Air-Liquid Interface Culture of Human and Mouse Airway Epithelial Cells

Tollip deficiency enhances mitophagy and reduces STING activation in influenza A virus-infected mice

Toll-interacting protein (Tollip) is an intracellular adaptor protein with diverse functions including regulation of autophagy of mitochondria-mitophagy. Tollip deficiency promotes viral infection, but whether mitophagy is involved remains unclear. We sought to determine if mitophagy and associated signaling such as mitochondrial DNA (mtDNA) release and activation of stimulator of interferon genes (STING) contribute to worsened viral infection due to Tollip deficiency. Wild-type and Tollip knockout (KO) C57/BL6 mice were intranasally infected with influenza A virus (IAV), and then treated with or without a STING agonist 2'3'cGAMP for 4 d. PINK1 (an initiator of mitophagy) KO mouse tracheal epithelial cells (mTECs) or PINK1 KO mice were infected with IAV to reveal the role of mitophagy in viral infection. In IAV-infected mice, Tollip deficiency enhanced lung mitophagy (more PINK1 and BNIP3L, but less p62), and decreased release of mtDNA. Furthermore, Tollip deficiency suppressed STING activation and the antiviral response (eg IFN-β and MX1), and increased viral load. In IAV-infected Tollip KO mice, 2'3'cGAMP activated STING and increased antiviral response coupled with less virus. PINK1-deficient mice increased lung release of mtDNA and augmented STING activation and antiviral responses. PINK1 deficiency in mTECs increased STING activation and significantly decreased the viral load. Our findings suggest that enhanced mitophagy due to Tollip deficiency reduces mtDNA release and STING activation during viral infection, resulting in decreased antiviral responses. Reduction of mitophagy and/or STING activation may open novel avenues for therapeutic intervention in human subjects with Tollip deficiency and viral infection.

Species- and strain-specific microbial modulation of interferon, innate immunity, and epithelial barrier in 2D air-liquid interface respiratory epithelial cultures

BACKGROUND

The microbiome regulates the respiratory epithelium's immunomodulatory functions. To explore how the microbiome's biodiversity affects microbe-epithelial interactions, we screened 58 phylogenetically diverse microbes for their transcriptomic effect on human primary bronchial air-liquid interface (ALI) cell cultures.

RESULTS

We found distinct species- and strain-level differences in host innate immunity and epithelial barrier response. Strikingly, we found that host interferon, an antiviral response, was one of the most variable host processes. This variability was not driven by microbial phylogenetic diversity, bioburden, nor by the microbe's ability to stimulate other innate immunity pathways.

CONCLUSIONS

Microbial colonization differentially stimulates host gene expression with variations observed across phylogenetically diverse microbes and across different strains of the same species. Our study provides a foundation for understanding how the respiratory microbiome's biodiversity affects epithelial, and particularly antiviral, innate immunity.

A novel approach to investigate severe asthma and COPD: the 3d ex vivo respiratory mucosa model

Purpose: This article illustrates the replication of asthma and COPD conditions in a laboratory setting and the potential applications of this methodology.

Introduction: Biologic drugs have been shown to enhance the treatment of severe asthma and COPD. Monoclonal antibodies against specific targets have dramatically changed the management of these conditions. Although the inflammatory pathways of asthma and COPD have already been clearly outlined, alternative mechanisms of action remain mostly unexplored. They could provide additional insights into these diseases and their clinical management.

Aims: In vivo or in vitro models have thus been developed to test alternative hypotheses. This study describes sophisticated ex vivo models that mimic the response of human respiratory mucosa to disease triggers, aiming to narrow the gap between laboratory studies and clinical practice.

Results: These models successfully replicate crucial aspects of these diseases, such as inflammatory cell presence, cytokine production, and changes in tissue structure, offering a dynamic platform for investigating disease processes and evaluating potential treatments, such as monoclonal antibodies. The proposed models have the potential to enhance personalized medicine approaches and patient-specific treatments, helping to advance the understanding and management of respiratory diseases.

Agarose hydrogel-mediated electroporation method for retinal tissue cultured at the air-liquid interface

It is advantageous to culture the ex vivo retina and other tissues at the air-liquid interface to allow for more efficient gas exchange. However, gene delivery to these cultures can be challenging. Electroporation is a fast and robust method of gene delivery, but typically requires submergence in liquid buffer for electrical current flow. We have developed a submergence-free electroporation technique that incorporates an agarose hydrogel disk between the positive electrode and retina. Inner retinal neurons and Müller glia are transfected with increased propensity toward Müller glia transfection after extended time in culture. We also observed an increase in BrdU incorporation in Müller glia following electrical stimulation, and variation in detection of transfected cells from expression vectors with different promoters. This method advances our ability to use ex vivo retinal tissue for genetic studies and should be adaptable for other tissues cultured at an air-liquid interface.

Interpretable machine learning uncovers epithelial transcriptional rewiring and a role for Gelsolin in COPD

Transcriptomic analyses have advanced the understanding of complex disease pathophysiology including chronic obstructive pulmonary disease (COPD). However, identifying relevant biologic causative factors has been limited by the integration of high dimensionality data. COPD is characterized by lung destruction and inflammation, with smoke exposure being a major risk factor. To define previously unknown biological mechanisms in COPD, we utilized unsupervised and supervised interpretable machine learning analyses of single-cell RNA-Seq data from the mouse smoke-exposure model to identify significant latent factors (context-specific coexpression modules) impacting pathophysiology. The machine learning transcriptomic signatures coupled to protein networks uncovered a reduction in network complexity and new biological alterations in actin-associated gelsolin (GSN), which was transcriptionally linked to disease state. GSN was altered in airway epithelial cells in the mouse model and in human COPD. GSN was increased in plasma from patients with COPD, and smoke exposure resulted in enhanced GSN release from airway cells from patients with COPD. This method provides insights into rewiring of transcriptional networks that are associated with COPD pathogenesis and provides a translational analytical platform for other diseases.

Single-cell RNA sequencing reveals heterogeneity of ALI model and epithelial cell alterations after exposure to electronic cigarette aerosol

Electronic cigarettes (e-cigarettes) have been advertised as a healthier alternative to traditional cigarettes; however, their exact effects on the bronchial epithelium are poorly understood. Air-liquid interface culture human bronchial epithelium (ALI-HBE) contains various cell types, including basal cell, ciliated cell and secretory cell, providing an in vitro model that simulates the biological characteristics of normal bronchial epithelium. Multiplex single-cell RNA sequencing of ALI-HBE was used to reveal previously unrecognized transcriptional heterogeneity within the human bronchial epithelium and cell type-specific responses to acute exposure to e-cigarette aerosol (e-aerosol) containing distinct components (nicotine and/or flavoring). The findings of our study show that nicotine-containing e-aerosol affected gene expression related to transformed basal cells into secretory cells after acute exposure; inhibition of secretory cell function by down-regulating genes related to epithelial cell differentiation, calcium ion binding, extracellular exosomes, and secreted proteins; and enhanced interaction between secretory cells and other cells. On the other hand, flavoring may alter the growth pattern of epithelial cells and make basal cells more susceptible to SARS-CoV infection. Besides, the data also indicate factors that may promote SARS-CoV-2 infection and suggest therapeutic targets for restoring normal bronchial epithelium function after e-cigarette use. In summary, the current study offered fresh perspectives on alterations in the cellular landscape and cell type-specific responses in human bronchial epithelium that are brought about by e-cigarette use.

A 3D Epithelial-Mesenchymal Co-Culture Model of the Airway Wall Using Native Lung Extracellular Matrix

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease characterized by ongoing inflammation, impaired tissue repair, and aberrant interplay between airway epithelium and fibroblasts, resulting in an altered extracellular matrix (ECM) composition. The ECM is the three-dimensional (3D) scaffold that provides mechanical support and biochemical signals to cells, now recognized not only as a consequence but as a potential driver of disease progression. To elucidate how the ECM influences pathophysiological changes occurring in COPD, in vitro models are needed that incorporate the ECM. ECM hydrogels are a novel experimental tool for incorporating the ECM in experimental setups. We developed an airway wall model by combining lung-derived ECM hydrogels with a co-culture of primary human fibroblasts and epithelial cells at an air-liquid interface. Collagen IV and a mixture of collagen I, fibronectin, and bovine serum albumin were used as basement membrane-mimicking coatings. The model was initially assembled using porcine lung-derived ECM hydrogels and subsequently with COPD and non-COPD human lung-derived ECM hydrogels. The resulting 3D construct exhibited considerable contraction and supported co-culture, resulting in a differentiated epithelial layer. This multi-component 3D model allows the investigation of remodelling mechanisms, exploring ECM involvement in cellular crosstalk, and holds promise as a model for drug discovery studies exploring ECM involvement in cellular interactions.

Bioengineering Human Upper Respiratory Mucosa: A Systematic Review of the State of the Art of Cell Culture Techniques

BACKGROUND

The upper respiratory mucosa plays a crucial role in both the physical integrity and immunological function of the respiratory tract. However, in certain situations such as infections, trauma, or surgery, it might sustain damage. Tissue engineering, a field of regenerative medicine, has found applications in various medical fields including but not limited to plastic surgery, ophthalmology, and urology. However, its application to the respiratory system remains somewhat difficult due to the complex morphology and histology of the upper respiratory tract. To date, a culture protocol for producing a handleable, well-differentiated nasal mucosa has yet to be developed. The objective of this review is to describe the current state of research pertaining to cell culture techniques used for producing autologous healthy human upper respiratory cells and mucosal tissues, as well as describe its clinical applications.

METHODS

A search of the relevant literature was carried out with no time restriction across Embase, Cochrane, PubMed, and Medline Ovid databases. Keywords related to "respiratory mucosa" and "culture techniques of the human airway" were the focus of the search strategy for this review. The risk of bias in retained studies was assessed using the Joanna Briggs Institute's (JBI) critical appraisal tools for qualitative research. A narrative synthesis of our results was then conducted.

RESULTS

A total of 33 studies were included in this review, and thirteen of these focused solely on developing a cell culture protocol without further use. The rest of the studies used their own developed protocol for various applications such as cystic fibrosis, pharmacological, and viral research. One study was able to develop a promising model for nasal mucosa that could be employed as a replacement in nasotracheal reconstructive surgery.

CONCLUSIONS

This systematic review extensively explored the current state of research regarding cell culture techniques for producing tissue-engineered nasal mucosa. Bioengineering the nasal mucosa holds great potential for clinical use. However, further research on mechanical properties is essential, as the comparison of engineered tissues is currently focused on morphology rather than comprehensive mechanical assessments.

Blood-brain barrier injury and neuroinflammation induced by SARS-CoV-2 in a lung-brain microphysiological system

In some patients, COVID-19 can trigger neurological symptoms with unclear pathogenesis. Here we describe a microphysiological system integrating alveolus and blood-brain barrier (BBB) tissue chips that recapitulates neuropathogenesis associated with infection by SARS-CoV-2. Direct exposure of the BBB chip to SARS-CoV-2 caused mild changes to the BBB, and infusion of medium from the infected alveolus chip led to more severe injuries on the BBB chip, including endothelial dysfunction, pericyte detachment and neuroinflammation. Transcriptomic analyses indicated downregulated expression of the actin cytoskeleton in brain endothelium and upregulated expression of inflammatory genes in glial cells. We also observed early cerebral microvascular damage following lung infection with a low viral load in the brains of transgenic mice expressing human angiotensin-converting enzyme 2. Our findings suggest that systemic inflammation is probably contributing to neuropathogenesis following SARS-CoV-2 infection, and that direct viral neural invasion might not be a prerequisite for this neuropathogenesis. Lung-brain microphysiological systems should aid the further understanding of the systemic effects and neurological complications of viral infection.

The Modulation of Respiratory Epithelial Cell Differentiation by the Thickness of an Electrospun Poly-ε-Carprolactone Mesh Mimicking the Basement Membrane

The topology of the basement membrane (BM) affects cell physiology and pathology, and BM thickening is associated with various chronic lung diseases. In addition, the topology of commercially available poly (ethylene terephthalate) (PET) membranes, which are used in preclinical in vitro models, differs from that of the human BM, which has a fibrous and elastic structure. In this study, we verified the effect of BM thickness on the differentiation of normal human bronchial epithelial (NHBE) cells. To evaluate whether the thickness of poly-ε-carprolactone (PCL) mesh affects the differentiation of NHBE cells, cells were grown on thin- (6-layer) and thick-layer (80-layer) meshes consisting of electrospun PCL nanofibers using an air-liquid interface (ALI) cell culture system. It was found that the NHBE cells formed a normal pseudostratified epithelium composed of ciliated, goblet, and basal cells on the thin-layer PCL mesh; however, goblet cell hyperplasia was observed on the thick-layer PCL mesh. Differentiated NHBE cells cultured on the thick-layer PCL mesh also demonstrated increased epithelial-mesenchymal transition (EMT) compared to those cultured on the thin-layer PCL mesh. In addition, expression of Sox9, nuclear factor (NF)-κB, and oxidative stress-related markers, which are also associated with goblet cell hyperplasia, was increased in the differentiated NHBE cells cultured on the thick-layer PCL mesh. Thus, the use of thick electrospun PCL mesh led to NHBE cells differentiating into hyperplastic goblet cells via EMT and the oxidative stress-related signaling pathway. Therefore, the topology of the BM, for example, thickness, may affect the differentiation direction of human bronchial epithelial cells.

Agarose disk electroporation method for ex vivo retinal tissue cultured at the air-liquid interface reveals electrical stimulus-induced cell cycle reentry in retinal cells

It is advantageous to culture the ex vivo murine retina along with many other tissue types at the air-liquid interface. However, gene delivery to these cultures can be challenging. Electroporation is a fast and robust method of gene delivery, but typically requires submergence in a liquid buffer to allow electric current flow. We have developed a submergence-free electroporation technique using an agarose disk that allows for efficient gene delivery to the ex vivo murine retina. This method advances our ability to use ex vivo retinal tissue for genetic studies and can easily be adapted for any tissue cultured at an air-liquid interface. We found an increased ability to transfected Muller glia at 14 days ex vivo and an increase in BrdU incorporation in Muller glia following electrical stimulation. Use of this method has revealed valuable insights on the state of ex vivo retinal tissues and the effects of electrical stimulation on retinal cells.

Delivery of a BET protein degrader via a CEACAM6-targeted antibody-drug conjugate inhibits tumour growth in pancreatic cancer models

Pancreatic ductal adenocarcinoma (PDAC) has the worst prognosis of all cancers. To improve PDAC therapy, we establish screening systems based on organoid and co-culture technologies and find a payload of antibody-drug conjugate (ADC), a bromodomain and extra-terminal (BET) protein degrader named EBET. We select CEACAM6/CD66c as an ADC target and developed an antibody, #84.7, with minimal reactivity to CEACAM6-expressing normal cells. EBET-conjugated #84.7 (84-EBET) has lethal effects on various PDAC organoids and bystander efficacy on CEACAM6-negative PDAC cells and cancer-associated fibroblasts. In mouse studies, a single injection of 84-EBET induces marked tumor regression in various PDAC-patient-derived xenografts, with a decrease in the inflammatory phenotype of stromal cells and without significant body weight loss. Combination with standard chemotherapy or PD-1 antibody induces more profound and sustained regression without toxicity enhancement. Our preclinical evidence demonstrates potential efficacy by delivering BET protein degrader to PDAC and its microenvironment via CEACAM6-targeted ADC.

The antiviral potential of the antiandrogen enzalutamide and the viral-androgen signaling interplay in seasonal coronaviruses

The sex disparity in COVID-19 outcomes with males generally faring worse than females has been associated with the androgen-regulated expression of the protease TMPRSS2 and the cell receptor ACE2 in the lung and fueled interest in antiandrogens as potential antivirals. In this study, we explored enzalutamide, an antiandrogen used commonly to treat prostate cancer, as a potential antiviral against the human coronaviruses which cause seasonal respiratory infections (HCoV-NL63, -229E, and -OC43). Using lentivirus-pseudotyped and authentic HCoV, we report that enzalutamide reduced 229E and NL63 entry and infection in both TMPRSS2- and nonexpressing immortalized cells, suggesting a TMPRSS2-independent mechanism. However, no effect was observed against OC43. To decipher this distinction, we performed RNA-sequencing analysis on 229E- and OC43-infected primary human airway cells. Our results show a significant induction of androgen-responsive genes by 229E compared to OC43 at 24 and 72 h postinfection. The virus-mediated effect on AR-signaling was further confirmed with a consensus androgen response element-driven luciferase assay in androgen-depleted MRC-5 cells. Specifically, 229E induced luciferase-reporter activity in the presence and absence of the synthetic androgen mibolerone, while OC43 inhibited induction. These findings highlight a complex interplay between viral infections and androgen-signaling, offering insights for disparities in viral outcomes and antiviral interventions.

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

Cold dispase digestion of murine lungs improves recovery and culture of airway epithelial cells

Airway epithelial cells (AECs) play a key role in maintaining lung homeostasis, epithelium regeneration and the initiation of pulmonary immune responses. To isolate and study murine AECs investigators have classically used short and hot (1h 37°C) digestion protocols. Here, we present a workflow for efficient AECs isolation and culture, utilizing long and cold (20h 4°C) dispase II digestion of murine lungs. This protocol yields a greater number of viable AECs compared to an established 1h 37°C dispase II digestion. Using a combination of flow cytometry and immunofluorescent microscopy, we demonstrate that compared to the established method, the cold digestion allows for recovery of a 3-fold higher number of CD45-CD31-EpCAM+ cells from murine lungs. Their viability is increased compared to established protocols, they can be isolated in larger numbers by magnetic-activated cell sorting (MACS), and they result in greater numbers of distal airway stem cell (DASC) KRT5+p63+ colonies in vitro. Our findings demonstrate that temperature and duration of murine lung enzymatic digestion have a considerable impact on AEC yield, viability, and ability to form colonies in vitro. We believe this workflow will be helpful for studying lung AECs and their role in the biology of lung.

A Novel Sandwich Method for Serial Block Face SEM Imaging of Airway Multiciliated Epithelium

Volume electron microscopy technologies such as serial block face scanning electron microscopy (SBF-SEM) allow the characterization of tissue organization and cellular content in three dimensions at nanoscale resolution. Here, we describe the procedure to process and image an air-liquid interface culture of human or mouse airway epithelial cells for visualization of the multiciliated epithelium by SBF-SEM in vertical or horizontal cross section.

Requisite instruments for the establishment of three-dimensional epidermal human skin equivalents-A methods review

Human skin equivalents (HSEs) are three-dimensional skin organ culture models raised in vitro. This review gives an overview of common techniques for setting up HSEs. The HSE consists of an artificial dermis and epidermis. 3T3-J2 murine fibroblasts, purchased human fibroblasts or freshly isolated and cultured fibroblasts, together with other components, for example, collagen type I, are used to build the scaffold. Freshly isolated and cultured keratinocytes are seeded on top. It is possible to add other cell types, for example, melanocytes, to the HSE-depending on the research question. After several days and further steps, the 3D skin can be harvested. Additionally, we show possible markers and techniques for evaluation of artificial skin. Furthermore, we provide a comparison of HSEs to human skin organ culture, a model which employs human donor skin. We outline advantages and limitations of both models and discuss future perspectives in using HSEs.

Wet-adhesive γ-PGA/ε-PLL hydrogel loaded with EGF for tracheal epithelial injury repair

Following the global COVID-19 pandemic, the incidence of tracheal epithelial injury is increasing. However, the repair of tracheal epithelial injury remains a challenge due to the slow renewal rate of tracheal epithelial cells (TECs). In traditional nebulized inhalation treatments, drugs are enriched in the lungs or absorbed into the blood, reducing drug concentration at the tracheal injury site. In this study, we prepared an epidermal growth factor (EGF)-loaded gamma-polyglutamic acid (γ-PGA)/epsilon-poly-L-lysine (ε-PLL) (PP) hydrogel (EGF@PP) to promote the repair of tracheal epithelial injury. Epidermal growth factor promotes the proliferation of TECs and enhances vascularization, thereby accelerating injury repair. The PP hydrogel exhibits outstanding wet adhesion, slow drug release, and antibacterial and anti-inflammatory properties, making it suitable for application in the airways and creating an environment conducive to epithelial repair. Here, we established a rabbit model of tracheal injury using a laser to destroy the tracheal epithelium and delivered EGF@PP powder to the injury site under fiberoptic bronchoscopy guidance. Our findings revealed that this was an effective therapeutic strategy for accelerating the repair of tracheal epithelial injury.

Bovine Airway Models: Approaches for Investigating Bovine Respiratory Disease

Bovine respiratory disease (BRD) is a multifactorial condition where different genera of bacteria, such as Mannheimia haemolytica, Histophilus somni, Pasteurella multocida, and Mycoplasma bovis, and viruses, like bovine respiratory syncytial virus, bovine viral diarrhea virus, and bovine herpes virus-1, infect the lower respiratory tract of cattle. These pathogens can co-infect cells in the respiratory system, thereby making specific treatment very difficult. Currently, the most common models for studying BRD include a submerged tissue culture (STC), where monolayers of epithelial cells are typically covered either in cellular or spent biofilm culture medium. Another model is an air-liquid interface (ALI), where epithelial cells are exposed on their apical side and allowed to differentiate. However, limited work has been reported on the study of three-dimensional (3D) bovine models that incorporate multiple cell types to represent the architecture of the respiratory tract. The roles of different defense mechanisms in an infected bovine respiratory system, such as mucin production, tight junction barriers, and the production of antimicrobial peptides in in vitro cultures require further investigation in order to provide a comprehensive understanding of the disease pathogenesis. In this report, we describe the different aspects of BRD, including the most implicated pathogens and the respiratory tract, which are important to incorporate in disease models assembled in vitro. Although current advancements of bovine respiratory cultures have led to knowledge of the disease, 3D multicellular organoids that better recapitulate the in vivo environment exhibit potential for future investigations.

Preterm ovine respiratory epithelial cell responses to mechanical ventilation, lipopolysaccharide, and interleukin-13

Mechanical ventilation causes airway injury, respiratory epithelial cell proliferation, and lung inflammation in preterm sheep. Whether preterm epithelial cells respond similarly to adult epithelial cells or are altered by mechanical ventilation is unknown. We test the hypothesis that mechanical ventilation alters the responses of preterm airway epithelium to stimulation in culture. Respiratory epithelial cells from the trachea, left mainstem bronchi (LMSB), and distal bronchioles were harvested from unventilated preterm lambs, ventilated preterm lambs, and adult ewes. Epithelial cells were grown in culture or on air-liquid interface (ALI) and challenged with combinations of either media only, lipopolysaccharide (LPS; 10 ng/mL), bronchoalveolar fluid (BALF), or interleukin-13 (IL-13). Cell lysates were evaluated for mRNA changes in cytokine, cell type markers, Notch pathway, and acute phase markers. Mechanical ventilation altered preterm respiratory epithelium cell types. Preterm respiratory epithelial cells responded to LPS in culture with larger IL-8 induction than adults, and mechanical ventilation further increased cytokines IL-1β and IL-8 mRNA induction at 2 h. IL-8 protein is detected in cell media after LPS stimulation. The addition of BALF from ventilated preterm animals increased IL-1β mRNA to LPS (fivefold) in both preterm and adult cells and suppressed IL-8 mRNA (twofold) in adults. Preterm respiratory epithelial cells, when grown on ALI, responded to IL-13 with an increase in goblet cell mRNA. Preterm respiratory epithelial cells responded to LPS and IL-13 with responses similar to adults. Mechanical ventilation or exposure to BALF from mechanically ventilated animals alters the responses to LPS.NEW & NOTEWORTHY Preterm lamb respiratory epithelial cells can be extracted from the trachea and bronchi and frozen, and the preterm cells can respond in culture to stimulation with LPS or IL-13. Brief mechanical ventilation changes the distribution and cell type of preterm respiratory cells toward an adult phenotype, and mechanical ventilation alters the response to LPS in culture. Bronchoalveolar lavage fluid from preterm lambs receiving mechanical ventilation also alters unventilated preterm and adult responses to LPS.

Biobanked tracheal basal cells retain the capacity to differentiate

Objective

While airway epithelial biorepositories have established roles in the study of bronchial progenitor stem (basal) cells, the utility of a bank of tracheal basal cells from pediatric patients, who have or are suspected of having an airway disease, has not been established. In vitro study of these cells can enhance options for tracheal restoration, graft design, and disease modeling. Development of a functional epithelium in these settings is a key measure. The aim of this study was the creation a tracheal basal cell biorepository and assessment of recovered cells.

Methods

Pediatric patients undergoing bronchoscopy were identified and endotracheal brush (N = 29) biopsies were collected. Cells were cultured using the modified conditional reprogramming culture (mCRC) method. Samples producing colonies by day 14 were passaged and cryopreserved. To explore differentiation potential, cells were thawed and differentiated using the air-liquid interface (ALI) method.

Results

No adverse events were associated with biopsy collection. Of 29 brush biopsies, 16 (55%) were successfully cultured to passage 1/cryopreserved. Samples with higher initial cell yields were more likely to achieve this benchmark. Ten unique donors were then thawed for analysis of differentiation. The average age was 2.2 ± 2.2 years with five donors (50%) having laryngotracheal pathology. Nine donors (90%) demonstrated differentiation capacity at 21 days of culture, as indicated by detection of ciliated cells (ACT+) and mucous cells (MUC5B+).

Conclusion

Pediatric tracheal basal cells can be successfully collected and cryopreserved. Recovered cells retain the ability to differentiate into epithelial cell types in vitro.

Level of Evidence

Level 3.

BPIFA1 is a secreted biomarker of differentiating human airway epithelium

In vitro culture and differentiation of human-derived airway basal cells under air-liquid interface (ALI) into a pseudostratified mucociliated mucosal barrier has proven to be a powerful preclinical tool to study pathophysiology of respiratory epithelium. As such, identifying differentiation stage-specific biomarkers can help investigators better characterize, standardize, and validate populations of regenerating epithelial cells prior to experimentation. Here, we applied longitudinal transcriptomic analysis and observed that the pattern and the magnitude of OMG, KRT14, STC1, BPIFA1, PLA2G7, TXNIP, S100A7 expression create a unique biosignature that robustly indicates the stage of epithelial cell differentiation. We then validated our findings by quantitative hemi-nested real-time PCR from in vitro cultures sourced from multiple donors. In addition, we demonstrated that at protein-level secretion of BPIFA1 accurately reflects the gene expression profile, with very low quantities present at the time of ALI induction but escalating levels were detectable as the epithelial cells terminally differentiated. Moreover, we observed that increase in BPIFA1 secretion closely correlates with emergence of secretory cells and an anti-inflammatory phenotype as airway epithelial cells undergo mucociliary differentiation under air-liquid interface in vitro.

In vivo correction of cystic fibrosis mediated by PNA nanoparticles

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We sought to correct the multiple organ dysfunction of the F508del CF-causing mutation using systemic delivery of peptide nucleic acid gene editing technology mediated by biocompatible polymeric nanoparticles. We confirmed phenotypic and genotypic modification in vitro in primary nasal epithelial cells from F508del mice grown at air-liquid interface and in vivo in F508del mice following intravenous delivery. In vivo treatment resulted in a partial gain of CFTR function in epithelia as measured by in situ potential differences and Ussing chamber assays and correction of CFTR in both airway and GI tissues with no off-target effects above background. Our studies demonstrate that systemic gene editing is possible, and more specifically that intravenous delivery of PNA NPs designed to correct CF-causing mutations is a viable option to ameliorate CF in multiple affected organs.

Porcine choroid plexus-Riems cell line demonstrates altered polarization of transport proteins compared with the native epithelium

The choroid plexus epithelium (CPe) forms a barrier between the cerebral blood supply and the cerebrospinal fluid (CSF), establishing the blood-CSF barrier (BCSFB). CSF is actively secreted by the CPe via tightly controlled processes involving multiple channels, transporters, and pumps. The importance of controlling CSF production and composition has been accentuated recently with an appreciation of CSF dysfunction in many pathologies. For mechanistic studies of CSF production, isolated CPe cell lines are valuable for the testing of hypotheses and potential drug targets. Although several continuous CPe cell lines have been described, none appear to have all the characteristics of the native epithelium and each must be used judiciously. The porcine choroid plexus-Riems (PCP-R) cell line forms a high-resistance monolayer characteristic of a barrier epithelium. Conservation of this phenotype is unusual among CPe cell lines, making this model useful for studies of the effects of infection, injury, and drugs on permeability. We have recently discovered that, although this line expresses many of the transporters expressed in the native tissue, some are mispolarized. As a result, inferences regarding fluid/electrolyte flux and the resultant CSF production should be pursued with caution. Furthermore, extended culture periods and changes in media composition result in significant morphological and functional variability. These studies provide a more detailed characterization of the PCP-R cell line concerning transporter expression, polarization, and functionality, as well as plasticity in culture, with the goal to provide the scientific community with information necessary to optimize future experiments with this model.

Tollip Inhibits IL-33 Release and Inflammation in Influenza A Virus-Infected Mouse Airways

Respiratory influenza A virus (IAV) infection continues to pose significant challenges in healthcare of human diseases including asthma. IAV infection in mice was shown to increase IL-33, a key cytokine in driving airway inflammation in asthma, but how IL-33 is regulated during viral infection remains unclear. We previously found that a genetic mutation in Toll-interacting protein (Tollip) was linked to less airway epithelial Tollip expression, increased neutrophil chemokines, and lower lung function in asthma patients. As Tollip is involved in maintaining mitochondrial function, and mitochondrial stress may contribute to extracellular ATP release and IL-33 secretion, we hypothesized that Tollip downregulates IL-33 secretion via inhibiting ATP release during IAV infection. Wild-type and Tollip knockout (KO) mice were infected with IAV and treated with either an ATP converter apyrase or an IL-33 decoy receptor soluble ST2 (sST2). KO mice significantly lost more body weight and had increased extracellular ATP, IL-33 release, and neutrophilic inflammation. Apyrase treatment reduced extracellular ATP levels, IL-33 release, and neutrophilic inflammation in Tollip KO mice. Excessive lung neutrophilic inflammation in IAV-infected Tollip KO mice was reduced by sST2, which was coupled with less IL-33 release. Our data suggest that Tollip inhibits IAV infection, potentially by inhibiting extracellular ATP release and reducing IL-33 activation and lung inflammation. In addition, sST2 may serve as a potential therapeutic approach to mitigate respiratory viral infection in human subjects with Tollip deficiency.

Interferon-γ promotes monocyte-mediated lung injury during influenza infection

Influenza A virus (IAV) infection triggers an exuberant host response that promotes acute lung injury. However, the host response factors that promote the development of a pathologic inflammatory response to IAV remain incompletely understood. In this study, we identify an interferon-γ (IFN-γ)-regulated subset of monocytes, CCR2⁺ monocytes, as a driver of lung damage during IAV infection. IFN-γ regulates the recruitment and inflammatory phenotype of CCR2⁺ monocytes, and mice deficient in CCR2 (CCR2^-/-) or IFN-γ (IFN-γ^-/-) exhibit reduced lung inflammation, pathology, and disease severity. Adoptive transfer of wild-type (WT) (IFN-γR1^+/+) but not IFN-γR1^-/- CCR2⁺ monocytes restore the WT-like pathological phenotype of lung damage in IAV-infected CCR2^-/- mice. CD8⁺ T cells are the main source of IFN-γ in IAV-infected lungs. Collectively, our data highlight the requirement of IFN-γ signaling in the regulation of CCR2⁺ monocyte-mediated lung pathology during IAV infection.

CTNNAL1 participates in the regulation of mucus overproduction in HDM‐induced asthma mouse model through the YAP‐ROCK2 pathway

Our previous study indicated that adhesion molecule catenin alpha‐like 1(CTNNAL1) is downregulated in airway epithelial cells of asthma patients and asthma animal model but little is known about how the CTNNAL1 affects asthma pathogenesis. To reveal the direct relationship between asthma and CTNNAL1, CTNNAL1‐deficient mouse model in bronchopulmonary tissue was constructed by introducing CTNNAL1‐siRNA sequence using adeno‐associated virus (AAV) as vector. The mouse model of asthma was established by stimulation of house dust mite (HDM). After HDM‐challenged, there was marked airway inflammation, especially mucus hypersecretion in the CTNNAL1‐deficient mice. In addition, the CTNNAL1‐deficient mice exhibited an increase of lung IL‐4 and IL‐13 levels, as well as a significant increase of goblet cell hyperplasia and MUC5AC after HDM exposure. The expression of Yes‐associated protein (YAP), protein that interacted with α‐catenin, was downregulated after CTNNAL1 silencing and was upregulated due to its overexpression. In addition, the interaction between CTNNAL1 and YAP was confirmed by CO‐IP. Besides, inhibition of YAP could decrease the secretion of MUC5AC, IL‐4 and IL‐13 in CTNNAL1‐deficient 16HBE14o‐cells. Above results indicated us that CTNNAL1 regulated mucus hypersecretion through YAP pathway. In addition, the expression of ROCK2 increased when CTNNAL1 was silenced and decreased after YAP silencing, and inhibition of YAP decreased the expression of ROCK2 in CTNNAL1‐deficient HBE cells. Inhibition of ROCK2 decreased MUC5AC expression and IL‐13 secretion. In all, our study demonstrates that CTNNAL1 plays an important role in HDM‐induced asthma, mediating mucus secretion through the YAP‐ROCK2 pathway.

Human Bronchial Epithelial Cell Culture Models for Cigarette Smoke and Vaping Studies

Despite the continuing public health efforts to stop or reduce smoking, cigarette smoke use remains popular in the youth and adult population. A recent surge in the use of electronic cigarette and vaping products has created another major health challenge in public health. There is an urgent need to use physiologically relevant models to study the health effect of smoking or vaping in human subjects. Airway diseases such as bronchitis (Landman et al., CMAJ 191:E1321-E1331, 2019; Goniewicz, et al. Harm Reduct J 17:91, 2020; Xie et al., JAMA Netw Open 3:e2020816, 2020) have been described in people who smoke, vape, or both. Here, we will describe methods to collect, expand, and culture human airway epithelial cells from endobronchial brushings and expose these cells cultured at the air-liquid interface to cigarette smoke or electronic cigarette vapor.

Cartilaginous Extracellular Matrix Enriched with Human Gingival Mesenchymal Stem Cells Derived "Matrix Bound Extracellular Vesicles" Enabled Functional Reconstruction of Tracheal Defect

Stem cells derived extracellular vesicles (EVs) conceive cues essential for tissue repair. Mammalian cartilaginous extracellular matrix (cECM) may not be optimally inductive for tracheal regeneration because of the granulomatous, instead of regenerative, responses in injured adult mammalian tracheas. Given the high regenerative capacity of gingiva, it is hypothesized human gingival mesenchymal stem cells derived EVs (gEVs) can induce mammalian tracheal epithelia regeneration. Coculturing chondrocytes with GMSCs produce abundant "matrix bound gEVs (gMVs)" in forming cartilaginous ECM, which are further preserved in acellular cECM (cACM) following mild, short-period decellularization. The results show that gMVs-cACM could be well anchored on polyglycerol sebacate microporous patch thus enforce the surgical suturability and mechanical strength. In rabbit tracheal defect, the gMVs-cACM patch induces rapid regeneration of vascularized ciliated columnar epithelium, which supports long-term survival of animals. gMVs-cACM treated groups exhibit proliferation of tracheal progenitors-basal epithelial cells, as well as, activation of JAK2/STAT1 pathway in reparative cells. This study departs from conventional focuses on tissue derived ECM and introduces a new approach for tracheal tissue regeneration.

Impaired Ciliary Beat Frequency and Ciliogenesis Alteration during Airway Epithelial Cell Differentiation in COPD

Chronic obstructive pulmonary disease (COPD) is a frequent respiratory disease. However, its pathophysiology remains partially elucidated. Epithelial remodeling including alteration of the cilium is a major hallmark of COPD, but specific assessments of the cilium have been rarely investigated as a diagnostic tool in COPD. Here we explore the dysregulation of the ciliary function (ciliary beat frequency (CBF)) and differentiation (multiciliated cells formation in air-liquid interface cultures) of bronchial epithelial cells from COPD (n = 17) and non-COPD patients (n = 15). CBF was decreased by 30% in COPD (11.15 +/- 3.37 Hz vs. 7.89 +/- 3.39 Hz, p = 0.037). Ciliary differentiation was altered during airway epithelial cell differentiation from COPD patients. While the number of multiciliated cells decreased (p < 0.005), the number of primary ciliated cells increased (p < 0.05) and primary cilia were shorter (p < 0.05). Altogether, we demonstrate that COPD can be considered as a ciliopathy through both primary non-motile cilia modifications (related to airway epithelial cell repair and remodeling) and motile cilia function impairment (associated with decrease sputum clearance and clinical respiratory symptoms). These observations encourage considering cilia-associated features in the complex COPD physiopathology and highlight the potential of cilia-derived biomarkers for diagnosis.

The human nose organoid respiratory virus model: an ex-vivo human challenge model to study RSV and SARS-CoV-2 pathogenesis and evaluate therapeutics

There is an unmet need for pre-clinical models to understand the pathogenesis of human respiratory viruses; and predict responsiveness to immunotherapies. Airway organoids can serve as an ex-vivo human airway model to study respiratory viral pathogenesis; however, they rely on invasive techniques to obtain patient samples. Here, we report a non-invasive technique to generate human nose organoids (HNOs) as an alternate to biopsy derived organoids. We made air liquid interface (ALI) cultures from HNOs and assessed infection with two major human respiratory viruses, respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Infected HNO-ALI cultures recapitulate aspects of RSV and SARS-CoV-2 infection, including viral shedding, ciliary damage, innate immune responses, and mucus hyper-secretion. Next, we evaluated the feasibility of the HNO-ALI respiratory virus model system to test the efficacy of palivizumab to prevent RSV infection. Palivizumab was administered in the basolateral compartment (circulation) while viral infection occurred in the apical ciliated cells (airways), simulating the events in infants. In our model, palivizumab effectively prevented RSV infection in a concentration dependent manner. Thus, the HNO-ALI model can serve as an alternate to lung organoids to study respiratory viruses and testing therapeutics.

Chr15q25 Genetic Variant rs16969968 Alters Cell Differentiation in Respiratory Epithelia

The gene cluster region, CHRNA3/CHRNA5/CHRNB4, encoding for nicotinic acetylcholine receptor (nAChR) subunits, contains several genetic variants linked to nicotine addiction and brain disorders. The CHRNA5 single-nucleotide polymorphism (SNP) rs16969968 is strongly associated with nicotine dependence and lung diseases. Using immunostaining studies on tissue sections and air-liquid interface airway epithelial cell cultures, in situ hybridisation, transcriptomic and cytokines detection, we analysed rs16969968 contribution to respiratory airway epithelial remodelling and modulation of inflammation. We provide cellular and molecular analyses which support the genetic association of this polymorphism with impaired ciliogenesis and the altered production of inflammatory mediators. This suggests its role in lung disease development.

State of the art on lung organoids in mammals

The number and severity of diseases affecting lung development and adult respiratory function have stimulated great interest in developing new in vitro models to study lung in different species. Recent breakthroughs in 3-dimensional (3D) organoid cultures have led to new physiological in vitro models that better mimic the lung than conventional 2D cultures. Lung organoids simulate multiple aspects of the real organ, making them promising and useful models for studying organ development, function and disease (infection, cancer, genetic disease). Due to their dynamics in culture, they can serve as a sustainable source of functional cells (biobanking) and be manipulated genetically. Given the differences between species regarding developmental kinetics, the maturation of the lung at birth, the distribution of the different cell populations along the respiratory tract and species barriers for infectious diseases, there is a need for species-specific lung models capable of mimicking mammal lungs as they are of great interest for animal health and production, following the One Health approach. This paper reviews the latest developments in the growing field of lung organoids.

Porcine Hemagglutinating Encephalomyelitis Virus Infection In Vivo and Ex Vivo

Porcine hemagglutinating encephalomyelitis virus (PHEV) is a betacoronavirus that causes vomiting and wasting disease and/or encephalomyelitis in suckling pigs. This study characterized PHEV infection, pathogenesis, and immune response in cesarean-derived, colostrum-deprived (CDCD) neonatal pigs. Infected animals developed mild respiratory, enteric, and neurological clinical signs between 2 to 13 days postoronasal inoculation (dpi). PHEV did not produce viremia, but virus shedding was detected in nasal secretions (1 to 10 dpi) and feces (2 to 7 dpi) by reverse transcriptase quantitative PCR (RT-qPCR). Viral RNA was detected in all tissues except liver, but the detection rate and RT-qPCR threshold cycle (C_T) values decreased over time. The highest concentration of virus was detected in inoculated piglets necropsied at 5 dpi in turbinate and trachea, followed by tonsils, lungs, tracheobronchial lymph nodes, and stomach. The most representative microscopic lesions were gastritis lymphoplasmacytic, moderate, multifocal, with perivasculitis, and neuritis with ganglia degeneration. A moderate inflammatory response, characterized by increased levels of interferon alpha (IFN-α) in plasma (5 dpi) and infiltration of T lymphocytes and macrophages were also observed. Increased plasma levels of interleukin-8 (IL-8) were detected at 10 and 15 dpi, coinciding with the progressive resolution of the infection. Moreover, a robust antibody response was detected by 10 dpi. An ex vivo air-liquid CDCD-derived porcine respiratory cells culture (ALI-PRECs) system showed virus replication in ALI-PRECs and cytopathic changes and disruption of ciliated columnar epithelia, thereby confirming the tracheal epithelia as a primary site of infection for PHEV.

IMPORTANCE Among the ∼46 virus species in the family Coronaviridae, many of which are important pathogens of humans and 6 of which are commonly found in pigs, porcine hemagglutinating encephalomyelitis remains one of the least researched. The present study provided a comprehensive characterization of the PHEV infection process and immune responses using CDCD neonatal pigs. Moreover, we used an ex vivo ALI-PRECs system resembling the epithelial lining of the tracheobronchial region of the porcine respiratory tract to demonstrate that the upper respiratory tract is a primary site of PHEV infection. This study provides a platform for further multidisciplinary studies of coronavirus infections.

Implications for Extracellular Matrix Interactions With Human Lung Basal Stem Cells in Lung Development, Disease, and Airway Modeling

The extracellular matrix (ECM) is not simply a quiescent scaffold. This three-dimensional network of extracellular macromolecules provides structural, mechanical, and biochemical support for the cells of the lung. Throughout life, the ECM forms a critical component of the pulmonary stem cell niche. Basal cells (BCs), the primary stem cells of the airways capable of differentiating to all luminal cell types, reside in close proximity to the basolateral ECM. Studying BC-ECM interactions is important for the development of therapies for chronic lung diseases in which ECM alterations are accompanied by an apparent loss of the lung's regenerative capacity. The complexity and importance of the native ECM in the regulation of BCs is highlighted as we have yet to create an in vitro culture model that is capable of supporting the long-term expansion of multipotent BCs. The interactions between the pulmonary ECM and BCs are, therefore, a vital component for understanding the mechanisms regulating BC stemness during health and disease. If we are able to replicate these interactions in airway models, we could significantly improve our ability to maintain basal cell stemness ex vivo for use in in vitro models and with prospects for cellular therapies. Furthermore, successful, and sustained airway regeneration in an aged or diseased lung by small molecules, novel compounds or via cellular therapy will rely upon both manipulation of the airway stem cells and their immediate niche within the lung. This review will focus on the current understanding of how the pulmonary ECM regulates the basal stem cell function, how this relationship changes in chronic disease, and how replicating native conditions poses challenges for ex vivo cell culture.

The mystery behind the nostrils - technical clues for successful nasal epithelial cell cultivation

OBJECTIVES

Research involving the nose reveals important information regarding the morphology and physiology of the epithelium and its molecular response to agents. The role of nasal epithelial cells and other cell subsets within the nasal epithelium play an interesting translational split between experimental and clinical research studying respiratory disorders or pathogen reactions. With an additional technical manuscript including a detailed description of important technical aspects, tips, tricks, and nuances for a successful culturing of primary, human nasal epithelial cells (NAEPCs), we here aim to improve the process of communication between experimentalists and physicians, supporting the purpose of a fruitful work for future translational projects.

METHODS

Based on previous work on various complex culture models of subject-derived NAEPCs, this additional manuscript harmonizes previously published facts combined with own experiences for a trouble-free implementation in laboratories.

RESULTS

A well-designed experimental question is essential prior to the establishment of different NAEPCs culture models. The correct method of cell extraction from the nasal cavity is essential and represent an important basis for successful culture work. Prior enzymatic processing of biopsy specimens, cell culture materials, collagenization procedure, culture conditions, and choice of culture medium are some important practical notes that increase the quality of the culture. Moreover, protocols on imaging techniques including histologic and electron microscopy must be adapted for NAEPC culture. Adapted flow cytometric protocols and transepithelial electrical resistance measurements can add valuable information.

OUTLOOK

A successful culturing of NAEPCs can provide an important basis for genetic studies and the implementation of omics-science, which is increasingly receiving broad attention in the scientific community. The common aim of in vitro 'mini-noses' will be a breakthrough in laboratories aiming to perform research under in vivo conditions. Here, organoid models are interesting models presenting a basis for translational studies.

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.

The Human Nose Organoid Respiratory Virus Model: an Ex Vivo Human Challenge Model To Study Respiratory Syncytial Virus (RSV) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Pathogenesis and Evaluate Therapeutics

There is an unmet need for preclinical models to understand the pathogenesis of human respiratory viruses and predict responsiveness to immunotherapies. Airway organoids can serve as an ex vivo human airway model to study respiratory viral pathogenesis; however, they rely on invasive techniques to obtain patient samples. Here, we report a noninvasive technique to generate human nose organoids (HNOs) as an alternative to biopsy-derived organoids. We made air-liquid interface (ALI) cultures from HNOs and assessed infection with two major human respiratory viruses, respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Infected HNO-ALI cultures recapitulate aspects of RSV and SARS-CoV-2 infection, including viral shedding, ciliary damage, innate immune responses, and mucus hypersecretion. Next, we evaluated the feasibility of the HNO-ALI respiratory virus model system to test the efficacy of palivizumab to prevent RSV infection. Palivizumab was administered in the basolateral compartment (circulation), while viral infection occurred in the apical ciliated cells (airways), simulating the events in infants. In our model, palivizumab effectively prevented RSV infection in a concentration-dependent manner. Thus, the HNO-ALI model can serve as an alternative to lung organoids to study respiratory viruses and test therapeutics. IMPORTANCE Preclinical models that recapitulate aspects of human airway disease are essential for the advancement of novel therapeutics and vaccines. Here, we report a versatile airway organoid model, the human nose organoid (HNO), that recapitulates the complex interactions between the host and virus. HNOs are obtained using noninvasive procedures and show divergent responses to SARS-CoV-2 and RSV infection. SARS-CoV-2 induces severe damage to cilia and the epithelium, no interferon-λ response, and minimal mucus secretion. In striking contrast, RSV induces hypersecretion of mucus and a profound interferon-λ response with ciliary damage. We also demonstrated the usefulness of our ex vivo HNO model of RSV infection to test the efficacy of palivizumab, an FDA-approved monoclonal antibody to prevent severe RSV disease in high-risk infants. Our study reports a breakthrough in both the development of a novel nose organoid model and in our understanding of the host cellular response to RSV and SARS-CoV-2 infection.

Development and validation of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts

Accessible in vitro models recapitulating the human airway that are amenable to study whole cannabis smoke exposure are needed for immunological and toxicological studies that inform public health policy and recreational cannabis use. In the present study, we developed and validated a novel three-dimensional (3D)-printed in vitro exposure system (IVES) that can be directly applied to study the effect of cannabis smoke exposure on primary human bronchial epithelial cells.

Using commercially available design software and a 3D printer, we designed a four-chamber Transwell insert holder for exposures to whole smoke. COMSOL Multiphysics software was used to model gas distribution, concentration gradients, velocity profile and shear stress within IVES. Following simulations, primary human bronchial epithelial cells cultured at the air–liquid interface on Transwell inserts were exposed to whole cannabis smoke using a modified version of the Foltin puff procedure. Following 24 h, outcome measurements included cell morphology, epithelial barrier function, lactate dehydrogenase (LDH) levels, cytokine expression and gene expression.

Whole smoke delivered through IVES possesses velocity profiles consistent with uniform gas distribution across the four chambers and complete mixing. Airflow velocity ranged between 1.0 and 1.5 µm·s⁻¹ and generated low shear stresses (<<1 Pa). Human airway epithelial cells exposed to cannabis smoke using IVES showed changes in cell morphology and disruption of barrier function without significant cytotoxicity. Cannabis smoke elevated interleukin-1 family cytokines and elevated CYP1A1 and CYP1B1 expression relative to control, validating IVES smoke exposure impacts in human airway epithelial cells at a molecular level.

The growing legalisation of cannabis on a global scale must be paired with research related to potential health impacts of lung exposures. IVES represents an accessible, open-source, exposure system that can be used to model varying types of cannabis smoke exposures with human airway epithelial cells grown under air–liquid interface culture conditions.

Development of an open-source, disposable, 3D-printed in vitro environmental exposure system for Transwell culture inserts that can be used for environmental exposures important for lung health, and validation with cannabis smoke exposurehttps://bit.ly/2JjgDrm

The MUC5B-associated variant rs35705950 resides within an enhancer subject to lineage- and disease-dependent epigenetic remodeling

The G/T transversion rs35705950, located approximately 3 kb upstream of the MUC5B start site, is the cardinal risk factor for idiopathic pulmonary fibrosis (IPF). Here, we investigate the function and chromatin structure of this –3 kb region and provide evidence that it functions as a classically defined enhancer subject to epigenetic programming. We use nascent transcript analysis to show that RNA polymerase II loads within 10 bp of the G/T transversion site, definitively establishing enhancer function for the region. By integrating Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq) analysis of fresh and cultured human airway epithelial cells with nuclease sensitivity data, we demonstrate that this region is in accessible chromatin that affects the expression of MUC5B. Through applying paired single-nucleus RNA- and ATAC-seq to frozen tissue from IPF lungs, we extend these findings directly to disease, with results indicating that epigenetic programming of the –3 kb enhancer in IPF occurs in both MUC5B-expressing and nonexpressing lineages. In aggregate, our results indicate that the MUC5B-associated variant rs35705950 resides within an enhancer that is subject to epigenetic remodeling and contributes to pathologic misexpression in IPF.

Optimizations of In Vitro Mucus and Cell Culture Models to Better Predict In Vivo Gene Transfer in Pathological Lung Respiratory Airways: Cystic Fibrosis as an Example

The respiratory epithelium can be affected by many diseases that could be treated using aerosol gene therapy. Among these, cystic fibrosis (CF) is a lethal inherited disease characterized by airways complications, which determine the life expectancy and the effectiveness of aerosolized treatments. Beside evaluations performed under in vivo settings, cell culture models mimicking in vivo pathophysiological conditions can provide complementary insights into the potential of gene transfer strategies. Such models must consider multiple parameters, following the rationale that proper gene transfer evaluations depend on whether they are performed under experimental conditions close to pathophysiological settings. In addition, the mucus layer, which covers the epithelial cells, constitutes a physical barrier for gene delivery, especially in diseases such as CF. Artificial mucus models featuring physical and biological properties similar to CF mucus allow determining the ability of gene transfer systems to effectively reach the underlying epithelium. In this review, we describe mucus and cellular models relevant for CF aerosol gene therapy, with a particular emphasis on mucus rheology. We strongly believe that combining multiple pathophysiological features in single complex cell culture models could help bridge the gaps between in vitro and in vivo settings, as well as viral and non-viral gene delivery strategies.

IL-33/ST2 signaling modulates Afghanistan particulate matter induced airway hyperresponsiveness in mice

Increased symptoms of asthma-like respiratory illnesses have been reported in soldiers returning from tours of duty in Afghanistan. Inhalation of desert particulate matter (PM) may contribute to this deployment-related lung disease (DRLD), but little is known about disease mechanisms. The IL-33 signaling pathway, including its receptor ST2, has been implicated in the pathogenesis of lung diseases including asthma, but its role in PM-mediated airway dysfunction has not been studied. The goal of this study was to investigate whether IL-33/ST2 signaling contributes to airway dysfunction in preclinical models of lung exposure to Afghanistan PM (APM). Wild-type (WT) and ST2 knockout (KO) mice on the BALB/C background were oropharyngeally instilled with a single dose of saline or 50 μg of APM in saline. Airway hyperresponsiveness (AHR) and inflammation were assessed after 24 h. In WT mice, a single APM exposure induced AHR and neutrophilic inflammation. Unlike the WT mice, ST2 KO mice that lack the receptor for IL-33 did not demonstrate AHR although airway neutrophilic inflammation was comparable to the WT mice. Oropharyngeal delivery of a soluble ST2 decoy receptor in APM-exposed WT mice significantly blocked AHR. Additional data in mouse tracheal epithelial cell and lung macrophage cultures demonstrated a role of APM-induced IL-33/ST2 signaling in suppression of regulator of G protein signaling 2 (RGS2), a gene known to protect against bronchoconstriction. We present for the first time that APM may increase AHR, one of the features of asthma, in part through the IL-33/ST2/RGS2 pathway.

Choice of Differentiation Media Significantly Impacts Cell Lineage and Response to CFTR Modulators in Fully Differentiated Primary Cultures of Cystic Fibrosis Human Airway Epithelial Cells

In vitro cultures of primary human airway epithelial cells (hAECs) grown at air–liquid interface have become a valuable tool to study airway biology under normal and pathologic conditions, and for drug discovery in lung diseases such as cystic fibrosis (CF). An increasing number of different differentiation media, are now available, making comparison of data between studies difficult. Here, we investigated the impact of two common differentiation media on phenotypic, transcriptomic, and physiological features of CF and non-CF epithelia. Cellular architecture and density were strongly impacted by the choice of medium. RNA-sequencing revealed a shift in airway cell lineage; one medium promoting differentiation into club and goblet cells whilst the other enriched the growth of ionocytes and multiciliated cells. Pathway analysis identified differential expression of genes involved in ion and fluid transport. Physiological assays (intracellular/extracellular pH, Ussing chamber) specifically showed that ATP12A and CFTR function were altered, impacting pH and transepithelial ion transport in CF hAECs. Importantly, the two media differentially affected functional responses to CFTR modulators. We argue that the effect of growth conditions should be appropriately determined depending on the scientific question and that our study can act as a guide for choosing the optimal growth medium for specific applications.

Protein profile of well-differentiated versus un-differentiated human bronchial/tracheal epithelial cells

Un-differentiated (UD) and well-differentiated (WD) normal human primary bronchial/tracheal epithelial cells are important respiratory cell models. Mature, WD cells which can be derived by culturing UD cells at an air-liquid interface represent a good surrogate for in vivo human airway epithelium. The overall protein profile of WD cells is poorly understood; therefore, the current study evaluated the proteomic characteristics of WD and UD cells using label-free LC-MS/MS and LC-PRM/MS. A total of 3,579 proteins were identified in WD and UD cells. Of these, 198 proteins were identified as differentially expressed, with 121 proteins upregulated and 77 proteins downregulated in WD cells compared with UD cells. Differentially expressed proteins were mostly enriched in categories related to epithelial structure formation, cell cycle, and immunity. Fifteen KEGG pathways and protein interaction networks were enriched and identified. The current study provides a global protein profile of WD cells, and contributes to understanding the function of human airway epithelium.

Airway epithelial cell differentiation relies on deficient Hedgehog signalling in COPD

BACKGROUND

Hedgehog (HH) pathway is constantly under scrutiny in the context of organ development. Lung morphogenesis requires HH signalling which participates thereafter to the pulmonary homeostasis by regulating epithelial cell quiescence and repair. Since epithelial remodelling is a hallmark of Chronic Obstructive Pulmonary Disease (COPD), we investigated whether the main molecular actors of HH pathway participate to airway epithelial cell differentiation and we analysed their alterations in COPD patients.

METHODS

Sonic HH (Shh) secretion was assessed by ELISA in airway epithelial cell (AEC) air-liquid interface culture supernatants. HH pathway activation was evaluated by RT-qPCR, western blot and immunostaining. Inhibition of HH signalling was achieved upon Shh chelation during epithelial cell differentiation. HH pathway core components localization was investigated in lung tissues from non-COPD and COPD patients.

FINDINGS

We demonstrate that progenitors of AEC produced Shh responsible for the activation of HH signalling during the process of differentiation. Preventing the ligand-induced HH activation led to the establishment of a remodelled epithelium with increased number of basal cells and reduced ciliogenesis. Gli2 activating transcription factor was demonstrated as a key-element in the regulation of AEC differentiation. More importantly, Gli2 and Smo were lost in AEC from COPD patients.

INTERPRETATION

Our data suggest that HH pathway is crucial for airway epithelial cell differentiation and highlight its role in COPD-associated epithelial remodelling.

The effect of BPIFA1/SPLUNC1 genetic variation on its expression and function in asthmatic airway epithelium

Bacterial permeability family member A1 (BPIFA1), also known as short palate, lung, and nasal epithelium clone 1 (SPLUNC1), is a protein involved in the antiinflammatory response. The goal of this study was to determine whether BPIFA1 expression in asthmatic airways is regulated by genetic variations, altering epithelial responses to type 2 cytokines (e.g., IL-13). Nasal epithelial cells from patients with mild to severe asthma were collected from the National Heart, Lung, and Blood Institute Severe Asthma Research Program centers, genotyped for rs750064, and measured for BPIFA1. To determine the function of rs750064, cells were cultured at air-liquid interface and treated with IL-13 with or without recombinant human BPIFA1 (rhBPIFA1). Noncultured nasal cells with the rs750064 CC genotype had significantly less BPIFA1 mRNA expression than the CT and TT genotypes. Cultured CC versus CT and TT cells without stimulation maintained less BPIFA1 expression. With IL-13 treatment, CC genotype cells secreted more eotaxin-3 than CT and TT genotype cells. Also, rhBPIFA1 reduced IL-13-mediated eotaxin-3. BPIFA1 mRNA levels negatively correlated with serum IgE and fractional exhaled nitric oxide. Baseline FEV1% levels were lower in the asthma patients with the CC genotype (n = 1,016). Our data suggest that less BPIFA1 in asthma patients with the CC allele may predispose them to greater eosinophilic inflammation, which could be attenuated by rhBPIFA1 protein therapy.