Abstract 87: KLF2 Regulates Aortic Aneurysm Morphology via Matrix Endopeptidase Regulation During Aneurysm Formation
Objective: Kruppel-like Factor 2(KLF2) is known to play an athero-protective role in the endothelium following statin treatment; however, its role in abdominal aortic aneurysm (AAA) formation remains unknown. We hypothesized that KLF2 is critical in aneurysm formation through IL-6 and matrix endopeptidase activation.
Methods: 8-12 wk male(n=6/group) C57/B6 mice underwent abdominal aortic elastase perfusion and were harvested at 3, 7, and 14 days for qPCR and immunohistochemistry(IHC) for KLF2. 8-12 wk male(n=6/group) MyH Cre+ KLF2 flx/flx (tamoxifen conditional smooth muscle(SMC) KLF2 KO) and MyH Cre+ KLF2 wt/wt mice underwent elastase perfusion following tamoxifen administration and harvested at 14 days. These mice were also bred to ApoE-/- and administered Angiotensin II for 28 days via osmotic pump(n=8/group). Separately, Angiotensin II treated KLF2 flx/wt ApoE-/- ERT Cre+ and KLF2 flx/wt ApoE-/- ERT Cre- mice(n=8/group) were also examined. Aortas were harvested at 14 and 28 days and evaluated by IHC. KLF2 was knocked down in vitro using siRNA in SMCs and macrophages and exposed to elastase, IL-1β or elastin degradation products(EDP).
Results: KLF2 was elevated via qPCR and IHC 7 and 14 days following elastase-perfusion. 14 days following elastase perfusion, aortic dilation was significantly reduced in SMC specific KLF2 KO mice versus controls(49.5±5.76% vs. 99±5.72%, p<0.05) with reduced macrophage, T-cell, and neutrophil staining and greater elastin preservation and α-actin expression. In the Angiotensin II model, there was greater survival by Kaplan-Meier analysis in Klf2 flx/wt ERT Cre+ mice(Chi2=4.215, p=0.0453) and in SM-MHC Klf2 flx/flx mice(Chi2=4.342, p=0.0413) compared to their WT controls. In vitro studies demonstrated KLF2 siRNA transfection of SMCs during elastase exposure resulted in an attenuation of the matrix endopeptidase Astl1 and Ssc5d while knock-down of KLF2 in macrophages during IL-1β exposure resulted in an attenuation of IL-6 up-regulation. KLF2 binds astl1 and Ssc5d following elastase treatment in SMCs.
Conclusions: Endogenous KLF2 activity is critical for AAA formation and SMCs appear to be an important source for KLF2. KLF2 could represent a putative therapeutic target to prevent aneurysm formation.
Author Disclosures: M. Salmon: None. N.H. Pope: None. J.P. Davis: None. W.F. Johnston: None. M. Vandenbosch: None. G. Su: None. G.K. Owens: None. G.R. Upchurch: None. G. Ailawadi: None.
- © 2014 by American Heart Association, Inc.