Establishment of a Rat Model of Pulmonary Fibrosis

Rats were randomly divided into pulmonary fibrosis group and control group (n = 3 per group). We established a rat model of pulmonary fibrosis by means of BLM administration as previously described.⁴ Briefly, the pulmonary fibrosis group received a single intratracheal instillation of 5 mg/kg BLM (Bleomycin Hydrochloride for Injection, Nippon Kayaku, Tokyo, Japan) diluted in saline solution. Control group was instilled with the same volume of saline instead. All instillations were performed on rats anesthetized with 2% pentobarbital sodium (0.225 mL/kg). At day 21 after instillation, all rats were used for PET/CT imaging with [¹⁸F]ML-8. After PET/CT scans, these rats were sacrificed under deep anesthesia, and lung tissues were collected for further histopathological analysis. Half of the lung was fixed in 4% paraformaldehyde for Masson trichrome staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining. The remaining half of the lung was prepared for flow cytometry and lung hydroxyproline content measurement.