The Impact of Estrogen on Stromal Elements in the Proximal Airway in Idiopathic Subglottic Stenosis.

OBJECTIVES: Idiopathic subglottic stenosis (iSGS) is an unexplained fibrosis of the proximal airway that predominantly impacts Caucasian women. Clinically, premenopausal patients suffer from higher recurrence rates, potentially implicating ovarian hormone 17B-estradiol (E2) in disease pathogenesis. Despite its relationship with disease phenotype and severity, the mechanistic role of E2 in subglottic fibrosis has not been investigated. METHODS: Primary human cell lines derived from the airway scar of iSGS patients were utilized for in vitro study to assess the impact of E2 on proximal airway cells (fibroblasts, epithelial cells, and endothelial cells). Alterations in RNA and extracellular matrix protein expression were assessed in fibroblasts (n = 5 primary cell lines) following E2 exposure. The impact of E2 on epithelial barrier function was assessed via transepithelial electrical resistance measurement (TEER) in iSGS-patient-derived epithelial primary cell lines (n = 3) grown via air-liquid interface (ALI) culture. The impact of E2 on iSGS-patient-derived endothelial lines was assessed using a Matrigel-based tube formation assay. RESULTS: There were no significant transcriptional changes induced in fibroblasts after exposure to E2 when compared to controls, nor was a difference in collagen production observed after E2 exposure. There was no significant difference in TEER measurements in airway epithelial cells grown at ALI following E2 exposure. Endothelial cells showed a significant increase in tube formation following E2 exposure. CONCLUSION: In vitro models suggest E2 may have limited direct impact on fibroblasts and epithelial cells in iSGS. Instead, estrogen acts directly on airway endothelial cells to drive vascular remodeling, potentially contributing to mucosal fibrosis. LEVEL OF EVIDENCE: NA.