Aortic Aneurysm: Etiopathogenesis and Clinicopathologic Correlations

Saccular and Fusiform Abdominal Aortic Aneurysms Treated With Endovascular Repair Differ in Presentation and Treatment Threshold: Analyses Using a National Clinical Database in Japan

BACKGROUND

Saccular abdominal aortic aneurysms (AAAs) are considered to be at higher risk of rupture than fusiform AAAs, but not much is known about the extent of this risk. Therefore, this study aimed to compare the rupture presentation between fusiform and saccular AAAs.

METHODS AND RESULTS

This is a retrospective cohort study on 27 290 patients who underwent primary endovascular repair for a degenerative AAA between 2016 and 2019, and who were registered in the National Clinical Database in Japan. At operation for nonruptured case, the aneurysm diameter was significantly smaller in saccular AAAs than in fusiform AAAs (median, 44.0 versus 51.0 mm; P<0.001). Similarly, aneurysm diameter at rupture was significantly smaller in saccular AAAs than in fusiform AAAs (median, 55.6 versus 68.0 mm; P<0.001). The likelihood of repair for rupture was significantly higher in saccular AAAs than in fusiform AAAs in the 40- to 54-mm diameter range, in which saccular morphology was found to be an independent risk factor for rupture against fusiform morphology by adjusting for sex and aneurysm diameter (odds ratio, 2.54 [95% CI, 1.75-3.69]). In addition, receiver-operating characteristic curve analysis revealed that the cutoff diameter to predict rupture was smaller in saccular AAAs than in fusiform AAAs (50.5 and 59.5 mm, respectively) based on the Youden index.

CONCLUSIONS

Saccular AAAs presented at smaller diameters than fusiform AAAs in patients with ruptured AAAs treated with endovascular aortic repair, which supports the idea that saccular AAAs should be treated at smaller diameters.

Biomechanical study on the effect of atherosclerosis on the vulnerability of thoracic aorta, and it's role in the development of traumatic aorta injury

Traumatic aorta injury (TAI) is the second most common traumatic cause of death preceded only by head injuries, being responsible for 5% to 30% of all mortalities in high-speed deceleration injuries. Multiple external factors might play a role such as impact speed, impact direction, occupant location, and presence or lack of restraining safety mechanism. Apart from these external factors, also human biological factors can influence its development. Based on the data of scientific literature, age clearly plays a role in suffering TAI, but the role of atherosclerosis-as a disease affecting the structure of the aorta-is unknown. Biomechanical properties of tissue samples of 104 aorta specimens removed during the autopsy from the posterior (Group 'A') and lateral wall (Group 'B') of descending aorta were analyzed. Specimens were examined by a Zwick/Roell Z5.0 biaxial tester. The Young's modulus (E (MPa)) was calculated using a linear regression procedure where the base of the elongation was the parallel length of the sample, the achieved maximal force (Fmax (N)), the elongation at the time of Fmax (Lmax (mm)), the force at the beginning of rupture (Fbreak (N)), the elongation at the time of Fbreak (Lbreak (mm)) were registered. Specimens were categorized based on macroscopic and microscopic appearance. In the posterior (A) samples the difference between Lbreak (p<0.001) and Lmax (p<0.001) was significant between the macroscopic group. Lbreak (p = 0.009) and Lmax (p = 0.003) showed similar pattern in the lateral (B) samples. Comparing the histological groups by the measured parameters (Fmax, Lmax, Fbreak, Lbreak) showed a significant difference in the means (p<0.001, p = 0.003, p<0.001 respectively). The study demonstrated that atherosclerosis decreases the resistance of the aorta. The rupture occurs at lower force (Fmax and Fbreak), and at shorter elongation (Lmax and Lbreak) in case of the presence of atherosclerosis. This effect is most substantial if calcification is present: the resistance of aorta affected by calcification is only two-thirds on average compared to aorta affected by the early phase of atherosclerosis. This phenomenon can be clearly explained by the weakening structure of the tunica intima.

Retrospective observational study evaluating zinc plasma level in patients undergoing thoracoabdominal aortic aneurysm repair and its correlation with outcome

Thoracoabdominal aortic aneurysm (TAAA) repair is related to a relevant morbidity and in-hospital mortality rate. In this retrospective observational single-center study including serum zinc levels of 33 patients we investigated the relationship between zinc and patients' outcome following TAAA repair. Six patients died during the hospital stay (18%). These patients showed significantly decreased zinc levels before the intervention (zinc levels before intervention: 60.09 µg/dl [survivors] vs. 45.92 µg/dl [non-survivors]). The post-interventional intensive care SOFA-score (Sepsis-related organ failure assessment) (at day 2) as well as the SAPS (Simplified Acute Physiology Score) (at day 2) showed higher score points in case of low pre-interventional zinc levels. No significant correlation between patient comorbidities and zinc level before intervention, except for peripheral arterial disease (PAD), which was significantly correlated to reduced baseline zinc levels, was observed. Septic shock, pneumonia and urinary tract infections were not associated to reduced zinc levels preoperatively as well as during therapy. Patients with adverse outcome after TAAA repair showed reduced pre-interventional zinc levels. We speculate that decreased zinc levels before intervention may be related to a poorer outcome because of poorer physical status as well as negatively altered perioperative inflammatory response.

LncRNA Sox2ot modulates the progression of thoracic aortic aneurysm by regulating miR-330-5p/Myh11

Thoracic aortic aneurysm (TAA) has been causing the death of elder people. Myosin heavy chain 11 (Myh11) has been reported associated with aortic aneurysm, but there is no specific study on its function on TAA. Here we aimed to explore the function of Myh11 on mouse aortic smooth muscle cells (SMCs) for studying the inner mechanism of TAA. H₂O₂ treatment was implemented on mouse aortic SMCs for detecting cell apoptosis. Meanwhile, functional assays were conducted to verify the function of Myh11 on mouse aortic SMCs. Also, pull-down assay, RIP assay were implemented to identify the potential RNAs for study. Quantitative real-time polymerase chain reaction (qRT-PCR) and luciferase reporter assay were implemented to identify the expression and binding relationships of RNAs. Myh11 expression was increased by treatment of H₂O₂. Myh11 could decrease proliferation and enhance apoptosis of mouse aortic SMCs. At the same time, mmu-miR-330-5p could bind to Myh11 and Sox2ot, forming a competing endogenous RNA (ceRNA) pathway to regulate the proliferation and apoptosis of mouse aortic SMCs. Moreover, both Sox2ot and Myh11 were proved to be up-regulated whereas miR-330-5p down-regulated in Fbn1^C1039G/+ mice, the in vivo model of TAA. In a word, long noncoding RNA (lncRNA) Sox2ot modulates the progression of TAA by regulating miR-330-5p/Myh11 axis.

TMT-Based Quantitative Proteomic Analysis Identification of Integrin Alpha 3 and Integrin Alpha 5 as Novel Biomarkers in Pathogenesis of Acute Aortic Dissection

Background

Acute aortic dissection (AAD) is a devastating cardiovascular disease with a high rate of disability and mortality. This disease often rapidly progresses to fatal multiple organ hypoperfusion, and the incidence has been increasing in recent years. However, the molecular mechanisms have yet to be clarified. This study is aimed at identifying the differential abundance proteins (DAPs) of aortic arch tissues in patients with AAD by proteomics and select possible proteins involved in AAD pathogenesis.

Methods

The fresh aortic arch tissues obtained from 5 AAD patients and 1 healthy donor were analyzed by amine-reactive tandem mass tag (TMT) labelling and mass spectrometry; then, the pathological sections of another 10 healthy donors and 20 AAD patients were chosen to verify the proteomic results by immunohistochemistry.

Results

Of 809 proteins identified by proteomic analysis, 132 differential abundance proteins (DAPs) were screened, of which 100 proteins were significantly downregulated while 32 upregulated. Among 100 downregulated proteins, two proteins with known function, integrin alpha 3 (ITGA-3) and ITGA-5, were selected as target proteins involved in AAD pathogenesis. Two target DAPs were verified by immunohistochemisty, and the results showed that the integrated option density (IOD) of ITGA-3 and ITGA-5 in AAD patients was significantly lower than that in healthy donors, which were consistent with the proteomic results (P < 0.001).

Conclusion

ITGA-3 and ITGA-5 represent novel biomarkers for the pathogenesis of AAD and might be a therapeutic target in the future.

Presentation and Management of Rare Saccular Superior Mesenteric Artery Trunk and Branch Aneurysms

Superior mesenteric artery (SMA) aneurysm is caused by degeneration of the visceral arteries. Although a rarely encountered entity, it requires timely management owing to the high mortality rate associated with rupture, particularly when the aneurysm is saccular in nature. As such, urgent treatment is generally indicated. We present five cases of SMA aneurysm arising from the main trunk or branches of the SMA.

Discovery of novel biomarkers for atherosclerotic aortic aneurysm through proteomics-based assessment of disease progression

Since aortic aneurysms (AAs) are mostly asymptomatic, but they have a high mortality rate upon rupture, their detection and progression evaluation are clinically important issues. To discover diagnostic biomarkers for AA, we performed proteome analysis of aortic media from patients with thoracic atherosclerotic AA (TAAA), comparing protein levels between the aneurysm and normal tissue areas. After hierarchical clustering analysis of the proteome analysis data, tissue samples were classified into three groups, regardless of morphological features. This classification was shown to reflect disease progression stage identified by pathological examination. This proteomics-based staging system enabled us to identify more significantly altered proteins than the morphological classification system. In subsequent data analysis, Niemann-Pick disease type C2 protein (NPC2) and insulin-like growth factor-binding protein 7 (IGFBP7) were selected as novel biomarker candidates for AA and were compared with the previously reported biomarker, thrombospondin 1 (THBS1). Blood concentrations of NPC2 and IGFBP7 were significantly increased, while THBS1 levels were decreased in TAAA and abdominal atherosclerotic AA patients. Receiver operating characteristic analysis of AA patients and healthy controls showed that NPC2 and IGFBP7 have higher specificity and sensitivity than THBS1. Thus, NPC2 and IGFBP7 are promising biomarkers for the detection and progression evaluation of AA.

Takayasu Arteritis with Dyslipidemia Increases Risk of Aneurysm

Low-density lipoprotein cholesterol (LDL-C) has been associated with the occurrence of abdominal aortic aneurysm. However, whether LDL-C elevation associated with aneurysms in large vessel vasculitis is unknown. The aim of this study is to investigate the clinical and laboratory features of Takayasu arteritis (TAK) and explore the risk factors that associated with aneurysm in these patients. This retrospective study compared the clinical manifestations, laboratory parameters, and imaging results of 103 TAK patients with or without aneurysms and analyzed the risk factors of aneurysm formation. 20.4% of TAK patients were found to have aneurysms. The LDL-C levels was higher in the aneurysm group than in the non-aneurysm group (2.9 ± 0.9 mmol/l vs. 2.4 ± 0.9 mmol/l, p = 0.032). Elevated serum LDL-C levels increased the risk of aneurysm by 5.8-fold (p = 0.021, odds ratio [OR] = 5.767, 95% confidence interval [CI]: 1.302-25.543), and the cutoff value of level of serum LDL-C was 3.08 mmol/l. The risk of aneurysm was 4.2-fold higher in patients with disease duration >5 years (p = 0.042, OR = 4.237, 95% CI: 1.055-17.023), and 2.9-fold higher when an elevated erythrocyte sedimentation rate was present (p = 0.077, OR = 2.851, 95% CI: 0.891-9.115). In this study, elevated LDL-C levels increased the risk of developing aneurysms in patients with TAK.

Screening key genes for abdominal aortic aneurysm based on gene expression omnibus dataset

Background

Abdominal aortic aneurysm (AAA) is a common cardiovascular system disease with high mortality. The aim of this study was to identify potential genes for diagnosis and therapy in AAA.

Methods

We searched and downloaded mRNA expression data from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) from AAA and normal individuals. Then, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, transcriptional factors (TFs) network and protein-protein interaction (PPI) network were used to explore the function of genes. Additionally, immunohistochemical (IHC) staining was used to validate the expression of identified genes. Finally, the diagnostic value of identified genes was accessed by receiver operating characteristic (ROC) analysis in GEO database.

Results

A total of 1199 DEGs (188 up-regulated and 1011 down-regulated) were identified between AAA and normal individual. KEGG pathway analysis displayed that vascular smooth muscle contraction and pathways in cancer were significantly enriched signal pathway. The top 10 up-regulated and top 10 down-regulated DEGs were used to construct TFs and PPI networks. Some genes with high degrees such as NELL2, CCR7, MGAM, HBB, CSNK2A2, ZBTB16 and FOXO1 were identified to be related to AAA. The consequences of IHC staining showed that CCR7 and PDGFA were up-regulated in tissue samples of AAA. ROC analysis showed that NELL2, CCR7, MGAM, HBB, CSNK2A2, ZBTB16, FOXO1 and PDGFA had the potential diagnostic value for AAA.

Conclusions

The identified genes including NELL2, CCR7, MGAM, HBB, CSNK2A2, ZBTB16, FOXO1 and PDGFA might be involved in the pathology of AAA.

The Obsolete Maximum Diameter Criterion, the Evident Role of Biomechanical (Pressure) Indices, the New Role of Hemodynamic (Flow) Indices, and the Multi-Modal Approach to the Rupture Risk Assessment of Abdominal Aortic Aneurysms

Although the therapeutic management of abdominal aortic aneurysms (AAAs) is currently based on the maximum diameter criterion, this has often proved inaccurate and misleading. Conversely, the biomechanical approach, which takes into account the pressure-induced wall stress exerted at every point throughout the aneurysmal surface, has been proven superior in predicting the rupture risk of AAAs, and its value is being increasingly recognized among physicians. More recently, hemodynamic indices, such as flow-induced wall shear stresses, have been indicated as potentially significant determinants of AAA natural history. Ultimately, a statistical model that takes into account all these factors may be relevant for making a sound prediction of the rupture risk of aneurysms and optimizing the management of these patients.

Genetic Disorders of the Thoracic Aorta and Indications for Surgery

Genetic disorders of the aorta are rare but can lead to life-threatening thoracic aortic aneurysms. Although the genetic causes of many of these connective tissue diseases are well defined, others such as familial thoracic aortic aneurysm and bicuspid aortic valve aortopathy are not. The natural history of genetic thoracic aortic aneurysms is not well understood or predictable, and surgical guidelines for treatment remain imprecise. Future research should strive to provide in-depth and detailed genetic profiling to drive clinical management, including medical and surgical therapies.