Smooth muscle cells of human intracranial aneurysms assume phenotypic features similar to those of the atherosclerotic plaque

Cerebral Aneurysm: Filling the Gap Between Pathophysiology and Nanocarriers

Intracranial aneurysms, characterized by abnormal dilations of cerebral arteries, pose significant health risks due to their potential to rupture, leading to subarachnoid hemorrhage with high mortality and morbidity rates. This paper aim is to explore the innovative application of nanoparticles in treating intracranial aneurysms, offering a promising avenue for enhancing current therapeutic strategies. We took into consideration the pathophysiology of cerebral aneurysms, focusing on the role of hemodynamic stress, endothelial dysfunction, and inflammation in their development and progression. By comparing cerebral aneurysms with other types, such as aortic aneurysms, we identify pathophysiological similarities and differences that could guide the adaptation of treatment approaches. The review highlights the potential of nanoparticles to improve drug delivery, targeting, and efficacy while minimizing side effects. We discuss various nanocarriers, including liposomes and polymeric nanoparticles, and their roles in overcoming biological barriers and enhancing therapeutic outcomes. Additionally, we discuss the potential of specific compounds, such as Edaravone and Tanshinone IIA, when used in conjunction with nanocarriers, to provide neuroprotective and anti-inflammatory benefits. By extrapolating insights from studies on aortic aneurysms, new research directions and therapeutic strategies for cerebral aneurysms are proposed. This interdisciplinary approach underscores the potential of nanoparticles to positively influence the management of intracranial aneurysms, paving the way for personalized treatment options that could significantly improve patient outcomes.

Apelin is expressed in intimal smooth muscle cells and promotes their phenotypic transition

During atherosclerotic plaque formation, smooth muscle cells (SMCs) switch from a contractile/differentiated to a synthetic/dedifferentiated phenotype. We previously isolated differentiated spindle-shaped (S) and dedifferentiated rhomboid (R) SMCs from porcine coronary artery. R-SMCs express S100A4, a calcium-binding protein. We investigated the role of apelin in this phenotypic conversion, as well as its relationship with S100A4. We found that apelin was highly expressed in R-SMCs compared with S-SMCs. We observed a nuclear expression of apelin in SMCs within experimentally-induced intimal thickening of the porcine coronary artery and rat aorta. Plasmids targeting apelin to the nucleus (N. Ap) and to the secretory vesicles (S. Ap) were transfected into S-SMCs where apelin was barely detectable. Both plasmids induced the SMC transition towards a R-phenotype. Overexpression of N. Ap, and to a lesser degree S. Ap, led to a nuclear localization of S100A4. Stimulation of S-SMCs with platelet-derived growth factor-BB, known to induce the transition toward the R-phenotype, yielded the direct interaction and nuclear expression of both apelin and S100A4. In conclusion, apelin induces a SMC phenotypic transition towards the synthetic phenotype. These results suggest that apelin acts via nuclear re-localization of S100A4, raising the possibility of a new pro-atherogenic relationship between apelin and S100A4.

Growth and rupture of an intracranial aneurysm: the role of wall aneurysmal enhancement and CD68

Introduction

Intracranial aneurysms occur in 3%-5% of the general population. While the precise biological mechanisms underlying the formation, growth, and sudden rupture of intracranial aneurysms remain partially unknown, recent research has shed light on the potential role of inflammation in aneurysm development and rupture. In addition, there are ongoing investigations exploring the feasibility of employing new drug therapies for controlling the risk factors associated with aneurysms. CD68, a glycosylated glycoprotein and the human homolog of macrosialin, is prominently expressed in monocyte/macrophages within inflamed tissues and has shown potential application in oncology. An observational study was conducted with the aim of comparing the histological characteristics of aneurysm walls with preoperative MRI scans, specifically focusing on CD68 activity.

Method

An observational pilot study was conducted to investigate the histological characteristics of the aneurysm wall that could be potentially associated with aneurysm growth and rupture. A total of 22 patients diagnosed with ruptured and unruptured intracranial aneurysms who had undergone conventional clipping between January 2017 and December 2022 were included in the study.

Results

A histopathological analysis of the aneurysm wall was performed in all patients, particularly focusing on the presence of CD68. A preoperative MRI with gadolinium was conducted in 10 patients with unruptured aneurysms and six patients with ruptured aneurysms. An emergency clipping was performed in the remaining six patients. The results showed that CD68 positivity and wall enhancement were significantly associated with intracranial aneurysm wall degeneration, growth, and rupture.

Conclusion

The histological and radiological inflammatory findings observed in the wall of cerebral aneurysms, as well as the CD68 positivity, are significantly associated with the risk of intracranial aneurysm growth and rupture. This study highlights the crucial importance of considering clinical and medical data when making treatment decisions for intracranial aneurysms. Furthermore, it emphasizes the relevance of evaluating wall enhancement in MRI scans as part of the diagnostic and prognostic process.

Identification of co-expressed central genes and transcription factors in atherosclerosis-related intracranial aneurysm

Background

Numerous clinical studies have shown that atherosclerosis is one of the risk factors for intracranial aneurysms. Calcifications in the intracranial aneurysm walls are frequently correlated with atherosclerosis. However, the pathogenesis of atherosclerosis-related intracranial aneurysms remains unclear. This study aims to investigate this mechanism.

Methods

The Gene Expression Omnibus (GEO) database was used to download the gene expression profiles for atherosclerosis (GSE100927) and intracranial aneurysms (GSE75436). Following the identification of the common differentially expressed genes (DEGs) of atherosclerosis and intracranial aneurysm, the network creation of protein interactions, functional annotation, the identification of hub genes, and co-expression analysis were conducted. Thereafter, we predicted the transcription factors (TF) of hub genes and verified their expressions.

Results

A total of 270 common (62 downregulated and 208 upregulated) DEGs were identified for subsequent analysis. Functional analyses highlighted the significant role of phagocytosis, cytotoxicity, and T-cell receptor signaling pathways in this disease progression. Eight hub genes were identified and verified, namely, CCR5, FCGR3A, IL10RA, ITGAX, LCP2, PTPRC, TLR2, and TYROBP. Two TFs were also predicted and verified, which were IKZF1 and SPI1.

Conclusion

Intracranial aneurysms are correlated with atherosclerosis. We identified several hub genes for atherosclerosis-related intracranial aneurysms and explored the underlying pathogenesis. These discoveries may provide new insights for future experiments and clinical practice.

A Novel Model of Tobacco Smoke-Mediated Aortic Injury

OBJECTIVE

Tobacco smoke exposure is a major risk factor for aortic aneurysm development. However, the initial aortic response to tobacco smoke, preceding aneurysm formation, is not well understood. We sought to create a model to determine the effect of solubilized tobacco smoke (STS) on the thoracic and abdominal aorta of mice as well as on cultured human aortic smooth muscle cells (HASMCs).

METHODS

Tobacco smoke was solubilized and delivered to mice via implanted osmotic minipumps. Twenty male C57BL/6 mice received STS or vehicle infusion. The descending thoracic, suprarenal abdominal, and infrarenal abdominal segments of the aorta were assessed for elastic lamellar damage, smooth muscle cell phenotype, and infiltration of inflammatory cells. Cultured HASMCs grown in media containing STS were compared to cells grown in standard media in order to verify our in vivo findings.

RESULTS

Tobacco smoke solution caused significantly more breaks in the elastic lamellae of the thoracic and abdominal aorta compared to control solution (P< .0001) without inciting an inflammatory infiltrate. Elastin breaks occurred more frequently in the abdominal aorta than the thoracic aorta (P < .01). Exposure to STS-induced aortic microdissections and downregulation of α-smooth muscle actin (α-SMA) by vascular smooth muscle cells (VSMCs). Treatment of cultured HASMCs with STS confirmed the decrease in α-SMA expression.

CONCLUSION

Delivery of STS via osmotic minipumps appears to be a promising model for investigating the early aortic response to tobacco smoke exposure. The initial effect of tobacco smoke exposure on the aorta is elastic lamellar damage and downregulation of (α-SMA) expression by VSMCs. Elastic lamellar damage occurs more frequently in the abdominal aorta than the thoracic aorta and does not seem to be mediated by the presence of macrophages or other inflammatory cells.

Neutralization of S100A4 induces stabilization of atherosclerotic plaques: role of smooth muscle cells

AIMS

During atherosclerosis, smooth muscle cells (SMCs) accumulate in the intima where they switch from a contractile to a synthetic phenotype. From porcine coronary artery, we isolated spindle-shaped (S) SMCs exhibiting features of the contractile phenotype and rhomboid (R) SMCs typical of the synthetic phenotype. S100A4 was identified as a marker of R-SMCs in vitro and intimal SMCs, in pig and man. S100A4 exhibits intra- and extracellular functions. In this study, we investigated the role of extracellular S100A4 in SMC phenotypic transition.

METHODS AND RESULTS

S-SMCs were treated with oligomeric recombinant S100A4 (oS100A4), which induced nuclear factor (NF)-κB activation. Treatment of S-SMCs with oS100A4 in combination with platelet-derived growth factor (PDGF)-BB induced a complete SMC transition towards a pro-inflammatory R-phenotype associated with NF-κB activation, through toll-like receptor-4. RNA sequencing of cells treated with oS100A4/PDGF-BB revealed a strong up-regulation of pro-inflammatory genes and enrichment of transcription factor binding sites essential for SMC phenotypic transition. In a mouse model of established atherosclerosis, neutralization of extracellular S100A4 decreased area of atherosclerotic lesions, necrotic core, and CD68 expression and increased α-smooth muscle actin and smooth muscle myosin heavy chain expression.

CONCLUSION

We suggest that the neutralization of extracellular S100A4 promotes the stabilization of atherosclerotic plaques. Extracellular S100A4 could be a new target to influence the evolution of atherosclerotic plaques.

Extreme Diversity of the Human Vascular Mesenchymal Cell Landscape

Background Human mesenchymal cells are culprit factors in vascular (patho)physiology and are hallmarked by phenotypic and functional heterogeneity. At present, they are subdivided by classic umbrella terms, such as "fibroblasts," "myofibroblasts," "smooth muscle cells," "fibrocytes," "mesangial cells," and "pericytes." However, a discriminative marker-based subclassification has to date not been established. Methods and Results As a first effort toward a classification scheme, a systematic literature search was performed to identify the most commonly used phenotypical and functional protein markers for characterizing and classifying vascular mesenchymal cell subpopulation(s). We next applied immunohistochemistry and immunofluorescence to inventory the expression pattern of identified markers on human aorta specimens representing early, intermediate, and end stages of human atherosclerotic disease. Included markers comprise markers for mesenchymal lineage (vimentin, FSP-1 [fibroblast-specific protein-1]/S100A4, cluster of differentiation (CD) 90/thymocyte differentiation antigen 1, and FAP [fibroblast activation protein]), contractile/non-contractile phenotype (α-smooth muscle actin, smooth muscle myosin heavy chain, and nonmuscle myosin heavy chain), and auxiliary contractile markers (h1-Calponin, h-Caldesmon, Desmin, SM22α [smooth muscle protein 22α], non-muscle myosin heavy chain, smooth muscle myosin heavy chain, Smoothelin-B, α-Tropomyosin, and Telokin) or adhesion proteins (Paxillin and Vinculin). Vimentin classified as the most inclusive lineage marker. Subset markers did not separate along classic lines of smooth muscle cell, myofibroblast, or fibroblast, but showed clear temporal and spatial diversity. Strong indications were found for presence of stem cells/Endothelial-to-Mesenchymal cell Transition and fibrocytes in specific aspects of the human atherosclerotic process. Conclusions This systematic evaluation shows a highly diverse and dynamic landscape for the human vascular mesenchymal cell population that is not captured by the classic nomenclature. Our observations stress the need for a consensus multiparameter subclass designation along the lines of the cluster of differentiation classification for leucocytes.

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

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

microRNA-331-3p maintains the contractile type of vascular smooth muscle cells by regulating TNF-α and CD14 in intracranial aneurysm

Dysfunction of vascular smooth muscle cells (VSMCs) may be linked to intracranial aneurysm (IA) formation. VSMCs possess a phenotypic plasticity, capable of changing from a mature, contractile to a less differentiated, synthetic phenotype. In this study, we identify a microRNA candidate miR-331-3p that participates in regulating differentiation properties of VSMCs. The expression of TNF-α and CD14 was quantified in IA wall tissues obtained from 96 IA patients and their associations with clinicopathological features of IA were assessed. Then the interactions between miR-331-3p, TNF-α and CD14 were evaluated by determination of luciferase activity. Differentiated properties of VSMCs were assessed from phenotypic markers of contractile VSMCs, a-SMA and E-cadherin, and of synthetic VSMCs, ICAM-1, MCP-1, IL-6, MMP-2 and MMP-9. Rat IA models by ligation of left carotid artery and left renal artery and histological analysis of induced IAs were performed. The TNF-α and CD14 was highly expressed in IA wall tissues and associated with the type and diameter of aneurysm. Depletion of TNF-α or CD14 retarded VSMC apoptosis and transformation to the synthetic type but facilitated cell proliferation. Elevations in miR-331-3p, a direct negative regulator of both TNF-α and CD14, also reduced VSMC apoptosis and prevented VSMCs from synthetic type and increase their proliferation. Furthermore, miR-331-3p was demonstrated to inhibit the formation of IA by down-regulating TNF-α and CD14 in vivo. In conclusion, miR-331-3p maintains the contractile type of VSMCs, thus possibly inhibiting the progression of IA. These findings provide potential new strategies for the clinical treatment of IA.

Calcification in Human Intracranial Aneurysms Is Highly Prevalent and Displays Both Atherosclerotic and Nonatherosclerotic Types

OBJECTIVE

Although the clinical and biological importance of calcification is well recognized for the extracerebral vasculature, its role in cerebral vascular disease, particularly, intracranial aneurysms (IAs), remains poorly understood. Extracerebrally, 2 distinct mechanisms drive calcification, a nonatherosclerotic, rapid mineralization in the media and a slower, inflammation driven, atherosclerotic mechanism in the intima. This study aims to determine the prevalence, distribution, and type (atherosclerotic, nonatherosclerotic) of calcification in IAs and assess differences in occurrence between ruptured and unruptured IAs. Approach and Results: Sixty-five 65 IA specimens (48 unruptured, 17 ruptured) were resected perioperatively. Calcification and lipid pools were analyzed nondestructively in intact samples using high resolution (0.35 μm) microcomputed tomography. Calcification is highly prevalent (78%) appearing as micro (<500 µm), meso (500 µm-1 mm), and macro (>1 mm) calcifications. Calcification manifests in IAs as both nonatherosclerotic (calcification distinct from lipid pools) and atherosclerotic (calcification in the presence of lipid pools) with 3 wall types: Type I-only calcification, no lipid pools (20/51, 39%), Type II-calcification and lipid pools, not colocalized (19/51, 37%), Type III-calcification colocalized with lipid pools (12/51, 24%). Ruptured IAs either had no calcifications or had nonatherosclerotic micro- or meso-calcifications (Type I or II), without macro-calcifications.

CONCLUSIONS

Calcification in IAs is substantially more prevalent than previously reported and presents as both nonatherosclerotic and atherosclerotic types. Notably, ruptured aneurysms had only nonatherosclerotic calcification, had significantly lower calcification fraction, and did not contain macrocalcifications. Improved understanding of the role of calcification in IA pathology should lead to new therapeutic targets.

Smooth muscle cell fate and plasticity in atherosclerosis

Current knowledge suggests that intimal smooth muscle cells (SMCs) in native atherosclerotic plaque derive mainly from the medial arterial layer. During this process, SMCs undergo complex structural and functional changes giving rise to a broad spectrum of phenotypes. Classically, intimal SMCs are described as dedifferentiated/synthetic SMCs, a phenotype characterized by reduced expression of contractile proteins. Intimal SMCs are considered to have a beneficial role by contributing to the fibrous cap and thereby stabilizing atherosclerotic plaque. However, intimal SMCs can lose their properties to such an extent that they become hard to identify, contribute significantly to the foam cell population, and acquire inflammatory-like cell features. This review highlights mechanisms of SMC plasticity in different stages of native atherosclerotic plaque formation, their potential for monoclonal or oligoclonal expansion, as well as recent findings demonstrating the underestimated deleterious role of SMCs in this disease.

Correlating Clinical Risk Factors and Histological Features in Ruptured and Unruptured Human Intracranial Aneurysms: The Swiss AneuX Study

Pathogenesis of intracranial aneurysm is complex and the precise biomechanical processes leading to their rupture are uncertain. The goal of our study was to characterize the aneurysmal wall histologically and to correlate histological characteristics with clinical and radiological factors used to estimate the risk of rupture. A new biobank of aneurysm domes resected at the Geneva University Hospitals (Switzerland) was used. Histological analysis revealed that unruptured aneurysms have a higher smooth muscle cell (SMC) content and a lower macrophage content than ruptured domes. These differences were associated with more collagen in unruptured samples, whereas the elastin content was not affected. Collagen content and type distribution were different between thick and thin walls of unruptured aneurysms. Classification of aneurysm domes based on histological characteristics showed that unruptured samples present organized wall rich in endothelial and SMCs compared with ruptured samples. Finally, aneurysm wall composition was altered in unruptured domes of patients presenting specific clinical factors used to predict rupture such as large dome diameter, dome irregularities, and smoking. Our study shows that the wall of aneurysm suspected to be at risk for rupture undergoes structural alterations relatively well associated with clinical and radiological factors currently used to predict this risk.

Plea for an international Aneurysm Data Bank: description and perspectives

The disease resulting in the formation, growth, and rupture of intracranial aneurysms is complex. Research is accumulating evidence that the disease is driven by many different factors, some constant and others variable over time. Combinations of factors may induce specific biophysical reactions at different stages of the disease. A better understanding of the biophysical mechanisms responsible for the disease initiation and progression is essential to predict the natural history of the disease. More accurate predictions are mandatory to adequately balance risks between observation and intervention at the individual level as expected in the age of personalized medicine. Multidisciplinary exploration of the disease also opens an avenue to the discovery of possible preventive actions or medical treatments. Modern information technologies and data processing methods offer tools to address such complex challenges requiring 1) the collection of a high volume of information provided globally, 2) integration and harmonization of the information, and 3) management of data sharing with a broad spectrum of stakeholders.Over the last decade an infrastructure has been set up and is now made available to the academic community to support and promote exploration of intracranial disease, modeling, and clinical management simulation and monitoring.The background and purpose of the infrastructure is reviewed. The infrastructure data flow architecture is presented. The basic concepts of disease modeling that oriented the design of the core information model are explained. Disease phases, milestones, cases stratification group in each phase, key relevant factors, and outcomes are defined. Data processing and disease model visualization tools are presented. Most relevant contributions to the literature resulting from the exploitation of the infrastructure are reviewed, and future perspectives are discussed.

Human Bone Marrow Contains Mesenchymal Stromal Stem Cells That Differentiate In Vitro into Contractile Myofibroblasts Controlling T Lymphocyte Proliferation

Mesenchymal stromal stem cells (MSC) that reside in the bone marrow (BM) can be amplified in vitro. In 2-dimension (D) cultures, MSC exhibit a morphology similar to fibroblasts, are able to inhibit T lymphocyte and natural killer cell proliferation, and can be differentiated into adipocytes, chondrocytes, or osteoblasts if exposed to specific media. Here we show that medullar MSC cultured in 2D formed an adherent stroma of cells expressing well-organized microfilaments containing α-smooth muscle actin and nonmuscle myosin heavy chain IIA. MSC could be grown in 3D in collagen membranes generating a structure which, upon exposition to 50 mM KCl or to an alternating electric current, developed a contractile strength that averaged 34 and 45 μN/mm2, respectively. Such mechanical tension was similar in intensity and in duration to that of human placenta and was annihilated by isosorbide dinitrate or 2,3-butanedione monoxime. Membranes devoid of MSC did not exhibit a significant contractility. Moreover, MSC nested in collagen membranes were able to control T lymphocyte proliferation, and differentiated into adipocytes, chondrocytes, or osteoblasts. Our observations show that BM-derived MSC cultured in collagen membranes spontaneously differentiate into contractile myofibroblasts exhibiting unexpected properties in terms of cell differentiation potential and of immunomodulatory function.

Cardiovascular homeostasis dependence on MICU2, a regulatory subunit of the mitochondrial calcium uniporter

Hypertension increases the risk for development of abdominal aortic aneurysms, a silent pathology that is prone to rupture and cause sudden cardiac death. Male gender, smoking, and hypertension appear to increase risk for development of abdominal aortic aneurysms by provoking oxidative stress responses in cardiovascular tissues. Here we uncovered unexpected linkages between the calcium-sensing regulatory subunit MICU2 of the mitochondrial calcium uniporter and stress responses. We show that naive Micu2^−/− mice had abnormalities of cardiac relaxation but, with modest blood pressure elevation, developed abdominal aortic aneurysms with spontaneous rupture. These findings implicate mitochondrial calcium homeostasis as a critical pathway involved in protecting cardiovascular tissues from oxidative stress.

Comparative analyses of transcriptional profiles from humans and mice with cardiovascular pathologies revealed consistently elevated expression of MICU2, a regulatory subunit of the mitochondrial calcium uniporter complex. To determine if MICU2 expression was cardioprotective, we produced and characterized Micu2^−/− mice. Mutant mice had left atrial enlargement and Micu2^−/− cardiomyocytes had delayed sarcomere relaxation and cytosolic calcium reuptake kinetics, indicating diastolic dysfunction. RNA sequencing (RNA-seq) of Micu2^−/− ventricular tissues revealed markedly reduced transcripts encoding the apelin receptor (Micu2^−/− vs. wild type, P = 7.8 × 10⁻⁴⁰), which suppresses angiotensin II receptor signaling via allosteric transinhibition. We found that Micu2^−/− and wild-type mice had comparable basal blood pressures and elevated responses to angiotensin II infusion, but that Micu2^−/− mice exhibited systolic dysfunction and 30% lethality from abdominal aortic rupture. Aneurysms and rupture did not occur with norepinephrine-induced hypertension. Aortic tissue from Micu2^−/− mice had increased expression of extracellular matrix remodeling genes, while single-cell RNA-seq analyses showed increased expression of genes related to reactive oxygen species, inflammation, and proliferation in fibroblast and smooth muscle cells. We concluded that Micu2^−/− mice recapitulate features of diastolic heart disease and define previously unappreciated roles for Micu2 in regulating angiotensin II-mediated hypertensive responses that are critical in protecting the abdominal aorta from injury.

Blockade of HMGB1 preserves vascular homeostasis and improves blood perfusion in rats of acute limb ischemia/reperfusion

Acute limb ischemia is one of the most common peripheral arterial disease, while surgical restoration of blood flow often results in ischemia/reperfusion (I/R) injury. Our previous study revealed the inflammation intensity in arterial tissue, characterized by expression of high mobility group box protein 1 (HMGB1), was contrary to the fluctuation of hemodynamics in reperfusion limbs in a rat model. This study meant to clarify the role of HMGB1 during this process. Laser Doppler perfusion imaging evaluated limb hemodynamics in mean and max perfusion unit (PU). Femoral arterial tissue was collected for molecular biology examination. The results revealed that HMGB1 promoted vascular structure remodeling and vasomotor dysfunction during acute I/R, characterized by degradation of collagenous fibers, disruption of elastic lamellae, intensive inflammation and phenotype transfer of smooth muscle cells. Blockade of HMGB1 preserved vascular homeostasis and improved PUs (PmeanPU<0.001, PmaxPU<0.001). The elevated expression of TNF-α, IL-6, ICAM, VCAM, MMP-2, MMP-9, α-SM actin correlated with HMGB1 positively. In conclusion, HMGB1 promoted vascular remodeling and dysfunction via initiating an inflammation cascade during I/R. Blockade of HMGB1 would preserve vascular homeostasis and facilitate the blood perfusion of ischemic limb.

The microRNA miR-124 inhibits vascular smooth muscle cell proliferation by targeting S100 calcium-binding protein A4 (S100A4)

S100 calcium-binding protein A4 (S100A4) induces proliferation and migration of vascular smooth muscle cells (VSMCs). We aimed to find the microRNA regulating S100A4 expression. S100A4 transcripts are abruptly increased in the acute phase of carotid arterial injury 1 day later (at day 1) but gradually decreases at days 7 and 14. Bioinformatics analysis reveals that miR-124 targets S100A4. VSMC survival is attenuated by miR-124 mimic but increased by miR-124 inhibitor. miR-124 decreases immediately after carotid arterial injury but dramatically increases at days 7 and 14. miR-124 inhibitor-induced cell proliferation is blocked by S100A4 siRNA, whereas miR-124-induced cell death is recovered by S100A4. Our findings suggest that miR-124 is a novel regulator of VSMC proliferation and may play a role in the development of neointimal proliferation.

Intracranial Aneurysms: Wall Motion Analysis for Prediction of Rupture

Intracranial aneurysms are a common pathologic condition with a potential severe complication: rupture. Effective treatment options exist, neurosurgical clipping and endovascular techniques, but guidelines for treatment are unclear and focus mainly on patient age, aneurysm size, and localization. New criteria to define the risk of rupture are needed to refine these guidelines. One potential candidate is aneurysm wall motion, known to be associated with rupture but difficult to detect and quantify. We review what is known about the association between aneurysm wall motion and rupture, which structural changes may explain wall motion patterns, and available imaging techniques able to analyze wall motion.