Expression profile of microRNAs in fetal lung development of Sprague-Dawley rats.

As well-known regulators of gene expression, microRNAs (miRNAs) play an important role not only in cell proliferation and differentiation, but also in tumorigenesis and organ development. Furthermore, it is estimated that miRNAs may be responsible for regulating the expression of nearly one-third of the human genome. Simultaneously, in the clinic, with advances in neonatal care, a larger number of premature infants are being saved, and thus diseases of lung development, including bronchopulmonary dysplasia (BPD) have become more and more common. However, only a few miRNA studies have studied their connection with diseases of lung development. In our study, we used a miRNA microarray including more than 1891 capture probes to profile the expression of miRNAs at three time points of rat lung development [embryonic (E) Day 16 (E16), E19, E21]. miRNAs found to have consistent fold-changes (fold-change>2.0) during all three time points were selected and validated by real-time PCR. As a result, 167 differentially expressed miRNAs were found during rat lung organogenesis, including 81 upregulated and 86 downregulated miRNAs. Seven miRNAs were selected and characterized by having a consistent >2-fold changes between all three groups. Among these 7 miRNAs, except for let-7a, the other 6 miRNAs (miR-1949, miR-125b-5p, miR-296, miR-93, miR-146b, miR-3560) are all first reported for the first time in lung development. Finally, due to the fact that they demonstrated higher fold changes, from these 7 miRNAs we selected miR-125b-5p, miR-296, miR-93, miR-146b and miR-3560 for real-time PCR. We hypothesized that these newly identified miRNAs may play an important role in fetal lung development, and this experimental result could help us to further clarify the mechanism of normal lung development including the development of type II pneumocytes. This may provide a physiological basis for future research on diseases of lung development.