miR-184 mediates hyperoxia-induced injury by targeting cell death and angiogenesis signalling pathways in the developing lung.

MicroRNAs (miRs) have been shown to disrupt normal lung development and function by interrupting alveolarization and vascularisation leading to development of bronchopulmonary dysplasia (BPD). Here we report that miR-184 has a critical role in the induction of BPD phenotype characterised by abnormal alveolarization and pulmonary angiogenesis in the developing lung. We observed an increased expression of miR-184 in BPD clinical specimens: tracheal aspirates (TA), human neonatal lungs with BPD and in fetal human lung Type II alveolar epithelial cells (TIIAECs) exposed to hyperoxia. Consistent with this, we also detected an upregulated miR-184-3p expression in whole lungs, in freshly isolated TIIAECs from lungs of hyperoxia-induced experimental BPD mice and in fetal mice lung TIIAECs exposed to hyperoxia. We demonstrate that overexpression of miR-184-3p exacerbates the BPD pulmonary phenotype, while downregulation of miR-184-3p expression ameliorated the BPD phenotype and also improved respiratory function. We identified miR-184 specific targets: platelet-derived growth factor-beta (Pdgf-β) and friend of Gata 2 (Fog2), also known as zinc finger protein family member (Zfpm2), and show that they are critically involved in pulmonary alveolarization and angiogenesis. Using cell-based luciferase analysis, downregulation of miR-184-3p expression and gene knockdown of miR-184-3p targets Pdgf-β and Fog2 in lung TIIAECs and endothelial cells, we mechanistically show that inhibition of miR-184-3p expression improves pulmonary alveolarization by regulating PDGF-β/AKT/Foxo3/Bax, Bcl2 signalling and enhances angiogenesis by Fog2/VEGF-A/Angiopoietin-1/2 pathway. Collectively, these data suggest that the use of miR-184-3p specific inhibitors may act as novel therapeutic interventions to control the adverse effects of hyperoxia on lung development and function.