First genetic analysis of aneurysm genes in familial and sporadic abdominal aortic aneurysm

Abdominal Aortic Aneurysm and Liver Fibrosis: Clinical Evidence and Molecular Pathomechanisms

To stimulate further research, this review summarizes studies linking liver fibrosis with the risk of abdominal aortic aneurysms (AAA). AAA is defined as a permanently weakened and dilated abdominal aorta, which develops due to inflammation of the tunica media, activation of the renin-angiotensin-aldosterone system, immune system activation, and coagulation disorders. Typically asymptomatic, AAA is often incidentally detected through imaging done for abdominal symptoms or as part of screening programs. AAA follows a variable course and has a mortality rate strongly dependent on age and sex. Risk factors for AAA include age, male sex, ethnicity, family history of AAA, lifestyle habits, arterial hypertension, dyslipidemia, and comorbid atherosclerotic cardiovascular disease. Conversely, individuals with type 2 diabetes, female sex, and certain ethnicities are at a reduced risk of AAA. Liver fibrosis, resulting from chronic liver diseases owing to varying etiologies, is increasingly recognized as a potential contributor to AAA development. Evidence increasingly indicates that metabolic dysfunction-associated steatotic liver disease (MASLD) and other chronic liver conditions may intensify inflammatory pathways shared with AAA, thereby potentially exacerbating AAA progression. This review specifically examines the epidemiology and risk factors associated with the link between AAA and liver fibrosis. It also highlights potential pathomechanisms, including systemic inflammation, oxidative stress, and extracellular matrix remodeling, which may contribute to both conditions. Although these findings underscore significant overlaps in risk profiles, additional research is needed to clarify whether type 2 diabetes, female sex, and certain ethnicities truly confer protection against AAA or if this association is influenced by other confounding variables. Ultimately, addressing these open questions will help guide targeted therapeutic interventions and the identification of novel biomarkers to predict disease progression.

Non-canonical splice variants in thoracic aortic dissection cases and Marfan syndrome with negative genetic testing

Individuals with heritable thoracic aortic disease (HTAD) face a high risk of deadly aortic dissections, but genetic testing identifies causative variants in only a minority of cases. We explored the contribution of non-canonical splice variants (NCVAS) to thoracic aortic disease (TAD) using SpliceAI and sequencing data from diverse cohorts, including 551 early-onset sporadic dissection cases and 437 HTAD probands with exome sequencing, 57 HTAD pedigrees with whole genome sequencing, and select sporadic cases with clinical panel testing. NCVAS were identified in syndromic HTAD genes such as FBN1, SMAD3, and COL3A1, including intronic variants in FBN1 in two Marfan syndrome (MFS) families. Validation in the Penn Medicine BioBank and UK Biobank showed enrichment of NCVAS in HTAD-associated genes among dissections. These findings suggest NCVAS are an underrecognized contributor to TAD, particularly in sporadic dissection and unsolved MFS cases, highlighting the potential of advanced splice prediction tools in genetic diagnostics.

Whole aorta imaging shows increased risk for thoracic aortic aneurysms and dilatations in relatives of abdominal aortic aneurysm patients

OBJECTIVE

For relatives of abdominal aortic aneurysm (AAA) patients, guidelines recommend abdominal imaging aimed at early detection and management of AAA, and do not include screening for thoracic aortic aneurysms (TAA). We aimed to investigate if TAA occur in undiagnosed relatives of patients with AAA without a known genetic susceptibility for aneurysms, similar to families with identified genetic susceptibilities for aneurysms like in Marfan and Loeys-Dietz syndrome, where both AAAs and TAAs occur.

METHODS

Relatives of patients with AAA were invited for noncontrast whole aorta computed tomography (CT) screening. Systematic measurements of the CT scans were used to detect aneurysms and dilatations. Classification into familial and nonfamilial was based on reported family histories. In addition, aneurysm gene panel testing of AAA index cases was used for the classification of high vs unknown genetic risk (high genetic risk: familial aneurysm or a pathogenic/likely pathogenic (P/LP) in an aneurysm gene; unknown genetic risk: no family history or P/LP).

RESULTS

Whole aorta imaging of 301 relatives of 115 index patients with AAA with noncontrast CT scans showed a 28-fold increase in TAAs in relatives (1.7% [P < .001] vs the age-adjusted population) and a high frequency of thoracic dilatations in 18% of the relatives. Thoracic aneurysms and dilatations in relatives occurred even when index patients were unaware of familial aneurysms. AAA was increased in the relatives compared with the age-adjusted population (8%; P < .001).

CONCLUSIONS

An increased risk for thoracic aneurysms and dilatations was detected by whole aorta imaging of relatives of index patients with AAA, even when index patients were unaware of familial aneurysms. These results indicate still unknown shared genetic susceptibilities for thoracic and abdominal aneurysms. Therefore, imaging of the whole aorta of relatives of all abdominal aneurysm patients, will improve early detection of aortic aneurysms in relatives of all patients with AAA.

Identification of TGFBR1 Gene Variants in Two Chinese Pedigrees with Loeys-Dietz Syndrome

OBJECTIVE

To investigate a precise treatment and related gene variants in some Loeys-Dietz syndrome (LDS) patients with vascular disease.

METHODS

Two probands (JX001-II1 and JX002-II1) diagnosed with LDS and their families were recruited. Routine blood test, antiphospholipid antibodies, immune globulins, nuclear antibodies (ANAs) and biochemical tests, and computed tomography angiography (CTA) were performed for probands. Deoxyribonucleic acid was collected from the two families and was sequenced by the next-generation sequencing employing the Ion Torrent platform (Life Technologies); the variants were confirmed by Sanger sequencing.

RESULTS

Two probands' antiphospholipid antibodies, immune globulins, and ANAs were near normal. CTA showed that both probands had an LDS patient typical arterial change: aortic aneurysm. Genetic testing of the 10 LDS-associated genes in the two probands showed that c.605C>T (JX001-II1) and c.679G>A (JX002-II1) variants were both positioned in exon 1 of TGFBR1 and it results in the substitution of highly conserved 202 alanine (Ala) for valine (Val) ( P. Ala 202Val, JX001-II1) and 227 glutamic acids (Glu) for lysine (Lys) ( P. Glu 227Lys, JX002-II1). However, the parents of both patients did not have similar symptoms and did not carry such gene variants. Proband 1 (JX001-II1) died unexpectedly during the operation preparations, whereas proband 2 (JX002-II1) underwent two operations, and the patient is currently in excellent health.

CONCLUSION

The two TGFBR1 gene variants may be a primary genetic cause of LDS. The results expand the TGFBR1 variant spectrum. Endovascular surgery can be a feasible option for LDS patients.

The proprotein convertase FURIN is a novel aneurysm predisposition gene impairing TGF-β signalling

AIMS

Aortic aneurysms (AA) frequently involve dysregulation of transforming growth factor β (TGF-β)-signalling in the aorta. Here, FURIN was tested as aneurysm predisposition gene given its role as proprotein convertase in pro-TGF-β maturation.

METHODS AND RESULTS

Rare FURIN variants were detected by whole-exome sequencing of 781 unrelated aortic aneurysm patients and affected relatives. Thirteen rare heterozygous FURIN variants occurred in 3.7% (29) unrelated index AA patients, of which 72% had multiple aneurysms or a dissection. FURIN maturation and activity of these variants were decreased in vitro. Patient-derived fibroblasts showed decreased pro-TGF-β processing, phosphorylation of downstream effector SMAD2 and kinases ERK1/2, and steady-state mRNA levels of the TGF-β-responsive ACTA2 gene. In aortic tissue, collagen and fibrillin fibres were affected. One variant (R745Q), observed in 10 unrelated cases, affected TGF-β signalling variably, indicating effect modification by individual genetic backgrounds.

CONCLUSION

FURIN is a novel, frequent genetic predisposition for abdominal-, thoracic-, and multiple aortic or middle sized artery aneurysms in older patients, by affecting intracellular TGF-β signalling, depending on individual genetic backgrounds.

Age-Disturbed Vascular Extracellular Matrix Links to Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a common but life-threatening vascular condition in men at an advanced age. However, the underlying mechanisms of age-increased incidence and mortality of AAA remain elusive. Here, we performed RNA sequencing (RNA-seq) of mouse aortas from males (young: 3-month, n = 4 vs old: 23-month, n = 4) and integrated with the data sets of human aortas (young: 20-39, n = 47 vs old: 60-79 years, n = 92) from GTEx project and the data set (GSE183464) for AAA to search for age-shifted aortic aneurysm genes, their relevant biological processes, and signaling pathways. Angiotensin II-induced AAA in mice was used to verify the critical findings. We found 1 001 genes transcriptionally changed with ages in both mouse and human. Most age-increased genes were enriched intracellularly and the relevant biological processes included mitochondrial function and translational controls, whereas the age-decreased genes were largely localized in extracellular regions and cell periphery and the involved biological processes were associated with extracellular matrix (ECM). Fifty-one were known genes for AAA and found dominantly in extracellular region. The common age-shifted vascular genes and known aortic aneurysm genes had shared functional influences on ECM organization, apoptosis, and angiogenesis. Aorta with angiotensin II-induced AAA exhibited similar phenotypic changes in ECM to that in old mice. Together, we present a conserved transcriptional signature for aortic aging and provide evidence that mitochondrial dysfunction and the imbalanced ribosomal homeostasis act likely as driven-forces for aortic aging and age-disturbed ECM is the substrate for developing AAA.

Elucidating the roles of SOD3 correlated genes and reactive oxygen species in rare human diseases using a bioinformatic-ontology approach

Superoxide Dismutase 3 (SOD3) scavenges extracellular superoxide giving a hydrogen peroxide metabolite. Both Reactive Oxygen Species diffuse through aquaporins causing oxidative stress and biomolecular damage. SOD3 is differentially expressed in cancer and this research utilises Gene Expression Omnibus data series GSE2109 with 2,158 cancer samples. Genome-wide expression correlation analysis was conducted with SOD3 as the seed gene. Categorical SOD3 Pearson Correlation gene lists incrementing in correlation strength by 0.01 from ρ≥|0.34| to ρ≥|0.41| were extracted from the data. Positively and negatively SOD3 correlated genes were separated for each list and checked for significance against disease overlapping genes in the ClinVar and Orphanet databases via Enrichr. Disease causal genes were added to the relevant gene list and checked against Gene Ontology, Phenotype Ontology, and Elsevier Pathways via Enrichr before the significant ontologies containing causal and non-overlapping genes were reviewed with a literature search for possible disease and oxidative stress associations. 12 significant individually discriminated disorders were identified: Autosomal Dominant Cutis Laxa (p = 6.05x10-7), Renal Tubular Dysgenesis of Genetic Origin (p = 6.05x10-7), Lethal Arteriopathy Syndrome due to Fibulin-4 Deficiency (p = 6.54x10-9), EMILIN-1-related Connective Tissue Disease (p = 6.54x10-9), Holt-Oram Syndrome (p = 7.72x10-10), Multisystemic Smooth Muscle Dysfunction Syndrome (p = 9.95x10-15), Distal Hereditary Motor Neuropathy type 2 (p = 4.48x10-7), Congenital Glaucoma (p = 5.24x210-9), Megacystis-Microcolon-Intestinal Hypoperistalsis Syndrome (p = 3.77x10-16), Classical-like Ehlers-Danlos Syndrome type 1 (p = 3.77x10-16), Retinoblastoma (p = 1.9x10-8), and Lynch Syndrome (p = 5.04x10-9). 35 novel (21 unique) genes across 12 disorders were identified: ADNP, AOC3, CDC42EP2, CHTOP, CNN1, DES, FOXF1, FXR1, HLTF, KCNMB1, MTF2, MYH11, PLN, PNPLA2, REST, SGCA, SORBS1, SYNPO2, TAGLN, WAPL, and ZMYM4. These genes are proffered as potential biomarkers or therapeutic targets for the corresponding rare diseases discussed.

Aortic aneurysm: pathophysiology and therapeutic options

Aortic aneurysm (AA) is an aortic disease with a high mortality rate, and other than surgery no effective preventive or therapeutic treatment have been developed. The renin-angiotensin system (RAS) is an important endocrine system that regulates vascular health. The ACE2/Ang-(1-7)/MasR axis can antagonize the adverse effects of the activation of the ACE/Ang II/AT1R axis on vascular dysfunction, atherosclerosis, and the development of aneurysms, thus providing an important therapeutic target for the prevention and treatment of AA. However, products targeting the Ang-(1-7)/MasR pathway still lack clinical validation. This review will outline the epidemiology of AA, including thoracic, abdominal, and thoracoabdominal AA, as well as current diagnostic and treatment strategies. Due to the highest incidence and most extensive research on abdominal AA (AAA), we will focus on AAA to explain the role of the RAS in its development, the protective function of Ang-(1-7)/MasR, and the mechanisms involved. We will also describe the roles of agonists and antagonists, suggest improvements in engineering and drug delivery, and provide evidence for Ang-(1-7)/MasR's clinical potential, discussing risks and solutions for clinical use. This study will enhance our understanding of AA and offer new possibilities and promising targets for therapeutic intervention.

The mitochondrial protease ClpP is a druggable target that controls VSMC phenotype by a SIRT1-dependent mechanism

Vascular smooth muscle cells (VSMCs), known for their remarkable lifelong phenotypic plasticity, play a pivotal role in vascular pathologies through their ability to transition between different phenotypes. Our group discovered that the deficiency of the mitochondrial protein Poldip2 induces VSMC differentiation both in vivo and in vitro. Further comprehensive biochemical investigations revealed Poldip2's specific interaction with the mitochondrial ATPase caseinolytic protease chaperone subunit X (CLPX), which is the regulatory subunit for the caseinolytic protease proteolytic subunit (ClpP) that forms part of the ClpXP complex - a proteasome-like protease evolutionarily conserved from bacteria to humans. This interaction limits the protease's activity, and reduced Poldip2 levels lead to ClpXP complex activation. This finding prompted the hypothesis that ClpXP complex activity within the mitochondria may regulate the VSMC phenotype. Employing gain-of-function and loss-of-function strategies, we demonstrated that ClpXP activity significantly influences the VSMC phenotype. Notably, both genetic and pharmacological activation of ClpXP inhibits VSMC plasticity and fosters a quiescent, differentiated, and anti-inflammatory VSMC phenotype. The pharmacological activation of ClpP using TIC10, currently in phase III clinical trials for cancer, successfully replicates this phenotype both in vitro and in vivo and markedly reduces aneurysm development in a mouse model of elastase-induced aortic aneurysms. Our mechanistic exploration indicates that ClpP activation regulates the VSMC phenotype by modifying the cellular NAD+/NADH ratio and activating Sirtuin 1. Our findings reveal the crucial role of mitochondrial proteostasis in the regulation of the VSMC phenotype and propose the ClpP protease as a novel, actionable target for manipulating the VSMC phenotype.

Unveiling cellular and molecular aspects of ascending thoracic aortic aneurysms and dissections

Ascending thoracic aortic aneurysm (ATAA) remains a significant medical concern, with its asymptomatic nature posing diagnostic and monitoring challenges, thereby increasing the risk of aortic wall dissection and rupture. Current management of aortic repair relies on an aortic diameter threshold. However, this approach underestimates the complexity of aortic wall disease due to important knowledge gaps in understanding its underlying pathologic mechanisms.Since traditional risk factors cannot explain the initiation and progression of ATAA leading to dissection, local vascular factors such as extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs) might harbor targets for early diagnosis and intervention. Derived from diverse embryonic lineages, VSMCs exhibit varied responses to genetic abnormalities that regulate their contractility. The transition of VSMCs into different phenotypes is an adaptive response to stress stimuli such as hemodynamic changes resulting from cardiovascular disease, aging, lifestyle, and genetic predisposition. Upon longer exposure to stress stimuli, VSMC phenotypic switching can instigate pathologic remodeling that contributes to the pathogenesis of ATAA.This review aims to illuminate the current understanding of cellular and molecular characteristics associated with ATAA and dissection, emphasizing the need for a more nuanced comprehension of the impaired ECM-VSMC network.

Vascular Ehlers-Danlos Syndrome: A Comprehensive Natural History Study in a Dutch National Cohort of 142 Patients

BACKGROUND

Vascular Ehlers-Danlos syndrome (vEDS) is a rare connective tissue disorder with a high risk for arterial, bowel, and uterine rupture, caused by heterozygous pathogenic variants in COL3A1. The aim of this cohort study is to provide further insights into the natural history of vEDS and describe genotype-phenotype correlations in a Dutch multicenter cohort to optimize patient care and increase awareness of the disease.

METHODS

Individuals with vEDS throughout the Netherlands were included. The phenotype was charted by retrospective analysis of molecular and clinical data, combined with a one-time physical examination.

RESULTS

A total of 142 individuals (50% female) participated the study, including 46 index patients (32%). The overall median age at genetic diagnosis was 41.0 years. More than half of the index patients (54.3%) and relatives (53.1%) had a physical appearance highly suggestive of vEDS. In these individuals, major events were not more frequent (P=0.90), but occurred at a younger age (P=0.01). A major event occurred more often and at a younger age in men compared with women (P<0.001 and P=0.004, respectively). Aortic aneurysms (P=0.003) and pneumothoraces (P=0.029) were more frequent in men. Aortic dissection was more frequent in individuals with a COL3A1 variant in the first quarter of the collagen helical domain (P=0.03).

CONCLUSIONS

Male sex, type and location of the COL3A1 variant, and physical appearance highly suggestive of vEDS are risk factors for the occurrence and early age of onset of major events. This national multicenter cohort study of Dutch individuals with vEDS provides a valuable basis for improving guidelines for the diagnosing, follow-up, and treatment of individuals with vEDS.

Cellular, Molecular and Clinical Aspects of Aortic Aneurysm-Vascular Physiology and Pathophysiology

A disturbance of the structure of the aortic wall results in the formation of aortic aneurysm, which is characterized by a significant bulge on the vessel surface that may have consequences, such as distention and finally rupture. Abdominal aortic aneurysm (AAA) is a major pathological condition because it affects approximately 8% of elderly men and 1.5% of elderly women. The pathogenesis of AAA involves multiple interlocking mechanisms, including inflammation, immune cell activation, protein degradation and cellular malalignments. The expression of inflammatory factors, such as cytokines and chemokines, induce the infiltration of inflammatory cells into the wall of the aorta, including macrophages, natural killer cells (NK cells) and T and B lymphocytes. Protein degradation occurs with a high expression not only of matrix metalloproteinases (MMPs) but also of neutrophil gelatinase-associated lipocalin (NGAL), interferon gamma (IFN-γ) and chymases. The loss of extracellular matrix (ECM) due to cell apoptosis and phenotype switching reduces tissue density and may contribute to AAA. It is important to consider the key mechanisms of initiating and promoting AAA to achieve better preventative and therapeutic outcomes.

Identification of Rare Genetic Variants in Familial Spontaneous Coronary Artery Dissection and Evidence for Shared Biological Pathways

Rare familial spontaneous coronary artery dissection (SCAD) kindreds implicate genetic disease predisposition and provide a unique opportunity for candidate gene discovery. Whole-genome sequencing was performed in fifteen probands with non-syndromic SCAD who had a relative with SCAD, eight of whom had a second relative with extra-coronary arteriopathy. Co-segregating variants and associated genes were prioritized by quantitative variant, gene, and disease-level metrics. Curated public databases were queried for functional relationships among encoded proteins. Fifty-four heterozygous coding variants in thirteen families co-segregated with disease and fulfilled primary filters of rarity, gene variation constraint, and predicted-deleterious protein effect. Secondary filters yielded 11 prioritized candidate genes in 12 families, with high arterial tissue expression (n = 7), high-confidence protein-level interactions with genes associated with SCAD previously (n = 10), and/or previous associations with connective tissue disorders and aortopathies (n = 3) or other vascular phenotypes in mice or humans (n = 11). High-confidence associations were identified among 10 familial SCAD candidate-gene-encoded proteins. A collagen-encoding gene was identified in five families, two with distinct variants in COL4A2. Familial SCAD is genetically heterogeneous, yet perturbations of extracellular matrix, cytoskeletal, and cell-cell adhesion proteins implicate common disease-susceptibility pathways. Incomplete penetrance and variable expression suggest genetic or environmental modifiers.

Linking single nucleotide polymorphisms to signaling blueprints in abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) is a multifactorial complex disease with life-threatening consequences. While Genome-wide association studies (GWAS) have revealed several single nucleotide polymorphisms (SNPs) located in the genome of individuals with AAA, the link between SNPs with the associated pathological signals, the influence of risk factors on their distribution and their combined analysis is not fully understood. We integrated 86 AAA SNPs from GWAS and clinical cohorts from the literature to determine their phenotypical vulnerabilities and association with AAA risk factors. The SNPs were annotated using snpXplorer AnnotateMe tool to identify their chromosomal position, minor allele frequency, CADD (Combined Annotation Dependent Depletion), annotation-based pathogenicity score, variant consequence, and their associated gene. Gene enrichment analysis was performed using Gene Ontology and clustered using REVIGO. The plug-in GeneMANIA in Cytoscape was applied to identify network integration with associated genes and functions. 15 SNPs affecting 20 genes with a CADD score above ten were identified. AAA SNPs were predominantly located on chromosome 3 and 9. Stop-gained rs5516 SNP obtained high frequency in AAA and associated with proinflammatory and vascular remodeling phenotypes. SNPs presence positively correlated with hypertension, dyslipidemia and smoking history. GO showed that AAA SNPs and their associated genes could regulate lipid metabolism, extracellular matrix organization, smooth muscle cell proliferation, and oxidative stress, suggesting that part of these AAA traits could stem from genetic abnormalities. We show a library of inborn SNPs and associated genes that manifest in AAA. We uncover their pathological signaling trajectories that likely fuel AAA development.

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.

Expression Pattern and Clinical Value of Key m6A RNA Modification Regulators in Abdominal Aortic Aneurysm

Background

Aberrant expression of N6-methyladenosine (m6A) RNA modification regulators plays a critical role in a variety of human diseases. However, their implication in abdominal aortic aneurysm (AAA) remains largely unknown. Herein, we sought to explore the general expression pattern and potential functions of m6A regulators in AAA.

Methods

We analyzed gene expression data of m6A regulators in human AAA and normal tissues from public GEO database. The R package and other tools such as m6A2Target database, Gene ontology (GO) functional and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses, gene set variation analysis (GSVA), Search Tool for the Retrieval of Interacting Genes (STRING), starBase, miRDB and Cytoscape software were applied for bioinformatics analysis to investigate the downstream molecular mechanisms and upstream regulatory mechanisms for distinctly expressed regulators. Quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were performed to validate the expression of key m6A regulators in our collected human AAA specimens.

Results

We found that METTL14 and HNRNPC were the downregulated m6A regulators, and RBM15B was the upregulated methylation transferase in human AAA. The modified genes were primarily enriched in RNA catabolic process, regulation of translation, focal adhesion, transcription coregulator activity, ribosome, RNA transport, cell cycle, et al. METTL14, HNRNPC and RBM15B levels were correlated with the immune infiltration degree of Tcm, macrophages, mast cells, Tgd and NK CD56bright cells. A total of 154 and 76 target genes of three regulators were separately involved in body metabolism and autophagy in AAA disease, and their interactive relationships and hub genes were identified. The lncRNA-miRNA-mRNA interaction regulatory networks were also constructed for METTL14, HNRNPC and RBM15B. Based on our clinical tissue and serum samples, METTL14 exhibited lower expression levels in AAA and its rupture type, and low METTL14 expression was associated with high levels of WBC and CRP (all P < 0.05).

Conclusion

Our study presents an overview of the expression pattern and functional significance of m6A regulators in human AAA. Our findings will provide a valuable resource that may guide both mechanistic and therapeutic analyses about the role of key m6A regulators in AAA.

Molecular phenotyping and functional assessment of smooth muscle like-cells with pathogenic variants in aneurysm genes ACTA2, MYH11, SMAD3 and FBN1

Aortic aneurysms (AAs) are pathological dilatations of the aorta. Pathogenic variants in genes encoding for proteins of the contractile machinery of vascular smooth muscle cells (VSMCs), genes encoding proteins of the transforming growth factor beta signaling pathway and extracellular matrix (ECM) homeostasis play a role in the weakening of the aortic wall. These variants affect the functioning of VSMC, the predominant cell type in the aorta. Many variants have unknown clinical significance, with unknown consequences on VSMC function and AA development. Our goal was to develop functional assays that show the effects of pathogenic variants in aneurysm-related genes. We used a previously developed fibroblast transdifferentiation protocol to induce VSMC-like cells, which are used for all assays. We compared transdifferentiated VSMC-like cells of patients with a pathogenic variant in genes encoding for components of VSMC contraction (ACTA2, MYH11), transforming growth factor beta (TGFβ) signaling (SMAD3) and a dominant negative (DN) and two haploinsufficient variants in the ECM elastic laminae (FBN1) to those of healthy controls. The transdifferentiation efficiency, structural integrity of the cytoskeleton, TGFβ signaling profile, migration velocity and maximum contraction were measured. Transdifferentiation efficiency was strongly reduced in SMAD3 and FBN1 DN patients. ACTA2 and FBN1 DN cells showed a decrease in SMAD2 phosphorylation. Migration velocity was impaired for ACTA2 and MYH11 cells. ACTA2 cells showed reduced contractility. In conclusion, these assays for showing effects of pathogenic variants may be promising tools to help reclassification of variants of unknown clinical significance in AA-related genes.

Neonatal Arterial Tortuosity and Adult Aortic Aneurysm-Is There a Missing Link?-A Case Report

We report a novel case of a full term newborn with non-immune fetal hydrops and arterial tortuosity mimicking a double aortic arch, and cranial fractures in the immediate neonatal period. The infant had no classic features of neonatal arterial tortuosity syndrome or Loeys Dietz syndrome apart from bilateral inguinal hernia. He also had skeletal manifestations in the form of fractures in the neonatal period without any trauma during birth and without clinical evidence of Osteogenesis Imperfecta. A heterozygous missense variant of uncertain significance was detected in MYH11 gene which is increasingly recognized to be belonging to the familial/hereditary thoracic aneurysm and aortic dissection group of disorders. Fetal hydrops as an association with arterial tortuosity has not been reported in the literature. We hypothesize the possible mechanism behind developing fetal hydrops in this case and discuss the genetic and phenotypic heterogeneity of the Familial Thoracic Aortic Aneurysm and Dissection (FTAAD) group of conditions highlighting the unique phenotypic and genotypic presentations. We recommend a high index of suspicion and vigilance in the early detection of such potentially lethal conditions with sequelae also in adulthood.

Systematic Review of the Co-Prevalence of Arterial Aneurysms Within the Vasculature

OBJECTIVE

Aneurysms are considered focal manifestations of a systemic vascular condition, and various studies report co-prevalence of aneurysms in different vascular beds. Insight into profiles of patients at risk of multiple aneurysms is lacking, and few clinical algorithms exist if additional screening is indicated. This systematic review assessed the co-prevalence of aneurysms in different vascular beds and analysed putative risk factors for multiple aneurysms.

METHODS

Medline, Embase, and Cochrane libraries were searched up to February 2020 for studies reporting co-prevalence of aneurysms in different vascular beds using the keywords: "aneurysm", "co-prevalence", or synonyms. All studies were reviewed by two authors independently. Studies were excluded if they described concomitant treatment of multi-aneurysms, or if the aneurysm was reported solely bilateral, post-dissection, mycotic, traumatic, iatrogenic, or caused by a connective tissue disease. Radar plots were used to indicate studies that found an association between the investigated features and aneurysm co-prevalence against those that did not.

RESULTS

Thirty-two studies met the inclusion criteria, describing in total 16 353 patients of whom 2 015 had at least one additional aneurysm. The weighted co-prevalence was 16.9% (95% confidence interval [CI] 11.8-22.6), I² > 90%. At least 19 combinations of aneurysms were described, mostly derived from retrospective studies. Seventeen of 32 (53%) studies described concurrent aneurysms in patients with an abdominal aortic aneurysm. Predominantly positive associations were found for higher age, hypertension, stenotic disease, presence of multiple (at least three) aneurysms, and primary aneurysm size.

CONCLUSION

Approximately one in six patients with a primary aneurysm harbours an additional aneurysm, increasing to one in four if the patient has a popliteal artery aneurysm. Higher age, hypertension, stenotic disease, presence of multiple (at least three) aneurysms, and primary aneurysm size were predictive of aneurysm co-prevalence. These clinical predictors may assist when deciding whether a patient with a primary aneurysm needs to be screened for additional aneurysms.

Exome sequencing of 112 trios identifies recessive genetic variants in brain arteriovenous malformations

BACKGROUND

Brain arteriovenous malformation (BAVM) is a main cause of cerebral hemorrhage and hemorrhagic stroke in adolescents. Morphologically, a BAVM is an abnormal connection between cerebrovascular arteries and veins. The genetic etiology of BAVMs has not been fully elucidated. In this study, we aim to investigate potential recessive genetic variants in BAVMs by interrogation of rare compound heterozygous variants.

METHODS

We performed whole exome sequencing (WES) on 112 BAVM trios and analyzed the data for rare and deleterious compound heterozygous mutations associated with the disease.

RESULTS

We identified 16 genes with compound heterozygous variants that were recurrent in more than one trio. Two genes (LRP2, MUC5B) were recurrently mutated in three trios. LRP2 has been previously associated with BAVM pathogenesis. Fourteen genes (MYLK, HSPG2, PEAK1, PIEZO1, PRUNE2, DNAH14, DNAH5, FCGBP, HERC2, HMCN1, MYH1, NHSL1, PLEC, RP1L1) were recurrently mutated in two trios, and five of these genes (MYLK, HSPG2, PEAK1, PIEZO1, PRUNE2) have been reported to play a role in angiogenesis or vascular diseases. Additionally, abnormal expression of the MYLK protein is related to spinal arteriovenous malformations.

CONCLUSION

Our study indicates that rare recessive compound heterozygous variants may underlie cases of BAVM. These findings improve our understanding of BAVM pathology and indicate genes for functional validation.

Identification of key microRNAs and genes associated with abdominal aortic aneurysm based on the gene expression profile

NEW FINDINGS

What is the central question of this study? The aim was to identify abdominal aortic aneurysm (AAA)-associated microRNAs and their target genes in AAA using microarray analysis. What is the main finding and its importance? The main finding was that miR-145 and miR-30c-2* were found to be downregulated microRNAs in AAA, which could exert suppressive effects on AAA progression, and that miR-145 might target RAC2, whereas miR-30c-2* might target PIK3CD, IL1B and RAC2. The findings obtained from the study provide an enhanced understanding of microRNA as a therapeutic target to limit AAA.

ABSTRACT

The aim of the study was to identify abdominal aortic aneurysm (AAA)-associated microRNAs (miRNAs) and genes potentially contributing to AAA. Differential analysis was performed to screen out differentially expressed genes (DEGs) and miRNAs in expression datasets of AAA-related miRNAs [GSE51226 (mouse)] and genes [GSE51227 (mouse) and GSE7084 (human)]. Then, gene ontology (GO) enrichment analysis of DEGs was compared with aneurysm-related GO to screen out DEGs related to the disease. The target genes of differential miRNAs were predicted and used to construct a miRNA-DEG regulatory network, followed by Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of target genes. Moreover, the protein-protein interaction network of target genes of miRNAs in the core position (hub-miRNA) with AAA-related genes was constructed to screen out hub genes. Finally, the target relationship between hub-miRNAs and their target genes was verified. There were 20 upregulated miRNAs and 20 downregulated miRNAs in AAA screened from the GSE51226 dataset (mouse). In addition, there were 1154 upregulated genes and 821 downregulated genes in the GSE51227 dataset (mouse), of which 246 DEGs were enriched in aneurysm-related GO entries in AAA. miR-145 and miR-30c-2* were the key miRNAs of AAA, both of which were downregulated in AAA and influenced pathways so as to affect AAA by regulating their respective target genes. The disease-related gene ACTA2 was downregulated, whereas DEGs including PIK3CD, IL1B, RAC2 and SELL were upregulated in AAA. Finally, it was proved that miR-145 targeted RAC2 and SELL, whereas miR-30c-2* targeted PIK3CD, IL1B and RAC2. Taken together, miR-145 and miR-30c-2*, downregulated in AAA, could potentially affect AAA, and miR-145 might target RAC2, whereas miR-30c-2* might target PIK3CD, IL1B and RAC2.

Inflammation and TGF-β Signaling Differ between Abdominal Aneurysms and Occlusive Disease

Abdominal aortic aneurysms (AAA), are usually asymptomatic until rupture causes fatal bleeding, posing a major vascular health problem. AAAs are associated with advanced age, male gender, and cardiovascular risk factors (e.g. hypertension and smoking). Strikingly, AAA and AOD (arterial occlusive disease) patients have a similar atherosclerotic burden, yet develop either arterial dilatation or occlusion, respectively. The molecular mechanisms underlying this diversion are yet unknown. As this knowledge could improve AAA treatment strategies, we aimed to identify genes and signaling pathways involved. We compared RNA expression profiles of abdominal aortic AAA and AOD patient samples. Based on differential gene expression profiles, we selected a gene set that could serve as blood biomarker or as pharmacological intervention target for AAA. In this AAA gene list we identified previously AAA-associated genes COL11A1, ADIPOQ, and LPL, thus validating our approach as well as novel genes; CXCL13, SLC7A5, FDC-SP not previously linked to aneurysmal disease. Pathway analysis revealed overrepresentation of significantly altered immune-related pathways between AAA and AOD. Additionally, we found bone morphogenetic protein (BMP) signaling inhibition simultaneous with activation of transforming growth factor β (TGF-β) signaling associated with AAA. Concluding our gene expression profiling approach identifies novel genes and an interplay between BMP and TGF-β signaling regulation specifically for AAA.

Epigenetic regulation of regulatory T cells in patients with abdominal aortic aneurysm

Abdominal arterial aneurysm (AAA) shares many features with autoimmune diseases and appears to be a T-cell-mediated process. In addition, certain epigenetic changes, including DNA methylation, are associated with AAA. In this study, we investigated epigenetic modifications in regulatory T cells (Tregs) from AAA patients. We used flow cytometry to sort FOXP3⁺ CD4⁺ CD25⁺ Tregs from the peripheral blood of AAA patients and from healthy controls (HC), and then detected DNA methylation and histone modifications by ELISA. The DNA methylation rate of Tregs was significantly higher in AAA patients than in the HC group (0.159 ± 0.08% vs 0.098 ± 0.03%, P < 0.05), while the acetylation rates of H3 and H3K9 histones were lower in the AAA than in the HC group. We also examined the expression of mRNA encoding enzymes that catalyze making and removing epigenetic modifications by real-time PCR: we found that mRNA levels of DNA methyltransferase (DNMT) 1 and DNMT3A were higher in the AAA than in the HC group, mRNA levels of methyl-CpG-binding domain protein (MBD) 2 and MBD4 were higher in the AAA than in the HC group (MBD2: 6.21 ± 2.57 vs 3.04 ± 1.45; MBD4: 7.76 ± 3.48 vs 4.97 ± 3.10; both P < 0.05), and mRNA levels of histone deacetylase (HDAC) 1 and HDAC5 were significantly up-regulated in the AAA compared with the HC group (HDAC1: 2.17 ± 1.18 vs 1.51 ± 0.99; HDAC5: 1.35 ± 0.49 vs 0.94 ± 0.76; both P < 0.05). Together, our results reveal that rates of DNA methylation and histone modifications of Tregs are significantly altered in AAA patients.

Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction

BACKGROUND

Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy.

METHODS

Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing.

KEY RESULTS

We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort.

CONCLUSIONS AND INFERENCES

ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.

Myosins as fundamental components during tumorigenesis: diverse and indispensable

Myosin is a kind of actin-based motor protein. As the crucial functions of myosin during tumorigenesis have become increasingly apparent, the profile of myosin in the field of cancer research has also been growing. Eighteen distinct classes of myosins have been discovered in the past twenty years and constitute a diverse superfamily. Various myosins share similar structures. They all convert energy from ATP hydrolysis to exert mechanical stress upon interactions with microfilaments. Ongoing research is increasingly suggesting that at least seven kinds of myosins participate in the formation and development of cancer. Myosins play essential roles in cytokinesis failure, chromosomal and centrosomal amplification, multipolar spindle formation and DNA microsatellite instability. These are all prerequisites of tumor formation. Subsequently, myosins activate various processes of tumor invasion and metastasis development including cell migration, adhesion, protrusion formation, loss of cell polarity and suppression of apoptosis. In this review, we summarize the current understanding of the roles of myosins during tumorigenesis and discuss the factors and mechanisms which may regulate myosins in tumor progression. Furthermore, we put forward a completely new concept of “chromomyosin” to demonstrate the pivotal functions of myosins during karyokinesis and how this acts to optimize the functions of the members of the myosin superfamily.

Postmortem genetic testing should be recommended in sudden cardiac death cases due to thoracic aortic dissection

BACKGROUND

Acute thoracic aortic dissections and ruptures, the main life-threatening complications of the corresponding aneurysms, are an important cause of sudden cardiac death. Despite the usefulness of the molecular diagnosis of these conditions in the clinical setting, the corresponding forensic field remains largely unexplored. The main goal of this study was to explore and validate a new massive parallel sequencing candidate gene​ assay as a diagnostic tool for acute thoracic aortic dissection autopsy cases.

MATERIALS AND METHODS

Massive parallel sequencing of 22 thoracic aortic disease candidate genes performed in 17 cases of thoracic aortic dissection using AmpliSeq and Ion Proton technologies. Genetic variants were filtered by location, type, and frequency at the Exome Aggregation Consortium and an internal database and further classified based on the American College of Medical Genetics and Genomics (ACMG) recommendations published in 2015. All prioritized results were confirmed by traditional sequencing.

RESULTS

From the total of 10 potentially pathogenic genetic variants identified in 7 out of the 17 initial samples, 2 of them were further classified as pathogenic, 2 as likely pathogenic, 1 as possibly benign, and the remaining 5 as variants of uncertain significance, reaching a molecular autopsy yield of 23%, approximately.

CONCLUSIONS

This massive parallel sequencing candidate gene approach proved useful for the molecular autopsy of aortic dissection sudden cardiac death cases and should therefore be progressively incorporated into the forensic field, being especially beneficial for the anticipated diagnosis and risk stratification of any other family member at risk of developing the same condition.

A novel SMAD3 mutation caused multiple aneurysms in a patient without osteoarthritis symptoms

Heterozygous mutations in the SMAD3 gene were recently described as the cause of a form of non-syndromic familial aortic thoracic aneurysm and dissection (FTAAD) transmitted as an autosomal dominant disorder and often associated with early-onset osteoarthritis. This new clinical entity, called aneurysms-osteoarthritis syndrome (AOS) or Loeys-Dietz syndrome 3 (LDS3), is characterized by aggressive arterial damages such as aneurysms, dissections and tortuosity throughout the arterial tree. We report, here, the case of a 45 year-old man presenting multiple visceral arteries and abdominal aortic aneurysms but without dissection of the thoracic aorta and without any sign of osteoarthritis. Exome-sequencing revealed a new frameshift heterozygous c.455delC (p.Pro152Hisfs*34) mutation in the SMAD3 gene. This deletion is located in the exon 3 coding for the linker region of the protein and causes a premature stop codon at positions 556-558 in the exon 4. The same mutation was found in the proband's mother and sister who had open surgery for abdominal aortic aneurysm and in one of his children who was 5 year-old and did not present aneurysm yet.

Aetiology and management of hereditary aortopathy

Aortic aneurysms are a major health problem because they account for 1-2% of all deaths in the Western population. Although abdominal aortic aneurysms (AAAs) are more prevalent than thoracic aortic aneurysms (TAAs), TAAs have been more exhaustively studied over the past 2 decades because they have a higher heritability and affect younger individuals. Gene identification in both syndromic and nonsyndromic TAA is proceeding at a rapid pace and has already pinpointed >20 genes associated with familial TAA risk. Whereas these genes explain <30% of all cases of familial TAA, their functional characterization has substantially improved our knowledge of the underlying pathological mechanisms. As such, perturbed extracellular matrix homeostasis, transforming growth factor-β signalling, and vascular smooth muscle cell contractility have been proposed as important processes in TAA pathogenesis. These new insights enable novel treatment options that are currently being investigated in large clinical trials. Moreover, together with the advent of next-generation sequencing approaches, these genetic findings are promoting a shift in the management of patients with TAA by enabling gene-tailored interventions. In this Review, we comprehensively describe the molecular landscape of familial TAA, and we discuss whether familial TAA, from a biological point of view, can serve as a paradigm for the genetically more complex forms of the condition, such as sporadic TAA or AAA.