[Role and mechanism of epithelial-mesenchymal transition in a rat model of bronchopulmonary dysplasia induced by hyperoxia exposure].

Objectives: To investigate the role and mechanism of epithelial-mesenchymal transition (EMT) in a rat model of bronchopulmonary dysplasia (BPD).

Methods: The experiment consisted of two parts. (1) Forty-eight preterm rats were randomly divided into a normoxia group and a hyperoxia group, with 24 rats in each group. The hyperoxia group was exposed to 85% oxygen to establish a BPD model, while the normoxia group was kept in room air at normal pressure. Lung tissue samples were collected on days 1, 4, 7, and 14 of the experiment. (2) Rat type II alveolar epithelial cells (RLE-6TN) were randomly divided into a normoxia group (cultured in air) and a hyperoxia group (cultured in 95% oxygen), and cell samples were collected 12, 24, and 48 hours after hyperoxia exposure. Hematoxylin-eosin staining was used to observe alveolarization in preterm rat lungs, and immunofluorescence was used to detect the co-localization of surfactant protein C (SPC) and α-smooth muscle actin (α-SMA) in preterm rat lung tissue and RLE-6TN cells. Quantitative real-time polymerase chain reaction and protein immunoblotting were used to detect the expression levels of EMT-related mRNA and proteins in preterm rat lung tissue and RLE-6TN cells.

Results: (1) Compared with the normoxia group, the hyperoxia group showed blocked alveolarization and simplified alveolar structure after 7 days of hyperoxia exposure. Co-localization of SPC and α-SMA was observed in lung tissue, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 7 and 14 days of hyperoxia exposure compared to the normoxia group. In the hyperoxia group, the mRNA and protein levels of TGF-β1, α-SMA, and N-cadherin were increased, while the mRNA and protein levels of SPC and E-cadherin were decreased at 7 and 14 days of hyperoxia exposure compared to the normoxia group (P<0.05). (2) SPC and α-SMA was observed in RLE-6TN cells, with decreased SPC expression and increased α-SMA expression in the hyperoxia group at 24 and 48 hours of hyperoxia exposure compared to the normoxia group. Compared to the normoxia group, the mRNA and protein levels of SPC and E-cadherin in the hyperoxia group were decreased, while the mRNA and protein levels of TGF-β1, α-SMA, and E-cadherin in the hyperoxia group increased at 48 hours of hyperoxia exposure (P<0.05).

Conclusions: EMT disrupts the tight connections between alveolar epithelial cells in a preterm rat model of BPD, leading to simplified alveolar structure and abnormal development, and is involved in the development of BPD. Citation:Chinese Journal of Contemporary Pediatrics, 2024, 26(7): 765-773.