Intracranial Aneurysm as a Macrophage-mediated Inflammatory Disease

Exploration of Immune-Related Transcription Control/Regulation in Intracranial Aneurysm Through KEGG Analysis and in-vivo Validation

Background

Intracranial aneurysms (IAs), a leading cause of subarachnoid hemorrhage, rank second only to cerebral thrombosis and hypertensive intracerebral hemorrhage among cerebrovascular diseases. However, the understanding of the regulatory mechanisms associated with IAs remains limited currently.

Methods

We obtained the GSE122897 dataset and analyzed differential expression genes (DEGs) from control, Ruptured intracranial aneurysm (RIA) and Unruptured intracranial aneurysm (UIA) samples under varied conditions. The correlation and differences of immune cell types across groups were examined. TF-target genes were obtained from the hTFtarget database, five immune-related TFs were identified and their expression was normalized and validated in an IA mouse model via qRT-PCR and Western blot analysis.

Results

1852 up-regulated and 971 down-regulated DEGs in Control vs RIA, 583 up-regulated and 389 down-regulated genes in Control vs UIA groups. Most DEGs enriched in immune response, such as circulating immunoglobulin, immunoglobulin mediated immune response and B cell mediated immunity. A TF-target regulatory network of these DEGs were predicted and suggested that TF RUNX3 has the most target genes, including SBDS, ARTN, LTA, GMFB and so on. qRT-PCR and Western blot validated the higher expression of DBP, NR3C2 and ZNF711, and lower expression of RUNX3 and ZFN711 in IA mice.

Conclusion

5 key TFs DBP, RUNX3, SPIB, NR3C2 and ZNF711 were found to be related to immune response and their up/down-regulated expression were observed in IA mice. As RUNX3, SPIB and NR3C2 shared common target genes, they may involved in co-regulated pathway during IA progression.

Two types of arteriopathies, arteriomegaly and aneurysms, frequently develop at diverse locations in vertebrobasilar dolichoectasia patients: A retrospective analysis and a meta-analysis

BACKGROUND

Past studies have reported that vertebrobasilar dolichoectasia (VBD) patients may develop similar arteriopathies other than the vertebrobasilar system. However, the details of these VBD-related arteriopathies are still unclear.

METHODS

We retrospectively enrolled patients diagnosed with VBD at two stroke centers in Japan between January 2012 and December 2023. Arteries of the brain and the trunk were assessed for arteriopathies resembling VBD by computed tomography angiography. Vessel sizes were defined as the maximum diameter measured on the cross-sectional plane. Age, sex, and race-matched stroke patients were recruited as a control group. Arterial ectasias were subdivided into arteriomegaly, which was defined as diffuse ectasia more than 1.5 times the mean size of the controls, or focal ectasia (i.e., aneurysms). A systematic review of PubMed and Scopus was performed between the date of the databases' inception and June 2024 using the keywords (vertebrobasilar OR basilar OR vertebral) AND (dolichoectasia OR dolichoectatic OR serpentiform OR serpentine OR "fusiform aneurysm"). The prevalences of VBD-related vasculopathy at each anatomical location were meta-analyzed by a random-effect model.

RESULTS

Nineteen VBD patients were enrolled. Radiological data of the brain and the trunk were available in 19 and 7 patients. The median VBD size was 13.4 (IQR, 11.3-19.6) mm. The vessel sizes of the anterior circulation were significantly larger in VBD patients than in the controls [internal carotid artery (ICA), 6.7 (IQR, 5.4-7.8) vs. 3.8 (IQR, 3.5-4.0) mm; M1 segment, 3.2 (IQR 2.9-4.2) vs. 2.5 (IQR 2.4-2.6) mm; P < 0.0001 in both]. These arterial sizes significantly correlated to contralateral counterparts [ICA, ρ = 0.86, P < 0.0001; M1, ρ = 0.62, P = 0.0049]. At the trunk, arteriomegaly or aneurysms were identified in five (71.4 %) patients. The systematic review identified 11 case series, including ours, that reported the prevalences of arteriopathies outside the vertebrobasilar system. The prevalences of arteriomegaly or aneurysms at the anterior circulation have been most frequently reported in 7 case series followed by those at the aorta and coronary artery in 6 and 2, respectively. Meta-analyses corroborated the high prevalences of arteriopathies at the anterior circulation (23 %; 95 % CI, 10-39 %), aorta (37 %; 95 % CI, 21-54 %), and coronary artery (43 %; 95 % CI, 23-65 %).

CONCLUSIONS

Our study suggests that the pathogenesis underlying VBD affects diverse arterial regions and causes two types of arterial remodeling, arteriomegaly and aneurysms.

Genetic susceptibility and potential therapeutic targets of unruptured intracranial aneurysms: A genome-wide study based on Mendelian randomization

BACKGROUND

At present, although some studies have offered certain insights into the genetic factors related to unruptured intracranial aneurysms (uIAs), the potential genetic targets associated with uIAs remain largely unknown. Thus, this research adopted Mendelian randomization (MR) analysis to study two genome-wide association studies on uIAs, aiming to determine the reliable genetic susceptibility and potential therapeutic targets for uIAs.

METHODS

This study summarizes the data of expression quantitative trait loci (eQTL) as exposure data. The outcome data of uIAs were derived from the study by Bakker et al. and the FinnGen Biobank (version R10). The reliable genetic susceptibility and potential therapeutic targets of uIAs were identified by means of Mendelian randomization (MR) methods, with the inverse variance weighting (IVW) method as the primary analytical approach. Simultaneously, sensitivity and pleiotropy analyses were carried out, and the results were visualized. Subsequently, drug predictions and molecular docking were conducted for the potential gene targets to verify their reliability.

RESULTS

The MR analysis of the training cohort identified 100 targets related to uIAs. Then, these 100 gene targets and eQTL data were verified by MR Analysis again with the testing cohort. Finally, 7 gene targets were selected, namely MTMR3, SERINC1, CITED2, NKX3-1, ATOX1, MYADM and SLC20A1-DT.GO/KEGG enrichment analysis confirmed that the 7 gene targets mainly participate in the process Biological functions and pathways such as art development, cellular response to hypoxia, male Gonad development, RNA polymerase II specific DNA binding transcription factor binding, DNA binding transcription factor binding, Mineral absorption, Inositol phase metabolism, Photoshatidylinositol signaling system, etc.The protein-protein interaction（PPI） network describes the interactions between seven gene targets and related proteins.The molecular docking diagram shows good binding between candidate drugs and proteins related to gene targets.

CONCLUSIONS

The study identified 7 reliable gene susceptibility and potential therapeutic targets associated with uIAs, offering new insights for clinical diagnosis and treatment of uIAs, and suggesting novel research directions for understanding the etiology and molecular mechanisms of uIAs.

Potential of the pharmacological inhibition of CCL2-CCR2 axis via targeting FROUNT to prevent the initiation and the progression of intracranial aneurysms in rats

Intracranial aneurysms (IAs) affect 1%-5% of the public and are a major cause of subarachnoid hemorrhage. Currently, there is no medical treatment to prevent the progression or rupture of IAs. Recent studies have defined IA as a chronic inflammatory disease in which macrophages infiltrate intracranial arteries via the CCL2-CCR2 axis. The chemokine signal regulator FROUNT mediates this axis, and it can be inhibited by the anti-alcoholism drug disulfiram. Therefore, inhibition of macrophage infiltration by interfering with FROUNT using disulfiram may represent a strategy to prevent exacerbation of IAs. Here, effects of disulfiram were investigated in vitro and in an animal model of IAs. FROUNT expression was observed on infiltrated macrophages both in human IAs and in the rat IA model by immunohistochemistry. In vitro treatment with disulfiram suppressed CCL2-mediated migration of cultured rat macrophages in a transwell system. Disulfiram administered in a rat model of IAs inhibited both the initiation and the enlargement of IAs in a dose-dependent manner; this was accompanied by suppression of macrophage infiltration. These results suggest that pharmacological inhibition of the CCL2-CCR2-FROUNT signaling cascade could be a treatment of patients with IAs.

Animal Models of Intracranial Aneurysms: History, Advances, and Future Perspectives

Intracranial aneurysms (IA) are a disease process with potentially devastating outcomes, particularly when rupture occurs leading to subarachnoid hemorrhage. While some candidates exist, there is currently no established pharmacological prevention of growth and rupture. The development of prophylactic treatments is a critical area of research, and preclinical models using animals play a pivotal role. These models, which utilize various species and induction methods, each possess unique characteristics that can be leveraged depending on the specific aim of the study. A comprehensive understanding of these models, including their historical development, is crucial for appreciating the advantages and limitations of aneurysm research in animal models.We summarize the significant roles of animal models in IA research, with a particular focus on rats, mice, and large animals. We discuss the pros and cons of each model, providing insights into their unique characteristics and contributions to our understanding of IA. These models have been instrumental in elucidating the pathophysiology of IA and in the development of potential therapeutic strategies.A deep understanding of these models is essential for advancing research on preventive treatments for IA. By leveraging the unique strengths of each model and acknowledging their limitations, researchers can conduct more effective and targeted studies. This, in turn, can accelerate the development of novel therapeutic strategies, bringing us closer to the goal of establishing an effective prophylactic treatment for IA. This review aims to provide a comprehensive view of the current state of animal models in IA research.

CD68 in Cerebral Aneurysms of Smokers and Nonsmokers: An Immunohistochemical Analysis

BACKGROUND

 There is some evidence indicating that inflammation of the aneurysmal wall is related to aneurysmal growth and rupture. The presence of CD68 may indicate greater inflammatory activity. The objective of this study is to evaluate CD68 immunoexpression in surgically resected brain aneurysms and its association with smoking.

METHODS

 The resected brain aneurysmal walls after microsurgical clipping were envoyed to immunohistochemistry investigation. The objective was to evaluate the expression of CD68 and CD34 antibodies. The associations between inflammatory markers, smoking, and rupture were tested using Fischer's exact test.

RESULTS

 CD68 immunoexpression in the tunica media was associated with larger aneurysms: 7.0 mm (7.0-9.0 mm) versus 5.0 mm (3.5-5 mm; p = 0.011). There was no statistically significant association between smoking and CD68 expression in the tunica media (p = 0.234) or in either the tunica media or the tunica intima (p = 0.628). There was also no statistically significant association between hemorrhagic presentation of the aneurysm and CD68 expression in the tunica media (p = 0.689) or in either the tunica media or the tunica intima (p = 0.348). Therefore, the presence of CD68-positive cells in the aneurysmal walls indicates an association with size, especially if the tunica media is exclusively compromised (p = 0.011).

CONCLUSION

 Immunohistochemistry investigation for CD68 antibodies was used to determine histiocytic infiltration. Adequately powered studies are necessary to further investigate the association between CD68-positive cells and both smoking history and hemorrhagic presentation of aneurysms.

JNK2-MMP-9 axis facilitates the progression of intracranial aneurysms

Intracranial aneurysm (IA) can cause subarachnoid hemorrhage or some other hemorrhagic stroke after rupture. Because of the poor outcome in spite of the intensive medical care after the onset of hemorrhage, the development of a novel therapeutic strategy like medical therapy to prevent the progression of the disease becomes a social need. As the reduction of arterial stiffness due to the degeneration of the extracellular matrix via Matrix Metalloproteinases (MMPs) becomes one of the central machineries leading to the progression of IAs through a series of studies, factors regulating the expression or the activity of MMPs could be a therapeutic target. In the present study, specimens from human IA lesions and the animal model of IAs were used to examine the expression of c-Jun N-terminal kinase (JNK) which might exacerbate expressions of MMPs in the lesions to weaken arterial walls resulting in the progression of the disease. In some human IA lesions examined, the expression of p-JNK, the activated form of JNK, could be detected mostly in the medial smooth muscle cells. In IA lesions induced in rats, the activation of JNK was induced during the progression of the disease and accompanied with the activation of downstream transcriptional factor c-Jun and importantly with the expression of MMP-2 or -9. The genetic deletion of Jnk2, not Jnk1, in mice significantly prevented the incidence of IAs with the suppression of the expression of MMP-2 or MMP-9. These results combined together have suggested the crucial role of JNK in the progression of IAs through regulating the expression of MMPs. The results from the present study provides the novel insights about the pathogenesis of IA progression and also about the therapeutic target.

Bioinformatics analysis revealed the potential crosstalk genes and molecular mechanisms between intracranial aneurysms and periodontitis

OBJECTIVES

The risk of intracranial aneurysms (IAs) development and rupture is significantly higher in patients with periodontitis (PD), suggesting an association between the two. However, the specific mechanisms of association between these two diseases have not been fully investigated.

MATERIALS AND METHODS

In this study, we downloaded IAs and PD data from the Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified, and functional enrichment analysis was performed. The protein-protein interaction (PPI) network and weighted gene co-expression network analysis (WGCNA) was performed to identified key modules and key crosstalk genes. In addition, the immune cell landscape was assessed and the correlation of key crosstalk genes with each immune cell was calculated. Finally, transcription factors (TFs) regulating key crosstalk genes were explored.

RESULTS

127 overlapping DEGs were identified and functional enrichment analysis highlighted the important role of immune reflection in the pathogenesis of IAs and PD. We identified ITGAX and COL4A2 as key crosstalk genes. In addition, the expression of multiple immune cells was significantly elevated in PDs and IAs compared to controls, and both key crosstalk genes were significantly negatively associated with Macrophages M2. Finally, GATA2 was identified as a potential key transcription factor (TF), which regulates two key crosstalk gene.

CONCLUSIONS

The present study identifies key crosstalk genes and TF in PD and IAs, providing new insights for further study of the co-pathogenesis of PD and IAs from an immune and inflammatory perspective. Also, this is the first study to report the above findings.

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.

Peripheral macrophages in the development and progression of structural cerebrovascular pathologies

The human cerebrovascular system is responsible for maintaining neural function through oxygenation, nutrient supply, filtration of toxins, and additional specialized tasks. While the cerebrovascular system has resilience imparted by elaborate redundant collateral circulation from supportive tertiary structures, it is not infallible, and is susceptible to developing structural vascular abnormalities. The causes of this class of structural cerebrovascular diseases can be broadly categorized as 1) intrinsic developmental diseases resulting from genetic or other underlying aberrations (arteriovenous malformations and cavernous malformations) or 2) extrinsic acquired diseases that cause compensatory mechanisms to drive vascular remodeling (aneurysms and arteriovenous fistulae). Cerebrovascular diseases of both types pose significant risks to patients, in some cases leading to death or disability. The drivers of such diseases are extensive, yet inflammation is intimately tied to all of their progressions. Central to this inflammatory hypothesis is the role of peripheral macrophages; targeting this critical cell type may lead to diagnostic and therapeutic advancement in this area. Here, we comprehensively review the role that peripheral macrophages play in cerebrovascular pathogenesis, provide a schema through which macrophage behavior can be understood in cerebrovascular pathologies, and describe emerging diagnostic and therapeutic avenues in this area.

Current understanding of macrophages in intracranial aneurysm: relevant etiological manifestations, signaling modulation and therapeutic strategies

Macrophages activation and inflammatory response play crucial roles in intracranial aneurysm (IA) formation and progression. The outcome of ruptured IA is considerably poor, and the mechanisms that trigger IA progression and rupture remain to be clarified, thereby developing effective therapy to prevent subarachnoid hemorrhage (SAH) become difficult. Recently, climbing evidences have been expanding our understanding of the macrophages relevant IA pathogenesis, such as immune cells population, inflammatory activation, intra-/inter-cellular signaling transductions and drug administration responses. Crosstalk between macrophages disorder, inflammation and cellular signaling transduction aggravates the devastating consequences of IA. Illustrating the pros and cons mechanisms of macrophages in IA progression are expected to achieve more efficient treatment interventions. In this review, we summarized the current advanced knowledge of macrophages activation, infiltration, polarization and inflammatory responses in IA occurrence and development, as well as the most relevant NF-κB, signal transducer and activator of transcription 1 (STAT1) and Toll-Like Receptor 4 (TLR4) regulatory signaling modulation. The understanding of macrophages regulatory mechanisms is important for IA patients' clinical outcomes. Gaining insight into the macrophages regulation potentially contributes to more precise IA interventions and will also greatly facilitate the development of novel medical therapy.

WNTA5-mediated miR-374a-5p regulates vascular smooth muscle cell phenotype transformation and M1 macrophage polarization impacting intracranial aneurysm progression

miR-374a-5p expression and localization in intracranial aneurysm (IA) tissues were detected, and its correlation with vascular smooth muscle cells (VSMCs) and macrophage markers was analyzed. Using platelet-derived growth factor-BB (PDGF-BB) induced VSMC model, elastase-induced IA rat model. Subsequently, miR-374a-5p was knocked down or overexpressed. We investigated the effects of miR-374a-5p on phenotypic conversion, and in vivo experiments were also carried out to verify the findings. The targeted relationship between miR-374a-5p and WNTA5 was analyzed. The effect of WNT5A inhibition on VSMC phenotypic transformation and THP-1-derived macrophage polarization was explored. Clinical studies have shown that miR-374a-5p was upregulated in IA patients. miR-374a-5p was negatively correlated with SM22α, α-SMA, CD206, and positively correlated with CD86. In vitro experiments showed that knocking down miR-374a-5p reversed the promotion of SM22α and α-SMA expression by PDGF-BB, while overexpression of miR-374a-5p had the opposite effect. In addition, knocking down miR-374a-5p also reversed the decrease in Calponin, TIMP3, TIMP4, and IL-10 levels caused by PDGF-BB, and further reduced the levels of MMP1, MMP3, MMP9, IL-1β, IL-6, and TNF-α. These findings were further validated in vivo. In IA rats, there were notable increases in both systolic and diastolic blood pressure, along with an elevated M1/M2 ratio and the occurrence of vascular lesions. However, these symptoms were improved after knocking down miR-374a-5p. Furthermore, miR-374a-5p could target the WNT signals (WNT2B, WNT3, and WNT5A). miR-374a-5p regulated the VSMC phenotypic conversion and M1 macrophage polarization by targeting WNT5A, thereby impacting the progression of IA.

Plasma levels of CD36 and glutathione as biomarkers for ruptured intracranial aneurysm

Evidence has proved that intracranial aneurysm (IA) formation and rupture might be closely related to inflammatory response and oxidative stress. Our objective was to evaluate the potential of CD36 and glutathione (GSH) as biomarkers for IA. In this study, the enzyme-linked immunosorbent assay was used to measure the plasma levels of CD36 and GSH in 30 IA patients and 30 healthy controls. Then, correlation analysis, receiver operating characteristic (ROC) curve, and logistic regression analysis were performed. The results showed that the plasma level of CD36 in IA patients was significantly higher than that in the control group (P < 0.0001), and plasma GSH was significantly lower compared with that in the control group (P < 0.0001). ROC analysis showed that CD36 and GSH had high sensitivity (90.0 and 96.6%) and specificity (96.6 and 86.6%) for IA diagnosis. The combined sensitivity and specificity achieved were 100 and 100%, respectively. The plasma levels of CD36 and GSH did not show a significant correlation with age, the Glasgow Coma Scale, Hunter-Hess score, aneurysm size, aneurysm height, aneurysm neck, and aspect ratio. The AUC of the logistic regression model based on CD36 and GSH was 0.505. Our results suggested that the combination of plasma CD36 and GSH could serve as potential biomarkers for IA rupture.

Identification of miRNAs Involved in Intracranial Aneurysm Rupture in Cigarette-Smoking Patients

INTRODUCTION

Smoking is an independent risk factor for the formation and rupture of intracranial aneurysms (IA). However, the underlying mechanism remains unclear.

METHODS

In this study, we performed miRNA sequencing on plasma from 10 smoking patients with IA, 10 non-smoking patients with IA, and 10 healthy controls. The differentially expressed miRNAs (DE miRNAs) between smoking and non-smoking patients with IA were identified. Functional and pathway enrichment analysis is employed to investigate the potential functions of those DE miRNA target genes. The correlations with the clinical parameters were assessed using receiver operating characteristic curve (ROC) analysis.

RESULTS

In total, we identified 428 DE miRNAs. Functional enrichment analysis showed the target genes were significantly enriched in biological aspects related to cell characteristics, such as cell cycle, cell differentiation, and cell migration. Pathway analysis showed DE miRNAs mainly enriched in the PI3K-Akt signaling pathway, Focal adhesion, and JAK-STAT signaling pathway. The expressions of miR-574-5p, miR-151a-3p, and miR-652-3p correlated well with aneurysm parameters. The AUC of miR-574-5p, miR-151a-3p, and miR-652-3p were 97%, 92%, and 99%, respectively.

CONCLUSION

Our study indicated that smoking significantly altered the plasma miRNA profile in patients with IA. The expression of miR-574-5p, miR-151a-3p, and miR-652-3p correlated with aneurysm parameters, which may play a significant role in the formation and rupture of IA.

A novel clinical-radscore nomogram for predicting ruptured intracranial aneurysm

Objectives

Our study aims to find the more practical and powerful method to predict intracranial aneurysm (IA) rupture through verification of predictive power of different models.

Methods

Clinical and imaging data of 576 patients with IAs including 192 ruptured IAs and matched 384 unruptured IAs was retrospectively analyzed. Radiomics features derived from computed tomography angiography (CTA) images were selected by t-test and Elastic-Net regression. A radiomics score (radscore) was developed based on the optimal radiomics features. Inflammatory markers were selected by multivariate regression. And then 4 models including the radscore, inflammatory, clinical and clinical-radscore models (C-R model) were built. The receiver operating characteristic curve (ROC) was performed to evaluate the performance of each model, PHASES and ELAPSS. The nomogram visualizing the C-R model was constructed to predict the risk of IA rupture.

Results

Five inflammatory features, 2 radiological characteristics and 7 radiomics features were significantly associated with IA rupture. The areas under ROCs of the radscore, inflammatory, clinical and C-R models were 0.814, 0.935, 0.970 and 0.975 in the training cohort and 0.805, 0.927, 0.952 and 0.962 in the validation cohort, respectively.

Conclusion

The inflammatory model performs particularly well in predicting the risk of IA rupture, and its predictive power is further improved by combining with radiological and radiomics features and the C-R model performs the best. The C-R nomogram is a more stable and effective tool than PHASES and ELAPSS for individually predicting the risk of rupture for patients with IA.

Comparison of clinical efficacy and safety between interventional embolization and craniotomy clipping for anterior circulation aneurysms

Objective

To investigate the clinical efficacy and safety of interventional embolization in the treatment of anterior circulation aneurysms.

Methods

Eighty patients with anterior circulation aneurysms admitted to People's Hospital of Leshan from June 2019 to December 2021 were retrospectively analyzed. According to the different surgical methods, they were divided into two groups: the observation group and the control group. Patients in the observation group were given interventional embolization, while those in the control group were given craniotomy clipping. The surgical efficacy, postoperative neurological function and quality of life, surgical prognosis and surgical complications of the two groups were compared.

Results

The intraoperative blood loss and hospitalization time in the observation group were lower than those in the control group (p<0.05). The scores of the Hunt-Hess and modified Rankin scale in the observation group were significantly lower than those in the control group three months after surgery (p<0.05). The good prognosis rate of the observation group was higher than that of the control group (p<0.05). Moreover, the complication rate of the observation group was 12.50%, which was significantly lower than 32.50% in the control group (p<0.05).

Conclusion

Interventional embolization shows the advantages of minimally invasive procedures such as shorter operative times and shorter hospital stays. It has better clinical safety because it can significantly improve the neurological function and quality of life of patients, improve the prognosis of patients, and reduce the incidence of complications.

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.

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.

Intramural Hematoma in Vertebrobasilar Dolichoectasia-Related Stroke: A Retrospective Analysis of Six Consecutive Patients

BACKGROUND

The pathophysiology underlying vertebrobasilar dolichoectasia (VBD) is largely unknown. However, a few reports have demonstrated that acute intramural hematoma (IMH) in VBD is associated with stroke. We aimed to investigate the clinical and radiological features of IMH in VBD and the role of IMH in predicting rupture and patient outcomes.

METHODS

We retrospectively reviewed the medical records of patients treated in 2 stroke centers between January 2012 and December 2021. Patients presenting with VBD and stroke were eligible for study inclusion. We excluded patients with stroke caused by arterial dissection or artery-to-artery embolism. IMH was defined as a crescent-shaped area of high signal density in the vessel wall on axial computed tomography in the absence of an intimal flap, double lumen, and pearl-and-string sign.

RESULTS

Six patients were analyzed. All presented with symptoms of brainstem/cerebellar infarction without headache. Interobserver agreement for the presence or absence of IMH was excellent (100%). IMH was detected in 5 patients. The positive predictive value of IMH for rupture was 80% (95% confidence interval, 28%-99.5%). The median time from symptom onset to rupture was 2.5 days (range, 1.5-4). Median computed tomography values were significantly higher within the IMH than those in the lumen of the basilar artery (70 vs. 44.5 Hounsfield units; P = 0.008). The modified Rankin scale score on day 30 after onset was 5 in 1 patient and 6 in the remaining 5.

CONCLUSIONS

IMH in patients with VBD presenting with brainstem/cerebellar infarction should be regarded as a sign associated with a high risk of rupture.

Clinical Usage of Different Doses of Cis-Atracurium in Intracranial Aneurysm Surgery and Its Effect on Motor-Evoked Potentials

The objective of this work was to investigate the effect of different doses of cis-atracurium on patients undergoing general anesthesia induction (GAI) during intracranial aneurysm surgery (ICAS). In this work, 90 patients who underwent ICAS under the elective motor-evoked potential (MEP) monitoring in the First Affiliated Hospital of Northwest University (Xi'an No. 1 Hospital) from January 2021 to May 2022 were enrolled as the research objects. Randomly, they were rolled into a S1 group (30 cases, 2 times 95% effective dose (ED95) cis-atracurium), a S2 group (30 cases, 3 times ED95 cis-atracurium), and a S3 group (30 cases, 4 times ED95 cis-atracurium). The endotracheal intubation conditions, the train-of-four (TOF) rate (TOFR), body movement, and spontaneous breathing were compared among the three groups of patients. The results showed that the MEP inhibition time of the patients in the S3 group was much longer than that of the S1 and S2 groups, but it showed no significant difference between the S1 group and S2 group (P > 0.05). The good rates of endotracheal intubation conditions in the S2 group (100%) and S3 group (100%) were obviously higher than the rate in the S1 group (43.33%). The TOFRs of patients in S2 and S3 groups at time t2 and t3 were lower obviously to that at time t0, while the TOFRs of patients in S3 group at time t2 and t3 were still lower in contrast to the S2 group (P < 0.05). The mean arterial pressure (MAP) and heart rate (HR) of patients in all groups were lower at t1, t2, and t3 than at t0 (P < 0.05), while the differences among different groups were not remarkable (P > 0.05). Finally, using 3 times ED95 cis-atracurium for GAI could reduce the risk of intraoperative body movement and spontaneous breathing, as well as the residual degree of muscle relaxation, in patients with ICAS, without affecting MEP monitoring, improving endotracheal intubation conditions, and increasing safety during open neurosurgery operations.

Impinging Flow Induces Expression of Monocyte Chemoattractant Protein-1 in Endothelial Cells Through Activation of the c-Jun N-terminal Kinase/c-Jun/p38/c-Fos Pathway

OBJECTIVE

Monocyte chemoattractant protein-1 (MCP-1) is an important regulator of the formation and development of intracranial aneurysms. This study explored the molecular mechanisms underlying the induction of MCP-1 and related inflammatory factors in human umbilical vein endothelial cells (HUVECs) under hemodynamic conditions.

METHODS

A modified T chamber was used to simulate fluid flow at the bifurcation of the artery and wall shear stress on HUVECs in vitro. Changes in HUVECs were analyzed in response to impinging flow. And HUVECs without impinging flow were used as the control group. Protein expression levels of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, activator protein-1, and MCP-1 were detected by Western blot, and the messenger RNA expression levels of MCP-1, interleukin (IL)-1β, and IL-6 were determined by quantitative reverse transcription polymerase chain reaction.

RESULTS

Under impinging flow, the phosphorylation levels of ERK, JNK, and p38, as well as the protein levels of MCP-1, c-Jun, and c-Fos, increased. The messenger RNA expression of MCP-1, IL-1β, and IL-6 also increased in HUVECs. Pretreatment of the HUVECs with inhibitors of JNK and p38 significantly attenuated the increased expression of MCP-1, IL-1β, and IL-6, while ERK inhibitors had no obvious effect.

CONCLUSIONS

Under impinging flow, MCP-1 and inflammatory factors are regulated through the JNK/c-Jun/p38/c-Fos pathway and participate in EC inflammation.

The bifurcation angle is associated with the progression of saccular aneurysms

The role of the bifurcation angle in progression of saccular intracranial aneurysms (sIAs) has been undetermined. We, therefore, assessed the association of bifurcation angles with aneurysm progression using a bifurcation-type aneurysm model in rats and anterior communicating artery aneurysms in a multicenter case–control study. Aneurysm progression was defined as growth by ≥ 1 mm or rupture during observation, and controls as progression-free for 30 days in rats and ≥ 36 months in humans. In the rat model, baseline bifurcation angles were significantly wider in progressive aneurysms than in stable ones. In the case–control study, 27 and 65 patients were enrolled in the progression and control groups. Inter-observer agreement for the presence or absence of the growth was excellent (κ coefficient, 0.82; 95% CI, 0.61–1.0). Multivariate logistic regression analysis showed that wider baseline bifurcation angles were significantly associated with subsequent progressions. The odds ratio for the progression of the second (145°–179°) or third (180°–274°) tertiles compared to the first tertile (46°–143°) were 5.5 (95% CI, 1.3–35). Besides, the bifurcation angle was positively correlated with the size of aneurysms (Spearman’s rho, 0.39; P = 0.00014). The present study suggests the usefulness of the bifurcation angle for predicting the progression of sIAs.

Impact of COVID-19 Pandemic on Treatment Management and Clinical Outcome of Aneurysmal Subarachnoid Hemorrhage – A Single-Center Experience

Background

Previous studies reported decreased volumes of acute stroke admissions during the COVID-19 pandemic. We aimed to examine whether aneurysmal subarachnoid hemorrhage (aSAH) volumes demonstrated similar declines in our department. Furthermore, the impact of the pandemic on disease progression should be analyzed.

Methods

We conducted a retrospective study in the neurosurgical department of the university hospital Frankfurt including patients with the diagnosis of aSAH during the first year of the COVID pandemic. One year cumulative volume for aSAH hospitalization procedures was compared to the year before (03/2020 – 02/2021 vs. 03/2019 – 02/2020) and the last 5 pre-COVID-pandemic years (2015-2020). All relevant patient characteristics concerning family history, disease history, clinical condition at admission, active/past COVID-infection, treatment management, complications, and outcome were analyzed.

Results

Compared to the 84 hospital admissions during the pre-pandemic years, the number of aSAH hospitalizations (n = 56) declined during the pandemic without reaching significance. No significant difference in the analyzed patient characteristics including clinical condition at onset, treatment, complications, and outcome, between 56 patients with aSAH admitted during the COVID pandemic and the treated patients in the last 5 years in the pre-COVID period were found. In our multivariable analysis, we detected young age (p &lt; 0.05; OR 4.2) and no existence of early hydrocephalus (p &lt; 0.05; OR 0.13) as important factors for a favorable outcome (mRS ≤ 0–2) after aSAH during the COVID pandemic. A past COVID-infection was detected in young patients suffering from aSAH (Age &lt;50years, p &lt; 0.05; OR 10.5) with an increased rate of cerebral vasospasm after aSAH onset (p &lt; 0.05; OR 26). Nevertheless, past COVID-infection did not reach significance as a high-risk factor for unfavorable outcomes.

Conclusion

There was a relative decrease in the number of patients with aSAH during the COVID-19 pandemic. Despite the extremely different conditions of hospitalization, there was no impairing significant effect on the treatment and outcome of admitted patients with aSAH. A past COVID infection seemed to be an irrelevant limiting factor concerning favorable outcomes.

Whole-exome sequencing in a Japanese multiplex family identifies new susceptibility genes for intracranial aneurysms

Background

Intracranial aneurysms (IAs) cause subarachnoid hemorrhage, which has high rates of mortality and morbidity when ruptured. Recently, the role of rare variants in the genetic background of complex diseases has been increasingly recognized. The aim of this study was to identify rare variants for susceptibility to IA.

Methods

Whole-exome sequencing was performed on seven members of a Japanese pedigree with highly aggregated IA. Candidate genes harboring co-segregating rare variants with IA were re-sequenced and tested for association with IA using additional 500 probands and 323 non-IA controls. Functional analysis of rare variants detected in the pedigree was also conducted.

Results

We identified two gene variants shared among all four affected participants in the pedigree. One was the splicing donor c.1515+1G>A variant in NPNT (Nephronectin), which was confirmed to cause aberrant splicing by a minigene assay. The other was the missense p.P83T variant in CBY2 (Chibby family member 2). Overexpression of p.P83T CBY2 fused with red fluorescent protein tended to aggregate in the cytoplasm. Although Nephronectin has been previously reported to be involved in endothelial angiogenic functions, CBY2 is a novel molecule in terms of vascular pathophysiology. We confirmed that CBY2 was expressed in cerebrovascular smooth muscle cells in an isoform2-specific manner. Targeted CBY2 re-sequencing in additional case-control samples identified three deleterious rare variants (p.R46H, p.P83T, and p.L183R) in seven probands, showing a significant enrichment in the overall probands (8/501) compared to the controls (0/323) (p = 0.026, Fisher’s extract test).

Conclusions

NPNT and CBY2 were identified as novel susceptibility genes for IA. The highly heterogeneous and polygenic architecture of IA susceptibility can be uncovered by accumulating extensive analyses that focus on each pedigree with a high incidence of IA.

Potential Role of the Chemotaxis System in Formation and Progression of Intracranial Aneurysms Through Weighted Gene Co-Expression Network Analysis

Background

Intracranial aneurysm (IA) is the most common and is the main cause of spontaneous subarachnoid hemorrhage (SAH). The underlying molecular mechanisms for preventing IA progression have not been fully identified. Our research aimed to identify the key genes and critical pathways of IA through gene co-expression networks.

Methods

Gene Expression Omnibus (GEO) datasets GSE13353, GSE54083 and GSE75436 were used in the study. The genetic data were analyzed by weighted gene co-expression network analysis (WGCNA). Then the clinically significant modules were identified and the differentially expressed genes (DEGs) with the genes were intersected in these modules. GO (gene ontology) and KEGG (Kyoto Gene and Genomic Encyclopedia) were used for gene enrichment analysis to determine the function or pathway. In addition, the composition of immune cells was analyzed by CIBERSORT algorithm. Finally, the hub genes and key genes were identified by GSE122897.

Results

A total of 266 DEGs and two modules with clinical significance were identified. The inflammatory response and immune response were identified by GO and KEGG. CCR5, CCL4, CCL20, and FPR3 were the key genes in the module correlated with IA. The proportions of infiltrating immune cells in IA and normal tissues were different, especially in terms of macrophages and mast cells.

Conclusion

The chemotactic system has been identified as a key pathway of IA, and interacting macrophages may regulate this pathological process.

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.

Disturbed flow's impact on cellular changes indicative of vascular aneurysm initiation, expansion, and rupture: A pathological and methodological review

Aneurysms are malformations within the arterial vasculature brought on by the structural breakdown of the microarchitecture of the vessel wall, with aneurysms posing serious health risks in the event of their rupture. Blood flow within vessels is generally laminar with high, unidirectional wall shear stressors that modulate vascular endothelial cell functionality and regulate vascular smooth muscle cells. However, altered vascular geometry induced by bifurcations, significant curvature, stenosis, or clinical interventions can alter the flow, generating low stressor disturbed flow patterns. Disturbed flow is associated with altered cellular morphology, upregulated expression of proteins modulating inflammation, decreased regulation of vascular permeability, degraded extracellular matrix, and heightened cellular apoptosis. The understanding of the effects disturbed flow has on the cellular cascades which initiate aneurysms and promote their subsequent growth can further elucidate the nature of this complex pathology. This review summarizes the current knowledge about the disturbed flow and its relation to aneurysm pathology, the methods used to investigate these relations, as well as how such knowledge has impacted clinical treatment methodologies. This information can contribute to the understanding of the development, growth, and rupture of aneurysms and help develop novel research and aneurysmal treatment techniques.

The roles and diagnostic value of miRNA-1246 in the serum of patients with intracranial aneurysms

Background

Inflammatory response is one of the important factors affecting the formation of intracranial aneurysm. miR-1246 is involved in the regulation of several inflammatory diseases; however, its expression levels and the mechanism of action in intracranial aneurysms remain further investigated.

Methods

Bioinformatics was used to analyze the levels of micro-RNAs (miRNAs) in the serum of intracranial aneurysm patients as well as in the intracranial aneurysm tissues downloaded from the GEO RNA-seq database. Blood samples were collected pre-operatively from patients with intracranial aneurysms as well as from healthy volunteers, and miRNA-1246 expression levels were detected using quantitative reverse transcriptase polymerase chain reaction. Meanwhile, the diagnostic value of miR-1246 for intracranial aneurysm was explored using the receiver operating characteristic (ROC) curve.

Principle findings and results

Serum levels of miR-1246 were elevated in intracranial aneurysm patients. Bioinformatics studies revealed that the target genes of miR-1246, TP53, glycogen synthetase kinase (GSK), and transcription factor YY1 may play important roles in the development of intracranial aneurysms. miR-1246 is involved in inflammatory response, lipid, and atherosclerotic signaling pathways.

Conclusions and significance

High level of miR-1246 is found in the serum of patients with intracranial aneurysms and may serve as a diagnostic or/and treatment marker for intracranial aneurysms.

Reduced M2 macrophages and adventitia collagen dampen the structural integrity of blood blister-like aneurysms and induce preoperative rerupture

Objective

Blood blister–like aneurysms (BBAs) are extremely rare aneurysms. They are predisposed to preoperative rerupture with a high case‐fatality rate. Here, we attempt to interrogate the distinct clinicopathology and the histological basis underlying its clinical rerupture.

Methods

Three middle meningeal arteries, 11 BBA (5 reruptured, 6 non‐rerupture) and 19 saccular aneurysm samples were obtained for histopathological investigation. Three reruptured BBAs, 3 non‐reruptured BBAs and 6 saccular (3 ruptured, 3 unruptured) aneurysms were obtained for quantitative flow cytometry analysis.

Results

Compared with true saccular aneurysms, the BBA aneurysm wall lacks arterial stroma cells including CD31+ endothelial cells and α‐SMA + smooth muscle cells. Only fibroblasts and adventitial collagen were observed in the BBA aneurysm wall. Meanwhile, BBAs were enriched with infiltrated inflammatory cells, especially polarized macrophages. Based on the rerupture status, those reruptured BBAs showed drastically reduced fibroblasts and adventitia collagen. Moreover, M2‐polarized macrophages were observed dominant in BBAs and exhibit repairing cellular functions based on their interplays with arterial fibroblasts. Reduced M2 macrophages and arterial tissue repairing modulation may be responsible for the decreasing collagen synthesis and fibrosis repairment, which potentially dampens the aneurysm integrity and induces BBA aneurysm reruputre.

Conclusions

BBAs poses histopathological features of occult pseudoaneurysms or dissecting aneurysms. Reduced M2 macrophages and adventitia collagen may dampen the structural integrity of BBAs and induce preoperative rerupture.

Aneurysmal Subarachnoid Hemorrhage in Patients with Coronavirus Disease 2019 (COVID-19): A Case Series

Objective

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is a pressing public health issue. Although most cases do not result in severe illness requiring hospitalization, there is increasing evidence that SARS-CoV-2–induced inflammation can exacerbate pre-existing diseases. We sought to describe the characteristics of patients with aneurysmal subarachnoid hemorrhage who were actively or very recently infected with SARS-CoV-2.

Methods

We reviewed subarachnoid hemorrhage cases of patients who also were positive for SARS-CoV-2 at 5 high-volume cerebrovascular centers in the United States from March 2020 to January 2021. Cases of aneurysmal subarachnoid hemorrhage were analyzed.

Results

A total of 10 patients were identified, consisting of 5 women (50%) and 5 men (50%). Median age was 38.5 years. Four of the 10 patients (40%) were asymptomatic with respect to SARS-CoV-2–related symptoms, 3 patients (30%) had mild-to-moderate symptoms, and 3 patients (30%) had severe coronavirus disease 2019 (COVID-19), with pneumonia and sepsis. Of the 10 cases, 4 had dissecting pseudoaneurysms (40%), 3 in the posterior circulation and 1 in the anterior circulation. Among 6 saccular/blister aneurysms, 4 (67%) were ≤4 mm in largest diameter.

Conclusions

Our experience with aneurysmal subarachnoid hemorrhage in patients positive for COVID-19 reveals a possibly distinct pattern compared with traditional aneurysmal subarachnoid hemorrhage, namely a high frequency of small aneurysms, dissecting pseudoaneurysms, and young patients.

Cerebrovascular Anomalies: Perspectives From Immunology and Cerebrospinal Fluid Flow

Appropriate vascular function is essential for the maintenance of central nervous system homeostasis and is achieved through virtue of the blood-brain barrier; a specialized structure consisting of endothelial, mural, and astrocytic interactions. While appropriate blood-brain barrier function is typically achieved, the central nervous system vasculature is not infallible and cerebrovascular anomalies, a collective terminology for diverse vascular lesions, are present in meningeal and cerebral vasculature supplying and draining the brain. These conditions, including aneurysmal formation and rupture, arteriovenous malformations, dural arteriovenous fistulas, and cerebral cavernous malformations, and their associated neurological sequelae, are typically managed with neurosurgical or pharmacological approaches. However, increasing evidence implicates interacting roles for inflammatory responses and disrupted central nervous system fluid flow with respect to vascular perturbations. Here, we discuss cerebrovascular anomalies from an immunologic angle and fluid flow perspective. We describe immune contributions, both common and distinct, to the formation and progression of diverse cerebrovascular anomalies. Next, we summarize how cerebrovascular anomalies precipitate diverse neurological sequelae, including seizures, hydrocephalus, and cognitive effects and possible contributions through the recently identified lymphatic and glymphatic systems. Finally, we speculate on and provide testable hypotheses for novel nonsurgical therapeutic approaches for alleviating neurological impairments arising from cerebrovascular anomalies, with a particular emphasis on the normalization of fluid flow and alleviation of inflammation through manipulations of the lymphatic and glymphatic central nervous system clearance pathways.

Hemodynamic Force as a Potential Regulator of Inflammation-Mediated Focal Growth of Saccular Aneurysms in a Rat Model

Past studies have elucidated the crucial role of macrophage-mediated inflammation in the growth of intracranial aneurysms (IAs), but the contributions of hemodynamics are unclear. Considering the size of the arteries, we induced de novo aneurysms at the bifurcations created by end-to-side anastomoses with the bilateral common carotid arteries in rats. Sequential morphological data of induced aneurysms were acquired by magnetic resonance angiography. Computational fluid dynamics analyses and macrophage imaging by ferumoxytol were performed. Using this model, we found that de novo saccular aneurysms with a median size of 3.2 mm were induced in 20/45 (44%) of animals. These aneurysms mimicked human IAs both in morphology and pathology. We detected the focal growth of induced aneurysms between the 10th and 17th day after the anastomosis. The regional maps of hemodynamic parameters demonstrated the area exposed to low wall shear stress (WSS) and high oscillatory shear index (OSI) colocalized with the regions of growth. WSS values were significantly lower in the growing regions than in ones without growth. Macrophage imaging showed colocalization of macrophage infiltration with the growing regions. This experimental model demonstrates the potential contribution of low WSS and high OSI to the macrophage-mediated growth of saccular aneurysms.

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.

Non-coding RNAs role in intracranial aneurysm: General principles with focus on inflammation

Intracranial aneurysm (IA) is one of the most challenging vascular lesions in the brain for clinicians. It was reported that 1%-6% of the world's population is affected by IAs. Owing to serious complications arising from these lesions, much attention has been paid to better understand their pathophysiology. Non-coding RNAs including short non-coding RNAs and long non-coding RNAs, have critical roles in modulating physiologic and pathological processes. These RNAs are emerging as new fundamental regulators of gene expression, are related with the progression of IA. Non-coding RNAs act via multiple mechanisms and be involved in vascular development, growth and remodeling. Furthermore, these molecules are involved in the regulation of inflammation, a key process in the formation and rupture of IA. Studying non-coding RNAs can yield a hypothetical mechanism for better understanding IA. The present study aims to focus on the role of these non-coding RNAs in the pathogenesis of IA.

Induction of CCN1 in Growing Saccular Aneurysms: A Potential Marker Predicting Unstable Lesions

Growing evidence has suggested that inflammatory responses promote the progression of saccular intracranial aneurysms (IAs). However, a biomarker predicting the progression has yet to be established. This study aimed to identify novel molecules upregulated during the progression using a previously established rat aneurysm model. In this model, aneurysms are induced at the surgically created common carotid artery (CCA) bifurcation. Based on sequential morphological data, the observation periods after the surgical manipulations were defined as the growing phase (on the 10th day) or the stable phase (on the 30th day). Total cell lysates from the CCA with or without an aneurysm lesion were prepared to perform protein array analysis. The protein array analysis revealed that the matricellular protein cellular communication network factor 1 (CCN1) is induced in lesions during the growing phase. Immunohistochemistry corroborated the significant upregulation of CCN1 in the growing phase compared with the stable phase. Simultaneously with the induction of CCN1, significant increases in the number of CD68-positive macrophages, myeloperoxidase-positive cells, and proliferating smooth muscle cells in lesions were observed. Immunohistochemistry of human IA specimens reproduced the induction of CCN1 in some lesions. These findings imply a potential role of CCN1 as a marker predicting the progression of saccular aneurysms.

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.

Candidate drugs for preventive treatment of unruptured intracranial aneurysms: A cross-sectional study

Background and purpose

Establishment of drug therapy to prevent rupture of unruptured intracranial aneurysms (IAs) is needed. Previous human and animal studies have gradually clarified candidate drugs for preventive treatment of IA rupture. However, because most of these candidates belong to classes of drugs frequently co-administered to prevent cardiovascular diseases, epidemiological studies evaluating these drugs simultaneously should be performed. Furthermore, because drugs included in the same class may have different effects in terms of disease prevention, drug-by-drug assessments are important for planning intervention trials.

Materials and methods

We performed a cross-sectional study enrolling patients diagnosed with IAs between July 2011 and June 2019 at our institution. Patients were divided into ruptured or unruptured groups. The drugs investigated were selected according to evidence suggested by either human or animal studies. Univariate and multivariate logistic regression analyses were performed to assess the association of drug treatment with rupture status. We also performed drug-by-drug assessments of the association, including dose-response relationships, with rupture status.

Results

In total, 310 patients with ruptured and 887 patients with unruptured IAs were included. Multivariate analysis revealed an inverse association of statins (odds ratio (OR), 0.54; 95% confidence interval (CI) 0.38–0.77), calcium channel blockers (OR, 0.41; 95% CI 0.30–0.58), and angiotensin II receptor blockers (ARBs) (OR, 0.67; 95% CI 0.48–0.93) with ruptured IAs. Moreover, inverse dose-response relationships with rupture status were observed for pitavastatin and rosuvastatin among statins, benidipine, cilnidipine, and amlodipine among calcium channel blockers, and valsartan, azilsartan, candesartan, and olmesartan among ARBs. Only non-aspirin non-steroidal anti-inflammatory drugs were positively associated with ruptured IAs (OR, 3.24; 95% CI 1.71–6.13).

Conclusions

The present analysis suggests that several types of statins, calcium channel blockers, and ARBs are candidate drugs for preventive treatment of unruptured IAs.

C-Reactive Protein Levels Are Higher in Patients With Fusiform Intracranial Aneurysms: A Case-Control Study

BACKGROUND

Comprehending the risk factors that contribute to the formation of fusiform aneurysms (FAs) might provide some insight into treatment and prevention strategies. This case-control study aimed to compare the levels of serum C-reactive protein (CRP), as a biomarker, between patients with fusiform and saccular intracranial aneurysms.

METHODS

We retrospectively analyzed medical records from 2010 to 2019. Thirty-five patients were identified as having FAs: 13 (37.1%) were ruptured, and 22 were unruptured. An age-matched sample of 70 controls (2:1) with saccular aneurysms was obtained from the same records: 36 (51.4%) ruptured and 34 unruptured.

RESULTS

Patients with FAs had median CRP values of 0.61 mg/dL (IQR: 1.5), compared with 0.29 mg/dL (IQR: 0.42) in controls (P < 0.01). Within both the ruptured and the unruptured group, median CRP was higher in patients with FAs compared with controls (P < 0.01). Diabetes, smoking status, hypertension, and sex did not significantly influence CRP levels. Age-adjusted analyses showed that fusiform morphology was independently associated with higher CRP levels for unruptured aneurysms (OR 1.2, 95% CI 1.05-1.43), but not for ruptured aneurysms (OR 1.02, 95%CI 0.99-1.05).

CONCLUSIONS

CRP was higher in patients with FAs than controls, and it constituted an independent predictor of fusiform morphology for patients with unruptured aneurysms. Inflammation might be an especially important factor in FA formation and growth, and further studies could use this finding to design new treatment strategies.

Involvement of neutrophils in machineries underlying the rupture of intracranial aneurysms in rats

Subarachnoid hemorrhage due to rupture of an intracranial aneurysm has a quite poor prognosis after the onset of symptoms, despite the modern technical advances. Thus, the mechanisms underlying the rupture of lesions should be clarified. To this end, we obtained gene expression profile data and identified the neutrophil-related enriched terms in rupture-prone lesions using Gene Ontology analysis. Next, to validate the role of neutrophils in the rupture of lesions, granulocyte-colony stimulating factor (G-CSF) was administered to a rat model, in which more than half of induced lesions spontaneously ruptured, leading to subarachnoid hemorrhage. As a result, G-CSF treatment not only increased the number of infiltrating neutrophils, but also significantly facilitated the rupture of lesions. To clarify the mechanisms of how neutrophils facilitate this rupture, we used HL-60 cell line and found an enhanced collagenolytic activity, corresponding to matrix metalloproteinase 9 (MMP9), upon inflammatory stimuli. The immunohistochemical analyses revealed the accumulation of neutrophils around the site of rupture and the production of MMP9 from these cells in situ. Consistently, the collagenolytic activity of MMP9 could be detected in the lysate of ruptured lesions. These results suggest the crucial role of neutrophils to the rupture of intracranial aneurysms; implying neutrophils as a therapeutic or diagnostic target candidate.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

The Bilateral Ovariectomy in a Female Animal Exacerbates the Pathogenesis of an Intracranial Aneurysm

Considering the poor outcome of subarachnoid hemorrhage (SAH) due to the rupture of intracranial aneurysms (IA), mechanisms underlying the pathogenesis of IAs, especially the rupture of lesions, should be clarified. In the present study, a rat model of IAs in which induced lesions spontaneously ruptured resulting in SAH was used. In this model, the combination of the female sex and the bilateral ovariectomy increased the incidence of SAH, similar to epidemiological evidence in human cases. Importantly, unruptured IA lesions induced in female animals with bilateral ovariectomy were histopathologically similar to ruptured ones in the presence of vasa vasorum and the accumulation of abundant inflammatory cells, suggesting the exacerbation of the disease. The post-stenotic dilatation of the carotid artery was disturbed by the bilateral ovariectomy in female rats, which was restored by hormone replacement therapy. The in vivo study thus suggested the protective effect of estrogen from the ovary on endothelial cells loaded by wall shear stress. β-estradiol or dihydrotestosterone also suppressed the lipopolysaccharide-induced expression of pro-inflammatory genes in cultured macrophages and neutrophils. The results of the present study have thus provided new insights about the process regulating the progression of the disease.

Dedifferentiation of smooth muscle cells in intracranial aneurysms and its potential contribution to the pathogenesis

Smooth muscle cells (SMCs) are the major type of cells constituting arterial walls and play a role to maintain stiffness via producing extracellular matrix. Here, the loss and degenerative changes of SMCs become the major histopathological features of an intracranial aneurysm (IA), a major cause of subarachnoid hemorrhage. Considering the important role of SMCs and the loss of this type of cells in IA lesions, we in the present study subjected rats to IA models and examined how SMCs behave during disease progression. We found that, at the neck portion of IAs, SMCs accumulated underneath the internal elastic lamina according to disease progression and formed the intimal hyperplasia. As these SMCs were positive for a dedifferentiation marker, myosin heavy chain 10, and contained abundant mitochondria and rough endoplasmic reticulum, SMCs at the intimal hyperplasia were dedifferentiated and activated. Furthermore, dedifferentiated SMCs expressed some pro-inflammatory factors, suggesting the role in the formation of inflammatory microenvironment to promote the disease. Intriguingly, some SMCs at the intimal hyperplasia were positive for CD68 and contained lipid depositions, indicating similarity with atherosclerosis. We next examined a potential factor mediating dedifferentiation and recruitment of SMCs. Platelet derived growth factor (PDGF)-BB was expressed in endothelial cells at the neck portion of lesions where high wall shear stress (WSS) was loaded. PDGF-BB facilitated migration of SMCs across matrigel-coated pores in a transwell system, promoted dedifferentiation of SMCs and induced expression of pro-inflammatory genes in these cells in vitro. Because, in a stenosis model of rats, PDGF-BB expression was expressed in endothelial cells loaded in high WSS regions, and SMCs present nearby were dedifferentiated, hence a correlation existed between high WSS, PDGFB and dedifferentiation in vivo. In conclusion, dedifferentiated SMCs presumably by PDGF-BB produced from high WSS-loaded endothelial cells accumulate in the intimal hyperplasia to form inflammatory microenvironment leading to the progression of the disease.

The inflammatory microenvironment in vestibular schwannoma

Vestibular schwannomas are tumors arising from the vestibulocochlear nerve at the cerebellopontine angle. Their proximity to eloquent brainstem structures means that the pathology itself and the treatment thereof can be associated with significant morbidity. The vast majority of these tumors are sporadic, with the remainder arising as a result of the genetic syndrome Neurofibromatosis Type 2 or, more rarely, LZTR1-related schwannomatosis. The natural history of these tumors is extremely variable, with some tumors not displaying any evidence of growth, others demonstrating early, persistent growth and a small number growing following an extended period of indolence. Emerging evidence now suggests that far from representing Schwann cell proliferation only, the tumor microenvironment is complex, with inflammation proposed to play a key role in their growth. In this review, we provide an overview of this new evidence, including the role played by immune cell infiltration, the underlying molecular pathways involved, and biomarkers for detecting this inflammation in vivo. Given the limitations of current treatments, there is a pressing need for novel therapies to aid in the management of this condition, and we conclude by proposing areas for future research that could lead to the development of therapies targeted toward inflammation in vestibular schwannoma.

Immune Characterization in Aneurysmal Subarachnoid Hemorrhage Reveals Distinct Monocytic Activation and Chemokine Patterns

The pathophysiology of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH) is incompletely understood. Intrathecal activation of inflammatory immune cells is suspected to play a major role for the induction of DCI. The aim of this study is to identify immune cell subsets and mediators involved in the pathogenesis of DCI. We prospectively collected blood and CSF from 25 patients with aSAH at early and late time points. We performed multicolor flow cytometry of peripheral blood and CSF, analyzing immune cell activation and pro-inflammatory cyto- and chemokines. In addition to the primary immune analysis, we retrospectively analyzed immune cell dynamics in the CSF of all our SAH patients. Our results show an increased monocyte infiltration secondary to aneurysm rupture in patients with DCI. Infiltrating monocytes are defined by a non-classical (CD14^dim CD16⁺) phenotype at early stages. The infiltration is most likely triggered by the intrathecal immune activation. Here, high levels of pro-inflammatory chemokines, such as CXCL1, CXCL9, CXCL10, and CXCL11, are detected. The intrathecal cellular activation profile of monocytes was defined by upregulation of CD163 and CD86 on monocytes and a presumable later differentiation into antigen-presenting plasmacytoid dendritic cells (pDCs) and hemosiderophages. Peripheral immune activation was reflected by CD69 upregulation on T cells. Analysis of DCI prevalence, Hunt and Hess grade, and clinical outcome correlated with the degree of immune activation. We demonstrate that monocytes and T cells are activated intrathecally after aSAH and mediate a local inflammatory response which is presumably driven by chemokines. Our data shows that the distinct pattern of immune activation correlates with the prevalence of DCI, indicating a pathophysiological connection to the incidence of vasospasm.

Macrophage Imaging of Intracranial Aneurysms

Considered with a poor outcome of subarachnoid hemorrhage due to rupture of intracranial aneurysms (IAs), treatment interventions to prevent rupture of the lesions are mandatory for social health. As treatment option is limited to surgical manipulations, like microsurgical clipping, endovascular coiling or deployment of flow diverter, and these surgical interventions have a potential risk of complications in nature, a proper selection of rupture-prone IAs among ones incidentally found is essential. Today, a rupture risk in each case is estimated by several factors like patient characteristics and morphological ones of each lesion. However, unfortunately, an IA without treatment sometimes unexpectedly ruptures resulting in a devastating outcome or an IA surgically treated is turned out to have a thick wall. To achieve more efficient treatment interventions, the development of a novel diagnostic modality is required. Here, mainly through the accumulation of experimental findings, the crucial contribution of macrophage-mediated chronic inflammatory responses to IA progression have been revealed, making macrophage being a promising target for a diagnosis. If we could non-invasively visualize accumulation of macrophages in lesions, this imaging technique ‘macrophage imaging’ may enable a qualitative evaluation of IAs to stratify rupture-prone ‘dangerous’ lesions among many stable ones. Thereby, a development of macrophage imaging makes an indication of surgical interventions being more accurate and also greatly facilitates a development of a novel medical therapy if used as a surrogate marker.