Thoracic Aortic Aneurysm Dissection Research Articles

A yeast based assay establishes the pathogenicity of novel missense ACTA2 variants associated with aortic aneurysms.

The ACTA2 gene codes for alpha-smooth muscle actin, a critical component of the contractile apparatus of the vascular smooth muscle cells. Autosomal dominant variants in the ACTA2 gene have been associated to familial non-syndromic thoracic aortic aneurysm/dissection (TAAD). They are thought to act through a dominant-negative mechanism. These variants display incomplete penetrance and variable expressivity, complicating the validation of ACTA2 variants pathogenicity by family segregation studies. In this study, we developed a yeast based assay to test putative TAAD-associated ACTA2 variants. We identified five new heterozygous ACTA2 missense variants in TAAD patients through next generation sequencing. We decided to test their pathogenicity in Saccharomyces cerevisiae, since yeast actin is very similar to human alpha-smooth muscle actin, and the residues at which the TAAD-associated variants occur in ACTA2 are well conserved. A wild type yeast strain was transformed with a vector expressing the different mutant alleles, to model the heterozygous condition of patients. Then, we evaluated yeast growth by spot test and cytoskeletal and mitochondrial morphology by fluorescence microscopy. We found that mutant yeast strains displayed only mild growth defects but a significant increase in the percentage of cells with abnormal mitochondrial distribution and abnormal organization of the actin cytoskeleton compared to controls. All variants appeared to interfere with the activity of wild type actin in yeast, suggesting a dominant-negative pathogenic mechanism. Our results demonstrate the utility of using the yeast actin model system to validate the pathogenicity of TAAD-associated ACTA2 variants.

Activation of the alternative complement pathway modulates inflammation in thoracic aortic aneurysm/dissection.

Thoracic aortic aneurysm/dissection (TAAD) is a lethal vascular disease, and several pathological factors participate in aortic medial degeneration. We previously discovered that the complement C3a-C3aR axis in smooth muscle cells promotes the development of thoracic aortic dissection (TAD) through regulation of matrix metalloproteinase 2. However, discerning the specific complement pathway that is activated and elucidating how inflammation of the aortic wall is initiated remain unknown. We ascertained that the plasma levels of C3a and C5a were significantly elevated in patients with TAD and that the levels of C3a, C4a, and C5a were higher in acute TAD than in chronic TAD. We also confirmed the activation of the complement in a TAD mouse model. Subsequently, knocking out Cfb (Cfb) or C4 in mice with TAD revealed that the alternative pathway and Cfb played a significant role in the TAD process. Activation of the alternative pathway led to generation of the anaphylatoxins C3a and C5a, and knocking out their receptors reduced the recruitment of inflammatory cells to the aortic wall. Moreover, we used serum from wild-type mice or recombinant mice Cfb as an exogenous source of Cfb to treat Cfb KO mice and observed that it exacerbated the onset and rupture of TAD. Finally, we knocked out Cfb in the FBN1C1041G/+ Marfan-syndrome mice and showed that the occurrence of TAA was reduced. In summary, the alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.NEW & NOTEWORTHY The alternative complement pathway promoted the development of TAAD by recruiting infiltrating inflammatory cells. Targeting the alternative pathway may thus constitute a strategy for preventing the development of TAAD.

Transcriptomic Analysis of Tight Junction Proteins Demonstrates the Aberrant Expression and Function of Zona Occludens 2 (ZO-2) Protein in Stanford Type A Aortic Dissection.

Thoracic aortic aneurysm dissection (TAAD) represents a cardiac surgery emergency characterized by the disrupted integrity of the aortic wall and is associated with poor prognosis. In this context, the identification of biomarkers implicated in the pathobiology of TAAD is crucial. Our aim in the present original in silico study is to assess the differential gene expression profile of the tight junction proteins (TJPs) in patients with TAAD and to propose novel biomarkers for the diagnosis and prognosis of this disease. We implemented bioinformatics methodology in order to construct the gene network of the TJPs family, identify the differentially expressed genes (DEGs) in pathologic aortic tissue excised from patients with TAAD as compared to healthy aortic tissue, and assess the related biological functions and the associated miRNA families. Data regarding the transcriptomic profile of selected genes were retrieved and incorporated from three microarray datasets, including 23 TAAD and 20 healthy control samples. A total of 32 TJPs were assessed. The zona occludens 2 (ZO-2) protein encoded by the gene TJP2 was significantly under-expressed in patients with TAAD compared to the control group (p = 0.009). ZO-2 was associated with fair discrimination and calibration traits in predicting the TAAD presentation. CpG islands of ZO-2 were demonstrated. No important difference was found regarding ZO-2 expression between aneurysmal non-dissected and healthy control aortic tissue. Finally, we performed gene set enrichment analysis (GSEA) and uncovered the major biological functions and miRNA families (hsa-miR-155-5p, hsa-miR-1-3p, hsa-miR-2118-5p, hsa-miR-4691-3p, and hsa-miR-1229-3p) relevant to ZO-2. These outcomes demonstrated the important role of ZO-2 in the pathobiology of TAAD.

Pulsatile Deformations of a Conformable Descending Thoracic Aortic Endograft in Aneurysm, Dissection, and Blunt Traumatic Aortic Injury Patients.

This study presents analytic techniques to quantify cardiac pulsatility-induced deformations of thoracic aortic endografts in patients with thoracic aortic aneurysm (TAA), dissection (TAD), and blunt thoracic aortic injury (BTAI) after thoracic endovascular aortic repair (TEVAR). We analyzed 19 image data sets from 14 patients treated for TAA, TAD, and BTAI with cardiac-gated post-TEVAR CTs. Systolic and diastolic geometric models were constructed and diametric, axial, and bending deformations were quantified. For patients with cardiac-gated pre-op scans, the damping of pulsatile diametric distension was computed. Maximum localized diametric distension was 2.4±1.0%, 4.2±1.7%, and 5.5±1.6%, and axial deformation was 0.0±0.1%, -0.1±0.3%, and 1.1±0.6% in the endografts of TAA, TAD, and BTAI cohorts, respectively. Diametric distension damping from pre- to post-TEVAR was ~50%. Diametric and bending deformations were localized at certain axial positions on the endograft, and the inner curve bends more than the centerline, especially adjacent to overlapping regions. The presented techniques support investigation of multi-axial endograft deformations between disease causes and geometric locations on the device. Discretized quantification of deformation is needed to define device fatigue testing conditions and predict device durability in patients. This study demonstrates analytic techniques to quantify discretized deformation of thoracic endografts. Cardiac-resolved computed tomography is sometimes acquired for surgical planning and follow-up, however, the dynamic data are not typically used to quantify pulsatile deformations. Our analytic techniques extract the centerline and surface geometry of the stented thoracic aorta during the cardiac cycle, which are used to quantify diametric, axial, and bending deformations to provide better understanding of device durability and impact on the native anatomy.

Angiopoietin-like protein 8 deficiency attenuates thoracic aortic aneurysm/dissection development in β-aminopropionitrile monofumarate-induced model mice

Thoracic aortic aneurysm/dissection (TAAD) is a life-threatening cardiovascular disorder. Endoplasmic reticulum stress (ERS) and vascular smooth muscle cell (VSMC) apoptosis are involved in TAAD progression. The Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) pathway is associated with VSMC apoptosis. Serum Angiopoietin-Like Protein 8 (ANGPTL8) levels are associated with aortic diameter and rupture rate of TAAD. However, a direct role of ANGPTL8 in TAAD has not been determined. β-Aminopropionitrile monofumarate (BAPN) was used to induce TAAD in C57BL/6 mice. ANGPTL8 knockout mice were used to detect the effects of ANGPTL8 on TAAD development. ANGPTL8knockdown in vitro was used to analyze the role of ANGPTL8 in VSMCs and ERS. In addition, over-expression of ANGPTL8 in VSMCs and a PERK inhibitor were used to assess the effect of ANGPTL8 on the PERK pathway. ANGPTL8 levels were increased in the aortic wall and VSMCs of BAPN-induced TAAD mice. Compared with BAPN-treated wild-type mice, ANGPTL8 knockout significantly reduced the rupture rate of TAAD to 0 %. In addition, the protein levels of proinflammatory cytokines and matrix metalloproteinase 9 (MMP9) and ERS proteins were decreased in the aorta wall. Angptl8 shRNA decreased MMP9 and ERS protein levels in VSMCs in vitro. Overexpression of ANGPTL8 significantly increased the levels of ERS proteins and MMPs, while a PERK inhibitor significantly decreased the effects of ANGPTL8 in VSMCs. ANGPTL8 contributed to TAAD development by inducing ERS activation and degradation of extracellular matrix in the aorta wall. Inhibition of ANGPTL8 may therefore represent a new strategy for TAAD therapy.

Long non-coding RNA RP11-465L10.10 promotes vascular smooth muscle cells phenotype switching and MMP9 expression via the NF-κB pathway.

BackgroundThoracic aortic aneurysm/dissection (TAA/D) are complicated vascular disorders with rapid development and high mortality. Vascular smooth muscle cells (VSMCs) phenotype switching plays an important role in the pathological process of TAA/D. Previous studies have indicated a potential correlation between long non-coding RNA (lncRNA) RP11-465L10.10 and matrix metallopeptidase 9 (MMP9) involved in the development of TAA/D. This study aims to investigate the role of lncRNA RP11-465L10.10 in VSMCs phenotype switching and the molecular mechanism in regulating MMP9 expression.MethodsThe expression of RP11-465L10.10 in vascular tissues and in VMSCs was detected by RT-qPCR. To investigate the role of RP11-465L10.10 on VSMCs phenotype switching, an RP11-465L10.10-overexpressed lentiviral vector was constructed and transfected into VSMCs. Through EdU staining, migration assay, flow cytometry analysis, the roles of RP11-465L10.10 were estimated. Bioinformatics indicated that RP11-465L10.10 upregulating MMP9 expression via NF-κB signaling, and SN50 (a specific inhibitor of NF-κB pathway) was used to inhibit the NF-κB pathway activation, then the expression of MMP9 was detected in RP11-465L10.10 overexpressed VMSCs.ResultsIn this study, we found RP11-465L10.10 and MMP9 were highly increased in TAD patient tissues, which was consistent in angiotensin II-induced VSMCs phenotype switching. RP11-465L10.10 overexpression facilitated VSMCs phenotype switching and MMP9 expression. Mechanismly, NF-κB signal pathway was involved in RP11-465L10.10 induced VSMCs phenotype switching and MMP9 expression by transcriptome data analysis and experimental confirm.ConclusionThis study demonstrated that RP11-465L10.10 induces VSMCs phenotype switching and MMP9 expression via the NF-κB signal pathway, suggesting that RP11-465L10.10 might be a potential therapeutic target for TAA/D treatment.

Psychological distress in response to physical activity restrictions in patients with non-syndromic thoracic aortic aneurysm/dissection.

Individuals diagnosed with thoracic aortic aneurysm/dissection (TAAD) are given activity restrictions in an attempt to mitigate serious health complications and sudden death. The psychological distress resulting from activity restrictions has been established for other diseases or patient populations; however, individuals with non-syndromic TAAD have not been previously evaluated. Seventy-nine participants completed a questionnaire utilizing the Patient Health Questionnaire (PHQ-9) and Generalized Anxiety Disorder (GAD-7) questionnaires, which assess levels of depression and anxiety respectively. Additionally, quantitative and qualitative questions explored self-reported psychological distress in response to activity restrictions. Individuals who reported higher PHQ + GAD scores had been living with a diagnosis longer than two years (p = 0.0004), were between 35 and 65years old (p = 0.05), reported not coping well (p = 0.0035), and reported physical activity was "very important" (p = 0.04). Results from individual questions showed that individuals who reported their diagnosis affected them financially were 3.5 times more likely to report "feeling nervous, anxious, or on edge" (CI = [0.81, 15.6], p = 0.094). Qualitative analysis revealed themes that identified participant beliefs regarding distress, ability to cope, hindrances to coping ability, and resources. These results show psychological distress can result from physical activity restrictions in non-syndromic TAAD individuals. Additionally, certain subpopulations may be more susceptible to distress. This is the first study to examine the psychological distress individuals with non-syndromic TAAD experience as a result of prescribed activity restrictions. Genetic counselors and other healthcare professionals can utilize this information to provide more tailored cardiovascular genetic counseling and increase its therapeutic potential for patients.

The Role of Genetics in Risk Stratification of Thoracic Aortic Aneurysm Dissection

Thoracic aortic aneurysms are prevalent in the Western population and are often caused by genetic defects. If undetected, aneurysms can dissect or rupture, which are events associated with a high mortality rate. Hitherto no cure exists other than elective surgery if aneurysm dimensions reach a certain threshold. In the past decades, genotype-phenotype associations have emerged that enable clinicians to start stratifying patients according to risk for dissection. Nonetheless, risk assessment is—to this day—confounded by the lack of full comprehension of underlying genetics and modifying genetic risk factors that complicate the yet established genotype-phenotype correlations. Further research that focuses on identifying these additional risk markers is crucial.

Smooth Muscle Sirtuin 1 Blocks Thoracic Aortic Aneurysm/Dissection Development in Mice.

Advancing age is the major risk factor for thoracic aortic aneurysm/dissection (TAAD). However, the causative link between age-related molecules and TAAD remains elusive. Here, we investigated the role of Sirtuin 1 (SIRT1, also known as class III histone deacetylase), the best studied member of the longevity-related Sirtuin family, in TAAD development in vivo. We used male smooth muscle-specific SIRT1 transgenic (ST-Tg) mice, smooth muscle-specific SIRT1 knockout (ST-KO) mice, and their wild-type (WT) littermates on a C57BL/6J background to establish a TAAD model induced by oral administration of 3-aminopropionitrile fumarate (BAPN). We analyzed the incidence and fatality rates of TAAD in the groups. We examined matrix metallopeptidase 2 (MMP2) and MMP9 expression in aortas or cultured A7r5 cells via western blotting and real-time polymerase chain reaction (PCR). We performed chromatin immunoprecipitation (ChIP) to clarify the epigenetic mechanism of SIRT1-regulated MMP2 expression in vascular smooth muscle cells (VSMCs). BAPN treatment markedly increased the incidence of TAAD in WT mice but caused less disease in ST-Tg mice. Moreover, ST-KO mice had the highest BAPN-induced TAAD fatality rate of all the groups. Mechanistically, SIRT1 overexpression resulted in lower MMP2 and MMP9 expression after BAPN treatment in both mouse aortas and cultured A7r5 cells. The downregulation of BAPN-induced MMP2 expression by SIRT1 was mediated by deacetylation of histone H3 lysine 9 (H3K9) on the Mmp2 promoter in the A7r5 cells. Our findings suggest that SIRT1 expression in SMCs protects against TAAD and could be a novel therapeutic target for TAAD management.

Sustained activation of ADP/P2ry12 signaling induces SMC senescence contributing to thoracic aortic aneurysm/dissection

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. However, the mechanism whereby signaling leads to SMC loss is unclear. We used senescence-associated (SA)-β-gal staining and analysis of expression of senescence-related proteins (p53, p21, p19) to show that excessive mechanical stretch (20% elongation, 3600cycles/h, 48h) induced SMC senescence. SMC senescence was also detected in TAAD specimens from both mice and humans. High-performance liquid chromatography and luciferin-luciferase–based assay revealed that excessive mechanical stretch increased adenosine diphosphate (ADP) release from SMCs both in vivo and in vitro. Elevated ADP induced SMC senescence while genetic knockout of the ADP receptor, P2Y G protein-coupled receptor 12 (P2ry12), in mice protected against SMC senescence and inflammation. Both TAAD formation and rupture were significantly reduced in P2ry12−/− mice. SMCs from P2ry12−/− mice were resistant to senescence induced by excessive mechanical stretch or ADP treatment. Mechanistically, ADP treatment sustained Ras activation, whereas pharmacological inhibition of Ras protected against SMC senescence and reduced TAAD formation. Taken together, excessive mechanical stress may induce a sustained release of ADP and promote SMC senescence via P2ry12-dependent sustained Ras activation, thereby contributing to excessive inflammation and degeneration, which provides insights into TAAD formation and progression.

A Case Based Approach to Clinical Genetics of Thoracic Aortic Aneurysm/Dissection.

Thoracic aortic aneurysm/dissection (TAAD) is a potential lethal condition with a rising incidence. This condition may occur sporadically; nevertheless, it displays familial clustering in >20% of the cases. Family history confers a six- to twentyfold increased risk of TAAD and has to be considered in the identification and evaluation of patients needing an adequate clinical follow-up. Familial TAAD recognizes a number of potential etiologies with a significant genetic heterogeneity, in either syndromic or nonsyndromic forms of the manifestation. The clinical impact and the management of patients with TAAD differ according to the syndromic and nonsyndromic forms of the manifestation. The clinical management of TAAD patients varies, depending on the different forms. Starting from the description of patient history, in this paper, we summarized the state of the art concerning assessment of clinical/genetic profile and therapeutic management of TAAD patients.

Is Emilin-1 a molecular link contributing to the extension of thoracic aortic aneurysm dissection and increasing the magnitude of the associated hypertension

Is Emilin-1 a molecular link contributing to the extension of thoracic aortic aneurysm dissection and increasing the magnitude of the associated hypertension

The genetic architecture of non-syndromic thoracic aortic aneurysm

### Learning objectives Curriculum topic : Disease of the aorta and trauma to the aorta and heart Aortic aneurysm/dissection is a common cause of cardiovascular morbidity and mortality in the...

Performant Mutation Identification Using Targeted Next-Generation Sequencing of 14 Thoracic Aortic Aneurysm Genes.

At least 14 causative genes have been identified for both syndromic and nonsyndromic forms of thoracic aortic aneurysm/dissection (TAA), an important cause of death in the industrialized world. Molecular confirmation of the diagnosis is increasingly important for gene-tailored patient management but consecutive, conventional molecular TAA gene screening is expensive and labor-intensive. To circumvent these problems, we developed a TAA gene panel for next-generation sequencing of 14 TAA genes. After validation, we applied the assay to 100 Marfan patients. We identified 90 FBN1 mutations, 44 of which were novel. In addition, Multiplex ligation-dependent probe amplification identified large deletions in six of the remaining samples, whereas false-negative results were excluded by Sanger sequencing of FBN1, TGFBR1, and TGFBR2 in the last four samples. Subsequently, we screened 55 syndromic and nonsyndromic TAA patients. We identified causal mutations in 15 patients (27%), one in each of the six following genes: ACTA2, COL3A1, TGFBR1, MYLK, SMAD3, SLC2A10 (homozygous), two in NOTCH1, and seven in FBN1. We conclude that our approach for TAA genetic testing overcomes the intrinsic hurdles of consecutive Sanger sequencing of all candidate genes and provides a powerful tool for the elaboration of clinical phenotypes assigned to different genes.

Mechanical stretch-induced endoplasmic reticulum stress, apoptosis and inflammation contribute to thoracic aortic aneurysm and dissection.

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. In response to certain stimuli, endoplasmic reticulum (ER) stress is activated and regulates apoptosis and inflammation. Excessive apoptosis promotes aortic inflammation and degeneration, leading to TAAD. Therefore, we studied the role of ER stress in TAAD formation. A lysyl oxidase inhibitor, 3‐aminopropionitrile fumarate (BAPN), was administrated to induce TAAD formation in mice, which showed significant SMC loss (α‐SMA level). Excessive apoptosis (TUNEL staining) and ER stress (ATF4 and CHOP), along with inflammation, were present in TAAD samples from both mouse and human. Transcriptional profiling of SMCs after mechanical stress demonstrated the expression of genes for ER stress and inflammation. To explore the causal role of ER stress in initiating degenerative signalling events and TAAD, we treated wild‐type (CHOP +/+) or CHOP −/− mice with BAPN and found that CHOP deficiency protected against TAAD formation and rupture, as well as reduction in α‐SMA level. Both SMC apoptosis and inflammation were significantly reduced in CHOP −/− mice. Moreover, SMCs isolated from CHOP −/− mice were resistant to mechanical stress‐induced apoptosis. Taken together, our results demonstrated that mechanical stress‐induced ER stress promotes SMCs apoptosis, inflammation and degeneration, providing insight into TAAD formation and progression. © 2015 Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Acute Aortic Dissection

A 27-year-old previously healthy woman presented to the emergency room after the sudden onset of severe chest pain and shortness of breath during the 37th week of pregnancy. Her examination was remarkable for a blood pressure of 118/70 mm Hg, heart rate of 100 bpm, and respiratory rate of 24 breaths per minute. The cardiovascular examination was notable for a soft systolic ejection murmur, and the pulmonary and general examinations were unremarkable. ECG demonstrated sinus tachycardia, and her chest x-ray was normal. A D-dimer level was elevated. She underwent a spiral computed tomography scan to evaluate for pulmonary embolism, which instead demonstrated an acute type A aortic dissection and a very small patent ductus arteriosus. The patient underwent emergency cesarean section, which delivered a viable baby, and repair of the type A dissection. Her aortic valve was trileaflet. She had no features on examination to suggest Marfan syndrome or Loeys-Dietz aneurysm syndrome. Her father had died suddenly at 31 years of age of a “presumed heart attack,” and her paternal uncle had undergone ascending aortic aneurysm resection at 42 years of age. Mutation analysis in this woman detected a heterozygous mutation in MYH11 , confirming familial thoracic aortic aneurysm/dissection (TAA/D). Acute aortic dissection is the most common life-threatening disorder affecting the aorta.1 The immediate mortality rate in aortic dissection is as high as 1% per hour over the first several hours, making early diagnosis and treatment critical for survival. Classification schemes for aortic dissection are based on anatomic involvement of the aortic dissection (Figure 1).2 In the DeBakey classification, type I dissections originate in the ascending aorta and extend to at least the aortic arch; type II dissections involve the ascending aorta only; and type III dissections begin in the descending aorta, usually just distal to the …