Epithelial to mesenchymal transition is increased in patients with COPD and induced by cigarette smoke
TL;DR: The EMT process is present in bronchial epithelial cells of the small bronchi of smokers and patients with COPD and is activated by cigarette smoke in vitro.
Abstract: Background Cigarette smoking contributes to lung remodelling in chronic obstructive pulmonary disease (COPD). As part of remodelling, peribronchiolar fibrosis is observed in the small airways of patients with COPD and contributes to airway obstruction. Epithelial to mesenchymal transition (EMT) appears to be involved in the formation of peribronchiolar fibrosis. This study examines the EMT process in human bronchial epithelial cells (HBECs) from non-smokers, smokers and patients with COPD as well as the in vitro effect of cigarette smoke extract (CSE) on EMT. Methods HBECs from non-smokers (n=5), smokers (n=12) and patients with COPD (n=15) were collected to measure the mesenchymal markers α-smooth muscle actin, vimentin and collagen type I and the epithelial markers E-cadherin, ZO-1 and cytokeratin 5 and 18 by real time-PCR and protein array. In vitro differentiated bronchial epithelial cells were stimulated with CSE. Results Mesenchymal markers were upregulated in HBECs of smokers and patients with COPD compared with non-smokers. In contrast, epithelial cell markers were downregulated. In vitro differentiated HBECs underwent EMT after 72 h of CSE exposure through the activation of intracellular reactive oxygen species, the release and autocrine action of transforming growth factor β 1 , the phosphorylation of ERK1/2 and Smad3 and by the downregulation of cyclic monophosphate. Conclusions The EMT process is present in bronchial epithelial cells of the small bronchi of smokers and patients with COPD and is activated by cigarette smoke in vitro.
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TL;DR: A brief insight is given into the mechanism and assessment methods of EMT in various pulmonary diseases and the recent literature highlighting the controversial experimental data and conclusions is summarized.
Abstract: Epithelial–mesenchymal transition (EMT) is a process when epithelial cells gradually transform into mesenchymal-like cells losing their epithelial functionality and characteristics. EMT is thought to be involved in the pathogenesis of numerous lung diseases ranging from developmental disorders, fibrotic tissue remodelling to lung cancer. The most important question—namely what is the importance and contribution of EMT in the pathogenesis of several chronic lung conditions (asthma, COPD, bronchiolitis obliterans syndrome and lung fibrosis)—is currently intensely debated. This review gives a brief insight into the mechanism and assessment methods of EMT in various pulmonary diseases and summarises the recent literature highlighting the controversial experimental data and conclusions.
230 citations
TL;DR: The hypothesis that rather than being a disease-dependent process, citrullination is an inflammatory-dependent condition that plays a central role in autoimmune diseases is supported.
197 citations
TL;DR: Recent advances in understanding the mechanisms of barrier dysfunction in COPD are discussed, as well as the molecular mechanisms that underlie the impaired repair response of the injured epithelium and its inability to redifferentiate into a functionally intact epithelia.
Abstract: The epithelial lining of the airway forms the first barrier against environmental insults, such as inhaled cigarette smoke, which is the primary risk factor for the development of chronic obstructive pulmonary disease (COPD). The barrier is formed by airway epithelial junctions, which are interconnected structures that restrict permeability to inhaled pathogens and environmental stressors. Destruction of the epithelial barrier not only exposes subepithelial layers to hazardous agents in the inspired air, but also alters the normal function of epithelial cells, which may eventually contribute to the development of COPD. Of note, disruption of epithelial junctions may lead to modulation of signaling pathways involved in differentiation, repair, and proinflammatory responses. Epithelial barrier dysfunction may be particularly relevant in COPD, where repeated injury by cigarette smoke exposure, pathogens, inflammatory mediators, and impaired epithelial regeneration may compromise the barrier function. In the current review, we discuss recent advances in understanding the mechanisms of barrier dysfunction in COPD, as well as the molecular mechanisms that underlie the impaired repair response of the injured epithelium in COPD and its inability to redifferentiate into a functionally intact epithelium.
189 citations
Cites background from "Epithelial to mesenchymal transitio..."
...The possible molecular mechanisms responsible for EMT are discussed subsequently here, but there are indications that cigarette smoke–induced oxidative stress can result in epithelial phenotype shift and EMT (34, 52)....
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...As PKA is a downstream effector of cAMP, these findings may help to explain why decreased cAMP levels lead to disrupted expression of E-cadherin (34)....
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...Moreover, Milara and colleagues (34) demonstrated that cigarette smoke extract reduces expression of E-cadherin and ZO-1 in vitro in primary epithelial cells from patients with COPD, but not control smokers, an effect that may be caused by reactive oxygen species (ROS)–dependent decrease in cAMP....
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...In addition to corticosteroids, Milara and colleagues (34, 149, 150) showed that treatment with cAMP-elevating compounds successfully restores airway epithelial barrier dysfunction induced by either cigarette smoke extract or TGF-b in vitro....
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...EMT may lead to increased production of collagen I and MMP-9 (34, 60), promoting thickening of the...
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TL;DR: The evidence of manifestation of EMT and its potential driving role in COPD, idiopathic pulmonary fibrosis, bronchiolitis obliterans syndrome, and lung cancer are discussed, while noting that all cells need not display a full EMT in any of these contexts.
Abstract: Epithelial-mesenchymal transition (EMT) plays key roles during lung development and many lung diseases such as chronic obstructive pulmonary disease (COPD), lung cancer, and pulmonary fibrosis. Here, integrating morphological observations with underlying molecular mechanisms, we highlight the functional role of EMT in lung development and injury repair, and discuss how it can contribute to pathogenesis of chronic lung disease. We discuss the evidence of manifestation of EMT and its potential driving role in COPD, idiopathic pulmonary fibrosis (IPF), bronchiolitis obliterans syndrome (BOS), and lung cancer, while noting that all cells need not display a full EMT in any of these contexts, i.e., often cells co-express epithelial and mesenchymal markers but do not fully convert to extracellular matrix (ECM) -producing fibroblasts. Finally, we discuss recent therapeutic attempts to restrict EMT in chronic lung disease. Developmental Dynamics 247:346-358, 2018. © 2017 Wiley Periodicals, Inc.
170 citations
Cites background from "Epithelial to mesenchymal transitio..."
...For example, RoflumilastTM (an inhibitor of phosphodiesterase-4 (PDE4) that elevates secondary signalling molecule cyclic adenosine monophosphate [cAMP]) has been shown to block cigarette smoke-induced EMT in bronchial epithelial cells (Milara et al., 2014)....
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TL;DR: This review paper explores the EMT process in a range of lung diseases, details the common links that these have to cystic fibrosis, and explores how understanding EMT in cystic Fibrosis may open up novel methods of treating patients with cysts fibrosis.
Abstract: Cystic Fibrosis (CF) is a genetic disorder that arises due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator gene, which encodes for a protein responsible for ion transport out of epithelial cells. This leads to a disruption in transepithelial Cl-, Na + and HCO3− ion transport and the subsequent dehydration of the airway epithelium, resulting in infection, inflammation and development of fibrotic tissue. Unlike in CF, fibrosis in other lung diseases including asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis has been well characterised. One of the driving forces behind fibrosis is Epithelial Mesenchymal Transition (EMT), a process where epithelial cells lose epithelial proteins including E-Cadherin, which is responsible for tight junctions. The cell moves to a more mesenchymal phenotype as it gains mesenchymal markers such as N-Cadherin (providing the cells with migration potential), Vimentin and Fibronectin (proteins excreted to help form the extracellular matrix), and the fibroblast proliferation transcription factors Snail, Slug and Twist. This review paper explores the EMT process in a range of lung diseases, details the common links that these have to cystic fibrosis, and explores how understanding EMT in cystic fibrosis may open up novel methods of treating patients with cystic fibrosis.
160 citations
References
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TL;DR: Progression of COPD is associated with the accumulation of inflammatory mucous exudates in the lumen and infiltration of the wall by innate and adaptive inflammatory immune cells that form lymphoid follicles, coupled to a repair or remodeling process that thickens the walls of these airways.
Abstract: Background Chronic obstructive pulmonary disease (COPD) is a major public health problem associated with long-term exposure to toxic gases and particles. We examined the evolution of the pathological effects of airway obstruction in patients with COPD. Methods The small airways were assessed in surgically resected lung tissue from 159 patients — 39 with stage 0 (at risk), 39 with stage 1, 22 with stage 2, 16 with stage 3, and 43 with stage 4 (very severe) COPD, according to the classification of the Global Initiative for Chronic Obstructive Lung Disease (GOLD). Results The progression of COPD was strongly associated with an increase in the volume of tissue in the wall (P<0.001) and the accumulation of inflammatory mucous exudates in the lumen (P<0.001) of the small airways. The percentage of the airways that contained polymorphonuclear neutrophils (P<0.001), macrophages (P<0.001), CD4 cells (P=0.02), CD8 cells (P=0.038), B cells (P<0.001), and lymphoid aggregates containing follicles (P=0.003) and the abs...
3,401 citations
TL;DR: The findings suggest that a substantial number of organ fibroblasts appear through a novel reversal in the direction of epithelial cell fate, which highlights the potential plasticity of differentiated cells in adult tissues under pathologic conditions.
Abstract: Interstitial fibroblasts are principal effector cells of organ fibrosis in kidneys, lungs, and liver While some view fibroblasts in adult tissues as nothing more than primitive mesenchymal cells surviving embryologic development, they differ from mesenchymal cells in their unique expression of fibroblast-specific protein-1 (FSP1) This difference raises questions about their origin Using bone marrow chimeras and transgenic reporter mice, we show here that interstitial kidney fibroblasts derive from two sources A small number of FSP1(+), CD34(-) fibroblasts migrate to normal interstitial spaces from bone marrow More surprisingly, however, FSP1(+) fibroblasts also arise in large numbers by local epithelial-mesenchymal transition (EMT) during renal fibrogenesis Both populations of fibroblasts express collagen type I and expand by cell division during tissue fibrosis Our findings suggest that a substantial number of organ fibroblasts appear through a novel reversal in the direction of epithelial cell fate As a general mechanism, this change in fate highlights the potential plasticity of differentiated cells in adult tissues under pathologic conditions
1,929 citations
TL;DR: Alveolar epithelial cells are revealed as progenitors for fibroblasts in vivo and implicate the provisional extracellular matrix as a key regulator of epithelial transdifferentiation during fibrogenesis.
Abstract: Mechanisms leading to fibroblast accumulation during pulmonary fibrogenesis remain unclear. Although there is in vitro evidence of lung alveolar epithelial-to-mesenchymal transition (EMT), whether EMT occurs within the lung is currently unknown. Biopsies from fibrotic human lungs demonstrate epithelial cells with mesenchymal features, suggesting EMT. To more definitively test the capacity of alveolar epithelial cells for EMT, mice expressing β-galactosidase (β-gal) exclusively in lung epithelial cells were generated, and their fates were followed in an established model of pulmonary fibrosis, overexpression of active TGF-β1. β-gal-positive cells expressing mesenchymal markers accumulated within 3 weeks of in vivo TGF-β1 expression. The increase in vimentin-positive cells within injured lungs was nearly all β-gal-positive, indicating epithelial cells as the main source of mesenchymal expansion in this model. Ex vivo, primary alveolar epithelial cells cultured on provisional matrix components, fibronectin or fibrin, undergo robust EMT via integrin-dependent activation of endogenous latent TGF-β1. In contrast, primary cells cultured on laminin/collagen mixtures do not activate the TGF-β1 pathway and, if exposed to active TGF-β1, undergo apoptosis rather than EMT. These data reveal alveolar epithelial cells as progenitors for fibroblasts in vivo and implicate the provisional extracellular matrix as a key regulator of epithelial transdifferentiation during fibrogenesis.
1,196 citations
TL;DR: Experiments in which the in vitro overexpression of FSP1 cDNA in tubular epithelium is accompanied by conversion to a mesenchymal phenotype are observed, as characterized by a more stellate and elongated fibroblast- like appearance, a reduction in cytokeratin, and new expression of vimentin.
Abstract: We performed subtractive and differential hybridization for transcript comparison between murine fibroblasts and isogenic epithelium, and observed only a few novel intracellular genes which were relatively specific for fibroblasts. One such gene encodes a filament-associated, calcium-binding protein, fibroblast-specific protein 1 (FSP1). The promoter/enhancer region driving this gene is active in fibroblasts but not in epithelium, mesangial cells or embryonic endoderm. During development, FSP1 is first detected by in situ hybridization after day 8.5 as a postgastrulation event, and is associated with cells of mesenchymal origin or of fibroblastic phenotype. Polyclonal antiserum raised to recombinant FSP1 protein stained the cytoplasm of fibroblasts, but not epithelium. Only occasional cells stain with specific anti-FSP1 antibodies in normal parenchymal tissue. However, in kidneys fibrosing from persistent inflammation, many fibroblasts could be identified in interstitial sites of collagen deposition and also in tubular epithelium adjacent to the inflammatory process. This pattern of anti-FSP1 staining during tissue fibrosis suggests, as a hypothesis, that fibroblasts in some cases arise, as needed, from the local conversion of epithelium. Consistent with this notion that FSP1 may be involved in the transition from epithelium to fibroblasts are experiments in which the in vitro overexpression of FSP1 cDNA in tubular epithelium is accompanied by conversion to a mesenchymal phenotype, as characterized by a more stellate and elongated fibroblast-like appearance, a reduction in cytokeratin, and new expression of vimentin. Similarly, tubular epithelium submerged in type I collagen gels exhibited the conversion to a fibroblast phenotype which includes de novo expression of FSP1 and vimentin. Use of the FSP1 marker, therefore, should further facilitate both the in vivo studies of fibrogenesis and the mapping of cell fate among fibroblasts.
1,035 citations
TL;DR: It is hoped that this review will stimulate further consideration of the cellular mechanisms of fibrogenesis in the lung and especially the role of the epithelium in this process, potentially leading to innovative avenues of investigation and treatment.
Abstract: Epithelial-mesenchymal transition (EMT), a process whereby fully differentiated epithelial cells undergo transition to a mesenchymal phenotype giving rise to fibroblasts and myofibroblasts, is increasingly recognized as playing an important role in repair and scar formation following epithelial injury. The extent to which this process contributes to fibrosis following injury in the lung is a subject of active investigation. Recently, it was demonstrated that transforming growth factor (TGF)-β induces EMT in alveolar epithelial cells (AEC) in vitro and in vivo, and epithelial and mesenchymal markers have been colocalized to hyperplastic type II (AT2) cells in lung tissue from patients with idiopathic pulmonary fibrosis (IPF), suggesting that AEC may exhibit extreme plasticity and serve as a source of fibroblasts and/or myofibroblasts in lung fibrosis. In this review, we describe the characteristic features of EMT and its mechanistic underpinnings. We further describe the contribution of EMT to fibrosis in adult tissues following injury, focusing especially on the critical role of TGF-β and its downstream mediators in this process. Finally, we highlight recent descriptions of EMT in the lung and the potential implications of this process for the treatment of fibrotic lung disease. Treatment for fibrosis of the lung in diseases such as IPF has heretofore focused largely on amelioration of potential inciting processes such as inflammation. It is hoped that this review will stimulate further consideration of the cellular mechanisms of fibrogenesis in the lung and especially the role of the epithelium in this process, potentially leading to innovative avenues of investigation and treatment.
906 citations