Crosstalk of platelets with macrophages and fibroblasts aggravates inflammation, aortic wall stiffening, and osteopontin release in abdominal aortic aneurysm

AIMS

Abdominal aortic aneurysm (AAA) is a highly lethal disease with progressive dilatation of the abdominal aorta accompanied by degradation and remodelling of the vessel wall due to chronic inflammation. Platelets play an important role in cardiovascular diseases, but their role in AAA is poorly understood.

METHODS AND RESULTS

The present study revealed that platelets play a crucial role in promoting AAA through modulation of inflammation and degradation of the extracellular matrix (ECM). They are responsible for the up-regulation of SPP1 (osteopontin, OPN) gene expression in macrophages and aortic tissue, which triggers inflammation and remodelling and also platelet adhesion and migration into the abdominal aortic wall and the intraluminal thrombus (ILT). Further, enhanced platelet activation and pro-coagulant activity result in elevated gene expression of various cytokines, Mmp9 and Col1a1 in macrophages and Il-6 and Mmp9 in fibroblasts. Enhanced platelet activation and pro-coagulant activity were also detected in AAA patients. Further, we detected platelets and OPN in the vessel wall and in the ILT of patients who underwent open repair of AAA. Platelet depletion in experimental murine AAA reduced inflammation and ECM remodelling, with reduced elastin fragmentation and aortic diameter expansion. Of note, OPN co-localized with platelets, suggesting a potential role of OPN for the recruitment of platelets into the ILT and the aortic wall.

CONCLUSION

In conclusion, our data strongly support the potential relevance of anti-platelet therapy to reduce AAA progression and rupture in AAA patients.

Lack of ATP2B1 in CD4+ T Cells Causes Colitis

BACKGROUND

The ATP2B1 gene encodes for a calcium pump, which plays a role in removing Ca2+ from cells and maintaining intracellular Ca2+ homeostasis. Reduction of the intracellular Ca2+ concentration in CD4+ T cells is thought to reduce the severity of colitis, while elevation of Ca2+ in CD4+ T cells induces T cell hyperactivity. Our aim was to clarify the role of ATP2B1 in CD4+ T cells and in inflammatory bowel disease development.

METHODS

A murine CD4+ T cell-specific knockout (KO) of ATP2B1 was created using a Cre-loxP system. CD4+ T cells were isolated from thymus, spleen, and blood using fluorescence-activated cell sorting. To quantify messenger RNA levels, quantitative real-time polymerase chain reaction was performed.

RESULTS

Although the percentages of CD4+ T cells in both KO mouse spleen and blood decreased compared with those of the control samples, both T-bet (a T helper 1 [Th1] activity marker) and GATA3 (a Th2 activity marker) expression levels were further increased in KO mouse blood CD4+ T cells (vs control blood). Diarrhea and colonic wall thickening (with mucosal changes, including crypt distortion) were seen in KO mice but not in control mice. Prior to diarrhea onset, the KO mouse colon length was already noted to be shorter, and the KO mouse stool water and lipid content were higher than that of the control mice. Tumor necrosis factor α and gp91 expressions were increased in KO mouse colon.

CONCLUSIONS

Lack of ATP2B1 in CD4+ T cells leads to Th1 and Th2 activation, which contributes to colitis via elevation of tumor necrosis factor α and oxidative stress.

Genome-wide association meta-analysis identifies risk loci for abdominal aortic aneurysm and highlights PCSK9 as a therapeutic target

Abdominal aortic aneurysm (AAA) is a common disease with substantial heritability. In this study, we performed a genome-wide association meta-analysis from 14 discovery cohorts and uncovered 141 independent associations, including 97 previously unreported loci. A polygenic risk score derived from meta-analysis explained AAA risk beyond clinical risk factors. Genes at AAA risk loci indicate involvement of lipid metabolism, vascular development and remodeling, extracellular matrix dysregulation and inflammation as key mechanisms in AAA pathogenesis. These genes also indicate overlap between the development of AAA and other monogenic aortopathies, particularly via transforming growth factor β signaling. Motivated by the strong evidence for the role of lipid metabolism in AAA, we used Mendelian randomization to establish the central role of nonhigh-density lipoprotein cholesterol in AAA and identified the opportunity for repurposing of proprotein convertase, subtilisin/kexin-type 9 (PCSK9) inhibitors. This was supported by a study demonstrating that PCSK9 loss of function prevented the development of AAA in a preclinical mouse model.

Serum microRNA-501-3p is a potential diagnostic tool for detecting mild cognitive impairment: Ehime genome study

Tight junction disruption and dysfunction are involved in the progression of blood-brain barrier (BBB) breakdown. Recent investigations have revealed BBB disruption in patients with vascular cognitive decline. Our previous studies showed that miR-501-3p negatively regulates cerebral endothelial tight junction protein-1, resulting in the disruption of the BBB, and playing an important role in the development of vascular cognitive impairment. BBB breakdown in white matter lesions is often seen in the patients with vascular mild cognitive impairment (MCI). We therefore hypothesize that most early-phase MCI patients may demonstrate elevated expression of miR-501-3p and sought to investigate whether serum exosome miR-501-3p levels could be a clinical indicator for detecting mild cognitive impairment. One hundred and seventy-eight subjects (aged 73 [68-75] years, 53% male) were recruited for this study. The Japanese version of the Montreal Cognitive Assessment (MoCA-J) was used for detecting MCI. Serum exosome miR-501-3p expression levels were measured by qPCR methods. Patients were divided into two groups depending on whether their miR-501-3p ∆Ct values were above ("High"; n = 74) or below ("Low"; n = 104) cutoff levels determined by ROC curve. MCI was detected significantly more often in the miR-501-3p-High group (vs. -Low group, 63.5% vs. 47.1%, respectively; p < 0.05). Multivariate logistic regression analysis showed a significant association between MCI status and High miR-501-3p (odds ratio 2.662; p < 0.01), improved vs. known risk factors. In non-diabetic patients, High miR-501-3p was positively associated with MCI status (odds ratio 3.633; p < 0.01) and also positively associated with MCI status in those with atherosclerosis (odds ratio 3.219; p < 0.01). The present study demonstrates that elevated expression of blood exosomal miR-501-3p can indicate the presence of MCI in human patients. Early detection of vascular injuries may allow a reduction in progressive dementia through the management of vascular risk factors.

E-cigarette exposure augments murine abdominal aortic aneurysm development: role of Chil1

AIMS

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease with a strong correlation to smoking, although underlying mechanisms have been minimally explored. Electronic cigarettes (e-cigs) have gained recent broad popularity and can deliver nicotine at comparable levels to tobacco cigarettes, but effects on AAA development are unknown.

METHODS AND RESULTS

We evaluated the impact of daily e-cig vaping with nicotine on AAA using two complementary murine models and found that exposure enhanced aneurysm development in both models and genders. E-cigs induced changes in key mediators of AAA development including cytokine chitinase-3-like protein 1 (CHI3L1/Chil1) and its targeting microRNA-24 (miR-24). We show that nicotine triggers inflammatory signalling and reactive oxygen species while modulating miR-24 and CHI3L1/Chil1 in vitro and that Chil1 is crucial to e-cig-augmented aneurysm formation using a knockout model.

CONCLUSIONS

In conclusion our work shows increased aneurysm formation along with augmented vascular inflammation in response to e-cig exposure with nicotine. Further, we identify Chil1 as a key mediator in this context. Our data raise concerns regarding the potentially harmful long-term effects of e-cig nicotine vaping.

Time-dependent effects of cellulose and gelatin-based hemostats on cellular processes of wound healing

INTRODUCTION

Oxidized regenerated cellulose-based (ORC - TABOTAMP), oxidized non-regenerated cellulose-based (ONRC - RESORBA CELL), and gelatin-based (GELA - GELITA TUFT-IT) hemostats are commonly used in surgery. However, their impact on the wound healing process remains largely unexplored. We here assess time-dependent effects of exposure to these hemostats on fibroblast-related wound healing processes.

MATERIAL AND METHODS

Hemostats were applied to fibroblast cell cultures for 5-10 (short-), 30 and 60 min (intermediate-) and 24 h (long-term). Representative images of the hemostat degradation process were obtained, and the pH value was measured. Cell viability, apoptosis and migration were analyzed after the above exposure times at 3, 6 and 24 h follow-up. Protein levels for tumor necrosis factor α (TNF-α) and transforming-growth factor β (TGF-β) were assessed.

RESULTS

ORC and ONRC reduced pH values during degradation, while GELA proved to be pH-neutral. Hemostat structural integrity was prolonged for GELA (vs. ORC and ONRC). TGF-β and TNF-α levels were reduced for ORC and ONRC (vs. GELA and control) (p < 0.05). Further, exposure of ORC and ONRC for longer than 5-10 min reduced cell viability vs. GELA and control at 3 h post-exposure (p < 0.05). Similarly, cell migration was impaired with ORC and ONRC exposure longer than 60 min at 24 h follow-up (p < 0.05).

CONCLUSIONS

Short-term exposure to ORC and ONRC impairs relevant wound healing-related processes in fibroblasts, and alters protein levels of key mediating cytokines. GELA does not show similar effects. We conclude that GELA may be preferred over ORC and ONRC over short-, intermediate- and long-term exposures. Future validation of the clinical relevance is warranted.

Role of MicroRNAs in acceleration of vascular endothelial senescence

Backgrounds

Many factors are involved in cellular aging, and senescence induction requires complex regulation of various signaling networks and processes. Specifically, in the area of aging-related vascular cognitive impairment, laboratory-based findings have not yet yielded agents of practical use for clinical settings. One possible reason is that the physiologic elements of aging have been insufficiently considered. We sought to establish techniques to better model cellular aging using modulation of microRNAs, aiming to identify key microRNAs capable of fine-tuning aging-associated genes, and thereby regulating the senescence of vascular endothelial cells.

Methods

We utilized expression microRNA arrays to evaluate control and senescent vascular endothelial cells in order to identify testable candidates. Bioinformatic analysis was used to select key microRNAs. These candidates were then modulated in vitro using microRNA mimics and inhibitors in endothelial cells, and senescence-associated gene expression patterns were evaluated by qPCR.

Results

Seventeen microRNAs were found to be significantly increased more than 2-fold in senescent cells. Of those, bioinformatic analysis concluded that miR-181a-5p, miR-30a-5p, miR-30a-3p, miR-100-5p, miR-21-5p, and miR-382-5p were likely associated with regulation of cellular senescence. We evaluated the potential targets of these six microRNAs by comparing them with cell-cycling and apoptosis-related genes from published mRNA transcriptional array data from aged tissues, and found that miR-181a-5p, miR-30a-5p and miR-30a-3p were enriched in overlapping targets compared with the other candidates. Modulation of these microRNAs in vascular endothelial cells revealed that over-expression of miR-30a-5p, and inhibition of both miR-30a-3p and miR-181a-5p, induced senescence.

Conclusion:

miR-181a-5p, miR-30a-5p and miR-30a-3p likely contribute to aging-associated vascular endothelial cell senescence.

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We aimed to identify key microRNAs regulating the senescence of vascular ECs.

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Bioinformatic analysis indicated miR-181a-5p, miR-30a-5p & 30a-3p as candidates.

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Overexpression of miR-30a-5p & inhibition of miR-30a-3p/181a-5p induce EC senescence.

peri-Adventitial delivery of smooth muscle cells in porous collagen scaffolds for treatment of experimental abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is associated with the loss of vascular smooth muscle cells (SMCs) within the vessel wall. Direct delivery of therapeutic cells is challenging due to impaired mechanical integrity of the vessel wall. We hypothesized that porous collagen scaffolds can be an effective vehicle for the delivery of human-derived SMCs to the site of AAA. The purpose was to evaluate if the delivery of cell-seeded scaffolds can abrogate progressive expansion in a mouse model of AAA. Collagen scaffolds seeded with either primary human aortic SMCs or induced pluripotent stem cell derived-smooth muscle progenitor cells (iPSC-SMPs) had >80% in vitro cell viability and >75% cell penetrance through the scaffold's depth, while preserving smooth muscle phenotype. The cell-seeded scaffolds were successfully transplanted onto the murine aneurysm peri-adventitia on day 7 following AAA induction using pancreatic porcine elastase infusion. Ultrasound imaging revealed that SMC-seeded scaffolds significantly reduced the aortic diameter by 28 days, compared to scaffolds seeded with iPSC-SMPs or without cells (acellular scaffold), respectively. Bioluminescence imaging demonstrated that both cell-seeded scaffold groups had cellular localization to the aneurysm but a decline in survival with time. Histological analysis revealed that both cell-seeded scaffold groups had more SMC retention and less macrophage invasion into the medial layer of AAA lesions, when compared to the acellular scaffold treatment group. Our data suggest that scaffold-based SMC delivery is feasible and may constitute a platform for cell-based AAA therapy.

Abstract 128: Nicotine Transgenerationally Alters Gene Methylation And Abdominal Aortic Aneurysm Risk

Significance: Both smoking and family history are major risk factors for abdominal aortic aneurysm (AAA). Smoking is a powerful modulator of DNA methylation, and nicotine alone can cause heritable epigenetic alterations in animal models and humans. Nicotine also increases aortic stiffness, predisposing towards AAA. We investigated the effects of parental nicotine exposure in mice on their offspring’s risk for experimental AAA and on transgenerational DNA methylation.

Methods: Male and female Apo E-/- mice (F0) were exposed to subcutaneous nicotine (25 mg/kg/day) or saline infusion for 28 days. After treatment completion, mice were mated to untreated controls. F1 generation offspring underwent Angiotensin II infusion (1μg/kg/min) to induce AAA at age 10-weeks. Aneurysm growth was tracked via ultrasound over 28 days. Subgroups of F1 mice underwent ex-vivo pressure myography assessment of the abdominal aorta. Germ and aortic tissue from both F0 and F1 were evaluated using RRBS-Seq genome-wide DNA methylation analysis.

Results: Parental nicotine augments model AAA formation, incidence, and rupture rates in their offspring. This effect was most significant in male offspring of nicotine-exposed females (vs. saline). Maternal nicotine exposure also increased F1 aortic stiffness. F0 nicotine exposure altered DNA methylation in multiple tissues, and led to numerous significant differentially methylated regions (DMRs) in their F1 offspring, many precisely conserved. Nicotine caused global DNA hypermethylation, altered maternally imprinted genes in F0 females, and had variable patterns depending on gender. Nicotine altered aortic methylation patterns in genes known to relate to AAA development, including lncRNAs/miRNAs. DMR pathway analysis revealed enrichment for transcription factors, suggesting that nicotine transgenerationally influences numerous genes through expression modulation.

Conclusion: Nicotine exposure can augment experimental AAA growth and aortic stiffness across generations. These effects are accompanied by widespread epigenetic changes in germ tissue and aorta, including several key AAA modulator genes, with enrichment in transcription factors, including many targeting known AAA-related genes.

Immunomodulation Therapy Using Tolerogenic Macrophages in a Rodent Model of Pulmonary Hypertension

Inflammation plays a major role in the pathogenesis of pulmonary hypertension (PH). We sought to investigate the effects of a cell-based immunomodulation in a dysimmune model of PH. PH was induced in athymic nude rats using semaxinib (Su group, n = 6). Tolerogenic macrophages (toM) were generated from monocyte isolation and then injected either the day before semaxinib injection (Prevention group, n = 6) or 3 weeks after (Reversion group, n = 6). Six athymic nude rats were used as controls. In vivo trafficking of toM was investigated with bioluminescence imaging showing that toM were mainly located into the lungs until 48 h after injection. Right ventricular (RV) end-systolic pressure and RV systolic function were assessed at 4 weeks using echocardiography. Morphometric analysis and RNA sequencing of the lungs were realized at 4 weeks. Rats treated with toM (Prevention and Reversion groups) had a significantly lower RV end-systolic pressure at 4 weeks (respectively, 25 ± 8 and 30 ± 6 mmHg vs. 67 ± 9 mmHg, P < 0.001), while RV systolic dysfunction was observed in Su and Reversion groups. Mean medial wall thickness of small arterioles was lower in Prevention and Reversion groups compared with the Su group (respectively, 10.9% ± 0.8% and 16.4% ± 1.3% vs. 28.2% ± 2.1%, P < 0.001). Similarly, cardiomyocyte area was decreased in rats treated with toM (150 ± 18 and 160 ± 86 μm2 vs. 279 ± 50 μm2, P < 0.001). A trend toward upregulation of genes involved in pulmonary arterial hypertension pathobiology was found in Su rats, while KCNK3 was significantly downregulated (fold-change = 9.8, P < 0.001). Injection of toM was associated with a less severe phenotype of PH in rats exposed to angioproliferative stress. Preserved expression of KCNK3 may explain the protective effect of toM.

MicroRNA miR-29b regulates diabetic aortic remodeling and stiffening

Patients with type 2 diabetes (T2D) are threatened by excessive cardiovascular morbidity and mortality. While accelerated arterial stiffening may represent a critical mechanistic factor driving cardiovascular risk in T2D, specific therapies to contain the underlying diabetic arterial remodeling have been elusive. The present translational study investigates the role of microRNA-29b (miR-29b) as a driver and therapeutic target of diabetic aortic remodeling and stiffening. Using a murine model (db/db mice), as well as human aortic tissue samples, we find that diabetic aortic remodeling and stiffening is associated with medial fibrosis, as well as fragmentation of aortic elastic layers. miR-29b is significantly downregulated in T2D and miR-29b repression is sufficient to induce both aortic medial fibrosis and elastin breakdown through upregulation of its direct target genes COL1A1 and MMP2 thereby increasing aortic stiffness. Moreover, antioxidant treatment restores aortic miR-29b levels and counteracts diabetic aortic remodeling. Concluding, we identify miR-29b as a comprehensive—and therefore powerful—regulator of aortic remodeling and stiffening in T2D that moreover qualifies as a (redox-sensitive) target for therapeutic intervention.

Exosome miR-501-3p Elevation Contributes to Progression of Vascular Stiffness

Background: Tight junction (TJ) disruption and dysfunction are involved in the progression of arteriosclerosis. miR-501-3p regulates endothelial TJ protein-1, resulting in TJ disruption. Because exosomal microRNAs can travel to distant tissues and influence cell behavior, patients with elevated miR-501-3p may experience accelerated vascular disease progression secondary to miR-501-3p-induced reductions in TJ. This study investigated whether plasma exosome miR-501-3p levels are associated with vascular stiffness, an indicator for arteriosclerotic changes. Methods and Results: Fifty-one subjects (mean [±SD] age 70±8 years, 37% male) enrolled in a medical checkup program were recruited to the study. Brachial-ankle arterial pulse wave velocity (baPWV) and plasma exosome miR-501-3p expression were measured. Patients were divided into 2 groups depending on whether their miR-501-3p ∆C_t values were above ("High"; n=24) or below ("Low"; n=27) the cut-off levels determined by receiver operating characteristic (ROC) curve analysis. Median (interquartile range) baPWV levels were significantly higher in the miR-501-3p High than Low group (1,664 [1,496-1,859] vs. 1,450 [1,353-1,686] cm/s, respectively; P<0.05). Multivariate logistic regression analysis showed a significant association between increased baPWV and High miR-501-3p expression (odds ratio 4.66). At follow-up visits (mean 62 months later), baPWV remained significantly higher in the miR-501-3p High than Low group (1,830 [1,624-2,056] vs. 1,620 [1,377-1,816] cm/s, respectively; P<0.05). Conclusions: High expression levels of exosome miR-501-3p contribute to arteriosclerotic changes.

Genetic Architecture of Abdominal Aortic Aneurysm in the Million Veteran Program

Supplemental Digital Content is available in the text.

Abdominal aortic aneurysm (AAA) is an important cause of cardiovascular mortality; however, its genetic determinants remain incompletely defined. In total, 10 previously identified risk loci explain a small fraction of AAA heritability.

Involvement of Myeloid Cells and Noncoding RNA in Abdominal Aortic Aneurysm Disease

Significance: Abdominal aortic aneurysm (AAA) is a potentially fatal condition, featuring the possibility of high-mortality rupture. To date, prophylactic surgery by means of open surgical repair or endovascular aortic repair at specific thresholds is considered standard therapy. Both surgical options hold different risk profiles of short- and long-term morbidity and mortality. Targeting early stages of AAA development to decelerate disease progression is desirable. Recent Advances: Understanding the pathomechanisms that initiate formation, maintain growth, and promote rupture of AAA is crucial to developing new medical therapeutic options. Inflammatory cells, in particular macrophages, have been investigated for their contribution to AAA disease for decades, whereas evidence on lymphocytes, mast cells, and neutrophils is sparse. Recently, there has been increasing interest in noncoding RNAs (ncRNAs) and their involvement in disease development, including AAA. Critical Issues: The current evidence on myeloid cells and ncRNAs in AAA largely originates from small animal models, making clinical extrapolation difficult. Although it is feasible to collect surgical human AAA samples, these tissues reflect end-stage disease, preventing examination of critical mechanisms behind early AAA formation. Future Directions: Gaining more insight into how myeloid cells and ncRNAs contribute to AAA disease, particularly in early stages, might suggest nonsurgical AAA treatment options. The utilization of large animal models might be helpful in this context to help bridge translational results to humans.

Low-Normal Platelets and Decreasing Platelets Are Risk Factors for Hearing Impairment Development

OBJECTIVE

Identification of undefined risk factors will be crucial for the development of therapeutic strategies in hearing impairment. Platelets are likely to affect the development of sudden sensorineural hearing loss, which is a primary risk factor for permanent hearing impairment. This implies that abnormal platelets might contribute to long-term hearing loss. This study investigated the role of platelets in the development of hearing impairment over a 5-year period.

METHODS

This study was a retrospective cohort study and consisted of a population-based survey, which was performed for 1,897 participants in 2014 to 2019. To evaluate the effect of platelet level on hearing ability, the subjects were divided into two groups: a high-normal platelet group (25 ∼ 40 × 10⁴ cells/μL) and a low-normal platelet group (15 ∼ 25 × 10⁴ cells/μL). Subjects were defined as having hearing impairment when pure tone audiometry was over 25 dB HL in either ear (tested in 2017 and 2019). Incidence of hearing impairment was analyzed.

RESULTS

Incidence of hearing impairment at low frequencies was significantly higher in the low-normal platelet group than in the high-normal group year over year. Low-normal platelet count associated with low-frequency hearing impairment (LFHI) incidence (odds ratio [OR], 2.34; 95% confidence interval [CI], 1.15-4.76). In the low-normal platelet group, subjects whose counts declined from baseline developed more LFHI than those whose counts increased over time. Further, decreasing platelets appeared to be an independent risk factor contributing to the incidence of LFHI (OR, 2.10; 95%CI, 1.09-4.06) in the low-normal platelet group.

CONCLUSION

Both a low-normal platelet and a declining platelet count were independently associated with the incidence of LFHI.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E1287-E1295, 2021.

Long noncoding RNAs in key cellular processes involved in aortic aneurysms

Aortic aneurysm (AA) is a complex and dangerous vascular disease, featuring progressive and irreversible vessel dilatation. AA is typically detected either by screening, or identified incidentally through imaging studies. To date, no effective pharmacological therapies have been identified for clinical AA management, and either endovascular repair or open surgery remains the only option capable of preventing aneurysm rupture. In recent years, multiple research groups have endeavored to both identify noncoding RNAs and to clarify their function in vascular diseases, including aneurysmal pathologies. Notably, the molecular roles of noncoding RNAs in AA development appear to vary significantly between thoracic aortic aneurysms (TAAs) and abdominal aortic aneurysms (AAAs). Some microRNAs (miRNA - a non-coding RNA subspecies) appear to contribute to AA pathophysiology, with some showing major potential for use as biomarkers or as therapeutic targets. Studies of long noncoding RNAs (lncRNAs) are more limited, and their specific contributions to disease development and progression largely remain unexplored. This review aims to summarize and discuss the most current data on lncRNAs and their mediation of AA pathophysiology.

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This current review covers studies that have identified long non-coding RNAs in aortic aneurysm development and progression.

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We separately discuss transcripts and mechanisms of importance to thoracic as well as abdominal aortic aneurysms.

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Functional data on lncRNAs being identified are highlighted.

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Some have been studied in human as well as experimental models of the disease pathology.

H19 Induces Abdominal Aortic Aneurysm Development and Progression

BACKGROUND

Long noncoding RNAs have emerged as critical molecular regulators in various biological processes and diseases. Here we sought to identify and functionally characterize long noncoding RNAs as potential mediators in abdominal aortic aneurysm development.

METHODS

We profiled RNA transcript expression in 2 murine abdominal aortic aneurysm models, Angiotensin II (ANGII) infusion in apolipoprotein E-deficient ( ApoE^-/-) mice (n=8) and porcine pancreatic elastase instillation in C57BL/6 wild-type mice (n=12). The long noncoding RNA H19 was identified as 1 of the most highly upregulated transcripts in both mouse aneurysm models compared with sham-operated controls. This was confirmed by quantitative reverse transcription-polymerase chain reaction and in situ hybridization.

RESULTS

Experimental knock-down of H19, utilizing site-specific antisense oligonucleotides (LNA-GapmeRs) in vivo, significantly limited aneurysm growth in both models. Upregulated H19 correlated with smooth muscle cell (SMC) content and SMC apoptosis in progressing aneurysms. Importantly, a similar pattern could be observed in human abdominal aortic aneurysm tissue samples, and in a novel preclinical LDLR^-/- (low-density lipoprotein receptor) Yucatan mini-pig aneurysm model. In vitro knock-down of H19 markedly decreased apoptotic rates of cultured human aortic SMCs, whereas overexpression of H19 had the opposite effect. Notably, H19-dependent apoptosis mechanisms in SMCs appeared to be independent of miR-675, which is embedded in the first exon of the H19 gene. A customized transcription factor array identified hypoxia-inducible factor 1α as the main downstream effector. Increased SMC apoptosis was associated with cytoplasmic interaction between H19 and hypoxia-inducible factor 1α and sequential p53 stabilization. Additionally, H19 induced transcription of hypoxia-inducible factor 1α via recruiting the transcription factor specificity protein 1 to the promoter region.

CONCLUSIONS

The long noncoding RNA H19 is a novel regulator of SMC survival in abdominal aortic aneurysm development and progression. Inhibition of H19 expression might serve as a novel molecular therapeutic target for aortic aneurysm disease.

Systemic Upregulation of IL-10 (Interleukin-10) Using a Nonimmunogenic Vector Reduces Growth and Rate of Dissecting Abdominal Aortic Aneurysm

Objective- Recruitment of immunologic competent cells to the vessel wall is a crucial step in formation of abdominal aortic aneurysms (AAA). Innate immunity effectors (eg, macrophages), as well as mediators of adaptive immunity (eg, T cells), orchestrate a local vascular inflammatory response. IL-10 (interleukin-10) is an immune-regulatory cytokine with a crucial role in suppression of inflammatory processes. We hypothesized that an increase in systemic IL-10-levels would mitigate AAA progression. Approach and Results- Using a single intravenous injection protocol, we transfected an IL-10 transcribing nonimmunogenic minicircle vector into the Ang II (angiotensin II)-ApoE^-/- infusion mouse model of AAA. IL-10 minicircle transfection significantly reduced average aortic diameter measured via ultrasound at day 28 from 166.1±10.8% (control) to 131.0±5.8% (IL-10 transfected). Rates of dissecting AAA were reduced by IL-10 treatment, with an increase in freedom from dissecting AAA from 21.5% to 62.3%. Using flow cytometry of aortic tissue from minicircle IL-10-treated animals, we found a significantly higher percentage of CD4⁺/CD25⁺/Foxp3 (forkhead box P3)⁺ regulatory T cells, with fewer CD8⁺/GZMB⁺ (granzyme B) cytotoxic T cells. Furthermore, isolated aortic macrophages produced less TNF-α (tumor necrosis factor-α), more IL-10, and were more likely to be MRC1 (mannose receptor, C type 1)-positive alternatively activated macrophages. These results concurred with gene expression analysis of lipopolysaccharide-stimulated and Ang II-primed human peripheral blood mononuclear cells. Conclusions- Taken together, we provide an effective gene therapy approach to AAA in mice by enhancing antiinflammatory and dampening proinflammatory pathways through minicircle-induced augmentation of systemic IL-10 expression.

Therapeutic perspective on vascular cognitive impairment

Dementia is one of the greatest public health concerns for the modern aging world. Over the last decade, most researchers developing new therapeutic strategies for dementia have focused on amyloid-β. In contrast, numerous recent studies have indicated that vascular risk factors are associated with various forms of dementia, and that in fact most forms of dementia can be considered an extension of vascular disease. Accordingly, it is sensible to pursue treatment approaches that focus on the blood vessels. Blood-brain barrier (BBB) disruptions in the white matter of patients with vascular cognitive impairment (VCI) have been observed using imaging analysis, and might be potential targets for novel VCI treatment. Tight junctions between cerebral endothelial cells play an important role in the function of the BBB, and recent studies have demonstrated the essential role of microRNAs in regulating tight junctions. Further elucidation of the mechanisms of tight junction-disruption in dementia are likely to lead to promising novel treatments. In this article, we summarize current knowledge regarding microRNAs and vascular cognitive impairment and the possibility of utilizing microRNAs as biomarkers for BBB dysfunction, and seek to envision future therapeutic strategies.

Chronic Nicotine Exposure Induces Murine Aortic Remodeling and Stiffness Segmentation-Implications for Abdominal Aortic Aneurysm Susceptibility

Aim: Arterial stiffness is a significant risk factor for many cardiovascular diseases, including abdominal aortic aneurysms (AAA). Nicotine, the major active ingredient of e-cigarettes and tobacco smoke, induces acute vasomotor effects that may temporarily increase arterial stiffness. Here, we investigated the effects of long-term nicotine exposure on structural aortic stiffness. Methods: Mice (C57BL/6) were infused with nicotine for 40 days (20 mg/kg/day). Arterial stiffness of the thoracic (TS) and abdominal (AS) aortic segments was analyzed using ultrasound (PWV, pulse wave velocity) and ex vivo pressure myograph measurements. For mechanistic studies, aortic matrix-metalloproteinase (MMP) expression and activity as well as medial elastin architecture were analyzed. Results: Global aortic stiffness increased with nicotine. In particular, local stiffening of the abdominal segment occurred after 10 days, while thoracic aortic stiffness was only increased after 40 days, resulting in aortic stiffness segmentation. Mechanistically, nicotine exposure enhanced expression of MMP-2/-9 and elastolytic activity in both aortic segments. Elastin degradation occurred in both segments; however, basal elastin levels were higher in the thoracic aorta. Finally, MMP-inhibition significantly reduced nicotine-induced MMP activity, elastin destruction, and aortic stiffening. Conclusion: Chronic nicotine exposure induces aortic MMP expression and structural aortic damage (elastin fragmentation), irreversibly increasing aortic stiffness. This process predominantly affects the abdominal aortic segment, presumably due in part to a lower basal elastin content. This novel phenomenon may help to explain the role of nicotine as a major risk factor for AAA formation and has health implications for ECIGs and other modes of nicotine delivery.

Non-coding RNAs in aneurysmal aortopathy

Aortic aneurysms represent a major public health burden, and currently have no medical treatment options. The pathophysiology behind these aneurysms is complex and variable, depending on location and underlying cause, and generally involves progressive dysfunction of all elements of the aortic wall. Changes in smooth muscle behavior, endothelial signaling, extracellular matrix remodeling, and to a variable extent inflammatory signaling and cells, all contribute to the dilation of the aorta, ultimately resulting in high mortality and morbidity events including dissection and rupture. A large number of researchers have identified non-coding RNAs as crucial regulators of aortic aneurysm development, both in humans and in animal models. While most work to-date has focused on microRNAs, intriguing information has also begun to emerge regarding the role of long-non-coding RNAs. This review summarizes the currently available data regarding the involvement of non-coding RNAs in aneurysmal aortopathies. Going forward, these represent key potential therapeutic targets that might be leveraged in the future to slow or prevent aortic aneurysm formation, progression and rupture.

Open surgery for iliofemoral deep vein thrombosis with temporary arteriovenous fistula remains valuable

Objective We assessed outcomes of open surgical venous thrombectomy with temporary arteriovenous fistula, and the procedure's effect on health-related quality of life. Method We retrospectively analyzed 48 (26 at long-term) patient medical records. Mortality rates, patency, and risk of post-thrombotic syndrome were analyzed using Kaplan-Meier estimation. The association between risk factors/coagulation disorders and patency/post-thrombotic syndrome along with patient health-related quality of life at long-term was analyzed employing various statistical methods. Results Patient one-year survival rate was 93 ± 4% and primary one-year patency rate was 89 ± 5% (secondary one-year patency rate 97 ± 3%). Freedom from post-thrombotic syndrome after eight years was 80 ± 12% (post-thrombotic syndrome rate 20 ± 12%). Health-related quality of life was impaired vs. normative data in the physical and social subscales, and in the mental component score ( p < .05). Conclusions Open surgical venous thrombectomy appears safe compared with literature-reported outcomes in similar patients using alternative approaches. Iliofemoral deep vein thrombosis impairs physical, social, and mental health-related quality of life.

Abstract 314: A Stent to Prevent: A Translational Approach Towards Small Abdominal Aortic Aneurysm (AAA) Therapy

Background: Abdominal aortic aneurysm (AAA) is defined as a permanent dilation of the abdominal aorta that is highly lethal in case of rupture. Current therapeutic approaches are limited to open surgery or stent-based endovascular aortic repair (EVAR) to exclude large sized AAA (>5.5 cm) from the circulation. However, to date there is no effective therapy to prevent small AAA formation and progression. Nonetheless, options for small AAA disease are highly desirable as even small AAA may rupture and app. 70% of all small AAA will grow and eventually require surgical repair.

Objective: Building on our previous experimental research findings we present a novel therapeutic approach for early AAA intervention.

Methods and Results: Our recent biomechanical studies in a murine model of AAA development (elastase model) as well as in human aortae indicate that early AAA growth is critically driven by a stiffness gradient between a stiff AAA segment and the adjacent more compliant aorta. As a promising therapeutic intervention, we found that stiffening of the AAA-adjacent aorta (by external glue application) was sufficient to stop murine AAA formation. In a translational approach we now aim to develop an intravascular stent prototype that is deployed in the neck region of a developing AAA to increase the mechanical stiffness of the AAA-adjacent aorta. We hypothesize that this intervention will decrease the aortic stiffness gradient towards the AAA segment – thereby preventing further AAA growth. Stent prototypes with varying designs will be tested in a pig model of AAA disease that closely resembles the human anatomic situation.

Conclusion: This project demonstrates a highly promising opportunity to directly translate novel pathomechanistic insights into AAA pathobiology from bench to bedside application and stop early AAA progression in humans.

Abstract 465: Nicotine Differentially Influences Segmental Aortic Stiffening

Background: Arterial stiffness is a major risk factor for various cardiovascular diseases and contributes to the development of abdominal aortic aneurysms (AAA). In this context, differential aortic stiffening of adjacent aortic segments increases aortic wall stress and accelerates the disease. Smoking is a major risk factor for AAA, in part due to nicotine. In this study, we investigated aortic stiffening of the thoracic and abdominal aorta and analyzed stiffness-related gene expression.

Methods: 36 WT mice (C57BL/6) mice were infused with nicotine or PBS using osmotic mini pumps for 42 days. Thoracic segment (TS) and abdominal segment (AS) aortic stiffness were analyzed using ultrasound (M-Mode and PW). TS and AS were further investigated by ex vivo myograph measurements. Gene expression for TMIP2, MT1-MMP, MMP2, collagen type I and type III was performed for both segments separately.

Results: Myograph measurements revealed increased strain within the AS after 2 weeks (p<.05) in response to nicotine (vs. PBS), but no stiffening of the TS. After 6 weeks, the AS showed additional increases in strain with nicotine (p<.05); however, only minor increases in stiffness could be observed for the TS. Ultrasound M-Mode results confirmed the myograph results. Nicotine treatment also led to increased aortic pulse wave velocity (PWV) after 2 weeks (p<.05) and 6 weeks (p<.05). Gene expression analysis revealed up-regulation in the TS and AS of MT1-MMP and MMP2 after 2 weeks of nicotine, while TIMP2 was downregulated, and collagen type I and type III were up-regulated in both TS and AS (p<.05). After 6 weeks, there were no longer significant differences in either segment for any of these genes.

Discussion: Aortic stiffening in response to nicotine varies between the TS and AS segment over a time course of 6 weeks. This leads to an increased stiffness gradient between the TS and AS. Gene expression changes in stiffness-related genes occurred in response to nicotine, although no difference appeared between the segments. We conclude that the difference in stiffness development for TS and AS could be based on a different basic morphological structure involving elastin and collagen load, and that these responses may in part explain nicotine’s role in promoting AAA.

Chronic Mesenteric Ischemia: Patient Outcomes Using Open Surgical Revascularization

BACKGROUND

Chronic mesenteric ischemia (CMI) is a rare disease. Open treatment (OT) remains a valuable treatment option. We analyzed patient outcomes after OT and investigated health-related quality of life (HRQoL).

METHODS

Data were analyzed retrospectively. The investigation period was from January 1, 2001, to December 31, 2014. We investigated mortality and patency rates using Kaplan-Meier analysis. HRQoL was measured using a 36-item health survey. Various statistical methods were employed.

RESULTS

A total of 100 patients (celiac trunk [TC: n = 23], superior mesenteric artery [SMA: n = 26], or both [n = 51]) were included. Median follow-up was 5 ± 35 months. One-year survival rate for TC was 75 ± 11%, for SMA: 79 ± 10%, and for both: 96 ± 3%. TC 5-year survival was 75 ± 11% (SMA: 57 ± 16%: both: 80 ± 8%). Obesity and the length of hospital stay were independently associated with patient survival (p < 0.05). Primary 1-year patency rate was 60 ± 13% for TC (SMA: 86 ± 10%; both: 71 ± 8%) and secondary 1-year patency rate was 84 ± 9% for TC (SMA: 100%; both: 79 ± 7%). HRQoL was inferior compared to the German normative data (p < 0.05).

CONCLUSION

CMI overlaps between gastrointestinal and vascular surgery. OT is safe, and simultaneous revascularization of the TC and the SMA does not affect mortality. Patients would not necessarily benefit from OT in terms of HRQoL.

A Pilot Study: The Beneficial Effects of Combined Statin-exercise Therapy on Cognitive Function in Patients with Coronary Artery Disease and Mild Cognitive Decline

Objective Hypercholesterolemia, a risk factor in cognitive impairment, can be treated with statins. However, cognitive decline associated with "statins" (HMG-CoA reductase inhibitors) is a clinical concern. This pilot study investigated the effects of combining statins and regular exercise on cognitive function in coronary artery disease (CAD) patients with prior mild cognitive decline. Methods We recruited 43 consecutive CAD patients with mild cognitive decline. These patients were treated with a statin and weekly in-hospital aerobic exercise for 5 months. We measured serum lipids, exercise capacity, and cognitive function using the mini mental state examination (MMSE). Results Low-density lipoprotein cholesterol levels were significantly decreased, and maximum exercise capacity (workload) was significantly increased in patients with CAD and mild cognitive decline after treatment compared with before. Combined statin-exercise therapy significantly increased the median (range) MMSE score from 24 (22-25) to 25 (23-27) across the cohort (p<0.01). Changes in body mass index (BMI) were significantly and negatively correlated with changes in the MMSE. After treatment, MMSE scores in the subgroup of patients that showed a decrease in BMI were significantly improved, but not in the BMI-increased subgroup. Furthermore, the patients already on a statin at the beginning of the trial displayed a more significant improvement in MMSE score than statin-naïve patients, implying that exercise might be the beneficial aspect of this intervention as regards cognition. In a multivariate logistic regression analysis adjusted for age >65 years, sex, and presence of diabetes mellitus, a decrease in BMI during statin-exercise therapy was significantly correlated with an increase in the MMSE score (odds ratio: 4.57, 95% confidence interval: 1.05-20.0; p<0.05). Conclusion Statin-exercise therapy may help improve cognitive dysfunction in patients with CAD and pre-existing mild cognitive decline.

Abstract 616: MicroRNA miR-29b is a Mediator of Aortic Stiffness and Hypertension in a Murine Model of Type 2 Diabetes Mellitus

Background: Accelerated arterial stiffening is a complication of diabetes mellitus and associated with the development of hypertension. Arterial stiffening results from extensive extracellular matrix remodeling (elastin breakdown, collagen accumulation). MicroRNA miR-29b directly regulates the expression of genes governing fibrosis (such as COL1A1, COL3A1) and elastin breakdown ( MMP2, MMP9 ). However, its impact on aortic stiffness is unclear.

Objective: This study was designed to investigate the role of miR-29b as potential mediator of diabetic aortic stiffening.

Methods and Results: Serial ex vivo mechanical testing of the thoracic aorta and volume-pressure recording (VPR) based tail-cuff blood pressure measurements revealed that aortic stiffening precedes blood (pulse) pressure elevations in diabetic db/db mice. Vascular stiffening was accompanied by increased elastin fragmentation and collagen deposition (EvG and Picrosirius Red staining). qRT-PCR, in-situ hybridization and immunohistochemistry revealed decreased expression of miR-29b and de-repression of target genes ( Col1A1, COL3A1, MMP2, MMP9 ) in db/db mice compared to controls. Investigating the mechanistic significance of miR-29b for arterial stiffening, forced downregulation of miR-29b (via systemic LNA-miR-29b inhibitor application) results in enhanced elastin fragmentation, increased medial collagen deposition, aortic stiffness and augmented pulse pressure.

Conclusions: In conclusion this study identifies miR-29b as a regulator and potential therapeutic target of diabetic aortic stiffening.

Abstract 567: Transcription Factor Runx2 is Induced in Vascular Aging and May Promote Age-related Arterial Stiffness

Background: Arterial stiffening is a hallmark of vascular aging and may constitute a critical mechanism linking age to increased cardiovascular risk. However, up to now there is no therapy available to efficiently and specifically target age-related arterial stiffening. We recently identified the osteogenic transcription factor Runx2 as an inducer of diabetic arterial stiffness.

Objective: The present study investigated the role of Runx2 in the setting of age-related arterial stiffness.

Methods and Results: Aortic stiffness – quantified by ex vivo mechanical testing (pressure myography) – was markedly increased in 1-year old male C57Bl/6 mice compared to young (10 week-old) controls. At the same time, Runx2 was aberrantly upregulated in the medial layer of aged aortae, coming along with significant medial fibrosis. Additionally, we detected increased aortic expression of interleukin 6 ( Il6 ) – a key cytokine involved in vascular “inflammaging”. Mechanistically, we found IL-6-induced RUNX2 expression in aortic smooth muscle cells (SMCs) via a NFkB-dependent pathway.

Conclusion: In conclusion this study suggests Runx2 as a potential mediator of age-related arterial fibrosis and stiffness warranting further interventional/therapeutic studies.

Heme Oxygenase-1 Expression Affects Murine Abdominal Aortic Aneurysm Progression

Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme degradation, is a cytoprotective enzyme upregulated in the vasculature by increased flow and inflammatory stimuli. Human genetic data suggest that a diminished HO-1 expression may predispose one to abdominal aortic aneurysm (AAA) development. In addition, heme is known to strongly induce HO-1 expression. Utilizing the porcine pancreatic elastase (PPE) model of AAA induction in HO-1 heterozygous (HO-1^+/-, HO-1 Het) mice, we found that a deficiency in HO-1 leads to augmented AAA development. Peritoneal macrophages from HO-1^+/- mice showed increased gene expression of pro-inflammatory cytokines, including MCP-1, TNF-alpha, IL-1-beta, and IL-6, but decreased expression of anti-inflammatory cytokines IL-10 and TGF-beta. Furthermore, treatment with heme returned AAA progression in HO-1 Het mice to a wild-type profile. Using a second murine AAA model (Ang II-ApoE^-/-), we showed that low doses of the HMG-CoA reductase inhibitor rosuvastatin can induce HO-1 expression in aortic tissue and suppress AAA progression in the absence of lipid lowering. Our results support those studies that suggest that pleiotropic statin effects might be beneficial in AAA, possibly through the upregulation of HO-1. Specific targeted therapies designed to induce HO-1 could become an adjunctive therapeutic strategy for the prevention of AAA disease.

CDKN2B Regulates TGFβ Signaling and Smooth Muscle Cell Investment of Hypoxic Neovessels

RATIONALE

Genetic variation at the chromosome 9p21 cardiovascular risk locus has been associated with peripheral artery disease, but its mechanism remains unknown.

OBJECTIVE

To determine whether this association is secondary to an increase in atherosclerosis, or it is the result of a separate angiogenesis-related mechanism.

METHODS AND RESULTS

Quantitative evaluation of human vascular samples revealed that carriers of the 9p21 risk allele possess a significantly higher burden of immature intraplaque microvessels than carriers of the ancestral allele, irrespective of lesion size or patient comorbidity. To determine whether aberrant angiogenesis also occurs under nonatherosclerotic conditions, we performed femoral artery ligation surgery in mice lacking the 9p21 candidate gene, Cdkn2b. These animals developed advanced hindlimb ischemia and digital autoamputation, secondary to a defect in the capacity of the Cdkn2b-deficient smooth muscle cell to support the developing neovessel. Microarray studies identified impaired transforming growth factor β (TGFβ) signaling in cultured cyclin-dependent kinase inhibitor 2B (CDKN2B)-deficient cells, as well as TGFβ1 upregulation in the vasculature of 9p21 risk allele carriers. Molecular signaling studies indicated that loss of CDKN2B impairs the expression of the inhibitory factor, SMAD-7, which promotes downstream TGFβ activation. Ultimately, this manifests in the upregulation of a poorly studied effector molecule, TGFβ1-induced-1, which is a TGFβ-rheostat known to have antagonistic effects on the endothelial cell and smooth muscle cell. Dual knockdown studies confirmed the reversibility of the proposed mechanism, in vitro.

CONCLUSIONS

These results suggest that loss of CDKN2B may not only promote cardiovascular disease through the development of atherosclerosis but may also impair TGFβ signaling and hypoxic neovessel maturation.

Transcription Factor Runx2 Promotes Aortic Fibrosis and Stiffness in Type 2 Diabetes Mellitus

RATIONALE

Accelerated arterial stiffening is a major complication of diabetes mellitus with no specific therapy available to date.

OBJECTIVE

The present study investigates the role of the osteogenic transcription factor runt-related transcription factor 2 (Runx2) as a potential mediator and therapeutic target of aortic fibrosis and aortic stiffening in diabetes mellitus.

METHODS AND RESULTS

Using a murine model of type 2 diabetes mellitus (db/db mice), we identify progressive structural aortic stiffening that precedes the onset of arterial hypertension. At the same time, Runx2 is aberrantly upregulated in the medial layer of db/db aortae, as well as in thoracic aortic samples from patients with type 2 diabetes mellitus. Vascular smooth muscle cell-specific overexpression of Runx2 in transgenic mice increases expression of its target genes, Col1a1 and Col1a2, leading to medial fibrosis and aortic stiffening. Interestingly, increased Runx2 expression per se is not sufficient to induce aortic calcification. Using in vivo and in vitro approaches, we further demonstrate that expression of Runx2 in diabetes mellitus is regulated via a redox-sensitive pathway that involves a direct interaction of NF-κB with the Runx2 promoter.

CONCLUSIONS

In conclusion, this study highlights Runx2 as a previously unrecognized inducer of vascular fibrosis in the setting of diabetes mellitus, promoting arterial stiffness irrespective of calcification.

Local MicroRNA Modulation Using a Novel Anti-miR-21-Eluting Stent Effectively Prevents Experimental In-Stent Restenosis

OBJECTIVE

Despite advances in stent technology for vascular interventions, in-stent restenosis (ISR) because of myointimal hyperplasia remains a major complication.

APPROACH AND RESULTS

We investigated the regulatory role of microRNAs in myointimal hyperplasia/ISR, using a humanized animal model in which balloon-injured human internal mammary arteries with or without stenting were transplanted into Rowett nude rats, followed by microRNA profiling. miR-21 was the only significantly upregulated candidate. In addition, miR-21 expression was increased in human tissue samples from patients with ISR compared with coronary artery disease specimen. We systemically repressed miR-21 via intravenous fluorescein-tagged-locked nucleic acid-anti-miR-21 (anti-21) in our humanized myointimal hyperplasia model. As expected, suppression of vascular miR-21 correlated dose dependently with reduced luminal obliteration. Furthermore, anti-21 did not impede reendothelialization. However, systemic anti-miR-21 had substantial off-target effects, lowering miR-21 expression in liver, heart, lung, and kidney with concomitant increase in serum creatinine levels. We therefore assessed the feasibility of local miR-21 suppression using anti-21-coated stents. Compared with bare-metal stents, anti-21-coated stents effectively reduced ISR, whereas no significant off-target effects could be observed.

CONCLUSION

This study demonstrates the efficacy of an anti-miR-coated stent for the reduction of ISR.

Abstract 38: Cyclin-Dependent Kinase Inhibitor 2B Regulates Transforming Growth Factor Beta 1 Mediated Smooth Muscle Cell Recruitment to Ischemic Blood Vessels

Peripheral artery disease (PAD) is a highly morbid condition affecting nearly 8.5 million Americans. Genome wide association studies (GWAS) have identified genetic variation at the chromosome 9p21 cardiovascular risk locus as an important source of heritable PAD risk. However, it is unknown whether this association is secondary to an increase in atherosclerosis or is the result of a separate angiogenesis-related mechanism.

Quantitative ultrastructural evaluation of human plaque laden vascular samples revealed that carriers of the 9p21 risk allele displayed a significantly increased burden of immature intraplaque microvessels than carriers of the ancestral allele. To determine whether this process occurs under non-atherosclerotic conditions, we performed femoral artery ligation surgery in mice lacking Cdkn2b; a candidate gene we previously identified to have reduced expression in human carriers of the 9p21 risk allele. These animals developed advanced hind-limb ischemia and digital auto-amputation, relative to wild-type controls. Interestingly, in situ and in vitro hypoxic assays identified this defect to be a consequence of pro-angiogenic behavior displayed by CDKN2B deficient endothelial cells (EC) and impaired smooth muscle cell (SMC) recruitment to the developing neovessel. Exploratory microarray studies performed to identify the mechanism involved, revealed that TGFβ1 signaling is significantly induced in cultured CDKN2B -deficient cells; a finding later confirmed in the vasculature of individuals carrying the 9p21 risk allele. Subsequent molecular signaling studies reveal this increase to be a result of impaired expression of the inhibitory factor, SMAD-7. Increased TGFβ1 signaling was ultimately found to manifest the upregulation of a poorly studied effector molecule, TGFβ1-induced-1, which is a TGFβ-‘rheostat’ known to have antagonistic effects on the EC and SMC. Dual knockdown and rescue studies confirmed the reversibility of the proposed mechanism, in vitro.

Taken together these findings suggest that loss of CDKN2B may not only promote cardiovascular disease through the development of atherosclerosis, but may also impair TGFβ1 signaling and hypoxic neovessel maturation consequently resulting in PAD.

Abstract 281: Local MicroRNA Modulation Using a Novel Anti-mir-21-eluting Stent Effectively Prevents In-stent Restenosis

The major limitation of vascular angioplasty remains the occurrence of in-stent restenosis (ISR). The central role of miRNAs in the pathophysiology of the proliferative response in cardiovascular disease offers attractive concepts for possible therapeutic interventions, with systemic miRNA modulation however potentially causing substantial off-target effects. Aim of the current study was to test the feasibility of local miRNA modulation using drug eluted stent (DES) technology.

Utilizing human ISR tissue samples, as well as a humanized rodent model of balloon-injured human internal mammary arteries with subsequent stent implantation in RNU rats, we were able to identify several miRNAs dys-regulated, including the well-characterized miR-21. We inhibited miR-21 (with a FAM-tagged-LNA-anti-miR-21), using either systemic or local delivery via DES.

Systemic suppression of miR-21 showed a dose-dependent reduction of luminal obliteration, while not impeding vascular re-endothelialization. However, miR-21 expression in liver, heart, lung, and kidney appeared significantly reduced, with increased levels of serum creatinine, pointing towards the expected off-target effects of systemic miRNA modulation. Local mir-21 suppression, using the anti-miR-21-DES, effectively reduced myointimal hyperplasia and ISR compared to bare metal stents, while not exerting detectable off-target effects on any other organ we investigated. Additional in vitro experiments in cultured human coronary artery smooth muscle and endothelial cells further confirmed the ability of anti_miR-21 to limit SMC proliferation and migration by repressing mRNA and protein levels of its established target PTEN, while not affecting the proliferative response in the ECs.

This is the first experimental study to demonstrate the efficacy, feasibility and suitability of an anti-miRNA-eluting stent (anti-miR-21-DES) for the reduction of ISR through dominant inhibition of SMC proliferation.

Abstract 676: Microrna-30 and Cthrc1: Translating Aging into Vascular Stiffness and Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a major source of vascular morbidity and mortality, with increasing age representing one of the strongest risk factors. While increases in aortic extra-cellular matrix deposition may be protective, changes in vessel architecture with age result in heterogeneous stiffness and vascular calcification, which appear to pre-dispose to AAA development. MicroRNAs (miRs) are key regulators of vascular homeostasis and pathobiology.

Array profiling and qRT-PCR of aneurysmal aortic tissue in a murine AAA model (elastase-infused C57/B6) showed significant down-regulation of the miR-30 family, which is believed to have a role in vascular calcification. Increased age augmented this response, particularly for miR-30a, 30b and 30c. RNASeq profiling of a related AAA model (Ang-II in ApoE-/- KO) showed similar aortic down-regulation. Further, of differentially down-regulated miRs, miR-30 had the highest inverse correlation with mRNA gene targets. One predicted target - Cthrc1 (collagen triple helix repeat containing-1) - was the most consistently and significantly up-regulated gene across all time points in the AAA models. The protein resides within vascular smooth muscle cells (SMCs) and fibroblasts, responds to injury, and may regulate collagen expression and deposition. Immunofluorescence staining of AAA vs. normal aortas revealed increased expression of CTHRC1.

We further found that miR-30 family members bind to the CTHRC1 3’ UTR and regulate gene expression in vitro, and that antagomir suppression of miR-30 upregulates CTHRC1 in SMCs. We also demonstrated that signaling pathways known to increase in activity with aging within the aorta, and which are associated with vascular calcification and fibrosis (e.g. IL6-based inflammatory signaling, TGF-β signaling, and BMP-2 signaling) down-regulate miR-30 family expression in SMCs, and inversely up-regulate CTHRC1 expression. Forced overexpression of miR-30 in SMC in vitro down-regulates RUNX2, a key promoter of vascular stiffness and calcification. Taken together, these results suggest a significant role for miR-30 in pathways related to matrix deposition and calcification, regulating aortic pathobiology and age-related susceptibility to AAA.

Abstract 681: The Effects of a Sustained-Release N-acetylcysteine Prodrug on Vascular Inflammation in Experimental Atherosclerosis

Background: Oxidative stress plays a key role in the development of atherosclerosis. N-acetylcysteine (NAC) has the potential to reduce oxidative stress and inflammation, but has a short half-life and low oral bioavailability. We studied a sustained-release formulation of NAC for the suppression of vascular inflammation in experimental atherosclerosis.

Methods: ApoE-deficient mice (n=17) were started on a high-fat diet at the age of 7-13 weeks and given a daily oral gavage of either sustained-release NAC (n=8, 200mg/kg/mouse, total ~5040mg) or phosphate buffered saline (n=9) for 12 weeks. The sustained-release NAC formulation was an esterified prodrug called SURE-NACTM (Tiara Pharmaceuticals, Inc., Sunnyvale, CA). After 12 weeks, aortae were harvested and histology/immunohistochemistry performed. The levels of inflammatory cytokines in the plasma were evaluated using antibody-conjugated bead sets for 26 mouse cytokines and chemokines in multiplexed sandwich immunoassay format.

Results: Lesion lipid area was significantly reduced in mice treated with sustained-release NAC compared to controls, for both the entire aorta and the aortic root: Lesion lipid area in entire aorta (% of total area) - 6.5±0.8% vs 13.3±1.1%, p<0.001; lesion lipid area in aortic root - 0.08±0.01mm2 vs 0.17±0.02mm2, p<0.001. Immunohistochemistry of the aortic root demonstrated that both macrophages and matrix metalloproteinase (MMP)-2 were also significantly suppressed by sustained-release NAC: Macrophages - 29.4±5.8% vs 55.6±3.2%, p<0.001; MMP-2 - 10.3±2.6% vs 19.2±2.9%, p<0.05. Inflammatory cytokines in mice treated with sustained-release NAC were significantly decreased compared to control (IL-2: 18.2%, IL-5: 47.6%, TNF-α: 34.2%, MIP-1α: 34.5% reduction). The levels of IL-2, IL-5, TNF-α, and MIP-1α showed a significant moderate correlation with both macrophage density and lipid area in the aortic sinus.

Conclusions: A sustained-release NAC prodrug showed substantial suppression of lesion lipid area, macrophage infiltration, and inflammatory cytokines in experimental atherosclerosis. This may provide a novel daily oral therapy to reduce vascular inflammation for the prevention and treatment of atherosclerosis.

Segmental aortic stiffening contributes to experimental abdominal aortic aneurysm development

BACKGROUND

Stiffening of the aortic wall is a phenomenon consistently observed in age and in abdominal aortic aneurysm (AAA). However, its role in AAA pathophysiology is largely undefined.

METHODS AND RESULTS

Using an established murine elastase-induced AAA model, we demonstrate that segmental aortic stiffening precedes aneurysm growth. Finite-element analysis reveals that early stiffening of the aneurysm-prone aortic segment leads to axial (longitudinal) wall stress generated by cyclic (systolic) tethering of adjacent, more compliant wall segments. Interventional stiffening of AAA-adjacent aortic segments (via external application of surgical adhesive) significantly reduces aneurysm growth. These changes correlate with the reduced segmental stiffness of the AAA-prone aorta (attributable to equalized stiffness in adjacent segments), reduced axial wall stress, decreased production of reactive oxygen species, attenuated elastin breakdown, and decreased expression of inflammatory cytokines and macrophage infiltration, and attenuated apoptosis within the aortic wall, as well. Cyclic pressurization of segmentally stiffened aortic segments ex vivo increases the expression of genes related to inflammation and extracellular matrix remodeling. Finally, human ultrasound studies reveal that aging, a significant AAA risk factor, is accompanied by segmental infrarenal aortic stiffening.

CONCLUSIONS

The present study introduces the novel concept of segmental aortic stiffening as an early pathomechanism generating aortic wall stress and triggering aneurysmal growth, thereby delineating potential underlying molecular mechanisms and therapeutic targets. In addition, monitoring segmental aortic stiffening may aid the identification of patients at risk for AAA.

Loss of somatostatin receptor subtype 2 in prostate cancer is linked to an aggressive cancer phenotype, high tumor cell proliferation and predicts early metastatic and biochemical relapse

Somatostatin receptor subtype 2 (SSTR2) is the most frequently expressed SSTR subtype in normal human tissues. SSTR2 expression is differentially regulated in various tumor types and therapeutic somatostatin analogs binding to SSTR2 are in clinical use. In prostate cancers highly contradictory results in terms of SSTR2 expression and its consequences have been published over the past years. The aim of this study was to clarify prevalence and clinical significance of SSTR2 expression in prostate cancer. Therefore, quantitative immunohistochemistry (IHC) using a tissue microarray containing samples from 3,261 prostate cancer patients with extensive clinical and molecular cancer characteristics and oncological follow-up data was performed. IHC data was compared to publicly available Gene Expression Omnibus datasets of human prostate cancer gene expression arrays. While membranous SSTR2 staining was always seen in normal prostate epithelium, SSTR2 staining was absent in more than half (56.1%) of 2,195 interpretable prostate cancer samples. About 13% of all analyzed prostate cancers showed moderate to strong cytoplasmic and membranous SSTR2 staining. Staining intensities were inversely correlated with high Gleason grade, advanced pT category, high tumor cell proliferation (p<0.0001 each), high pre-operative PSA levels, (p = 0.0011) and positive surgical margins (p = 0.006). In silico analysis confirmed lower SSTR2 gene expression in prostate cancers vs. normal adjacent tissue (p = 0.0424), prostate cancer metastases vs. primary cancers (p = 0.0011) and recurrent vs. non-recurrent prostate cancers (p = 0.0438). PSA-free survival gradually declined with SSTR2 staining intensity (p<0.0001). SSTR2-negative cancers were more likely to develop metastases over time (p<0.05). In conclusion, most prostate cancers are indeed SSTR2-negative and loss of SSTR2 strongly predicts an unfavorable tumor phenotype and poor prognosis. Therefore, SSTR2 expression seems an important factor in the pathogenesis of prostate cancer and re-introduction of the receptor in SSTR2-negative prostate cancers may feature a promising target for novel gene therapy approaches.

Abstract 297: Segmental Aortic Stiffening is a Mechanism Driving Early Abdominal Aortic Aneurysm Pathogenesis

Stiffening of the aortic wall is a phenomenon consistently observed in abdominal aortic aneurysm (AAA). However, its role in AAA pathophysiology is largely undefined.

Using an established murine elastase-induced AAA model, we demonstrate that segmental aortic stiffening (SAS) precedes aneurysm growth. Finite elements analysis (FEA)-based wall stress calculations reveal that early stiffening of the aneurysm-prone aortic segment leads to axial (longitudinal) stress generated by cyclic (systolic) tethering of adjacent, more compliant wall segments. Interventional stiffening of AAA-adjacent segments (via external application of surgical adhesive) significantly reduces aneurysm growth. These changes correlate with reduced segmental stiffness of the AAA-prone aorta (due to equalized stiffness in adjacent aortic segments), reduced axial wall stress, decreased production of reactive oxygen species (ROS), attenuated elastin breakdown, and decreased expression of inflammatory cytokines and macrophage infiltration, as well as attenuated apoptosis within the aortic wall. Cyclic pressurization of stiffened aortic segments ex vivo increases the expression of genes related to inflammation and extracellular matrix (ECM) remodeling. Finally, human ultrasound studies reveal that aging, a significant AAA risk factor, is accompanied by segmental infrarenal aortic stiffening.

The present study introduces the novel concept of segmental aortic stiffening (SAS) as an early pathomechanism generating aortic wall stress and thereby triggering AAA growth. Therefore monitoring SAS by ultrasound might help to better identify patients at risk for AAA disease and better predict the susceptibility of small AAA to further growth. Moreover our results suggest that interventional mechanical stiffening of the AAA-adjacent aorta may be further tested as a novel treatment option to limit early AAA growth.

Abstract 529: Cbfa1 (Runx2) is a Mediator of Aortic Stiffness and Hypertension in a Murine Model of Diabetes Mellitus Type 2

Accelerated arterial stiffening is a complication of diabetes mellitus and associated with the development of hypertension. Arterial stiffening results from extensive extracellular matrix remodeling (elastin breakdown, collagen accumulation). The osteogenic transcription factor Cbfa1 (Runx2) has been identified as a mediator of aortic calcification and regulator of matrix protein expression. However, its impact on aortic stiffness is unclear.

This study was designed to elucidate the temporal relation between aortic stiffening and the development of arterial hypertension in a murine model of diabetes mellitus type 2. Moreover we aimed to investigate the role of Cbfa1 as potential mediator diabetic aortic stiffening.

Serial ex vivo mechanical testing of the thoracic aorta and volume-pressure recording (VPR) based tail-cuff blood pressure measurements revealed that aortic stiffening precedes blood (pulse) pressure elevations in diabetic db/db mice. Vascular stiffening was accompanied by increased medial collagen deposition Picrosirius Red staining). qRT-PCR and immunohistochemistry revealed enhanced expression of Cbfa1 and target genes (Col1a1, Col1a2, FN1, Spp1) in db/db mice compared to controls. Moreover, overexpression of Cbfa1 in vascular smooth muscle (Cbfa1-smTg mice) results in increased medial collagen deposition, aortic stiffness and augmented pulse pressure. Interestingly, Cbfa1-smTg mice did not exhibit enhanced vascular calcification (by von Kossa and Alizarin Red staining).

In conclusion we demonstrated that aortic stiffening precedes the onset of hypertension in db/db mice and identified Cbfa1 as mediator of aortic stiffening - presumably via pro-fibrotic mechanisms.

Dichloroacetate prevents restenosis in preclinical animal models of vessel injury

Despite the introduction of antiproliferative drug-eluting stents, coronary heart disease remains the leading cause of death in the United States. In-stent restenosis and bypass graft failure are characterized by excessive smooth muscle cell (SMC) proliferation and concomitant myointima formation with luminal obliteration. Here we show that during the development of myointimal hyperplasia in human arteries, SMCs show hyperpolarization of their mitochondrial membrane potential (ΔΨm) and acquire a temporary state with a high proliferative rate and resistance to apoptosis. Pyruvate dehydrogenase kinase isoform 2 (PDK2) was identified as a key regulatory protein, and its activation proved necessary for relevant myointima formation. Pharmacologic PDK2 blockade with dichloroacetate or lentiviral PDK2 knockdown prevented ΔΨm hyperpolarization, facilitated apoptosis and reduced myointima formation in injured human mammary and coronary arteries, rat aortas, rabbit iliac arteries and swine (pig) coronary arteries. In contrast to several commonly used antiproliferative drugs, dichloroacetate did not prevent vessel re-endothelialization. Targeting myointimal ΔΨm and alleviating apoptosis resistance is a novel strategy for the prevention of proliferative vascular diseases.

Hemodynamic regulation of reactive oxygen species: implications for vascular diseases

SIGNIFICANCE

Arterial blood vessels functionally and structurally adapt to altering hemodynamic forces in order to accommodate changing needs and to provide stress homeostasis. This ability is achieved at the cellular level by converting mechanical stimulation into biochemical signals (i.e., mechanotransduction). Physiological mechanical stress helps maintain vascular structure and function, whereas pathologic or aberrant stress may impair cellular mechano-signaling, and initiate or augment cellular processes that drive disease.

RECENT ADVANCES

Reactive oxygen species (ROS) may represent an intriguing class of mechanically regulated second messengers. Chronically enhanced ROS generation may be induced by adverse mechanical stresses, and is associated with a multitude of vascular diseases. Although a causal relationship has clearly been demonstrated in large numbers of animal studies, an effective ROS-modulating therapy still remains to be established by clinical studies.

CRITICAL ISSUES AND FUTURE DIRECTIONS

This review article focuses on the role of various mechanical forces (in the form of laminar shear stress, oscillatory shear stress, or cyclic stretch) as modulators of ROS-driven signaling, and their subsequent effects on vascular biology and homeostasis, as well as on specific diseases such as arteriosclerosis, hypertension, and abdominal aortic aneurysms. Specifically, it highlights the significance of the various NADPH oxidase (NOX) isoforms as critical ROS generators in the vasculature. Directed targeting of defined components in the complex network of ROS (mechano-)signaling may represent a key for successful translation of experimental findings into clinical practice.

Micromanaging abdominal aortic aneurysms

The contribution of abdominal aortic aneurysm (AAA) disease to human morbidity and mortality has increased in the aging, industrialized world. In response, extraordinary efforts have been launched to determine the molecular and pathophysiological characteristics of the diseased aorta. This work aims to develop novel diagnostic and therapeutic strategies to limit AAA expansion and, ultimately, rupture. Contributions from multiple research groups have uncovered a complex transcriptional and post-transcriptional regulatory milieu, which is believed to be essential for maintaining aortic vascular homeostasis. Recently, novel small noncoding RNAs, called microRNAs, have been identified as important transcriptional and post-transcriptional inhibitors of gene expression. MicroRNAs are thought to "fine tune" the translational output of their target messenger RNAs (mRNAs) by promoting mRNA degradation or inhibiting translation. With the discovery that microRNAs act as powerful regulators in the context of a wide variety of diseases, it is only logical that microRNAs be thoroughly explored as potential therapeutic entities. This current review summarizes interesting findings regarding the intriguing roles and benefits of microRNA expression modulation during AAA initiation and propagation. These studies utilize disease-relevant murine models, as well as human tissue from patients undergoing surgical aortic aneurysm repair. Furthermore, we critically examine future therapeutic strategies with regard to their clinical and translational feasibility.