Novel insight into the pathobiology of abdominal aortic aneurysm and potential future treatment concepts

Associations of Preoperative Nutritional Status and Sarcopenia With Mortality in Patients With Abdominal Aortic Aneurysm After Open and Endovascular Abdominal Aortic Aneurysm Repair: A Retrospective Study

OBJECTIVE

The effect of preoperative malnutrition and sarcopenia on outcomes in patients with abdominal aortic aneurysm (AAA) after open surgical repair (OSR) and endovascular abdominal aortic aneurysm repair is undefined. The authors conducted the study to address this issue in this population.

DESIGN

A retrospective observational study.

SETTING

A large tertiary hospital.

PARTICIPANTS

Patients with AAA who underwent OSR and endovascular aneurysm repair (EVAR).

INTERVENTIONS

Evaluation of nutritional status (Nutritional Risk Screening 2002 [NRS 2002] and the Controlling Nutritional Status [CONUT] scores), muscle size (skeletal muscle index), and postoperative parameters.

MEASUREMENTS AND MAIN RESULTS

A total of 199 patients were reviewed from January 2020 to December 2022. Patients weew categorized into group A (CONUT <4) and group B (CONUT ≥4) based on whether their CONUT scores were less than 4. The mortality (p = 0.004) and the incidence of Clavien-Dindo class III complications (p = 0.007) in group B were higher than those in group A. CONUT score was an independent risk factor for midterm mortality (hazard ratio 1.329; 95% CI, 1.104-1.697; p = 0.002) and Clavien-Dindo class III complications (odds ratio 1.225; 95% CI, 1.012-1.482; p = 0.037) according to univariate and multivariate analyses, whereas NRS 2002 score and sarcopenia were not. Kaplan-Meier curves showed a lower midterm survival rate in group B (log-rank p < 0.001).

CONCLUSION

In patients with AAA undergoing OSR or EVAR, a CONUT score ≥4 was associated with increased Clavien-Dindo class III complications and mortality. Preoperative nutritional status should be evaluated and optimized in this high-risk population.

Controlling the nutritional status score: a new tool for predicting postoperative mortality in patients with infrarenal abdominal aortic aneurysm treated with endovascular aneurysm repair

Background

AAA is a fatal condition that commonly occurs during vascular surgery. Nutritional status exerts a significant influence on the prognosis of various pathological conditions Scores from the CONUT screening tool have been shown to predict outcomes of certain malignancies and chronic diseases. However, the ramifications of nutritional status on AAA patients undergoing EVAR have not been elucidated in prior studies. In this study, we aimed to elucidate the correlation between CONUT scores and postoperative prognostic outcomes in patients with AAA undergoing EVAR.

Methods

This was a retrospective review of 177 AAA patients treated with EVAR from June 2018 to November 2019 in a single center. Patient characteristics, CONUT scores, and postoperative status were collected. These patients were stratified into groups A and B according to CONUT scores. Subsequently, a comparative analysis of the baseline characteristics between the two cohorts was conducted. Cox proportional hazards and logistic regression analyses were employed to identify the autonomous predictors of mid-term mortality and complications, respectively.

Results

Compared with group A, patients in group B had higher midterm mortality (p < 0.001). Univariate analysis showed that CONUT scores; respiratory diseases; stent types; preoperative Hb, CRP, PT, and Fb levels were risk factors for death. Multivariate analysis confirmed that CONUT score [HR, 1.276; 95% CI, 1.029-1.584; p = 0.027] was an independent risk factor for mortality. Logistic regression analysis showed that prior arterial disease, smoking, and D-dimer levels were risk factors, although multivariate analysis showed smoking (OR, 3.492; 95% CI, 1.426-8.553; p = 0.006) was an independent risk factor. Kaplan-Meier curves showed that patients in group B had shorter mid-term survival than those in group A (log-rank p < 0.001).

Conclusion

Malnutrition was strongly associated with mid-term mortality in patients with infrarenal AAA treated with EVAR.

The controlling nutritional status score predicts postoperative mortality in patients with ruptured abdominal aortic aneurysm: a retrospective study

Background

Ruptured abdominal aortic aneurysms (rAAAs) are challenging for vascular surgeons because they have a high mortality rate. In many diseases, nutritional status is closely associated with prognosis. The Controlling Nutritional Status (CONUT) screening tool score is a prognostic factor in some malignant and chronic diseases; however, the impact of nutritional status on rAAA has not yet been reported. In this study, we explored the relationship between the CONUT score and the postoperative prognosis of patients with rAAA.

Methods

This was a retrospective review of 39 patients with rAAA who underwent surgical treatment from March 2018 to September 2021 at one center. Patient characteristics, nutritional status (CONUT score), and postoperative status were recorded. The patients were divided into groups A and B based on the CONUT score. The baseline characteristics of the two groups were compared, and Cox proportional hazards and logistic regression analyses were used to determine independent predictors of mid-term mortality and complications, respectively.

Results

The overall mid-term mortality rate was 28.21% (11/39). Compared with group A, group B had higher intraoperative (P = 0.047) and mid-term mortality (P = 0.033) rates. The univariate analysis showed that age [hazard ratio (HR), 1.098; 95% confidence interval (CI), 1.019-1.182; P = 0.014], CONUT score (HR, 1.316; 95% CI, 1.027-1.686; P = 0.03), and surgical procedure (HR, 0.127; 95% CI, 0.016-0.992; P = 0.049) were associated with mid-term mortality, whereas the multivariate analysis showed that the CONUT score (HR, 1.313; 95% CI, 1.009-1.710; P = 0.043) was an independent predictor of mid-term mortality. The multivariate logistic regression analysis did not reveal any associations with complications. The Kaplan-Meier curves showed that group B had a lower mid-term survival rate (log-rank P = 0.024).

Conclusion

Malnutrition is closely associated with the prognosis of patients with rAAA, and the CONUT score can be used to predict mid-term mortality.

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.

Platelet protects angiotensin II-driven abdominal aortic aneurysm formation through inhibition of inflammation

BACKGROUND

Inflammation is the primary cause of abdominal aortic aneurysm (AAA) formation and development. It has been reported that platelets protect against septic shock by inhibiting inflammation. However, it is unclear whether platelets protect AAA progress via suppressing inflammation.

METHODS

A mouse model of AAA was established by a daily administration of angiotensin II (Ang II, 1000 ng/kg/min) for 28-day. The AAA mice received 1 × 10⁹ platelets transfusion in normal saline every 3rd day for 1 month. Hematoxylin and eosin, Masson's trichrome, and elastic van Gieson staining techniques were used to analyze the morphology of the abdominal aorta. Immunohistochemistry was used to detect any infiltration of inflammatory cells, inflammatory factors, and matrix metalloproteins (MMPs) in the aortic tissue. Western blot and enzyme-linked immunosorbent assay (ELISA) were used to examine the inflammatory factor proteins levels in the aortic wall and peripheral blood, respectively.

RESULTS

Platelets infusion significantly suppressed the Ang II-driven elevation of aortic diameter, AAA formation (52.38% decrease, P < 0.05), aortic expansion, elastic lamina destruction, and inflammatory response. In addition, MMP-2 and MMP-9 production were also reduced by platelets transfusion.

CONCLUSIONS

For the first time, our study reported the beneficial effect of platelet transfusion in suppressing the Ang II-driven AAA progress in mice through the inhibition of inflammation.

Profiling of Histone Modifications Reveals Epigenomic Dynamics During Abdominal Aortic Aneurysm Formation in Mouse Models

Introduction: Abdominal aortic aneurysms (AAA) are characterized by localized inflammation, extracellular matrix degradation, and apoptosis of smooth muscle cells, which together lead to progressive and irreversible aortic dilation. Major risk factors for AAA include smoking and aging, both of which prominently alter gene expression via epigenetic mechanisms, including histone methylation (me) and acetylation (ac).However, little is known about epigenomic dynamics during AAA formation. Here, we profiled histone modification patterns in aortic tissues during AAA formation in two distinct mouse models; (1) angiotensin II (AngII) infusion in low density lipoprotein receptor (LDLR) knockout (KO) mice, and (2) calcium chloride (CaCl₂) application in wild type mice.

Methods and Results: AAA formed in both models, in conjunction with enhanced macrophage infiltration, elastin degradation and matrix metalloproteinases expression as evaluated by immunohistochemistry. To investigate the histone modification patterns during AAA formation, total histone proteins were extracted from AAA tissues, and histone H3 modifications were quantified using profiling kits. Intriguingly, we observed dynamic changes in histone H3 modifications of lysine (K) residues at different time points during AAA formation. In mature aneurysmal tissues at 3 weeks after AngII infusion, we detected reduced K4/K27/K36 monomethylation, K9 trimethylation K9, and K9/K56 acetylation (<70%), and increased K4 trimethylation (>130%). Conversely, in CaCl₂-induced AAA, K4/K9/K27/K36/K79 monomethylation and K9/K18/K56 acetylation were reduced in AAA tissues, whereas K27 di-/tri-methylation and K14 acetylation were upregulated. Interestingly, K4/K27/K36 monomethylation, K9 trimethylation, and K9/K56 acetylation were commonly downregulated in both animal models, while no H3 modifications were uniformly upregulated. Western blot of AAA tissues confirmed markedly reduced levels of key H3 modifications, including H3K4me1, H3K9me3, and H3K56ac. Furthermore, pathway enrichment analysis using an integrative bioinformatics approach identified specific molecular pathways, including endocytosis, exon guidance and focal adhesion signaling, that may potentially be linked to these histone H3 modifications during AAA formation.

Conclusions: Dynamic modifications of histone H3 occur during AAA formation in both animal models. We identified 6 discreet H3 modifications that are consistently downregulated in both models, suggesting a possible role in AAA pathobiology. Identifying the functional mechanisms may facilitate development of novel strategies for AAA prevention or treatment.

Inhibitory effects of cycloastragenol on abdominal aortic aneurysm and its related mechanisms

BACKGROUND AND PURPOSE

Abdominal aortic aneurysm (AAA) is a degenerative disease affecting human health, but there are no safe and effective medications for AAA therapy. Cycloastragenol (CAG), derived from Astragali Radix, has various pharmacological effects. However, whether CAG can protect against AAA remains elusive. In this study, we investigated whether CAG has an inhibitory effect on AAA and its related mechanism.

EXPERIMENTAL APPROACH

The AAA mouse model was induced by incubating the abdominal aorta with elastase. CAG was administered by gavage at different doses beginning on the same day or 14 days after inducing AAA to explore its preventive or therapeutic effects respectively. The preventive effects of CAG on AAA were verified in another AAA mouse model induced by angiotensin II in ApoE-/- mouse. In vitro experiments were implemented on rat vascular smooth muscle cells (VSMCs) stimulated by TNF-α.

KEY RESULTS

Compared to the control AAA model group, CAG (125 mg·kg-1 body weight day-1 ) reduced the incidence of AAA, the dilatation of aorta and elastin degradation in media in both mouse models of AAA. CAG suppressed the inflammation, oxidation, phenotype switch and apoptosis in TNF-α-stimulated VSMCs, ameliorated the expression and activity of MMPs and decreased the activation of the ERK/JNK signalling pathway. CAG also inhibited the degradation of elastin in TNF-α-stimulated VSMCs.

CONCLUSION AND IMPLICATIONS

CAG presents protective effects against AAA through down-regulation of the MAPK signalling pathways and thus attenuates inflammation, oxidation, VSMC phenotype switch and apoptosis and the expression of MMPs as well as increasing elastin biosynthesis.

Licochalcone A attenuates abdominal aortic aneurysm induced by angiotensin II via regulating the miR-181b/SIRT1/HO-1 signaling

Licochalcone A (LA), a chalcone derived from liquorice, exhibits multiple biological activities, including anti-oxidation and anti-inflammation. This study aimed to investigate the role and underlying mechanism of LA in the abdominal aortic aneurysm (AAA). AAA model was established by continuous infusion of 1000 ng/kg/min of angiotensin II (AngII) in ApoE ^-/- mice for 4 weeks. At 7 days before AngII administration, 5 mg/kg/day or 10 mg/kg/day of LA was intraperitoneally administered to mice and continued for 4 weeks. The characteristics and quantification of AAAs were determined in situ. Real-time PCR or western blot was used to measure mRNA or protein levels of matrix metalloproteinase 2 and matrix metalloproteinase 9; pro-inflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6; apoptosis-related proteins Bax, Bcl-2, and active caspase-3; miR-181b; Sirtuin 1 (SIRT1); and heme oxygenase-1 (HO-1). Mouse-aorta-origin vascular smooth muscle (MOVAS) cells were used to confirm the involved pathways in vitro. We found LA administration dose-dependently reduced the incidence of AngII-induced AAA, aneurysm diameter enlargement, elastin degradation, matrix metalloproteinase production, pro-inflammatory cytokines and miR-181b expression, and vascular smooth muscle cell apoptosis. It elevated SIRT1 and HO-1 expression that was suppressed by AngII. AngII enhanced miR-181b but reduced SIRT1 and HO-1 expression in MOVAS cells. In AngII-stimulated MOVAS cells, downregulation of miR-181b significantly upregulated the expression of SIRT1 and HO-1, the effect of which was abrogated by SIRT1 siRNA. Collectively, LA could attenuate AngII-induced AAA by modulating the miR-181b/SIRT1/HO-1 signaling. LA might be a potential medical therapy for small AAA.

Ruptured hepatic artery aneurysm in a domestic yak

A 19.5-y-old, male domestic yak ( Bos grunniens) with a history of sudden unexpected death was submitted for autopsy. The yak had hemoabdomen, and a large blood clot was attached to the liver and forestomachs. The hepatic artery had a saccular aneurysm with a 1-cm tear. The arterial wall at the site of the rupture was thin, and the luminal surface was roughened with yellow streaks. The arterial wall adjacent to the rupture was thickened, white, firm, and less elastic than normal arterial walls. Cause of death was concluded to be acute exsanguination. Similar cases with sudden death have been reported in domestic cattle and humans. No risk factors, such as nutritional deficiencies, genetic predisposition, or blunt trauma, were identified in this case, and there was no gross or histologic evidence of generalized vascular disease.

Thermosensitive Hydrogel Containing Doxycycline Exerts Inhibitory Effects on Abdominal Aortic Aneurysm Induced By Pancreatic Elastase in Mice

Doxycycline (DOX) is reported to exert therapeutic effects against abdominal aortic aneurysm (AAA), a severe degenerative disease. In this study, a DOX hydrogel formulation of DOX/PECT^gel is studied, and its phase transition behavior and in vitro release profiles are explored. In addition, the anti-AAA effects and bioavailability of DOX/PECT^gel are evaluated in an elastase induced AAA mouse model. The results show that the phase transition temperature of 30% poly(e-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone) (PECT) solution is above 34 °C. In vitro release profiles of DOX/PECT^gel indicate a fast release of DOX at the first two days, followed by a slow and sustained release for 14 d. In vivo single-dose single subcutaneous injection of DOX/PECT^gel containing 8.4 or 4.2 mg mL^-1 DOX presents comparatively preventive effects on AAA, compared to intraperitoneal injections of DOX alone at a dose of 15 mg kg^-1 for seven injections, while DOX bioavailability of the DOX/PECT^gel treated groups is 1.39 times or 1.19 times of the DOX alone treated group, respectively.

Abdominal aortic aneurysm-an independent disease to atherosclerosis?

Atherosclerosis and abdominal aortic aneurysms (AAAs) are multifactorial and polygenic diseases with known environmental and genetic risk factors that contribute toward disease development. Atherosclerosis represents an important independent risk factor for AAA, as people with AAA often have atherosclerosis. Studies have shown that comorbidity is usually between ~25% and 55%, but it is still not fully known whether this association is causal or a result of common shared risk profiles. Most recent epidemiological, clinical, and biological evidence suggests that the two pathologies are more distinct than traditionally thought. For instance diabetes mellitus, hypercholesterolemia, and obesity are high risk for atherosclerosis development but are not as pronounced in AAA, whereas smoking, gender, and ethnicity are particularly high risk for AAA but less so for atherosclerosis. In addition, genetic and epigenetic studies have identified independent risk loci involved in AAA susceptibility that are not associated with other cardiovascular diseases, and research on important common cardiovascular biomarkers has illustrated discrepancies in those with AAA.

Inhibition of early AAA formation by aortic intraluminal pentagalloyl glucose (PGG) infusion in a novel porcine AAA model

Background

The vast majority of abdominal aortic aneurysms found in screening programs are small, and as no effective treatment exits, many will expand until surgery is indicated. Therefore, it remains intriguing to develop a safe and low cost treatment of these small aneurysms, that is able to prevent or delay their expansion.

In this study, we investigated whether intraluminal delivered pentagalloyl glucose (PGG) can impair the early AAA development in a porcine model.

Methods

The infrarenal aorta was exposed in thirty pigs. Twenty underwent an elastase based AAA inducing procedure and ten of these received an additional intraluminal PGG infusion. The final 10 were sham operated and served as controls.

Results

All pigs who only had an elastase infusion developed macroscopically expanding AAAs. In pigs treated with an additional PGG infusion the growth rate of the AP-diameter rapidly returned to physiological values as seen in the control group. In the elastase group, histology revealed more or less complete resolution of the elastic lamellae in the media while they were more abundant, coherent and structurally organized in the PGG group. The control group displayed normal physiological growth and histology.

Conclusion

In our model, intraluminal delivered PGG is able to penetrate the aortic wall from the inside and impair the early AAA development by stabilizing the elastic lamellae and preserving their integrity. The principle holds a high clinical potential if it can be translated to human conditions, since it, if so, potentially could represent a new drug for stabilizing small abdominal aneurysms.

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Pentagalloyl glucose impairs the early AAA development in a porcine model.

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Pentagalloyl glucose stabilizes arterial elastic lamellae and preserves their integrity.

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Pentagalloyl glucose can penetrate the arterial wall in large AAA prone arteries from the inside.

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Pentagalloyl glucose, a potential new drug for stabilizing small abdominal aneurysms.

Inhibition of development of experimental abdominal aortic aneurysm by c-jun N-terminal protein kinase inhibitor combined with lysyl oxidase gene modified smooth muscle progenitor cells

Chronic inflammation, imbalance between the extracellular matrix synthesis and degradation, and loss of vascular smooth muscle cells (SMCs) contribute to the development of abdominal aortic aneurysm (AAA). The purpose of this study was to investigate the effect of the therapy with periaortic incubation of c-Jun N-terminal protein kinase inhibitor SP600125 infused from an osmotic pump and subadventitial injection of lysyl oxidase (LOX) gene modified autologous smooth muscle progenitor cells (SPCs) on treatment of AAA in a rabbit model. Obvious dilation of the abdominal aorta in the control group was caused by periaortic incubation of calcium chloride and elastase. But the progression of aortic dilation was significantly decreased after the treatment with SP600125 and LOX gene modified SPCs compared to the treatment with phosphate-buffered saline. This therapy could inhibit matrix metalloproteinases expression, enhance elastin synthesis, improve preservation of elastic laminar integrity, benefit SPCs survival and restore SMCs population. It seemed that this method might provide a novel therapeutic strategy to treat AAA.

Systemic oxidant/antioxidant balance in human abdominal aortic aneurysm

The aim of this study was to evaluate the oxidant-antioxidant balance in patients with abdominal aortic aneurysms (AAA). Forty-two consecutive patients with AAA and 46 control subjects were included. Total oxidant status (TOS) and total antioxidant status (TAS) levels were measured and the oxidative stress index (OSI) value determined. Serum TOS and OSI values in patients with AAA were higher than those in the controls (p<0.001, p<0.001, respectively). There was a positive correlation between abdominal aortic diameters, serum TOS levels (r=0.592, p<0.001) and OSI values (r=0.598, p<0.001). A cut-off value of 17.68 µmol H2O2 equivalent/L for TOS was associated with 86% sensitivity and 83% specificity and a cut-off value of 1.77 for OSI was associated with 86% sensitivity and 81% specificity for predicting AAA. Systemic oxidative imbalance develops in patients with AAA, particularly as a result of an increase in TOS.

Male gender and smoking are related to single, but not to multiple, human aortic aneurysms

There is scanty information concerning multiple aortic aneurysms. Thus, we verified if clinical or pathological characteristics are different in patients with multiple (two or more) aortic aneurysms in comparison with those with only one.

MATERIAL AND METHODS

We selected at the necropsy files of the Heart Institute, São Paulo University School of Medicine, the last 100 cases with aortic aneurysms, comparing between the two groups: sex, age, presence of systemic arterial hypertension, diabetes, dyslipedemia, history of smoking habit, cause of the aneurysm, cause of death, and if the diagnosis was reached during life. Age was analysed by Mann-Whitney test, and the other variables by chi-square or Fisher's exact test.

RESULTS

Multiple aneurysms corresponded to 14% of cases. The proportion of women among patients with multiple aneurysms was higher than among those with single aneurysm (64.3% versus 20.9%, P<.01), even if only cases with atherosclerosis were taken into consideration (women among multiple-6/10, 60.0%; among single-14/70, 20.0%; P=.01). Smoking was less reported in cases with multiple (4/14, 28.6%) than with single aneurysm (53/86, 61.6%; P=.04); considering cases with atherosclerosis, such difference decreases (40.0% of multiple versus 68.6% of single, P=.09).

CONCLUSION

although atherosclerosis is present in most cases of both single and multiple aortic aneurysms, male gender and smoking, considered highly influential in such lesions, are less frequent in patients with multiple than in patients with single aneurysms. Thus mechanisms underlying multiple aortic aneurysms are probably different from those related to single, more common aneurysms.

Thrombospondin-1 (TSP1) contributes to the development of vascular inflammation by regulating monocytic cell motility in mouse models of abdominal aortic aneurysm

RATIONALE

Histological examination of abdominal aortic aneurysm (AAA) tissues demonstrates extracellular matrix destruction and infiltration of inflammatory cells. Previous work with mouse models of AAA has shown that anti-inflammatory strategies can effectively attenuate aneurysm formation. Thrombospondin-1 is a matricellular protein involved in the maintenance of vascular structure and homeostasis through the regulation of biological functions, such as cell proliferation, apoptosis, and adhesion. Expression levels of thrombospondin-1 correlate with vascular disease conditions.

OBJECTIVE

To use thrombospondin-1-deficient (Thbs1(-/-)) mice to test the hypothesis that thrombospondin-1 contributes to pathogenesis of AAAs.

METHODS AND RESULTS

Mouse experimental AAA was induced through perivascular treatment with calcium phosphate, intraluminal perfusion with porcine elastase, or systemic administration of angiotensin II. Induction of AAA increased thrombospondin-1 expression in aortas of C57BL/6 or apoE-/- mice. Compared with Thbs1(+/+) mice, Thbs1(-/-) mice developed significantly smaller aortic expansion when subjected to AAA inductions, which was associated with diminished infiltration of macrophages. Thbs1(-/-) monocytic cells had reduced adhesion and migratory capacity in vitro compared with wild-type counterparts. Adoptive transfer of Thbs1(+/+) monocytic cells or bone marrow reconstitution rescued aneurysm development in Thbs1(-/-) mice.

CONCLUSIONS

Thrombospondin-1 expression plays a significant role in regulation of migration and adhesion of mononuclear cells, contributing to vascular inflammation during AAA development.

Antagonism of toll-like receptor 2 attenuates the formation and progression of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is an inflammatory vascular disorder with high mortality. Accumulating evidence shows that toll-like receptor 2 (TLR2) plays a critical role in the regulation of wound-repairing process after tissue injury. We wondered if TLR2 signaling contributed to the pathogenesis of AAA and that targeting TLR2 would attenuate AAA development and progression. In this study, enhanced expression of TLR2 and its ligands were observed in human AAA tissue. Neutralization of TLR2 protected against AAA development and caused established AAA to regress in mouse models of AAA. In addition, TLR2-deficient mice also failed to develop AAA. The prophylactic and therapeutic effects of blocking TLR2 were accompanied by a significant resolution of inflammation and vascular remodeling, as indicated by the decreased expression or activity of MMP-2/9, α-SMA, inflammatory cytokines, and transcription factors NF-κB, AP-1 and STAT1/3 in AAA tissue. Mechanistically, blocking TLR2 decreased the expression and interaction of TLR2 and several endogenous ligands, which diminished chronic inflammation and vascular remodeling in the vascular tissue of AAA. Our studies indicate that the interactions between TLR2 and its endogenous ligands contribute to the pathogenesis of AAA and that targeting TLR2 offers great potential toward the development of therapeutic agents against AAA.

Analysis of multiple genetic polymorphisms in aggressive-growing and slow-growing abdominal aortic aneurysms

BACKGROUND

The natural history of abdominal aortic aneurysms (AAAs) suggests that some remain slow in growth rate whereas many develop a more accelerated growth rate and reach a threshold for intervention. We hypothesized that different mechanisms are responsible for AAAs that remain slow growing and never become actionable vs the aggressive AAAs that require intervention and may be reflected by distinct associations with genetic polymorphisms.

METHODS

AAA growth rate was determined from serial imaging data in 168 control and 141 AAA patients with ultrasound or computed tomography imaging studies covering ∼5 years. Genetic polymorphisms all previously reported as showing a significant correlation with AAA with functional effects on the expression or function were determined by analysis of the genomic DNA, including angiotensin 1 receptor (rs5186), interleukin-10 (IL-10; rs1800896), methyl-tetrahydrofolate reductase (rs1801133), low-density lipoprotein receptor-related protein 1 (LRP1; rs1466535), angiotensin-converting enzyme (rs1799752), and several matrix metalloproteinase 9 (MMP-9) single nucleotide polymorphisms.

RESULTS

Of the AAA patients, 81 were classified as slow AAA growth rate (<3.25 mm/y) vs 60 with aggressive AAA growth rate (>3.25 mm/y, those presenting with a rupture, or those with maximal aortic diameter >5.5 cm [male] or >5.0 cm [female]). Discriminating confounds between the groups were identified by logistic regression. Analyses identified MMP-9 p-2502 single nucleotide polymorphism (odds ratio [OR], 0.54; 95% confidence interval [CI], 0.31-0.94; P = .029) as a significant confound discriminating between control vs slow-growth AAA, MMP-9 D165N (OR, 0.49; 95% CI, 0.26-0.95; P = .035) and LRP1 (OR, 4.99; 95% CI, 1.13-22.1; P = .034) between control vs aggressive-growth AAAs, and methyltetrahydrofolate reductase (OR, 2.99; 95% CI, 1.01-8.86; P = .048), MMP-9 p-2502 (OR, 2.19; 95% CI, 1.05-4.58; P = .037), and LRP1 (OR, 4.96; 95% CI, 1.03-23.9; P = .046) as the statistically significant confounds distinguishing slow-growth AAAs vs aggressive-growth AAAs.

CONCLUSIONS

Logistic regression identified different genetic confounds for the slow-growth and aggressive-growth AAAs, indicating a potential for different genetic influences on AAAs of distinct aggressiveness. Future logistic regression studies investigating for potential genetic or clinical confounds for this disease should take into account the growth rate and size of the AAA to better identify confounds likely to be associated with aggressive AAAs likely to require intervention.

Risk factors in abdominal aortic aneurysm and in Polish population aortoiliac occlusive disease and differences between them [corrected]

Abdominal aortic aneurysm (AAA) and aortoiliac occlusive disease (AIOD) are multifactorial vascular disorders caused by complex genetic and environmental factors. The purpose of this study was to define risk factors of AAA and AIOD in the Polish population and indicate differences between diseases.

Development of abdominal aortic aneurysm is decreased in mice with plasma phospholipid transfer protein deficiency

Plasma phospholipid transfer protein (PLTP) increases the circulating levels of proatherogenic lipoproteins, accelerates blood coagulation, and modulates inflammation. The role of PLTP in the development of abdominal aortic aneurysm (AAA) was investigated by using either a combination of mechanical and elastase injury at one site of mouse aorta (elastase model) or continuous infusion of angiotensin II in hyperlipidemic ApoE-knockout mice (Ang II model). With the elastase model, complete PLTP deficiency was associated with a significantly lower incidence and a lesser degree of AAA expansion. With the Ang II model, findings were consistent with those in the elastase model, with a lower severity grade in PLTP-deficient mice, an intermediate phenotype in PLTP-deficient heterozygotes, and a blunted effect of the PLTP-deficient trait when restricted to bone marrow-derived immune cells. The protective effect of whole-body PLTP deficiency in AAA was illustrated further by a lesser degree of adventitia expansion, reduced elastin degradation, fewer recruited macrophages, and less smooth muscle cell depletion in PLTP-deficient than in wild-type mice, as evident from comparative microscopic analysis of aorta sections. Finally, cumulative evidence supports the association of PLTP deficiency with reduced expression and activity levels of matrix metalloproteinases, known to degrade elastin and collagen. We conclude that PLTP can play a significant role in the pathophysiology of AAA.

Murine ultrasound imaging for circumferential strain analyses in the angiotensin II abdominal aortic aneurysm model

OBJECTIVE

The underlying causes of abdominal aortic aneurysms (AAAs) remain obscure, although research tools such as the angiotensin II (Ang II) apolipoprotein E-deficient (apoE(-/-)) mouse model have aided investigations. Longitudinal imaging and determination of biomechanical forces in this small-scale model have been difficult. We hypothesized that high-frequency ultrasound biomicroscopy combined with speckle-tracking analytical strategies can be used to define the role of circumferential mechanical strain in AAA formation in the Ang II/apoE(-/-) mouse model of AAAs. We simultaneously examined dietary perturbations that might impact the biomechanical properties of the aortic wall, hypothesizing that the generalized inflammatory phenotype associated with diet-induced obesity would be associated with accelerated loss of circumferential strain and aneurysmal aortic degeneration.

METHODS

Receiving either a 60 kcal% fat Western diet or standard 10 kcal% fat normal chow, Ang II-treated apoE(-/-) mice (n = 34) underwent sequential aortic duplex ultrasound scan imaging (Vevo 2100 System; VisualSonics, Toronto, Ontario, Canada) of their entire aorta. Circumferential strains were calculated using speckle-tracking algorithms and a custom MatLab analysis.

RESULTS

Decreased strains in all aortic locations after just 3 days of Ang II treatment were observed, and this effect progressed during the 4-week observation period. Anatomic segments along the aorta impacted wall strain (baseline highest in ascending aorta; P < .05), whereas diet did not. At 2 and 4 weeks, there was the largest progressive decrease in strain in the paravisceral/supraceliac aorta (P < .05), which was the segment most likely to be involved in aneurysm formation in this model.

CONCLUSIONS

In the Ang II/apoE(-/-) aneurysm model, the aorta significantly stiffens (with decreased strain) shortly after Ang II infusion, and this progressively continues through the next 4 weeks. High-fat feeding did not have an impact on wall strain. Delineation of biomechanical factors and AAA morphology via duplex scan and speckle-tracking algorithms in mouse models should accelerate insights into human AAAs.

Abdominal Aortic Aneurysms

Abdominal aortic aneurysms represent both an individual risk of mortality and a socioeconomic burden for health care systems worldwide, but screening is not performed in all countries. Here, the authors summarize the pros and cons of screening to reduce abdominal aortic aneurysm–related mortality.

In Vivo Study on the Expression Pattern of Resistin in Patients With Abdominal Aortic Aneurysm

Objective: To study the expression pattern of resistin in abdominal aortic aneurysms and to correlate its plasma levels to aneurysm size and statin therapy. Patients and Methods: From 25 patients on regular and 38 patients without statin therapy tissue specimen and plasma samples were obtained for analysis. Results: Demographic data, past medical history, and body mass index showed no significant differences between the statin and no statin group. Immunohistochemistry showed positive stainings for resistin in all sections and in part colocalization to CD 68 positive cells. Patients with large aneurysms showed significant correlation of C-reactive protein (CRP) and interleukin 10 (IL-10) levels; patients on statin medication had significantly lower plasma levels of resistin and CRP. Conclusion: In contrast to IL-10 and CRP plasma levels of resistin are not correlated to aneurysm diameter; yet statin therapy results in decrease of resistin and CRP, suggesting an anti-inflammatory action in patients with abdominal aortic aneurysms (AAAs).

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

[Abdominal aortic aneurysm]

Abdominal aortic aneurysms (AAA) confer a substantial healthcare burden in the Western world. Surgical or endovascular therapy is indicated in patients with a maximum diameter exceeding 5.5 cm. Patients with smaller AAA must undergo a specific ultrasound surveillance program aimed at avoiding exposure to an increased risk of rupture once their AAA exceeds the threshold for active treatment. Based on improved understanding of the pathophysiology of AAA, recent years provided initial insight into potential medical treatment options. The presence of AAA is currently regarded a coronary artery disease risk equivalent. ACE inhibitors, statins and JNK-inhibitors were shown to have the potential to slow down progression. Since cigarette smoking is the main risk factor for both the development and progression of AAA, smoking cessation remains a key goal. Further prospective studies will assess the clinical efficacy of various promising drug treatment approaches aimed at slowing disease progression of small AAA and after endovascular therapy.

Endovascular repair of abdominal aortic aneurysms: only a mechanical solution for a biological problem?

Endovascular aneurysm repair has matured significantly over the last 20 years and is becoming increasingly popular as a minimally invasive treatment option for patients with abdominal aortic aneurysms (AAA). Long-term durability of this fascinating treatment, however, is in doubt as continuing aneurysmal degeneration of the aortoiliac graft attachment zones is clearly associated with late adverse sequelae. In recent years, our growing understanding of the physiopathology of AAA formation has facilitated scrutiny of various potential drug treatment concepts. In this article we review the mechanical and biological challenges associated with endovascular treatment of infrarenal AAAs and discuss potential approaches to ongoing aneurysmal degeneration, which hampers long-term outcomes of this minimally invasive therapy.

Effect of statin therapy on serum activity of proteinases and cytokines in patients with abdominal aortic aneurysm

Background and aims:

Metalloproteinases (MMPs) are considered to be key enzymes in the pathogenesis of abdominal aortic aneurysms (AAA), with elevated levels in diseased aorta and in patient sera. Statins seem to exert an inhibitory effect on MMP activity in the aortic wall. No data exist on the effect of statins on serum activity of MMPs and inflammatory cytokines (interleukins, IL).

Methods:

The serum activities of MMP2 and MMP9, osteoprotegerin (OPG), and IL6 and IL10 in 63 patients undergoing elective infrarenal aneurysm repair were measured on the day before surgery. Levels were correlated to statin therapy and aneurysm diameter.

Results:

There was no significant difference between the two groups in the activity of circulating levels of MMP2/9, OPG, and IL6/10 in patients with infrarenal aortic aneurysm. IL6 levels in patients with AAA larger than 6 cm were significantly elevated; differences in serum activities of MMP2/9, OPG, and IL10 were not related to AAA diameter.

Conclusion:

Serum activities of MMP2/9, OPG, and IL6/10 are not correlated to statin therapy; IL6 levels are higher in patients with large aneurysms. Hence the effect of statin therapy in the treatment of aneurismal disease remains to be elucidated.

Apelin prevents aortic aneurysm formation by inhibiting macrophage inflammation

Apelin is a potent inodilator with recently described antiatherogenic properties. We hypothesized that apelin might also attenuate abdominal aortic aneurysm (AAA) formation by limiting disease-related vascular wall inflammation. C57BL/6 mice implanted with osmotic pumps filled with apelin or saline were treated with pancreatic elastase to create infrarenal AAAs. Mice were euthanized for aortic PCR analysis or followed ultrasonographically and then euthanized for histological analysis. The cellular expression of inflammatory cytokines and chemokines in response to apelin was also assessed in cultured macrophages, smooth muscle cells, and fibroblasts. Apelin treatment resulted in diminished AAA formation, with a 47% reduction in maximal cross-sectional area (0.74 vs. 1.39 mm(2), P < 0.03) and a 57% reduction in macrophage infiltrate (113 vs. 261.3 cells/high-power field, P < 0.0001) relative to the saline-treated group. Apelin infusion was also associated with significantly reduced aortic macrophage colony-stimulating factor expression and decreased monocyte chemattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha mean mRNA levels. Apelin stimulation of cultured macrophages significantly reduced MCP-1 and TNF-alpha mRNA levels relative to baseline (2.03- and 1.89-fold reduction, P < 0.03, respectively) but did not affect intimal adhesion molecule expression or medial or adventitial cell cytokine production. Apelin significantly reduces aneurysm formation in the elastase model of human AAA disease. The mechanism appears to be decreased macrophage burden, perhaps related to an apelin-mediated decrease in proinflammatory cytokine and chemokine activation.