Epithelial-mesenchymal Trophic Unit Research Articles

Teatime: epigallocatechin gallate targets fibroblast-epithelial cell crosstalk to combat lung fibrosis.

Epigallocatechin gallate (EGCG) is a polyphenol plant metabolite abundant in tea that has demonstrated antifibrotic properties in the lung. In this issue of the JCI, Cohen, Brumwell, and colleagues interrogated the mechanistic action of EGCG by investigating lung biopsies of patients with mild interstitial lung disease (ILD) who had undergone EGCG treatment. EGCG targeted the WNT inhibitor SFRP2, which was enriched in fibrotic fibroblasts and acted as a TGF-β target, with paracrine effects leading to pathologic basal metaplasia of alveolar epithelial type 2 cells. This study emphasizes the epithelial-mesenchymal trophic unit as a central signaling hub in lung fibrosis. Understanding and simultaneous targeting of interlinked signaling pathways, such as TGF-β and WNT, paves the road for future treatment options for pulmonary fibrosis.

Airway epithelial overexpressed cathepsin K induces airway remodelling through epithelial-mesenchymal trophic unit activation in asthma.

Airway epithelial cells (AECs) regulate the activation of epithelial-mesenchymal trophic units (EMTUs) during airway remodelling through secretion of signalling mediators. However, the major trigger and the intrinsic pathogenesis of airway remodelling is still obscure. The differing expressed genes in airway epithelia related to airway remodelling were screened and verified by RNA-sequencing and signalling pathway analysis. Then, the effects of increased cathepsin K (CTSK) in airway epithelia on airway remodelling and EMTU activation were identified both in vitro and in vivo, and the molecular mechanism was elucidated in the EMTU model. The potential of CTSK as an an effective biomarker of airway remodelling was analysed in an asthma cohort of differing severity. Finally, an inhibitor of CTSK was administered for potential therapeutic intervention for airway remodelling in asthma. The expression of CTSK in airway epithelia increased significantly along with the development of airway remodelling in a house dust mite (HDM)-stressed asthma model. Increased secretion of CTSK from airway epithelia induced the activation of EMTUs by activation of the PAR2-mediated pathway. Blockade of CTSK inhibited EMTU activation and alleviated airway remodelling as an effective intervention target of airway remodelling. Increased expression of CTSK in airway epithelia is involved in the development of airway remodelling in asthma through EMTU activation, mediated partly through the PAR2-mediated signalling pathway. CTSK is a potential biomarker for airway remodelling, and may also be a useful intervention target for airway remodelling in asthma patients.

The Role of Proprotein Convertases in Upper Airway Remodeling.

Chronic rhinosinusitis (CRS) is a multifactorial, heterogeneous disease characterized by persistent inflammation of the sinonasal mucosa and tissue remodeling, which can include basal/progenitor cell hyperplasia, goblet cell hyperplasia, squamous cell metaplasia, loss or dysfunction of ciliated cells, and increased matrix deposition. Repeated injuries can stimulate airway epithelial cells to produce inflammatory mediators that activate epithelial cells, immune cells, or the epithelial–mesenchymal trophic unit. This persistent inflammation can consequently induce aberrant tissue remodeling. However, the molecular mechanisms driving disease within the different molecular CRS subtypes remain inadequately characterized. Numerous secreted and cell surface proteins relevant to airway inflammation and remodeling are initially synthesized as inactive precursor proteins, including growth/differentiation factors and their associated receptors, enzymes, adhesion molecules, neuropeptides, and peptide hormones. Therefore, these precursor proteins require post-translational cleavage by proprotein convertases (PCs) to become fully functional. In this review, we summarize the roles of PCs in CRS-associated tissue remodeling and discuss the therapeutic potential of targeting PCs for CRS treatment.

Extracellular Vesicles in Airway Homeostasis and Pathophysiology

The epithelial–mesenchymal trophic unit (EMTU) is a morphofunctional entity involved in the maintenance of the homeostasis of airways as well as in the pathogenesis of several diseases, including asthma and chronic obstructive pulmonary disease (COPD). The “muco-microbiotic layer” (MML) is the innermost layer of airways made by microbiota elements (bacteria, viruses, archaea and fungi) and the surrounding mucous matrix. The MML homeostasis is also crucial for maintaining the healthy status of organs and its alteration is at the basis of airway disorders. Nanovesicles produced by EMTU and MML elements are probably the most important tool of communication among the different cell types, including inflammatory ones. How nanovesicles produced by EMTU and MML may affect the airway integrity, leading to the onset of asthma and COPD, as well as their putative use in therapy will be discussed here.

Responsiveness of human bronchial fibroblasts and epithelial cells from asthmatic and non-asthmatic donors to the transforming growth factor-\u03b21 in epithelial-mesenchymal trophic unit model

BackgroundThe asthma-related airway wall remodeling is associated i.a. with a damage of bronchial epithelium and subepithelial fibrosis. Functional interactions between human bronchial epithelial cells and human bronchial fibroblasts are known as the epithelial-mesenchymal trophic unit (EMTU) and are necessary for a proper functioning of lung tissue. However, a high concentration of the transforming growth factor-β1 (TGF-β1) in the asthmatic bronchi drives the structural disintegrity of epithelium with the epithelial-to-mesenchymal transition (EMT) of the bronchial epithelial cells, and of subepithelial fibrosis with the fibroblast-to-myofibroblast transition (FMT) of the bronchial fibroblasts. Since previous reports indicate different intrinsic properties of the human bronchial epithelial cells and human bronchial fibroblasts which affect their EMT/FMT potential beetween cells derived from asthmatic and non-asthmatic patients, cultured separatelly in vitro, we were interested to see whether corresponding effects could be obtained in a co-culture of the bronchial epithelial cells and bronchial fibroblasts. In this study, we investigate the effects of the TGF-β1 on the EMT markers of the bronchial epithelial cells cultured in the air-liquid-interface and effectiveness of FMT in the bronchial fibroblast populations in the EMTU models.ResultsOur results show that the asthmatic co-cultures are more sensitive to the TGF-β1 than the non-asthmatic ones, which is associated with a higher potential of the asthmatic bronchial cells for a profibrotic response, analogously to be observed in '2D' cultures. They also indicate a noticeable impact of human bronchial epithelial cells on the TGF-β1-induced FMT, stronger in the asthmatic bronchial fibroblast populations in comparison to the non-asthmatic ones. Moreover, our results suggest the protective effects of fibroblasts on the structure of the TGF-β1–exposed mucociliary differentiated bronchial epithelial cells and their EMT potential.ConclusionsOur data are the first to demonstrate a protective effect of the human bronchial fibroblasts on the properties of the human bronchial epithelial cells, which suggests that intrinsic properties of not only epithelium but also subepithelial fibroblasts affect a proper condition and function of the EMTU in both normal and asthmatic individuals.

What Have In Vitro Co-Culture Models Taught Us about the Contribution of Epithelial-Mesenchymal Interactions to Airway Inflammation and Remodeling in Asthma?

As the lung develops, epithelial-mesenchymal crosstalk is essential for the developmental processes that drive cell proliferation, differentiation, and extracellular matrix (ECM) production within the lung epithelial-mesenchymal trophic unit (EMTU). In asthma, a number of the lung EMTU developmental signals have been associated with airway inflammation and remodeling, which has led to the hypothesis that aberrant activation of the asthmatic EMTU may lead to disease pathogenesis. Monoculture studies have aided in the understanding of the altered phenotype of airway epithelial and mesenchymal cells and their contribution to the pathogenesis of asthma. However, 3-dimensional (3D) co-culture models are needed to enable the study of epithelial-mesenchymal crosstalk in the setting of the in vivo environment. In this review, we summarize studies using 3D co-culture models to assess how defective epithelial-mesenchymal communication contributes to chronic airway inflammation and remodeling within the asthmatic EMTU.

Epithelial-mesenchymal crosstalk in COPD: An update from in vitro model studies.

Chronic Obstructive Pulmonary disease (COPD) involves airway inflammation and remodeling leading to small airways disease and emphysema, which results in irreversible airflow obstruction. During lung development, reciprocal interactions between the endoderm and mesoderm (epithelial-mesenchymal trophic unit (EMTU)) are essential for morphogenetic cues that direct cell proliferation, differentiation, and extracellular (ECM) production. In COPD, a significant number of the inflammation and remodeling mediators resemble those released during lung development, which has led to the hypothesis that aberrant activation of the EMTU may occur in the disease. Studies assessing lung epithelial and fibroblast function in COPD, have been primarily focused on monoculture studies. To capture the in vivo environment of the human lung and aid in the understanding of mechanisms and mediators involved in abnormal epithelial-fibroblast communication in COPD, complex co-culture models are required. In this review, we describe the studies that have used co-culture models to assess epithelial-fibroblast interactions and their role in the pathogenesis of COPD.

MiR-146a-5p plays an essential role in the aberrant epithelial-fibroblast cross-talk in COPD.

We previously reported that epithelial-derived interleukin (IL)-1α drives fibroblast-derived inflammation in the lung epithelial-mesenchymal trophic unit. Since miR-146a-5p has been shown tonegatively regulate IL-1 signalling, we investigated the role of miR-146a-5p in the regulation of IL-1α-driven inflammation in chronic obstructive pulmonary disease (COPD).Human bronchial epithelial (16HBE14o-) cells were co-cultured with control and COPD-derived primary human lung fibroblasts (PHLFs), and miR-146a-5p expression was assessed with and without IL-1α neutralising antibody. Genomic DNA was assessed for the presence of the single nucleotide polymorphism (SNP) rs2910164. miR-146a-5p mimics were used for overexpression studies to assess IL-1α-induced signalling and IL-8 production by PHLFs.Co-culture of PHLFs with airway epithelial cells significantly increased the expression of miR-146a-5p and this induction was dependent on epithelial-derived IL-1α. miR-146a-5p overexpression decreased IL-1α-induced IL-8 secretion in PHLFs via downregulation of IL-1 receptor-associated kinase-1. In COPD PHLFs, the induction of miR-146a-5p was significantly less compared with controls and was associated with the SNP rs2910164 (GG allele) in the miR-146a-5p gene.Our results suggest that induction of miR-146a-5p is involved in epithelial-fibroblast communication in the lungs and negatively regulates epithelial-derived IL-1α induction of IL-8 by fibroblasts. The decreased levels of miR-146a-5p in COPD fibroblasts may induce a more pro-inflammatory phenotype, contributing to chronic inflammation in COPD.

NF-κB Mediates Mesenchymal Transition, Remodeling, and Pulmonary Fibrosis in Response to Chronic Inflammation by Viral RNA Patterns.

Airway remodeling is resultant of a complex multicellular response associated with a progressive decline of pulmonary function in patients with chronic airway disease. Here, repeated infections with respiratory viruses are linked with airway remodeling through largely unknown mechanisms. Although acute activation of the Toll-like receptor (TLR) 3 pathway by extracellular polyinosinic:polycytidylic acid (poly[I:C]) induces innate signaling through the NF-κB transcription factor in normal human small airway epithelial cells, prolonged (repetitive or tonic) poly(I:C) stimulation produces chronic stress fiber formation, mesenchymal transition, and activation of a fibrotic program. Chronic poly(I:C) stimulation enhanced the expression of core mesenchymal regulators Snail family zinc finger 1, zinc finger E-box binding homeobox, mesenchymal intermediate filaments (vimentin), and extracellular matrix proteins (fibronectin-1), and collagen 1A. This mesenchymal transition was prevented by silencing expression of NF-κB/RelA or administration of a small-molecule inhibitor of the IκB kinase, BMS345541. Acute poly(I:C) exposure in vivo induced profound neutrophilic airway inflammation. When administered repetitively, poly(I:C) resulted in enhanced fibrosis observed by lung micro-computed tomography, second harmonic generation microscopy of optically cleared lung tissue, and by immunohistochemistry. Epithelial flattening, expansion of the epithelial mesenchymal trophic unit, and enhanced Snail family zinc finger 1 and fibronectin 1 expression in airway epithelium were also observed. Repetitive poly(I:C)-induced airway remodeling, fibrosis, and epithelial-mesenchymal transition was inhibited by BMS345541 administration. Based on this novel model of viral inflammation-induced remodeling, we conclude that NF-κB is a major controller of epithelial-mesenchymal transition and pulmonary fibrosis, a finding that has potentially important relevance to airway remodeling produced by repetitive viral infections.

Functional characterization of a novel 3D model of the epithelial-mesenchymal trophic unit

ABSTRACTBackground/Aim: Epithelial-mesenchymal communication plays a key role in tissue homeostasis and abnormal signaling contributes to chronic airways disease such as COPD. Most in vitro models are limited in complexity and poorly represent this epithelial-mesenchymal trophic unit. We postulated that cellular outgrowth from bronchial tissue would enable development of a mucosal structure that recapitulates better in vivo tissue architecture. Materials and Methods: Bronchial tissue was embedded in Matrigel and outgrowth cultures monitored using time-lapse microscopy, electrical resistance, light and electron microscopy. Cultures were challenged repetitively with cigarette smoke extract (CSE). Results: The outgrowths formed as a multicellular sheet with motile cilia becoming evident as the Matrigel was remodeled to provide an air interface; cultures were viable for more than one year. Immunofluorescence and electron microscopy (EM) identified an upper layer of mucociliary epithelium and a lower layer of highly organized extracellular matrix (ECM) interspersed with fibroblastic cells separated by a basement membrane. EM analysis of the mucosal construct after repetitive exposure to CSE revealed epithelial damage, loss of cilia, and ECM remodeling, as occurs in vivo. Conclusions: We have developed a robust bronchial mucosal model. The structural changes observed following CSE exposure suggest the model should have utility for drug discovery and preclinical testing, especially those targeting airway remodeling.

A Heterotopic Xenograft Model of Human Airways for Investigating Fibrosis in Asthma.

Limited in vivo models exist to investigate the lung airway epithelial role in repair, regeneration, and pathology of chronic lung diseases. Herein, we introduce a novel animal model in asthma-a xenograft system integrating a differentiating human asthmatic airway epithelium with an actively remodeling rodent mesenchyme in an immunocompromised murine host. Human asthmatic and nonasthmatic airway epithelial cells were seeded into decellularized rat tracheas. Tracheas were ligated to a sterile cassette and implanted subcutaneously in the flanks of nude mice. Grafts were harvested at 2, 4, or 6 weeks for tissue histology, fibrillar collagen, and transforming growth factor-β activation analysis. We compared immunostaining in these xenografts to human lungs. Grafted epithelial cells generated a differentiated epithelium containing basal, ciliated, and mucus-expressing cells. By 4 weeks postengraftment, asthmatic epithelia showed decreased numbers of ciliated cells and decreased E-cadherin expression compared with nonasthmatic grafts, similar to human lungs. Grafts seeded with asthmatic epithelial cells had three times more fibrillar collagen and induction of transforming growth factor-β isoforms at 6 weeks postengraftment compared with nonasthmatic grafts. Asthmatic epithelium alone is sufficient to drive aberrant mesenchymal remodeling with fibrillar collagen deposition in asthmatic xenografts. Moreover, this xenograft system represents an advance over current asthma models in that it permits direct assessment of the epithelial-mesenchymal trophic unit.

IL-1α mediates cellular cross-talk in the airway epithelial mesenchymal trophic unit

ABSTRACTThe bronchial epithelium and underlying fibroblasts form an epithelial mesenchymal trophic unit (EMTU) which controls the airway microenvironment. We hypothesized that cell-cell communication within the EMTU propagates and amplifies the innate immune response to respiratory viral infections.EMTU co-culture models incorporating polarized (16HBE14o-) or differentiated primary human bronchial epithelial cells (HBECs) and fibroblasts were challenged with double-stranded RNA (dsRNA) or rhinovirus.In the polarized EMTU model, dsRNA affected ionic but not macromolecular permeability or cell viability. Compared with epithelial monocultures, dsRNA-stimulated pro-inflammatory mediator release was synergistically enhanced in the basolateral compartment of the EMTU model, with the exception of IL-1α which was unaffected by the presence of fibroblasts. Blockade of IL-1 signaling with IL-1 receptor antagonist (IL-1Ra) completely abrogated dsRNA-induced basolateral release of mediators except CXCL10. Fibroblasts were the main responders to epithelial-derived IL-1 since exogenous IL-1α induced pro-inflammatory mediator release from fibroblast but not epithelial monocultures. Our findings were confirmed in a differentiated EMTU model where rhinovirus infection of primary HBECs and fibroblasts resulted in synergistic induction of basolateral IL-6 that was significantly abrogated by IL-1Ra. This study provides the first direct evidence of integrated IL-1 signaling within the EMTU to propagate inflammatory responses to viral infection.

Pathological changes in the COPD lung mesenchyme – Novel lessons learned from in vitro and in vivo studies

Chronic obstructive pulmonary disease (COPD) is currently the fourth leading cause of death worldwide and, in contrast to the trend for cardiovascular diseases, mortality rates still continue to climb. This increase is in part due to an aging population, being expanded by the “Baby boomer” generation who grew up when smoking rates were at their peak and by people in developing countries living longer. Sadly, there has been a disheartening lack of new therapeutic approaches to counteract the progressive decline in lung function associated with the disease that leads to disability and death. COPD is characterized by irreversible chronic airflow limitation that is caused by emphysematous destruction of lung elastic tissue and/or obstruction in the small airways due to occlusion of their lumen by inflammatory mucus exudates, narrowing and obliteration. These lesions are mainly produced by the response of the tissue to the repetitive inhalational injury inflicted by noxious gases, including cigarette smoke, which involves interaction between infiltrating inflammatory immune cells, resident cells (e.g. epithelial cells and fibroblasts) and the extra cellular matrix. This interaction leads to tissue destruction and airway remodeling with changes in elastin and collagen, such that the epithelial–mesenchymal trophic unit is dysregulated in both the disease pathologies. This review focuses on: 1 – novel inflammatory and remodeling factors that are altered in COPD; 2 – in vitro and in vivo models to understand the mechanism whereby the extra cellular matrix environment in altered in COPD; and 3 – COPD in the context of wound-repair tissue responses, with a focus on the regulation of mesenchymal cell fate and phenotype.

Ozone Exposure Alters Serotonin and Serotonin Receptor Expression in the Developing Lung

Ozone, a pervasive environmental pollutant, adversely affects functional lung growth in children. Animal studies demonstrate that altered lung development is associated with modified signaling within the airway epithelial mesenchymal trophic unit, including mediators that can change nerve growth. We hypothesized that ozone exposure alters the normal pattern of serotonin, its transporter (5-HTT), and two key receptors (5-HT2A and 5-HT4), a pathway involved in postnatal airway neural, epithelial, and immune processes. We exposed monkeys to acute or episodic ozone during the first 2 or 6 months of life. There were three exposure groups/age: (1) filtered air, (2) acute ozone challenge, and (3) episodic ozone + acute ozone challenge. Lungs were prepared for compartment-specific qRT-PCR, immunohistochemistry, and stereology. Airway epithelial serotonin immunopositive staining increased in all exposure groups with the most prominent in 2-month midlevel and 6-month distal airways. Gene expression of 5-HTT, 5-HT2AR, and 5-HT4R increased in an age-dependent manner. Overall expression was greater in distal compared with midlevel airways. Ozone exposure disrupted both 5-HT2AR and 5-HT4R protein expression in airways and enhanced immunopositive staining for 5-HT2AR (2 months) and 5-HT4R (6 months) on smooth muscle. Ozone exposure increases serotonin in airway epithelium regardless of airway level, age, and exposure history and changes the spatial pattern of serotonin receptor protein (5-HT2A and 5-HT4) and 5-HTT gene expression depending on compartment, age, and exposure history. Understanding how serotonin modulates components of reversible airway obstruction exacerbated by ozone exposure sets the foundation for developing clinically relevant therapies for airway disease.

Respiratory epithelial imbalances in asthma pathophysiology

The pathophysiology of asthma is complex and involves a number of factors including atopy and bronchial hyperreactivity. A strong body of evidence suggests that structural and functional respiratory epithelial alterations play a crucial role in both development and persistence of this condition. From the onset of symptoms the airways epithelium of asthmatic patients seems to be altered and unable to repair. The interactions between the epithelium and the underlying mesenchyma, which are jointly referred to as the epithelial-mesenchymal trophic unit (EMTU), are thought to result in a self-sustaining damage of the airways and, ultimately, in a chronic inflammatory scenario. A better understanding of the relationship occurring across EMTU, environmental noxae, and factors of susceptibility to epithelial damage is likely to pave the way to future new preventive and therapeutic strategies for this condition.

Mechanisms of Asthma and Implications for Its Prevention and Treatment: A Personal Journey

My research career has focused on the causes of asthma and its treatment. After establishing the key role that mast cells play in the inflammatory response in asthma, attention was turned towards understanding disease chronicity and variability across the lifecourse. Through a combination of studies on airway biopsies and primary cell cultures we have established that asthma is primarily an epithelial disease driven by increased environmental susceptibility to injury and an altered repair response as depicted by sustained activation of the epithelial mesenchymal trophic unit (EMTU) that is invoked in foetal branching morphogenesis. Varied activation of the EMTU connects the origins of asthma to its progression over time with involvement of epithelial susceptibility through impaired barrier and innate immune functions and altered mesenchymal susceptibility as exemplified by polymorphisms of the metalloprotease gene, ADAM33. Taken together these observations have led to a fundamental re-evaluation of asthma pathogenesis. Rather than placing allergic inflammation as the prime abnormality, it is proposed that the airway epithelium lies at the center of asthma pathogenesis, and that in conjunction with the underlying mesenchyme, it is the principle orchestrator of both the induction of asthma and its evolution over the lifecourse. This concept has provided 'the basis for a new preventative and therapeutic approach focused more on increasing the airways resistance to environmental insults rather than suppressing downstream inflammation once it is established.

Advances in pediatric asthma in 2012: Moving toward asthma prevention

Last year's "Advances in pediatric asthma: moving forward" concluded the following: "Now is also the time to utilize information recorded in electronic medical records to develop innovative disease management plans that will track asthma over time and enable timely decisions on interventions in order to maintain control that can lead to disease remission and prevention." This year's summary will focus on recent advances in pediatric asthma on modifying disease activity, preventing asthma exacerbations, managing severe asthma, and risk factors for predicting and managing early asthma, as indicated in Journal of Allergy and Clinical Immunology publications in 2012. Recent reports continue to shed light on methods to improve asthma management through steps to assess disease activity, tools to standardize outcome measures in asthma, genetic markers that predict risk for asthma and appropriate treatment, and interventions that alter the early presentation of asthma to prevent progression. We are well on our way to creating a pathway around wellness in asthma care and also to use new tools to predict the risk for asthma and take steps to not only prevent asthma exacerbations but also to prevent the early manifestations of the disease and thus prevent its evolution to severe asthma.

171 Augmentation of cxcl10 Expression in Nasal Fibroblasts Derived from Patients With Recalcitrant Chronic Rhinosinusitis Associated With Bronchial Asthma

BackgroundThe prevalence of chronic rhinosinusitis (CRS) that is refractory to traditional therapy appears to be increasing, and CRS that is refractory to traditional therapy tends to be associated with bronchial asthma (BA), especially, aspirin-intolerant asthma (AIA). After viral infections, patients with CRS associated with BA usually experience exacerbations of their CRS symptoms, including nasal polyposis, in comparison with CRS patients without BA. Alternatively tissue fibroblasts as an important component of the epithelial mesenchymal trophic unit play a key role in maintaining tissue homeostasis and may also have the potential to contribute to disease pathogenesis through their contribution to inflammatory responses. On the basis of these findings, we hypothesized that CRS patients with BA are more susceptible to inflammation of the nasal and paranasal mucosa depending on the antiviral response of nasal fibroblasts.MethodsTissue specimens were obtained from the nasal polyps of 3 groups of CRS patients, a group that did not have BA (CRS-NA group), a group with aspirin-tolerant asthma (CRS-ATA group), and a group with AIA (CRS-AIA group). Nasal polyp fibroblasts (NPFs) were isolated from the specimens and stimulated with poly I: C. By using a DNA microarray and performing a hierarchical clustering analysis we were able to identify a cluster containing genes that were up-regulated after poly I: C stimulation. To confirm the results of the analysis data, we used quantitative real-time PCR (qRT-PCR) and an enzyme-linked immunoadsorbent assay (ELISA).ResultsExpression of IFN-inducible protein 10 (IP-10)/CXCL10 transcript was higher in the NPFs of the CRS-AIA group and CRS-ATA group than in the CRS-NA group and control group. These findings were confirmed by qRT-PCR and ELISA.ConclusionsThe results of this study suggest that the increased poly I:C-induced CXCL10 expression in NPFs derived from the CRS patients with BA is involved in susceptible to T helper (Th)1-type immune response in the nasal and paranasal mucosa by viral infection compared with CRS patients without BA.

Transforming Growth Factor Beta: A Role in the Upper Airway and Rhinosinusitis—Dermatophagoides Pteronyssinus–Induced Apoptosis with Pulmonary Alveolar Cells

There is a link with the upper and lower airway and disruption of alveolar epithelial cells, which is a potential trigger for the reactivation of the epithelial-mesenchymal trophic unit (EMTU) and induced characteristic airway changes associated with allergic asthma. Dermatophagoides pteronyssinus is a common inhalant indoor allergen and is known for causing allergic rhinitis and airway inflammation. Transforming growth factor beta 1 (TGF-beta1) is a major participant in the airway remodeling of asthma, a component of cellular stress response pathways, and enhanced epithelial immunoreactivity is known to occur in allergic rhinitis. In this study, we show the ability of D. pteronyssinus allergens from dialyzed standardized immunotherapy extract to induce apoptosis and increase TGF-beta1 secretion in a confluent A549 cell line model. A549 cells were treated with either 600 AU/mL dialyzed D. pteronyssinus immunotherapy extract (eDp) or Ctl media (Ctl) for 24 hours. Cells and supernatants were collected, washed, and treated with Annexin V-FITC Apoptosis Detection Kit II (BD Pharmingen, La Jolla, CA) and then analyzed by flow cytometry. TGF-beta1 secretion was determined by ELISA using cell culture supernatants. The eDp group showed a fourfold increase in early apoptotic cells with a twofold increase in late apoptotic cells versus the Ctl group, along with a 1.65-fold increase of TGF-beta1. eDp induced viable A549 cells to undergo apoptosis determined by flow cytometry analysis with a significant increase in TGF-beta1 secretion compared with Ctl.

Development of the bronchial epithelial reticular basement membrane: relationship to epithelial height and age

BackgroundThe bronchial epithelium and underlying reticular basement membrane (RBM) have a close spatial and functional inter-relationship and are considered an epithelial–mesenchymal trophic unit (EMTU). An understanding of RBM development is...