Aortic Rupture Research Articles

Acute Symptomatic Isolated Abdominal Aortic Dissection – Clinical Characteristics, Outcome, and Sex Differences

Acute isolated abdominal aortic dissection (IAAD) is a rare condition and treatment recommendations are lacking. Most previous studies included both symptomatic and asymptomatic patients. The aims were to determine the proportion of IAAD among patients with acute type B aortic dissection as well as to describe patient characteristics, radiological findings, and frequency of early and late complications and to explore sex differences. This was a retrospective cohort study including all patients hospitalized with acute symptomatic IAAD in Stockholm County during 2012-2021. A total of 277 patients with acute type B aortic dissection were identified, of whom 10% (n=28/277) had acute IAAD. Median age was 56years and 43% (n=12/28) were women. Hypertension was diagnosed in 46% (n=13/28) prior to admission. At onset, abdominal pain was the predominant complaint (93%, n=26/28) and 93% (n=26/28) were hypertensive on admission. The suprarenal aorta was involved in 39% (n=11/28) and at least 1 of the iliac arteries in 50% (n=14/28). All but 1 patient had uncomplicated IAAD (96%, n=27/28). One patient presented with aortic rupture, treated with open surgical repair. Among patients with primarily uncomplicated IAAD, 7% eventually developed chronic complications (n=2/27). Median maximum aortic diameter at 1-year follow-up was 21mm (interquartile range 17-28). Only 1 patient had an aortic diameter exceeding 30mm. None of the patients died during follow-up; median follow-up was 3.0years (interquartile range 2-8). Early and late complications are rare in patients with acute symptomatic IAAD and a conservative approach with antihypertensive treatment and surveillance in uncomplicated cases seems reasonable.

Analysis of the effect and safety of lumen reshaping after endovascular repair of Stanford B type aortic dissection at different intervention times

Objective: To Compare the effects and safety of lumen reshaping after thoracic endovascular aortic repair (TEVAR) for Stanford B type aortic dissection (AD) at different intervention times. Methods: A retrospective analysis was conducted on the clinical data of 189 patients with Stanford type B aortic dissection treated with TEVAR at the Affiliated Hospital of Chengde Medical College from January 2016 to December 2020.Based on the time from onset to surgery, patients were divided into an early intervention group (≤14 days, n=127) and a delayed intervention group (>14 days, n=62).The diameters of the total aorta, true lumen and false lumen at different times and planes (S1 plane: at the bifurcation of the pulmonary artery; S2 plane: at the lower edge of the left atrium; S3 plane: at the upper edge of the celiac trunk) post-surgery were compared between the two groups, and the rate of change in diameters of true and false lumens across these planes was calculated. The patients were followed until December 1st, 2023, and the median follow-up time was 45(40, 49) months. The postoperative complications and survival of the two groups were compared. Results: The early intervention group comprised 86 men and 41 women, with an average age of (58.3±10.7) years. The delayed intervention group included 41 men and 21 women, with an average age of (58.5±9.2) years. Both groups had an operation success rate of 100%. Six months post-surgery, the early intervention group had an expansion rate of the true lumen diameter at planes S2 and S3 of 40.1%(25.5%, 56.1%) and 5.3%(-2.5%, 15.8%), respectively, which was superior to the delayed intervention group's 18.5%(10.6%, 39.8%) and 1.0%(-8.2%, 9.6%) (both P<0.05).The early intervention group had a reduction rate of the false lumen diameter at planes S1, S2, and S3 of -56.2%(-61.3%, -48.8%), -70.4%(-81.8%, -56.6%), and -5.4%(-17.4%, 0.1%), respectively, better than the delayed intervention group's -44.2%(-53.7%, -38.3%), -49.0%(-57.6%, -35.8%), and -3.1%(-6.7%, 1.8%) (all P<0.05).At plane S1, the true lumen diameter of patients in both groups showed an increasing trend over 36 months post-surgery, while the false lumen diameter showed a decreasing trend (both P<0.05).At plane S2, the true lumen diameter of patients in the early intervention group exhibited an increasing trend over 36 months post-surgery, and the false lumen diameter exhibited a decreasing trend (both P<0.05).At plane S3, the total aortic diameter of patients in the delayed intervention group showed a slight increasing trend over 36 months post-surgery (P<0.05).The overall survival time were 45.0 months (95%CI: 42.9-47.1) for patients in the early intervention group and 46.0 months (95%CI: 43.5-48.5) for those in the delayed intervention group, with no statistically significant difference observed (P>0.05).The incidence rates of complications such as aortic rupture, retrograde Type A dissection, new distal endograft dissection, endoleak, paraplegia, and others showed no statistically significant difference between the two groups (all P>0.05), with no cases of stent migration or deformation observed. Conclusion: Early intervention for Stanford type B aortic dissection provides a better aortic remodeling outcome than delayed intervention, with similar safety.

Predictors of Late Adverse Events in Patients with Surgically Treated Type I Aortic Dissection

Residual aortic dissection (AD) following DeBakey type I AD repair is associated with a high rate of adverse events that need additional intervention or surgery. This study aimed to identify clinical and early post-operative computed tomography (CT) imaging factors associated with adverse events in patients with type I AD after ascending aorta replacement. This single centre, retrospective cohort study included consecutive patients with type I AD who underwent ascending aorta replacement from January 2011 to December 2017 and post-operative CT within 3 months. The primary outcome was AD related adverse events, defined as AD related death and re-operation due to aortic aneurysm or impending rupture. The location and size of the primary intimal tears, aortic diameter, and false lumen status were evaluated. Regression analyses were performed to identify factors associated with AD related adverse events. A decision tree model was used to classify patients as high or low risk. Of 103 participants (55.43 ± 13.94 years; 49.5% males), 24 (23.3%) experienced AD related adverse events. In multivariable Cox regression analysis, connective tissue disease (hazard ratio [HR] 15.33; p < .001), maximum aortic diameter ≥ 40 mm (HR 4.90; p < .001), and multiple (three or more) intimal tears (HR 7.12; p < .001) were associated with AD related adverse events. The 3 year cumulative survival free from AD related events was lower in the high risk group with aortic diameter ≥ 40 mm and multiple intimal tears (41.7% vs. 90.9%; p < .001). Early post-operative CT findings indicating a maximum aortic diameter ≥ 40 mm and multiple intimal tears may predict a higher risk of adverse events. These findings suggest the need for careful monitoring and more vigilant management approaches in these cases.

Peak wall rupture index is associated with risk of rupture of abdominal aortic aneurysms, independent of size and sex.

Information on the predictive determinants of abdominal aortic aneurysm rupture from CT angiography are scarce. The aim of this study was to investigate biomechanical parameters in abdominal aortic aneurysms and their association with risk of subsequent rupture. In this retrospective study, the digital radiological archive was searched for 363 patients with ruptured abdominal aortic aneurysms. All patients who underwent at least one CT angiography examination before aneurysm rupture were included. CT angiography results were analysed to determine maximum aneurysm diameter, aneurysm volume, and biomechanical parameters (peak wall stress and peak wall rupture index). In the primary survival analysis, patients with abdominal aortic aneurysms less than 70 mm were considered. Sensitivity analyses including control patients and abdominal aortic aneurysms of all sizes were performed. A total of 67 patients who underwent 109 CT angiography examinations before aneurysm rupture were identified. The majority were men (47, 70%) and the median age at the time of CTA examination was 77 (71-83) years. The median maximum aneurysm diameter was 56 (interquartile range 46-65) mm and the median time to rupture was 2.13 (interquartile range 0.64-4.72) years. In univariable analysis, maximum aneurysm diameter, aneurysm volume, peak wall stress, and peak wall rupture index were all associated with risk of rupture. Women had an increased HR for rupture when adjusted for maximum aneurysm diameter or aneurysm volume (HR 2.16, 95% c.i. 1.23 to 3.78 (P = 0.007) and HR 1.92, 95% c.i. 1.06 to 3.50 (P = 0.033) respectively). In multivariable analysis, the peak wall rupture index was associated with risk of rupture. The HR for peak wall rupture index was 1.05 (95% c.i. 1.03 to 1.08) per % (P < 0.001) when adjusted for maximum aneurysm diameter and 1.05 (95% c.i. 1.02 to 1.08) per % (P < 0.001) when adjusted for aneurysm volume. Biomechanical factors appear to be important in the prediction of abdominal aortic aneurysm rupture. Women are at increased risk of rupture when adjustments are made for maximum aneurysm diameter alone.

Abstract 1005: Hypertriglyceridemia Promotes Aortic Aneurysm Formation And Rupture In Angiotensin Ii Infused Mice

Plasma total cholesterol (TC) and triglyceride (TG) are reported to be positively associated with the risk of abdominal aortic aneurysm (AAA). Our group discovered that hypercholesterolemia augments angiotensin II-induced AAA in mice. We also found that remnants of triglyceride-rich lipoproteins (TRLs) may be crucial for AngII-induced AAA. Recently, it was reported that hypertriglyceridemia (HTG) caused by inducible lipoprotein lipase deficiency (iLpl-/-) results in uptake and accumulation of TRL lipid in aortic endothelial cells in vivo. Based upon these findings, we hypothesized that HTG stimulates AAA formation. Methods: Adult male and female Lplf/f.beta-actin-Mer/Cre/Mer 1/0 and Lplf/f mice were administered 75 mg/kg/day tamoxifen for 5 consecutive days. Mice were fed either a standard diet (SD) throughout the study or a Western-type diet (WD) starting 1 wk after the completion of tamoxifen administration and continuing for a total of 5 wks. Mini osmotic pumps were implanted in mice 2 wks after completion of tamoxifen administration and delivered saline or AngII at 1,000 ng/kg/min for 4 wks. Results: AngII infused and SD fed iLpl-/- versus Lplf/f mice had elevated plasma TG and TC levels but similar abdominal aortic external diameter and AAA incidence. Since the SD was low in fat, a high fat WD was then fed to AngII-infused mice. Plasma TG and TC were increased in female iLpl-/- versus Lplf/f mice. However, plasma lipid concentrations could not be measured in male iLpl-/- because 10 of 11 animals had died from aortic rupture. In contrast, none of the male Lplf/f mice died and only 4 of 11 had abdominal aortic dilation. Female compared to male iLpl-/- mice were protected from AngII-induced aortic rupture (1/11 died) and only 1 of 9 females had abdominal aortic dilation. To eliminate the possibility that HTG alone caused aortic rupture in male mice, the study was repeated with the addition of saline infusion. In agreement with the first study, AngII plus WD lead to death by aortic rupture in all male iLpl-/- mice (9/9). In contrast, iLpl-/- male mice infused with saline had markedly greater survival (1/5 died of unknown cause). Conclusions: HTG causes aortic aneurysm development in AngII-infused male iLpl-/- mice. Thus, treating HTG could reduce AAA risk.

Abstract 128: Blood TMAO Predicts Abdominal Aortic Aneurysm Growth Rate And Need For Surgical Intervention

Background: Patients known to have abdominal aortic aneurysms (AAAs) undergo surveillance imaging to predict both the risk for acute aortic syndromes including aortic dissection and aortic rupture, and the need for surgical intervention. Aortic rupture is a feared consequence of rapidly expanding AAAs. Aims: A blood biomarker that predicts risk for AAA and distinguishes slow from fast AAA growth does not exist but could be a valuable tool for risk stratification. We recently reported systemic levels of the gut microbe-generated metabolite trimethylamine N-oxide (TMAO) are associated with the presence of AAA in humans, and directly contribute to AAA progression in animal models. Methods: We leveraged access 805 patients in two cohorts from Europe (n=237) and the United States (n=658) undergoing serial aortic imaging surveillance. Blood TMAO concentration was measured by stable isotope dilution mass spectrometry. Results: TMAO was positively associated with larger baseline and follow-up abdominal aortic diameter beyond traditional factors (Adjusted OR 3.87, 95% CI, 2.70-5.58, P&lt;0.001). In addition, TMAO predicted rapid AAA growth (HR 1.81, 95%CI, 1.23-2.67, P=0.0029). When TMAO was added to a predictive model of traditional risk factors for AAA, we saw a significant improvement in the net reclassification index (NRI, 0.43, P &lt; 0.001; C statistic, 0.77 (0.72–0.81) with TMAO vs. NRI 0.73 (0.69–0.78) without TMAO, P =0.005). Finally, including TMAO in a predictive model for assessing need for surgical intervention among AAA patients significantly improved the prognostic performance of the model (NRI, 0.44, P &lt; 0.001; C statistic, 0.78 (0.73–0.82) with TMAO vs. 0.75 (0.70–0.79) without TMAO, P =0.004) (Fig. 1). Conclusions: Elevated TMAO levels predict increased risk of AAA, and identify patients with fast-growing AAA and those who may benefit from early surgical intervention to prevent acute aortic syndromes.

Abstract 2010: Atherosclerotic Plaque Macrophages Drive Abdominal Aortic Aneurysm Formation

Introduction: Cigarette smoking (CS) contributes to the most deaths in abdominal aortic aneurysms (AAA) and tobacco use associates with early damage to the abdominal aorta. Associated risk factors, such as hyperlipidemia, link clinical AAA to the atherosclerotic process, suggesting common pathogenetic features with plaque development. We hypothesized that CS exposure exacerbates atherosclerotic disease in the abdominal aorta by increasing the recruitment of inflammatory macrophages that mediate arterial degradation and AAA formation. Methods: Adult male Apoe deficient mice commenced a high cholesterol diet and were concomitantly exposed to CS or room air (RA) for 4, 8, 12, and 16 weeks. As plaque macrophages are highly prevalent in advanced AAA, additional CS exposed mice received a selective CSF1R inhibitor, PLX3397, for up to 16 weeks to deplete macrophages. AAA incidence, atherosclerotic plaque burden and lesion composition were assessed in the aorta by immunofluorescence, Movat, EVG, and Oil Red O staining. Results: CS induced AAA at all timepoints with the highest incidence of 37% at 16 weeks of exposure (n=151 CS, n=75 RA p&lt; 0.05). Aneurysms always coincided with atherosclerosis (n=7 CS, n=7 CS/AAA p&lt;0.05), and severe elastin fragmentation was consistently overlaid by plaque (n=20 CS p&lt;0.05, Fig 1A and B). In some cases, lesions also associated with aortic rupture, causing death in ~11% of animals (n = 35 RA, n = 46 CS p&lt;0.04). CD68+ macrophages associated highly with severe elastin damage but less at intact regions (2.6-fold p&lt;0.0001, Fig 1C). PLX3397-mediated macrophage depletion attenuated plaque development and prevented AAA (n=20 treated, n=27 control p&lt;0.05, Fig 1D). Conclusion: CS exacerbates atherosclerosis and increases the accumulation of macrophages at sites of arterial injury. Depletion of macrophages results in a lack of aneurysm formation, highlighting their capacity to directly injure the aortic wall and necessity to mediate AAA.

Abstract 1014: Molecular Dynamics In The Progression Of Aortic Dissection With Emphasis On De Novo Elastic Fiber Synthesis

Background: Aortic dissection (AD) confined to the descending thoracic aorta is typically managed conservatively in the acute phase. However, these patients often require surgeries due to aortic dilatation in the chronic phase. Although preclinical studies have been conducted to investigate the mechanism of AD, most studies focused on the acute phase, especially the cause of AD. It remains unknown how molecular mechanisms alter following AD. Methods and Results: To determine the molecular alteration after AD, bulk RNA sequencing was performed using aortas from mice administered β-aminopropionitrile (BAPN) for 1, 4, or 12 weeks that represent pre, acute, and chronic phases of ADs, respectively. There were 6,755 differentially expressed genes (DEGs), and 2,667 and 1,173 DEGs were upregulated in the acute and chronic phases, respectively. Gene ontology analysis revealed that DEGs in the acute phase were related to inflammation, whereas DEGs in the chronic phase were associated with extracellular matrix. Those DEGs in the chronic phase included tropoelastin ( Eln ), the precursor of elastic fibers. In situ hybridization and immunostaining demonstrated that Eln mRNA and protein were distributed in the vascular wall of the false lumen. Of note, these molecules formed new elastic fibers, as evidenced by Verhoeff’s iron hematoxylin staining. The de novo fibers were thinner than native fibers; however, ultrasonography revealed that aortas with AD lesions had higher elasticity and distensibility compared to intact aortas. These data suggest that new elastic fibers protect against aortic rupture after AD. Next, a transcriptional factor prediction analysis was performed to identify a potential regulator of Eln transcription and found that Etv5 could be aligned in both the promoter and enhancer regions of Eln . Immunostaining showed that ETV5 was spatially coincident with Eln mRNA and de novo fibers. Conclusion: Genes related to the extracellular matrix are upregulated in response to AD in BAPN-administered mice. Elastic fibers are newly formed in the vascular wall of the false lumen in chronic AD accompanied by enhanced Etv5 .

Abstract 149: The Protective Effect Of Vamp8 Deficiency In Aortopathies: Potential Impact Of Impaired Platelet Cargo Release

Introduction and Objective: Platelet activation and subsequent cargo secretion play a critical role in thrombus formation and aortic remodeling, factors potentially influencing the growth and rupture of abdominal aortic aneurysms (AAA). Despite the compelling data that platelet activation is associated with AAA and rupture, the underlying mechanisms remain poorly understood. This study hypothesizes that VAMP8, a key element of platelets’ secretory machinery, significantly contributes to AAA formation. Approach and Results: A retrospective, single-center multiple comparisons study of adult aneurysmal patients admitted to UKHealthCare between 2004 and 2023 revealed a significantly lower platelet count in AAA patients (n=3131, 213.76 ± 3.46) vs. healthy individuals (n= 6309, 243.18 ± 4.09) suggesting an increase in platelets consumption, potentially in the aneurysmal sack. Thoracic aortic aneurysm and aortic dissection patients also indicated lower platelet count. In vivo , platelets were shown to accumulate at elastin break sites and false lumens of abdominal aortas from 28-day AngII-infused hypercholesteremic mice. To assess the role of platelets, specifically platelet secretion, we utilized VAMP8 null mice. We first validated the platelet secretion defect in these mice and then used RNASeq and proteomics array to define the role of VAMP8 in platelet cargo packaging. Next, VAMP8 -/- or WT hypercholesterolemic male mice fed a Western diet were infused with AngII (1,000 ng/kg/min) for 4 weeks. Our results revealed that VAMP8 -/- mice are protected against AngII-driven aortic rupture. Additionally, aortic ex vivo analysis indicated that the VAMP8 deficiency (n=15, aortic diameter: 0.9 mm ± 0.03) profoundly attenuated AngII-induced AAA compared to control (n=9, aortic diameter: 2.0 mm ± 0.2). Further analysis also indicated a marked reduction in thoracic aortic aneurysm and atherosclerosis development in VAMP8 -\- vs. Control group. Conclusion: Our results elucidate that a deficiency in VAMP8 results in the profound attenuation of aortic aneurysms and atherosclerosis development, introducing a novel paradigm for understanding the impact of platelet cargo secretion in the development of aortopathies.

Abstract 3015: Matrix Metalloproteinase Inhibition In Rat Abdominal Aortic Aneurysm

Background: Matrix metalloproteinases (MMPs) have a robust proteolytic activity and play a fundamental role in degradation of extracellular matrix proteins. This degradation is a hallmark of the initiation, progression, and rupture of abdominal aortic aneurysms (AAAs). Hypothesis: We hypothesized that broad inhibition of MMPs with a 3 rd generation MMP inhibitor (GM6001) can reduce AAA inflammation and rupture using an established rat model. Aims: Our study aimed to investigate the potential of GM6001 in reducing AAA-related inflammation using a rat model, filling a critical gap in AAA research. Methods: Male Sprague-Dawley rats underwent intraluminal infrarenal perfusion of abdominal aorta using porcine pancreatic elastase (PPE), and daily β-aminopropionitrile (BAPN) to promote AAA rupture. Starting on postoperative day 3 (POD3) rats were treated daily either with or without GM6001 via intraperitoneal injections. On POD6, treated and untreated groups, underwent PET/CT imaging using a pan-MMP radiotracer 64Cu-RYM2 and in vivo aortic diameter measurement using ultrasound. Rate of rupture of treated and untreated groups was observed until POD14 (Fig 1A). Results: Treated rats demonstrated no evidence of toxicity or weight loss. Compared to untreated rats, treated rats had lower AAA rupture rates (P&lt;0.01; Fig 1B), smaller AAA diameters (P&lt;0.05; Fig 1C), and lower AAA MMP radiotracer uptake (P&lt;0.05; Fig 1D,1G). Total and active MMP-9 were significantly lower in treated rats (Fig 1E-F). In addition, IL-1B, IL-17A, IL-18, IFN-y, and RANTAS were significantly lower in treated rats, but TNF-a was higher (Fig 1H-M). VVG staining demonstrated a higher content of preserved elastin in treated rats (Fig 1N). Conclusion: Inhibition of MMPs with a 3 rd generation MMP inhibitor appears to be a promising therapeutic approach to impede the progression, inflammation, and rupture of AAAs in rats. This may represent a renewed pathway for MMP inhibition in human subjects with AAAs.

Abstract 1010: Novel Murine Model For Infrarenal Abdominal Aortic Aneurysm Development And Rupture

Introduction: Abdominal Aortic Aneurysm (AAA) rupture is linked with increased mortality. Multiple rodent models attempt to capitulate AAA pathology to investigate a preventative cure. However, there are currently no murine models that reliably mimic AAA rupture. Compounds such as porcine pancreatic elastase (PPE), papain, β-aminopropionitrile (BAPN) and angiotensin II (ANG II) can independently promote AAA formation in rodents. We hypothesize that combining these agents can lead to reliable infrarenal AAA rupture model in mice. Methods: 28 male C57BL/6 mice underwent aortic topical exposure to 50μL of either saline (sham), PPE, papain or both PPE+papain (20 &amp; 10.3mg/mL respectively) for 20 minutes with a cotton ball to induce AAA degeneration. A group of 10 mice were also exposed to BAPN at 0.3% via drinking water (Fig 1A). After 3 days, another group of 5 mice was further exposed to ANG II subcutaneous pump. Weight and in vivo aortic size were measured longitudinally. Mice that died spontaneously were promptly assessed to evaluate for AAA rupture (Fig 1B). All remaining mice were sacrificed at week 4. Results: Compared to sham, mice exposed to papain or PPE+papain, but no BAPN or ANG II, demonstrated no change in weight gain, but significantly increased aortic diameter at week 4 (p&lt;0.01) while administration of 0.3% BAPN demonstrated further increase in AAA diameter in both groups (p=0.002 and p&lt;0.001, respectively; Fig 1C). All mice that received PPE+papain+0.3% BAPN as well as ANG II pump developed infrarenal AAAs and 80% developed a free rupture by day 9 (Fig 1D). Conclusion: We present a novel murine model that provides a high rate of infrarenal AAA development and rupture. The model not only combines matrix degradation, but also impulse risk factors known to enhance AAA rupture in humans. The feasibility and reliability of the model facilitates its use in future murine genetic and pharmacological studies that aim to understand AAA pathophysiology and methods of prevention.

Abstract 2015: Pyruvate Carboxylase-mediated Vascular Smooth Muscle Cell Mitochondrial Dysfunction Activates Cgas-sting Signaling In Aortic Dissection.

Background: Aortic Dissection (AD), characterized by the loss of vascular smooth muscle cells (VSMC) and degradation of the extracellular matrix, carries an exceptionally high mortality rate, and as of now, there are no effective drugs to impede its occurrence and progression. Deciphering the mechanisms governing the onset and progression of aortic dissection is paramount for the development of innovative therapeutic modalities. Recent evidence suggests a pivotal role of mitochondrial metabolism in vascular inflammation, with pyruvate carboxylase (PC) emerging as a crucial component of the tricarboxylic acid cycle. In this study, we investigated the influence of PC on the occurrence and development of AD, elucidating the underlying mechanisms. Methods: Investigating alterations in PC expression levels in aortic tissues of both humans and C57BL/6 mice, and assessing the impact of PC on the occurrence and AD in PC SMKO mice. The study further explores the role of PC through both in vivo and in vitro investigations to delineate the associated pathways. Results: We observed a significant upregulation in the expression of PC in AD tissues. In the AD model of mice, the occurrence rate of AD and the mortality resulting from aortic dissection rupture were significantly reduced in PC SMKO mice. Transcriptomic results revealed that overexpression of PC in VSMCs could activate the STING pathway. Inhibition of the STING pathway significantly reduced both the occurrence and mortality rates of AD in mice. Mechanistically, overexpression of PC induced mitochondrial metabolic dysregulation, leading to nuclear and mitochondrial DNA damage. The released DNA into the cytoplasm activated the transduction of the STING signaling pathway, consequently causing necrosis of VSMC. Conclusions: Our results indicated that PC could facilitate the occurrence and progression of AD by activating the STING pathway. Targeting PC has the potential to prevent the onset of AD.

Abstract 2022: AlphaV Integrins Inhibition Downregulates Pro-fibrotic Events In Human Aortic Smooth Muscle Cells And Limits Thoracic Aortic Aneurysm Progression In Marfan Mice

Aortic dilation can often lead to lethal events, such as aortic dissection and/or vessel rupture. The aneurysms occurring in the thoracic aortic trait (TAA) may depend on comorbidities, such as hypertension, or on genetically determined conditions, such as Marfan syndrome (MFS). To date, the surgical replacement of aorta represents the most effective therapeutic approach in all TAA patients, since an etiologic pharmacological treatment is still lacking. Integrin receptors are key players in cellular mechanotransduction responses and the role of integrins containing αV subunit have been described as responsible for pro-fibrotic molecular events. Recently, it has been reported the effectiveness of a pan αV integrin inhibitor ( i.e. , GLPG0187) in limiting the TAA progression in MFS in vivo model. However, the specific αV integrin subgroup directly involved in this detrimental process is yet not known. We evaluated the effectiveness of the specific αVβ3 and αVβ5 integrin inhibitor cilengitide in downregulating pro-fibrotic in vitro events on MFS patients’ vascular smooth muscle cells (MFS-VSMC), and in limiting in vivo thoracic aortic dilation on a MFS mice model. By comparison with healthy control (HC)-VSMC, MFS-VSMC showed higher levels of αVβ3 and αVβ5 integrins as well as pro-fibrotic collagen I. When compared with GLPG0187, the cilengitide-mediated in vitro inhibition of these integrins determined a more effective downregulation of TGF-β downstream pathways (SMAD2/3 and ERK1/2) as well as a statistical tempered expression of pro-fibrotic mechanotransduction mediators, such as RhoA GTPase. The 2D-echocardiographic results on MFS mice (Fbn1 C1039G/+ ) treated with cilengitide confirmed the greater effectiveness of this drug in limiting the TAA progression, not only in comparison with vehicle but also with the broad pan αV integrin inhibitor GLPG0187. Altogether, our results improve the know-how on αV integrin involvement in MFS-TAA scenario, unveiling the specific detrimental role of αVβ3 and αVβ5 in this pathological context. The selective inhibition of these integrins exerted by cilengitide highlights the role of this compound as a potential and more targeted tool for future therapeutic approaches to limit TAA progression in MFS patients.

Abstract 139: Contribution Of Platelet Granule Cargo Uptake And Secretion To The Initiation And Progression Of Aortic Aneurysms

Aortic aneurysms present as aortic widening and often catastrophic rupture. While precipitated by a thrombo-inflammatory environment, underlying pathological mechanisms are unclear and adequate treatment is lacking. Antithrombotics have been implied as therapy, but few studies have defined how platelets contribute to aortic aneurysms. We studied the role of platelet granule cargo uptake and secretion in aortic aneurysm formation. Aneurysms were induced in mice defective in platelet α-granule biogenesis (Nbeal2 -/- , Serglycin -/- ), endocytosis (Arf6 -/- , VAMP2/3 Δ ), and exocytosis (Munc13-4 Jinx ) via: i.p. injection of an AAV vector with a mouse PCSK9 gain-of-function mutation; western diet; and continuous s.c. infusion of angiotensin II. Thoracic and abdominal aneurysm formation was assessed with ultrasound. At 4 and 12 weeks, or after rupture, aortas were harvested, analyzed, and prepared for histology. During the study, 30% (3/10) of Nbeal2 -/- and 21.4% (3/18) of Munc13-4 Jinx mice suffered aortic rupture, compared to 0% (0/26) of wildtype mice. In the survivors, the inner diameter of neither the thoracic nor abdominal aorta of Nbeal2 -/- mice changed over time. Ex vivo , Serglycin -/- mice showed a clear, more distributed, widening of the thoracic and descending aorta instead of local aneurysm formation with an increased maximum outer diameter of the ascending region. Munc13-4 Jinx mice had an all-or-nothing phenotype; either early-stage massive aneurysm formation or rupture, or a more diffused phenotype. Mice with platelet endocytosis defects survived and at early stages, the differential increase in the inner diameter of both the thoracic and abdominal aorta was higher in female Arf6 -/- mice. Similarly, VAMP2/3 Δ mice had the largest inner thoracic diameter increase after 28 days. Arf6 -/- and VAMP2/3 Δ mice showed a smaller maximum outer diameter of the descending aorta as wildtype. Preliminary histology shows reduced elastin breaks in all genetic strains, especially in Nbeal2 -/- and VAMP2/3 Δ mice. Our data show that platelet granule cargo exerts significant but perhaps contrasting effects on aortic aneurysm formation. By comparing phenotypes, more detailed mechanistic insights into the role of platelets in aortic aneurysms are possible.

Rolipram impacts on redox homeostasis and cellular signaling in an experimental model of abdominal aortic aneurysm

IntroductionCyclic nucleotide phosphodiesterases (PDEs) of the PDE4 subfamily are responsible for the hydrolysis and subcellular compartmentalization of cAMP, a second messenger that modulates vascular functionality. We had shown that PDE4B is induced in abdominal aortic aneurysms (AAA) and that PDE4 inhibition by rolipram limits experimental aneurysms. In this study we have delved into the mechanisms underlying the beneficial effect of rolipram on AAA. MethodsAAA were induced in ApoE−/− mice by angiotensin II (Ang II) infusion. Aneurysm formation was evaluated by ultrasonography. The expression of enzymes involved in redox homeostasis was analyzed by real-time RT-PCR and the activation of signaling pathways by Western blot. ResultsInduction of PDE4B in human AAA has been confirmed in a second cohort of patients. In Ang II-infused ApoE−/− mice, rolipram increased the percentage of animals free of aneurysms without affecting the percentage of aortic ruptures. Quantitative analyses determined that this drug significantly attenuated aortic collagen deposition. Additionally, rolipram reduced the increased Nox2 expression triggered by Ang II, exacerbated Sod1 induction, and normalized Sod3 expression. Likewise, PDE4 inhibition decreased the activation of both ERK1/2 and the canonical Wnt pathway, while AKT activity was not altered. ConclusionsThe inhibition of PDE4 activity modulates the expression of enzymes involved in redox homeostasis and affects cell signaling pathways involved in the development of AAA.

Abstract 2020: Vascular Glucose Transporter 1 Is Dispensable For Abdominal Aortic Aneurysm Induced By Angiotensin II

Background: Pharmacological inhibition of glycolysis attenuated abdominal aortic aneurysm (AAA) development in mice. Glucose transporters (GLUTs) incorporate glucose as a first step of glycolysis. GLUT1 over-expression in vascular smooth muscle cells (VSMC) leads to enhancement of atherosclerosis. However, the role of VSMC GLUT1 in AAA remains unclear. Hypothesis: VSMC GLUT1 deletion attenuates AAA development and rupture in mice. Goals/Aims: Our goal was to establish contribution of VSMC GLUT1 in AAA. Methods: The glucose consumption of cultured VSMCs was evaluated in the presence or absence of AngII stimulation and GLUT1 inhibitor BAY-876. GLUT1 floxed mice were crossed with tamoxifen-inducible SMMHC-Cre mice. At 6 weeks of age, mice were injected with tamoxifen. As a control, tamoxifen-treated SMMHC-Cre male mice were utilized. At 8 weeks, angiotensin II (AngII, 1 μg/kg/min) was delivered for 4 weeks. In addition, mice received 1 mg/mL BAPN during the first 2 weeks of AngII infusion. After 4weeks, all animals were euthanized and maximal external diameter of the abdominal aorta was measured. Results: In cultured VSMC, the glucose consumption increased by AngII was attenuated by pretreatment with GLUT1 inhibitor (media glucose 257.9±4.5 vs 238.9±6.2 mg/dL, p&lt;0.05). AngII plus BAPN significantly developed AAA in control mice (diameter 1.05±0.07 vs 2.37±0.31mm, p&lt;0.05). However, silencing of VSMC GLUT1 did not affect AAA development by AngII plus BAPN (2.41±0.46mm, p=0.66). The survival rate due to aortic rupture in VSMC GLUT1 silenced mice and control mice treated with BAPN and AngII were 60.0% and 57.1%, respectively (p=0.820). AngII induced hypertension in control mice (102±3.8 vs 133±7.1mmHg, p&lt;0.05) and VSMC GLUT1 silenced mice (149±11.4mmHg, p=0.99). Discussion Although GLUT1 may be a primary VSMC GLUT to enhance glucose utilization in response to AngII stimulation, VSMC GLUT1 silencing did not alter AngII-dependent AAA development or rupture in a mouse model. Since pharmacological inhibition of GLUT attenuated AAA and associated macrophage infiltration, it is possible that GLUT1 expressed in macrophages may contribute to development of AAA. Conclusion: VSMC GLUT1 silencing did not alter AngII-dependent AAA development in a mouse model.

Abstract 1007: A Novel Heterogeneous Murine Aortic Model Derived From Micro-computed Tomography

Introduction: Strength and structural stability of the aorta primarily comes from collagen that is mostly found in the media layer of the aorta along with elastin. The risk of life-threatening aortic rupture increases in cases of aortic aneurysm diseases due to local deformation and weakening of the aortic wall. How does local structure affect how the aorta responds to stress? We hypothesize that material and geometric heterogeneity affect the local biomechanics of the aortic wall and that the local responses to stress are not necessarily the same as the global response. Our goal is to develop a novel finite element model (FEM) of collagen and elastin behavior in murine aorta derived from high-resolution micro-computed tomography (microCT). This model will allow us to study how the aorta deforms to blood pressure at the local level. Approach: The collagen and elastin from 100 vertical slices of microCT scans of a murine aorta were segmented, smoothed and meshed to create 3D models for FEM and the aortic ring was divided into 8 sections of varying geometry and composition. Local stress-strain relationships were extracted from uniaxial loading conditions. Simulations were conducted where the stiffness of collagen was set equal to (1X) or made stiffer than elastin by a factor of 10 (10X) or 100 (100X). The average Young’s modulus, E, for each section was calculated and used as parameters for FEM of the aortic ring to investigate the global mechanical behavior of the aortic wall. Results/Conclusions: The strains generated in the radial direction are greater than the strains in the hoop direction in each of the 8 heterogeneous sections of the aortic ring. There was significant variability in the E values in the 10X and 100X systems. FEM of a materially uniform aortic ring yielded smaller maximum principal logarithmic strains compared to a ring that was materially heterogeneous. This study provides evidence that local structure and material distribution are important in aortic biomechanics. Pathogenesis of aneurysmal disease is dependent on collagen and elastin turnover. Aneurysm rupture results from mechanical failure: peak wall stress exceeds local tissue strength. This novel method will allow for development of a complex aortic fracture model to study aortic pathologies.

Abstract 2040: Rapamycin Extends Life Of Matrix Gla Protein Knockout Mice Independent Of Vascular Calcification Content.

Background: Peripheral artery disease (PAD) is characterized by the narrowing and blockage of the vessels in lower extremities. While atherosclerosis has been the assumed culprit of PAD recent data now shows that medial arterial calcification (MAC) is the cause of below-the knee ischemia. MAC promotes thrombosis via inward remodeling, reduced elasticity, and arterial stiffness. The mechanisms driving MAC pathogenesis are unclear. Matrix Gla Protein (MGP) is an inhibitor of vascular calcification and present in arterial vessel walls. MGP -/- mice exhibit extensive MAC throughout their vasculature and die within 5-7 weeks due to aortic rupture or heart failure. The drug rapamycin functions as an inhibitor of cell proliferation and an activator of autophagy. Hypothesis: That rapamycin reduces MAC in MGP -/- mice via inhibiting inward remodeling and activating autophagy. Methods: MGP +/+ and MGP -/- mice treated with vehicle or rapamycin (5mg/kg, 3x weekly) starting at 10 days old for 2 weeks. Calcification was quantified via micro-computed tomography (uCT). Collagen structure and elastin quality were assessed histological staining. Markers of proliferation (Ki-67), cell death (Caspase 3), autophagy (LC3), and calcification (Runx2) were quantified via immunofluorescence staining. Western blot was used to assess autophagy flux and proliferation in smooth muscle cells (SMCs) isolated from MGP +/+ and MGP -/- mice. Results: While rapamycin treatment doubled the life-expectancy of MGP -/- mice, the calcification content was unchanged compared to the vehicle. However, rapamycin caused a significant decline in mineral density. Higher collagen content and improved elastin structure were observed in MGP -/- treated with rapamycin compared to vehicle. Runx2 and Ki-67 were elevated in MGP -/- mice compared to MGP +/+ , but there was no difference in response to rapamycin treatment. No difference was observed in caspase 3 levels. Under rapamycin treatment, MGP -/- SMCs exhibited higher autophagy flux than MGP +/+ SMCs. Conclusion: While rapamycin did not reduce MAC, our data suggest that rapamycin potentially preserves the integrity of the aortic vessel wall by inducing autophagy, which requires further investigation.

Abstract 3016: Cytoplasmic And Nuclear Nfatc3 Cooperatively Contributes To Vascular Smooth Muscle Cell Dysfunction And Drives Aortic Aneurysm And Dissection

Background: Aortic aneurysm and aortic dissection (AAD) are fatal diseases resulting in catastrophic aortic rupture and sudden death. The degradation of the extracellular matrix (ECM) and the phenotypic transformation of vascular smooth muscle cells (VSMCs) are crucial pathological mechanisms in AAD. We previously found that macrophage NFATc3 inhibits atherosclerosis and foam cell formation. However, the precise role of VSMC-NFATc3 in AAD remains unknown. Aims: This study investigates the role of NFATc3 in VSMCs in AAD progression and the molecular mechanisms. Methods: To investigate the role of NFATc3 in VSMCs in AAD, we used VSMC-NFATc3-specific knockout and knock-in mice. By establishing mouse models for thoracic AAD (TAAD) and abdominal aortic aneurysm (AAA), we employed techniques such as RNA sequencing, mass spectrometry, and chromatin immunoprecipitation to study the mechanistic role of VSMC-NFATc3 in AAD. Results: Cytoplasmic and nuclear NFATc3 levels are elevated in human and mouse AAD. VSMC-NFATc3 deletion reduces TAAD and AAA progression in mice, contrary to VSMC-NFATc3 overexpression. VSMC-NFATc3 deletion reduces ECM degradation and maintains the VSMC contractile phenotype. Nuclear NFATc3 targets and transcriptionally upregulates MMP9 and MMP2, promoting ECM degradation and AAD development. NFATc3 promotes VSMC phenotypic switching by binding to eukaryotic elongation factor 2 (eEF2) and inhibiting its phosphorylation in the VSMC cytoplasm. Restoring eEF2 reverses the beneficial effects in VSMC-specific NFATc3-knockout mice. Cabamiquine—targets eEF2 and inhibits protein synthesis—inhibited AAD development and progression in VSMC-NFATc3-overexpressing mice. Conclusion: VSMC-NFATc3 promotes VSMC switch and ECM degradation while exacerbating AAD development, making it a novel potential therapeutic target for preventing and treating AAD.

Initial experience of endovascular aneurysm repair at the Dr. Eduardo Liceaga General Hospital of Mexico

Background: Abdominal aortic aneurysm (AAA) is the permanent and irreversible dilation of the lower part of the aorta where the vessel expands, making it susceptible to rupture, which represents a high mortality incident. Methods: A review of clinical records was carried out from September 2021 to March 2023, patients who were diagnosed with aortic aneurysm were included in whom endovascular exclusion of abdominal and thoracic aortic aneurysm was performed at the General Hospital of Mexico by the angiology vascular and endovascular surgery department. Results: 18 endovascular repairs of aortic aneurysms were performed, of which 15.4% were female (n=6) and 84.6% male (n=12). The average proximal neck diameter in the thoracic aorta was 31 mm, average proximal neck diameter in infrarenal AAA 22.2 mm, average aneurysmal diameter in infrarenal segment 63.8 mm, thoracic 31 mm. Regarding the type of endovascular procedure, 11.1% were repaired with the fenestrated endovascular aneurysm repair (FEVAR) technique, and the same proportion with chimney endovascular aneurysm repair (ChEVAR), for a resolution with conventional EVAR of 77.7%. Complications occurred in 3 patients, 2 of which resulted in type 1a and 1b endoleaks that were reoperated and repaired with a proximal cuff, balloon angioplasty, and embolization of the aneurysmal sac with coils. Conclusions: Aortic aneurysm remains a major cause of death in adults because of aortic rupture despite advances over the past two decades that have been made in the endovascular management of large, symptomatic, and ruptured. Timely treatment is essential to prevent rupture and poor patient outcomes.