Abstract： Objective To investigate the effect of hypoxia-inducible factor 2α (HIF-2α) gene on the expression of Forkhead box M1 (FoxM1) protein in the proliferation of hypoxic rat pulmonary artery smooth muscle cells (PASMC).Methods HIF-2α overexpression lentiviral vector (LV-HIF-2α) and silencing RNA (siRNA) were constructed and transfected into rat PASMC under normoxia and hypoxia,respectively.The PASMC under normoxia were classified into normoxic control group,normoxia + LV-HIF-2α empty group,normoxia + LV-HIF-2α group;the PASMC under hypoxia were classified into hypoxic control group,hypoxia + siRNA-HIF-2α empty group,hypoxia + siRNA-HIF-2α group.The expression of HIF-2α and its downstream proteins FoxM1,cyclin D1 and Aurora A expressions were detected by Western blot.5-Ethyny-2'-deoxyuridine (EdU) cell proliferation assay was used to evaluate the effect of overexpression and inhibition of HIF-2α expression on the proliferation of rat PASMC.Results The expression of HIF-2α in normoxia + LV-HIF-2α group was significantly higher than that in normoxic control group and normoxia+LV-HIF-2α empty group (0.17±0.02 vs 0.09±0.01 and 0.07±0.00),while the expression of HIF-2α in PASMC of hypoxia + siRNA-HIF-2α group was significantly lower than that of hypoxic control group and hypoxia + siRNA-HIF-2α empty group (0.28±0.01 vs 0.35±0.02 and 0.30±0.01) (all P＜0.05);the expression of FoxM! protein,cyclinD1 and cell proliferation-related Aurora A protein in normoxia+ LV-HIF-2α group were significantly higher than that in normoxic control group and normoxia+ LV-HIF-2α empty group (0.40±0.03 vs 0.24±0.01 and 0.30±0.01,0.22±0.02 vs 0.09±0.01 and 0.08±0.02,0.29 ±0.02 vs 0.04±0.01 and 0.07 ±0.01,respectively) (all P＜0.05);the expressions of FoxM1 protein,cyclinD1 and Aurora A protein in hypoxia + siRNA-HIF-2α group were significantly lower than those in hypoxic control group and hypoxia + siRNA-HIF-2α empty group (0.23±0.01 vs 0.36±0.02 and 0.32±0.01,0.15±0.01 vs 0.31±0.01 and 0.28±0.03,0.14±0.02 vs 0.33±0.03 and 0.27±0.02,respectively) (all P＜0.05);the positive expression rate of EdU in the normoxic control group was significantly lower than that in the normoxia + LV-HIF-2α group [(30.77 ± 2.43)％ vs (55.56 ± 3.01)％],while the hypoxic control group was significantly higher than the hypoxic+siRNA-HIF-2α group [(65.28±3.21)％ vs (44.64±2.78)％] (both P＜ 0.05).Conclusion HIF-2α up-regulates the expression of FoxM1 and promotes the proliferation of pulmonary artery smooth muscle cells in hypoxic rats.