Abstract: ObjectiveTo analyze the optimal time course and relevant molecular mechanism of recombinant human angiopoietin1 (rHuANG1) in the treatment of pulmonary fibrosis in mice. MethodsThe model of pulmonary fibrosis was established on C57/BL6 mice. And 40 mice were subdivided into NS group and rHuANG1 group (20 mice per group). NS group experienced treatment of intraperitoneal injection NS  0.2 ml/d， while rHuANG1 group was treated rHuANG1 for 5 mg·kg-1·d-1. The samples of 5 mice were obtained at d2，d4，d6 and d9 after treatment in NS group and rHuANG1 group， respectively. Regulator of Gprotein signaling 5(RGS5) was estimated by ELISA in lung. Results①The pulmonary fibrosis model on C57/BL6 mice was established successfully. ②Hydroxyprolinc in the lung of NS group and rHuANG1 group at d6  and d9 reduced significantly(P<0.01). ③ ELISA results indicated the expression of RGS5 in the lung of rHuANG1 group at d4 and d6 increased as compared with that of NS group(P<0.05). ④HE staining results showed that different degrees of pulmonary fibrosis were observed at different periods. The degree of necrosis in NS group was higher than that of rHuANG1 group. Among them， tissue repair in rHuANG1 group was more obvious at d4 and d6， while NS group did not present the same result at the corresponding time. ⑤The results of immunohistochemistry assay showed that the expression of VEGF in rHuANG1 group had significalnt decrease at d4 and d6 as compared with that of in NS group(P<0.05).ConclusionrHuANG1 could have positive effect on pulmonary fibrosis model of C57/BL6 mice. The time d4d6 was considered as a brief normalized time window due to the normalization of VEGF.

Key words: pulmonary fibrosis, human angiopoietin1, regulator of Gprotein signaling 5, vascular endothelial growth factors