Discussion
The epithelium of the nasal airway is inhabited by basal, ciliated, and secretory epithelial cells Similar to epithelium of bronchial airway.19 As such, the nasal airway provides an readily accessible counterpart to the bronchial airway and may represent much of the pathology present in the bronchial asthmatic airway. In the Support of this, roughly 2300 genes expression study in nasal and bronchial airway brushings revealed a close association between these 2 airway sites. 20
The decision to perform our research on upper rather than the lower airway epithelium was inspired by its non-invasive sampling, which is readily applicable in young children. It helps recruiting true pulmonary disease-free controls, a circumstance which is simply not possible in researches using bronchoscopic specimen 21.It also helps patients with severe or uncontrolled asthma phenotypes to be investigated without stopping their long-term inhaled corticosteroid therapy for asthma, because nasal deposition can be considered as negligible with the tools used in this study.