Abstract Abdominal Aortic Aneurysm Research Articles

Inhibition of microRNA-33b specifically ameliorates abdominal aortic aneurysm formation via suppression of inflammatory pathways

Abdominal aortic aneurysm (AAA) is a lethal disease, but no beneficial therapeutic agents have been established to date. Previously, we found that AAA formation is suppressed in microRNA (miR)-33-deficient mice compared with wild-type mice. Mice have only one miR-33, but humans have two miR-33 s, miR-33a and miR-33b. The data so far strongly support that inhibiting miR-33a or miR-33b will be a new strategy to treat AAA. We produced two specific anti-microRNA oligonucleotides (AMOs) that may inhibit miR-33a and miR-33b, respectively. In vitro studies showed that the AMO against miR-33b was more effective; therefore, we examined the in vivo effects of this AMO in a calcium chloride (CaCl2)-induced AAA model in humanized miR-33b knock-in mice. In this model, AAA was clearly improved by application of anti-miR-33b. To further elucidate the mechanism, we evaluated AAA 1 week after CaCl2 administration to examine the effect of anti-miR-33b. Histological examination revealed that the number of MMP-9-positive macrophages and the level of MCP-1 in the aorta of mice treated with anti-miR-33b was significantly reduced, and the serum lipid profile was improved compared with mice treated with control oligonucleotides. These results support that inhibition of miR-33b is effective in the treatment for AAA.

Association between gene polymorphism of inflammatory factors, thrombogenic factors, and stress-related proteins and abdominal aortic aneurysm: A meta-analysis and systematic review.

Abdominal aortic aneurysm (AAA) is a deadly disease in the elderly population. Currently, the association between single nucleotide polymorphisms (SNPs) and the presence of AAAs has become a hot topic and is a concern for many researchers. We performed a document retrieval in PubMed, EMBASE, and the Cochrane Library (to January 2020). A total of 17 case-control reports on SNPs of AAAs and eight SNPs of correlation factors were selected. All essential data, including race, age, country, criteria of AAA diagnosis, method of AAA measurement, method of genotype detection, name of SNPs, minor allele frequency (MAF), Hardy Weinberg equilibrium (HWE) of the control group, and number of cases and control groups were extracted by two reviewers independently. The fixed-effect model and random-effect model were used to calculate the overall odds ratios (ORs) and 95% confidence intervals (CIs). The association between selected SNPs and the presence of AAAs was evaluated under different genetic models (dominant, codominant, recessive, overdominant, and allele models). A total of 17 articles (sample size ranging from to 42-665 AAA cases and 49-2,297 controls) and 23 SNPs of related factors were identified. Eight SNPs were assessed in at least two studies and were selected for further meta-analysis. We found that the A allele of interleukin (IL)-10 (-1082G/A) (OR: 1.35, 95% CI: 1.18-1.54, p < 0.0001) was a risk factor for AAAs under random and fixed-effect models. In addition, partial genetic models of these SNPs were confirmed to be related to the presence of AAA. Subgroup analysis revealed that haptoglobin (HP)-1 was a risk factor for AAAs (OR: 1.30, 95% CI: 1.04-1.63, p = 0.02) in the European population. No association was found between the occurrence of AAA and the other SNPs. In our current meta-analysis, we speculated that the genotype distribution of IL-10 (-1082G/A) may be associated with the emergence of AAA.

MiR-143 Mediates the TLR2/NF-κB Pathway to Attenuate AngII-induced Damage to VSMCs

Abdominal aortic aneurysm (AAA) is a perilous vascular disease with inflammatory response as its main feature. It is known that the expression of miR-143 is down-regulated in the human aortic aneurysm. In this study, we investigated the effect of miR-143 on AngII-induced VSMCs to learn the potential mechanisms of miR-143 on AAA at the cellular level. The experimental results showed that the expressions of IL-1β, MCP-1, MMP9/13, TLR2, and NF-κB p65 and the percentage of TUNEL-positive cells in AngII-VSMCs were increased significantly compared with the control group. miR-143 had the opposite result. When the expression of miR-143 was up-regulated, the expression of IL-β, MCP-1, and MMP9/13 and the percentage of TUNEL-positive cells in AngII-VSMCs was suppressed. With the transfection of miR-143 over-expression plasmid, IL-1β, MCP-1, and MMP9/13 and the percentage of TUNEL-positive cells were reversed, compared to the AngII group and the AngII+oe-TLR2+miR-143 mimic group. In AngII-induced mouse VSMC, the up-regulation of the miR-143 expression could inactivate the TLR2/NF-κB pathway, thereby alleviating inflammatory response, ECM degradation, and cell apoptosis.

Basement membrane collagen IV deficiency promotes abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) is a complex disease which is incompletely accounted for. Basement membrane (BM) Collagen IV (COL4A1/A2) is abundant in the artery wall, and several lines of evidence indicate a protective role of baseline COL4A1/A2 in AAA development. Using Col4a1/a2 hemizygous knockout mice (Col4a1/a2+/−, 129Svj background) we show that partial Col4a1/a2 deficiency augmented AAA formation. Although unchallenged aortas were morphometrically and biomechanically unaffected by genotype, explorative proteomic analyses of aortas revealed a clear reduction in BM components and contractile vascular smooth muscle cell (VSMC) proteins, suggesting a central effect of the BM in maintaining VSMCs in the contractile phenotype. These findings were translated to human arteries by showing that COL4A1/A2 correlated to BM proteins and VSMC markers in non-lesioned internal mammary arteries obtained from coronary artery bypass procedures. Moreover, in human AAA tissue, MYH11 (VSMC marker) was depleted in areas of reduced COL4 as assessed by immunohistochemistry. Finally, circulating COL4A1 degradation fragments correlated with AAA progression in the largest Danish AAA cohort, suggesting COL4A1/A2 proteolysis to be an important feature of AAA formation. In sum, we identify COL4A1/A2 as a critical regulator of VSMC phenotype and a protective factor in AAA formation.

Endoleak Detection after Endovascular Aortic Aneurysm Repair Using Ultrasound Based on Nanoscale Bubble Contrast Agents and Their Effects on Vascular Smooth Muscle Cell Proliferation and Migration

Abdominal aortic aneurysm (AAA) is the most common vascular disease that causes disability and death. Its morbidity is relatively subtle, and the mortality rate is high. Clinically, endovascular aortic aneurysm repair (EVAR) has gradually become the primary treatment of AAA due to its unique advantages such as low trauma and low incidence of short-term complications. However, the outcome of EVAR is greatly compromised by the possible occurrence of endoleaks. Contrast-enhanced ultrasound (CEUS) is a promising alternative technique to detect endoleaks following EVAR due to lack of exposure to ionizing radiation. Traditional ultrasound contrast agents with an overlarge size (microscale) leading to reluctant accumulation in target organs and instability trigger the requirement of nanoscale contrast agents that enter tumor tissues through the enhanced permeability and retention effect. In this study, we used ultrasound based on nanoscale bubble contrast agents to evaluate endoleak detection after endovascular aortic aneurysm repair and analyzed the effects of nanoscale bubble contrast agents on vascular smooth muscle cell (VSMC) proliferation and migration. Among 52 AAA patients a month following EVAR, there were 16 cases of endoleaks after EVAR detected by nanobubble contrast-enhanced ultrasound, including 6 cases of type I endoleak (1 case of type Ia endoleak and 5 cases of type Ib endoleak), 7 cases of type II endoleak, and 3 cases of type III endoleak; there were 12 cases of endoleak after EVAR detected by computed tomography angiography (CTA), including 6 cases of type I endoleak (1 case of type Ia and 5 cases of type Ib), 5 cases of type II endoleak, and 1 case of type III endoleak. Six months after EVAR, 3 cases of type III endoleak were detected by both nanobubble contrast-enhanced ultrasound and CTA. Vascular smooth muscle cells (VSMCs) used for in vitro experiments were subjected to ultrasound irradiation and platelet-derived growth factor (PDGF) treatment with or without the addition of nanobubble contrast agents. After high-intensity and long-term irradiation (0.75 W/cm2 and 1 W/cm2 irradiation for 120 s and 150 s, respectively) by ultrasound with or without the addition of nanobubble contrast agents, PDGF-induced VSMC migration was inhibited ( P &lt; 0.01 ). Low-intensity and short-term ultrasound irradiation did not differ PDGF-induced VSMC migration ( P &gt; 0.05 ), but 0.5 W/cm2 and 90 s ultrasound irradiation could significantly inhibit PDGF-induced VSMC migration without the addition of nanobubble contrast agents ( P &lt; 0.05 ). When VSMCs were irradiated at 1, 0.75, 0.5, and 0.35 W/cm2 for 30 s to 150 s, ultrasound irradiation with or without the addition of nanobubble contrast agents remarkably reduced PDGF-induced VSMC proliferation, as evidenced by reduced OD values ( P &lt; 0.05 ). In conclusion, ultrasound based on nanoscale bubble contrast agents is an effective alternative detection method for the occurrence of AAA patients who are not suitable for CTA.

AN EASY AFFORDABLE STATISTICAL AND ECONOMIC (EASE) APPROACH TO AVOID UNNECESSARY AND EXPENSIVE EXAMS TO MONITOR PATIENTS WITH SMALL AAA

Abdominal Aortic Aneurysm (AAA) is a localized enlargement of the abdominal aorta, such that the diameter exceeds 30 mm. AAA is a progressive growth leading to rupture, with high risk of mortality, therefore elective surgical repair is indicated when AAA diamenter is &gt;55 mm. Screening programs, that use morphological imaging, have been developed internationally with the aim of detecting AAA before rupture with important limitations in term of cost and benefit for patients. Furthermore, different biochemical markers have been proposed to monitor AAA progression to overcome the above-mentioned limitations but none of them is used in the clinical practice. In fact, most of the biomarkers proposed are expensive and not feasible in the majority of laboratories. Combining different methodologies coming from Statistics and Operational Research fields, we developed an algorithm able to assess the importance of common biomarkers, requested in the clinical practice to evaluate the health of patient, and therefore no exams are required. Furthermore, we develop an Easy, Affordable Statistics and Economic (EASE) model able to identify if the AAA remain below the cut off for surgical repair. This prediction can provide guidance to how closely the patient’s abdominal aorta should be monitored avoiding additional and expensive exams.

Pathophysiological Aspects of the Development of Abdominal Aortic Aneurysm with a Special Focus on Mitochondrial Dysfunction and Genetic Associations.

Abdominal aortic aneurysm (AAA) is a complex degenerative vascular disease, with considerable morbidity and mortality rates among the elderly population. The mortality of AAA is related to aneurysm expansion (the enlargement of the aortic diameter up to 30 mm and above) and the subsequent rupture. The pathogenesis of AAA involves several biological processes, including aortic mural inflammation, oxidative stress, vascular smooth muscle cell apoptosis, elastin depletion, and degradation of the extracellular matrix. Mitochondrial dysfunction was also found to be associated with AAA formation. The evidence accumulated to date supports a close relationship between environmental and genetic factors in AAA initiation and progression. However, a comprehensive pathophysiological understanding of AAA formation remains incomplete. The open surgical repair of AAA is the only therapeutic option currently available, while a specific pharmacotherapy is still awaited. Therefore, there is a great need to clarify pathophysiological cellular and molecular mechanisms underlying AAA formation that would help to develop effective pharmacological therapies. In this review, pathophysiological aspects of AAA development with a special focus on mitochondrial dysfunction and genetic associations were discussed.

Evaluation of Survival Outcomes of Endovascular Versus Open Aortic Repair for Abdominal Aortic Aneurysms with a Big Data Approach.

Abdominal aortic aneurysm (AAA) is a localized enlargement of the abdominal aorta. Once ruptured AAA (rAAA) happens, repairing procedures need to be applied immediately, for which there are two main options: open aortic repair (OAR) and endovascular aortic repair (EVAR). It is of great clinical significance to objectively compare the survival outcomes of OAR versus EVAR using randomized clinical trials; however, this has serious feasibility issues. In this study, with the Medicare data, we conduct an emulation analysis and explicitly “assemble” a clinical trial with rigorously defined inclusion/exclusion criteria. A total of 7826 patients are “recruited”, with 3866 and 3960 in the OAR and EVAR arms, respectively. Mimicking but significantly advancing from the regression-based literature, we adopt a deep learning-based analysis strategy, which consists of a propensity score step, a weighted survival analysis step, and a bootstrap step. The key finding is that for both short- and long-term mortality, EVAR has survival advantages. This study delivers a new big data strategy for addressing critical clinical problems and provides valuable insights into treating rAAA using OAR and EVAR.

Vinpocetine protects against the development of experimental abdominal aortic aneurysms.

Abdominal aortic aneurysm (AAA), commonly occurring in the aged population, is a degenerative disease that dilate and weaken infrarenal aorta due to progressive degeneration of aortic wall integrity. Vinpocetine, a derivative of alkaloid vincamine, has long been used for cerebrovascular disorders and cognitive impairment in the aged population. Recent studies have indicated that vinpocetine antagonizes occlusive vascular disorders such as intimal hyperplasia and atherosclerosis. However, its role in vascular degenerative disease AAA remains unexplored. Herein, we determined the effect of vinpocetine on the formation of AAA as well as the intervention of pre-existing moderate AAA. AAA was induced by periaortic elastase application in C57BL/6J mice. Systemic vinpocetine treatment was applied daily via intraperitoneal injection. We showed that vinpocetine pre-treatment remarkably attenuated aneurysmal dilation assessed by diameter and volume. More importantly, vinpocetine also significantly suppressed the progression of pre-existing moderate AAA in a post-intervention model. Vinpocetine improved multiple cellular and molecular changes associated with AAA, such as elastin degradation, media smooth muscle cell depletion, collagen fibers remodeling and macrophage infiltration in aneurysmal tissues. Vinpocetine potently suppressed tumor necrosis factor-α-induced nuclear factor kappa-light-chain-enhancer of activated B cells activation and proinflammatory mediator expression in primary cultured macrophages in vitro, as well as in the aorta wall in vivo, suggesting vinpocetine conferred anti-AAA effect at least partially via the inhibition of inflammation. Taken together, our findings reveal a novel role of vinpocetine in AAA formation, development and progression. Given the excellent safety profile of vinpocetine, the present study suggests vinpocetine may be a novel therapeutic agent for AAA prevention and treatment.

Comparison of open versus endovascular surgical treatment of abdominal aortic aneurysm

Abstract Abdominal aortic aneurysm (AAA) is a common condition of increasing prevalence, particularly among older men. An AAA is defined as a permanent dilation of the abdominal aorta, with a diameter greater than 30 mm or a diameter greater than 50% of the aortic diameter at the level of the diaphragm. As the size of the aneurysm increases, so does the risk of rupture. Therefore, prophylactic repair with insertion of a prosthetic graft is offered. Since 1951 traditional open aneurysm repair (OAR) was reported and minimally invasive endovascular repair (EVAR) was first reported in 1986. Data from four randomized controlled trials (EVAR-1, DREAM, OVER, ACE) for abdominal aortic aneurysm, which enrolled almost 3000 patients, in a period from 1999 to 2008, were summarized. In addition, registry databases on the treatment of AAA of average 4000 patients per year, based from 2015 to 2018 of the German Institute for Vascular Medicine Healthcare Research of the German Society for Vascular Surgery and Vascular Medicine, were compared. The EVAR procedure for AAA showed a lower risk of perioperative mortality but was associated with a higher cardiovascular and aneurysm-related complication rate. In particular, patients aged 80 years or older benefited from EVAR since the 30-day mortality of patients receiving OAR was higher. In mid-term and long-term follow-up there were no differences in survival after endovascular and open aortic repair. Overall, it depends on the respective underlying disease and anatomy which of the two approaches is to be preferred. In conclusion, both treatment options can be considered as equal and can be offered to patients.

Noninvasive imaging of vascular permeability to predict the risk of rupture in abdominal aortic aneurysms using an albumin-binding probe

Abdominal aortic aneurysm (AAA) remains a fatal disease. Its development encompasses a complex interplay between hemodynamic stimuli on and changes in the arterial wall. Currently available biomarkers fail to predict the risk of AAA rupture independent of aneurysm size. Therefore, novel biomarkers for AAA characterization are needed. In this study, we used a mouse model of AAA to investigate the potential of magnetic resonance imaging (MRI) with an albumin-binding probe to assess changes in vascular permeability at different stages of aneurysm growth. Two imaging studies were performed: a longitudinal study with follow-up and death as endpoint to predict rupture risk and a week-by-week study to characterize AAA development. AAAs, which eventually ruptured, demonstrated a significantly higher in vivo MR signal enhancement from the albumin-binding probe (p = 0.047) and a smaller nonenhancing thrombus area compared to intact AAAs (p = 0.001). The ratio of albumin-binding-probe enhancement of the aneurysm wall to size of nonenhancing-thrombus-area predicted AAA rupture with high sensitivity/specificity (100%/86%). More advanced aneurysms with higher vascular permeability demonstrated an increased uptake of the albumin-binding-probe. These results indicate that MRI with an albumin-binding probe may enable noninvasive assessment of vascular permeability in murine AAAs and prediction of rupture risk.

Up-regulation of exosomal miR-106a may play a significant role in abdominal aortic aneurysm by inducing vascular smooth muscle cell apoptosis and targeting TIMP-2, an inhibitor of metallopeptidases that suppresses extracellular matrix degradation.

Abdominal aortic aneurysm (AAA) rupture is a dramatic and lethal clinical condition with a high risk of death. Emerging evidence indicates a role for miRNAs in AAA pathogenesis, therefore we aimed to identify miRNAs that differently expressed in exosomes from AAA patients and explore the underlying mechanisms of how miR-106a plays its role in this disease. Exosomes were isolated from plasma of AAA patients, as well as from the tissue-conditioned culture medium. The exosomal expression profiles of several miRNAs including miR-106a were analyzed by quantitative RT-PCR. To determine the potential role of miR-106a in the pathogenesis of AAA, miR-106a was overexpressed in vascular smooth muscle cells (VSMCs), and then cell viability and apoptosis were evaluated by performing CCK-8 assay and flow cytometry, respectively. Afterwards, enzyme-linked immunosorbent assay (ELISA) was applied to assess the expression levels of some proteins involved in the modulation of extracellular matrix (ECM) homeostasis. Furthermore, the target gene of miR-106a was predicted and verified through Dual-Luciferase reporter assay. MiR-106a was up-regulated in exosomes from plasma of those patients with AAA as compared with healthy peers. Likely, increased level of miR-106a was observed in exosomes released from AAA tissue in comparison to those from adjacent normal tissues. Enhanced expression of miR-106a in VSMCs suppressed cell viability but promoted cellular apoptosis, whereas inhibition of miR-106a in VSMCs resulted in a significant decrease in the percentage of apoptotic cells compared to the control group. In addition, the protein levels of matrix metalloproteinases (MMPs, including MMP-2 and MMP-12) secreted from VSMCs were significantly up-regulated, while their inhibitor TIMP-2 was down-regulated due to miR-106a overexpression. Finally, TIMP-2 was validated subsequently as the direct target of miR-106a through Dual-Luciferase reporter assay. In aggregate, our results suggest that increased expression of miR-106a promotes VSMC cell apoptosis and down-regulates TIMP-2 through directly targeting its 3'-UTR, which in turn restores MMP production and ultimately accelerates ECM degradation. Therefore miR-106a is proposed to play a crucial role in AAA development and this will provide an update on the understanding of the clinical value of miRNAs as novel therapeutic targets for the treatment of this disease.

Ovariectomy increases the incidence and diameter of abdominal aortic aneurysm in a hypoperfusion-induced abdominal aortic aneurysm animal model

Abdominal aortic aneurysm (AAA) is a vascular disease characterized by weakening of the vascular walls. Male sex is a risk factor for AAA, and peak AAA incidence occurs in men 10 years earlier than in women. However, the growth rate of AAA is faster in women, and women have a higher mortality due to AAA rupture. The mechanisms underlying sex-related differences in AAA remain unknown. Herein, we evaluated the effects of ovariectomy (OVX) on AAA in rats. Upon evaluation of the effects of OVX and AAA induction, AAA incidence rate and the aneurysm diameter increased in the OVX group. However, the histopathology in the developed AAA wall was not different between groups. When the effects of OVX on the vascular wall without AAA induction were evaluated, elastin and collagen levels were significantly decreased. Furthermore, the level of matrix metalloproteinase-9 significantly increased in the OVX group. According to our results, it is speculated that decreased levels of collagen and elastin fibers induced by OVX might be involved in increased incidence rate and diameter of AAA. Weakening of the vascular wall before the onset of AAA might be one reason for the faster rate of AAA growth in women.

Up-regulated MCPIP1 in abdominal aortic aneurysm is associated with vascular smooth muscle cell apoptosis and MMPs production.

Abdominal aortic aneurysm (AAA) is often clinically silent before rupture characterized by extensive vascular inflammation and degenerative elasticity of aortic wall. Monocyte chemotactic protein-induced protein-1 (MCPIP1) exhibits anti-infllammatory and pro-apoptotic effects involved in atherogenesis. However, little is known about the expression and the contribution of MCPIP1 in AAA. In the present study, we collected clinical AAA specimens and constructed AAA mice model through Ang-II infusion, and found apparently increased MCPIP1 expression and severe inflammatory infiltration in AAA aortic membrane as evidenced by elevated levels of monocyte chemotactic protein 1 (MCP-1), interleukin 1 β (IL-1β) and NF-κB, as well as HE staining. The elasticity of aortic tunica media was impaired along with multiple apoptosis of vascular smooth muscle cells (VSMCs) in Ang-II-induced aneurysmal mouse. In vitro Ang-II administration of VSMCs induced MCPIP1 expression, accompanied by up-regulation of matrix metalloproteinase (MMP) 2 (MMP-2) and MMP-9, as well as enhancement of VSMCs proliferation and apoptosis, which may cause damage of intima–media elasticity. Silencing MCPIP1 reversed above effects to further restore the balance of proliferation and apoptosis in VSMCs. Overall, our data indicated that up-regulation of MCPIP1 may become a promising candidate for the diagnosis of AAA, and specific knockdown of MCPIP1 in VSMCs could inhibit VSMCs apoptosis and down-regulate MMPs to maintain vascular wall elasticity. Therefore, knockdown of MCPIP1 may serve as a potential target for gene therapy of AAA.

Enhanced endoplasmic reticulum and mitochondrial stress in abdominal aortic aneurysm.

Abdominal aortic aneurysm (AAA) is a degenerative vascular disease with a complex aetiology that remains to be fully elucidated. Clinical management of AAA is limited to surgical repair, while an effective pharmacotherapy is still awaited. Endoplasmic reticulum (ER) stress and mitochondrial dysfunction have been involved in the pathogenesis of cardiovascular diseases (CVDs), although their contribution to AAA development is uncertain. Therefore, we aimed to determine their implication in AAA and investigated the profile of oxysterols in plasma, specifically 7-ketocholesterol (7-KC), as an ER stress inducer.In the present study, we determined aortic ER stress activation in a large cohort of AAA patients compared with healthy donors. Higher gene expression of activating transcription factor (ATF) 6 (ATF6), IRE-1, X-binding protein 1 (XBP-1), C/EBP-homologous protein (CHOP), CRELD2 and suppressor/enhancer of Lin-12-like (SEL1L) and greater protein levels of active ATF6, active XBP1 and of the pro-apoptotic protein CHOP were detected in human aneurysmatic samples. This was accompanied by an exacerbated apoptosis, higher reactive oxygen species (ROS) production and by a reduction in mitochondrial biogenesis in the vascular wall of AAA. The quantification of oxysterols, performed by liquid chromatography-(atmospheric pressure chemical ionization (APCI))-mass spectrometry, showed that levels of 7-KC were significantly higher while those of 7α-hydroxycholesterol (HC), 24-HC and 27-HC were lower in AAA patients compared with healthy donors. Interestingly, the levels of 7-KC correlate with the expression of ER stress markers.Our results evidence an induction of ER stress in the vascular wall of AAA patients associated with an increase in circulating 7-KC levels and a reduction in mitochondrial biogenesis suggesting their implication in the pathophysiology of this disease.

IL-27 Receptor Signaling potentiates Angiotensin II induced myelopoiesis and promotes Abdominal Aortic Aneurysm

Abstract Abdominal Aortic Aneurysm (AAA) is a vascular disease, where aortic wall degradation is in part mediated by the accumulation of immune cells leading to aortic wall rupture and bleeding which is often fatal for the patient. Smoking, age, male gender, hypertension and atherosclerosis are major risk factors, however the mechanism of AAA development is still elusive. Though cytokines regulate the inflammatory milieu within the aortic wall, their possible role in systemic regulation of this disease, particularly in the control of hematopoietic stem cell proliferation, myeloid cell differentiation and their subsequent accumulation in AAA remains poorly defined. Here we report an unexpected pathogenic role of IL-27R signaling in the development of AAA. We found that in an animal model of AAA, prolonged infusion of Angiotensin (Ang) II robustly induces AAA formation in hyperlipidemic Apoe−/− and Apoe−/−Il27ra+/− mice but not in IL-27R deficient Apoe−/− mice. This mitigation of AAA formation in Apoe−/−Il27ra−/− mice is associated with a blunted accumulation of myeloid cells in suprarenal aortas due to a reduction of Ang II-induced hematopoietic stem and progenitor cell (HSPCs) expansion. We found that the absence of IL-27R signaling engages transcriptional programs that promote HSCs self-renewal program and suppress myeloid lineage differentiation, resulting in decreased mature myeloid cell production and thus a concomitant lack of Ang II-induced myeloid cell accumulation in the suprarenal aortas. Collectively, these data demonstrate that IL-27R signaling influences AAA development by potentiating Ang II induced myelopoiesis and may represent a molecular point of therapeutic intervention in AAA.

Animal models in experimental abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a prevalent and potentially life-threatening disease. Many animal models have been developed to simulate the natural history of the disease or test preclinical endovascular devices and surgical procedures. The aim of this review is to describe different methods of AAA induction in animal models and report on the effectiveness of the methods described in inducing an analog of a human AAA. The PubMed database was searched for publications with titles containing the following terms “animal” or ''animal model(s)'' and keywords “research,” “aneurysm(s),” “aorta,” “pancreatic elastase,” “angiotensin,” “AngII” “calcium chloride” or “CaCl2.” Starting date for this search was set to 2010. We focused on animal studies that reported a model of aneurysm development and progression. A number of different approaches of AAA induction in animal models have been developed, used, and combined since the first report in the 1960s. Although specific methods are successful in AAA induction in animal models, it is necessary that these methods and their respective results are in line with the pathophysiology and the mechanisms involved in human AAA development. A researcher should know the advantages or disadvantages of each animal model and choose the appropriate model.

Abstract 112: IL-27 Receptor Signaling Potentiates Angiotensin II Induced Myelopoiesis and Promotes Abdominal Aortic Aneurysm

Abdominal Aortic Aneurysm (AAA) is a vascular disease, where aortic wall degradation is mediated by accumulated immune cells. Several cytokines have been suggested to play role in AAA, however the role of cytokines in immune cell accumulation and AAA progression remains poorly defined. Here we report an unexpected role of IL-27R signaling in the development of AAA. We found that in an animal model of AAA, prolonged infusion of Angiotensin (Ang) II robustly induced AAA formation in hyperlipidemic Apoe -/- and Apoe -/- Il27ra +/- mice but failed to do so in Apoe -/- Il27ra -/- mice. This mitigation of AAA formation in Apoe -/- Il27ra -/- mice was associated with a blunted accumulation of pathogenic myeloid cells in suprarenal aortas resulting from a reduction in Ang II-induced hematopoietic stem and progenitor cell (HSPCs) expansion. We found that in the absence of IL-27R signaling HSPCs were unable to fully downregulate p21 expression in response to Ang II, which impeded the ability of Apoe -/- Il27ra -/- HSPCs to proliferate. Collectively, these data demonstrate that IL-27R signaling influences AAA development by activating emergency hematopoiesis in response to elevated Ang II. Further, they provide new insights into how the immunoregulatory cytokine IL-27 drives a prominent lethal vascular disease by distant regulation of stress/emergency hematopoiesis.

Abstract 705: Nudt6 Inhibition Limits Smooth Muscle Cell Apoptosis and Abdominal Aortic Aneurysm Progression

Abdominal Aortic Aneurysm (AAA) is a highly lethal disease, of which diagnosis and treatment is still a major burden. Natural Antisense Transcripts (NAT) are known to inhibit key transcripts by antisense targeting. Their contribution to the development and progression of aneurysm disease has not been studied to date. The aim of this study was to investigate the role of the NAT Nudix Hydrolase 6 (Nudt6) and its antisense target Fibroblast growth factor (Fgf2) in AAA disease, by modulating NUDT6 in vivo in Angiotensin II (AngII)-induced experimental AAA via sonoporation (microbubble procedure) as well as in vitro in primary mouse aortic smooth muscle cells (mAoSMCs) via transfection . Further, primary mAoSMCs were observed using the IncuCyte imaging system to monitor changes in dynamic processes like proliferation and apoptosis. FGF2 is known to be a potent mitogen of smooth muscle cell (SMC) proliferation; a process being drastically diminished in AAA progression. By inhibiting Nudt6 with GapmeR in vivo we could observe smaller aortic diameters, increased both Fgf2 expression and SMCs survival by immunohistochemistry. In vitro , proliferation was increased in Nudt6 inhibited AngII-stimulated primary mouse aortic SMCs. Overexpression of Nudt6 did not have a significant effect on proliferation. Nudt6 and Fgf2 gene expression are inversely correlated and experience a switch of expression patterns during AngII stimulation over a longer period of time if primary SMCs are transfected with Nudt6 inhibitor and treated with AngII. All findings suggest a beneficial effect of Nudt6 inhibition in experimental AAA. In the future, it could be used as a potential therapeutic target in AAA by increasing SMC survival rates.

Abstract 21236: Novel Immune Regulatory Defects Contribute to Abdominal Aortic Aneurysm Formation

Abdominal aortic aneurysm (AAA) is a significant and serious health problem with an incidence as high as 9% and is associated with 15,000 deaths each year in the U.S. Recently AAA has increasingly been considered to be an autoimmune disease, where a pro-inflammatory cascade with cytotoxic and proteolytic features results aortic wall degradation and aneurysm formation, but the underlying causes of this imbalance remain unknown. Regulatory T cells prevent both the activation and effector function of reactive T cells sensitized to auto-antigens. Critical in this process are Type 1 regulatory T-cells (Tr1) which are antigen-specific and identified by expression of CD49b and lymphocyte activation gene 3 (LAG-3). Tr1 cells exhibit strong immunosuppressive activity and are able to restore tolerance in several immune-mediated diseases, through the secretion of high amounts of IL-10. Most importantly IL-10 is essential in the induction as well as immune suppressor activity of Tr1 cells. We found that AAA patients have a decreased number of Tr1 cells compared to risk-factor matched controls, and that those cells are functionally defective, producing reduced levels of IL-10 and having impaired immune suppression abilities. Moreover, naive CD4+ T cells from AAA patients were resistant to Tr1 induction in vitro , and AAA plasma likewise impaired the induction of Tr1 cells from healthy CD4+ T cells. Plasma miRNA analysis revealed a profile of expression changes in AAA patients that inhibit IL-10 expression. Together, these results suggest a critical defect of Tr1 cells in AAA, driven by impaired IL-10 expression, which could contribute to AAA disease pathology.