Lineage-specific events underlie aortic root aneurysm pathogenesis in Loeys-Dietz syndrome
Elena Gallo MacFarlane, … , Jennifer P. Habashi, Harry C. Dietz
Elena Gallo MacFarlane, … , Jennifer P. Habashi, Harry C. Dietz
Published February 5, 2019; First published January 7, 2019
Citation Information: J Clin Invest. 2019;129(2):659-675. https://doi.org/10.1172/JCI123547.
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Research Article Vascular biology

Lineage-specific events underlie aortic root aneurysm pathogenesis in Loeys-Dietz syndrome

Abstract

The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-β (TGF-β) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-β receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field–derived (SHF-derived), but not neighboring cardiac neural crest–derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-β, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-β ligands. The preserved TGF-β signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.

Authors

Elena Gallo MacFarlane, Sarah J. Parker, Joseph Y. Shin, Benjamin E. Kang, Shira G. Ziegler, Tyler J. Creamer, Rustam Bagirzadeh, Djahida Bedja, Yichun Chen, Juan F. Calderon, Katherine Weissler, Pamela A. Frischmeyer-Guerrerio, Mark E. Lindsay, Jennifer P. Habashi, Harry C. Dietz

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Figure 4

Defective induction of Smad-dependent pathways in SHF-, but not in CNC-derived, primary VSMCs generated from Tbr1MR/+ mice.

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Defective induction of Smad-dependent pathways in SHF-, but not in CNC-d...
(A) Representative flow cytometry histogram plots and quantification of p-Smad2/3 induction over baseline in serum-starved SHF- and CNC-derived VSMCs from mice of the indicated genotypes after exposure to 1 ng/ml or 10 ng/ml TGF-β1 for 1 hour. Levels of p-Smad2/3 were assessed by phospho–flow cytometry using an antibody specific for p-Smad2/3 (SHF samples: control n = 5, mutant n = 4; CNC samples, control n = 5, mutant n = 5). P values shown refer to Kruskal-Wallis test with FDR-based multiple comparison correction. (B) Immunoblot of cell lysates from serum-starved SHF and CNC-derived VSMCs stimulated with 1 ng/ml TGF-β1 for 1 hour. Levels of p-Smad2 and p-Smad3 were assessed with antibodies detecting p-Smad2 or p-Smad2/3; arrow identifies the band quantified for p-Smad3. Quantification of p-Smad2 and p-Smad3 induction relative to baseline is shown below (n = 3). P values shown refer to Kruskal-Wallis test with FDR-based multiple comparison correction. (C) Quantification of normalized Ctgf and Serpine1 induction relative to baseline upon stimulation of serum-starved SHF- and CNC-derived VSMCs from mice of the indicated genotypes with TGF-β1 (10 ng/ml) for 3 hours (SHF samples: control n = 4, mutant n = 4; CNC samples, control n = 4, mutant n = 5). P values shown refer to Kruskal-Wallis test with FDR-based multiple comparison correction. Numerical data are presented as scatter dot-plots with boxes, with the box denoting the mean; error bars identify the 95% confidence interval. NS, not significant.