poorly characterized. Cigarette smoking is the dominant global environmental influence on lung function, and asthma has become the most prevalent chronic respiratory disease worldwide. Both conditions have major microbial components that are incompletely defined.

METHODS

We investigated airway bacterial communities in a general population sample of 529 Australian adults. Posterior oropharyngeal swabs were analyzed by sequencing of the 16S rRNA gene. The microbiota were characterized according to their prevalence, abundance and network memberships.

FINDINGS

The microbiota were similar across the general population, and were strongly organized into co-abundance networks. Smoking was associated with diversity loss, negative effects on abundant taxa, profound alterations to network structure and expansion of Streptococcus spp. By contrast, the asthmatic microbiota were selectively affected by an increase in Neisseria spp. and by reduced numbers of low abundance but prevalent organisms.

INTERPRETATION

Our study shows that the healthy airway microbiota in this population were contained within a highly structured ecosystem, suggesting balanced relationships between the microbiome and human host factors. The marked abnormalities in smokers may contribute to chronic obstructive pulmonary disease (COPD) and lung cancer. The narrow spectrum of abnormalities in asthmatics encourages investigation of damaging and protective effects of specific bacteria.

FUNDING

The study was funded by the Asmarley Trust and a Wellcome Joint Senior Investigator Award to WOCC and MFM (WT096964MA and WT097117MA). The Busselton Healthy Ageing Study is supported by the Government of Western Australia (Office of Science, Department of Health) the City of Busselton, and private donations.

Differences and similarities between the upper and lower airway: focusing on innate immunity

The nose is the first respiratory barrier to external pathogens, allergens, pollutants, or cigarette smoke, and vigorous immune responses are triggered when external pathogens come in contact with the nasal epithelium. The mucosal epithelial cells of the nose are essential to the innate immune response against external pathogens and transmit signals that modulate the adaptive immune response. The upper and lower airways share many physiological and immunological features, but there are also numerous differences. It is crucial to understand these differences and their contribution to pathophysiology in order to optimize treatments for inflammatory diseases of the respiratory tract. This review summarizes important differences in the embryological development, histological features, microbiota, immune responses, and cellular subtypes of mucosal epithelial cells of the nose and lungs.

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.

Nasal Epithelial Cell-Based Models for Individualized Study in Cystic Fibrosis

The emergence of highly effective CFTR modulator therapy has led to significant improvements in health care for most patients with cystic fibrosis (CF). For some, however, these therapies remain inaccessible due to the rarity of their individual CFTR variants, or due to a lack of biologic activity of the available therapies for certain variants. One proposed method of addressing this gap is the use of primary human cell-based models, which allow preclinical therapeutic testing and physiologic assessment of relevant tissue at the individual level. Nasal cells represent one such tissue source and have emerged as a powerful model for individual disease study. The ex vivo culture of nasal cells has evolved over time, and modern nasal cell models are beginning to be utilized to predict patient outcomes. This review will discuss both historical and current state-of-the art use of nasal cells for study in CF, with a particular focus on the use of such models to inform personalized patient care.

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.

Losartan reduces cigarette smoke-induced airway inflammation and mucus hypersecretion

The aim was to determine whether losartan reduces cigarette smoke (CS)-induced airway inflammation and mucus hypersecretion in an in vitro model and a small clinical trial. Primary human bronchial epithelial cells (HBECs) were differentiated at the air-liquid interface (ALI) and exposed to CS. Expression of transforming growth factor (TGF)-β1 and the mucin MUC5AC, and expression or activity of matrix metalloproteinase (MMP)-9 were measured after CS exposure. Parameters of mucociliary clearance were evaluated by measuring airway surface liquid volumes, mucus concentrations, and conductance of cystic fibrosis transmembrane conductance regulator (CFTR) and large conductance, Ca²⁺-activated and voltage-dependent potassium (BK) channels. Nasal cells were collected from study participants and expression of MUC5AC, TGF-β1, and MMP-9 mRNAs was measured before and after losartan treatment. In vitro, CS exposure of HBECs caused a significant increase in mRNA expression of MUC5AC and TGF-β1 and MMP-9 activity and decreased CFTR and BK channel activities, thereby reducing airway surface liquid volumes and increasing mucus concentrations. Treatment of HBECs with losartan rescued CS-induced CFTR and BK dysfunction and caused a significant decrease in MUC5AC expression and mucus concentrations, partially by inhibiting TGF-β signalling. In a prospective clinical study, cigarette smokers showed significantly reduced mRNA expression levels of MUC5AC, TGF-β1, and MMP-9 in the upper airways after 2 months of losartan treatment. Our findings suggest that losartan may be an effective therapy to reduce inflammation and mucus hypersecretion in CS-induced chronic airway diseases.

Porphyromonas gingivalis gingipains potentially affect MUC5AC gene expression and protein levels in respiratory epithelial cells

Porphyromonas gingivalis (Pg) is a periodontopathic pathogen that may affect MUC5AC‐related mucus hypersecretion along airway epithelial cells. Here, we attempted to establish whether Pg virulence factors (lipopolysaccharide, FimA fimbriae, gingipains) affect MUC5AC in immortalized and primary bronchial cells. We report that MUC5AC gene expression and protein levels are affected by Pg culture supernatant, but not by lipopolysaccharide or FimA fimbriae. Cells treated with either Pg single (Kgp or Rgp) or double (Kgp/Rgp) mutants had altered levels of MUC5AC gene expression and protein levels, and MUC5AC staining of double mutant‐treated mouse lung cells showed that MUC5AC protein levels were unaffected. Taken together, we propose that Pg gingipains may be the primary virulence factor that influences both MUC5AC gene expression and protein levels.

Susceptibility of primary human airway epithelial cells to Bordetella pertussis adenylate cyclase toxin in two- and three-dimensional culture conditions

The human pathogen Bordetella pertussis targets the respiratory epithelium and causes whooping cough. Its virulence factor adenylate cyclase toxin (CyaA) plays an important role in the course of infection. Previous studies on the impact of CyaA on human epithelial cells have been carried out using cell lines derived from the airways or the intestinal tract. Here, we investigated the interaction of CyaA and its enzymatically inactive but fully pore-forming toxoid CyaA-AC^– with primary human airway epithelial cells (hAEC) derived from different anatomical sites (nose and tracheo-bronchial region) in two-dimensional culture conditions. To assess possible differences between the response of primary hAEC and respiratory cell lines directly, we included HBEC3-KT in our studies. In comparative analyses, we studied the impact of both the toxin and the toxoid on cell viability, intracellular cAMP concentration and IL-6 secretion. We found that the selected hAEC, which lack CD11b, were differentially susceptible to both CyaA and CyaA-AC^–. HBEC3-KT appeared not to be suitable for subsequent analyses. Since the nasal epithelium first gets in contact with airborne pathogens, we further studied the effect of CyaA and its toxoid on the innate immunity of three-dimensional tissue models of the human nasal mucosa. The present study reveals first insights in toxin–cell interaction using primary hAEC.

Genomics of asthma, allergy and chronic rhinosinusitis: novel concepts and relevance in airway mucosa

Genome wide association studies (GWASs) have revealed several airway disease-associated risk loci. Their role in the onset of asthma, allergic rhinitis (AR) or chronic rhinosinusitis (CRS), however, is not yet fully understood. The aim of this review is to evaluate the airway relevance of loci and genes identified in GWAS studies. GWASs were searched from databases, and a list of loci associating significantly (p < 10-8) with asthma, AR and CRS was created. This yielded a total of 267 significantly asthma/AR-associated loci from 31 GWASs. No significant CRS -associated loci were found in this search. A total of 170 protein coding genes were connected to these loci. Of these, 76/170 (44%) showed bronchial epithelial protein expression in stained microscopic figures of Human Protein Atlas (HPA), and 61/170 (36%) had a literature report of having airway epithelial function. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analyses were performed, and 19 functional protein categories were found as significantly (p < 0.05) enriched among these genes. These were related to cytokine production, cell activation and adaptive immune response, and all were strongly connected in network analysis. We also identified 15 protein pathways that were significantly (p < 0.05) enriched in these genes, related to T-helper cell differentiation, virus infection, JAK-STAT signaling pathway, and asthma. A third of GWAS-level risk loci genes of asthma or AR seemed to have airway epithelial functions according to our database and literature searches. In addition, many of the risk loci genes were immunity related. Some risk loci genes also related to metabolism, neuro-musculoskeletal or other functions. Functions overlapped and formed a strong network in our pathway analyses and are worth future studies of biomarker and therapeutics.

In vitro 3D culture lung model from expanded primary cystic fibrosis human airway cells

BACKGROUND

In vitro cystic fibrosis (CF) models are crucial for understanding the mechanisms and consequences of the disease. They are also the gold standard for pre-clinical efficacy studies of current and novel CF drugs. However, few studies have investigated expansion and differentiation of primary CF human bronchial epithelial (CF-HBE) cells. Here we describe culture conditions to expand primary CF airway cells while preserving their ability to differentiate into 3D epithelial cultures expressing functional cystic fibrosis transmembrane conductance regulator (CFTR) ion channels that responds to CFTR modulators.

METHODS

Primary CF airway cells were expanded using PneumaCult^TM-Ex Plus (StemCell Technologies) medium with no feeder cells or added Rho kinase (ROCK) inhibitor. Differentially passaged CF-HBE cells at the air-liquid interface (ALI) were characterized phenotypically and functionally in response to the CFTR corrector drug VX-661 (Tezacaftor).

RESULTS

CF-HBE primary cells, expanded up to six passages (~25 population doublings), differentiated into 3D epithelial cultures as evidenced by trans-epithelial electrical resistance (TEER) of >400 Ohms∙cm² and presence of pseudostratified columnar ciliated epithelium with goblet cells. However, up to passage five cells from most donors showed increased CFTR-mediated short-circuit currents when treated with the corrector drug, VX-661. Ciliary beat frequency (CBF) also increased with the corrector VX-661.

CONCLUSIONS

CF donor-derived airway cells can be expanded without the use of feeder cells or additional ROCK inhibitor, and still achieve optimal 3D epithelial cultures that respond to CFTR modulators. The study of rare CF mutations could benefit from cell expansion and could lead to the design of personalized medicine/treatments.

Real-time measurement of cellular bioenergetics in fully differentiated human nasal epithelial cells grown at air-liquid-interface

Shifts in cellular metabolic phenotypes have the potential to cause disease-driving processes in respiratory disease. The respiratory epithelium is particularly susceptible to metabolic shifts in disease, but our understanding of these processes is limited by the incompatibility of the technology required to measure metabolism in real-time with the cell culture platforms used to generate differentiated respiratory epithelial cell types. Thus, to date, our understanding of respiratory epithelial metabolism has been restricted to that of basal epithelial cells in submerged culture, or via indirect end point metabolomics readouts in lung tissue. Here we present a novel methodology using the widely available Seahorse Analyzer platform to monitor real-time changes in the cellular metabolism of fully differentiated primary human airway epithelial cells grown at air-liquid interface (ALI). We show increased glycolytic, but not mitochondrial, ATP production rates in response to physiologically relevant increases in glucose availability. We also show that pharmacological inhibition of lactate dehydrogenase is able to reduce glucose-induced shifts toward aerobic glycolysis. This method is timely given the recent advances in our understanding of new respiratory epithelial subtypes that can only be observed in vitro through culture at ALI and will open new avenues to measure real-time metabolic changes in healthy and diseased respiratory epithelium, and in turn the potential for the development of novel therapeutics targeting metabolic-driven disease phenotypes.

Electronic cigarette vapour increases virulence and inflammatory potential of respiratory pathogens

INTRODUCTION

Bacteria have been extensively implicated in the development of smoking related diseases, such as COPD, by either direct infection or bacteria-mediated inflammation. In response to the health risks associated with tobacco exposure, the use of electronic cigarettes (e-cigs) has increased. This study compared the effect of e-cig vapour (ECV) and cigarette smoke (CSE) on the virulence and inflammatory potential of key lung pathogens (Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa).

METHODS

Biofilm formation, virulence in the Galleria mellonella infection model, antibiotic susceptibility and IL-8/TNF-α production in A549 cells, were compared between bacteria exposed to ECV, CSE and non-exposed bacteria.

RESULTS

Statistically significant increases in biofilm and cytokine secretion were observed following bacterial exposure to either ECV or CSE, compared to non-exposed bacteria; the effect of exposure to ECV on bacterial phenotype and virulence was comparable, and in some cases greater, than that observed following CSE exposure. Treatment of A549 cells with cell signaling pathway inhibitors prior to infection, did not suggest that alternative signaling pathways were being activated following exposure of bacteria to either ECV or CSE.

CONCLUSIONS

These findings therefore suggest that ECV and CSE can induce changes in phenotype and virulence of key lung pathogens, which may increase bacterial persistence and inflammatory potential.

Cell-Type-Specific Transcription of Innate Immune Regulators in response to HMPV Infection

Human metapneumovirus (HMPV) may cause severe respiratory disease. The early innate immune response to viruses like HMPV is characterized by induction of antiviral interferons (IFNs) and proinflammatory immune mediators that are essential in shaping adaptive immune responses. Although innate immune responses to HMPV have been comprehensively studied in mice and murine immune cells, there is less information on these responses in human cells, comparing different cell types infected with the same HMPV strain. The aim of this study was to characterize the HMPV-induced mRNA expression of critical innate immune mediators in human primary cells relevant for airway disease. In particular, we determined type I versus type III IFN expression in human epithelial cells and monocyte-derived macrophages (MDMs) and dendritic cells (MDDCs). In epithelial cells, HMPV induced only low levels of IFN-β mRNA, while a robust mRNA expression of IFN-λs was found in epithelial cells, MDMs, and MDDCs. In addition, we determined induction of the interferon regulatory factors (IRFs) IRF1, IRF3, and IRF7 and critical inflammatory cytokines (IL-6, IP-10, and IL-1β). Interestingly, IRF1 mRNA was predominantly induced in MDMs and MDDCs. Overall, our results suggest that for HMPV infection of MDDCs, MDMs, NECs, and A549 cells (the cell types examined), cell type is a strong determinator of the ability of HMPV to induce different innate immune mediators. HMPV induces the transcription of IFN-β and IRF1 to higher extents in MDMs and MDDCs than in A549s and NECs, whereas the induction of type III IFN-λ and IRF7 is considerable in MDMs, MDDCs, and A549 epithelial cells.

Characterisation of morphological differences in well-differentiated nasal epithelial cell cultures from preterm and term infants at birth and one-year

BACKGROUND

Innate immune responses of airway epithelium are important defences against respiratory pathogens and allergens. Newborn infants are at greater risk of severe respiratory infections compared to older infants, while premature infants are at greater risk than full term infants. However, very little is known regarding human neonatal airway epithelium immune responses and whether age-related morphological and/or innate immune changes contribute to the development of airway disease.

METHODS

We collected nasal epithelial cells from 41 newborn infants (23 term, 18 preterm) within 5 days of birth. Repeat sampling was achieved for 24 infants (13 term, 11 preterm) at a median age of 12.5 months. Morphologically- and physiologically-authentic well-differentiated primary paediatric nasal epithelial cell (WD-PNEC) cultures were generated and characterised using light microscopy and immunofluorescence.

RESULTS

WD-PNEC cultures were established for 15/23 (65%) term and 13/18 (72%) preterm samples at birth, and 9/13 (69%) term and 8/11 (73%) preterm samples at one-year. Newborn and infant WD-PNEC cultures demonstrated extensive cilia coverage, mucous production and tight junction integrity. Newborn WD-PNECs took significantly longer to reach full differentiation and were noted to have much greater proportions of goblet cells compared to one-year repeat WD-PNECs. No differences were evident in ciliated/goblet cell proportions between term- and preterm-derived WD-PNECs at birth or one-year old.

CONCLUSION

We describe the successful generation of newborn-derived WD-PNEC cultures and their revival from frozen. We also compared the characteristics of WD-PNECs derived from infants born at term with those born prematurely at birth and at one-year-old. The development of WD-PNEC cultures from newborn infants provides a powerful and exciting opportunity to study the development of airway epithelium morphology, physiology, and innate immune responses to environmental or infectious insults from birth.

Human Cellular Models for the Investigation of Lung Inflammation and Mucus Production in Cystic Fibrosis

Chronic inflammation, oxidative stress, mucus plugging, airway remodeling, and respiratory infections are the hallmarks of the cystic fibrosis (CF) lung disease. The airway epithelium is central in the innate immune responses to pathogens colonizing the airways, since it is involved in mucociliary clearance, senses the presence of pathogens, elicits an inflammatory response, orchestrates adaptive immunity, and activates mesenchymal cells. In this review, we focus on cellular models of the human CF airway epithelium that have been used for studying mucus production, inflammatory response, and airway remodeling, with particular reference to two- and three-dimensional cultures that better recapitulate the native airway epithelium. Cocultures of airway epithelial cells, macrophages, dendritic cells, and fibroblasts are instrumental in disease modeling, drug discovery, and identification of novel therapeutic targets. Nevertheless, they have to be implemented in the CF field yet. Finally, novel systems hijacking on tissue engineering, including three-dimensional cocultures, decellularized lungs, microfluidic devices, and lung organoids formed in bioreactors, will lead the generation of relevant human preclinical respiratory models a step forward.

Characterizing well-differentiated culture of primary human nasal epithelial cells for use in wound healing assays

The nasal epithelium is the initial contact between the external environment and the respiratory tract and how it responds to noxious stimuli and repairs epithelial damage is important. Growing airway epithelial cells in culture at air-liquid interface allows for a physiologically relevant model of the human upper airways. The aim of the present study was to characterize human primary nasal epithelial cells grown at the air-liquid interface and establish a model for use in wound healing assays. This study determined the time required for full differentiation of nasal epithelial cells in an air-liquid interface culture to be at least 7 weeks using the standardized B-ALI media. Also, a model was established that studied the response to wounding and the effect of EGFR inhibition on this process. Nasal epithelial cultures from healthy subjects were differentiated at air-liquid interface and manually wounded. Wounds were monitored over time to complete closure using a time lapse imaging microscope with cultures identified to have a rate of wound healing above 2.5%/h independent of initial wound size. EGFR inhibition caused the rate of wound healing to drop a significant 4.6%/h with there being no closure of the wound after 48 h. The robust model established in this study will be essential for studying factors influencing wound healing, including host disease status and environmental exposures in the future.

The "one airway, one disease" concept in light of Th2 inflammation

In line with the pathophysiological continuum described between nose and bronchus in allergic respiratory diseases, we assessed whether nasal epithelium could mirror the Type 2 T-helper cell (Th2) status of bronchial epithelium.Nasal and bronchial cells were collected by brushing from healthy controls (C, n=13), patients with allergic rhinitis and asthma (AR, n=12), and patients with isolated allergic rhinitis (R, n=14). Cellular composition was assessed by flow cytometry, gene expression was analysed by RNA sequencing and Th2, Type 17 T-helper cell (Th17) and interferon (IFN) signatures were derived from the literature.Infiltration by polymorphonuclear neutrophils (PMN) in the nose excluded 30% of the initial cohort. All bronchial samples from the AR group were Th2-high. The gene expression profile of nasal samples from the AR group correctly predicted the paired bronchial sample Th2 status in 71% of cases. Nevertheless, nasal cells did not appear to be a reliable surrogate for the Th2 response, in particular due to a more robust influence of the IFN response in 14 out of 26 nasal samples. The Th2 scores in the nose and bronchi correlated with mast cell count (both p<0.001) and number of sensitisations (p=0.006 and 0.002), while the Th17 scores correlated with PMN count (p=0.006 and 0.003).The large variability in nasal cell composition and type of inflammation restricts its use as a surrogate for assessing bronchial Th2 inflammation in AR patients.

Comparison of paired human nasal and bronchial airway epithelial cell responses to rhinovirus infection and IL-13 treatment

BACKGROUND

Because of its advantage as a minimally invasive procedure, nasal brushings have been increasingly used and proposed as a valuable approach to study lower airway diseases in lieu of bronchial epithelial cells. However, there is limited or conflicting evidence pertaining to whether nasal samples can be surrogates to bronchial samples. The goal of the present study is to test whether nasal epithelial cells have similar antiviral and inflammatory responses to IL-13 treatment and rhinovirus infection, a condition mimicking virally induced asthma exacerbation. Nasal and bronchial airway epithelial cells taken from the same patient were cultured under submerged and air-liquid interface (ALI) culture in the absence or presence of rhinovirus and IL-13 treatment. Inflammatory cytokines IP-10 and eotaxin-3, antiviral gene Mx1 and viral levels were measured.

RESULTS

In the absence of IL-13 treatment, nasal and bronchial cells showed a similar IP-10 response in both ALI and submerged cultures. Under the ALI culture, short term (e.g., 3 days) IL-13 treatment had a minimal effect on viral and Mx1 levels in both cell types. However, prolonged (e.g., 14 days) IL-13 treatments in both cell types decreased viral load and Mx1 expression. Under the submerged culture, IL-13 treatment in both cell types has minimal effects on viral load, IP-10 and Mx1. IL-13-induced eotaxin-3 production was similar in both types of cells under either submerged or ALI culture, which was not affected by viral infection.

CONCLUSIONS

Our data suggest that nasal epithelial cells could serve as a surrogate to bronchial epithelial cells in future studies aimed at defining the role of type 2 cytokine IL-13 in regulating pro-inflammatory and antiviral responses.

Characterization of pediatric cystic fibrosis airway epithelial cell cultures at the air-liquid interface obtained by non-invasive nasal cytology brush sampling

Background

In vitro systems of primary cystic fibrosis (CF) airway epithelial cells are an important tool to study molecular and functional features of the native respiratory epithelium. However, undifferentiated CF airway cell cultures grown under submerged conditions do not appropriately represent the physiological situation. A more advanced CF cell culture system based on airway epithelial cells grown at the air-liquid interface (ALI) recapitulates most of the in vivo-like properties but requires the use of invasive sampling methods. In this study, we describe a detailed characterization of fully differentiated primary CF airway epithelial cells obtained by non-invasive nasal brushing of pediatric patients.

Methods

Differentiated cell cultures were evaluated with immunolabelling of markers for ciliated, mucus-secreting and basal cells, and tight junction and CFTR proteins. Epithelial morphology and ultrastructure was examined by histology and transmission electron microscopy. Ciliary beat frequency was investigated by a video-microscopy approach and trans-epithelial electrical resistance was assessed with an epithelial Volt-Ohm meter system. Finally, epithelial permeability was analysed by using a cell layer integrity test and baseline cytokine levels where measured by an enzyme-linked immunosorbent assay.

Results

Pediatric CF nasal cultures grown at the ALI showed a differentiation into a pseudostratified epithelium with a mucociliary phenotype. Also, immunofluorescence analysis revealed the presence of ciliated, mucus-secreting and basal cells and tight junctions. CFTR protein expression was observed in CF (F508del/F508del) and healthy cultures and baseline interleukin (IL)-8 and IL-6 release were similar in control and CF ALI cultures. The ciliary beat frequency was 9.67 Hz and the differentiated pediatric CF epithelium was found to be functionally tight.

Conclusion

In summary, primary pediatric CF nasal epithelial cell cultures grown at the ALI showed full differentiation into ciliated, mucus-producing and basal cells, which adequately reflect the in vivo properties of the human respiratory epithelium.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0706-7) contains supplementary material, which is available to authorized users.

Evaluation of the innate immune responses to influenza and live-attenuated influenza vaccine infection in primary differentiated human nasal epithelial cells

The host innate immune response to influenza virus is a key determinant of pathogenic outcomes and long-term protective immune responses against subsequent exposures. Here, we present a direct contrast of the host responses in primary differentiated human nasal epithelial cell (hNEC) cultures following infection with either a seasonal H3N2 influenza virus (WT) or the antigenically-matched live-attenuated vaccine (LAIV) strain. Comparison of the transcriptional profiles obtained 24 and 36h post-infection showed that the magnitude of gene expression was greater in LAIV infected relative to that observed in WT infected hNEC cultures. Functional enrichment analysis revealed that the antiviral and inflammatory responses were largely driven by type III IFN induction in both WT and LAIV infected cells. However, the enrichment of biological pathways involved in the recruitment of mononuclear leukocytes, antigen-presenting cells, and T lymphocytes was uniquely observed in LAIV infected cells. These observations were reflective of the host innate immune responses observed in individuals acutely infected with influenza viruses. These findings indicate that cell-intrinsic type III IFN-mediated innate immune responses in the nasal epithelium are not only crucial for viral clearance and attenuation, but may also play an important role in the induction of protective immune responses with live-attenuated vaccines.

Novel freeze-dried DDA and TPGS liposomes are suitable for nasal delivery of vaccine

There is a pressing need for effective needle-free vaccines that are stable enough for use in the developing world and stockpiling. The inclusion of the cationic lipid DDA and the PEG-containing moiety TPGS into liposomes has the potential to improve mucosal delivery. The aim of this study was to develop stable lyophilized cationic liposomes based on these materials suitable for nasal antigen delivery. Liposomes containing DDA and TPGS were developed. Size and zeta potential measurements, ex vivo, CLSM cell penetration study and cell viability investigations were made. Preliminary immunisation and stability studies using ovalbumin were performed. The liposomes exhibited suitable size and charge for permeation across nasal mucosa. DDA and TPGS increased tissue permeation in ex vivo studies and cell uptake with good cell viability. The liposomes improved immune response both locally and vaginally when compared to i.m administration or control liposomes delivered nasally. Additionally, the lyophilized products demonstrated good stability in terms of Tg, size and antigen retention. This study has shown that the novel liposomes have potential for development as a mucosal vaccine delivery system. Furthermore, the stability of the lyophilized liposomes offers potential additional benefits in terms of thermal stability over liquid formats.

The identification of the TRPM8 channel on primary culture of human nasal epithelial cells and its response to cooling

BACKGROUND

It has been proposed that the transient receptor potential (TRP) channel Melastatin 8 (TRPM8) is a cold-sensing TRP channel. However, its presence and its role in the nasal cavity have not yet been fully studied.

METHODS

Immunohistology was used to study TRPM8 receptors in both the nasal mucosa tissue and the primary cultures of human nasal cells. Cells from primary cultures were immunostained with antibodies to TRPM8, mucin, cytokeratin (CK)-14, CK-18, and vimentin. Western blotting and real-time polymerase chain reaction (PCR) were used to determine the physiological role of TRPM8 in mucus production in the nasal cavity, with and without its agonist and antagonist.

RESULTS

The TRPM8 is clearly present in the epithelium, mucous glands, and vessels. No obvious TRPM8-immunoreactive cells were detected in the connective tissue. Immunostaining of cytospin preparations showed that epithelial cells test positive for CK-14, CK-18, TRPM8, and mucin 5AC (MUC5AC). Fibroblastic cells are stained negative for TRPM8. Secreted mucins in the cultured supernatant are detected after exposure to menthol and moderate cooling to 24°C. Both induce a statistically significant increase in the level of MUC5AC mRNA and mucin production. BCTC, a TRPM8 antagonist, has a statistically significant inhibitory effect on MUC5AC mRNA expression and MUC5AC protein production that is induced by menthol and moderate cooling to 24°C.

CONCLUSIONS

The study demonstrates that TRPM8 is present in the nasal epithelium. When it is activated by moderate cooling to 24°C or menthol, TRPM8 induces the secretion of mucin. This study shows that TRPM8 channels are important regulators of mucin production. Therefore, TRPM8 antagonists could be used to treat refractory rhinitis.

Mechanistic Evaluation of the Impact of Smoking and Chronic Obstructive Pulmonary Disease on the Nasal Epithelium

Chronic obstructive pulmonary disease (COPD) is one of the major causes of chronic morbidity and mortality worldwide. The development of markers of COPD onset is hampered by the lack of accessibility to the primary target tissue, and there is a need to consider other sample sources as surrogates for biomarker research. Airborne toxicants pass through the nasal epithelium before reaching the lower airways, and the similarity with bronchial histology makes it an attractive surrogate for lower airways. In this work, we describe the transcriptomics findings from the nasal epithelia of subjects enrolled in a clinical study focusing on the identification of COPD biomarkers. Transcriptomic data were analyzed using the biological network approach that enabled us to pinpoint the biological processes affected in the upper respiratory tract in response to smoking and mild-to-moderate COPD. Our results indicated that nasal and lower airway immune responses were considerably different in COPD subjects and caution should be exercised when using upper airway samples as a surrogate for the lower airway. Nevertheless, the network approach described here could present a sensitive means of identifying smokers at risk of developing COPD.

Association between cigarette smoking and interleukin-17A expression in nasal tissues of patients with chronic rhinosinusitis and asthma

Cigarette smoke plays a substantial role in the development of airway inflammatory diseases, including asthma and chronic rhinosinusitis (CRS). Interleukin (IL)-17A might contribute to cigarette smoke-related inflammation of the airway. This study aimed to investigate the association between cigarette smoking and IL-17A expression in the nasal tissues of patients with CRS and asthma.We prospectively recruited 24 patients (13 smokers, 11 nonsmokers) with CRS and asthma and 6 patients with asthma but without CRS (control group) in a tertiary medical center. Nasal mucosa was obtained as part of the nasal surgery. Protein and mRNA levels of IL-17A in the nasal tissues were determined by immunostaining and real-time polymerase chain reaction.The number of unexpected emergency clinic visits for acute asthma attacks were higher among smokers than among nonsmokers. Interleukin-17A protein and mRNA levels in the nasal tissues of smokers were greater compared to those in the nasal tissues of nonsmokers (P = 0.02 both) and control patients (P = 0.05 and 0.04, respectively).Cigarette smoking was associated with an increase in the number of unexpected emergency clinic visits due to acute asthma attack and in the expression of IL-17A in the nasal tissues of patients with airway inflammatory diseases.

Cytotoxicity of carbon nanohorns in different human cells of the respiratory system

One of the new synthetic carbon-based nanomaterials is carbon nanohorns (CNH). A potential risk for employees of production processes is an unintentional intake of these nanomaterials via inhalation. Once taken up, nanoparticles might interact with cells of different tissues as well as with intercellular substances. These interactions may have far-reaching consequences for human health. Currently, many gaps in available information on the CNH toxicological profile remain. The aim of this study was to determine the cytotoxicity of CNH particles on human epithelial cells of the respiratory system with special consideration given to different particle sizes. In all cell lines, cell viability was reduced after 24 h of exposure up to 60% and metabolic activity as evidenced by mitochondrial activity was lowered to 9% at a concentration of 1 g/L. The three respiratory cell lines differed in their sensitivity. The most robust cells were the bronchial epithelial cells. Further, particle size fractions induced different adverse effect strength, whereby no correlation between particle size fraction and toxicity was found. These findings demonstrate the need for further information regarding the behavior and effect strength of nanomaterial. To avoid the production of new harmful materials, a more comprehensive integration of results from toxicity studies in the development processes of engineered nanomaterials is recommended not only from an occupational viewpoint but also from an environmental perspective.

Bronchial epithelial cell lines and primary nasal epithelial cells from cystic fibrosis respond differently to cigarette smoke exposure

The effects of cigarette smoke extract (CSE) on airway epithelial cells (AECs) from cystic fibrosis (CF) and non-cystic fibrosis (non-CF) individuals are not fully understood. It has been suggested that CSE modulates inflammatory cytokine release from AECs by modulating the epidermal growth factor receptor (EGFR) pathway; these pathways could reveal novel therapeutic targets. We compared the effect of CSE pre-incubation on IL-8 release from CF and non-CF bronchial epithelial cell lines, and separately, with primary nasal epithelial cells (NECs) retrieved from CF and non-CF individuals. We also determined if the EGFR pathway regulates IL-8 release by LPS or cytomix in non-CF and CF AECs at baseline and following CSE exposure. CF and non-CF cell lines, NECs derived from both CF patients (R117H heterozygous and F508del homozygous), and from healthy subjects, were cultured in the presence or absence of CSE, and subsequently exposed to inflammatory stimuli. In cell lines CSE significantly reduced IL-8 release following inflammatory challenge. Conversely, CSE pre-treatment was pro-inflammatory in primary NECs. In NECs from control subjects, CSE increased cytomix and LPS induced IL-8 release, and for the R117H heterozygous NEC cultures, CSE enhanced basal IL-8 release. Cytomix and LPS induced IL-8 release from F508del homozygous NEC cultures was further heightened following CSE pre-treatment. EGFR inhibition mitigated IL-8 release from immortalised and primary non-CF and CF AECs, suggesting that constitutive and CSE elicited IL-8 release from AECs is partly regulated via the EGFR pathway. This study demonstrates the importance of the EGFR cascade in the regulation of constitutive and CSE induced inflammatory mediator release from immortalised and primary AECs. Moreover, it clearly highlights the significance of using primary cells to confirm results obtained from immortalised cell studies, as these model systems may respond very differently to the stimuli under investigation.

Differential response of human nasal and bronchial epithelial cells upon exposure to size-fractionated dairy dust

Exposure to organic dusts is associated with increased respiratory morbidity and mortality in agricultural workers. Organic dusts in dairy farm environments are complex, polydisperse mixtures of toxic and immunogenic compounds. Previous toxicological studies focused primarily on exposures to the respirable size fraction; however, organic dusts in dairy farm environments are known to contain larger particles. Given the size distribution of dusts from dairy farm environments, the nasal and bronchial epithelia represent targets of agricultural dust exposures. In this study, well-differentiated normal human bronchial epithelial cells and human nasal epithelial cells were exposed to two different size fractions (PM10 and PM>10) of dairy parlor dust using a novel aerosol-to-cell exposure system. Levels of proinflammatory transcripts (interleukin [IL]-8, IL-6, and tumor necrosis factor [TNF]-α) were measured 2 h after exposure. Lactate dehydrogenase (LDH) release was also measured as an indicator of cytotoxicity. Cell exposure to dust was measured in each size fraction as a function of mass, endotoxin, and muramic acid levels. To our knowledge, this is the first study to evaluate the effects of distinct size fractions of agricultural dust on human airway epithelial cells. Our results suggest that both PM10 and PM>10 size fractions elicit a proinflammatory response in airway epithelial cells and that the entire inhalable size fraction needs to be considered when assessing potential risks from exposure to agricultural dusts. Further, data suggest that human bronchial cells respond differently to these dusts than human nasal cells, and therefore that the two cell types need to be considered separately in airway cell models of agricultural dust toxicity.

Comparison of three different brushing techniques to isolate and culture primary nasal epithelial cells from human subjects

PURPOSE

Primary nasal epithelial cells are used for diagnostic purposes in clinical routine and have been shown to be good surrogate models for bronchial epithelial cells in studies of airway inflammation and remodeling. We aimed at comparing different instruments allowing isolation of nasal epithelial cells.

METHODS

Primary airway epithelial cell cultures were established using cells acquired from the inferior surface of the middle turbinate of both nostrils. Three different instruments to isolate nasal cells were used: homemade cytology brush, nasal swab, and curette. Cell count, viability, time until a confluent cell layer was reached, and success rate in establishing cell cultures were evaluated. A standard numeric pain intensity scale was used to assess the acceptability of each instrument.

RESULTS

Sixty healthy adults (median with interquartile range [IQR] age of 31 [26-37] years) participated in the study. Higher number of cells (×10(5) cells/ml) was obtained using brushes (9.8 [5.9-33.5]) compared to swabs (2.4 [1.5-3.9], p < 0.0001) and curettes (5.5 [4.4-6.9], p < 0.01). Cell viability was similar between groups. Cells obtained by brushes had the fastest growth rate, and the success rate in establishing primary cell cultures was highest with brushes (90% vs. 65% for swabs and 70% for curettes). Pain was highest with curettes (VAS score 4.0 [3.0-5.0] out of 10). The epithelial phenotype of the cultures was confirmed through cytokeratin and E-cadherin staining.

CONCLUSIONS

All three types of instruments allow collection and growth of human nasal epithelial cells with good acceptability to study participants. The most efficient instrument is the nasal brush.

A model of human nasal epithelial cells adapted for direct and repeated exposure to airborne pollutants

Airway epithelium lining the nasal cavity plays a pivotal role in respiratory tract defense and protection mechanisms. Air pollution induces alterations linked to airway diseases such as asthma. Only very few in vitro studies to date have succeeded in reproducing physiological conditions relevant to cellular type and chronic atmospheric pollution exposure. We therefore, set up an in vitro model of human Airway Epithelial Cells of Nasal origin (hAECN) close to real human cell functionality, specifically adapted to study the biological effects of exposure to indoor gaseous pollution at the environmental level. hAECN were exposed under air-liquid interface, one, two, or three-times at 24 h intervals for 1 h, to air or formaldehyde (200 μg/m(3)), an indoor air gaseous pollutant. All experiments were ended at day 4, when both cellular viability and cytokine production were assessed. Optimal adherence and confluence of cells were obtained 96 h after cell seeding onto collagen IV-precoated insert. Direct and repeated exposure to formaldehyde did not produce any cellular damage or IL-6 production change, although weak lower IL-8 production was observed only after the third exposure. Our model is significantly better than previous ones due to cell type and the repeated exposure protocol.

Advances in asthma drug discovery: evaluating the potential of nasal cell sampling and beyond

INTRODUCTION

Inhaled corticosteroid anti-inflammatory therapy is effective at controlling disease symptoms of asthma, but a subset of patients remains symptomatic despite optimal treatment, creating a clear unmet medical need. Moreover, none of the currently available drugs for asthma are really disease-modifying or curative. Although murine models of asthma, based on transgenic and knockout animals, may offer an integrated pathophysiological system for studying the characteristics of airway inflammation and hyperresponsiveness, these alterations are noteworthily different compared with those observed in asthmatic patients. Since a clear functional and inflammatory relationship between the nasal mucosa and bronchial tissue in patients suffering from asthma and allergic rhinitis has been recognized, using preclinical models based on human nasal cells sampling might support a prompt and effective anti-inflammatory drug discovery in asthma.

AREAS COVERED

The authors provide a review, which discusses the potential role of nasal cell sampling and its application in advanced drug discovery for asthma. The contents range from the similarities and differences between asthma and allergic rhinitis up to artificial airway models based on sophisticated human lung-on-a-chip devices.

EXPERT OPINION

Nasal cell sampling and processing have reached a great potential in asthma drug discovery. The authors believe that models of asthma, which are based on human nasal cells, can provide valuable indications of proof of pharmacological and potential therapeutic efficacy in both preclinical and early clinical settings.

Inflammatory and cytotoxic effects of acrolein, nicotine, acetylaldehyde and cigarette smoke extract on human nasal epithelial cells

BACKGROUND

Cigarette smoke induces a pro-inflammatory response in airway epithelial cells but it is not clear which of the various chemicals contained within cigarette smoke (CS) should be regarded as predominantly responsible for these effects. We hypothesised that acrolein, nicotine and acetylaldehyde, important chemicals contained within volatile cigarette smoke in terms of inducing inflammation and causing addiction, have immunomodulatory effects in primary nasal epithelial cell cultures (PNECs).

METHODS

PNECs from 19 healthy subjects were grown in submerged cultures and were incubated with acrolein, nicotine or acetylaldehyde prior to stimulation with Pseudomonas aeruginosa lipopolysaccharide (PA LPS). Experiments were repeated using cigarette smoke extract (CSE) for comparison. IL-8 was measured by ELISA, activation of NF-κB by ELISA and Western blotting, and caspase-3 activity by Western blotting. Apoptosis was evaluated using Annexin-V staining and the terminal transferase-mediated dUTP nick end-labeling (TUNEL) method.

RESULTS

CSE was pro-inflammatory after a 24 h exposure and 42% of cells were apoptotic or necrotic after this exposure time. Acrolein was pro-inflammatory for the PNEC cultures (30 μM exposure for 4 h inducing a 2.0 fold increase in IL-8 release) and also increased IL-8 release after stimulation with PA LPS. In contrast, nicotine had anti-inflammatory properties (0.6 fold IL-8 release after 50 μM exposure to nicotine for 24 h), and acetylaldehyde was without effect. Acrolein and nicotine had cellular stimulatory and anti-inflammatory effects respectively, as determined by NF-κB activation. Both chemicals increased levels of cleaved caspase 3 and induced cell death.

CONCLUSIONS

Acrolein is pro-inflammatory and nicotine anti-inflammatory in PNEC cultures. CSE induces cell death predominantly by apoptotic mechanisms.