MicroRNAs are key regulators of organogenesis and during the last years many studies focused on microRNA expression during embryonic development. To date, there is no study to report possible roles of microRNAs in late lung development and especially during the alveolarization process.The objective of this study was to identify microRNAs that are deregulated under hyperoxic conditions and to assess whether microRNA expression can be modulated in vivo. Lung microRNA expression screening was assessed at four time points under normoxic conditions by microRNA microarray; the time points were P2.5 and P3.5 (pre-septation), P5.5 (peak septation) and P14.5 (post-septation). Also, lung microRNA expression screening was assessed in pups exposed to hyperoxia (85% O2) for 14 days. In total, 55 microRNAs were deregulated. Amongst the most up-regulated microRNAs were miR-15b and miR-497, both belong to miR-15 family. Target prediction analysis suggested that miR-15 family regulates Smad7 expression. Using a luciferase-based reporter assay, Smad7 was validated as a direct target of miR-15b suggesting an impact on TGF-beta signaling during alveolarization. In vitro, overexpression of miR-15b and miR-497 down-regulated Smad7 expression and increased TGF-beta responsiveness, as assessed by a p(CAGA)9 reporter assay in primary lung fibroblasts.In vivo silencing of miR-15b and miR-497 (by using LNA-antagomirs) restored alveolarization by ~50 % in developing lungs of mouse pups exposed to hyperoxia and was assessed by using a stereological approach. The mean linear intercept (MLI) was notably decreased in the hyperoxia treated group but the septal thickness (St) remained unchanged. These data reveal a causal role for the deregulated miR-15 family in arrested lung development associated with hyperoxia exposure. These data are also the first to report that microRNA inhibition, using LNA-antagomirs, is a viable interventional method to restore perturbed alveolarization.
Verknüpfung zu Publikationen oder weiteren Datensätzen
