Inflammation, metalloproteinases, and increased proteolysis: an emerging pathophysiological paradigm in aortic aneurysm

Morphology and biomechanical index predict the rupture location and rupture risk of abdominal aortic aneurysm

The integration of biomechanical and morphological analyses holds tremendous potential for assessing the rupture risk of abdominal aortic aneurysms (AAA). We employed a one-way fluid-structure interaction (FSI) model to distinguish between ruptured AAA (RAAA) and asymptomatic intact AAA (IAAA), focusing on morphological and computational fluid dynamics (CFD) indices. Patient groups with ruptured RAAA and asymptomatic IAAA were matched by diameter, age, and sex. AAA morphology was analyzed via CT segmentation, and biomechanical indices-including wall shear stress (WSS), peak wall stress (PWS), maximum deformation (MD), and other indices-were determined using FSI analysis. Statistical comparisons were performed using paired t-tests or Wilcoxon rank sum tests. Multivariate and LASSO regression analyses identified predictive factors, and a nomogram was developed. Model accuracy was assessed using the area under the curve (AUC). In our study with 66 RAAA and 66 asymptomatic IAAA patients, the tortuosity of the RAAAs was 1.4 times that of the asymptomatic IAAAs (P = 0.0005). The PWS, MD and peak wall rupture index (PWRI) of the RAAAs was 1.18, 1.32 and 1.27 times that of the asymptomatic IAAAs (P = 0.0158, 0.0036, 0.0071). The MD position demonstrated high consistency with RAAA rupture locations (94.12%). Four variables were selected for a nomogram, predicting AAA rupture with an AUC of 0.7604 (95% CI 0.6653-0.8556) and an internal validation AUC of 0.8051 (95% CI 0.6400-0.9703). In this study, we demonstrated that the location of MD is valuable for predicting the rupture location of AAA. We constructed a nomogram incorporating four key predictors-aortic neck length (ANL), intraluminal thrombus volume relative to AAA volume (VILT/VAAA), tortuosity, and MD-that enhances the prediction of AAA rupture risk, offering a more personalized assessment beyond traditional diameter-based methods.

The relationship between abdominal aortic aneurysm diameter and its risk factors: a retrospective cohort study

Background

Abdominal aortic aneurysm is defined as a focal and persistent dilatation of the abdominal portion of the aorta to a diameter ≥50% larger than the diameter of adjacent segments and involving all three layers of the vessel wall.

Objectives

To evaluate whether risk factors (diabetes mellitus, hypertension, dyslipidemia, smoking, and age) influence aneurysm expansion.

Methods

This is a retrospective observational study of a series of cases that included 299 patients treated from January 2007 to January 2020, separated into exposed and unexposed groups by risk factors. Student's t test was used to assess whether mean aneurysm diameters showed statistically relevant differences between groups. A multivariate regression analysis was also conducted with the same groups.

Results

Smokers had larger aneurysms than those who had never smoked (p=0.002) and than former smokers (p<0.01) and patients ≤65 years old had larger diameters compared to patients aged 66 to 75 years old (p=0.0226). There were no significant correlations with the other risk factors (diabetes mellitus, dyslipidemia, hypertension). Multivariate regression analysis confirmed the same result, but with a coefficient of determination of 0.0608. Furthermore, smokers, patients with hypertension, patients with dyslipidemia, and patients without diabetes had higher frequencies of much larger aneurysm diameters.

Conclusions

It was observed that age ≤65 years and current smoking were related to greater aneurysm diameter. In contrast, the same statistical relationship was not observed for hypertension, absence of diabetes, or dyslipidemia, since there was a greater frequency of discrepant values for these groups. Studies are needed with a more comprehensive analysis of determinants of aneurysm diameter.

Risk factors for abdominal aortic aneurysm in patients with diabetes

OBJECTIVE

Although diabetes has been shown to be negatively associated with development of abdominal aortic aneurysm (AAA), patients with diabetes may still develop aneurysms. In this study, we examined risk factors for the development of AAA in patients with diabetes.

METHODS

Adults >50 years of age with diabetes who underwent health screening between 2009 and 2012 were followed for incident AAA until December 31, 2019. Cox proportional hazard regression models were used to calculate multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk factors associated with AAA.

RESULTS

Among 1,913,066 participants (55.3% men), 6996 AAA cases were identified during a mean follow-up of 7.7 years. Increased AAA risk was observed for age ≥65 years (HR, 2.69; 95% CI, 2.55-2.83), men (HR, 1.81; 95% CI, 1.69-1.94), smoking (former smoker ≥20 pack-years [PY]; HR, 1.75; 95% CI, 1.61-1.89; current smoker <20 PY; HR, 1.76; 95% CI, 1.59-1.94; current smoker ≥20 PY; HR, 2.40; 95% CI, 2.23-2.59), abdominal obesity (HR, 1.30; 95% CI, 1.23-1.38), and comorbidities, including hypertension (HR, 1.63; 95% CI, 1.53-1.73), dyslipidemia (HR, 1.35; 95% CI, 1.29-1.42), chronic kidney disease (HR, 1.52; 95% CI, 1.44-1.61), and cardiovascular disease (HR, 1.71; 95% CI, 1.58-1.86). Heavy (HR, 0.67; 95% CI, 0.61-0.74) and mild alcohol consumption (HR, 0.78; 95% CI, 0.74-0.83), overweight (HR, 0.87; 95% CI, 0.81-0.93) and obesity (HR, 0.81; 95% CI, 0.75-0.87), longer diabetes duration (≥5 years: HR, 0.74; 95% CI, 0.70-0.78), and using three or more oral hypoglycemic agents (OHA) (HR, 0.84; 95% CI, 0.79-0.90) were associated with decreased AAA risk, whereas insulin use was associated with a marginally increased risk (HR, 1.09; 95% CI, 1.00-1.18). Among the OHAs, metformin (HR, 0.95; 95% CI, 0.90-1.00), thiazolidinediones (HR, 0.87; 95% CI, 0.79-0.97), and sulfonylureas (HR, 0.88; 95% CI, 0.83-0.93) were associated with a decreased risk of AAA.

CONCLUSIONS

Although diabetes is associated with decreased AAA risk, those with comorbid cardiometabolic diseases, abdominal obesity, and a smoking history should be aware of an increased AAA risk. Further studies are warranted to verify the potential use of OHAs for decreasing AAA risk.

Investigating tissue factor pathway inhibitor and other protease and protease inhibitors and their association with major adverse aortic events in patients with abdominal aortic aneurysm

Background

Abdominal aortic aneurysm (AAA) is characterized by the proteolytic breakdown of the extracellular matrix, leading to dilatation of the aorta and increased risk of rupture. Biomarkers that can predict major adverse aortic events (MAAEs) are needed to risk stratify patients for more rigorous medical treatment and potential earlier surgical intervention.

Objectives

The primary objective was to identify the association between baseline levels of these biomarkers and MAAEs over a period of 5 years.

Methods

Baseline levels of 3 proteases (matrix metalloproteinases 7, 8, and 10) and 3 protease inhibitors (tissue factor pathway inhibitor [TFPI], SerpinA12, SerpinB3) were investigated. Plasma levels of these biomarkers were quantified in 134 patients with AAA and 134 matched controls. Patients were followed for a 5-year period during which MAAEs were documented. The association between these markers and MAAEs was evaluated using Cox regression and Kaplan-Meier survival curves.

Results

TFPI was significantly elevated in patients with AAA and significantly associated with MAAE during the 5-year period (hazard ratio, 1.52; 95% CI, 1.15-2.01; P = .003) after adjusting for covariates. Kaplan-Meier survival analyses demonstrated that patients in the high TFPI group (defined as plasma levels >25.961 ng/mL) had significantly reduced freedom from the need for aortic repair and MAAEs.

Conclusion

These findings suggest that TFPI may serve as a valuable prognostic marker for the risk of MAAEs within 5 years in patients with AAA, potentially offering new tools for the medical management of patients with AAA.

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.

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.

The role of transcription factors in the pathogenesis and therapeutic targeting of vascular diseases

Transcription factors (TFs) constitute an essential component of epigenetic regulation. They contribute to the progression of vascular diseases by regulating epigenetic gene expression in several vascular diseases. Recently, numerous regulatory mechanisms related to vascular pathology, ranging from general TFs that are continuously activated to histiocyte-specific TFs that are activated under specific circumstances, have been studied. TFs participate in the progression of vascular-related diseases by epigenetically regulating vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs). The Krüppel-like family (KLF) TF family is widely recognized as the foremost regulator of vascular diseases. KLF11 prevents aneurysm progression by inhibiting the apoptosis of VSMCs and enhancing their contractile function. The presence of KLF4, another crucial member, suppresses the progression of atherosclerosis (AS) and pulmonary hypertension by attenuating the formation of VSMCs-derived foam cells, ameliorating endothelial dysfunction, and inducing vasodilatory effects. However, the mechanism underlying the regulation of the progression of vascular-related diseases by TFs has remained elusive. The present study categorized the TFs involved in vascular diseases and their regulatory mechanisms to shed light on the potential pathogenesis of vascular diseases, and provide novel insights into their diagnosis and treatment.

Association of alcohol consumption with aortic aneurysm and dissection risk: results from the UK Biobank cohort study

BACKGROUND

Previous studies have reported inconsistent results with positive, negative, and J-shaped associations between alcohol consumption and the hazard of aortic aneurysm and dissection (AAD). This study aimed to examine the connections between weekly alcohol consumption and the subsequent risk of AAD.

METHODS

The UK Biobank study is a population-based cohort study. Weekly alcohol consumption was assessed using self-reported questionnaires and the congenital risk of alcohol consumption was also evaluated using genetic risk score (GRS). Cox proportional hazards models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for the associations between alcohol consumption and AAD. Several sensitivity analyses were performed to assess the robustness of the results.

RESULTS

Among the 388,955 participants (mean age: 57.1 years, 47.4% male), 2,895 incident AAD cases were documented during a median follow-up of 12.5 years. Compared with never-drinkers, moderate drinkers (adjusted HR: 0.797, 95%CI: 0.646-0.984, P<0.05) and moderate-heavy drinkers (adjusted HR: 0.794, 95%CI: 0.635-0.992, P<0.05) were significantly associated with a decreased risk of incident AAD. Interaction-based subgroup analysis revealed that the protective effect of moderate drinking was reflected mainly in participants younger than 65 years and women.

CONCLUSION

Our findings support a protective effect of moderate alcohol consumption on AAD, but are limited to participants younger than 65 years and women.

Dynamic Contrast-Enhanced MRI in Abdominal Aortic Aneurysms as a Potential Marker for Disease Progression

BACKGROUND

Abdominal aortic aneurysms (AAAs) may rupture before reaching maximum diameter (Dmax ) thresholds for repair. Aortic wall microvasculature has been associated with elastin content and rupture sites in specimens, but its relation to progression is unknown.

PURPOSE

To investigate whether dynamic contrast-enhanced (DCE) MRI of AAA is associated with Dmax or growth.

STUDY TYPE

Prospective.

POPULATION

A total of 27 male patients with infrarenal AAA (mean age ± standard deviation = 75 ± 5 years) under surveillance with DCE MRI and 2 years of prior follow-up intervals with computed tomography (CT) or MRI.

FIELD STRENGTH/SEQUENCE

A 3-T, dynamic three-dimensional (3D) fast gradient-echo stack-of-stars volumetric interpolated breath-hold examination (Star-VIBE).

ASSESSMENT

Wall voxels were manually segmented in two consecutive slices at the level of Dmax . We measured slope to 1-minute and area under the curve (AUC) to 1 minute and 4 minutes of the signal intensity change postcontrast relative to that precontrast arrival, and, Ktrans , a measure of microvascular permeability, using the Patlak model. These were averaged over all wall voxels for association to Dmax and growth rate, and, over left/right and anterior/posterior quadrants for testing circumferential homogeneity. Dmax was measured orthogonal to the aortic centerline and growth rate was calculated by linear fit of Dmax measurements.

STATISTICAL TESTS

Pearson correlation and linear mixed effects models. A P value <0.05 was considered statistically significant.

RESULTS

In 44 DCE MRIs, mean Dmax was 45 ± 7 mm and growth rate in 1.5 ± 0.4 years of prior follow-up was 1.7 ± 1.2 mm per year. DCE measurements correlated with each other (Pearson r = 0.39-0.99) and significantly differed between anterior/posterior versus left/right quadrants. DCE measurements were not significantly associated with Dmax (P = 0.084, 0.289, 0.054 and 0.255 for slope, AUC at 1 minute and 4 minutes, and Ktrans , respectively). Slope and 4 minutes AUC significantly associated with growth rate after controlling for Dmax .

CONCLUSION

Contrast uptake may be increased in lateral aspects of the AAA. Contrast enhancement 1-minute slope and 4-minutes AUC may be associated with a period of recent AAA growth that is independent of Dmax .

EVIDENCE LEVEL

3.

TECHNICAL EFFICACY

Stage 2.

Status of diagnosis and therapy of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are characterized by localized dilation of the abdominal aorta. They are associated with several serious consequences, including compression of adjacent abdominal organs, pain, treatment-related financial expenditure. The main complication of AAA is aortic rupture, which is responsible for about 200,000 deaths per year worldwide. An increasing number of researchers are dedicating their efforts to study AAA, resulting in significant progress in this field. Despite the commendable progress made thus far, there remains a lack of established methods to effectively decelerate the dilation of aneurysms. Therefore, further studies are imperative to expand our understanding and enhance our knowledge concerning AAAs. Although numerous factors are known to be associated with the occurrence and progression of AAA, the exact pathway of development remains unclear. While asymptomatic at most times, AAA features a highly unpredictable disease course, which could culminate in the highly deadly rupture of the aneurysmal aorta. Current guidelines recommend watchful waiting and lifestyle adjustment for smaller, slow-growing aneurysms, while elective/prophylactic surgical repairs including open repair and endovascular aneurysm repair are recommended for larger aneurysms that have grown beyond certain thresholds (55 mm for males and 50 mm for females). The latter is a minimally invasive procedure and is widely believed to be suited for patients with a poor general condition. However, several concerns have recently been raised regarding the postoperative complications and possible loss of associated survival benefits on it. In this review, we aimed to highlight the current status of diagnosis and treatment of AAA by an in-depth analysis of the findings from literatures.

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

BACKGROUND

Macrophage activation plays a critical role in abdominal aortic aneurysm (AAA) development. However, molecular mechanisms controlling macrophage activation and vascular inflammation in AAA remain largely unknown. The objective of the study was to identify novel mechanisms underlying adenosine deaminase acting on RNA (ADAR1) function in macrophage activation and AAA formation.

METHODS

Aortic transplantation was conducted to determine the importance of nonvascular ADAR1 in AAA development/dissection. Ang II (Angiotensin II) infusion of ApoE-/- mouse model combined with macrophage-specific knockout of ADAR1 was used to study ADAR1 macrophage-specific role in AAA formation/dissection. The relevance of macrophage ADAR1 to human AAA was examined using human aneurysm specimens. Moreover, a novel humanized AAA model was established to test the role of human macrophages in aneurysm formation in human arteries.

RESULTS

Allograft transplantation of wild-type abdominal aortas to ADAR1+/- recipient mice significantly attenuated AAA formation, suggesting that nonvascular ADAR1 is essential for AAA development. ADAR1 deficiency in hematopoietic cells decreased the prevalence and severity of AAA while inhibited macrophage infiltration and aorta wall inflammation. ADAR1 deletion blocked the classic macrophage activation, diminished NF-κB (nuclear factor kappa B) signaling, and enhanced the expression of a number of anti-inflammatory microRNAs. Mechanistically, ADAR1 interacted with Drosha to promote its degradation, which attenuated Drosha-DGCR8 (DiGeorge syndrome critical region 8) interaction, and consequently inhibited pri- to pre-microRNA processing of microRNAs targeting IKKβ, resulting in an increased IKKβ (inhibitor of nuclear factor kappa-B) expression and enhanced NF-κB signaling. Significantly, ADAR1 was induced in macrophages and interacted with Drosha in human AAA lesions. Reconstitution of ADAR1-deficient, but not the wild type, human monocytes to immunodeficient mice blocked the aneurysm formation in transplanted human arteries.

CONCLUSIONS

Macrophage ADAR1 promotes aneurysm formation in both mouse and human arteries through a novel mechanism, that is, Drosha protein degradation, which inhibits the processing of microRNAs targeting NF-kB signaling and thus elicits macrophage-mediated vascular inflammation in AAA.

Macrophage elastase derived from adventitial macrophages modulates aortic remodeling

Abdominal aortic aneurysm (AAA) is pathologically characterized by intimal atherosclerosis, disruption and attenuation of the elastic media, and adventitial inflammatory infiltrates. Although all these pathological events are possibly involved in the pathogenesis of AAA, the functional roles contributed by adventitial inflammatory macrophages have not been fully documented. Recent studies have revealed that increased expression of matrix metalloproteinase-12 (MMP-12) derived from macrophages may be particularly important in the pathogenesis of both atherosclerosis and AAA. In the current study, we developed a carrageenan-induced abdominal aortic adventitial inflammatory model in hypercholesterolemic rabbits and evaluated the effect of adventitial macrophage accumulation on the aortic remodeling with special reference to the influence of increased expression of MMP-12. To accomplish this, we compared the carrageenan-induced aortic lesions of transgenic (Tg) rabbits that expressed high levels of MMP-12 in the macrophage lineage to those of non-Tg rabbits. We found that the aortic medial and adventitial lesions of Tg rabbits were greater in degree than those of non-Tg rabbits, with the increased infiltration of macrophages and prominent destruction of elastic lamellae accompanied by the frequent appearance of dilated lesions, while the intimal lesions were slightly increased. Enhanced aortic lesions in Tg rabbits were focally associated with increased dilation of the aortic lumens. RT-PCR and Western blotting revealed high levels of MMP-12 in the lesions of Tg rabbits that were accompanied by elevated levels of MMP-2 and -3, which was caused by increased number of macrophages. Our results suggest that adventitial inflammation constitutes a major stimulus to aortic remodeling and increased expression of MMP-12 secreted from adventitial macrophages plays an important role in the pathogenesis of vascular diseases such as AAA.

Combination of folic acid with nifedipine is completely effective in attenuating aortic aneurysm formation as a novel oral medication

Aortic aneurysms are prevalent and severe vascular diseases with high mortality from unpredicted ruptures, while the only treatment option is surgical correction of large aneurysms with considerable risk. We have shown that folic acid (FA) is highly effective in alleviating development of aneurysms although not sufficient to completely attenuate aneurysm formation. Here, we examined therapeutic effects on aneurysms of combining FA with Nifedipine as novel and potentially more effective oral medication. Oral administration with FA (15 mg/kg/day) significantly reduced incidence of AAA from 85.71% to 18.75% in Ang II-infused apolipoprotein E (apoE) null mice, while combination of FA with Nifedipine (1.5, 5.0 or 20 mg/kg/day) substantially and completely further reduced incidence of AAA to 12.5%, 11.76% and 0.00% respectively in a dose-dependent manner. The combinatory therapy substantially and completely further alleviated enlargement of abdominal aortas defined by ultrasound, vascular remodeling characterized by elastin degradation and adventitial hypertrophy, as well as aortic superoxide production and eNOS uncoupling activity also in a dose-dependent manner, with combination of FA with 20 mg/kg/day Nifedipine attenuating all of these features by 100% to control levels. Aortic NO and H4B bioavailabilities were also dose-dependently further improved by combining FA with Nifedipine. These data establish entirely innovative and robust therapeutic regime of FA combined with Nifedipine for the treatment of aortic aneurysms. The comminatory therapy can serve as a first-in-class and most effective oral medication for aortic aneurysms, which can be rapidly translated into clinical practice to revolutionize management of the devastating vascular diseases of aortic aneurysms known as silent killers.

Effect of statins on abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a prevalent condition which causes progressive growth and rupture of aortic wall with a high death rate. Several studies have found that treatment with statins may decrease the progress of AAA and the risk of rupture by suppressing the inflammatory mediators, decreasing oxidative stress, and inhibiting mechanisms involved in extracellular matrix (ECM) degradation. Moreover, some studies have reported that prehospital therapy with statins can decrease mortality after surgery. The novelty of this paper is that different studies including those performed in humans and animals were reviewed and the potential mechanisms by which statins can have an effect on AAA were summarized. Overall, the evidence suggested an association between treatment with statins and improvement of AAA.

Cysteine-rich protein 2 deficiency attenuates angiotensin II-induced abdominal aortic aneurysm formation in mice

Background

Abdominal aortic aneurysm (AAA) is a relatively common and often fatal condition. A major histopathological hallmark of AAA is the severe degeneration of aortic media with loss of vascular smooth muscle cells (VSMCs), which are the main source of extracellular matrix (ECM) proteins. VSMCs and ECM homeostasis are essential in maintaining structural integrity of the aorta. Cysteine-rich protein 2 (CRP2) is a VSMC-expressed protein; however, the role of CRP2 in AAA formation is unclear.

Methods

To investigate the function of CRP2 in AAA formation, mice deficient in Apoe (Apoe^−/−) or both CRP2 (gene name Csrp2) and Apoe (Csrp2^−/−Apoe^−/−) were subjected to an angiotensin II (Ang II) infusion model of AAA formation. Aortas were harvested at different time points and histological analysis was performed. Primary VSMCs were generated from Apoe^−/− and Csrp2^−/−Apoe^−/− mouse aortas for in vitro mechanistic studies.

Results

Loss of CRP2 attenuated Ang II-induced AAA incidence and severity, accompanied by preserved smooth muscle α-actin expression and reduced elastin degradation, matrix metalloproteinase 2 (MMP2) activity, deposition of collagen, particularly collagen III (Col III), aortic tensile strength, and blood pressure. CRP2 deficiency decreased the baseline MMP2 and Col III expression in VSMCs and mitigated Ang II-induced increases of MMP2 and Col III via blunting Erk1/2 signaling. Rescue experiments were performed by reintroducing CRP2 into Csrp2^−/−Apoe^−/− VSMCs restored Ang II-induced Erk1/2 activation, MMP2 expression and activity, and Col III levels.

Conclusions

Our results indicate that in response to Ang II stimulation, CRP2 deficiency maintains aortic VSMC density, ECM homeostasis, and structural integrity through Erk1/2–Col III and MMP2 axis and reduces AAA formation. Thus, targeting CRP2 provides a potential therapeutic strategy for AAA.

Supplementary information

The online version contains supplementary material available at 10.1186/s12929-022-00808-z.

Experimental aortic aneurysm severity and growth depend on topical elastase concentration and lysyl oxidase inhibition

Abdominal aortic aneurysm (AAA) formation and expansion is highly complex and multifactorial, and the improvement of animal models is an important step to enhance our understanding of AAA pathophysiology. In this study, we explore our ability to influence aneurysm growth in a topical elastase plus β-Aminopropionitrile (BAPN) mouse model by varying elastase concentration and by altering the cross-linking capability of the tissue. To do so, we assess both chronic and acute effects of elastase concentration using volumetric ultrasound. Our results suggest that the applied elastase concentration affects initial elastin degradation, as well as long-term vessel expansion. Additionally, we assessed the effects of BAPN by (1) removing it to restore the cross-linking capability of tissue after aneurysm formation and (2) adding it to animals with stable aneurysms to interrupt cross-linking. These results demonstrate that, even after aneurysm formation, lysyl oxidase inhibition remains necessary for continued expansion. Removing BAPN reduces the aneurysm growth rate to near zero, resulting in a stable aneurysm. In contrast, adding BAPN causes a stable aneurysm to expand. Altogether, these results demonstrate the ability of elastase concentration and BAPN to modulate aneurysm growth rate and severity. The findings open several new areas of investigation in a murine model that mimics many aspects of human AAA.

Cardiac Structures in Marine Animals Provide Insight on Potential Directions for Interventions for Pediatric Congenital Heart Defects

Despite recent advances in pediatric diagnosis and surgical intervention, mortality and morbidity continue to be a prevalent issue in both Tetralogy of Fallot (ToF) and Hypoplastic Left Heart Syndrome (HLHS). Therefore, novel approaches to studying both of these conditions is warranted. Investigating cardiac anatomical features of different species in the animal kingdom similar to the defects and complications present in ToF and HLHS (as well as others) could serve as a new avenue for improving the management of congenital heart diseases (CHD). This review reveals that although structures found in HLHS and ToF are pathological, similar structures are found in diving mammals and reptiles that are adaptive. Pathologic aortic dilation in CHD resembles the aortic bulb present in diving mammals, but the latter is more elastic and distensible compared to the former. The unrepaired HLHS heart resembles the univentricular heart of non-crocodilian reptiles. Right ventricle hypertrophy is pathological in HLHS and ToF, but adaptive in crocodilians and diving mammals. Lastly, the increased pulmonary resistance due to pulmonary stenosis in ToF is comparable to increased pulmonary resistance in crocodilians due to the presence of an active valve proximal to the pulmonary valve. Some of these anatomical structures could potentially be adapted for palliative surgery in children with HLHS or ToF. Moreover, further investigating the underlying molecular signals responsible for the adaptive tissue responses seen in other species may also be useful for developing novel strategies for preventing some of the complications that occur after surgical repair in both of these CHDs.

Histologic Abnormalities of the Ascending Aorta: Effects on Aortic Remodeling after Intracardiac Repair of Tetralogy of Fallot

We evaluated aortic tissue specimens from patients undergoing tetralogy of Fallot repair, to determine whether histologic abnormalities affect postsurgical aortic remodeling and other patient-related variables. Using light microscopy, we studied full-thickness aortic wall tissue operatively excised from 118 consecutive patients undergoing intracardiac repair of tetralogy of Fallot. We performed multiple linear regression analysis to identify independent predictors of change in aortic root dimensions, which we measured with echocardiography after repair and every 3 months thereafter. Thirty histologically normal specimens were used as controls. Elastic fiber fragmentation was found in 74.6% of the abnormal specimens, mucoid extracellular matrix accumulation in 49.2%, smooth muscle cell nuclei loss in 39%, smooth muscle cell disorganization in 28.8%, and medial fibrosis in 52.5%. At a mean follow-up time of 83.55 ± 42.08 months, mean aortic sinotubular diameter decreased from 28.79 ± 9.15 to 27.16 ± 8.52 mm/m2 (r =-0.43; P <0.001). Aortic sinotubular diameter decreased by 0.6 mm/m2 among females (β =0.6, SE=0.31; P =0.05) and by 0.88 mm/m2 in patients who had elastic fiber fragmentation or loss (β =0.88, SE=0.38; P =0.02). In bivariate and multiple linear regression analysis, duration of follow-up emerged as an independent predictor of aortic remodeling. The aortic histopathologic changes in our patients had an independent negative impact on the degree of aortic remodeling after surgery. We observed the most improved aortic sinotubular diameter in patients who had either histologically normal aortas or aortas with elastic fragmentation.

Regression of corpus luteum in cetaceans: A systematic review

Functional and structural change of corpus luteum through the cascade of several genes in the ovary leads to ovulation and pregnancy. In most mammals, the absence of pregnancy leads to the disintegration of the corpus luteum. In the ovary of cetaceans, the regression of the corpus luteum gets delayed and persists on the surface as scars (corpus albicans). The database on luteolysis of mammals was collected and examined to know the mechanisms involved in the corpus luteum regression of cetaceans. Surprisingly, there existed no data on the concerned topic. Some past findings reported the persistence of ovarian scars through the entire life span, while few reported the regression. Also, those investigations were about the physiology and histology of corpus luteum regression. The pathways and the genes involved in the regression of the cetacean corpus luteum remain unexplored. This review is all about the regression of corpus luteum and recommends gene-based evolutionary studies in the future to resolve the existing theories on ovarian scar persistence in cetaceans.

Maresin 1 activates LGR6 signaling to inhibit smooth muscle cell activation and attenuate murine abdominal aortic aneurysm formation

The specialized pro-resolving lipid mediator maresin 1 (MaR1) is involved in the resolution phase of tissue inflammation. It was hypothesized that exogenous administration of MaR1 would attenuate abdominal aortic aneurysm (AAA) growth in a cytokine-dependent manner via LGR6 receptor signaling and macrophage-dependent efferocytosis of smooth muscle cells (SMCs). AAAs were induced in C57BL/6 wild-type (WT) mice and smooth muscle cell specific TGF-β2 receptor knockout (SMC-TGFβr2-/- ) mice using a topical elastase AAA model. MaR1 treatment significantly attenuated AAA growth as well as increased aortic SMC α-actin and TGF-β2 expressions in WT mice, but not SMC-TGFβr2-/- mice, compared to vehicle-treated mice. In vivo inhibition of LGR6 receptors obliterated MaR1-dependent protection in AAA formation and SMC α-actin expression. Furthermore, MaR1 upregulated macrophage-dependent efferocytosis of apoptotic SMCs in murine aortic tissue during AAA formation. In vitro studies demonstrate that MaR1-LGR6 interaction upregulates TGF-β2 expression and decreases MMP2 activity during crosstalk of macrophage-apoptotic SMCs. In summary, these results demonstrate that MaR1 activates LGR6 receptors to upregulate macrophage-dependent efferocytosis, increases TGF-β expression, preserves aortic wall remodeling and attenuate AAA formation. Therefore, this study demonstrates the potential of MaR1-LGR6-mediated mitigation of vascular remodeling through increased efferocytosis of apoptotic SMCs via TGF-β2 to attenuate AAA formation.

Resveratrol ameliorated endothelial injury of thoracic aorta in diabetic mice and Gly-LDL-induced HUVECs through inhibiting TLR4/HIF-1α

To explore the effects of resveratrol on the levels of inflammatory cytokines and Toll-like receptor-4/ hypoxia-inducible transcription factors-1α (TLR4/HIF-1α) signalling pathway in diabetes mellitus. C57BL/6 mice received intraperitoneal injection of streptozocin for constructing diabetic mice models. Human umbilical vein endothelial cells (HUVECs) were treated with 50 µg/mL Gly-LDL for inducing injury models. 10, 100 and 1000 mmol/L resveratrol were obtained and added into each group. Haematoxylin-eosin (H&E) staining was used for histological evaluation. CCK8 assay was performed for determination of cell viability, and Transwell assay was implemented for detecting cell migration ability. Cell apoptosis was analysed using flow cytometry. The content of inflammatory factors including interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), vascular adhesion molecule-1 (VCAM-1) and vascular endothelial growth factor (VEGF) were measured by ELISA. GST pull-down assay was employed for determining interactions between TLR4 and HIF-1α. The protein expression of TLR4 and HIF-1α was detected using Western blotting and immunohistochemistry, while relative mRNA expression was measured by RT-qRCR. Resveratrol could reduce bodyweight and ameliorate endothelial injury of thoracic aorta in diabetic mice. Both in vivo and in vitro results revealed that the level of IL-6, TNF-α, VCAM-1 and VEGF was significantly down-regulated after being treated with resveratrol. Resveratrol inhibited the increase of MDA and ROS and increased the level of SOD in diabetic mice. Western blotting, IHC and RT-qPCR results showed that the levels of TLR4 and HIF-1α were significantly down-regulated in resveratrol group. Overexpression of TLR4 or HIF-1α could reverse the effect of resveratrol. GST pull-down elucidated that there might be a close interaction between TLR4 and HIF-1α. Resveratrol ameliorated endothelial injury of thoracic aorta in diabetic mice and Gly-LDL-induced HUVECs through inhibiting TLR4/HIF-1α signalling pathway.

Doxycycline Therapy for Abdominal Aortic Aneurysm: Inhibitory Effect on Matrix Metalloproteinases

Abdominal aortic aneurysm (AAA) is a life-threatening condition associated with smoking, aging, atherosclerosis, and destruction of the connective tissue in the abdominal aortic wall. Disturbances in the synthesis and degradation of matrix metalloproteinase (MMP) have been known to contribute to the development of AAAs. The only available treatment of AAA is surgical repair. Doxycycline, a tetracycline analog, is thought to have an inhibitory effect on MMPs. Knowing the effect of doxycycline, there may be some favorable effects of the drug to reduce the growth of small AAAs and avoid the need for invasive treatment. This article aims to determine the relationship between doxycycline and the MMPs to prevent the growth of small AAAs. We conducted our review using online resources such as PubMed, Google Scholar, The Journal of Vascular Surgery, and ResearchGate. The result of our study supports the effect of doxycycline in preventing the growth of small AAAs. We conclude that therapeutic treatment with doxycycline in patients with small AAAs can prevent the growth of aneurysms, life-threatening aneurysm rupture, and reduce the need for expensive, invasive treatment.

Effect of Doxycycline on Survival in Abdominal Aortic Aneurysms in a Mouse Model

Background

Currently, there is no reliable nonsurgical treatment for abdominal aortic aneurysm (AAA). This study, therefore, investigates if doxycycline reduces AAA growth and the number of rupture-related deaths in a murine ApoE-/- model of AAA and whether gadofosveset trisodium-based MRI differs between animals with and without doxycycline treatment.

Methods

Nine ApoE-/- mice were implanted with osmotic minipumps continuously releasing angiotensin II and treated with doxycycline (30 mg/kg/d) in parallel. After four weeks, MRI was performed at 3T with a clinical dose of the albumin-binding probe gadofosveset (0.03 mmol/kg). Results were compared with previously published wild-type control animals and with previously studied ApoE-/- animals without doxycycline treatment. Differences in mortality were also investigated between these groups.

Results

In a previous study, we found that approximately 25% of angiotensin II-infused ApoE-/- mice died, whereas in the present study, only one out of 9 angiotensin II-infused and doxycycline-treated ApoE-/- mice (11.1%) died within 4 weeks. Furthermore, doxycycline-treated ApoE-/- mice showed significantly lower contrast-to-noise (CNR) values (p=0.017) in MRI compared to ApoE-/- mice without doxycycline treatment. In vivo measurements of relative signal enhancement (CNR) correlated significantly with ex vivo measurements of albumin staining (R ² = 0.58). In addition, a strong visual colocalization of albumin-positive areas in the fluorescence albumin staining with gadolinium distribution in LA-ICP-MS was shown. However, no significant difference in aneurysm size was observed after doxycycline treatment.

Conclusion

The present experimental in vivo study suggests that doxycycline treatment may reduce rupture-related deaths in AAA by slowing endothelial damage without reversing aneurysm growth.

The Role of Matrix Metalloproteinases in the Progression and Vulnerabilization of Coronary Atherosclerotic Plaques

Extracellular matrix (ECM) plays an important role in the development and progression of atherosclerotic lesions. Changes in the ECM are involved in the pathophysiology of many cardiovascular diseases, including atherosclerosis. Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteases, also known as matrixins, with proteolytic activity in the ECM, being responsible for the process of tissue remodeling in various systemic pathologies, including cardiac and vascular diseases. MMPs play an important role in maintaining normal vascular structure, but also in secondary cardiovascular remodeling, in the formation of atherosclerotic plaques and in their vulnerabilization process. In addition to the assigned effect of MMPs in vulnerable plaques, they have a well-defined role in post-infarction ventricular remodeling and in various types of cardiomyopathies, followed by onset of congestive heart failure, with repeated hospitalizations and death. The aim of this manuscript was to provide a summary on the role of serum matrix metalloproteinases in the process of initiation, progression and complication of atherosclerotic lesions, from a molecular level to clinical applicability and risk prediction in patients with vulnerable coronary plaques.

Association of Fluoroquinolones With the Risk of Aortic Aneurysm or Aortic Dissection

IMPORTANCE

Previous observational studies have suggested that fluoroquinolones are associated with aortic aneurysm or dissection, but these studies may be subject to confounding by indication or surveillance bias.

OBJECTIVE

To assess the association of fluoroquinolones with risk of aortic aneurysm or aortic dissection (AA/AD) while accounting for potential confounding by fluoroquinolone indication and bias owing to differential surveillance.

DESIGN, SETTING, AND PARTICIPANTS

In an observational cohort study using a US commercial claims database, 2 pairwise 1:1 propensity score-matched cohorts were identified: patients aged 50 years or older with a diagnosis of pneumonia 3 days or less before initiating treatment with a fluoroquinolone or azithromycin and patients aged 50 years or older with a urinary tract infection (UTI) diagnosis 3 days or less before initiating a fluoroquinolone or combined trimethoprim and sulfamethoxazole. Hazard ratios (HRs) and 95% CIs were estimated controlling for 85 baseline confounders. In a secondary analysis, patients receiving fluoroquinolones were compared with those receiving amoxicillin, both with and without considering baseline aortic imaging, to address differences in detection of AA/AD before antibiotic use. Data on patients within the database from January 1, 2003, through September 30, 2015, were analyzed. Data analysis was conducted from July 23, 2019, to July 6, 2020.

MAIN OUTCOMES AND MEASURES

Hospitalization for AA/AD occurring within 60 days following treatment initiation.

RESULTS

After propensity score matching, patient characteristics were well balanced, with 279 554 patients (mean [SD] age, 63.66 [10.93] years; 149 976 women [53.6%]) in the pneumonia cohort and 948 364 patients (mean [SD] age, 62.06 [10.33] years; 823 667 women [86.9%]) in the UTI cohort. Initiators of fluoroquinolones (n = 139 772 pairs in the pneumonia cohort and n = 474 182 pairs in the UTI cohort) had an increased rate of AA/AD compared with initiators of azithromycin (HR, 2.57; 95% CI, 1.36-4.86; incidence, 0.03% for fluoroquinolones vs 0.01% for azithromycin) but no increased rate compared with initiators of combined trimethoprim and sulfamethoxazole (HR, 0.99; 95% CI, 0.62-1.57; incidence, <0.01% in both UTI groups). Secondary analysis using amoxicillin as a comparator (n = 3 976 162 pairs) produced results consistent with those from earlier studies (HR, 1.54; 95% CI, 1.33-1.79; incidence, <0.01% in both groups). Requiring baseline imaging in this cohort (n = 542 649 pairs) to address surveillance bias attenuated the increased rate (HR, 1.13; 95% CI, 0.96-1.33; incidence, 0.06% for fluoroquinolones vs 0.05% for amoxicillin).

CONCLUSIONS AND RELEVANCE

The findings of this nationwide cohort study of adults with pneumonia or UTI suggest an increased relative rate of AA/AD associated with fluoroquinolones within the pneumonia cohort but not within the UTI cohort. In both cohorts, the absolute rate of AA/AD appeared to be low (<0.1%). The increased relative rate observed in the pneumonia cohort may be due to residual confounding or surveillance bias.

Oxidative stress parameters in patients with ascending aortic dilatation

Background/aim

This study aimed to determine plasma thiol, disulphide, and serum ischemia-modified albumin (IMA) levels and ferroxidase activity in patients with ascending aorta dilatation (AAD) in comparison to those without AAD and to evaluate the predictive value of these oxidative stress parameters for AAD.

Materials and methods

This study was designed as a cross-sectional study of 184 patients who applied to our cardiology clinic. Our study population consisted of patients with AAD (n = 85) and without AAD (n = 99). A spectrophotometric method was used to determine plasma thiol, disulphide, and serum IMA levels and ferroxidase activity.

Results

The native thiol and the total thiol levels were significantly higher in the control group than the AAD group (P < 0.001), whereas the disulphide and IMA levels and the ferroxidase activity were similar between the groups. The native thiol and the total thiol levels were inversely and significantly correlated with ascending aortic diameter (r = –0.38, P < 0.001; r = –0.39, P < 0.001; respectively). The left ventricle mass and the total thiol levels were independent predictors of ascending aortic diameter (β= 0.223, P = 0.02; β= –0.340, P < 0.001; respectively).

Conclusion

Among oxidative stress parameters including thiols, disulphide, IMA, and ferroxidase activity, only the lower total thiol levels appear to confer a high risk for AAD development. Along with the proven diagnostic imaging methods, thiol levels may be helpful to diagnose and stratify patients with AAD.

Reduced Nhe1 (Na+-H+ Exchanger-1) Function Protects ApoE-Deficient Mice From Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysms

IgE-mediated activation of Nhe1 (Na⁺-H⁺ exchanger-1) induces aortic cell extracellular acidification and promotes cell apoptosis. A pH-sensitive probe pHrodo identified acidic regions at positions of macrophage accumulation, IgE expression, and cell apoptosis in human and mouse abdominal aortic aneurysm (AAA) lesions. Ang II (angiotensin II)-induced AAA in Nhe1-insufficient Apoe^-/-Nhe1^+/- mice and Apoe^-/-Nhe1^+/+ littermates tested Nhe1 activity in experimental AAA, because Nhe1^-/- mice develop ataxia and epileptic-like seizures and die early. Nhe1 insufficiency reduced AAA incidence and size, lesion macrophage and T-cell accumulation, collagen deposition, elastin fragmentation, cell apoptosis, smooth muscle cell loss, and MMP (matrix metalloproteinase) activity. Nhe1 insufficiency also reduced blood pressure and the plasma apoptosis marker TCTP (translationally controlled tumor protein) but did not affect plasma IgE. While pHrodo localized the acidic regions to macrophage clusters, IgE expression, and cell apoptosis in AAA lesions from Apoe^-/-Nhe1^+/+ mice, such acidic areas were much smaller in lesions from Apoe^-/-Nhe1^+/- mice. Nhe1-FcεR1 colocalization in macrophages from AAA lesions support a role of IgE-mediated Nhe1 activation. Gelatin zymography, immunoblot, and real-time polymerase chain reaction analyses demonstrated that Nhe1 insufficiency reduced the MMP activity, cysteinyl cathepsin expression, IgE-induced apoptosis, and NF-κB activation in macrophages and blocked IgE-induced adhesion molecule expression in endothelial cells. A near-infrared fluorescent probe (LS662) together with fluorescence reflectance imaging of intact aortas showed reduced acidity in AAA lesions from Nhe-1-insufficient mice. This study revealed extracellular acidity at regions rich in macrophages, IgE expression, and cell apoptosis in human and mouse AAA lesions and established a direct role of Nhe1 in AAA pathogenesis.

Twenty years of bioinformatics research for protease-specific substrate and cleavage site prediction: a comprehensive revisit and benchmarking of existing methods

The roles of proteolytic cleavage have been intensively investigated and discussed during the past two decades. This irreversible chemical process has been frequently reported to influence a number of crucial biological processes (BPs), such as cell cycle, protein regulation and inflammation. A number of advanced studies have been published aiming at deciphering the mechanisms of proteolytic cleavage. Given its significance and the large number of functionally enriched substrates targeted by specific proteases, many computational approaches have been established for accurate prediction of protease-specific substrates and their cleavage sites. Consequently, there is an urgent need to systematically assess the state-of-the-art computational approaches for protease-specific cleavage site prediction to further advance the existing methodologies and to improve the prediction performance. With this goal in mind, in this article, we carefully evaluated a total of 19 computational methods (including 8 scoring function-based methods and 11 machine learning-based methods) in terms of their underlying algorithm, calculated features, performance evaluation and software usability. Then, extensive independent tests were performed to assess the robustness and scalability of the reviewed methods using our carefully prepared independent test data sets with 3641 cleavage sites (specific to 10 proteases). The comparative experimental results demonstrate that PROSPERous is the most accurate generic method for predicting eight protease-specific cleavage sites, while GPS-CCD and LabCaS outperformed other predictors for calpain-specific cleavage sites. Based on our review, we then outlined some potential ways to improve the prediction performance and ease the computational burden by applying ensemble learning, deep learning, positive unlabeled learning and parallel and distributed computing techniques. We anticipate that our study will serve as a practical and useful guide for interested readers to further advance next-generation bioinformatics tools for protease-specific cleavage site prediction.

ShRNA-mediated matrix metalloproteinase-2 gene silencing protects normal cells and sensitizes cancer cells against ionizing-radiation induced damage

INTRODUCTION

Ionizing radiation (IR) affects healthy tissues during the treatment of cancer radiation therapy and other nuclear and radiological accidents. Some natural compounds showed nonspecific radioprotective activity with severe side effects. The present study is aimed to develop potent and specific radioprotective short hairpin RNA (shRNA), which selectively protects normal cells from IR by specifically targeting matrix metalloproteinases (MMP-2).

RESULTS

IR reduced the viability of human normal dermal fibroblasts (HDFs) in a dose-response manner. It enhanced the expression of MMP-2 at 10 Gy. Plasmid MMP-2shRNA (pMMP-2) reduced the IR (10 Gy) induced cytotoxicity analyzed by lactate dehydrogenase (LDH) assay, normalized IR induced cellular and morphological changes with enhanced the clonogenicity in 48 hours at 2 µg/mL. It reduced the ROS generation, released HDFs from G₂ /M arrest and rescued from apoptosis analyzed by DCFDA dye, cell cycle analysis by PI stain and annexin V assay, respectively. pMMP-2 also modulates the expression of EGFR and reduced IR induced expression of DNA damage response protein, ATM and increased the expression of repair proteins, KU70/KU80, and RAD51. In addition, decreased the expression of cell cycle regulatory proteins cyclin-dependent kinases (CDK1) and Cyclin B as well as proapoptotic proteins BAX, caspase-3, and Cytochrome-C and increased the expression of survival protein, Bcl-2. In contrary pMMP-2 decreased the LDH activity, survival fraction and blocked G₂ /M phase of cell cycle and increased apoptosis in MCF-7 cells. In addition, decreased the expression of EGFR, proapoptotic BAX and DNA repair proteins ATM, KU70/80 and RAD51, increased expression of cyclinB as well as CDK1.

CONCLUSION

Results conclude that pMMP-2 protected HDFs from IR and sensitized the MCF-7 cells. Therefore, pMMP-2 can be employed for better treatment of radiation accidents and during the treatment of radiotherapy.

Anti-inflammatory diet and risk of abdominal aortic aneurysm in two Swedish cohorts

Objective

The relationship between dietary patterns and development of abdominal aortic aneurysm (AAA) is not well understood. Thus, we prospectively evaluated the association between the anti-inflammatory potential of diet and risk of AAA.

Methods

The study population included the Cohort of Swedish Men (45 072 men) and the Swedish Mammography Cohort (36 633 women), aged 45–83 years at baseline. The anti-inflammatory potential of diet was estimated using Anti-inflammatory Diet Index (AIDI) based on 11 foods with anti-inflammatory potential and 5 with proinflammatory potential (maximum 16 points) that was validated againsthigh sensitivity C reactive protein (hsCRP). Cox proportional hazard regression models were used to estimate HRs and 95% CIs. During the 14.9 years of follow-up (1 217 263 person-years), 1528 AAA cases (277 (18%) ruptured, 1251 non-ruptured) were ascertained via the Swedish Inpatient Register, the National Cause of Death Register and the Register for Vascular Surgery (Swedvasc).

Results

We observed an inverse association between the AIDI and AAA risk in women and men; HRs between extreme quartiles of the AIDI (≥8 vs ≤5 points) were 0.55 (95% CI 0.36 to 0.83) in women and 0.81 (95% CI 0.68 to 0.98) in men. The AIDI was inversely associated with both ruptured and non-ruptured AAA incidence; the HR of participants in the highest quartile of AIDI compared with those in the lowest quartile was 0.61 (95% CI 0.41 to 0.90) for ruptured AAA and 0.79 (95% CI 0.65 to 0.95) for non-ruptured AAA.

Conclusion

Adherence to diet with a high anti-inflammatory potential was associated with a reduced AAA risk, an association that was even more pronounced for AAA rupture.

Hair whitening and obesity are independently related to ascending aorta dilatation in young-middle aged men

OBJECTIVE

Hair whitening (HW) is strongly linked with aging. Ascending aortic dilation (AAD) and HW share common etiologic factors. We investigated the association of HW with ascending aortic diameters.

METHODS

Our study included 93 male subjects aged below 50 years. All patients underwent echocardiography to measure ascending aortic diameter, in addition to routine biochemistry tests, physical examination, and thorough medical history. HW score (HWS) was defined according to the percentage of white hair (HWS 1: <25%; HWS 2: 25-50%; HWS 3: 50-75%; and HWS 4: 75-100).

RESULTS

Patients with highest HWS were older and had a higher percentage of hypertension (HT) and family history of HW. Moreover, this subgroup had increased ascending aortic diameter, higher serum uric acid, and lower total bilirubin concentrations. Multivariate analyses including age, HT, height, waist circumference, c-reactive protein, and family history of HW identified body weight and HWS as the independent predictors of ascending aortic diameter.

CONCLUSION

An independent association between the degree of HW and AAD exists in middle-aged men, which may depend on coexisting factors that enhance both pathologies rather than causality. We think that oxidative stress may be one of these stressors.

Screening Program of Abdominal Aortic Aneurysm

In Europe, the prevalence of abdominal aortic aneurysms (AAAs) in the elderly population (≥65 year old) has declined in the past decades to <4%. Aneurysmal degeneration of the aorta is a serious and potentially life-threatening vascular disease. Abdominal aortic aneurysms typically develop subclinically and often only become symptomatic when complicated by impending rupture. Most AAAs are discovered incidentally while investigating for an unrelated pathology. Ruptured AAA is the tenth leading cause of death in Belgium (0.32% of all deaths in 2014). Health-care providers have emphasized the importance of early detection of AAA and elective repair when the rupture risk outweighs operative risk (usual diameter threshold of 55 mm). Routine AAA screening programs, consisting of a single abdominal ultrasonography at the age of 65 years, aim to reduce the number of AAA-related deaths. Does population-based ultrasound screening for AAA achieve its objective and is it cost-effective? This literature review tries to answer these challenging questions.

A diet enriched with tree nuts reduces severity of atherosclerosis but not abdominal aneurysm in angiotensin II-infused apolipoprotein E deficient mice

BACKGROUND AND AIMS

Diets enriched with tree nuts have been demonstrated to reduce the risk of atherosclerosis-related cardiovascular events. Abdominal aortic aneurysm (AAA) shares common risk factors with atherosclerosis and AAA patients commonly have atherosclerosis related cardiovascular events. AAA has some distinct pathological and clinical characteristics to those of atherosclerosis. No previous study has examined the effect of a diet enriched with tree nuts on experimental or clinical AAA. This study investigated the effect of a diet enriched with tree nuts on the development and severity of AAA within an experimental rodent model.

METHODS

Male apolipoprotein E deficient mice were allocated to a diet enriched with tree nuts or control diet for 56 days (n = 17 per group). After 28 days, all mice were infused with angiotensin II whilst being maintained on their respective diets. The primary outcome was AAA severity assessed by the supra-renal aortic diameter, measured by ultrasound and ex vivo morphometric analysis. The severity of atherosclerosis was assessed by computer-aided analysis of Sudan IV stained aortic arches and sections of brachiocephalic arteries prepared with Van Gieson's stain.

RESULTS

The diet enriched with tree nuts did not influence aortic diameter or aortic rupture incidence. Mice receiving the diet enriched with tree nuts had significantly less atherosclerosis within the brachiocephalic artery (p = 0.033) but not in the aortic arch.

CONCLUSIONS

This experimental study suggests that a diet enriched with tree nuts does not reduce the severity of AAA, but does reduce the severity of atherosclerosis within the brachiocephalic artery. The study was not powered to identify a moderate effect of the diet on the primary outcome and therefore this cannot be excluded.

Associations between serum relaxin 2, aneurysm formation/size and severity of atherosclerosis: a preliminary prospective analysis

Serum relaxin 2 (RL2) is a pleiotropic hormone that acts on various organs and systems, particularly the cardiovascular system. Although RL2 seems to upregulate the synthesis of nitric monoxide (NO) and matrix metalloproteinase (MMP)-2 and -9, current literature on its role in atherosclerosis and aneurysm formation is scarce. The aim of this study was to investigate the levels of serum RL2 in patients with an arterial aneurysm as well as in atherosclerotic patients, and correlate them with the severity of their related vascular disease. A total of 53 subjects were enrolled in this study: 37 patients were scheduled to undergo surgery: 21 patients for different forms of atherosclerotic disease (ATH), 16 patients for an arterial aneurysm (AA), 6 patients for undergoing temporal artery biopsy (TAB), and 10 healthy blood donors (HBD) served as the control groups. RL2 was measured using enzymelinked immunosorbent assay. RL2 was significantly higher in AA patients compared to ATH (P<0.01), TAB (P<0.001) and HBD (P<0.01). No significant difference was found between the ATH and TAB groups (P>0.05). In addition, ATH and AA patients were further subdivided based on the severity of their disease. Serum RL2 was progressively increased in patients with arterial aneurysms, showing a positive relationship with the size of the aneurysmatic dilatation. By contrast, the RL2 level was inversely related to the severity of the atherosclerotic disease. Studies with a larger cohort incorporating a consistent study population are warranted to verify our results and shed light on the mechanistic background of these processes.

Chinese Herbal Medicine as a Potential Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is an irreversible condition where the abdominal aorta is dilated leading to potentially fatal consequence of aortic rupture. Multiple mechanisms are involved in the development and progression of AAA, including chronic inflammation, oxidative stress, vascular smooth muscle (VSMC) apoptosis, immune cell infiltration and extracellular matrix (ECM) degradation. Currently surgical therapies, including minimally invasive endovascular aneurysm repair (EVAR), are the only viable interventions for AAAs. However, these treatments are not appropriate for the majority of AAAs, which measure <50 mm. Substantial effort has been invested to identify and develop pharmaceutical treatments such as statins and doxycycline for this potentially lethal condition but these interventions failed to offer a cure or to retard the progression of AAA. Chinese herbal medicine (CHM) has been used for the management of cardiovascular diseases for thousands of years in China and other Asian countries. The unique multi-component and multi-target property of CHMs makes it a potentially ideal therapy for multifactorial diseases such as AAA. In this review, we review the current scientific evidence to support the use of CHMs for the treatment of AAA. Mechanisms of action underlying the effects of CHMs on AAA are also discussed.

Heme oxygenase-1 deficiency exacerbates angiotensin II-induced aortic aneurysm in mice

Abdominal aortic aneurysm (AAA) is a chronic but often fatal disease in elderly population. Heme oxygenase-1 (HO-1) is a stress response protein with antioxidative and anti-inflammatory properties. HO-1 has been shown to protect against atherogenesis and arterial intimal thickening. Emerging evidences suggest that AAA and arterial occlusive disease have distinct pathogenic mechanisms. Thus, in this study we investigated the role of HO-1 in angiotensin II-induced AAA formation in HO-1^+/+apoE^−/− and HO-1^−/−apoE^−/− mice. We found that complete loss of HO-1 increased AAA incidence and rupture rate, and drastically increased aneurysmal area and severity, accompanied with severe elastin degradation and medial degeneration. Interestingly, we often observed not only AAA but also thoracic aortic aneurysm in HO-1^−/−apoE^−/− mice. Furthermore, reactive oxygen species levels, vascular smooth muscle cell (VSMC) loss, macrophage infiltration, matrix metalloproteinase (MMP) activity were markedly enhanced in the aneurysmal aortic wall in HO-1^−/−apoE^−/− mice. In addition, HO-1^−/−apoE^−/− VSMCs were more susceptible to oxidant-induced cell death and macrophages from HO-1^−/−apoE^−/− mice had aggravated responses to angiotensin II with substantial increases in inflammatory cytokine productions and MMP9 activity. Taken together, our results demonstrate the essential roles of HO-1 in suppressing the pathogenesis of AAA. Targeting HO-1 might be a promising therapeutic strategy for AAA.

The Effect of a High-Fat Diet on the Development of Abdominal Aortic Aneurysm in a Vascular Hypoperfusion-Induced Animal Model

Abdominal aortic aneurysm (AAA) is a vascular disease characterized by chronic inflammation in the infrarenal aorta. Most cases of AAA remain asymptomatic until rupture, and the mortality rate of patients with AAA rupture is very high. Currently, the relation between dietary habits and AAA development remains unknown. In this study, we evaluated the effects of a high-fat diet on the development of AAA in a vascular hypoperfusion-induced animal model. The risk of AAA rupture and AAA diameter in the high-fat group significantly increased compared with those in the control group. The number and size of adipocytes in the vascular wall in the high-fat group significantly increased as compared with those in the control group. Additionally, the collagen-positive sections in the areas with adipocytes significantly decreased as compared with those without adipocytes. The protein levels of matrix metalloproteinase (MMP)-2, MMP-9, and MMP-12, and macrophage-positive areas in the parts with adipocytes also significantly increased as compared with those without adipocytes. These data suggested that AAA rupture risk increased through accelerating chronic inflammation due to the accumulation of adipocytes in the vascular wall in the high-fat group.

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.

Mouse macrophage specific knockout of SIRT1 influences macrophage polarization and promotes angiotensin II-induced abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) is a vascular degenerative disease. Macrophage polarization and the balance between classically activated macrophages (M1) and alternatively activated macrophages (M2) are crucial for AAA pathogenesis. The present study aims to investigate the roles of macrophage SIRT1 in AAA formation and macrophage polarization. We found that in mouse peritoneal macrophages, SIRT1 expression was decreased after M1 stimulation, but was enhanced after M2 stimulation. Results from SIRT1^flox/flox mice and macrophage specific SIRT1 knockout mice with treatment of angiotensin II (Ang II) for 4 weeks showed that macrophage specific deficiency of SIRT1 increased the incidence of AAA and exacerbated the severity, including more severe aneurysm types, enlarged diameter of the aneurysm and increased degradation of elastin. In mouse aortas, SIRT1 deficiency increased the pro-inflammatory M1 molecule inducible nitric oxide synthase (iNOS), and decreased M2 molecules such as arginase 1 (Arg1) and mannose receptor (MR). Furthermore, in peritoneal macrophages, SIRT1 deficiency increased the expression of M1 inflammatory molecules, but decreased the expression of M2 molecules. Overexpression of SIRT1 had the opposite effects. Thus, macrophage specific knockout of SIRT1 influences macrophage polarization and accelerates Ang II-induced AAA formation.

Pravastatin activates activator protein 2 alpha to augment the angiotensin II-induced abdominal aortic aneurysms

We have previously reported that activation of AMP-activated kinase alpha 2 (AMPKa2) by nicotine or angiotensin II (AngII) instigates formation of abdominal aortic aneurysms (AAA) in Apoe−/− mice. Statins, used to treat hyperlipidemia widely, activate AMPK in vascular cells. We sought to examine the effects of pravastatin on AAA formation and uncover the molecular mechanism. The AAA model was induced by AngII and evaluated by incidence, elastin degradation, and maximal abdominal aortic diameter in Apoe−/− mice. The phosphorylated levels of AMPKa2 and activator protein 2 alpha (AP-2a) were examined in cultured vascular smooth muscle cells (VSMCs) or in mice. We observed that pravastatin (50 mg/kg/day, 8 weeks) remarkably increased the AngII-induced AAA incidence in mice. In VSMCs, pravastatin increased the levels of pAMPK, pAP-2a, and MMP2 in both basal and AngII-stressed conditions, which were abolished by tempol and compound C. Pravastatin-upregulated MMP2 was abrogated by AMPKa2 or AP-2a siRNA. Lentivirus-mediated gene silence of AMPKa2 or AP-2a abolished pravastatin-worsened AAA formations in AngII-infused Apoe−/− mice. Clinical investigations demonstrated that both AMPKa2 and AP-2a phosphorylations were increased in AAA patients or human subjects taking pravastatin. In conclusion, pravastatin promotes AAA formation through AMPKa2-dependent AP-2a activations.

Remnant Epitope Autoimmunity in Human Abdominal Aortic Aneurysm: A Pilot Study with Elastin Peptides

BACKGROUND

Abdominal aortic aneurysm (AAA) is a prevalent disease affecting around 5% of the population aged more than 65 years. The exact etiology and physiopathology of AAA still raises questions, and elective surgery is currently the only treatment option for this often progressive disease. In this study, we hypothesized and tested a pathophysiological model that depicts AAA as an inflammation-triggered autoimmune disease with remnant vessel wall peptide fragments as the antigen.

METHODS

A pilot study with male AAA patients (n = 14) and male controls (n = 8) was conducted. In both study groups, peripheral blood monocytes and plasma were separated from whole blood by centrifugation. An ELISpot test was performed on cultured white blood cells for the presence of elastin-specific T-lymphocytes. An Enzyme-linked immuno sorbent assay (ELISA) was performed on plasma for the presence of elastin-specific IgG molecules.

RESULTS

ELISpot interferon-gamma secretion in AAA (7.7 ± 9.5%) and control (4.6 ± 3.5%) and ELISA anti-elastin IgG titer in AAA (77.5 ± 17.8%) and control (78.2 ± 31.5%) were not significantly different (P = 0.94 and P = 0.55, respectively). Both results are expressed as a percentage relative to the respective positive and negative control.

CONCLUSIONS

The results of our pilot study did not indicate a clear and invariable autoimmune process directed against remnant elastin peptide fragments. Further research into the model mechanics and a possible antigen is still necessary. In the mean time, the model as presented here already offers a pathophysiological framework to further research into the possible remnant epitope-driven AAA etiology.

High Structural Stress and Presence of Intraluminal Thrombus Predict Abdominal Aortic Aneurysm 18F-FDG Uptake: Insights From Biomechanics

Supplemental Digital Content is available in the text.

Background—

Abdominal aortic aneurysm (AAA) wall inflammation and mechanical structural stress may influence AAA expansion and lead to rupture. We hypothesized a positive correlation between structural stress and fluorine-18-labeled 2-deoxy-2-fluoro-d-glucose (¹⁸F-FDG) positron emission tomography–defined inflammation. We also explored the influence of computed tomography–derived aneurysm morphology and composition, including intraluminal thrombus, on both variables.

Methods and Results—

Twenty-one patients (19 males) with AAAs below surgical threshold (AAA size was 4.10±0.54 cm) underwent ¹⁸F-FDG positron emission tomography and contrast-enhanced computed tomography imaging. Structural stresses were calculated using finite element analysis. The relationship between maximum aneurysm ¹⁸F-FDG standardized uptake value within aortic wall and wall structural stress, patient clinical characteristics, aneurysm morphology, and compositions was explored using a hierarchical linear mixed-effects model. On univariate analysis, local aneurysm diameter, thrombus burden, extent of calcification, and structural stress were all associated with ¹⁸F-FDG uptake (P<0.05). AAA structural stress correlated with ¹⁸F-FDG maximum standardized uptake value (slope estimate, 0.552; P<0.0001). Multivariate linear mixed-effects analysis revealed an important interaction between structural stress and intraluminal thrombus in relation to maximum standardized uptake value (fixed effect coefficient, 1.68 [SE, 0.10]; P<0.0001). Compared with other factors, structural stress was the best predictor of inflammation (receiver-operating characteristic curve area under the curve =0.59), with higher accuracy seen in regions with high thrombus burden (area under the curve =0.80). Regions with both high thrombus burden and high structural stress had higher ¹⁸F-FDG maximum standardized uptake value compared with regions with high thrombus burdens but low stress (median [interquartile range], 1.93 [1.60–2.14] versus 1.14 [0.90–1.53]; P<0.0001).

Conclusions—

Increased aortic wall inflammation, demonstrated by ¹⁸F-FDG positron emission tomography, was observed in AAA regions with thick intraluminal thrombus subjected to high mechanical stress, suggesting a potential mechanistic link underlying aneurysm inflammation.

Laparoscopic surgery for elective abdominal aortic aneurysm repair

BACKGROUND

Abdominal aortic aneurysm (AAA) is an abnormal dilatation of the infradiaphragmatic aorta that is equal to or greater than 30 mm or a local dilatation of equal to or greater than 50% compared to the expected normal diameter of the artery. AAAs rarely occur in individuals under 50 years of age, but thereafter the prevalence dramatically increases with age, with men at a six-fold greater risk of developing an AAA than women. Prevalence of AAA has been reported to range from 1.3% in women aged 65 to 80 years to between 4% and 7.7% in men aged 65 to 80 years.There is evidence that the risk of rupture increases as the aneurysm diameter increases from 50 mm to 60 mm. People with AAAs over 55 mm in diameter are therefore generally referred for consideration of repair, as the risk of rupture exceeds the risk of repair. The traditional treatment for AAA is open surgical repair (OSR) which involves a large abdominal incision and is associated with a significant risk of complications. Two less invasive procedures have recently become more widely used: endovascular aneurysm repair (EVAR) and laparoscopic repair. EVAR is carried out through sheaths inserted in the femoral artery in the groin: thereafter, a stent graft is placed within the aneurysm sac under radiological image guidance and anchored in place to form a new channel for blood flow. Laparoscopic repair involves the use of a laparoscope which is inserted through small cuts in the abdomen and the synthetic graft is sewn in place to replace the weakened area of the aorta. Laparoscopic AAA repair falls into two categories: hand-assisted laparoscopic surgery (HALS), where an incision is made to allow the surgeon's hand to assist in the repair; and total laparoscopic surgery (TLS). Both EVAR and laparoscopic repair are favourable over OSR as they are minimally invasive, less painful, associated with fewer complications and lower mortality rate and have a shorter duration of hospital stay.Current evidence suggests that elective laparoscopic AAA repair has a favourable safety profile comparable with that of EVAR, with low conversion rates as well as similar mortality and morbidity rates. As a result, it has been suggested that elective laparoscopic AAA repair may have a role in treating those patients for whom EVAR is unsuitable.

OBJECTIVES

To assess the effects of laparoscopic surgery for elective abdominal aortic aneurysm repair.The primary objective of this review was to assess the perioperative mortality and operative time of laparoscopic (total and hand-assisted) surgical repair of abdominal aortic aneurysms (AAA) compared to traditional open surgical repair or EVAR. The secondary objective was to assess complication rates, all-cause mortality (> 30 days), hospital and intensive care unit (ICU) length of stay, conversion and re-intervention rates, and quality of life associated with laparoscopic (total and hand-assisted) surgical repair compared to traditional open surgical repair or EVAR.

SEARCH METHODS

The Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (last searched August 2016) and CENTRAL (2016, Issue 7). In addition the CIS searched trials registries for details of ongoing or unpublished studies. We searched the reference lists of relevant articles retrieved by electronic searches for additional citations.

SELECTION CRITERIA

Randomised controlled trials and controlled clinical trials in which patients with an AAA underwent elective laparoscopic repair (total laparoscopic repair or hand-assisted laparoscopic repair) compared with either open surgical repair or EVAR.

DATA COLLECTION AND ANALYSIS

Studies identified for potential inclusion were independently assessed for inclusion by at least two review authors.

MAIN RESULTS

One randomised controlled trial with a total of 100 male participants was included in the review. The trial compared hand-assisted laparoscopic repair with EVAR and provided results for in-hospital mortality, operative time, length of hospital stay and lower limb ischaemia. The included study did not report on the other pre-planned outcomes of this review. No in-hospital deaths occurred in the study. Hand-associated laparoscopic repair was associated with a longer operative time (MD 53.00 minutes, 95% CI 36.49 to 69.51) than EVAR. The incidence of lower limb ischaemia was similar between the two treatment groups (risk ratio (RR) 0.50, 95% confidence interval (CI) 0.05 to 5.34). The mean length of hospital stay was 4.2 days and 3.4 days in the hand-assisted laparoscopic repair and EVAR groups respectively but standard deviations were not reported and therefore it was not possible to independently test the statistical significance of this result. The quality of evidence was downgraded for imprecision due to the inclusion of one small study; and wide confidence intervals and indirectness due to the study including male participants only. No study compared laparoscopic repair (total or hand-assisted) with open surgical repair or total laparoscopic surgical repair with EVAR.

AUTHORS' CONCLUSIONS

There is insufficient evidence to draw any conclusions about effectiveness and safety of laparoscopic (total and hand-assisted) surgical repair of AAA versus open surgical repair or EVAR, because only one small randomised trial was eligible for inclusion in this review. High-quality randomised controlled trials are needed.

Abdominal Aortic Aneurysms and Risk Factors for Adverse Events

An abdominal aortic aneurysm (AAA) is a focal full thickness dilatation of the abdominal aorta, greater than 1.5 times its normal diameter. Although some patients with AAA experience back or abdominal pain, most remain asymptomatic until rupture. The prognosis after AAA rupture is poor. Management strategies for patients with asymptomatic AAAs include risk factor reduction, such as smoking cessation, optimizing antihypertensive treatment, and treating dyslipidemia, as well as surveillance by ultrasound. Currently, aneurysm diameter alone is often used to assess risk of rupture. Once the aneurysm diameter reaches 5.5 cm, the risk of rupture is considered greater than the risk of intervention and elective aneurysm repair is undertaken. There is increasing interest in detecting AAAs early, and national screening programs are now in place. Furthermore, there is increasing research interest in biomarkers, genetics, and functional imaging to improve detection of AAAs at risk of progression and rupture. In this review, we discuss risk factors for AAA rupture, which should be considered during the management process, to advance current deficiencies in management pathways.

Aneurysmal degeneration of vein conduit used for vascular reconstruction-Case report and literature review

INTRODUCTION

Popliteal artery aneurysms (PAA) are the most prevalent form of peripheral arterial aneurysms. Greater saphenous vein grafts and endoaneurysmorrhaphy remains the mainstay therapy for open repair of PAA. True aneurysmal degeneration of lower extremity infrainguinal autologous vein grafts are relatively rare and its etiology is not completely understood.

CASE PRESENTATION

We present a case of a 57-year-old man with recurrent autologous venous graft aneurysmal dilatations following a surgical popliteal artery aneurysm repair.

DISCUSSION

The pathogenesis of true aneurysmal graft dilatation remains speculative with possible pathogenesis including progression of underlying atherosclerosis, systemic dilating diathesis, autologous venous graft varicosities, low-grade infections and post-stenotic dilatations. Management of venous graft aneurysms should be subjected to the same criteria as other aneurysms. Diagnosis requires a high index of suspicion. The initial study of choice is duplex ultrasonography as it can diagnose the aneurysm and distinguish it from other popliteal masses, provide accurately measurements and identify thrombus within the aneurysm. Once diagnosed, surgical repair should be performed as soon as possible as graft dilatation tends to occur overtime and is typically followed by a rapid increase in size over a short period of time.

CONCLUSION

Aneurysmal degeneration of autologous saphenous venous graft following PAA repairs occur infrequently. Its etiology remains largely speculative. Accurate diagnosis and early surgical intervention can prevent progression of aneurysmal dilatation and minimize the potential of complications.

The Potential Role of Kallistatin in the Development of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a vascular condition that causes permanent dilation of the abdominal aorta, which can lead to death due to aortic rupture. The only treatment for AAA is surgical repair, and there is no current drug treatment for AAA. Aortic inflammation, vascular smooth muscle cell apoptosis, angiogenesis, oxidative stress and vascular remodeling are implicated in AAA pathogenesis. Kallistatin is a serine proteinase inhibitor, which has been shown to have a variety of functions, potentially relevant in AAA pathogenesis. Kallistatin has been reported to have inhibitory effects on tumor necrosis factor alpha (TNF-α) signaling induced oxidative stress and apoptosis. Kallistatin also inhibits vascular endothelial growth factor (VEGF) and Wnt canonical signaling, which promote inflammation, angiogenesis, and vascular remodeling in various pre-clinical experimental models. This review explores the potential protective role of kallistatin in AAA pathogenesis.