Epithelial plasticity in COPD results in cellular unjamming due to an increase in polymerized actin

Epigenetic Reprogramming Drives Epithelial Disruption in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) remains a major public health challenge that contributes greatly to mortality and morbidity worldwide. Although it has long been recognized that the epithelium is altered in COPD, there has been little focus on targeting it to modify the disease course. Therefore, mechanisms that disrupt epithelial cell function in patients with COPD are poorly understood. In this study, we sought to determine whether epigenetic reprogramming of the cell-cell adhesion molecule E-cadherin, encoded by the CDH1 gene, disrupts epithelial integrity. By reducing these epigenetic marks, we can restore epithelial integrity and rescue alveolar airspace destruction. We used differentiated normal and COPD-derived primary human airway epithelial cells, genetically manipulated mouse tracheal epithelial cells, and mouse and human precision-cut lung slices to assess the effects of epigenetic reprogramming. We show that the loss of CDH1 in COPD is due to increased DNA methylation site at the CDH1 enhancer D through the downregulation of the ten-eleven translocase methylcytosine dioxygenase (TET) enzyme TET1. Increased DNA methylation at the enhancer D region decreases the enrichment of RNA polymerase II binding. Remarkably, treatment of human precision-cut slices derived from patients with COPD with the DNA demethylation agent 5-aza-2'-deoxycytidine decreased cell damage and reduced air space enlargement in the diseased tissue. Here, we present a novel mechanism that targets epigenetic modifications to reverse the tissue remodeling in human COPD lungs and serves as a proof of concept for developing a disease-modifying target.

Assessment of wood smoke induced pulmonary toxicity in normal- and chronic bronchitis-like bronchial and alveolar lung mucosa models at air-liquid interface

BACKGROUND

Chronic obstructive pulmonary disease (COPD) has the highest increased risk due to household air pollution arising from biomass fuel burning. However, knowledge on COPD patho-mechanisms is mainly limited to tobacco smoke exposure. In this study, a repeated direct wood smoke (WS) exposure was performed using normal- (bro-ALI) and chronic bronchitis-like bronchial (bro-ALI-CB), and alveolar (alv-ALI) lung mucosa models at air-liquid interface (ALI) to assess broad toxicological end points.

METHODS

The bro-ALI and bro-ALI-CB models were developed using human primary bronchial epithelial cells and the alv-ALI model was developed using a representative type-II pneumocyte cell line. The lung models were exposed to WS (10 min/exposure; 5-exposures over 3-days; n = 6-7 independent experiments). Sham exposed samples served as control. WS composition was analyzed following passive sampling. Cytotoxicity, total cellular reactive oxygen species (ROS) and stress responsive NFkB were assessed by flow cytometry. WS exposure induced changes in gene expression were evaluated by RNA-seq (p ≤ 0.01) followed by pathway enrichment analysis. Secreted levels of proinflammatory cytokines were assessed in the basal media. Non-parametric statistical analysis was performed.

RESULTS

147 unique compounds were annotated in WS of which 42 compounds have inhalation toxicity (9 very high). WS exposure resulted in significantly increased ROS in bro-ALI (11.2%) and bro-ALI-CB (25.7%) along with correspondingly increased NFkB levels (bro-ALI: 35.6%; bro-ALI-CB: 18.1%). A total of 1262 (817-up and 445-down), 329 (141-up and 188-down), and 102 (33-up and 69-down) genes were differentially regulated in the WS-exposed bro-ALI, bro-ALI-CB, and alv-ALI models respectively. The enriched pathways included the terms acute phase response, mitochondrial dysfunction, inflammation, oxidative stress, NFkB, ROS, xenobiotic metabolism of AHR, and chronic respiratory disorder. The enrichment of the 'cilium' related genes was predominant in the WS-exposed bro-ALI (180-up and 7-down). The pathways primary ciliary dyskinesia, ciliopathy, and ciliary movement were enriched in both WS-exposed bro-ALI and bro-ALI-CB. Interleukin-6 and tumor necrosis factor-α were reduced (p < 0.05) in WS-exposed bro-ALI and bro-ALI-CB.

CONCLUSION

Findings of this study indicate differential response to WS-exposure in different lung regions and in chronic bronchitis, a condition commonly associated with COPD. Further, the data suggests ciliopathy as a candidate pathway in relation to WS-exposure.

Modelling bronchial epithelial-fibroblast cross-talk in idiopathic pulmonary fibrosis (IPF) using a human-derived in vitro air liquid interface (ALI) culture

Idiopathic Pulmonary Fibrosis (IPF) is a devastating form of respiratory disease with a life expectancy of 3-4 years. Inflammation, epithelial injury and myofibroblast proliferation have been implicated in disease initiation and, recently, epithelial-fibroblastic crosstalk has been identified as a central driver. However, the ability to interrogate this crosstalk is limited due to the absence of in vitro models that mimic physiological conditions. To investigate IPF dysregulated cross-talk, primary normal human bronchial epithelial (NHBE) cells and primary normal human lung fibroblasts (NHLF) or diseased human lung fibroblasts (DHLF) from IPF patients, were co-cultured in direct contact at the air-liquid interface (ALI). Intercellular crosstalk was assessed by comparing cellular phenotypes of co-cultures to respective monocultures, through optical, biomolecular and electrical methods. A co-culture-dependent decrease in epithelium thickness, basal cell mRNA (P63, KRT5) and an increase in transepithelial electrical resistance (TEER) was observed. This effect was significantly enhanced in DHLF co-cultures and lead to the induction of epithelial to mesenchymal transition (EMT) and increased mRNA expression of TGFβ-2, ZO-1 and DN12. When stimulated with exogenous TGFβ, NHBE and NHLF monocultures showed a significant upregulation of EMT (COL1A1, FN1, VIM, ASMA) and senescence (P21) markers, respectively. In contrast, direct NHLF/NHBE co-culture indicated a protective role of epithelial-fibroblastic cross-talk against TGFβ-induced EMT, fibroblast-to-myofibroblast transition (FMT) and inflammatory cytokine release (IL-6, IL-8, IL-13, IL-1β, TNF-α). DHLF co-cultures showed no significant phenotypic transition upon stimulation, likely due to the constitutively high expression of TGFβ isoforms prior to any exogenous stimulation. The model developed provides an alternative method to generate IPF-related bronchial epithelial phenotypes in vitro, through the direct co-culture of human lung fibroblasts with NHBEs. These findings highlight the importance of fibroblast TGFβ signaling in EMT but that monocultures give rise to differential responses compared to co-cultures, when exposed to this pro-inflammatory stimulus. This holds implications for any translation conclusions drawn from monoculture studies and is an important step in development of more biomimetic models of IPF. In summary, we believe this in vitro system to study fibroblast-epithelial crosstalk, within the context of IPF, provides a platform which will aid in the identification and validation of novel targets.

Decreased fucosylation impacts epithelial integrity and increases risk for COPD

COPD causes significant morbidity and mortality worldwide. Epithelial damage is fundamental to disease pathogenesis, although the mechanisms driving disease remain undefined. Published evidence from a COPD cohort (SPIROMICS) and confirmed in a second cohort (COPDgene) demonstrate a polymorphism in Fucosyltransferese-2 (FUT2) is a trans-pQTL for E-cadherin, which is critical in COPD pathogenesis. We found by MALDI-TOF analysis that FUT2 increased terminal fucosylation of E-cadherin. Using atomic force microscopy, we found that FUT2-dependent fucosylation enhanced E-cadherin-E-cadherin bond strength, mediating the improvement in monolayer integrity. Tracheal epithelial cells from Fut2-/- mice have reduced epithelial integrity, which is recovered with reconstitution of Fut2. Overexpression of FUT2 in COPD derived epithelia rescues barrier function. Fut2-/- mice show increased susceptibility in an elastase model of disease developing both emphysema and fibrosis. We propose this is due to the role of FUT2 in proliferation and cell differentiation. Overexpression of FUT2 significantly increased proliferation. Loss of Fut2 results in accumulation of Spc+ cells suggesting a failure of alveolar type 2 cells to undergo transdifferentiation to alveolar type 1. Using a combination of population data, genetically manipulated mouse models, and patient-derived cells, we present a novel mechanism by which post-translational modifications modulate tissue pathology and serve as a proof of concept for the development of a disease-modifying target in COPD.

Microphysiological Models of Lung Epithelium-Alveolar Macrophage Co-Cultures to Study Chronic Lung Disease

The interactions between immune cells and epithelial cells influence the progression of many respiratory diseases, such as chronic obstructive pulmonary disease (COPD). In vitro models allow for the examination of cells in controlled environments. However, these models lack the complex 3D architecture and vast multicellular interactions between the lung resident cells and infiltrating immune cells that can mediate cellular response to insults. In this study, three complementary microphysiological systems are presented to delineate the effects of cigarette smoke and respiratory disease on the lung epithelium. First, the Transwell system allows the co-culture of pulmonary immune and epithelial cells to evaluate cellular and monolayer phenotypic changes in response to cigarette smoke exposure. Next, the human and mouse precision-cut lung slices system provides a physiologically relevant model to study the effects of chronic insults like cigarette smoke with the dissection of specific interaction of immune cell subtypes within the structurally complex tissue environment. Finally, the lung-on-a-chip model provides an adaptable system for live imaging of polarized epithelial tissues that mimic the in vivo environment of the airways. Using a combination of these models, a complementary approach is provided to better address the intricate mechanisms of lung disease.

Cigarette smoke-induced injury induces distinct sex-specific transcriptional signatures in mice tracheal epithelial cells

The airway epithelial barrier is crucial for defending against respiratory insults and diseases. Disruption of epithelial integrity contributes to respiratory diseases, and sex-specific differences in susceptibility and severity have been observed. However, sex-specific differences in the context of respiratory diseases are often overlooked, especially in murine models. In this study, we investigated the in vitro transcriptomics of male and female murine tracheal epithelial cells (mTECs) in response to chronic cigarette smoke (CS) exposure using an International Organization for Standardization (ISO) puff regimen. Our findings reveal sex-specific differences in the baseline characteristics of airway epithelial cells. Female mTECs demonstrated stronger barrier function and higher ciliary function compared with males. The barrier function was disrupted in both males and females following chronic CS, but the difference was more significant in females due to their higher baseline. Female mice exhibited transcriptional signatures suggesting dedifferentiation with increased basal cells and markers of cellular senescence. Pathway analysis indicated potential protective roles of planar cell polarity (PCP) in preventing dedifferentiation in male mice exposed to CS. We also observed sex-specific differences in the DNA damage response and antioxidant levels, suggesting distinct mechanisms underlying cellular stress. Understanding these sex-specific mechanisms could facilitate the development of targeted therapeutic strategies for lung diseases associated with environmental insults. Recognizing sex-based differences in disease susceptibility and treatment response can lead to personalized care and improved outcomes. Clinical trials should consider sex as a biological variable to develop effective interventions that address the unique differences between men and women in respiratory diseases.NEW & NOTEWORTHY The study underscores the importance of considering sex-specific differences in the airway epithelium in respiratory diseases such as COPD. Differences in gene expression between males and females at baseline and in response to chronic injury in the airway epithelium could have implications on disease susceptibility, both in COPD and other respiratory diseases. Therefore, understanding these differences is crucial for developing targeted therapies to treat respiratory diseases based on a sex-specific manner.

Human Leukocyte Antigen Genotyping of Idiopathic Subglottic Stenosis

OBJECTIVE

Despite recent scientific inquiry, idiopathic subglottic stenosis (iSGS) remains an enigmatic disease. The consistent demographics of the affected population suggest genetic factors may contribute to disease susceptibility. Given the inflammation observed in the affected proximal airway mucosa, we interrogated disease association with human leukocyte antigen (HLA) polymorphisms. Polymorphisms in the HLA locus have previously been shown to influence individuals' susceptibility to distinct inflammatory diseases.

METHODS

High-resolution HLA typing of 37 iSGS patients was compared with 1,242,890 healthy Caucasian controls of European ancestry from the USA National Marrow Donor Program and 281 patients with granulomatosis with polyangiitis (GPA).

RESULTS

Complete HLA genotyping of an iSGS population showed no significant associations when compared to a North American Caucasian control population. Unlike GPA patients, iSGS was not associated with allele DPB1*04:01 nor did allele homozygosity correlate with disease severity.

CONCLUSIONS

There was not a detectable HLA association observed in iSGS. These results support the concept that iSGS possesses a distinct genetic architecture from GPA. If genetic susceptibility exists in iSGS, it likely lies outside the HLA locus.

LEVEL OF EVIDENCE

NA, basic science Laryngoscope, 133:2533-2539, 2023.

SARS-CoV-2 infection alters mitochondrial and cytoskeletal function in human respiratory epithelial cells mediated by expression of spike protein

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, SCV2), which has resulted in higher morbidity and mortality rate than other respiratory viral infections, such as Influenza A virus (IAV) infection. Investigating the molecular mechanisms of SCV2-host infection vs IAV is vital in exploring antiviral drug targets against SCV2. We assessed differential gene expression in human nasal cells upon SCV2 or IAV infection using RNA sequencing. Compared to IAV, we observed alterations in both metabolic and cytoskeletal pathways suggestive of epithelial remodeling in the SCV2-infected cells, reminiscent of pathways activated as a response to chronic injury. We found that spike protein interaction with the epithelium was sufficient to instigate these epithelial responses using a SCV2 spike pseudovirus. Specifically, we found downregulation of the mitochondrial markers SIRT3 and TOMM22. Moreover, SCV2 spike infection increased extracellular acidification and decreased oxygen consumption rate in the epithelium. In addition, we observed cytoskeletal rearrangements with a reduction in the actin-severing protein cofilin-1 and an increase in polymerized actin, indicating epithelial cytoskeletal rearrangements. This study revealed distinct epithelial responses to SCV2 infection, with early mitochondrial dysfunction in the host cells and evidence of cytoskeletal remodeling that could contribute to the worsened outcome in COVID-19 patients compared to IAV patients. These changes in cell structure and energetics could contribute to cellular resilience early during infection, allowing for prolonged cell survival and potentially paving the way for more chronic symptoms. IMPORTANCE COVID-19 has caused a global pandemic affecting millions of people worldwide, resulting in a higher mortality rate and concerns of more persistent symptoms compared to influenza A. To study this, we compare lung epithelial responses to both viruses. Interestingly, we found that in response to SARS-CoV-2 infection, the cellular energetics changed and there were cell structural rearrangements. These changes in cell structure could lead to prolonged epithelial cell survival, even in the face of not working well, potentially contributing to the development of chronic symptoms. In summary, these findings represent strategies utilized by the cell to survive the infection but result in a fundamental shift in the epithelial phenotype, with potential long-term consequences, which could set the stage for the development of chronic lung disease or long COVID-19.

Human Airway Basal Cells Undergo Reversible Squamous Differentiation and Reshape Innate Immunity

Histological and lineage immunofluorescence examination revealed that healthy conducting airways of humans and animals harbor sporadic poorly differentiated epithelial patches mostly in the dorsal noncartilage regions that remarkably manifest squamous differentiation. In vitro analysis demonstrated that this squamous phenotype is not due to intrinsic functional change in underlying airway basal cells. Rather, it is a reversible physiological response to persistent Wnt signaling stimulation during de novo differentiation. Squamous epithelial cells have elevated gene signatures of glucose uptake and cellular glycolysis. Inhibition of glycolysis or a decrease in glucose availability suppresses Wnt-induced squamous epithelial differentiation. Compared with pseudostratified airway epithelial cells, a cascade of mucosal protective functions is impaired in squamous epithelial cells, featuring increased epithelial permeability, spontaneous epithelial unjamming, and enhanced inflammatory responses. Our study raises the possibility that the squamous differentiation naturally occurring in healthy airways identified herein may represent "vulnerable spots" within the airway mucosa that are sensitive to damage and inflammation when confronted by infection or injury. Squamous metaplasia and hyperplasia are hallmarks of many airway diseases, thereby expanding these areas of vulnerability with potential pathological consequences. Thus, investigation of physiological and reversible squamous differentiation from healthy airway basal cells may provide critical knowledge to understand pathogenic squamous remodeling, which is often nonreversible, progressive, and hyperinflammatory.

First person – Baishakhi Ghosh and Kristine Nishida

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Baishakhi Ghosh and Kristine Nishida are co-first authors on ‘ Epithelial plasticity in COPD results in cellular unjamming due to an increase in polymerized actin’, published in JCS. Baishakhi is a post-doctoral fellow in the lab of Venkataramana K. Sidhaye at Johns Hopkins Bloomberg School of Public Health, Maryland, USA, evaluating the mechanisms by which inhaled pollutants can cause chronic injury to model chronic lung diseases. Kristine is a Research Associate in the FastForward Facility at Maryland, where she is interested in increasing the accessibility of cell and gene therapies to patients.