Kinetics of pathologic changes in bleomycin-induced murine pulmonary fibrosis model

AIM: To Investigate the kinetics of pathologic changes in bleomycin-induced pulmonary fibrosis in rats.METHODS: Sixty male SD rats were randomized as a negative control group and pulmonary fibrosis model groups(B3,B7,B14,B28,B56 sub-groups).Except for control group,rats in the other groups were intratracheally administered with bleomycin.Animals in pulmonary fibrosis model groups were sacrificed on day 3,7,14,28 and 56.The sections of the right lung were stained by HE,Masson and sirius red.The left lung was weighed and its hydroxyproline content was assayed.The mRNAs of TGF-β1,MMP-9 and TIMP-1 in the lung homogenate were measured by semi-quantitative RT-PCR.The expressions of TGF-β1,MMP-9 and TIMP-1 in lungs were observed by immunohistochemistry.RESULTS:(1) The content of lung hydroxyproline in pulmonary fibrosis model groups was significantly increased than that in control group(P0.05).The pulmonary inflammation in pulmonary fibrosis model groups was significantly serious than that in control group,pulmonary fibrosis in B14,B28 and B56 groups was also significantly serious than that in control group.(2) A small quantity of TGF-β1,MMP-9 and TIMP-1mRNA were measured in normal lung,and the expression increased significantly after administration of bleomycin.Different expressions of TGF-β1,MMP-9 and TIMP-1 in different days after bleomycin administration were observed.CONCLUSION: The pathological changes in different days after bleomycin administration are different.TGF-β1,MMP-9 and TIMP-1 may play important roles in the pathogenesis of pulmonary fibrotic process.