Hypoxia Marker Carbonic Anhydrase IX Is Present in Abdominal Aortic Aneurysm Tissue and Plasma

Abdominal aortic aneurysms (AAA) are a significant cause of premature deaths worldwide. Since there is no specific treatment for reducing AAA progression, it is crucial to understand the pathogenesis leading to aneurysm wall weakening/remodeling and identify new proteins involved in this process which could subsequently serve as novel therapeutic targets. In this study, we analyzed the presence of the hypoxia-related proteins carbonic anhydrase IX (CA IX), hypoxia-inducible factor 1α (HIF-1α), and AKT as the key molecule in the phosphoinositide-3-kinase pathway in the AAA wall. Additionally, we used a blood-based assay to examine soluble CA IX (s-CA IX) levels in the plasma of AAA patients. Using western blotting, we detected CA IX protein in 12 out of 15 AAA tissue samples. Immunohistochemistry staining proved CA IX expression in the media of the aneurysmal wall. Evaluation of phosphorylated (p-AKT) and total AKT showed elevated levels of both forms in AAA compared to normal aorta. Using ELISA, we determined the concentration of s-CA IX >20 pg/mL in 13 out of 15 AAA patients. Results obtained from in silico analysis of CA9 and aneurysm-associated genes suggest a role for CA IX in aneurysmal wall remodeling. Our results prove the presence of hypoxia-related CA IX in AAA tissues and indicate a possible role of CA IX in hypoxia-associated cardiovascular diseases.

Fluid-structure interaction simulation of tissue degradation and its effects on intra-aneurysm hemodynamics

Tissue degradation plays a crucial role in vascular diseases such as atherosclerosis and aneurysms. We present a novel finite element method-based approach to model the microscopic degradation of an aneurysmal wall due to its interaction with blood flow. The model is applied to study the combined effects of pulsatile flow and tissue degradation on the deformation and intra-aneurysm hemodynamics. Our computational analysis reveals that tissue degradation leads to a weakening of the aneurysmal wall, which manifests itself in a larger deformation and a smaller von Mises stress. Moreover, simulation results for different heart rates, blood pressures and aneurysm geometries indicate consistently that, upon tissue degradation, wall shear stress increases near the flow-impingement region and decreases away from it. These findings are discussed in the context of recent reports regarding the role of both high and low wall shear stress for the progression and rupture of aneurysms.

Neutrophil to Lymphocyte Ratio Reflects the Proteolytic Activity of the Abdominal Aortic Aneurysm Wall

Background: This study aims to evaluate the local proteolytic activity from the level of Abdominal Aortic Aneurysm (AAA) wall and correlate the obtained values with the preoperative values of NLRs (Neutrophil-Lymphocyte Ratio), evaluating a possible association between the two variables and, implicitly, between the local proteolysis process and the systemic inflammatory response of those patients diagnosed with AAA. Methods: The current study is monocentric, observational, and prospective, taking place at the Department of Cardiovascular Surgery, Cluj-Napoca, Romania. Patients undergoing elective or emergency classical surgery for unruptured AAA or ruptured AAA were included in the study. During classical surgery, samples from the infrarenal aortic aneurysmal wall were collected in a standardized manner, from the central part of the anterior wall from uAAA and rAAA and were analyzed by gel zymography. Results: The concentration of MMP2 was similar in the ruptured/non-ruptured group, without any statistical significance. In the MMP-9 case, we obtained a mean of 821.35 U arb/µg at the level of unruptured aneurysmal wall and 1411.57 U arb/µg at the level of the ruptured aneurysmal wall. According to the ANOVA test, there is a significant difference between the two categories of aneurysms. The same correlation was observed regarding both the zymogen category, pro-MMP-2, as well as pro-MMP-9: they expressed significant higher quantities of inactive enzymes in rAAA. We splitted the study population into two categories: patients who presented preoperative NLR values < 5 and > 5. MMP-2 collagenase levels did not register statistical differences between the two groups, p = 0.3236. High levels of MMP-9 are positively associated with increased values of NLR, the NLR<5 group had an MMP-9 mean of 902.41(473.71) U arb/µg, statistically lower than the MMP-9 mean indicated in the NLR>5 group, 1474(521.21) U arb/µg. Similarly, MMP-2 and MMP-9 zymogens were found in statistically higher quantities (p < 0.05) in the NLR>5 group of patients. Conclusions: This is the first study that analyzes a possible correlation between the local proteolytic activity at the site of the dilated aneurysmal aortic wall and circulating levels of NLR. Following the results obtained, we conclude that the group of patients presenting with NLR>5 preoperatively, as in the rAAA group, significantly greater levels of MMP-9 and inactive proenzymes were identified. Local metalloproteinase MM9 activity is proportional to the systemic inflammatory activity. Concomitantly, we hypothesize that the increased sensitivity of NLR as a prognostic marker in AAA pathology, which is ensured and confirmed by its strong association with local proteolytic activity, directly implied in the evolution of the disease.

Oxidative Stress and Inflammatory Markers in Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is increasing due to aging of the population and is a major cause of death among the elderly. Ultrasound screening programs are useful in early diagnosis, but aneurysm size is not always a good predictor of rupture. Our aim was to analyze the value of circulating molecules related to oxidative stress and inflammation as new biomarkers to assist the management of AAA. The markers were quantified by ELISA, and their expression in the aneurysmal wall was studied by real-time PCR and by immunostaining. Correlation analysis of the studied markers with aneurysm diameter and peak wall stress (PWS), obtained by finite element analysis, and multivariate regression analysis to assess potential confounding factors were performed. Our study shows an extensive inflammatory infiltration in the aneurysmal wall, mainly composed by T-cells, macrophages and B-cells and altered levels of reactive oxygen species (ROS), IgM, IgG, CD38, GDF15, S100A4 and CD36 in plasma and in the aneurysmal tissue of AAA patients compared with controls. Circulating levels of IgG, CD38 and GDF15 positively correlated with abdominal aortic diameter, and CD38 was correlated with PWS. Our data show that altered levels of IgG, CD38 and GDF15 have potential diagnostic value in the assessment of AAA.

Increased contrast enhancement of the parent vessel of unruptured intracranial aneurysms in 7T MR imaging

BackgroundInflammation of the arterial wall may lead to aneurysm formation. The presence of aneurysm enhancement on high-resolution vessel wall imaging (HR-VWI) is a marker of wall inflammation and instability. We aim to determine if there is any association between increased contrast enhancement in the aneurysmal wall and its parent artery.MethodsPatients with unruptured intracranial aneurysms (UIAs) prospectively underwent 7T HR-VWI. Regions of interest were selected manually and with a semi-automated protocol based on gradient algorithms of intensity patterns. Mean signal intensities in pre- and post-contrast T1-weighted sequences were adjusted to the enhancement of the pituitary stalk and then subtracted to objectively determine: circumferential aneurysmal wall enhancement (CAWE); parent vessel enhancement (PVE); and reference vessel enhancement (RVE). PVE was assessed over regions located 3- and 5 mm from the aneurysm’s neck. RVE was assessed in arteries located in a different vascular territory.ResultsTwenty-five UIAs were analyzed. There was a significant moderate correlation between CAWE and 5 mm PVE (Pearson R=0.52, P=0.008), whereas no correlation was found between CAWE and RVE (Pearson R=0.20, P=0.33). A stronger correlation was found between CAWE and 3 mm PVE (Pearson R=0.78, P<0.001). Intra-class correlation analysis demonstrated good reliability between measurements obtained using semi-automated and manual segmentation (ICC coefficient=0.790, 95% CI 0.58 to 0.90).ConclusionParent arteries exhibit higher contrast enhancement in regions closer to the aneurysm’s neck, especially in aneurysms≥7 mm. A localized inflammatory/vasculopathic process in the wall of the parent artery may lead to aneurysm formation and growth.

Decreased contrast enhancement on high-resolution vessel wall imaging of unruptured intracranial aneurysms in patients taking aspirin

OBJECTIVEInflammation plays an integral role in the formation, growth, and progression to rupture of unruptured intracranial aneurysms (UIAs). Animal and human studies have suggested that, due to its antiinflammatory effect, aspirin (ASA) may decrease the risks of growth and rupture of UIAs. High-resolution vessel wall imaging (HR-VWI) has emerged as a noninvasive method to assess vessel wall inflammation and UIA instability. To the authors’ knowledge, to date no studies have found a significant correlation between patient use of ASA and contrast enhancement of UIAs on HR-VWI.METHODSThe University of Iowa HR-VWI Project database was analyzed. This database is a compilation of data on patients with UIAs who prospectively underwent HR-VWI on a 3T Siemens MRI scanner. The presence of aneurysmal wall enhancement was objectively defined using the aneurysm-to–pituitary stalk contrast ratio (CRstalk). This ratio was calculated by measuring the maximal signal intensity in the aneurysmal wall and the pituitary stalk on postcontrast T1-weighted images. Data on aneurysm size, morphology, and location and patient demographics and comorbidities were collected. Use of ASA was defined as daily intake of ≥ 81 mg during the previous 6 months or longer. Univariate and multivariate logistic regression analyses were performed to determine factors independently associated with increased contrast enhancement of UIAs on HR-VWI.RESULTSIn total, 74 patients harboring 96 UIAs were included in the study. The mean patient age was 64.7 ± 12.4 years, and 60 patients (81%) were women. Multivariate analysis showed that age (OR 1.12, 95% CI 1.05–1.19), aneurysm size ≥ 7 mm (OR 21.3, 95% CI 4.88–92.8), and location in the anterior communicating, posterior communicating, and basilar arteries (OR 10.7, 95% CI 2.45–46.5) were significantly associated with increased wall enhancement on HR-VWI. On the other hand, use of ASA was significantly associated with decreased aneurysmal wall enhancement on HR-VWI (OR 0.22, 95% CI 0.06–0.83, p = 0.026).CONCLUSIONSThe study results establish a correlation between use of ASA daily for ≥ 6 months and significant decreases in wall enhancement of UIAs on HR-VWI. The findings also demonstrate that detection of wall enhancement using HR-MRI may be a valuable noninvasive method for assessing aneurysmal wall inflammation and UIA instability.