Angiotensin II–dependent TGF-β signaling contributes to Loeys-Dietz syndrome vascular pathogenesis
Elena M. Gallo, … , David L. Huso, Harry C. Dietz
Elena M. Gallo, … , David L. Huso, Harry C. Dietz
Published December 20, 2013
Citation Information: J Clin Invest. 2014;124(1):448-460. https://doi.org/10.1172/JCI69666.
View: Text | PDF
Research Article

Angiotensin II–dependent TGF-β signaling contributes to Loeys-Dietz syndrome vascular pathogenesis

Abstract

Loeys-Dietz syndrome (LDS) is a connective tissue disorder that is characterized by a high risk for aneurysm and dissection throughout the arterial tree and phenotypically resembles Marfan syndrome. LDS is caused by heterozygous missense mutations in either TGF-β receptor gene (TGFBR1 or TGFBR2), which are predicted to result in diminished TGF-β signaling; however, aortic surgical samples from patients show evidence of paradoxically increased TGF-β signaling. We generated 2 knockin mouse strains with LDS mutations in either Tgfbr1 or Tgfbr2 and a transgenic mouse overexpressing mutant Tgfbr2. Knockin and transgenic mice, but not haploinsufficient animals, recapitulated the LDS phenotype. While heterozygous mutant cells had diminished signaling in response to exogenous TGF-β in vitro, they maintained normal levels of Smad2 phosphorylation under steady-state culture conditions, suggesting a chronic compensation. Analysis of TGF-β signaling in the aortic wall in vivo revealed progressive upregulation of Smad2 phosphorylation and TGF-β target gene output, which paralleled worsening of aneurysm pathology and coincided with upregulation of TGF-β1 ligand expression. Importantly, suppression of Smad2 phosphorylation and TGF-β1 expression correlated with the therapeutic efficacy of the angiotensin II type 1 receptor antagonist losartan. Together, these data suggest that increased TGF-β signaling contributes to postnatal aneurysm progression in LDS.

Authors

Elena M. Gallo, David C. Loch, Jennifer P. Habashi, Juan F. Calderon, Yichun Chen, Djahida Bedja, Christel van Erp, Elizabeth E. Gerber, Sarah J. Parker, Kimberly Sauls, Daniel P. Judge, Sara K. Cooke, Mark E. Lindsay, Rosanne Rouf, Loretha Myers, Colette M. ap Rhys, Kathleen C. Kent, Russell A. Norris, David L. Huso, Harry C. Dietz

×

Figure 2

Knockin LDS mutant mice, but not TGF-β receptor haploinsufficient mice, recapitulate vascular LDS phenotypes.

Options: View larger image (or click on image) Download as PowerPoint
Knockin LDS mutant mice, but not TGF-β receptor haploinsufficient mice, ...
(A) Aortic root growth from 4 to 24 weeks of age in LDS knockin and haploinsufficient mouse models, as measured by echocardiography (n ≥ 9). (B) Representative echocardiographic images of the aortic roots (arrows) of wild-type and Tgfbr1M318R/+ mice at 24 weeks of age. Scale bar: 1 mm. (C) Quantification of elastic fiber breaks per high-power field (hpf) in LDS knockin and haploinsufficient mouse models (n ≥ 6). (A and C) The upper and lower margins of the box define the 75th and 25th percentiles, respectively; the internal line defines the median, and the whiskers define the range. (D) Representative aortic wall sections of LDS knockin and haploinsufficient mouse models, at 24 weeks of age, stained with VVG for elastin. Scale bar: 40 μm. (E) Representative images of vascular anatomy in LDS knockin and haploinsufficient mouse models. (F) Kaplan-Meier survival curve showing diminished life span of Tgfbr1M318R/+ and Tgfbr2G357W/+ mice but not haploinsufficient mice (wild-type, n = 46; Tgfbr1+/–, n = 39; Tgfbr2+/–, n = 32; Tgfbr1M318R/+, n = 50; Tgfbr2G357W/+, n = 49). *P < 0.05, **P < 0.005, ††P < 0.00005.