Involvement of Fibronectin and Matrix Metalloproteinases in Airway Smooth Muscle Cell Migration for the Process of Airway Remodeling

ABSTRACT: Background: Airway remodeling is a repair process occurring after airway injury; its primary histopathological features are subepithelial fibrosis and smooth muscle thickening of the bronchi. These histopathological changes are considered to occur due to bronchial smooth muscle cells (bSMC) that secrete extracellular matrix (ECM) proteins, which work as chemoattractants and influence cell migration. Therefore, we examined the interaction between bSMCs and ECM proteins in vitro for understanding the remodeling process in the bronchi. Methods: bSMCs were cultured to collect a bSMC-conditioned medium. Using the bSMC-conditioned medium thus obtained, we performed a cell migration assay, characterized p integrin expression, and identified ECM proteins and matrix metalloproteinases by western blotting and gelatin zymography, respectively. Results: The response of bSMC migration to bSMC-conditioned medium increased with time in culture, and fibronectin (FIB) was detected as a chemoattractant for bSMCs in bSMC-conditioned medium by western blot analysis and a cell migration assay using anti-FIB antibodies. The involvement of p1 integrin in the migration of bSMCs toward FIB contained in bSMC-conditioned medium was demonstrated by inhibition of cell migration using anti-p1 integrin antibodies. Expression of p1 integrin on bSMCs was confirmed by using a p-integrinmediated cell adhesion array. In addition, metalloproteinases detected in bSMC-conditioned medium by gelatin zymography were suggested to be matrix metalloproteinase-1 and 2 by western blotting and amino acid sequencing. Conclusions: Our results suggest that FIB and matrix metalloproteinases secreted from bSMCs might play major roles in bSMC migration in the process of airway remodeling. KEY WORDS: airway remodeling, cell migration, fibronectin, matrix metalloproteinases, smooth muscle cell