Hypoxia-preconditioned mesenchymal stem cell transplantation reduces pulmonary collagen deposition and fibrosis-related genes expression in the bleomycin-induced pulmonary fibrosis mouse model. (A,B) Quantitative real-time RT-PCR was performed to analyze the expression of fibrotic indicators (A) connective tissue growth factor (CTGF) and (B) collagen type III (Col III) in the lung tissues of mice that received normoxia-preconditioned mesenchymal stem cells (NP-MSCs), hypoxia-preconditioned mesenchymal stem cells (HP-MSCs) or phosphate-buffered saline (PBS) for 18 days following bleomycin (BLM) administration on day 3. Values are normalized to the GAPDH gene and are expressed relative to the PBS group. (C) Total collagen content of whole lung tissues from each group was determined by Sircol Collagen Assay. *P < 0.05, ***P < 0.001; n ≥ 5. (D) Western blot analysis of hepatocyte growth factor (HGF) in whole lung tissues from each group.