Genetic risk factors for intracranial aneurysms: a meta-analysis in more than 116,000 individuals

Association between polymorphisms of DNA repair genes and intracranial aneurysms: A systematic review and meta‑analysis

Intracranial aneurysms (IAs) are present in ~2% of the general population, and genetic factors cannot be excluded for the risk of their development. The gene factors that result in the changes in the vascular extracellular matrix (ECM) may also be a key reason for IAs being hereditary. The VCAN gene [also known as chondroitin sulfate proteoglycan 2 (CSPG2)] plays various roles in maintaining ECM functions. The present systematic review and meta-analysis aimed to investigate all eligible articles involving IAs on the association with germ line SNPs of DNA repair genes (up to January, 2024). The total number of patients was 2,308 [987 cases (poor outcomes) and 1,321 controls (good outcomes)]. The results revealed that rs2287926 G/G genotype and G allele and rs251124 T/T genotype and minor allele T increased the risk of developing IAs. However, further studies are required to examine these gene polymorphisms as screening markers for IAs.

Risk factors and predictive indicators of rupture in cerebral aneurysms

Cerebral aneurysms are abnormal dilations of blood vessels in the brain that have the potential to rupture, leading to subarachnoid hemorrhage and other serious complications. Early detection and prediction of aneurysm rupture are crucial for effective management and prevention of rupture-related morbidities and mortalities. This review aims to summarize the current knowledge on risk factors and predictive indicators of rupture in cerebral aneurysms. Morphological characteristics such as aneurysm size, shape, and location, as well as hemodynamic factors including blood flow patterns and wall shear stress, have been identified as important factors influencing aneurysm stability and rupture risk. In addition to these traditional factors, emerging evidence suggests that biological and genetic factors, such as inflammation, extracellular matrix remodeling, and genetic polymorphisms, may also play significant roles in aneurysm rupture. Furthermore, advancements in computational fluid dynamics and machine learning algorithms have enabled the development of novel predictive models for rupture risk assessment. However, challenges remain in accurately predicting aneurysm rupture, and further research is needed to validate these predictors and integrate them into clinical practice. By elucidating and identifying the various risk factors and predictive indicators associated with aneurysm rupture, we can enhance personalized risk assessment and optimize treatment strategies for patients with cerebral aneurysms.

Association of the blood levels of specific volatile organic compounds with nonfatal cardio-cerebrovascular events in US adults

BACKGROUND

Cardio-cerebrovascular diseases constitute a major global public health burden. Volatile organic compounds (VOCs) exposure has become progressively severe, endangering human health and becoming one of the main concerns in environmental pollution. The associations of VOCs exposure with nonfatal cardio-cerebrovascular events have not been identified in observational study with a large sample size, so we aim to examine the association in US adult population.

METHODS

Adults aged > 18 years with complete data regarding selected blood levels of VOCs (including benzene, ethylbenzene, o-xylene, and m-/p-xylene) and nonfatal cardio-cerebrovascular events were included in the analysis (n = 3,968, National Health and Nutrition Examination Survey, NHANES, 2013-2018 survey cycle). Participants were classified into low- and high-exposure based on whether above selected VOCs low limit detect concentration or median value. Weighted multivariate logistic analyses and subgroup analyses were used to detect the association between selected VOCs exposure and nonfatal cardio-cerebrovascular events in US adults.

RESULTS

Weighted multivariate logistic analyses showed that the high-VOCs exposure group had an increased risk of nonfatal cardio-cerebrovascular events compared with the low-VOCs exposure group; the adjusted odds ratios (OR) and 95% confidence intervals (CI) of nonfatal cardio-cerebrovascular events for the high-VOCs exposure group were 1.41 (0.91, 2.19), 1.37 (0.96, 1.95), 1.32 (0.96, 1.82), and 1.17 (0.82, 1.67) for benzene, ethylbenzene, o-xylene, and m-/p-xylene, respectively, which was not significant assuming statistical significance at a 0.05 significance level (95% CI) for a two-tailed test. Lastly, we found high-VOCs exposure was associated with increased incidence of nonfatal cardio-cerebrovascular events in both daily smokers an non-daily smokers (p-interaction > 0.01), but the association was not statistically significant in non-daily smokers.

CONCLUSIONS

This study found that VOCs (benzene, ethylbenzene, o-xylene, and m-/p-xylene) exposure was associated with increased incidence of nonfatal cardio-cerebrovascular events in US adults, and the results need to be confirmed by larger cohort studies.

Unruptured intracranial aneurysms: Why should we focus on small aneurysms? A comprehensive update of recent findings

Intracranial aneurysms (IAs) are a significant public health concern because they have the potential to cause deva-stating consequences, including death and disability. Despite advances in diagnostic and treatment modalities, the outcomes for patients with aneurysmal subarachnoid haemorrhage (aSAH) remain poor, with high rates of rebleeding, vasospasm, and cerebral ischaemia. IAs are a significant risk factor for aSAH, and it is estimated that up to 3% of the general population have IAs. Recent studies using novel imaging modalities have shown that the prevalence of IAs may be much higher, with 6.6% of adults aged 40-84 years having intradural saccular IAs ≥ 2 mm. The risk of rupture for IAs is difficult to predict, and the decision to treat them invasively is based on a balance between the estimated rupture risk and the procedural risks of the treatment. However, the mortality and morbidity rates among patients treated for IAs can be as high as 5%. There is a need for clear guidelines on the treatment of IAs, and this review aims to provide an update on recent findings in this area. To achieve this goal, the authors identified and summarized recent, high-impact studies on IAs. The review focuses on the diagnostic and treatment options for IAs, as well as the risks associated with these interventions. The authors also provide an overview of the natural history of IAs and discuss the challenges and uncertainties in managing these patients.

Prevalence and Characteristics of Intracranial Aneurysms in Hereditary Hemorrhagic Telangiectasia

BACKGROUND AND PURPOSE

The association between hereditary hemorrhagic telangiectasia and intracranial aneurysms remains controversial. This study evaluated the prevalence and characteristics of intracranial aneurysms in patients with hereditary hemorrhagic telangiectasia with brain vascular malformations.

MATERIALS AND METHODS

Between 2007 and 2021, patients enrolled in the Brain Vascular Malformation Consortium with definite hereditary hemorrhagic telangiectasia, the presence of brain vascular malformations, and available angiographic studies of the brain were retrospectively reviewed. Angiographic features of intracranial aneurysms and their relationship to coexisting brain vascular malformations were analyzed. We also examined the association between baseline clinical features and the presence of intracranial aneurysms.

RESULTS

One hundred eighty patients were included. A total of 14 intracranial aneurysms were found in 9 (5%) patients, and 4 intracranial aneurysms were considered flow-related aneurysms. Patients with intracranial aneurysms were significantly older than patients without intracranial aneurysms (mean, 48.1 [SD, 18.2] years versus 33.5 [SD, 21.0] years; P = .042). If we excluded flow-related intracranial aneurysms, the prevalence of intracranial aneurysms was 3.3%. All intracranial aneurysms were in the anterior circulation, were unruptured, and had an average maximal diameter of 3.9 (SD, 1.5) mm. No intracranial aneurysms were found in pediatric patients with hereditary hemorrhagic telangiectasia. No statistically significant correlation was observed among other baseline demographics, hereditary hemorrhagic telangiectasia features, and the presence of intracranial aneurysms.

CONCLUSIONS

The prevalence of intracranial aneurysms in this large cohort study is comparable with that in the general population and might be increased slightly due to hemodynamic factors associated with shunting brain vascular malformations.

Intracranial Aneurysms and Genetics: An Extensive Overview of Genomic Variations, Underlying Molecular Dynamics, Inflammatory Indicators, and Forward-Looking Insights

This review initiates by outlining the clinical relevance of IA, underlining the pressing need to comprehend its foundational elements. We delve into the assorted risk factors tied to IA, spotlighting both environmental and genetic influences. Additionally, we illuminate distinct genetic syndromes linked to a pronounced prevalence of intracranial aneurysms, underscoring the pivotal nature of genetics in this ailment's susceptibility. A detailed scrutiny of genome-wide association studies allows us to identify key genomic changes and locations associated with IA risk. We further detail the molecular and physiopathological dynamics instrumental in IA's evolution and escalation, with a focus on inflammation's role in affecting the vascular landscape. Wrapping up, we offer a glimpse into upcoming research directions and the promising horizons of personalized therapeutic strategies in IA intervention, emphasizing the central role of genetic insights. This thorough review solidifies genetics' cardinal role in IA, positioning it as a cornerstone resource for professionals in the realms of neurology and genomics.

A Review of Artificial Intelligence in the Rupture Risk Assessment of Intracranial Aneurysms: Applications and Challenges

Intracranial aneurysms (IAs) are highly prevalent in the population, and their rupture poses a significant risk of death or disability. However, the treatment of aneurysms, whether through interventional embolization or craniotomy clipping surgery, is not always safe and carries a certain proportion of morbidity and mortality. Therefore, early detection and prompt intervention of IAs with a high risk of rupture is of notable clinical significance. Moreover, accurately predicting aneurysms that are likely to remain stable can help avoid the risks and costs of over-intervention, which also has considerable social significance. Recent advances in artificial intelligence (AI) technology offer promising strategies to assist clinical trials. This review will discuss the state-of-the-art AI applications for assessing the rupture risk of IAs, with a focus on achievements, challenges, and potential opportunities.

Interruption of TRPC6-NFATC1 signaling inhibits NADPH oxidase 4 and VSMCs phenotypic switch in intracranial aneurysm

Intracranial aneurysm (IA) is a frequent cerebrovascular disorder with unclear pathogenesis. The vascular smooth muscle cells (VSMCs) phenotypic switch is essential for IA formation. It has been reported that Ca2+ overload and excessive reactive oxygen species (ROS) are involved in VSMCs phenotypic switch. The transient receptor potential canonical 6 (TRPC6) and NADPH oxidase 4 (NOX4) are the main pathway to participate in Ca2+ overload and ROS production in VSMCs. Ca2+ overload can activate calcineurin (CN), leading to nuclear factor of activated T cell (NFAT) dephosphorylation to regulate the target gene's transcription. We hypothesized that activation of TRPC6-NFATC1 signaling may upregulate NOX4 and involve in VSMCs phenotypic switch contributing to the progression of IA. Our results showed that the expressions of NOX4, p22phox, p47phox, TRPC6, CN and NFATC1 were significantly increased, and VSMCs underwent a significant phenotypic switch in IA tissue and cellular specimens. The VIVIT (NFATC1 inhibitor) and BI-749327 (TRPC6 inhibitor) treatment reduced the expressions of NOX4, p22phox and p47phox and the production of ROS, and significantly improved VSMCs phenotypic switch in IA rats and cells. Consistent results were obtained from IA Trpc6 knockout (Trpc6-/-) mice. Furthermore, the results also revealed that NFATC1 could regulate NOX4 transcription by binding to its promoter. Our findings reveal that interrupting the TRPC6-NFATC1 signaling inhibits NOX4 and improves VSMCs phenotypic switch in IA, and regulating Ca2+ homeostasis may be an important therapeutic strategy for IA.

Endothelial nitric oxide synthase rs1799983 gene polymorphism is associated with the risk of developing intracranial aneurysm

PURPOSE

The intracranial aneurysm (IA) rupture is associated with a subarachnoid hemorrhage. One third of patients die, and one third remain depend for daily activities. Genetic factors are crucial in the formation and clinical evolution of IAs. Multiple loci have been associated with AIs, much of them implicating multiple pathways related to vascular endothelial maintenance and extracellular matrix integrity. Thus, the aim of our study was to characterize whether polymorphisms in genes implicated in the vascular endothelial maintenance could modify the risk of developing IAs.

SUBJECTS AND METHODS

We have studied 176 patients with IA recruited in the Service of Neurosurgery at the University Hospital of Valladolid (Spain) and a control group if 150 sex-matched healthy subjects. Clinical variables were collected from each patient. We have analyzed VEGFA rs833061, VEGFR2 rs2071559, endothelin rs5370, endoglin rs3739817, and eNOS rs1799983 polymorphisms.

RESULTS

Our results showed that allele T of the eNOS rs1799983 polymorphism is correlated with decreased risk of developing the disease; thus, allele G of the eNOS rs1799983 polymorphism increased the risk of developing IA.

CONCLUSION

The association of eNOS rs1799983 polymorphism with the risk to suffer IA reinforces the hypothesis that genetic variants in eNOS gene could be crucial in the pathogenesis of IA.

Lack of the human choline transporter-like protein SLC44A2 causes hearing impairment and a rare red blood phenotype

Blood phenotypes are defined by the presence or absence of specific blood group antigens at the red blood cell (RBC) surface, due to genetic polymorphisms among individuals. The recent development of genomic and proteomic approaches enabled the characterization of several enigmatic antigens. The choline transporter-like protein CTL2 encoded by the SLC44A2 gene plays an important role in platelet aggregation and neutrophil activation. By investigating alloantibodies to a high-prevalence antigen of unknown specificity, found in patients with a rare blood type, we showed that SLC44A2 is also expressed in RBCs and carries a new blood group system. Furthermore, we identified three siblings homozygous for a large deletion in SLC44A2, resulting in complete SLC44A2 deficiency. Interestingly, the first-ever reported SLC44A2-deficient individuals suffer from progressive hearing impairment, recurrent arterial aneurysms, and epilepsy. Furthermore, SLC44A2_null individuals showed no significant platelet aggregation changes and do not suffer from any apparent hematological disorders. Overall, our findings confirm the function of SLC44A2 in hearing preservation and provide new insights into the possible role of this protein in maintaining cerebrovascular homeostasis.

Association of rare RNF213 variants and intracranial aneurysm risk in a Chinese population

Background

Genetic factors play important roles in the development of intracranial aneurysm (IA). Rare RNF213 variants have been identified as being susceptible to Moyamoya disease (MMD), non-MMD intracranial artery stenosis/occlusion disease, and other vascular disorders. This study aimed to investigate the association between rare RNF213 variants and the risk of IA in a Chinese population.

Methods

We recruited 174 patients with IA for RNF213 target exome sequencing. Information on the control subjects was obtained from the 1,000 Genome Project and GeneSky in-house database. After prioritizing rare RNF213 variants, the filtered variants were confirmed by Sanger sequencing. Gene-based association analyses were performed to identify the association between variants and the disease using burden and variance component methods; that is, the weighted-sum statistic (WSS) and the sequence kernel association test (SKAT), respectively. The Student's t-test, Chi-squared test, and Fisher's exact test were used to compare the clinical characteristics between carriers and non-carriers of the RNF213 variants.

Results

After filtering, there were 14 RNF213 variants in 18 patients with IA, which were significantly associated with the disease after the gene-based association tests [minor allele frequency (MAF) <0.01, WSS P value 5.08×10^-9; SKAT P value 2.96×10^-6; SKAT-O P value 3.56×10^-8]. Significant difference was not obtained between the carriers and non-carriers of the RNF213 variants in terms of the clinical characteristics.

Conclusions

Rare RNF213 variants were associated with sporadic IA in a Chinese population. Our findings suggest that these rare RNF213 variants might have potentially important roles in IA. However, more comprehensive studies need to be conducted to confirm this association and causality.

Incidence rate and predictors of recurrent aneurysms after clipping: long-term follow-up study of survivors of subarachnoid hemorrhage

Recurrent aneurysms are a major cause of re-aneurysmal subarachnoid hemorrhage (aSAH), but information on long-term clip durability and predictors is insufficient. This study aimed to present the incidence rate of > 10 years and investigate predictors of a recurrent aneurysm in aSAH survivors. We included 1601 patients admitted with aSAH and treated by microsurgical clipping between January 1993 and May 2010. Of these patients, 435 aSAH survivors were included in this study (27.2%). The total follow-up time was 5680.9 patient-years, and the overall incidence rate was 0.77% per patient-year. The cumulative probability of recurrence without residua and regrowth of the neck remnant was 0.7% and 13.9% at 10 years, respectively. Neck remnant (hazard ratio [HR], 10.311; 95% confidence interval [CI], 5.233-20.313) and alcohol consumption over the moderate amount (HR, 3.166; 95% CI, 1.313-7.637) were independent risk factors of recurrent aneurysm. Current smoking and multiplicity at initial aSAH presentation were significant factors in a univariate analysis. Furthermore, de novo intracranial aneurysms (DNIAs) were more common in the recurrent group than in the non-recurrent group (40.9% vs. 11.5%, P < 0.001). In the present study, we noted the long-term clip durability and predictor of recurrence after microsurgical clipping. These findings can assist clinicians in identifying patients at a high risk of recurrent aneurysm and recommending selective long-term surveillance after microsurgical clipping.

Experimental Induction of Intracranial Aneurysms in Rats: A New Model Utilizing a Genetic Modification within the EDNRA Gene

The rupture of an intracranial aneurysm (IA) leads to life-threatening subarachnoid hemorrhage. Aside from well-established risk factors, recently published genome-wide association studies of IA revealed the strong association of a common variant near the endothelin receptor type A (EDNRA) gene with IA risk. However, the role of EDNRA in the pathogenesis of IA remains unclear. The aim of this study was to investigate the influence of a genetic modification within the EDNRA gene on IA pathogenesis in a novel in vivo model. Adult wild-type Sprague–Dawley rats (WT rats) and genetically modified rats (EDNRA rats) were used for the induction of IA using arterial hypertension (HT). Animals were stratified into four groups: WT rats without (WT_CTL) and with induction of HT (WT + HT), as well as EDNRA rats without (EDNRA_CTL) and with induction of HT (EDNRA + HT). Blood pressure (BP) was observed for 12 weeks. After the observation period, cerebral arteries were analyzed for morphological (i.e., aneurysmal) changes as well as histological and functional changes by immunofluorescence and functional investigation. In the groups of rats with induction of HT, BP was higher in EDNRA + HT compared with that in WT + HT. No IAs were observed in WT_CTL and EDNRA_CTL but were found in WT + HT and EDNRA + HT. There was no histological difference in the immunofluorescence of EDNRA between all groups. Contractility and potency of endothelin-1 differed between the groups in functional investigation. In summary, we created a new model that is suitable for further studies for better understanding of the role of EDNRA in IA pathogenesis.

Rs12976445 polymorphism is associated with the risk of post-SAH re-bleeding by modulating the expression of microRNA-125 and ET-1

This study aimed to study the association between rs12976445 polymorphism and the incidence of IA re-bleeding. Genotype and allele frequency analysis was performed to study the association between rs12976445 polymorphism and the risk of IA re-bleeding. Western blot, ELISA and real-time RT-PCR were conducted to measure the relative expression of miR-125a, ET1 mRNA and ET1 protein. Computational analysis and luciferase assays were utilized to investigate the association between the expression of miR-125a and ET1 mRNA. No significant differences were observed between IA patients with or without symptoms of re-bleeding. Subsequent analyses indicated that the T allele was significantly associated with the reduced risk of IA re-bleeding. In patients carrying the CC genotype, miR-125a level was up-regulated while ET1 mRNA/protein levels were reduced compared with those in patients carrying the CT or TT genotype. And ET1 mRNA was identified as a virtual target gene of miR-125a with a potential miR-125a binding site located on its 3’UTR. Accordingly, the ET mRNA/protein levels could be suppressed by the transfection of miR-125a precursors, but the transfection of ET1 siRNA exhibited no effect on the expression of miR-125a. Therefore, an increased level of miR-125a can lead to the increased risk of IA re-bleeding. Since miR-125a level is higher in CC-genotyped patients, it can be concluded that the presence of T allele in the rs12976445 polymorphism is associated with a lower risk of IA re-bleeding, and miR-125a may be used as a novel diagnostic and therapeutic target for IA rupture.

Kunming mouse strain is less susceptible to elastase-induced abdominal aortic aneurysms

BACKGROUND

Porcine pancreatic elastase (PPE) is successfully used to induce abdominal aortic aneurysm (AAA) in mice. However, differences between mouse strains in susceptibility to PPE induction have been reported. Kunming mouse is one of the most frequently used strains in China but whether it is suitable for induction of AAA by PPE application remains unclear.

METHODS

PPE infusion (1.5 units/ml) in temporary controlled aorta was performed to induce AAAs in both C57BL/6J and Kunming mice. Phosphate-buffered saline (PBS) application was used as vehicle control. The aorta diameters of all mice were measured at days 0 and 14 after surgery to evaluate the AAA formation.

RESULTS

After 14 days of PPE or PBS infusion, all mice were sacrificed and aorta tissues were collected for histological staining analysis. At the 14th day after infusion, PPE successfully induced aortic dilation in Kunming mice and typical AAA in C57BL/6J mice. The aorta diameter increased by 0.23 mm in Kunming mice after PPE infusion, while it was 0.72 mm in the C57BL/6J strain. PPE induced mild elastin degradation, smooth muscle cell (SMC) depletion and mural leucocyte infiltration in Kunming mice, but in PPE-sensitive C57BL/6J mice, it induced total loss of SMCs, elastin disappearance and diffused infiltrated leucocytes in aortic aneurysmal segments. The effects of PPE in inducing angiogenesis and upregulating matrix metalloproteinase 2 and 9 expression in Kunming mice were also weaker than that in C57BL/6J mice.

CONCLUSION

At the reported dose of PPE, Kunming mouse is not as susceptible to AAA formation as C57BL/6J mice. The failure of PPE to induce AAA formation in Kunming mice may be associated to its inability to boost a strong inflammatory response.

The rs13330s40 and rs10757278 9p21 locus polymorphisms in patients with intracranial aneurysm: a Meta-analysis

Introduction: The formation of intracranial aneurysms (IAs) has been associated with genetic polymorphisms. A few genome-wide (GWAS) and candidate gene association studies (CGAS) have reported that single nucleotide polymorphisms (SNPs) in locus 9p21 have been associated with the formation of IAs.Materials & Methods: We performed a meta-analysis of case-control studies to investigate the association of two SNPs (rs1333040, rs10757278), located at the 9p21 locus, with the formation of IAs. MEDLINE, EMBASE, Google Scholar and CENTRAL databases were comprehensively searched.Results: For the rs1333040 (C > T) polymorphism, a significant association with IA was observed in the dominant [OR (95% CI): 1.39 (1.24, 1.56); Pz <0.00001], recessive [OR (95% CI): 1.38 (1.28, 1.49); Pz <0.00001] and over-dominant [OR (95% CI): 0.85 (0.79, 0.91); Pz <0.00001] models. For the rs10757278(A > G) SNP, we observed a statistically significant association with IAs in the dominant [OR (95% CI): 1.41 (1.28, 1.56); Pz <0.01] and recessive [OR (95% CI): 1.42 (1.29, 1.56); Pz <0.01] models, while statistical significance was not revealed in the over-dominant model [OR (95% CI): 1.01 (0.93, 1.10); P_z=0.83].Discussion: A possible association between the two SNPs and IAs was indicated. The associations reported by our meta-analysis need to be further studied and validated by larger CGAS and GWAS.

MicroRNA-124-5p delays the progression of cerebral aneurysm by regulating FoxO1

Cerebral aneurysm (CA) is a common brain disease, and the development of cerebral aneurysm is driven by inflammation and hemodynamic stress. MicroRNA (miR)-124-5p is reported to be associated with inflammatory response in brain disease such as cerebral ischemia-reperfusion injury. However, the function and molecular mechanism of miR-124-5p in CA are not clear, thus, the effects of miR-124-5p on inflammatory response in CA were explored. Firstly, the expression of miR-124-5p in the peripheral blood of patients with CA and the control group was detected by reverse transcription-quantitative PCR. Then, the human umbilical vein endothelial cells (HUVECs) were used as an in vitro model system and stimulated with interleukin (IL)-1β to simulate the inflammatory environment of CA, and the expression of miR-124-5p was detected. Next, the effect of miR-124-5p on the migration and invasion of HUVECs was detected using Transwell assays. Meanwhile, the function of miR-124-5p on various inflammatory factors was determined by western blotting and enzyme-linked immunosorbent assay (ELISA). Next, the TargetScan website was used to predict FoxO1 as a target gene of miR-124-5p, and this target association was validated by double luciferase reporter assay and western blotting. Finally, the interaction of miR-124-5p with FoxO1 in CA was measured by Transwell western blotting and ELISA assays. The results showed that the expression level of miR-124-5p in the peripheral blood of patients with CA was lower compared with that of control group, and the miR-124-5p in HUVECs stimulated by IL-1β was less compared with that in normal HUVECs. Besides, miR-124-5p could inhibit the migration and invasion abilities of HUVECs and the release of inflammatory factors. Additionally, the overexpression of miR-124-5p was able to inhibit the expression of FoxO1. miR-124-5p-inhibitor promoted the migration and invasion of HUVECs, as well as inflammatory response, which was weakened following the introduction of FoxO1 small interfering RNA. Overall, the present study demonstrated that miR-124-5p could prevent the occurrence and development of cerebral aneurysm by downregulating the expression of FoxO1.

Genetics of Intracranial Aneurysms

Rupture of an intracranial aneurysm leads to aneurysmal subarachnoid hemorrhage, a severe type of stroke which is, in part, driven by genetic variation. In the past 10 years, genetic studies of IA have boosted the number of known genetic risk factors and improved our understanding of the disease. In this review, we provide an overview of the current status of the field and highlight the latest findings of family based, sequencing, and genome-wide association studies. We further describe opportunities of genetic analyses for understanding, prevention, and treatment of the disease.

Shedding the Light on the Natural History of Intracranial Aneurysms: An Updated Overview

The exact molecular pathways underlying the multifactorial natural history of intracranial aneurysms (IAs) are still largely unknown, to the point that their understanding represents an imperative challenge in neurovascular research. Wall shear stress (WSS) promotes the genesis of IAs through an endothelial dysfunction causing an inflammatory cascade, vessel remodeling, phenotypic switching of the smooth muscle cells, and myointimal hyperplasia. Aneurysm growth is supported by endothelial oxidative stress and inflammatory mediators, whereas low and high WSS determine the rupture in sidewall and endwall IAs, respectively. Angioarchitecture, age older than 60 years, female gender, hypertension, cigarette smoking, alcohol abuse, and hypercholesterolemia also contribute to growth and rupture. The improvements of aneurysm wall imaging techniques and the implementation of target therapies targeted against inflammatory cascade may contribute to significantly modify the natural history of IAs. This narrative review strives to summarize the recent advances in the comprehension of the mechanisms underlying the genesis, growth, and rupture of IAs.

Diagnosis and Treatment of Unruptured Intracranial Aneurysms and Aneurysmal Subarachnoid Hemorrhage

Unruptured intracranial aneurysms (UIAs) are commonly acquired vascular lesions that form an outpouching of the arterial wall due to wall thinning. The prevalence of UIAs in the general population is 3.2%. In contrast, an intracranial aneurysm may be manifested after rupture with classic presentation of a thunderclap headache suggesting aneurysmal subarachnoid hemorrhage (SAH). Previous consensus suggests that although small intracranial aneurysms (<7 mm) are less susceptible to rupture, aneurysms larger than 7 mm should be treated on a case-by-case basis with consideration of additional risk factors of aneurysmal growth and rupture. However, this distinction is outdated. The PHASES score, which comprises data pooled from several prospective studies, provides precise estimates by considering not only the aneurysm size but also other variables, such as the aneurysm location. The International Study of Unruptured Intracranial Aneurysms is the largest observational study on the natural history of UIAs, providing the foundation to the current guidelines for the management of UIAs. Although SAH accounts for only 3% of all stroke subtypes, it is associated with considerable burden of morbidity and mortality. The initial management is focused on stabilizing the patient in the intensive care unit with close hemodynamic and serial neurologic monitoring with endovascular or open surgical aneurysm treatment to prevent rebleeding. Since the results of the International Subarachnoid Aneurysm Trial, treatment of aneurysmal SAH has shifted from surgical clipping to endovascular coiling, which demonstrated higher odds of survival free of disability at 1 year after SAH. Nonetheless, aneurysmal SAH remains a public health hazard and is associated with high rates of disability and death.

Epigenetic landscapes of intracranial aneurysm risk haplotypes implicate enhancer function of endothelial cells and fibroblasts in dysregulated gene expression

BACKGROUND

Genome-wide association studies have identified many single nucleotide polymorphisms (SNPs) associated with increased risk for intracranial aneurysm (IA). However, how such variants affect gene expression within IA is poorly understood. We used publicly-available ChIP-Seq data to study chromatin landscapes surrounding risk loci to determine whether IA-associated SNPs affect functional elements that regulate gene expression in cell types comprising IA tissue.

METHODS

We mapped 16 significant IA-associated SNPs to linkage disequilibrium (LD) blocks within human genome. Using ChIP-Seq data, we examined these regions for presence of H3K4me1, H3K27ac, and H3K9ac histone marks (typically associated with latent/active enhancers). This analysis was conducted in several cell types that are present in IA tissue (endothelial cells, smooth muscle cells, fibroblasts, macrophages, monocytes, neutrophils, T cells, B cells, NK cells). In cell types with significant histone enrichment, we used HiC data to investigate topologically associated domains (TADs) encompassing the LD blocks to identify genes that may be affected by IA-associated variants. Bioinformatics were performed to determine the biological significance of these genes. Genes within HiC-defined TADs were also compared to differentially expressed genes from RNA-seq/microarray studies of IA tissues.

RESULTS

We found that endothelial cells and fibroblasts, rather than smooth muscle or immune cells, have significant enrichment for enhancer marks on IA risk haplotypes (p < 0.05). Bioinformatics demonstrated that genes within TADs subsuming these regions are associated with structural extracellular matrix components and enzymatic activity. The majority of histone marked TADs (83% fibroblasts [IMR90], 77% HUVEC) encompassed at least one differentially expressed gene from IA tissue studies.

CONCLUSIONS

These findings provide evidence that genetic variants associated with IA risk act on endothelial cells and fibroblasts. There is strong circumstantial evidence that this may be mediated through altered enhancer function, as genes in TADs encompassing enhancer marks have also been shown to be differentially expressed in IA tissue. These genes are largely related to organization and regulation of the extracellular matrix. This study builds upon our previous (Poppenberg et al., BMC Med Genomics, 2019) by including a more diverse set of data from additional cell types and by identifying potential affected genes (i.e. those in TADs).

Morphology-based radiomics signature: a novel determinant to identify multiple intracranial aneurysms rupture

We aimed to develop and validate a morphology-based radiomics signature nomogram for assessing the risk of intracranial aneurysm (IA) rupture. A total of 254 aneurysms in 105 patients with subarachnoid hemorrhage and multiple intracranial aneurysms from three centers were retrospectively reviewed and randomly divided into the derivation and validation cohorts. Radiomics morphological features were automatically extracted from digital subtraction angiography and selected by the least absolute shrinkage and selection operator algorithm to develop a radiomics signature. A radiomics signature-based nomogram was developed by incorporating the signature and traditional morphological features. The performance of calibration, discrimination, and clinical usefulness of the nomogram was assessed. Ten radiomics morphological features were selected to build the radiomics signature model, which showed better discrimination with an area under the curve (AUC) equal to 0.814 and 0.835 in the derivation and validation cohorts compared with 0.747 and 0.666 in the traditional model, which only include traditional morphological features. When radiomics signature and traditional morphological features were combined, the AUC increased to 0.842 and 0.849 in the derivation and validation cohorts, thus showing better performance in assessing aneurysm rupture risk. This novel model could be useful for decision-making and risk stratification for patients with IAs.

Endovascular Treatment of Intracranial Aneurysms

Traditionally, surgical clipping was the only available treatment modality for intracranial aneurysms. However, in the last few decades, the endovascular therapy of intracranial aneurysms (IAs) has seen a tremendous evolution and development. From coiling to flow diversion and flow disruptor devices, endovascular treatment modalities have increased in number and received broader indications throughout the years. In this review article, the treatment modalities for the endovascular management of IAs are presented, emphasizing newer devices and technologies.

MSK1 downregulation is involved in inflammatory responses following subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) is a life-threatening neurological disease. Recently, inflammatory factors have been confirmed to be responsible for the brain damage associated with SAH. Therefore, studying the post-SAH inflammatory reaction may clarify the mechanism of SAH. Mitogen and stress-activated protein kinase 1 (MSK1) causes the phosphorylation of NF-κB and regulates the activity of pro-inflammatory transcription factors. The present study aimed to identify the potential role of MSK1 in inflammation and brain damage development following SAH. A cisterna magna blood injection model was established in Sprague-Dawley rats. Hematoxylin and eosin staining, reverse transcription-quantitative polymerase chain reaction assays and double immunofluorescence staining were used to analyze the role of MSK1, IL-1β and TNF-α in the inflammatory process after SAH. In a model of lipopolysaccharide-induced astrocyte inflammation, the effect of overexpressing MSK1 overexpression was analyzed by western blot analysis. The results demonstrated that MSK1 expression were negatively correlated with TNF-α and IL-1β expression levels, and reached peak levels 2 days after TNF-α and IL-1β. The double immunofluorescence staining results showed that the expression of MSK1 was in the same plane of view as TNF-α and IL-1β in the brain cortex. Furthermore, the in vitro studies indicated that the overexpression of MSK1 inhibited the expression of TNF-α and IL-1β following LPS challenge. These results imply that MSK1 may be involved in the inflammatory reaction following SAH, and may potentially serve as a negative regulator of inflammation.

The role of imaging in the management of non-traumatic subarachnoid hemorrhage: a practical review

The purpose of this review is to understand the role of imaging in the diagnosis and management of non-traumatic subarachnoid hemorrhage (SAH). SAH is a life-threatening emergency and a relatively common entity, the most common etiology being ruptured aneurysms. Multiple conundrums exist in literature at various steps of its imaging workup: diagnosis, management, and follow-up. We target our review to highlight the most effective practice and suggest efficient workup plans based on literature search, and describe in detail the clinical diagnostic and prognostic scales, role of CT scan, lumbar puncture, and MR, including angiography in the diagnosis and workup of SAH and its complications, and try to simplify the conundrums. Practical knowledge of imaging workup of SAH can help guide correct management of these patients, so as to reduce morbidity and mortality without resource overutilization.

[Efficiency and safety of minimally invasive approaches for microsurgical treatment of brain aneurysms]

Background. Brain aneurysms are found in 1-2% of population and cause subarachnoid hemorrhage (SAH) in 80-85% of cases. In recent decades, the incidence of unruptured aneurysms has increased due to widespread availability of CT and MRI. Microsurgery is still essential in the treatment of cerebral aneurysms.

OBJECTIVE

To assess the effectiveness and safety of minimally invasive approaches in microsurgical treatment of brain aneurysms in comparison with traditional approaches, to clarify the indications and contraindications for minimally invasive approaches.

MATERIAL AND METHODS

There were 394 patients with cerebral aneurysms for the period 2014-2019. All patients were divided into 2 groups depending on surgical approach: traditional approach (TrA) (n=171, 43.4%) and minimally invasive approach (MiniAp) (n=223, 56.6%). In the TrA group, pterional (n=85), orbitozygomatic (n=23) and lateral supraorbital approaches (n=63) were used. In the MiniAp group, transbrow supraorbital (n=88), mini-pterional (n=62), transbrow transorbital (n=37) and transpalpebral transorbital approaches (n=36) were used. Treatment outcomes were compared in both groups for patients with ruptured and unruptured aneurysms. We evaluated intra- and postoperative complications, surgery time and postoperative hospital-stay. Neurological outcomes were assessed using the Glasgow Outcome Scale (GOS) and the modified Rankin Scale (mRs). Cosmetic outcomes were compared using the visual analogue cosmetic scale. Unilateral hypesthesia and eyebrow movement were assessed separately after 3, 6 and 12 months.

RESULTS

In acute period of SAH, surgery time was significantly less in the MiniAp group (p=0.001). There were no significant between-group differences in the incidence of intraoperative rupture, surgical and neurological complications (p>0.05). Postoperative hospital-stay was significantly less in the MiniAp group (p=0.006). In this group, neurological outcomes were slightly better (p<0.001), there was no mortality, adverse outcomes occurred in 5.3% of cases (n=5). In the TrA group, 1 patient died from postoperative hematoma, adverse outcomes were noted in 9 (8.7%) patients. Cosmetic outcomes were significantly better in the MiniAp group (p<0.001). In delayed period of SAH and unruptured aneurysms, surgery time was less in the MiniAp group (p=0.051). Incidence of intra- and postoperative complications was similar in both groups (p>0.05). Hospital-stay was significantly shorter in the MiniAp group (p<0.001). Functional outcomes were comparable in both groups. Cosmetic outcomes were significantly better in the MiniAp group (p<0.05).

CONCLUSION

MiniAp and TrA are characterized by similar efficacy in microsurgical treatment of cerebral aneurysms. MiniAp is recommended only for experienced neurosurgeons in a specialized hospital. Safety and effectiveness of MiniAp are achieved by careful selection of patients, individual neuroimaging and preoperative planning.

Circular RNA expression profile in human primary multiple intracranial aneurysm

Primary multiple intracranial aneurysm (MIA) is a vascular disease that frequently leads to fatal vascular rupture and subarachnoid hemorrhage. However, the epigenetic regulation associated with MIA has remained largely elusive. Circular RNAs (circRNAs) serve important roles in cardiovascular diseases; however, their association with MIA has remained to be investigated. The present study initially aimed to explore novel mechanisms of MIA through examining circRNA expression profiles. Comprehensive circRNA expression profiles were detected by RNA sequencing (RNA-Seq) in human peripheral blood mononuclear cells. The RNA-Seq results were validated by reverse transcription-quantitative PCR. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested the functions of these circRNAs. A competing endogenous RNA network was constructed to reveal the circRNA-microRNA-mRNA relationship. Among the 3,328 differentially expressed circRNAs between the MIA and matched control groups, 60 exhibited significant expression changes (|log2 fold change|≥2; P<0.05). Among these 60 circRNAs, 20 were upregulated, while the other 40 were downregulated. A number of downregulated circRNAs were involved in inflammation. The most significant KEGG pathway was ‘leukocyte transendothelial migration’. The circRNAs Homo sapiens (hsa)_circ_0135895, hsa_circ_0000682 and hsa_circ_0000690, which were also associated with the above-mentioned pathway, were indicated to be able to regulate protein tyrosine kinase 2, protein kinase Cβ and integrin subunit αL, respectively. To the best of our knowledge, the present study was the first to perform a circRNA sequencing analysis of MIA. The results specifically predicted the regulatory role of circRNAs in the pathogenesis of MIA. ‘Leukocyte transendothelial migration’ may be critical for the pathogenesis of MIA.

Neurovascular disease, diagnosis, and therapy: Brain aneurysms

Unruptured intracranial aneurysms (UIAs) have a prevalence of 3% in the adult population worldwide. The majority of UIAs are incidental findings, but some UIAs cause cranial nerve palsies, brainstem compression, ischemic events, or epileptic seizures. The most frequent clinical presentation of intracranial aneurysms is, however, rupture and thereby subarachnoid hemorrhage (SAH). To avoid SAH with its fatal consequences, patients with UIAs require counseling by dedicated and interdisciplinary neurovascular specialists. For the purpose of assessment and decision-making for the management of patients with UIAs, numerous aspects have to be considered: radiological characteristics, clinical symptoms, estimated rupture risk of an individual aneurysm as well as patient- and aneurysm-related risks of preventive repair. Generally, two management options exist: observation with follow-up imaging or preventive repair. This chapter discusses current data on pathogenesis, clinical presentation, diagnostics, risk factors for rupture and preventive repair, and guidance tools for the management of patients with UIAs according to current evidence.

Intracranial Aneurysms: Does Size Really Matter?

BACKGROUND

To stratify the risk of aneurysmal rupture, size remains the primary criterion as proposed by 2 ISUIA (International Study of Unruptured Intracranial Aneurysms) trials that recommend the observation of ≤7 mm aneurysms because of their low propensity to rupture. These recommendations are controversial, given the severe outcomes following hemorrhage.

OBJECTIVE

To retrospectively assess whether size correlates with aneurysmal rupture, and to analyze outcomes of endovascular and microsurgical procedures.

METHODS

All aneurysms presenting between 2016 and 2019 were reviewed. Age, gender, comorbidities, ruptured status, modes of treatment, and their outcomes were noted. Regression analysis was performed to correlate size with rupture. The type of intervention was based on clinical and aneurysmal characteristics and the likelihood of obliteration.

RESULTS

Of the 668 aneurysms, 116 had ruptured. In size groups 0 to 6 mm,  7 to 12 mm,  13 to 18 mm,  18 to 24 mm, and giant, the ruptured aneurysms were 60.3%, 30.2%, 1.7%, 0.9%, and 6.9%, respectively. The majority (423) were managed endovascularly, of which 84 (19.9%) were ruptured. A total of 97 (14.5%) underwent clipping, of which 31 were ruptured. The mean modified Rankin Scale for both treated groups was zero. One death in each group and a single brainstem stroke in the coiled group were noted. A total of 139 were followed, of which none had ruptured. The mean modified Raymond-Roy classification for endovascular therapy was 1.1, with 380 completely occluded; 15 had a score of 2, and 28 of score 3.

CONCLUSION

The ruptured aneurysms were mostly smaller than reported previously. Surgical clipping was at equipoise with endovascular treatments. Further studies to correlate aneurysmal characteristics to the risk of rupture are needed.

ANGPTL6 Genetic Variants Are an Underlying Cause of Familial Intracranial Aneurysms

Purpose

To understand the role of the angiopoietin-like 6 gene (ANGPTL6) in intracranial aneurysms (IAs), we investigated its role in a large cohort of familial IAs.

Methods

Individuals with family history of IA were recruited to the Genetic and Observational Subarachnoid Haemorrhage (GOSH) study. The ANGPTL6 gene was sequenced using Sanger sequencing. Identified genetic variants were compared to a control population.

Results

We found 6 rare ANGPTL6 genetic variants in 9/275 individuals with a family history of IA (3.3%) (5 missense mutations and 1 nonsense mutation leading to a premature stop codon), none present in controls. One of these had been previously reported: c.392A>T (p.Glu131Val) on exon 2; another was very close: c.332G>A (p.Arg111His). Two further genetic variants lie within the fibrinogen-like domain of the ANGPTL6 gene, which may influence function or level of the ANGPTL6 protein. The last 2 missense mutations lie within the coiled-coil domain of the ANGPTL6 protein. All genetic variants were well conserved across species.

Conclusion

ANGPTL6 genetic variants are an important cause of IA. Defective or lack of ANGPTL6 protein is therefore an important factor in blood vessel proliferation leading to IA; dysfunction of this protein is likely to cause abnormal proliferation or weakness of vessel walls. With these data, not only do we emphasize the importance of screening familial IA cases for ANGPTL6 and other genes involved in IA, but also highlight the ANGPTL6 pathway as a potential therapeutic target.

Classification of Evidence

This is a Class III study showing some specificity of presence of the ANGPTL6 gene variant as a marker of familial intracranial aneurysms in a small subset of individuals with familial aneurysms.

Sex and Genetic Background Effects on the Outcome of Experimental Intracranial Aneurysms

BACKGROUND AND PURPOSE

Intracranial aneurysm formation and rupture risk are, in part, determined by genetic factors and sex. To examine their role, we compared 3 mouse strains commonly used in cerebrovascular studies in a model of intracranial aneurysm formation and rupture.

METHODS

Intracranial aneurysms were induced in male CD1 (Crl:CD1[ICR]), male and female C57 (C57BL/6NCrl), and male 129Sv (129S2/SvPasCrl or 129S1/SvImJ) mice by stereotaxic injection of elastase at the skull base, combined with systemic deoxycorticosterone acetate-salt hypertension. Neurological deficits and mortality were recorded. Aneurysms and subarachnoid hemorrhage grades were quantified postmortem, either after spontaneous mortality or at 7 to 21 days if the animals survived. In separate cohorts, we examined proinflammatory mediators by quantitative reverse transcriptase-polymerase chain reaction, arterial blood pressure via the femoral artery, and the circle of Willis by intravascular latex casting.

RESULTS

We found striking differences in aneurysm formation, rupture, and postrupture survival rates among the groups. 129Sv mice showed the highest rates of aneurysm rupture (80%), followed by C57 female (36%), C57 male (27%), and CD1 (21%). The risk of aneurysm rupture and the presence of unruptured aneurysms significantly differed among all 3 strains, as well as between male and female C57. The same hierarchy was observed upon Kaplan-Meier analysis of both overall survival and deficit-free survival. Subarachnoid hemorrhage grades were also more severe in 129Sv. CD1 mice showed the highest resistance to aneurysm rupture and the mildest outcomes. Higher mean blood pressures and the major phenotypic difference in the circle of Willis anatomy in 129Sv provided an explanation for the higher incidence of and more severe aneurysm ruptures. TNFα (tumor necrosis factor-alpha), IL-1β (interleukin-1-beta), and CCL2 (chemokine C-C motif ligand 2) expressions did not differ among the groups.

CONCLUSIONS

The outcome of elastase-induced intracranial aneurysm formation and rupture in mice depends on genetic background and shows sexual dimorphism.

Unruptured Intracranial Aneurysms- Pathogenesis and Individualized Management

BACKGROUND

About 2 million adults in Germany harbor an unruptured intracranial aneurysm (IA). Rupture can lead to a life-threatening subarachnoid hemorrhage. If an IA is detected incidentally in cranial imaging, it must be decided how to proceed.

METHODS

This review includes key publications that were identified by a selective search in the PubMed database using the search term "unruptured intracranial aneurysms," which was performed in July 2019, and based on information obtained from the German Federal Statistical Office on the frequency of the hospital discharge diagnosis "cerebral aneurysm," excluding the diagnosis "subarachnoid hemorrhage," in Germany from 2005 to 2017.

RESULTS

The number of patients in Germany who were admitted or treated for an unruptured IA increased by a factor of 2.3 from 2005 to 2017. The average 5-year rupture risk of approximately 3% must be weighed against the approximately 4% risk associated with an endovascular or microneurosurgical treatment. This emphasizes the need for more precise data on the risk of rupture and for algorithms enabling individualized decision-making for patients with unruptured IA. Risk factors such as IA morphology, arterial hypertension, active smoking, and alcohol consumption (>150 g/week) can markedly increase the risk of rupture, which is generally relatively low. Growing aneurysms are 12 times more likely to rupture than stable ones. Follow-up imaging is thus essential whenever observation rather than intervention is chosen as the initial management.

CONCLUSION

Patients with unruptured IA should be massessed and managed individually. It is also important that risk factors should be treated, if present. Eligible patients are currently being recruited for a phase III clinical trial on the efficacy of blood pressure reduction combined with acetylsalicylic acid intake to counteract inflammatory processes in the arterial wall.

A Preliminary Study of the Association between SOX17 Gene Variants and Intracranial Aneurysms Using Exome Sequencing

OBJECTIVE

Conflicting results regarding SOX17 genes and the risk of intracranial aneurysms (IA) exist in the Korean population, although significant positive correlations were noted in genome-wide association studies in European and Japanese populations. Therefore, we aimed to investigate an association between SOX17 gene variants and IA using exome sequencing data.

METHODS

This study included 26 age-gender matched IA patients and 26 control subjects. The SOX17 gene variants identified from whole-exome sequencing data were examined. Genetic associations to estimate odds ratio (OR) and 95% confidence interval (CI) were performed using the software EPACTS.

RESULTS

The mean age of the IA and control groups were 51.0±9.3 years and 49.4±14.3 years, respectively (p=0.623). Seven variants of SOX17, including six single nucleotide polymorphisms and one insertion and deletion, were observed. Among these variants, rs12544958 (A>G) showed the most association with IA, but the association was not statistically significant (OR, 1.97; 95% CI, 0.81-4.74; p=0.125). Minor allele frequencies of the IA patients and controls were 0.788 and 0.653, respectively. None of the remaining variants were significantly associated with IA formation.

CONCLUSION

No significant association between SOX17 gene variants and IA were noted in the Korean population. A large-scale exome sequencing study is necessary to investigate any Korean-specific genetic susceptibility to IA.

The Role of Long Non-Coding RNAs in Intracranial Aneurysms and Subarachnoid Hemorrhage

Intracranial aneurysms (IAs) represent the most complex and relevant problem of modern neurology and neurosurgery. They serve as one of the main causes of non-traumatic subarachnoid hemorrhage (SAH), causing up to 85% of all cases of intracranial hemorrhage, which is associated with frequent disability and high mortality among patients. Unfortunately, the molecular mechanisms of the development and rupture of IAs are still under study. Long non-coding RNAs (lncRNAs) are non-coding RNAs that typically have a length of more than 200 nucleotides. It is known that lncRNAs regulate many processes, such as transcription, translation, cell differentiation, regulation of gene expression, and regulation of the cell cycle. In recent years, a lot of evidence has established their role in human diseases from oncology to cardiovascular disease. Recent studies have shown that lncRNAs may be involved in the pathogenesis of IAs. The study of lncRNAs and its targets in various pathological conditions of a person is a rapidly developing field, and it is likely that the knowledge obtained from these studies regarding the pathogenesis of intracranial aneurysms will have the potential to use lncRNAs in therapy, as well as in the diagnosis and prediction of high aneurysms risk of rupture.

Association of Genetic Variants With Moyamoya Disease in 13 000 Individuals: A Meta-Analysis

Background and Purpose- A growing body of evidence indicates genetic components play critical roles in moyamoya disease (MMD). Firm conclusions from studies of this disease have been stymied by small sample sizes and a lack of replicative results. This meta-analysis was conducted to determine whether these genetic polymorphisms are associated with MMD. Methods- PubMed, Google Scholar, Embase, Wanfang, Web of Science, and China National Knowledge Infrastructure databases were used to identify potentially relevant studies published until January 2020. The Review Manager 5.2 and Stata 15.0 software programs were used to perform the statistical analysis. Heterogeneity was assessed using the Cochran Q test and quantified using the I² test. Results- Four thousand seven hundred eleven MMD cases and 8704 controls in 24 studies were included, evaluating 7 polymorphisms in 6 genes. The fixed-effect odds ratios (95% CI) in allelic model of MMP-2 rs243865 were 0.60 (0.41-0.88) (P=0.008). In the country-based subgroup analysis, the fixed-effect odds ratios (95% CI) of RNF213 rs112735431 in allelic model were China, 39.74 (26.63-59.31), Japan, 74.65 (42.79-130.24) and Korea, 50.04 (28.83-86.88; all P<0.00001). In the sensitivity analysis, the fixed-effect odds ratios (95% CI) of allelic and dominant models were the RNF213 rs148731719 variant, 2.17 (1.36-3.48; P=0.001), 2.20 (1.35-3.61; P=0.002), the TIMP-2 rs8179090 variant, 0.33 (0.25-0.43; P<0.00001), 0.88 (0.65-1.21; P=0.440) and the MMP-3 rs3025058 variant, 0.61 (0.47-0.79; P=0.0002), 0.55 (0.41-0.75; P=0.0001), respectively. Conclusions- RNF213 rs112735431 and rs148731719 were positively, and TIMP-2 rs8179090, MMP-2 rs243865, and MMP-3 rs3025058 were inversely associated with MMD using multiple pathophysiologic pathways. Studies in larger population should be conducted to clarify whether and how these variants are associated with MMD.

Weighted gene co-expression network analysis identified six hub genes associated with rupture of intracranial aneurysms

Intracranial aneurysms (IAs) are characterized by localized dilation or ballooning of a cerebral artery. When IAs rupture, blood leaks into the space around the brain to create a subarachnoid hemorrhage. The latter is associated with a higher risk of disability and mortality. The aims of this study were to gain greater insight into the pathogenesis of ruptured IAs, and to clarify whether identified hub genes represent potential biological markers for assessing the likelihood of IA progression and rupture. Briefly, the GSE36791 and GSE73378 datasets from the National Center of Biotechnology Information Gene Expression Omnibus database were reanalyzed and subjected to a weighted gene co-expression network analysis to test the association between gene sets and clinical features. The clinical significance of these genes as potential biomarkers was also examined, with their expression validated by quantitative real-time PCR. A total of 14 co-expression modules and 238 hub genes were identified. In particular, three modules (labeled turquoise, blue, and brown) were found to highly correlate with IA rupture events. Additionally, six potential biomarkers were identified (BASP1, CEBPB, ECHDC2, GZMK, KLHL3, and SLC2A3), which are strongly associated with the progression and rupture of IAs. Taken together, these findings provide novel insights into potential molecular mechanisms responsible for IAs and they highlight the potential for these particular genes to serve as biomarkers for monitoring IA rupture.

Saccular Aneurysm Models Featuring Growth and Rupture: A Systematic Review

BACKGROUND

Most available large animal extracranial aneurysm models feature healthy non-degenerated aneurysm pouches with stable long-term follow-ups and extensive healing reactions after endovascular treatment. This review focuses on a small subgroup of extracranial aneurysm models that demonstrated growth and potential rupture during follow-up.

METHODS

The literature was searched in Medline/Pubmed to identify extracranial in vivo saccular aneurysm models featuring growth and rupture, using a predefined search strategy in accordance with the PRISMA guidelines. From eligible studies we extracted the following details: technique and location of aneurysm creation, aneurysm pouch characteristics, time for model creation, growth and rupture rate, time course, patency rate, histological findings, and associated morbidity and mortality.

RESULTS

A total of 20 articles were found to describe growth and/or rupture of an experimentally created extracranial saccular aneurysm during follow-up. Most frequent growth was reported in rats (n = 6), followed by rabbits (n = 4), dogs (n = 4), swine (n = 5), and sheep (n = 1). Except for two studies reporting growth and rupture within the abdominal cavity (abdominal aortic artery; n = 2) all other aneurysms were located at the neck of the animal. The largest growth rate, with an up to 10-fold size increase, was found in a rat abdominal aortic sidewall aneurysm model.

CONCLUSIONS

Extracranial saccular aneurysm models with growth and rupture are rare. Degradation of the created aneurysmal outpouch seems to be a prerequisite to allow growth, which may ultimately lead to rupture. Since it has been shown that the aneurysm wall is important for healing after endovascular therapy, it is likely that models featuring growth and rupture will gain in interest for preclinical testing of novel endovascular therapies.

Prerupture Intracranial Aneurysm Morphology in Predicting Risk of Rupture: A Matched Case-Control Study

BACKGROUND

Maximal size and other morphological parameters of intracranial aneurysms (IAs) are used when deciding if an IA should be treated prophylactically. These parameters are derived from postrupture morphology. As time and rupture may alter the aneurysm geometry, possible morphological predictors of a rupture should be established in prerupture aneurysms.

OBJECTIVE

To identify morphological parameters of unruptured IAs associated with later rupture.

METHODS

Nationwide matched case-control study. Twelve IAs that later ruptured were matched 1:2 with 24 control IAs that remained unruptured during a median follow-up time of 4.5 (interquartile range, 3.7-8.2) yr. Morphological parameters were automatically measured on 3-dimensional models constructed from angiograms obtained at time of diagnosis. Cases and controls were matched by aneurysm location and size, patient age and sex, and the PHASES (population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, and site of aneurysm) score did not differ between the 2 groups.

RESULTS

Only inflow angle was significantly different in cases vs controls in univariate analysis (P = .045), and remained significant in multivariable analysis. Maximal size correlated with size ratio in both cases and controls (P = .015 and <.001, respectively). However, maximal size and inflow angle were correlated in cases but not in controls (P = .004. and .87, respectively).

CONCLUSION

A straighter inflow angle may predispose an aneurysm to changes that further increase risk of rupture. Traditional parameters of aneurysm morphology may be of limited value in predicting IA rupture.

Epigenetic landscapes suggest that genetic risk for intracranial aneurysm operates on the endothelium

BACKGROUND

Genetics play an important role in intracranial aneurysm (IA) pathophysiology. Genome-wide association studies have identified several single nucleotide polymorphisms (SNPs) that are linked to IA but how they affect disease pathobiology remains poorly understood. We used Encyclopedia of DNA Elements (ENCODE) data to investigate the epigenetic landscapes surrounding genetic risk loci to determine if IA-associated SNPs affect functional elements that regulate gene expression and if those SNPs are most likely to impact a specific type of cells.

METHODS

We mapped 16 highly significant IA-associated SNPs to linkage disequilibrium (LD) blocks within the human genome. Within these regions, we examined the presence of H3K4me1 and H3K27ac histone marks and CCCTC-binding factor (CTCF) and transcription-factor binding sites using chromatin immunoprecipitation-sequencing (ChIP-Seq) data. This analysis was conducted in several cell types relevant to endothelial (human umbilical vein endothelial cells [HUVECs]) and inflammatory (monocytes, neutrophils, and peripheral blood mononuclear cells [PBMCs]) biology. Gene ontology analysis was performed on genes within extended IA-risk regions to understand which biological processes could be affected by IA-risk SNPs. We also evaluated recently published data that showed differential methylation and differential ribonucleic acid (RNA) expression in IA to investigate the correlation between differentially regulated elements and the IA-risk LD blocks.

RESULTS

The IA-associated LD blocks were statistically significantly enriched for H3K4me1 and/or H3K27ac marks (markers of enhancer function) in endothelial cells but not in immune cells. The IA-associated LD blocks also contained more binding sites for CTCF in endothelial cells than monocytes, although not statistically significant. Differentially methylated regions of DNA identified in IA tissue were also present in several IA-risk LD blocks, suggesting SNPs could affect this epigenetic machinery. Gene ontology analysis supports that genes affected by IA-risk SNPs are associated with extracellular matrix reorganization and endopeptidase activity.

CONCLUSION

These findings suggest that known genetic alterations linked to IA risk act on endothelial cell function. These alterations do not correlate with IA-associated gene expression signatures of circulating blood cells, which suggests that such signatures are a secondary response reflecting the presence of IA rather than indicating risk for IA.

Causes, Predictors, and Trends of Unplanned Readmissions after Elective Endovascular Embolization of Cerebral Aneurysms

BACKGROUND

30- and 90-day readmissions (dRA) are being increasingly scrutinized as quality metrics for hospital and provider performances. Little information regarding risk factors for readmission after elective endovascular treatment (EVT) of an unruptured cerebral aneurysm (UCA) is available.

METHODS

The Nationwide Readmissions Database was used to identify patients who underwent elective endovascular embolization of an unruptured aneurysm between 2010 and 2014. The primary outcomes of interest were unplanned readmissions occurring within 30 or 90 days of discharge. Binary logistic regressions were used to identify variables related to patients' demographics, comorbidities, and index hospital admission that were associated with 30dRA and 90dRA.

RESULTS

A total of 8588 patients met the inclusion criteria for 30dRA analysis and 7289 patients were eligible for 90dRA analysis. The 5-year 30dRA and 90dRA readmission rates were 7.1% and 13.5%, respectively. The annual incidences of 30dRAs and 90dRAs between 2010 and 2014 decreased significantly (pooled odds ratio (OR) for 30dRA: .874, 95% confidence interval (CI) .765-.998; pooled OR for 90dRA: .841, 95% CI .755-.938). Patients in higher income quartiles experienced decreased odds of 30dRA and 90dRA. Nonroutine disposition following the index admission and greater comorbidity burdens were associated with higher likelihoods of both 30dRA and 90dRA. The presence of pulmonary or cardiac complications was associated with increased odds of 90dRA.

CONCLUSION

Readmission rates after elective EVT of UCAs decreased between 2010 and 2014. We identified several novel risk factors for both 30dRAs and 90dRAs that can be used to identify patients who are at highest risk of readmission.

Association of Bone Mineral Density With the Risk of Intracranial Aneurysm

Importance

Disruption of extracellular matrix integrity is critically involved in both intracranial aneurysm and bone fragility. Furthermore, both intracranial aneurysm and osteoporosis have a female predominance, and sex hormones are considered to affect this discrepancy.

Objective

To evaluate the association between bone mineral density and intracranial aneurysm.

Design, Setting, and Participants

A cross-sectional study conducted with 14 328 patients who underwent brain magnetic resonance angiography and bone mineral densitometry as a part of a health examination at a specialized center for comprehensive health examination in Seoul, the largest metropolitan area in the Republic of Korea, between December 2004 and November 2015. After excluding patients with insufficient clinical information (n = 1102) and with ambiguous intracranial arterial lesion (n = 441), 12 785 were included in the analysis.

Exposures

Bone mineral density was measured at the lumbar vertebrae (L1 to L4), femur neck, and total hip using dual-energy x-ray absorptiometry.

Main Outcomes and Measures

Multiple logistic regression or linear regression was used to examine the association between tertiles of bone mineral density and the presence, size, and multiplicity of intracranial aneurysms. In secondary analyses, we analyzed postmenopausal women and men 50 years and older (n = 8722) because they are particularly at risk of decreased bone mineral density.

Results

Among 12 785 patients in the study (7242 women [56.6%]; mean [SD] age, 54.8 [10.1] years) intracranial aneurysms were found in 472 patients (3.7%). Lower bone mineral density was associated with an increased risk of harboring intracranial aneurysm. In multivariable logistic regression analyses, odds ratios for the highest compared with the lowest bone mineral density tertile were 1.30 (95% CI, 1.03-1.64) in the lumbar spine, 1.30 (95% CI, 1.03-1.64) in the femoral neck, and 1.27 (95% CI, 1.01-1.60) in the total hip after adjusting for age, sex, and vascular risk factors. In a linear regression model adjusted for age, sex, and vascular risk factors, the lowest tertile of bone mineral density in the lumbar spine was associated with an increased log-transformed size of aneurysm (β, 0.196; SE, 0.047). In secondary analyses, these associations were more definite and a low T score (<-1 SD) was additionally associated with multiple aneurysms (OR, 1.84; 95% CI, 1.05-3.30) after adjusting for age, sex, and vascular risk factors.

Conclusions and Relevance

Bone mineral density may be associated with the presence, size, and multiplicity of intracranial aneurysm. The study findings provide evidence for shared pathophysiology between intracranial aneurysm and bone fragility.

Smooth muscle cells of intracranial vessels: from development to disease

Cerebrovascular diseases that cause ischaemic or haemorrhagic stroke with subsequent loss of life or functional capacity due to damage of the brain tissue are among the leading causes of human suffering and economic burden inflicted by diseases in the developed world. Diseases affecting intracranial vessels are significant contributors to ischaemic and haemorrhagic strokes. Brain arteriovenous malformations, which are a collection of abnormal blood vessels connecting arteries to veins, are the most common cause of intracranial haemorrhage in children and young adults. Saccular intracranial aneurysms, which are pathological saccular dilations mainly occurring at bifurcations of the large intracranial arteries near the circle of Willis, are highly prevalent in the middle-aged population, causing significant anxiety and concern; their rupture, although rare, is a significant cause of intracranial haemorrhage in those past middle age that is associated with a very sinister prognosis. Cerebral small-vessel disease, which comprise all pathological processes affecting vessels <500 microns in diameter, account for the majority of intracerebral haemorrhages and ∼25% of ischaemic strokes and 45% of dementias in the elderly. In this review, we summarize the developmental, structural, and functional features of intracranial vessels. We then describe the role of smooth muscle cells in brain arteriovenous malformations, intracranial aneurysms, and small-vessel diseases, and discuss how the peculiar ontogeny, structure, and function of intracranial vessels are related to the development of these diseases.

Association of Endothelin Receptor Type A with Intracranial Aneurysm in 20,609 East Asians: An Updated Meta-Analysis

INTRODUCTION

Genome-wide association studies have reported an association between the EDNRA gene and intracranial aneurysm (IA) in European and Japanese populations; however, there is no study on this polymorphism in other Asian populations. Therefore, we performed an extensive large-scale meta-analysis for association of the rs6841581 variant of EDNRA with IA susceptibility in East Asian population.

METHODS

We conducted a systemic review via electronic search for papers published between January 2002 and February 2019. We used fixed and random effect models and applied the inverse variance method. The statistical power of the result was estimated in the genome-wide significant threshold under an additive inheritance model.

RESULTS

Our meta-analysis included 5873 patients with IA and 14,736 non-IA controls from 6 independent populations: 4 Japanese, 1 Chinese, and 1 Korean. The risk (major) G allele of rs6841581 showed the highest significant association with the increased risk of IA under the fixed effect model in the East-Asian population (odds ratio = 1.244, 95% confidence interval: 1.174-1.318, P = 1.36E-13). The rs6841581 variant showed sufficient statistical power (80.3%) in this meta-analysis under the additive model. In subsequent analysis, the frequencies of the risk G allele showed similar pattern in all of the Japanese, Chinese, and Korean populations (69%, 80%, and 78%, respectively). In the in silico functional analysis, none of the functional variants was correlated with rs6841581.

CONCLUSIONS

The genetic variant of EDNRA, rs6841581, was significantly associated with increased risk of IA. Our findings indicate that it could be used as an IA-predicting variant in East Asian populations.

Genetic basis of intracranial aneurysm formation and rupture: clinical implications in the postgenomic era

OBJECTIVE

Despite the prevalence and impact of intracranial aneurysms (IAs), the molecular basis of their pathogenesis remains largely unknown. Moreover, there is a dearth of clinically validated biomarkers to efficiently screen patients with IAs and prognosticate risk for rupture. The aim of this study was to survey the literature to systematically identify the spectrum of genetic aberrations that have been identified in IA formation and risk of rupture.

METHODS

A literature search was performed using the Medical Subject Headings (MeSH) system of databases including PubMed, EMBASE, and Google Scholar. Relevant studies that reported on genetic analyses of IAs, rupture risk, and long-term outcomes were included in the qualitative analysis.

RESULTS

A total of 114 studies were reviewed and 65 were included in the qualitative synthesis. There are several well-established mendelian syndromes that confer risk to IAs, with variable frequency. Linkage analyses, genome-wide association studies, candidate gene studies, and exome sequencing identify several recurrent polymorphic variants at candidate loci, and genes associated with the risk of aneurysm formation and rupture, including ANRIL (CDKN2B-AS1, 9p21), ARGHEF17 (11q13), ELN (7q11), SERPINA3 (14q32), and SOX17 (8q11). In addition, polymorphisms in eNOS/NOS3 (7q36) may serve as predictive markers for outcomes following intracranial aneurysm rupture. Genetic aberrations identified to date converge on posited molecular mechanisms involved in vascular remodeling, with strong implications for an associated immune-mediated inflammatory response.

CONCLUSIONS

Comprehensive studies of IA formation and rupture have identified candidate risk variants and loci; however, further genome-wide analyses are needed to identify high-confidence genetic aberrations. The literature supports a role for several risk loci in aneurysm formation and rupture with putative candidate genes. A thorough understanding of the genetic basis governing risk of IA development and the resultant aneurysmal subarachnoid hemorrhage may aid in screening, clinical management, and risk stratification of these patients, and it may also enable identification of putative mechanisms for future drug development.

Associations among Genetic Variants and Intracranial Aneurysm in a Chinese Population

PURPOSE

Genome-wide association studies (GWAS) have revealed that common variants on or near EDNRA, HDAC9, SOX17, RP1, CDKN2B-AS1, and RBBP8 genes are associated with intracranial aneurysm (IA) in European or Japanese populations. However, due to population heterogeneity, whether these loci are associated with IA pathogenesis in Chinese individuals is still unknown. The purpose of this study was to investigate associations among GWAS-identified loci and risk of IA in a Chinese population.

MATERIALS AND METHODS

A total of 765 individuals (including 230 IA patients and 535 controls) were involved in this study. Twelve single nucleotide polymorphisms (SNPs) of candidate loci were genotyped using the Sequenom MassARRAY platform. Associations were analyzed using univariate or multivariate logistic regression analysis.

RESULTS

SNPs in CDKN2B-AS1 (especially rs10757272) showed significant associations with IA in dominant and additive models [odds ratio (OR), 2.99 and 1.43; 95% confidence interval (CI), 1.44-6.24 and 1.10-1.86, respectively]. A SNP near HDAC9 (rs10230207) was associated with IA in the dominant model (OR, 1.42; 95% CI, 1.01-1.99). One SNP near RP1 (rs1072737) showed a protective effect on IA in the dominant model (OR, 0.66; 95% CI, 0.46-0.95), while another SNP in RP1 (rs9298506) showed a risk effect on IA in a recessive model (OR, 3.82; 95% CI, 1.84-7.91). No associations were observed among common variants near EDNRA, SOX17, or RBBP8 and IA.

CONCLUSION

These data partially confirmed earlier results and showed that variants in CDKN2B-AS1, RP1, and HDAC9 could be genetic susceptibility factors for IA in a Chinese population.

Association of Opium Addiction with Rupture of Intracranial Aneurysms: A Case-Control Study

BACKGROUND

Disorders related to opioid use account for the most substantial burden of disease attributable to drug use disorders. We aimed to justify if there is an association between either opium consumption or addiction and rupture of intracranial aneurysms.

METHODS

In this case-control study, we enrolled 50 cases with ruptured intracranial aneurysms and 43 control subjects with an incidental finding of an intracranial aneurysm without history of subarachnoid hemorrhage (SAH). Four major risk factors of rupture including age, sex, size, and site of aneurysm were matched among both groups. All participants were asked about cigarette smoking state, opium addiction, opium consumption, and duration and route of opium consumption. Eight other trigger factors were assessed in the period soon before SAH (hazard period). The odds ratio (OR) of all factors was calculated separately, and then a logistic regression for the factors with significant odds was calculated.

RESULTS

Sixty-two percent of cases and 32.6% of control subjects were addicted to opium. The OR for opium consumption in the hazard period was 8.1 (95% confidence interval [CI], 2.2-30.1) and for opium addiction was 3.3 (95% CI, 1.4-7.9). Of those trigger factors, cola consumption was included in the logistic regression model. After adjustment, results demonstrated an OR of 9.2 (95% CI, 2.4-34.7) for opium consumption in the hazard period.

CONCLUSIONS

There is an association between opium addiction and opium consumption in the hazard period with the occurrence of aneurysmal SAH. Replication of the study with a larger sample size and conduction of prospective studies is suggested.

Associations of EDNRA and EDNRB Polymorphisms with Intracerebral Hemorrhage

OBJECTIVE

The most potent vasoconstrictor, endothelin-1 and its receptors, endothelin receptor A (EDNRA) and endothelin receptor B (EDNRB) are involved in hypertension. Hypertension is a major risk factor of intracerebral hemorrhage (ICH). Recent studies have demonstrated increased plasma endothelin-1 level in ICH patients and relationships between EDNRA and EDNRB genetic variants and ischemic stroke. The aim of the current study was to investigate whether EDNRA and EDNRB polymorphisms are associated with ICH by interacting with blood pressure levels.

METHODS

Five EDNRA and EDNRB polymorphisms were genotyped in this case-control study.

RESULTS

We identified that EDNRA rs5333 T allele might be a protective factor of ICH (adjusted odds ratio [OR] = 0.638, 95% CI: 0.417-0.977, P = 0.038), while EDNRB rs5351 A allele could be a risk factor of ICH (adjusted OR = 1.476, 95% CI: 1.042-2.089, P = 0.028). Moreover, we only found that the GG genotype of EDNRA rs5335 had higher diastolic blood pressure than the GC + CC genotypes in ICH patients (91.69 ± 18.77 vs. 84.71 ± 21.48, P = 0.004).

CONCLUSIONS

These findings support the important role of EDNRA and EDNRB polymorphisms in ICH, and suggest that they do not interact with blood pressure levels on altering ICH risk.