Pilot Gene Expression and Histopathologic Analysis of Tracheal Resections in Tracheobronchomalacia

The airway structures and messenger RNA expression of genes that regulate airway inflammation and remodeling may be altered in the trachea of patients with tracheobronchomalacia (TBM).

Fourteen tracheal specimens obtained from 2005 to 2018 were used in this study. Surgical resection specimens from patients with TBM and tracheal stenosis (TS) were compared with control tracheal specimens obtained from autopsy cases. We investigated the messenger RNA expression of genes encoding fibroblast growth factor (FGF) binding protein 2 (FGFBP2), FGF receptor R3 (FGFR3), interleukin-1β (IL1β), tumor growth factor-β1 (TGFβ1), tissue inhibitor of metalloproteinases 1 (TIMP1), and intercellular adhesion molecule 1 (ICAM1) as well as established markers of airway inflammation including interferon-γ (IFNγ) and tumor necrosis factor (TNF). The relative expression of target transcripts was assessed by quantitative real-time polymerase chain reaction. A histologic examination of the same resected airway specimens was performed on formalin-fixed paraffin-embedded tissue sections.

FGFBP2 and FGFR3 showed higher expression in TBM compared with TS and control groups (P < .05 and P < .01, respectively). Furthermore, both TGFβ1 and TIMP1 were elevated in TBM patients compared with control subjects (P < .05). Conversely ICAM1 was downregulated in TBM versus TS and control subjects (P < .05). IL1β, IFNγ, and TNF were increased in TBM, although it did not achieve statistical significance. Histologically compared with control airways both TBM and TS demonstrated submucosal fibrotic changes, with TBM additionally demonstrating alterations in elastin fiber quality and density in the posterior membrane.

Significant changes in gene expression are observed in the tracheal walls of patients with TBM and TS compared with control subjects.