Role of miR-29 in mediating offspring lung phenotype in a rodent model of intrauterine growth restriction.

Considerable epidemiological and experimental evidence supports the concept that the adult chronic lung disease (CLD), is due, at least in part, to aberrations in early lung development in response to an abnormal intrauterine environment; however, the underlying molecular mechanisms remain unknown. We used a well-established rat model of maternal undernutrition (MUN) during pregnancy that results in offspring intrauterine growth restriction (IUGR) and adult CLD to test the hypothesis that in response to MUN, excess maternal glucocorticoids (GCs) program offspring lung development to a CLD phenotype by altering microRNA (miR)-29 expression, which is a key miR in regulating extracellular matrix (ECM) deposition during development and injury-repair. At postnatal day 21 and 5 mo, compared with the control offspring lung, MUN offspring lung miR-29 expression was significantly decreased in conjunction with an elevated expression of multiple downstream target ECM proteins [collagen (COL)1A1, COL3A1, COL4A5, and elastin], at both mRNA and protein levels. Importantly, MUN-induced changes in miR-29 and target gene expressions were at least partially blocked in the lungs of offspring of MUN dams treated with metyrapone, a selective GC synthesis inhibitor. Furthermore, dexamethasone treatment of cultured fetal rat lung fibroblasts significantly induced miR-29 expression along with the suppression of target ECM proteins. These data, along with the previously known role of miR-29 in regulating ECM deposition in vascular tissue in the MUN offspring, suggest miR-29 to be a common mechanistic denominator for the vascular and pulmonary phenotypes in the IUGR offspring, providing a novel potential therapeutic target.