Decoding the Genomics of Abdominal Aortic Aneurysm.

A key aspect of genomic medicine is to make individualized clinical decisions from personal genomes. We developed a machine-learning framework to integrate personal genomes and electronic health record (EHR) data and used this framework to study abdominal aortic aneurysm (AAA), a prevalent irreversible cardiovascular disease with unclear etiology. Performing whole-genome sequencing on AAA patients and controls, we demonstrated its predictive precision solely from personal genomes. By modeling personal genomes with EHRs, this framework quantitatively assessed the effectiveness of adjusting personal lifestyles given personal genome baselines, demonstrating its utility as a personal health management tool. We showed that this new framework agnostically identified genetic components involved in AAA, which were subsequently validated in human aortic tissues and in murine models. Our study presents a new framework for disease genome analysis, which can be used for both health management and understanding the biological architecture of complex diseases. VIDEO ABSTRACT.

Thrombospondin-1 in vascular development, vascular function, and vascular disease.

Angiogenesis is vital to developmental, regenerative and repair processes. It is normally regulated by a balanced production of pro- and anti-angiogenic factors. Alterations in this balance under pathological conditions are generally mediated through up-regulation of pro-angiogenic and/or downregulation of anti-angiogenic factors, leading to growth of new and abnormal blood vessels. The pathological manifestation of many diseases including cancer, ocular and vascular diseases are dependent on the growth of these new and abnormal blood vessels. Thrompospondin-1 (TSP1) was the first endogenous angiogenesis inhibitor identified and its anti-angiogenic and anti-inflammatory activities have been the subject of many studies. Studies examining the role TSP1 plays in pathogenesis of various ocular diseases and vascular dysfunctions are limited. Here we will discuss the recent studies focused on delineating the role TSP1 plays in ocular vascular development and homeostasis, and pathophysiology of various ocular and vascular diseases with a significant clinical relevance to human health.

Spatiotemporal ATF3 Expression Determines VSMC Fate in Abdominal Aortic Aneurysm.

BACKGROUND: Abdominal aortic aneurysm (AAA) is a catastrophic disease with little effective therapy, likely due to the limited understanding of the mechanisms underlying AAA development and progression. ATF3 (activating transcription factor 3) has been increasingly recognized as a key regulator of cardiovascular diseases. However, the role of ATF3 in AAA development and progression remains elusive. METHODS: Genome-wide RNA sequencing analysis was performed on the aorta isolated from saline or Ang II (angiotensin II)-induced AAA mice, and ATF3 was identified as the potential key gene for AAA development. To examine the role of ATF3 in AAA development, vascular smooth muscle cell-specific ATF3 knockdown or overexpressed mice by recombinant adeno-associated virus serotype 9 vectors carrying ATF3, or shRNA-ATF3 with SM22α (smooth muscle protein 22-α) promoter were used in Ang II-induced AAA mice. In human and murine vascular smooth muscle cells, gain or loss of function experiments were performed to investigate the role of ATF3 in vascular smooth muscle cell proliferation and apoptosis. RESULTS: In both Ang II-induced AAA mice and patients with AAA, the expression of ATF3 was reduced in aneurysm tissues but increased in aortic lesion tissues. The deficiency of ATF3 in vascular smooth muscle cell promoted AAA formation in Ang II-induced AAA mice. PDGFRB (platelet-derived growth factor receptor ß) was identified as the target of ATF3, which mediated vascular smooth muscle cell proliferation in response to TNF-alpha (tumor necrosis factor-α) at the early stage of AAA. ATF3 suppressed the mitochondria-dependent apoptosis at the advanced stage by upregulating its direct target BCL2. Our chromatin immunoprecipitation results also demonstrated that the recruitment of NFκB1 and P300/BAF/H3K27ac complex to the ATF3 promoter induces ATF3 transcription via enhancer activation. NFKB1 inhibitor (andrographolide) inhibits the expression of ATF3 by blocking the recruiters NFKB1 and ATF3-enhancer to the ATF3-promoter region, ultimately leading to AAA development. CONCLUSIONS: Our results demonstrate a previously unrecognized role of ATF3 in AAA development and progression, and ATF3 may serve as a novel therapeutic and prognostic marker for AAA.

Single-cell RNA sequencing reveals that NRF2 regulates vascular smooth muscle cell phenotypic switching in abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a life-threatening disease characterized by extensive membrane destruction in the vascular wall that is closely associated with vascular smooth muscle cell (VSMC) phenotypic switching. A thorough understanding of the changes in regulatory factors during VSMC phenotypic switching is essential for managing AAA therapy. In this study, we revealed the impact of NRF2 on the modulation of VSMC phenotype and the development of AAA based on single-cell RNA sequencing analysis. By utilizing a murine model of VSMC-specific knockout of nuclear factor E2-related factor 2 (NRF2), we observed that the absence of NRF2 in VSMCs exacerbated AAA formation in an angiotensin II-induced AAA model. The downregulation of NRF2 promoted VSMC phenotypic switching, leading to an enhanced inflammatory response. Through genome-wide transcriptome analysis and loss- or gain-of-function experiments, we discovered that NRF2 upregulated the expression of VSMC contractile phenotype-specific genes by facilitating microRNA-145 (miR-145) expression. Our data identified NRF2 as a novel regulator involved in maintaining the VSMC contractile phenotype while also influencing AAA formation through an miR-145-dependent regulatory mechanism.

Ferrostatin-1 inhibits ferroptosis of vascular smooth muscle cells and alleviates abdominal aortic aneurysm formation through activating the SLC7A11/GPX4 axis.

Ferroptosis, a type of iron-catalyzed necrosis, is responsible for vascular smooth muscle cell (VSMC) death and serves as a potential therapeutic target for alleviating aortic aneurysm. Here, our study explored the underlying mechanism of ferroptosis affecting VSMC functions and the resultant formation of AAA using its inhibitor Ferrostatin-1 (Fer-1). Microarray-based gene expression profiling was employed to identify differentially expressed genes related to AAA and ferroptosis. An AAA model was established by angiotensin II (Ang II) induction in apolipoprotein E-knockout (ApoE-/- ) mice, followed by injection of Fer-1 and RSL-3 (ferroptosis inducer). Then, the role of Fer-1 and RSL-3 in the ferroptosis of VSMCs and AAA formation was analyzed in Ang II-induced mice. Primary mouse VSMCs were cultured in vitro and treated with Ang II, Fer-1, sh-SLC7A11, or sh-GPX4 to assess the effect of Fer-1 via the SLC7A11/GPX axis. Bioinformatics analysis revealed that GPX4 was involved in the fibrosis formation of AAA, and there was an interaction between SLC7A11 and GPX4. In vitro assays showed that Fer-1 alleviated Ang II-induced ferroptosis of VSMCs and retard the consequent AAA formation. The mechanism was associated with activation of the SLC7A11/GPX4 pathway. Silencing of SLC7A11 or GPX4 could inhibit the ameliorating effect of Fer-1 on the ferroptosis of VSMCs. In vivo animal studies further demonstrated that Fer-1 inhibited Ang II-induced ferroptosis and vessel wall structural abnormalities in AAA mouse through activation of the SLC7A11/GPX4 pathway. Fer-1 may prevent AAA formation through activation of the SLC7A11/GPX4 pathway.

ADAR1 Non-Editing Function in Macrophage Activation and Abdominal Aortic Aneurysm.

BACKGROUND: Macrophage activation plays a critical role in abdominal aortic aneurysm (AAA) development. However, molecular mechanisms controlling macrophage activation and vascular inflammation in AAA remain largely unknown. The objective of the study was to identify novel mechanisms underlying adenosine deaminase acting on RNA (ADAR1) function in macrophage activation and AAA formation. METHODS: Aortic transplantation was conducted to determine the importance of nonvascular ADAR1 in AAA development/dissection. Ang II (Angiotensin II) infusion of ApoE-/- mouse model combined with macrophage-specific knockout of ADAR1 was used to study ADAR1 macrophage-specific role in AAA formation/dissection. The relevance of macrophage ADAR1 to human AAA was examined using human aneurysm specimens. Moreover, a novel humanized AAA model was established to test the role of human macrophages in aneurysm formation in human arteries. RESULTS: Allograft transplantation of wild-type abdominal aortas to ADAR1+/- recipient mice significantly attenuated AAA formation, suggesting that nonvascular ADAR1 is essential for AAA development. ADAR1 deficiency in hematopoietic cells decreased the prevalence and severity of AAA while inhibited macrophage infiltration and aorta wall inflammation. ADAR1 deletion blocked the classic macrophage activation, diminished NF-κB (nuclear factor kappa B) signaling, and enhanced the expression of a number of anti-inflammatory microRNAs. Mechanistically, ADAR1 interacted with Drosha to promote its degradation, which attenuated Drosha-DGCR8 (DiGeorge syndrome critical region 8) interaction, and consequently inhibited pri- to pre-microRNA processing of microRNAs targeting IKKß, resulting in an increased IKKß (inhibitor of nuclear factor kappa-B) expression and enhanced NF-κB signaling. Significantly, ADAR1 was induced in macrophages and interacted with Drosha in human AAA lesions. Reconstitution of ADAR1-deficient, but not the wild type, human monocytes to immunodeficient mice blocked the aneurysm formation in transplanted human arteries. CONCLUSIONS: Macrophage ADAR1 promotes aneurysm formation in both mouse and human arteries through a novel mechanism, that is, Drosha protein degradation, which inhibits the processing of microRNAs targeting NF-kB signaling and thus elicits macrophage-mediated vascular inflammation in AAA.

Leveraging cell-type-specific regulatory networks to interpret genetic variants in abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a common degenerative cardiovascular disease whose pathobiology is not clearly understood. The cellular heterogeneity and cell-type-specific gene regulation of vascular cells in human AAA have not been well-characterized. Here, we performed analysis of whole-genome sequencing data in AAA patients versus controls with the aim of detecting disease-associated variants that may affect gene regulation in human aortic smooth muscle cells (AoSMC) and human aortic endothelial cells (HAEC), two cell types of high relevance to AAA disease. To support this analysis, we generated H3K27ac HiChIP data for these cell types and inferred cell-type-specific gene regulatory networks. We observed that AAA-associated variants were most enriched in regulatory regions in AoSMC, compared with HAEC and CD4+ cells. The cell-type-specific regulation defined by this HiChIP data supported the importance of ERG and the KLF family of transcription factors in AAA disease. The analysis of regulatory elements that contain noncoding variants and also are differentially open between AAA patients and controls revealed the significance of the interleukin-6-mediated signaling pathway. This finding was further validated by including information from the deleteriousness effect of nonsynonymous single-nucleotide variants in AAA patients and additional control data from the Medical Genome Reference Bank dataset. These results shed important insights into AAA pathogenesis and provide a model for cell-type-specific analysis of disease-associated variants.

Sex-specific differences in alive hospital discharge following infrarenal abdominal aortic aneurysm repair.

BACKGROUND AND AIMS: A longer time to alive hospital discharge following infrarenal abdominal aortic aneurysm (AAA) repair is associated with reduced patient-satisfaction and increased length of stay, hospital-acquired deconditioning, infection and costs. This study investigated sex-specific differences in, and drivers of, the rate of alive hospital discharge. METHODS: Examination of UK National Vascular Registry (UK NVR), 2014-2019 and Swedish National Patient Registry (SE NPR) elective AAA patients, 2010-2018, for endovascular (EVAR) or open (OAR) aneurysm repair. Cox models assessed sex-specific difference in rate of alive hospital discharge, adjusting for co-morbidity, anatomy, standard-of-care, post-operative complications, and year, with in-hospital death as the competing risk. RESULTS: 29,751 AAA repairs (UK NVR -EVAR 12518:1532; OAR 6803:837; SE NPR - EVAR 4234:792; OAR 2638:497, men:women) were assessed. For EVAR, the unadjusted rate of alive hospital discharge was ∼25% lower for women (UK NVR HR 0.75 [0.71-0.80], p<.001; SE NPR HR 0.75 [0.69-0.81], p<.001). Following adjustment the sex-specific hazard ratio narrowed but remained significant (UK NVR: HR 0.83 [0.79-0.88], p<.001; SE NPR HR 0.83 [0.76-0.89], p<.001). For OAR, the rate of alive hospital discharge was 23-27% lower for women (UK NVR HR 0.73 [0.67-0.78], p<.001; SE NPR HR 0.77 [0.70-0.85], p<.001). Following adjustment the sex-specific hazard ratio narrowed (UK NVR HR 0.82 [0.76-0.88], p<.001; SE NPR HR 0.79 [0.72-0.88], p<.001) but remained significant. CONCLUSIONS: Women have a 25% lower rate of alive discharge after aortic surgery, despite adjustment for pre/peri- and postoperative parameters. Efforts to increase rate of alive hospital discharge for women should be sought.

Air pollutants, genetic susceptibility, and abdominal aortic aneurysm risk: a prospective study.

BACKGROUND AND AIMS: Air pollutants are important contributors to cardiovascular diseases, but associations between long-term exposure to air pollutants and the risk of abdominal aortic aneurysm (AAA) are still unknown. METHODS: This study was conducted using a sample of 449 463 participants from the UK Biobank. Hazard ratios and 95% confidence intervals for the risk of AAA incidence associated with long-term exposure to air pollutants were estimated using the Cox proportional hazards model with time-varying exposure measurements. Additionally, the cumulative incidence of AAA was calculated by using the Fine and Grey sub-distribution hazards regression model. Furthermore, this study investigated the combined effects and interactions between air pollutants exposure and genetic predisposition in relation to the risk of AAA onset. RESULTS: Long-term exposure to particulate matter with an aerodynamic diameter <2.5 µm [PM2.5, 1.21 (1.16, 1.27)], particulate matter with an aerodynamic diameter <10 µm [PM10, 1.21 (1.16, 1.27)], nitrogen dioxide [NO2, 1.16 (1.11, 1.22)], and nitrogen oxides [NOx, 1.10 (1.05, 1.15)] was found to be associated with an elevated risk of AAA onset. The detrimental effects of air pollutants persisted even in participants with low-level exposure. For the joint associations, participants with both high levels of air pollutants exposure and high genetic risk had a higher risk of developing AAA compared with those with low concentrations of pollutants exposure and low genetic risk. The respective risk estimates for AAA incidence were 3.18 (2.46, 4.12) for PM2.5, 3.09 (2.39, 4.00) for PM10, 2.41 (1.86, 3.13) for NO2, and 2.01 (1.55, 2.61) for NOx. CONCLUSIONS: In this study, long-term air pollutants exposure was associated with an increased risk of AAA incidence.

Identification and Evaluation of Blood-Based Biomarkers for Abdominal Aortic Aneurysm.

INTRODUCTION: Blood-based biomarkers for abdominal aortic aneurysm (AAA) have been studied individually; however, we considered a panel of proteins to investigate AAA prognosis and its potential to improve predictive accuracy. MATERIALS AND METHODS: Using a prospectively recruited cohort of patients with/without AAA (n = 452), we conducted a prognostic study to develop a model that accurately predicts AAA outcomes using clinical features and circulating biomarker levels. Serum concentrations of 9 biomarkers were measured at baseline, and the cohort was followed for 2 years. The primary outcome was major adverse aortic event (MAAE; composite of rapid AAA expansion [>0.5 cm/6 months or >1 cm/12 months], AAA intervention, or AAA rupture). Using 10-fold cross-validation, we trained a random forest model to predict 2 year MAAE using (1) clinical characteristics, (2) biomarkers, and (3) clinical characteristics and biomarkers. RESULTS: Two-year MAAE occurred in 114 (25%) patients. Two proteins were significantly elevated in patients with AAA compared with those without AAA (angiopoietin-2 and aggrecan), composing the protein panel. For predicting 2 year MAAE, our random forest model achieved area under the receiver operating characteristic curve (AUROC) 0.74 using clinical features alone, and the addition of the 2-protein panel improved performance to AUROC 0.86. CONCLUSIONS: Using a combination of clinical/biomarker data, we developed a model that accurately predicts 2 year MAAE.