Pathophysiology and epidemiology of abdominal aortic aneurysms

Targeting GPX4 alleviates ferroptosis and retards abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) is a potentially fatal cardiovascular disease, closely related to inflammation and loss of vascular smooth muscle cells (VSMCs). Ferroptosis is an iron-dependent cell death associated with peroxidation of lipids. However, the direct role of glutathione peroxidase 4 (GPX4) itself determined ferroptosis in the course of AAA pathogenesis remains unknown. Here, we reported that ferroptosis was triggered in human AAA, elastase- and angiotensin II (Ang II)-induced mouse AAA, and Ang II-incubated VSMCs. Inhibition of ferroptosis via global genetic overexpression of GPX4, a critical anti-ferroptosis molecule, markedly prevented both vascular remodeling and inflammatory response. Mechanistically, GPX4 changed the migration and activation of macrophages/monocytes in AAA tissues in mice. Experiments in vitro demonstrated that overexpression of GPX4 prevented the JAK1/STAT3 signaling activation in VSMCs induced by IL-6, production of pro-inflammatory macrophages. Finally, the role of ferroptosis was confirmed on an Ang II-induced mice AAA model. These results emphasized the significance of ferroptosis in AAA, and provided novel insights that therapy focusing on GPX4 might be a promising strategy for treatment of AAA in the clinic.

Protein Drug Targets for Abdominal Aortic Aneurysm and Proteomic Associations Between Modifiable Risk Factors and Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe aortic disease for which no pharmacological interventions have yet been developed. This investigation focused on identifying protein-based therapeutic targets and assessing how proteins mediate the interplay between modifiable risk factors and AAA development.

METHODS

Causal inferences between plasma proteins and AAA were drawn using 2-sample Mendelian randomization, followed by comprehensive sensitivity testing, colocalization, and replication efforts. Further analyses included database interrogation, single-cell RNA data analysis, enrichment analysis, protein-protein interaction networks, and immunohistochemistry to map the tissue-specific expression of these proteins, their expression within AAA tissues, and their biological roles. Mediation Mendelian randomization was employed to evaluate the mediating effects of AAA-related proteins on the associations between AAA and 3 risk factors: hypertension, smoking, and obesity.

RESULTS

A total of 43 proteins were identified as having causal links to AAA. Colocalization analysis pinpointed 13 proteins with strong evidence of colocalization with AAA. Of these, the causal involvement of 10 proteins was substantiated by external validation data. Consistent evidence for PCSK9 (proprotein convertase subtilisin/kexin type 9), IL6R (interleukin-6R), ECM1 (extracellular matrix protein 1), and ANGPTL4 (angiopoietin-related protein 4) was further validated through tissue immunohistochemistry and blood data. Moreover, Mendelian randomization analysis identified 10 proteins as mediators of the influence of hypertension, smoking, and obesity on AAA development.

CONCLUSIONS

This analysis identifies 4 proteins (PCSK9, IL6R, ECM1, and ANGPTL4) as high-priority therapeutic targets for AAA and emphasizes the intermediary role of plasma proteins in linking hypertension, smoking, obesity, and AAA. Further investigations are needed to clarify the specific roles of these proteins in AAA pathology.

The Impact of Physical Activity on Abdominal Aortic Aneurysm: A Scoping Review

BACKGROUND

Abdominal aortic aneurysm (AAA), a condition primarily affecting older men, is often asymptomatic but becomes life-threatening if rupture occurs. While AAA risk factors such as age, gender, and smoking are well-studied, physical activity (PA) may also play a critical role in managing AAA progression, though this relationship remains understudied. This scoping review aims to synthesize current knowledge on the impact of PA on AAA, examining safety, physiological effects, and potential protective effects against AAA progression.

METHODS

A comprehensive scoping review methodology was applied, covering databases from their inception to October 2024, including MEDLINE, CINAHL, Scopus, and Web of Science. Seven studies meeting the inclusion criteria were analyzed, with intervention designs ranging from cross-sectional to longitudinal studies.

RESULTS

After full-text review of 44 articles, 38 were excluded due to focus on surgical intervention or flow models. The manual screening adding one study, resulting in 7 articles included in this review. PA appears generally safe for individuals with small AAAs, with minimal adverse events reported in most studies, though one study noted a cardiac incident during exercise. PA interventions often improved cardiovascular metrics, including ventilatory threshold and inflammatory markers, yet demonstrated mixed effects on AAA growth. Notably, the protective effect of PA against AAA progression remains inconclusive, requiring further investigation.

CONCLUSIONS

This review indicates that moderate PA is generally safe and may provide health benefits for individuals with small AAAs. However, significant knowledge gaps remain, especially regarding the optimal frequency, intensity, and duration of PA, as well as its long-term impact on aneurysm progression. All these issues require objective measurement of PA to develop targeted physical activity guidelines for this population.

Inhibition of ATP-citrate lyase by bempedoic acid protects against abdominal aortic aneurysm formation in mice

Abdominal aortic aneurysm (AAA) is a prevalent degenerative disease characterized by an exacerbated inflammation and destructive vascular remodeling. Unfortunately, effective pharmacological tools for the treatment of this disease remain a challenge. ATP-citrate lyase (ACLY), the primary enzyme responsible for acetyl-CoA biosynthesis, is a key regulator of inflammatory signaling in macrophages and lymphocytes. Here, we found increased levels of the active (phosphorylated) form of ACLY (p-ACLY) in the inflammatory infiltrate of AAA from patients and in aneurysmal lesions from angiotensin II (Ang II)-infused apolipoprotein E-deficient mice (ApoE-/-). Furthermore, plasma ACLY levels positively correlates with IL6 and IFNγ levels in patients with AAA, while inflammatory stimuli strongly upregulated ACLY expression in macrophages and Jurkat cells. The administration of the ACLY inhibitor bempedoic acid (BemA) protected against Ang II-induced AAA formation in ApoE-/- mice, limiting the progression of aortic dilatation and reducing mortality due to aortic rupture. BMS-303141, another ACLY inhibitor, also ameliorated AAA formation, although to a lesser extent. BemA attenuated vascular remodeling and the disorganization and rupture of elastic fibers induced by Ang II, as well as vascular inflammation, decreasing the recruitment of macrophages (CD68 +) and neutrophils (Ly-6G+) into the aortic wall. Moreover, BemA shifted splenic monocytes toward a functionally anti-inflammatory phenotype, and increased the percentage of CD4+CD69+ cells. Taken together, these results support the contribution of ACLY to AAA and point to BemA as a promising tool to be considered for future clinical trials addressing the management of this disease which is quite often associated with disorders of lipoprotein metabolism.

Global Epidemiology of Early-Onset Aortic Aneurysm: Temporal Trends, Risk Factors, and Future Burden Projections

BACKGROUND

Aortic aneurysm has a subtle onset, high rupture mortality, rapid progression in younger individuals, and increasing annual mortality rates. Our study aimed to estimate the global burden and trends of early-onset aortic aneurysm from 1990 to 2021.

METHODS

Participants aged 15-39 years from 204 countries and regions (Global Burdern of Disease, GBD) from 1990 to 2021.The primary assessment indicators include age-standardized death rates (ASDR), age-standardized disability-adjusted life years rates (ASDALYR), annual average percent change (AAPC), attributable risk factor proportions, slope index, concentration index, and predictive model for early-onset aortic aneurysm.

RESULTS

From 1990 to 2021, the ASDR for aortic aneurysm in adolescents and young adults increased from 0.12 (95% confidence interval [CI] 0.11, 0.14) to 0.13 (0.11, 0.14) per 100,000 population, with an AAPC of 0.08% (-0.08%, 0.25%). The ASDALYR rose from 7.25 (6.52, 8.30) to 7.35 (6.51, 8.37), with an AAPC of 0.07% (-0.09%, 0.23%). Both ASDR and ASDALYR are higher in males than females, with a declining trend in females. Higher Socio-Demographic Index (SDI) countries exhibit higher ASDR and ASDALYR compared to lower SDI countries, with a continuous decline observed in high SDI nations. Smoking remains the top risk factor, with population growth being the primary driver. Models predict a global increase in aortic aneurysm deaths, predominantly among males.

CONCLUSION

The overall burden of early-onset aortic aneurysms has exhibited an increasing trend over the last three decades, especially in lower SDI countries. There is an urgent need to develop targeted prevention and control strategies across different regions and countries worldwide.

Proteome-Wide Mendelian Randomization Identifies Therapeutic Targets for Abdominal Aortic Aneurysm

BACKGROUND

The proteome is a key source of therapeutic targets. We conducted a comprehensive Mendelian randomization analysis across the proteome to identify potential protein markers and therapeutic targets for abdominal aortic aneurysm (AAA).

METHODS AND RESULTS

Our study used plasma proteomics data from the UK Biobank, comprising 2923 proteins from 54 219 individuals, and from deCODE Genetics, which measured 4907 proteins across 35 559 individuals. Significant proteomic quantitative trait loci were used as instruments for Mendelian randomization. Genetic associations with AAA were sourced from the AAAgen consortium, a large-scale genome-wide association study meta-analysis involving 37 214 cases and 1 086 107 controls, and the FinnGen study, which included 3869 cases and 381 977 controls. Sequential analyses of colocalization and summary-data-based Mendelian randomization were performed to verify the causal roles of candidate proteins. Additionally, single-cell expression analysis, protein-protein interaction network analysis, pathway enrichment analysis, and druggability assessments were conducted to identify cell types with enriched expression and prioritize potential therapeutic targets. The proteome-wide Mendelian randomization analysis identified 34 proteins associated with AAA risk. Among them, 2 proteins, COL6A3 and PRKD2, were highlighted by colocalization analysis, summary-data-based Mendelian randomization, and the heterogeneity in an independent instrument test, providing the most convincing evidence. These protein-coding genes are primarily expressed in macrophages, smooth muscle cells, and mast cells within abdominal aortic aneurysm tissue. Several causal proteins are involved in pathways regulating lipid metabolism, immune responses, and extracellular matrix organization. Nine proteins have already been targeted for drug development in diabetes and other cardiovascular diseases, presenting opportunities for repurposing as AAA therapeutic targets.

CONCLUSIONS

This study identifies causal proteins for AAA, enhancing our understanding of its molecular cause and advancing the development of therapeutics.

Nitric oxide and mitochondrial function in cardiovascular diseases

Nitric oxide (NO) has been highlighted as an important factor in cardiovascular system. As a signaling molecule in the cardiovascular system, NO can relax blood vessels, lower blood pressure, and prevent platelet aggregation. Mitochondria serve as a central hub for cellular metabolism and intracellular signaling, and their dysfunction can lead to a variety of diseases. Accumulating evidence suggests that NO can act as a regulator of mitochondria, affecting mitochondrial function and cellular activity, which in turn mediates the onset and progression of disease. However, there is a lack of comprehensive understanding of how NO regulates mitochondrial function in the cardiovascular system. This review aims to summarize the regulation of mitochondrial function by nitric oxide in cardiovascular related diseases, as well as the multifaceted and complex roles of NO in the cardiovascular system. Understanding the mechanism of NO mediated mitochondrial function can provide new insights for the prevention and treatment of cardiovascular diseases.

Myeloid Cell mPGES-1 Deletion Attenuates Calcium Phosphate-induced Abdominal Aortic Aneurysm in Male Mice

Microsomal PGE2 synthase (mPGES)-1 is the key enzyme responsible for synthesizing inflammatory prostaglandin E2 (PGE2). Our previous studies have shown that deletion mPGES-1 in myeloid cells hinders atherogenesis, suppresses vascular proliferative response to injury and enhances survival after myocardial infarction. Here we aimed to further explore the influence of myeloid cell mPGES-1 deletion in abdominal aortic aneurysm (AAA) formation. The AAA was triggered by applying 0.5 M calcium phosphate (CaPO4) to the infrarenal aorta of both myeloid mPGES-1 knockout (Mac-mPGES-1-KO) and their littermate control Mac-mPGES-1-WT mice. AAA induction was assessed by calculating the expansion of the infrarenal aortic diameter 4 weeks after CaPO4 application. The maximum diameters of the aortas were measured by morphometry and the mean maximal diameters were calculated. Paraffin sections of the infrarenal aortas were examined for morphological analysis and immunohistochemical staining. The results showed that myeloid cell mPGES-1 deletion significantly mitigated AAA formation, including reducing expansion of the infrarenal aorta, preventing elastic lamellar degradation, and decreasing aortic calcium deposition. Immunohistochemical staining further indicated that macrophage infiltration and matrix metalloproteinase 2 (MMP2) expression was attenuated in the Mac-mPGES-1-KO aortas. Consistently, in vitro experiments showed that expression of pro-inflammatory cytokines and MMPs was significantly reduced when mPGES-1 was lacking in the primary cultured peritoneal macrophages. These data altogether demonstrated that deletion of mPGES-1 in myeloid cells may attenuate AAA formation and targeting myeloid cell mPGES-1 could potentially offer an effective strategy for the treatment and prevention of vascular inflammatory diseases.

CIDEC/FSP27 exacerbates obesity-related abdominal aortic aneurysm by promoting perivascular adipose tissue inflammation

Abdominal aortic aneurysm (AAA) is strongly correlated with obesity, partially due to the abnormal expansion of abdominal perivascular adipose tissue (PVAT). Cell death-inducing DNA fragmentation factor-like effector C (CIDEC), also known as fat-specific protein 27 (FSP27) in rodents, is specifically expressed in adipose tissue where it mediates lipid droplet fusion and adipose tissue expansion. Whether and how CIDEC/FSP27 plays a role in AAA pathology remains elusive. Here, we show that FSP27 exacerbates obesity and angiotensin Ⅱ (Ang Ⅱ)-induced AAA progression. FSP27 deficiency in mice inhibited high-fat diet-induced PVAT expansion and inflammation. Both global and adipose tissue-specific FSP27 ablation significantly decreased obesity-related AAA incidence. Deficiency of FSP27 in adipocytes abrogated matrix metalloproteinase-12 (MMP12) expression in aortic tissues. Infiltrated macrophages, which partially colocalize with MMP12, were significantly decreased in the FSP27-deficient aorta. Mechanistically, knockdown of Fsp27 in 3T3-L1 adipocytes inhibited C-C motif chemokine ligand 2 (CCL2) expression and secretion through a c-Jun N-terminal kinase (JNK)-dependent pathway, thereby leading to reduced induction of macrophage migration, while Cidec overexpression rescued this effect. Overall, our study demonstrates that CIDEC/FSP27 in adipose tissue contributes to obesity-related AAA formation, at least in part, by enhancing PVAT inflammation and macrophage infiltration, thus shedding light on its significance as a key regulator in the context of obesity-related AAA.

A Narrative Review: Syndecans in Aortic Aneurysm Pathogenesis and Course-Biomarkers and Targets?

The maintenance of the integrity of the entire endothelium, glycocalyx included, and, therefore, of tissue aorta's homeostasis, depends on the expressions of several molecular pathways and their interactions, such as syndecan molecules. Alterations in syndecans, i.e., quantitative alterations or linking to their shedding, contributes to invoking endothelium dysfunction, which causes damage to the vessel wall due to the increased production of growth-stimulating and pro-inflammatory gene products. Inflammatory processes negatively affect the integrity of the endothelial glycocalyx, a dynamic layer of the luminal portion of endothelial cells composed of proteoglycans, glycoproteins, and glycosaminoglycans, i.e., syndecans. In turn, structural alterations in the endothelial glycocalyx influence the coagulative state, increasing pro-thrombotic processes. The family of syndecans constitutes a major component of glycocalyx or, more accurately, the major source of cell surface heparan sulfate. It encompasses four components: syndecan-1, syndecan-2, and syndecan-4 (with syndecan-3 only expressed in neural tissue), which have a fundamental role in regulating the events of acute and chronic aorta damage subsequently correlated with the formation of aneurysms. As such, the aim of our review is to highlight the current knowledge on the roles of syndecans and to analyze their relationship with the pathological processes of the aortic wall based on the most recent literature.

Inhibition of vascular smooth muscle cell PERK/ATF4 ER stress signaling protects against abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) are a life-threatening cardiovascular disease for which there is a lack of effective therapy preventing aortic rupture. During AAA formation, pathological vascular remodeling is driven by vascular smooth muscle cell (VSMC) dysfunction and apoptosis, for which the mechanisms regulating loss of VSMCs within the aortic wall remain poorly defined. Using single-cell RNA-Seq of human AAA tissues, we identified increased activation of the endoplasmic reticulum stress response pathway, PERK/eIF2α/ATF4, in aortic VSMCs resulting in upregulation of an apoptotic cellular response. Mechanistically, we reported that aberrant TNF-α activity within the aortic wall induces VSMC ATF4 activation through the PERK endoplasmic reticulum stress response, resulting in progressive apoptosis. In vivo targeted inhibition of the PERK pathway, with VSMC-specific genetic depletion (Eif2ak3fl/fl Myh11-CreERT2) or pharmacological inhibition in the elastase and angiotensin II-induced AAA model preserved VSMC function, decreased elastin fragmentation, attenuated VSMC apoptosis, and markedly reduced AAA expansion. Together, our findings suggest that cell-specific pharmacologic therapy targeting the PERK/eIF2α/ATF4 pathway in VSMCs may be an effective intervention to prevent AAA expansion.

Disruption of PCSK9 Suppresses Inflammation and Attenuates Abdominal Aortic Aneurysm Formation

BACKGROUND

Abdominal aortic aneurysm (AAA) is a chronic vascular inflammatory disease without effective medications. PCSK9 (proprotein convertase subtilisin/kexin 9), a serine protease from the proprotein convertase family, has recently been associated with AAA in human genome-wide association studies. However, its role in AAA is unknown.

METHODS

Transcriptional and histological expression of PCSK9 was examined in AAA tissues and healthy controls. The impact of PCSK9 deletion and inhibition on AAA formation was assessed in mice with hyperlipidemia and Ang II (angiotensin II) overproduction. AAA lesion morphology was assessed by tissue staining. MMP (matrix metalloproteinase) activity was evaluated by gelatin zymography, and leukocyte-vessel wall interaction was monitored by intravital microscopy. RNA sequencing was used to characterize the downstream signaling of PCSK9.

RESULTS

PCSK9 expression was upregulated and colocalized with macrophages in human and mouse AAAs. Pcsk9 deletion attenuated AAA formation, improved survival, and decreased systemic inflammation, without altering circulating cholesterol levels. Pcsk9 deficiency reduced aortic infiltration of macrophages and elastin degradation, without affecting vascular smooth muscle cell apoptosis and proliferation. Mechanistically, PCSK9 was essential in leukocyte-endothelium adhesion and expression of proinflammatory cytokines and MMP9 by macrophages. RNA sequencing of stimulated macrophages revealed that Pcsk9 deficiency upregulated histone deacetylase SIRT1 (sirtuin-1) and suppressed NF-κB (nuclear factor-κB) inflammatory signaling. SIRT1 inhibition attenuated the proinflammatory actions of PCSK9. Furthermore, administration of PCSK9 small interfering RNA or antibody constrained AAA formation/progression and inhibited vascular inflammation.

CONCLUSIONS

PCSK9 critically mediates macrophage inflammation and elastin degradation, promoting AAA formation. PCSK9 inhibitors bear a promise to curtail AAA, beyond being used as cholesterol-lowering drugs.

ATG4B as a novel biomarker for abdominal aortic aneurysm: integrated evaluation through experimental and bioinformatics analyses

Autophagy related gene 4B (ATG4B) plays a central role in autophagy machinery, but its clinical relevance to AAA remains unknown. In this study, 205 AAA patients and 205 age- and sex-matched controls were included to detect the serum ATG4B levels. Meanwhile, abdominal aortic specimens from 24 AAA patients and 6 human organ donors were collected to evaluate the mRNA and in situ protein expression of ATG4B. We observed significantly higher ATG4B mRNA and protein expression levels in AAA group compared to those in control group, with a positive correlation between mRNA levels and serum/in situ protein levels (serum, r = 0.518, P = 0.010; in situ, r = 0.453, P = 0.026). Serum ATG4B exhibited the diagnostic potential for AAA (AUC = 0.702, sensitivity = 75.6%) and intraluminal thrombus recognition (AUC = 0.602, sensitivity = 67.9%). Logistic regression revealed a significant association between elevated serum ATG4B and an increased risk of AAA and intraluminal thrombus formation. Deceased patients displayed higher baseline serum ATG4B levels, which could predict postoperative mortality (HR = 1.028, 95%CI = 1.007-1.049, P = 0.009, AUC = 0.612, sensitivity = 84.6%). The bioinformatics analysis suggested that ATG4B may modulate cellular autophagy and influence pathways associated with inflammation, lipid metabolism, or apoptosis, thereby contributing to the occurrence and development of AAA. The drug-gene interaction network identified 13 potential therapeutic drugs targeting ATG4B. In conclusion, ATG4B may serve as a promising biomarker for the diagnosis and prognostic assessment of AAA patients and play a key role in the pathogenesis of AAA.

A Comprehensive Review on Computational Analysis, Research Advances, and Major Findings on Abdominal Aortic Aneurysms for the Years 2021 to 2023

BACKGROUND

Abdominal aortic aneurysm (AAA) is a pathological condition characterized by the dilation of the lower part of the aorta, where significant hemodynamic forces are present. The prevalence and high mortality risk associated with AAA remain major concerns within the scientific community. There is a critical need for extensive research to understand the underlying mechanisms, pathophysiological characteristics, and effective detection methods for abdominal aortic abnormalities. Additionally, it is imperative to develop and refine both medical and surgical management strategies. This review aims to indicate the role of computational analysis in the comprehension and management of AAAs and covers recent research studies regarding the computational analysis approach conducted between 2021 and 2023. Computational analysis methods have emerged as sophisticated and noninvasive approaches, providing detailed insights into the complex dynamics of AAA and enhancing our ability to study and manage this condition effectively.

METHODS

Computational analysis relies on fluid mechanics principles applied to arterial flow, using the Navier-Stokes equations to model blood flow dynamics. Key hemodynamic indicators relevant to AAAs include Time-Average Wall Shear Stress, Oscillatory Shear Index, Endothelial Cell Activation Potential, and Relative Residence Time. The primary methods employed for simulating the abdominal aorta and studying its biomechanical environment are computational fluid dynamics and Finite Element Methods. This review article encompasses a thorough examination of recent literature, focusing on studies conducted between 2021 and 2023.

RESULTS

The latest studies have elucidated crucial insights into the blood flow characteristics and geometric attributes of AAAs. Notably, blood flow patterns within AAAs are associated with increased rupture risk, along with elevated intraluminal thrombus volume and specific calcification thresholds. Asymmetric AAAs exhibit heightened risks of rupture and thrombus formation due to low and oscillating wall shear stresses. Moreover, larger aneurysms demonstrate increased wall stress, pressure, and energy loss. Advanced modeling techniques have augmented predictive capabilities concerning growth rates and surgical thresholds. Additionally, the influence of material properties and thrombus volume on wall stress levels is noteworthy, while inlet velocity profiles significantly modulate blood flow dynamics within AAAs.

CONCLUSIONS

This review highlights the potential utility of computational modeling. However, the clinical applicability of computational modeling has been limited by methodological variability despite the ongoing accumulation of evidence supporting the prognostic significance of biomechanical and hemodynamic indices in this field. The establishment of standardized reporting is critical for clinical implementation.

Cellular Senescence Genes as Cutting-Edge Signatures for Abdominal Aortic Aneurysm Diagnosis: Potential for Innovative Therapeutic Interventions

Abdominal aortic aneurysm (AAA) is the most prevalent dilated arterial aneurysm that poses a significant threat to older adults, but the molecular mechanisms linking senescence to AAA progression remain poorly understood. This study aims to identify cellular senescence-related genes (SRGs) implicated in AAA development and assess their potential as therapeutic targets. Four hundred and twenty-nine differentially expressed genes (DEGs) were identified from the GSE57691 training set, and 867 SRGs were obtained. Through the intersection of DEGs with SRGs, 19 differentially expressed senescence-related genes (DESRGs) were uncovered. Functional enrichment analysis was performed to explore their biological roles in AAA. To identify hub genes, we applied machine learning algorithms, including LASSO, SVM-RFE and random forest. These hub genes were then validated in two independent datasets. In the initial validation cohort, significant differences in the expression levels of BTG2, ETS1, ID1 and ITPR3 were observed between the AAA and control groups. Receiver operating characteristic (ROC) analysis demonstrated a robust diagnostic performance. Further validation across different AAA stages (small, large and ruptured AAA) identified ETS1 and ITPR3 as potential diagnostic genes. Subsequently, the diagnostic relevance of ETS1 and ITPR3 was further validated in human serum samples and mouse models of AAA. In addition, single-cell RNA sequencing suggests that senescent endothelial cells play a pivotal role in AAA progression, we further confirmed the correlation between ETS1 and ITPR3 and senescent endothelial cells by WB, IF and RT-qPCR. In conclusion, our study reveals the pivotal role of cellular senescence in AAA progression and identifies ETS1 and ITPR3 as promising diagnostic biomarkers.

Revealing the roles of IL-7R in abdominal aortic aneurysm through integrated analysis of single-cell RNA-seq and bulk RNA-seq

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease in the elderly, but there are still no therapeutic targets for this disease. In this study, we collected and analyzed bulk RNA sequencing (bulk RNA-seq) and single-cell RNA sequencing (scRNA-seq) data of AAA from the Gene Expression Omnibus (GEO) database. The immune infiltration-related genes were identified and categorized into various cell types, revealing potential key genes and pathways. Examination of three bulk RNA-seq datasets revealed a total of 4087 differentially expressed genes. The expression levels of the immune-related genes IL-7R were significantly elevated in AAA tissues across all three datasets. Furthermore, scRNA-Seq analysis revealed increased expression of IL-7R in CD4+ memory cells within AAA tissues. Immunofluorescence staining corroborated these findings, demonstrating increased expression of IL-7R in CD4+ T cells in AAA tissues. In vitro, activation of IL-7R elevated the activation of JAK/STAT pathway and phenotypic switching in SMCs, while inhibition of IL-7R abolished these effects and suppressed the secretion of IFN-γ. In conclusion, the activation of IL-7R in CD4+ T cells is a key contributor to the pathogenesis of AAA, as it can promote secretion of IFN-γ via JAK/STAT pathway and induce phenotypic switching of SMCs.

Effective Hydrogel Vascular Patch Dual-Loaded with Cycloastragenol Nanostructured Lipid Carriers and Doxycycline for Repairing Extravascular Injury in Abdominal Aortic Aneurysm

Endovascular aneurysm repair (EVAR) plays a crucial role in the treatment of abdominal aortic aneurysm (AAA) in the clinic, but the aneurysm remains in the patient's body after surgery, continuing to pose a risk of progression. Cycloastragenol (CAG) is proven to be an effective anti-AAA drug, and its vascular protective effects can be further improved when the hydrophobic CAG is encapsulated into nano-sized formulations to enhance its bioavailability. In this context, this study developed an extravascular patch hydrogel loaded with CAG nanostructured lipid carriers and a hydrophilic drug of doxycycline hydrochloride (DOX). The extravascular patch delivered onto the mouse abdominal aortas can promote local permeation of hydrophilic/hydrophobic drugs at the vessel sites and provide effective vascular protection against AAA injury induced by elastase. This study introduces a novel and promising approach for AAA treatment, which can serve as a supplementary strategy after EVAR surgery.

Thymidine Phosphorylase Promotes Abdominal Aortic Aneurysm via VSMC Modulation and Matrix Remodeling in Mice and Humans

Background: Thymidine phosphorylase (TYMP) promotes platelet activation and thrombosis while suppressing vascular smooth muscle cell (VSMC) proliferation. Both processes are central to the development and progression of abdominal aortic aneurysms (AAAs). We hypothesize that TYMP plays a role in AAA development. Methods: Male wild-type (WT) C57BL/6J and Tymp-/- mice, fed a Western diet (WD) (TD.88137), were subjected to the 4-week Ang II infusion-induced AAA model. AAA progression was monitored by echography and confirmed through necropsy. Whole-body inflammation was assessed using a plasma cytokine array. Mechanistic studies were conducted using TYMP-overexpressing rat VSMC cell lines and primary VSMCs cultured from WT and Tymp-/- mouse thoracic aortas. Histological studies were performed on human AAA and normal aorta samples. Results: Elevated TYMP levels were observed in human AAA vessel walls. While WT mice exhibited a 28.6% prevalence of Ang II infusion-induced AAA formation, Tymp-/- mice were protected. TYMP enhanced MMP2 expression, secretion, and activation in VSMCs, which was inhibited by tipiracil, a selective TYMP inhibitor. Systemically, TYMP promoted proinflammatory cytokine expression, and its absence attenuated TNF-α-induced MMP2 and AKT activation. WT VSMCs treated with platelets lacking TYMP showed a higher proliferation rate than cells treated with WT platelets. Additionally, TYMP increased activated TGFβ1 expression in cultured VSMCs and human AAA vessel walls. In WT VSMCs, TYMP augmented thrombospondin-1 type 1 repeat domain (TSR)-stimulated TGFβ1 signaling, increasing connective tissue growth factor and MMP2 production. TSR also enhanced AKT activation in WT VSMCs but had the opposite effect in Tymp-/- cells. TSR-enhanced MMP2 activation in WT VSMCs was attenuated by LY294002 (a PI3K inhibitor) but not by SB431542 (a TGFβ1 inhibitor); both inhibitors had indiscernible effects on Tymp-/- VSMC. Conclusion: TYMP emerges as a novel regulatory force in vascular biology, influencing VSMC function and inflammatory responses to promote AAA development.

Identification of Macrophage-Related Biomarkers for Abdominal Aortic Aneurysm Through Combined Single-Cell Sequencing and Machine Learning

Purpose

The relationship between macrophages and the progression of abdominal aortic aneurysms (AAA) remains unclear, and effective biomarkers are lacking. In this study, we elucidated the mechanism whereby macrophages promote AAA development and identified associated biomarkers, with the goal of developing new targeted therapies and improving patient outcomes.

Patients and Methods

Differential expression analysis, weighted gene co-expression network analysis, and single-cell analysis were used to identify macrophage-related genes in an AAA dataset. Machine learning algorithms identified THBS1, HCLS1, DMXL2, and ZEB2 as key macrophage-related genes upregulated in AAA; these four hub genes were then used to construct a nomogram as an auxiliary tool for clinical diagnosis. Subsequent downstream single-cell and CellChat analyses were conducted to observe the interactions between macrophages and fibroblasts and analyze potential pathways.

Results

Single-cell validation confirmed enhanced THBS1 expression in macrophages in AAA. CellChat analysis revealed enhanced interactions between macrophages and fibroblasts in AAA through THBS1-CD47 signaling. Finally, an analysis of clinical samples from patients with AAA confirmed the high expression of THBS1 and CD47 in AAA and that THBS1 promotes the progression of AAA through the TNF-NFκB signaling pathway. Our findings reveal the THBS1-CD47 signaling pathway as a critical mechanism in macrophage-driven AAA progression, highlighting THBS1's potential as a therapeutic target.

Conclusion

Our findings highlight THBS1 as a potential driver of macrophage-mediated AAA formation and an important biomarker for AAA diagnosis. The study results would help in improving treatment outcomes in patients with AAA. These findings provide a foundation for the development of diagnostic tools and targeted therapies for AAA, potentially improving early detection and patient outcomes.

Mechanism and clinical implication of gut dysbiosis in degenerative abdominal aortic aneurysm: A systematic review

The gut microbiome is the entirety of microorganisms and their genomes residing in the gut, characterised by diversity, stability, and resilience. Disrupted gut microbiome has been implicated in multiple disease entities. The aim of this paper is to summarise the rapidly evolving contemporary evidence of gut dysbiosis on the development and progression of abdominal aortic aneurysm (AAA), discuss possible mechanisms, and explore potential microbiota-targeted interventions and prognostic markers for AAA. A systematic literature search was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, using PubMed, ScienceDirect, Web of Science, Ovid, Embase. Search terms of "microbiome" OR "dysbiosis" OR "microorganism"; AND "aneurysm" OR "dilatation" OR "aorta" were used. Study endpoints included effects of microbiota on AAA formation, effects of specific type of bacteria and its metabolite on AAA formation, and pre- or post-treatment by novel small-molecules/inhibitors. From May to August 2023, a total of twelve animal studies and eight human studies were included. Akkermansia muciniphila, Lactobacillus acidophilus and species from the Bacteroidetes phylum were associated with lower AAA incidence in both animal and human studies, while Proteobacteria phylum, Campylobacter, Fusobacterium and Faecalibacterium prausnitzii were found to be in abundance in the AAA group and were associated with larger aneurysms. The diversity of gut microbiota was inversely correlated with AAA diameter. Three important mechanisms were identified: including trimethylamine N-oxide pathway, butyric acid pathway, and aberrant tryptophan metabolism. With our expanding knowledge of the downstream pathogenic mechanisms of gut dysbiosis, novel therapeutics such as short-chain fatty acids and spermidine, as well as prognostic biomarkers such as TMAO have yielded promising preclinical results. In conclusion, there is strong evidence corroborating the role of gut dysbiosis in the pathogenesis of AAA, wherein its therapeutic and prognostic potential deserves further exploration.

Clinical and computed tomography angiography characteristics of infected vs. non-infected abdominal aortic aneurysm: a comparative study

PURPOSE

The aim of this study was to investigate the clinical and multi-slice spiral computed tomography angiography (MSCTA) characteristics for the diagnosis of infected AAA.

METHODS

This retrospective comparative study included patients who were diagnosed with AAA at our hospital between January 2014 and May 2023.

RESULTS

A total of 40 patients were included, comprising 20 with infected AAA and 20 with non-infected AAA. Patients with infected AAA were more likely to be younger (62.9 ± 10.1 vs. 70.0 ± 4.4 years, P = 0.007) and to present with fever [7 (35%) vs. 1 (5%), P = 0.026], pain [15 (75%) vs. 2 (10%), P < 0.001], higher C-reactive protein levels (60.4 ± 57.0 vs. 4.1 ± 2.9 mg/l, P = 0.005), and higher erythrocyte sedimentation rates (47.7 ± 23.4 vs. 15.2 ± 8.3 mm/h, P < 0.001) compared to those with non-infected AAA. Moreover, those with infected AAA exhibited significantly more eccentric saccular morphology [17 (85%) vs. 1 (5%), P = 0.002], a smaller longitudinal-transverse ratio (1.12 ± 0.33 vs. 2.33 ± 0.54, P = 0.001), thicker peri-aneurysmal soft tissue (2.29 ± 1.48 vs. 0.73 ± 0.55 cm, P < 0.001), more lobulated margins [18 (90%) vs. 1 (5%), P = 0.001], lower aortic calcification scores (49 vs. 56, P < 0.001), more pneumatosis [6 (30%) vs. 0 (0%), P = 0.014], more ruptures [15 (75%) vs. 5 (20%), P = 0.002], more blurred peri-abdominal aortic fat spaces [16 (80%) vs. 2 (10%), P = 0.001], more adjacent bone destruction [5 (25%) vs. 0 (0%), P = 0.025], more involvement of the psoas major muscle [8 (40%) vs. 1 (5%), P = 0.005], more lymphadenectasis [8 (40%) vs. 1 (5%), P = 0.020], and less tortuous aortas [2 (10%) vs. 9 (45%), P = 0.034] compared with those with non-infected AAA.

CONCLUSION

The clinical manifestations and MSCTA characteristics may differ between infected and non-infected AAA.

Macrophage polarization and metabolic reprogramming in abdominal aortic aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) is a macrovascular disease with high morbidity and mortality in the elderly. The limitation of the current management is that most patients can only be followed up until the AAA diameter increases to a threshold, and surgical intervention is recommended. The development of preventive and curative drugs for AAA is urgently needed. Macrophage-mediated immune inflammation is one of the key pathological links in the occurrence and development of AAA.

AIMS

This review article aims to evaluate the impact of immunometabolism on macrophage biology and its role in AAA.

METHODS

We analyze publications focusing on the polarization and metabolic reprogramming in macrophages as well as their potential impact on AAA, and summarize the potential interventions that are currently available to regulate these processes.

RESULTS

The phenotypic and functional changes in macrophages are accompanied by significant alterations in metabolic pathways. The interaction between macrophage polarization and metabolic pathways significantly influences the progression of AAA.

CONCLUSION

Macrophage polarization is a manifestation of the gross dichotomy of macrophage function into pro-inflammatory killing and tissue repair, that is, classically activated M1 macrophages and alternatively activated M2 macrophages. Macrophage functions are closely linked to metabolic changes, and the emerging field of immunometabolism is providing unique insights into the role of macrophages in AAA. It is essential to further investigate the precise metabolic changes and their functional consequences in AAA-associated macrophages.

Mendelian randomization did not support the causal effect of diabetes on aortic diseases

Observational studies revealed paradoxically inverse associations between diabetes and aortic diseases (aortic aneurysm or aortic dissection), yet the causality remains to be determined. To investigate the causal associations between diabetes and aortic diseases using Mendelian randomization (MR) analyses. Summary-level data for exposures (type 1 diabetes, type 2 diabetes, fasting glucose, fasting insulin, glycated hemoglobin) and outcomes (aortic dissection and aortic aneurysm) were obtained from public genome-wide association study data. The principal analysis was the inverse-variance weighted (IVW) method. Sensitivity analyses were also carried out, including weighted median, MR-Egger, and multivariable MR methods. According to IVW results, type 1 diabetes (odds ratio [OR]: 0.99; 95% confidence interval [CI] 0.93-1.07; P = 0.87), type 2 diabetes (OR: 0.97; 95% CI 0.77-1.20; P = 0.75), fasting glucose (OR: 1.16; 95% CI 0.48-2.84; P = 0.74), fasting insulin (OR: 2.75; 95% CI 0.53-14.26; P = 0.23), or glycated hemoglobin (OR: 0.33; 95% CI 0.09-1.17; P = 0.09) had no causal effect on aortic dissection. Similarly, type 1 diabetes, type 2 diabetes, fasting glucose, fasting insulin, or glycated hemoglobin had no causal effect on aortic aneurysm. Sensitivity analyses revealed consistent results. MR-Egger method and funnel plot yielded no indication of directional pleiotropy. Diabetes had no causal associations with aortic dissection or aortic aneurysm. The observed inverse associations in previous cohort studies may be explained by confounding factors or reverse causation.

Construction of the miRNA/Pyroptosis-Related Molecular Regulatory Axis in Abdominal Aortic Aneurysm: Evidence From Transcriptome Data Combined With Multiple Machine Learning Approaches Followed by Experiment Validation

Background: Abdominal aortic aneurysm (AAA) represents a permanent and localized widening of the abdominal aorta, posing a potentially lethal risk of aortic rupture. Several recent studies have highlighted the role of pyroptosis, a pro-inflammatory programed cell death, as critical molecular regulators in AAA occurrence, progression, and rupture. However, the potential effects of pyroptosis in AAA and its upstream microRNA (miRNA) have not been comprehensively clarified. Methods: Through a search of the gene expression omnibus (GEO) database, the expression profiles of mRNAs (GSE7084, GSE57691, and GSE98278) and miRNAs (GSE62179) and corresponding clinical features were downloaded, respectively. Expression profiles of 15 AAA and 10 normal vascular samples were consecutively collected for in vitro experimentation and subsequent analysis. Various machine learning techniques were employed to identify hub pyroptosis-related genes (PRGs), leading to the development of a predictive model termed the PRG classifier. Quantitative real-time-polymerase chain reaction (qRT-PCR), western blot (WB), and enzyme-linked immunosorbent assay (ELISA) were used to confirm the expression of the hub PRGs. The diagnostic and predictive capabilities of the model were comprehensively evaluated in GEO and hospital cohorts. Then, the crucial immune cell infiltration and molecular pathways implicated in the initiation and rupture of AAA and their association with pyroptosis were explored. Lastly, a miRNA/hub pyroptosis-related molecular regulatory axis was constructed using the TargetScan dataset, which was further explored through loss-of-function assays. Results: Differential analysis, enrichment score analysis, and principal component analysis (PCA) revealed that pyroptosis-related molecules were significantly involved in the occurrence of AAA. Utilizing multiple machine learning algorithms, eight key PRGs (cysteinyl aspartate specific proteinase [CASP]1, infiltrating lymphocyte [IL]1B, IL18, IL6, NOD-, LRR- and pyrin domain-containing protein [NLRP]1, NLRP2, NLRP3, and tumor necrosis factor [TNF]) were integrated to establish a PRG classifier. Demonstrating robust diagnostic capabilities (area under curve [AUC] > 0.90), the PRG classifier provided clinical insights across two GEO datasets and effectively differentiated small AAA from large AAA, elective stable AAA (eAAA), and ruptured AAA (rAAA), respectively. qRT-PCR, WB, and ELISA verified the mRNA and protein expression of the hub PRGs. Notably, in hospital cohorts, a substantial positive link was unveiled between the PRG classifier and AAA risk factors (hypertension history, diastolic pressure, triglyceride levels, and aneurysm diameter). Furthermore, immune cell infiltration and functional enrichment analysis revealed significant associations of the PRG classifier/PRGs with M2 macrophage infiltration, activated dendritic cells, and enrichment scores of the cytosolic deoxyribonucleic acid (DNA) sensing pathway and tryptophan metabolism, potentially mediating AAA onset and rupture. Finally, based on 90 differentially expressed miRNAs (DEmiRNAs) and eight hub PRGs through TargetScan dataset, a hsa-miR-331-3p/TNF regulatory axis was constructed, wherein upregulation of hsa-miR-331-3p expression significantly reduced TNF and CASP1 protein levels. Conclusion: A predictive model (PRG classifier) incorporating eight PRGs through multiple machine learning algorithms was developed and validated. This model may stand as a potent tool for diagnosing AAA and assessing disease severity. The identification of the cytosolic DNA sensing pathway and the hsa-miR-331-3p/TNF interaction axis may represent crucial targets for AAA treatment, offering deeper insights into its potential pathogenesis.

A bibliometric and visualization analysis of global trends and frontiers on macrophages in abdominal aortic aneurysms research

BACKGROUND

Macrophages are key regulators of the inflammatory and innate immune responses. Researchers have shown that aberrant expression of macrophages contributes to the development of abdominal aortic aneurysms (AAA). However, a comprehensive bibliometric analysis exploring the research status and knowledge mapping of this area is lacking. This study aimed to explore the research status, knowledge mapping and hotspots of macrophages in AAA research from a bibliometric perspective.

METHODS

In this study, we retrieved articles published between 2000 and 2022 on macrophages associated with AAA research from the Web of Science Core Collection (WoSCC) database. The retrieved literature data were further analyzed using Citespace and VOSviewer software.

RESULTS

A total of 918 qualified publications related to AAA-associated macrophages were retrieved. The number of publications in this field has been increasing annually. China and the United States were the 2 main drivers in this field, contributing to more than 64% of the publications. In addition, the US had the most publications, top institutions, and expert researchers, dominating in research on macrophages in AAA. The Harvard University was the most productive institution, with 60 publications. The journal with the most publications was Arteriosclerosis, Thrombosis, and Vascular Biology (86). Daugherty Alan was the most prolific author (28 publications) and he was also the most cited co- author. Furthermore, the exploration of established animal models, macrophage-related inflammatory-microenvironment, macrophage-related immune mechanism, clinical translation and molecular imaging research remained future research directions in this field.

CONCLUSIONS

Our findings offered new insights for scholars in this field. They will help researchers explore new directions for their work.

Circulating inflammatory proteins and abdominal aortic aneurysm: A two-sample Mendelian randomization and colocalization analyses

OBJECTIVES

Inflammatory proteins are implicated in the progression of abdominal aortic aneurysms (AAA); however, it remains debated whether they are causal or consequential. This study aimed to assess the influence of circulating inflammatory proteins on AAA via two-sample Mendelian randomization (MR) and colocalization analysis.

METHODS

Summary data on 91 circulating inflammatory protein levels were extracted from a comprehensive protein quantitative trait loci (pQTL) study involving 14,824 individuals. Genetic associations with AAA were derived from the FinnGen study (3,869 cases and 381,977 controls). MR analysis was conducted to assess the relationships between proteins and AAA risk. Colocalization analysis was employed to explore potential shared causal variants between identified proteins and AAA.

RESULTS

Using a two-sample bidirectional MR study, our findings suggested that genetically predicted elevated levels of TGFB1 (OR = 1.21, P = 0.003), SIRT2 (OR = 1.196, P = 0.031) and TNFSF14 (OR = 1.129, P = 0.034) were linked to an increased risk of AAA. Conversely, genetically predicted higher levels of CD40 (OR = 0.912, P = 0.049), IL2RB (OR = 0.839, P = 0.028) and KITLG (OR = 0.827, P = 0.008) were associated with a decreased risk of AAA. Colocalization analyses supported the association of TGFB1 and SIRT2 levels with AAA risk.

CONCLUSIONS

The proteome-wide MR and colocalization study identified TGFB1 and SIRT2 as being associated with the risk of AAA, warranting further investigation as potential therapeutic targets.

The effect of edoxaban on apoptosis in an abdominal aortic aneurysm model in rats

Background

This study aimed to evaluate the effects of edoxaban, which is used in venous thrombosis, systemic embolism, and stroke, on an aortic aneurysm model and to demonstrate the pharmacokinetic and molecular effects of edoxaban through the induction of apoptosis.

Methods

In this double-blind experimental study, 21 Wistar albino male rats (mean weight: 290 g; range, 280 to 300 g) were divided into three groups: the sham group (n=7), the abdominal aortic aneurysm (AAA) group (n=7), and the AAA-edoxaban group (n=7). Edoxaban 10 mg/kg was given to the AAA-edoxaban group by oral gavage daily for 30 days. At the end of 30 days, the aneurysmal aorta was surgically removed and histologically examined. The abdominal aorta was surgically exposed and wrapped with a calcium chloride (0.5 mol/L) sponge for 10 min.

Results

Immunohistochemically, aortic sections were marked with caspase-3 and caspase-9 antibodies. It was observed that the pathways that trigger apoptosis (caspase-3 and caspase-9; p <0.004 and p <0.005, respectively) were significantly reduced in the AAA-edoxaban group compared to the AAA group. In the AAA-edoxaban group, it was observed that the expansion in aortic diameter and the deterioration in the elastic fibril structure in the aortic aneurysm were decreased as a result of edoxaban treatment. Edoxaban treatment was observed to reduce cell death in both the tunica intima and tunica media.

Conclusion

This study provided strong evidence of the protective effect of edoxaban on aortic aneurysm-related vascular damage by reducing apoptosis and mitophagy.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part two: Current and emerging concepts in the clinical use of PCSK9 inhibition

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have emerged as a novel class of drugs with cardioprotective effects through their lipid-lowering effects.

OBJECTIVE

This review aims to discuss existing and novel strategies of PCSK9 inhibition, providing an overview of established randomized controlled trials and ongoing outcome trials that assess the efficacy and long-term safety of PCSK9 inhibitors. It also explores the evolving role of PCSK9 beyond lipid metabolism and outlines the pleiotropic actions of PCSK9 inhibition in various disorders and future directions including novel strategies to target PCSK9.

CONCLUSION

PCSK9 inhibition shows promise not only in lipid metabolism but also in other disease processes, including atherosclerotic plaque remodeling, acute coronary syndrome, stroke, inflammation, and immune response.

A preliminary study of sirtuin-1 on angiotensin II-induced senescence and inflammation in abdominal aortic aneurysms

Objective

Recent evidence suggests the involvement of senescence and inflammation in abdominal aortic aneurysm (AAA). Considering the role of sirtuin-1 (SIRT1) in delaying senescence, we aimed to preliminarily investigate the potential mechanism underlying the effects of SIRT1 in senescence and inflammation during AAA.

Material and Methods

A cell AAA model was established using angiotensin II (Ang II) as the inducer, which was applied to treat human aortic vascular smooth muscle cells (HASMCs). The senescence and cell cycle of treated HASMCs were evaluated based on senescence-associated (SA)-b-galactosidase (b-gal) assay and flow cytometry, respectively. The levels of inflammatory cytokines and proteins related to senescence-associated secretory phenotype (SASP), along with nuclear factor-kappa B (NF-kB) and mitogen-activated protein kinases (MAPK) pathways, as well as SIRT1, were gauged. The correlation between SIRT1 and NF-kB and MAPK pathway-related proteins was further estimated.

Results

In Ang II-treated HASMCs, reduced SIRT1 and B-cell lymphoma-2 levels yet increased levels of SASP-related proteins P16 and P21, inflammatory cytokines, as well as Bax and caspases were all visible. In the meantime, Ang II exposure enhanced the number of b-gal-positive HASMCs and promoted cell cycle arrest. SIRT1 was also repressed following Ang II treatment and negatively correlated with NF-kB and MAPK pathway-related proteins (P < 0.05). Furthermore, the overexpression of SIRT1 diminished the levels of SASP-related proteins and reduced the phosphorylation of extracellular regulated kinase 1/2 and P65 in Ang II-treated HASMCs (P < 0.05).

Conclusion

Taken together, our results indicate that SIRT1 overexpression attenuates the inflammatory and senescent responses of HASMCs in the Ang II-induced AAA cell model. This finding suggests that SIRT1 can be a highly promising target for clinical treatment of AAA.

Adenosine kinase inhibition protects mice from abdominal aortic aneurysm via epigenetic modulation of VSMC inflammation

AIMS

Abdominal aortic aneurysm (AAA) is a common, serious vascular disease with no effective pharmacological treatment. The nucleoside adenosine plays an important role in modulating vascular homeostasis, which prompted us to determine whether adenosine kinase (ADK), an adenosine metabolizing enzyme, modulates AAA formation via control of the intracellular adenosine level, and to investigate the underlying mechanisms.

METHODS AND RESULTS

We used a combination of genetic and pharmacological approaches in murine models of AAA induced by calcium chloride (CaCl2) application or angiotensin II (Ang II) infusion to study the role of ADK in the development of AAA. In vitro functional assays were performed by knocking down ADK with adenovirus-short hairpin RNA in human vascular smooth muscle cells (VSMCs), and the molecular mechanisms underlying ADK function were investigated using RNA-sequencing, isotope tracing, and chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR). The heterozygous deficiency of ADK protected mice from CaCl2- and Ang II-induced AAA formation. Moreover, specific knockout of ADK in VSMCs prevented Ang II-induced AAA formation, as evidenced by reduced aortic extracellular elastin fragmentation, neovascularization, and aortic inflammation. Mechanistically, ADK knockdown in VSMCs markedly suppressed the expression of inflammatory genes associated with AAA formation, and these effects were independent of adenosine receptors. The metabolic flux and ChIP-qPCR results showed that ADK knockdown in VSMCs decreased S-adenosylmethionine (SAM)-dependent transmethylation, thereby reducing H3K4me3 binding to the promoter regions of the genes that are associated with inflammation, angiogenesis, and extracellular elastin fragmentation. Furthermore, the ADK inhibitor ABT702 protected mice from CaCl2-induced aortic inflammation, extracellular elastin fragmentation, and AAA formation.

CONCLUSION

Our findings reveal a novel role for ADK inhibition in attenuating AAA via epigenetic modulation of key inflammatory genes linked to AAA pathogenesis.

Medical treatments for abdominal aortic aneurysm: an overview of clinical trials

INTRODUCTION

Abdominal aortic aneurysm is a progressive, segmental, abdominal aortic dilation associated with a high mortality rate. Abdominal aortic aneurysms with diameters larger than 55 mm are associated with a high risk of rupture, and the most effective treatment options are surgical repair. Close observation and lifestyle adjustments are recommended for smaller abdominal aortic aneurysms with lower rupture risk. The development of medical therapies that limit or prevent the progression, expansion, and eventual rupture of abdominal aortic aneurysms remains an unmet clinical need.

AREAS COVERED

This review provides an overview of completed and ongoing clinical trials examining the efficacies of various drug classes, including antibiotics, antihypertensive drugs, hypolipidemic drugs, hypoglycemic drugs, and other potential therapies for abdominal aortic aneurysms. A search of PubMed, Web of Science, Clinical Trials, and another six clinical trial registries was conducted in January 2024.

EXPERT OPINION

None of the drugs have enough evidence to indicate that they can effectively inhibit the dilation of abdominal aortic aneurysm. More clinical trial data is required to support the efficacy of propranolol. Future research should also explore different drug delivery mechanisms, such as nanoparticles, to elevate drug concentration at the aneurysm wall.

Effects of a high-phosphate diet on vascular calcification and abdominal aortic aneurysm in mice

AIM

Vascular aging is an important risk factor for cardiovascular diseases, including abdominal aortic aneurysm (AAA) and pathological aortic dilatation, playing a critical role in the morbidity and mortality of older adults. Vascular calcification, a phenotype of vascular aging, is frequently associated with AAA. However, this association remains unclear owing to the lack of animal models. This study investigated the effects of a high-phosphate diet (HPD), a prominent trigger of vascular calcification in AAA.

METHODS

Eight-week-old male mice were fed either a normal diet (ND; Ca 1.18%/P 1.07% = 1.10) or an HPD (Ca 1.23%/P 1.65% = 0.75) for 4 weeks. Subsequently, AAA was induced using CaCl2 application and angiotensin II (AngII) infusion for 4 weeks.

RESULTS

The HPD resulted in more pronounced AAA formation than did the ND. Importantly, vascular calcification was observed only in the aorta of the HPD mice. Enhanced Runt-related transcription factor 2 expression and apoptosis (downregulation of growth arrest-specific gene 6/pAkt survival pathway), two major mechanisms of vascular calcification, were also observed. Furthermore, increased IL-6 and F4/80 expression was observed in the aorta of HPD mice. In RAW264.7 cells, inorganic phosphate enhanced IL-6 and IL-1β expression under AngII priming. Ferric citrate, a phosphate binder, significantly inhibited HPD-induced AAA formation.

CONCLUSIONS

These findings suggest that HPD induces vascular calcification and AAA formation, possibly through inflammation. This murine model suggests that vascular calcification induced by phosphate burden may be a therapeutic target for vascular diseases, including AAA. Geriatr Gerontol Int 2024; 24: 973-981.

Comparison of Various Functional Assessment Tools to Identify Older Patients Undergoing Aortic Aneurysm Repair at Risk for Postoperative Complications

BACKGROUND

To estimate whether the benefits of aortic aneurysm repair will outweigh the risks, determining individual risks is essential. This single-center prospective cohort study aimed to compare the association of functional tools with postoperative complications in older patients undergoing aortic aneurysm repair.

METHODS

Ninety-eight patients (≥65 years) who underwent aortic aneurysm repair were included. Four functional tools were administered: the Montreal Cognitive Assessment (MoCA); the 4-Meter Walk Test (4-MWT); handgrip strength; and the Groningen Frailty Indicator (GFI). Primary outcome was the association between all tests and 30-day postoperative complications.

RESULTS

After adjusting for confounders, the odds ratio for MoCA was 1.39 (95% confidence interval [CI] 0.450; 3.157; P = 0.723), for 4-MWT 0.63 (95% CI 0.242; 1.650; P = 0.348), for GFI 1.82 (95% CI 0.783; 4.323, P = 0.162), and for weak handgrip strength 4.78 (95% CI 1.338; 17.096, P = 0.016).

CONCLUSIONS

Weak handgrip strength is significantly associated with the development of postoperative complications after aortic aneurysm repair. This study strengthens the idea that implementing a quick screening tool for risk assessment at the outpatient clinic, such as handgrip strength, identifies patients who may benefit from preoperative enhancement with help from, for example, Comprehensive Geriatric Assessment, eventually leading to better outcomes for this patient group.

Influence of Bridging Stent Graft Implantation into the Renal Artery during Complex Endovascular Aortic Procedures on the Renal Resistance Index

Comparative sonographic examination of the renal resistance index (RRI) can provide evidence of renal artery stenosis. The extent to which the RRI is changed after stent graft implantation is not known. The aim of this study was to investigate the influence of stent graft implantation into non-diseased renal arteries during endovascular treatment of pararenal aortic aneurysms on the RRI. Sonographic examinations of the kidneys were conducted using a GE ultrasound system. The evaluation was performed according to the European Society for Vascular Surgery (ESVS) 2D standard criteria. RRI values were determined in consecutive patients on the day before and after stent graft implantation and compared for each kidney. A total of 32 consecutive patients (73.9 ± 8.2 years, 5 females, 27 males) were treated with a fenestrated or branched aortic stent graft including bridging stent graft implantations into both renal arteries and received pre- and postinterventional examinations. Sonomorphologically, the examined kidneys were inconspicuous. The arborisation of the renal perfusion was preserved pre- and post-implantation. The RRI did not differ (0.66 ± 0.06 versus 0.67 ± 0.07; p = ns). Successful stent graft implantation into non-stenosed renal arteries did not lead to a relevant change in RRI. Therefore, the RRI is a suitable tool for assessing renal perfusion after fenestrated or branched endovascular aortic therapy.

Neutrophil extracellular trap-induced ferroptosis promotes abdominal aortic aneurysm formation via SLC25A11-mediated depletion of mitochondrial glutathione

BACKGROUND

Neutrophil extracellular traps (NETs) induce oxidative stress, which may initiate ferroptosis, an iron-dependent programmed cell death, during abdominal aortic aneurysm (AAA) formation. Mitochondria regulate the progression of ferroptosis, which is characterized by the depletion of mitochondrial glutathione (mitoGSH) levels. However, the mechanisms are poorly understood. This study examined the role of mitoGSH in regulating NET-induced ferroptosis of smooth muscle cells (SMCs) during AAA formation.

METHODS

Concentrations of NET markers were tested in plasma samples. Western blotting and immunofluorescent staining were performed to detect the expression and localization of NET and ferroptosis markers in tissue samples. The role of NETs and SMC ferroptosis during AAA formation was investigated using peptidyl arginine deiminase 4 gene (Padi4) knockout or treatment with a PAD4 inhibitor, ferroptosis inhibitor or activator in an angiotensin II-induced AAA mouse model. The regulatory effect of SLC25A11, a mitochondrial glutathione transporter, on mitoGSH and NET-induced ferroptosis of SMCs was investigated using in vitro and in vivo experiments. Transmission electron microscopy was used to detect mitochondrial damage. Blue native polyacrylamide gel electrophoresis was used to analyze the dimeric and monomeric forms of the protein.

RESULTS

Significantly elevated levels of NETosis and ferroptosis markers in aortic tissue samples were observed during AAA formation. Specifically, NETs promoted AAA formation by inducing ferroptosis of SMCs. Subsequently, SLC25A11 was identified as a potential biomarker for evaluating the clinical prognosis of patients with AAA. Furthermore, NETs decreased the stability and dimerization of SLC25A11, leading to the depletion of mitoGSH. This depletion induced the ferroptosis of SMCs and promoted AAA formation.

CONCLUSION

During AAA formation, NETs regulate the stability of the mitochondrial carrier protein SLC25A11, leading to the depletion of mitoGSH and subsequent activation of NET-induced ferroptosis of SMCs. Preventing mitoGSH depletion and ferroptosis in SMCs is a potential strategy for treating AAA.

Hypertriglyceridemia as a Key Contributor to Abdominal Aortic Aneurysm Development and Rupture: Insights from Genetic and Experimental Models

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease without effective medications. This study integrated genetic, proteomic, and metabolomic data to identify causation between increased triglyceride (TG)-rich lipoproteins and AAA risk. Three hypertriglyceridemia mouse models were employed to test the hypothesis that increased plasma TG concentrations accelerate AAA development and rupture. In the angiotensin II-infusion AAA model, most Lpl -deficient mice with severely high plasma TG concentrations died of aortic rupture. Consistently, Apoa5 -deficient mice with moderately increased TG concentrations had accelerated AAA development, while human APOC3 transgenic mice with dramatically increased TG concentrations exhibited aortic dissection and rupture. Increased TG concentrations and palmitate inhibited lysyl oxidase maturation. Administration of antisense oligonucleotide targeting Angptl3 profoundly inhibited AAA progression in human APOC3 transgenic mice and Apoe -deficient mice. These results indicate that hypertriglyceridemia is a key contributor to AAA pathogenesis, highlighting the importance of triglyceride-rich lipoprotein management in treating AAA.

Effect of differences in proximal neck angles on biomechanics of abdominal aortic aneurysm based on fluid dynamics

BACKGROUND

This study aimed to analyze the effect of proximal neck angulation on the biomechanical indices of abdominal aortic aneurysms (AAA) and to investigate its impact on the risk of AAA rupture.

METHODS

CT angiography (CTA) data of patients with AAA from January 2015 to January 2022 were collected. Patients were divided into three groups based on the angle of the proximal neck: Group A (∠β ≤ 30°), Group B (30°<∠β ≤ 60°), and Group C (∠β > 60°). Biomechanical indices related to the rupture risk of AAA were analyzed using computational fluid dynamics modeling (CFD-Post) based on the collected data.

RESULTS

Group A showed slight turbulence in the AAA lumen with a mixed laminar flow pattern. Group B had a regular low-speed eddy line characterized by cross-flow dominated by lumen blood flow and turbulence. In Group C, a few turbulent lines appeared at the proximal neck, accompanied by eddy currents in the lumen expansion area following the AAA shape. Significant differences were found in peak wall stress, shear stress, and the maximum blood flow velocity impact among the three groups. The maximum blood flow velocity at the angle of the proximal neck impact indicated the influence of the proximal neck angle on the blood flow state in the lumen.

CONCLUSION

As the angle of the proximal neck increased, it caused stronger eddy currents and turbulent blood flow due to a high-speed area near the neck. The region with the largest diameter in the abdominal aortic aneurysm was prone to the highest stress, indicating a higher risk of rupture. The corner of the proximal neck experienced the greatest shear stress, potentially leading to endothelial injury and further enlargement of the aneurysm.

L-Wnk1 Deletion in Smooth Muscle Cells Causes Aortitis and Inflammatory Shift

BACKGROUND

The long isoform of the Wnk1 (with-no-lysine [K] kinase 1) is a ubiquitous serine/threonine kinase, but its role in vascular smooth muscle cells (VSMCs) pathophysiology remains unknown.

METHODS

AngII (angiotensin II) was infused in Apoe-/- to induce experimental aortic aneurysm. Mice carrying an Sm22-Cre allele were cross-bred with mice carrying a floxed Wnk1 allele to specifically investigate the functional role of Wnk1 in VSMCs.

RESULTS

Single-cell RNA-sequencing of the aneurysmal abdominal aorta from AngII-infused Apoe-/- mice revealed that VSMCs that did not express Wnk1 showed lower expression of contractile phenotype markers and increased inflammatory activity. Interestingly, WNK1 gene expression in VSMCs was decreased in human abdominal aortic aneurysm. Wnk1-deficient VSMCs lost their contractile function and exhibited a proinflammatory phenotype, characterized by the production of matrix metalloproteases, as well as cytokines and chemokines, which contributed to local accumulation of inflammatory macrophages, Ly6Chi monocytes, and γδ T cells. Sm22Cre+Wnk1lox/lox mice spontaneously developed aortitis in the infrarenal abdominal aorta, which extended to the thoracic area over time without any negative effect on long-term survival. AngII infusion in Sm22Cre+Wnk1lox/lox mice aggravated the aortic disease, with the formation of lethal abdominal aortic aneurysms. Pharmacological blockade of γδ T-cell recruitment using neutralizing anti-CXCL9 (anti-CXC motif chemokine ligand 9) antibody treatment, or of monocyte/macrophage using Ki20227, a selective inhibitor of CSF1 receptor, attenuated aortitis. Wnk1 deletion in VSMCs led to aortic wall remodeling with destruction of elastin layers, increased collagen content, and enhanced local TGF-β (transforming growth factor-beta) 1 expression. Finally, in vivo TGF-β blockade using neutralizing anti-TGF-β antibody promoted saccular aneurysm formation and aorta rupture in Sm22 Cre+ Wnk1lox/lox mice but not in control animals.

CONCLUSION

Wnk1 is a key regulator of VSMC function. Wnk1 deletion promotes VSMC phenotype switch toward a pathogenic proinflammatory phenotype, orchestrating deleterious vascular remodeling and spontaneous severe aortitis in mice.

Spontaneous ilio-iliac arteriovenous fistula: A rare complication of aorto-iliac aneurysm

Ilio-iliac arteriovenous fistula is an unusual complication of aorto-iliac aneurysms that can occur spontaneously, traumatically or iatrogenically. The typical clinical presentation includes the characteristic triad of high-output heart failure, a pulsatile abdominal mass with unilateral limb ischemia, or signs of venous congestion. We describe a rare case of spontaneous rupture of an aortoiliac aneurysm into the left common iliac vein of a 65-year-old man, easily diagnosed by angiography. We highlight here the angiographic findings of the ilio-iliac fistula, which was the means of diagnosis in this presentation, especially in patients with atypical clinical features at the outset, and we report the difficulties in choosing the optimal vascular approach.

An Expert-Based Review on the Relevance and Management of Type 2 Endoleaks Following Endovascular Repair of Ruptured Abdominal Aortic Aneurysms

Ruptured abdominal aortic aneurysms (rAAAs) are life-threatening and require emergent surgical therapy. Endovascular aortic repair for rupture (rEVAR) has become the leading strategy due to its minimal invasive approach with expected lower morbidity and mortality, especially in patients presenting with hemodynamic instability and relevant comorbidities. Following rEVAR, intraoperative angiography or early postinterventional computed tomography angiography have to exclude early type 1 or 3 endoleaks requiring immediate reintervention. Persistent type 2 endoleaks (T2ELs) after rEVAR, in contrast to elective cases, can cause possibly lethal situations due to continuing extravascular blood loss through the remaining aortic aneurysm rupture site. Therefore, early identification of relevant persistent T2ELs associated with continuous bleeding and hemodynamic instability and immediate management is mandatory in the acute postoperative setting following rEVAR. Different techniques and concepts for the occlusion of T2ELs after rEVAR are available, and most of them are also used for relevant T2ELs after elective EVAR. In addition to various interventional embolization procedures for persistent T2ELs, some patients require open surgical occlusion of T2EL-feeding arteries, abdominal compartment decompression or direct surgical patch occlusion of the aneurysm rupture site after rEVAR. So far, in the acute situation of rAAAs, indications for preemptive or intraoperative T2EL embolization during rEVAR have not been established. In the long term, persistent T2ELs after rEVAR can lead to continuous aneurysm expansion with the possible development of secondary proximal type I endoleaks and an increased risk of re-rupture requiring regular follow-up and early consideration for reintervention. To date, only very few studies have investigated T2ELs after rEVAR or compared outcomes with those from elective EVAR regarding the special aspects of persisting T2ELs. This narrative review is intended to present the current knowledge on the incidence, natural history, relevance and strategies for T2EL management after rEVAR.

Changes in global mortality from aortic aneurysm

OBJECTIVE

Globally, there has been a marked increase in aortic aneurysm-related deaths between 1990 and 2019. We sought to understand the underlying etiologies for this mortality trend by examining secular changes in both demographics and the prevalence of risk factors, and how these changes may vary across sociodemographic index (SDI) regions.

METHODS

We queried the Global Burden of Disease Study (GBD) for aortic aneurysm deaths from 1990 to 2019 overall and by age group. We identified the percentage of aortic aneurysm deaths attributable to each risk factor identified by GBD modeling (smoking, hypertension, lead exposure, and high sodium diet) and their respective changes over time. We then analyzed aneurysm mortality by SDI region.

RESULTS

The number of aortic aneurysm-related deaths have increased from 94,968 in 1990 to 172,427 in 2019, signifying an 81.6% increase, which greatly exceeds the 18.2% increase in all-cause mortality observed over the same time interval. Examination of age-specific mortality demonstrated that the number of aortic aneurysm deaths markedly correlated with advancing age. However, when considering rate of death rather than mortality count, overall age-standardized death rates decreased 18% from 2.72 per 100,000 in 1990 to 2.21 per 100,000 in 2019. Analysis of the specific risk factors associated with aneurysm death revealed that the percentage of deaths attributable to smoking decreased from 45.6% in 1990 to 34.6% in 2019, and deaths attributable to hypertension decreased from 38.7% to 34.7%. Globally, hypertension surpassed smoking as the leading risk factor. The reported rate of death was consistently greater as SDI increased, and this effect was most pronounced among low-middle and middle SDI regions (173.2% and 170.4%, respectively).

CONCLUSIONS

Despite an overall increase in the number of aneurysm deaths, there was a decrease in the age-standardized death rate, demonstrating that the observed increased number of aortic aneurysm deaths between 1990 and 2019 was primarily driven by an overall increase in the age of the global population. Fortunately, it appears that the increase in overall aneurysm-related deaths has been modulated by improved risk factor modification, in particular smoking. Given the rise in aneurysm-related deaths, global expansion of vascular specialty capabilities is warranted and will serve to amplify improvements in population-based aneurysm health achieved with risk factor control.

Bridging the gap: Navigating the impact of dietary supplements on abdominal aortic aneurysm progression- A systematic review

BACKGROUND

Vitamins D, E, A, B, C, and Omega-3 play crucial roles in modulating inflammatory and oxidative stress pathways, both implicated in abdominal aortic aneurysm (AAA) development. Recent research has explored the potential impact of dietary supplements on AAA progression. The systematic review aims to assess interventional studies investigating the effects of various dietary supplements on the development and severity of abdominal aortic aneurysms.

METHOD

A systematic search using relevant keywords related to abdominal aortic aneurysm and dietary supplements was conducted across four databases (PubMed, Embase, Scopus, and Web of Science). Quality assessment for animal studies employed SYRCLE and the Cochrane Collaboration Risk of Bias Tool for randomized control trials. The study protocol is registered in PROSPERO under the registry code CRD42023455958.

RESULTS

Supplementation with Omega-3, Vitamins A, C, D, E, and the Vitamin B family exhibited positive effects in AAA progression. These supplements contributed to a reduction in AAA diameter, elastin degradation, inflammatory responses, and reactive oxygen species. Additional supplements such as Zinc, methionine, and phytoestrogen also played roles in mitigating AAA progression.

CONCLUSION

The findings of this study underscore the potential role of dietary supplements in the progression of AAA. Predominantly based on animal studies, the results indicate that these supplements can limit AAA progression, primarily evidenced by their ability to mitigate inflammatory processes and oxidative stress pathways.

Assessing the causal relationship between circulating immune cells and abdominal aortic aneurysm by bi-directional Mendelian randomization analysis

Although there is an association between abdominal aortic aneurysm (AAA) and circulating immune cell phenotypes, the exact causal relationship remains unclear. This study aimed to explore the causal relationships between immune cell phenotypes and AAA risk using a bidirectional two-sample Mendelian randomization approach. Data from genome-wide association studies pertaining to 731 immune cell traits and AAA were systematically analyzed. Using strict selection criteria, we identified 339 immune traits that are associated with at least 3 single nucleotide polymorphisms. A comprehensive MR analysis was conducted using several methods including Inverse Variance Weighted, Weighted Median Estimator, MR-Egger regression, Weighted Mode, and Simple Median methods. CD24 on switched memory cells (OR = 0.922, 95% CI 0.914-0.929, P = 2.62e-79) at the median fluorescence intensities level, and SSC-A on HLA-DR + natural killer cells (OR = 0.873, 95% CI 0.861-0.885, P = 8.96e-81) at the morphological parameter level, exhibited the strongest causal associations with AAA. In the reverse analysis, no significant causal effects of AAA on immune traits were found. The study elucidates the causal involvement of multiple circulating immune cell phenotypes in AAA development, signifying their potential as diagnostic markers or therapeutic targets. These identified immune traits may be crucial in modulating AAA-related inflammatory pathways.

Comprehensive transcriptomic analysis unveils macrophage-associated genes for establishing an abdominal aortic aneurysm diagnostic model and molecular therapeutic framework

BACKGROUND

Abdominal aortic aneurysm (AAA) is a highly lethal cardiovascular disease. The aim of this research is to identify new biomarkers and therapeutic targets for the treatment of such deadly diseases.

METHODS

Single-sample gene set enrichment analysis (ssGSEA) and CIBERSORT algorithms were used to identify distinct immune cell infiltration types between AAA and normal abdominal aortas. Single-cell RNA sequencing data were used to analyse the hallmark genes of AAA-associated macrophage cell subsets. Six macrophage-related hub genes were identified through weighted gene co-expression network analysis (WGCNA) and validated for expression in clinical samples and AAA mouse models. We screened potential therapeutic drugs for AAA through online Connectivity Map databases (CMap). A network-based approach was used to explore the relationships between the candidate genes and transcription factors (TFs), lncRNAs, and miRNAs. Additionally, we also identified hub genes that can effectively identify AAA and atherosclerosis (AS) through a variety of machine learning algorithms.

RESULTS

We obtained six macrophage hub genes (IL-1B, CXCL1, SOCS3, SLC2A3, G0S2, and CCL3) that can effectively diagnose abdominal aortic aneurysm. The ROC curves and decision curve analysis (DCA) were combined to further confirm the good diagnostic efficacy of the hub genes. Further analysis revealed that the expression of the six hub genes mentioned above was significantly increased in AAA patients and mice. We also constructed TF regulatory networks and competing endogenous RNA networks (ceRNA) to reveal potential mechanisms of disease occurrence. We also obtained two key genes (ZNF652 and UBR5) through a variety of machine learning algorithms, which can effectively distinguish abdominal aortic aneurysm and atherosclerosis.

CONCLUSION

Our findings depict the molecular pharmaceutical network in AAA, providing new ideas for effective diagnosis and treatment of diseases.

Advances and challenges in regenerative therapies for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a significant source of mortality worldwide and carries a mortality of greater than 80% after rupture. Despite extensive efforts to develop pharmacological treatments, there is currently no effective agent to prevent aneurysm growth and rupture. Current treatment paradigms only rely on the identification and surveillance of small aneurysms, prior to ultimate open surgical or endovascular repair. Recently, regenerative therapies have emerged as promising avenues to address the degenerative changes observed in AAA. This review briefly outlines current clinical management principles, characteristics, and pharmaceutical targets of AAA. Subsequently, a thorough discussion of regenerative approaches is provided. These include cellular approaches (vascular smooth muscle cells, endothelial cells, and mesenchymal stem cells) as well as the delivery of therapeutic molecules, gene therapies, and regenerative biomaterials. Lastly, additional barriers and considerations for clinical translation are provided. In conclusion, regenerative approaches hold significant promise for in situ reversal of tissue damages in AAA, necessitating sustained research and innovation to achieve successful and translatable therapies in a new era in AAA management.

Spatio-temporal Relationship between Three-Dimensional Deformations of a Collapsible Tube and the Downstream Flowfield

The interactions between fluid flow and structural components of collapsible tubes are representative of those in several physiological systems. Although extensively studied, there exists a lack of characterization of the three-dimensionality in the structural deformations of the tube and its influence on the flow field. This experimental study investigates the spatio-temporal relationship between 3D tube geometry and the downstream flow field under conditions of fully open, closed, and slamming-type oscillating regimes. A methodology is implemented to simultaneously measure three-dimensional surface deformations in a collapsible tube and the corresponding downstream flow field. Stereophotogrammetry was used to measure tube deformations, and simultaneous flow field measurements included pressure and planar Particle Image Velocimetry (PIV) data downstream of the collapsible tube. The results indicate that the location of the largest collapse in the tube occurs close to the downstream end of the tube. In the oscillating regime, sections of the tube downstream of the largest mean collapse experience the largest oscillations in the entire tube that are completely coherent and in phase. At a certain streamwise distance upstream of the largest collapse, a switch in the direction of oscillations occurs with respect to those downstream. Physically, when the tube experiences constriction downstream of the location of the largest mean collapse, this causes the accumulation of fluid and build-up of pressure in the upstream regions and an expansion of these sections. Fluctuations in the downstream flow field are significantly influenced by tube fluctuations along the minor axes. The fluctuations in the downstream flowfield are influenced by the propagation of disturbances due to oscillations in tube geometry, through the advection of fluid through the tube. Further, the manifestation of the LU-type pressure fluctuations is found to be due to the variation in the propagation speed of the disturbances during the different stages within a period of oscillation of the tube.

Sleep Pattern, Genetic Susceptibility, and Abdominal Aortic Aneurysm in UK Biobank Participants: Large-Scale Cohort Study

Background

Abdominal aortic aneurysm (AAA) is an important cause of cardiovascular mortality.

Objectives

The authors aimed to explore the associations between sleep patterns and genetic susceptibility to AAA.

Methods

We included 344,855 UK Biobank study participants free of AAA at baseline. A sleep pattern was defined by chronotype, sleep duration, insomnia, snoring, and daytime sleepiness, and an overall sleep score was constructed with a range from 0 to 5, where a high score denotes a healthy sleep pattern. Polygenic risk score based on 22 single nucleotide polymorphisms was categorized into tertiles and used to evaluate the genetic risk for AAA. Cox proportional hazards regression models were used to assess the association between sleep, genetic factors, and the incidence of AAA.

Results

During a median of 12.59 years of follow-up, 1,622 incident AAA cases were identified. The HR per 1-point increase in the sleep score was 0.91 (95% CI: 0.86-0.96) for AAA. Unhealthy sleep patterns, defined as a sleep score ranging from 0 to 3, were found to be associated with a higher risk of AAA for the intermediate (HR: 1.18, 95% CI: 1.06-1.31) and poor sleep patterns (HR: 1.40, 95% CI: 1.13-1.73), respectively, compared to the healthy pattern. Participants with poor sleep patterns and high genetic risks had a 2.5-fold higher risk of AAA than those with healthy sleep patterns and low genetic risk.

Conclusions

In this large prospective study, healthy sleep patterns were associated with a lower risk of AAA among participants with low, intermediate, or high genetic risk.

The incidence rate and histological characteristics of intimal hyperplasia in elastase-induced experimental abdominal aortic aneurysms in mice

Intimal hyperplasia (IH) is a negative vascular remodeling after arterial injury. IH occasionally occurs in elastase-induced abdominal aortic aneurysm (AAA) mouse models. This study aims to clarify the incidence and histological characteristics of IH in aneurysmal mice. A retrospective study was conducted by including 42 male elastase-induced mouse AAA models. The IH incidence, aortic diameters with or without IH, and hyperplasia lesional features of mice were analyzed. Among 42 elastase-induced AAA mouse models, 10 mice developed mild IH (24%) and severe IH was found in only 2 mice (5%). The outer diameters of the AAA segments in mice with and without IH did not show significant difference. Both mild and severe IH lesions show strong smooth muscle cell positive staining, but endothelial cells were occasionally observed in severe IH lesions. There was obvious macrophage infiltration in the IH lesions of the AAA mouse models, especially in mice with severe IH. However, only a lower numbers of T cells and B cells were found in the IH lesion. Local cell-secreted matrix metalloproteinases (MMP) 2 was highly expressed in all IH lesions, but MMP9 was only overexpressed in severe lesions. In conclusion, this study is the first to demonstrate the occurrence of aneurysmal IH and its histological characteristics in an elastase-induced mouse AAA model. This will help researchers better understand this model, and optimize it for use in AAA-related research.

Implantable Pressure-Sensing Devices for Monitoring Abdominal Aortic Aneurysms in Post-Endovascular Aneurysm Repair

Over the past two decades, there has been extensive research into surveillance methods for the post-endovascular repair of abdominal aortic aneurysms, highlighting the importance of these technologies in supplementing or even replacing conventional image-screening modalities. This review aims to provide an overview of the current status of alternative surveillance solutions for endovascular aneurysm repair, while also identifying potential aneurysm features that could be used to develop novel monitoring technologies. It offers a comprehensive review of these recent clinical advances, comparing new and standard clinical practices. After introducing the clinical understanding of abdominal aortic aneurysms and exploring current treatment procedures, the paper discusses the current surveillance methods for endovascular repair, contrasting them with recent pressure-sensing technologies. The literature on three commercial pressure-sensing devices for post-endovascular repair surveillance is analyzed. Various pre-clinical and clinical studies assessing the safety and efficacy of these devices are reviewed, providing a comparative summary of their outcomes. The review of the results from pre-clinical and clinical studies suggests a consistent trend of decreased blood pressure in the excluded aneurysm sac post-repair. However, despite successful pressure readings from the aneurysm sac, no strong link has been established to translate these measurements into the presence or absence of endoleaks. Furthermore, the results do not allow for a conclusive determination of ongoing aneurysm sac growth. Consequently, a strong clinical need persists for monitoring endoleaks and aneurysm growth following endovascular repair.