Inhibition of prostaglandin E2 protects abdominal aortic aneurysm from expansion through regulating miR-29b-mediated fibrotic ECM expression.

The risk of rupture, the most feared clinical consequence of abdominal aortic aneurysm, increases with the enlargement of aorta. MicroRNA-29b (miR-29b) has emerged as a key modulator of extracellular matrix (ECM) homeostasis and thereby is proposed to play a crucial role in vascular remodeling. However, agents that alter miR-29b expression are relatively inefficient in the aorta, likely due to inferior uptake. Herein we found that miR-29b was upregulated in aortic smooth muscle cells upon prostaglandin E2 (PGE2) stimulation whereas indomethacin treatment downregulated miR-29b expression. In order to obtain insight into the pathological processes associated with the vascular remodeling that accompanies aortic dilatation, we compared expression profiles of several representative ECM components in aortic walls. Notably, PGE2 induced a dramatic decline in these ECM components, which was rescued by introduction of indomethacin. In addition, COL1A1 was validated as a direct target gene of miR-29b by dual-luciferase reporter assay. In aggregate, our study suggests that PGE2 may accelerate ECM degradation through decreasing miR-29b expression. Thus those anti-inflammatory drugs that inhibit PGE2 synthesis represent an effective means of inducing an augmented profibrotic response in the aortic walls and thereby inhibiting aneurysmal expansion.