miR-29b Participates in Early Aneurysm Development in Marfan Syndrome
Rationale: Marfan syndrome (MFS) is a systemic connective tissue disorder notable for the development of aortic root aneurysms and the subsequent life-threatening complications of aortic dissection and rupture. Underlying fibrillin-1 gene mutations cause increased transforming growth factor-β (TGF-β) signaling. Although TGF-β blockade prevents aneurysms in MFS mouse models, the mechanisms through which excessive TGF-β causes aneurysms remain ill-defined.
Objective: We investigated the role of microRNA-29b (miR-29b) in aneurysm formation in MFS.
Methods and Results: Using quantitative polymerase chain reaction, we discovered that miR-29b, a microRNA regulating apoptosis and extracellular matrix synthesis/deposition gene, is increased in the ascending aorta of Marfan (Fbn1C1039G/+) mice. Increased apoptosis, assessed by increased cleaved caspase-3 and caspase-9, enhanced caspase-3 activity, and decreased levels of the antiapoptotic proteins, Mcl-1 and Bcl-2, were found in the Fbn1C1039G/+ aorta. Histological evidence of decreased and fragmented elastin was observed exclusively in the Fbn1C1039G/+ ascending aorta in association with repressed elastin mRNA and increased matrix metalloproteinase-2 expression and activity, both targets of miR-29b. Evidence of decreased activation of nuclear factor κB, a repressor of miR-29b, and a factor suppressed by TGF-β, was also observed in Fbn1C1039G/+ aorta. Furthermore, administration of a nuclear factor κB inhibitor increased miR-29b levels, whereas TGF-β blockade or losartan effectively decreased miR-29b levels in Fbn1C1039G/+ mice. Finally, miR-29b blockade by locked nucleic acid antisense oligonucleotides prevented early aneurysm development, aortic wall apoptosis, and extracellular matrix deficiencies.
Conclusions: We identify increased miR-29b expression as key to the pathogenesis of early aneurysm development in MFS by regulating aortic wall apoptosis and extracellular matrix abnormalities.
- Received July 27, 2011.
- Revision received November 9, 2011.
- Accepted November 15, 2011.
- © 2011 American Heart Association, Inc.