ObjectiveTo investigate the effect of pirfenidone (PFD) on tracheal scar stenosis and fibroblast function in rats.Methods20 SD male rats were undergone tracheotomy and tracheal injury surgery to establish tracheal stenosis model, and then randomly divided into two groups. The rats of experimental group (n=10) were fed with PFD capsule powder by gavage at 50 mg/case/day, and those of control group were treated with sterile water at 5 ml/case/day. All rats in both groups were continuously administered for 10 days. Fourteen days after surgery, the thickness of tracheal scar was detected on HE staining, and the expressions of TGFβ1, Collagen I and αSMA in scar tissue were detected by immunohistochemistry. Survival rates of RFL6 cells treated with PFD of different concentrations were measured by CCK8, cell invasion and metastasis ability was determined by scratch and transwell experiments, and protein expression level was detected by Western blot.ResultsHE staining showed that the thickness of tracheal scar of the experimental group was (337.5 ± 33.5) μm, which was significantly lower than that of the control group［(537.0 ± 38.8)μm］(P<0.001). Immunohistochemical results showed that the expression intensities of TGFβ1, Collagen I and αSMA in the experimental group were significantly weaker than those in the control group (all P<0.001). PFD inhibited the growth of RFL6 cells with most obvious effect at the concentration of 1.5 mM (P<0.001). Moreover, PFD reduced the scratch healing of cells and the ability to penetrate the transwell cell (P<0.05). Western blot revealed significantly downregulated expressions of TGFβ1, collagen I and αSMA in RFL6 cells by PFD (all P<0.001).ConclusionPFD can significantly attenuate tracheal scar formation in rats, and inhibit the function of proliferation, transformation, migration, healing and the secretion of extracellular matrix in fibroblasts.