Anthony Kicic

Induction of Epithelial–Mesenchymal Transition in Primary Airway Epithelial Cells from Patients with Asthma by Transforming Growth Factor-β1

RATIONALE Airway remodeling in asthma is associated with the accumulation of fibroblasts, the primary cell responsible for synthesis and secretion of extracellular matrix proteins. The process by which the number of fibroblasts increases in asthma is poorly understood, but epithelial-mesenchymal transition (EMT) may play a significant role. OBJECTIVES To evaluate whether EMT occurs in primary airway epithelial cells (AECs), the mechanisms involved, and if this process is altered in asthmatic AECs. METHODS AECs were obtained from subjects with asthma (n = 8) and normal subjects without asthma (n = 10). Monolayer and air-liquid interface-AEC (ALI-AEC) cultures were treated with transforming growth factor (TGF)-beta1 (10 ng/ml) for 72 hours and assayed for mesenchymal and epithelial markers using quantitative polymerase chain reaction, confocal microscopy, and immunoblot. The involvement of BMP-7, Smad3, and MAPK-mediated signaling were also evaluated. MEASUREMENTS AND MAIN RESULTS TGF-beta1-induced EMT in AEC monolayers derived from subjects with asthma and normal donors. EMT was characterized by changes in cell morphology, increased expression of mesenchymal markers EDA-fibronectin, vimentin, alpha-smooth muscle actin, and collagen-1, and loss of epithelial markers E-cadherin and zonular occludin-1. Inhibition of TGF-beta1-induced signaling with Smad3-inhibiting siRNA or TGF-beta1-neutralizing antibodies prevented and reversed EMT, respectively, whereas BMP-7 had no effect. In ALI-AEC cultures derived from normal subjects, EMT was confined to basally situated cells, whereas in asthmatic ALI-AEC cultures EMT was widespread throughout the epithelium. CONCLUSIONS TGF-beta1 induces EMT in a Smad3-dependent manner in primary AECs. However, in asthmatic-derived ALI-AEC cultures, the number of cells undergoing EMT is greater. These findings support the hypothesis that epithelial repair in asthmatic airways is dysregulated.

Characterization of Side Population Cells from Human Airway Epithelium

The airway epithelium is the first line of contact with the inhaled external environment and is continuously exposed to and injured by pollutants, allergens, and viruses. However, little is known about epithelial repair and in particular the identity and role of tissue resident stem/progenitor cells that may contribute to epithelial regeneration. The aims of the present study were to identify, isolate, and characterize side population (SP) cells in human tracheobronchial epithelium. Epithelial cells were obtained from seven nontransplantable healthy lungs and four asthmatic lungs by pronase digestion. SP cells were identified by verapamil‐sensitive efflux of the DNA‐binding dye Hoechst 33342. Using flow cytometry, CD45− SP, CD45+ SP, and non‐SP cells were isolated and sorted. CD45− SP cells made up 0.12% ± 0.01% of the total epithelial cell population in normal airway but 4.1% ± 0.06% of the epithelium in asthmatic airways. All CD45− SP cells showed positive staining for epithelial‐specific markers cytokeratin‐5, E‐cadherin, ZO‐1, and p63. CD45− SP cells exhibited stable telomere length and increased colony‐forming and proliferative potential, undergoing population expansion for at least 16 consecutive passages. In contrast with non‐SP cells, fewer than 100 CD45− SP cells were able to generate a multilayered and differentiated epithelium in air‐liquid interface culture. SP cells are present in human tracheobronchial epithelium, exhibit both short‐ and long‐term proliferative potential, and are capable of generation of differentiated epithelium in vitro. The number of SP cells is significantly greater in asthmatic airways, providing evidence of dysregulated resident SP cells in the asthmatic epithelium.

Limbal stem cells : the search for a marker

The corneal epithelium is a self‐renewing tissue and must, by definition, have a resident basal cell population necessary for homeostasis and wound healing. There is a substantial body of evidence, both experimental and clinical, pointing to the basal cells of the limbus as the location of corneal epithelial stem cells. However, in the absence of a definitive marker of limbal stem cells, the evidence remains largely circumstantial. Many markers such as p63 and integrin α9 are preferentially localized to the limbus but cannot be regarded as stem cell‐specific. Other markers such as K3 and connexin 43 can be regarded as markers of corneal differentiation. The discovery of stem cell markers in other organ systems, such as the haematopoietic system, offers optimism that a marker of limbal stem cells will one day be found. Such a discovery will have far‐reaching implications for the study of ocular surface biology and stratified squamous epithelia in general.

Dysregulated repair in asthmatic paediatric airway epithelial cells: the role of plasminogen activator inhibitor-1

Background Asthma is associated with structural changes to airways such as extracellular matrix deposition and epithelial damage. Evidence suggests that asthmatic airway epithelial repair is abnormal and that elevated plasminogen activator inhibitor‐1 levels observed in asthma may be involved in the epithelial repair process and in excessive matrix accumulation.

DNA Methylation Profiles of Airway Epithelial Cells and PBMCs from Healthy, Atopic and Asthmatic Children

Background Allergic inflammation is commonly observed in a number of conditions that are associated with atopy including asthma, eczema and rhinitis. However, the genetic, environmental or epigenetic factors involved in these conditions are likely to be different. Epigenetic modifications, such as DNA methylation, can be influenced by the environment and result in changes to gene expression. Objectives To characterize the DNA methylation pattern of airway epithelial cells (AECs) compared to peripheral blood mononuclear cells (PBMCs) and to discern differences in methylation within each cell type amongst healthy, atopic and asthmatic subjects. Methods PBMCs and AECs from bronchial brushings were obtained from children undergoing elective surgery for non-respiratory conditions. The children were categorized as atopic, atopic asthmatic, non-atopic asthmatic or healthy controls. Extracted DNA was bisulfite treated and 1505 CpG loci across 807 genes were analyzed using the Illumina GoldenGate Methylation Cancer Panel I. Gene expression for a subset of genes was performed using RT-PCR. Results We demonstrate a signature set of CpG sites that are differentially methylated in AECs as compared to PBMCs regardless of disease phenotype. Of these, 13 CpG sites were specific to healthy controls, 8 sites were only found in atopics, and 6 CpGs were unique to asthmatics. We found no differences in the methylation status of PBMCs between disease phenotypes. In AECs derived from asthmatics compared to atopics, 8 differentially methylated sites were identified including CpGs in STAT5A and CRIP1. We demonstrate STAT5A gene expression is decreased whereas CRIP1 gene expression is elevated in the AECs from asthmatic compared to both healthy and atopic subjects. Discussion We characterized a cell specific DNA methylation signature for AECs compared to PBMCs regardless of asthmatic or atopic status. Our data highlight the importance of understanding DNA methylation in the epithelium when studying the epithelial contribution to asthma.

Innate inflammatory responses of pediatric cystic fibrosis airway epithelial cells: Effects of nonviral and viral stimulation

There is controversy regarding whether cystic fibrosis (CF) airway epithelial cells (AECs) are intrinsically proinflammatory. The objective of the current study was to characterize the inflammatory profiles of AECs from children with CF compared with cells from healthy control subjects. We obtained AECs from healthy children (12) and children with CF (27). Biochemical and functional characteristics were assessed by stimulating cells with IFNγ, LPS, a cocktail referred to as cytomix, which consists of IFNγ, IL-1β, TNF-α, and LPS, or with human rhinovirus (HRV). Cytokine production was assessed using ELISA. Apoptotic responses to HRV infection were measured via production of single-stranded DNA. Our results indicated that CF and healthy cells exhibited similar morphology in monolayer culture. CF cells constitutively produced greater amounts of IL-6, IL-1β, and prostaglandin E(2), but similar levels of IL-8 and soluble intracellular adhesion molecule-1 compared with healthy cells, and this profile was maintained through repeated passage. Stimulation with LPS or cytomix elicited similar levels of IL-8 in CF and non-CF cells. In contrast, exposure to HRV1b resulted in a marked increase in IL-8 production from CF compared with non-CF cells. CF cells also exhibited reduced apoptosis and increased viral replication compared with non-CF cells after exposure to HRV1b. We conclude that CF and healthy AECs have similar basal and stimulated expression of IL-8 in response to proinflammatory stimuli, but elevated IL-8 release in response to HRV infection. The elevated IL-8, together with dampened apoptotic responses by CF cells to HRV, could contribute to augmented airway inflammation in the setting of recurrent viral infections early in life.

Posttransplant Bronchiolitis Obliterans Syndrome Is Associated with Bronchial Epithelial to Mesenchymal Transition

Bronchiolitis obliterans syndrome (BOS) compromises lung transplant outcomes and is characterised by airway epithelial damage and fibrosis. The process whereby the normal epithelial configuration is replaced by fibroblastic scar tissue is poorly understood, but recent studies have implicated epithelial mesenchymal transition (EMT). The primary aim of this study was to assess the utility of flow cytometry in detecting and quantifying EMT in bronchial epithelial cells.

Selection of housekeeping genes for real-time PCR in atopic human bronchial epithelial cells

The stability of housekeeping genes (HKGs) is critical when performing real-time quantitative PCR. To date, the stability of common HKGs has not been systematically compared in human airway epithelial cells (AEC) in normal and atopic subjects. Expression levels of 12 HKGs were measured in AECs from a cohort of 30 healthy atopic nonasthmatic or atopic asthmatic children. Gene expression stability was determined using three different Visual Basic for Applications applets (geNorm, NormFinder and BestKeeper). All 12 HKGs were expressed in AECs. However, the hypoxanthine ribosyltransferase and TATA-binding protein genes were excluded from further analysis due to low expression levels. The cyclophilin A gene was ranked the most stable by all three methods. The expression levels of the β-actin and glyceraldehyde-3-phosphate dehydrogenase genes were significantly different between the three groups of patients, with atopic asthmatics showing the highest expression levels for both genes. The results suggest that the cyclophilin A gene is the most suitable housekeeping gene analysed for expression studies utilising uncultured bronchial airway epithelial cells from healthy and asthmatic children, and highlight the importance of validating housekeeping genes for each experimental model.

Inducible NO synthase expression is low in airway epithelium from young children with cystic fibrosis

Background: This is the first study to measure inducible nitric oxide synthase (iNOS) gene and protein expression quantitatively in primary epithelial cells from very young children with cystic fibrosis (CF). Low levels of exhaled nitric oxide (NO) in CF suggest dysregulation of NO production in the airway. Due to the importance of NO in cell homeostasis and innate immunity, any defect in the pathway associated with CF would be a potential target for treatment. Methods: Cells were obtained by tracheobronchial brushing from 40 children with CF of mean (SD) age 2.1 (1.5) years and from 12 healthy non-atopic children aged 3.4 (1.2) years. Expression of iNOS mRNA was measured using quantitative PCR and iNOS protein by immunofluorescence and Western blot analysis. Results: Inducible NOS mRNA expression was significantly lower in CF patients with and without bacterial infection than in healthy children (0.22 and 0.23 v 0.76; p = 0.002 and p = 0.01, respectively). Low levels of iNOS gene expression were accompanied by low levels of iNOS protein expression as detected by Western blot analysis. Conclusions: These results support the findings of previous studies in adult patients with advanced disease, cell lines, and animal models. Our findings reflect the situation in children with mild lung disease. They indicate that low iNOS expression may be an innate defect in CF with potential consequences for local antimicrobial defence and epithelial cell function and provide evidence for an approach to treatment based on increasing epithelial NO production or the sensitivity of NO dependent cellular processes.

The use of non-bronchoscopic brushings to study the paediatric airway

BackgroundThe use of cytology brushes for the purpose of obtaining respiratory cells from adults for clinical and research purposes is well established. However, the safety and utility of non-bronchoscopic brushings to study the paediatric airway has not been assessed. The purpose of this study was to assess the practicality of using non-bronchoscopic brushing to sample epithelial cells from children for investigation of epithelial function in health and disease using a wide range of molecular and cellular techniques.MethodsNon-bronchoscopic brushing was investigated in a non-selected cohort of healthy, and mildly asthmatic children presenting for surgery unrelated to respiratory conditions, at the major childrens hospital in Perth. Safety and side-effects of the procedure were assessed. Cell number, phenotype and viability were measured for all samples. The potential of these cells for use in long-term cell culture, immunohistochemistry, western blotting, quantitative PCR and gene arraying was examined.ResultsNon-bronchoscopic brushing was well tolerated in all children. The only significant side effect following the procedure was cough: nursing staff reported cough in 20% of patients; parents reported cough in 40% of patients. Cells sampled were of sufficient quantity and quality to allow cell culture in 93% of samples. Similarly, protein and RNA extracted from the cells was suitable for investigation of both gene and protein expression using micro-array and real-time PCR.ConclusionNon-bronchoscopic brushing in children is safe and easy to perform, and is not associated with any complications. Using this technique, adequate numbers of epithelial cells can be retrieved to allow cell culture, western blotting, real time PCR, and microarray analysis. The purpose of this study is to demonstrate the utility of non-bronchoscopic airway brushing to obtain and study epithelial cells and to encourage others so that we can accelerate our knowledge regarding the role of the epithelium in childhood respiratory disease.