Development Of Thoracic Aortic Aneurysm Research Articles

Metabolic plasma signatures in thoracic aortic aneurysm associated to tricuspid and bicuspid aortic valves

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Instituto de Salud Carlos III with co-funding from the ERDF and Comunidad de Madrid Background/Introduction Thoracic aortic aneurysm (TAA) develops asymptomatic with life-threatening consequences and its diagnosis is usually fortuitous. TAA is mostly idiopathic, although its prevalence is significantly higher in subjects with bicuspid aortic valve (BAV) for unknown reasons. We hypothesize that it is essential to investigate idiopathic TAA by differentiating between BAV and tricuspid aortic valve (TAV) patients for personalized diagnosis and treatment. Purpose We aimed to identify plasma metabolic profiles of aortic dilatation in idiopathic TAA, differentiating between subjects with BAV or TAV. Methods Plasma samples from 41 idiopathic TAA patients and 57 subjects without aortic dilatation (control, C) were collected and classified according to aortic valve type (BAV or TAV). Full metabolomics coverage was carried out by 1H RMN and LC-MS/MS untargeted analysis, including reverse phase and hydrophilic interaction chromatography and positive and negative electrospray ionization modes. Significant variation in metabolite levels were considered if FDR-adjusted p-value <0.05. Results Our analyses highlighted a metabolic signature specific for BAV and TAV subjects. BAV patients presented a marked glycerophospholipid metabolism alteration involving different lysophospholipids (LPAs, LPCs and LPEs) and phospholipids (PCs, PEs, PAs and PIs). Particularly, LPCs and LPEs were increased in BAV-TAA vs BAV-C, being an indicator of stimulation of glucose utilization through glycolysis and suppression of fatty acid biosynthesis. In contrast, carnitine-related metabolism was the most altered pathway observed in TAV subjects. In particular, we detected an increment in plasma acylcarnitines in TAV-TAA compared to TAV-C suggesting an altered β-oxidation of fatty acids and mitochondrial overload. Conclusions Idiopathic TAA development is differentially reflected in plasma from BAV and TAV patients, supporting an individualized diagnosis valve-dependent and suggesting also differential therapeutic targets.

Divergent and Compensatory Effects of BMP2 and BMP4 on the VSMC Phenotype and BMP4's Role in Thoracic Aortic Aneurysm Development.

Vascular smooth muscle cells (VSMCs) play a key role in aortic aneurysm formation. Bone morphogenetic proteins (BMPs) have been implicated as important regulators of VSMC phenotype, and dysregulation of the BMP pathway has been shown to be associated with vascular diseases. The aim of this study was to investigate for the first time the effects of BMP-4 on the VSMC phenotype and to understand its role in the development of thoracic aortic aneurysms (TAAs). Using the angiotensin II (AngII) osmotic pump model in mice, aortas from mice with VSMC-specific BMP-4 deficiency showed changes similar to AngII-infused aortas, characterised by a loss of contractile markers, increased fibrosis, and activation of matrix metalloproteinase 9. When BMP-4 deficiency was combined with AngII infusion, there was a significantly higher rate of apoptosis and aortic dilatation. In vitro, VSMCs with mRNA silencing of BMP-4 displayed a dedifferentiated phenotype with activated canonical BMP signalling. In contrast, BMP-2-deficient VSMCs exhibited the opposite phenotype. The compensatory regulation between BMP-2 and BMP-4, with BMP-4 promoting the contractile phenotype, appeared to be independent of the canonical signalling pathway. Taken together, these results demonstrate the impact of VSMC-specific BMP-4 deficiency on TAA development.

Association between vascular FDG uptake during follow-up and the development of thoracic aortic aneurysms in giant cell arteritis.

A positive PET scan at diagnosis was associated with a greater yearly increase in ascending and descending aortic diameter and thoracic aortic volume in patients with giant cell arteritis (GCA). Radiologic and histopathologic vascular abnormalities persist in a subset of treated patients despite clinical remission. The aim of this study was to evaluate the association between vascular FDG uptake during follow-up and the development of thoracic aortic aneurysms. We recently performed a prospective cohort study of 106 GCA patients, who underwent FDG PET and CT imaging at diagnosis and CT imaging yearly for a maximum of 10 years. In this post hoc analysis, GCA patients who also have had FDG PET imaging during follow-up were included. PET scans were visually scored (0-3) at 7 vascular areas. PET scans were considered positive in case of FDG uptake ≥grade 2 in any large vessel. Eighty-eight repeat PET scans were performed in 52 out of 106 GCA patients, who were included in the original prospective cohort. Fifty-five (63%) PET scans were done at the time of a relapse and 33 (38%) were done while in remission. Nine out of ten patients with an incident thoracic aortic aneurysm had both a positive PET scan at diagnosis and during follow-up. In addition to the intensity and extent of the initial vascular inflammation, ongoing aortic inflammation may contribute to the development of thoracic aortic aneurysms in GCA. However, this hypothesis should be confirmed in a large prospective trial with repeat PET scans at predefined time points during follow-up.

Enhancer of zeste homolog 2 facilitates phenotypic transition of vascular smooth muscle cells leading to aortic aneurysm/dissection.

Thoracic aortic aneurysms (TAAs) are a major cause of death owing to weaker blood vessel walls and higher rupture rates in affected individuals. Vascular smooth muscle cells (VSMCs) are the predominant cell type within the aortic wall and their dysregulation may contribute to TAA progression. Enhancer of zeste homolog 2 (EZH2), a histone methyltransferase, is involved in several pathological processes; however, the biological functions and mechanisms underlying VSMC phenotype transition and vascular intimal hyperplasia remain unclear. The present study aimed to determine the involvement of EZH2 in mediating VSMC function in the development of TAAs. The expression of EZH2 was revealed to be elevated in patients with thoracic aortic dissection and TAA mouse model through western blotting and reverse transcription-quantitative PCR experiments. Subsequently, a mouse model was established using β-aminopropionitrile. In vitro, EdU labeling, Transwell assay, wound healing assay and hematoxylin-eosin staining revealed that knocking down the Ezh2 gene could reduce the proliferation, invasion, migration, and calcification of mouse primary aortic smooth muscle cells. Flow cytometry analysis found that EZH2 deficiency increased cell apoptosis. Depletion of Ezh2 in mouse primary aortic VSMCs promoted the transformation of VSMCs from a synthetic to a contractile phenotype. Using RNA-sequencing analysis, it was demonstrated that Ezh2 regulated a group of genes, including integrin β3 (Itgb3), which are critically involved in the extracellular matrix signaling pathway. qChIP found Ezh2 occupies the Itgb3 promoter, thereby suppressing the expression of Itgb3. Ezh2 promotes the invasion and calcification of VSMCs, and this promoting effect is partially reversed by co-knocking down Itgb3. In conclusion, the present study identified a previously unrecognized EZH2-ITGB3 regulatory axis and thus provides novel mechanistic insights into the pathophysiological function of EZH2. EZH2 may thus serve as a potential target for the management of TAAs.

Animal Models, Pathogenesis, and Potential Treatment of Thoracic Aortic Aneurysm.

Thoracic aortic aneurysm (TAA) has a prevalence of 0.16-0.34% and an incidence of 7.6 per 100,000 person-years, accounting for 1-2% of all deaths in Western countries. Currently, no effective pharmacological therapies have been identified to slow TAA development and prevent TAA rupture. Large TAAs are treated with open surgical repair and less invasive thoracic endovascular aortic repair, both of which have high perioperative mortality risk. Therefore, there is an urgent medical need to identify the cellular and molecular mechanisms underlying TAA development and rupture to develop new therapies. In this review, we summarize animal TAA models including recent developments in porcine and zebrafish models: porcine models can assess new therapeutic devices or intervention strategies in a large mammal and zebrafish models can employ large-scale small-molecule suppressor screening in microwells. The second part of the review covers current views of TAA pathogenesis, derived from recent studies using these animal models, with a focus on the roles of the transforming growth factor-beta (TGFβ) pathway and the vascular smooth muscle cell (VSMC)-elastin-contractile unit. The last part discusses TAA treatment options as they emerge from recent preclinical studies.

Silencing COQ8B in Aortic Smooth Muscle Cells Reveals Cellular Dysfunction Related to Changes in Cell Proliferation

Background/Objective: Thoracic aortic aneurysm (TAA) is a prevalent disorder that predisposes to aortic dissection. Prior work identified the ubiquinone biosynthesis gene COQ8B as a genetic modifier of TAA progression. We sought to determine the impact of decreased COQ8B on global transcription in aortic smooth muscle cells (SMCs).
 Methods: Primary human aortic SMCs from a healthy donor were seeded in 12-well plates. Six experimental conditions were created, each with 3 replicates: 1) siRNA targeting COQ8B (siCOQ8B); 2) siRNA targeting the dominant TAA gene SMAD3 (siSMAD3); 3) negative controlsiRNA (siNeg); 4) siCOQ8B and siSMAD3; 5) siCOQ8B with Angiotensin II (AngII) stimulation (siCOQ8B+AngII); 6) siNeg+AngII. RNA was extracted approximately 48 hours post-siRNA transfection and, for AngII conditions, after 1 hour of incubation with AngII (100 nM). mRNAsequencing was performed and downstream analysis utilized R packages EdgeR and topGO.
 Results: Multidimensional scaling identified distinct clustering of samples by experimental condition. Downregulated genes in siCOQ8B were enriched for Gene Ontology pathways related to cell proliferation including cell cycle regulators, DNA replication, and mitosis. MYOCD, a master regulator of SMC homeostasis, was downregulated. Similar proliferation-related pathways were enriched in siCOQ8B+siSMAD3 and siCOQ8B+AngII compared to siNeg. Pathways related to cell proliferation in siCOQ8B+AngII cells were downregulated when compared to siCOQ8B which indicates that AngII infusion in the context of COQ8B silencing may further dysregulate cell proliferation pathways.
 Conclusion: The results indicate that COQ8B has an important role in cell cycle processes in aortic SMCs, including when SMCs are exposed to stressors associated with TAA development. Stimulation of angiotensin receptors may exacerbate the effects of decreased COQ8B in these processes. To investigate these experimental results in human pathology, bulk RNA samples and intact nuclei have been isolated from frozen human aortic specimens and prepared for transcriptomic analysis.

From Natural History to Contemporary Management of Aortic Diseases: A State-of-the-Art Review of Thoracic Aortic Aneurysm

Thoracic aortic aneurysms (TAAs) are commonly seen in cardiovascular practice. Acquired and genetic conditions contribute to TAA formation. The natural history of genetically mediated TAA underscores the importance of early detection, regular monitoring, and prompt treatment to prevent complications, including dissection or rupture. The prognosis is poor in the event of acute dissection, with high rates of in-hospital mortality. Healthcare providers need to remain vigilant in their efforts to identify and surveil TAA to reduce the risk of complications. In this manuscript, we review the natural history of TAA, discuss the most common causes leading to the development of TAA, assess the value and limitations of diagnostic modalities, and review the management and long-term surveillance of patients with aortic disease.

Dissecting aortic aneurysm in Marfan syndrome is associated with losartan-sensitive transcriptomic modulation of aortic cells.

To improve our limited understanding of the pathogenesis of thoracic aortic aneurysm (TAA) that leads to acute aortic dissection, single-cell RNA sequencing (scRNA-seq) was employed to profile disease-relevant transcriptomic changes of aortic cell populations in a well-characterized mouse model of the most commonly diagnosed form of Marfan syndrome (MFS). As result, 2 discrete subpopulations of aortic cells (SMC3 and EC4) were identified only in the aorta of Fbn1mgR/mgR mice. SMC3 cells highly express genes related to extracellular matrix formation and nitric oxide signaling, whereas the EC4 transcriptional profile is enriched in smooth muscle cell (SMC), fibroblast, and immune cell-related genes. Trajectory analysis predicted close phenotypic modulation between SMC3 and EC4, which were therefore analyzed together as a discrete MFS-modulated (MFSmod) subpopulation. In situ hybridization of diagnostic transcripts located MFSmod cells at the intima of Fbn1mgR/mgR aortas. Reference-based data set integration revealed transcriptomic similarity between MFSmod- and SMC-derived cell clusters modulated in human TAA. Consistent with the angiotensin II type I receptor (At1r) contribution to TAA development, MFSmod cells were absent in the aorta of Fbn1mgR/mgR mice treated with the At1r antagonist losartan. Altogether, our findings indicate that a discrete dynamic alteration of aortic cell identity is associated with dissecting TAA in MFS mice and increased risk of aortic dissection in MFS patients.

Dysfunctions of the C-type natriuretic peptide signaling pathway involved in the development of thoracic aortic aneurysm in Marfan patients

Marfan Syndrome (MFS) is an autosomal dominant inherited connective tissue disorder affecting the cardio-vascular system. Development of thoracic aortic aneurysms (TAA) leading to dissections and ruptures is the primary cause of morbidity and mortality in these patients. No treatment really cures Marfan patients. Interestingly, in humans, mutations in the gene coding for the C-type natriuretic peptide (CNP) or its receptors lead to a “Marfan-like syndrome”. CNP is a local regulator of skeletal growth and of vascular homeostasis, remodeling and angiogenesis. CNP binds to NPR-B or NPR-C receptors, both expressed on endothelial and vascular smooth muscle cells (vSMCs) and modulates the intracellular cGMP and cAMP levels. The aim of this project is to determine whether altered CNP signaling pathway contributes to TAA development and progression to rupture in Marfan patients. Plasma and aorta biopsies were taken from Marfan patients and from Fbn1C1039G/+ mice. The CNP, TGF-beta, cAMP and cGMP concentrations were measured in the plasma. mRNA and protein levels evaluated by qRT-PCR, and Western blot analysis in aortic tissue. Male and female mice studied and alterations of the aorta structure analyzed by ultrasound imaging. Plasma proCNP level in Marfan patients depends on the age and the TAA development. Increased levels found in young patients presenting no or reduced TAA and decreased levels in patients with TAA compared to age and sex-matched non-Marfan patients. CNP and NPR-C decreased at the mRNA and protein levels in the aorta of Marfan patients when compared to the same aorta in non-Marfan patients. In Fbn1+/- mice, aortic structure alterations are detected from 10 weeks in males and 34 weeks in females. CNP and NPR-C mRNA and protein levels drastically decreased in the thoracic aorta in 2–7 week-old male mice and in 34 week-old female mice. In 52-week old Fbn1+/- mice, the plasma cAMP level is increased in males and not in females, whereas the plasma cGMP protein level is increased in females but not in males. CNP injections in 3-week old Fbn1+/- male mice partially prevented the aorta structure alterations. A deficit in CNP protein level or in the expression of the NPR-C receptor contributes to the development and progression of TAA.

340 The Effects of PTSD-Dependent Neurogenic Hypertension and Inflammation on Thoracic Aortic Aneurysm Progression

OBJECTIVES/GOALS: Nearly all thoracic aortic aneurysm patients suffer from hypertension leading to elevated wall tension and abnormal extracellular matrix remodeling. PTSD patients have higher blood pressure both at rest and in response to stimuli. Although stress is associated with cardiovascular disease, the exact mechanism linking the two is still unknown. METHODS/STUDY POPULATION: Adult C57BL/6 mice underwent a PTSD induction protocol consisting of inescapable foot shock followed by single prolonged stress. The mice were assessed incrementally for their PTSD-like phenotype using specific behavioral tests chosen to assess for each of the human criteria of PTSD according to the DSM-V. Tail cuff blood pressure measurements were taken serially throughout the 16-week protocol. At terminal study, thoracic aortic diameter measurements were obtained through digital microscopy and plasma was harvested for cytokine analysis. Thoracic aortic aneurysms (TAA) were induced through periadventitial application of a calcium chloride solution on the descending thoracic aorta in BPH/2J and BPN/3J adult mice. The thoracic aortic diameter was measured at terminal study through digital microscopy. RESULTS/ANTICIPATED RESULTS: Using our PTSD-like mouse model we have demonstrated that PTSD-like mice have significantly higher systolic blood pressure following a reminder of the traumatic event than control mice recapitulating the human phenotype. They also had increased plasma proinflammatory cytokines and larger thoracic aortic diameters than control mice. Although the increased thoracic aortic diameter is not an aneurysm, it suggests ECM remodeling is occurring predisposing the aorta to aneurysm formation. Finally, we have shown that in neurogenic hypertensive mice, TAA formation was accelerated by 12 weeks with roughly 70% dilation at 4 weeks post-TAA induction surgery as compared to roughly a 20% dilation in control mice. DISCUSSION/SIGNIFICANCE: Altogether, these studies reinforce the link between stress and TAA development, and our mouse model will allow for the underlying mechanism to be elucidated. Better understanding of the mechanism linking PTSD and TAA will allow for the creation of novel therapeutics to treat PTSD symptoms while also delaying TAA progression.

Attenuation of Smooth Muscle Cell Phenotypic Switching by Angiotensin 1-7 Protects against Thoracic Aortic Aneurysm.

Thoracic aortic aneurysm (TAA) involves extracellular matrix (ECM) remodeling of the aortic wall, leading to reduced biomechanical support with risk of aortic dissection and rupture. Activation of the renin-angiotensin system, and resultant angiotensin (Ang) II synthesis, is critically involved in the onset and progression of TAA. The current study investigated the effects of angiotensin (Ang) 1-7 on a murine model of TAA. Male 8-10-week-old ApoEKO mice were infused with Ang II (1.44 mg/kg/day) and treated with Ang 1-7 (0.576 mg/kg/day). ApoEKO mice developed advanced TAA in response to four weeks of Ang II infusion. Echocardiographic and histological analyses demonstrated increased aortic dilatation, excessive structural remodelling, perivascular fibrosis, and inflammation in the thoracic aorta. Ang 1-7 infusion led to attenuation of pathological phenotypic alterations associated with Ang II-induced TAA. Smooth muscle cells (SMCs) isolated from adult murine thoracic aorta exhibited excessive mitochondrial fission, oxidative stress, and hyperproliferation in response to Ang II. Treatment with Ang 1-7 resulted in inhibition of mitochondrial fragmentation, ROS generation, and hyperproliferation. Gene expression profiling used for characterization of the contractile and synthetic phenotypes of thoracic aortic SMCs revealed preservation of the contractile phenotype with Ang 1-7 treatment. In conclusion, Ang 1-7 prevented Ang II-induced vascular remodeling and the development of TAA. Enhancing Ang 1-7 actions may provide a novel therapeutic strategy to prevent or delay the progression of TAA.

Impacts of Telomeric Length, Chronic Hypoxia, Senescence, and Senescence-Associated Secretory Phenotype on the Development of Thoracic Aortic Aneurysm

Thoracic aortic aneurysm (TAA) is an age-related and life-threatening vascular disease. Telomere shortening is a predictor of age-related diseases, and its progression is associated with premature vascular disease. The aim of the present work was to investigate the impacts of chronic hypoxia and telomeric DNA damage on cellular homeostasis and vascular degeneration of TAA. We analyzed healthy and aortic aneurysm specimens (215 samples) for telomere length (TL), chronic DNA damage, and resulting changes in cellular homeostasis, focusing on senescence and apoptosis. Compared with healthy thoracic aorta (HTA), patients with tricuspid aortic valve (TAV) showed telomere shortening with increasing TAA size, in contrast to genetically predisposed bicuspid aortic valve (BAV). In addition, TL was associated with chronic hypoxia and telomeric DNA damage and with the induction of senescence-associated secretory phenotype (SASP). TAA-TAV specimens showed a significant difference in SASP-marker expression of IL-6, NF-κB, mTOR, and cell-cycle regulators (γH2AX, Rb, p53, p21), compared to HTA and TAA-BAV. Furthermore, we observed an increase in CD163+ macrophages and a correlation between hypoxic DNA damage and the number of aortic telocytes. We conclude that chronic hypoxia is associated with telomeric DNA damage and the induction of SASP in a diseased aortic wall, promising a new therapeutic target.

The CCN2 Polymorphism rs12526196 Is a Risk Factor for Ascending Thoracic Aortic Aneurysm.

Cellular communication network factor 2 (CCN2/CTGF) has been traditionally described as a downstream mediator of other profibrotic factors including transforming growth factor (TGF)-β and angiotensin II. However, recent evidence from our group demonstrated the direct role of CCN2 in maintaining aortic wall homeostasis and acute and lethal aortic aneurysm development induced by angiotensin II in the absence of CCN2 in mice. In order to translate these findings to humans, we evaluated the potential association between three polymorphisms in the CCN2 gene and the presence of a thoracic aortic aneurysm (TAA). Patients with and without TAA retrospectively selected were genotyped for rs6918698, rs9402373 and rs12526196 polymorphisms related to the CCN2 gene. Multivariable logistic regression models were performed. In our population of 366 patients (69 with TAA), no associations were found between rs6918698 and rs9402373 and TAA. However, the presence of one C allele from rs12526196 was associated with TAA comparing with the TT genotype, independently of risk factors such as sex, age, hypertension, type of valvulopathy and the presence of a bicuspid aortic valve (OR = 3.17; 95% CI = 1.30-7.88; p = 0.011). In conclusion, we demonstrated an association between the C allele of rs12526196 in the CCN2 gene and the presence of TAA. This study extrapolates to humans the relevance of CCN2 in aortic aneurysm observed in mice and postulates, for the first time, a potential protective role to CCN2 in aortic aneurysm pathology. Our results encourage future research to explore new variants in the CCN2 gene that could be predisposed to TAA development.

Short-term rapamycin treatment increases life span and attenuates aortic aneurysm in a murine model of Marfan-Syndrome

BackgroundMarfan syndrome (MFS) is a genetic disorder leading to medial aortic degeneration and life-limiting dissections. To date, there is no causal prevention or therapy. Rapamycin is a potent and selective inhibitor of the mechanistic target of rapamycin (mTOR) protein kinase, regulating cell growth and metabolism. The mgR/mgR mice represent an accepted MFS model for studying aortic pathologies to understand the underlying molecular pathomechanisms. This study investigated whether rapamycin inhibits the development of thoracic aortic aneurysms and dissections in mgR/mgR mice. MethodsIsolated primary aortic smooth muscle cells (mAoSMCs) from mgR/mgR mice were used for in vitro studies. Two mg kg/BW rapamycin was injected intraperitoneally daily for two weeks, beginning at 7–8 weeks of age. Mice were sacrificed 30 days post-treatment. Histopathological and immunofluorescence analyses were performed using adequate tissue specimens and techniques. Animal survival was evaluated accompanied by periodic echocardiographic examinations of the aorta. ResultsThe protein level of the phosphorylated ribosomal protein S6 (p-RPS6), a downstream target of mTOR, was significantly increased in the aortic tissue of mgR/mgR mice. In mAoSMCs isolated from these animals, expression of mTOR, p-RPS6, tumour necrosis factor α, matrix metalloproteinase-2 and -9 was significantly suppressed by rapamycin, demonstrating its anti-inflammatory capacity. Short-term rapamycin treatment of Marfan mice was associated with delayed aneurysm formation, medial aortic elastolysis and improved survival. ConclusionsShort-term rapamycin-mediated mTOR inhibition significantly reduces aortic aneurysm formation and thus increases survival in mgR/mgR mice. Our results may offer the first causal treatment option to prevent aortic complications in MFS patients.

ANGIOTENSIN 1-7 EXERTS PROTECTIVE EFFECTS IN THORACIC AORTIC ANEURYSM BY ATTENUATING SMOOTH MUSCLE CELL PHENOTYPIC SWITCHING

ANGIOTENSIN 1-7 EXERTS PROTECTIVE EFFECTS IN THORACIC AORTIC ANEURYSM BY ATTENUATING SMOOTH MUSCLE CELL PHENOTYPIC SWITCHING

Low copper levels measured in the aortic wall of New Zealand patients with non-syndromic ascending thoracic aortic aneurysm.

OBJECTIVESStudies in animals have shown causal relationships between copper (Cu) deficiency and the development of thoracic aortic aneurysms (TAAs) [1, 2]. Cu deficiency is widespread in New Zealand (NZ) soils; the high soil pH from the use of lime fertilizers reduces the bioavailability of Cu for grazing animals and growing plants; this, in turn, reduces Cu availability in the NZ human food chain. Our study is a pilot study to explore associations between Cu and TAA. We measured Cu levels in aneurysmal aortic tissues in patients undergoing Bentall procedures and non-aneurysmal aortic tissue from coronary artery bypass graft patients.METHODSAortic samples were collected from 2 groups of patients during elective open-heart surgery over 4 months between November 2017 and February 2018. The groups were a TAA group, patients with non-syndromic aortic aneurysm and without the bicuspid aortic valve or known infectious or inflammatory condition (ANEURYSM; n = 13), and a control coronary artery bypass graft group (CONTROL; n = 44). Standardized digested dry tissue weighed samples were analysed from both groups. Tissue extraction of trace elements was carried out using HCl-H2O2 digestion and a highly sensitive analytical technique, inductively coupled plasma mass spectrometry—used to measure elemental concentrations.RESULTSCu concentration (mean ± SD) was significantly lower in ANEURYSM (3.34 ± 0.16 µg/g) when compared to the CONTROL group tissues (4.33 ± 0.20 µg/g) (dry weight; mean ± SD; Student's t-test, P < 0.05). Over 46% of the Aneurysm patients were Maori and live in a geographically Cu-deficient NZ territory.CONCLUSIONSCu deficiency may play a role in the development or progression of non-syndromic ascending aortic aneurysms in NZ. Maori patients are more at risk as they commonly live in rural NZ, dependent on locally grown nutritional sources. Further studies are required to confirm this exciting finding and to establish cause and effect relationship.

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.

Abstract 301: Inhibition Of Tlr-7 Signaling Attenuates TAAD Formation

The critical role for chronic inflammation in the development of thoracic aortic aneurysms and dissections (TAADs) has been recognized in both experimental and clinical settings. However, challenges remain on translating this knowledge to clinical applications. In this study, we tested the hypothesis that TLR-7 signaling triggered by self-RNAs substantiates chronic inflammation, promoting TAAD formation. A mouse TAAD model induced by SMC-specific deletion of Tgfbr1 ( Tgfbr1 iko ) was used. In this model, the expression of TLR-7 was progressively upregulated during the early stages, resulting in a two-fold differential at two weeks compared to control aortas ( P =0.003). RNAScope assays showed that cells located in the media and adventitia were responsible for the upregulation. Additionally, immunofluorescence (IF) staining showed that TLR-7 is induced in human TAADs. Treatment with hydroxychloroquine, which inhibits TLR-7 receptor function, significantly reduced the number of intimal/medial tears ( P =0.026) and mitigated intramural hemorrhage ( P =0.007) compared with vehicle controls (n=7/group). Further assays with bone marrow derived dendritic cells demonstrated that RNAs, particularly small RNAs, extracted from TAADs induced significantly higher IFNα/β levels compared with normal aortas ( P =0.025). Similarly, RNAs extracted from Tgfbr1 iko SMCs induced higher levels of IFNα, IP-10, and MCP1 compared with those harvested from wild type SMCs. Necroptosis (labeled with RIPK3 and pMLKL) and RNA-oxidation (labeled with 8-OHG) were evident in the media of TAADs, and might serve as the source for the endogenous TLR-7 ligand. Finally, treatment with the TLR-7 specific inhibitor, M5049, at a dose of 1.0 or 5.0 mg/kg/day via oral gavage prevented dilation of TAADs at four weeks compared with vehicle controls (9% vs. 8% vs. 23%, P&lt;0.001). In conclusion, self-RNAs released from stressed and dying cells is associated with chronically inflamed aortic tissue and promotes TAAD development via triggering TLR-7 signaling. Blocking TLR-7 signaling may represent a novel strategy to treat human TAADs.

Abstract 348: Angiotensin 1-7 Exerts Protective Effects In Thoracic Aortic Aneurysm By Attenuating Smooth Muscle Cell Phenotypic Switching

Background: Thoracic aortic aneurysm (TAA) involves extracellular matrix (ECM) remodeling of the aortic wall, leading to reduced biomechanical support with risk of aortic dissection and rupture. Elusive pathophysiology of initiation and progression of TAA has hindered efforts to develop pharmacological therapeutic interventions to delay or prevent progressive aortic dilatation. Activation of the renin-angiotensin system, and resultant Angiotensin (Ang) II synthesis, is critically involved in the onset and progression of TAA. The current study investigated the effects of Angiotensin (Ang) 1-7 on a murine model of TAA. Methods &amp; Results: 8-10 weeks old apolipoprotein-deficient mice (ApoEKO) were infused with Ang II (1.44 mg/kg/day) and treated with Ang 1-7 (0.576 mg/kg/day). Echocardiography and histological analyses revealed increased thoracic aortic dilatation, ECM remodeling, perivascular fibrosis, and inflammation in Ang II-treated mice. Infusion of Ang 1-7 led to suppression of Ang II-induced dilatation, remodeling, and inflammation in the thoracic aorta. The immunofluorescence imaging showed reduced α-SMA fluorescence (contractile marker) in vascular smooth muscle cells (VSMCs) of the aortic media indicating phenotypic switching. In response to Ang II, the thoracic VSMCs from ApoEKO mice exhibited phenotypic switching indicated by reduced contractile ( Acta2, Cnn1, Myh11 ) and increased synthetic ( Il-6, Mmp2, Mmp9, Col1a1, Col3a1 ) gene expression. Ki67 staining and flow cytometry analysis showed VSMCs hyperproliferation with Ang II treatment. Ang 1-7 preserved the contractile phenotype of VSMCs and attenuated hyperproliferation. The mitochondrial structure was assessed using MitoTracker Red staining which showed Ang II-induced excessive mitochondrial fission. DHE and MitoSOX Red staining were used to assess the reactive oxygen species (ROS). Ang II-treated thoracic VSMCs demonstrated elevated cellular and mitochondrial ROS generation. Ang 1-7 mitigated Ang II-induced mitochondrial fission and oxidative stress. Conclusion: Ang 1-7 prevented Ang II-induced vascular remodeling and the development of TAA. Enhancing Ang 1-7 actions may provide a novel therapeutic strategy to prevent or delay the progression of TAA.

The role of biglycan in the healthy and thoracic aneurysmal aorta.

The class I small leucine-rich proteoglycan biglycan is a crucial structural extracellular matrix component that interacts with a wide range of extracellular matrix molecules. In addition, biglycan is involved in sequestering growth factors such as transforming growth factor-β and bone morphogenetic proteins and thereby regulating pathway activity. Biglycan consists of a 42-kDa core protein linked to two glycosaminoglycan side chains and both are involved in protein interactions. Biglycan is encoded by the BGN gene located on the X-chromosome and is expressed in various tissues, including vascular tissue, skin, brain, kidney, lung, the immune system, and the musculoskeletal system. Although an increasing amount of data on the biological function of biglycan in the vasculature has been produced, its role in thoracic aortic aneurysms is still not fully elucidated. This review focuses on the role of biglycan in the healthy thoracic aorta and the development of thoracic aortic aneurysm and dissections in both mice and humans.