Establishment and verification of the mouse model of pulmonary fibrosis induced by bleomycin

Objective To investigate the change of molecular biology and histopalhology in the different periods of pulmonary fibrosis model induced by instillation of bleomycin(BLM).Methods Lung fibrosis was induced by a single intratracheal instillation of bleomycin(2.5 mg/kg) in C57BL/6 female mice of 6 to 8 weeks.To judge the development of pulmonary fibrosis of the mouse model,lung samples were collected from these mice to measure the gene expression,collagen content and histopathological status.Results Mice in the normal control group shown no significant changes in lung tissues.But infiltration of the lymphocytes into the mice lung interstitial,thickening of the alveolar septa,collapse of the alveolar spaces, and excessive deposition of collagen were observed in the bleomycin treated mice lungs.The mRNA levels of IL-4,IL-13 were examined to assess the inflammation status.The mRNA level of IL4,IL-13 was enhanced by bleomycin.Correspondingly, the expression levels of Colla2,Col3a1,connective tissue growth factor(CTGF) and transforming growth factor-β_1(TGF-β_1) were higher than the normal group.The results are concordant with that of pathological findings.Conclusion Pulmonary fibrosis model could successfully establish by a single intratracheal instillation of bleomycin.At the early stage after the administration of BLM,the inflammatory response was acute and this response last about one week,and then followed by fibrogenic changes,and in the third week,pulmonary fibrosis was most significant,but the fibrosis has been eased by the fifth week.