Airway Remodeling in Ferrets with Cigarette Smoke Induced COPD using µCT Imaging Supplement File

Abstract 

RATIONALE:  Structural changes to airway morphology such as increased bronchial wall thickness (BWT) and airway wall area are cardinal features of chronic obstructive pulmonary disease (COPD). Ferrets are a recently established animal model uniquely exhibiting similar clinical and pathological characteristics of COPD as humans, including chronic bronchitis.

OBJECTIVES:  Develop a µCT method for evaluating structural changes to the airways in ferrets, and assess whether the effects of smoking induce changes consistent with chronic bronchitis in humans.

METHODS:  Ferrets were exposed to mainstream cigarette smoke or air control twice daily for 6 months.  µCT was conducted in vivo at 6 months; a longitudinal cohort was imaged monthly.  Manual measurements of BWT, luminal diameter (LD), and BWT:LD ratio were conducted, and confirmed by a semi-automated algorithm.  The square root of bronchial wall area (WA) vs. luminal perimeter was determined on an individual ferret basis. 

MEASUREMENTS AND MAIN RESULTS:  Smoke exposed ferrets reproducibly demonstrated 34% increased BWT (P<0.001); along with increased LD, and BWT:LD ratio vs. air controls.  Regression indicated the effect of smoking on BWT persisted despite controlling for covariates.  Semi-automated measurements replicated findings.  WA for the theoretical median airway luminal perimeter of 4 mm (Pi4) was elevated 4.4% in smoke exposed ferrets (P=0.015).  Increased BWT and Pi4 developed steadily over time.

CONCLUSIONS:  µCT-based airway measurements in ferrets are feasible and reproducible.  Smoke exposed ferrets develop increased BWT and Pi4, changes similar to humans with chronic bronchitis.  µCT can be used as a significant translational platform to measure dynamic airway morphological changes.