Abstract
Nasal polyposis is a condition characterized by chronic inflammation and structual abnormalities including thickening of the basement menbrane and stromal fibrosis. Myofibroblasts (MF) are fibroblast-like cells with contractile features and thought to express different types of collagen and extracellular matrix, thus contributing to the fibrotic process. A phenotypic hallmark of myofi-broblasts is the expression of α-smooth muscle actin (αSMA). In this study, We used immunohistochemistry applied periodatelysine-paraformaldehyde (PLP) fixed nasal polyp (NP) tissues and fibroblast cell lines from nasal polyps to investigate whether nasal polyps contain myofibroblasts, and topical steroid (ST) treatment affects the expression of the myofibroblast phenotype or not. NP tissues from both ST-treated and STuntreated patients contained a similar number of spindle-shape vimentin positive cells. In contrast, NP tissues from ST-untreated patients contained a substantial number of αSMA positive fibroblasts. The percentage of αSMA positive area/total area except blood vessels in tissues from ST-untreated patients was significantly higher than that in tissues from ST-treated patients (p<0.005). Exposure of fibroblast cell lines from nasal polyps to budesonide (10-10, 10-8, 10-6M) decreased the number of αSMA positive cells in the cultures in a dose-dependent manner. NP tissues from ST-untreated patients, suggesting, taken together with our in vitro results, that this is due, in part, to a direct inhibitory effect of ST on αSMA expression of NP stromal cells.
