Abstract Objective The therapeutic effect of umbilical cord-derived mesenchymal stem cells (hUC-MSCs) in combination with pirfenidone (PFD) on pulmonary fibrosis in mice and its possible mechanism were investigated. Methods C57BL/6 mice were randomly divided into six groups: control group, model group, P10 group, P30 group, P100 group, and P300 group. Modeled by tracheal intubation with 3 mg/kg bleomycin drip, each dose of PFD was administered daily by gavage from day 7 onwards. The mice were...