The main purpose of the present study was to develop a respirable
powder (RP) formulation of
bleomycin (BLM) as a research tool for developing a
pulmonary fibrosis animal model. The BLM-RP was prepared with a jet-milling system, the physicochemical properties of which were characterized focusing on morphology, stability, particle size distribution, and inhalation performance. Under an accelerated condition, the BLM-RP was superior to BLM
solution in terms of its stability. Cascade impactor analyses demonstrated high inhalation performance with emitted dose and fine particle fraction of approximately 99% and 46%, respectively. Intratracheal administration of the BLM-RP (3 mg BLM/kg) in rats led to significant increases in
collagen production and recruitment of inflammatory cells in lung by approximately 1.5- and 29-fold, respectively. The
collagen overexpression was consistent with the results from
picrosirius red staining of lung tissues in the rats treated with BLM-RP. Inhaled
tranilast (TL; 100 μg/rat), an antifibrotic agent, could ameliorate inflammatory/fibrotic responses with reductions of recruited inflammatory cells and
collagen content by 32% and 59%, respectively, validating the
pulmonary fibrosis animal model. From these findings, the BLM-RP with improved stability could be a beneficial research tool for developing a
pulmonary fibrosis model in
drug discovery for antifibrotic
drug candidates.