Disease introduction: Pulmonary fibrosis is the common outcome of a variety of chronic lung diseases, with inflammatory cell infiltration, excessive proliferation of fibroblasts, and excessive collagen deposition as the main pathological features.

　　Experimental animals: C57BL/6 mice (6-8 weeks)

　　Experimental method: 1. After the model rats were anesthetized with inhaled isoflurane, the neck skin was prepared, the neck skin was cut with surgical scissors, the subcutaneous muscles were bluntly 

separated, and the trachea was exposed. 2. A single injection of bleomycin (BLM) into the trachea through a micro-injector to prepare a model. 3. The models were sacrificed 28 days after modeling, and the model was determined by pathological HE staining.