Objective To study the possible mechanisms of marrow mesenchymal stem cells(MSC) in therapy of bleomycin(BLM)-induced pulmonary fibrosis in rats. Methods Fifty-four female Wistar rats were randomly divided into a control group,a BLM group and a MSC group. The control group receivel intratracheal normal Objective To study the possible mechanisms of marrow mesenchymal stem cells (MSC) in therapy of bleomycin (BLM) -induced pulmonary fibrosis in rats. Methods Fifty-four female Wistar rats were randomly divided into a control group, a BLM group and a MSC group The control group receivel intratracheal normal