Research

Myofibroblast expression in airways and alveoli is affected by smoking and COPD

Henna M Karvonen, Siri T Lehtonen, Terttu Harju, Raija T Sormunen, Elisa Lappi-Blanco,Johanna M Mäkinen, Kirsi Laitakari, Shirley Johnson and Riitta L Kaarteenaho

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Respiratory Research 2013, 14:84 doi:10.1186/1465-9921-14-84

Published: 11 August 2013

Abstract (provisional)

Background

Chronic obstructive pulmonary disease (COPD) is characterized by structural changes in alveoli and airways. Our aim was to analyse the numbers of alpha-smooth muscle actin (alpha-SMA) positive cells, as a marker of myofibroblasts, in different lung compartments in non-smokers and smokers with normal lung function or COPD.

Methods

alpha-SMA, tenascin-C (Tn-C) and EDA-fibronectin in alveolar level and airways were assayed by immunohistochemistry and quantified by image analysis. Immunohistochemical findings were correlated with clinical data. alpha-SMA protein was also analysed by Western blotting from fibroblastic cells cultured from peripheral lung of non-smokers, smokers without COPD and smokers with COPD.

Results

In many cases, the endings of the detached alveolar walls were widened, the structures of which were named as widened alveolar tips. Widened alveolar tips contained alpha-SMA positive cells, which were obviously myofibroblasts. There were less alveolar tips containing positive cells for alpha-SMA in alveoli and alpha-SMA positive cells in bronchioles in smokers and in COPD compared to non-smokers. The quantity of alpha-SMA positive cells was increased in bronchi in COPD. Tn-C was elevated in bronchi in COPD and smokers' lung. The alpha-SMA protein level was 1.43-fold higher in stromal cells cultured from non-smokers than in those of smokers.

Conclusions

Myofibroblasts are localized variably in normal and diseased lung. This indicates that they have roles in both regeneration of lung and pathogenesis of COPD. The widened alveolar tips, these newly characterized histological structures, seemed to be the source of myofibroblasts at the alveolar level.

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