Endothelial damage due to impaired nitric oxide bioavailability triggers cerebral aneurysm formation in female rats

Prescribed Drug Use and Aneurysmal Subarachnoid Hemorrhage Incidence: A Drug-Wide Association Study

BACKGROUND AND OBJECTIVES

Current benefits of invasive intracranial aneurysm treatment to prevent aneurysmal subarachnoid hemorrhage (aSAH) rarely outweigh treatment risks. Most intracranial aneurysms thus remain untreated. Commonly prescribed drugs reducing aSAH incidence may provide leads for drug repurposing. We performed a drug-wide association study (DWAS) to systematically investigate the association between commonly prescribed drugs and aSAH incidence.

METHODS

We defined all aSAH cases between 2000 and 2020 using International Classification of Diseases codes from the Secure Anonymised Information Linkage databank. Each case was matched with 9 controls based on age, sex, and year of database entry. We investigated commonly prescribed drugs (>2% in study population) and defined 3 exposure windows relative to the most recent prescription before index date (i.e., occurrence of aSAH): current (within 3 months), recent (3-12 months), and past (>12 months). A logistic regression model was fitted to compare drug use across these exposure windows vs never use, controlling for age, sex, known aSAH risk factors, and health care utilization. The family-wise error rate was kept at p < 0.05 through Bonferroni correction.

RESULTS

We investigated exposure to 205 commonly prescribed drugs between 4,879 aSAH cases (mean age 61.4, 61.2% women) and 43,911 matched controls. We found similar trends for lisinopril and amlodipine, with a decreased aSAH risk for current use (lisinopril odds ratio [OR] 0.63, 95% CI 0.44-0.90, amlodipine OR 0.82, 95% CI 0.65-1.04) and an increased aSAH risk for recent use (lisinopril OR 1.30, 95% CI 0.61-2.78, amlodipine OR 1.61, 95% CI 1.04-2.48). A decreased aSAH risk in current use was also found for simvastatin (OR 0.78, 95% CI 0.64-0.96), metformin (OR 0.58, 95% CI 0.43-0.78), and tamsulosin (OR 0.55, 95% CI 0.32-0.93). By contrast, an increased aSAH risk was found for current use of warfarin (OR 1.35, 95% CI 1.02-1.79), venlafaxine (OR 1.67, 95% CI 1.01-2.75), prochlorperazine (OR 2.15, 95% CI 1.45-3.18), and co-codamol (OR 1.31, 95% CI 1.10-1.56).

DISCUSSION

We identified several drugs associated with aSAH, of which 5 drugs (lisinopril and possibly amlodipine, simvastatin, metformin, and tamsulosin) showed a decreased aSAH risk. Future research should build on these signals to further assess the effectiveness of these drugs in reducing aSAH incidence.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that some commonly prescribed drugs are associated with subsequent development of aSAH.

MiR-221-5p regulates blood-brain barrier dysfunction through the angiopoietin-1/-2/Tie-2 signaling axis after subarachnoid hemorrhage

AIM

To explore the potential role of microRNA miR-221-5p on the angiopoietin-1 (Ang-1)/Ang-2/Tie-2 signaling axis after subarachnoid hemorrhage (SAH) in a rat model.

METHODS

Aspects of the rat's behavior were measured using the Kaoutzanis scoring system to test neurological responses. This included feeding behavior, body contraction, motor, and eye-opening responses. Brain sections were studied using transmission electron microscopy and Evans blue extravasation. Levels of Ang-1, Ang-2, and Tie-2 were determined by Western blot, while miR-221-5p was quantified using stem-loop real-time quantitative PCR (RT-qPCR).

RESULTS

The SAH group responded worse to the neurological response test than the sham-operated group. The intercellular space was widened in the SAH group, but not in the sham-operated group. Evans blue dye leaked significantly more into brain tissue cells of the SAH group. Stem-loop qRT-PCR showed elevated miR-221-5p levels. Additionally, Ang-1 and Tie-2 were reduced but Ang-2 expression was increased after SAH. This led to a significant reduction of the Ang-1/Ang-2 ratio in the brain tissue, which was associated with the destruction of the blood-brain barrier.

CONCLUSION

The data indicate that miR-221-5p might regulate blood-brain barrier dysfunction through the Ang-1/Ang-2/Tie-2 signaling axis, suggesting that it should be further investigated as a potential novel biomarker.

Activation of the NLRP3/IL-1β/MMP-9 pathway and intracranial aneurysm rupture associated with the depletion of ERα and Sirt1 in oophorectomized rats

OBJECTIVE

Subarachnoid hemorrhage (SAH) due to intracranial aneurysm (IA) rupture is often a devastating event. Since the incidence of SAH increases especially in menopause, it is crucial to clarify the detailed pathogenesis of these events. The activation of vascular nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes has been studied in ischemic stroke and cardiovascular disease. However, the role of NLRP3 in IA rupture still needs to be explained. The authors sought to test their hypothesis that, under estrogen-deficient conditions, activation of NLRP3 inflammasomes via downregulation of the estrogen receptor (ER) facilitates IA rupture.

METHODS

Ten-week-old female Sprague Dawley rats with and without oophorectomy were subjected to hemodynamic changes and hypertension (OVX+/HT and OVX-/HT, respectively) and fed a high-salt diet. Separately, using human brain endothelial cells (HBECs) and human brain smooth muscle cells (HBSMCs), the authors tested the effect of NLRP3 under estrogen-free conditions and in the presence of estradiol or of ER agonists.

RESULTS

In OVX+/HT rats, the frequency of IA rupture was significantly higher than in OVX-/HT rats (p = 0.03). In the left posterior cerebral artery prone to rupture in OVX+/HT rats, the levels of the mRNAs encoding ERα and Sirt1, but not of that encoding ERβ, were decreased, and the levels of the mRNAs encoding NLRP3, interleukin-1β (IL-1β), and matrix metalloproteinase 9 (MMP-9) were elevated. Immunohistochemical analysis demonstrated that the expression profiles of these proteins correlated with their mRNA levels. Treatment with an ER modulator, bazedoxifene, normalized the expression profiles of these proteins and improved SAH-free survival. In HBECs and HBSMCs under estrogen-free conditions, the depletion of ERα and Sirt1 and the accumulation of NLRP3 were counteracted by exposure to estradiol or to an ERα agonist but not to an ERβ agonist.

CONCLUSIONS

To the authors' knowledge, this work represents the first demonstration that, in an aneurysm model under estrogen-deficient conditions, the depletion of ERα and Sirt1 may contribute to activation of the NLRP3/IL-1β/MMP-9 pathway, facilitating the rupture of IAs in the estrogen-deficient rat IA rupture model.

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.

Lumen-oriented versus wall-oriented treatment strategies for intracranial aneurysms - A systematic review of suggested therapeutic concepts

The development of new treatment strategies for intracranial aneurysms (IAs) has been and continues to be a major interest in neurovascular research. Initial treatment concepts were mainly based on a physical-mechanistic disease understanding for IA occlusion (lumen-oriented therapies). However, a growing body of literature indicates the important role of aneurysm wall biology (wall-oriented therapies) for complete IA obliteration. This systematic literature review identified studies that explored endovascular treatment strategies for aneurysm treatment in a preclinical setting. Of 5278 publications screened, 641 studies were included, categorized, and screened for eventual translation in a clinical trial. Lumen-oriented strategies included (1) enhanced intraluminal thrombus organization, (2) enhanced intraluminal packing, (3) bridging of the intraluminal space, and (4) other, alternative concepts. Wall-oriented strategies included (1) stimulation of proliferative response, (2) prevention of aneurysm wall cell injury, (3) inhibition of inflammation and oxidative stress, and (4) inhibition of extracellular matrix degradation. Overall, lumen-oriented strategies numerically still dominate over wall-oriented strategies. Among the plethora of suggested preclinical treatment strategies, only a small minority were translated into clinically applicable concepts (36 of 400 lumen-oriented and 6 of 241 wall-oriented). This systematic review provides a comprehensive overview that may provide a starting point for the development of new treatment strategies.

Phoenixin-14 alleviates inflammatory smooth muscle cell-induced endothelial cell dysfunction in vitro

BACKGROUND

Intracranial aneurysm (IA) is cerebrovascular disorder which refers to local vessel wall damage to intracranial arteries, forming abnormal bulge. Both endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) are closely associated with IA formation and rupture. Inflammatory SMCs (iSMCs) were reported to induce EC dysfunction and result in IA progression. Phoenixin-14 (PNX-14) is a recently discovered brain peptide with pleiotropic roles, which participates in reproduction, cardio protection, lipid deposition and blood glucose metabolism. PNX-14 was previously reported to protect brain endothelial cells against oxygen-glucose deprivation/reoxygenation (OGD/R)-induced cell injury. Therefore, our study was designed to investigate the influence of PNX-14 on iSMCs-induced endothelial dysfunction.

METHODS

Inflammation in SMCs was induced by cyclic mechanical stretch. Human umbilical vein endothelial cells (HUVECs) were exposed to SMC- or iSMC-conditioned medium and then treated with 100 nM PNX-14 for 24 h. The levels of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) in cell supernatants were analyzed by ELISA. Cell viability, apoptosis, angiogenesis and migration were subjected to CCK-8 assay, flow cytometry analysis, tube formation assay and Transwell migration assay. The protein levels of proinflammatory cytokines and apoptosis markers (Bcl-2 and Bax) were evaluated by western blotting.

RESULTS

Cyclic mechanical stretch upregulated IL-1β, IL-6 and TNF-α levels in SMCs. Treatment with SMC- or iSMC-conditioned medium HUVECs inhibited cell viability, angiogenesis and migration and induced apoptosis in HUVECs. iSMC-conditioned medium has more significant effects on cell functions. However, the influence of SMC- or iSMC-conditioned medium treatment on HUVEC biological functions were reversed by PNX-14 treatment. PNX-14 exerts no significant influence on the biological functions of HUVECs treated with SMC medium.

CONCLUSION

PNX-14 alleviates iSMCs-induced endothelial cell dysfunction in vitro.

A two-sample Mendelian randomization analysis of modifiable risk factors and intracranial aneurysms

We aimed to investigate the causality between potentially modifiable risk factors and the risk of intracranial aneurysm. Genetic instruments for 51 modifiable factors and intracranial aneurysm data were obtained from recently published genome-wide association studies. We applied two-sample Mendelian randomization methods to investigate their causal relationships. Genetically predicted cigarettes per day, smoking initiation, systolic blood pressure, hypertension and body fat percentage were significantly associated with an increased risk of intracranial aneurysm [odds ratios (OR) 2.67, 95% confidence interval (CI) 1.75–4.07, p = 5.36 × 10^–6, OR 1.53, 95% CI 1.32–1.77, p = 9.58 × 10^–9, OR 1.05, 95% CI 1.02–1.08, p = 1.18 × 10^–3, OR 1.65, 95% CI 1.19–2.28, p = 2.56 × 10^–3 and OR 1.29, 95% CI 1.11–1.52, p = 1.33 × 10^–3, respectively]. Type 2 diabetes mellitus was significantly associated with a decreased risk of intracranial aneurysm (OR 0.89, 95% CI 0.83–0.95, p = 8.54 × 10^–4). Body fat percentage was significantly associated with subarachnoid haemorrhage (p = 5.70 × 10^–5). This study provided genetic evidence of causal effects of smoking, blood pressure, type 2 diabetes mellitus and obesity on the risk of intracranial aneurysm.

Nonlinear Association of Glycosylated Hemoglobin With Single Intracranial Aneurysm Rupture in Patients With Diabetes Mellitus: A Cross-Sectional Study

Background

The published literature linking diabetes mellitus (DM) to intracranial aneurysm (IA) ruptured has been controversial and limited by methodology. Thus, this study was performed to examine whether hyperglycemia control status is independently associated with single IA rupture in patients with DM.

Methods

We conducted a cross-sectional study on two Chinese hospitals between January 2010 and November 2017. Medical records of 223 patients with single IA and DM were reviewed and analyzed. We used glycosylated hemoglobin (GHB) as the independent variable of interest, and the outcome variable was ruptured status of IA. Covariates included data on demographics, morphological parameters, lifestyle habits, clinical features, and comorbidities.

Results

Multivariable adjusted binary logistic regression and sensitivity analyses indicated that GHB was not associated with IA rupture (odds ratio OR, = 1.07, 95% CI 0.84-1.35). A nonlinear association between GHB and IA rupture was observed, whose inflection points were 5.5 and 8.9. The OR values (95% confidence intervals) were 0.38 (0.16-0.9) at the range of 1.88-5.5% of GHB, 1.6 (1.03, 2.5) at the range of 5.5-8.9%, and 0.56 (0.06-5.34) at the range of 8.9-10.1, respectively.

Conclusion

The independent correlation between GHB and risk of IA rupture presented is nonlinear. The good glycemic control in single IA patients with DM can reduce the risk of IA rupture, and vice versa.

Why Are Women Predisposed to Intracranial Aneurysm?

Intracranial aneurysm (IA) is a frequent and generally asymptomatic cerebrovascular abnormality characterized as a localized dilation and wall thinning of intracranial arteries that preferentially arises at the arterial bifurcations of the circle of Willis. The devastating complication of IA is its rupture, which results in subarachnoid hemorrhage that can lead to severe disability and death. IA affects about 3% of the general population with an average age for detection of rupture around 50 years. IAs, whether ruptured or unruptured, are more common in women than in men by about 60% overall, and more especially after the menopause where the risk is double-compared to men. Although these data support a protective role of estrogen, differences in the location and number of IAs observed in women and men under the age of 50 suggest that other underlying mechanisms participate to the greater IA prevalence in women. The aim of this review is to provide a comprehensive overview of the current data from both clinical and basic research and a synthesis of the proposed mechanisms that may explain why women are more prone to develop IA.

Microbial disruption in the gut promotes cerebral endothelial dysfunction

Cerebrovascular disease is a group of conditions characterized by disorders of the cerebral vessels. Endothelial dysfunction renders the vasculature at risk of impaired blood flow and increases the potential of developing cerebrovascular disease. The gut microbiota has been recently identified as a possible risk factor of cerebrovascular disease. However, a direct link between gut microbiota and cerebral vascular function has not been established. Therefore, the aim of this study was to determine the effect of gut bacterial disruption on cerebral endothelial function. Male inbred Sprague-Dawley rats were randomly assigned to receive either drinking water with (n = 4) or without (n = 4) a cocktail of nonabsorbable broad-spectrum antibiotics (streptomycin, neomycin, bacitracin, and polymyxin B). Three weeks of antibiotic treatment resulted in a significant reduction in bacterial load and shifts within the bacterial sub-populations as assessed using flow cytometry. Using pressure myography, we found that spontaneous tone significantly increased and L-NAME-induced vasoconstriction was significantly blunted in middle cerebral arteries (MCAs) harvested from antibiotic-treated rats. ATP-mediated dilations were significantly blunted in MCAs from antibiotic-treated rats compared to their control counterparts. Immunoblotting revealed that the eNOS-P/total eNOS ratio was significantly reduced in cerebral artery lysates from antibiotic-treated rats compared to controls. Our findings suggest that disruption of the gut microbiota leads to cerebral endothelial dysfunction through reduction of eNOS activity. This study highlights the potential of the microbiota as a target to reverse endothelial dysfunction and a preventative approach to reducing risk of stroke and aneurysms.

Simvastatin increases circulating endothelial progenitor cells and inhibits the formation of intracranial aneurysms in rats with diet-induced hyperhomocysteinemia

BACKGROUND AND PURPOSE

Endothelial dysfunction triggers early pathological changes in artery, leading to the formation of intracranial aneurysm (ICA). Increase in plasma homocysteine (Hcy) impairs endothelium and endothelial progenitor cells (EPCs) are critical in repairing damaged endothelium. The aim of this study was to assess the impact of simvastatin on ICA formation in rats with hyperhomocysteinemia (HHcy).

METHODS

ICAs were induced in Male Sprague-Dawley rats after surgical induction in the presence of HHcy induced by a high L-methionine diet with or without oral simvastatin treatment. The size and media thickness of ICAs were evaluated 2 months after aneurysm induction. EPCs and serum vascular endothelial grow factor (VEGF) were measured be flow cytometry and ELISA respectively. Plasma Hcy levels and expression of VEGF, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2), and MMP-9 in aneurysmal walls were examined and correlated with ICA formation.

RESULTS

HHcy accelerates ICA formation and rats treated with simvastatin exhibited a significant increase in media thickness and a reduction in aneurysmal size. Simvastatin increased levels of circulating EPCs and decreased iNOS, MMP-2, MMP-9 and VEGF mRNA levels, while increased eNOS mRNA in aneurysmal tissue.

CONCLUSION

In a rat model, HHcy reduces circulating EPCs and accelerates ICA formation. Simvastatin treatment increases circulating EPCs and inhabits the formation of ICA. We have shown a close association among circulating EPCs, biochemical markers related to vascular remodeling and the formation of ICA.

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.

Risk factors involved in the formation of multiple intracranial aneurysms

BACKGROUND

Although several risk factors of the multiple intracranial aneurysms (MIAs) formation has been reported, the results are controversial. We aimed to find out the risk factors of MIAs formation by analyzing our clinic data combined with a meta-analysis.

MATERIAL AND METHODS

A retrospective review work of medical records for the patients with aneurysms was undertaken. Univariate analysis was used to examine all mentioned variables. Binary logistic regression analysis was used to identify the risk factors of MIAs formation.

RESULTS

In the retrospective review work, a total of 565 patients with aneurysm were included in this study. Of these 565 participants, 449 patients suffered SIAs and 116 patients suffered MIAs. Univariate analysis showed a significant difference in terms of female, cigarette smoking, family history of hypertension, and primary hypertension between the SIAs and MIAs group. The binary logistic regression analysis showed that the female (OR = 1.624), primary hypertension (OR = 1.563), and family history of hypertension (OR = 2.496) were independent risk factors of the formation of MIAs (for each P < 0.05). With regard to the meta-analysis results, it revealed that there was significant difference in the rates of female (P < 0.001), cigarette smoking (P < 0.001), primary hypertension (P = 0.001), and higher age (P = 0.011) among the MIAs patients.

CONCLUSIONS

A higher rate of the formation of MIAs is closely associated with the elder and female. Patients with hypertension history, cigarette smoking, and family primary hypertension history also affected the formation of MIAs, these risk factors should be a guard against.

Role of pregnancy and female sex steroids on aneurysm formation, growth, and rupture: a systematic review of the literature

OBJECTIVE

Women have been shown to have a higher risk of cerebral aneurysm formation, growth, and rupture than men. The authors present a review of the recently published neurosurgical literature that studies the role of pregnancy and female sex steroids, to provide a conceptual framework with which to understand the various risk factors associated with cerebral aneurysms in women at different stages in their lives.

METHODS

The PubMed database was searched for "("intracranial" OR "cerebral") AND "aneurysm" AND ("pregnancy" OR "estrogen" OR "progesterone")" between January 1980 and February 2019. A total of 392 articles were initially identified, and after applying inclusion and exclusion criteria, 20 papers were selected for review and analysis. These papers were then divided into two categories: 1) epidemiological studies about the formation, growth, rupture, and management of cerebral aneurysms in pregnancy; and 2) investigations on female sex steroids and cerebral aneurysms (animal studies and epidemiological studies).

RESULTS

The 20 articles presented in this study include 7 epidemiological articles on pregnancy and cerebral aneurysms, 3 articles reporting case series of cerebral aneurysms treated by endovascular therapies in pregnancy, 3 epidemiological articles reporting the relationship between female sex steroids and cerebral aneurysms through retrospective case-control studies, and 7 experimental studies using animal and/or cell models to understand the relationship between female sex steroids and cerebral aneurysms. The studies in this review report similar risk of aneurysm rupture in pregnant women compared to the general population. Most ruptured aneurysms in pregnancy occur during the 3rd trimester, and most pregnant women who present with cerebral aneurysm have caesarean section deliveries. Endovascular treatment of cerebral aneurysms in pregnancy is shown to provide a new and safe form of therapy for these cases. Epidemiological studies of postmenopausal women show that estrogen hormone therapy and later age at menopause are associated with a lower risk of cerebral aneurysm than in matched controls. Experimental studies in animal models corroborate this epidemiological finding; estrogen deficiency causes endothelial dysfunction and inflammation, which may predispose to the formation and rupture of cerebral aneurysms, while exogenous estrogen treatment in this population may lower this risk.

CONCLUSIONS

The aim of this work is to equip the neurosurgical and obstetrical/gynecological readership with the tools to better understand, critique, and apply findings from research on sex differences in cerebral aneurysms.

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.

Time-dependent and site-dependent morphological changes in rupture-prone arteries: ovariectomized rat intracranial aneurysm model

OBJECTIVE

The pathogenesis of intracranial aneurysm rupture remains unclear. Because it is difficult to study the time course of human aneurysms and most unruptured aneurysms are stable, animal models are used to investigate the characteristics of intracranial aneurysms. The authors have newly established a rat intracranial aneurysm rupture model that features site-specific ruptured and unruptured aneurysms. In the present study the authors examined the time course of changes in the vascular morphology to clarify the mechanisms leading to rupture.

METHODS

Ten-week-old female Sprague-Dawley rats were subjected to hemodynamic changes, hypertension, and ovariectomy. Morphological changes in rupture-prone intracranial arteries were examined under a scanning electron microscope and the association with vascular degradation molecules was investigated.

RESULTS

At 2-6 weeks after aneurysm induction, morphological changes and rupture were mainly observed at the posterior cerebral artery; at 7-12 weeks they were seen at the anterior Willis circle including the anterior communicating artery. No aneurysms at the anterior cerebral artery-olfactory artery bifurcation ruptured, suggesting that the inception of morphological changes is site dependent. On week 6, the messenger RNA level of matrix metalloproteinase-9, interleukin-1β, and the ratio of matrix metalloproteinase-9 to the tissue inhibitor of metalloproteinase-2 was significantly higher at the posterior cerebral artery, but not at the anterior communicating artery, of rats with aneurysms than in sham-operated rats. These findings suggest that aneurysm rupture is attributable to significant morphological changes and an increase in degradation molecules.

CONCLUSIONS

Time-dependent and site-dependent morphological changes and the level of degradation molecules may be indicative of the vulnerability of aneurysms to rupture.

Endothelial dysfunction in cerebral aneurysms

Endothelial cell (EC) dysfunction is known to contribute to cerebral aneurysm (CA) pathogenesis. Evidence shows that damage or injury to the EC layer is the first event in CA formation. The mechanisms behind EC dysfunction in CA disease are interrelated and include hemodynamic stress, hazardous nitric oxide synthase (NOS) activity, oxidative stress, estrogen imbalance, and endothelial cell-to-cell junction compromise. Abnormal variations in hemodynamic stress incite pathological EC transformation and inflammatory zone formation, ultimately leading to destruction of the vascular wall and aneurysm dilation. Hemodynamic stress activates key molecular pathways that result in the upregulation of chemotactic cytokines and adhesion molecules, leading to inflammatory cell recruitment and infiltration. Concurrently, oxidative stress damages EC-to-EC junction proteins, resulting in interendothelial gap formation. This further promotes leukocyte traffic into the vessel wall and the release of matrix metalloproteinases, which propagates vascular remodeling and breakdown. Abnormal hemodynamic stress and inflammation also trigger adverse changes in NOS activity, altering proper EC mediation of vascular tone and the local inflammatory environment. Additionally, the vasoprotective hormone estrogen modulates gene expression that often suppresses these harmful processes. Crosstalk between these sophisticated pathways contributes to CA initiation, progression, and rupture. This review aims to outline the complex mechanisms of EC dysfunction in CA pathogenesis.

Inflammatory Smooth Muscle Cells Induce Endothelial Cell Alterations to Influence Cerebral Aneurysm Progression via Regulation of Integrin and VEGF Expression

Cerebral aneurysm growth is characterized by vessel wall frailness, although the underlying cellular mechanisms are unclear. Here, we examined the relationship between inflammatory smooth muscle cells (SMCs) and endothelial cells (ECs) in cerebral aneurysms, including the mechanisms underlying inflammatory SMC-induced changes in ECs. Five saccular cerebral aneurysms were collected and five temporal artery samples were used as controls. Cells and cytokines were detected by immunohistochemistry and TUNEL (transferase dUTP nick end labeling) assays performed to evaluate apoptosis. Human umbilical vein endothelial cells (HUVECs) were seeded on collagen I, IV, and VI-coated plates for cell adhesion assays and inflammatory SMCs (iSMCs) were established by culture in flexible silicone chambers subjected to cyclic mechanical stretch. HUVECs were cultured in iSMC-conditioned medium, followed by evaluation of their viability, apoptosis, and function, and determination of VEGF (vascular endothelial growth factor) -A and integrin levels by western blotting. Aneurysm tissue contained fewer SMCs and lacked ECs. In aneurysm walls, more matrix metalloproteinase (MMP) -1, MMP-3, and apoptotic cells were detected, accompanied by decreased collagen IV and VI levels. Cell adhesion assays revealed that more HUVECs were attached in collagen IV and VI-coated plates compared with controls. iSMC-conditioned medium significantly reduced HUVEC viability and apoptosis showed an increased trend; however, the difference was not significant. iSMC medium also reduced tube formation and migration of HUVECs. Moreover, iSMC medium reduced HUVEC expression of VEGF-A, integrin α1, integrin α2, and integrin β. Our data demonstrate a lack of SMCs and ECs in aneurysm walls, accompanied by elevated MMP and decreased collagen levels. In vitro assays showed that iSMCs induced reduction in EC adhesion, and caused EC dysfunction. Understanding of the relationships among SMC, EC, and collagens during aneurysm progression provides an additional therapeutic option for prevention of cerebral aneurysm progression.

The active participation of p22phox-214T/C in the formation of intracranial aneurysm and the suppressive potential of edaravone

Oxidative stress reactions play an important role in the pathogenesis of intracranial aneurysm (IA). p22phox is involved in the oxidative stress reaction, and it is a critical subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The present study investigated the association of genetic variants within the gene encoding p22phox‑214T/C with IA. The p22phox‑214T/C gene polymorphisms in 192 cases of IA and 112 controls were analyzed by polymerase chain reaction‑restriction fragment length polymorphism (PCR‑RFLP). The mRNA expression of NADPH oxidase was also analyzed by RT‑PCR. The results of RT‑PCR were validated by ELISA. In a rabbit model of elastase‑induced aneurysm, we used edaravone for anti‑oxidative stress treatment to observe the curative effects. In the clinical cases, a significant difference in p22phox‑214T/C allele frequencies in the IA group was observed compared with the control group (P<0.001). The expression level of NADPH oxidase was differed significantly between the IA group and the control group. In the rabbit model of elastase‑induced aneurysm, the success rate of the aneurysmal model in the edaravone group and the wound ulcer rate were lower than those in the control group. In addition, the diameter of the aneurysm was smaller than in the edaravone group than in the control group (3.26±0.13 mm vs. 3.85±0.07 mm), and the expression of matrix metalloproteinase‑9 (MMP‑9) was significantly lower than that in the control group (P<0.0001). Thus, these data suggest the active participation of p22phox‑214T/C in the formation of IA and the suppressive potential of edaravone against IA formation.

Comparative transcriptome analysis reveals involvement of TLR-2 signaling in the pathogenesis of intracranial aneurysm

In this study, we collected and analyzed 15 aneurysmal and 17 superficial temporal artery (STA) specimens from 32 Chinese patients with intracranial aneurysm. Total RNA was extracted and reverse transcribed to cDNA, and genome-wide expression profiling was performed by using the Affymetrix Human Genome U133 Plus 2.0 Array which allows a total number of 38,500 genes to be analyzed at the same time. Real-time RT-PCR was performed to verify the expression level of 8 selected genes. We found significant up-regulation of the TLR-2 gene. This result suggests that TLR-2 plays a key role in the formation of intracranial aneurysm in a Chinese population. To our knowledge, this study is the first to use the Human Genome U133 Plus 2.0 Array to analyze the gene expression profiles in Chinese patients with intracranial aneurysm.

Bazedoxifene, a selective estrogen receptor modulator, reduces cerebral aneurysm rupture in Ovariectomized rats

Background

Estrogen deficiency is thought to be responsible for the higher frequency of aneurysmal subarachnoid hemorrhage in post- than premenopausal women. Estrogen replacement therapy appears to reduce this risk but is associated with significant side effects. We tested our hypothesis that bazedoxifene, a clinically used selective estrogen receptor (ER) modulator with fewer estrogenic side effects, reduces cerebral aneurysm rupture in a new model of ovariectomized rats.

Methods

Ten-week-old female Sprague-Dawley rats were subjected to ovariectomy, hemodynamic changes, and hypertension to induce aneurysms (ovariectomized aneurysm rats) and treated with vehicle or with 0.3 or 1.0 mg/kg/day bazedoxifene. They were compared with sham-ovariectomized rats subjected to hypertension and hemodynamic changes (HT rats). The vasoprotective effects of bazedoxifene and the mechanisms underlying its efficacy were analyzed.

Results

During 12 weeks of observation, the incidence of aneurysm rupture was 52% in ovariectomized rats. With no effect on the blood pressure, treatment with 0.3 or 1.0 mg/kg/day bazedoxifene lowered this rate to 11 and 17%, almost the same as in HT rats (17%). In ovariectomized rats, the mRNA level of ERα, ERβ, and the tissue inhibitor of metalloproteinase-2 was downregulated in the cerebral artery prone to rupture at 5 weeks after aneurysm induction; the mRNA level of interleukin-1β and the matrix metalloproteinase-9 was upregulated. In HT rats, bazedoxifene restored the mRNA level of ERα and ERβ and decreased the level of interleukin-1β and matrix metalloproteinase-9. These findings suggest that bazedoxifene was protective against aneurysmal rupture by alleviating the vascular inflammation and degradation exacerbated by the decrease in ERα and ERβ.

Conclusions

Our observation that bazedoxifene decreased the incidence of aneurysmal rupture in ovariectomized rats warrants further studies to validate this response in humans.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-0966-7) contains supplementary material, which is available to authorized users.

Site-specific elevation of interleukin-1β and matrix metalloproteinase-9 in the Willis circle by hemodynamic changes is associated with rupture in a novel rat cerebral aneurysm model

The pathogenesis of subarachnoid hemorrhage remains unclear. No models of cerebral aneurysms elicited solely by surgical procedures and diet have been established. Elsewhere we reported that only few rats in our original rat aneurysm model manifested rupture at the anterior and posterior Willis circle and that many harbored unruptured aneurysms at the anterior cerebral artery-olfactory artery bifurcation. This suggests that rupture was site-specific. To test our hypothesis that a site-specific response to hemodynamic changes is associated with aneurysmal rupture, we modified our original aneurysm model by altering the hemodynamics. During 90-day observation, the incidence of ruptured aneurysms at the anterior and posterior Willis circle was significantly increased and the high incidence of unruptured aneurysms at the anterior cerebral artery-olfactory artery persisted. This phenomenon was associated with an increase in the blood flow volume. Notably, the level of matrix metalloproteinase-9 associated with interleukin-1β was augmented by the increase in the blood flow volume, suggesting that these molecules exacerbated the vulnerability of the aneurysmal wall. The current study first demonstrates that a site-specific increase in interleukin-1β and matrix metalloproteinase-9 elicited by hemodynamic changes is associated with rupture. Our novel rat model of rupture may help to develop pharmaceutical approaches to prevent rupture.

Late onset MELAS with m.3243A > G mutation and its association with aneurysm formation

We reported a 53-year-old with late-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) accompanied by aneurysm and large vessel dilations. Most studies have focused on microangiopathy causing stroke-like episodes. We report a case to describe large vessel involvement in clinical considerations, and possible mechanisms of aneurysm formation. We recommended regular angiographic examination for patients with MELAS.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

Biology of Saccular Cerebral Aneurysms: A Review of Current Understanding and Future Directions

Understanding the biology of intracranial aneurysms is a clinical quandary. How these aneurysms form, progress, and rupture is poorly understood. Evidence indicates that well-established risk factors play a critical role, along with immunologic factors, in their development and clinical outcomes. Much of the expanding knowledge of the inception, progression, and rupture of intracranial aneurysms implicates inflammation as a critical mediator of aneurysm pathogenesis. Thus, therapeutic targets exploiting this arm of aneurysm pathogenesis have been implemented, often with promising outcomes.

Hyperhomocysteinemia induced by excessive methionine intake promotes rupture of cerebral aneurysms in ovariectomized rats

Background

Hyperhomocysteinemia (HHcy) is associated with inflammation and a rise in the expression of matrix metalloproteinase-9 (MMP-9) in the vascular wall. However, the role of HHcy in the growth and rupture of cerebral aneurysms remains unclear.

Methods

Thirteen-week-old female Sprague-Dawley rats were subject to bilateral ovariectomy and ligation of the right common carotid artery and fed an 8 % high-salt diet to induce cerebral aneurysms. Two weeks later, they underwent ligation of the bilateral posterior renal arteries. They were divided into two groups and methionine (MET) was or was not added to their drinking water. In another set of experiments, the role of folic acid (FA) against cerebral aneurysms was assessed.

Results

During a 12-week observation period, subarachnoid hemorrhage due to aneurysm rupture was observed at the anterior communicating artery (AcomA) or the posterior half of the circle of Willis. HHcy induced by excessive MET intake significantly increased the incidence of ruptured aneurysms at 6–8 weeks. At the AcomA of rats treated with MET, we observed the promotion of aneurysmal growth and infiltration by M1 macrophages. Furthermore, the mRNA level of MMP-9, the ratio of MMP-9 to the tissue inhibitor of metalloproteinase-2, and the level of interleukin-6 were higher in these rats. Treatment with FA abolished the effect of MET, suggesting that the inflammatory response and vascular degradation at the AcomA is attributable to HHcy due to excessive MET intake.

Conclusions

We first demonstrate that in hypertensive ovariectomized rats, HHcy induced by excessive MET intake may be associated with the propensity of the aneurysm wall to rupture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0634-3) contains supplementary material, which is available to authorized users.

Diabetes may affect intracranial aneurysm stabilization in older patients: Analysis based on intraoperative findings

BACKGROUND

Only a small proportion of aneurysms progress to rupture. Previous studies have focused on predicting the rupture risk of intracranial aneurysms. Atherosclerotic aneurysm wall appears resistant to rupture. The purpose of this study was to evaluate clinical and morphological factors affecting atherosclerosis of an aneurysm and identify the parameters that predict aneurysm stabilization.

METHODS

We conducted a retrospective analysis of 253 consecutive patients with 291 unruptured aneurysms who underwent clipping surgery in a single institution between January 2012 and October 2013. Aneurysms were categorized based on intraoperative video findings and assessed morphologic and demographic data. Aneurysms which had the atherosclerotic wall without any super thin and transparent portion were defined as stabilized group and the others as a not-stabilized group.

RESULTS

Of the 207 aneurysms, 176 (85.0%) were assigned to the not-stabilized group and 31 (15.0%) to the stabilized group. The relative proportion of stabilized aneurysms increased significantly as the age increased (P < 0.001). Univariate logistic analysis showed that age ≥65 years (P < 0.001), hypertension (P = 0.012), diabetes (P = 0.007), and height ≥3 mm (P = 0.007) were correlated with stabilized aneurysms. Multivariate logistic analysis showed that age ≥65 years (P = 0.009) and hypertension (P = 0.041) were strongly correlated with stable aneurysms. In older patients (≥65 years of age), multivariate logistic regression revealed that only diabetes was associated with stabilized aneurysms (P = 0.027).

CONCLUSIONS

In patients ≥65 years of age, diabetes mellitus may highly predict the stabilized aneurysms. These results provide useful information in determining treatment and follow-up strategies, especially in older patients.

Preemptive Medicine for Cerebral Aneurysms

Most of cerebral aneurysms (CAs) are incidentally discovered without any neurological symptoms and the risk of rupture of CAs is relatively higher in Japanese population. The goal of treatments for patients with CAs is complete exclusion of the aneurysmal rupture risk for their lives. Since two currently available major treatments, microsurgical clipping and endovascular coiling, have inherent incompleteness to achieve cure of CAs with some considerable treatment risks, and there is no effective surgical or medical intervention to inhibit the formation of CAs in patients with ruptured and unruptured CAs, new treatment strategies with lower risk and higher efficacy should be developed to prevent the formation, growth, and rupture of CAs. Preemptive medicine for CAs should be designed to prevent or delay the onset of symptoms from CAs found in an asymptomatic state or inhibit the de novo formation of CAs, but we have no definite methods to distinguish rupture-prone aneurysms from rupture-resistant ones. Recent advancements in the research of CAs have provided us with some clues, and one of the new treatment strategies for CAs will be developed based on the findings that several inflammatory pathways may be involved in the formation, growth, and rupture of CAs. Preemptive medicine for CAs will be established with specific biomarkers and imaging modalities which can sensor the development of CAs.

Sex Differences in the Formation of Intracranial Aneurysms and Incidence and Outcome of Subarachnoid Hemorrhage: Review of Experimental and Human Studies

Intracranial aneurysms are defined as pathological dilatations of cerebral arteries and rupture of intracranial aneurysms leads to subarachnoid hemorrhage (SAH). The goal of this review was to outline the sex differences in the formation and progression of intracranial aneurysms as well as sex-related differences in incidence and outcome of SAH. The literature review was performed using PubMed with a combination of these search terms: "subarachnoid hemorrhage," "incidence," "outcome," "sex," "gender," "male," "female," "experimental," "mice," and "rats." Studies written in English were used. Female sex is thought to be a risk factor for aneurysm formation, especially in postmenopausal age populations, suggesting the potential protective involvement of sex steroids. Female sex is also considered a risk factor for SAH occurrence. Although incidence and mortality are confirmed to be higher in females in most studies, they elucidated no clear differences in the functional outcome among SAH survivors. The effect of gender on the pathophysiology of SAH is not very well understood; nevertheless, the majority of pre-clinical studies suggest a beneficial effect of sex steroids in experimental SAH. Moreover, conflicting results exist on the role and effect of hormone replacement therapies and oral contraceptive pills on the incidence and outcome of human SAH. Sex differences exist in the formation of aneurysms as well as the incidence and mortality of SAH. Potential therapeutic effects of sex steroids have been replicated in many animal studies, but their potential use in the treatment of acute SAH in human populations needs more future study.

Aspirin Inhibits Degenerative Changes of Aneurysmal Wall in a Rat Model

Aneurysmal subarachnoid hemorrhage still has a high mortality and morbidity despite notable advances in surgical approaches to cerebral aneurysm (CA). We examined the role of aspirin in vascular inflammation and degeneration. CA was induced in male Sprague-Dawley rats by ligating left common carotid artery and bilateral posterior renal arteries with or without aspirin treatment. The right anterior cerebral artery/olfactory artery (ACA/OA) bifurcations were stripped and assessed morphologically after Verhoeff's Van Gieson staining. Blood sample was obtained to examine circulating CD34(+) CD133(+) endothelial progenitor cells (EPCs), platelet aggregation and platelet counts. Macrophages infiltration in aneurysmal wall was evaluated by immunohistochemistry. Expression of matrix metalloproteinase-2 and 9 (MMP-2 and 9), nuclear factor kappa B (NF-κB), macrophage chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) was examined by RT-PCR. 2 months after CA induction, surgically treated rats manifested aneurysmal degeneration in ACA/OA bifurcations. Aspirin-treated rats exhibited a significant decrease in degradation of internal elastic lamina (IEL), medial layer thinning, CA size and macrophages infiltration with reduced expression of MMP-2 and 9 compared with rats in the CA group. RT-PCR demonstrated that the upregulation of NF-κB, MCP-1 and VCAM-1 after CA induction was reversed by aspirin treatment. Aspirin treatment following CA induction increased circulating EPCs to near control levels and reduced platelet aggregation without changing platelet counts. The evidence suggested that aspirin significantly reduced degeneration of aneurysm walls by inhibiting macrophages-mediated chronic inflammation and mobilizing EPCs.

High Angiopoietin-1 levels predict a good functional outcome within 72 h of an aneurysmal subarachnoid hemorrhage: A prospective study from a single center

BACKGROUND

The consequences of aneurysmal subarachnoid hemorrhage (aSAH) are lifelong and fatal. Angiopoietin-1 (Ang-1) and Angiopoietin-2 (Ang-2) play an important role in the regulation of vascular structure and function. Our study examined the association between angiopoietin levels and functional outcomes among aSAH patients.

METHODS

We enrolled 37 aSAH patients and 39 controls (matched on age and sex) at the Department of Neurosurgery in Tianjin Medical University General Hospital. Serum Ang-1, Ang-2, and Tie-2 levels were collected at 8, 24, and 72 hours post-hemorrhage. After a 3-month follow-up period, patient outcomes were evaluated using the Glasgow Outcome Score (GOS). Logistic regression examined the association between angiopoietin levels and outcomes (good [GOS: 4-5] vs. poor [GOS: 1-3]).

RESULTS

aSAH patients had higher levels of Ang-1 at 8 hours post-hemorrhage compared to controls. Among aSAH patients, Ang-1 levels at 8, 24, and 72 hours post-hemorrhage were higher among patients with a good outcome. Compared to patients with low Ang-1 levels, high Ang-1 levels at 72 hours post-hemorrhage were associated with a good outcome.

CONCLUSIONS

High Ang-1 levels were associated with a good functional outcome after aSAH. Abnormal angiopoietin levels may disrupt the blood-brain barrier and contribute to functional outcomes in aSAH patients.

Molecular mechanisms of the formation and progression of intracranial aneurysms

Until recently, only a little was understood about molecular mechanisms of the development of an intracranial aneurysm (IA). Recent advancements over the last decade in the field of genetics and molecular biology have provided us a wide variety of evidences supporting the notion that chronic inflammation is closely associated with the pathogenesis of IA development. In the field of genetics, large-scale Genome-wide association studies (GWAS) has identified some IA susceptible loci and genes related to cell cycle and endothelial function. Researches in molecular biology using human samples and animal models have revealed the common pathway of the initiation, progression, and rupture of IAs. IA formation begins with endothelial dysfunction followed by pathological remodeling with degenerative changes of vascular walls. Medical treatments inhibiting inflammatory cascades in IA development are likely to prevent IA progression and rupture. Statins and aspirin are expected to suppress IA progression by their anti-inflammatory effects. Decoy oligodeoxynucleotides (ODNs) inhibiting inflammatory transcription factors such as nuclear factor kappa-B (NF-κB) and Ets-1 are the other promising choice of the prevention of IA development. Further clarification of molecular mechanisms of the formation and progression of IAs will shed light to the pathogenesis of IA development and provide insight into novel diagnostic and therapeutic strategies for IAs.

Roles of estrogen in the formation of intracranial aneurysms in ovariectomized female mice

BACKGROUND

Epidemiological studies have indicated that postmenopausal women have a higher incidence of intracranial aneurysms than men in the same age group.

OBJECTIVE

To investigate whether estrogen or estrogen receptors (ERs) mediate protective effects against the formation of intracranial aneurysms.

METHODS

Intracranial aneurysms were induced in mice by combining a single injection of elastase into the cerebrospinal fluid with deoxycorticosterone acetate salt hypertension. The mice were treated with estrogen (17β-estradiol), an ERα agonist (propyl pyrazole triol), and an ERβ agonist (diarylpropionitrile) with and without a nitric oxide synthase inhibitor.

RESULTS

The ovariectomized female mice had a significantly higher incidence of aneurysms than the male mice, which was consistent with findings in previous epidemiological studies. In ovariectomized female mice, an ERβ agonist, but not an ERα agonist or 17β-estradiol, significantly reduced the incidence of aneurysms. The protective effect of the ERβ agonist was absent in the ovariectomized ERβ knockout mice. The protective effect of the ERβ agonist was negated by treatment with a nitric oxide synthase inhibitor.

CONCLUSION

The effects of sex, menopause, and estrogen treatment observed in this animal study were consistent with previous epidemiological findings. Stimulation of estrogen receptor-β was protective against the formation of intracranial aneurysms in ovariectomized female mice.

Intravenous transfusion of endothelial colony-forming cells attenuates vascular degeneration after cerebral aneurysm induction

Cerebral aneurysm (CA) rupture is a major cause of subarachnoid hemorrhage with high morbidity and mortality. Using an animal model, we examined the potential of endothelial colony-forming cells (ECFCs) transfusion on vascular degeneration after CA induction and underlying mechanisms. CA was induced in the right anterior cerebral artery-olfactory artery (ACA/OA) bifurcations in Sprague-Dawley rats with or without ECFCs transfusion. The degeneration of internal elastic lamina (IEL), media thickness and CA size were evaluated. Expression of matrix metalloproteinase-2 and 9 (MMP-2 and 9), tissue inhibitor of metalloproteinase-1 (TIMP-1), macrophage chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), nuclear factor κB (NF-κB), endothelial nitric oxide synthase (eNOS), B-cell leukemia/lymphoma-2 (Bcl-2), and inducible nitric oxide synthase (iNOS) were analyzed by quantitative real-time polymerase chain reaction. The macrophages infiltration and apoptosis of smooth muscle cells (SMCs) were examined immunohistologically. Rats in CA+ECFCs transfusion group showed a notable reduction in IEL degeneration, media thinning and CA size compared with those in CA+saline group. ECFCs transfusion inhibited the MMP-driven wall destruction by downregulating MMP-2, MMP-9 expression and upregulating TIMP-1. ECFCs transfusion dramatically decreased VCAM-1 and NF-κB expression, increased eNOS expression and caused no change in MCP-1 expression, which was accompanied by reduced macrophages infiltration. Moreover, ECFCs transfusion reversed downregulation of Bcl-2 expression and upregulation of iNOS expression, and decreased SMCs apoptosis. Collectively, these findings suggest that ECFCs transfusion confers protection against degeneration of aneurysmal wall by inhibiting inflammatory cascades and SMCs apoptosis.

Female sex as a risk factor for the growth of asymptomatic unruptured cerebral saccular aneurysms in elderly patients

Object

The prevalence of patients with asymptomatic unruptured intracranial aneurysms (UIAs) increases with the advancing age of the general population. The goal of the present study was to identify risk factors for the growth of UIAs detected with serial MR angiography (MRA) in patients 70 years of age or older.

Methods

This prospective study enrolled 79 patients (age range 70–84 years) with 98 UIAs. Patients were followed up every 4 months, including an assessment of the aneurysm diameter and morphological changes on MRA, neurological status, and other medical conditions. Aneurysm growth was categorized into two different patterns on the basis of the MRA findings: 1) maximum increase in aneurysm diameter of 2 mm or more; and 2) obvious morphological change, such as the appearance of a bleb.

Results

The mean duration of follow-up was 38.5 months (250.2 patient-years). Aneurysm rupture did not occur, but aneurysm growth was observed in 8 aneurysms (8 patients) during the study period. Univariate analysis showed that female sex, patient age ≥ 75 years, and an aneurysm location in the internal carotid artery (ICA) or middle cerebral artery (MCA) were associated with aneurysm growth (p = 0.04, p = 0.04, and p < 0.001, respectively). Multivariate analysis demonstrated that female sex was the only independent predictor of aneurysm growth (p = 0.0313, OR 2.3, 95% CI 1.3–30.2).

Conclusions

Female sex is an independent risk factor for the growth of UIAs in elderly patients. In addition, an age ≥ 75 years and aneurysm location in the ICA or MCA are characteristics that may warrant additional attention during follow-up imaging.

Estrogen protects against intracranial aneurysm rupture in ovariectomized mice

Clinical observations suggest that postmenopausal women have a higher incidence of aneurysmal rupture than premenopausal women. We hypothesize that a relative deficiency in estrogen may increase the risks of aneurysmal growth and subarachnoid hemorrhage in postmenopausal women. We assessed the effects of estrogen and selective estrogen receptor subtype agonists on the development of aneurysmal rupture in ovariectomized female mice. We used an intracranial aneurysm mouse model that recapitulates the key features of human intracranial aneurysms, including spontaneous rupture. Ten- to 12-week-old ovariectomized female mice received treatment with estrogen, nonselective estrogen receptor antagonist, estrogen receptor-α agonist, or estrogen receptor-β agonist starting 6 days after aneurysm induction so that the treatments affected the development of aneurysmal rupture without affecting aneurysmal formation. Estrogen significantly reduced the incidence of ruptured aneurysms and rupture rates in ovariectomized mice. Nonselective estrogen receptor antagonist abolished the protective effect of estrogen. Although estrogen receptor-α agonist did not affect the incidence of ruptured aneurysms or rupture rates, estrogen receptor-β agonist prevented aneurysmal rupture without affecting the formation of aneurysms. The protective role of estrogen receptor-β agonist was abolished by the inhibition of nitric oxide synthase. We showed that estrogen prevented aneurysmal rupture in ovariectomized female mice. The protective effect of estrogen seemed to occur through the activation of estrogen receptor-β, a predominant subtype of estrogen receptor in human intracranial aneurysms and cerebral arteries.

Factors affecting formation and rupture of intracranial saccular aneurysms

Unruptured intracranial aneurysms represent a decisional challenge. Treatment risks have to be balanced against an unknown probability of rupture. A better understanding of the physiopathology is the basis for a better prediction of the natural history of an individual patient. Knowledge about the possible determining factors arises from a careful comparison between ruptured versus unruptured aneurysms and from the prospective observation and analysis of unbiased series with untreated, unruptured aneurysms. The key point is the correct identification of the determining variables for the fate of a specific aneurysm in a given individual. Thus, the increased knowledge of mechanisms of formation and eventual rupture of aneurysms should provide significant clues to the identification of rupture-prone aneurysms. Factors like structural vessel wall defects, local hemodynamic stress determined also by peculiar geometric configurations, and inflammation as trigger of a wall remodeling are crucial. In this sense the study of genetic modifiers of inflammatory responses together with the computational study of the vessel tree might contribute to identify aneurysms prone to rupture. The aim of this article is to underline the value of a unifying hypothesis that merges the role of geometry, with that of hemodynamics and of genetics as concerns vessel wall structure and inflammatory pathways.

The role of oxidative stress in cerebral aneurysm formation and rupture

Oxidative stress is known to contribute to the progression of cerebrovascular disease. Additionally, oxidative stress may be increased by, but also augment inflammation, a key contributor to cerebral aneurysm development and rupture. Oxidative stress can induce important processes leading to cerebral aneurysm formation including direct endothelial injury as well as smooth muscle cell phenotypic switching to an inflammatory phenotype and ultimately apoptosis. Oxidative stress leads to recruitment and invasion of inflammatory cells through upregulation of chemotactic cytokines and adhesion molecules. Matrix metalloproteinases can be activated by free radicals leading to vessel wall remodeling and breakdown. Free radicals mediate lipid peroxidation leading to atherosclerosis and contribute to hemodynamic stress and hypertensive pathology, all integral elements of cerebral aneurysm development. Preliminary studies suggest that therapies targeted at oxidative stress may provide a future beneficial treatment for cerebral aneurysms, but further studies are indicated to define the role of free radicals in cerebral aneurysm formation and rupture. The goal of this review is to assess the role of oxidative stress in cerebral aneurysm pathogenesis.

Intracranial aneurysm formation in type-one diabetes rats

BACKGROUND & OBJECTIVE

Diabetes mellitus (DM) plays an important role in the pathogenesis of vascular complications including arteriosclerosis and ischemic stroke. Whether DM impacts intracranial aneurysm (IA) formation has not been extensively investigated. In this study, we tested the underlying mechanism of type one DM (T1DM) induced IA formation in rats.

EXPERIMENTAL APPROACHES

T1DM was induced by streptozotocin injection. Rats were euthanized at 0, 4 and 10 weeks after T1DM induction. To evaluate cerebral vascular perfusion, Fluorescein isothiocyanate - dye was injected at 5 min prior to euthanasia. Vascular perfusion was measured by laser scanning confocal microscopy. Trichrome, Elastica van Gieson, alpha-smooth muscle actin (a-SMA) and receptor of advanced glycation end-products (RAGE), toll-like receptor 4 (TLR4) and matrix metalloproteinase 9 (MMP9) immunostaining were performed. The IA formation was classified by 0-3 stages: 0: Normal; 1: Endothelial damage; 2: Moderate protrusion; and 3: Saccular aneurysm formation.

RESULTS

T1DM significantly increased IA formation identified by the classification of aneurysmal changes compared with non-DM rats (p<0.05). However, T1DM induced IA formations were classified as stage 1 and stage 2, but not stage 3. Cerebral vascular perfusion was significantly decreased in T1DM rats compared to non-DM rats (p<0.01). DM10W rats exhibited a significant decrease of cerebral vascular perfusion compared to DM4W rats (p<0.05). T1DM rats also significantly increased the internal carotid artery (ICA) intimae and media thickness, and decreased the internal carotid artery diameter compared to non-DM rats. RAGE, MMP9 and TLR4 expression were significantly increased in T1DM rats compared to non-DM rats. The increased RAGE, TLR4 and MMP9 significantly correlated with IA formation (p<0.05).

CONCLUSION

T1DM increases IA formation. The increased RAGE, MMP9 and TLR4 expressions might contribute to IA formation in T1DM rats.

Aqueous extract of danshen (Salvia miltiorrhiza Bunge) protects ovariectomized rats fed with high-fat diet from endothelial dysfunction

OBJECTIVE

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality in postmenopausal women. Danshen, the dried root of Salvia miltiorrhiza Bunge, has been used clinically in China to treat CVD and dyslipidemia in postmenopausal women, and its major active ingredients have been found to have an estrogenic effect. The aim of this study was to elucidate the underlying mechanism of danshen's protective effects on vascular function in an ovariectomized (OVX) hyperlipidemic rat model.

METHODS

Thirty-five 6-month-old female Sprague-Dawley rats were randomly divided into five groups: sham-operated rats with low-fat control diet + vehicle, sham-operated rats with high-fat diet (HFD) + vehicle, OVX rats with HFD + vehicle, OVX rats with HFD + 17β-estradiol (1 mg kg d, PO), and OVX rats with HFD + danshen aqueous extract (600 mg kg d, PO). After 12 weeks of treatment, gains in body weight and serum lipid profile levels in rats were measured and histological examination of livers was carried out. Vascular function was evaluated by measuring relaxation responses. Molecular mechanisms were also analyzed in isolated aorta.

RESULTS

Treatment with danshen aqueous extract reduced body weight gain, improved serum lipid profiles, and prevented formation of fatty liver induced by HFD and OVX. In addition, danshen could increase endothelial-dependent vasorelaxation and displayed vasoprotection in OVX rats fed with HFD, primarily by stimulating nitric oxide (NO) production, up-regulating the mRNA expression of endothelial NO synthase, and down-regulating the mRNA expression of tumor necrosis factor α, intercellular cell adhesion molecule-1, and vascular cell adhesion molecule-1 in the isolated aortas.

CONCLUSIONS

We conclude for the first time that danshen aqueous extract could protect OVX rats fed with HFD from endothelial dysfunction. Its effect may be related to its abilities to normalize serum lipid profiles and enhance NO availability in the vascular system. Our findings indicate that danshen aqueous extract could be a promising natural supplement for postmenopausal women for preventing CVD.

Numerical simulation of hemodynamics in intracranial saccular aneurysm treated with a novel stent

Different from the traditional stents, a novel stent with triangular wire cross-section is proposed, and numerical simulation is performed to compare the hemodynamic effect of the novel stent with that of traditional ones. Three kinds of stents with circular, rectangular, and triangular wire cross-sections were designed to treat saccular aneurysm, which were named the C-stent model, the R-stent model, and the T-stent model, respectively. An unstented aneurysm model (named the Unstented model), as a control, was also designed. Fluid-structure interaction in these four models was simulated. The results demonstrate that the resistance of the novel T-stent model is lower than that of the R-stent model, but higher than that of the C-stent model. Compared with the C-stent model, the T-stent model exhibits greater velocity decrease and longer turnover time. Meanwhile, the pressure increase of the T-stent model is lower than the R-stent model, and the magnitude and the fluctuation of wall shear stress is optimized in the T-stent model. The novel stent with a bare triangular wire cross-section has some comparative advantages. These results may provide some theoretical guidance for the structural design of an endovascular stent for the interventional treatment of aneurysm.

Increase in body Na+/water ratio is associated with cerebral aneurysm formation in oophorectomized rats

The incidence of cerebral aneurysms is higher in women than in men, especially postmenopause. Although hypertension is thought to be associated with a high incidence of stroke, not all patients with unruptured cerebral aneurysms are hypertensive. The possibility of water-free Na(+) storage associated with hypertension has been raised. However, whether the increase in the body Na(+)/water ratio that characterizes water-free Na(+) accumulation is associated with the formation of cerebral aneurysms remains obscure. To examine this relationship, Sprague-Dawley female rats subjected to carotid artery ligation were divided into 3 groups: a high-salt diet group (HSD) without and another with bilateral oophorectomy (HSD/OVX) and a third group that underwent additional renal artery ligation (HSD/OVX/RL). Compared with rats receiving a normal diet (shams), water retention was increased in HSD rats but not in HSD/OVX rats. Interestingly, compared with HSD rats, the incidence of cerebral aneurysms and the body Na(+)/water ratio were significantly higher in HSD/OVX and HSD/OVX/RL rats, independent of hypertension. In their aneurysmal wall, ATP1α2, a subtype of Na(+)/K(+)-ATPase, was downregulated, whereas inflammatory-related molecules were upregulated. Treatment with low-dose olmesartan that did not affect the blood pressure in hypertensive HSD/OVX/RL rats reduced the rate of cerebral aneurysm formation, body Na(+) retention, and the Na(+)/water ratio and upregulated ATP1α2. These results suggest that the increase in the Na(+)/water ratio and a reduction in ATP1α2 may be associated with cerebral aneurysm formation. We provide the new insight that the management of water-free Na(+) is important to prevent their development.

Biology of intracranial aneurysms: role of inflammation

Intracranial aneurysms (IAs) linger as a potentially devastating clinical problem. Despite intense investigation, our understanding of the mechanisms leading to aneurysm development, progression and rupture remain incompletely defined. An accumulating body of evidence implicates inflammation as a critical contributor to aneurysm pathogenesis. Intracranial aneurysm formation and progression appear to result from endothelial dysfunction, a mounting inflammatory response, and vascular smooth muscle cell phenotypic modulation producing a pro-inflammatory phenotype. A later final common pathway appears to involve apoptosis of cellular constituents of the vessel wall. These changes result in degradation of the integrity of the vascular wall leading to aneurysmal dilation, progression and eventual rupture in certain aneurysms. Various aspects of the inflammatory response have been investigated as contributors to IA pathogenesis including leukocytes, complement, immunoglobulins, cytokines, and other humoral mediators. Furthermore, gene expression profiling of IA compared with control arteries has prominently featured differential expression of genes involved with immune response/inflammation. Preliminary data suggest that therapies targeting the inflammatory response may have efficacy in the future treatment of IA. Further investigation, however, is necessary to elucidate the precise role of inflammation in IA pathogenesis, which can be exploited to improve the prognosis of patients harboring IA.

Plasma follistatin-like protein 1 is elevated in Kawasaki disease and may predict coronary artery aneurysm formation

OBJECTIVE

To determine whether plasma levels of follistatin-like protein 1 (FSTL-1), a pro-inflammatory protein produced by mesenchymal tissue, including cardiac myocytes, correlate with the development of Kawasaki disease (KD) and coronary artery aneurysms (CAA).

STUDY DESIGN

FSTL-1 plasma levels were measured serially with enzyme-linked immunosorbent assay in 48 patients with KD at time of diagnosis and, when available, 2 weeks, 6 weeks, and 6 months after onset of disease. These were compared with FSTL-1 plasma levels in 23 control subjects. Data were analyzed with generalized estimating equations.

RESULTS

Plasma FSTL-1 levels were elevated in patients with acute KD compared with control subjects (P = .0086). FSTL-1 levels remained significantly elevated at 2 weeks after disease onset, but returned to control levels by 6 months. Seven patients with CAA had significantly higher FSTL-1 levels at the time of diagnosis than patients in whom aneurysms did not develop (P = .0018). Sensitivity and specificity rates for CAA at a specific FSTL-1 cutoff point (178 ng/mL) were 85% and 71%.

CONCLUSIONS

Plasma levels of FSTL-1 are elevated in acute KD and may predict cardiac morbidity in this disease. These results suggest a possible role for FSTL-1 in the formation of CAAs.