Pathogenesis Of Thoracic Aortic Aneurysm Research Articles

Mendelian randomization analysis of the causal relationship between serum metabolites and thoracic aortic aneurysm.

Thoracic aortic aneurysm (TAA) is associated with changes in the levels of metabolites; however, the exact causal relationships remain unclear. Identifying this complex relationship may provide new insights into the pathogenesis of TAA. We used genome-wide association studies to investigate the relationship between metabolites and TAA in this study. A total of 1400 serum metabolites were investigated for their potential causal effects on the risk of TAA. We performed bidirectional and 2-sample Mendelian randomization (MR) analysis using 5 MR tests: MR-Egger, weighted mode, weighted median, inverse variance weighted (IVW), and simple mode. We also performed sensitivity analysis to verify our findings, including heterogeneity analysis using IVW and MR-Egger tests and pleiotropy analysis using the MR-Egger test. Multiple metabolites were identified as having a causal effect on the risk of TAA, particularly those related to lipid metabolites; the top 2 risk factors identified using the IVW test were 3-carboxy-4-methyl-5-pentyl-2-furanpropionate (P = .019) and 5alpha-androstan-3alpha,17alpha-diol (P = .021), whereas the 2 top protective factors were 1-stearoyl-2-docosahexaenoyl-gpc (P = .023) and 1-oleoyl-2-docosahexaenoyl-GPC (P = .005). Sensitivity analysis verified the lack of heterogeneity (P = .499, .584, .232, and .624, respectively; IVW test) or pleiotropy (P = .621, .483, .598, and .916, respectively; Egger test). Our study provides new evidence of a causal relationship between metabolites and the risk of TAA, thus providing new insights into the pathogenesis of this disease. These findings suggest a promising approach for metabolite-based therapeutic interventions.

Bioengineered vascular grafts with a pathogenic TGFBR1 variant model aneurysm formation in vivo and reveal underlying collagen defects.

Thoracic aortic aneurysm (TAA) is a life-threatening vascular disease frequently associated with underlying genetic causes. An inadequate understanding of human TAA pathogenesis highlights the need for better disease models. Here, we established a functional human TAA model in an animal host by combining human induced pluripotent stem cells (hiPSCs), bioengineered vascular grafts (BVGs), and gene editing. We generated BVGs from isogenic control hiPSC-derived vascular smooth muscle cells (SMCs) and mutant SMCs gene-edited to carry a Loeys-Dietz syndrome (LDS)-associated pathogenic variant (TGFBR1A230T). We also generated hiPSC-derived BVGs using cells from a patient with LDS (PatientA230T/+) and using genetically corrected cells (Patient+/+). Control and experimental BVGs were then implanted into the common carotid arteries of nude rats. The TGFBR1A230T variant led to impaired mechanical properties of BVGs, resulting in lower burst pressure and suture retention strength. BVGs carrying the variant dilated over time in vivo, resembling human TAA formation. Spatial transcriptomics profiling revealed defective expression of extracellular matrix (ECM) formation genes in PatientA230T/+ BVGs compared with Patient+/+ BVGs. Histological analysis and protein assays validated quantitative and qualitative ECM defects in PatientA230T/+ BVGs and patient tissue, including decreased collagen hydroxylation. SMC organization was also impaired in PatientA230T/+ BVGs as confirmed by vascular contraction testing. Silencing of collagen-modifying enzymes with small interfering RNAs reduced collagen proline hydroxylation in SMC-derived tissue constructs. These studies demonstrated the utility of BVGs to model human TAA formation in an animal host and highlighted the role of reduced collagen modifying enzyme activity in human TAA formation.

Genetic liability to elevated circulating IP-10, IFNγ and SCGFβ levels in relation to thoracic aortic aneurysm: A mendelian randomization study

Inflammation is associated with thoracic aortic aneurysm (TAA) but the effects of each circulating inflammatory factor on TAA remain unclear. In this study, we explored the relationship between circulating inflammatory factors and TAA risk using Mendelian randomization (MR) approach based on summary statistics from the latest genome-wide association study (GWAS) of 41 circulating inflammatory factors in 8293 Finns and a GWAS involving 1351 TAA cases and 18,295 controls of European ancestry. In univariable MR, higher interferon gamma-induced protein 10 (IP-10) levels, higher interferon gamma (IFNγ) levels and higher stem cell growth factor beta (SCGFβ) levels were associated with an increased risk of TAA (OR = 1.37, 95 % CI = 1.17–1.59, p = 7.42 × 10−5; OR = 1.43, 95 % CI = 1.19–1.74, p = 2.04 × 10−4; OR = 1.27, 95 % CI = 1.09–1.48, p = 2.40 × 10−3, respectively). In multivariable MR, the patterns of associations for the three cytokines remained adjusting for each other or smoking, but were attenuated differently with adjustment for other cardiovascular risk factors, especially for lipids and body mass index. Bidirectional MR approach did not identify any significant associations between cytokines and risk factors. Our results indicated that circulating cytokines may play mediation roles in the pathogenesis of TAA. Further studies are needed to determine whether these biomarkers can be used to prevent and treat TAA.

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.

Redox Dysregulation of Vascular Smooth Muscle Sirtuin-1 in Thoracic Aortic Aneurysm in Marfan Syndrome.

Thoracic aortic aneurysms (TAAs) are abnormal aortic dilatations and a major cardiovascular complication of Marfan syndrome. We previously demonstrated a critical role for vascular smooth muscle (VSM) SirT1 (sirtuin-1), a lysine deacetylase, against maladaptive aortic remodeling associated with chronic oxidative stress and aberrant activation of MMPs (matrix metalloproteinases). In this study, we investigated whether redox dysregulation of SirT1 contributed to the pathogenesis of TAA using fibrillin-1 hypomorphic mice (Fbn1mgR/mgR), an established model of Marfan syndrome prone to aortic dissection/rupture. Oxidative stress markers 3-nitrotyrosine and 4-hydroxynonenal were significantly elevated in aortas of patients with Marfan syndrome. Moreover, reversible oxidative post-translational modifications (rOPTM) of protein cysteines, particularly S-glutathionylation, were dramatically increased in aortas of Fbn1mgR/mgR mice, before induction of severe oxidative stress markers. Fbn1mgR/mgR aortas and VSM cells exhibited an increase in rOPTM of SirT1, coinciding with the upregulation of acetylated proteins, an index of decreased SirT1 activity, and increased MMP2/9 activity. Mechanistically, we demonstrated that TGFβ (transforming growth factor beta), which was increased in Fbn1mgR/mgR aortas, stimulated rOPTM of SirT1, decreasing its deacetylase activity in VSM cells. VSM cell-specific deletion of SirT1 in Fbn1mgR/mgR mice (SMKO-Fbn1mgR/mgR) caused a dramatic increase in aortic MMP2 expression and worsened TAA progression, leading to aortic rupture in 50% of SMKO-Fbn1mgR/mgR mice, compared with 25% of Fbn1mgR/mgR mice. rOPTM of SirT1, rOPTM-mediated inhibition of SirT1 activity, and increased MMP2/9 activity were all exacerbated by the deletion of Glrx (glutaredoxin-1), a specific deglutathionylation enzyme, while being corrected by overexpression of Glrx or of an oxidation-resistant SirT1 mutant in VSM cells. Our novel findings strongly suggest a causal role of S-glutathionylation of SirT1 in the pathogenesis of TAA. Prevention or reversal of SirT1 rOPTM may be a novel therapeutic strategy to prevent TAA and TAA dissection/ruptures in individuals with Marfan syndrome, for which, thus far, no targeted therapy has been developed.

SIRT6 is an epigenetic repressor of thoracic aortic aneurysms via inhibiting inflammation and senescence

Thoracic aortic aneurysms (TAAs) develop asymptomatically and are characterized by dilatation of the aorta. This is considered a life-threating vascular disease due to the risk of aortic rupture and without effective treatments. The current understanding of the pathogenesis of TAA is still limited, especially for sporadic TAAs without known genetic mutation. Sirtuin 6 (SIRT6) expression was significantly decreased in the tunica media of sporadic human TAA tissues. Genetic knockout of Sirt6 in mouse vascular smooth muscle cells accelerated TAA formation and rupture, reduced survival, and increased vascular inflammation and senescence after angiotensin II infusion. Transcriptome analysis identified interleukin (IL)-1β as a pivotal target of SIRT6, and increased IL-1β levels correlated with vascular inflammation and senescence in human and mouse TAA samples. Chromatin immunoprecipitation revealed that SIRT6 bound to the Il1b promoter to repress expression partly by reducing the H3K9 and H3K56 acetylation. Genetic knockout of Il1b or pharmacological inhibition of IL-1β signaling with the receptor antagonist anakinra rescued Sirt6 deficiency mediated aggravation of vascular inflammation, senescence, TAA formation and survival in mice. The findings reveal that SIRT6 protects against TAA by epigenetically inhibiting vascular inflammation and senescence, providing insight into potential epigenetic strategies for TAA treatment.

Circ_0008285 silencing suppresses angiotensin II-induced vascular smooth muscle cell apoptosis in thoracic aortic aneurysm via miR-150-5p/BASP1 axis.

Vascular smooth muscle cells (VSMCs) are the predominant cell type of the aortic middle layer, the abnormal number or function of which has been demonstrated to have a role in thoracic aortic aneurysm (TAA). Here, this study aimed to identify the function of circ_0008285 in VSMC apoptosis. Human VSMCs were treated with angiotensin II (Ang II) for functional experiments. Cell counting kit-8, 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry were applied for function analysis. The interaction between miR-150-5p and circ_0008285 or brain acid-soluble protein 1 (BASP1) was also evaluated by dual-luciferase reporter assay and RNA immunoprecipitation assay. Exosomes were isolated by the commercial kit. A highly expressed circ_0008285 was observed in the aortic tissues of TAA patients and Ang-II-induced VSMCs. Circ_0008285 deficiency dramatically reversed Ang-II-induced proliferation arrest and apoptosis promotion in VSMCs. Circ_0008285 functionally targeted miR-150-5p. MiR-150-5p inhibition attenuated the inhibitory effects of circ_0008285 silencing on Ang-II-evoked apoptosis in VSMCs. BASP1 was verified to be a target of miR-150-5p, and was proved to attenuate miR-150-5p-triggered apoptosis arrest in Ang-II-stimulated VSMCs. Additionally, extracellular circ_0008285 was packaged into exosomes, which could be transferred into the recipient cells. Circ_0008285 silencing could suppress Ang-II-induced VSMCs apoptosis via miR-150-5p/BASP1 axis, adding further understanding of the pathogenesis of TAA.

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.

Tandem mass tag-based quantitative proteomic analysis identification of succinylation related proteins in pathogenesis of thoracic aortic aneurysm and aortic dissection.

Thoracic aortic aneurysm and dissection (TAAD) are devastating cardiovascular diseases with a high rate of disability and mortality. Lysine succinylation, a newly found post-translational modification, has been reported to play an important role in cardiovascular diseases. However, how succinylation modification influences TAAD remains obscure. Ascending aortic tissues were obtained from patients with thoracic aortic aneurysm (TAA, n = 6), thoracic aortic dissection (TAD) with pre-existing aortic aneurysm (n = 6), and healthy subjects (n = 6). Global lysine succinylation level was analyzed by Western blotting. The differentially expressed proteins (DEPs) were analyzed by tandem mass tag (TMT) labeling and mass spectrometry. Succinylation-related proteins selected from the literature review and AmiGO database were set as a reference inventory for further analysis. Then, the pathological aortic sections were chosen to verify the proteomic results by Western blotting and qRT-PCR. The level of global lysine succinylation significantly increased in TAA and TAD patients compared with healthy subjects. Of all proteins identified by proteomic analysis, 197 common DEPs were screened both in TAA and TAD group compared with the control group, of which 93 proteins were significantly upregulated while 104 were downregulated. Among these 197 DEPs, OXCT1 overlapped with the succinylation-related proteins and was selected as the target protein involved in thoracic aortic pathogenesis. OXCT1 was further verified by Western blotting and qRT-PCR, and the results showed that OXCT1 in TAA and TAD patients was significantly lower than that in healthy donors (p < 0.001), which was consistent with the proteomic results. OXCT1 represents novel biomarkers for lysine succinylation of TAAD and might be a therapeutic target in the future.

Abstract 286: Identification Of Microrna Regulators Of Cell Signalling In Marfan Aorta Using Machine Learning

Marfan syndrome (MFS), due to FBN1 mutations, is associated with thoracic aortic aneurysm (TAA). The TGFß and other signalling pathways have been implicated in TAA formation, however, regulators of cell signalling in MFS are yet to be defined. We hypothesized that distinct microRNA (miRNA) expression profiles occur in MFS aorta and that these can illuminate novel cell signalling targets contributing to TAA. MiRNAs were extracted from MFS (n=15) and controls (n=11) ascending aortic tissue, for discovery open-array panel profiling of miRNA expression. Individual miRNA expression profiles were compared between MFS and controls by random forest machine learning algorithm (Python). The miRNAs identified with a significant importance value were selected for gene target prediction (score &gt;90) through miRDB, followed by KEGG analysis. Any miRNA with more than 2000 predicted targets in the genome was excluded. P=0.05 was used as a cut-off value for KEGG analysis. The random forest classifier identified 53 miRNAs with differential expression between MFS and controls, contributing to the model (predictive accuracy 73%). The five most significant miRNAs were miR-181a-3p, miR-144-3p, miR-545-5p, miR-27a-5p and miR-181c-3p. 2984 unique target genes were identified from 53 significant miRNAs. KEGG analysis of these target genes identified multiple pathways as having potential differential regulation by miRNAs between MFS and controls. The most significant and relevant pathways identified were PI3K/AKT (p&lt;0.00001) and the downstream FOXO (p&lt;0.0004) pathways. Others include the MAPK (p&lt;0.00001), mTOR (p&lt;0.00002), RAP1 (p&lt;0.005), ErbB (p&lt;0.003) and RAS (p&lt;0.001) pathways, in addition to TGFß (p&lt;0.01). Mapping miRNA targets to KEGG pathways identified potential regulatory points, e.g., miR-29c-3p affecting FBN1, AKT3, PTEN (within the TGFß and PI3K/AKT pathways); miR-19a-3p affecting RAF1 , FMR1, RIN2 (within the MAPK, fragile X and adherens junction pathways); miR-27a-5p affecting LTBP1 (within the TGFß pathway). In conclusion, machine learning analysis identifies differential expression of multiple miRNAs in aortic tissue from MFS, which map to cell signalling pathways implicated in the pathogenesis of TAA in MFS.

Influence of aortic aneurysm on the local distribution of NO and O2 using image-based computational fluid dynamics

There is a pressing need to establish novel biomarkers to predict the progression of thoracic aortic aneurysm (TAA) dilatation. Aside from hemodynamics, the roles of oxygen (O2) and nitric oxide (NO) in TAA pathogenesis are potentially significant. As such, it is imperative to comprehend the relationship between aneurysm presence and species distribution in both the lumen and aortic wall. Given the limitations of existing imaging methods, we propose the use of patient-specific computational fluid dynamics (CFD) to explore this relationship. We have performed CFD simulations of O2 and NO mass transfer in the lumen and aortic wall for two cases: a healthy control (HC) and a patient with TAA, both acquired using 4D-flow magnetic resonance imaging (MRI). The mass transfer of O2 was based on active transport by hemoglobin, while the local variations of the wall shear stress (WSS) drove NO production. Comparing hemodynamic properties, the time-averaged WSS was considerably lower for TAA, while the oscillatory shear index and endothelial cell activation potential were notably elevated. O2 and NO showed a non-uniform distribution within the lumen and an inverse correlation between the two species. We identified several locations of hypoxic regions for both cases due to lumen-side mass transfer limitations. In the wall, NO varied spatially, with a clear distinction between TAA and HC. In conclusion, the hemodynamics and mass transfer of NO in the aorta exhibit the potential to serve as a diagnostic biomarker for TAA. Furthermore, hypoxia may provide additional insights into the onset of other aortic pathologies.

Thoracic aortopathy in Marfan syndrome overlaps with mechanisms seen in bicuspid aortic valve disease.

Thoracic aortopathy is a serious complication which is more often seen in patients with Marfan syndrome (MFS) and patients with a bicuspid aortic valve (BAV) than in individuals with a tricuspid aortic valve (TAV). The identification of common pathological mechanisms leading to aortic complications in non-syndromic and syndromic diseases would significantly improve the field of personalized medicine. This study sought to compare thoracic aortopathy between MFS, BAV, and TAV individuals. Bicuspid aortic valve (BAV; n = 36), TAV (n = 23), and MFS (n = 8) patients were included. Ascending aortic wall specimen were studied for general histologic features, apoptosis, markers of cardiovascular ageing, expression of synthetic and contractile vascular smooth muscle cells (VSMC), and fibrillin-1 expression. The MFS group showed many similarities with the dilated BAV. Both patient groups showed a thinner intima (p < 0.0005), a lower expression of contractile VSMCs (p < 0.05), more elastic fiber thinning (p < 0.001), lack of inflammation (p < 0.001), and a decreased progerin expression (p < 0.05) as compared to the TAV. Other features of cardiovascular ageing differed between the BAV and MFS. Dilated BAV patients demonstrated less medial degeneration (p < 0.0001), VSMC nuclei loss (p < 0.0001), apoptosis of the vessel wall (p < 0.03), and elastic fiber fragmentation and disorganization (p < 0.001), as compared to the MFS and dilated TAV. This study showed important similarities in the pathogenesis of thoracic aortic aneurysms in BAV and MFS. These common mechanisms can be further investigated to personalize treatment strategies in non-syndromic and syndromic conditions.

Molecular Mechanisms in Genetic Aortopathy-Signaling Pathways and Potential Interventions.

Thoracic aortic disease affects people of all ages and the majority of those aged &lt;60 years have an underlying genetic cause. There is presently no effective medical therapy for thoracic aneurysm and surgery remains the principal intervention. Unlike abdominal aortic aneurysm, for which the inflammatory/atherosclerotic pathogenesis is well established, the mechanism of thoracic aneurysm is less understood. This paper examines the key cell signaling systems responsible for the growth and development of the aorta, homeostasis of endothelial and vascular smooth muscle cells and interactions between pathways. The evidence supporting a role for individual signaling pathways in pathogenesis of thoracic aortic aneurysm is examined and potential novel therapeutic approaches are reviewed. Several key signaling pathways, notably TGF-β, WNT, NOTCH, PI3K/AKT and ANGII contribute to growth, proliferation, cell phenotype and survival for both vascular smooth muscle and endothelial cells. There is crosstalk between pathways, and between vascular smooth muscle and endothelial cells, with both synergistic and antagonistic interactions. A common feature of the activation of each is response to injury or abnormal cell stress. Considerable experimental evidence supports a contribution of each of these pathways to aneurysm formation. Although human information is less, there is sufficient data to implicate each pathway in the pathogenesis of human thoracic aneurysm. As some pathways i.e., WNT and NOTCH, play key roles in tissue growth and organogenesis in early life, it is possible that dysregulation of these pathways results in an abnormal aortic architecture even in infancy, thereby setting the stage for aneurysm development in later life. Given the fine tuning of these signaling systems, functional polymorphisms in key signaling elements may set up a future risk of thoracic aneurysm. Multiple novel therapeutic agents have been developed, targeting cell signaling pathways, predominantly in cancer medicine. Future investigations addressing cell specific targeting, reduced toxicity and also less intense treatment effects may hold promise for effective new medical treatments of thoracic aortic aneurysm.

Transcriptomics Provides Novel Insights into the Regulatory Mechanism of IncRNA HIF1 A-AS1 on Vascular Smooth Muscle Cells.

Thoracic aortic aneurysm is a potentially fatal disease with a strong genetic contribution. The dysfunction of vascular smooth muscle cells (VSMCs) contributes to the formation of this aneurysm. Although previous studies suggested that long non-coding ribonucleic acid (RNA) hypoxia inducible factor 1 α-antisense RNA 1 (HIF1A-AS1) exerted a vital role in the progression and pathogenesis of thoracic aortic aneurysm, we managed to find a new regulatory mechanism of HIF1A-AS1 in VSMCs via transcriptomics. Cell viability was detected by the cell counting kit-8 assay. Cell apoptosis was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide double staining. Transwell migration assay and wound healing assay were performed to check the migration ability of HIF1A-AS1 on VSMCs. The NextSeq XTen system (Illumina) was used to collect RNA sequencing data. Lastly, reverse transcription-quantitative polymerase chain reaction confirmed the veracity and reliability of RNA-sequencing results. We observed that overexpressing HIF1A-AS1 successfully promoted apoptosis, significantly altered cell cycle distribution, and greatly attenuated migration in VSMCs, further highlighting the robust promoting effects of HIF1A-AS1 to thoracic aortic aneurysm. Moreover, transcriptomics was implemented to uncover its underlying mechanism. A total of 175 differently expressed genes were identified, with some of them enriched in apoptosis, migration, and cell cycle-related pathways. Intriguingly, some differently expressed genes were noted in vascular development or coagulation function pathways. We suggest that HIF1A-AS1 mediated the progression of thoracic aortic aneurysm by not only regulating the function of VSMCs, but also altering vascular development or coagulation function.

Construction of a high-throughput aorta smooth muscle-on-a-chip for thoracic aortic aneurysm drug screening

Thoracic aortic aneurysm (TAA), in which arteries enlarge asymptomatically over time until dissection or rupture occurs, is a serious health risk. The mainstay of TAA treatment remains surgical repair due to the lack of effective drugs. The complex etiology and pathogenesis of TAA, including hemodynamic alterations and genetic factors, lead to inaccuracies in preclinical models for drug screening. Previously, our group designed an aorta smooth muscle-on-a-chip to emulate human aorta physiology and pathophysiology and screened three promising therapeutic drugs targeting mitochondrial dynamics in TAA. On this foundation, we updated the one-channel chip to an eighteen-well chip platform with four polydimethylsiloxane layers. Benefiting from this high-throughput chip, we rapidly screened multiple drugs simultaneously using distinct cell lines in vitro. In addition, we observed the abnormal activation of hypoxia-inducible factor 1-alpha (HIF-1alpha) in aortas from TAA patients by Western blot and bioinformatics analyses. Intriguingly, this phenomenon was replicated only when smooth muscle cells (SMCs) were strained on the chip. We then screened seven specific HIF-1alpha inhibitors and selected the two most effective drugs (2-methoxyestradiol and digoxin) by quantitative PCR and colorimetric methods. The results demonstrated that these two drugs can improve respiratory chain function and rescue the SMC contractile phenotype, showing applicability for the clinical treatment of TAA. This high-throughput aorta smooth muscle-on-a-chip will become a potential preclinical model for TAA drug screening.

ProvinLong non-coding RNA XIST negatively regulates thoracic aortic aneurysm cell proliferation by targeting the miR-193a-5p/KLF7 axis

Non-coding RNAs (ncRNAs) are important molecular modulators in diverse pathological processes, influencing the occurrence and progression of carcinomas. Thoracic aortic aneurysm (TAA) is an infrequent disease among aneurysmal diseases and accounts for nearly 3% of diagnosed aneurysms. The functional roles of long ncRNA (lncRNA) XIST and miR-193a-5p and the associated molecular mechanisms are yet to be investigated. In the current study, we discovered that miR-193a-5p was expressed at low levels in the blood of TAA patients. Further, loss-of-function and gain-of-function assays disclosed that miR-195-3p impacted the proliferation ability of TAA cells. XIST was found to be the most overexpressed lncRNA among predicted lncRNAs binding to miR-193a-5p. The promotive function of XIST in TAA was also explored. Subsequently, KLF7 was proved to be the downstream factor of the XIST/miR-193a-5p axis. Rescue assays testified the whole regulation mechanism of the XIST/miR-193a-5p/KLF7 axis in TAA. MiR-193a-5p was absorbed by XIST for the improvement of KLF7 in TAA. These results concluded that XIST might be engaged in TAA pathogenesis via regulation of the miR-193a-5p/KLF7 axis, supplementing more therapeutic options for TAA treatment.

A human importin-β-related disorder: Syndromic thoracic aortic aneurysm caused by bi-allelic loss-of-function variants in IPO8

Importin 8, encoded by IPO8, is a ubiquitously expressed member of the importin-β protein family that translocates cargo molecules such as proteins, RNAs, and ribonucleoprotein complexes into the nucleus in a RanGTP-dependent manner. Current knowledge of the cargoes of importin 8 is limited, but TGF-β signaling components such as SMAD1-4 have been suggested to be among them. Here, we report that bi-allelic loss-of-function variants in IPO8 cause a syndromic form of thoracic aortic aneurysm (TAA) with clinical overlap with Loeys-Dietz and Shprintzen-Goldberg syndromes. Seven individuals from six unrelated families showed a consistent phenotype with early-onset TAA, motor developmental delay, connective tissue findings, and craniofacial dysmorphic features. A C57BL/6N Ipo8 knockout mouse model recapitulates TAA development from 8-12weeks onward in both sexes but most prominently shows ascending aorta dilatation with a propensity for dissection in males. Compliance assays suggest augmented passive stiffness of the ascending aorta in male Ipo8-/- mice throughout life. Immunohistological investigation of mutant aortic walls reveals elastic fiber disorganization and fragmentation along with a signature of increased TGF-β signaling, as evidenced by nuclear pSmad2 accumulation. RT-qPCR assays of the aortic wall in male Ipo8-/- mice demonstrate decreased Smad6/7 and increased Mmp2 and Ccn2 (Ctgf) expression, reinforcing a role for dysregulation of the TGF-β signaling pathway in TAA development. Because importin 8 is the most downstream TGF-β-related effector implicated in TAA pathogenesis so far, it offers opportunities for future mechanistic studies and represents a candidate drug target for TAA.

Weighted miRNA co-expression network reveals potential roles of apoptosis related pathways and crucial genes in thoracic aortic aneurysm

BackgroundThoracic aortic aneurysm (TAA) is a potentially life-threatening disease for which few medical therapies are available. Thus, it is critically important to investigate the underlying molecular mechanisms of TAA, and identify potential targets for TAA treatment.MethodsDifferentially expressed miRNAs (DEMs) and differentially expressed genes (DEGs) were screened, and a weighted correlation network analysis (WGCNA) was employed to construct a weighted miRNA co-expression network using GSE110527. The DEMs were then mapped into the whole co-expression network of all samples, and a DEM coexpression network was created. Molecular Complex Detection (MCODE) was used to identify crucial miRNAs. Target genes were predicted using the miRTarbase database, and further screened by identifying genes that overlapped with the DEGs of GSE26155. The screened target genes were validated using GSE9106, and the successfully validated genes were considered as crucial genes. Finally, a miRNA risk score for diagnosing TAA was calculated by undertaking a least absolute shrinkage and selection operator (LASSO) regression.ResultsThe tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) signaling pathway was found in DEM functional enrichment. Crucial miRNAs were identified and target genes were predicted and associated with the regulation of the TRAIL signaling pathway. Next, 113 important target genes were identified as overlapping with the DEGs of GSE26155. These genes were further validated, and 5 successfully validated genes were considered as crucial genes. Finally, the miRNA risk score calculated by the LASSO regression was shown to have potential diagnostic value.ConclusionsWe performed a WGCNA analysis to construct a weighted miRNA co-expression network, predicted target genes of crucial miRNAs, identified crucial genes, and finally calculated a miRNA risk score. The results showed that pathways and genes associated with apoptosis appear to play an important role in TAA pathogenesis, and that medications targeting apoptosis might slow TAA progression. Future in vitro and in vivo experimental studies need to be undertaken to further validate our findings and investigate the mechanistic details of these crucial miRNAs and crucial genes.

Abstract 13562: COQ8B : A Candidate Genetic Modifier of Thoracic Aortic Aneurysm Severity

Thoracic aortic aneurysm (TAA) is a latent aortopathy that predisposes to life-threatening aortic dissection. Personalized prediction of the risk for progressive aortic dilation and dissection is currently limited. The identification of genetic modifiers may facilitate more precise risk prediction and optimize clinical decisions. We previously identified COQ8B , a gene important for mitochondrial biosynthesis of coenzyme Q, as a candidate modifier of TAA severity. Biological evidence for a mitochondrial role in TAA pathogenesis includes severe mitochondrial ultrastructural defects in aortic smooth muscle cells (SMCs) and nitrated tyrosine residues in TAA tissues consistent with oxidative stress. In this study, we hypothesized that a common single nucleotide polymorphism (SNP) rs3865452 in COQ8B (c.521A&gt;G, p.H174R) modifies the rate of aortic root dilation. Forty-eight patients with TAA and a mean age at first echocardiogram of 10 ± 5 years were genotyped for rs3865452. Echocardiograms (mean 6.8 ± 4.0 per patient) were performed clinically over a mean interval of 5.3 ± 4.1 years. In mixed model analysis of longitudinal aortic root Z-scores, the c.521G allele was associated with a decreased rate of aortic root dilation in univariate analysis (p=0.0003) and multivariate analysis (p=0.03) that included sex and genetic syndrome as covariates. Hypothesizing a modifier role for COQ8B , we analyzed a separate cohort of 230 individuals with early onset thoracic aortic dissection. The c.521G allele was less frequent in dissection cases than controls (p=0.04), also consistent with a protective effect for this SNP. To better understand the mechanism of COQ8B effect in TAA, RNA levels of COQ8B in SMCs cultured directly from the aorta were assayed, demonstrating levels 2-fold lower in TAA compared with controls. siRNA knockdown of COQ8B in aortic SMCS resulted in decreased mitochondrial respiration, increased lipid peroxidation, and altered expression of SMC contractile genes. In conclusion, the findings of this study support a modifier role for the rs3865452 SNP in COQ8B in TAA, which may involve mitochondrial pathology and oxidative stress. This suggests that this SNP may be useful for clinical risk prediction.

P1448 Thoracic aorta and circulating transforming growth factor-b in marfan syndrome and marfanoid habitus

Abstract Purpose Current understanding of the pathogenesis of thoracic aortic aneurysm (TAA) in Marfan syndrome (MS) focuses upon abnormal activity of the transforming growth factor beta (TGF-β) signalling pathway. Circulating TGF-β predicts cardiovascular events in patients with MS and is elevated in the entire spectrum of aortic syndromes. Marfanoid habitus (MH) patients not meeting the MS criteria (TAA, ectopia lentis, family history), but share the same skeletal features and are the part of the Marfan continuum. Our aim was to evaluate the possible role of elevated TGF-β level in the aortic dilatation at mid-term follow-up in Marfanoid habitus patients. Methods 33 consecutive patients with a presumptive clinical diagnosis of Marfan syndrome were referred to Almazov centre and enrolled in our observational, prospective, single-center study. Nine of them (mean age 27.9 ± 9.3) fulfilled diagnosis of MS according to revised Ghent criteria. 24 subjects (mean age 21.8 ± 3.4) with skeletal features of Marfanoid habitus have had no major findings of MS. Proximal aortic segments were visualized in the parasternal long-axis and suprasternal views. Concentration of TGF-β1 and TGF-β2 in serum was determined using a test system Human Platinum ELISA. End points analyzed during 5 years of follow-up were mortality, aortic-related events, and aortic dimension changes. Results During 122 person-years of the follow-up (median 5.1 years) no deaths or aortic-related events occurred in Marfanoid habitus patients. TGF-β1 and TGF-β2 serum levels were elevated in patients with Marfanoid habitus (14.2 ± 27.6 and 2.1 ± 1.7 ng/ml, respectively) but were lower than in MS group (44.6 ± 47.3 ng/ml, p = 0.03 and 2.7 ± 1.7 ng/ml, p = 0.39, respectively). A high TGF-β1 serum level (cutoff &amp;gt;14.75 ng/ml, provided by the manufacturer of our TGF-β assay) was detected in 44% and TGF-β2 (&amp;gt;2.0 ng/ml) in majority patients (67%) of the MS group. In Marfanoid habitus group we found a high TGF-β1 serum level only in 4 (17%) patients and TGF-β2 in 9 (38%) patients. Aortic diameter at the sinuses of Valsalva and Z-score were significantly lower in Marfanoid habitus group (29.2 ± 2.8 mm and 1.56 ± 0.93) than in MS patients (43.1 ± 15.1 mm, p = 0.0007 and 6.86 ± 5.83, p = 0.004) at the beginning of study and significantly increased during the follow-up (31.3 ± 2.9 mm and 1,69 ± 0,15, p &amp;lt; 0.001 for both). There was no correlation between TGF-β level and aortic dimensions in patients with MS and marfanoid habitus. Conclusion In young adults with Marfanoid habitus and the current absence of ascending aortic aneurysm we found the increased TGF-β level and aortic root enlargement during the follow-up. High TGF-β serum level may contribute to the excessive progression of aortic dilatation later over mid-to-late aging and requires further investigation to establish its role in the aortic aneurysm pathogenesis.