Aspirin Inhibits Degenerative Changes of Aneurysmal Wall in a Rat Model

Potential role of endothelial progenitor cells in the pathogenesis and treatment of cerebral aneurysm

Cerebral aneurysm (CA) is a significant health concern that results from pathological dilations of blood vessels in the brain and can lead to severe and potentially life-threatening conditions. While the pathogenesis of CA is complex, emerging studies suggest that endothelial progenitor cells (EPCs) play a crucial role. In this paper, we conducted a comprehensive literature review to investigate the potential role of EPCs in the pathogenesis and treatment of CA. Current research indicates that a decreased count and dysfunction of EPCs disrupt the balance between endothelial dysfunction and repair, thus increasing the risk of CA formation. Reversing these EPCs abnormalities may reduce the progression of vascular degeneration after aneurysm induction, indicating EPCs as a promising target for developing new therapeutic strategies to facilitate CA repair. This has motivated researchers to develop novel treatment options, including drug applications, endovascular-combined and tissue engineering therapies. Although preclinical studies have shown promising results, there is still a considerable way to go before clinical translation and eventual benefits for patients. Nonetheless, these findings offer hope for improving the treatment and management of this condition.

Aspirin treatment for unruptured intracranial aneurysms: Focusing on its anti-inflammatory role

Intracranial aneurysms (IAs), as a common cerebrovascular disease, claims a worldwide morbidity rate of 3.2%. Inflammation, pivotal in the pathogenesis of IAs, influences their formation, growth, and rupture. This review investigates aspirin's modulation of inflammatory pathways within this context. With IAs carrying significant morbidity and mortality upon IAs rupture and current interventions limited to surgical clipping and endovascular coiling, the quest for pharmacological options is imperative. Aspirin's role in cardiovascular prevention, due to its anti-inflammatory effects, presents a potential therapeutic avenue for IAs. In this review, we examine aspirin's efficacy in experimental models and clinical settings, highlighting its impact on the progression and rupture risks of unruptured IAs. The underlying mechanisms of aspirin's impact on IAs are explored, with its ability examined to attenuate endothelial dysfunction and vascular injury. This review may provide a theoretical basis for the use of aspirin, suggesting a promising strategy for IAs management. However, the optimal dosing, safety, and long-term efficacy remain to be established. The implications of aspirin therapy are significant in light of current surgical and endovascular treatments. Further research is encouraged to refine aspirin's clinical application in the management of unruptured IAs, with the ultimate aim of reducing the incidence of aneurysms rupture.

The Role of the NF-kB Pathway in Intracranial Aneurysms

The pathophysiology of intracranial aneurysms (IA) has been proven to be closely linked to hemodynamic stress and inflammatory pathways, most notably the NF-kB pathway. Therefore, it is a potential target for therapeutic intervention. In the present review, we investigated alterations in the vascular smooth muscle cells (VSMCs), extracellular matrix, and endothelial cells by the mediators implicated in the NF-kB pathway that lead to the formation, growth, and rupture of IAs. We also present an overview of the NF-kB pathway, focusing on stimuli and transcriptional targets specific to IAs, as well as a summary of the current strategies for inhibiting NF-kB activation in IAs. Our report adds to previously reported data and future research directions for treating IAs using compounds that can suppress inflammation in the vascular wall.

The Role of NF-κB in Intracranial Aneurysm Pathogenesis: A Systematic Review

Intracranial aneurysms (IAs) are abnormal dilations of the cerebral vessels, which pose a persistent threat of cerebral hemorrhage. Inflammation is known to contribute to IA development. The nuclear factor "kappa-light-chain-enhancer" of activated B-cells (NF-κB) is the major driver of inflammation. It increases the expression of inflammatory markers and matrix metalloproteinases (MMPs), which contribute heavily to the pathogenesis of IAs. NF-κB activation has been linked to IA rupture and resulting subarachnoid hemorrhage. Moreover, NF-κB activation can result in endothelial dysfunction, smooth muscle cell phenotypic switching, and infiltration of inflammatory cells in the arterial wall, which subsequently leads to the initiation and progression of IAs and consequently results in rupture. After a systematic search, abstract screening, and full-text screening, 30 research articles were included in the review. In this systematic review, we summarized the scientific literature reporting findings on NF-κB's role in the pathogenesis of IAs. In conclusion, the activation of the NF-κB pathway was associated with IA formation, progression, and rupture.

Integrated analysis of C3AR1 and CD163 associated with immune infiltration in intracranial aneurysms pathogenesis

Background

To identify potential immune-related biomarkers, molecular mechanism, and therapeutic agents of intracranial aneurysms (IAs).

Methods

We identified the differentially expressed genes (DEGs) between IAs and control samples from GSE75436, GSE26969, GSE6551, and GSE13353 datasets. We used weighted gene co-expression network analysis (WGCNA) and protein-protein interaction (PPI) analysis to identify immune-related hub genes. We evaluated the expression of hub genes by using qRT-PCR analysis. Using miRNet, NetworkAnalyst, and DGIdb databases, we analyzed the regulatory networks and potential therapeutic agents targeting hub genes. Least absolute shrinkage and selection operator (LASSO) logistic regression was performed to identify optimal biomarkers among hub genes. The diagnostic value was validated by external GSE15629 dataset.

Results

We identified 227 DEGs and 22 differentially infiltrating immune cells between IAs and control samples from GSE75436, GSE26969, GSE6551, and GSE13353 datasets. We further identified 41 differentially expressed immune-related genes (DEIRGs), which were primarily enriched in the chemokine-mediated signaling pathway, myeloid leukocyte migration, endocytic vesicle membrane, chemokine receptor binding, chemokine activity, and viral protein interactions with cytokines and their receptors. Among 41 DEIRGs, 10 hub genes including C3AR1, CD163, CCL4, CXCL8, CCL3, TLR2, TYROBP, C1QB, FCGR3A, and FCGR1A were identified with good diagnostic values (AUC >0.7). Hsa-mir-27a-3p and transcription factors, including YY1 and GATA2, were identified the primary regulators of hub genes. 92 potential therapeutic agents targeting hub genes were predicted. C3AR1 and CD163 were finally identified as the best diagnostic biomarkers using LASSO logistic regression (AUC = 0.994). The diagnostic value of C3AR1 and CD163 was validated by the external GSE15629 dataset (AUC = 0.914).

Conclusions

This study revealed the importance of C3AR1 and CD163 in immune infiltration in IAs pathogenesis. Our finding provided a valuable reference for subsequent research on the potential targets for molecular mechanisms and intervention of IAs.

Aspirin and growth, rupture of unruptured intracranial aneurysms: A systematic review and meta-analysis

OBJECTIVES

Aspirin has been suggested as a potential therapeutic strategy to prevent the growth and rupture of unruptured intracranial aneurysms (UIAs), but there is still controversy. The aim of this systematic review and meta-analysis is to determine the association between aspirin use and growth, rupture of UIAs.

METHODS

We performed a systematic literature search of electronic databases to identify cohort and case-control studies investigating the relationship between aspirin use and growth or rupture of UIAs. Pooled odds ratio (OR) with corresponding 95% confidence interval (CI) were calculated using a random effects model. Heterogeneity among studies was quantified using the I² statistic, and potential publication bias was assessed using funnel plots. Sensitivity analysis was performed to verify the robustness of the intention-to-treat results. Subgroup analysis was conducted according to the frequency of aspirin use.

RESULTS

We identified 8 studies comprising 10,518 participants. The risk of bias was low to moderate. The pooled estimate showed that aspirin use was associated with a lower likelihood of growth of UIAs (OR = 0.25, 95% CI = 0.11-0.55; p = 0.0005) without statistical heterogeneity (p for Cochran Q statistic = 0.62, I² = 0%). Likewise, aspirin intake also significant decreased 58% risk of intracranial aneurysms rupture (OR = 0.42, 95% CI = 0.29-0.60; p < 0.00001) with moderate heterogeneity (p for Cochran Q statistic = 0.005, I² = 66%). Similar results were observed in the sensitivity analysis. Pooled OR of aspirin frequency subgroup analysis for less than or equal to 2 times per week was 0.82 (95%CI = 0.40-1.72; I² = 0%), for at least 3 times per week to daily was 0.25 (95%CI = 0.12-053; I² = 0%), for daily was 0.59 (95%CI: 0.47-0.74; I² = 0%), and for unknown was 0.26 (95%CI: 0.15-0.45; I² = 51%).

CONCLUSIONS

The results of this systematic review and meta-analysis indicates a beneficial effect of aspirin on growth and rupture of UIAs.

Incidental Unruptured Intracranial Aneurysms Do Not Impact Outcome in Patients With Acute Cerebral Infarction

Background: This study was to examine the patients with acute cerebral infarction (ACI) treated at a single center over 9 years and who underwent Unruptured intracranial aneurysm (UIA) screening by three-dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA), and to explore the factors associated with outcomes.

Methods: The outcome was the modified Rankin scale (mRS) score at 90 days after stroke onset. The outcome was classified into a good outcome (mRS score of 0–2 points) and poor outcome (mRS score of 3–6 points).

Results: UIAs were found in 260 (6.5%) of 4,033 patients with ACI; 2,543 (63.1%) had a good outcome, and 1,490 (36.9%) had a poor outcome. There was no difference in outcomes between the two groups (P = 0.785). The multivariable analysis showed that age (OR = 1.009, 95%CI: 1.003–1.014, P = 0.003), diabetes (OR = 1.179, 95%CI: 1.035–1.342, P = 0.013), ischemic stroke history (OR = 1.451, 95%CI: 1.256–1.677, P < 0.001), and baseline NIHSS score (OR = 1.034, 95%CI: 1.018–1.050, P < 0.001) were independently associated with the 90-day outcomes in patients with ACI. The presence of incidental UIA was not associated with outcomes after ACI.

Conclusions: Age, diabetes, ischemic stroke history, and baseline NIHSS score were independently associated with the early outcomes of patients with ACI.

Antiplatelet Drugs for Neurointerventions: Part 2 Clinical Applications

Endovascular techniques have expanded to include balloon and stent-assistance, flow diversion and individualized endovascular occlusion devices, to widen the treatment spectrum for more complex aneurysm morphologies. While usually well-tolerated by patients, endovascular treatment of intracranial aneurysms carries the risk of complications, with procedure-related ischemic complications being the most common. Several antiplatelet agents have been studied in a neurointerventional setting for both prophylaxis and in the setting of intraprocedural thrombotic complications. Knowledge of these antiplatelet agents, evidence for their use and common dosages is important for the practicing neurointerventionist to ensure the proper application of these agents.Part one of this two-part review focused on basic platelet physiology, pharmacology of common antiplatelet medications and future directions and therapies. Part two focuses on clinical applications and evidence based therapeutic regimens.

Effect of combined acetylsalicylic acid and statins treatment on intracranial aneurysm rupture

Background

Acetylsalicylic acid (ASA) and statins have been identified as potentially reducing the risk of intracranial aneurysms (IA) rupture. We aim to determine the effect of this drugs on the risk of rupture of IA.

Patients and methods

We performed a retrospective cohort study from a prospective database of patients with IA treated in our institution between January 2013 and December 2018. Demographics, previous oral treatments, presence of multiple aneurysms, size of aneurysm, lobulation, location and morphology of the aneurysms were recorded. Patients were dichotomized as ruptured and unruptured IA.

Results

A total of 408 IA were treated, of which 283 (68.6%) were in women. The median age was 53, 194 (47.5%) were ruptured IA. 38 patients (9.3%) were receiving ASA and 84 (20.6%) were receiving statins at the moment of the IA diagnosis. In the multivariable regression analysis, ASA plus statin use and multiple aneurysms were independently associated with unruptured IA (OR 5.01, 95% CI, 1.37–18.33, P = 0.015 and OR 2.72, 95% CI 1.68–4.27, P<0.001, respectively). Whereas, lobulated wall aneurysm and PComA/AComA location were inversely and independently associated with unruptured IA condition (OR 0.34, 95% CI 0.21–0.55, P<0.001 and OR 0.37, 95% CI 0.23–0.60, P<0.001, respectively). However, ASA and statins in monotherapy were not independently associated with unruptured IA condition.

Conclusions

In our study population ASA plus statins treatment is independently associated with unruptured IA. Larger and prospective studies are required to explore this potential protective effect against IA 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.

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.

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.

Aspirin associated with decreased rate of intracranial aneurysm growth

OBJECTIVE

Aspirin has emerged as a potential agent in the prevention of rupture of intracranial aneurysms (IAs). In this study, the authors' goal was to test if aspirin is protective against aneurysm growth in patients harboring multiple IAs ≤ 5 mm.

METHODS

The authors performed a retrospective review of a prospectively maintained database covering the period July 2009 through January 2019. Patients' data were included if the following criteria were met: 1) the patient harbored multiple IAs; 2) designated primary aneurysms were treated by surgical/endovascular means; 3) the remaining aneurysms were observed for growth; and 4) a follow-up period of at least 5 years after the initial treatment was available. Demographics, earlier medical history, the rupture status of designated primary aneurysms, aneurysms' angiographic features, and treatment modalities were gathered.

RESULTS

The authors identified 146 patients harboring a total of 375 IAs. At the initial encounter, 146 aneurysms were treated and the remaining 229 aneurysms (2-5 mm) were observed. During the follow-up period, 24 (10.48%) of 229 aneurysms grew. All aneurysms observed to grow later underwent treatment. None of the observed aneurysms ruptured. Multivariate analysis showed that aspirin was significantly associated with a decreased rate of growth (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.05-0.63). Variables associated with an increased rate of growth included hypertension (OR 14.38, 95% CI 3.83-53.94), drug abuse (OR 11.26, 95% CI 1.21-104.65), history of polycystic kidney disease (OR 9.48, 95% CI 1.51-59.35), and subarachnoid hemorrhage at presentation (OR 5.91, 95% CI 1.83-19.09).

CONCLUSIONS

In patients with multiple IAs, aspirin significantly decreased the rate of aneurysm growth over time. Additional prospective interventional studies are needed to validate these findings.

Eicosapentaenoic acid prevents the progression of intracranial aneurysms in rats

Background

As subarachnoid hemorrhage due to rupture of an intracranial aneurysm (IA) has quite a poor outcome despite of an intensive medical care, development of a novel treatment targeting unruptured IAs based on the correct understanding of pathogenesis is mandatory for social health.

Methods

Using previously obtained gene expression profile data from surgically resected unruptured human IA lesions, we selected G-protein coupled receptor 120 (GPR120) as a gene whose expression is significantly higher in lesions than that in control arterial walls. To corroborate a contribution of GPR120 signaling to the pathophysiology, we used an animal model of IAs and examine the effect of a GPR120 agonist on the progression of the disease. IA lesion was induced in rats through an increase of hemodynamic stress achieved by a one-sided carotid ligation and induced hypervolemia. Eicosapentaenoic acid (EPA) was used as an agonist for GPR120 in this study and its effect on the size of IAs, the thinning of media, and infiltration of macrophages in lesions were examined.

Result

EPA administered significantly suppressed the size of IAs and the degenerative changes in the media in rats. EPA treatment also inhibited infiltration of macrophages, a hallmark of inflammatory responses in lesions. In in vitro experiments using RAW264.7 cells, pre-treatment of EPA partially suppressed lipopolysaccharide-induced activation of nuclear factor-kappa B and also the transcriptional induction of monocyte chemoattractant protein 1 (MCP-1), a major chemoattractant for macrophages to accumulate in lesions. As a selective agonist of GPR120, TUG-891, could reproduce the effect of EPA in RAW264.7 cells, EPA presumably acted on this receptor to suppress inflammatory responses. Consistently, EPA remarkably suppressed MCP-1 expression in lesions, suggesting the in vivo relevance of in vitro studies.

Conclusions

These results combined together suggest the potential of the medical therapy targeting GPR120 or using EPA to prevent the progression of IAs.

Preclinical Intracranial Aneurysm Models: A Systematic Review

Intracranial aneurysms (IA) are characterized by weakened cerebral vessel walls that may lead to rupture and subarachnoid hemorrhage. The mechanisms behind their formation and progression are yet unclear and warrant preclinical studies. This systematic review aims to provide a comprehensive, systematic overview of available animal models for the study of IA pathobiology. We conducted a systematic literature search using the PubMed database to identify preclinical studies employing IA animal models. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included studies were reviewed and categorized according to the experimental animal and aneurysm model. Of 4266 returned results, 3930 articles were excluded based on the title and/or abstract and further articles after screening the full text, leaving 123 studies for detailed analysis. A total of 20 different models were found in rats (nine), mice (five), rabbits (four), and dogs (two). Rat models constituted the most frequently employed intracranial experimental aneurysm model (79 studies), followed by mice (31 studies), rabbits (12 studies), and two studies in dogs. The most common techniques to induce cerebral aneurysms were surgical ligation of the common carotid artery with subsequent induction of hypertension by ligation of the renal arteries, followed by elastase-induced creation of IAs in combination with corticosterone- or angiotensin-induced hypertension. This review provides a comprehensive summary of the multitude of available IA models to study various aspects of aneurysm formation, growth, and rupture. It will serve as a useful reference for researchers by facilitating the selection of the most appropriate model and technique to answer their scientific question.

Nonsteroidal Anti-Inflammatory Drugs: A Potential Pharmacological Treatment for Intracranial Aneurysm

Background

Saccular intracranial aneurysms (IAs) are outpouchings of the vessel wall of intracranial arteries. Rupture of IAs results in subarachnoid hemorrhage which is associated with high morbidity and mortality. Surgical interventions, such as clipping and coiling, have associated risks. Currently, there are no proven pharmacological treatments to prevent the growth or rupture of IAs. Infiltration of proinflammatory cytokines in response to increased wall sheer stress is a hallmark of IA. Nonsteroidal anti-inflammatory drugs (NSAIDs) are being investigated as potential therapeutic agents for reduction in growth and/or prevention of IA through inhibition of inflammatory pathways.

Summary

This review will discuss the role of NSAIDs in attenuating the inflammation that drives IA progression and rupture. There are two main subtypes of NSAIDs, nonselective COX and selective COX-2 inhibitors, both of which have merit in treating IA. Evidence will be presented which shows that NSAIDs inhibit several key inflammatory mediators involved in IA progression including nuclear factor-κB, tumor necrosis factor-α, and matrix metalloproteinases. In addition, the role of NSAIDs in limiting inflammatory cell adhesion to endothelial cells and attenuating endothelial cell senescence will be discussed.

Key Messages

There is an abundance of basic science and preclinical data that support NSAIDs as a promising treatment for IA. Additionally, a combination treatment strategy of low-dose aspirin given concomitantly with a selective COX-2 inhibitor may result in a reduced side effect profile compared to aspirin or selective COX-2 inhibitor use alone. Several large clinical trials are currently planned to further investigate the efficacy of NSAIDs as an effective nonsurgical treatment for IAs.

Intracranial Aneurysm as a Macrophage-mediated Inflammatory Disease

Subarachnoid hemorrhage (SAH) is mainly attributable to the rupture of intracranial aneurysms (IAs). Although the outcome of SAH is considerably poor in spite of the recent intensive medical care, mechanisms regulating the progression of IAs or triggering rupture remain to be clarified, making the development of effective preemptive medicine to prevent SAH difficult. However, a series of recent studies have been expanding our understanding of the pathogenesis of IAs. These studies have suggested the crucial role of macrophage-mediated chronic inflammation in the pathogenesis of IAs. In histopathological analyses of IA lesions in humans and induced in animal models, the number of macrophages infiltrating in lesions is positively correlated with enlargement or rupture of IAs. In animal models, a genetic deletion or an inhibition of monocyte chemotactic protein-1, a major chemoattractant for macrophages, or a pharmacological depletion of macrophages consistently suppresses the development and progression of IAs. Furthermore, a macrophage-specific deletion of Ptger2 (gene for prostaglandin E receptor subtype 2) or a macrophage-specific expression of a mutated form of IκBα which inhibits nuclear translocation of nuclear factor κB significantly suppress the development of IAs, supporting the role of macrophages and the inflammatory signaling functioning there in the pathogenesis of IAs. The development of drug therapies suppressing macrophage-mediated inflammatory responses in situ can thus be a potential strategy in the pre-emptive medicine targeting SAH. In this manuscript, we summarize the experimental evidences about the pathogenesis of IAs focused on inflammatory responses and propose the definition of IAs as a macrophage-mediated inflammatory disease.

The role of inflammation and potential pharmacological therapy in intracranial aneurysms

Intracranial aneurysms remain important clinical concern. There is relatively low risk of rupture of symptomless aneurysms incidentally found in MRA or CTA performed due to other indications. Not all of the intracranial aneurysms should or can be treated with neurosurgery intervention or endovascular embolization. Clinical strategy for small, symptomless, unruptured aneurysms is still questionable. Mechanisms underlying aneurysms formation, progression and rupture are poorly understood. Inflammation is one of the factors suspected to participate in these processes. Therefore the aim of this manuscript is to present current state of knowledge about the role of inflammation in the formation and progression of intracranial aneurysms and in their rupture process. Current knowledge about possible pharmacological treatment of intracranial aneurysms will also be presented. Macrophages infiltration seems to participate in the formation of intracranial aneurysms. Inhibition of signals sent by macrophages may prevent the aneurysms formation. Inflammation present in the wall of the aneurysm seems to be also related to the aneurysm's rupture risk. However it does not seem to be the only cause of the degeneration, but it can be a possible target of drug therapy. Some preliminary studies in humans indicate the potential role of aspirin as a factor that decrease the level of inflammation and lower the risk of rupture of intracranial aneurysms. However further research including a greater number of subjects and a prospective randomized design are necessary to assess the role of aspirin in preventing strategy for small, symptomless, unruptured intracranial aneurysms.

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

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