Recent studies have associated osteopontin (OPN) with allergic inflammation; however, its role in human asthma remains unclear. The aim of this study was to measure OPN levels in the serum, bronchoalveolar lavage fluid (BALF) and bronchial tissue of healthy controls and asthmatics, identify cellular sources of OPN and examine possible correlations between OPN expression, disease severity and airway remodelling.
Serum samples were obtained from 35 mild-to-moderate asthmatics, 19 severe asthmatics and 17 healthy controls in the steady state and in cases of exacerbation. Of these subjects, 29 asthmatics and nine controls underwent bronchoscopy with endobronchial biopsy and BALF collection. OPN expression was determined by ELISA and immunohistochemistry/immunofluorescence. Reticular basement membrane thickness and goblet cell hyperplasia were also determined.
Serum and BALF OPN levels were significantly increased in all asthmatics in the steady state, whereas serum levels decreased during exacerbations. OPN was upregulated in the bronchial tissue of all patients, and expressed by epithelial, airway and vascular smooth muscle cells, myofibroblasts, T-lymphocytes and mast cells. OPN expression correlated with reticular basement membrane thickness and was more prominent in subepithelial inflammatory cells in severe compared to mild-to-moderate asthma.
OPN expression is upregulated in human asthma and associated with remodelling changes, and its subepithelial expression correlates with disease severity.
K. Samitas was funded by a European Academy of Allergy and Clinical Immunology (Zurich, Switzerland) fellowship. G. Xanthou and V. Panoutsakopoulou are supported by the Hellenic Ministries of Health (Athens, Greece) and Education (Marousi, Greece), and V. Panoutsakopoulou by a grant award (03ED750) from the General Secretariat for Research and Technology of the Hellenic Ministry of Development (Athens, Greece). A. Bossios and J. Lötvall are funded by the VBG GROUP Centre for Asthma and Allergy Research (Vänersborg, Sweden) and the Swedish Heart and Lung Foundation (Stockholm, Sweden; project No. 20070575).
Statement of Interest
Statements of interest for M. Gaga, K. Samitas and E. Zervas and the study itself can be found at www.erj.ersjournals.com/site/misc/statements.xhtml
- Received February 2, 2010.
- Accepted May 28, 2010.
- ©ERS 2011