Molecular Basis of Cerebral Vasospasm: What Can We Learn from Transcriptome and Temporal Gene Expression Profiling in Intracranial Aneurysm?

Cerebral vasospasm (CV) is a significant complication following aneurysmal subarachnoid hemorrhage (aSAH), and lacks a comprehensive molecular understanding. Given the temporal trajectory of intracranial aneurysm (IA) formation, its rupture, and development of CV, altered gene expression might be a molecular substrate that runs through these clinical events, influencing both disease inception and progression. Utilizing RNA-Seq, we analyzed tissue samples from ruptured IAs with and without vasospasm to identify the dysregulated genes. In addition, temporal gene expression analysis was conducted. We identified seven dysregulated genes in patients with ruptured IA with vasospasm when compared with those without vasospasm. We found 192 common genes when the samples of each clinical subset of patients with IA, that is, unruptured aneurysm, ruptured aneurysm without vasospasm, and ruptured aneurysm with vasospasm, were compared with control samples. Among these common genes, TNFSF13B, PLAUR, OSM, and LAMB3 displayed temporal expression (progressive increase) with the pathological progression of disease that is formation of aneurysm, its rupture, and consequently the development of vasospasm. We validated the temporal gene expression pattern of OSM at both the transcript and protein levels and OSM emerges as a crucial gene implicated in the pathological progression of disease. In addition, RSAD2 and ATP1A2 appear to be pivotal genes for CV development. To the best of our knowledge, this is the first study to compare the transcriptome of aneurysmal tissue samples of aSAH patients with and without CV. The findings collectively provide new insights on the molecular basis of IA and CV and new leads for translational research.

Identification of DLEU2 as biomarker based on lncRNA-Mediated ceRNA network in rupture of intracranial aneurysm

Intracranial aneurysms (IA) is a potentially devastating clinical problem that may cause lethal subarachnoid hemorrhage upon rupture, but the molecular mechanisms remain further elucidated. Our goal in this work was to build the lncRNA-mediated ceRNA network in IS and explore the associated pathways and functions. The deep transcriptome sequencing dataset profile of rupture of IA and normal tissues (SRP150595) was obtained from NCBI database. To determine which genes were differently expressed, weighted gene co-expression network analysis and other integrated bioinformatics techniques were used (DEGs). The action mechanism and associated pathways of DEGs in IA were investigated using GO annotations and KEGG analysis. The Starbase database was used to build the ceRNA network. Vascular smooth muscle cells (VSMC) were used for the transwell assay and CCK-8. A total of 248 common differentially expressed-protein coding RNA and 76 DE-lncRNAs were obtained. Functional enrichment analysis indicated that the DEGs of IA are involved in pathways of inflammation and immune response. A lncRNAs-mediated ceRNA network including lncRNAs BASP1-AS1, DLEU2, LINC02035, LINC02363, MMP25-AS1, AC008771.1 was constructed. The biological behavior of VSMC was suppressed when DLEU2 was knocked down. In conclusion, a lncRNAs-mediated ceRNA network was constructed in IA based on the integrated bioinformatics analyses, in which DLEU2 was identified to be a novel and potential biomarker of IA.

Profiling of immune infiltration landscape of ruptured intracranial aneurysm

BACKGROUND

Previous research has indicated that the rupture of intracranial aneurysm (IA) is a significant contributor to mortality from stroke. The objective of this present study was to examine the infiltration patterns in ruptured intracranial aneurysm (RIA), with the aim of generating insights that could inform the development of effective immunotherapeutic approaches.

METHODS

To achieve this, we obtained Gene Expression Omnibus datasets pertaining to ruptured aneurysms, encompassing a total of 19 unruptured intracranial aneurysms (UIA) and 27 RIA. Subsequently, we conducted differential gene analysis and immune cell analysis specifically for the RIA.

RESULTS

According to the conducted studies, the analysis has identified 10 hub genes within key modules. Through the utilization of Kyoto Encyclopedia of Genes and Genomes pathway and gene ontology terms analyses, it has been established that genes exhibiting differential expression are associated with immune cell infiltration in the aneurysm wall. Furthermore, the implementation of the CIBERSORT algorithm has revealed that there are 22 distinct immune cells between RIA and tissues of UIA. IA samples contained a higher proportion of macrophages M1, mast cells resting, and CD4 naive T cells, while macrophages M0 and neutrophils were relatively lower in RIA compared with those in UIA.

CONCLUSION

The current study initially identified highly conservative hub genes and immune cell infiltration patterns in IA. Data presented in the current study improved understanding of immune genes that drive IA which can be exploited in development of effective immunotherapies.

Decoding the Cell Atlas and Inflammatory Features of Human Intracranial Aneurysm Wall by Single-Cell RNA Sequencing

BACKGROUND

Intracranial aneurysm (IA) is common and occasionally results in life-threatening hemorrhagic strokes. However, the cell architecture and inflammation in the IA dome remain less understood.

METHODS AND RESULTS

Single-cell RNA sequencing was performed on ruptured and unruptured human IA domes for delineating the cell atlas, gene expression perturbations, and inflammation features. Two external bulk mRNA sequencing-based data sets and serological results of 126 patients were collected for validation. As a result, a total of 21 332 qualified cells were captured. Vascular cells, including endothelial cells, smooth muscle cells, fibroblasts, and pericytes, were assigned in extremely sparse numbers (4.84%), and were confirmed by immunofluorescence staining. Pericytes, characterized by ABCC9 and HIGD1B, were identified in the IA dome for the first time. Abundant immune cells were identified, with the proportion of monocytes/macrophages and neutrophils being remarkably higher in ruptured IA. The lymphocyte compartment was also thoroughly categorized. By leveraging external data sets and machine learning algorithms, macrophages were robustly associated with IA rupture, irrespective of their polarization status. The single nucleotide polymorphism rs2280543, which is identified in East Asian populations, was associated with macrophage metabolic reprogramming through regulating TALDO1 expression.

CONCLUSIONS

This study provides insights into the cellular architecture and inflammatory features in the IA dome and may enlighten novel therapeutics for unruptured IA.

Transcription factor CEBPB mediates intracranial aneurysm rupture by inflammatory and immune response

INTRODUCTION

Genetic factors play a major part in mediating intracranial aneurysm (IA) rupture. However, research on the role of transcription factors (TFs) in IA rupture is rare.

AIMS

Bioinformatics analysis was performed to explore the TFs and related functional pathways involved in IA rupture.

RESULTS

A total of 63 differentially expressed transcription factors (DETFs) were obtained. Significantly enriched biological processes of these DETFs were related to regulation of myeloid leukocyte differentiation. The top 10 DETFs were screened based on the MCC algorithm from the protein-protein interaction network. After screening and validation, it was finally determined that CEBPB may be the hub gene for aneurysm rupture. The GSEA results of CEBPB were mainly associated with the inflammatory response, which was also verified by the experimental model of cellular inflammation in vitro.

CONCLUSION

The inflammatory and immune response may be closely associated with aneurysm rupture. CEBPB may be the hub gene for aneurysm rupture and may have diagnostic value. Therefore, CEBPB may serve as the diagnostic signature for RIAs and a potential target for intervention.

Vascular aneurysms in Ehlers-Danlos syndrome subtypes: A systematic review

Aneurysmal lesions are commonly seen in Ehlers-Danlos Syndrome (EDS). To better identify the regional and vessel-specific spectrum of aneurysms in different subtypes of EDS, we performed a systematic review. We searched Medline for relevant studies from 1963 to April 2022. Studies providing a report of any EDS subtype by genetic diagnosis, histologic analysis, or clinical criteria were included. A total of 448 patients from 220 studies were included. 720 vessel-specific aneurysms were reported: 386 in the abdominopelvic area, 165 in the intracranial region, 98 in the thorax, 2 in the extremities, and 6 in the venous system. In 27 out of the 65 patients with ruptured aneurysms, the ruptured aneurysm was the initial presentation. Multiple aneurysms were present in 163 out of 249 patients who had been systematically evaluated for other locations of aneurysms. The head and neck and abdominopelvic regions are two potential foci for aneurysm formation in patients with EDS. The aneurysm development in EDS is not confined to arteries; the venous system and cardiac septa may also be affected. Many patients develop multiple aneurysms, either at the time of the initial presentation or throughout their lifetime and aneurysm formation or rupture may be the first presentation of EDS.

Profiling of Circulating Gene Expression Reveals Molecular Signatures Associated with Intracranial Aneurysm Rupture Risk

BACKGROUND

Following detection, rupture risk assessment for intracranial aneurysms (IAs) is critical. Towards molecular prognostics, we hypothesized that circulating blood RNA expression profiles are associated with IA risk.

METHODS

We performed RNA sequencing on 68 blood samples from IA patients. Here, patients were categorized as either high or low risk by assessment of aneurysm size (≥ 5 mm = high risk) and Population, Hypertension, Age, Size, Earlier subarachnoid hemorrhage, Site (PHASES) score (≥ 1 = high risk). Modified F-statistics and Benjamini-Hochberg false discovery rate correction was performed on transcripts per million-normalized gene counts. Protein-coding genes expressed in ≥ 50% of samples with a q value < 0.05 and an absolute fold-change ≥ 2 were considered significantly differentially expressed. Bioinformatics in Ingenuity Pathway Analysis was performed to understand the biology of risk-associated expression profiles. Association was assessed between gene expression and risk via Pearson correlation analysis. Linear discriminant analysis models using significant genes were created and validated for classification of high-risk cases.

RESULTS

We analyzed transcriptomes of 68 IA patients. In these cases, 31 IAs were large (≥ 5 mm), while 26 IAs had a high PHASES score. Based on size, 36 genes associated with high-risk IAs, and two were correlated with the size measurement. Alternatively, based on PHASES score, 76 genes associated with high-risk cases, and nine of them showed significant correlation to the score. Similar ontological terms were associated with both gene profiles, which reflected inflammatory signaling and vascular remodeling. Prediction models based on size and PHASES stratification were able to correctly predict IA risk status, with > 80% testing accuracy for both.

CONCLUSIONS

Here, we identified genes associated with IA risk, as quantified by common clinical metrics. Preliminary classification models demonstrated feasibility of assessing IA risk using whole blood expression.

[Current Knowledge on the Genetic Analysis and Development of Medical Therapy for Intracranial Aneurysms]

Genetic studies on intracranial aneurysms(IAs), like genome-wide association studies, or studies analyzing familial intracranial aneurysms, have successfully revealed the potential contribution of a set of genes to the pathology of IAs. Some of the genes may promote the formation of IAs or the process leading to rupture of the lesions through exacerbating inflammatory responses or facilitating the degenerative changes of arterial walls. Many genes or single-nucleotide polymorphisms have been identified through extensive analyses, but they can only explain one-fifth of the IA pathology; therefore, the pathogenesis of IAs is influenced by many factors, including environmental factors, and not only genetic ones. Intriguingly, a somatic mutation in the PDGFRB gene has recently been identified in more than half of the cases with fusiform aneurysms, making the development of medical therapy targeting PDGFRβ signaling realistic. Nowadays, following a series of recent experimental studies, IA is considered a chronic inflammatory disease affecting intracranial arteries, indicating the potential of anti-inflammatory drugs as therapeutic drugs for the treatment of IAs. No wonder, recently published observational studies have revealed the preventive effect of statins and aspirin, with potent anti-inflammatory effects on the rupture of IAs.

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.

MicroRNA-513b-5p targets COL1A1 and COL1A2 associated with the formation and rupture of intracranial aneurysm

Collagen-type I alpha 1 chain (COL1A1) and COL1A2 are abnormally expressed in intracranial aneurysm (IA), but their mechanism of action remains unclear. This study was performed to investigate the mechanism of COL1A1 and COL1A2 affecting the occurrence and rupture of IA. Quantitative real-time polymerase chain reaction was used to measure the expression of hsa-miR-513b-5p, COL1A1, COL1A2, TNF-α, IL-6, MMP2, MMP3, MMP9 and TIMP4 in patients with ruptured IA (RA) (n = 100), patients with un-ruptured IA (UA) (n = 100), and controls (n = 100). Then, human vascular smooth muscle cells (HASMCs) were cultured, and dual luciferase reporter assay was performed to analyse the targeting relationship between miR-513b-5p and COL1A1 or COL1A2. The effects of the miR-513b-5p mimic and inhibitor on the proliferation, apoptosis, and death of HASMC and the RIP1-RIP3-MLKL and matrix metalloproteinase pathways were also explored. The effect of silencing and over-expression of COL1A1 and COL1A2 on the role of miR-513b-5p were also evaluated. Finally, the effects of TNF-α on miR-513b-5p targeting COL1A1 and COL1A2 were tested. Compared with those in the control group, the serum mRNA levels of miR-513b-5p, IL-6 and TIMP4 were significantly decreased in the RA and UA groups, but COL1A1, COL1A2, TNF-α, IL-1β, MMP2, MMP3 and MMP9 were significantly increased (p < 0.05). Compared with those in the UA group, the expression of COL1A1, COL1A2, TNF-α, IL-1β and MMP9 was significantly up-regulated in the RA group (p < 0.05). Results from the luciferase reporter assay showed that COL1A1 and COL1A were the direct targets of miR-513b-5p. Further studies demonstrated that miR-513b-5p targeted COL1A1/2 to regulate the RIP1-RIP3-MLKL and MMP pathways, thereby enhancing cell death and apoptosis. Over-expression of COL1A1 or COL1A2, rather than silencing COL1A1/2, could improve the inhibitory effect of miR-513b-5p on cell activity by regulating the RIP1-RIP3-MLKL and MMP pathways. Furthermore, over-expression of miR-513b-5p and/or silencing COL1A1/2 inhibited the TNF-α-induced cell proliferation and enhanced the TNF-α-induced cell death and apoptosis. The mechanism may be related to the inhibition of collagen I and TIMP4 expression and promotion of the expression of RIP1, p-RIP1, p-RIP3, p-MLKL, MMP2 and MMP9. MiR-513b-5p targeted the inhibition of COL1A1/2 expression and affected HASMC viability and extracellular mechanism remodelling by regulating the RIP1-RIP3-MLKL and MMP pathways. This process might be involved in the formation and rupture of IA.

Construction of competitive endogenous RNA network reveals regulatory role of long non-coding RNAs in intracranial aneurysm

BACKGROUND

Rupture of intracranial aneurysm (IA) is the main cause of devastating subarachnoid hemorrhage, which urges our understanding of the pathogenesis and regulatory mechanisms of IA. However, the regulatory roles of long non-coding RNAs (lncRNAs) in IA is less known.

RESULTS

We processed the raw SRR files of 12 superficial temporal artery (STA) samples and 6 IA samples to count files. Then the differentially expressed (DE) mRNAs, miRNAs, and lncRNAs between STAs and IAs were identified. The enrichment analyses were performed using DEmRNAs. Next, a lncRNA-miRNA-mRNA regulatory network was constructed using integrated bioinformatics analysis. In summary, 341 DElncRNAs, 234 DEmiRNAs, and 2914 DEmRNAs between the STA and IA. The lncRNA-miRNA-mRNA regulatory network of IA contains 91 nodes and 146 edges. The subnetwork of hub lncRNA PVT1 was extracted. The expression level of PVT1 was positively correlated with a majority of the mRNAs in its subnetwork. Moreover, we found that several mRNAs (CCND1, HIF1A, E2F1, CDKN1A, VEGFA, COL1A1 and COL5A2) in the PVT1 subnetwork served as essential components in the PI3K-Akt signaling pathway, and that some of the non-coding RNAs (ncRNAs) (PVT1, HOTAIR, hsa-miR-17, hsa-miR-142, hsa-miR-383 and hsa-miR-193b) interacted with these mRNAs.

CONCLUSION

Our annotations noting ncRNA's role in the pathway may uncover novel regulatory mechanisms of ncRNAs and mRNAs in IA. These findings provide significant insights into the lncRNA regulatory network in IA.

Pharmacological inhibition of STAT3 by BP-1-102 inhibits intracranial aneurysm formation and rupture in mice through modulating inflammatory response

As an inhibitor of STAT3, BP-1-102 can regulate the inflammation response caused by vascular smooth muscle cells (VSMCs) by inhibiting the JAK/STAT3/NF-κB pathway, thereby attenuating the symptoms of intracranial aneurysm (IA). IA mouse model was established by stereotactic injection of elastase to evaluate the effect of BP-1-102. The expression levels of smooth muscle markers and matrix metalloproteinases (MMPs) were detected by qRT-PCR, and the levels of inflammatory factors were detected by ELISA and qRT-PCR. The protein levels of the NF-κB signaling pathway factors were examined by Western blot. BP-1-102 reduced blood pressure in aneurysm mice, up-regulated smooth muscle cell markers MHC, SMA, and SM22, and down-regulated the expression of MMP2 and MMP9 in vascular tissues. At the same time, BP-1-102 also down-regulated the expression levels of inflammatory response factors and the NF-κB pathway proteins. In the IA model, BP-1-102 can reduce the expression of inflammatory factors and MMPs bound to NF-κB by inhibiting the activation of the JAK/STAT3/NF-κB pathway proteins, and then restore the vascular wall elastin to reduce blood pressure, thereby treating aneurysm.

Exosome-Derived MiRNAs as Biomarkers of the Development and Progression of Intracranial Aneurysms

AIM

Exosome-derived microRNAs (miRNAs) are potential diagnostic biomarkers. However, little is known about their effectiveness as diagnostic biomarkers of intracranial aneurysms (IAs). This study aimed to explore miRNA levels in plasma exosomes of patients with IA to identify potential biomarkers that predict the development and progress of IA.

METHODS

A total of 69 patients with IA and 30 healthy controls (HC) were recruited, among whom 30 had unruptured IA (UA), and 39 had ruptured IA (RA). The miRNA expression profiles of plasma exosomes in 12 IA patients (4 UA and 8 RA) and 4 HC were determined using next-generation sequencing. In addition, significantly differentially expressed miRNAs were further analyzed by Quantitative Real-Time PCR (qRT-PCR) in a validation cohort of 99 subjects.

RESULTS

From the sequencing analysis, 181 miRNAs were identified to be differently (p＜0.05) expressed. Of these, 9 miRNAs were up-regulated, and 20 were down-regulated in patients with UA compared with HC. Also, 21 were up-regulated, and 10 were down-regulated in patients with RA compared with HC. In addition, compared with UA, 92 miRNAs were up-regulated in RA, whereas 29 were down-regulated. Furthermore, qRT-PCR analysis confirmed that miR-145-5p and miR-29a-3p were up-regulated in IA samples. To distinguish IA patients from controls, the area under the receiver operating characteristic curve was 0.791 for miR-29a-3p, while that of miRNA-145-5p was 0.773 in terms of discriminating whether the aneurysm was ruptured.

CONCLUSIONS

Circulating exosomal miRNAs can serve as biomarkers of the development and progression of IA.

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.

Microenvironment of ruptured cerebral aneurysms discovered using data driven analysis of gene expression

BACKGROUND

It is well known that ruptured intracranial aneurysms are associated with substantial morbidity and mortality, yet our understanding of the genetic mechanisms of rupture remains poor. We hypothesize that applying novel techniques to the genetic analysis of aneurysmal tissue will yield key rupture-associated mechanisms and novel drug candidates for the prevention of rupture.

METHODS

We applied weighted gene co-expression networks (WGCNA) and population-specific gene expression analysis (PSEA) to transcriptomic data from 33 ruptured and unruptured aneurysm domes. Mechanisms were annotated using Gene Ontology, and gene network/population-specific expression levels correlated with rupture state. We then used computational drug repurposing to identify plausible drug candidates for the prevention of aneurysm rupture.

RESULTS

Network analysis of bulk tissue identified multiple immune mechanisms to be associated with aneurysm rupture. Targeting these processes with computational drug repurposing revealed multiple candidates for preventing rupture including Btk inhibitors and modulators of hypoxia inducible factor. In the macrophage-specific analysis, we identify rupture-associated mechanisms MHCII antigen processing, cholesterol efflux, and keratan sulfate catabolism. These processes map well onto several of highly ranked drug candidates, providing further validation.

CONCLUSIONS

Our results are the first to demonstrate population-specific expression levels and intracranial aneurysm rupture, and propose novel drug candidates based on network-based transcriptomics.

Patient and aneurysm characteristics in familial intracranial aneurysms. A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Patient and aneurysm characteristics have been reported to differ between patients with familial and non-familial intracranial aneurysms (IAs), although results are inconsistent. We systematically reviewed and meta-analyzed the literature to identify and quantify patient- and aneurysm characteristics associated with familial IAs.

METHODS

We searched PubMed and EMBASE for case-control and cohort studies comparing patient- and aneurysm characteristics between familial and non-familial IAs. Two observers independently assessed study eligibility and appraised quality with the Newcastle Ottawa Scale. With univariable weighted linear regression analysis we calculated β-coefficients with corresponding 95% confidence intervals (CIs) for ruptured and unruptured IAs combined and for ruptured IAs only. Heterogeneity was assessed with Higgins I2.

RESULTS

A total of 15 articles were included in the meta-analysis in which 16,346 patients were analyzed with a total of 14,225 IAs. For ruptured and unruptured IAs combined, multiple IAs were more prevalent in familial (28.5%) than in non-familial IAs (20.4%; β = 0.10, 95% CI, 0.04 to 0.16; I2 0%). For ruptured IAs only, in familial patients IAs were more prevalent on the middle cerebral artery (41.1% versus 29.5%; β = 0.12, 95% CI, 0.01 to 0.24; I2 12%) and ruptured at a younger age (46.5 years versus 50.8 years; β = -5.00, 95% CI, -9.31 to -0.69; I2 98%) than in non-familial patients. No significant differences were found for the proportion of women, size of the aneurysm at time of rupture, smoking or hypertension.

CONCLUSION

These results suggest that characteristics of familial and non-familial IAs show considerable overlap, yet differ on specific aspects. However, results for age at rupture showed considerable heterogeneity. These findings should be taken into consideration for future etiological research into IAs.

Biomarkers from circulating neutrophil transcriptomes have potential to detect unruptured intracranial aneurysms

BACKGROUND

Intracranial aneurysms (IAs) are dangerous because of their potential to rupture and cause deadly subarachnoid hemorrhages. Previously, we found significant RNA expression differences in circulating neutrophils between patients with unruptured IAs and aneurysm-free controls. Searching for circulating biomarkers for unruptured IAs, we tested the feasibility of developing classification algorithms that use neutrophil RNA expression levels from blood samples to predict the presence of an IA.

METHODS

Neutrophil RNA extracted from blood samples from 40 patients (20 with angiography-confirmed unruptured IA, 20 angiography-confirmed IA-free controls) was subjected to next-generation RNA sequencing to obtain neutrophil transcriptomes. In a randomly-selected training cohort of 30 of the 40 samples (15 with IA, 15 controls), we performed differential expression analysis. Significantly differentially expressed transcripts (false discovery rate < 0.05, fold change ≥ 1.5) were used to construct prediction models for IA using four well-known supervised machine-learning approaches (diagonal linear discriminant analysis, cosine nearest neighbors, nearest shrunken centroids, and support vector machines). These models were tested in a testing cohort of the remaining 10 neutrophil samples from the 40 patients (5 with IA, 5 controls), and model performance was assessed by receiver-operating-characteristic (ROC) curves. Real-time quantitative polymerase chain reaction (PCR) was used to corroborate expression differences of a subset of model transcripts in neutrophil samples from a new, separate validation cohort of 10 patients (5 with IA, 5 controls).

RESULTS

The training cohort yielded 26 highly significantly differentially expressed neutrophil transcripts. Models using these transcripts identified IA patients in the testing cohort with accuracy ranging from 0.60 to 0.90. The best performing model was the diagonal linear discriminant analysis classifier (area under the ROC curve = 0.80 and accuracy = 0.90). Six of seven differentially expressed genes we tested were confirmed by quantitative PCR using isolated neutrophils from the separate validation cohort.

CONCLUSIONS

Our findings demonstrate the potential of machine-learning methods to classify IA cases and create predictive models for unruptured IAs using circulating neutrophil transcriptome data. Future studies are needed to replicate these findings in larger cohorts.

Association of functional MMP-2 gene variant with intracranial aneurysms: case-control genetic association study and meta-analysis

INTRODUCTION

Abnormalities in Matrix Metalloproteinase (MMP) genes, which are important in extracellular matrix (ECM) maintenance and therefore arterial wall integrity are a plausible underlying mechanism of intracranial aneurysm (IA) formation, growth and subsequent rupture. We investigated whether the rs243865 C > T SNP (single nucleotide polymorphism) within the MMP-2 gene (which influences gene transcription) is associated with IA compared to matched controls.

MATERIALS AND METHODS

We conducted a case-control genetic association study, adjusted for known IA risk factors (smoking and hypertension), in a UK Caucasian population of 1409 patients with intracranial aneurysms (IA), and 1290 matched controls, to determine the association of the rs243865 C > T functional MMP-2 gene SNP with IA (overall, and classified as ruptured and unruptured). We also undertook a meta-analysis of two previous studies examining this SNP.

RESULTS

The rs243865 T allele was associated with IA presence in univariate (OR 1.18 [95% CI 1.04-1.33], p = .01) and in multi-variable analyses adjusted for smoking and hypertension status (OR 1.16 [95% CI 1.01-1.35], p = .042). Subgroup analysis demonstrated an association of the rs243865 SNP with ruptured IA (OR 1.18 [95% CI 1.03-1.34] p = .017), but, not unruptured IA (OR 1.17 [95% CI 0.97-1.42], p = .11).

CONCLUSIONS

Our study demonstrated an association between the functional MMP-2 rs243865 variant and IAs. Our findings suggest a genetic role for altered extracellular matrix integrity in the pathogenesis of IA development and rupture.

Circulating neutrophil transcriptome may reveal intracranial aneurysm signature

Background

Unruptured intracranial aneurysms (IAs) are typically asymptomatic and undetected except for incidental discovery on imaging. Blood-based diagnostic biomarkers could lead to improvements in IA management. This exploratory study examined circulating neutrophils to determine whether they carry RNA expression signatures of IAs.

Methods

Blood samples were collected from patients receiving cerebral angiography. Eleven samples were collected from patients with IAs and 11 from patients without IAs as controls. Samples from the two groups were paired based on demographics and comorbidities. RNA was extracted from isolated neutrophils and subjected to next-generation RNA sequencing to obtain differential expressions for identification of an IA-associated signature. Bioinformatics analyses, including gene set enrichment analysis and Ingenuity Pathway Analysis, were used to investigate the biological function of all differentially expressed transcripts.

Results

Transcriptome profiling identified 258 differentially expressed transcripts in patients with and without IAs. Expression differences were consistent with peripheral neutrophil activation. An IA-associated RNA expression signature was identified in 82 transcripts (p<0.05, fold-change ≥2). This signature was able to separate patients with and without IAs on hierarchical clustering. Furthermore, in an independent, unpaired, replication cohort of patients with IAs (n = 5) and controls (n = 5), the 82 transcripts separated 9 of 10 patients into their respective groups.

Conclusion

Preliminary findings show that RNA expression from circulating neutrophils carries an IA-associated signature. These findings highlight a potential to use predictive biomarkers from peripheral blood samples to identify patients with IAs.

Comparison between smaller ruptured intracranial aneurysm and larger un-ruptured intracranial aneurysm: gene expression profile analysis

As it grows in size, an intracranial aneurysm (IA) is prone to rupture. In this study, we compared two extreme groups of IAs, ruptured IAs (RIAs) smaller than 10 mm and un-ruptured IAs (UIAs) larger than 10 mm, to investigate the genes involved in the facilitation and prevention of IA rupture. The aneurismal walls of 6 smaller saccular RIAs (size smaller than 10 mm), 6 larger saccular UIAs (size larger than 10 mm) and 12 paired control arteries were obtained during surgery. The transcription profiles of these samples were studied by microarray analysis. RT-qPCR was used to confirm the expression of the genes of interest. In addition, functional group analysis of the differentially expressed genes was performed. Between smaller RIAs and larger UIAs, 101 genes and 179 genes were significantly over-expressed, respectively. In addition, functional group analysis demonstrated that the up-regulated genes in smaller RIAs mainly participated in the cellular response to metal ions and inorganic substances, while most of the up-regulated genes in larger UIAs were involved in inflammation and extracellular matrix (ECM) organization. Moreover, compared with control arteries, inflammation was up-regulated and muscle-related biological processes were down-regulated in both smaller RIAs and larger UIAs. The genes involved in the cellular response to metal ions and inorganic substances may facilitate the rupture of IAs. In addition, the healing process, involving inflammation and ECM organization, may protect IAs from rupture.

Twin-like appearance of an unruptured intracerebral anterior communicating artery (ACom) aneurysm in a male sibling of a patient with a ruptured ACom aneurysm

BACKGROUND

Increased risk of intracranial aneurysm rupture with subsequent subarachnoid haemorrhage (SAH) is related to several possible factors, including first-grade familial aneurysms.

METHODS AND RESULTS

Here we present a case of one ruptured and one unruptured identical twin-like anterior communicating artery (ACom) aneurysm present in two male siblings, without any proven genetic predisposition. According to evidence-based scores, aneurysm rupture risk for the younger (51 years old) sibling (with an unruptured ACom aneurysm) would be low, leaving the decision for either treatment or clinical follow-up to the discretion of the treating physician.

CONCLUSIONS

From a clinical neurosurgical perspective, however, especially since his older brother suffered an aneurysmal SAH at age 57 (i.e. 6 life-years later) from a twin-like-appearing ACom aneurysm, in our opinion rupture seems almost inevitable, thus prompting treatment at an early stage.

Whole Blood Gene Expression Profiles of Patients with a Past Aneurysmal Subarachnoid Hemorrhage

Background

The pathogenesis of development and rupture of intracranial aneurysms (IA) is largely unknown. Also, screening for IA to prevent aneurysmal subarachnoid hemorrhage (aSAH) is inefficient, as disease markers are lacking. We investigated gene expression profiles in blood of previous aSAH patients, who are still at risk for future IA, aiming to gain insight into the pathogenesis of IA and aSAH, and to make a first step towards improvement of aSAH risk prediction.

Methods and Results

We collected peripheral blood of 119 patients with aSAH at least two years prior, and 118 controls. We determined gene expression profiles using Illumina HumanHT-12v4 BeadChips. After quality control, we divided the dataset in a discovery (2/3) and replication set (1/3), identified differentially expressed genes, and applied (co-)differential co-expression to identify disease-related gene networks. No genes with a significant (false-discovery rate <5%) differential expression were observed. We detected one gene network with significant differential co-expression, but did not find biologically meaningful gene networks related to a history of aSAH. Next, we applied prediction analysis of microarrays to find a gene set that optimally predicts absence or presence of a history of aSAH. We found no gene sets with a correct disease state prediction higher than 40%.

Conclusions

No gene expression differences were present in blood of previous aSAH patients compared to controls, besides one differentially co-expressed gene network without a clear relevant biological function. Our findings suggest that gene expression profiles, as detected in blood of previous aSAH patients, do not reveal the pathogenesis of IA and aSAH, and cannot be used for aSAH risk prediction.

Molecular diagnosis in vascular Ehlers-Danlos syndrome predicts pattern of arterial involvement and outcomes

OBJECTIVE

The management of arterial pathology in individuals with vascular Ehlers-Danlos syndrome (vEDS) remains a challenge. Here we describe the correlation between COL3A1 gene mutation type and the clinical phenotype in individuals with vEDS.

METHODS

Individuals with confirmed molecular diagnoses of vEDS were enrolled in a multi-institutional natural history study. Data collected included demographics, clinical and family histories, arterial pathology (aneurysm, dissection, and rupture), operative details, and autopsy reports. Individuals were classified into two cohorts by the type of COL3A1 mutations and their effect on the amount of normal collagen produced: those with mutations that lead to minimal (MIN) production (10%-15%) of normal type III collagen and those with haploinsufficiency (HI) mutations that lead to production of 50% of the normal type III collagen.

RESULTS

A cohort of 68 individuals (72%) from 56 families had arterial pathology (44% male) with 13% HI. The HI group was older at the time of their first vascular event (mean, 42 [range, 26-58] years vs 33 [range, 8-62] years; P = .016) and had a higher incidence of aortic pathology than the MIN group (56% vs 21%; P = .025). Visceral arterial pathology was seen in 43 arteries in 23 individuals in the MIN group vs only one artery in five individuals in the HI group. Emergency surgical procedures were more likely to be undertaken when vEDS diagnosis was not known (81% vs 41%; P = .005), and 81% of these procedures were open surgical repair compared with 19% endovascular repairs (P = .019). Open and endovascular repairs were equally used in the elective setting. Postoperative complications were highest when the diagnosis of vEDS was not known (62% vs 14%; P < .001) and when procedures were undertaken in an emergency setting (5% vs 55% P < .001). Mortality due to arterial complications was 0% in the HI cohort and 21% in the MIN cohort (P = .132).

CONCLUSIONS

Arterial pathology in vEDS individuals is related to the underlying COL3A1 mutation type. The arterial pathology in individuals with HI mutations occurs at later ages with a higher incidence of aortic disease compared with other COL3A1 mutation types. Molecular diagnosis is recommended because diagnosis confirmation, appropriate surveillance, and prophylactic interventions in an elective setting improve surgical outcomes.

Gene expression analysis of ruptured and un-ruptured saccular intracranial aneurysm

BACKGROUND

Although Saccular intracranial aneurysm (sIA) is the most common type abnormality of all intracranial aneurysms, the biological mechanisms of sIA are not fully understood.

METHODS

We downloaded microarray datasets from Gene Expression Omnibus (GEO) database which includes 11 ruptured intracranial aneurysm samples and 8 unruptured intracranial aneurysm samples. Significant Analysis of Microarray (SAM) was employed to identify the differentially expressed genes (DEGs) between ruptured and unruptured intracranial aneurysms.

RESULTS

We found 2129 genes differentially expressed in rupture sIA, of which 1062 genes up-regulated and 1057 genes down-regulated. Functional analysis demonstrated these genes were significantly associated with inflammatory response, wounding response and defense response. Protein-protein interaction (PPI) analysis revealed that these genes may play important roles in the pathogenesis of sIAs. Results suggested that four transcription factors (TFs) could cooperated with each other, together with several microRNAs play roles in the pathonegensis of ruptured sIAs.

CONCLUSIONS

All of above results indicate the existence of DEGs between ruptured and unruptured sIAs, which regulating the pathogenesis of ruptured sIAs. TFs and microRNAs may also play key roles in ruptured sIAs. This research hints a new thought to the therapy of ruptured sIAs.

Comparative evaluation of genome-wide gene expression profiles in ruptured and unruptured human intracranial aneurysms

Few studies have evaluated the over or the underexpression of genes directly in samples of aneurysmal wall and extracranial pericranial vascular tissue to investigate the genetic influence in formation and rupture of intracranial aneurysms. We present the results obtained using the DNA microarray technique analysis on sample tissues collected during surgery. We collected and analyzed 12 aneurismal and 9 peripheral arteries (superficial temporal (STA) and middle meningeal artery (MMA) specimens from ruptured aneurysm group patients (13 cases), 10 aneurismal and 12 STA and MMA samples from unruptured aneurysm group patients (14 cases) and 5 STA and MMA artery specimens from control group patients (4 cases). Total RNA was isolated from samples and subjected to cDNA microarray analysis with the use of the human genome U133A GeneChip oligonucleotide microarray (Affymetrix, Santa Clara, CA), which allows to analyze a total number of 14,500 genes in the same time. For genes of interest, real-time RT-PCR was performed to confirm their expression level. Total RNA was isolated from samples and subjected to DNA microarray analysis with the use of the human genome U133A GeneChip oligonucleotide microarray, which allows to analyze a total number of 14,500 genes at the same time. For genes of interest, real-time RT-PCR was performed to confirm their expression level. Regarding ruptured aneurysms, genes were identified showing differential expressions (overexpressed or downregulated) pertaining to specific pathways, particularly those for the structural proteins of the extracellular matrix, members of matrix metalloproteinase (MMP) family (which resulted as being overexpressed) and genes involved in apoptotic phenomena. Particularly, real-time RT-PCR analysis confirmed the upregulation of MMP-2, MMP-9 and pro-apoptotic genes, such as Fas, Bax and Bid, and the downregulation of anti-apoptotic genes, such as Bcl-X(L) and Bcl-2. In a compared analyses of ruptured vs unruptured aneurysms, a different expression was also detected regarding gene coding the tissue inhibitor of matrix metalloproteinases 3 (TIMP-3), which appeared markedly downregulated in unruptured aneurysms, where its expression in unruptured aneurysms was similar to that observed in controls. Another gene differently expressed is nitric oxide synthase (iNOS), which appeared overexpressed in ruptured aneurysms when compared to unruptured aneurysms. Our study is the first, to our knowledge, that compares gene expression profiles (genoma-wide) in intracranial aneurysms. The results of our study suggest that the inhibitor of the metalloproteinase, the pathway of nitric oxide and the apoptotic process play a key-role in reducing the resistance of the arterial wall, that can result in formation and rupture of the intracranial aneurysms.

The genetics of primary haemorrhagic stroke, subarachnoid haemorrhage and ruptured intracranial aneurysms in adults

Background

The genetic basis of haemorrhagic stroke has proved difficult to unravel, partly hampered by the small numbers of subjects in any single study. A meta-analysis of all candidate gene association studies of haemorrhagic stroke (including ruptured subarachnoid haemorrhage and amyloid angiopathy-related haemorrhage) was performed, allowing more reliable estimates of risk.

Methods

A systematic review and meta-analysis of all genetic studies in haemorrhagic stroke was conducted. Electronic databases were searched until and including March 2007 for any candidate gene in haemorrhagic stroke. Odds ratio (OR) and 95% confidence intervals (CI) were determined for each gene disease association using fixed and random effect models.

Results

Our meta-analyses included 6,359 cases and 13,805 controls derived from 55 case-control studies, which included 12 genes (13 polymorphisms). Statistically significant associations with haemorrhagic stroke were identified for those homozygous for the ACE/I allele (OR, 1.48; 95% CI, 1.20–1.83; p = 0.0003) and for the 5G allele in the SERPINE1 4G/5G polymorphism (OR, 1.42; 95% CI, 1.03–1.96; p = 0.03). In addition, both &b.epsi;2 and &b.epsi;4 alleles of APOE were significantly associated with lobar haemorrhage (OR, 1.81; 95% CI, 1.26–2.62; p = 0.002 and OR, 1.49; 95% 1.08–2.05; p = 0.01 respectively). Furthermore, a significant protective association against haemorrhagic stroke was found for the factor V Leiden mutation (OR, 0.30; 95% CI, 0.10–0.87; p = 0.03).

Conclusion

Our data suggests a genetic contribution to some types of haemorrhagic stroke, with no overall responsible single gene but rather supporting a polygenic aetiology . However, the evidence base is smaller compared to ischaemic stroke. Importantly, for several alleles previously found to be associated with protection from ischaemic stroke, there was a trend towards an increased risk of haemorrhagic stroke.

[Genetic dissection of intracranial aneurysm]

Subarachnoid hemorrhage (SAH) due to rupture of an intracranial aneurysm (IA) is a devastating condition with high mortality and morbidity. Genetic as well as environment factors play important roles in the pathogenesis of SAH and IAs. We review the present knowledge on the genetic factors responsible for SAH or IAs. Linkage analysis and association study are used for genetic dissection. Genome-wide linkage analyses have specified several genetic loci for IAs and 6 loci (1p34-36, 7q11, 11q24-25, 14q22-31, 19q13, and Xp22) have been replicated in different populations. Numerous functional and/or positional candidate genes for IAs have been investigated by case-control association studies. The results of genetic association studies are modest because of small sample sizes. To date, no specific genes have been identified as responsible for IA development or rupture. Recent, large-scale genome-wide association (GWA) studies have revealed consistent and replicable genetic markers of several complex diseases such as coronary artery disease and type 2 diabetes. Although, thus far, no GWA studies have been performed for IAs, such a study may accomplish the breakthrough of genetic dissection of IAs. The identification of susceptible genes might lead to the understanding of the mechanism of IA formation or rupture and to novel therapeutic strategies.

The influence of genetics on intracranial aneurysm formation and rupture: current knowledge and its possible impact on future treatment

The etiology of intracranial aneurysm formation and rupture remains mostly unknown, but lately several studies have increasingly supported the role of genetic factors. In reports so far, genome-wide linkage studies suggest several susceptibility loci that may contain one or more predisposing genes. Depending on the examined ethnic population, several different non-matching chromosomal regions have been found. Studies of several candidate genes report association with intracranial aneurysms. To date, no single gene has been identified as responsible for intracranial aneurysm formation or rupture. In addition to the well-published environmental factors, such as alcohol intake, hypertension and smoking, only the recent progress in molecular genetics enables us to investigate the possible genetic determinants of this disease. Although a familial predisposition is the strongest risk factor for the development of intracranial aneurysms, the mode of Mendelian inheritance is uncertain in most families. Therefore, multiple genetic susceptibilities in conjunction with the environmental factors are considered to act together in the disease's etiology. Accordingly, researchers performed linkage studies and case-control association studies for the genetic analysis and have identified several genes to be susceptible to intracranial aneurysms. The identification of susceptible genes may lead to the understanding of the mechanism of formation and rupture and possibly lead to the development of a pharmacological therapy. Furthermore, should it be possible to identify a genetic marker associated with an increased risk of formation and rupture of an intracranial aneurysm, the necessity for screening and urgency of treatment could be determined more easily. In this review we summarize the current knowledge of intracranial aneurysm genetics and also discuss the method to detect the causalities. In view of the recent advances made in this field, we also give an outlook on possible future genetically engineered therapies, whose development are well underway.

Risk of intracranial aneurysm bleeding in autosomal-dominant polycystic kidney disease

Patients with autosomal-dominant polycystic kidney disease (ADPKD) carry an increased risk of developing intracranial aneurysms. Bleeding from these sites is a significant complication with the events reported to cluster in some families. In this study we determined if individualized risk of aneurysm rupture can be estimated based on family history using a Bayesian random effects model. Previously reported data were used to define distributions and to construct a model that fit these data. Our results confirm that intracerebral aneurysm bleeding in ADPKD patients tends to cluster in families and that basic family history can provide a simple estimate of family-specific risk.

Ruptured Aneurysm of the Sinus of Valsalva With Wildervanck Syndrome (Cervico-Oculo-Acoustic Syndrome), Blepharoptosis and Short Stature Case Report

A 62-year-old woman was admitted to hospital because of nausea. A grade 5/6 continuous murmur was audible near the left sternal border at the second intercostal space. Chest X-ray showed cardiomegaly and bilateral pleural effusion. She was diagnosed as heart failure and a diuretic was prescribed. After remission of the heart failure, echocardiography showed shunt flow from the right coronary cusp to the right ventricle. Aortography revealed that an aneurysm of the right coronary sinus of Valsalva had ruptured into the right ventricle. Coronary angiography revealed a single coronary artery. Chest computed tomography revealed persistent left superior vena cava. Surgical repair was carried out and the patient made an uneventful recovery. In addition to these cardiovascular abnormalities, she had Wildervanck syndrome (Klippel-Feil syndrome, Duane syndrome and sensorineural hearing disturbance), blepharoptosis and short stature. This rare combination has not been reported previously.

Using endothelial nitric oxide synthase gene polymorphisms to identify intracranial aneurysms more prone to rupture in Japanese patients

Object

Recent investigators found that the presence of three tandem polymorphisms of the endothelial nitric oxide synthase (eNOS) gene—promoter single nucleotide polymorphism (SNP) T-786C, intron-4 27-bp variable number of tandem repeats, and the G894T SNP in exon 7—was indicative of intracranial aneurysms more prone to rupture in a Caucasian patient sample. In the present study, the authors sought to determine whether the presence of these eNOS polymorphisms could indicate which Japanese patients with aneurysms were more endangered by a subarachnoid hemorrhage (SAH).

Methods

The three eNOSpolymorphisms were genotyped in 297 patients with ruptured aneurysms (RAs), 108 patients with unruptured aneurysms (UAs), and 176 healthy volunteers by using polymerase chain reaction.

The distribution of the variant alleles did not differ significantly (p > 0.05) between the RA group and the UA group. The frequency of the corresponding genotypes between the two groups and a haplotype analysis did not show any significant differences. Further comparisons of the RA and UA groups with the control group did not yield any significant allele or genotype frequency differences.

Conclusions

These data show that the examined set of eNOS polymorphisms were not indicative of which Japanese patients with intracranial aneurysms would suffer an SAH. The presence of eNOS polymorphisms is not useful in identifying intracranial aneurysms that are more prone to rupture in a Japanese patient sample.

The alanine/threonine polymorphism of the alpha-1-antichymotrypsin (SERPINA3) gene and ruptured intracranial aneurysms in the Japanese population

BACKGROUND

Serine protease inhibitor member 3 of clade A (SERPINA3), also known as alpha-1-antichymotrypsin, inhibits the activity of cathepsin G. The release of neutrophil cathepsin G (proteolytic enzyme) can destroy the vascular matrix through degradation, platelet aggregation and coagulation disorders. In a previous report there was evidence that an alanine/threonine polymorphism was associated with the risk factor for aneurysmal subarachnoid hemorrhage (SAH) in a Polish population. We performed this study to determine whether this A15T polymorphism shows the same association in a Japanese population.

METHODS

A total of 437 patients with an aneurysmal SAH and 405 control cases of Japanese origin were genotyped for the A15T polymorphism and 2 further intronic single nucleotide polymorphisms by using polymerase chain reaction and direct sequencing.

RESULTS

In the patients with intracranial aneurysms the SERPINA3 A15T allele and genotype distribution did not differ significantly from the controls.

CONCLUSION

In the Japanese population the A15T polymorphism of the SERPINA3 gene is not associated with aneurysmal SAH.

Ruptured intracranial aneurysm associated with von Hippel-Lindau syndrome: a molecular link?

OBJECT

Research into the etiopathogenesis of intracranial aneurysms has failed to demonstrate molecular markers or pathognomonic genetic sequences. The authors describe the case of aneurysmal rupture in a patient with von Hippel-Lindau (VHL) syndrome and explore a possible molecular link.

METHODS

A 17-year-old girl underwent endovascular coiling for an aneurysmal subarachnoid hemorrhage. Six years later, she developed spinocerebellar hemangioblastomas. Gene sequencing revealed a heterozygous, germline point mutation at nucleotide 469 in the VHL locus on chromosome 3. The mutation changed a codon for proline (CCC) to one for serine (TCC) at amino acid position 86.

CONCLUSIONS

The VHL tumor suppressor gene may be causally related to aneurysm formation through the effects of transcription factors, growth factors, and matrix metalloproteinases. Although a single point mutation is unlikely to be responsible for the complex phenotype of intracranial aneurysm, further research on aneurysmal domes and VHL gene expression may help validate the theory that extracellular matrix destruction is the final common pathway to aneurysm formation.

The presence of tandem endothelial nitric oxide synthase gene polymorphisms identifying brain aneurysms more prone to rupture

Object. It is becoming apparent that the presence of certain genetic variations (polymorphisms) may increase the individual's susceptibility to cardiovascular diseases, even in the absence of a family history. We hypothesized that brain aneurysms more prone to rupture may be identified on the basis of an individual's genotype for endothelial nitric oxide synthase (eNOS), a critical vasomodulatory protein found to be increasingly relevant to the pathobiology of aneurysms.

Methods. Patients' clinical data were recorded prospectively. Genomic DNA was isolated from blood samples obtained from individuals presenting consecutively to the Mayo Clinic with ruptured (58 patients) or unruptured (49 patients) intracranial saccular aneurysms. Using polymerase chain reaction and gene microarray technology, the following eNOS genetic polymorphisms were studied: intron-4 27—base pair variable number of tandem repeats (27 VNTR); promoter single nucleotide polymorphism (T-786C SNP); and exon-7 SNP (G894T SNP).

Both groups of patients had similar demographic and clinical characteristics. For all three polymorphisms, variant alleles (p ≤ 0.003) and their corresponding genotypes (p ≤ 0.006) were found two to four times more frequently in patients with ruptured aneurysms than in patients with unruptured aneurysms. Strikingly, the odds ratio for presenting with a ruptured brain aneurysm among individuals demonstrating the copresence of all three variant alleles was 11.4 (95% confidence interval 1.7–75.9, p = 0.004).

Conclusions. The authors have uniquely identified a set of tandem eNOS gene variations whose presence can be used to identify patients with aneurysms likely to rupture. We believe that if this finding is reproducible in a large multicenter study, in addition to known anatomical factors a rapid and cost-effective screening tool will become available to clinicians as a genetic aid to predict the risks of rupture in patients presenting with unruptured intracranial aneurysms.

Genetic risk factor characterizes abdominal aortic aneurysm from arterial occlusive disease in human beings: CCR5 Delta 32 deletion

OBJECTIVE

Inflammation is involved in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA), and chemokines are mediators of the inflammatory process. The homozygous Delta 32 deletion mutation of the gene of the chemokine receptor CCR5 is a cause of its lack in inflammatory cells. The purpose of this study was to investigate the relationship between CCR5 Delta 32 deletion mutation and AAA, peripheral arterial occlusive disease (PAOD), and carotid stenosis.

METHODS

The CCR5 Delta 32 polymorphism was genotyped in 380 subjects: 70 patients operated on to treat AAA (21 ruptured AAAs, 49 elective repair), 76 patients with PAOD, 62 patients with carotid stenosis, and 172 age-matched and sex-matched healthy control subjects. Risk factors for AAA were considered. Each patient was assessed according to a diagnostic procedure tailored to symptoms at presentation.

RESULTS

In patients with AAA the Delta allelic variation was significantly different compared with control subjects (P = .002; odds ratio [OR], 2.7; 95% confidence interval [CI], 1.41-5.15). The increased presence of this allele differentiates AAA from both PAOD (P = .017; OR, 2.77; 95% CI, 1.17-6.52) and carotid stenosis (P = .01; OR, 3.47; 95% CI, 1.31-9.11). The presence in the genotype of patients with AAA of at least 1 Delta 32 allele is more frequent in ruptured AAAs than in electively repaired AAAs (genotype: OR, 4.04; 95% CI, 1.34-12.1; P = .011; allelic frequency: OR, 2.75; 95% CI, 1.07-7.07; P = .035). Among the patients, multiple regression analysis showed that the Delta 32 allele is an independent risk factor for AAA vs PAOD (OR, 3.13; 95% CI, 1.33-7.33; P = .012) and for ruptured AAAs vs electively repaired AAAs (OR, 3.52; 95% CI, 1.01-11.80; P = .045).

CONCLUSIONS

CCR5 Delta 32 deletion mutation is significantly more frequent in patients with AAA than in control subjects and in both patients with PAOD and carotid stenosis, and could be a factor that differentiates AAA from PAOD, and ruptured AAAs from AAAs that can be electively repaired.

CLINICAL RELEVANCE

The major threat of abdominal aortic aneurysm (AAA) is rupture, accounting for extremely high mortality. This occurrence has been correlated to aneurysm size, but it is a common observation that small AAAs can rupture and large AAAs can remain stable for many years. This study was carried out in an attempt to search for genetic markers of aneurysm rupture. Some single nucleotide polymorphisms are implicated in acceleration of transcription for enzymes involved in the inflammatory process and in extracellular matrix remodeling. An association between single nucleotide polymorphisms and aneurysm rupture could enable better selection for surgical indications in patients with small AAs and in patients at poor risk with large AAAs.

Update on genetic evidence for rupture-prone compared with rupture-resistant intracranial saccular aneurysms

Object

Anecdotal evidence exists for at least two subpopulations of intracranial saccular aneurysms; those that form rapidly and rupture when small and those that enlarge slowly and are particularly prone to rupture when they are 10 mm or more in diameter. The goal in this study was to determine if there was genetic evidence to support the classification of intracranial saccular aneurysms as “rupture-prone” or “rupture-resistant” lesions.

Methods

The authors prospectively obtained and analyzed clinical and genetic data in a cohort of 197 individuals composed of 58 patients with ruptured intracranial saccular aneurysms, 49 with unruptured aneurysms, and 90 healthy community volunteers. Based on recent studies supporting an increasingly relevant role for the critical vasomodulatory protein endothelial nitric oxide synthase (eNOS) in aneurysm pathobiology, the authors assayed blood from all 197 participants to determine and compare their eNOS genotypes.

TheeNOSgene intron 4 27–base pair variable-number tandem-repeat polymorphism was significantly overrepre-sented in persons with ruptured intracranial saccular aneurysms compared with community volunteers (p <0.002). When comparing eNOS genotypes among patients with ruptured or unruptured aneurysms, an approximately 10-fold increase in the odds of presenting with brain aneurysm rupture was found among individuals with multiple variant eNOS alleles (p = 0.004).

Conclusions

Uniquely, the authors have identified a set ofeNOSgene variations whose presence indicates patients with intracranial saccular aneurysms that are more prone to rupture. The authors conclude that if these findings are reproducible in the setting of a large multicenter study, then in addition to known anatomical factors, a rapid and cost-effective genetic screening tool will become available to clinicians as an aid to predicting rupture risks in patients presenting with unruptured intracranial aneurysms.

[Cerebral aneurysms in identical twins]

The hypothesis that genetic factors play a role in the genesis of cerebral aneurysms may be supported by clinical analysis of cerebral aneurysms in identical twins. In addition to reporting the present case, we review the literature on clinical features and genetical considerations in this matter. A forty-two-year-old male presented with subarachnoid hemorrhage (SAH) due to a left MCA aneurysm. At the age of 39, his identical twin brother also had SAH due to a ruptured left MCA aneurysm. This identical twin brother and his father's sisters died of SAH. Venous blood of the patient and his parents was collected to determine apolipoprotein E, angiotensinogen, angiotensin-converting enzyme, and very low density lipoprotein receptor genes. This analysis suggested a strong genetic association of apolipoprotein E epsilon4 with the pathogenesis. Including our cases, 13 cases of cerebral aneurysms in identical twins have been reported. There was a total of 37 aneurysms. Six twins had the same sites of aneurysm. These aneurysms show a tendency to be small in size, and to cause a high frequency of SAH occurring at a similar age. In young adults, cerebral aneurysms in identical twins tend to rupture. A screening diagnosis should be carried out as early as possible on an asymptomatic twin when the other has been discovered to have a ruptured cerebral aneurysm. Preventive treatment and systemic genome-wide linkage study should be conducted.

II Genotype of the Angiotensin-Converting Enzyme Gene Increases the Risk for Subarachnoid Hemorrhage From Ruptured Aneurysm

BACKGROUND AND PURPOSE

Evidence exists in support of a role of genetic factors in susceptibility to aneurysmal subarachnoid hemorrhage (SAH) in humans. Meta-analysis of 2 previous studies showed that the I allele of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism was a weak, but significant, risk factor for aneurysmal SAH. Moreover, a recent study has shown that the local renin-angiotensin system (RAS) is involved in the development of intracranial aneurysm. The aim of this study was to investigate the association between ACE I/D polymorphism and a risk for aneurysmal SAH in a Polish population.

METHODS

Ninety patients with aneurysmal SAH (mean age: 48.9+/-14.0 years) and 128 healthy controls matched for age and sex were genotyped for the ACE I/D polymorphism. Aneurysmal SAH was diagnosed by cranial computed tomography and/or lumbar puncture and digital subtraction angiography. ACE gene polymorphism was detected by polymerase chain reaction amplification of the intron 16-specific I/D fragments, 490-bp and 190-bp, respectively.

RESULTS

The ACE genotype distribution in patients with aneurysmal SAH (II, 52.2%; ID, 15.6%; DD, 32.2%) differed significantly from controls (II, 23.4%; ID, 50.8%; DD, 25.8%) (P<0.001). A logistic regression model showed that the II genotype of ACE gene was independent from female sex and smoking as a risk factor for aneurysmal SAH (OR, 4.57; 95% CI, 2.35 to 8.90).

CONCLUSIONS

Here we report that II genotype of ACE gene is a risk factor for aneurysmal SAH.

Endothelial Nitric Oxide Synthase T-786C Single Nucleotide Polymorphism

Background and Purpose— Anecdotal evidence exists for at least 2 subpopulations of intracranial saccular aneurysms, namely, those that may form rapidly and rupture when small versus those that enlarge slowly and may rupture particularly when ≥10 mm in diameter. We sought to determine whether the endothelial nitric oxide synthase (eNOS) T-786C single nucleotide polymorphism (SNP), implicated in cardiovascular disease susceptibility, could facilitate differentiation between small (≤5 mm) versus large (≥10 mm) ruptured aneurysms.

Methods— In accordance with institutional guidelines, clinical data were recorded prospectively and genomic DNA was isolated from blood samples obtained from 52 aneurysmal subarachnoid hemorrhage (SAH) patients (cases) and 90 randomly selected controls. Samples were assayed for eNOS gene promoter T-786C SNP with the use of gene microarray technology. Statistical analyses included multiple logistic regression.

Results— Although there was no difference in genotype distributions between cases and controls, all 13 patients with large aneurysms were ( T / C ) heterozygous for the polymorphism, while 9 of 22 patients (41%) with small aneurysms were ( T / T or C / C ) homozygous ( P =0.01). The mean (±SD) ruptured aneurysm diameter among all heterozygotes (8.5±5.2 mm) was significantly greater than that for C / C (6.0±2.3 mm) or T / T (4.7±1.8 mm) homozygotes ( P =0.04). With the use of multivariate analysis, heterozygosity remained significantly associated with aneurysm size ≥10 mm ( P =0.03).

Conclusions— The eNOS T-786C SNP distinguishes genetically between small and large ruptured aneurysms. Although not predictive of SAH in the population at large, our data suggest that among persons with known intracranial aneurysms, eNOS T-786C genotype may be a factor influencing the size at which an aneurysm ruptures, a finding that should be taken into consideration along with other anatomic features of the aneurysm.

Can genetic material retrotransposition be a cause of pathology accompanying cerebral aneurysm rupture?

Our considerations were prompted by observation of patients who underwent surgery due to cerebral aneurysm rupture. Elevated anti-HIV antibody titers were detected in such patients. The above condition was not observed either in subjects with intracranial hemorrhages from cerebral angiomas. The observed titers remained certainly below the cut off level indicating contact with HIV. We analyzed the subpopulations of peripheral blood lymphocytes both in the surgery patients and in the control group represented by blood collected from blood donors. On the other hand, the proliferation potential of circulating lymphocytes in the blood of patients with subarachnoid hemorrhages due to cranial aneurysm ruptures was found to be decreased. Dislocation of transposons, so-called 'unauthorized recombination' is known to occur within the framework of genetic code pathology. Endogenous human viruses have been described, and they may be involved in the development of autoimmune disorders. Additionally, viruses involved in autoimmune processes, which may be 'identical' with retrotransposons, have been described. Moreover, there are studies demonstrating that AIDS is caused by retrotransposition of genetic code material fragments. Our considerations are substantiated by ultrastructural analyses of material coming from the gyrus rectus cortex fragments, resected in patients who underwent clipping of a ruptured aneurysm of the anterior communicating artery. We demonstrated in neuronal chromatin the presence of a molecule ca. 80 nm in diameter, corresponding with its size to retroviruses or genetic material molecules with altered substructure. The authors suggest a new mechanism of development of neurological deficits in patients with ruptured cerebral aneurysms.

The role of cytokine gene polymorphisms in the pathogenesis of abdominal aortic aneurysms: a case-control study

BACKGROUND

Cytokines are the primary mediators of inflammation and also influence matrix metalloproteinase expression, both of which are important in development of abdominal aortic aneurysm (AAA). A significant, but as yet unknown, familial factor contributes to the pathogenesis of AAA. Many cytokine genes contain polymorphic sites, some of which affect cytokine production in vitro. Cytokine gene polymorphisms may therefore influence the pathogenesis of AAA. The purpose of this study was to determine whether there is any association between cytokine gene polymorphisms and AAA.

METHODS AND RESULTS

This case-control study comprised 100 patients with AAA and 100 age-matched and sex-matched control subjects. For each case and control subject in the study, genotypes at the following cytokine gene polymorphic loci were determined: interleukin (IL)-1beta +3953, IL-6 -174, IL-10 -1082, IL-10 -592, and tumor necrosis factors-alpha -308. Allele and genotype frequencies were compared between AAA and control groups, and odds ratios (OR) were calculated for the presence of AAA with each allele at each locus examined as risk factors. The IL-10 -1082 A allele was significantly more common in the AAA group than the control group (P =.03). The OR for the IL-10 -1082 A allele as a risk factor for AAA was 1.8 (95% confidence interval, 0.9-3.6).

DISCUSSION

These associations suggest a significant role for IL-10 in the pathogenesis of AAA. This association of AAA with the IL-10 -1082 A allele is also biologically plausible; the IL-10 -1082 A allele is associated with low IL-10 secretion, and it may be that AAA develops in patients who are unable to mount the same anti-inflammatory response as those who do not have AAA.

Familial aggregation of intracranial aneurysms in an Inuit patient population in Kalaallit Nunaat (Greenland)

OBJECTIVE

The incidence of subarachnoid hemorrhage (SAH) and intracranial aneurysm (IA) has been reported to be higher in Greenlandic Inuits than in Caucasian Danes, but the rate of familial aggregation in Inuits is unknown.

METHODS

This study retrospectively compared the rate of familial aggregation of SAH and IA (at least one first- or second-degree relative with presumed SAH and/or IA) in 120 Inuit patients from Greenland admitted to the Copenhagen University Hospital in Copenhagen, Denmark, from 1978 to 1998 with a diagnosis of ruptured IA with that in 1,037 Caucasian Danes admitted from 1978 to 1983.

RESULTS

Inuit patients had a much higher rate of familial history of SAH (23.1%) and of IA (9.6%) than Danish patients (4.3 and 1.6%, respectively). In both populations, familial SAH was associated with lower age at the time of aneurysm rupture. Danish patients with familial SAH showed a higher rate of middle cerebral artery aneurysms (40 versus 26% in sporadic SAH). In Inuit patients with familial and nonfamilial SAH, 42 and 38% of the aneurysms originated from the middle cerebral artery. The overall rate of multiple aneurysms was highest among Inuits, and in both populations, it was increased in the presence of a positive family history.

CONCLUSION

The rate of a positive family history of presumed SAH and IA is high among Inuits who present with SAH compared with Caucasian Danes who present with SAH. This finding, coupled with a higher rate of multiple aneurysms and younger age at presentation, suggests a potential genetic influence among Inuit families.

Familial clustering of ruptured intracranial aneurysms in autosomal dominant polycystic kidney disease

Ruptured intracranial aneurysm (RICA) is a life-threatening complication of autosomal dominant polycystic kidney disease (ADPKD). A family history of RICA may be a risk factor for RICA. Six hundred eight adult members of 199 ADPKD families were interviewed, and family pedigrees were constructed. Individuals were classified as having definite, probable, or possible RICAs from evidence and history obtained in interviews. Central nervous system (CNS) events not consistent with RICA were classified as other CNS events. Seventy-seven CNS events occurred in 906 subjects with ADPKD (8.5%) versus 13 events in 823 subjects without ADPKD (1.6%; P < 0.0001). No event in subjects without ADPKD was consistent with an RICA. Twenty-seven other (non-RICA) CNS events occurred in subjects with ADPKD (3%) versus 13 events in subjects without ADPKD (1.6%; P = 0.05). The frequency of RICA was increased in subjects with ADPKD: 21 definite RICAs in subjects with ADPKD (2%) versus none in subjects without ADPKD (P < 0.001); 28 definite and probable RICAs in subjects with ADPKD (3%) versus none in subjects without ADPKD (P < 0.001); and 50 definite, probable, and possible RICAs in subjects with ADPKD (5.5%) versus none in subjects without ADPKD (P < 0.001). The null hypothesis that RICAs are randomly distributed among subjects with ADPKD was tested for definite RICAs (n = 21), definite and probable RICAs (n = 28), and definite, probable, and possible RICAs (n = 50). In the three categories, the null hypothesis was rejected at P less than 0.05, P less than 0.05, and P less than 0.005, respectively. Vascular CNS events occurred more frequently in ADPKD than non-ADPKD family members, and clustering of RICAs occurred in families with ADPKD.

The ACE I allele is associated with increased risk for ruptured intracranial aneurysms

Genetic and environmental factors play roles in the aetiology of ruptured intracranial aneurysms. Hypertension has been reported as a risk factor for intracranial aneurysm haemorrhage. We have tested if genotypes at the angiotensin converting enzyme (ACE) gene locus are associated with ruptured intracranial aneurysms. The insertion/deletion polymorphism in the ACE gene was genotyped in 258 subjects presenting in East Anglia with ruptured intracranial aneurysms (confirmed at surgery or angiographically) and 299 controls from the same region. ACE allele frequencies were significantly different in the cases and the controls (alleles chi(2)(1)=4.67, p=0.03). The I allele was associated with aneurysm risk (odds ratio for I allele v D allele = 1.3 (95% CI=1.02-1-65); odds ratio for II v DD genotype = 1.67 (95% CI=1.04-2.66)). The I allele at the ACE locus is over-represented in subjects with ruptured intracranial aneurysms. These data are supported by non-significant trends in the same direction in two previous smaller studies. Thus, this allele may be associated with risk for ruptured intracranial aneurysms.

Clinical features of intracranial aneurysms in siblings

OBJECTIVE

Among the family members of patients with aneurysmal subarachnoid hemorrhage (SAH), siblings have been documented to be at high risk of SAH and to have a high prevalence of unruptured aneurysms. We studied the distinctive features of aneurysms in siblings and attempted to determine the risk of rupture.

METHODS

We analyzed detailed data on 159 patients with siblings who had ruptured and unruptured aneurysms in 77 families from throughout Japan.

RESULTS

Seventy-three percent of the patients were female, and the mean age at the time of rupture was 55.6 years. In 39 families, two or more siblings had SAH. Eighty of 107 patients with ruptured aneurysms and 28 of 52 with unruptured aneurysms had a family history of SAH in siblings (P = 0.0082). Multiple and mirror-image aneurysms were found in 42 and 21 patients, respectively. Among 218 aneurysms, middle cerebral artery aneurysms were the most common type (43%). Anterior communicating artery aneurysms were underrepresented (15%). There were significantly more ruptured than unruptured anterior communicating artery aneurysms, compared with other aneurysms (P = 0.01).

CONCLUSION

The clinical features of aneurysms in siblings in this population agreed well with those reported for familial intracranial aneurysms and SAH, except for the age at the time of rupture. It is suggested that the risk of rupture is greater when patients with unruptured aneurysms have siblings with aneurysmal SAH and/or anterior communicating artery aneurysms.