Gene Expression Profiling in Acute Stanford Type B Aortic Dissection

The Complicated Genetics behind Uncomplicated Type B Aortic Dissection

BACKGROUND

Up to 50% of uncomplicated type B aortic dissection (unTBAD) cases progress to become complicated with a mortality rate of up to 42% within 5 years of onset. Morphological and clinical parameters have previously been defined for the decision of surgical intervention in unTBAD to improve clinical outcomes. The analysis of genetic variants in this risk stratification has demonstrated a lack of evidence to influence clinical decision-making.

METHODS

A comprehensive literature review was conducted using multiple electronic databases. A selection of genes recognized in thoracic aortic aneurysms and dissections were investigated in association with clinical outcomes in type B aortic dissections.

RESULTS

Case studies highlighted the impact of variants in fibrillin-1, type III collagen, alpha-actin 2, MYH11, protein kinase cGMP-dependent type I, transforming growth factor beta 1, type I transforming growth factor β receptor, and type II transforming growth factor β receptor on clinical outcomes in type B aortic dissection. Patients who carry variants in these genes experience more rapid disease progression and benefit from surgery.

CONCLUSION

The presence of a variant in genes that underlie unTBAD etiology could impact clinical decision-making and risk stratification in unTBAD. Emerging evidence supports thoracic endovascular aortic repair for unTBAD patients who have a higher risk of developing complications. The use of genetics in the management of unTBAD patients may help to improve the adverse clinical outcomes in unTBAD.

Association of genetic variants in ULK4 with the age of first onset of type B aortic dissection

Background: The association between autophagy, structural alterations of the aortic wall, and endothelial dysfunction in humans has yet to be fully elucidated. The family of ULK (UNC51-like) enzymes plays critical roles in autophagy and development. This study aimed to evaluate the association between ULK gene family members and patient age of first type B aortic dissection (TBAD) onset.

Methods: The genotype data in a TBAD cohort from China and the related summary-level datasets were analyzed. We applied the sequence kernel association test (SKAT) to test the association between single-nucleotide polymorphisms (SNPs) and age of first onset of TBAD controlling for gender, hypertension, and renal function. Next, we performed a 2-sample Mendelian randomization (MR) to explore the potential causal relationship between ULK4 and early onset of TBAD at the level of gene expression coupled with DNA methylation with genetic variants as instrumental variables.

Results: A total of 159 TBAD patients with 1,180,097 SNPs were included. Concerning the association between the ULK gene family and the age of first onset of the TBAD, only ULK4 was found to be significant according to SKAT analysis (q-FDR = 0.0088). From 2-sample MR, the high level of ULK4 gene expression was related to a later age of first onset of TBAD (β = 4.58, p = 0.0214).

Conclusion: This is the first study of the ULK gene family in TBAD, regarding the association with the first onset age. We demonstrated that the ULK4 gene is associated with the time of onset of TBAD based on both the SKAT and 2-sample MR analyses.

Crucial Genes in Aortic Dissection Identified by Weighted Gene Coexpression Network Analysis

Background

Aortic dissection (AD) is a lethal vascular disease with high mortality and morbidity. Though AD clinical pathology is well understood, its molecular mechanisms remain unclear. Specifically, gene expression profiling helps illustrate the potential mechanism of aortic dissection in terms of gene regulation and its modification by risk factors. This study was aimed at identifying the genes and molecular mechanisms in aortic dissection through bioinformatics analysis.

Method

Nine patients with AD and 10 healthy controls were enrolled. The gene expression in peripheral mononuclear cells was profiled through next-generation RNA sequencing. Analyses including differential expressed gene (DEG) via DEGseq, weighted gene coexpression network (WGCNA), and VisANT were performed to identify crucial genes associated with AD. The Database for Annotation, Visualization, and Integrated Discovery (DAVID) was also utilized to analyze Gene Ontology (GO).

Results

DEG analysis revealed that 1,113 genes were associated with AD. Of these, 812 genes were markedly reduced, whereas 301 genes were highly expressed, in AD patients. DEGs were rich in certain categories such as MHC class II receptor activity, MHC class II protein complex, and immune response genes. Gene coexpression networks via WGCNA identified 3 gene hub modules, with one positively and 2 negatively correlated with AD, respectively. Specifically, module 37 was the most strongly positively correlated with AD with a correlation coefficient of 0.72. Within module 37, five hub genes (AGFG1, MCEMP1, IRAK3, KCNE1, and CLEC4D) displayed high connectivity and may have clinical significance in the pathogenesis of AD.

Conclusion

Our analysis provides the possible association of specific genes and gene modules for the involvement of the immune system in aortic dissection. AGFG1, MCEMP1, IRAK3, KCNE1, and CLEC4D in module M37 were highly connected and strongly linked with AD, suggesting that these genes may help understand the pathogenesis of aortic dissection.

Integrin α9 is involved in the pathopoiesis of acute aortic dissection via mediating phenotype switch of vascular smooth muscle cell

Acute aortic dissection (AAD) is a devastating disease with high mortality; however, the pathogenic mechanisms of AAD remain poorly understood. Our present study aimed to identify genes associated with AAD and explore the molecular function of candidate genes in the pathogenesis of AAD. We used a whole-genome transcriptional microarray to identify putative AAD genes using ascending aortic tissues from four patients with AAD and four healthy organ donors. The differentially expressed genes were further validated in eight patients with AAD and eight healthy organ donors. Functional assessments were conducted to analyze the effects of the identified AAD genes on the phenotype of aortic vascular smooth muscle cells (VSMCs). The whole-genome transcriptional microarray analysis found 129 dysregulated genes in the ascending aortic tissues of AAD (fold change≥2), which were mainly associated with the focal adhesion pathway and actin cytoskeleton regulation pathway. Among these genes, integrin α9 (ITGA9) was identified to be involved in both pathways and downregulated by 50% in AAD patients. The association of ITGA9 with AAD was confirmed by Western blotting analysis (P = 0.003). Functional studies showed that knocking down ITGA9 in VSMCs resulted in a decrease in contractile markers (SM22α and α-SMA) and an increase in synthetic markers (OPN and SMemb), suggesting that the VSMCs switched from a contractile to a synthetic phenotype. After overexpression of ITGA9 by a recombinant adenovirus vector in VSMCs, SM22α and α-SMA were upregulated, while SMemb was downregulated, indicating a phenotypic switch from the synthetic to contractile phenotype of VSMCs. In conclusion, our study identified ITGA9 as a novel AAD gene. This gene is downregulated in patients with AAD and is involved in the regulation of the phenotypic switch of VSMCs from a contractile to a synthetic phenotype.

Downregulation of HDAC1 suppresses media degeneration by inhibiting the migration and phenotypic switch of aortic vascular smooth muscle cells in aortic dissection

Although much progress has been made in the diagnosis and treatment of thoracic aortic dissection (TAD), the overall morbidity and mortality rates of TAD are still high. Therefore, the molecular pathogenesis and etiology of TAD need to be elucidated. In this study, we found that histone deacetylase 1 (HDAC1) expression is dramatically higher in the aortic wall of patients with TAD (than that in a normal group) and negatively correlates with the levels of the vascular smooth muscle cell (SMC) contractile-phenotype markers. Knockdown of HDAC1 upregulated both smooth muscle 22 α (SM22α) and α-smooth muscle actin (α-SMA) in platelet-derived growth factor (PDGF)-BB-treated and -untreated SMCs. In addition, the knockdown of HDAC1 markedly decreased SMC viability and migration in contrast to the control group under the conditions of quiescence and PDGF-BB treatment. We also showed that the expression of polycystic kidney disease 1 (PKD1) is decreased in the aortic wall of patients with TAD and negatively correlates with HDAC1 expression. Overexpressed PKD1 obviously increased SM22α and α-SMA expression and reduced the viability and migration of SMCs, but these effects were attenuated by HDAC1. Furthermore, we demonstrated that HDAC1 serves as an important modulator of the migration and phenotypic switch of SMCs by suppressing the PKD1- mammalian target of the rapamycin signaling pathway. HDAC1 downregulation inhibited media degeneration and attenuated the loss of elastic-fiber integrity in a mouse model of TAD. Our results suggest that HDAC1 might be a new target for the treatment of a macrovascular disease such as TAD.

Integrative bioinformatics analysis of miRNA and mRNA expression profiles and identification of associated miRNA-mRNA network in aortic dissection

BACKGROUND

Aortic dissection (AD) is one of the most lethal cardiovascular diseases. The aim of this study was to identify core genes and pathways revealing pathogenesis in AD.

METHODS

We screened differentially expressed mRNAs and miRNAs using mRNA and miRNA expression profile data of AD from Gene Expression Omnibus. Then functional and pathway enrichment analyses of differential expression genes (DEGs) was performed utilizing the database for annotation, visualization, and integrated discovery (DAVID). Target genes with differential expression miRNAs (DEMIs) were predicted using the miRWalk database, and the intersection between these predictions and DEGs was selected as differentially expressed miRNA-target genes. In addition, a protein-protein interaction (PPI) network and miRNA-mRNA regulatory network were constructed.

RESULTS

In total, 130 DEGs and 47 DEMIs were identified from mRNA and miRNA microarray, respectively, and 45 DEGs were DEMI-target genes. The PPI and miRNA-mRNA network included 79 node genes and 74 node genes, respectively, while 23 hub genes and 2 hub miRNAs were identified. The DEGs, PPI and modules differential expression miRNA-target genes were all mainly enriched in cell cycle, cell proliferation and cell apoptosis signaling pathways.

CONCLUSION

Taken above, the study reveals some candidate genes and pathways potentially involving molecular mechanisms of AD. These findings provide a new insight for research and treatment of AD.