miR-29c induction contributes to downregulation of vascular extracellular matrix proteins by glucocorticoids.

Maternal undernutrition increases maternal glucocorticoids (GCs) and alters microRNA expression in offspring. Given that the mechanisms of GC action on vascular development are not clear, this study examined the influence of GCs on microRNA 29c (miR-29c) and its predicted targets in primary rat aorta smooth muscle cells (RAOSMCs). Dexamethasone (Dex) and corticosterone (Cor) time-dependently increased miR-29c expression and reduced collagen type III (Col3A1), collagen type IV (Col4A5), elastin (ELN), and matrix metalloproteinase-2 (MMP2) protein in RAOSMCs. These effects were blocked by mifepristone. These genes were also targeted by miR-29c, as confirmed by a significant decrease in luciferase reporter activity of Col3A1 (34%), Col4A5 (45%), ELN (17%), and MMP2 (28%). In cells transfected with reporter plasmids, including the 3'-untranslated region of genes targeted by miR-29c, treatment with Dex or Cor also resulted in decreases in luciferase activity. Gain or loss of function of miR-29c significantly altered mRNA expression of Col3A1 (26% and 26%, respectively), Col4A5 (28% and 32%, respectively), and MMP2 (24% and 14%, respectively) but did not affect ELN. Gain or loss of function of miR-29c also significantly altered protein levels of Col3A1 (51% and 16%, respectively), Col4A5 (56% and 22%, respectively), ELN (53% and 71%, respectively), and MMP2 (28% and 53%, respectively). Coincubation of anti-miR-29c with Dex or Cor partially attenuated the effects of these steroids on protein expression of Col3A1 (25% and 24%, respectively), Col4A5 (26% and 44%, respectively), ELN (31% and 55%, respectively), and MMP2 (46% and 26%, respectively) in RAOSMCs compared with anti-miR negative controls. Our results demonstrate that GCs regulate the expression of Col3A1, Col4A5, ELN, and MMP2, at least in part, through induction of miR-29c.