Reticular basement membrane in asthma and COPD: Similar thickness, yet different composition

Jeroen JW Liesker1, Nick H Ten Hacken1, Mieke Zeinstra-Smith2, Steven R Rutgers1, Dirkje S Postma1, Wim Timens21Department of Pulmonology; 2Department of Pathology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands Background: Reticular basement membrane (RBM) thickening has been variably associated with asthma and chronic obstructive pulmonary disease (COPD). Even if RBM thickness is similar in both diseases, its composition might still differ. Objective: To assess whether RBM thickness and composition differ between asthma and COPD. Methods: We investigated 24 allergic asthmatics (forced expiratory volume in one second [FEV1] 92% predicted), and 17 nonallergic COPD patients (FEV1 60% predicted), and for each group a control group of similar age and smoking habits (12 and 10 persons, respectively). Snap-frozen sections of bronchial biopsies were stained with hematoxylin/eosin and for collagen I, III, IV, V, laminin and tenascin. RBM thickening was assessed by digital image analysis. Relative staining intensity of each matrix component was determined.Results: Mean (SD) RBM thickness was not significantly different between asthma and COPD 5.5 (1.3) vs 6.0 (1.8) μm, but significantly larger than in their healthy counterparts, ie, 4.7 (0.9) and 4.8 (1.2) μm, respectively. Collagen I and laminin stained significantly stronger in asthma than in COPD. Tenascin stained stronger in asthma than in healthy controls of similar age, and stronger in COPD controls than in asthma controls (p 0.05).Conclusion: RBM thickening occurs both in asthma and COPD. We provide supportive evidence that its composition differs in asthma and COPD. Keywords: reticular basement membrane thickness, reticular basement membrane composition, asthma, biopsy, COPD, remodelin

Change in inflammation in out-patient COPD patients from stable phase to a subsequent exacerbation

BACKGROUND: Inflammation increases during exacerbations of COPD, but only a few studies systematically assessed these changes. Better identification of these changes will increase our knowledge and potentially guide therapy, for instance by helping with quicker distinction of bacterially induced exacerbations from other causes. AIM: To identify which inflammatory parameters increase during COPD exacerbations compared to stable disease, and to compare bacterial and non-bacterial exacerbations. METHODS: In 45 COPD patients (37 male/8 female, 21 current smokers, mean age 65, FEV(1) 52% predicted, pack years 38) sputum was collected during a stable phase and subsequently during an exacerbation. RESULTS: Sputum total cell counts (9.0 versus 7.9 x 10(6)/mL), eosinophils (0.3 versus 0.2 x 10(6)/mL), neutrophils (6.1 versus 5.8 x 10(6)/mL), and lymphocytes (0.07 versus 0.02 x 10(6)/mL) increased significantly during an exacerbation compared to stable disease. A bacterial infection was demonstrated by culture in 8 sputum samples obtained during an exacerbation. These exacerbations had significantly increased sputum total cell and neutrophil counts, leukotriene-B4, myeloperoxidase, interleukin-8 and interleukin-6, and tumor necrosis factor-alpha (TNF-alpha) levels, and were also associated with more systemic inflammation compared to exacerbations without a bacterial infection. Sputum TNF-alpha level during an exacerbation had the best test characteristics to predict a bacterial infection. CONCLUSION: Sputum eosinophil, neutrophil, and lymphocyte counts increase during COPD exacerbations. The increase in systemic inflammation during exacerbations seems to be limited to exacerbations caused by bacterial infections of the lower airways. Sputum TNF-alpha is a candidate marker for predicting airway bacterial infection