Circ-ECH1 May Compete With miR-708-5p to Regulate Ntrk2 in Bronchopulmonary Dysplasia.

Bronchopulmonary dysplasia (BPD) affects patients' quality of life. Circular RNAs participated in BPD. However, circ-ECH1's role in BPD has not been reported yet. This study aimed to explore the role and mechanism of circ-ECH1 in BPD. Hyperoxia-treated type II alveolar epithelial cells (L2 cells) were used as the in vitro BPD model. CCK-8, flow cytometry, and reactive oxygen species (ROS) were used to evaluate cell viability. Fluorescence in situ hybridization confirmed the subcellular localization. Circ-ECH1 overexpression (or inhibited) and miR-708-5p mimics were used to investigate the roles of circ-ECH1 and miR-708-5p in BPD. Quantitative reverse-transcription polymerase reaction (qRT-PCR) detected the expressions of circ-ECH1, miR-708-5p, and neurotrophic receptor tyrosine kinase 2 (Ntrk2). Ntrk2 expression was evaluated by Western blot analysis. Changes in lung tissues were evaluated by hematoxylin and eosin staining. Pulmonary fibrosis was examined by Mason staining. TUNEL staining was performed to evaluate cell apoptosis in lung tissues. RNA sequencing was performed in the lung tissues of BPD rats. The binding between circ-ECH1 and miR-708-5p was confirmed through dual luciferase activity. Hyperoxia reduced cell viability and increased cell apoptosis and ROS accumulation. In addition, hyperoxia decreased the expression levels of circ-ECH1, which is mainly located in the cytoplasm. Circ-ECH1 overexpression increased cell viability but reduced cell apoptosis and ROS accumulation. On the contrary, interference with circ-ECH1 further promoted cell apoptosis and reduced cell activity. Furthermore, circ-ECH1 overexpression reduced the incidence of pulmonary fibrosis and lung cell apoptosis. RNA sequencing, followed by qRT-PCR, confirmed that the expressions of Ntrk2 and miR-708-5p were affected by circ-ECH1. miR-708-5p mimics reversed the role of circ-ECH1 in the BPD. Mechanistically, circ-ECH1 may bind with miR-708-5p to regulate Ntrk2 expression. Circ-ECH1 may compet with miR-708-5p to regulate Ntrk2 expression in BPD. The findings provided a new target for BPD treatment.