Transforming growth factor-beta signaling in thoracic aortic aneurysm development: a paradox in pathogenesis

Unveiling cellular and molecular aspects of ascending thoracic aortic aneurysms and dissections

Ascending thoracic aortic aneurysm (ATAA) remains a significant medical concern, with its asymptomatic nature posing diagnostic and monitoring challenges, thereby increasing the risk of aortic wall dissection and rupture. Current management of aortic repair relies on an aortic diameter threshold. However, this approach underestimates the complexity of aortic wall disease due to important knowledge gaps in understanding its underlying pathologic mechanisms.Since traditional risk factors cannot explain the initiation and progression of ATAA leading to dissection, local vascular factors such as extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs) might harbor targets for early diagnosis and intervention. Derived from diverse embryonic lineages, VSMCs exhibit varied responses to genetic abnormalities that regulate their contractility. The transition of VSMCs into different phenotypes is an adaptive response to stress stimuli such as hemodynamic changes resulting from cardiovascular disease, aging, lifestyle, and genetic predisposition. Upon longer exposure to stress stimuli, VSMC phenotypic switching can instigate pathologic remodeling that contributes to the pathogenesis of ATAA.This review aims to illuminate the current understanding of cellular and molecular characteristics associated with ATAA and dissection, emphasizing the need for a more nuanced comprehension of the impaired ECM-VSMC network.

Recent advances of myotubularin-related (MTMR) protein family in cardiovascular diseases

Belonging to a lipid phosphatase family containing 16 members, myotubularin-related proteins (MTMRs) are widely expressed in a variety of tissues and organs. MTMRs preferentially hydrolyzes phosphatidylinositol 3-monophosphate and phosphatidylinositol (3,5) bis-phosphate to generate phosphatidylinositol and phosphatidylinositol 5-monophosphate, respectively. These phosphoinositides (PIPs) promote membrane degradation during autophagosome-lysosomal fusion and are also involved in various regulatory signal transduction. Based on the ability of modulating the levels of these PIPs, MTMRs exert physiological functions such as vesicle trafficking, cell proliferation, differentiation, necrosis, cytoskeleton, and cell migration. It has recently been found that MTMRs are also involved in the occurrence and development of several cardiovascular diseases, including cardiomyocyte hypertrophy, proliferation of vascular smooth muscle cell, LQT1, aortic aneurysm, etc. This review summarizes the functions of MTMRs and highlights their pathophysiological roles in cardiovascular diseases.

Coordination between cytoskeletal organization, cell contraction and extracellular matrix development, is depended on LOX for aneurysm prevention

Distinct, seemingly independent, cellular pathways affecting intracellular machineries or extracellular matrix (ECM) deposition and organization, have been implicated in aneurysm formation. One of the key genes associated with the pathology in both humans and mice is Lysyl oxidase (LOX), a secreted ECM-modifying enzyme, highly expressed in medial vascular smooth muscle cells. To dissect the mechanisms leading to aneurysm development, we conditionally deleted Lox in smooth muscle cells. We find that cytoskeletal organization is lost following Lox deletion. Cell culture assays and in vivo analyses demonstrate a cell-autonomous role for LOX affecting myosin light chain phosphorylation and cytoskeletal assembly resulting in irregular smooth muscle contraction. These results not only highlight new intracellular roles for LOX, but notably they link between multiple processes leading to aneurysm formation suggesting LOX coordinates ECM development, cytoskeletal organization and cell contraction required for media development and function.

Endovascular Treatment of a Giant Aneurysm of the Aberrant Right Hepatic Artery in a Patient with Osler-Weber-Rendu Syndrome: A Case Report

Osler-Weber-Rendu syndrome (OWR) is an autosomal dominant disorder characterized by recurrent epistaxis, mucocutaneous or visceral telangiectasias, and arteriovenous malformations in the lungs, liver, brain, and gastrointestinal tract. Hepatic artery aneurysms (HAAs) can also occur in OWR patients. HAAs are the second most common type of visceral artery aneurysm, and mortality rates are high owing to the lack of a tamponade effect. Anatomical variations of the celiacomesenteric vasculature are common, and the most common variation is that of the right hepatic artery originating from the superior mesenteric artery (SMA). We present the endovascular treatment of a patient with OWR and an aberrant right HAA originating from the SMA, with coil embolization and stent grafting. Giant HAAs can be treated endovascularly. However, stent graft placement should be reconsidered because of the need for antithrombotic medication, which may increase the incidence of epistaxis attacks in that patient group.

METTL3-METTL14 complex induces necroptosis and inflammation of vascular smooth muscle cells via promoting N6 methyladenosine mRNA methylation of receptor-interacting protein 3 in abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) have the highest incidence and rupture rate of all aortic aneurysms. The N6 methyladenosine (m6A) modification is closely associated with angiotensin (Ang II)-induced aortic diseases. This study aimed to identify whether the m6A writer METTL3/METTL4 regulates rip3 mRNA expression in AAA. To induce the mouse AAA model, apolipoprotein E-deficient (ApoE-/-) mice were subcutaneously infused with Ang II, and C57BL/6 mice were infused with type I elastase. Vascular smooth muscle cells (VSMCs) were induced with Ang II. Necroptosis was detected using an Annexin V-FITC/PI apoptosis detection kit, and ELISA assays measured inflammatory cytokines. The RNA immunoprecipitation-qPCR determined the methylated rip3 mRNA level. The increased expressions of inflammatory factors, aortic adventitia injury, degradation of elastin, and CD68-positive cells suggested the successful establishment of mouse AAA models. In AAA aorta wall tissues, the m6A modification level and the expression of METTL3/METTL14 were elevated. In Ang II-induced VSMCs, necroptosis and inflammatory cytokines in the supernatants were increased. RNA immunoprecipitation and co-immunoprecipitation assays confirmed the binding between the METTL3-METTL14 complex and rip3 mRNA, the interaction between YTHDF3 and rip3 mRNA, and between the METTL3-METTL14 complex and SMAD2/3. Interference with METTL3/METTL14 attenuated VSMC necroptosis, inflammatory response, and the AAA pathological process in vivo. The METTL3-METTL14 complex, which was increased by the activation of the SMAD2/3, elevated the m6A modification of rip3 mRNA by promoting the binding between YTHDF3 and rip3 mRNA, thus contributing to the progression of AAA. The activation of SMAD2/3 in VSMCs of abdominal aortic wall tissues is stimulated by Ang II. Subsequently, it promotes METTL3 METTL14 complex mediated m6A modification of rip3 mRNA. Meanwhile, the level of rip3 mRNA becomes more stable under the m6A reader of YTHDF3, which increases the protein level of RIP3 and further induces VSMC necroptosis. In addition, cell debris induces inflammatory factors in neighboring VSMCs and recruit monocytes/macrophages to the lesion.

The Role of ADAMTS Proteoglycanases in Thoracic Aortic Disease

Thoracic aortic aneurysm and dissection (TAAD) are complex disease states with high morbidity and mortality that pose significant challenges to early diagnosis. Patients with an aneurysm are asymptomatic and typically present to the emergency department only after the development of a dissection. The extracellular matrix (ECM) plays a crucial role in regulating the aortic structure and function. The histopathologic hallmark termed medial degeneration is characterised by smooth muscle cell (SMC) loss, the degradation of elastic and collagen fibres and proteoglycan (PG) accumulation. Covalently attached to the protein core of PGs are a number of glycosaminoglycan chains, negatively charged molecules that provide flexibility, compressibility, and viscoelasticity to the aorta. PG pooling in the media can produce discontinuities in the aortic wall leading to increased local stress. The accumulation of PGs is likely due to an imbalance between their synthesis by SMCs and decreased proteolysis by A Disintegrin-like and Metalloproteinase with Thrombospondin motifs (ADAMTS) proteoglycanases in the ECM. Mouse models of TAAD indicated that these proteases exert a crucial, albeit complex and not fully elucidated, role in this disease. This has led to a mounting interest in utilising ADAMTS proteoglycanases as biomarkers of TAAD. In this review, we discuss the role of ADAMTSs in thoracic aortic disease and their potential use in facilitating the clinical diagnosis of TAAD and disease progression.

Systematic Assessment of Protein C-Termini Mutated in Human Disorders

All proteins have a carboxyl terminus, and we previously summarized eight mutations in binding and trafficking sequence determinants in the C-terminus that, when disrupted, cause human diseases. These sequence elements for binding and trafficking sites, as well as post-translational modifications (PTMs), are called minimotifs or short linear motifs. We wanted to determine how frequently mutations in minimotifs in the C-terminus cause disease. We searched specifically for PTMs because mutation of a modified amino acid almost always changes the chemistry of the side chain and can be interpreted as loss-of-function. We analyzed data from ClinVar for disease variants, Minimotif Miner and the C-terminome for PTMs, and RefSeq for protein sequences, yielding 20 such potential disease-causing variants. After additional screening, they include six with a previously reported PTM disruption mechanism and nine with new hypotheses for mutated minimotifs in C-termini that may cause disease. These mutations were generally for different genes, with four different PTM types and several different diseases. Our study helps to identify new molecular mechanisms for nine separate variants that cause disease, and this type of analysis could be extended as databases grow and to binding and trafficking motifs. We conclude that mutated motifs in C-termini are an infrequent cause of disease.

Hypertrophic cardiomyopathy is associated with dilated sinus of Valsalva: A case-control study

Background

We aimed to test the hypothesis that there is an association between hypertrophic cardiomyopathy and dilated aorta in a case-control, matched-design fashion.

Methods

Of 65,843 studies done from November 2011 to December 2015, we found, after detailed evaluation by a single author, 153 cases of hypertrophic cardiomyopathy and 3,213 controls who were classified as normal clinically and echocardiographically. Controls were defined as normal patients referred to the echocardiography laboratory with no diagnoses and no known risk factors for dilated aorta (e.g., aortic stenosis, hypertension, aortic regurgitation). Clinical chart review showed none of the risk factors for dilated aorta, and echocardiography did not reveal any abnormalities. Of these 3,213 patients, 153 controls were matched to cases by age and sex by propensity score. Dilated aorta was defined according to clinical, Goldstein, and Lang's criteria.

Results

The prevalence of a dilated sinus of Valsalva was 9 times higher in hypertrophic cardiomyopathy patients than controls (OR = 9.4, P = 0.003). The 9-fold higher prevalence in hypertrophic cardiomyopathy patients persisted after adjusting for height, weight, and aortic pathology. Association of dilated mid-ascending aorta with hypertrophic cardiomyopathy was significant after adjustment for height and body surface area but became borderline insignificant after adjusting for weight and aortic valve pathology.

Conclusion

Hypertrophic cardiomyopathy appears to be associated with a dilated sinus of Valsalva, even after adjusting for height, weight, and aortic valve pathology.

Isolated aneurysmal disease as an underestimated finding in individuals with JAG1 pathogenic variants

Pathogenic variants in JAG1 are known to cause Alagille syndrome (ALGS), a disorder that primarily affects the liver, lung, kidney, and skeleton. Whereas cardiac symptoms are also frequently observed in ALGS, thoracic aortic aneurysms have only been reported sporadically in postmortem autopsies. We here report two families with segregating JAG1 variants that present with isolated aneurysmal disease, as well as the first histological evaluation of aortic aneurysm tissue of a JAG1 variant carrier. Our observations shed more light on the pathomechanisms behind aneurysm formation in JAG1 variant harboring individuals and underline the importance of cardiovascular imaging in the clinical follow-up of such individuals.

LncRNA AK131850 is downregulated in thoracic aortic aneurysm and negatively affects the levels of TGF-β1 in aortic smooth muscle cells

This study aimed to investigate the role of lncRNA AK131850 in thoracic aortic aneurysm (TAA). We found that AK131850 was downregulated, while TGF-β1 was upregulated in aortic media specimen of thoracic aortic aneurysm (TAA) patients. In addition, AK131850 and TGF-β1 inversely correlated. Altered expression levels of AK131850 and TGF-β1 distinguished TAA patients from healthy controls. In human aortic smooth muscle cells (HAOSMC), AK131850 overexpression led to downregulated, while AK131850 siRNA silencing led to upregulated TGF-β1. AK131850 overexpression resulted in promoted, while siRNA silencing led to inhibited proliferation of HAOSMC. Therefore, AK131850 is downregulated in thoracic aortic aneurysm and negatively affects the levels of TGF-β1 in aortic smooth muscle cells.

The Genetics and Typical Traits of Thoracic Aortic Aneurysm and Dissection

Genetic predisposition and risk factors such as hypertension and smoking can instigate the development of thoracic aortic aneurysm (TAA), which can lead to highly lethal aortic wall dissection and/or rupture. Monogenic defects in multiple genes involved in the elastin-contractile unit and the TGFβ signaling pathway have been associated with TAA in recent years, along with several genetic modifiers and risk-conferring polymorphisms. Advances in omics technology have also provided significant insights into the processes behind aortic wall degeneration: inflammation, epigenetics, vascular smooth muscle phenotype change and depletion, reactive oxygen species generation, mitochondrial dysfunction, and angiotensin signaling dysregulation. These recent advances and findings might pave the way for a therapy that is capable of stopping and perhaps even reversing aneurysm progression.

Copper-Binding Domain Variation in a Novel Murine Lysyl Oxidase Model Produces Structurally Inferior Aortic Elastic Fibers Whose Failure Is Modified by Age, Sex, and Blood Pressure

Lysyl oxidase (LOX) is a copper-binding enzyme that cross-links elastin and collagen. The dominant LOX variation contributes to familial thoracic aortic aneurysm. Previously reported murine Lox mutants had a mild phenotype and did not dilate without drug-induced provocation. Here, we present a new, more severe mutant, Loxb2b370.2Clo (c.G854T; p.Cys285Phe), whose mutation falls just N-terminal to the copper-binding domain. Unlike the other mutants, the C285F Lox protein was stably produced/secreted, and male C57Bl/6J Lox+/C285F mice exhibit increased systolic blood pressure (BP; p < 0.05) and reduced caliber aortas (p < 0.01 at 100mmHg) at 3 months that independently dilate by 6 months (p < 0.0001). Multimodal imaging reveals markedly irregular elastic sheets in the mutant (p = 2.8 × 10−8 for breaks by histology) that become increasingly disrupted with age (p < 0.05) and breeding into a high BP background (p = 6.8 × 10−4). Aortic dilation was amplified in males vs. females (p < 0.0001 at 100mmHg) and ameliorated by castration. The transcriptome of young Lox mutants showed alteration in dexamethasone (p = 9.83 × 10−30) and TGFβ-responsive genes (p = 7.42 × 10−29), and aortas from older C57Bl/6J Lox+/C285F mice showed both enhanced susceptibility to elastase (p < 0.01 by ANOVA) and increased deposition of aggrecan (p < 0.05). These findings suggest that the secreted Lox+/C285F mutants produce dysfunctional elastic fibers that show increased susceptibility to proteolytic damage. Over time, the progressive weakening of the connective tissue, modified by sex and blood pressure, leads to worsening aortic disease.

Association of TGF-β Canonical Signaling-Related Core Genes With Aortic Aneurysms and Aortic Dissections

Transforming growth factor-beta (TGF-β) signaling is essential for the maintenance of the normal structure and function of the aorta. It includes SMAD-dependent canonical pathways and noncanonical signaling pathways. Accumulated genetic evidence has shown that TGF-β canonical signaling-related genes have key roles in aortic aneurysms (AAs) and aortic dissections and many gene mutations have been identified in patients, such as those for transforming growth factor-beta receptor one TGFBR1, TGFBR2, SMAD2, SMAD3, SMAD4, and SMAD6. Aortic specimens from patients with these mutations often show paradoxically enhanced TGF-β signaling. Some hypotheses have been proposed and new AA models in mice have been constructed to reveal new mechanisms, but the role of TGF-β signaling in AAs is controversial. In this review, we focus mainly on the role of canonical signaling-related core genes in diseases of the aorta, as well as recent advances in gene-mutation detection, animal models, and in vitro studies.

The Predictive Role of Plasma Biomarkers in the Evolution of Aortopathies Associated with Congenital Heart Malformations

Dilatation of the aorta is a constantly evolving condition that can lead to the ultimate life-threatening event, acute aortic dissection. Recent research has tried to identify quantifiable biomarkers, with both diagnostic and prognostic roles in different aortopathies. Most studies have focused on the bicuspid aortic valve, the most frequent congenital heart disease (CHD), and majorly evolved around matrix metalloproteinases (MMPs). Other candidate biomarkers, such as asymmetric dimethylarginine, soluble receptor for advanced glycation end-products or transforming growth factor beta have also gained a lot of attention recently. Most of the aortic anomalies and dilatation-related studies have reported expression variation of tissular biomarkers. The ultimate goal remains, though, the identification of biomarkers among the serum plasma, with the upregulation of circulating MMP-1, MMP-2, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), asymmetric dimethylarginine (ADMA), soluble receptor for advanced glycation end-products (sRAGE) and transforming growth factor beta (TGF-β) being reported in association to several aortopathies and related complications in recent research. These molecules are apparently quantifiable from the early ages and have been linked to several CHDs and hereditary aortopathies. Pediatric data on the matter is still limited, and further studies are warranted to elucidate the role of plasmatic biomarkers in the long term follow-up of potentially evolving congenital aortopathies.

Proteomic analysis of descending thoracic aorta identifies unique and universal signatures of aneurysm and dissection

Objective

Methods

Results

Conclusions

Diseases of the descending thoracic aorta such as aneurysms and dissections carry a high degree of morbidity and mortality. At present, a complete understanding is still lacking of the genetics that drive these diseases and why some aortic segments dissect in the presence or absence of an aneurysm. We compared and contrasted the whole proteome expression of descending aortas from patients with normal, dissected, aneurysmal, and aneurysmal with dissected pathology aortic tissue. We uncovered potential tissue markers that might serve as future targets for therapy or predictors of disease progression.

RUNX3 is up-regulated in abdominal aortic aneurysm and regulates the function of vascular smooth muscle cells by regulating TGF-β1

Abdominal aortic aneurysm (AAA) has been associated with the dysfunction of vascular smooth muscle cells (VSMCs) and extracellular matrix (ECM) remodelling. Runt-related transcription factor 3 (RUNX3) has been reported to be up-regulated in aneurysmal aorta samples compared with normal aorta. However, its function in VSMCs and the mechanism of function remains unknown. Therefore, our study aimed to investigate the role of RUNX3 in ECM remodelling and VSMC function, and further explore the underlying mechanism. Our results verified that RUNX3 was increased in aortic samples of AAA compared with healthy controls. Overexpression vectors of RUNX3 (ov-RUNX3) and siRNA of RUNX3 (si-RUNX3) were transfected into Human aortic smooth muscle cells (HAoSMCs). The results indicated that ov-RUNX3 promoted cell proliferation, migration, and MMP-2/3/9 secretion, and suppressed TIMP-1, collagen I/III, SM22, MYH11 and CNN1 expression in HAoSMCs. The silencing of RUNX3 has the opposite effect. Furthermore, we found that RUNX3 targets TGF-β1 and suppressed its transcription. The silencing of TGF-β1 increased cell proliferation, migration and MMP-2/3/9 expression, and inhibited TIMP-1, Collagen I/III, SM22, MYH11 and CNN1 expression. In addition, TGF-β1 reversed the effect of RUNX3 overexpression on HAoSMCs. Hence, our study indicated that RUNX3 promotes cell proliferation, migration, and ECM remodelling through suppressing TGF-β1.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Prevalence of and Factors Associated with Arterial Aneurysms in Patients with Hereditary Hemorrhagic Telangiectasia: 17-Year Retrospective Series of 418 Patients

PURPOSE

To estimate the prevalence of and identify characteristics associated with the presence of aneurysms in a cohort of patients with hereditary hemorrhagic telangiectasia (HHT).

MATERIALS AND METHODS

In the study institution's HHT database, 418 patients with a definite HHT diagnosis were identified based on the clinical Curaçao criteria and/or an HHT-associated genetic mutation. Regression modeling was used to evaluate the association between arterial aneurysms and older age, male sex, smoking, alcohol consumption, hypertension, hyperlipidemia, genetic mutations, the presence of arteriovenous malformations (AVMs) unrelated to the aneurysms, and HHT-related genetic mutations.

RESULTS

Forty-three (10.3%) patients had at least 1 aneurysm. Sixteen (3.8%) patients had multiple aneurysms. Of the variables analyzed, older age (odds ratio [OR] = 1.02; 95% confidence interval [CI]: 1.0-1.1), the presence of anatomically and flow-unrelated AVMs (OR = 3.2; 95% CI: 1.3-8.0), and the presence of activin A receptor type II-like 1 (ACVRL1) mutation (OR = 4.0; 95% CI: 1.5-10) were associated with the presence of at least 1 aneurysm.

CONCLUSIONS

In this cohort of patients with HHT, the prevalence of intracranial and visceral arterial aneurysms was estimated to be 10.3%. Older age, the presence of unrelated AVMs, and the presence of the ACVRL1 mutation were associated with the presence of arterial aneurysms. Further study is required to assess the clinical importance and risk of rupture of aneurysms in patients with HHT.

Anti-TGFβ (Transforming Growth Factor β) Therapy With Betaglycan-Derived P144 Peptide Gene Delivery Prevents the Formation of Aortic Aneurysm in a Mouse Model of Marfan Syndrome

Objective

We investigated the effect of a potent TGFβ (transforming growth factor β) inhibitor peptide (P144) from the betaglycan/TGFβ receptor III on aortic aneurysm development in a Marfan syndrome mouse model.

Approach and Results

We used a chimeric gene encoding the P144 peptide linked to apolipoprotein A-I via a flexible linker expressed by a hepatotropic adeno-associated vector. Two experimental approaches were performed: (1) a preventive treatment where the vector was injected before the onset of the aortic aneurysm (aged 4 weeks) and followed-up for 4 and 20 weeks and (2) a palliative treatment where the vector was injected once the aneurysm was formed (8 weeks old) and followed-up for 16 weeks. We evaluated the aortic root diameter by echocardiography, the aortic wall architecture and TGFβ signaling downstream effector expression of pSMAD2 and pERK1/2 by immunohistomorphometry, and Tgfβ1 and Tgfβ2 mRNA expression levels by real-time polymerase chain reaction. Marfan syndrome mice subjected to the preventive approach showed no aortic dilation in contrast to untreated Marfan syndrome mice, which at the same end point age already presented the aneurysm. In contrast, the palliative treatment with P144 did not halt aneurysm progression. In all cases, P144 improved elastic fiber morphology and normalized pERK1/2-mediated TGFβ signaling. Unlike the palliative treatment, the preventive treatment reduced Tgfβ1 and Tgfβ2 mRNA levels.

Conclusions

P144 prevents the onset of aortic aneurysm but not its progression. Results indicate the importance of reducing the excess of active TGFβ signaling during the early stages of aortic disease progression.

Genetic variants in Chinese patients with sporadic Stanford type A aortic dissection

Background

Genetic disorders are strongly associated with aortic disease. However, the identities of genetic mutations in sporadic Stanford type A aortic dissection (STAAD) are not clear. The present study analysed the possible genetic mutations of the known pathogenic genes of aortic disease and the clinical characteristics in patients with sporadic STAAD.

Methods

We analysed genetic mutations in 26 genes that underlie aortic aneurysms and dissections in 100 sporadic STAAD patients and 568 healthy controls after whole-genome sequencing (WGS). Clinical features and in-hospital death were determined in all STAAD patients.

Results

In total, 60 suspicious pathogenic mutations (56 novel and 4 previously reported) in 19 genes were identified in 50% (50/100) of patients, and 14 patients had more than 1 mutation. The ascending aortic diameter was extended in patients with mutations (49.1±12.3 vs. 43.7±11.2 mm, P=0.023), and the DeBakey type I phenotype was more common in patients with mutations in genes that coded extracellular matrix (ECM) components than in patients with mutations in other genes (96.6% vs. 66.7%, P=0.007). Patients with fibrillin-1 (FBN1) mutations were younger than patients without FBN1 mutations (44.7±11.0 vs. 53.5±12.1, P=0.030). Subgroup analyses revealed an increased risk of in-hospital mortality in mutation carriers (44.4% vs. 10.5%, P=0.029) but only in patients who received conservative treatment.

Conclusions

Half of Chinese patients with a sporadic form of STAAD may carry mutations in known pathogenic genes of aortic disease, and these patients may exhibit distinct clinical features and poor clinical outcomes with the use of conservative treatment.

miR-133a Replacement Attenuates Thoracic Aortic Aneurysm in Mice

Background Thoracic aortic aneurysms (TAAs) occur because of abnormal remodeling of aortic extracellular matrix and are accompanied by the emergence of proteolytically active myofibroblasts. The microRNA miR-133a regulates cellular phenotypes and is reduced in clinical TAA specimens. This study tested the hypothesis that miR-133a modulates aortic fibroblast phenotype, and overexpression by lentivirus attenuates the development of TAA in a murine model. Methods and Results TAA was induced in mice. Copy number of miR-133a was reduced in TAA tissue and linear regression analysis confirmed an inverse correlation between aortic diameter and miR-133a. Analyses of phenotypic markers revealed an mRNA expression profile consistent with myofibroblasts in TAA tissue. Fibroblasts were isolated from the thoracic aortae of mice with/without TAA. When compared with controls, miR-133a was reduced, migration was increased, adhesion was reduced, and the ability to contract a collagen disk was increased. Overexpression/knockdown of miR-133a controlled these phenotypes. After TAA induction in mice, a single tail-vein injection of either miR-133a overexpression or scrambled sequence (control) lentivirus was performed. Overexpression of miR-133a attenuated TAA development. The pro-protein convertase furin was confirmed to be a target of miR-133a by luciferase reporter assay. Furin was elevated in this murine model of TAA and repressed by miR-133a replacement in vivo resulting in reduced proteolytic activation. Conclusions miR-133a regulates aortic fibroblast phenotype and over-expression prevented the development of TAA in a murine model. These findings suggest that stable alterations in aortic fibroblasts are associated with development of TAA and regulation by miR-133a may lead to a novel therapeutic strategy.

Mechano-chemo-biological Computational Models for Arteries in Health, Disease and Healing: From Tissue Remodelling to Drug-eluting Devices

This review aims to highlight urgent priorities for the computational biomechanics community in the framework of mechano-chemo-biological models. Recent approaches, promising directions and open challenges on the computational modelling of arterial tissues in health and disease are introduced and investigated, together with in silico approaches for the analysis of drug-eluting stents that promote pharmacological-induced healing. The paper addresses a number of chemo-biological phenomena that are generally neglected in biomechanical engineering models but are most likely instrumental for the onset and the progression of arterial diseases. An interdisciplinary effort is thus encouraged for providing the tools for an effective in silico insight into medical problems. An integrated mechano-chemo-biological perspective is believed to be a fundamental missing piece for crossing the bridge between computational engineering and life sciences, and for bringing computational biomechanics into medical research and clinical practice.

Expression and role of lumican in acute aortic dissection: A human and mouse study

Introduction

Aortic dissection (AD) is a life-threatening emergency, and lumican (LUM) is a potential Biomarker for AD diagnosis. We investigated LUM expression patterns in patients with AD and explored the molecular functions of Lum in AD mice model.

Methods

LUM expression patterns were analyzed using aortic tissues of AD patients, and serum soluble LUM (s-LUM) levels were compared between patients with acute AD (AAD) and chronic AD (CAD). Lum-knockout (Lum^−/−) mice were challenged with β-aminopropionitrile (BAPN) and angiotensin II (Ang II) to induce AD. The survival rate, AD incidence, and aortic aneurysm (AA) in these mice were compared with those in BAPN–Ang II–challenged wildtype (WT) mice. Tgf-β/Smad2, Mmps, Lum, and Nox expression patterns were examined.

Results

LUM expression was detected in the intima and media of the ascending aorta in patients with AAD. Serum s-LUM levels were significantly higher in patients with AAD than CAD. Furthermore, AD-associated mortality and thoracic aortic rupture incidence were significantly higher in the Lum^−/− AD mice than in the WT AD mice. However, no significant pathologic changes in AA were observed in the Lum^−/− AD mice compared with the WT AD mice. The BAPN–Ang II–challenged WT and Lum^−/− AD mice had higher Tgf-β, p-Smad2, Mmp2, Mmp9, and Nox4 levels than those of non-AD mice. We also found that Lum expression was significantly higher in the BAPN-Ang II–challenged WT in comparison to the unchallenged WT mice.

Conclusion

LUM expression was altered in patients with AD display increased s-LUM in blood, and Lum^−/− mice exhibited augmented AD pathogenesis. These findings support the notion that LUM is a biomarker signifying the pathogenesis of injured aorta seen in AAD. The presence of LUM is essential for maintenance of connective tissue integrity. Future studies should elucidate the mechanisms underlying LUM association in aortic changes.

Non-syndromic thoracic aortic aneurysm: cellular and molecular insights

Thoracic aortic aneurysm (TAA) develops silently and asymptomatically and is a major cause of mortality. TAA prevalence is greatly underestimated, it is usually diagnosed incidentally, and its treatment consists mainly of prophylactic surgery based on the aortic diameter. The lack of effective drugs and biological markers to identify and stratify TAAs by risk before visible symptoms results from scant knowledge of its pathophysiological mechanisms. Here we integrate the structural impairment affecting non-syndromic non-familial TAA with the main cellular and molecular changes described so far and consider how these changes are interconnected through specific pathways. The ultimate goal is to define much-needed novel markers of TAA, and so the potential of previously identified molecules to aid in early diagnosis/prognosis is also discussed. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

MicroRNAs in ascending thoracic aortic aneurysms

Thoracic Aortic Aneurysm (TAA) is characterized by the dilation of the aorta and is fatal if not diagnosed and treated appropriately. The underlying genetic mechanisms have not been completely delineated, so better knowledge of the physiopathology of TAAs is needed to improve detection and therapy. MicroRNAs (miRNAs) regulate gene expression post-transcriptionally and are known to be involved in cardiovascular diseases (CVDs). The current study aimed to identify miRNAs that can be used as possible biomarkers for the early diagnosis of patients with ascending TAAs (ATAAs). MiRNA expression was profiled by NanoString nCounter technology using 12 samples including tissue and pre- and post-surgical plasma from ATAA patients. Four miRNAs were selected and further validated by real time polymerase chain reaction (RT-PCR) in 22 plasma samples from which three miRNAs (hsa-miR140-5p, hsa-miR-191-5p and hsa-miR-214-3p) showed significant expression level differences between the two types of plasma samples. Further analyses of the corresponding predicted target genes by these miRNAs, revealed two genes (Myotubularin-related protein 4 (MTMR4) and Phosphatase 1 catalytic subunit β (PPP1CB)) whose expression was inversely correlated with the expression of their respective miRNAs. Overall, in this pilot study, we identified three miRNAs that might serve as potential biomarkers and therapeutic targets in ATAA.

ADAMTS proteases in cardiovascular physiology and disease

The a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS) family comprises 19 proteases that regulate the structure and function of extracellular proteins in the extracellular matrix and blood. The best characterized cardiovascular role is that of ADAMTS-13 in blood. Moderately low ADAMTS-13 levels increase the risk of ischeamic stroke and very low levels (less than 10%) can cause thrombotic thrombocytopenic purpura (TTP). Recombinant ADAMTS-13 is currently in clinical trials for treatment of TTP. Recently, new cardiovascular roles for ADAMTS proteases have been discovered. Several ADAMTS family members are important in the development of blood vessels and the heart, especially the valves. A number of studies have also investigated the potential role of ADAMTS-1, -4 and -5 in cardiovascular disease. They cleave proteoglycans such as versican, which represent major structural components of the arteries. ADAMTS-7 and -8 are attracting considerable interest owing to their implication in atherosclerosis and pulmonary arterial hypertension, respectively. Mutations in the ADAMTS19 gene cause progressive heart valve disease and missense variants in ADAMTS6 are associated with cardiac conduction. In this review, we discuss in detail the evidence for these and other cardiovascular roles of ADAMTS family members, their proteolytic substrates and the potential molecular mechanisms involved.

Surgical Single Stage Treatment for Obstructive Hypertrophic Cardiomyopathy and Aortic Arch Aneurysm

Coexistence of obstructive hypertrophic cardiomyopathy and severe aortic pathology is extremely rare; nonetheless, the association between these two diseases is fascinating. Here we present a unique case report of a patient with obstructive hypertrophic cardiomyopathy and aortic arch aneurysm treated by a single surgical procedure.

Endothelial TGF-β signaling instructs smooth muscle cell development in the cardiac outflow tract

The development of the cardiac outflow tract (OFT), which connects the heart to the great arteries, relies on a complex crosstalk between endothelial (ECs) and smooth muscle (SMCs) cells. Defects in OFT development can lead to severe malformations, including aortic aneurysms, which are frequently associated with impaired TGF-β signaling. To better understand the role of TGF-β signaling in OFT formation, we generated zebrafish lacking the TGF-β receptor Alk5 and found a strikingly specific dilation of the OFT: alk5-/- OFTs exhibit increased EC numbers as well as extracellular matrix (ECM) and SMC disorganization. Surprisingly, endothelial-specific alk5 overexpression in alk5-/- rescues the EC, ECM, and SMC defects. Transcriptomic analyses reveal downregulation of the ECM gene fibulin-5, which when overexpressed in ECs ameliorates OFT morphology and function. These findings reveal a new requirement for endothelial TGF-β signaling in OFT morphogenesis and suggest an important role for the endothelium in the etiology of aortic malformations.

Specific miRNA and Gene Deregulation Characterize the Increased Angiogenic Remodeling of Thoracic Aneurysmatic Aortopathy in Marfan Syndrome

Marfan syndrome (MFS) is a connective tissue disease caused by mutations in the FBN1 gene, leading to alterations in the extracellular matrix microfibril assembly and the early formation of thoracic aorta aneurysms (TAAs). Non-genetic TAAs share many clinico-pathological aspects with MFS and deregulation of some microRNAs (miRNAs) has been demonstrated to be involved in the progression of TAA. In this study, 40 patients undergoing elective ascending aorta surgery were enrolled to compare TAA histomorphological features, miRNA profile and related target genes in order to find specific alterations that may explain the earlier and more severe clinical outcomes in MFS patients. Histomorphological, ultrastructural and in vitro studies were performed in order to compare aortic wall features of MFS and non-MFS TAA. MFS displayed greater glycosaminoglycan accumulation and loss/fragmentation of elastic fibers compared to non-MFS TAA. Immunohistochemistry revealed increased CD133⁺ angiogenic remodeling, greater MMP-2 expression, inflammation and smooth muscle cell (SMC) turnover in MFS TAA. Cultured SMCs from MFS confirmed higher turnover and α-smooth muscle actin expression compared with non-MFS TAA. Moreover, twenty-five miRNAs, including miR-26a, miR-29, miR-143 and miR-145, were found to be downregulated and only miR-632 was upregulated in MFS TAA in vivo. Bioinformatics analysis revealed that some deregulated miRNAs in MFS TAA are implicated in cell proliferation, extracellular matrix structure/function and TGFβ signaling. Finally, gene analysis showed 28 upregulated and seven downregulated genes in MFS TAA, some of them belonging to the CDH1/APC and CCNA2/TP53 signaling pathways. Specific miRNA and gene deregulation characterized the aortopathy of MFS and this was associated with increased angiogenic remodeling, likely favoring the early and more severe clinical outcomes, compared to non-MFS TAA. Our findings provide new insights concerning the pathogenetic mechanisms of MFS TAA; further investigation is needed to confirm if these newly identified specific deregulated miRNAs may represent potential therapeutic targets to counteract the rapid progression of MFS aortopathy.

PRDM16 Upregulation Induced by MicroRNA-448 Inhibition Alleviates Atherosclerosis via the TGF-β Signaling Pathway Inactivation

The dysregulated expression of microRNAs (miRs) has been associated with pathological and physiological processes of atherosclerosis (AS). In addition, PR domain-containing 16 (PRDM16), a transcriptional mediator of brown fat cell identity and smooth muscle cell activities, may be involved in the hypercholesterolemia during development of AS. The bioinformatic analysis identified a regulatory miR-448 of PRDM16. Hence, the current study aimed to explore whether miR-448 influenced the activities of aortic smooth muscle cell (ASMCs) in AS. We validated that miR-448 was highly expressed in peripheral blood of patients with AS and aortic smooth muscle of AS model mice. Whereas, PRDM16 was downregulated in the aortic smooth muscle of AS model mice. PRDM16 overexpression was observed to inhibit oxidative stress injury and cell proliferation, and promote apoptosis of ASMCs. Mechanistic studies revealed that miR-448 targeted PRDM16 and negatively regulated the PRDM16 expression, while PRDM16 blocked the TGF-β signaling pathway. Furthermore, Downregulated miR-448 alleviated oxidative stress injury, and attenuated ASMC cell proliferation, migration and enhanced cell apoptosis through upregulation of PRDM16. Taken together, silencing of miR-448 upregulates PRDM16 and inactivates the TGF-β signaling pathway, thereby impeding development of AS by repressing the proliferation, migration and invasion of ASMCs.

Apoptosis and fibrosis of vascular smooth muscle cells in aortic dissection: an immunohistochemical study

Aortic dissection (AD) is a fatal disease characterized by a ruptured intima that leads to the complete rupture of the aorta. The aim of this study is to examine the immunohistochemical expression of inflammation/fibrosis-associated chemical mediators in AD patients. Surgical specimens of aortic tissues were obtained from 37 patients who underwent an open thoracic aortic repair. AD was detected with histological staining. Local congestion and hemorrhage as well as chronic inflammatory cells infiltrations were observed at the dissection. Moreover, extensive disarrangement and disruption of elastic fibers were observed in the medial layer of the aorta with dissection. In summary, our study revealed that the apoptotic rate of vascular SMCs (VSMCs) in the vascular middle layer is higher in the dissected aortas than in the control aortas, suggesting that abnormally elevated apoptosis is correlated with AD pathogenesis. Functional studies of key genes identified in the apoptotic pathways as well as in extracellular matrix would be critical in thoroughly understanding the underlying mechanisms of AD development. Targeting the mediators related to TGF-β1, the Smad family proteins, and caspase 3 or anti-apoptotic agents may provide diagnostic markers and therapeutic targets that could be used to prevent AD.

Loeys-Dietz syndrome pathology and aspects of cardiovascular management: A systematic review

Loeys-Dietz syndrome is an autosomal dominant genetic disorder which is associated with significant and often crucial vascular manifestations. This review is aimed to examine current evidence on pathophysiology and management of Loeys-Dietz syndrome in current era. A comprehensive electronic search was done to identify the articles that discussed all the aspects of Loeys-Dietz syndrome, combined key words and Medical Subject Headings (MeSH) terms were used. Relevant articles have been summarized in each relevant section. Loeys-Dietz syndrome is an autosomal dominant genetic disorder which has combined and multi-systemic manifestations. The increased breakdown of extracellular matrix predisposes an individual to developing aneurysms in the aortic tree which is undoubtedly the most significant complication of this disorder. Understanding the pathophysiology and natural history of Loeys-Dietz syndrome and regular surveillance is important to plan prophylactic interventions to prevent life-threatening aortic emergencies which can be fatal. Loeys-Dietz syndrome is an aggressive genetic condition that predisposes an individual to the development of life-threatening aortic aneurysms. Our understanding of Loeys-Dietz syndrome remains ever-changing and it is likely that the knowledge regarding its diagnosis and treatment will become more clearly defined in the coming years with deeper genetic studies.

Functional characterization and circulating expression profile of dysregulated microRNAs in BAV-associated aortopathy

Compelling evidence has shown that microRNAs (miRs) are involved in the pathophysiology of BAV-associated aortopathy. The purpose of this study was to assess the biological role as well as the circulating expression of two miRs (miR-424-3p and miR-3688-3p) that have been previously identified as significantly dysregulated in thoracic aortic aneurysm specimens of BAV patients. Bioinformatic tools were used to predict miR gene targets followed by functional validation transfecting synthetic miR mimics and negative controls into human aortic smooth muscle cells (HASMCs). Levels of miRs and target genes were evaluated by qRT-PCR. The circulating miR expression profile analysis was assessed on plasma samples collected from a cohort of 72 patients with aortopathy including 39 BAV (33 males; 58 ± 13 years) and 33 TAV patients (26 males; 67 ± 9 years). Computational analysis revealed that SMAD7 and YAP1 were potential targets of miR-424-3p and miR-3688-3p, respectively. Transfection with mimics confirmed a significantly decreased gene expression of SMAD7 and YAP1 compared to mimic negative control (p = 0.04 and p = 0.0005, respectively) or blank control (p = 0.01 and p = 0.0007, respectively). Overexpression of miR-3688-3p also significantly upregulated pro-apoptotic caspase-3 gene expression compared to mimic negative control (p = 0.02) or blank control (p = 0.01). Furthermore, a significant down-regulation of the circulating miR-424-3p was observed in BAV compared to TAV patients (p = 0.001). In multiple linear regression analysis, the aortic valve morphology (β = - 0.29, p = 0.04) and the presence of aortic stenosis (β = - 0.28, p = 0.03) had a significant effect on the miR-424-3p expression. In conclusion, our study demonstrated that miR-424-3p and miR-3688-3p directly targeted SMAD7 and YAP1 in HASMCs, pivotal genes of the TGF-β and Hippo-signaling pathways. Circulating miR-424-3p was also found to be significantly decreased in BAV patients when compared to TAV patients, especially in patients with aortic stenosis. Further large studies of well-characterized BAV patient cohorts are needed to define the clinical significance of the miR-424-3p.

Higher prevalence of splenic artery aneurysms in hereditary hemorrhagic telangiectasia: Vascular implications and risk factors

BACKGROUND

Splenic artery aneurysm (SAA) is a rare but potentially fatal condition. Rupture results in 25% mortality up to 75% in pregnant women with 95% fetal mortality. Brief reports suggest an increased risk of developing SAA in patients with HHT.

METHODS

We analyzed enhanced multidetector CT data in 186 HHT patients matched (gender and ± 5 year old) with 186 controls. We screened for SAA and recorded diameter of splenic and hepatic arteries and hepatic, pancreatic and splenic parenchymal involvements. We determined by univariate and multivariate analysis, the relationship with age, sex, genetic status, cardiovascular risk factors (CVRF) and visceral involvement.

RESULTS

SAA concerned 24.7% of HHT patients and 5.4% of controls, p<0.001. Factors associated with increased risk of SAA in HHT were female gender (p = 0.04, OR = 2.12, IC 95% = 1.03-4.50), age (p = 0.0003, OR = 1.04, 95% CI = 1.02-1.06) and pancreatic parenchymal involvement (p = 0.04, OR = 2.13, 95% CI = 1.01-4.49), but not type of mutation, hepatic or splenic parenchymal involvements, splenic size or splenic artery diameter or CVRF.

CONCLUSIONS

We found a 4.57 higher rate of SAA in HHT patients without evidence of splenic high output related disease or increased CVRF. These results suggest the presence of a vascular intrinsic involvement. It should lead to screening all HHT patients for SAA. The vasculopathy hypothesis could require a change in management as screening of all systemic arteries and even the aorta and to further research in the field.

Genetics of Thoracic and Abdominal Aortic Diseases

Dissections or ruptures of aortic aneurysms remain a leading cause of death in the developed world, with the majority of deaths being preventable if individuals at risk are identified and properly managed. Genetic variants predispose individuals to these aortic diseases. In the case of thoracic aortic aneurysm and dissections (thoracic aortic disease), genetic data can be used to identify some at-risk individuals and dictate management of the associated vascular disease. For abdominal aortic aneurysms, genetic associations have been identified, which provide insight on the molecular pathogenesis but cannot be used clinically yet to identify individuals at risk for abdominal aortic aneurysms. This compendium will discuss our current understanding of the genetic basis of thoracic aortic disease and abdominal aortic aneurysm disease. Although both diseases share several pathogenic similarities, including proteolytic elastic tissue degeneration and smooth muscle dysfunction, they also have several distinct differences, including population prevalence and modes of inheritance.

Deficiency of IL12p40 (Interleukin 12 p40) Promotes Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysm

Objective- Abdominal aortic aneurysm is caused by the accumulation of inflammatory cells in the aortic wall. Our recent studies demonstrated that inhibition of Notch signaling attenuates abdominal aortic aneurysm formation by shifting the macrophage balance towards anti-inflammatory (M2) phenotype. Using IL12p40^-/- (interleukin 12 p40) mice, we investigated the effects of M2-predominant macrophages on the development of abdominal aortic aneurysm. Approach and Results- Male (8-10 week-old) wild-type and IL12p40^-/- mice (n=15) on C57BL/6 background were infused with Ang II (angiotensin II, 1000 ng/kg per minute) by implanting osmotic pumps subcutaneously for 28 days. In the IL12p40^-/- mice, Ang II significantly increased the maximal intraluminal diameter (9/15) as determined by transabdominal ultrasound imaging. In addition, IL12p40-deletion significantly increased aortic stiffness in response to Ang II as measured by pulse wave velocity and atomic force microscopy. Histologically, IL12p40^-/- mice exhibited increased maximal external diameter of aorta and aortic lesions associated with collagen deposition and increased elastin fragmentation compared with wild-type mice infused with Ang II. Mechanistically, IL12p40 deficiency by siRNA (small interfering RNA) augmented the Tgfβ2-mediated Mmp2 expression in wild-type bone marrow-derived macrophages without affecting the expression of Mmp9. No such effects of IL12p40 deficiency on MMP2/MMP9 was observed in human aortic smooth muscle cells or fibroblasts. Depletion of macrophages in IL12p40^-/- mice by clodronate liposomes significantly decreased the maximal external diameter of aorta and aortic stiffness in response to Ang II as determined by imaging and atomic force microscopy. Conclusions- IL12p40 depletion promotes the development of abdominal aortic aneurysm, in part, by facilitating recruitment of M2-like macrophages and potentiating aortic stiffness and fibrosis mediated by Tgfβ2.

A functional variant of SMAD4 enhances macrophage recruitment and inflammatory response via TGF-β signal activation in Thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm and dissection (TAAD) is the most fatal macro vascular disease. The mortality of 48h after diagnosis of dissection is up to approximately 50-68%. However, the genetic factors and potential mechanism underlying sporadic TAAD remain largely unknown. Our previous study suggested rs12455792 variant of SMAD4 gene significantly contributed to the increased risk and might participated the pathological progression of TAAD. This investigation aims to test (1) the associations between rs12455792 and MØ recruitment, inflammatory response in aggressiveness of TAAD, and (2) the molecular mechanism accounting for their effects. In TGF-β signaling molecular detection, rs12455792 C>T variant activated the canonical and non-canonical TGF-β mediators. It also increased the secretion of chemotactic factors of HASMCs. To confirm the impact of this change, we detected MØ recruitment and infiltration in HASMCs and aortic tissues of TAAD patients. We found that MØ recruitment in cells and tissues with rs12455792 variant genotypes was increased than that in wild type groups. Moreover, rs12455792 variant increased M1 type inflammatory response, which might contribute much to TAAD progression. To mimic the SMAD4 suppression effect of rs12455792 in vivo, we constructed the SMAD4 KD mouse. After induction with Ang II for 4w, the thoracic aorta dilatation and vascular remodeling were more serious than that of wild type group. In conclusion, rs12455792 increased MØ recruitment, M1 type inflammatory response via activated TGF-β signaling, and further promoted vascular remodeling and pathological progress of TAAD.

Bicuspid aortic valve-associated aortopathy: Where do we stand?

Herein we summarize the current knowledge on the bicuspid aortic valve (BAV)-associated aortopathy regarding clinical presentation and disease sub-classification, genetic background, hemodynamics, histopathology, cells and signaling, animal models, and biomarkers. Despite enormous efforts in research in all of the above areas, important issues remain unknown: (i) what is the ontogenetic basis of BAV development? (ii) how can we explain the diversity of BAV and associated aortopathy phenotypes? (iii) what are the signaling processes in aortopathy pathogenesis and how can we interfere with these processes? Despite undoubtedly great progress that has been made in the understanding of BAV-associated aortopathy, so far researchers have put together a heap of Lego bricks, but at present it is unclear if the bricks are compatible, how they fit together, and which parts are missing to build the true model of the BAV aorta. A joint approach is needed to accelerate research progress.

Inhibition of Marfan Syndrome Aortic Root Dilation by Losartan: Role of Angiotensin II Receptor Type 1-Independent Activation of Endothelial Function

Marfan syndrome (MFS) is a genetic disorder that frequently leads to aortic root dissection and aneurysm. Despite promising preclinical and pilot clinical data, a recent large-scale study using antihypertensive angiotensin II (AngII) receptor type 1 (ATR1) blocker losartan has failed to meet expectations at preventing MFS-associated aortic root dilation, casting doubts about optimal therapy. To study the deleterious role of normal ATR1 signaling in aortic root widening, we generated MFS mice lacking ATR1a expression in an attempt to preserve protective ATR2 signaling. Despite being hypotensive and resistant to AngII vasopressor effects, MFS/ATR1a-null mice showed unabated aortic root enlargement and remained fully responsive to losartan, confirming that blood pressure lowering is of minor therapeutic value in MFS and that losartan's antiremodeling properties may be ATR1 independent. Having shown that MFS causes endothelial dysfunction and that losartan can activate endothelial function in mice and patients, we found that nitric oxide synthase (NOS) inhibition renders losartan therapeutically inactive, whereas multiple transgenic and pharmacologic models of endothelial NOS activation block aortic root dilation by correcting extracellular signal-regulated kinase signaling. In vitro, losartan can increase endothelial NO release in the absence of AngII and correct MFS NO levels in vivo. Our data suggest that increased protective endothelial function, rather than ATR1 inhibition or blood pressure lowering, might be of therapeutic significance in preventing aortic root disease in MFS.

Expressions of Transforming Growth Factor β1 Signaling Cytokines in Aortic Dissection

Objective

To demonstrate the underlying mechanisms of aortic dissection compared to those of coronary artery disease in terms of the transforming growth factor-beta (TGF-β) signaling pathway.

Methods

Twenty consecutive aortic dissection patients and 20 consecutive coronary artery disease patients undergoing a surgical treatment in this hospital were enrolled into this study. The aortic tissues were sampled and the TGF-β₁ and its receptor TGF-β receptor I (TβRI) were detected by Western blotting assay.

Results

TGF-β₁ and TβRI were positively expressed in the aortic tissues in both groups by Western blotting assay. The expressions of the two proteins were significantly higher in the aortic tissue of patients with aortic dissection than in those with coronary artery disease. The quantitative analyses of the relative gray scales of the proteins disclosed close correlations between the expressions of TGF-β1 and TβRI in both the study and control group patients.

Conclusions

The aortic remodeling of aortic dissection might differ from that of coronary artery atherosclerosis concerning the nature, mechanism, mode, and activities of TGF-β signaling pathway. The development of aortic dissection could be associated with a significantly enhanced function of TGF-β₁/Smad signaling transduction as a result of aortic remodeling incorporating both vascular injury and repair.

Increased risk of aortic aneurysm and dissection in patients with Sjögren's syndrome: a nationwide population-based cohort study in Taiwan

OBJECTIVES

Sjögren's syndrome (SS) is a systemic autoimmune disorder. Several molecular pathways and the activation of matrix metalloproteinases associated with the pathogenesis of SS participate in the initiation and progression of aortic aneurysm (AA) and aortic dissection (AD). In this study, we aimed to evaluate whether patients with SS exhibit an increased risk of AA or AD.

METHODS

We conducted a retrospective cohort study using a database extracted from Taiwan's National Health Insurance Research Database. All medical conditions for each case and control were categorised using the International Classification of Diseases, Ninth Revision. HRs and 95% CIs for associations between SS and AA/AD were estimated using Cox regression and adjusted for comorbidities.

RESULTS

Our analyses included 10 941 SS cases and 43 764 propensity score-matched controls. Compared with the controls, the patients with SS exhibited a significantly increased risk of developing an AA or AD (adjusted HR=3.642, p<0.001). Subgroup analysis revealed that compared with patients without SS, patients with primary and secondary SS both exhibited a significantly increased risk of developing AA or AD (adjusted HR=1.753, p=0.042; adjusted HR=3.693, p<0.001).

CONCLUSION

Patients with SS exhibit increased risks of developing AA or AD, and healthcare professionals should be aware of this risk when treating patients with SS. Increased aortic surveillance may be required for patients with SS.

A chemo-mechano-biological formulation for the effects of biochemical alterations on arterial mechanics: the role of molecular transport and multiscale tissue remodelling

This paper presents a chemo-mechano-biological framework for arterial physiopathology. The model accounts for the fine remodelling in the multiscale hierarchical arrangement of tissue constituents and for the diffusion of molecular species involved in cell-cell signalling pathways. Effects in terms of alterations in arterial compliance are obtained. A simple instructive example is introduced. Although oversimplified with respect to realistic case studies, the proposed application mimics the biochemical activity of matrix metalloproteinases, transforming growth factors beta and interleukins on tissue remodelling. Effects of macrophage infiltration, of intimal thickening and of a healing phase are investigated, highlighting the corresponding influence on arterial compliance. The obtained results show that the present approach is able to capture changes in arterial mechanics as a consequence of the alterations in tissue biochemical environment and cellular activity, as well as to incorporate the protective role of both autoimmune responses and pharmacological treatments.

Differential expression profile of long non-coding RNAs in human thoracic aortic aneurysm

Thoracic aortic aneurysm (TAA) is progressive fatal aortic pathological dilation, which is characterized by increased proteoglycans and loss of elastic fibers. Recent advances in long non-coding RNAs (lncRNAs), an important regulator in many biological processes, suggested the close correlation between expression patterns and disease progression. In the present study, the ascending aortic tissues were collected from ascending TAA patients (n = 33) and organ donors (n = 16). Microarray analysis and real-time PCR were then applied to detect the lncRNA expression profiles. A total of 147 differentially expressed lncRNAs were determined, including 104 upregulated and 43 downregulated lncRNAs. Bioinformatics analysis showed 51.7% of differentially expressed lncRNAs were sense-overlapping, and most of the down-regulated lncRNAs were located on chromosome 1, 7, and 12. Subgroup analysis of TAA patients indicated that the expression of lnc-HLTF-5 was significantly higher in hypertension group than non-hypertension group (P < 0.05). Spearman correlation analysis further confirmed that the lnc-HLTF-5 level was positively correlated with the expanded ascending aortic diameter (r_s  = 0.483, P = 0.004) and MMP9 level (r_s  = 0.465, P = 0.006). Our results expanded the lncRNA expression patterns in aortic disease, and provided experimental basis for future investigation on TAA pathogenesis.

Role of ADAMTS-5 in Aortic Dilatation and Extracellular Matrix Remodeling

Supplemental Digital Content is available in the text.

Objective—

Thoracic aortic aneurysm (TAA), a degenerative disease of the aortic wall, is accompanied by changes in the structure and composition of the aortic ECM (extracellular matrix). The ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) family of proteases has recently been implicated in TAA formation. This study aimed to investigate the contribution of ADAMTS-5 to TAA development.

Approach and Results—

A model of aortic dilatation by AngII (angiotensin II) infusion was adopted in mice lacking the catalytic domain of ADAMTS-5 (Adamts5^Δcat). Adamts5^Δcat mice showed an attenuated rise in blood pressure while displaying increased dilatation of the ascending aorta (AsAo). Interestingly, a proteomic comparison of the aortic ECM from AngII-treated wild-type and Adamts5^Δcat mice revealed versican as the most upregulated ECM protein in Adamts5^Δcat mice. This was accompanied by a marked reduction of ADAMTS-specific versican cleavage products (versikine) and a decrease of LRP1 (low-density lipoprotein-related protein 1). Silencing LRP1 expression in human aortic smooth muscle cells reduced the expression of ADAMTS5, attenuated the generation of versikine, but increased soluble ADAMTS-1. A similar increase in ADAMTS-1 was observed in aortas of AngII-treated Adamts5^Δcat mice but was not sufficient to maintain versican processing and prevent aortic dilatation.

Conclusions—

Our results support the emerging role of ADAMTS proteases in TAA. ADAMTS-5 rather than ADAMTS-1 is the key protease for versican regulation in murine aortas. Further studies are needed to define the ECM substrates of the different ADAMTS proteases and their contribution to TAA formation.

Increased blood levels of transforming growth factor β in patients with aortic dilatation

OBJECTIVES

Recent studies have shown that patients with syndromic thoracic aortic aneurysm, particularly patients with bicuspid aortic valve, have increased blood levels of transforming growth factor β1 (TGF-β1), indicating this molecule as a prognostic biomarker. However, it is not known whether TGF-β1 is also elevated in the blood of patients with tricuspid aortic valve and aortic dilatation.

METHODS

We analysed the plasma levels of TGF-β1 in 52 patients with tricuspid or bicuspid aortic valve and with normal or dilated ascending aorta who underwent cardiac surgery in our hospital.

RESULTS

TGF-β1 blood level was significantly increased two-fold in patients with tricuspid aortic valve and dilated aorta compared to patients with tricuspid aortic valve and normal aorta.

CONCLUSIONS

Our results suggest that TGF-β1 blood levels may serve as a prognostic biomarker for patients with syndromic and non-syndromic thoracic aortic aneurysm. Further studies with larger cohorts of patients should be performed to confirm these results.

Deregulated TGF-β/BMP Signaling in Vascular Malformations

Correct organization of the vascular tree requires the balanced activities of several signaling pathways that regulate tubulogenesis and vascular branching, elongation, and pruning. When this balance is lost, the vessels can be malformed and fragile, and they can lose arteriovenous differentiation. In this review, we concentrate on the transforming growth factor (TGF)-β/bone morphogenetic protein (BMP) pathway, which is one of the most important and complex signaling systems in vascular development. Inactivation of these pathways can lead to altered vascular organization in the embryo. In addition, many vascular malformations are related to deregulation of TGF-β/BMP signaling. Here, we focus on two of the most studied vascular malformations that are induced by deregulation of TGF-β/BMP signaling: hereditary hemorrhagic telangiectasia (HHT) and cerebral cavernous malformation (CCM). The first of these is related to loss-of-function mutation of the TGF-β/BMP receptor complex and the second to increased signaling sensitivity to TGF-β/BMP. In this review, we discuss the potential therapeutic targets against these vascular malformations identified so far, as well as their basis in general mechanisms of vascular development and stability.