OBJECTIVETo compare two methods of bleomycin administration for inducing lung fibrosis in mice.

METHODSBleomycin (5 mg/kg) was intratracheally instilled or by intratracheal administration of its aerosol (100 µl) in mice. Evans Blue instead of bleomycin was intratracheally administered in the two manners to observe the liquid distribution in the lungs. On Days 14 after bleomycin treatment, the mice were sacrificed and the lungs were removed en bloc to determine the lung coefficient and hydroxyproline concentration, and the histological changes and lung fibrosis were evaluated by HE and Masson's trichrome staining, respectively.

RESULTSEvans Blue intratracheal aerosol distribution in the lung lobes. Intratracheal administration of bleomycin and its aerosol produced no obvious changes in the lung coefficient (P=0.434), and resulted in similar total histopathological scores and fibrosis level in mice (P=0.244 and 0.686, respectively). Bleomycin instillation caused obvious lung injury and lung fibrotic foci with significantly different histological and fibrotic scores between the pulmonary lobes (P=0.016 and 0.038, respectively), while bleomycin aerosol inhalation resulted in similar histological and fibrotic scores in the pulmonary lobes (P=0.466 and 0.29, respectively). A higher level of hydroxyproline was observed in mice with bleomycin aerosol administration (P=0.020).

CONCLUSIONIntratracheal bleomycin instillation and bleomycin aerosol inhalation induce similar levels of fibrosis in the lungs of mice, but the latter causes more extensive and more evenly distributed fibrosis in the lungs.