Inflammation and intracranial aneurysms

Aneurysmal Wall Enhancement of Non-Ruptured Intracranial Aneurysms after Endovascular Treatment Correlates with Higher Aneurysm Reperfusion Rates, but Only in Large Aneurysms

INTRODUCTION

Aneurysmal wall enhancement (AWE) of non-ruptured sacular intracranial aneurysms (IA) after endovascular treatment (ET) is a frequently observed imaging finding using AWE-sequences in brain magnetic resonance imaging (MRI). So far, its value remains unclear. We aimed to investigate the effect of AWE on aneurysm reperfusion rates in a longitudinal cohort.

METHODS

This is a retrospective MRI study over the timespan of up to 5 years, assessing the correlation of increased AWE of non-ruptured IAs and events of aneurysm reperfusion and retreatment, PHASES Score and grade of AWE. T1 SPACE fat saturation (FS) and T1 SE FS blood suppression sequences after contrast administration were used for visual interpretation of increased AWE. The IAs' sizes were assessed via the biggest diameter. The grade of enhancement was defined in a grading system from grade 1 to grade 3.

RESULTS

127 consecutive non ruptured IA-patients (58.9 ± 9.0 years, 94 female, 33 male) who underwent elective aneurysm occlusion were included. AWE was observed in 40.2% of patients (51/127) after ET, 6 patients already showed AWE before treatment. In large IAs (which were defined as a single maximum diameter of over 7.5 mm), AWE was significantly associated with aneurysm reperfusion in contrast to large aneurysm without AWE). All grades of AWE were significantly associated with reperfusion.

CONCLUSIONS

Our data suggests that in patients with initially large IAs, AWE is correlated with aneurysm reperfusion.

The relationship between autoimmune disorders and intracranial aneurysms in East Asian and European populations: a bidirectional and multivariable two-sample Mendelian randomization study

Background

It remains unclear about the pathogenesis of intracranial aneurysms (IAs) in the setting of autoimmune disorders (ADs). However, the underlying systemic inflammatory characteristics of ADs may affect IAs through shared inflammatory pathways. Therefore, this study was conducted to explore the relationship between ADs and IAs and assess causal effects.

Methods

In this study, 6 common ADs were included to explore their causal relationship with IAs. Besides, a bidirectional two-sample univariable Mendelian randomization (UVMR) analysis was performed. In addition, the primary analysis was performed by the inverse variance weighted (IVW) and Bayesian weighted Mendelian randomization (BWMR) method, and a series of sensitivity analyses were performed to assess the robustness of the results. Further, the data related to ADs and IAs were collected from open genome-wide association study studies (GWASs) and the Cerebrovascular Disease Knowledge Portal (CDKP) (including 11,084 cases and 311,458 controls), respectively. These analyses were conducted based on both the East Asian and European populations. Moreover, 6 ADs were subject to grouping according to connective tissue disease, inflammatory bowel disease, and thyroid disease. On that basis, a multivariate MR (MVMR1) analysis was further performed to explore the independent causal relationship between each AD and IAs, and an MVMR 2 analysis was conducted to investigate such potential confounders as smoking, alcohol consumption, and systolic blood pressure. Finally, these results were verified based on the data from another GWAS of IAs.

Results

The UVMR analysis results demonstrated that systemic lupus erythematosus (SLE) was associated with a high risk of IAs in the East Asian population (IVW OR, 1.06; 95%CI, 1.02-1.11; p = 0.0065, UVMR), which was supported by the results of BWMR (OR, 1.06; 95%CI, 1.02-1.11; p = 0.0067, BWMR), MVMR1 (OR, 1.06; 95%CI, 1.01-1.10; p = 0.015, MVMR1), MVMR2 (OR, 1.05; 95%CI, 1.00-1.11; p = 0.049, MVMR2), and sensitivity analyses. The results in the validation group also suggested a causal relationship between SLE and IAs (IVW OR, 1.04; 95% CI, 1.00-1.09; p = 0.046). The reverse MR analysis results did not reveal a causal relationship between IAs and ADs.

Conclusion

In this MR study, SLE was validated to be a risk factor for IAs in the East Asian population. Therefore, the management of IAs in patients with SLE should be highlighted to avoid stroke events.

Role of inflammatory mediators in intracranial aneurysms: A review

The formation, growth, and rupture of intracranial aneurysms (IAs) involve hemodynamics, blood pressure, external stimuli, and a series of hormonal changes. In addition, inflammatory response causes the release of a series of inflammatory mediators, such as IL, TNF-α, MCP-1, and MMPs, which directly or indirectly promote the development process of IA. However, the specific role of these inflammatory mediators in the pathophysiological process of IA remains unclear. Recently, several anti-inflammatory, lipid-lowering, hormone-regulating drugs have been found to have a potentially protective effect on reducing IA formation and rupture in the population. These therapeutic mechanisms have not been fully elucidated, but we can look for potential therapeutic targets that may interfere with the formation and breakdown of IA by studying the relevant inflammatory response and the mechanism of IA formation and rupture involved in inflammatory mediators.

Histopathological analysis of the wall enhancement of the spinal dural arteriovenous fistulae's draining veins

OBJECTIVE

The mechanism behind SDAVF is still unclear. We discovered that the vessel wall of the SDAVF-DV occasionally showed enhancement in MRI, and this study assessed the relationship between the enhancement of the draining vein's wall and its histology.

METHODS

For histopathologic analysis, 16 draining vein samples from 16 patients with SDAVF were included, 3 normal arteries and 3 normal veins were chosen as comparison. We assessed the imaging and microscopic characteristics of the draining veins in SDAVF patients. The former included the presence of significant enhancement of the wall of the draining vein in MRI, and the latter included the adherence, aggregation, infiltration of pro-inflammatory factors and inflammatory cells. Immuno-histochemical staining was performed using IL-1β, IL-8, TGF-β as well as MPO and MMP-9, and positive results were counted. Multiple logistic regression analysis was used to determine whether the infiltration of inflammatory cells was connected to vessel wall enhancement in the SDAVF-DV.

RESULTS

Infiltration of inflammatory cells was significantly higher in SDAVF-DV compared to normal vessels, 7 out of 16 patients significantly had enhancement of the vessel wall of SDAVF-DV, and logistic regression analysis showed that samples with more infiltration of inflammatory cells were more likely to show enhancement of the SDAVF-DV walls.

CONCLUSION

There was considerable inflammatory cells infiltration in SDAVF-DV, and this may explain why their vessel wall had such a significant enhancement in MRI.

The association between hematologic traits and aneurysm-related subarachnoid hemorrhage: a two-sample mendelian randomization study

Several hematologic traits have been suggested to potentially contribute to the formation and rupture of intracranial aneurysms (IA). The purpose of this study is to explore the causal association between hematologic traits and the risk of IA. To explore the causal association between hematologic traits and the risk of IA, we employed two-sample Mendelian randomization (MR) analysis. Two independent summary-level GWAS data were used for preliminary and replicated MR analyses. The inverse variance weighted (IVW) method was employed as the primary method in the MR analyses. The stabilities of the results were further confirmed by a meta-analysis. In the preliminary MR analysis, hematocrit, hemoglobin concentration (p = 0.0047), basophil count (p = 0.0219) had a suggestive inverse causal relationship with the risk of aneurysm-associated subarachnoid hemorrhage (aSAH). The monocyte percentage of white cells (p = 0.00956) was suggestively positively causally correlated with the risk of aSAH. In the replicated MR analysis, only the monocyte percentage of white cells (p = 0.00297) remained consistent with the MR results in the preliminary analysis. The hematocrit, hemoglobin concentration, and basophil count no longer showed significant causal relationship (p > 0.05). Meta-analysis results further confirmed that only the MR result of monocyte percentage of white cells reached significance in the random effect model and fixed effect model. None of the 25 hematologic traits was causally associated with the risk of unruptured intracranial aneurysms (uIA). This study revealed a suggestive positive association between the monocyte percentage of white cells and the risk of aSAH. This finding contributes to a better understanding that monocytes/macrophages could participate in the risk of aSAH.

MR Imaging of the Cerebral Aneurysmal Wall for Assessment of Rupture Risk

The evaluation of unruptured intracranial aneurysms requires a comprehensive and multifaceted approach. The comprehensive analysis of aneurysm wall enhancement through high-resolution MRI, in tandem with advanced processing techniques like finite element analysis, quantitative susceptibility mapping, and computational fluid dynamics, has begun to unveil insights into the intricate biology of aneurysms. This enhanced understanding of the etiology, progression, and eventual rupture of aneurysms holds the potential to be used as a tool to triage patients to intervention versus observation. Emerging tools such as radiomics and machine learning are poised to contribute significantly to this evolving landscape of diagnostic refinement.

Factors associated with early-onset intracranial aneurysms in patients with autosomal dominant polycystic kidney disease

BACKGROUND

Recently, the importance of attribute-based medicine has been emphasized. The effects of early-onset intracranial aneurysms on patients can be significant and long-lasting. Herein, we compared the factors associated with intracranial aneurysms in patients with autosomal dominant polycystic kidney disease (ADPKD) according to age categories (≥ 50 years, < 50 years).

METHODS

We included 519 ADPKD patients, with a median age of 44 years, estimated glomerular filtration rate of 54.5 mL/min/1.73 m2, and total follow-up duration of 3104 patient-years. Logistic regression analyses were performed to determine factors associated with intracranial aneurysms.

RESULTS

Regarding the presence of intracranial aneurysm, significant interactions were identified between the age category (age ≥ 50 years), female sex (P = 0.0027 for the interaction) and hypertension (P = 0.0074 for the interaction). Female sex and hypertension were associated with intracranial aneurysm risk factors only in patients aged ≥ 50 years. The presence of intracranial aneurysm was significantly associated with chronic kidney disease (CKD) stages 4-5 (odds ratio [OR] = 3.87, P = 0.0007) and family history of intracranial aneurysm or subarachnoid hemorrhage (OR = 2.30, P = 0.0217) in patients aged < 50 years. For patients aged ≥ 50 years, in addition to the abovementioned factors [OR = 2.38, P = 0.0355 for CKD stages 4-5; OR = 3.49, P = 0.0094 for family history of intracranial aneurysm or subarachnoid hemorrhage], female sex (OR = 4.51, P = 0.0005), and hypertension (OR = 5.89, P = 0.0012) were also associated with intracranial aneurysm.

CONCLUSION

Kidney dysfunction and family history of intracranial aneurysm or subarachnoid hemorrhage are risk factors for early-onset intracranial aneurysm. Patients aged < 50 years with a family history of intracranial aneurysm or subarachnoid hemorrhage or with CKD stages 4-5 may be at an increased risk of early-onset intracranial aneurysm.

Changes in Adhesion and the Expression of Adhesion Molecules in PBMCs after Aneurysmal Subarachnoid Hemorrhage: Relation to Cerebral Vasospasm

Aneurysmal subarachnoid hemorrhage (aSAH) is a neurovascular disease produced by extravasation of blood to the subarachnoid space after rupture of the cerebral vessels. After bleeding, the immune response is activated. The role of peripheral blood mononuclear cells (PBMCs) in this response is a current subject of research. We have analysed the changes in PBMCs of patients with aSAH and their interaction with the endothelium, focusing on their adhesion and the expression of adhesion molecules. Using an in vitro adhesion assay, we observed that the adhesion of PBMCs of patients with aSAH is increased. Flow cytometry analysis shows that monocytes increased significantly in patients, especially in those who developed vasospasm (VSP). In aSAH patients, the expression of CD162, CD49d, CD62L and CD11a in T lymphocytes and of CD62L in monocytes increased. However, the expression of CD162, CD43, and CD11a decreased in monocytes. Furthermore, monocytes from patients who developed arteriographic VSP had lower expression of CD62L. In conclusion, our results confirm that after aSAH, monocyte count and adhesion of PBMCs increase, especially in patients with VSP, and that the expression of several adhesion molecules is altered. These observations can help predict VSP and to improve the treatment of this pathology.

CD68 Antigen and Cerebral Aneurysms: A Case-Control Study

BACKGROUND

 Intracranial aneurysms are more commonly associated with inflammation as a cause of their development, progression, and rupture. Macrophages and other cells can express the CD68 antigen. The aim of this study was to assess the CD68 antigen levels in cerebral aneurysm (CA) patients compared to a control group at a referral center in Iran.

METHODS

 A case-control investigation was undertaken on 88 individuals (44 of whom were cases and 44 were controls). Individuals with CA as the case group consisted of 28 ruptured and 16 unruptured subgroups. Clinical, radiographic, and CD68 levels were evaluated and registered.

RESULTS

 The average age of the participants was 49 years. Males comprised 43.2% of the patients, while 56.8% were females (p = 0.002). There was a statistically significant difference in the CD68 levels between the two groups. There was no significant difference (p = 0.42) between the ruptured and unruptured subgroups (23.66 and 20.47, respectively) in this comparison. No significant correlation was seen between the patients' CD68 and Glasgow Coma Scale (GCS) levels and their aneurysm diameter (p = 0.74 and 0.45, respectively). A link between CD68 levels and age was found, but it was not statistically significant (r = 0.44 and p = 0.002).

CONCLUSIONS

 A possible involvement of CD68 as an inflammatory agent in the development of CAs but not in aneurysm rupture has been suggested. Inflammation and CD68 were positively associated with age. The CD68 antigen should be studied further in population-based cohort studies.

Integrative analysis of multi-omics data to identify three immune-related genes in the formation and progression of intracranial aneurysms

OBJECTIVE AND DESIGN

The prevalence of intracranial aneurysms (IAs) has increased globally. We performed bioinformatics analysis to identify key biomarkers associated with IA formation.

METHODS AND RESULTS

We conducted a comprehensive analysis combined with multi-omics data and methods to identify immune-related genes (IRGs) and immunocytes involved in IAs. Functional enrichment analyses showed enhanced immune responses and suppressed organizations of extracellular matrix (ECM) during aneurysm progression. xCell analyses showed that the abundance of B cells, macrophages, mast cells, and monocytes significantly increased from levels in control to unruptured aneurysms and to ruptured aneurysms. Of 21 IRGs identified by overlapping, a three-gene (CXCR4, S100B, and OSM) model was constructed through LASSO logistic regression. The diagnostic ability of the three biomarkers in discriminating aneurysms from the control samples demonstrated a favorable diagnostic value. Among the three genes, OSM and CXCR4 were up-regulated and hypomethylated in IAs, while S100B was down-regulated and hypermethylated. The expression of the three IRGs was further validated by qRT-PCR and immunohistochemistry and mouse IA model using scRNA-seq analysis.

CONCLUSION

The present study demonstrated heightened immune response and suppressed ECM organization in aneurysm formation and rupture. The three-gene immune-related signature (CCR4, S100B, and OSM) model may facilitate IA diagnosis and prevention.

Hypoxic microenvironment as a crucial factor triggering events leading to rupture of intracranial aneurysm

Subarachnoid hemorrhage being the rupture of intracranial aneurysm (IA) as a major cause has quite poor prognosis, despite the modern technical advances. Thereby, the mechanisms underlying the rupture of lesions should be clarified. Recently, we and others have clarified the formation of vasa vasorum in IA lesions presumably for inflammatory cells to infiltrate in lesions as the potential histopathological alternation leading to rupture. In the present study, we clarified the origin of vasa vasorum as arteries located at the brain surface using 3D-immunohistochemistry with tissue transparency. Using Hypoxyprobe, we then found the presence of hypoxic microenvironment mainly at the adventitia of intracranial arteries where IA is formed. In addition, the production of vascular endothelial growth factor (VEGF) from cultured macrophages in such a hypoxic condition was identified. Furthermore, we found the accumulation of VEGF both in rupture-prone IA lesions induced in a rat model and human unruptured IA lesions. Finally, the VEGF-dependent induction of neovessels from arteries on brain surface was confirmed. The findings from the present study have revealed the potential role of hypoxic microenvironment and hypoxia-induced VEGF production as a machinery triggering rupture of IAs via providing root for inflammatory cells in lesions to exacerbate inflammation.

Association of elevated neutrophil-to-lymphocyte ratio with increased intracranial aneurysm stability scores and aneurysm growth

BACKGROUND AND PURPOSE

Inflammation involves in the progression of intracranial aneurysms (IAs). However, whether the neutrophil-to-lymphocyte ratio (NLR) as an inflammatory marker links to IAs stability is unidentified. This study was performed to assess the association of the NLR with IAs stability.

METHODS

We retrospectively reviewed the medical records of patients diagnosed with unruptured IAs from January 2014 to June 2018. According to the quartiles of the NLR, patients with unruptured IAs were categorized into four groups. We evaluated the association between the NLR and IAs stability scores and IAs growth. Multiple logistic regression models were used in the analysis.

RESULTS

A significant dose-response association was found between the NLR with IAs stability scores and IAs growth. After adjustment for potential confounders, an elevated NLR (fourth quartile) was associated with increased PHASES score (>5) (adjusted odds ratio [OR], 2.007; 95% confidence interval [CI], 1.361-2.960; p<0.001 [p for trend <0.001]), increased ELAPSS score (>15) (adjusted OR, 1.581; 95% CI, 1.074-2.328; p=0.020 [p for trend =0.001]), increased JAPAN 3-year rupture risk score (>5) (adjusted OR, 1.512; 95% CI, 1.033-2.215; p=0.034 [p for trend <0.001]), and IAs growth (adjusted OR, 16.759; 95% CI, 3.022-92.928; p=0.001 [p for trend <0.001]).

CONCLUSION

An elevated NLR was associated with increased IAs stability scores and IAs growth. The association between NLR and IAs stability need further investigate.

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.

The clinical significance of peripheral blood cell ratios in patients with intracranial aneurysm

Background and objective

Inflammation is an important factor in the development of aneurysm, and has been identified as a key characteristic predictive of rupture of intracranial aneurysm (IA). However, the role of inflammatory peripheral blood cell ratios in patients with IA has not been well delineated.

Methods

A total of 1,209 patients, including 1,001 with unruptured IA and 208 with ruptured IA, were enrolled in this study. Neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), platelet-to-neutrophil ratio (PNR), and platelet-to-white-blood-cell ratio (PWR) were compared between ruptured and unruptured IA.

Results

Compared with the ruptured IA group, the unruptured IA group had higher PNR {median, 65.96 [interquartile range (IQR) 48.95-85.05] vs. 37.78 (IQR, 23.17-54.05); p < 0.001} and PWR [median, 36.89 (IQR 29.38-44.56) vs. 22.39 (IQR, 16.72-29.29); p < 0.001]. In multivariate analysis, PNR and PWR were independently associated with ruptured IA (p = 0.001 and p < 0.001, respectively). Unruptured IA subgroup analyses according to the PHASES scores showed that a higher PHASES score was associated with significantly higher NLR and erythrocyte sedimentation rate (p < 0.001 and p = 0.025) and lower PNR and PWR (p < 0.001 and p = 0.007).

Conclusions

We demonstrated that lower PNR and PWR levels are associated with ruptured IA and a higher PHASES score. Unlike many other inflammatory markers and bioassays, peripheral blood cell ratios are inexpensive and readily available biomarkers that may be useful for risk stratification in patients with cerebral aneurysm. However, a long-term prospective study is needed to clarify this matter.

Endothelial cell malfunction in unruptured intracranial aneurysm lesions revealed using a 3D-casted mold

Intracranial aneurysms (IA) are major causes of devastating subarachnoid hemorrhages. They are characterized by a chronic inflammatory process in the intracranial arterial walls triggered and modified by hemodynamic force loading. Because IA lesion morphology is complex, the blood flow conditions loaded on endothelial cells in each portion of the lesion in situ vary greatly. We created a 3D-casted mold of the human unruptured IA lesion and cultured endothelial cells on this model; it was then perfused with culture media to model physiological flow conditions. Gene expression profiles of endothelial cells in each part of the IA lesion were then analyzed. Comprehensive gene expression profile analysis revealed similar gene expression patterns in endothelial cells from each part of the IA lesion but gene ontology analysis revealed endothelial cell malfunction within the IA lesion. Histopathological examination, electron microscopy, and immunohistochemical analysis indicated that endothelial cells within IA lesions are damaged and dysfunctional. Thus, our findings reveal endothelial cell malfunction in IA lesions and provided new insights into IA pathogenesis.

Comprehensive analysis of immune cell infiltration and role of MSR1 expression in aneurysmal subarachnoid haemorrhage

Aneurysmal subarachnoid haemorrhage (aSAH), resulting from the rupture of intracranial aneurysms, can yield high mortality and disability. This study aimed to explore the immune infiltration of aneurysmal tissues and investigate a novel mechanism underlying aSAH. We downloaded datasets containing expression profiles of aneurysmal and normal arterial tissues from the online database. Then a comprehensive bioinformatic strategy was conducted to select the biomarkers of aneurysmal tissues. Two calculation algorithms were performed to identify the unique immune characteristics between aneurysmal tissues and normal arteries. Double immunofluorescence staining was used to investigate the role of pathway-related proteins in the inflammatory process after aSAH. Six microarray datasets were integrated, and another RNA-sequencing dataset was used as the validation dataset. Functional enrichment analysis of the differentially expressed genes indicated that immune-related processes were closely related to the progression of aSAH. We then performed immune microenvironment infiltration analysis, and the results suggested macrophages were abnormally enriched in aneurysmal tissues. Core gene MSR1 was filtered through a comprehensive bioinformatic strategy. Our analysis suggested that MSR1 might be associated with macrophage activation and migration. Our study elucidated the impact of macrophage and MSR1 on aSAH progression. These findings were helpful in gaining insight into the immune heterogeneity of aneurysmal tissues and normal arteries, and in identifying patients who might benefit from immunotherapy.

Computational fluid dynamic analysis of the initiation of cerebral aneurysms

OBJECTIVE

Relationships between aneurysm initiation and hemodynamic factors remain unclear since de novo aneurysms are rarely observed. Most previous computational fluid dynamics (CFD) studies have used artificially reproduced vessel geometries before aneurysm initiation for analysis. In this study, the authors investigated the hemodynamic factors related to aneurysm initiation by using angiographic images in patients with cerebral aneurysms taken before and after an aneurysm formation.

METHODS

The authors identified 10 cases of de novo aneurysms in patients who underwent follow-up examinations for existing cerebral aneurysms located at a different vessel. The authors then reconstructed the vessel geometry from the images that were taken before aneurysm initiation. In addition, 34 arterial locations without aneurysms were selected as control cases. Hemodynamic parameters acting on the arterial walls were calculated by CFD analysis.

RESULTS

In all de novo cases, the aneurysmal initiation area corresponded to the highest wall shear stress divergence (WSSD point), which indicated that there was a strong tensile force on the arterial wall at the initiation area. The other previously reported parameters did not show such correlations. Additionally, the pressure loss coefficient (PLc) was statistically significantly higher in the de novo cases (p < 0.01). The blood flow impact on the bifurcation apex, or the secondary flow accompanied by vortices, resulted in high tensile forces and high total pressure loss acting on the vessel wall.

CONCLUSIONS

Aneurysm initiation may be more likely in an area where both tensile forces acting on the vessel wall and total pressure loss are large.

High-Dimensional Immune Profiling by Mass Cytometry Revealed the Circulating Immune Cell Landscape in Patients With Intracranial Aneurysm

Background

Increasing evidence supports a critical role of chronic inflammation in intracranial aneurysm (IA). Understanding how the immunological alterations in IA provides opportunities for targeted treatment. However, there is a lack of comprehensive and detailed characterization of the changes in circulating immune cells in IA.

Objective

To perform a comprehensive and detailed characterization of the changes in circulating immune cells in patients with IA.

Methods

Peripheral blood mononuclear cell samples from IA patients (n = 26) and age-and sex-matched healthy controls (HCs, n = 20) were analyzed using high dimensional mass cytometry, and the frequency and phenotype of immune cell subtypes were assessed.

Results

We identified 28 cell clusters and found that the immune signature of IA consists of cluster changes. IA patients exhibited dysfunction of immunity, with dysregulation of CD4⁺ T-cell clusters, increased B cells and monocytes, and decreased CD8⁺ T cells, DNT cells, and DPT cells. Moreover, compared with findings in HC, IA was associated with enhanced lymphocyte and monocyte immune activation, with a higher expression of HLA-DR, CXCR3, and CX3CR1. In addition, the expression of TLR4, p-STAT3, and the exhaustion marker PD1 was increased in T cells, B cells, and NK cells in IA patients.

Conclusions

Our data provide an overview of the circulating immune cell landscape of IA patients, and reveal that the dysfunction of circulating immunity may play a potential role in the development of IA.

Deep Phenotyping of T-Cells Derived From the Aneurysm Wall in a Pediatric Case of Subarachnoid Hemorrhage

Intracranial aneurysms (IAs) are very rare in children, and the characteristics of the T-cells in the IA wall are largely unknown. A comatose 7-years-old child was admitted to our center because of a subarachnoid hemorrhage due to a ruptured giant aneurysm of the right middle cerebral artery. Two days after the aneurysm clipping the patient was fully awake with left hemiparesis. T-cells from the IA wall and from peripheral blood of this patient were analyzed by multi-dimensional flow cytometry. Unbiased analysis, based on the use of FlowSOM clustering and dimensionality reduction technique UMAP, indicated that there was virtually no overlap between circulating and tissue-infiltrating T-cells. Thus, naïve T-cells and canonical memory T-cells were largely restricted to peripheral blood, while CD4^-CD8^-T-cells were strongly enriched in the IA wall. The unique CD4⁺, CD8⁺ and CD4^-CD8^-T-cell clusters from the IA wall expressed high levels of CCR5, Granzyme B and CD69, displaying thus characteristics of cytotoxic and tissue-resident effector cells. Low Ki67 expression indicated that they were nevertheless in a resting state. Among regulatory T-cell subsets, Eomes⁺Tr1-like cells were strongly enriched in the IA wall. Finally, analysis of cytokine producing capacities unveiled that the IA wall contained poly-functional T-cells, which expressed predominantly IFN-γ, TNF and IL-2. CD4⁺T-cells co-expressed also CD40L, and produced some IL-17, GM-CSF and IL-10. This report provides to our knowledge the first detailed characterization of the human T-cell compartment in the IA wall.

Increased Levels of Serum IL-15 and TNF-β Indicate the Progression of Human Intracranial Aneurysm

Objective

Existing evidence suggests that chronic inflammation promotes the progression of human intracranial aneurysm (IA) and many cytokines have been detected to participate in the process of inflammation. However, rare cytokines in plasma have been used as proxies for progression of IA. This study aimed to identify novel cytokines as biomarkers to predict the development of IA.

Methods

Patients with unruptured intracranial aneurysms (UIAs) undergoing microsurgical clipping were prospectively recruited from January 2017 to June 2020 and were separated into two groups based on their ELAPSS score (low risk group < 10, intermediate-high risk group ≥ 10). Propensity score matching (PSM) was used to reduce imbalances in the baseline characteristics between groups. All blood samples were collected before surgery. A human serum 48-cytokines examination was performed to analyze the concentrations of serological cytokines. Clinical data and cytokines were compared between groups.

Results

A total of 184 patients were enrolled in this study. The low risk group contained 77 patients and 107 patients were included in the intermediate-high risk group. Finally, there were 69 patients in each group after PSM with a matching rate of 1:1. The concentrations of 3 serum cytokines were significantly increased in intermediate-high risk patients, namely, interleukin-15 (IL-15), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-β (TNF-β) (P < 0.05, |log₂ fold change| > 2). The result of receiver operator characteristic (ROC)curve revealed that TNF-β had the highest predictive accuracy, with an area under the curve (AUC) value of 0.725 [95% confidence interval (CI) 0.639–0.811, P < 0.001] followed by IL-15 (AUC = 0.691, 95% CI 0.602–0.781, P < 0.001) and MCP-1 (AUC = 0.661, 95% CI 0.569–0.753, P = 0.001). Multivariate logistic analysis demonstrated high IL-15 [odds ratio (OR), 3.23; 95% CI, 1.47–7.12; P = 0.004] and high TNF-β (OR, 8.30; 95% CI, 3.25–21.25; P < 0.001) as the risk factors that correlated with intermediate-high risk of IA progression.

Conclusion

UIA patients with intermediate-high growth risk exhibited increased serum levels of IL-15, MCP-1, and TNF-β. Serum IL-15, and TNF-β could serve as biomarkers to predict the progression of UIAs.

Unruptured cerebral aneurysm risk stratification: Background, current research, and future directions in aneurysm assessment

Background:

The optimal management of unruptured cerebral aneurysms is widely debated in the medical field. Rapid technology advances, evolving understanding of underlying pathophysiology, and shifting practice patterns have made the cerebrovascular field particularly dynamic in recent years. Despite progress, there remains a dearth of large randomized studies to help guide the management of these controversial patients.

Methods:

We review the existing literature on the natural history of unruptured cerebral aneurysms and highlight ongoing research aimed at improving our ability to stratify risk in these patients.

Results:

Landmark natural history studies demonstrated the significance of size, location, and other risk factors for aneurysm rupture, but prior studies have significant limitations. We have begun to understand the underlying pathophysiology behind aneurysm formation and rupture and are now applying new tools such as flow dynamics simulations and machine learning to individualize rupture risk stratification.

Conclusion:

Prior studies have identified several key risk factors for aneurysmal rupture, but have limitations. New technology and research methods have enabled us to better understanding individual rupture risk for patients with unruptured cerebral aneurysms.

Prevalence of cerebral aneurysms in autopsy studies: a review of the literature

Cerebral aneurysms (CAs) are one of the most important causes of stroke, but details of their prevalence remain under-researched. Autopsy data for CAs were reviewed using standard search engines. Based on previously published autopsy and clinical studies, the prevalence of CAs with respect to age, gender, and aneurysm site, size, and multiplicity was investigated, and the natural course of CA prevalence was estimated. In autopsy studies, the prevalence of CAs across all age groups was 0.3-4.0% for unruptured cerebral aneurysms (UCAs) and 1.3-7.6% for CAs including UCAs and ruptured cerebral aneurysms (RCAs). Patients with UCAs were generally older than those with RCAs. Middle cerebral artery aneurysms were more predominant in autopsy studies than in clinical studies. UCAs tended to be smaller than RCAs, and minute UCAs (< 2 mm), diagnosed microscopically at autopsy and thought to be in the very early stages of formation, were present in 10-20% of the general population. Taking into consideration the clinical data for UCAs and RCAs, 10% of minute UCAs enlarge to major UCAs (≥ 2 mm) detectable by conventional imaging techniques, and 10% of major UCAs eventually rupture within 10 years. The high prevalence of UCAs and RCAs in the elderly and women can be attributed to the more frequent occurrence of minute UCAs in these populations. Minute UCAs occur at a high rate, but only a few enlarge to become major UCAs and rupture. Further advances in diagnostic technology are essential for revealing the true natural course of CA prevalence.

Macrophage activation in response to shape memory polymer foam-coated aneurysm occlusion devices

Brain aneurysms can be treated with embolic coils using minimally invasive approaches. It is advantageous to modulate the biologic response of platinum embolic coils. Our previous studies demonstrated that shape memory polymer (SMP) foam coated embolization coils (FCC) devices demonstrate enhanced healing responses in animal models compared with standard bare platinum coil (BPC) devices. Macrophages are the most prevalent immune cell type that coordinate the greater immune response to implanted materials. Hence, we hypothesized that the highly porous SMP foam coatings on embolic coils activate a pro-regenerative healing phenotype. To test this hypothesis, we analyzed the number and type of infiltrating macrophages in FCC or BPC devices implanted in a rabbit elastase aneurysm model. FCC devices elicited a great number of infiltration macrophages, skewed significantly to a pro-regenerative M2-like phenotype 90 days following implantation. We devised an in vitro assay, where monocyte-derived macrophages were placed in close association with FCC or BPC devices for 6-72 h. Macrophages encountering SMP FCC-devices demonstrated highly mixed activation phenotypes at 6 h, heavily skewing toward an M2-like phenotype by 72 h, compared with macrophages encountering BPC devices. Macrophage activation was evaluated using gene expression analysis, and secreted cytokine evaluation. Together, our results demonstrate that FCC devices promoted a pro-regenerative macrophage activation phenotype, compared with BPC devices. Our in vitro findings corroborate with in vivo observations that SMP-based modification of embolic coils can promote better healing of the aneurysm site, by sustaining a pro-healing macrophage phenotype.

Vessel wall imaging with advanced flow suppression in the characterization of intracranial aneurysms following flow diversion with Pipeline embolization device

BACKGROUND

High-resolution vessel wall MRI (VWI) is increasingly used to characterize intramural disorders of the intracranial vasculature unseen by conventional arteriography.

OBJECTIVE

To evaluate the use of VWI for surveillance of flow diverter (FD) treated aneurysms.

MATERIALS AND METHODS

Retrospective study of 28 aneurysms (in 21 patients) treated with a FD (mean 57 years; 14 female). All examinations included VWI and a contemporaneously obtained digital subtraction angiogram. Multiplanar pre- and post-gadolinium 3D, variable flip-angle T1 black-blood VWI was obtained using delay alternating nutation for tailored excitation (DANTE) at 3T. 3D time-of-flight MR angiography (MRA) was also carried out. Images were assessed for in-stent stenosis, aneurysm occlusion, presence and pattern/distribution of aneurysmal or parent vessel gadolinium enhancement.

RESULTS

The VWI-MRI was performed on average at 361±259 days after the intervention. Follow-up DSA was performed at 338±254 days postintervention. Good or excellent black-blood angiographic quality was recorded in 22/28 (79%) pre-contrast and 21/28 (75%) post-contrast VWI, with no cases excluded for image quality. Aneurysm enhancement was noted in 24/28 (85.7%) aneurysms, including in 79% of angiographically occluded aneurysms and 100% of angiographically non-occluded aneurysms. Enhancement of the stented parent-vessel wall occurred significantly more often when aneurysm enhancement was present (92% vs 33%, p=0.049).

CONCLUSION

Advanced VWI produces excellent depiction of FD-treated aneurysms, with robust evaluation of the parent vessel and aneurysm wall to an extent not achievable with conventional MRI/MRA. Gadolinium enhancement may, however, continue even after enduring catheter angiographic occlusion, confounding interpretation, and requiring cognizance of this potentially prolonged effect in such patients.

Circulating proteomic panels for risk stratification of intracranial aneurysm and its rupture

The prevalence of intracranial aneurysm (IA) is increasing, and the consequences of its rupture are severe. This study aimed to reveal specific, sensitive, and non-invasive biomarkers for diagnosis and classification of ruptured and unruptured IA, to benefit the development of novel treatment strategies and therapeutics altering the course of the disease. We first assembled an extensive candidate biomarker bank of IA, comprising up to 717 proteins, based on altered proteins discovered in the current tissue and serum proteomic analysis, as well as from previous studies. Mass spectrometry assays for hundreds of biomarkers were efficiently designed using our proposed deep learning-based method, termed DeepPRM. A total of 113 potential markers were further quantitated in serum cohort I (n = 212) & II (n = 32). Combined with a machine-learning-based pipeline, we built two sets of biomarker combinations (P6 & P8) to accurately distinguish IA from healthy controls (accuracy: 87.50%) or classify IA rupture patients (accuracy: 91.67%) upon evaluation in the external validation set (n = 32). This extensive circulating biomarker development study provides valuable knowledge about IA biomarkers.

IL-6 Quotient (The Ratio of Cerebrospinal Fluid IL-6 to Serum IL-6) as a Biomarker of an Unruptured Intracranial Aneurysm

Background

Studies conducted so far have focused mainly on the assessment of IL-6 levels in patients with ruptured brain aneurysms. Carrying out detailed studies in patients with un-ruptured brain aneurysms (UIA) would be extremely important, as it would answer the question of whether IL-6 plays also a role in primary aneurysm formation and growth.

Methods

IL-6, S100, NSE, and albumin concentrations in 67 UIA patients and 17 individuals without vascular lesions in the brain were tested using in vitro diagnostic immunoassays according to the manufacturers' instructions. IL-6 Quotient was calculated by dividing cerebrospinal fluid (CSF) IL-6 by serum IL-6.

Results

We showed that IL-6 Quotient was significantly higher in UIA patients (1.78) compared to the control group (0.87; p<0.001). Multivariate logistic regression analysis demonstrated that a growth in IL-6 Quotient increases the probability of UIA diagnosis. In UIA patients CSF IL-6 concentration was significantly higher (4.55 pg/ml) compared to the serum concentration (2.39 pg/ml; p<0.001). In both the study and control group, the blood-brain barrier was intact, thus the CSF-blood gradient of the IL-6 concentration in UIA patients was likely to be the expression of local synthesis of the cytokine within the central nervous system. Patients with multiple brain aneurysms had significantly higher CSF IL-6 levels (5.08 pg/ml) compared to individuals with a single aneurysm (4.14 pg/ml; p=0.0227).

Conclusion

This totality of the may suggest IL-6 as a biomarker for UIA formation; however, further studies are needed to unequivocally confirm clinical application of IL-6 concentration evaluation.

Role of magnetic resonance vessel wall imaging in detecting and managing ruptured aneurysms among multiple intracranial aneurysms

Background

Wall enhancement of intracranial saccular aneurysms in high-resolution magnetic resonance vessel wall imaging (MR-VWI) might indicate a ruptured aneurysm. Therefore, this study aimed to determine the diagnostic ability of wall enhancement to detect the ruptured aneurysms among multiple aneurysms.

Methods

Patients with subarachnoid hemorrhage (SAH) and multiple intracranial aneurysms who underwent MR-VWI before craniotomy and clipping were included in the study. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after gadolinium injection. Aneurysm rupture was estimated based on the subarachnoid clot distribution, aneurysmal contours, and MR-VWI findings. We selectively performed surgical clipping and confirmed the rupture site intraoperatively.

Results

Thirteen patients with SAH with 13 ruptured and 17 unruptured aneurysms were treated at out facility. The accuracy rate of rupture site diagnosis using MR-VWI was 69.2% (9/13 cases). Each unruptured aneurysm was equally or more strongly enhanced in the other four cases than the ruptured aneurysms. In three of the four unruptured aneurysms with positive MR-VWI findings, atherosclerosis of the aneurysmal wall was observed during simultaneous or elective clipping surgery. Further, clipping surgery was performed without intraoperative rupture in two cases with the help of MR-VWI findings.

Conclusion

Correct diagnosis of the rupture site using MR-VWI alone was unreliable due to false positives caused by the wall enhancement of unruptured aneurysms with atherosclerosis. Therefore, ruptured aneurysms should be detected using more information in addition to MR-VWI images. MR-VWI may be advantageous to determine surgical strategies when managing patients with SAH and multiple aneurysms.

Current Clinical Applications of Intracranial Vessel Wall MR Imaging

Intracranial vessel wall MR imaging (VWI) is increasingly being used as a valuable adjunct to conventional angiographic imaging techniques. This article will provide an updated review on intracranial VWI protocols and image interpretation. We review VWI technical considerations, describe common VWI imaging features of different intracranial vasculopathies and show illustrative cases. We review the role of VWI for differentiating among steno-occlusive vasculopathies, such as intracranial atherosclerotic plaque, dissections and Moyamoya disease. We also highlight how VWI may be used for the diagnostic work-up and surveillance of patients with vasculitis of the central nervous system and cerebral aneurysms.

Aneurysm Wall Enhancement Is Associated With Decreased Intrasaccular IL-10 and Morphological Features of Instability

BACKGROUND

High-resolution vessel wall imaging plays an increasingly important role in assessing the risk of aneurysm rupture.

OBJECTIVE

To introduce an approach toward the validation of the wall enhancement as a direct surrogate parameter for aneurysm stability.

METHODS

A total of 19 patients harboring 22 incidental intracranial aneurysms were enrolled in this study. The aneurysms were dichotomized according to their aneurysm-to-pituitary stalk contrast ratio using a cutoff value of 0.5 (nonenhancing < 0.5; enhancing ≥ 0.5). We evaluated the association of aneurysm wall enhancement with morphological characteristics, hemodynamic features, and inflammatory chemokines directly measured inside the aneurysm.

RESULTS

Differences in plasma concentration of chemokines and inflammatory molecules, morphological, and hemodynamic parameters were analyzed using the Welch test or Mann-Whitney U test. The concentration ΔIL-10 in the lumen of intracranial aneurysms with low wall enhancement was significantly increased compared to aneurysms with strong aneurysm wall enhancement (P = .014). The analysis of morphological and hemodynamic parameters showed significantly increased values for aneurysm volume (P = .03), aneurysm area (P = .044), maximal diameter (P = .049), and nonsphericity index (P = .021) for intracranial aneurysms with strong aneurysm wall enhancement. None of the hemodynamic parameters reached statistical significance; however, the total viscous shear force computed over the region of low wall shear stress showed a strong tendency toward significance (P = .053).

CONCLUSION

Aneurysmal wall enhancement shows strong associations with decreased intrasaccular IL-10 and established morphological indicators of aneurysm instability.

Association of Periodontal Disease with the Occurrence of Unruptured Cerebral Aneurysm among Adults in Korea: A Nationwide Population-Based Cohort Study TRANSLATE with x EnglishArabicHebrewPolishBulgarianHindiPortugueseCatalanHmong DawRomanianChinese SimplifiedHungarianRussianChinese TraditionalIndonesianSlovakCzechItalianSlovenianDanishJapaneseSpanishDutchKlingonSwedishEnglishKoreanThaiEstonianLatvianTurkishFinnishLithuanianUkrainianFrenchMalayUrduGermanMalteseVietnameseGreekNorwegianWelshHaitian CreolePersian// TRANSLATE with COPY THE URL BELOW Back EMBED THE SNIPPET BELOW IN YOUR SITE Enable collaborative features and customize widget: Bing Webmaster PortalBack//

Background and Objectives: Cerebral aneurysms can cause disability or death during rupture, but information on the etiology of cerebral aneurysms is currently lacking. Periodontal disease causes both systemic inflammation and local inflammation of the oral cavity. Systemic inflammation is a major cause of cerebral aneurysms. The aim of our study was to determine whether the presence of periodontal disease is related to the occurrence of unruptured cerebral aneurysms in a nationwide population-based cohort. Materials and Methods: We analyzed data on demographics, previous medical history, and laboratory test results of 209,620 participants from the Korean National Health Insurance System-Health Screening Cohort. The presence of periodontal disease and oral hygiene parameters, including the number of lost teeth, tooth brushing frequency per day, dental visits for any reason, and expert teeth scaling, were investigated. The occurrences of unruptured cerebral aneurysms (I67.1) were defined according to the International Statistical Classification of Diseases Related Health Problems-10. Results: The mean age of the participants was 53.7 ± 8.7 years, and 59.4% were male. Periodontal disease was found in 20.9% of the participants. A total of 2160 (1.0%) cases of unruptured cerebral aneurysms developed after 10.3 years of median follow up. In multivariate analysis, the presence of periodontal disease was significantly associated with an increased risk of unruptured cerebral aneurysms (hazard ratio: 1.21, 95% confidence interval: 1.09–1.34, p < 0.001). Conclusion: The presence of periodontal disease could be associated with the occurrence of unruptured cerebral aneurysms. It should be noted that when periodontal diseases are present, the risk of aneurysms is increased in the future.

EP2 Antagonists (2011-2021): A Decade's Journey from Discovery to Therapeutics

In the wake of health disasters associated with the chronic use of cyclooxygenase-2 (COX-2) inhibitor drugs, it has been widely proposed that modulation of downstream prostanoid synthases or receptors might provide more specificity than simply shutting down the entire COX cascade for anti-inflammatory benefits. The pathogenic actions of COX-2 have long been thought attributable to the prostaglandin E2 (PGE2) signaling through its Gαs-coupled EP2 receptor subtype; however, the truly selective EP2 antagonists did not emerge until 2011. These small molecules provide game-changing tools to better understand the EP2 receptor in inflammation-associated conditions. Their applications in preclinical models also reshape our knowledge of PGE2/EP2 signaling as a node of inflammation in health and disease. As we celebrate the 10-year anniversary of this breakthrough, the exploration of their potential as drug candidates for next-generation anti-inflammatory therapies has just begun. The first decade of EP2 antagonists passes, while their future looks brighter than ever.

RNA Sequencing Data from Human Intracranial Aneurysm Tissue Reveals a Complex Inflammatory Environment Associated with Rupture

BACKGROUND

Intracranial aneurysm (IA) rupture leads to deadly subarachnoid hemorrhages. However, the mechanisms leading to rupture remain poorly understood. Altered gene expression within IA tissue is linked to the pathobiology of aneurysm development and progression. Here, we analyzed expression patterns of control tissue samples and compared them to those of unruptured and ruptured IA tissue samples using data from the Gene Expression Omnibus (GEO).

METHODS

FASTQ files for 21 ruptured IAs, 21 unruptured IAs, and 16 control tissue samples were accessed from the GEO database. DESeq2 was used for differential expression analysis in three comparisons: unruptured IA versus control, ruptured IA versus control, and ruptured versus unruptured IA. Genes that were differentially expressed in multiple comparisons were evaluated to find those progressively increasing/decreasing from control to unruptured to ruptured. Significance was tested by either analysis of variance/Gabriel or Brown-Forsythe/Games Howell (p < 0.05 was considered significant). We used additional RNA sequencing and proteomics datasets to evaluate if our differentially expressed genes (DEGs) were present in other studies. Bioinformatics analyses were performed with g:Profiler and Ingenuity Pathway Analysis.

RESULTS

In total, we identified 1768 DEGs, of which 318 were found in multiple comparisons. Unruptured versus control reflected vascular remodeling processes, while ruptured versus control reflected inflammatory responses and cell activation/signaling. When comparing ruptured to unruptured IAs, we found massive activation of inflammation, inflammatory responses, and leukocyte responses. Of the 318 genes in multiple comparisons, 127 were found to be significant in the multi-cohort correlation analysis. Those that progressively increased (70 genes) were associated with immune system processes, while those that progressively decreased (38 genes) did not return any gene ontology terms. Many of our DEGs were also found in the other IA tissue sequencing studies.

CONCLUSIONS

We found unruptured IAs relate more to remodeling processes, while ruptured IAs reflect more inflammatory and immune responses.

Aberrant Whole Blood Gene Expression in the Lumen of Human Intracranial Aneurysms

The rupture of an intracranial aneurysm (IA) causes devastating hemorrhagic strokes. Yet, most IAs remain asymptomatic and undetected until they rupture. In the search for circulating biomarkers of unruptured IAs, we previously performed transcriptome profiling on whole blood and identified an IA-associated panel of 18 genes. In this study, we seek to determine if these genes are also differentially expressed within the IA lumen, which could provide a mechanistic link between the disease and the observed circulating gene expression patterns. To this end, we collected blood from the lumen of 37 IAs and their proximal parent vessels in 31 patients. The expression levels of 18 genes in the lumen and proximal vessel were then measured by quantitative polymerase chain reaction. This analysis revealed that the expression of 6/18 genes (CBWD6, MT2A, MZT2B, PIM3, SLC37A3, and TNFRSF4) was significantly higher in intraluminal blood, while the expression of 3/18 genes (ST6GALNAC1, TCN2, and UFSP1) was significantly lower. There was a significant, positive correlation between intraluminal and proximal expression of CXCL10, MT2A, and MZT2B, suggesting local increases of these genes is reflected in the periphery. Expression of ST6GALNAC1 and TIFAB was significantly positively correlated with IA size, while expression of CCDC85B was significantly positively correlated with IA enhancement on post-contrast MRI, a metric of IA instability and risk. In conclusion, intraluminal expression differences in half of the IA-associated genes observed in this study provide evidence for IA tissue-mediated transcriptional changes in whole blood. Additionally, some genes may be informative in assessing IA risk, as their intraluminal expression was correlated to IA size and aneurysmal wall enhancement.

Differential polarization and activation dynamics of systemic T helper cell subsets after aneurysmal subarachnoid hemorrhage (SAH) and during post-SAH complications

Aneurysmal subarachnoid hemorrhage (SAH) is associated with high morbidity and mortality. Devastating post-SAH complications, such as cerebral vasospasm (CVS), delayed cerebral ischemia or seizures to mention a few, are mainly responsible for the poor clinical outcome. Inflammation plays an indispensable role during early brain injury (EBI) and delayed brain injury (DBI) phases over which these complications arise. T helper cells are the major cytokine secreting cells of adaptive immunity that can polarize to multiple functionally unique sub-populations. Here, we investigate different CD4+ T cell subsets during EBI and DBI phases after SAH, and their dynamics during post-SAH complications. Peripheral venous blood from 15 SAH patients during EBI and DBI phases, was analyzed by multicolour flowcytometry. Different subsets of CD3+ CD4+ T cells were characterized by differential cell surface expression of CXCR3 and CCR6 into Th1, Th2, Th17, whereas Tregs were defined by CD25^hiCD127^lo. The analysis of activation states was done by the expression of stable activation markers CD38 and HLA-DR. Interestingly, compared to healthy controls, Tregs were significantly increased during both EBI and DBI phases. Different activation states of Tregs showed differential significant increase during EBI and DBI phases compared to controls. HLA-DR− CD38+ Tregs were significantly increased during DBI phase compared to EBI phase in SAH patients developing CVS, seizures and infections. However, HLA-DR− CD38− Tregs were significantly reduced during EBI phase in patients with cerebral ischemia (CI) compared to those without CI. HLA-DR− CD38− Th2 cells were significantly increased during EBI phase compared to controls. A significant reduction in Th17/Tregs and HLA-DR− CD38+ Th17/Tregs ratios was observed during both EBI and DBI phases compared to controls. While HLA-DR− CD38− Th17/Tregs and HLA-DR− CD38− Th1/Th2 ratios were impaired only during EBI phase compared to controls. In conclusion, CD4+ T cell subsets display dynamic and unique activation patterns after SAH and during the course of the manifestation of post-SAH complications, which may be helpful for the development of precision neurovascular care. However, to claim this, confirmatory studies with larger patient cohorts, ideally from different ethnic backgrounds, are required. Moreover, our descriptive study may be the grounds for subsequent lab endeavors to explore the underlying mechanisms of our observations.

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).

Identification of Circulating Gene Expression Signatures of Intracranial Aneurysm in Peripheral Blood Mononuclear Cells

Peripheral blood mononuclear cells (PBMCs) play an important role in the inflammation that accompanies intracranial aneurysm (IA) pathophysiology. We hypothesized that PBMCs have different transcriptional profiles in patients harboring IAs as compared to IA-free controls, which could be the basis for potential blood-based biomarkers for the disease. To test this, we isolated PBMC RNA from whole blood of 52 subjects (24 with IA, 28 without) and performed next-generation RNA sequencing to obtain their transcriptomes. In a randomly assigned discovery cohort of n = 39 patients, we performed differential expression analysis to define an IA-associated signature of 54 genes (q < 0.05 and an absolute fold-change ≥ 1.3). In the withheld validation dataset, these genes could delineate patients with IAs from controls, as the majority of them still had the same direction of expression difference. Bioinformatics analyses by gene ontology enrichment analysis and Ingenuity Pathway Analysis (IPA) demonstrated enrichment of structural regulation processes, intracellular signaling function, regulation of ion transport, and cell adhesion. IPA analysis showed that these processes were likely coordinated through NF-kB, cytokine signaling, growth factors, and TNF activity. Correlation analysis with aneurysm size and risk assessment metrics showed that 4/54 genes were associated with rupture risk. These findings highlight the potential to develop predictive biomarkers from PBMCs to identify patients harboring IAs.

Correlation of Aneurysmal Wall Enhancement of Unruptured Intracranial Aneurysms on High-Resolution Vessel-Wall Imaging With Clinical Indices and Surgical Findings

BACKGROUND

Many physicians consider aneurysmal wall enhancement (AWE) on high resolution-vessel wall imaging (HR-VWI) as an imaging biomarker of unstable unruptured intracranial aneurysms (UIAs).

OBJECTIVE

To evaluate the clinical value of different AWE signal intensities (SIs) by assessing the correlation between the AWE SIs and surgical findings and rupture risk assessment tools.

METHODS

Twenty-six patients with 34 aneurysms who underwent surgical clipping were included. The corrected AWE SI was calculated by comparing T1-weighted images with post-gadolinium enhanced T1-weighted images. The correlation of AWE with the population, hypertension, age, size of aneurysm, earlier subarachnoid hemorrhage from another aneurysm, site of aneurysm (PHASES) and earlier subarachnoid hemorrhage, location of the aneurysm, age >60 years, population, size of the aneurysm, shape of the aneurysm (ELAPSS) scores was evaluated using correlation and linear regression analysis. To quantify the surgical findings, the average color value of the aneurysms expressed in the CIELCh system was measured. Δh, color difference from yellow, was used for statistical analysis.

RESULTS

The mean age of the patients and aneurysm size were 64.08 yr and 6.95 mm, respectively. The mean AWE SI, PHASES and ELAPSS scores, and Δh were 22.30, 8.41, 20.32, and 41.36, respectively. The coefficients of correlation of AWE SI with the PHASES and ELAPSS scores and Δh were 0.526, 0.563, and -0.431. We found that the AWE SI affected the PHASES (β = 0.430) and ELAPSS scores (β = 0.514) and Δh (β = -0.427) in simple linear regression analysis.

CONCLUSION

The AWE on HR-VWI was correlated with the PHASES and ELAPSS scores and the color. The stronger the AWE, the higher were the PHASES and ELAPSS scores and the more abnormal was the color. The AWE might indicate the degree of inflammation.

Ischemic Stroke as a Warning Sign of Impending Aneurysmal Rupture: A Report of Two Cases

Ischemic stroke associated with intracranial aneurysm is rare but potentially happens because of emboli originating from aneurysm sac or aneurysmal thrombosis extension to the parent artery. We describe two patients who present subarachnoid hemorrhage (SAH) soon after ischemic stroke. Case 1. A 51-year-old woman with a history of multiple endovascular therapy for ruptured basilar top aneurysm presented with double vision. Magnetic resonance imaging (MRI) revealed infarcts in the right thalamus and left occipital cortex. Four days after ischemic stroke, she suffered from sudden onset headache, computed tomography (CT) showed diffuse SAH with intraventricular hemorrhage. Case 2. A 62-year-old man presented with right facial palsy and sensory disorder. MRI revealed an infarct in the left pons. Four days after ischemic stroke, he became comatose and CT showed diffuse SAH. Both cases develop ischemic stroke adjacent to the aneurysms and subsequently cause devasting aneurysm rupture, suggesting ischemic stroke as a warning sign of aneurysm rupture. In such cases, early treatment of the aneurysm should be considered.

The association between hemodynamics and wall characteristics in human intracranial aneurysms: a review

Hemodynamics plays a key role in the natural history of intracranial aneurysms (IAs). However, studies exploring the association between aneurysmal hemodynamics and the biological and mechanical characteristics of the IA wall in humans are sparse. In this review, we survey the current body of literature, summarize the studies' methodologies and findings, and assess the degree of consensus among them. We used PubMed to perform a systematic review of studies that explored the association between hemodynamics and human IA wall features using different sources. We identified 28 publications characterizing aneurysmal flow and the IA wall: 4 using resected tissues, 17 using intraoperative images, and 7 using vessel wall magnetic resonance imaging (MRI). Based on correlation to IA tissue, higher flow conditions, such as high wall shear stress (WSS) with complex pattern and elevated pressure, were associated with degenerated walls and collagens with unphysiological orientation and faster synthesis. MRI studies strongly supported that low flow, characterized by low WSS and high blood residence time, was associated with thicker walls and post-contrast enhancement. While significant discrepancies were found among those utilized intraoperative images, they generally supported that thicker walls coexist at regions with prolonged residence time and that thinner regions are mainly exposed to higher pressure with complex WSS patterns. The current body of literature supports a theory of two general hemodynamic-biologic mechanisms for IA development. One, where low flow conditions are associated with thickening and atherosclerotic-like remodeling, and the other where high and impinging flow conditions are related to wall degeneration, thinning, and collagen remodeling.

Vascular Macrophages as Therapeutic Targets to Treat Intracranial Aneurysms

Aneurysmal subarachnoid hemorrhage (aSAH) is a highly fatal and morbid type of hemorrhagic strokes. Intracranial aneurysms (ICAs) rupture cause subarachnoid hemorrhage. ICAs formation, growth and rupture involves cellular and molecular inflammation. Macrophages orchestrate inflammation in the wall of ICAs. Macrophages generally polarize either into classical inflammatory (M1) or alternatively-activated anti-inflammatory (M2)-phenotype. Macrophage infiltration and polarization toward M1-phenotype increases the risk of aneurysm rupture. Strategies that deplete, inhibit infiltration, ameliorate macrophage inflammation or polarize to M2-type protect against ICAs rupture. However, clinical translational data is still lacking. This review summarizes the contribution of macrophage led inflammation in the aneurysm wall and discuss pharmacological strategies to modulate the macrophageal response during ICAs formation and rupture.

Construction and Validation of a New Model for the Prediction of Rupture in Patients with Intracranial Aneurysms

BACKGROUND

Despite progress in the detection of biological molecules that contribute to intracranial aneurysm (IA) development, many pathophysiological mechanisms remain unclear, particularly with regard to predicting IA rupture. In this study, we aimed to identify hub genes and construct a new model to predict IA rupture.

METHODS

Four datasets (62 ruptured IAs, 16 unruptured IAs, and 31 normal controls) were downloaded from the Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified between the IAs and normal controls. All overlapping genes were analyzed using weighted gene co-expression network analysis. Functional enrichment analyses were performed using key modules. We then intersected the key module genes with DEGs. Protein-protein interaction networks were assessed to identify key hub genes. Least absolute shrinkage and selection operator logistic regression analysis was performed to construct a prediction model. A receiver operating characteristic curve was constructed to evaluate the reliability of the scoring system.

RESULTS

After intersection and normalization, 433 DEGs were identified and 15,388 genes were selected for weighted gene co-expression network analysis. The black module with 1145 genes exhibited the highest correlation with IA rupture. Many potential mechanisms are involved, such as the inflammatory response, innate immune response, extracellular exosome, and extracellular space. Thirty hub genes were selected from the protein-protein interaction, and 4 independent risk genes, TNFAIP6, NCF2, OSM, and IRAK3, were identified in the least absolute shrinkage and selection operator logistic regression model.

CONCLUSIONS

Our prediction model not only serves as a useful tool for assessing the risk of IA rupture, but the key genes identified herein could also serve as biomarkers and therapeutic targets.

Endogenous animal models of intracranial aneurysm development: a review

The pathogenesis and natural history of intracranial aneurysm (IA) remains poorly understood. To this end, animal models with induced cerebral vessel lesions mimicking human aneurysms have provided the ability to greatly expand our understanding. In this review, we comprehensively searched the published literature to identify studies that endogenously induced IA formation in animals. Studies that constructed aneurysms (i.e., by surgically creating a sac) were excluded. From the eligible studies, we reported information including the animal species, method for aneurysm induction, aneurysm definitions, evaluation methods, aneurysm characteristics, formation rate, rupture rate, and time course. Between 1960 and 2019, 174 articles reported endogenous animal models of IA. The majority used flow modification, hypertension, and vessel wall weakening (i.e., elastase treatment) to induce IAs, primarily in rats and mice. Most studies utilized subjective or qualitative descriptions to define experimental aneurysms and histology to study them. In general, experimental IAs resembled the pathobiology of the human disease in terms of internal elastic lamina loss, medial layer degradation, and inflammatory cell infiltration. After the early 2000s, many endogenous animal models of IA began to incorporate state-of-the-art technology, such as gene expression profiling and 9.4-T magnetic resonance imaging (MRI) in vivo imaging, to quantitatively analyze the biological mechanisms of IA. Future studies aimed at longitudinally assessing IA pathobiology in models that incorporate aneurysm growth will likely have the largest impact on our understanding of the disease. We believe this will be aided by high-resolution, small animal, survival imaging, in situ live-cell imaging, and next-generation omics technology.

Rabbit Elastase Aneurysm: Imaging and Histology Correlates for Inflammation and Healing

OBJECTIVE

Aneurysmal subarachnoid hemorrhage remains a devastating event with poorly understood pathophysiology. Previous studies have suggested that aneurysm wall inflammation may play a part in the development and potential rupture of aneurysms. The rabbit elastase aneurysm model is a well-established model, which produces aneurysms closely mimicking human cerebral aneurysms in flow dynamics and histopathology. The primary aim of this study was to correlate inflammatory changes after aneurysm formation using sequential vessel wall imaging with histopathologic analysis. A secondary aim was to evaluate the potential effect of gender and anti-inflammatory treatment with aspirin on this inflammatory response.

METHODS

Twenty-seven New Zealand rabbits underwent surgery to create an aneurysm using elastase infusion at the right common carotid artery origin. Vessel wall imaging and histopathologic analysis was obtained at different time points after aneurysm creation. The rabbits were also randomized by gender and to treatment groups with or without aspirin.

RESULTS

Histopathologic analysis revealed 3 distinct phases after aneurysm formation. These phases were an initial inflammatory phase, followed by a regeneration phase, and finally a connective tissue deposition phase. Vessel wall imaging demonstrated 2 distinct imaging patterns. No appreciable differences were seen in histology or imaging when comparing gender or treatment with aspirin.

CONCLUSIONS

Inflammatory changes induced by the rabbit elastase aneurysm model can be correlated with histopathologic findings and observed on noninvasive vessel wall imaging. This may provide a method to study the inflammatory pathway as it pertains to aneurysmal development and subsequent rupture.

Comparative bioinformatics analysis between proteomes of rabbit aneurysm model and human intracranial aneurysm with label-free quantitative proteomics

Aims

This study aimed to find critical proteins involved in the development of intracranial aneurysm by comparing proteomes of rabbit aneurysm model and human aneurysms.

Methods

Five human intracranial aneurysm samples and 5 superficial temporal artery samples, and 4 rabbit aneurysm samples and 4 control samples were collected for protein mass spectrometry. Four human intracranial aneurysm samples and 4 superficial temporal artery samples, and 6 rabbit aneurysm samples and 6 control samples were used for immunochemistry.

Results

Proteomic analysis revealed 180 significantly differentially expressed proteins in human intracranial aneurysms and 716 significantly differentially expressed proteins in rabbit aneurysms. Among them, 57 proteins were differentially expressed in both species, in which 24 were increased and 33 were decreased in aneurysms compared to the control groups. Proteins were involved in focal adhesion and extracellular matrix‐receptor interaction pathways. We found that COL4A2, MYLK, VCL, and TAGLN may be related to aneurysm development.

Conclusion

Proteomics analysis provided fundamental insights into the pathogenesis of aneurysm. Proteins related to focal adhesion and extracellular matrix‐receptor interaction pathways play an important role in the occurrence and development of intracranial aneurysm.

Roles of inflammation in the natural history of intracranial saccular aneurysms

Aneurysmal subarachnoid hemorrhage is caused by intracranial aneurysm (IA) rupture and results in high rates of mortality and morbidity. Factors contributing to IA generation, growth and rupture can involve genetics, injury, hemodynamics, environmental factors, and inflammation, in which inflammatory factors are believed to play central roles in the whole natural history. Inflammatory reactions that contribute to IA development may involve synthesis of many functional proteins and expression of genes induced by changes of blood flow, external stimuli such as smoking, internal balance such as hormonal status changes, and blood pressure. Meanwhile, inflammatory reactions itself can evoke inflammatory cytokines release and aggregation such as MMPs, MCP-1, TNF-α and ZO-1, directly or indirectly promoting aneurysm growth and rupture. However, the details of these inflammatory reactions and their action on inflammatory chemokines are still unknown. Moreover, some agents with the function of anti-inflammation, lipid-lowering, antihypertension or inflammatory factor inhibition may have the potential benefit to reduce the risk of aneurysm development or rupture in a group of population despite the underlying mechanism remains unclear. Consequently, we reviewed the potential inflammatory responses and their mechanisms contributing to aneurysm development and rupture and sought intervention targets that may prevent IA rupture or generation.

Whole blood transcriptome biomarkers of unruptured intracranial aneurysm

BACKGROUND

The rupture of an intracranial aneurysm (IA) causes devastating subarachnoid hemorrhages, yet most IAs remain undiscovered until they rupture. Recently, we found an IA RNA expression signature of circulating neutrophils, and used transcriptome data to build predictive models for unruptured IAs. In this study, we evaluate the feasibility of using whole blood transcriptomes to predict the presence of unruptured IAs.

METHODS

We subjected RNA from peripheral whole blood of 67 patients (34 with unruptured IA, 33 without IA) to next-generation RNA sequencing. Model genes were identified using the least absolute shrinkage and selection operator (LASSO) in a random training cohort (n = 47). These genes were used to train a Gaussian Support Vector Machine (gSVM) model to distinguish patients with IA. The model was applied to an independent testing cohort (n = 20) to evaluate performance by receiver operating characteristic (ROC) curve. Gene ontology and pathway analyses investigated the underlying biology of the model genes.

RESULTS

We identified 18 genes that could distinguish IA patients in a training cohort with 85% accuracy. This SVM model also had 85% accuracy in the testing cohort, with an area under the ROC curve of 0.91. Bioinformatics reflected activation and recruitment of leukocytes, activation of macrophages, and inflammatory response, suggesting that the biomarker captures important processes in IA pathogenesis.

CONCLUSIONS

Circulating whole blood transcriptomes can detect the presence of unruptured IAs. Pending additional testing in larger cohorts, this could serve as a foundation to develop a simple blood-based test to facilitate screening and early detection of IAs.