miR-375 regulates rat alveolar epithelial cell trans-differentiation by inhibiting Wnt/β-catenin pathway.

Alveolar epithelial cell (AEC) trans-differentiation is a process where type II alveolar epithelial cells (AEC II) trans-differentiate into type I alveolar epithelial cells (AEC I) during lung recovery after various injuries, in which AEC I are damaged. This process is critical for lung tissue repair. MicroRNAs are a group of small RNAs that regulate gene expression at the post-transcriptional level. They have the potential to regulate almost every aspect of cell physiology. However, whether AEC trans-differentiation is regulated by microRNAs is completely unknown. In this study, we found that miR-375 was downregulated during AEC trans-differentiation. The overexpression of miR-375 with an adenoviral vector inhibited alveolar epithelial trans-differentiation as indicated by an increase in the AEC II marker, surfactant protein C, and decreases in the AEC I markers, T1α and advanced glycosylation end product-specific receptor. miR-375 also inhibited the Wnt/β-catenin pathway. The constitutively activation of Wnt/β-catenin signaling with a stabilized form of β-catenin blocked the miR-375 effects. Frizzled 8 was identified as a target of miR-375. In summary, our results demonstrate that miR-375 regulates AEC trans-differentiation through the Wnt/β-catenin pathway. This discovery may provide new targets for therapeutic intervention to benefit lung recovery from injuries.