Objective      To investigate the possible underlying mechanism of mycophenolate mofetil (MMF) in treating bleomycin (BLM)-induced pulmonary fibrosis in mice.       Methods      Thirty-six C57BL/6 mice were randomly divided into 6 groups (n=6 for each group)

including normal control group

MMF control group

BLM model group and MMF treatment groups at low

media and high doses. In 1 d after BLM (6 mg/kg) was intratracheally instilled to the mice from BLM model group and MMF treatment groups

MMF was given orally in the later groups at a dose of 20

60 and 100 mg/kg respectively once per day for 2 weeks. All mice were killed after the treatment

and their lung tissues were collected. Pulmonary fibrosis was evaluated by Ashcroft score after HE and masson trichrome staining. The expression of collagen 1 (COLA1) and COLA2 at mRNA levels was determined by RT-PCR. TGF-β1 protein was analyzed by immunohistochemistry.       Results      BLM-induced pulmonary fibrosis model was successfully constructed. High dose MMF treatment resulted in significant attenuated fibrosis

lower expression of COLA and COLA2 at mRNA level

and decreased TGF-β1 protein (P0.01) when compared with BLM group. No statistic difference was found between the other MMF treatment groups and BLM model groups

MMF control group and normal control group (P0.05).       Conclusion      MMF significantly attenuates BLM-induce pulmonary fibrosis in mice

which may be due to its inhibition of TGF-β1 expression.