Airway hyperresponsiveness (AHR) has been proposed as a feature of pathogenesis of\neosinophilic upper airway inflammation such as allergic rhinitis (AR). The measurement system for\nupper AHR (UAHR) in rodents is poorly developed, although measurements of nasal resistance\nhave been reported. Here we assessed UAHR by direct measurement of swelling of the nasal\nmucosa induced by intranasal methacholine (MCh) using micro-computed tomography (micro-CT).\nMicro-CT analysis was performed in both naïve and ovalbumin-induced AR mice following intranasal\nadministration of MCh. The nasal cavity was segmented into two-dimensional horizontal and axial\nplanes, and the data for nasal mucosa were acquired for the region of interest threshold. Then, a ratio\nbetween the nasal mucosa area and nasal cavity area was calculated as nasal mucosa index. Using\nour novel method, nasal cavity structure was clearly identified on micro-CT, and dose-dependent\nincreased swelling of the nasal mucosa was observed upon MCh treatment. Moreover, the nasal\nmucosa index was significantly increased in AR mice compared to controls following MCh treatment,\nwhile ovalbumin administration did not affect swelling of the nasal mucosa in either group. This\nUAHR following MCh treatment was completely reversed by pretreatment with glucocorticoids.\nThis novel approach using micro-CT for investigating UAHR reflects a precise assessment system for\nswelling of the nasal mucosa following MCh treatment; it not only sheds light on the mechanism of\nAR but also contributes to the development of new therapeutic drugs in AR patients.
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