Abdominal Aortic Aneurysm Specimens Research Articles

LncRNA CARMN inhibits abdominal aortic aneurysm formation and vascular smooth muscle cell phenotypic transformation by interacting with SRF

Phenotypic transformation of vascular smooth muscle cells (VSMCs) plays a crucial role in abdominal aortic aneurysm (AAA) formation. CARMN, a highly conserved, VSMC-enriched long noncoding RNA (lncRNA), is integral in orchestrating various vascular pathologies by modulating the phenotypic dynamics of VSMCs. The influence of CARMN on AAA formation, particularly its mechanisms, remains enigmatic. Our research, employing single-cell and bulk RNA sequencing, has uncovered a significant suppression of CARMN in AAA specimens, which correlates strongly with the contractile function of VSMCs. This reduced expression of CARMN was consistent in both 7- and 14-day porcine pancreatic elastase (PPE)-induced mouse models of AAA and in human clinical cases. Functional analyses disclosed that the diminution of CARMN exacerbated PPE-precipitated AAA formation, whereas its augmentation conferred protection against such formation. Mechanistically, we found CARMN's capacity to bind with SRF, thereby amplifying its role in driving the transcription of VSMC marker genes. In addition, our findings indicate an enhancement in CAMRN transcription, facilitated by the binding of NRF2 to its promoter region. Our study indicated that CARMN plays a protective role in preventing AAA formation and restrains the phenotypic transformation of VSMC through its interaction with SRF. Additionally, we observed that the expression of CARMN is augmented by NRF2 binding to its promoter region. These findings suggest the potential of CARMN as a viable therapeutic target in the treatment of AAA.Graphical abstract

The circular RNA Ataxia Telangiectasia Mutated regulates oxidative stress in smooth muscle cells in expanding abdominal aortic aneurysms

An abdominal aortic aneurysm (AAA) is a pathological widening of the aortic wall characterized by loss of smooth muscle cells (SMCs), extracellular matrix degradation, and local inflammation. This condition is often asymptomatic until rupture occurs, leading to high morbidity and mortality rates. Diagnosis is mostly accidental and the only currently available treatment option remains surgical intervention. Circular RNAs (circRNAs) represent a novel class of regulatory non-coding RNAs that originate from backsplicing. Their highly stable loop structure, combined with a remarkable enrichment in body fluids, make circRNAs promising disease biomarkers. We investigated the contribution of circRNAs to AAA pathogenesis and their potential application to improve AAA diagnostics. Gene expression analysis revealed the presence of deregulated circular transcripts stemming from AAA-relevant gene loci. Among these, the circRNA to the Ataxia Telangiectasia Mutated gene (cATM) was upregulated in human AAA specimens, in AAA-derived SMCs, and serum samples collected from aneurysm patients. In primary aortic SMCs, cATM increased upon angiotensin II and doxorubicin stimulation, while its silencing triggered apoptosis. Higher cATM levels made AAA-derived SMCs less vulnerable to oxidative stress, compared with control SMCs. These data suggest that cATM contributes to elicit an adaptive oxidative-stress response in SMCs and provides a reliable AAA disease signature.

Hsa_circ_0087352 promotes the inflammatory response of macrophages in abdominal aortic aneurysm by adsorbing hsa-miR-149-5p

Abdominal aortic aneurysms (AAA) is a common cardiovascular disease with the risk of rupture. Macrophage depletion can significantly limit the formation of experimental AAA. However, how macrophages in the arterial wall affect the focal distribution and progression of AAA remains unclear. Here, we aimed to evaluate whether circRNAs characterized by stable structure and high tissue specific expression can regulate the inflammatory response of macrophages in AAA. First, we applied bioinformatics to analyze circRNA expression profile in human AAA specimens, and screened out hsa_circ_0087352, which is up-regulated in human AAA specimens and related to inflammatory response of THP-1 macrophages induced by LPS. Besides, hsa_circ_0087352 is stably expressed in THP-1 and mainly distributed in the nucleus. Then, we constructed ceRNA network of circRNA-miRNA-mRNA (IL-6/CCL2/NF-κB) in AAA and found that hsa_circ_0087352 promotes IL-6 transcription and the secretion of inflammatory cytokines by sponging endogenous hsa-miR-149-5p in macrophages. Dual luciferase reporter gene and RNA pull-down suggested hsa_circ_0087352 directly binds to hsa-miR-149-5p. Fluorescence in situ hybridization assay showed the localization of hsa_circ_0087352 and hsa-miR-149-5p in the nucleus of macrophages. Further, western blot demonstrated hsa_circ_0087352 expands the signal transduction of ERK/NF-κB pathway, then IκB phosphorylation promotes NF-κB p65 phosphorylation and nuclear translocation. In addition, hsa_circ_0087352 overexpression in macrophages induces human vascular smooth muscle cells (VSMC) apoptosis in macrophage-VSMC coculture system via the release of proapoptotic cytokines, such as IL-6, TNF-α and IL-1β. Overall, this study provides experimental evidence that hsa_circ_0087352 can be used as a new biomarker and therapeutic target for abdominal aortic aneurysm.

Abstract 10828: Stem-Cell Therapy for Abdominal Aortic Aneurysms in Swine

Introduction: The current treatment paradigm of abdominal aortic aneurysms (AAA) focuses on observing patients until their disease reaches certain thresholds for intervention, with no preceding treatment available. There is an opportunity to develop drug or cell-based therapies to prevent further aneurysmal growth and decrease the risk of a highly morbid rupture. A previously validated acute AAA swine model was treated directly with gelfoam containing human adipose-derived stem cells (h-ADSCs). Methods: Male Yorkshire swine (n=16) received periadventitial injections (type 1 collagenase and porcine pancreatic elastase) into a 4 cm segment of infrarenal aorta. Experimental group (n=7) received gel foam soaked with 10 million h-ADSCs and control group (n=9) media-soaked gel foam. Aortic diameters (AD) were monitored at post-operative day (POD) 7 and 14 using ultrasound with euthanasia on POD 21. Suprarenal (control) and infrarenal aortas (experimental) were harvested for PCR, mechanical tensiometry testing, histopathological analyses as well as immunohistochemistry (IHC). Each animal served as their own control. Groups were compared with paired t-tests and Mann Whitney U tests. Results: Twelve animals survived until POD 21. Stem cell treated AAAs, unlike controls, demonstrated no growth (-1.6 ± 8.8% vs. 34.8 ± 13.7%, p<0.001), and had greater medial thickness (682.7 ± 149.1 um vs. 321.7 ± 194.0 um, p<0.001), and greater areas of elastin (5.33 ± 1.49% vs. 2.57 ± 2.25%, p<0.0001), smooth muscle (55.8 ±6.59% vs. 24.0 ± 6.84%, p<0.001), collagen 1 (p=.014), and VEGF (p=.009) than untreated controls. MMP9 mRNA expression in stem cell AAA specimens was downregulated 0.501 (±0.464) fold compared to control segments from those same animals (p= 0.025). Though tensiometry data displayed greater strength within the stem cell AAA rings, this did not reach statistical significance (p=.15). Conclusion: Stem cell therapy prevents the development of aortic aneurysms in a swine model. Stem cell treated swine with induced AAAs show more normal gross features, histologic, and biochemical properties compared to untreated controls with induced AAAs. Further investigation is merited as a possible translatable therapy for aneurysmal disease.

The elevated expression of TLR4 and MMP9 in human abdominal aortic aneurysm tissues and its implication

BackgroundToll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) have been investigated to play significant roles in the formation of abdominal aortic aneurysm (AAA). But the reports on the expression pattern of TLR4 and MMP9 in human AAA specimens were relatively scant. The aim of this study was to make a detailed analysis of TLR4 and MMP9 expression in situ and their association with clinical parameters involved in human AAA.Methods40 AAA specimens were obtained from full-thickness aneurysmal tissues at the maximal dilation area during the open surgical repair, and 8 non-aneurysmal abdominal aortas from transplant donors served as controls. Expression of TLR4 and MMP9 protein was determined by immunohistochemistry.ResultsThere were increased levels of TLR4 and MMP9 expression in human AAA tissues. Compared with macrophages or SMCs, lymphocytes showed a higher positive rate of TLR4 and MMP9 staining, and an elevated ratio of high MMP9 expression (all P < 0.05). There existed a significant association between TLR4 and MMP9 expression (r = 0.767, P < 0.001), and both TLR4 and MMP9 levels were statistically related to circulating CRP. Moreover, TLR4 expression in situ indicated a positive correlation with its serum level (r = 0.654, P = 0.006). Multiple analysis revealed that high TLR4 expression in situ was associated with the risk of large AAA (OR = 6.211, 95%CI = 1.226–31.480, P = 0.027), while high MMP9 expression was correlated to the presence of thrombus within AAA (OR = 5.494, 95%CI = 1.181–25.562, P = 0.030), separately compared with their low expression.ConclusionsThis study confirmed the overexpression of TLR4 and MMP9 in human AAA tissues, and their close relationship implying in the pathogenesis of AAA. We further provided evidence that TLR4 had a potential effect on AAA size and MMP9 could influence the occurrence of thrombus within AAA.

Lysyl hydroxylase 1 (LH1) deficiency promotes angiotensin II (Ang II)-induced dissecting abdominal aortic aneurysm.

Rationale: The progressive disruption of extracellular matrix (ECM) proteins, particularly early elastin fragmentation followed by abnormalities in collagen fibril organization, are key pathological processes that contribute to dissecting abdominal aortic aneurysm (AAA) pathogenesis. Lysyl hydroxylase 1 (LH1) is essential for type I/III collagen intermolecular crosslinking and stabilization. However, its function in dissecting AAA has not been explored. Here, we investigated whether LH1 is significantly implicated in dissecting AAA progression and therapeutic intervention.Methods and Results: Sixteen-week-old male LH1-deficient and wild-type (WT) mice on the C57Bl/6NCrl background were infused with angiotensin II (Ang II, 1000 ng/kg per minute) via subcutaneously implanted osmotic pumps for 4 weeks. Ang II increased LH1 levels in the abdominal aortas of WT mice, whereas mice lacking LH1 developed dissecting AAA. To evaluate the related mechanism, we performed whole-transcriptomic analysis, which demonstrated that LH1 deficiency aggravated gene transcription alterations; in particular, the expression of thrombospondin-1 was markedly upregulated in the aortas of LH1-deficient mice. Furthermore, targeting thrombospondin-1 with TAX2 strongly inhibited the proinflammatory process, matrix metalloproteinase (MMP) activity and vascular smooth muscle cells (VSMCs) apoptosis, ultimately decreasing the incidence of dissecting AAA. Restoration of LH1 protein expression in LH1-deficient mice by intraperitoneal injection of an adeno-associated virus normalized thrombospondin-1 levels, subsequently alleviating dissecting AAA formation and preserving aortic structure and function. Consistently, in human AAA specimens, decreased LH1 expression was associated with increased thrombospondin-1 levels.Conclusions: LH1 deficiency contributes to dissecting AAA pathogenesis, at least in part, by upregulating thrombospondin-1 expression, which subsequently enables proinflammatory processes, MMP activation and VSMCs apoptosis. Our study provides evidence that LH1 is a potential critical therapeutic target for AAA.

ADAM (a Disintegrin and Metalloproteinase) 15 Deficiency Exacerbates Ang II (Angiotensin II)-Induced Aortic Remodeling Leading to Abdominal Aortic Aneurysm.

ADAM (a disintegrin and metalloproteinase) 15-a membrane-bound metalloprotease from the ADAM (disintegrin and metalloproteinase) family-has been linked to endothelial permeability, inflammation, and metastasis. However, its function in aortic aneurysm has not been explored. We aimed to determine the function of ADAM15 in the pathogenesis of aortic remodeling and aneurysm formation. Approach and Results: Male Adam15-deficient and WT (wild type) mice (10 weeks old), on standard laboratory diet, received Ang II (angiotensin II; 1.5 mg/kg per day) or saline (Alzet pump) for 2 or 4 weeks. Ang II increased ADAM15 in WT aorta, while Adam15-deficiency resulted in abdominal aortic aneurysm characterized by loss of medial smooth muscle cells (SMCs), elastin fragmentation, inflammation, but unaltered Ang II-mediated hypertension. In the abdominal aortic tissue and primary aortic SMCs culture, Adam15 deficiency decreased SMC proliferation, increased apoptosis, and reduced contractile properties along with F-actin depolymerization to G-actin. Ang II triggered a markedly greater increase in THBS (thrombospondin) 1 in Adam15-deficient aorta, primarily the medial layer in vivo, and in aortic SMC in vitro; increased SSH1 (slingshot homolog 1) phosphatase activity and cofilin dephosphorylation that promoted F-actin depolymerization and G-actin accumulation. rhTHBS1 (recombinant THBS1) alone was sufficient to activate the cofilin pathway, increase G-actin, and induce apoptosis of aortic SMCs, confirming the key role of THBS1 in this process. Further, in human abdominal aortic aneurysm specimens, decreased ADAM15 was associated with increased THBS1 levels and loss of medial SMCs. This study is the first to demonstrate a key role for ADAM15 in abdominal aortic aneurysm through regulating the SMC function, thereby placing ADAM15 in a critical position as a potential therapeutic target for abdominal aortic aneurysm.

Microarray analysis of human abdominal aortic aneurysm (AAA) detected altered gene expression profiles including H19

Abstract AAA is often a life-threatening disease with poorly understood pathogenesis. We examined gene expression profiles between AAA and normal aorta specimens by cDNA microarray analysis. AAA wall specimens from 5 patients with AAA and grossly normal aortic walls from 3 transplant donors were employed in this study. Total RNA was extracted from each specimen, RT into cDNA, and labeled with phosphorus α-32P. cDNA probes were then hybridized onto human cardiovascular microarray and analyzed by densitometry. Quantitative differences of some genes were further explored by SYBR green-mediated qRT-PCR analysis. Pairwise comparisons of both microarray and qRT-PCR results were made by Student t-test. Most of the 588 genes studied had similar expression among AAA specimens and control aortas, however, 25 genes were upregulated and 26 downregulated. Expression of MMP-9, TIMP3, collagen 1A1 (COL1A1), COL6A3, COL15A1, decorin, MCP 1, Apo E, Apo D, H19 and others was increased. Expression of COL4A4, biglycan, caveolin 3, galectin 1, LDL receptor-related protein 1, extracellular SOD 3, ANP receptor A precursor and others was decreased. Most qRT-PCR results agreed well with those from microarray analysis, with few exceptions. A number of genes that have been previously postulated to participate in AAA pathogenesis, have been upregulated or their expression has been altered. We also revealed some genes that have not been yet studied in human AAA. Of note, H19, one of the most highly up-regulated transcripts in two mouse aneurysm models, was also significantly upregulated in human AAA. These results indicate that many genes involved in different cellular functions might contribute to the pathogenesis of AAA. Supported in part by grant RO1 HL64340 from NIH.

MiR-144-5p limits experimental abdominal aortic aneurysm formation by mitigating M1 macrophage-associated inflammation: Suppression of TLR2 and OLR1

BackgroundIt has been noted that dysregulation of microRNAs (miRNAs) contributes to the formation of abdominal aortic aneurysm (AAA), a vascular disease associated with progressive aortic dilatation and degradation, and pathological infiltration and activation of inflammatory cells, such as macrophages. Our microarray data revealing that miR-144-5p was the top 1 downregulated miRNA in mouse AAA tissues as compared to normal aortas motivated us to explore its role in AAA development. MethodsWe profiled miRNA and mRNA expression in Angiotensin II (Ang II)- (n = 3) and saline-infused abdominal aortas (n = 4) via Agilent microarrays, and further validated the data with real-time QPCR. In vivo, miR-144-5p or control agomirs were given to Apoe−/− mice with Ang II infusion-induced AAA. In vitro, mouse RAW 264.7 macrophages and human THP-1 macrophage-like cells were transfected with miR-144-5p or control agomirs/antagomirs, and oxidized Low Density Lipoprotein (ox-LDL) was used to stimulate M1 macrophage polarization. ResultsBased on the microarray and real-time QPCR validation data, we identified miR-144-5p as a novel downregulated miRNA in AAA tissues. Overexpression of miR-144-5p by utilizing its specific agomirs in vivo significantly attenuated Ang II-induced aortic dilatation and elastic degradation in Apoe−/− mice and improved their survival. AAA incidence was reduced by miR-144-5p as well. MiR-144-5p polarized macrophages to M2 type in Ang II-infused aortas. Further, the expression levels of two predictive targets for miR-144-5p, Toll Like Receptor 2 (TLR2) and ox-LDL Receptor 1 (OLR1), were higher in AAA specimens, and negatively correlated to miR-144-5p (Pearson correlation coefficient r < −0.9, P < .01). These two molecules were then confirmed as novel miR-144-5p targets via dual-luciferase assay. MiR-144-5p agomirs suppressed ox-LDL-induced upregulation of M1 macrophage markers, including interleukin 1β (IL1β), tumor necrosis factor α (TNFα), prostaglandin-endoperoxide synthase 2 (PTGS2) and nitric oxide synthase 2 (NOS2), in macrophages probably by targeting TLR2. MiR-144-5p also inhibited the signaling transduction of pathways downstream to TLR2 and OLR1, including NF-κB and ERK1/2 pathways, whose abnormal activation contributed AAA formation. ConclusionOur work suggests miR-144-5p as a novel regulator for AAA pathology. Management of miR-144-5p and its targets TLR2 and OLR1 provides therapeutic potential for limiting AAA formation.

Inflammasome activity in leucocytes decreases with abdominal aortic aneurysm progression.

Abdominal aortic aneurysms (AAAs) are characterized by chronic inflammatory cell infiltration. The present extended immunohistochemistry study aimed to characterize inflammation in AAA and aortic control samples. In specific, the composition of the infiltrating immune cells and the expression of five inflammasome components in these immune cells were evaluated, in order to characterize their role in AAA development. A total of 104 biopsies from 48 AAA patients and 40 healthy specimens from organ donors were evaluated for their grade of inflammation. Infiltrating leukocytes were characterized by specific markers (CD3, CD20 and CD68), intramural localization and inflammasome protein expression [NLR family pyrin domain containing 3 (NLRP3), absent in melanoma 2 (AIM2), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), Caspase-1 and Caspase-5]. Macrophages, B and T lymphocytes were detected to a similar extent in grade 1, 2 and 3 AAA specimens, whereas in control samples, B and T lymphocytes were rarely observed in grade 1 lesions. Expression frequencies of NLRP3, AIM2 and Caspase-5 were significantly higher in grade 1 lesions of AAA samples compared with grade 1 lesions in control samples. Finally, AIM2, ASC, and Caspase-5 displayed significantly lower expression frequencies in grade 3 compared with grade 2 AAA specimens, and all inflammasome components were less frequently detected in grade 3 than in grade 1 lesions of AAA. This indicates that inflammasome activities decrease with AAA progression in infiltrating leukocytes. No statistically significant association was found for grade 2 and grade 3 lesions and total leukocyte count, C-reactive protein levels, maximal aortic diameter, plasma cholesterol level or biomechanical parameters (derived from finite element analysis) of the respective patients. Overall, the aortic wall of AAA contained lymphocytes and macrophages with different states of activity. The present data suggested that therapeutic inhibition of specific inflammasome components might counteract AAA development and progression.

Long noncoding RNA GAS5 induces abdominal aortic aneurysm formation by promoting smooth muscle apoptosis.

Objective: Long noncoding RNAs (lncRNAs) may serve as specific targets for the treatment of abdominal aortic aneurysms (AAAs). LncRNA GAS5, functionally associated with smooth muscle cell (SMC) apoptosis and proliferation, is likely involved in AAA formation, but the exact role of GAS5 in AAA is unknown. We thus explored the contribution of GAS5 to SMC-regulated AAA formation and its underlying mechanisms.Methods: Human specimens were used to verify the diverse expression of GAS5 in normal and AAA tissues. The angiotensin II (Ang II)-induced AAA model in ApoE-/- mice and the CaCl2-induced AAA model in wild-type C57BL/6 mice were used. RNA pull-down and luciferase reporter gene assays were performed in human aortic SMCs to detect the interaction between GAS5 and its downstream targets of protein or microRNA (miR).Results: GAS5 expression was significantly upregulated in human AAA specimens and two murine AAA models compared to human normal aortas and murine sham-operated controls. GAS5 overexpression induced SMC apoptosis and repressed its proliferation, thereby promoting AAA formation in two murine AAA models. Y-box-binding protein 1 (YBX1) was identified as a direct target of GAS5 while it also formed a positive feedback loop with GAS5 to regulate the downstream target p21. Furthermore, GAS5 acted as a miR-21 sponge to release phosphatase and tensin homolog from repression, which blocked the activation and phosphorylation of Akt to inhibit proliferation and promote apoptosis in SMCs.Conclusion: The LncRNA GAS5 contributes to SMC survival during AAA formation. Thus, GAS5 might serve as a novel target against AAA.

The Effect of Pentagalloyl Glucose on the Wall Mechanics and Inflammatory Activity of Rat Abdominal Aortic Aneurysms.

An abdominal aortic aneurysm (AAA) is a permanent localized expansion of the abdominal aorta with mortality rate of up to 90% after rupture. AAA growth is a process of vascular degeneration accompanied by a reduction in wall strength and an increase in inflammatory activity. It is unclear whether this process can be intervened to attenuate AAA growth, and hence, it is of great clinical interest to develop a technique that can stabilize the AAA. The objective of this work is to develop a protocol for future studies to evaluate the effects of drug-based therapies on the mechanics and inflammation in rodent models of AAA. The scope of the study is limited to the use of pentagalloyl glucose (PGG) for aneurysm treatment in the calcium chloride rat AAA model. Peak wall stress (PWS) and matrix metalloproteinase (MMP) activity, which are the biomechanical and biological markers of AAA growth and rupture, were evaluated over 4 weeks in untreated and treated (with PGG) groups. The AAA specimens were mechanically characterized by planar biaxial tensile testing and the data fitted to a five-parameter nonlinear, hyperelastic, anisotropic Holzapfel–Gasser–Ogden (HGO) material model, which was used to perform finite element analysis (FEA) to evaluate PWS. Our results demonstrated that there was a reduction in PWS between pre- and post-AAA induction FEA models in the treatment group compared to the untreated group using either animal-specific or average material properties. However, this reduction was not statistically significant. Conversely, there was a statistically significant reduction in MMP-activated fluorescent signal between pre- and post-AAA induction models in the treated group compared to the untreated group. Therefore, the primary contribution of this work is the quantification of the stabilizing effects of PGG using biomechanical and biological markers of AAA, thus indicating that PGG could be part of a new clinical treatment strategy that will require further investigation.

Aneurysm-Specific miR-221 and miR-146a Participates in Human Thoracic and Abdominal Aortic Aneurysms.

Altered microRNA expression is implicated in cardiovascular diseases. Our objective was to determine microRNA signatures in thoracic aortic aneurysms (TAAs) and abdominal aortic aneurysms (AAAs) compared with control non-aneurysmal aortic specimens. We evaluated the expression of fifteen selected microRNA in human TAA and AAA operative specimens compared to controls. We observed significant upregulation of miR-221 and downregulation of miR-1 and -133 in TAA specimens. In contrast, upregulation of miR-146a and downregulation of miR-145 and -331-3p were found only for AAA specimens. Upregulation of miR-126 and -486-5p and downregulation of miR-30c-2*, -155, and -204 were observed in specimens of TAAs and AAAs. The data reveal microRNA expression signatures unique to aneurysm location and common to both thoracic and abdominal pathologies. Thus, changes in miR-1, -29a, -133a, and -221 are involved in TAAs and miR-145, -146, and -331-3p impact AAAs. This work validates prior studies on microRNA expression in aneurysmal diseases.

Characterization of Fc gamma receptor IIb expression within abdominal aortic aneurysm

ObjectiveTo evaluate protein profiles and Fc gamma receptor IIb (FCGRIIB) expression in abdominal aortic aneurysm (AAA) compared to the expression in normal aortas. MethodsWe performed a protein array to study the protein expression profiles within AAA and normal aortic tissues. FCGRIIB was found to be significantly elevated in AAA samples. Quantitative PCR and Western blot analyses were performed to study the expression of FCGRIIB in AAA compared to that in normal aortic tissue. Immunohistochemistry was used to locate FCGRIIB and the B cell marker CD19 in AAA and normal aortas specimens. ResultsFCGRIIB was significantly elevated in AAA tissues in both mRNA (AAA vs. normal control: about 5.8 folds, p < 0.001) and protein levels (AAA vs. normal control: about 6.3 folds, p < 0.001). In AAA specimens, immunohistochemistry revealed that FCGRIIB localized to the area of inflammatory infiltrates, which consisted of CD 19+ B cells and other inflammatory cells. FCGRIIB and CD19 were undetectable in normal aortas. ConclusionsFCGRIIB was significantly elevated in AAA tissues compared to normal aortas. FCGRIIB may be involved in the pathogenesis of AAA by regulation of inflammatory reactions.

Expression of Matrix Metalloproteinases and Endogenous Inhibitors in Abdominal Aortic Aneurysm and Aortoiliac Occlusive Disease (Syndrome Leriche)

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play a complex role in the pathogenesis of atherosclerosis. We compared (1) the histopathological findings in patients with abdominal aortic aneurysms (AAA) and aortoiliac occlusive disease (AOD); (2) the expression of MMP-2/MMP-9 and TIMP-1/TIMP-2 in aortic layers, inflammatory cells and smooth muscle cells (SMCs), aiming to identify the common underlying pathogenic mechanisms of the disease development. Samples were obtained from 30 patients with AAA and 30 with AOD. Aortic histology and immunohistochemistry were performed to evaluate inflammatory changes and MMP and TIMP expression. Thrombosis and ulceration were more frequent in AOD than in AAA. The MMP-9 expression was elevated in all aortic layers of AAA patients and in media/adventitia of AOD patients, mainly followed by lower expression of its inhibitor TIMP-1. Higher MMP-9 expression was also found in SMCs and macrophages of both AAA and AOD specimens, while higher TIMP-1/TIMP-2 were predominantly observed in the lymphocytes and macrophages of the aneurysm. These results showed that both conditions exhibited increased MMP-9 expression; however, the MMP expression pattern differed to some degree between the aneurysms and occlusive disease. The variations in molecular mechanisms underlying dilatative/stenosing disease warrant further investigation.

Role of MicroRNA-103a Targeting ADAM10 in Abdominal Aortic Aneurysm.

MicroRNAs (miRNAs) are deregulated in various vascular ailments including abdominal aortic aneurysm (AAA). MiR-103 is involved in vascular, metabolic, and malignant diseases, but whether it participates in the pathogenesis of AAA remains elusive. ADAM10 plays a vital role in the formation of aneurysm, but whether miRs modulate its activity during AAA formation is totally unknown. In this study, we detected the significantly increased protein expression of ADAM10 in angiotensin II induced murine AAA specimens, while the mRNA expression of ADAM10 was similar between AAA and control, suggesting the posttranscriptional regulation. The ADAM10 specific inhibitor GI254023X dramatically reduced the macrophage infiltration of murine abdominal aorta. Bioinformatic predictions suggest that ADAM10 is the target of miR-103a/107 but the binding site is exclusive. At the cellular level, miR-103a-1 suppressed the protein expression of ADAM10, while antisense miR-103a-1 increased its expression. Particularly, with the progression of murine AAA, the mRNA expression of miR-103a/107 substantially decreased and the protein expression of ADAM10 greatly increased. Together, our data afford the new insight that miR-103a inhibited AAA growth via targeting ADAM10, which might be a promising therapeutic strategy to alleviate AAA.

Probabilistic noninvasive prediction of wall properties of abdominal aortic aneurysms using Bayesian regression

Multiple patient-specific parameters, such as wall thickness, wall strength, and constitutive properties, are required for the computational assessment of abdominal aortic aneurysm (AAA) rupture risk. Unfortunately, many of these quantities are not easily accessible and could only be determined by invasive procedures, rendering a computational rupture risk assessment obsolete. This study investigates two different approaches to predict these quantities using regression models in combination with a multitude of noninvasively accessible, explanatory variables. We have gathered a large dataset comprising tensile tests performed with AAA specimens and supplementary patient information based on blood analysis, the patients medical history, and geometric features of the AAAs. Using this unique database, we harness the capability of state-of-the-art Bayesian regression techniques to infer probabilistic models for multiple quantities of interest. After a brief presentation of our experimental results, we show that we can effectively reduce the predictive uncertainty in the assessment of several patient-specific parameters, most importantly in thickness and failure strength of the AAA wall. Thereby, the more elaborate Bayesian regression approach based on Gaussian processes consistently outperforms standard linear regression. Moreover, our study contains a comparison to a previously proposed model for the wall strength.

Abstract 18182: Phosphodiesterase 10A Regulates Vascular Inflammation and Pathogenesis of Abdominal Aortic Aneurysms

Rationale: Abdominal aortic aneurysms (AAA) are characterized by aortic enlargement and underlying weakness of the vessel wall. Experimental and clinical evidence suggests that vascular inflammation is a central trigger of AAA formation. Phosphodiesterases (PDEs), known regulators of cyclic nucleotide signaling, play a critical role in vascular inflammation. Objective: In this study, we sought to determine the role and function of PDE10A in vascular inflammation and AAA formation. Methods and Results: Extensive evidence suggests that angiotensin II (Ang II) signaling plays an important causative role in AAA formation. Therefore, Real-time PCR array for all 22 known PDE genes was performed in control and Ang II-treated VSMCs. We observed that PDE10A elicited the highest levels of induction by Ang II among all PDEs. Moreover, we found that PDE10A was dramatically upreguated in the Ang II-infused AAA mouse model and in human AAA specimens. PDE10A was primarily expressed in medial VSMCs and infiltrating macrophages in AAA. More importantly, deficiency of PDE10A or PDE10A inhibition significantly attenuated AAA formation in vivo. In cultured VSMCs, knockdown of PDE10A with specific siRNA and inhibition of PDE10A by papaverine markedly suppressed Ang II-induced vascular cell adhesion molecule 1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1) and MMP2 expression. Deficiency of PDE10A also blocked lipopolysaccharide (LPS)-induced TNF-α, MCP-1, and MMP9 expression in peritoneal macrophages isolated from PDE10A knockout mice. Further mechanistic studies revealed that histone deacetylase 5 (HDAC5) plays an important role in PDE10A-regulated vascular inflammation via cAMP-dependent protein kinase (PKA). Conclusions: These findings demonstrate that PDE10A is an important regulator of vascular inflammation and AAA development. They further provide evidence for PDE10A as a potential therapeutic target for aortic aneurysms and other vascular diseases.

Abstract 228: Histology and Pathophysiology Study of Renal Aneurysm

Objectives: While progress has been made over the past 2 decades in our understanding of the development of abdominal aortic aneurysms (AAA), far less is understood about the development and pathobiology of aneurysms of the renal arteries. A valuable collection of renal artery tissue collected over the course of many years was used to directly compare histology, as well as some known mediators of AAA development in end-stage tissue from renal arteries aneurysm (RAA) and AAA. Methods: Tissues were collected and stored (frozen fresh and FFPE) at the time of aneurysm repair or renal transplant for normal aortic specimens. Histologic morphometry was performed to quantify elastin staining and immunohistochemistry for CD68, alpha-actin, MMP9 and Osteopontin (OPN). Gelatin zymography was performed on protein extracts from the tissues. Results: All aneurysms (AAA, n=9, RAA, n=9) tissues demonstrated a significantly (P&lt;0.05) reduced percentage of mural elastin than that seen in normal aorta (16.3±3.4%, n=5). Loss of medial elastin was nearly complete in AAA (.11±.04%). Elastin in all RAA was substantially greater (3.6±1.4%) than AAA but this did not reach statistical significance (P=0.1). Elastin content is significantly greater in RAA due to fibromuscular dysplasia (RAA-FMD, n=5, 6.6±1.8%) than AAA (P&lt;. 02) and idiopathic RAA (iRAA, 0.72±0.48%, P&lt;.03). RAA had greater preservation of smooth muscle cell (SMC) mass in the aortic wall, and unlike AAA, the cells were in typical laminar formation in the media. Few macrophages were seen in any RAA tissue. By immunohistology, qualitatively there is substantially greater OPN in all RAA. There was also very little immunreactive MMP-9 in the RAA specimens, whereas AAA specimens had substantial MMP-9 present in inflammatory cells and SMC. MMP9 activity on zymography was found to be significantly lower in RAA (n=3) than in AAA (n=3; p=0.03). Conclusions: These important and unique studies demonstrate that the histology and general pathobiology of RAA is distinct from AAA. Elastin degradation is significantly lower in RAA, particularly in RAA-FMD. Infiltrating macrophages and elastolytic enzyme MMP-9 appear to play a relatively small role in the development of RAA.

Abstract 457: Mirnas 362-3p, 194 and 9b-1 In Aaa and Popliteal Aneurysm Pathogenesis

Introduction: Abdominal aortic aneurysm (AAA) remains a major challenge in treatment and cause of death in cardiovascular patients. Despite open surgery or endovascular stent exclusion no therapeutic option remains to clinicians. Similar in severity but much less known are popliteal aneurysms (PA) arising from muscular type arteries often resulting in leg ischemia. So far focus has been on atherosclerosis and inflammation involved in this largely unclear pathogenesis as relevant pathways that could be influenced by i.e. medication in order to prevent growth and possible rupture. Material and methods: miRNA global expression profiles and RT-PCR for confirmation experiments have been used on human tissue samples. DIANA based pathway prediction and immunhistochemical examinations were applied. Results: miRNAs 362-3p, 194 and 9b-1 revealed by a global expression assays from AAA specimens were found to be differentially regulated between the two aneurysm entities. Computational pathway analysis predicted enrichment in metabolic, ECM and cell-cell-interatcion pathways. Here distinct features were found in immunhistochemical analysis and apoptosis assays. Conclusion: Further experiments are needed to confirm the involvement of alternative pathway in AAA and PA pathogenesis. The comparison between elastic and muscular type arteries however may result in exclusive aneurysm mechanisms.