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.

Objective: Abundant neutrophils have been identified in both ruptured and unruptured intracranial aneurysm (IA) domes, with their function and clinical implication being poorly characterized.Materials and Methods: We employed single‐cell RNA sequencing (scRNA‐Seq) datasets of both human and murine model, and external bulk mRNA sequencing datasets to thoroughly explore the features and functional heterogeneous of neutrophils infiltrating the IA dome.Results: We found that both unruptured and ruptured IA dome contain a substantial population of neutrophils, characterized by FCGR3B, G0S2, CSF3R, and CXCR2. These cells exhibited heterogeneity in terms of function and differentiation. Despite similar transcriptional activation, neutrophils in IA dome expressed a repertoire of gene programs that mimicked transcriptomic alterations observed from bone marrow to peripheral blood, showing self‐similarity. In addition, the recruitment of neutrophils in unruptured IA was primarily mediated by monocytes/macrophages, and once ruptured, both neutrophils, and a specific subset of inflammatory smooth muscle cells (SMCs) were involved in the process. The receiver operator characteristic curve (ROC) analysis indicated that distinct neutrophil subclusters were associated with IA formation and rupture, respectively. By reviewing current studies, we found that neutrophils play a detrimental role to IA wall integrity through secreting specific ligands, ferroptosis driven by ALOX5AP and PTGS2, and the formation of neutrophil extracellular traps (NETs) mediated by PADI4.Interpretation: This study delineated the biology and potential clinical implications of neutrophils in IA dome and provided a reliable basis for future researches.

Background: Intracranial aneurysm (IA) is a prevalent cerebrovascular disorder, but its pathogenesis remains elusive. Materials and Methods: This study integrated transcriptome-wide association study (TWAS), two-sample Mendelian randomization (MR), Bayesian-based co-localization, and summary-data-based MR (SMR) leveraging arterial cis-eQTL data. These analyses were complemented by single-cell RNA-seq (scRNA-seq) and multiplexed immunofluorescence (mIHC) to prioritize causal genes for IA. Results: Multi-omics analyses nominate BCAR1 as a top candidate, demonstrating a consistent, protective causal effect on IA across methodologies (TWAS P = 0.007 ~ 0.012, MR IVW P = 8.24 × 10 ⁻¹¹ ~ 7.95 × 10 ⁻¹³ , coloc PPH4 = 0.735 ~ 0.747). In contrast, RP11-252K23.2 is identified as a risk locus (TWAS P = 0.010 ~ 0.013; MR IVW P = 8.66 × 10 ⁻⁵ ~ 7.44 × 10 ⁻¹¹ ; coloc PPH4 = 0.700 ~ 0.992). ScRNA-seq of human IA domes shows specific enrichment of BCAR1 within a stressed subcluster of vascular smooth muscle cells, a finding validated by mIHC at the protein level. Furthermore, a machine learning-based gene signature centered on BCAR1 robustly predicts IA formation (AUC ≥ 0.926, C-index ≥ 0.926, AUPRC ≥ 0.842). Cross-disease analyses also implicate BCAR1 in atherosclerosis and thoracic aortic aneurysm through co-localization and SMR. Conclusion: Our study establishes BCAR1 as a novel protective factor and potential therapeutic target for IA, underscoring its broader role in maintaining vascular integrity.

Background: Intracranial aneurysms (IA) is a common condition and may ultimately result in life-threatening hemorrhagic strokes. A precise understanding of the cellular and gene expression perturbations in human IA tissue may enlighten additional therapeutics for unruptured IA. Methods: A total of 21,332 qualified cells were obtained from four cell-sparse ruptured and unruptured human IA tissues. Detailed cell atlas and dynamics, gene expression perturbations, and inflammation features were thoroughly investigated using multiple machine learning-based algorithms. Results: Endothelial cells, smooth muscle cells (SMCs), fibroblasts and, for the first time, pericytes have been identified in human IA tissue. A significant proportion of immune cells are also identified, with the number of monocyte/macrophages and neutrophils being notably higher in ruptured IA. By leveraging external datasets, macrophages characterized by transcriptional activation of NF-κB and HIVEP2 is most strongly associated with IA rupture. Interestingly, the recruitment and activation of macrophages and their functional characteristics in terms of TNFα and chemokine production remain consistent between unruptured and ruptured IA. Conclusions: This study provides insights into the pathophysiology and molecular underpinnings of the IA wall and may motivate novel therapeutic options for unruptured IA.

Observational studies have demonstrated associations between mental disorders and stroke, yet causal relationships and potential molecular mechanisms remain elusive. To clarify this, we performed a bidirectional 2-sample Mendelian randomization (MR) analysis using genome-wide association studies summary statistics to assess the causal effects of 7 major mental disorders (schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorder, attention-deficit/hyperactivity disorder [ADHD], Alzheimer disease, and Parkinson disease) on stroke subtypes. Analyses were divided into discovery and validation cohorts of European ancestry, followed by MRlap and meta-analysis to obtain pooled estimates. To explore potential circulating protein mediators, 4907 plasma cis-protein quantitative trait loci (cis-pQTLs) from deCODE Genetics were screened, followed by Bayesian co-localization and 2-step MR mediation analyses. Our findings revealed that ADHD was consistently associated with an increased risk of any stroke (AS), any ischemic stroke (AIS), and particularly large-artery atherosclerotic stroke (LAS; odds ratio = 1.455; 95% confidence interval: 1.077–1.967). Mediators screening showed genetic liability to ADHD was linked to elevated circulating matrix metallopeptidase-12 (MMP12; β = 0.141, P = .005), which conferred protection against AIS and LAS, potentially lowering LAS risk by 7.5%. In conclusion, this MR study suggests ADHD is a causal risk factor for ischemic stroke, especially LAS. Paradoxically, circulating MMP12 acts as a protective mediator, modestly reducing this risk by 7.5%. These findings require validation in future experimental and cohort studies.

The presence of aneurysms, encompassing cerebral and abdominal aortic aneurysms, poses significant risks to individuals' health. The serum fatty acids (FAs) are implicated in various diseases, yet their causal association with different aneurysms remain less understood. In this study, the summary-level datasets associated with FAs and cerebral and abdominal aortic aneurysms from the UK Biobank and BioBank Japan were included. Two-sample Mendelian randomization (MR) analysis, replicated and reverse MR analysis were conducted to explore the causal association between serum FA levels with both cerebral aneurysm (CA) and abdominal aortic aneurysm (AA). The inverse variance weighting (IVW) was used as the primary method, together with sensitivity analyses for pleiotropy and heterogenous tests. As a result, the ratio of omega-6 FAs to omega-3 FAs serves as a detrimental effector of CA, and ratio of docosahexaenoic acid to total FA levels, omega-3 FA levels and ratio of omega-3 FAs to total FAs are beneficial effectors. Counterintuitively, monounsaturated FAs (MUFAs), ratio of MUFAs to total FAs, and omega-6 FAs serve as detrimental effectors of AA. Collectively, these results suggest novel serum FA levels of causal association with CA and AA, and shed light upon the distinct molecular underpinnings of the two types of aneurysms.