Distinct central and peripheral airway features in bronchiolitis obliterans and COPD: an observational study.

[BACKGROUND] Bronchiolitis obliterans (BO) and chronic obstructive pulmonary disease (COPD) are both characterized by small airway obstruction. However, their pathogenesis and clinical presentations differ, and the underlying mechanisms of BO remain unclear. This study investigated disease-specific alterations in the small (peripheral) and large (central) airways in BO compared with COPD.

[METHODS] This retrospective single-center study included patients with BO and COPD who underwent lung transplantation and patients with normal spirometry who underwent lobectomy for lung cancer (controls). Central airway tree morphology and peripheral airway pathology, including epithelial composition, were assessed using computed tomography (CT) and histology of resected lung tissue, respectively.

[RESULTS] Patients with BO, COPD, and controls (n = 43, 13, and 17, respectively) exhibited median ages of 24, 52, and 59 years and median % predicted forced expiratory volume in 1 s of 22%, 17%, and 103%, respectively. The airway tree-to-lung volume ratio on CT and epithelial erosion in peripheral airways were greater in patients with BO than in those with COPD and controls, whereas FOXJ1-positive cells, indicating ciliated cells, were fewer. The number of p40-positive cells was greater in COPD than in the other groups. PAS score, representing mucus-producing cells, was lower in the BO group than in the COPD group.

[CONCLUSIONS] Central airway volume and peripheral airway epithelial erosion were greater, with fewer FOXJ1-positive and PAS-positive cells in BO than COPD, despite similar lung function. Central airway dilation and peripheral airway obstruction associated with epithelial erosion and ciliated cell reduction may be key pathological features of BO.