Unraveling divergent gene expression profiles in bicuspid and tricuspid aortic valve patients with thoracic aortic dilatation: the ASAP study

The causal relationship between thoracic aortic aneurysm and immune cells: a mendelian randomization study

One of the pathogenic causes of thoracic aortic aneurysm (TAA), a dangerous vascular condition that can cause aortic rupture, is autoimmune disorders. Currently, immune cell clustering is becoming more and more refined, and the specific immune cell phenotypes involved are yet unknown. Here, we want to clarify the causal link between TAA risk and 731 immune cell traits. There was a Mendelian randomization analysis (MR). We discovered that the presence of TAA led to an increase in CD45 on CD33- HLA-DR- myeloid cells, an increase in CD45 on natural killer cells, and a decrease in FSC-A on granulocytes after applying FDR correction. Our research also revealed a strong correlation between the incidence of TAA and an increase in immune cells with CD3 on CD39+ CD4+, and CD25 on IgD- CD27- phenotypes. Through genetic techniques, our research has shown the intimate relationship between immune cells and TAA, offering direction for future clinical investigations.

Single-cell RNA sequencing and ATAC sequencing identify novel biomarkers for bicuspid aortic valve-associated thoracic aortic aneurysm

Introduction

Bicuspid aortic valve (BAV) is the most prevalent congenital cardiovascular defect and known to cause thoracic aortic aneurysms (TAAs). To improve our understanding of BAV pathogenesis, we characterized the cellular composition of BAV tissues and identified molecular changes in each cell population.

Methods

Tissue samples from two patients with BAV and two heart transplant donors were analyzed using single-cell RNA sequencing, assay for transposase-accessible chromatin using sequencing, and weighted gene coexpression network analysis for differential gene analysis. TAA-related changes were evaluated by comparing the proportion of each cell type and gene expression profiles between TAA and control tissues. Further, by combining our single-cell RNA sequencing data with publicly available data from genome-wide association studies, we determined critical genes for BAV.

Results

We found 20 cell subpopulations in TAA tissues, including multiple subtypes of smooth muscle cells, fibroblasts, macrophages, and T lymphocytes. This result suggested that these cells play multiple functional roles in BAV development. Several differentially expressed genes, including CD9, FHL1y, HSP90AA1, GAS6, PALLD, and ACTA2, were identified.

Discussion

We believe that this comprehensive assessment of the cellular composition of TAA tissues and the insights into altered gene expression patterns can facilitate identification of novel diagnostic biomarkers and therapeutic targets for BAV-associated TAA.

Predictive machine learning models for ascending aortic dilatation in patients with bicuspid and tricuspid aortic valves undergoing cardiothoracic surgery: a prospective, single-centre and observational study

OBJECTIVES

The objective of this study was to develop clinical classifiers aiming to identify prevalent ascending aortic dilatation in patients with bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV).

DESIGN AND SETTING

A prospective, single-centre and observational cohort.

PARTICIPANTS

The study involved 543 BAV and 491 TAV patients with aortic valve disease and/or ascending aortic dilatation, excluding those with coronary artery disease, undergoing cardiothoracic surgery at the Karolinska University Hospital (Sweden).

MAIN OUTCOME MEASURES

Predictors of high risk of ascending aortic dilatation (defined as ascending aorta with a diameter above 40 mm) were identified through the application of machine learning algorithms and classic logistic regression models.

EXPOSURES

Comprehensive multidimensional data, including valve morphology, clinical information, family history of cardiovascular diseases, prevalent diseases, demographic details, lifestyle factors, and medication.

RESULTS

BAV patients, with an average age of 60.4±12.4 years, showed a higher frequency of aortic dilatation (45.3%) compared with TAV patients, who had an average age of 70.4±9.1 years (28.9% dilatation, p <0.001). Aneurysm prediction models for TAV patients exhibited mean area under the receiver-operating-characteristic curve (AUC) values above 0.8, with the absence of aortic stenosis being the primary predictor, followed by diabetes and high-sensitivity C reactive protein. Conversely, prediction models for BAV patients resulted in AUC values between 0.5 and 0.55, indicating low usefulness for predicting aortic dilatation. Classification results remained consistent across all machine learning algorithms and classic logistic regression models.

CONCLUSION AND RECOMMENDATION

Cardiovascular risk profiles appear to be more predictive of aortopathy in TAV patients than in patients with BAV. This adds evidence to the fact that BAV-associated and TAV-associated aortopathy involves different pathways to aneurysm formation and highlights the need for specific aneurysm preventions in these patients. Further, our results highlight that machine learning approaches do not outperform classical prediction methods in addressing complex interactions and non-linear relations between variables.

Integrative multi-omics analyses reveal vesicle transport as a potential target for thoracic aortic aneurysm

BACKGROUND

Thoracic aortic aneurysm (TAA) refers to dilation and enlargement of the thoracic aorta caused by various reasons. Most patients have no apparent symptoms in the early stage and are subject to a poor prognosis once the aneurysm ruptures. It is crucial to identify individuals who are predisposed to TAA and to discover effective therapeutic targets for early intervention.

METHODS

We conducted a label-free quantitative proteomic analysis among aorta tissue samples from TAA patients to screen differentially expressed proteins (DEPs) and key co-expression modules. Two datasets from Gene Expression Omnibus (GEO) database were included for integrative analysis, and the identified genes were subjected to immunohistochemistry (IHC) validation. Detailed vesicle transport related enrichment analysis was conducted and two FDA-approved drugs, chlorpromazine (CPZ) and chloroquine (CQ), were selected for in vivo inhibition of vesicle transport in mice TAA model. The diameter of thoracic aorta, mortality and histological differences after interventions were evaluated.

RESULTS

We found significant enrichments in functions involved with vesicle transport, extracellular matrix organizing, and infection diseases in TAA. Endocytosis was the most essential vesicle transport process in TAA formation. Interventions with CPZ and CQ significantly reduced the aneurysm diameter and elastin degradation in vivo and enhanced the survival rates of TAA mice.

CONCLUSIONS

We systematically screened the aberrantly regulated bioprocesses in TAA based on integrative multi-omics analyses, identified and demonstrated the importance of vesicle transport in the TAA formation. Our study provided pilot evidence that vesicular transport was a potential and promising target for the treatment of TAA.

Transcriptomic Analysis of Tight Junction Proteins Demonstrates the Aberrant Expression and Function of Zona Occludens 2 (ZO-2) Protein in Stanford Type A Aortic Dissection

OBJECTIVE

Thoracic aortic aneurysm dissection (TAAD) represents a cardiac surgery emergency characterized by the disrupted integrity of the aortic wall and is associated with poor prognosis. In this context, the identification of biomarkers implicated in the pathobiology of TAAD is crucial. Our aim in the present original in silico study is to assess the differential gene expression profile of the tight junction proteins (TJPs) in patients with TAAD and to propose novel biomarkers for the diagnosis and prognosis of this disease.

METHODS

We implemented bioinformatics methodology in order to construct the gene network of the TJPs family, identify the differentially expressed genes (DEGs) in pathologic aortic tissue excised from patients with TAAD as compared to healthy aortic tissue, and assess the related biological functions and the associated miRNA families.

RESULTS

Data regarding the transcriptomic profile of selected genes were retrieved and incorporated from three microarray datasets, including 23 TAAD and 20 healthy control samples. A total of 32 TJPs were assessed. The zona occludens 2 (ZO-2) protein encoded by the gene TJP2 was significantly under-expressed in patients with TAAD compared to the control group (p = 0.009). ZO-2 was associated with fair discrimination and calibration traits in predicting the TAAD presentation. CpG islands of ZO-2 were demonstrated. No important difference was found regarding ZO-2 expression between aneurysmal non-dissected and healthy control aortic tissue. Finally, we performed gene set enrichment analysis (GSEA) and uncovered the major biological functions and miRNA families (hsa-miR-155-5p, hsa-miR-1-3p, hsa-miR-2118-5p, hsa-miR-4691-3p, and hsa-miR-1229-3p) relevant to ZO-2.

CONCLUSIONS

These outcomes demonstrated the important role of ZO-2 in the pathobiology of TAAD.

Identification of immune-related signatures and pathogenesis differences between thoracic aortic aneurysm patients with bicuspid versus tricuspid valves via weighted gene co-expression network analysis

BACKGROUND

Thoracic aortic aneurysm (TAA) occurs due to pathological aortal dilation, and both individuals with normal tricuspid aortic valves (TAV) or abnormal bicuspid aortic valves (BAV), the latter being a congenital condition, are at risk. However, some differences are present between TAA/BAV and TAA/TAV with respect to their pathophysiological processes and molecular mechanisms, but their exact nature is still mostly unknown. Therefore, it is necessary to elucidate TAA developmental differences among BAV vs. TAV patients.

METHODS

Publically-available gene expression datasets, aortic tissue derived from TAA/BAV and TAA/TAV individuals, were analyzed by weighted gene co-expression network analysis (WGCNA) to identify gene modules associated with those conditions. Gene Ontology (GO) enrichment analysis was performed on those modules to identify the enriched genes within those modules, which were verified by Gene Set Variation Analysis (GSVA) on a dataset derived from aortic smooth muscle cell gene expression between TAA/TAV and TAV/BAV patients. Immune cell infiltration patterns were then analyzed by CIBERSORT, and a protein-protein interaction (PPI) network was constructed based on WGCNA and enrichment analysis results to identify hub genes, followed by validation via stepwise regression analysis. Three signatures most strongly associated with TAA/TAV were confirmed by receiver operating characteristic (ROC) and decision curve analyses (DCA) between prior-established training and testing gene sets.

RESULTS

WGCNA delineated 2 gene modules being associated with TAA/TAV vs. TAA/BAV; both were enriched for immune-associated genes, such as those relating to immune responses, etc., under enrichment analysis. TAA/TAV and TAA/BAV tissues also had differing infiltrating immune cell proportions, particularly with respect to dendritic, mast and CD4 memory T cells. Identified three signatures, CD86, integrin beta 2 (ITGB2) and alpha M (ITGAM), as yielding the strongest associations with TAA/TAV onset, which was verified by areas under the curve (AUC) at levels approximating 0.8 or above under ROC analysis, indicating their predictive value for TAA/TAV onset. However, we did not examine possible confounding variables, so there are many alternative explanations for this association.

CONCLUSIONS

TAA/TAV pathogenesis was found to be more associated with immune-related gene expression compared to TAA/BAV, and the identification of three strongly-associated genes could facilitate their usage as future biomarkers for diagnosing the likelihood of TAA/TAV onset vs. TAA/BAV, as well as for developing future treatments.

Bicuspid aortic valve aortopathy is characterized by embryonic epithelial to mesenchymal transition and endothelial instability

Bicuspid aortic valve (BAV) is the most common congenital heart malformation frequently associated with ascending aortic aneurysm (AscAA). Epithelial to mesenchymal transition (EMT) may play a role in BAV-associated AscAA. The aim of the study was to investigate the type of EMT associated with BAV aortopathy using patients with a tricuspid aortic valve (TAV) as a reference. The state of the endothelium was further evaluated. Aortic biopsies were taken from patients undergoing open-heart surgery. Aortic intima/media miRNA and gene expression was analyzed using Affymetrix human transcriptomic array. Histological staining assessed structure, localization, and protein expression. Migration/proliferation was assessed using ORIS migration assay. We show different EMT types associated with BAV and TAV AscAA. Specifically, in BAV-associated aortopathy, EMT genes related to endocardial cushion formation were enriched. Further, BAV vascular smooth muscle cells were less proliferative and migratory. In contrast, TAV aneurysmal aortas displayed a fibrotic EMT phenotype with medial degenerative insults. Further, non-dilated BAV aortas showed a lower miRNA-200c-associated endothelial basement membrane LAMC1 expression and lower CD31 expression, accompanied by increased endothelial permeability indicated by increased albumin infiltration. Embryonic EMT is a characteristic of BAV aortopathy, associated with endothelial instability and vascular permeability of the non-dilated aortic wall. KEY MESSAGES: Embryonic EMT is a feature of BAV-associated aortopathy. Endothelial integrity is compromised in BAV aortas prior to dilatation. Non-dilated BAV ascending aortas are more permeable than aortas of tricuspid aortic valve patients.

NOTCH1 Gene as a Novel Cause of Thoracic Aortic Aneurysm in Patients with Tricuspid Aortic Valve: Two Cases Reported

Thoracic aortic aneurysms (TAA) consist of abnormal dilation or the widening of a portion of the ascending aorta, due to weakness or destructuring of the walls of the vessel and are potentially lethal. The congenital bicuspid aortic valve (BAV) is considered a risk factor for the development of TAA because asymmetric blood flow through the bicuspid aortic valve detrimentally influences the wall of the ascending aorta. NOTCH1 mutations have been associated with non-syndromic TAAs as a consequence of BAV, but little is known regarding its haploinsufficiency and its relationship with connective tissue abnormalities. We report two cases in which there is clear evidence that alterations in the NOTCH1 gene are the cause of TAA in the absence of BAV. On the one hand, we describe a 117 Kb deletion that includes a large part of the NOTCH1 gene and no other coding genes, suggesting that haploinsufficiency can be considered a pathogenic mechanism for this gene associated with TAA. In addition, we describe two brothers who carry two variants, one in the NOTCH1 gene and another in the MIB1 gene, corroborating the involvement of different genes of the Notch pathway in aortic pathology.

Adventitial adaptive immune cells are associated with ascending aortic dilatation in patients with a bicuspid aortic valve

Background

Bicuspid aortic valve (BAV) is associated with ascending aorta aneurysms and dissections. Presently, genetic factors and pathological flow patterns are considered responsible for aneurysm formation in BAV while the exact role of inflammatory processes remains unknown.

Methods

In order to objectify inflammation, we employ a highly sensitive, quantitative immunohistochemistry approach. Whole slides of dissected, dilated and non-dilated ascending aortas from BAV patients were quantitatively analyzed.

Results

Dilated aortas show a 4-fold increase of lymphocytes and a 25-fold increase in B lymphocytes in the adventitia compared to non-dilated aortas. Tertiary lymphoid structures with B cell follicles and helper T cell expansion were identified in dilated and dissected aortas. Dilated aortas were associated with an increase in M1-like macrophages in the aorta media, in contrast the number of M2-like macrophages did not change significantly.

Conclusion

This study finds unexpected large numbers of immune cells in dilating aortas of BAV patients. These findings raise the question whether immune cells in BAV aortopathy are innocent bystanders or contribute to the deterioration of the aortic wall.

Common molecular mechanism and immune infiltration patterns of thoracic and abdominal aortic aneurysms

BACKGROUND

Aortic disease (aortic aneurysm (AA), dissection (AD)) is a serious threat to patient lives. Little is currently known about the molecular mechanisms and immune infiltration patterns underlying the development and progression of thoracic and abdominal aortic aneurysms (TAA and AAA), warranting further research.

METHODS

We downloaded AA (includes TAA and AAA) datasets from the GEO database. The potential biomarkers in TAA and AAA were identified using differential expression analysis and two machine-learning algorithms. The discrimination power of the potential biomarkers and their diagnostic accuracy was assessed in validation datasets using ROC curve analysis. Then, GSEA, KEGG, GO and DO analyses were conducted. Furthermore, two immuno-infiltration analysis algorithms were utilized to analyze the common immune infiltration patterns in TAA and AAA. Finally, a retrospective clinical study was performed on 78 patients with AD, and the serum from 6 patients was used for whole exome sequencing (WES).

RESULTS

The intersection of TAA and AAA datasets yielded 82 differentially expressed genes (DEGs). Subsequently, the biomarkers (CX3CR1 and HBB) were acquired by screening using two machine-learning algorithms and ROC curve analysis. The functional analysis of DEGs showed significant enrichment in inflammation and regulation of angiogenic pathways. Immune cell infiltration analysis revealed that adaptive and innate immune responses were closely linked to AA progression. However, neither CX3CR1 nor HBB was associated with B cell-mediated humoral immunity. CX3CR1 expression was correlated with macrophages and HBB with eosinophils. Finally, our retrospective clinical study revealed a hyperinflammatory environment in aortic disease. The WES study identified disease biomarkers and gene variants, some of which may be druggable.

CONCLUSION

The genes CX3CR1 and HBB can be used as common biomarkers in TAA and AAA. Large numbers of innate and adaptive immune cells are infiltrated in AA and are closely linked to the development and progression of AA. Moreover, CX3CR1 and HBB are highly correlated with the infiltration of immune cells and may be potential targets of immunotherapeutic drugs. Gene mutation research is a promising direction for the treatment of aortic disease.

Therapeutic potential of the Proprotein Convertase Subtilisin/Kexin family in vascular disease

Proprotein convertase subtilisin/kexins (PCSKs) constitute a family of nine related proteases: PCSK1-7, MBTPS1, and PCSK9. Apart from PCSK9, little is known about PCSKs in cardiovascular disease. Here, we aimed to investigate the expression landscape and druggability potential of the entire PCSK family for CVD. We applied an integrative approach, combining genetic, transcriptomic and proteomic data from three vascular biobanks comprising carotid atherosclerosis, thoracic and abdominal aneurysms, with patient clinical parameters and immunohistochemistry of vascular biopsies. Apart from PCSK4, all PCSK family members lie in genetic regions containing variants associated with human cardiovascular traits. Transcriptomic analyses revealed that FURIN, PCSK5, MBTPS1 were downregulated, while PCSK6/7 were upregulated in plaques vs. control arteries. In abdominal aneurysms, FURIN, PCSK5, PCSK7, MBTPS1 were downregulated, while PCSK6 was enriched in diseased media. In thoracic aneurysms, only FURIN was significantly upregulated. Network analyses of the upstream and downstream pathways related to PCSKs were performed on the omics data from vascular biopsies, revealing mechanistic relationships between this protein family and disease. Cell type correlation analyses and immunohistochemistry showed that PCSK transcripts and protein levels parallel each other, except for PCSK9 where transcript was not detected, while protein was abundant in vascular biopsies. Correlations to clinical parameters revealed a positive association between FURIN plaque levels and serum LDL, while PCSK6 was negatively associated with Hb. PCSK5/6/7 were all positively associated with adverse cardiovascular events. Our results show that PCSK6 is abundant in plaques and abdominal aneurysms, while FURIN upregulation is characteristic for thoracic aneurysms. PCSK9 protein, but not the transcript, was present in vascular lesions, suggesting its accumulation from circulation. Integrating our results lead to the development of a novel ‘molecular’ 5D framework. Here, we conducted the first integrative study of the proprotein convertase family in this context. Our results using this translational pipeline, revealed primarily PCSK6, followed by PCSK5, PCSK7 and FURIN, as proprotein convertases with the highest novel therapeutic potential.

Acetylsalicylic Acid Is Associated With a Lower Prevalence of Ascending Aortic Aneurysm and a Decreased Aortic Expression of Cyclooxygenase 2

Background Acetylsalicylic acid (ASA) therapy has been associated with a reduced prevalence and growth rate of abdominal as well as intracranial aneurysms, but the relationship between ASA and ascending aortic aneurysm formation remains largely unknown. The aim of the present study was to investigate whether ASA therapy is associated with a lower prevalence of ascending aortic aneurysm in a surgical cohort. Methods and Results One thousand seven hundred patients undergoing open-heart surgery for ascending aortic aneurysm and/or aortic valve disease were studied in this retrospective cross-sectional study. Aortic dilatation was defined as an aortic root or ascending aortic diameter ≥45 mm. Medications were self-reported by the patients in a systematic questionnaire. Cyclooxygenase gene expression was measured in the intima-media portion of the ascending aorta (n=117). In a multivariable analysis, ASA was associated with a reduced prevalence of ascending aortic aneurysm (relative risk, 0.68 [95% CI, 0.48-0.95], P=0.026) in patients with tricuspid aortic valves, but not in patients with bicuspid aortic valves (relative risk, 0.93 [95% CI, 0.64-1.34], P=0.687). Intima-media cyclooxygenase expression was positively correlated with ascending aortic dimensions (P<0.001 for cyclooxygenase-1 and P=0.05 for cyclooxygenase-2). In dilated, but not nondilated tricuspid aortic valve aortic specimens, ASA was associated with significantly lower cyclooxygenase-2 levels (P=0.034). Conclusions Our findings are consistent with the hypothesis that ASA treatment may attenuate ascending aortic aneurysmal growth, possibly via cyclooxygenase-2 inhibition in the ascending aortic wall and subsequent anti-inflammatory actions.

Different gene co-expression patterns of aortic intima-media and adventitia in thoracic aortic aneurysm

BACKGROUND

Due to permanent aortic dilation, thoracic aortic aneurysm (TAA) is a life-threatening disease. Once ruptured, TAA has a high lethality and disability rate. Although studies have focused on transcriptomic alterations in TAA, more detailed analysis is still lacking, especially the different aortic intima-media and adventitia roles. This study aimed to identify the different co-expression patterns between the aortic intima-media and the adventitia underlying the aortic dilation.

METHODS

We analyzed the gene expression profiles obtained from Gene Expression Omnibus (GEO, GSE26155) database. With a false discovery rate (FDR) < 0.05 and |log2FC| ≥ 1, 56 and 33 differential genes in the intima-media and adventitia, respectively, between the non-dilated and dilated status. Gene ontology (GO) and gene set enrichment analysis revealed that degranulation and activation of neutrophils play an essential role in the intima-media of dilated aortas. Through weighted gene co-expression network analysis (WGCNA), we identified essential co-expressed modules and hub genes to explore the biological functions of the dysregulated genes.

RESULTS

Functional pathway analysis suggested that lipid metabolism, C-C motif chemokine pathways were significantly enriched in the adventitia, whereas ribosome proteins and related mRNA translation pathways were closely related to intima and media. Furthermore, the ssGSEA analysis indicated that macrophages, helper T cells, and neutrophils were higher in the intima-media of the dilated thoracic aorta. Finally, we validated the critical findings of the study with the murine model of TAA.

CONCLUSION

This study identified and verified hub genes and pathways in aortic intima-media and adventitia prominently associated with aortic dilation, providing practical understanding in the perspective of searching for new molecular targets.

Integrating Bulk Transcriptome and Single-Cell RNA Sequencing Data Reveals the Landscape of the Immune Microenvironment in Thoracic Aortic Aneurysms

Thoracic aortic aneurysm (TAA) is a life-threatening cardiovascular disease whose formation is reported to be associated with massive vascular inflammatory responses. To elucidate the roles of immune cell infiltration in the pathogenesis underlying TAA, we utilized multiple TAA datasets (microarray data and scRNA-seq data) and various immune-related algorithms (ssGSEA, CIBERSORT, and Seurat) to reveal the landscapes of the immune microenvironment in TAA. The results exhibited a significant increase in the infiltration of macrophages and T cells, which were mainly responsible for TAA formation among the immune cells. To further reveal the roles of immunocytes in TAA, we inferred the intercellular communications among the identified cells of aortic tissues. Notably, we found that in both normal aortic tissue and TAA tissue, the cells that interact most frequently are macrophages, endothelial cells (ECs), fibroblasts, and vascular smooth muscle cells (VSMCs). Among the cells, macrophages were the most prominent signal senders and receivers in TAA and normal aortic tissue. These findings suggest that macrophages play an important role in both the physiological and pathological conditions of the aorta. The present study provides a comprehensive evaluation of the immune cell composition and reveals the intercellular communication among aortic cells in human TAA tissues. These findings improve our understanding of TAA formation and progression and facilitate the development of effective medications to treat these conditions.

The role of vascular smooth muscle cells in the development of aortic aneurysms and dissections

BACKGROUND

Aortic aneurysms (AA) are pathological dilations of the aorta, associated with an overall mortality rate up to 90% in case of rupture. In addition to dilation, the aortic layers can separate by a tear within the layers, defined as aortic dissections (AD). Vascular smooth muscle cells (vSMC) are the predominant cell type within the aortic wall and dysregulation of vSMC functions contributes to AA and AD development and progression. However, since the exact underlying mechanism is poorly understood, finding potential therapeutic targets for AA and AD is challenging and surgery remains the only treatment option.

METHODS

In this review, we summarize current knowledge about vSMC functions within the aortic wall and give an overview of how vSMC functions are altered in AA and AD pathogenesis, organized per anatomical location (abdominal or thoracic aorta).

RESULTS

Important functions of vSMC in healthy or diseased conditions are apoptosis, phenotypic switch, extracellular matrix regeneration and degradation, proliferation and contractility. Stressors within the aortic wall, including inflammatory cell infiltration and (epi)genetic changes, modulate vSMC functions and cause disturbance of processes within vSMC, such as changes in TGF-β signalling and regulatory RNA expression.

CONCLUSION

This review underscores a central role of vSMC dysfunction in abdominal and thoracic AA and AD development and progression. Further research focused on vSMC dysfunction in the aortic wall is necessary to find potential targets for noninvasive AA and AD treatment options.

Sex differences in aortopathy and valve diseases among patients undergoing cardiac surgery

BACKGROUND

We aimed to study sex differences in aortopathy and valve disease among patients undergoing aortic valve replacement and/or surgery for ascending aortic aneurysm, and assess whether differences are specific for patients with bicuspid (BAV) compared to patients with tricuspid aortic valve (TAV).

METHODS

We used a single-center and observational cohort including 1,045 patients undergoing elective open-heart surgery for aortic valve disease and/or ascending aortic aneurysm at the Karolinska Hospital (Sweden).

RESULTS

Women (33.0%) were older than men (mean [SD]; 67.9 [11] years vs 62.5 [13] years for men; P < 0.001). No significant sex difference in prevalence of ascending aortic aneurysm was found according to absolute measures (P = 0.19), however, women had a greater dilation of the ascending aorta when normalized for body surface area (mean [SD], 21.8 [6.3] mm/m² vs 19.3 [4.4] mm/m² for men; P < 0.001). Among the 560 patients with BAV, women had significantly more AS (adjusted OR, 2.23; 95% CI, 1.19-4.20; P = 0.013) and less AI (adjusted OR 0.42; 95% CI, 0.23-0.78; P < 0.01); whereas no sex difference was found among patients with TAV.

CONCLUSIONS

In this large study of patients undergoing cardiac surgery, we found greater degree of aortic dilation in women compared to men suggesting a need for earlier monitoring of women. Moreover, women with BAV had a significantly higher prevalence of AS compared to men. These results describe the aorta and valvular characteristics of patients by sex and provide guidance regarding which patients might benefit from closer surveillance.

Bicuspid Valve Sizing for Transcatheter Aortic Valve Implantation: The Missing Link

Transcatheter aortic valve implantation (TAVI) is a well-recognized and established therapy for severe aortic stenosis, with expanding indications toward younger patients with low surgical risk profile. As bicuspid aortic valve (BAV) affects ~1-2% of the population, it may be speculated that an increasing number of patients with degenerated BAV may eventually need TAVI during the course of the disease. On the other hand, BAV represents a challenge due to its peculiar anatomical features and the lack of consensus on the optimal sizing strategy. The aim of this paper is to review the peculiar aspects of BAV and to discuss and compare the currently available sizing methods. Special attention is given to the role of pre-procedural imaging, mostly with multislice computed tomography, and to the aspects that operators should evaluate in order to ensure an optimal procedural planning and avoid procedural-related complications.

In-depth bioinformatic study of the cadherin 5 interactome in patients with thoracic aortic aneurysm unveils 8 novel biomarkers

OBJECTIVES

Thoracic aortic aneurysm (TAA) is characterized by the dilation of the aorta and is associated with poor prognosis if not diagnosed and treated early. In this context, the identification of biomarkers regarding the TAA diagnosis, monitoring and prognosis is crucial. The purpose of the current study was to investigate the differential gene expression profile of the cadherin 5 (CDH5 or VE-Cadherin) gene network in patients with TAA, to propose novel biomarkers.

METHODS

In silico techniques were used to construct the interactome of the CDH5 network, identify the differentially expressed genes (DEGs) in TAA as compared to healthy controls, and uncover the related molecular functions and the regulating miRNAs.

RESULTS

Transcriptomic data of one microarray dataset were included, incorporating 43 TAA and 43 control samples. Eight DEGs were identified; 7 were up-regulated and 1 was down-regulated. A molecular signature of 8 genes (CDH5; Calcitonin Receptor-Like Receptor-CALCRL; Activin A Receptor-Like Type 1-ACVRL1, Tryptophanyl-TRNA Synthetase 1-WARS; Junction Plakoglobin-JUP, Protein Tyrosine Phosphatase Receptor Type J-PTPRJ, Purinergic Receptor P2X 4-P2RX4, Kinase Insert Domain Receptor-KDR) were identified as biomarkers associated with TAA. PTPRJ was associated with excellent discrimination and calibration in predicting TAA presentation. Positive correlations were reported regarding the expression of CDH5-CALCRL, CDH5-ACVRL1, CDH5-WARS and CDH5-PTPRJ. Finally, gene set enrichment analysis indicated the molecular functions and miRNA families (hsa-miR-296-5p, hsa-miR-6836-5p, hsa-miR-6132, hsa-miR-27a-5p and hsa-miR-6773-5p) relevant to the 8 biomarkers.

CONCLUSIONS

These outcomes propose an 8-gene molecular panel associated with TAA.

Aortic Dilatation in Patients With Bicuspid Aortic Valve

Bicuspid aortic valve (BAV) is the most common congenital cardiac abnormality. BAV aortic dilatation is associated with an increased risk of adverse aortic events and represents a potentially lethal disease and hence a considerable medical burden. BAV with aortic dilatation warrants frequent monitoring, and elective surgical intervention is the only effective method to prevent dissection or rupture. The predictive value of the aortic diameter is known to be limited. The aortic diameter is presently still the main reference standard for surgical intervention owing to the lack of a comprehensive understanding of BAV aortopathy progression. This article provides a brief comprehensive review of the current knowledge on BAV aortopathy regarding clinical definitions, epidemiology, natural course, and pathophysiology, as well as hemodynamic and clinically significant aspects on the basis of the limited data available.

Cardiac Neural Crest Cells: Their Rhombomeric Specification, Migration, and Association with Heart and Great Vessel Anomalies

Outflow tract abnormalities are the most frequent congenital heart defects. These are due to the absence or dysfunction of the two main cell types, i.e., neural crest cells and secondary heart field cells that migrate in opposite directions at the same stage of development. These cells directly govern aortic arch patterning and development, ascending aorta dilatation, semi-valvular and coronary artery development, aortopulmonary septation abnormalities, persistence of the ductus arteriosus, trunk and proximal pulmonary arteries, sub-valvular conal ventricular septal/rotational defects, and non-compaction of the left ventricle. In some cases, depending on the functional defects of these cells, additional malformations are found in the expected spatial migratory area of the cells, namely in the pharyngeal arch derivatives and cervico-facial structures. Associated non-cardiovascular anomalies are often underestimated, since the multipotency and functional alteration of these cells can result in the modification of multiple neural, epidermal, and cervical structures at different levels. In most cases, patients do not display the full phenotype of abnormalities, but congenital cardiac defects involving the ventricular outflow tract, ascending aorta, aortic arch and supra-aortic trunks should be considered as markers for possible impaired function of these cells. Neural crest cells should not be considered as a unique cell population but on the basis of their cervical rhombomere origins R3-R5 or R6-R7-R8 and specific migration patterns: R3-R4 towards arch II, R5-R6 arch III and R7-R8 arch IV and VI. A better understanding of their development may lead to the discovery of unknown associated abnormalities, thereby enabling potential improvements to be made to the therapeutic approach.

Mechanisms of Action of the KCa2-Negative Modulator AP30663, a Novel Compound in Development for Treatment of Atrial Fibrillation in Man

Aims

Small conductance Ca²⁺-activated K⁺ channels (SK channels, K_Ca2) are a new target for treatment of atrial fibrillation (AF). AP30663 is a small molecule inhibitor of K_Ca2 channels that is currently in clinical development for treatment of AF. The aim of this study is to present the electrophysiological profile and mechanism of action of AP30663 and its efficacy in prolonging atrial refractoriness in rodents, and by bioinformatic analysis investigate if genetic variants in KCNN2 or KCNN3 influence the expression level of these in human heart tissue.

Methods and Results

Whole-cell and inside-out patch-clamp recordings of heterologously expressed K_Ca2 channels revealed that AP30663 inhibits K_Ca2 channels with minor effects on other relevant cardiac ion channels. AP30663 modulates the K_Ca2.3 channel by right-shifting the Ca²⁺-activation curve. In isolated guinea pig hearts AP30663 significantly prolonged the atrial effective refractory period (AERP) with minor effects on the QT-interval corrected for heart rate. Similarly, in anaesthetized rats 5 and 10 mg/kg of AP30663 changed the AERP to 130.7±5.4% and 189.9±18.6 of baseline values. The expression quantitative trait loci analyses revealed that the genome wide association studies for AF SNP rs13376333 in KCNN3 is associated with increased mRNA expression of KCNN3 in human atrial appendage tissue.

Conclusions

AP30663 is a novel negative allosteric modulator of K_Ca2 channels that concentration-dependently prolonged rodent atrial refractoriness with minor effects on the QT-interval. Moreover, AF associated SNPs in KCNN3 influence KCNN3 mRNA expression in human atrial tissue. These properties support continued development of AP30663 for treatment of AF in man.

Integrated analysis of immunocyte infiltration and differential gene expression in tricuspid aortic valve-associated thoracic aortic aneurysms

Background

Progressive dilatation is responsible for significant mortality and morbidity in patients with thoracic aortic aneurysms (TAAs). Studies have shown that the development and progression of TAAs are closely related to immune regulatory pathways and genes. Therefore, it is important to understand the immune regulatory mechanisms and biomarkers of TAA dilatation.

Methods

Systematic bioinformatics analysis was applied, including linear models for microarray data (LIMMA) differential expression analyses, principal component analysis (PCA), immunocyte identification, and genetic function enrichment analysis.

Results

Our results showed that both aortic intima-media (AMed) and outer aortic adventitia (AAdv) tissues were closely associated with T cell activation during the process of tricuspid aortic valve (TAV)-associated TAA dilation. Additionally, the degree of infiltration of resting memory CD4+ T cells was linked to both AAdv and AMed vascular dilation. The core regulators PPTRC, IL1B, CD4, CD3G, and IL2RA were also identified and are closely related to resting memory CD4+ T cell infiltration in this pathological process.

Conclusions

The candidate genes PPTRC, IL1B, CD4, CD3G, and IL2RA were involved in the regulation of resting memory CD4 T cell tissue infiltration, which is closely related to the process of AAdv and AMed vascular dilation in TAV patients.

Endothelial/Epithelial Mesenchymal Transition in Ascending Aortas of Patients With Bicuspid Aortic Valve

Thoracic aortic aneurysm (TAA) is the progressive enlargement of the aorta due to destructive changes in the connective tissue of the aortic wall. Aneurysm development is silent and often first manifested by the drastic events of aortic dissection or rupture. As yet, therapeutic agents that halt or reverse the process of aortic wall deterioration are absent, and the only available therapeutic recommendation is elective prophylactic surgical intervention. Being born with a bicuspid instead of the normal tricuspid aortic valve (TAV) is a major risk factor for developing aneurysm in the ascending aorta later in life. Although the pathophysiology of the increased aneurysm susceptibility is not known, recent studies are suggestive of a transformation of aortic endothelium into a more mesenchymal state i.e., an endothelial-to-mesenchymal transition in these individuals. This process involves the loss of endothelial cell features, resulting in junction instability and enhanced vascular permeability of the ascending aorta that may lay the ground for increased aneurysm susceptibility. This finding differentiates and further emphasizes the specific characteristics of aneurysm development in individuals with a bicuspid aortic valve (BAV). This review discusses the possibility of a developmental fate shared between the aortic endothelium and aortic valves. It further speculates about the impact of aortic endothelium phenotypic shift on aneurysm development in individuals with a BAV and revisits previous studies in the light of the new findings.

Notch signaling in the pathogenesis of thoracic aortic aneurysms: A bridge between embryonic and adult states

Aneurysms of the thoracic aorta are a "silent killer" with no evident clinical signs until the fatal outcome. Molecular and genetic bases of thoracic aortic aneurysms mainly include transforming growth factor beta signaling, smooth muscle contractile units and metabolism genes, and extracellular matrix genes. In recent studies, a role of Notch signaling, among other pathways, has emerged in disease pathogenesis. Notch is a highly conserved signaling pathway that regulates the development and differentiation of many types of tissues and influences major cellular processes such as cell proliferation, differentiation and apoptosis. Mutations in several Notch signaling components have been associated with a number of heart defects, demonstrating an essential role of Notch signaling both in cardiovascular system development and its maintenance during postnatal life. This review discusses the role of Notch signaling in the pathogenesis of thoracic aortic aneurysms considering development and maintenance of the aortic root and how developmental regulations by Notch signaling may influence thoracic aortic aneurysms.

Strong Signs for a Weak Wall in Tricuspid Aortic Valve Associated Aneurysms and a Role for Osteopontin in Bicuspid Aortic Valve Associated Aneurysms

Central processes in the pathogenesis of TAV- (tricuspid aortic valve) and BAV- (bicuspid aortic valve) associated ascending thoracic aortic aneurysm (ATAA) development are still unknown. To gain new insights, we have collected aortic tissue and isolated smooth muscle cells of aneurysmal tissue and subjected them to in situ and in vitro analyses. We analyzed aortic tissue from 78 patients (31 controls, 28 TAV-ATAAs, and 19 BAV-ATAAs) and established 30 primary smooth muscle cell cultures. Analyses included histochemistry, immuno-, auto-fluorescence-based image analyses, and cellular analyses including smooth muscle cell contraction studies. With regard to TAV associated aneurysms, we observed a strong impairment of the vascular wall, which appears on different levels—structure and dimension of the layers (reduced media thickness, increased intima thickness, atherosclerotic changes, degeneration of aortic media, decrease of collagen, and increase of elastic fiber free area) as well as on the cellular level (accumulation of fibroblasts/myofibroblasts, and increase in the number of smooth muscle cells with a reduced alpha smooth muscle actin (α-SM actin) content per cell). The pathological changes in the aortic wall of BAV patients were much less pronounced—apart from an increased expression of osteopontin (OPN) in the vascular wall which stem from smooth muscle cells, we observed a trend towards increased calcification of the aortic wall (increase significantly associated with age). These observations provide strong evidence for different pathological processes and different disease mechanisms to occur in BAV- and TAV-associated aneurysms.

Cardiac expression of the microsomal triglyceride transport protein protects the heart function during ischemia

AIMS

The microsomal triglyceride transport protein (MTTP) is critical for assembly and secretion of apolipoprotein B (apoB)-containing lipoproteins and is most abundant in the liver and intestine. Surprisingly, MTTP is also expressed in the heart. Here we tested the functional relevance of cardiac MTTP expression.

MATERIALS AND METHODS

We combined clinical studies, advanced expression analysis of human heart biopsies and analyses in genetically modified mice lacking cardiac expression of the MTTP-A isoform of MTTP.

RESULTS

Our results indicate that lower cardiac MTTP expression in humans is associated with structural and perfusion abnormalities in patients with ischemic heart disease. MTTP-A deficiency in mice heart does not affect total MTTP expression, activity or lipid concentration in the heart. Despite this, MTTP-A deficient mice displayed impaired cardiac function after a myocardial infarction. Expression analysis of MTTP indicates that MTTP expression is linked to cardiac function and responses in the heart.

CONCLUSIONS

Our results indicate that MTTP may play an important role for the heart function in conjunction to ischemic events.

Bicuspid aortic valve-associated aortopathy: Where do we stand?

Herein we summarize the current knowledge on the bicuspid aortic valve (BAV)-associated aortopathy regarding clinical presentation and disease sub-classification, genetic background, hemodynamics, histopathology, cells and signaling, animal models, and biomarkers. Despite enormous efforts in research in all of the above areas, important issues remain unknown: (i) what is the ontogenetic basis of BAV development? (ii) how can we explain the diversity of BAV and associated aortopathy phenotypes? (iii) what are the signaling processes in aortopathy pathogenesis and how can we interfere with these processes? Despite undoubtedly great progress that has been made in the understanding of BAV-associated aortopathy, so far researchers have put together a heap of Lego bricks, but at present it is unclear if the bricks are compatible, how they fit together, and which parts are missing to build the true model of the BAV aorta. A joint approach is needed to accelerate research progress.

The mir-200 family regulates key pathogenic events in ascending aortas of individuals with bicuspid aortic valves

BACKGROUND

An individual with a bicuspid aortic valve (BAV) runs a substantially higher risk of developing aneurysm in the ascending aorta compared to the normal population with tricuspid aortic valves (TAV). Aneurysm formation in patients with BAV and TAV is known to be distinct at the molecular level but the underlying mechanisms are undefined. Here, we investigated the still incompletely described role of microRNAs (miRNAs), important post-transcriptional regulators of gene expression, in such aortic disease of patients with BAV as compared with TAV.

METHODS AND RESULTS

Using a system biology approach, based on data obtained from proteomic analysis of non-dilated aortas from BAV and TAV patients, we constructed a gene-interaction network of regulatory microRNAs associated with the observed differential protein signature. The miR-200 family was the highest ranked miRNA, hence potentially having the strongest effect on the signalling network associated with BAV. Further, qRT-PCR and ChIP analyses showed lower expression of miR-200c, higher expression of miR-200 target genes, ZEB1/ZEB2 transcription factors, and higher chromatin occupancy of the miR-200c promoter by ZEB1/ZEB2 in BAV patients, indicating a miR-200c/ZEBs negative feedback loop and induction of endothelial/epithelial mesenchymal transition (EndMT/EMT).

CONCLUSION

We propose that a miR-200-dependent process of EndMT/EMT is a plausible biological mechanism rendering the BAV ascending aorta more prone to aneurysm development. Although initially supported by a miR-200c/ZEB feedback loop, this process is most probably advanced by cooperation of other miRNAs.

DNA methylation age is associated with an altered hemostatic profile in a multiethnic meta-analysis

Many hemostatic factors are associated with age and age-related diseases; however, much remains unknown about the biological mechanisms linking aging and hemostatic factors. DNA methylation is a novel means by which to assess epigenetic aging, which is a measure of age and the aging processes as determined by altered epigenetic states. We used a meta-analysis approach to examine the association between measures of epigenetic aging and hemostatic factors, as well as a clotting time measure. For fibrinogen, we performed European and African ancestry-specific meta-analyses which were then combined via a random effects meta-analysis. For all other measures we could not estimate ancestry-specific effects and used a single fixed effects meta-analysis. We found that 1-year higher extrinsic epigenetic age as compared with chronological age was associated with higher fibrinogen (0.004 g/L/y; 95% confidence interval, 0.001-0.007; P = .01) and plasminogen activator inhibitor 1 (PAI-1; 0.13 U/mL/y; 95% confidence interval, 0.07-0.20; P = 6.6 × 10-5) concentrations, as well as lower activated partial thromboplastin time, a measure of clotting time. We replicated PAI-1 associations using an independent cohort. To further elucidate potential functional mechanisms, we associated epigenetic aging with expression levels of the PAI-1 protein encoding gene (SERPINE1) and the 3 fibrinogen subunit-encoding genes (FGA, FGG, and FGB) in both peripheral blood and aorta intima-media samples. We observed associations between accelerated epigenetic aging and transcription of FGG in both tissues. Collectively, our results indicate that accelerated epigenetic aging is associated with a procoagulation hemostatic profile, and that epigenetic aging may regulate hemostasis in part via gene transcription.

Diabetes, Incretin Therapy and Thoracic Aortic Aneurysm - What Does the Evidence Show?

Epidemiological evidence supports a reduced prevalence of Thoracic Aortic Aneurysm (TAA) and Abdominal Aortic Aneurysm (AAA) in patients with Diabetes (DM). The mechanisms underlying this negative association are unknown. Some studies support that hyperglycemia has effects on the Extracellular Matrix (ECM), resulting in collagen cross-links and altered proteolytic activity, which ultimately counteracts aneurysm formation. However, recent experimental research indicates that incretin- based anti-diabetic therapy and Glucagon-Like Peptide-1 (GLP-1) may reduce the formation of TAA. GLP-1 is a peptide hormone, released from intestinal L-cells in response to hormonal, neural and nutrient stimuli. In addition to potentiation of meal-stimulated insulin secretion, GLP-1 signaling exerts numerous pleiotropic effects on various tissues, including protective effects on the myocardium and vascular endothelium. Recent studies also report protective effects of GLP-1 based therapy on the formation of aneurysms in animal models and direct effects of GLP-1 signaling on the molecular mechanisms suggested to influence TAA formation, including inflammation, proteolytic activity and collagen composition. In this narrative review, we present the available evidence for effects of GLP-1 on experimental aneurysm development and discuss the potential role of GLP-1 in aneurysm formation based on available data from pre-clinical and clinical studies.

Candidate plasma biomarkers for predicting ascending aortic aneurysm in bicuspid aortic valve disease

Background

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac abnormality affecting 1–2% of the population and is associated with a significantly increased risk of ascending aortic aneurysm. However, predicting which patients will develop aneurysms remains a challenge. This pilot study aimed to identify candidate plasma biomarkers for monitoring ascending aortic diameter and predicting risk of future aneurysm in BAV patients.

Methods

Plasma samples were collected pre-operatively from BAV patients undergoing aortic valve surgery. Maximum ascending aortic diameter was measured on pre-operative transoesophageal echocardiography. Maximum diameter ≥ 45 mm was classified as aneurysmal. Sequential Window Acquisition of all THeoretical Mass Spectra (SWATH-MS), an advanced mass spectrometry technique, was used to identify and quantify all proteins within the samples. Protein abundance and aortic diameter were correlated using logistic regression. Levene’s test was used to identify proteins demonstrating low abundance variability in the aneurysmal patients (consistent expression in disease), and high variability in the non-aneurysmal patients (differential expression between ‘at risk’ and not ‘at risk’ patients).

Results

Fifteen plasma samples were collected (seven non-aneurysmal and 8 aneurysmal BAV patients). The mean age of the patients was 55.5 years and the majority were female (10/15, 67%). Four proteins (haemoglobin subunits alpha, beta and delta and mannan-binding lectin serine protease) correlated significantly with maximal ascending aortic diameter (p < 0.05, r = 0.5–0.6). Five plasma proteins demonstrated significantly lower variability in the aneurysmal group and may indicate increased risk of aneurysm in non-aneurysmal patients (DNA-dependent protein kinase catalytic subunit, lumican, tetranectin, gelsolin and cartilage acidic protein 1). A further 7 proteins were identified only in the aneurysmal group (matrin-3, glucose-6-phosphate isomerase, coactosin-like protein, peptidyl-prolyl cis-trans isomerase A, golgin subfamily B member 1, myeloperoxidase and 2′-deoxynucleoside 5′-phosphate N-hydrolase 1).

Conclusions

This study is the first to identify candidate plasma biomarkers for predicting aortic diameter and risk of future aneurysm in BAV patients. It provides valuable pilot data and proof of principle that could be used to design a large-scale prospective investigation. Ultimately, a more affordable ‘off-the-shelf’ follow-on blood assay could then be developed in place of SWATH-MS, for use in the healthcare setting.

Electronic supplementary material

The online version of this article (10.1186/s13019-018-0762-1) contains supplementary material, which is available to authorized users.

Defective NOTCH signaling drives increased vascular smooth muscle cell apoptosis and contractile differentiation in bicuspid aortic valve aortopathy: A review of the evidence and future directions

Bicuspid aortic valve (BAV) disease remains the most common congenital cardiac disease and is associated with an increased risk of potentially fatal aortopathy including aortic aneurysm and dissection. Mutations in the NOTCH1 gene are one of only a few genetic anomalies identified in BAV disease; however evidence for defective NOTCH signaling, and its involvement in the characteristic histological changes of VSMC apoptosis and differentiation in ascending aortae of BAV patients is lacking. This review scrutinizes the evidence for the interactions of NOTCH signaling, cellular differentiation and apoptosis in the context of aortic VSMCs and provides focus for future research efforts in the diagnosis of BAV aortopathy and prevention of catastrophic complications through NOTCH signaling manipulation.

Enlightening the Association between Bicuspid Aortic Valve and Aortopathy

Bicuspid aortic valve (BAV) patients have an increased incidence of developing aortic dilation. Despite its importance, the pathogenesis of aortopathy in BAV is still largely undetermined. Nowadays, intense focus falls both on BAV morphology and progression of valvular dysfunction and on the development of aortic dilation. However, less is known about the relationship between aortic valve morphology and aortic dilation. A better understanding of the molecular pathways involved in the homeostasis of the aortic wall, including the extracellular matrix, the plasticity of the vascular smooth cells, TGFβ signaling, and epigenetic dysregulation, is key to enlighten the mechanisms underpinning BAV-aortopathy development and progression. To date, there are two main theories on this subject, i.e., the genetic and the hemodynamic theory, with an ongoing debate over the pathogenesis of BAV-aortopathy. Furthermore, the lack of early detection biomarkers leads to challenges in the management of patients affected by BAV-aortopathy. Here, we critically review the current knowledge on the driving mechanisms of BAV-aortopathy together with the current clinical management and lack of available biomarkers allowing for early detection and better treatment optimization.

Altered DNA methylation indicates an oscillatory flow mediated epithelial-to-mesenchymal transition signature in ascending aorta of patients with bicuspid aortic valve

Disturbed flow has been suggested to contribute to aneurysm susceptibility in bicuspid aortic valve (BAV) patients. Lately, flow has emerged as an important modulator of DNA methylation. Hear we combined global methylation analysis with in vitro studies of flow-sensitive methylation to identify biological processes associated with BAV-aortopathy and the potential contribution of flow. Biopsies from non-dilated and dilated ascending aortas were collected from BAV (n = 21) and tricuspid aortic valve (TAV) patients (n = 23). DNA methylation and gene expression was measured in aortic intima-media tissue samples, and in EA.hy926 and primary aortic endothelial cells (ECs) isolated from BAV and TAV exposed to oscillatory (±12 dynes/cm²) or laminar (12 dynes/cm²) flow. We show methylation changes related to epithelial-mesenchymal-transition (EMT) in the non-dilated BAV aorta, associated with oscillatory flow related to endocytosis. The results indicate that the flow-response in BAV ECs involves hypomethylation and increased expression of WNT/β-catenin genes, as opposed to an angiogenic profile in TAV ECs. The EMT-signature was exasperated in dilated BAV aortas. Aberrant EMT in BAV aortic walls could contribute to increased aneurysm susceptibility, and may be due to disturbed flow-exposure. Perturbations during the spatiotemporally related embryonic development of ascending aorta and semilunar valves can however not be excluded.

Characteristics of aorto-iliofemoral arterial tree according to aortic valve morphology in chinese patients considered for TAVR

To characterize the anatomy of aorto-iliofemoral arterial tree according to aortic valve phenotype by CT in patients referred for transcatheter aortic valve replacement (TAVR). We retrospectively enrolled 215 patients screened for TAVR who underwent CT. Dimensions, calcification, vascular tortuosity index score and other putative risk features of 13 different regions were evaluated for bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) morphology. The study consisted of 44% BAVs with younger age than TAVs. The dimensions of the annulus, sinus of Valsalva, ascending aorta and aortic arch were consistently larger in BAVs. The prevalence of calcification of aortic arch was significantly higher in TAVs even after adjustment for atherosclerotic risk factors. BAVs was associated with two-fold higher odds of having over I degree AA calcification (odds ratio 2.02; 95% CI 1.60-5.31; p < 0.001). The prevalence of severe iliac tortuosity was higher among BAVs (11.7 vs. 2.5%, p = 0.015). BAVs had a trend to more atheroma than TAVs in the abdominal aortic artery and iliofemoral artery. BAV anatomy is common in Chinese AS patients screened for TAVR. Aorto-iliofemoral pathology varies according to aortic valve phenotype, which may contribute to technical challenges in BAV vs. TAV anatomy and support the need for the integrated risk assessment for each valve phenotype.

Mechanisms of Smooth Muscle Cell Differentiation Are Distinctly Altered in Thoracic Aortic Aneurysms Associated with Bicuspid or Tricuspid Aortic Valves

Cellular and molecular mechanisms of thoracic aortic aneurysm are not clear and therapeutic approaches are mostly absent. Thoracic aortic aneurysm is associated with defective differentiation of smooth muscle cells (SMC) of aortic wall. Bicuspid aortic valve (BAV) comparing to tricuspid aortic valve (TAV) significantly predisposes to a risk of thoracic aortic aneurysms. It has been suggested recently that BAV-associated aortopathies represent a separate pathology comparing to TAV-associated dilations. The only proven candidate gene that has been associated with BAV remains NOTCH1. In this study we tested the hypothesis that Notch-dependent and related TGF-β and BMP differentiation pathways are differently altered in aortic SMC of BAV- vs. TAV-associated aortic aneurysms. SMC were isolated from aortic tissues of the patients with BAV- or TAV-associated aortic aneurysms and from healthy donors used as controls. Gene expression was verified by qPCR and Western blotting. For TGF-β induced differentiation SMC were treated with the medium containing TGF-β1. To induce proosteogenic signaling we cultured SMC in the presence of specific osteogenic factors. Notch-dependent differentiation was induced via lentiviral transduction of SMC with activated Notch1 domain. MYOCD expression, a master gene of SMC differentiation, was down regulated in SMC of both BAV and TAV patients. Discriminant analysis of gene expression patterns included a set of contractile genes specific for SMC, Notch-related genes and proosteogenic genes and revealed that control cells form a separate cluster from both BAV and TAV group, while BAV- and TAV-derived SMC are partially distinct with some overlapping. In differentiation experiments TGF-β caused similar patterns of target gene expression for BAV- and TAV derived cells while the induction was higher in the diseased cells than in control ones. Osteogenic induction caused significant change in RUNX2 expression exclusively in BAV group. Notch activation induced significant ACTA2 expression also exclusively in BAV group. We show that Notch acts synergistically with proosteogenic factors to induce ACTA2 transcription and osteogenic differentiation. In conclusion we have found differences in responsiveness of SMC to Notch and to proosteogenic induction between BAV- and TAV-associated aortic aneurysms.

Elevated oxidative stress in the aortic media of patients with bicuspid aortic valve

OBJECTIVE

Congenital bicuspid aortic valve (BAV) is distinctly associated with the development of ascending aortopathy in adulthood, portending risk of both ascending aortic aneurysm and dissection. Our previous work implicated deficiency in oxidative stress response as a mediator of the BAV-associated aortopathy. We hypothesize that reactive oxygen species generation invokes elevated local oxidative tissue damage in ascending aorta of patients with BAV.

METHODS

Ascending aortic specimens were obtained from patients undergoing elective aortic replacement and/or aortic valve replacement and during heart transplant operations. Levels of superoxide anion were measured via high-pressure liquid chromatography-based detection of 2-hydroxyethidium in aortic specimens. Lipid peroxidation and enzymatic activity of superoxide dismutase and peroxidase were quantified in aortic specimens.

RESULTS

Superoxide anion production was elevated in aortic specimens from patients with nonaneurysmal BAV (n = 59) compared with specimens from patients with the morphologically normal tricuspid aortic valve (TAV, n = 38). Total superoxide dismutase activity was similar among aortic specimens from patients with TAV versus BAV (n = 27 and 26, respectively), whereas peroxidase activity was increased in aortic specimens from patients with BAV compared with specimens from patients with TAV (n = 14 for both groups). Lipid peroxidation was elevated in aortic specimens from BAV patients compared with TAV patients (n = 14 and 11, respectively).

CONCLUSIONS

Superoxide anion accumulation and increased lipid peroxidation demonstrate that, despite increased peroxidase activity, the ascending aortopathy of patients with BAV involves oxidative stress. In addition, the absence of increased superoxide dismutase activity in BAV specimens indicates a deficiency in antioxidant defense. This suggests that the characteristic smooth muscle cell loss observed in BAV aortopathy may be a consequence of superoxide-mediated cell damage.

Nanonet force microscopy for measuring forces in single smooth muscle cells of the human aorta

A number of innovative methods exist to measure cell-matrix adhesive forces, but they have yet to accurately describe and quantify the intricate interplay of a cell and its fibrous extracellular matrix (ECM). In cardiovascular pathologies, such as aortic aneurysm, new knowledge on the involvement of cell-matrix forces could lead to elucidation of disease mechanisms. To better understand this dynamics, we measured primary human aortic single smooth muscle cell (SMC) forces using nanonet force microscopy in both inside-out (I-O intrinsic contractility) and outside-in (O-I external perturbation) modes. For SMC populations, we measured the I-O and O-I forces to be 12.9 ± 1.0 and 57.9 ± 2.5 nN, respectively. Exposure of cells to oxidative stress conditions caused a force decrease of 57 and 48% in I-O and O-I modes, respectively, and an increase in migration rate by 2.5-fold. Finally, in O-I mode, we cyclically perturbed cells at constant strain of varying duration to simulate in vivo conditions of the cardiac cycle and found that I-O forces decrease with increasing duration and O-I forces decreased by half at shorter cycle times. Thus our findings highlight the need to study forces exerted and felt by cells simultaneously to comprehensively understand force modulation in cardiovascular disease.

Mapping of 79 loci for 83 plasma protein biomarkers in cardiovascular disease

Recent advances in highly multiplexed immunoassays have allowed systematic large-scale measurement of hundreds of plasma proteins in large cohort studies. In combination with genotyping, such studies offer the prospect to 1) identify mechanisms involved with regulation of protein expression in plasma, and 2) determine whether the plasma proteins are likely to be causally implicated in disease. We report here the results of genome-wide association (GWA) studies of 83 proteins considered relevant to cardiovascular disease (CVD), measured in 3,394 individuals with multiple CVD risk factors. We identified 79 genome-wide significant (p<5e-8) association signals, 55 of which replicated at P<0.0007 in separate validation studies (n = 2,639 individuals). Using automated text mining, manual curation, and network-based methods incorporating information on expression quantitative trait loci (eQTL), we propose plausible causal mechanisms for 25 trans-acting loci, including a potential post-translational regulation of stem cell factor by matrix metalloproteinase 9 and receptor-ligand pairs such as RANK-RANK ligand. Using public GWA study data, we further evaluate all 79 loci for their causal effect on coronary artery disease, and highlight several potentially causal associations. Overall, a majority of the plasma proteins studied showed evidence of regulation at the genetic level. Our results enable future studies of the causal architecture of human disease, which in turn should aid discovery of new drug targets.

Several proteins that circulate in blood have been linked to cardiovascular disease through the use of classic epidemiology and correlation studies. If individuals with higher risk of disease have higher levels of a protein, the protein may be associated with disease. However, this does not necessarily mean that the protein causes disease; it may merely be an innocent bystander or a consequence of the disease process. To establish whether a protein causes disease, a genetic approach, insensitive to reverse causation, can be used. Instead of correlating the levels of the protein itself, gene variants that regulate the protein levels are used in the analysis. This approach requires prior knowledge of which genetic variants are linked to individual proteins. Therefore we completed a map of how common genetic variants affect the blood concentration levels of 83 proteins that have been implicated in cardiovascular disease. By using this map of cause-to-effect findings, we gained insights into the regulation of a majority of the proteins under study and how they relate to risk of coronary artery disease. This study provides a map of genetic regulation of important cardiovascular plasma proteins, insights into their upstream regulatory environment, as well as novel leads for cardiovascular drug development.

Mesenchymal state of intimal cells may explain higher propensity to ascending aortic aneurysm in bicuspid aortic valves

Individuals with a bicuspid aortic valve (BAV) are at significantly higher risk of developing aortic complications than individuals with tricuspid aortic valves (TAV) and defective signaling during the embryonic development and/or life time exposure to abnormal hemodynamic have been proposed as underlying factors. However, an explanation for the molecular mechanisms of aortopathy in BAV has not yet been provided. We combined proteomics, RNA analyses, immunohistochemistry, and electron microscopy to identify molecular differences in samples of non-dilated ascending aortas from BAV (N = 62) and TAV (N = 54) patients. Proteomic analysis was also performed for dilated aortas (N = 6 BAV and N = 5 TAV) to gain further insight into the aortopathy of BAV. Our results collectively showed the molecular signature of an endothelial/epithelial-mesenchymal (EndMT/EMT) transition-like process, associated with instability of intimal cell junctions and activation of RHOA pathway in the intima and media layers of ascending aorta in BAV patients. We propose that an improper regulation of EndMT/EMT during the spatiotemporally related embryogenesis of semilunar valves and ascending aorta in BAV individuals may result in aortic immaturity and instability prior to dilation. Exasperation of EndMT/EMT state in post embryonic life and/or exposure to non-physiological hemodynamic could lead to the aneurysm of ascending aorta in BAV individuals.

Identification of Reference Genes for Quantitative Real Time PCR Assays in Aortic Tissue of Syrian Hamsters with Bicuspid Aortic Valve

Bicuspid aortic valve (BAV) is the most frequent congenital cardiac malformation in humans, and appears frequently associated with dilatation of the ascending aorta. This association is likely the result of a common aetiology. Currently, a Syrian hamster strain with a relatively high (∼40%) incidence of BAV constitutes the only spontaneous animal model of BAV disease. The characterization of molecular alterations in the aorta of hamsters with BAV may serve to identify pathophysiological mechanisms and molecular markers of disease in humans. In this report, we evaluate the expression of ten candidate reference genes in aortic tissue of hamsters in order to identify housekeeping genes for normalization using quantitative real time PCR (RT-qPCR) assays. A total of 51 adult (180-240 days old) and 56 old (300-440 days old) animals were used. They belonged to a control strain of hamsters with normal, tricuspid aortic valve (TAV; n = 30), or to the affected strain of hamsters with TAV (n = 45) or BAV (n = 32). The expression stability of the candidate reference genes was determined by RT-qPCR using three statistical algorithms, GeNorm, NormFinder and Bestkeeper. The expression analyses showed that the most stable reference genes for the three algorithms employed were Cdkn1β, G3pdh and Polr2a. We propose the use of Cdkn1β, or both Cdkn1β and G3pdh as reference genes for mRNA expression analyses in Syrian hamster aorta.

Fibrillin 2 is upregulated in the ascending aorta of patients with bicuspid aortic valve

OBJECTIVES

Bicuspid aortic valve (BAV) is the most prevalent congenital cardiac malformation, frequently associated with aortic dilatation (AD). The molecular mechanisms involved in AD and its aetiological link with BAV formation are poorly understood. Altered fibrillin-1 (FBN1) and metalloprotease-2, -9 (MMP2,9) protein activities have been suggested to be involved in BAV aortopathy. In addition, FBN2 participates in embryonic valve formation, but its possible involvement in BAV-associated AD has never been explored. In this report, we evaluate the expression levels of MMP2,9 and FBN1,2 in the ascending aorta of patients with normal or dilated aortas and with tricuspid aortic valve (TAV) or BAV, using appropriate tissue-specific reference genes.

METHODS

Gene expression was quantified by real-time quantitative polymerase chain reaction in 52 patients, using one or three reference genes previously validated in the same patient population.

RESULTS

FBN2 expression was significantly increased in the aortas of patients with BAV compared with individuals with TAV (0.178 ± 0.042 vs 0.096 ± 0.021, P = 0.015), whereas differences in FBN1 did not reach statistical significance (1.946 ± 0.228 vs 1.430 ± 0.114, P = 0.090). When four groups of samples were considered, FBN2 expression was significantly higher in patients with BAV and AD compared with patients with TAV and AD (0.164 ± 0.035 vs 0.074 ± 0.027, P = 0.040). No significant differences were found when FBN1/FBN2 ratio, and MMP2 and MMP9 expression levels were analysed. No linear relationship between aortic diameter and gene expression levels were found.

CONCLUSIONS

BAV patients have an increased FBN (especially FBN2) gene expression level in the ascending aorta, irrespective of dilatation, whereas MMP expression does not change significantly. These results add a new piece of information to the pathophysiology of BAV disease and point to FBN2 as a new molecular player.

Adenosine-to-inosine RNA editing controls cathepsin S expression in atherosclerosis by enabling HuR-mediated post-transcriptional regulation

Adenosine-to-inosine (A-to-I) RNA editing, which is catalyzed by a family of adenosine deaminase acting on RNA (ADAR) enzymes, is important in the epitranscriptomic regulation of RNA metabolism. However, the role of A-to-I RNA editing in vascular disease is unknown. Here we show that cathepsin S mRNA (CTSS), which encodes a cysteine protease associated with angiogenesis and atherosclerosis, is highly edited in human endothelial cells. The 3' untranslated region (3' UTR) of the CTSS transcript contains two inverted repeats, the AluJo and AluSx⁺ regions, which form a long stem-loop structure that is recognized by ADAR1 as a substrate for editing. RNA editing enables the recruitment of the stabilizing RNA-binding protein human antigen R (HuR; encoded by ELAVL1) to the 3' UTR of the CTSS transcript, thereby controlling CTSS mRNA stability and expression. In endothelial cells, ADAR1 overexpression or treatment of cells with hypoxia or with the inflammatory cytokines interferon-γ and tumor-necrosis-factor-α induces CTSS RNA editing and consequently increases cathepsin S expression. ADAR1 levels and the extent of CTSS RNA editing are associated with changes in cathepsin S levels in patients with atherosclerotic vascular diseases, including subclinical atherosclerosis, coronary artery disease, aortic aneurysms and advanced carotid atherosclerotic disease. These results reveal a previously unrecognized role of RNA editing in gene expression in human atherosclerotic vascular diseases.