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Original Research: COPD |

Epithelial Mucin Stores Are Increased in the Large Airways of Smokers With Airflow Obstruction* FREE TO VIEW

Anh L. Innes, MD; Prescott G. Woodruff, MD; Ronald E. Ferrando, MA; Samantha Donnelly, PhD; Gregory M. Dolganov, PhD; Stephen C. Lazarus, MD; John V. Fahy, MD
Author and Funding Information

*From the Department of Medicine, Division of Pulmonary and Critical Care Medicine, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA.

Correspondence to: John V. Fahy, MD, Box 0111, University of California, San Francisco, 505 Parnassus Ave, San Francisco, CA 94143; e-mail: john.fahy@ucsf.edu.



Chest. 2006;130(4):1102-1108. doi:10.1378/chest.130.4.1102
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Published online

Background: Habitual cigarette smoking is associated with chronic mucus hypersecretion, but the relationship between mucus abnormalities and airflow obstruction in smokers is uncertain.

Methods: We collected bronchial biopsy samples and epithelial brushings from 24 smokers with and without airflow obstruction and 19 nonsmoking healthy control subjects. Epithelial mucin stores, mucin immunostains, and goblet cell morphology were quantified in bronchial biopsy samples using stereology, and mucin gene expression was quantified in epithelial brushings using real-time reverse transcriptase-polymerase chain reaction.

Results: Goblet cell size and number were higher than normal in smokers (both p < 0.05), leading to a 2.2-fold increase in the volume of stored mucin in the epithelium per surface area of basal lamina (1.94 ± 0.31 μm3/μm2 vs 4.32 ± 0.55 μm3/μm2 in control subjects vs smokers, p = 0.001). The increase in stored mucin occurred because of an increase in MUC5AC (p = 0.018) and despite a decrease in MUC5B (p < 0.0001). Stored mucin was significantly higher in the subgroup of smokers with airflow obstruction (p = 0.029) and correlated with FEV1/FVC even when controlling for diffusing capacity as a measure of emphysema (p = 0.034).

Conclusions: Epithelial mucin stores are increased in habitual smokers because of goblet cell hypertrophy and hyperplasia, and the pattern of mucin gene expression is abnormal. The highest epithelial mucin stores are found in smokers with airflow obstruction, suggesting a mechanistic link between epithelial mucin dysregulation and airflow obstruction.

Figures in this Article

The mechanisms of airway remodeling leading to airflow obstruction in habitual smokers are not well understood. One possibility is that smoking damages the airway epithelium, thereby promoting airway infection. Normally, the airway is defended from exogenous insults by the secreted mucus layer, which traps invading pathogens and propels them out of the lung by the mucociliary escalator.1Airflow obstruction in smokers may therefore be the consequence of recurrent airway infections, occurring because of smoking-induced increases in airway mucus and poor mucus clearance (a concept known as the British hypothesis).3

Pathology studies46 demonstrate that the airways of habitual smokers are characterized by goblet cell metaplasia and proliferation of submucosal glands. The consequence of these changes is the subject of debate. Although goblet cell metaplasia and gland proliferation provide an explanation for the sputum symptoms that occur in habitual smokers, the relationships between sputum symptoms, airway infections, and airflow obstruction have been difficult to determine in clinical studies. The initial studies of Fletcher et al7suggested no relationship between severity of sputum symptoms, frequency of airway infections, and development of airflow obstruction. But subsequent studies89 have suggested otherwise, and there is now a growing consensus that exacerbations of chronic bronchitis play a role in accelerated loss of lung function in smokers, and that sputum symptoms are more than an epiphenomenon.1011

Resistance to airflow in smokers occurs largely because of increased resistance in small airways12; this knowledge has led to doubt about the relevance of large airway pathology, such as changes in goblet cells and glands as well as the sputum symptoms that reflect this pathology. But central airway pathology may indirectly reflect peripheral airway pathology because both occur as a consequence of susceptibility to cigarette smoke. Also, poor mucus clearance in the central airways could have consequences for the health and sterility of small airways because mucus retention centrally will adversely affect mucus clearance from more peripheral airways and may even result in peripheral aspiration of mucus originating in large airways.

In this study, we set out to explore structure-function relationships in the airways of habitual smokers with an emphasis on goblet cell mucins in the large airways. Although a study13has reported no relationship between mucin markers in central airways and airflow in smokers, we applied developed quantitative methods (based on design-based stereology) to measure mucin content and composition in central airways, and to relate those measures to degree of airflow obstruction. Stereology has advantages in morphology studies because it provides unbiased quantitative estimates of tissue structure and protein expression that are well suited to structure-function correlations.1417

Subjects

We enrolled 24 cigarette smokers (defined as current smoking of at least 10 cigarettes per day and a minimum history of 10 pack-years of exposure) and 19 nonsmoking control subjects (defined as < 10 pack-years of smoking with no smoking in the previous 10 years). For all subjects, inclusion criterion was age 30 to 65 years. Exclusion criteria were as follows: FEV1/FVC < 0.4; provocative concentration of methacholine resulting in 20% decrease in FEV1 from baseline value (PC20) [< 1 mg/mL]; history of asthma; recent upper respiratory tract infection; significant medical problems other than smoking-related lung disease; history of home oxygen use; or admission to an ICU for respiratory failure. The study was approved by the University of California, San Francisco Committee on Human Research, and all subjects provided signed informed consent.

Subjects completed two visits 1 week apart. At visit 1, subjects provided medical history and underwent physical examination, spirometry, and methacholine challenge; the subjects also underwent 12-lead ECG and determination of single-breath diffusing capacity for carbon monoxide (Dlco) [details in on-line supplement[. Measurements for Dlco were made after a minimum 4-h hold of cigarette smoking for all smokers. Subjects also completed a detailed respiratory questionnaire, which included the following questions: “Do you cough on most days for 3 consecutive months or more during a 12-month period?” and “Do you bring up phlegm on most days for 3 consecutive months or more during a 12-month period?.” After each question, subjects were asked to indicate the number of years that they have had those symptoms.

At visit 2, FEV1/FVC was measured before and 20 min after albuterol, 360 μg, in all subjects; smokers with a postbronchodilator FEV1/FVC < 0.7 were categorized as having airway obstruction.18 Bronchoscopy was performed, and bronchial biopsy specimens and epithelial brushings were collected. Biopsy specimens were processed in formalin and paraffin. Tissue sections were cut and stained with Alcian-blue periodic acid-Schiff and with immunostaining protocols specific for MUC2, MUC5AC, and MUC5B. Stereology was used to quantify goblet cells and mucin outcomes.16 Primary outcome measurements were made on 5.0 ± 1.5 biopsies and 99 ± 58 fields per subject (mean± SD). Bronchial brushings were processed to allow quantification of messenger RNA transcripts for mucin genes, using methods of real-time reverse transcriptase-polymerase chain reaction19 (details for methods in on-line supplement).

Statistics

Baseline characteristics, morphometric outcomes, and messenger RNA copy numbers for genes of interest (log transformed for normality) were compared in smokers and nonsmokers using Student t test and rank-sum test. Three-group comparisons were performed using analysis of variance, with p values for subsequent pairwise comparisons adjusted using the Sidak correction.20 We developed multivariate linear regression models to examine the relationship between airflow obstruction (postbronchodilator FEV1/FVC) and morphometric outcomes while controlling for potential confounders and diffusing capacity as a measure of emphysema. Data analysis was performed using STATA 5.0 (StataCorp; College Station, TX). All tests were two sided; p < 0.05 indicated statistical significance.

The baseline clinical characteristics of the 24 smokers and the 19 nonsmoking control subjects showed that more of the smokers were male, and that the smokers were older and had lower values for FEV1 and FEV1/FVC (Table 1 ). Although on average the smokers were more hyperresponsive to methacholine than the healthy subjects (Table 1), 17 of the 24 smokers had PC20 in the normal range (> 8 mg/mL). Sixteen of the 24 smokers had Dlco in the normal range (> 80% of predicted). All 19 healthy subjects were lifetime nonsmokers with one exception, a subject with a distant 4-pack-year smoking history. Of the 24 smokers, 9 had airflow obstruction (postbronchodilator FEV1/FVC < 0.7). Compared to the 15 smokers without airflow obstruction, the 9 with obstruction had a higher pack-year smoking history, lower Dlco, and lower PC20 (Table 2 ). By the Global Initiative for Chronic Obstructive Lung Disease classification18 of COPD severity, three subjects were stage 0, four were stage I, and five were stage II.

We systematically measured both the volume of epithelium and the surface area of basal lamina for use as reference compartments for our morphometric measures.16 The mean height of the airway epithelium was greater in smokers than in nonsmokers (Table 3 ); therefore, we used the surface area of the basal lamina as our primary reference compartment. The mean value for airway epithelial mucin stores, assessed as volume of mucin per surface area of basal lamina, was twofold higher than normal in smokers (p = 0.001; Table 3; Fig 1, 2 ) and 1.7-fold higher in smokers with airflow obstruction than smokers without airflow obstruction (p = 0.029; Fig 2). To further assess the relationship between epithelial mucin stores and airflow obstruction, we developed a multivariate linear regression model to examine the relationship between postbronchodilator FEV1/FVC (outcome variable) and the volume of mucin per surface area of basal lamina (predictor variable), while controlling for age, sex, pack-years of smoking, and PC20. These variables were different between the smoker subgroups and could confound interpretation of the relationship between epithelial mucin stores and airflow obstruction. We also developed a model that controlled for all of the above factors plus Dlco (expressed as percentage of predicted) as a measure of emphysema. In models with and without Dlco, higher levels of epithelial mucin per surface area of basal lamina were independently associated with degree of airflow obstruction (p = 0.013 and 0.034, respectively; models 1 and 2 in Table 4 ). These associations persisted when we used volume of epithelium as an alternative reference compartment (p < 0.01 with and without controlling for Dlco; models 3 and 4 in Table 4).

To determine if goblet cell hyperplasia or hypertrophy accounts for higher epithelial mucin stores in smokers, we measured goblet cell number and size and found that the mean number of goblet cells per surface area of basal lamina was 80% higher in smokers (p = 0.003, Table 3). In addition, the mean volume of individual goblet cells was 30% higher in smokers as compared to nonsmoking control subjects (p = 0.014; Table 3). Thus, higher stores of epithelial mucin in smokers result from both goblet cell hyperplasia and hypertrophy, a difference that was driven by the subgroup of smokers with airflow obstruction.

To determine whether the relative proportions of various gel-forming mucins in the airway epithelium are changed in smokers, we performed immunohistochemical studies using antibodies for the principal gel-forming mucins: MUC5AC, MUC5B, MUC2, and MUC6. We found that MUC5AC immunostaining in the surface airway epithelium (Fig 1, center left, C and center right, D) was 80% higher in smokers than nonsmoking control subjects (p < 0.05; Table 3). In contrast, surface MUC5B immunostaining (Fig 1, bottom left, E and bottom right, F) was fivefold lower in smokers (n = 24) than nonsmoking control subjects (n = 15) [p < 0.0001, Table 3]. MUC2 immunostaining was detectable in goblet cells but at much lower levels than either MUC5AC or MUC5B, with similar staining in smokers (n = 24) and nonsmoking control subjects (n = 15) [Table 3]. MUC6 was undetectable in the goblet cells and submucosal gland cells of one nonsmoking control subject and two smokers in formalin-fixed and paraffin-embedded tissue blocks (on-line supplement Fig 1). In addition, MUC6 was undetectable in goblet cells in frozen bronchial biopsy sections of from three smokers. A positive control (sections of human gastric mucosa, formalin fixed, and paraffin embedded) exhibited intense MUC6 staining in mucus-secreting cells of the crypts (on-line supplement Fig 1).

In additional analyses, we developed multivariate linear regression models to examine the relationship between FEV1/FVC (outcome variable) and goblet cell size, goblet cell number, and stores of specific mucin proteins (assessed by immunohistochemistry) in our smokers while controlling for potential confounders (age, sex, pack-years of smoking, PC20, and Dlco; on-line supplement Table 3). These analyses suggest additional morphologic abnormalities in the mucus-producing apparatus of the airway epithelium that correlate with degree of airflow obstruction in smokers, including mean goblet cell volume, number of goblet cells in the epithelium, and volume of staining for MUC5AC and MUC2.

To confirm our immunohistochemical studies for the gel-forming mucins, we quantified the gene expression of the gel-forming mucins using two-step real-time reverse transcriptase-polymerase chain reaction.19 We found an abnormal pattern of gene expression in smokers that mirrored the immunohistochemical findings (Table 5 ). Specifically, we found that expression of MUC5AC in smokers was higher than in healthy control subjects, and expression of MUC5B in smokers was lower than in healthy control subjects (Table 5).

To determine whether there is a dose-response relationship between tobacco smoke exposure (pack-years) and either pulmonary function, mucin gene expression, or mucin protein expression, we performed the relevant correlations. We found that there is indeed a relationship between pack-years and pulmonary function (ie, postbronchodilator FEV1/FVC) in our smokers (r = − 0.54, p = 0.006 by Pearson correlation). We also found that pack-years correlated inversely with MUC5B expression at both the messenger RNA and protein levels (r = − 0.41, p = 0.011 for MUC5B immunostaining [volume of mucin per surface area of basal lamina], and r = − 0.46, p = 0.003 for MUC5B copy number). There was no relationship between pack-years and the expression of MUC5AC at either the messenger RNA or protein level.

We report that goblet cell hypertrophy and hyperplasia occur in the large airways of habitual cigarette smokers and result in epithelial mucin stores that are significantly higher than normal. The increase in stored mucin occurs because of an increase in MUC5AC and despite a decrease in MUC5B. Notably, the highest epithelial mucin stores are in the smoker subgroup with airflow obstruction, and mucin stores correlate with FEV1/FVC, even when controlling for diffusing capacity as a measure of emphysema. These findings suggest that smoking-induced increases in epithelial mucins may contribute to mechanisms of smoking-induced airflow obstruction.

Goblet cell hyperplasia has been described in the small airways of smokers with COPD,5,21 and increased MUC5AC has been described in large airways of smokers,13 but our data are novel in several ways. First, using methods of stereology, which permit precise estimates of mucin volume and the size and number of goblet cells, we show that the twofold increase in epithelial mucin stores in smokers occurs because of the combined effects of goblet cell hypertrophy and hyperplasia. Second, we show that MUC5AC is not the only gel-forming mucin whose expression is altered in smokers, but that MUC5B expression is also significantly decreased. Third, we show that the increases in epithelial mucins are higher in smokers with airflow obstruction than without.

Stereology provides quantitative estimates of outcomes such as number, volume, and surface area by providing methods for converting two-dimensional information from tissue sections into three-dimensional estimates.1415 The term design-based stereology acknowledges that strategies for avoiding measurement bias begin with the experimental design and includes methods of tissue embedding, such as the isector method used here and described previously.,15 In these ways, stereology accounts for the volume bias inherent in two-dimensional sections and also enables accurate estimates of orientation-sensitive outcomes, such as surface area and thickness.

Our finding that MUC5AC protein is increased in the airway epithelium in smokers is in agreement with a report13 in similar subject populations. However, those authors report no significant change in MUC5B expression in smokers, whereas we report a large and statistically significant decrease. The difference in our results may reflect differences in methods, including choice of MUC5B antibody and the methods used to quantify the immunostains. The decrease in MUC5B protein that we found using our methods is corroborated by a similarly large and significant reduction in MUC5B gene expression in epithelial brushings. These changes in the relative amounts of MUC5AC and MUC5B in smokers are difficult to interpret because not much is known about the specific properties of the protein products of different gel-forming mucins. However, it is reasonable to hypothesize that changes from normal in stored mucins will be reflected in similar changes in secreted mucins. These changes could have deleterious consequences for the mucus gel matrix if they disturb the optimal physiology of the gel and render epithelial cells more vulnerable to airborne toxins. The alternative hypothesis—that these mucin changes are a protective response that is helpful to the host—also needs to be considered. In this regard, the mucociliary apparatus has adaptive capacities that can benefit the host in response to noxious environmental stimuli. However, there is likely a point at which abnormal concentrations of mucins in secretions render cilia less efficient, the gel less transportable, and the airway less healthy. Genetic perturbations in the mucociliary apparatus, such as those that occur in immotile cilia syndrome and cystic fibrosis, demonstrate that the consequences of a poorly functioning mucociliary apparatus are airway infection and airflow obstruction, two characteristics of smoking-associated airway disease.

We found that epithelial mucin stores are higher in smokers with airflow obstruction than smokers without. Not all previously published studies have found this relationship. Researchers in two pathology studies have, like us, examined lung tissue from well-characterized smokers. O’Donnell et al13 measured epithelial mucins in smokers but found no difference between smokers with and without airflow obstruction. In contrast, Hogg et al22 found that progression of airflow obstruction in smokers is associated with mucous plugs in the lumen of small airways. Epithelial mucin stores were not quantified, but several other remodeling changes in the small airways of smokers were described,22specifically thickening of the airway wall. These findings and our own lead us to consider that increased epithelial mucins in smokers may occur in the context of other remodeling changes—such as collagen deposition—that can affect airflow. The time course for the development of epithelial and mesenchymal remodeling in smokers may differ, however. For example, one possibility is that smoking-induced changes in epithelial mucins occur early, promote epithelial cell activation, and thereby initiate mesenchymal remodeling directed by epithelial cell mediators.23

Goblet cells are not the only source of mucins in the airway. Mucous cells in submucosal glands also contribute mucins to airway secretions, and enlargement of submucosal glands has been found in autopsy studies of patients with COPD.4,24 However, it is unknown if changes in submucosal glands occur in smokers with only mild airway disease such as those described here, or if the goblet cell changes we observed may occur independently of changes in submucosal glands. These questions were not addressed by our study.

Whether the smoking-associated changes in epithelial mucin stores and epithelial mucin gene expression that we have observed are reversible is uncertain. The Lung Health Study25found that symptoms of cough and sputum production in smokers with chronic bronchitis improve during the first year after smoking cessation. Similarly, cytologic examination of tracheobronchial cells in the sputum of smokers entering a smoking cessation program suggested a decrease in sputum mucus and mucous cell metaplasia in sustained quitters over the course of 1 year.26 On the basis of those results, one might speculate that goblet cell hypertrophy and hyperplasia improve over a similar time course with smoking cessation; however, we are not aware of any studies that have studied this directly.

In summary, we find that the airway epithelium of habitual cigarette smokers is characterized by hypertrophy and hyperplasia of goblet cells leading to increased stores of gel-forming mucins. In addition, the pattern of expression of gel-forming mucins is abnormal in smokers, with an increase in MUC5AC and a decrease in MUC5B. Finally, the levels of stored mucins in the epithelium are highest in smokers with airflow obstruction, suggesting a mechanistic link between epithelial mucin dysregulation and airflow obstruction. Such a link raises the possibility that therapies that normalize epithelial mucins may improve airflow obstruction in smokers.

Abbreviations: Dlco = single-breath diffusing capacity for carbon monoxide; PC20 = provocative concentration of methacholine resulting in 20% decrease in FEV1 from baseline value

Drs. Innes and Woodruff contributed equally to the article.

This work was performed at the University of California, San Francisco.

The authors have no financial or potential conflicts of interest.

Financial support was provided by an RO1 grant (HL66564) to Dr. Fahy from the National Heart, Lung, and Blood Institute, and by a K23 award (RR17002) to Dr. Woodruff from the National Center for Research Resources. In addition, Dr. Innes was supported by an institutional training grant (HL-07185) from the National Heart, Lung, and Blood Institute.

Table Graphic Jump Location
Table 1. Baseline Clinical Characteristics of the Nonsmoking Control Subjects and Cigarette Smokers*
* 

Data are mean ± SD or median (range) unless otherwise indicated. BD = bronchodilator.

 

p < 0.05 vs healthy control subjects by t test.

 

p < 0.002 vs healthy control subjects by rank-sum test.

Table Graphic Jump Location
Table 2. Clinical Characteristics of Smoker Subgroups*
* 

Data are presented as mean ± SD or median (range) unless otherwise indicated. Airway obstruction is defined as postbronchodilator FEV1/FVC < 0.70.

 

p = 0.09 vs smokers without obstruction by t test.

 

p < 0.05 vs smokers without obstruction by t test.

§ 

p = 0.05 vs smokers without obstruction by rank-sum test.

Table Graphic Jump Location
Table 3. Epithelial Layer Height, Mucin Stores, Goblet Cell Characteristics, and Mucin Protein Immunohistochemistry in the Airway Epithelium of Healthy Subjects and Cigarette Smokers*
* 

Data are presented as mean ± SEM.

Figure Jump LinkFigure 1. Photomicrographs of representative sections from endobronchial biopsies from healthy subjects (left panels) and smokers (right panels). Mucin stores in goblet cells appear as a mixture of blue and purple when stained sequentially with Alcian-blue and periodic acid-Schiff stains (top left, A and top right, B). Note that mucin staining in the epithelium is more prominent than normal in smokers because of goblet cell hypertrophy and hyperplasia. Different gel-forming mucins detected with specific antibodies appear as brown immunostains (center left, C through bottom right, F). MUC5AC immunostain is higher than normal in smokers (center left, C and center right, D), whereas MUC5B immunostains are lower than normal (bottom left, E and bottom right, F). Sizebar = 20 μm; original × 2,000.Grahic Jump Location
Figure Jump LinkFigure 2. The volume of stored mucin per surface area of basal lamina in the bronchial epithelium of healthy subjects and smokers (left) and in the subgroups of smokers with (n = 9) and without (n = 15) airflow obstruction (right). Data are presented as mean ± SE.Grahic Jump Location
Table Graphic Jump Location
Table 4. Relationship Between Epithelial Mucin Stores and Lung Function (Postbronchodilator FEV1/FVC) in Smokers
* 

Age, gender, pack-years of smoking, PC20.

Table Graphic Jump Location
Table 5. Expression Profile of Gel-Forming Mucins in Bronchial Epithelial Brushings From Smokers and Healthy Control Subjects*
* 

Data are presented mean transcript copy No. × 103 ± SEM.

The authors thank the following staff at University of California, San Francisco for assistance with this study: Peggy Cadbury and Hofer Wong for recruiting subjects and for assistance with bronchoscopy; and Roderick Carter and Ronald Ferrando for assistance in tissue processing and analysis. The authors also thank Mimi Zeiger for editing the manuscript and Ingemar Carlstedt for the generous contribution of the monoclonal antibodies LUM2-3 and LUM5B-2.

Fahy, JV (2003) Airway mucus and the mucociliary system. Adkinson, NF Bochner, BS Yunginger, JWet al eds.Allergy principles and practice,741-757 Mosby. Philadelphia, PA:
 
Vestbo, J, Hogg, JC Convergence of the epidemiology and pathology of COPD.Thorax2006;61,86-88. [PubMed]
 
Thurlbeck, WM, Angus, GE The relationship between emphysema and chronic bronchitis as assessed morphologically.Am Rev Respir Dis1963;87,815-819. [PubMed]
 
Reid, LM Pathology of chronic bronchitis.Lancet1954;266,274-278. [PubMed]
 
Saetta, M, Turato, G, Baraldo, S, et al Goblet cell hyperplasia and epithelial inflammation in peripheral airways of smokers with both symptoms of chronic bronchitis and chronic airflow limitation.Am J Respir Crit Care Med2000;161,1016-1021. [PubMed]
 
Saetta, M, Turato, G, Facchini, FM, et al Inflammatory cells in the bronchial glands of smokers with chronic bronchitis.Am J Respir Crit Care Med1997;156,1633-1639. [PubMed]
 
Fletcher, CM, Peto, R, Tinker, CM, et al. The natural history of chronic bronchitis and emphysema. 1976; Oxford University Press. New York, NY:.
 
Vestbo, J, Prescott, E, Lange, P Association of chronic mucus hypersecretion with FEV1decline and chronic obstructive pulmonary disease morbidity: Copenhagen City Heart Study Group.Am J Respir Crit Care Med1996;153,1530-1535. [PubMed]
 
Banerjee, D, Khair, OA, Honeybourne, D Impact of sputum bacteria on airway inflammation and health status in clinical stable COPD.Eur Respir J2004;23,685-691. [CrossRef] [PubMed]
 
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Anthonisen, NR The British hypothesis revisited.Eur Respir J2004;23,657-658. [CrossRef] [PubMed]
 
Jeffery, PK Remodeling in asthma and chronic obstructive lung disease.Am J Respir Crit Care Med2001;164,S28-S38. [PubMed]
 
O’Donnell, RA, Richter, A, Ward, J, et al Expression of ErbB receptors and mucins in the airways of long term current smokers.Thorax2004;59,1032-1040. [CrossRef] [PubMed]
 
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Hays, SR, Woodruff, PG, Khashayar, R, et al Allergen challenge causes inflammation but not goblet cell degranulation in asthmatic subjects.J Allergy Clin Immunol2001;108,784-790. [CrossRef] [PubMed]
 
Woodruff, PG, Dolganov, GM, Ferrando, RE, et al Hyperplasia of smooth muscle in mild to moderate asthma without changes in cell size or gene expression.Am J Respir Crit Care Med2004;169,1001-1006. [CrossRef] [PubMed]
 
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Dolganov, GM, Woodruff, PG, Novikov, AA, et al A novel method of gene transcript profiling in airway biopsy homogenates reveals increased expression of a Na+-K+-Cl- cotransporter (NKCC1) in asthmatic subjects.Genome Res2001;11,1473-1483. [CrossRef] [PubMed]
 
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Hogg, JC, Chu, F, Utokaparch, S, et al The nature of small-airway obstruction in chronic obstructive pulmonary disease.N Engl J Med2004;350,2645-2653. [CrossRef] [PubMed]
 
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Figures

Figure Jump LinkFigure 1. Photomicrographs of representative sections from endobronchial biopsies from healthy subjects (left panels) and smokers (right panels). Mucin stores in goblet cells appear as a mixture of blue and purple when stained sequentially with Alcian-blue and periodic acid-Schiff stains (top left, A and top right, B). Note that mucin staining in the epithelium is more prominent than normal in smokers because of goblet cell hypertrophy and hyperplasia. Different gel-forming mucins detected with specific antibodies appear as brown immunostains (center left, C through bottom right, F). MUC5AC immunostain is higher than normal in smokers (center left, C and center right, D), whereas MUC5B immunostains are lower than normal (bottom left, E and bottom right, F). Sizebar = 20 μm; original × 2,000.Grahic Jump Location
Figure Jump LinkFigure 2. The volume of stored mucin per surface area of basal lamina in the bronchial epithelium of healthy subjects and smokers (left) and in the subgroups of smokers with (n = 9) and without (n = 15) airflow obstruction (right). Data are presented as mean ± SE.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. Baseline Clinical Characteristics of the Nonsmoking Control Subjects and Cigarette Smokers*
* 

Data are mean ± SD or median (range) unless otherwise indicated. BD = bronchodilator.

 

p < 0.05 vs healthy control subjects by t test.

 

p < 0.002 vs healthy control subjects by rank-sum test.

Table Graphic Jump Location
Table 2. Clinical Characteristics of Smoker Subgroups*
* 

Data are presented as mean ± SD or median (range) unless otherwise indicated. Airway obstruction is defined as postbronchodilator FEV1/FVC < 0.70.

 

p = 0.09 vs smokers without obstruction by t test.

 

p < 0.05 vs smokers without obstruction by t test.

§ 

p = 0.05 vs smokers without obstruction by rank-sum test.

Table Graphic Jump Location
Table 3. Epithelial Layer Height, Mucin Stores, Goblet Cell Characteristics, and Mucin Protein Immunohistochemistry in the Airway Epithelium of Healthy Subjects and Cigarette Smokers*
* 

Data are presented as mean ± SEM.

Table Graphic Jump Location
Table 4. Relationship Between Epithelial Mucin Stores and Lung Function (Postbronchodilator FEV1/FVC) in Smokers
* 

Age, gender, pack-years of smoking, PC20.

Table Graphic Jump Location
Table 5. Expression Profile of Gel-Forming Mucins in Bronchial Epithelial Brushings From Smokers and Healthy Control Subjects*
* 

Data are presented mean transcript copy No. × 103 ± SEM.

References

Fahy, JV (2003) Airway mucus and the mucociliary system. Adkinson, NF Bochner, BS Yunginger, JWet al eds.Allergy principles and practice,741-757 Mosby. Philadelphia, PA:
 
Vestbo, J, Hogg, JC Convergence of the epidemiology and pathology of COPD.Thorax2006;61,86-88. [PubMed]
 
Thurlbeck, WM, Angus, GE The relationship between emphysema and chronic bronchitis as assessed morphologically.Am Rev Respir Dis1963;87,815-819. [PubMed]
 
Reid, LM Pathology of chronic bronchitis.Lancet1954;266,274-278. [PubMed]
 
Saetta, M, Turato, G, Baraldo, S, et al Goblet cell hyperplasia and epithelial inflammation in peripheral airways of smokers with both symptoms of chronic bronchitis and chronic airflow limitation.Am J Respir Crit Care Med2000;161,1016-1021. [PubMed]
 
Saetta, M, Turato, G, Facchini, FM, et al Inflammatory cells in the bronchial glands of smokers with chronic bronchitis.Am J Respir Crit Care Med1997;156,1633-1639. [PubMed]
 
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