Effect of bone morphogenetic protein-7 on the expression of collagen and transforming growth factor-1 in pulmonary fibrosis rats

Objective To study the effects of bone morphogenetic protein 7 (BMP-7) on the expressions of collagen and transforming growth factor-β1 (TGF-β1) in lung tissues of rats with pulmonary fibrosis.Methods Forty-eight male Wistar rats were randomly divided into four groups with 12 rats in each group:the normal control group,the fibrosis group,the low-dose group,and the high-dose group.Pulmonary fibrosis was induced by intra-bronchial injection of bleomycin A5.Rats in low-dose group and high-dose group were intra-peritoneal injection of BMP-7 with dosages of 100 μtg/kg,500 μtg/kg once daily,respectively.Six rats in each group were sacrificed randomly on the 14 th and 28 th day after bleomycin A5 administration.The histological changes of lung tissue were evaluated by HE and Masson' s trichome stains.The level of tissue hydroxyproline was measured.The type Ⅰ collagen and TGF-β1 protein expressions were analyzed by immunohistochemistry.The TGF-β1 mRNA expression was detected by the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR).Results When treated with BMP-7,pulmonary inflammation and fibrosis were significantly reduced respectively as compared with the fibrosis group on the 14th and 28th day (P ＜0.05).Compared with fibrosis group,BMP-7 could decrease the level of tissue hydroxyproline both on 14th and 28th day (P ＜0.05).And after BMP-7 treatment,the expressions of type Ⅰ collagen and TGF-β1 protein,both on 14th and 28th day,were significantly decreased than that in fibrosis group (P ＜0.05).Also,the TGF-β1 mRNA expression,on 14th and 28th day after BMP-7 treatment,was significantly decreased than that in fibrosis group (P ＜0.05).Above effects of BMP-7 were more obvious in high-dose group than in low-dose group (P ＜ 0.05).Conclusions BMP-7 could suppress bleomycin A5-induced rat pulmonary inflammation and fibrosis in dose-depended manner,with the possible mechanism of inhibiting the deposition of type Ⅰ collagen protein and decreasing the expression of TGF-β1 in lung tissue. Key words: Bone morphogenetic protein-7;  Pulmonary fibrosis;  Transforming growth factor-β1 ;  Collagen