Circulating markers of abdominal aortic aneurysm presence and progression

Innovation in pathogenesis and management of aortic aneurysm

Aortic aneurysm (AA) refers to the persistent dilatation of the aorta, exceeding three centimeters. Investigating the pathophysiology of this condition is important for its prevention and management, given its responsibility for more than 25000 deaths in the United States. AAs are classified based on their location or morphology. various pathophysiologic pathways including inflammation, the immune system and atherosclerosis have been implicated in its development. Inflammatory markers such as transforming growth factor β, interleukin-1β, tumor necrosis factor-α, matrix metalloproteinase-2 and many more may contribute to this phenomenon. Several genetic disorders such as Marfan syndrome, Ehler-Danlos syndrome and Loeys-Dietz syndrome have also been associated with this disease. Recent years has seen the investigation of novel management of AA, exploring the implication of different immune suppressors, the role of radiation in shrinkage and prevention, as well as minimally invasive and newly hypothesized surgical methods. In this narrative review, we aim to present the new contributing factors involved in pathophysiology of AA. We also highlighted the novel management methods that have demonstrated promising benefits in clinical outcomes of the AA.

Pharmacological Inhibition of MMP-12 Exerts Protective Effects on Angiotensin II-Induced Abdominal Aortic Aneurysms in Apolipoprotein E-Deficient Mice

Human abdominal aortic aneurysms (AAAs) are characterized by increased activity of matrix metalloproteinases (MMP), including MMP-12, alongside macrophage accumulation and elastin degradation, in conjunction with superimposed atherosclerosis. Previous genetic ablation studies have proposed contradictory roles for MMP-12 in AAA development. In this study, we aimed to elucidate if pharmacological inhibition of MMP-12 activity with a phosphinic peptide inhibitor protects from AAA formation and progression in angiotensin (Ang) II-infused Apoe-/- mice. Complimentary studies were conducted in a human ex vivo model of early aneurysm development. Administration of an MMP-12 inhibitor (RXP470.1) protected hypercholesterolemia Apoe-/- mice from Ang II-induced AAA formation and rupture-related death, associated with diminished medial thinning and elastin fragmentation alongside increased collagen deposition. Proteomic analyses confirmed a beneficial effect of MMP-12 inhibition on extracellular matrix remodeling proteins combined with inflammatory pathways. Furthermore, RXP470.1 treatment of mice with pre-existing AAAs exerted beneficial effects as observed through suppressed aortic dilation and rupture, medial thinning, and elastin destruction. Our findings indicate that pharmacological inhibition of MMP-12 activity retards AAA progression and improves survival in mice providing proof-of-concept evidence to motivate translational work for MMP-12 inhibitor therapy in humans.

Can Biomarkers and PET Imaging Predict Abdominal Aortic Aneurysm Growth Rate?

Background: Abdominal aortic aneurysm (AAA) is a life-threatening condition due to the risk of aneurysm growth and rupture. Biomarkers linked to AAA pathogenesis are attractive candidates for AAA diagnosis and prognosis. The aim of this study was to assess circulating biomarkers levels relationship with PET imaging positivity and their predictive value in AAA growth rate. Methods: A total of 164 patients with AAA had whole body [18F]FDG PET/CT examination and blood drawn for biomarkers analysis at inclusion. Of these, 121 patients had at least one follow-up imaging assessment for AAA progression. Median (quartiles) imaging follow-up period was 32.8 months (15.2-69.6 months). Results: At baseline, PET was visually positive in 28 (17%) patients. Among PET+ patients, female proportion was higher compared to PET-patients (respectively, n = 6, 21.4% vs. n = 11, 8.1%, p = 0.046). Biomarkers of inflammation (CRP, CCL18), of proteolytic activity (MMP9), of extracellular matrix, and calcification regulation (OPN, OPG) were all significantly increased in PET+ patients (p < 0.05). During follow-up, rapid AAA growth (increase in size ≥ 1 cm per year) was observed in 36 (29.8%) patients and several biomarkers (CRP, MMP9, OPN, and OPG) were increased in those patients compared to patients without rapid growth (p < 0.05). Conclusions: Although PET positivity at baseline was not associated with rapid growth, CRP levels showed a significant association.

Automated detection of incidental abdominal aortic aneurysms on computed tomography

PURPOSE

To detect and assess abdominal aortic aneurysms (AAAs) on CT in a large asymptomatic adult patient population using fully-automated deep learning software.

MATERIALS AND METHODS

The abdominal aorta was segmented using a fully-automated deep learning model trained on 66 manually-segmented abdominal CT scans from two datasets. The axial diameters of the segmented aorta were extracted to detect the presence of AAAs-maximum axial aortic diameter greater than 3 cm were labeled as AAA positive. The trained system was then externally-validated on CT colonography scans of 9172 asymptomatic outpatients (mean age, 57 years) referred for colorectal cancer screening. Using a previously-validated automated calcified atherosclerotic plaque detector, we correlated abdominal aortic Agatston and volume scores with the presence of AAA.

RESULTS

The deep learning software detected AAA on the external validation dataset with a sensitivity, specificity, and AUC of 96%, (95% CI 89%, 100%), 96% (96%, 97%), and 99% (98%, 99%) respectively. The Agatston and volume scores of reported AAA-positive cases were statistically significantly greater than those of reported AAA-negative cases (p < 0.0001). Using plaque alone as a AAA detector, at a threshold Agatston score of 2871, the sensitivity and specificity were 84% (73%, 94%) and 87% (86%, 87%), respectively.

CONCLUSION

Fully-automated detection and assessment of AAA on CT is feasible and accurate. There was a strong statistical association between the presence of AAA and the quantity of abdominal aortic calcified atherosclerotic plaque.

Vasculoprotective Potential of Baicalein in Angiotensin II-Infused Abdominal Aortic Aneurysms through Inhibiting Inflammation and Oxidative Stress

Aortic wall inflammation, abnormal oxidative stress and progressive degradation of extracellular matrix proteins are the main characteristics of abdominal aortic aneurysms (AAAs). The nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome dysregulation plays a crucial role in aortic damage and disease progression. The first aim of this study was to examine the effect of baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one) on AAA formation in apolipoprotein E-deficient (ApoE-/-) mice. The second aim was to define whether baicalein attenuates aberrant vascular smooth muscle cell (VSMC) proliferation and inflammation in VSMC culture. For male ApoE-/- mice, a clinically relevant AAA model was randomly divided into four groups: saline infusion, baicalein intraperitoneal injection, Angiotensin II (Ang II) infusion and Ang II + baicalein. Twenty-seven days of treatment with baicalein markedly decreased Ang II-infused AAA incidence and aortic diameter, reduced collagen-fiber formation, preserved elastic structure and density and prevented smooth muscle cell contractile protein degradation. Baicalein inhibited rat VSMC proliferation and migration following the stimulation of VSMC cultures with Ang II while blocking the Ang II-inducible cell cycle progression from G0/G1 to the S phase in the synchronized cells. Cal-520 AM staining showed that baicalein decreased cellular calcium in Ang II-induced VSMCs; furthermore, a Western blot assay indicated that baicalein inhibited the expression of PCNA and significantly lowered levels of phospho-Akt and phospho-ERK, along with an increase in baicalein concentration in Ang II-induced VSMCs. Immunofluorescence staining showed that baicalein pretreatment reduced NF-κB nuclear translocation in Ang II-induced VSMCs and furthered the protein expressions of NLRP3 while ASC and caspase-1 were suppressed in a dose-dependent manner. Baicalein pretreatment upregulated Nrf2/HO-1 signaling in Ang II-induced VSMCs. Thus, 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining showed that its reactive oxygen species (ROS) production decreased, along with the baicalein pretreatment. Our overall results indicate that baicalein could have therapeutic potential in preventing aneurysm development.

The contribution of matrix metalloproteinases and their inhibitors to the development, progression, and rupture of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) account for up to 8% of deaths in men aged 65 years and over and 2.2% of women. Patients with AAAs often have atherosclerosis, and intimal atherosclerosis is generally present in AAAs. Accordingly, AAAs are considered a form of atherosclerosis and are frequently referred to as atherosclerotic aneurysms. Pathological observations advocate inflammatory cell infiltration alongside adverse extracellular matrix degradation as key contributing factors to the formation of human atherosclerotic AAAs. Therefore, macrophage production of proteolytic enzymes is deemed responsible for the damaging loss of ECM proteins, especially elastin and fibrillar collagens, which characterise AAA progression and rupture. Matrix metalloproteinases (MMPs) and their regulation by tissue inhibitors metalloproteinases (TIMPs) can orchestrate not only ECM remodelling, but also moderate the proliferation, migration, and apoptosis of resident aortic cells, alongside the recruitment and subsequent behaviour of inflammatory cells. Accordingly, MMPs are thought to play a central regulatory role in the development, progression, and eventual rupture of abdominal aortic aneurysms (AAAs). Together, clinical and animal studies have shed light on the complex and often diverse effects MMPs and TIMPs impart during the development of AAAs. This dichotomy is underlined from evidence utilising broad-spectrum MMP inhibition in animal models and clinical trials which have failed to provide consistent protection from AAA progression, although more encouraging results have been observed through deployment of selective inhibitors. This review provides a summary of the supporting evidence connecting the contribution of individual MMPs to AAA development, progression, and eventual rupture. Topics discussed include structural, functional, and cell-specific diversity of MMP members; evidence from animal models of AAA and comparisons with findings in humans; the dual role of MMPs and the requirement to selectively target individual MMPs; and the advances in identifying aberrant MMP activity. As evidenced, our developing understanding of the multifaceted roles individual MMPs perform during the progression and rupture of AAAs, should motivate clinical trials assessing the therapeutic potential of selective MMP inhibitors, which could restrict AAA-related morbidity and mortality worldwide.

Prevalence of risk factors associated with rupture of abdominal aortic aneurysm (AAA): a single center retrospective study

BACKGROUND

Abdominal aortic aneurysm (AAA) is a severe cardiovascular disease. The mortality rate for an AAA rupture is very high. Understanding the risk factors for AAA rupture would help AAA management, but little is known about these risk factors in the Chinese population.

METHODS

This retrospective study included patients that were diagnosed with AAA during the last 5 years in a large national hospital in southern China. AAA patients were divided into a rupture and non-rupture group. Clinical data were extracted from the hospital medical record system. Clinical features were compared between the rupture and non-rupture groups. The associations between potential risk factors and rupture risk were evaluated using a multivariate logistic regression analysis.

RESULTS

A total of 337 AAA patients were included for analysis in the present study. AAA diameter was significantly larger, and high-sensitivity C-reactive protein (hs-CRP) and serum creatinine levels were both significantly higher in AAA rupture patients. High-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels were significantly lower in AAA rupture patients. After adjustment, the multivariate logistic analysis found that AAA diameter and hs-CRP were independently positively associated with AAA rupture, and HDL-C level was adversely associated with AAA rupture.

CONCLUSIONS

Our data suggests that larger AAA diameter and higher hs-CRP level are associated with a higher risk of AAA rupture, and higher HDL-C level is associated with a lower risk of AAA rupture. The results of this study may be helpful for the management of AAA patients in southern China.

Dysregulations of Key Regulators of Angiogenesis and Inflammation in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a chronic vascular disease caused by localized weakening and broadening of the abdominal aorta. AAA is a clearly underdiagnosed disease and is burdened with a high mortality rate (65-85%) from AAA rupture. Studies indicate that abnormal regulation of angiogenesis and inflammation contributes to progression and onset of this disease; however, dysregulations in the molecular pathways associated with this disease are not yet fully explained. Therefore, in our study, we aimed to identify dysregulations in the key regulators of angiogenesis and inflammation in patients with AAA in peripheral blood mononuclear cells (using qPCR) and plasma samples (using ELISA). Expression levels of ANGPT1, CXCL8, PDGFA, TGFB1, VEGFB, and VEGFC and plasma levels of TGF-alpha, TGF-beta 1, VEGF-A, and VEGF-C were found to be significantly altered in the AAA group compared to the control subjects without AAA. Associations between analyzed factors and risk factors or biochemical parameters were also explored. Any of the analyzed factors was associated with the size of the aneurysm. The presented study identified dysregulations in key angiogenesis- and inflammation-related factors potentially involved in AAA formation, giving new insight into the molecular pathways involved in the development of this disease and providing candidates for biomarkers that could serve as diagnostic or therapeutic targets.

Associations of Tissue and Soluble LOX-1 with Human Abdominal Aortic Aneurysm

Background Indication for prophylactic surgical abdominal aortic aneurysm (AAA) repair depends on the maximal aortic diameter. The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major receptor for uptake of oxidized low-density lipoprotein cholesterol and is implicated in atherosclerosis. A soluble form of LOX-1 (sLOX-1) has been discussed as a novel biomarker in coronary artery disease and stroke. Herein, we assessed the regulation of aortic LOX-1 as well as the diagnostic and risk stratification potential of sLOX-1 in patients with AAA. Methods and Results Serum sLOX-1 was assessed in a case-control study in AAA (n=104) and peripheral artery disease (n=104). sLOX-1 was not statistically different between AAA and peripheral artery disease but was higher in AAA (β=1.28, P=0.04) after adjusting for age, atherosclerosis, type 2 diabetes, prescription of statins, β-blockers, ACE inhibitors, and therapeutic anticoagulation. sLOX-1 was not associated with the aortic diameter, AAA volume, or the thickness of the intraluminal thrombus. Aortic LOX-1 mRNA expression tended to be higher in AAA when compared with disease, and expression was positively associated with cleaved caspase-3, smooth muscle actin, collagen, and macrophage content. Conclusions In AAA, sLOX-1 was differently affected by age, cardiometabolic diseases, and corresponding medical therapies. Comparison with nonatherosclerotic disease would be beneficial to further elucidate the diagnostic potential of sLOX-1, although it was not useful for risk stratification. Aneurysmal LOX-1 mRNA expression was increased and positively associated with smooth muscle cells and collagen content, suggesting that LOX-1 is eventually not deleterious in human AAA and could counteract AAA rupture.

Plasma Lipidomics Analysis Reveals the Potential Role of Lysophosphatidylcholines in Abdominal Aortic Aneurysm Progression and Formation

Abdominal aortic aneurysm (AAA) is hallmarked by irreversible dilation of the infrarenal aorta. Lipid deposition in the aortic wall and the potential importance of a lipid disorder in AAA etiology highlight the need to explore lipid variation during AAA development. This study aimed to systematically characterize the lipidomics associated with AAA size and progression. Plasma lipids from 106 subjects (36 non-AAA controls and 70 AAA patients) were comprehensively analyzed using untargeted lipidomics. An AAA animal model was established by embedding angiotensin-II pump in ApoE^-/- mice for four weeks and blood was collected at 0, 2 and 4 weeks for lipidomic analysis. Using a false-discovery rate (FDR) < 0.05, a group of lysophosphatidylcholines (lysoPCs) were specifically decreased in AAA patients and mice. LysoPCs were principally lower in the AAA patients with larger diameter (diameter > 50 mm) than those with a smaller size (30 mm < diameter < 50 mm), and levels of lysoPCs were also found to be decreased with modelling time and aneurysm formation in AAA mice. Correlation matrices between lipids and clinical characteristics identified that the positive correlation between lysoPCs and HDL-c was reduced and negative correlations between lysoPCs and CAD rate, lysoPCs and hsCRP were converted to positive correlations in AAA compared to control. Weakened positive correlations between plasma lysoPCs and circulating HDL-c in AAA suggested that HDL-lysoPCs may elicit instinctive physiological effects in AAA. This study provides evidence that reduced lysoPCs essentially underlie the pathogenesis of AAA and that lysoPCs are promising biomarkers for AAA development.

The predictive value of four serum biomarkers for major adverse events in patients with small abdominal aortic aneurysm

BACKGROUND

The primary aim of this study was to test which of a group of four inflammation and thrombosis biomarkers were independently predictive of major adverse cardiovascular events (MACE) in patients with small abdominal aortic aneurysm (AAA).

METHODS

A total of 471 participants with a 30- to 54-mm AAA had serum C-reactive protein (CRP), fibrinogen, neutrophil-lymphocyte ratio (NLR), and homocysteine measured. The primary outcome was MACE, which was defined as the first occurrence of myocardial infarction, stroke, or cardiovascular death. The association of biomarkers with events was assessed using Kaplan-Meier and Cox proportional hazard analyses. The net improvement in risk of event categorization with addition of a biomarker to clinical risk factors alone was assessed using net reclassification index.

RESULTS

Participants were followed for a median of 2.4 years (interquartile range, 0.8-5.4 years), and 102 (21.7%) had a MACE. The incidence of MACE was 13.2% in participants with CRP >3.0 mg/L, compared with 10.1% in those with CRP ≤3.0 mg/L at 2.5 years (P = .047). After adjusting for other risk factors, higher CRP was associated with a significantly higher risk of MACE (hazard ratio, 1.19; 95% confidence interval, 1.05-1.35). None of the other biomarkers were associated with the risk of MACE. According to the net reclassification index, CRP significantly improved the risk classification of MACE compared with clinical risk factors alone.

CONCLUSIONS

CRP can assist in classification of risk of MACE for patients with small AAA.

Association Between Obesity and Outcomes Following Endovascular Aneurysm Repair

BACKGROUND

Obesity is prevalent in patients with abdominal aortic aneurysms (AAA). There is an association between increasing body mass index (BMI) and increased overall cardiovascular mortality and morbidity. This study aims to assess the difference in mortality and complication rates between normal weight (NW), overweight (OW), and obese patients undergoing endovascular aneurysm repair (EVAR) for infrarenal AAA.

METHODS

This is a retrospective analysis of consecutive patients undergoing EVAR for AAA between January 1998 and December 2019. Weight classes were defined as: BMI<18.5 kg/m², underweight; BMI 18.5-24.9 kg/m², NW; BMI 25.0-29.9 kg/m², OW; BMI 30.0-39.9 kg/m², obese; BMI>39.9 kg/m² morbidly obese. Primary outcomes were long-term all-cause mortality and freedom from reintervention. Secondary outcome was aneurysm sac regression (defined as a reduction in sac diameter of 5 mm or more). Kaplan-Meier survival estimates and mixed model analysis of variance were used.

RESULTS

The study included 515 patients (83% males, mean age 77 ± 8 years) with a mean follow-up of 3.8 ± 2.8 years. In terms of weight class, 2.1% (n = 11) were underweight, 32.4% (167) were NW, 41.6% (n = 214) were OW, 21.2% (n = 109) were obese, and 2.7% (n = 14) were morbidly obese. Obese patients were younger (mean difference -5.0 years) but had a higher prevalence of diabetes mellitus (33.3% vs. 10.6% for NW) and dyslipidemia (82.4% vs. 60.9% for NW). Obese patients had similar freedom from all-cause mortality (88%) compared to OW (78%) and NW (81%) patients. The same findings were evident for freedom from reintervention where obese (79%) was similar to OW (76%) and NW (79%). At a mean follow-up of 5.1 ± 0.4 years, sac regression was observed similarly across weight classes at 49.6%, 50.6%, and 51.8% for NW, OW, and obese, respectively (P = 0.501). There was a significant difference in mean AAA diameter pre- and post-EVAR [F(2,318) = 24.37, P < 0.001] across weight classes. NW [mean reduction 4.8 mm (2.0-7.6 mm, P < 0.001)], OW [mean reduction 3.9 mm (1.5-6.3 mm, P < 0.001)], and obese [mean reduction 5.7 mm (2.3-9.1 mm, P < 0.001)] achieved similar reductions.

CONCLUSIONS

Obesity was not associated with increased mortality or reintervention in patients undergoing EVAR. Obese patients achieved similar rates of sac regression on imaging follow-up.

Dynamic Loading-A New Marker for Abdominal Aneurysm Growth?

The growing possibilities of non-invasive heart rate and blood pressure measurement with mobile devices allow vital data to be continuously collected and used to assess patients' health status. When it comes to the risk assessment of abdominal aortic aneurysms (AAA), the continuous tracking of blood pressure and heart rate could enable a more patient-specific approach. The use of a load function and an energy function, with continuous blood pressure, heart rate, and aneurysm stiffness as input parameters, can quantify dynamic load on AAA. We hypothesise that these load functions correlate with aneurysm growth and outline a possible study procedure in which the hypothesis could be tested for validity. Subsequently, uncertainty quantification of input quantities and derived quantities is performed.

Aortic aneurysms and markers of platelet activation, hemostasis, and endothelial disruption in people living with HIV

Introduction

People living with HIV (PLWH) are at twice the risk of developing cardiovascular diseases and have more than four times higher odds of aortic aneurysm (AA) than the uninfected population. However, biomarkers of AA in PLWH are yet to be discovered. We aimed to investigate whether circulating biomarkers reflecting platelet activation, hemostasis and endothelial disruption, i.e. sCD40L, D-dimer, syndecan-1, and thrombomodulin, were associated with AA in PLWH.

Methods

Five hundred seventy one PLWH from the Copenhagen Comorbidity in HIV Infection (COCOMO) study ≥40 years of age with an available contrast-enhanced CT scan as well as available biomarker analyses were included. The biomarkers were analyzed on thawed plasma. For each biomarker, we defined high level as a concentration in the upper quartile and low level as a concentration below the upper quartile. For D-dimer, the cut-off was defined as the lower limit of detection. Using unadjusted and adjusted logistic and linear regression models, we analyzed associations between AA and sCD40L, D-dimer, syndecan-1, and thrombomodulin, respectively in PLWH.

Results

PLWH had median (IQR) age 52 years (47-60), 88% were male, median (IQR) time since HIV diagnosis was 15 years (8-23), and 565 (99%) were currently on antiretroviral treatment. High level of sCD40L was associated with lower odds of AA in both unadjusted (odds ratio, OR, 0.23 (95% CI 0.07-0.77; P=0.017)) and adjusted models (adjusted OR, aOR, 0.23 (95% CI 0.07-0.78; P=0.019)). Detectable level of D-dimer was associated with higher odds of AA in both unadjusted (OR 2.76 (95% CI 1.34-5.67; P=0.006)) and adjusted models (aOR 2.22 (95% CI 1.02-4.85; P=0.045)).

Conclusions

SCD40L was associated with lower odds of AA whereas D-dimer was independently associated with higher odds of AA in PLWH. This calls for further investigations into specific biomarkers to aid early diagnosis of AA in PLWH.

Identification of PTPN22 as a potential genetic biomarker for abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a severe life-threatening disease that is generally asymptomatic and is diagnosed at a very late stage. The genetic component underpinning AAA is considerable, with an estimated heritability of up to 70%. Therefore, identifying genetic biomarkers for AAA is valuable for predicting high-risk populations. We used integrative bioinformatics and cellular AAA model-based validation to reveal that the gene encoding protein tyrosine phosphatase non-receptor type 22 (PTPN22) may be a potentially useful diagnostic biomarker for AAA. Integrative bioinformatics analyses of clinical specimens showed that PTPN22 expression was consistently upregulated in aortic tissues and peripheral blood mononuclear cells (PBMCs) derived from patients with AAA. Moreover, transcriptomics data revealed that PTPN22 is a potential biomarker for AAA with limited diagnostic value in patients with thoracic aortic aneurysm/dissection. Single-cell RNA sequencing-based findings further highlight PTPN22 expression in aortic immune cells and vascular smooth muscle cells (VSMCs) is consistently upregulated in patients with AAA. A cellular AAA model was eventually employed to verify the increase in PTPN22 expression. Collectively, the results indicate that PTPN22 could be a potentially useful diagnostic biomarker for AAA.

Plasma complement component C2: a potential biomarker for predicting abdominal aortic aneurysm related complications

Blood-based adjunctive measures that can reliably predict abdominal aortic aneurysm (AAA)-related complications hold promise for mitigating the AAA disease burden. In this pilot study, we sought to evaluate the prognostic performance of complement factors in predicting AAA-related clinical outcomes. We recruited consecutive AAA patients (n = 75) and non-AAA patients (n = 75) presenting to St. Michael's Hospital. Plasma levels of complement proteins were assessed at baseline, as well as prospectively measured regularly over a period of 2 years. The primary outcome was the incidence of rapidly progressing AAA (i.e. aortic expansion), defined as change in AAA diameter by either 0.5 cm in 6 months, or 1 cm in 12 months. Secondary outcomes included incidence of major adverse aortic events (MAAE) and major adverse cardiovascular events (MACE). All study outcomes (AAA diameter, MACE and MAAE) were obtained during follow-up. Multivariable adjusted Cox regression analyses were performed to assess the prognostic value of plasma C2 levels in patients with AAA regarding rapid aortic expansion and MAAE and MACE. Event-free survival rates of both groups were also compared. Compared to non-AAA patients, patients with AAA demonstrated significantly higher plasma concentrations of C1q, C4, Factor B, Factor H and Factor D, and significantly lower plasma concentrations of C2, C3, and C4b (p = 0.001). After a median of 24 months from initial baseline measurements, C2 was determined as the strongest predictor of rapid aortic expansion (HR 0.10, p = 0.040), MAAE (HR 0.09, p = 0.001) and MACE (HR 0.14, p = 0.011). Based on the data from the survival analysis, higher levels of C2 at admission in patients with AAA predicted greater risk for rapid aortic expansion and MAAE (not MACE). Plasma C2 has the potential to be a biomarker for predicting rapid aortic expansion, MAAE, and the eventual need for an aortic intervention in AAA patients.

Ultrasensitive Troponin I and Incident Cardiovascular Disease

BACKGROUND

To examine the association of ultrasensitive cTnI (cardiac troponin I) with incident cardiovascular disease events (CVDs) in the primary prevention setting.

METHODS

cTnI was analyzed in the baseline plasma (2008-2012) of CVD-free volunteers from the Paris Prospective Study III using a novel ultrasensitive immunoassay (Simoa Troponin-I 2.0 Kit, Quanterix, Lexington) with a limit of detection of 0.013 pg/mL. Incident CVD hospitalizations (coronary heart disease, stroke, cardiac arrhythmias, deep venous thrombosis or pulmonary embolism, heart failure, or arterial aneurysm) were validated by critical review of the hospital records. Hazard ratios were estimated per log-transformed SD increase of cTnI in Cox models using age as the time scale.

RESULTS

The study population includes 9503 participants (40% women) aged 59.6 (6.3) years. cTnI was detected in 99.6% of the participants (median value=0.63 pg/mL, interquartile range, 0.39-1.09). After a median follow-up of 8.34 years (interquartile range, 8.0-10.07), 516 participants suffered 612 events. In fully adjusted analysis, higher cTnI (per 1 SD increase of log cTnI) was significantly associated with CVD events combined (hazard ratio, 1.18 [1.08-1.30]). Among all single risk factors, cTnI had the highest discrimination capacity for incident CVD events (C index=0.6349). Adding log cTnI to the SCORE 2 (Systematic Coronary Risk Evaluation) risk improved moderately discriminatory capacity (C index 0.698 versus 0.685; bootstrapped C index difference: 0.0135 [95% CI, 0.0131-0.0138]), and reclassification of the participants (categorical net reclassification index, 0.0628 [95% CI, 0.023-0.102]). Findings were consistent using the US pooled cohort risk equation.

CONCLUSIONS

Ultrasensitive cTnI is an independent marker of CVD events in the primary prevention setting.

Diagnostic and predictive values of circulating tetrahydrobiopterin levels as a novel biomarker in patients with thoracic and abdominal aortic aneurysms

We have previously shown that circulating levels of tetrahydrobiopterin (H4B) function as a robust biomarker for aortic aneurysms in several independent animal models. In the present study, we examined diagnostic and predictive values of circulating H4B levels in human patients of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) for the first time, while clinically applicable biomarkers for aortic aneurysms have never been previously available. Ninety-five patients scheduled for TAA repair surgeries and 53 control subjects were recruited at University of California Los Angeles (UCLA) Ronald Regan Medical Center, while 44 control subjects and 29 AAA patients were recruited through National Institute of Health (NIH) National Disease Research Interchange (NDRI) program. We had intriguing observations that circulating H4B levels were substantially lower in TAA and AAA patients, linearly correlated with aortic H4B levels (blood: R = 0.8071, p < 0.0001, n = 75; plasma: R = 0.7983, p < 0.0001, n = 75), and associated with incidence of TAA (blood: adjusted OR 0.495; 95% CI 0.379-0.647; p < 0.001; plasma: adjusted OR 0.501; 95% CI 0.385-0.652; p < 0.001) or AAA (blood: adjusted OR 0.329; 95% CI 0.125-0.868; p = 0.025) after adjustment for other factors. Blood or plasma H4B levels below 0.2 pmol/μg serve as an important threshold for prediction of aortic aneurysms independent of age and gender (for TAA risk - blood: adjusted OR 419.67; 95% CI 59.191-2975.540; p < 0.001; plasma: adjusted OR 206.11; 95% CI 40.956-1037.279; p < 0.001). This threshold was also significantly associated with incidence of AAA (p < 0.001 by Chi-square analysis). In addition, we observed previously unrecognized inverse association of Statin use with TAA, and an association of AAA with arrhythmia. Taken together, our data strongly demonstrate for the first time that circulating H4B levels can serve as a first-in-class, sensitive, robust and independent biomarker for clinical diagnosis and prediction of TAA and AAA in human patients, which can be rapidly translated to bedside to fundamentally improve clinical management of the devastating human disease of aortic aneurysms.

Single-Cell Sequencing Analysis and Multiple Machine Learning Methods Identified G0S2 and HPSE as Novel Biomarkers for Abdominal Aortic Aneurysm

Identifying biomarkers for abdominal aortic aneurysms (AAA) is key to understanding their pathogenesis, developing novel targeted therapeutics, and possibly improving patients outcomes and risk of rupture. Here, we identified AAA biomarkers from public databases using single-cell RNA-sequencing, weighted co-expression network (WGCNA), and differential expression analyses. Additionally, we used the multiple machine learning methods to identify biomarkers that differentiated large AAA from small AAA. Biomarkers were validated using GEO datasets. CIBERSORT was used to assess immune cell infiltration into AAA tissues and investigate the relationship between biomarkers and infiltrating immune cells. Therefore, 288 differentially expressed genes (DEGs) were screened for AAA and normal samples. The identified DEGs were mostly related to inflammatory responses, lipids, and atherosclerosis. For the large and small AAA samples, 17 DEGs, mostly related to necroptosis, were screened. As biomarkers for AAA, G0/G1 switch 2 (G0S2) (Area under the curve [AUC] = 0.861, 0.875, and 0.911, in GSE57691, GSE47472, and GSE7284, respectively) and for large AAA, heparinase (HPSE) (AUC = 0.669 and 0.754, in GSE57691 and GSE98278, respectively) were identified and further verified by qRT-PCR. Immune cell infiltration analysis revealed that the AAA process may be mediated by T follicular helper (Tfh) cells and the large AAA process may also be mediated by Tfh cells, M1, and M2 macrophages. Additionally, G0S2 expression was associated with neutrophils, activated and resting mast cells, M0 and M1 macrophages, regulatory T cells (Tregs), resting dendritic cells, and resting CD4 memory T cells. Moreover, HPSE expression was associated with M0 and M1 macrophages, activated and resting mast cells, Tregs, and resting CD4 memory T cells. Additional, G0S2 may be an effective diagnostic biomarker for AAA, whereas HPSE may be used to confer risk of rupture in large AAAs. Immune cells play a role in the onset and progression of AAA, which may improve its diagnosis and treatment.

Epicardial adipose tissue volume is associated with abdominal aortic aneurysm expansion

BACKGROUND

Epicardial adipose tissue volume (EATV) is associated with cardiovascular diseases such as coronary artery disease. However, no information is available regarding the relationship between EATV and abdominal aortic aneurysm (AAA) expansion. This study aimed to evaluate the association between EATV and the growth of AAA, and to identify predictors of AAA expansion.

METHODS

Between June 2009 and December 2019, a total of 906 patients underwent endovascular or open repair of AAA at our institution. Patients with previous cardiac surgery, previous ascending thoracic aortic surgery, ruptured AAA, infected AAA, inflammatory AAA, saccular aneurysm, solitary iliac aneurysm, or reintervention after treatment for AAA were excluded. Two hundred and thirty-seven patients with at least two preoperative computed tomography (CT) scans performed more than 180 days apart were included in this study. EATV within the pericardium was retrospectively quantified from preoperative non-contrast CT images using a 3D workstation. The EATV index was defined as EATV divided by body surface area. The AAA expansion rate was defined as the increase in AAA diameter per year, and patients were divided into the slow-expansion group, with an expansion rate < 5 mm/year, and the fast-expansion group, with an expansion rate ≥ 5 mm/year. The correlation between expansion rate and the EATV index was analyzed, and the cut-off value of the EATV index was determined using a receiver operating characteristics curve. Multivariate analysis was used to assess predictors of the AAA expansion rate.

RESULTS

The expansion rate of AAA was positively correlated with the EATV index (R = .237, P < .001). The initial aneurysm diameter (P < .001) and EATV index (P = .009) differed significantly between the two groups. The cut-off value of the EATV index was 60.3 cm³/m² (area under the curve, .658; 95% confidence interval [CI], .568-.749; sensitivity, 1.000; specificity, .309). Multivariate analysis revealed that the initial aneurysm diameter and an EATV index > 60.3 cm³/m² were significantly associated with the AAA expansion rate.

CONCLUSIONS

This study demonstrated that the EATV index was associated with AAA expansion.

Research progress on the pathogenesis of aortic dissection

Aortic dissection (AD) is a critical cardiovascular disease due to the separation of media and adventitia caused by the rupture of vascular wall intima. The disease has a high mortality rate of about 1% to 3% for each additional hour, since the adventitia of the aorta can rupture and bleed to death at any time. Although great progress has been made in clinical treatment of aortic dissection, and the mortality rate has been significantly reduced, the pathogenesis is still not very clear. At present, related studies have confirmed that inflammation of aortic wall promotes the occurrence and development of AD. Although the mechanism of aortic dissection is more complicated, some studies have shown that the infiltration of monocytes/macrophages into the aortic wall is the main pathogenic mechanism of the disease. This review introduces the latest research results on the mechanism of macrophage infiltration and plasticity in aortic dissection.

JNK2 Gene Silencing for Elastic Matrix Regenerative Repair

Elastic fibers do not naturally regenerate in many proteolytic disorders, such as in abdominal aortic aneurysms, and prevent restoration of tissue homeostasis. We have shown drug-based attenuation of the stress-activated protein kinase, JNK-2 to stimulate elastic matrix neoassembly and to attenuate cellular proteolytic activity. We now investigate if JNK2 gene knockdown with small interfering RNA (siRNA) provides greater specificity of action and improved regenerative/antiproteolytic outcomes in a proteolytic injury culture model of rat aneurysmal smooth muscle cells (EaRASMCs). A siRNA dose of 12.5 nM delivered with a transfection reagent significantly enhanced downstream elastic fiber assembly and maturation versus untreated EaRASMC cultures. The optimal siRNA dose was also delivered as a complex with a polymeric transfection vector, polyethyleneimine (PEI) in preparation for future in vivo delivery. Linear 25 kDa PEI-siRNA (5:1 molar ratio of amine to phosphate) and linear 40 kDa PEI-siRNA (2.5:1 ratio) were effective in downregulating the JNK2 gene, and significantly increasing expression of elastic fiber assembly proteins, and decreases in elastolytic matrix metalloprotease-2 versus treatment controls to significantly increase mature elastic fiber assembly. The current work has identified siRNA dosing and siRNA-PEI complexing conditions that are safe and efficient in stimulating processes contributing to improved elastic matrix neoassembly via JNK2 gene knockdown. The results represent a mechanistic basis of a broader therapeutic approach to reverse elastic matrix pathophysiology in tissue disorders involving aberrations of elastic matrix homeostasis, such as in aortic aneurysms. Impact statement The elastic matrix and elastic fibers are key components of the structural extracellular matrix of elastic tissues and are essential to their stretch and recoil and to maintain healthy cell phenotype. Regeneration and repair of elastic matrix is naturally poor and impaired and is an unresolved challenge in tissue engineering. In this work, we investigate a novel gene silencing approach based on inhibiting the JNK2 gene, which provides significant downstream benefits to elastic fiber assembly and maturation. Combined with novel delivery strategies such as nanoparticles, we expect our approach to effect in situ elastic matrix repair in the future.

Carbon monoxide releasing molecule-2 attenuates angiotensin II-induced IL-6/Jak2/Stat3-associated inflammation by inhibiting NADPH oxidase- and mitochondria-derived ROS in human aortic smooth muscle cells

Abdominal aortic aneurysm (AAA) is a common inflammatory vascular disease. Angiotensin II (Ang II) involves in AAA progression by promoting the proliferation and migration of vascular smooth muscle cells, the degradation of extracellular matrices, and the generation of ROS to lead to vascular inflammation. Carbon monoxide releasing molecule-2 (CORM-2) is known to exert anti-inflammatory and antioxidant activities. However, it remains unclear whether CORM-2 can suppress Ang II-induced vascular inflammation to prevent AAA progression. Therefore, this study aimed to investigate the vasoprotective effects of CORM-2 against Ang II-induced inflammatory responses of human aortic smooth muscle cells (HASMCs) and the underlying mechanisms of those effects. The results showed that Ang II induced inflammatory responses of HASMCs via NADPH oxidase- and mitochondria-derived ROS/NF-κB/IL-6/Jak2/Stat3 pathway which was attenuated by the pretreatment with CORM-2. Additionally, CORM-2 further exhibited anti-inflammatory activities in Ang II-stimulated HASMCs, as indicated by the reduction of monocyte adhesion to HASMCs and migration of HASMCs via the suppression of ICAM-1 and VCAM-1 as well as MMP-2 and MMP-9 levels, respectively. Moreover, Ang II-induced COX-2-mediated PGE₂ secretion was also inhibited by the pretreatment with CORM-2. Importantly, our data demonstrated that CORM-2 reversed Ang II-induced IL-6 overexpression dependent on Nrf2 activation and HO-1 expression. Taken together, the present study indicates that CORM-2-induced Nrf2/HO-1 alleviates IL-6/Jak2/Stat3-mediated inflammatory responses to Ang II by inhibiting NADPH oxidase- and mitochondria-derived ROS, suggesting that CORM-2 is a promising pharmacologic candidate to reverse the pathological changes involved in the inflammation of vessel wall for the prevention and treatment of AAA.

A stable aneurysm sac after endovascular aneurysm repair as a predictor for mortality, an in-depth analysis

OBJECTIVES

The aim of this study was to compare the long-term survival in patients with a stable aneurysmal sac and those with aneurysmal sac regression after endovascular aneurysm repair (EVAR) and to identify independent risk factors for aneurysmal sac regression and mortality after EVAR.

METHODS

We reviewed all patients who underwent EVAR between 2005 and 2018 with a computed tomography angiography available at 1-year follow-up. Aneurysm sac regression was defined as a diameter decrease of more than 10%. We used a multivariable regression to identify independent risk factors for sac regression. Kaplan-Meier analysis and Cox regression were done to test differences in 5-year mortality between a stable sac and sac regression.

RESULTS

The inclusion criteria were met by 325 patients, 185 in the sac regression group and 140 in the stable sac group. Multivariable logistic regression analysis showed that treatment for a ruptured aneurysm was an independent risk factor for aneurysmal sac regression (hazard ratio [HR], 0.26; 95% confidence interval [CI], 0.07-0.96). Age (HR, 1.05; 95% CI, 1.01-1.09), ischemic heart disease (HR, 1.94; 95% CI, 1.13-3.31), neck thrombus (HR, 2.72; 95% CI, 1.07-6.95), and a type II endoleak (HR, 19.21; 95% CI, 7.32-50.40) were independent risk factors for a stable aneurysm sac diameter. Multivariable Cox regression showed a significantly increased risk of mortality for patients with a stable aneurysm sac after EVAR (odds ratio, 2.25; 95% CI, 1.36-3.72). There was no significant difference in cause of death between the two groups.

CONCLUSION

A stable aneurysm sac after EVAR is associated with increased mortality. Age, ischemic heart disease, neck thrombus, and a type II endoleak are independent risk factors for a stable sac. However, a well-founded explanation for this finding is still lacking. Future research should be focussed on aggressive treatment of type II endoleaks and inflammatory processes as potential pathophysiological mechanisms.

Biomolecular assembly on interdigitated electrode nanosensor for selective detection of insulin-like growth factor-1

This research is focussed to quantify IGF1 by electroanalytical analysis on InterDigitated electrode surface and characterized by the microscopic observations. For the detection, antibody and aptamer were used to analyze the level of IGF1. The sandwich pattern (aptamer-IGF1-antibody) was designed on the chemically modified IDE surface and reached the limit of detection to 10 fM with 100 folds enhancement in the sensitivity. Different control experiments (absence of IGF1, binding with IGF2 and with non-complementary aptamer) were failed to show the current changes, discriminated the specific detection. A good detection strategy is to complement the currently following imaging systems for AAA.

The elevated expression of TLR4 and MMP9 in human abdominal aortic aneurysm tissues and its implication

Background

Toll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) have been investigated to play significant roles in the formation of abdominal aortic aneurysm (AAA). But the reports on the expression pattern of TLR4 and MMP9 in human AAA specimens were relatively scant. The aim of this study was to make a detailed analysis of TLR4 and MMP9 expression in situ and their association with clinical parameters involved in human AAA.

Methods

40 AAA specimens were obtained from full-thickness aneurysmal tissues at the maximal dilation area during the open surgical repair, and 8 non-aneurysmal abdominal aortas from transplant donors served as controls. Expression of TLR4 and MMP9 protein was determined by immunohistochemistry.

Results

There were increased levels of TLR4 and MMP9 expression in human AAA tissues. Compared with macrophages or SMCs, lymphocytes showed a higher positive rate of TLR4 and MMP9 staining, and an elevated ratio of high MMP9 expression (all P < 0.05). There existed a significant association between TLR4 and MMP9 expression (r = 0.767, P < 0.001), and both TLR4 and MMP9 levels were statistically related to circulating CRP. Moreover, TLR4 expression in situ indicated a positive correlation with its serum level (r = 0.654, P = 0.006). Multiple analysis revealed that high TLR4 expression in situ was associated with the risk of large AAA (OR = 6.211, 95%CI = 1.226–31.480, P = 0.027), while high MMP9 expression was correlated to the presence of thrombus within AAA (OR = 5.494, 95%CI = 1.181–25.562, P = 0.030), separately compared with their low expression.

Conclusions

This study confirmed the overexpression of TLR4 and MMP9 in human AAA tissues, and their close relationship implying in the pathogenesis of AAA. We further provided evidence that TLR4 had a potential effect on AAA size and MMP9 could influence the occurrence of thrombus within AAA.

Galectin-3 as a Biomarker for Stratifying Abdominal Aortic Aneurysm Size in a Taiwanese Population

Abdominal aortic aneurysm (AAA) ruptures are unpredictable and lethal. A biomarker predicting AAA rupture risk could help identify patients with small, screen-detected AAAs. Galectin-3 (Gal-3), a β-galactosidase–binding lectin, is involved in inflammatory processes and may be associated with AAA incidence. We investigated whether Gal-3 can be used as a biomarker of AAA size. Plasma Gal-3 protein concentrations were examined in patients with AAA (n = 151) and control patients (n = 195) using Human ProcartaPlex multiplex and simplex kits. Circulating Gal-3 levels were significantly higher in patients with AAA than in control patients. The area under the receiver operating characteristic curve for Gal-3 was 0.91. Multivariate logistic regression analysis revealed a significant association between Gal-3 level and the presence of AAA. Circulating Gal-3 levels were significantly correlated with aortic diameter in a concentration-dependent manner. In conclusion, higher plasma Gal-3 concentrations may be a useful biomarker of AAA progression.

Circulating Biomarkers for the Prediction of Abdominal Aortic Aneurysm Growth

BACKGROUND

Abdominal aortic aneurysm represents a distinct group of vascular lesions, in terms of surveillance and treatment. Screening and follow-up of patients via duplex ultrasound has been well established and proposed by current guidelines. However, serum circulating biomarkers could earn a position in individualized patient surveillance, especially in cases of aggressive AAA growth rates. A systematic review was conducted to assess the correlation of AAA expansion rates with serum circulating biomarkers.

METHODS

A data search of English medical literature was conducted, using PubMed, EMBASE, and CENTRAL, until 7 March 2021, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement (PRISMA) guidelines. Studies reporting on humans, on abdominal aortic aneurysm growth rates and on serum circulating biomarkers were included. No statistical analysis was conducted.

RESULTS

A total of 25 studies with 4753 patients were included. Studies were divided in two broad categories: Those reporting on clinically applicable (8 studies) and those reporting on experimental (17 studies) biomarkers. Twenty-three out of 25 studies used duplex ultrasound (DUS) for following patients. Amongst clinically applicable biomarkers, D-dimers, LDL-C, HDL-C, TC, ApoB, and HbA1c were found to bear the most significant association with AAA growth rates. In terms of the experimental biomarkers, PIIINP, osteopontin, tPA, osteopontin, haptoglobin polymorphisms, insulin-like growth factor I, thioredoxin, neutrophil extracellular traps (NETs), and genetic factors, as polymorphisms and microRNAs were positively correlated with increased AAA expansion rates.

CONCLUSION

In the presence of future robust data, specific serum biomarkers could potentially form the basis of an individualized surveillance strategy of patients presenting with increased AAA growth rates.

Association of Abdominal Aortic Aneurysm and Simple Renal Cysts: A Systematic Review and Meta-Analysis

BACKGROUND-OBJECTIVE

Prior studies have suggested a higher prevalence of simple renal cysts (SRC) among patients with aortic disease, including abdominal aortic aneurysms (AAA). Thus, the aim of this study was to systematically review all currently available literature and investigate whether patients with AAA are more likely to have SRC.

METHODS

This study was performed according to the PRISMA guidelines. A meta-analysis was conducted with the use of random effects modeling and the I-square was used to assess heterogeneity. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were synthesized to compare the prevalence of several patients' characteristics between AAA vs. no-AAA cases.

RESULTS

Eleven retrospective studies, 9 comparative (AAA vs. no-AAA groups) and 3 single-arm (AAA group), were included in this meta-analysis, enrolling patients (AAA: N = 2,297 vs. no-AAA: N = 35,873) who underwent computed tomography angiography as part of screening or preoperative evaluation for reasons other than AAA. The cumulative incidence of SRC among patients with AAA and no-AAA was 55% (95% CI: 49%-61%) and 32% (95% CI: 22%-42%) respectively, with a statistically higher odds of SRC among patients with AAA (OR: 3.02; 95% CI: 2.01-4.56; P< 0.001). The difference in SRC prevalence remained statistically significant in a sensitivity analysis, after excluding the study with the largest sample size (OR: 2.71; 95% CI: 1.91-3.84; P< 0.001).

CONCLUSIONS

Our meta-analysis demonstrated a 3-fold increased prevalence of SRC in patients with AAA compared to no-AAA cases, indicating that the pathogenic processes underlying SRC and AAA could share a common pathophysiologic mechanism. Thus, patients with SRC could be considered at high risk for AAA formation, potentially warranting an earlier AAA screening.

Abdominal Aortic Aneurysm: Roles of Inflammatory Cells

Abdominal aortic aneurysms (AAAs) are local dilations of infrarenal segment of aortas. Molecular mechanisms underlying the pathogenesis of AAA remain not fully clear. However, inflammation has been considered as a central player in the development of AAA. In the past few decades, studies demonstrated a host of inflammatory cells, including T cells, macrophages, dendritic cells, neutrophils, B cells, and mast cells, etc. infiltrating into aortic walls, which implicated their crucial roles. In addition to direct cell contacts and cytokine or protease secretions, special structures like inflammasomes and neutrophil extracellular traps have been investigated to explore their functions in aneurysm formation. The above-mentioned inflammatory cells and associated structures may initiate and promote AAA expansion. Understanding their impacts and interaction networks formation is meaningful to develop new strategies of screening and pharmacological interventions for AAA. In this review, we aim to discuss the roles and mechanisms of these inflammatory cells in AAA pathogenesis.

Serum Lipid Oxidative Stress Products as Risk Factors Are the Candidate Predictive Biomarkers for Human Abdominal Aortic Aneurysms

This research was designed to determine the association of serum lipid peroxidation products with disease severity in patients with abdominal aortic aneurysm (AAA). In total, 76 pairs of AAA cases as well as matched controls were enrolled in our research using propensity score matching (PSM). And their malondialdehyde (MDA), lipid hydroperoxide (LPO), and glutathione peroxidase (GSH-Px) levels were also detected through enzyme-linked immunosorbent assay (ELISA). Additionally, the relative clinical data of enrolled participants were extracted. The serum biomarker concentrations were measured in 76 patients with AAAs (diameter between 30 and 54 mm, n = 54; diameter ≥55 mm, n = 22) and 76 control patients from observational cohort study. After PSM adjustment for clinical variables, including age, gender, heart ratio, body mass index, smoking, hypertension, diabetes mellitus, coronary heart disease, and stroke, the serum MDA and LPO among AAA cases were remarkably increased compared with those from the normal patients. Inversely, serum GSH-Px was significantly decreased in patients with AAA compared to the control group. Besides, the serum levels of MDA and LPO were independently associated with AAA risk. Typically, there was significantly positive correlation between MDA level and LPO level (R = 0.358) but negative correlation of MDA level with GSH-Px (R = -0.203) level in patients with AAA. Meanwhile, the area under the receiver operating characteristic curve was 0.965 when MDA was used to diagnose AAA, and the optimal threshold value was 0.242 nmol/mL. Moreover, serum MDA level was significantly increased in cases with rupture AAA compared to those in selective AAA cases. Logistic regression analysis suggested that a higher serum MDA level indicated an elevated risk of AAA rupture (odds ratio = 2.536; 95% CI: 1.037-6.203; P =0.041). Our present findings suggest that serum peroxidation contents were evidently changed among AAA cases. Serum MDA and LPO concentrations could be used to predict disease severity in patients with AAA. Moreover, serum MDA may serve as the candidate biomarker for diagnosis of AAA and accurate identification of increased risks of AAA rupture.

FRZB as a key molecule in abdominal aortic aneurysm progression affecting vascular integrity

Abdominal aortic aneurysm (AAA), when ruptured, results in high mortality. The identification of molecular pathways involved in AAA progression is required to improve AAA prognosis. The aim of the present study was to assess the key genes for the progression of AAA and their functional role. Genomic and clinical data of three independent cohorts were downloaded from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) (GSE57691, GSE7084, and GSE98278). To develop AAA diagnosis and progression-related differentially expressed genes (DEGs), we used a significance analysis of microarray (SAM). Spearman correlation test and gene set analysis were performed to identify potential enriched pathways for DEGs. Only the Frizzled-related protein (FRZB) gene and chromosome 1 open reading frame 24 (C1orf24) exhibited significant down-regulation in all analyses. With FRZB, the pathways were associated with RHO GTPase and elastin fiber formation. With C1orf24, the pathways were elastic fiber formation, extracellular matrix organization, and cell–cell communication. Since only FRZB was evolutionally conserved in the vertebrates, function of FRZB was validated using zebrafish embryos. Knockdown of frzb remarkably reduced vascular integrity in zebrafish embryos. We believe that FRZB is a key gene involved in AAA initiation and progression affecting vascular integrity.

Molecular MR-Imaging for Noninvasive Quantification of the Anti-Inflammatory Effect of Targeting Interleukin-1β in a Mouse Model of Aortic Aneurysm

Background:

Molecular-MRI is a promising imaging modality for the assessment of abdominal aortic aneurysms (AAAs). Interleukin-1β (IL-1β) represents a new therapeutic tool for AAA-treatment, since pro-inflammatory cytokines are key-mediators of inflammation. This study investigates the potential of molecular-MRI to evaluate therapeutic effects of an anti-IL-1β-therapy on AAA-formation in a mouse-model.

Methods:

Osmotic-minipumps were implanted in apolipoprotein-deficient-mice (N = 27). One group (Ang-II+01BSUR group, n = 9) was infused with angiotensin-II (Ang-II) for 4 weeks and received an anti-murine IL-1β-antibody (01BSUR) 3 times. One group (Ang-II-group, n = 9) was infused with Ang-II for 4 weeks but received no treatment. Control-group (n = 9) was infused with saline and received no treatment. MR-imaging was performed using an elastin-specific gadolinium-based-probe (0.2 mmol/kg).

Results:

Mice of the Ang-II+01BSUR-group showed a lower aortic-diameter compared to mice of the Ang-II-group and control mice (p < 0.05). Using the elastin-specific-probe, a significant decrease in elastin-destruction was observed in mice of the Ang-II+01BSUR-group. In vivo MR-measurements correlated well with histopathology (y = 0.34x-13.81, R² = 0.84, p < 0.05), ICP-MS (y = 0.02x+2.39; R² = 0.81, p < 0.05) and LA-ICP-MS. Immunofluorescence and western-blotting confirmed a reduced IL-1β-expression.

Conclusions:

Molecular-MRI enables the early visualization and quantification of the anti-inflammatory-effects of an IL-1β-inhibitor in a mouse-model of AAAs. Responders and non-responders could be identified early after the initiation of the therapy using molecular-MRI.

Matrix metalloproteinases and acute aortic dissection: Et Tu, Brute?

OBJECTIVES

To summarize the present evidence for the association of matrix metalloproteinases (MMPs) with acute aortic dissection (AAD), we performed the first meta-analysis of all currently available case-control studies comparing circulating MMP levels between AAD patients and control subjects.

METHODS

To identify all studies investigating the levels of circulating MMPs in AAD patients, PubMed and Web of Science were searched up to July 2019. The levels of MMPs in AAD patients and control subjects were extracted from each study, and the standardized mean differences (SMDs) in MMP levels were generated. The study-specific estimates were combined in the random-effects model.

RESULTS

Twelve studies enrolling a total of 458 AAD patients and 711 control subjects were identified and included. Pooled analyses demonstrated no significant differences in MMP-1 (4 studies; P = 0.21), MMP-2 (5 studies; P = 0.62) and MMP-3 levels (2 studies; P = 0.94) between AAD patients and control subjects; and significantly higher MMP-8 (2 studies; SMD 2.11; P = 0.020), MMP-9 (9 studies; SMD 1.54; P < 0.001) and MMP-12 levels (2 studies; SMD 1.33; P < 0.001) in AAD patients than in control subjects.

CONCLUSION

High circulating MMP-9 levels are associated with AAD, and MMP-8 and MMP-12 levels may be related to AAD.

Association of C-Reactive Protein-to-Albumin Ratio With the Presence and Progression of Abdominal Aortic Aneurysm

Aortic dilatation due to inflammation may lead to an increase in C-reactive protein (CRP) levels. We investigated the possible relationship between CRP-to-albumin ratio (CAR) and presence and progression of abdominal aortic aneurysms (AAAs). The study included 150 patients previously diagnosed with AAA (diameter 40-54 mm) and 100 normal controls. Clinical and laboratory parameters and maximal cross-sectional AAA diameters (measured by computed tomography angiography) were obtained from all participants at baseline assessment as well as after 1 year for those with an AAA. The patients with AAA had significantly higher serum CAR compared with controls at baseline (P < .001). Increased serum CAR was found to be an independent predictor of the presence of AAA (odds ratio: 3.162, 95% CI: 1.690-5.126, P = .001) after multivariate logistic regression analysis. There was a significant increase in aortic diameter and CAR after 1 year in the patients with AAA (P < .001; P = .003); a significant correlation was found between changes in the diameter of AAAs and CAR (r = 0.414; P = .005). Serum CAR may be useful as an inflammatory biomarker for the presence and progression of AAA.

Pathophysiology of Aortic Aneurysms: Insights from Animal Studies

Aortic aneurysms are defined as dilations of the aorta greater than 50 percent. Currently, the only effective treatment for aortic aneurysms is surgical repair, which is recommended only to those that meet criteria. There is no available pharmaceutical therapy to slow aneurysm growth and thus prevent lethal rupture. The development of a number of murine models has allowed in depth studies of various cellular and extracellular components of aneurysm pathophysiology. The identification of key therapeutic targets has resulted in several clinical trials evaluating pharmaceutical candidates to treat aneurysm progression. In this review, we focus on providing recent updates on developments in murine models of aortic aneurysm. In addition, we discuss recent studies of the various cellular and extracellular components of the aorta along with the abutting aortic structures that contribute to aneurysm development and progression.

A Randomised Controlled Trial Assessing the Effects of Peri-operative Fenofibrate Administration on Abdominal Aortic Aneurysm Pathology: Outcomes From the FAME Trial

OBJECTIVE

Experimental studies suggest that fenofibrate prevents abdominal aortic aneurysm (AAA) development by lowering aortic osteopontin (OPN) concentration and reducing the number of macrophages infiltrating the aortic wall. The current study examined the effects of a short course of fenofibrate on AAA pathology in people with large AAAs awaiting aortic repair.

METHODS

This randomised double blind parallel trial included male and female participants aged ≥ 60 years who had an asymptomatic AAA measuring ≥ 50 mm and were scheduled to undergo open AAA repair. Participants were allocated to fenofibrate (145 mg/day) or matching placebo for at least two weeks before elective AAA repair. Blood samples were collected at recruitment and immediately prior to surgery. AAA biopsies were obtained during aortic surgery. The primary outcomes were (1) AAA OPN concentration; (2) serum OPN concentration; and (3) number of AAA macrophages. Exploratory outcomes included circulating and aortic concentrations of other proteins previously associated with AAA. Outcomes assessed at a single time point were compared using logistic regression. Longitudinal outcomes were compared using linear mixed effects models.

RESULTS

Forty-three participants were randomised. After three withdrawals, 40 were followed until the time of surgery (21 allocated fenofibrate and 19 allocated placebo). As expected, serum triglycerides reduced significantly from recruitment to the time of surgery in participants allocated fenofibrate. No differences in any of the primary and exploratory outcomes were observed between groups.

CONCLUSION

A short course of 145 mg of fenofibrate/day did not lower concentrations of OPN or aortic macrophage density in people with large AAAs.

Interleukin-6 Receptor Signaling and Abdominal Aortic Aneurysm Growth Rates

Supplemental Digital Content is available in the text.

Background:

The Asp358Ala variant (rs2228145; A>C) in the IL (interleukin)-6 receptor (IL6R) gene has been implicated in the development of abdominal aortic aneurysms (AAAs), but its effect on AAA growth over time is not known. We aimed to investigate the clinical association between the IL6R-Asp358Ala variant and AAA growth and to assess the effect of blocking the IL-6 signaling pathway in mouse models of aortic aneurysm rupture or dissection.

Methods:

Using data from 2863 participants with AAA from 9 prospective cohorts, age- and sex-adjusted mixed-effects linear regression models were used to estimate the association between the IL6R-Asp358Ala variant and annual change in AAA diameter (mm/y). In a series of complementary randomized trials in mice, the effect of blocking the IL-6 signaling pathways was assessed on plasma biomarkers, systolic blood pressure, aneurysm diameter, and time to aortic rupture and death.

Results:

After adjusting for age and sex, baseline aneurysm size was 0.55 mm (95% CI, 0.13–0.98 mm) smaller per copy of the minor allele [C] of the Asp358Ala variant. Change in AAA growth was −0.06 mm per year (−0.18 to 0.06) per copy of the minor allele; a result that was not statistically significant. Although all available worldwide data were used, the genetic analyses were not powered for an effect size as small as that observed. In 2 mouse models of AAA, selective blockage of the IL-6 trans-signaling pathway, but not combined blockage of both, the classical and trans-signaling pathways, was associated with improved survival (P<0.05).

Conclusions:

Our proof-of-principle data are compatible with the concept that IL-6 trans-signaling is relevant to AAA growth, encouraging larger-scale evaluation of this hypothesis.

The Role of Macrophages in Aortic Dissection

Aortic dissection (AD) is a fatal disease that accounts for a large proportion of aortic-related deaths and has an incidence of about 3–4 per 100,000 individuals every year. Recent studies have found that inflammation plays an important role in the development of AD, and that macrophages are the hub of inflammation in the aortic wall. Aortic samples from AD patients reveal a large amount of macrophage infiltration. The sites of macrophage infiltration and activity vary throughout the different stages of AD, with involvement even in the tissue repair phase of AD. Angiotensin II has been shown to be an important factor in the stimulation of macrophage activity. Stimulated macrophages can secrete metalloproteinases, inflammatory factors and other substances to cause matrix destruction, smooth muscle cell apoptosis, neovascularization and more, all of which destroy the aortic wall structure. At the same time, there are a number of factors that regulate macrophages to reduce the formation of AD and induce the repair of torn aortic tissues. The aim of this review is to take a close look at the roles of macrophages throughout the course of AD disease.

Endovascular Aneurysm Sealing is Associated with Higher Medium-Term Survival than Traditional EVAR

BACKGROUND

Endovascular aneurysm repair (EVAR) is the dominant treatment modality for abdominal aortic aneurysm (AAA). Periprocedural risks are low, and cardiovascular events are the principle determinants of long-term survival. Recently, the concept of endovascular aneurysm sealing (EVAS) has been introduced into clinical investigation. In previous cohort studies, EVAS has been associated with a lower all-cause mortality than expected despite device issues. We used a propensity weighted approach to investigate whether EVAS was associated with lower all-cause mortality after aneurysm repair.

METHODS

We compared 333 patients in the Nellix United States Investigational Device Exemption trial to 15,431 controls from the Vascular Quality Initiative between 2014 and 2016 after applying the exclusion criteria from the investigational device exemption (hemodialysis, creatinine > 2.0 mg/dL, or rupture). We calculated propensity scores and applied inverse probability weighting to compare risk adjusted medium-term survival using Kaplan-Meier and Cox regression.

RESULTS

After weighting, patients treated with the Nellix EVAS system experienced higher 3-year survival than controls from the Vascular Quality Initiative (93% vs. 88%, respectively). This corresponded to a 41% lower risk of mortality for EVAS compared with EVAR (HR 0.59 [0.38-0.92], P = 0.02). Subgroup analysis demonstrated that the association between EVAS and higher survival was strongest in the subgroup of patients with aneurysms over 5.5 cm (P for interaction < 0.001). In this subgroup, EVAS patients experienced half the rate of mortality as those patients treated with EVAR, with 3-year survival of 92% compared with 86% (HR 0.5 [0.3-0.9], P = 0.02).

CONCLUSIONS

In this select group of patients, EVAS was associated with higher medium-term survival than traditional EVAR. Although issues with the device have recently surfaced, this exploratory analysis shows that the concept of sac sealing may hold promise. Further study is needed to confirm this finding and determine whether EVAS is associated with lower rates of cardiovascular events.

Plasma D-dimer as a predictor of intraluminal thrombus burden and progression of abdominal aortic aneurysm

AIM

Intraluminal thrombus (ILT) is presented in most abdominal aortic aneurysms (AAAs) and is suggested to promote AAA expansion. D-dimer, a breakdown product in the thrombus remodeling, may have prognostic value for AAA. This study investigated the interrelation between plasma D-dimer level, ILT volume, AAA size and progression.

MAIN METHODS

This was a retrospective observational study that involved 181 patients with infra-renal AAA. They were divided into small and large AAA groups according to AAA diameter. 24 of them had repeated abdominal computed tomography angiography (CTA) scan and were divided into slow-growing and fast-growing AAA groups according to the median value of AAA growth rate. Baseline and follow-up plasma D-dimer level, maximum diameter of AAA, total infra-renal aortic volume and ILT volume were analyzed.

KEY FINDINGS

Plasma D-dimer level was positively correlated with ILT volume (R = 0.382, P < 0.001) and maximum diameter of AAA (R = 0.442, P < 0.001). Increasing value of plasma D-dimer was positively associated with the accelerated growth rate of AAA (R = 0.720, P < 0.01). ILT volume showed positive correlation with maximum diameter (R = 0.859, P < 0.001) and growth rate of AAA (R = 0.490, P < 0.05). After adjusting the baseline ILT volume, the positive correlations remained to be statistically significant between plasma D-dimer level and AAA size (R = 0.200, P < 0.05), as well as increasing value of plasma D-dimer and growth rate of AAA (R = 0.642, P < 0.05).

SIGNIFICANCE

Plasma D-dimer level reflected ILT burden in AAAs. Plasma D-dimer level and ILT volume were positively correlated with AAA size. Increasing value of plasma D-dimer and baseline ILT volume could be predictors of AAA progression.

Lipid management in people with peripheral artery disease

PURPOSE OF REVIEW

To summarize recent data on the role of dyslipidaemia and the benefit from managing this in people with disease of the abdominal aorta and its peripheral branches (peripheral artery disease, PAD).

RECENT FINDINGS

Findings from the Further Cardiovascular Outcomes Research with Proprotein convertase subtilisin/kexin type 9 (PCSK9) Inhibition in Subjects with Elevated Risk (FOURIER) trial demonstrate the benefit of intensely lowering low-density lipoprotein-cholesterol (LDL-c) in people with PAD to substantially reduce the incidence of major cardiovascular events (MACE; myocardial infarction, stroke or cardiovascular death) and major adverse limb events (MALE). Despite the evidence of substantial benefits from lowering LDL-c, the uptake of drug therapies to lower LDL-c remains sub-optimal in people with PAD.

SUMMARY

Effective methods to educate physicians and patients on best medical management are needed. Further research is needed to examine the benefit of LDL-c lowering and other lipid therapies for PAD-specific problems like abdominal aortic aneurysm progression and walking impairment. Other novel lipid therapies, such as those that lower lipoprotein (a), maybe particularly beneficial to people with PAD given the evidence indicating high concentrations in this population and the high incidence of MACE in these individuals.

Randomized Placebo-Controlled Trial Assessing the Effect of 24-Week Fenofibrate Therapy on Circulating Markers of Abdominal Aortic Aneurysm: Outcomes From the FAME -2 Trial

Background

There is no drug therapy for abdominal aortic aneurysm (AAA). FAME‐2 (Fenofibrate in the Management of Abdominal Aortic Aneurysm 2) was a placebo‐controlled randomized trial designed to assess whether administration of 145 mg of fenofibrate/d for 24 weeks favorably modified circulating markers of AAA.

Methods and Results

Patients with AAAs measuring 35 to 49 mm and no contraindication were randomized to fenofibrate or identical placebo. The primary outcome measures were the differences in serum osteopontin and kallistatin concentrations between groups. Secondary analyses compared changes in the circulating concentration of AAA‐associated proteins, and AAA growth, between groups using multivariable linear mixed‐effects modeling. A total of 140 patients were randomized to receive fenofibrate (n=70) or placebo (n=70). By the end of the study 3 (2.1%) patients were lost to follow‐up and 18 (12.9%) patients had ceased trial medication. A total of 85% of randomized patients took ≥80% of allocated tablets and were deemed to have complied with the medication regimen. Patients’ allocated fenofibrate had expected reductions in serum triglycerides and estimated glomerular filtration rate, and increases in serum homocysteine. No differences in serum osteopontin, kallistatin, or AAA growth were observed between groups.

Conclusions

Administering 145 mg/d of fenofibrate for 24 weeks did not significantly reduce serum concentrations of osteopontin and kallistatin concentrations, or rates of AAA growth in this trial. The findings do not support the likely benefit of fenofibrate as a treatment for patients with small AAAs.

Clinical Trial Registration

URL: http://www.anzctr.org.au. Unique identifier: ACTRN12613001039774.

Plasma Desmosine and Abdominal Aortic Aneurysm Disease

Background

It is recognized that factors beyond aortic size are important in predicting outcome in abdominal aortic aneurysm (AAA) disease. AAA is characterized by the breakdown of elastin within the aortic tunica media, leading to aortic dilatation and rupture. The aim of this study was to investigate the association of plasma desmosine (pDES), an elastin‐specific degradation product, with disease severity and clinical outcome in patients with AAA.

Methods and Results

We measured pDES and serum biomarker concentrations in 507 patients with AAAs (94% men; mean age, 72.4±6.1 years; mean AAA diameter, 48±8 mm) and 162 control subjects (100% men; mean age, 71.5±4.4 years) from 2 observational cohort studies. In the longitudinal cohort study (n=239), we explored the incremental prognostic value of pDES on AAA events. pDES was higher in patients with AAA compared with control subjects (mean±SD: 0.46±0.22 versus 0.33±0.16 ng/mL; P<0.001) and had the strongest correlation with AAA diameter (r=0.39; P<0.0001) of any serum biomarker. After adjustment for baseline AAA diameter, pDES was associated with an AAA event (hazard ratio, 2.03 per SD increase [95% CI, 1.02–4.02]; P=0.044). In addition to AAA diameter, pDES provided incremental improvement in risk stratification (continuous net reclassification improvement, 34.4% [95% CI, −10.8% to 57.5%; P=0.09]; integrated discrimination improvement, 0.04 [95% CI, 0.00–0.15; P=0.050]).

Conclusions

pDES concentrations predict disease severity and clinical outcomes in patients with AAA.

Clinical Trial Registration

http://www.isrctn.com. Unique identifier: ISRCTN76413758.

Positive association between abdominal aortic diameter and serum collagen XVIII levels

BACKGROUND

The identification of abdominal aortic aneurysm (AAA) biomarker offers a perspective to determine disease progress and rupture risk. The aim of our study was to evaluate the association between selected circulating biomarkers and diameter of abdominal aorta.

METHODS

One hundred and two patients (88 men and 14 women) with mean age 70.0±8.7 years were included in a single center cross-sectional study conducted between February 2016 and October, 2018. AAA was defined as subrenal aortic dilatation ≥3 cm. Serum biomarker concentrations (insulin-like growth factor-1, peroxiredoxin-1, collagen IV, collagen XVIII) were measured by an enzyme-linked immunosorbent assay (ELISA). Adjustments including variables with different baseline distribution at univariate level with P<0.1 (age, body mass index, coronary artery disease, fibrinogen) were performed in multivariate models.

RESULTS

Higher collagen XVIII was found in AAA patients in comparison with the control group of patients (39.5 vs. 25.0 ng/mL; P=0.002). Diameter of abdominal aorta was positively associated with collagen XVIII levels in univariate (B=0.16; P=0.004), and in multivariate analysis (B=0.14; P=0.027), i.e. increase in collagen XVIII by 1 ng/mL corresponded to an increase in abdominal aortic diameter by 0.14 mm. Patients with serum collagen XVIII levels in the third tertile (˃47 ng/mL) had 4.23 times higher risk of AAA compared to patients with collagen XVIII levels in the first and second tertiles (OR 4.23; 95% CI 1.42-11.6; P=0.020). No association was found between other examined biomarkers and abdominal aortic diameter.

CONCLUSIONS

Diameter of abdominal aorta was positively associated with serum collagen XVIII level.

Prognostic value of D-dimer and markers of coagulation for stratification of abdominal aortic aneurysm growth

Abdominal aortic aneurysm (AAA) is associated with high morbidity and mortality and is an established cause of unbalanced hemostasis. A number of hemostatic biomarkers have been associated with AAA; however, the utility of hemostatic biomarkers in AAA diagnosis and prognosis is unclear. The aim of the present study was to characterize the potential prognostic value of D-dimer and markers of altered hemostasis in a large cohort of patients with AAAs characterized by either fast or slow aneurysm growth (frequency matched for baseline diameter) and subaneurysmal dilations. We measured plasma concentrations of thrombin-antithrombin (TAT) complex, platelet factor 4 (PF4), and D-dimer in 352 patients with either fast-growing AAAs (>2 mm/y), slow-growing AAAs (<2 mm/y), subaneurysmal aortic dilations, or nonaneurysmal aortas. Plasma D-dimer and TAT were significantly elevated in both AAA and subaneurysmal dilation patients compared with controls. Individuals with D-dimer levels ≥500 ng/mL had 3.09 times the odds of subaneurysms, 6.23 times the odds of slow-growing AAAs, and 7.19 times the odds of fast-growing AAAs than individuals with D-dimer level <500 ng/mL. However, no differences in D-dimer concentration were noted between fast- and slow-growing aneurysms. Plasma D-dimer and TAT were strong independent predictors of AAA growth rate with multivariate analysis revealing a 500-ng/mL increase in D-dimer or 1-µg/mL increase in TAT led to additional 0.21-mm and 0.24-mm changes in aortic diameter per year, respectively. Rising levels of plasma TAT, in addition to D-dimer, may predict disease progression and aneurysm growth in patients with AAA or subaneurysmal dilation.