A Refined Aerosol-Based Intratracheal Bleomycin Delivery Method for Reproducible and Minimally Invasive Mouse Models of Pulmonary Fibrosis

Pulmonary fibrosis is characterized by progressive deposition of fibrotic scar tissue within the lung parenchyma, leading to severely impaired gas exchange. It underlies a spectrum of chronic interstitial lung diseases, notably idiopathic pulmonary fibrosis, a condition associated with an exceedingly poor prognosis. Given the lack of effective therapies, robust mouse models are critical for elucidating underlying pathological mechanisms and evaluating novel antifibrotic interventions. Bleomycin-induced pulmonary fibrosis remains the most extensively utilized experimental model. Common routes of administration in mice include intravenous and intraperitoneal injections, invasive open-tracheal instillation, and noninvasive tracheal dripping. However, invasive surgical methods often cause secondary tissue injury, potentially compromising model reproducibility and stability. Conversely, noninvasive tracheal dripping usually results in uneven bleomycin distribution across lung lobes and poses a risk of asphyxiation, thus reducing reproducibility and increasing technical challenges. To address these limitations, a refined aerosol-based intratracheal delivery method is developed that is operationally simpler, minimally invasive, highly reproducible, and ethically superior by significantly reducing animal distress. Using a small-animal laryngoscope to visualize the rima glottidis directly, a specialized aerosolizing needle is inserted into the trachea, markedly narrower than the mouse tracheal diameter. Bleomycin solution is delivered under precisely controlled pressure, generating a fine aerosol. This ensures uniform and efficient distribution of the agent throughout the lung parenchyma. Moreover, one can selectively target the left or right lung by directing the needle into the appropriate bronchus. This optimized model's dose-response relationship is extensively characterized by systematically monitoring changes in lung function, histopathological manifestations, and lung hydroxyproline content. This refined experimental protocol is anticipated to facilitate laboratory standardization, ultimately accelerating the development and preclinical validation of novel antifibrotic therapeutics.