Objective To investigate the expression of long non-coding RNA H19 (LncRNA H19)and its regulation of histone methyltransferase 2 (enhancer of zeste homolog 2,EZH2) in the lung tissue of neonatal rats with bronchopulmonary dysplasia (BPD),and to lay a foundation for elucidating the pathogenesis of BPD lung epithelium-interstitial transformation (EMT).Methods The BPD model of SD neonatal rats was induced by hyperoxia (inhalation oxygen concentration was 85％) (n =50),and oxygen inhalation concentration of the control group was 21％ (n =50).The two groups were collected at ld,3d,7d,14d and 21d after birth in lung tissue.Immunohistochemistry,Western blot,real-time quantitative PCR and other techniques were used to detect the intracellular localization,and the expression level of EZH2 protein and the mRNA expression level of H19 and EZH2.Results Immunohistochemistry showed that EZH2 protein was located in the nucleus and cytoplasm of alveolar epithelial cells,and the expression of EZH2 protein in the model group was significantly enhanced compared with the control group.Similarly,the results of Western blot demonstrated that the expression of EZH2 protein in the model group increased from ld (control group:0.196 ± 0.030,model group 0.650 ±0.149) to 21d (control group 0.934 ± 0.215,model group 1.785 ± 0.298) rather than the control group (P ＜ 0.05).Compared with the control group,the mRNA expression level of H19 in the model group increased from 7d (control group 2.591 ± 0.211,model group 3.558 ± 0.093,P ＜ 0.05) and the expression level of EZH2 mRNA started to increase from 3d (control group 1.246 ±0.015,model group 2.148 ± 0.215,P ＜0.05).Moreover,the differences between the two groups were obvious with the time of hyperoxia exposure.Conclusion In the development of BPD,the expression levels of H19 and EZH2 protein in lung tissue is up-regulated,and the peak of H19 expression precedes EZH2,which suggest that H19 might be involved in the pathogenesis of pulmonary dysplasia induced by EZH2-mediated EMT.