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Aortopathy in a Mouse Model of Marfan Syndrome Is Not Mediated by Altered Transforming Growth Factor ? Signaling.

ABSTRACT: BACKGROUND:Marfan syndrome (MFS) is caused by mutations in the gene encoding fibrillin-1 (FBN1); however, the mechanisms through which fibrillin-1 deficiency causes MFS-associated aortopathy are uncertain. Recently, attention was focused on the hypothesis that MFS-associated aortopathy is caused by increased transforming growth factor-? (TGF-?) signaling in aortic medial smooth muscle cells (SMC). However, there are many reasons to doubt that TGF-? signaling drives MFS-associated aortopathy. We used a mouse model to test whether SMC TGF-? signaling is perturbed by a fibrillin-1 variant that causes MFS and whether blockade of SMC TGF-? signaling prevents MFS-associated aortopathy. METHODS AND RESULTS:MFS mice (Fbn1C1039G/+ genotype) were genetically modified to allow postnatal SMC-specific deletion of the type II TGF-? receptor (TBRII; essential for physiologic TGF-? signaling). In young MFS mice with and without superimposed deletion of SMC-TBRII, we measured aortic dimensions, histopathology, activation of aortic SMC TGF-? signaling pathways, and changes in aortic SMC gene expression. Young Fbn1C1039G/+ mice had ascending aortic dilation and significant disruption of aortic medial architecture. Both aortic dilation and disrupted medial architecture were exacerbated by superimposed deletion of TBRII. TGF-? signaling was unaltered in aortic SMC of young MFS mice; however, SMC-specific deletion of TBRII in Fbn1C1039G/+ mice significantly decreased activation of SMC TGF-? signaling pathways. CONCLUSIONS:In young Fbn1C1039G/+ mice, aortopathy develops in the absence of detectable alterations in SMC TGF-? signaling. Loss of physiologic SMC TGF-? signaling exacerbates MFS-associated aortopathy. Our data support a protective role for SMC TGF-? signaling during early development of MFS-associated aortopathy.

SUBMITTER: Wei H

PROVIDER: S-EPMC5523644 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Aortopathy in a Mouse Model of Marfan Syndrome Is Not Mediated by Altered Transforming Growth Factor β Signaling.

Wei Hao H Hu Jie Hong JH Angelov Stoyan N SN Fox Kate K Yan James J Enstrom Rachel R Smith Alexandra A Dichek David A DA

Journal of the American Heart Association 20170124 1

<h4>Background</h4>Marfan syndrome (MFS) is caused by mutations in the gene encoding fibrillin-1 (FBN1); however, the mechanisms through which fibrillin-1 deficiency causes MFS-associated aortopathy are uncertain. Recently, attention was focused on the hypothesis that MFS-associated aortopathy is caused by increased transforming growth factor-β (TGF-β) signaling in aortic medial smooth muscle cells (SMC). However, there are many reasons to doubt that TGF-β signaling drives MFS-associated aortopa ...[more]

PMID: 28119285

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Project description:Loeys-Dietz syndrome (LDS) is a syndromic connective tissue disorder caused by a heterozygous missense mutation in genes that encode transforming growth factor (TGF)-β receptor (TGFBR) 1 and 2. We encountered a patient with LDS, who had severe periodontal tissue destruction indicative of aggressive periodontitis. The patient had a missense mutation in the glycine and serine-rich domain of TGFBR1 exon 3. This G-to-T mutation at base 563 converted glycine to valine. We established an LDS model knock-in mouse that recapitulated the LDS phenotype. Homozygosity of the mutation caused embryonic lethality and heterozygous knock-in mice showed distorted and ruptured elastic fibers in the aorta at 24 weeks of age and died earlier than wildtype (WT) mice. We stimulated mouse embryonic fibroblasts (MEFs) from the knock-in mouse with TGF-β and examined their responses. The knock-in MEFs showed downregulated Serpine 1 mRNA expression and phosphorylation of Smad2 to TGF-β compared with WT MEFs. To clarify the influence of TGF-β signaling abnormalities on the pathogenesis or progression of periodontitis, we performed pathomolecular analysis of the knock-in mouse. There were no structural differences in periodontal tissues between WT and LDS model mice at 6 or 24 weeks of age. Micro-computed tomography revealed no significant difference in alveolar bone resorption between WT and knock-in mice at 6 or 24 weeks of age. However, TGF-β-related gene expression was increased significantly in periodontal tissues of the knock-in mouse compared with WT mice. Next, we assessed a mouse periodontitis model in which periodontal bone loss was induced by oral inoculation with the bacterial strain Porphyromonas gingivalis W83. After inoculation, we collected alveolar bone and carried out morphometric analysis. P. gingivalis-induced alveolar bone loss was significantly greater in LDS model mice than in WT mice. Peritoneal macrophages isolated from Tgfbr1 G188V/+ mice showed upregulation of inflammatory cytokine mRNA expression induced by P. gingivalis lipopolysaccharide compared with WT macrophages. In this study, we established an LDS mouse model and demonstrated that LDS model mice had elevated susceptibility to P. gingivalis-induced periodontitis, probably through TGF-β signal dysfunction. This suggests that TGF-β signaling abnormalities accelerate the pathogenesis or progression of periodontitis.

Project description:Variations in the Toll-interacting protein (TOLLIP) gene have been identified in genome-wide association studies to correlate with risk of disease, mortality, and response to N-acetylcysteine therapy in idiopathic pulmonary fibrosis. Although TOLLIP is known to modulate innate immune responses, its relevance in organ fibrogenesis remains unknown. Prior work in the literature suggests TOLLIP dampens transforming growth factor beta (TGFβ) signaling in human cell lines. In this study, we examined the role of TOLLIP in mouse lung fibroblast (MLF) responses to TGFβ and in the bleomycin model of experimental lung fibrosis using Tollip-/- mice. We hypothesize that if TOLLIP negatively regulates TGFβ signaling, then Tollip-/- mouse lung fibroblasts (MLFs) would have enhanced response to TGFβ treatment, and Tollip-/- mice would develop increased fibrosis following bleomycin challenge. Primary MLFs were stimulated with TGFβ (1 ng/mL) for 24 h. RNA was obtained to assess global transcriptional responses by RNA-seq and markers of myofibroblast transition by qPCR. Functional assessment of TGFβ-stimulated MLFs included cell migration by scratch assay, cell proliferation, and matrix invasion through Matrigel. In the in vivo model of lung fibrosis, Tollip-/- mice and wild-type (WT) littermates were administered bleomycin intratracheally and assessed for fibrosis. We further examined TGFβ signaling in vivo after bleomycin injury by SMAD2, ERK1/2, and TGFβR1 Western blot. In response to TGFβ treatment, both WT and Tollip-/- MLFs exhibited global transcriptional changes consistent with myofibroblast differentiation. However, Tollip-/- MLFs showed greater number of differentially expressed genes compared to WT MLFs and greater upregulation of Acta2 by qPCR. Functionally, Tollip-/- MLFs also exhibited increased migration and Matrigel invasiveness compared to WT. We found evidence of enhanced TGFβ signaling in Tollip-/- through SMAD2 in vitro and in vivo. Tollip-/- mice experienced lower survival using a standard weight-adjusted dosing without evidence of differences in fibrosis at Day 21. With adjustment of dosing for sex, no differences were observed in fibrosis at Day 21. However, Tollip-/- mice had greater weight loss and increased bronchoalveolar lavage fluid total protein during early resolution at Day 14 compared to WT without evidence of differences in acute lung injury at Day 7, suggesting impaired resolution of lung injury.

Project description:RationaleAlveolar transforming growth factor (TGF)-?1 signaling and expression of TGF-?1 target genes are increased in patients with idiopathic pulmonary fibrosis (IPF) and in animal models of pulmonary fibrosis. Internalization and degradation of TGF-? receptor T?RI inhibits TGF-? signaling and could attenuate development of experimental lung fibrosis.ObjectivesTo demonstrate that after experimental lung injury, human syndecan-2 confers antifibrotic effects by inhibiting TGF-?1 signaling in alveolar epithelial cells.MethodsMicroarray assays were performed to identify genes differentially expressed in alveolar macrophages of patients with IPF versus control subjects. Transgenic mice that constitutively overexpress human syndecan-2 in macrophages were developed to test the antifibrotic properties of syndecan-2. In vitro assays were performed to determine syndecan-2-dependent changes in epithelial cell TGF-?1 signaling, TGF-?1, and T?RI internalization and apoptosis. Wild-type mice were treated with recombinant human syndecan-2 during the fibrotic phase of bleomycin-induced lung injury.Measurements and main resultsWe observed significant increases in alveolar macrophage syndecan-2 levels in patients with IPF. Macrophage-specific overexpression of human syndecan-2 in transgenic mice conferred antifibrotic effects after lung injury by inhibiting TGF-?1 signaling and downstream expression of TGF-?1 target genes, reducing extracellular matrix production and alveolar epithelial cell apoptosis. In vitro, syndecan-2 promoted caveolin-1-dependent internalization of TGF-?1 and T?RI in alveolar epithelial cells, which inhibited TGF-?1 signaling and epithelial cell apoptosis. Therapeutic administration of human syndecan-2 abrogated lung fibrosis in mice.ConclusionsAlveolar macrophage syndecan-2 exerts antifibrotic effects by promoting caveolin-1-dependent TGF-?1 and T?RI internalization and inhibiting TGF-?1 signaling in alveolar epithelial cells. Hence, molecules that facilitate T?RI degradation via endocytosis represent potential therapies for pulmonary fibrosis.

Dataset Information

Aortopathy in a Mouse Model of Marfan Syndrome Is Not Mediated by Altered Transforming Growth Factor ? Signaling.

Publications

Aortopathy in a Mouse Model of Marfan Syndrome Is Not Mediated by Altered Transforming Growth Factor β Signaling.

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