High-Level Expression of Matrix-Associated Transforming Growth Factor-β1 in Benign Airway Stenosis

Study objectivesAcquired tracheal and subglottic stenosis frequently leads to severe airway narrowing, which requires repeated interventions, such as dilatation, laser resection, stent implantation, or surgery. To get a more detailed insight into the pathogenesis of this condition, we investigated the expression of profibrotic cytokines and the proliferation of the airway wall in benign human airway stenoses.MethodsSpecimens from patients with subglottic and tracheal stenosis and stent-related stenoses were obtained (n = 20) for reverse transcription (RT) polymerase chain reaction (PCR) analysis and immunohistochemistry testing.ResultsTransforming growth factor (TGF)-β1 messenger RNA expression was significantly increased in biopsy specimens from stent-related stenoses compared to nonstenotic control sections. In contrast, TGF-β3 and interleukin-1β showed no such differences in messenger RNA expression. Immunohistochemistry revealed a strong matrix-associated, subepithelial expression of TGF-β1 in tracheal stenosis. Proliferating Ki-67-positive cells were mainly localized in the basal epithelial layer. Only 2 of 16 patients with tracheal stenoses and 3 of 4 patients with stent-related stenoses showed a weak expression of Ki-67-positive cells in the subepithelium. Furthermore, TGF-β1 dose-dependently enhanced the proliferation of human lung fibroblasts in vitro, even in the presence of mitomycin-C.ConclusionWhile a weak subepithelial proliferation occurs in stent-related stenoses, the dominant factor in late stages of untreated tracheal stenoses seems to be the high-level expression of TGF-β1 and the deposition of extracellular matrix.