Expression of matrix proteins in an in vitro model of airway remodeling in asthma

Acute asthma is characterized by a decrease in the pH of the exhaled breath condensate and bronchoconstriction. These perturbations may injure the epithelium in a chronic, intermittent pattern, leading to subepithelial fibrosis. We used an in vitro three-dimensional model of the bronchial mucosa to elucidate the response to a repeated chemical or physical insult to the epithelium in the postcontraction phase. We used enzyme-linked immunosorbent assay and reverse transcriptase - polymerase chain reaction to assess the production of the following proteins: matrix metalloproteinase (MMP) 3, MMP-9, tissue inhibitor of MMP-1, transforming growth factor β₁, thrombospondin 1, tenascin, and fibronectin. The presence of the epithelium enhanced the degree of tissue contraction (50.1 ± 4.4% of original area versus 75.4 ± 2.3%). In the absence of injury, tenascin, fibronectin, MMP-3, and tissue inhibitor of MMP-1 are actively expressed. However, the chronic chemical wound markedly inhibited the expression of all proteins. We conclude that the epithelium, wound type, and age of the tissue (contracting versus postcontraction) impact the expression of key proteins in an in vitro model of subepithelial fibrosis in asthma.