Objective To investigate the effects of polydatin(PD)on the proliferation and apoptosis of pulmonary artery smooth muscle cells(PASMCs)in hypoxic pulmonary hypertension(HPH)neonatal rats,and its mechanism of action.Methods Neonatal rats were randomly separated into six groups:control group,model group,low dose PD group,medium dose PD group,high dose PD group,and high dose PD+Hippo pathway inhibitor(high dose PD+XMU-MP-1)group,with 10 rats in each group.After 2 weeks of hypoxia treatment,the right ventricular systolic blood pressure(RVSP)and right ventricular hypertro-phy index(RVHI)of rats in each group were measured.Hematoxylin-eosin(HE)staining was applied to observe pathological changes in lung tissue,and the percentage of pulmonary artery wall thickness to total thickness(WT)and the percentage of wall area to total area(WA)were calculated.Neonatal rat PASMCs were separated from each group,which were divided into NC group,hypoxia group,low dose PD group,medium dose PD group,high dose PD group,and high dose PD+XMU-MP-1 group.Cell counting kit 8(CCK-8)and 5-ethynyl-2'-deoxyuridine(EdU)were applied to detect cell proliferation.Flow cytometry was applied to detect cell apoptosis.Western blot was applied to detect the expression of Yes-associated protein 1(YAP1),tran-scriptional coactivator with PDZ-binding motif(TAZ),mammalian sterile 20-like kinase 1(MST1),B-cell lymphoma 2(Bcl-2),and Bcl-2 associated protein(Bax)in lung tissue and PASMCs.Results Compared with the control group,the pulmonary artery wall in the model group was significantly thickened,lumen was narrowed,and protein expressions of RVSP,RVHI,WT％,WA％,YAP1,MST1 and TAZ were significantly increased(all P＜0.05).Compared with the model group,pulmonary artery thickening and lumen enlargement were observed in the low,medium and high dose PD groups,and the protein expressions of RVSP,RVHI,WT％,WA％,YAP1,MST1 and TAZ were significantly decreased,which showed a dose-dependent relationship(all P＜0.05).The effect could be reversed by XMU-MP-1.Compared with the NC group,the cell A450nm value,EdU positive rate,the protein expression of YAP1,MST1,TAZ and Bcl-2 in the hydropoxia group were significantly increased.The apoptosis rate and the expression of Bax protein were obviously reduced(all P＜0.05).Compared with the hypoxia group,the cell A450nm value,EdU positive rate,the protein expression of YAP1,MST1,TAZ and Bcl-2 in the low,medium and high dose PD groups were obviously reduced.The apoptosis rate and the expression of Bax were significantly increased,which showed a dose-depend-ent relationship(all P＜0.05).The effect could be reversed by XMU-MP-1.Conclusion PD may inhibit the proliferation of PASMCs in HPH neonatal rats and promote apoptosis by inhibiting YAP1/TAZ signaling pathway.