Metalloproteinases in Development and Progression of Vascular Disease

Eccentric saccular aneurysm formation of the infrarenal aorta from an arterial wall tear

Eccentric saccular aneurysms result from a focal weakness of the arterial wall that may be due to a focal tear or a partial disruption of the arterial wall. Saccular morphology itself is often used as a factor for immediate intervention, because the risk of rupture is higher than that of the common fusiform aneurysms. We present a case of a 72-year-old female patient with a huge saccular aneurysm of the infrarenal aorta. In this case report, we discuss the algorithm that can be used for the differential diagnosis of any saccular shape aneurysm and that the main parameter that needs to be clarified before the endovascular treatment of any saccular aneurysm is the presence or absence of infection of the arterial wall.

The Role of Natural Killer (NK) Cells in Acute Coronary Syndrome: A Comprehensive Review

With poor outcomes and an immense financial burden, acute coronary syndrome (ACS) and its ischemic repercussions still present a major global health problem. Unfavorable outcomes seem to be mainly due to adverse cardiac remodeling. Since the inflammatory response takes an important role in remodeling secondary to myocardial infarction (MI), and as inflammation in this manner has not been completely elucidated, we attempted to give rise to a further understanding of ACS pathophysiology. Hence, in this review, we integrated current knowledge of complex communication networks between natural killer (NK) cells and immune and resident heart cells in the context of ACS. Based on available data, the role of NK cells seems to be important in the infarcted myocardium, where it affects heart remodeling. On the other hand, in atherosclerotic plaque, NK cells seem to be mere passers-by, except in the case of chronic infections by atherogenic pathogens. In that case, NK cells seem to support proinflammatory milieu. NK cell research is challenging due to ethical reasons, convergent evolution, and phenotypic diversity among individuals. Therefore, we argue that further research of NK cells in ACS is valuable, given their therapeutic potential in improving postischemic heart remodeling.

Exploring the role of extracellular matrix proteins to develop biomarkers of plaque vulnerability and outcome

Cardiovascular disease (CVD) is the most common cause of death in industrialized countries. One underlying cause is atherosclerosis, which is a systemic disease characterized by plaques of retained lipids, inflammatory cells, apoptotic cells, calcium and extracellular matrix (ECM) proteins in the arterial wall. The biologic composition of an atherosclerotic plaque determines whether the plaque is more or less vulnerable, that is prone to rupture or erosion. Here, the ECM and tissue repair play an important role in plaque stability, vulnerability and progression. This review will focus on ECM remodelling in atherosclerotic plaques, with focus on how ECM biomarkers might predict plaque vulnerability and outcome.

Factors which Influence the Levels of ST-2, Galectin-3 and MMP-9 in Acute Coronary Syndrome

BACKGROUND

Several cardiac biomarkers are being studied to explore their potential in the prognostication of Acute Coronary Syndrome (ACS). However, there are limited studies exploring the relationship between these biomarkers and clinical, laboratory and demographic characteristics.

OBJECTIVE

We sought to determine the factors which influence the concentration of novel cardiac biomarkers such as Galectin-3, suppression of tumorigenicity-2 (ST-2) and Matrix Metallopeptidase-9 (MMP-9) in patients with ACS.

METHODS

A total of 122 patients with ACS were enrolled in the study. The study patients were categorized into two groups namely: STEMI (n=58) and NSTEMI/UA (n=64). Plasma samples were used to determine the level of biomarkers, Galectin-3 and ST-2, and serum samples were used to determine the levels of MMP-9 using the Enzyme-linked immunosorbent assay (ELISA). The association between the plasma and serum levels of biomarkers and, demographic, clinical and laboratory variables were determined. Statistical analyses for the study were performed using SPSS 16.0 software (SPSS Inc., Chicago, IL, USA).

RESULTS

Elderly aged [0.107 (0.012-0.969); p=0.047] patients had higher ST-2. Galectin-3 was higher among female patients [3.693(1.253-10.887); p=0.018] and patients with low left ventricular ejection fraction [2.882 (1.041-7.978); p=0.042]. Patients with lower body mass index [3.385 (1.241-9.231); p=0.017], diabetes [3.650 (1.302-10.237); p=0.014] and high total leukocyte count [2.900 (1.114-7.551; p=0.029] had higher MMP-9 levels.

CONCLUSION

The concentration of galectin-3, ST-2 and MMP-9 are independently influenced by demographic, clinical and laboratory characteristics. It is estimated that these factors should be accounted for when interpreting the results of the biomarker assays.

Cardiovascular protection in females linked to estrogen-dependent inhibition of arterial stiffening and macrophage MMP12

Arterial stiffening is a consequence of aging and a cholesterol-independent risk factor for cardiovascular disease (CVD). Arterial stiffening and CVD show a sex bias, with men more susceptible than premenopausal women. How arterial stiffness and sex interact at a molecular level to confer risk of CVD is not well understood. Here, we used the sexual dimorphism in LDLR-null mice to show that the protective effect of female sex on atherosclerosis is linked to reduced aortic stiffness and reduced expression of matrix metalloproteinase-12 (MMP12) by lesional macrophages. Deletion of MMP12 in LDLR-null mice attenuated the male sex bias for both arterial stiffness and atherosclerosis, and these effects occurred despite high serum cholesterol. Mechanistically, we found that oxidized LDL stimulates secretion of MMP12 in human as well as mouse macrophages. Estrogen antagonizes this effect by downregulating MMP12 expression. Our data support cholesterol-independent causal relationships between estrogen, oxidized LDL-induced secretion of macrophage MMP12, and arterial stiffness that protect against atherosclerosis in females and emphasize that reduced MMP12 functionality can confer atheroprotection to males.

MMP-2: is too low as bad as too high in the cardiovascular system?

Matrix metalloproteinase (MMP)-2 cleaves a broad spectrum of substrates, including extracellular matrix components (responsible for normal tissue remodeling) and cytokines (modulators of the inflammatory response to physiological insults such as tissue damage). MMP-2 expression is elevated in many cardiovascular pathologies (e.g., myocardial infarction, hypertensive heart disease) where tissue remodeling and inflammatory responses are perturbed. Thus, it has generally been assumed that blockade of MMP-2 activity will yield therapeutic effects. Here, we provide a counterargument to this dogma based on 1) preclinical studies on Mmp2-null ( Mmp2−/−) mice and 2) clinical studies on patients with inactivating MMP2 gene mutations. Furthermore, we put forward the hypothesis that, when MMP-2 activity falls below baseline, the bioavailability of proinflammatory cytokines normally cleaved and inactivated by MMP-2 increases, leading to the production of cytokines and cardiac secretion of phospholipase A2activity into the circulation, which stimulate systemic inflammation that perturbs lipid metabolism in target organs. Finally, we suggest that insufficient understanding of the consequences of MMP-2 deficiency remains a major factor in the failure of MMP-2 inhibitor-based therapeutic approaches. This paucity of knowledge precludes our ability to effectively intervene in cardiovascular and noncardiovascular pathologies at the level of MMP-2.

Association of serum prolidase activity in patients with isolated coronary artery ectasia

Objective:

Coronary artery ectasia (CAE) is defined as an angiographic enlargement of a portion of the coronary artery between 1.5 and 2 times the diameter of the adjacent normal coronary artery. It has been demonstrated that increased serum prolidase activity (SPA) is associated with increased collagen turnover. We aimed to analyze the relationship between CAE and serum SPA levels.

Methods:

This study used a prospective case protocol design. A total of 40 consecutive patients with isolated right CAE and normal coronary arteries (23 men, 17 women; mean age, 62.4±10.8 years) were evaluated. The control group included the same number of consecutive patients with angiographically normal coronary arteries (20 men, 20 women; mean age, 63.8±11.1 years). Clinical characteristics, laboratory results, cardiovascular risk factors, and medication use were recorded. SPA was measured using a spectrophotometer. Student’s t-test, Mann–Whitney U test, chi-square test, Pearson’s and Spearman’s correlations, logistic regression analysis, and ROC curve analysis were used for statistical analysis.

Results:

SPA was significantly higher in the CAE group compared with the control group (1635.2±492.0 U/L and 986.2±422.3 U/L, respectively; p<0.001). The relationship of SPA with CAE proved to be significant (r=0.512; p<0.001). SPA also served as an independent predictor of CAE (OR=1.003; 95% CI, 1.001–1.005; p=0.002). The SPA value of 1170 U/L was predictive of CAE, with a sensitivity of 85% and specificity of 60% (AUC=0.854; 95% CI, 0.763–0.944; p<0.001).

Conclusion:

The activity of this enzyme was significantly correlated with CAE.

Circulating Prolidase Activity in Patients with Myocardial Infarction

Background

Collagen is a major determinant of atherosclerotic plaque stability. Thus, identification of differences in enzymes that regulate collagen integrity could be useful for predicting susceptibility to atherothrombosis or for diagnosing plaque rupture. In this study, we sought to determine whether prolidase, the rate-limiting enzyme of collagen turnover, differs in human subjects with acute myocardial infarction (MI) versus those with stable coronary artery disease (CAD).

Methods

We measured serum prolidase activity in 15 patients with stable CAD and 49 patients with acute MI, of which a subset had clearly defined thrombotic MI (n = 22) or non-thrombotic MI (n = 12). Prolidase activity was compared across study time points (at cardiac catheterization, T0; 6 h after presentation, T6; and at a quiescent follow-up, Tf/u) in acute MI and stable CAD subjects. We performed subgroup analyses to evaluate prolidase activity in subjects presenting with acute thrombotic versus non-thrombotic MI.

Results

Although prolidase activity was lower at T0 and T6 versus the quiescent phase in acute MI and stable CAD subjects (p < 0.0001), it was not significantly different between acute MI and stable CAD subjects at any time point (T0, T6, and Tf/u) or between thrombotic and non-thrombotic MI groups. Preliminary data from stratified analyses of a small number of diabetic subjects (n = 8) suggested lower prolidase activity in diabetic acute MI subjects compared with non-diabetic acute MI subjects (p = 0.02).

Conclusion

Circulating prolidase is not significantly different between patients with acute MI and stable CAD or between patients with thrombotic and non-thrombotic MI. Further studies are required to determine if diabetes significantly affects prolidase activity and how this might relate to the risk of MI.

Association of MMP-9 gene polymorphisms with nephrolithiasis patients

BACKGROUND

Nephrolithiasis is one of the causes which lead to chronic kidney disease (CKD). Matrix metalloproteinases (MMPs) are endopeptidases degrading extracellular matrix which correlate with the pathogenesis of atherosclerosis. The current study was designed to analyze the association of (R279Q, C1562T) polymorphism of MMP-9 with nephrolithiasis patients.

METHODS

Genotyping of MMP-9/R279Q and of MMP-9/C1562T polymorphism were carried out by PCR-based restriction digestion method. Serum level of MMP-9, oxidative stress marker, MDA, and uric acid were measured in patients and control.

RESULTS

Allele frequencies of the MMP-9/C1562T polymorphism for C and T allele were 71.25% and 28.75% in patients, 87.08% and 12.92% in control respectively. The homozygote TT was more frequent in the nephrolithiasis patients group, while T allele frequency was significantly higher in the nephrolithiasis patients group than in the control group. The patients with CT and TT genotype showed a significant increase in serum MMP-9, Total Oxidant Status (TOS), Oxidative Stress Index (OSI), Malondialdehyde (MDA), and uric acid when compared to CC genotype in patients with nephrolithiasis. The R279Q polymorphism site with regard to the relationship with nephrolithiasis was not significant.

CONCLUSION

The result indicates that patients with TT genotype had an increased risk of stones. Also, the results demonstrate that TT allele of the C1562T polymorphism in the MMP-9gene is related with an increase of oxidative stress in nephrolithiasis patients and may possibly impose a risk for cardiovascular diseases in patients with TT genotype of MMP-9.

TIMP1 and MMP9 are predictors of mortality in septic patients in the emergency department and intensive care unit unlike MMP9/TIMP1 ratio: Multivariate model

INTRODUCTION

Matrix metalloproteinases and tissue inhibitors of metalloproteinases could be promising biomarkers for establishing prognosis during the development of sepsis. It is necessary to clarify the relationship between matrix metalloproteinases and their tissue inhibitors. We conducted a cohort study with 563 septic patients, in order to elucidate the biological role and significance of these inflammatory biomarkers and their relationship to the severity and mortality of patients with sepsis.

MATERIALS AND METHODS

A multicentric prospective cohort was performed. The sample was composed of patients who had sepsis as defined by the International Conference 2001. Serum procalcitonin, creatinine, urea nitrogen, C-Reactive protein, TIMP1, TIMP2, MMP2 and MMP9 were quantified; each patient was followed until death or up to 30 days. A descriptive analysis was performed by calculating the mean and the 95% confidence interval for continuous variables and proportions for categorical variables. A multivariate logistic regression model was constructed by the method of intentional selection of covariates with mortality at 30 days as dependent variable and all the other variables as predictors.

RESULTS

Of the 563 patients, 68 patients (12.1%) died within the first 30 days of hospitalization in the ICU. The mean values for TIMP1, TIMP2 and MMP2 were lower in survivors, MMP9 was higher in survivors. Multivariate logistic regression showed that age, SOFA and Charlson scores, along with TIMP1 concentration, were statistically associated with mortality at 30 days of septic patients; serum MMP9 was not statistically associated with mortality of patients, but was a confounder of the TIMP1 variable.

CONCLUSION

It could be argued that plasma levels of TIMP1 should be considered as a promising prognostic biomarker in the setting of sepsis. Additionally, this study, like other studies with large numbers of septic patients does not support the predictive value of TIMP1 / MMP9.

Matrix metalloproteinases and risk stratification in patients undergoing surgical revascularisation for critical limb ischaemia

Critical limb ischaemia (CLI) is the most advanced form of peripheral artery disease (PAD) and it is often associated with foot gangrene, which may lead to major amputation of lower limbs, and also with a higher risk of death due to fatal cardiovascular events. Matrix metalloproteinases (MMPs) seem to be involved in atherosclerosis, PAD and CLI. Aim of this study was to evaluate variations in MMP serum levels in patients affected by CLI, before and after lower limb surgical revascularisation through prosthetic or venous bypass. A total of 29 patients (7 females and 22 males, mean age 73·4 years, range 65-83 years) suffering from CLI and submitted to lower extremity bypass (LEB) in our Institution were recruited. Seven patients (group I) underwent LEB using synthetic polytetrafluoroethylene (PTFE) graft material and 22 patients (group II) underwent LEB using autogenous veins. Moreover, 30 healthy age-sex-matched subjects were also enrolled as controls (group III). We documented significantly higher serum MMPs levels (P < 0·01) in patients with CLI (groups I and II) with respect to control group (group III). Finally, five patients with CLI (17·2%) showed poor outcomes (major amputations or death), and enzyme-linked immunosorbent assay (ELISA) test showed very high levels of MMP-1 and MMP-8. MMP serum levels seem to be able to predict the clinical outcomes of patients with CLI.

Multidimensional Contribution of Matrix Metalloproteinases to Atherosclerotic Plaque Vulnerability: Multiple Mechanisms of Inhibition to Promote Stability

The prevalence of atherosclerotic disease continues to increase, and despite significant reductions in major cardiovascular events with current medical interventions, an additional therapeutic window exists. Atherosclerotic plaque growth is a complex integration of cholesterol penetration, inflammatory cell infiltration, vascular smooth muscle cell (VSMC) migration, and neovascular invasion. A family of matrix-degrading proteases, the matrix metalloproteinases (MMPs), contributes to all phases of vascular remodeling. The contribution of specific MMPs to endothelial cell integrity and VSMC migration in atherosclerotic lesion initiation and progression has been confirmed by the increased expression of these proteases in plasma and plaque specimens. Endogenous blockade of MMPs by the tissue inhibitors of metalloproteinases (TIMPs) may attenuate proteolysis in some regions, but the progression of matrix degeneration suggests that MMPs predominate in atherosclerotic plaque, precipitating vulnerability. Plaque neovascularization also contributes to instability and, coupling the known role of MMPs in angiogenesis to that of atherosclerotic plaque growth, interest in targeting MMPs to facilitate plaque stabilization continues to accumulate. This article aims to review the contributions of MMPs and TIMPs to atherosclerotic plaque expansion, neovascularization, and rupture vulnerability with an interest in promoting targeted therapies to improve plaque stabilization and decrease the risk of major cardiovascular events.

Plasma Levels of Inflammatory Biomarkers in Peripheral Arterial Disease: Results of a Cohort Study

Previous research analyzed the level of plasma inflammatory markers in patients with coronary disease, but very few studies have evaluated these markers in patients with peripheral arterial disease (PAD). The objective of this study was to investigate the plasma levels of inflammatory markers in patients with PAD and in healthy controls. The following plasma levels of biomarkers were measured in 80 patients with PAD (mean age 68 ± 5 years) and in 72 healthy participants (mean age 67 ± 6 years): interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), L-selectin (LS), neopterin (N), P-selectin (PS), E-selectin (ES), vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1), and matrix metalloproteinase 2 (MMP-2), and 9 (MMP-9). Significantly higher levels of IL-6 (P < .001), TNF-α (P < .0001), ES (P < .0001), LS (P < .0001), PS (P < .0001), ICAM-1 (P < .001), VCAM-1 (P < .001), N (P < .001), MMP-2 (P < .001), and MMP-9 (P < .005) were found in the patients with PAD. Patients with PAD show a inflammation marker profile different from that of control participants. Reducing the high plasma levels of inflammatory markers could be a new therapeutic approach both for the prevention and the treatment of PAD.

Association of Matrix Metalloproteinase 9 C-1562T Polymorphism with Genetic Susceptibility to Myocardial Infarction: A Meta-Analysis

BACKGROUND

Myocardial infarction (MI) is the major cause of death by disease in the world. Many studies have identified the associations between matrix metalloproteinase 9 (MMP9) C-1562T polymorphisms and MI. However, the results remain inconclusive. To clarify the role of MMP9 C-1562T polymorphism in MI risk, we conducted a systematic review and large-scale meta-analysis.

METHODS

Studies published between January 2005 and March 2014 were obtained from the electronic databases PubMed, Medline, and Embase. The odds ratios (ORs) with 95% CIs were calculated for comparisons of the alleles and genotypes in the overall population and in ethnicity subgroups to measure the strength of genetic associations.

RESULTS

A total of 7 related studies, including 3952 MI cases and 4977 healthy control subjects were included in our meta-analysis. Our results show a statistically significant association between T allele and MI in the overall population (OR = 1.23; 95% CI, 1.02-1.48; P = 0.03). The risk of MI was also significantly higher in patients carrying the T allele (TC + TT genotypes) than in those with the CC genotype (P < 0.05). In stratified analysis by ethnicity, we found the T allele was strongly associated with MI in white populations, whereas in Asian populations there appeared no significant association.

CONCLUSIONS

Our data show that the MMP9 C-1562T polymorphism is a risk factor associated with increased MI susceptibility in the total population and white populations, although no significant association was observed in Asians populations. Further studies with larger sample sizes and assessing gene-gene and gene-environment interactions are required.

Adult vascular wall resident multipotent vascular stem cells, matrix metalloproteinases, and arterial aneurysms

Evidences have shown the presence of multipotent stem cells (SCs) at sites of arterial aneurysms: they can differentiate into smooth muscle cells (SMCs) and are activated after residing in a quiescent state in the vascular wall. Recent studies have implicated the role of matrix metalloproteinases in the pathogenesis of arterial aneurysms: in fact the increased synthesis of MMPs by arterial SMCs is thought to be a pivotal mechanism in aneurysm formation. The factors and signaling pathways involved in regulating wall resident SC recruitment, survival, proliferation, growth factor production, and differentiation may be also related to selective expression of different MMPs. This review explores the relationship between adult vascular wall resident multipotent vascular SCs, MMPs, and arterial aneurysms.

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.

Endarteritis obliterans in the pathogenesis of Buerger's disease from the pathological and immunohistochemical points of view

Buerger's disease (thromboangiitis obliterans) is considered to be a nonatherosclerotic, inflammatory, and vaso-occlusive disease, although the details of the mechanisms of pathogenesis remain unknown. The occurrence of the disease is strongly related to tobacco abuse and its progression is closely linked to continued smoking. The purpose of this review article is to demonstrate the pathological characteristics of arteries affected with Buerger's disease from a possible immunoreactive point of view. In addition, we present the mechanisms for preserving the architecture of the arterial wall in affected vasculatures. Thereafter, we discuss the possibility that the pathogenesis of Buerger's disease is a type of endarteritis obliterans, deeply connected to the Notch pathway, distinct from arteriosclerosis obliterans and other vasculitides.

Saturated fatty acid palmitate aggravates neointima formation by promoting smooth muscle phenotypic modulation

OBJECTIVE

Obesity is a major risk factor of atherosclerotic cardiovascular disease. Circulating free fatty acid levels are known to be elevated in obese individuals and, along with dietary saturated fatty acids, are known to associate with cardiovascular events. However, little is known about the molecular mechanisms by which free fatty acids are linked to cardiovascular disease.

APPROACH AND RESULTS

We found that administration of palmitate, a major saturated free fatty acid, to mice markedly aggravated neointima formation induced by carotid artery ligation and that the neointima primarily consisted of phenotypically modulated smooth muscle cells (SMCs). In cultured SMCs, palmitate-induced phenotypic modulation was characterized by downregulation of SMC differentiation markers, such as SM α-actin and SM-myosin heavy chain, and upregulation of mediators involved in inflammation and remodeling of the vessel wall, such as platelet-derived growth factor B and matrix metalloproteinases. We also found that palmitate induced the expression of proinflammatory genes via a novel toll-like receptor 4/myeloid differentiation primary response 88/nuclear factor-κB/NADPH oxidase 1/reactive oxygen species signaling pathway: nuclear factor-κB was activated by palmitate via toll-like receptor 4 and its adapter, MyD88, and once active, it transactivated Nox1, encoding NADPH oxidase 1, a major reactive oxygen species generator in SMCs. Pharmacological inhibition and small interfering RNA-mediated knockdown of the components of this signaling pathway mitigated the palmitate-induced upregulation of proinflammatory genes. More importantly, Myd88 knockout mice were resistant to palmitate-induced exacerbation of neointima formation.

CONCLUSIONS

Palmitate seems to promote neointima formation by inducing inflammatory phenotypes in SMCs.

Biological responses in stented arteries

Vascular walls change their dimension and mechanical properties in response to injury such as balloon angioplasty and endovascular stent implantation. Placement of bare metal stents induces neointimal proliferation/restenosis which progresses through different phases of repair with time involving a cascade of cellular reactions. These phases just like wound healing comprise distinct steps consisting of thrombosis, inflammation, proliferation, and migration followed by remodelling. It is noteworthy that animals show a rapid progression of healing after stent deployment compared with man. During stenting, endothelial cells are partially to completely destroyed or crushed along with medial wall injury and stretching promoting activation of platelets, and thrombus formation accompanied by inflammatory reaction. Macrophages and platelets play a central role through the release of cytokines and growth factors that induce vascular smooth muscle cell accumulation within the intima. Smooth muscle cells undergo complex phenotypic changes including migration and proliferation from the media towards the intima, and transition from a contractile to a synthetic phenotype; the molecular mechanisms responsible for this change are highlighted in this review. Since studies in animals and man show that smooth muscle cells play a dominant role in restenosis, drugs like rapamycin and paclitaxel have been coated on stent with polymers to allow local slow release of drugs, which have resulted in dramatic reduction of restenosis that was once the Achilles' heel of interventional cardiologists.

Heart disease, overweight, and cigarette smoking are associated with increased prevalence of extra-cranial venous abnormalities

OBJECTIVES

Most of the extra-cranial venous abnormalities have been previously described as truncular venous malformations. In this hypothesis-driven study, we evaluated possible association of risk/protective factors with the presence of truncular and functional venous abnormalities in internal jugular veins (IJVs) in a large cohort of volunteers without known central nervous system (CNS) pathology.

METHODS

The study included 240 controls who underwent physical and Doppler sonography (DS) examinations for the presence of intra- and extra-luminal structural and functional abnormalities of the IJVs, and were assessed with a physical examination and structured environmental questionnaire for demographic characteristics, presence of autoimmune and other concomitant diseases, vascular risk factors, environmental factors, and habits. Logistic regression analysis was used to test which risk/protective factors were associated with the presence and number of extra-cranial venous abnormalities.

RESULTS

Subjects with heart disease (P<0·001), overweight (P = 0·005), and smoking (P = 0·016) had a significantly increased number of intra-luminal structural venous abnormalities. Presence of heart disease increased the risk of a malformed valve 12·9 times (95% CI: 5·4-31·3, P<0·001), while smoking increased it 2·21 times (95% CI: 1-4·9, P = 0·033). Being overweight (P = 0·003), a history of mononucleosis (P = 0·012) and smoking (P = 0·042) increased risk for presence of a flap. No association was found between the investigated risk factors and extra-luminal or functional venous abnormalities. However, use of dietary and herbal supplements had a protective role for the presence of functional venous abnormalities.

CONCLUSIONS

There is a close association between intra-luminal, structural, extra-cranial, venous system pathology and the presence of heart disease, overweight, and smoking.

Interleukin-33, matrix metalloproteinase-9, and tissue inhibitor [corrected] of matrix metalloproteinase-1 in myocardial infarction

BACKGROUND/AIMS

Acute coronary syndrome (ACS) is characterized by increased inflammatory processes and endothelial activation. We investigated the association between ACS and inflammatory mediators and matrix-degrading enzymes.

METHODS

We prospectively enrolled 55 consecutive patients with ACS: 25 with unstable angina (UA) and 30 with non-ST elevated myocardial infarction (NSTEMI). For comparison, 25 age- and sex-matched subjects with no significant coronary artery stenosis were included as the control group. Peripheral serum levels of interleukin (IL)-33, matrix metalloproteinase (MMP)-9, tissue inhibitor of MMP-1, and C-reactive protein (CRP) were measured on admission, and at 12, 24, 48, and 72 hours after the initial evaluation.

RESULTS

Compared to serum levels in the control group, serum levels of IL-33 decreased in the NSTEMI group (p < 0.05), and levels of MMP-9 and tissue inhibitor of matrix metalloproteinase (TIMP)-1 increased in the UA group (p < 0.01, p < 0.05, respectively) and NSTEMI group (p < 0.05, p < 0.05, respectively). IL-33 levels were significantly lower on admission than at 12 hours after the initial evaluation (p < 0.05). IL-33 levels were negatively correlated with MMP-9 levels (r = -0.461, p < 0.05) and CRP levels (r = -0.441, p < 0.05).

CONCLUSIONS

Elevated levels of MMP-9, TIMP-1, and decreased levels of IL-33 play a role in the development and progression of ACS.

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.

Pathology of urethral fibromuscular system related to parturition-induced stress urinary incontinence and TGF-β1/Smad pathway

To study pathological changes of fibromuscular system and the role of TGF-β1/Smad pathway in the urethra of a parturition-induced stress urinary incontinence (SUI) rat model. Twenty-eight 8-week-old Sprague-Dawley female rats at gestational day 16 were used and randomized into two groups: sham group and SUI group. After delivery, rats in the SUI group underwent postpartum vaginal balloon dilation and bilateral ovariectomy. 1 month after ovariectomy, urodynamics was assessed. Histological examination (Masson's trichrome stain, picrosirius red stain, Hart's elastin stain, Gordon & Sweet's stain, and immunohistochemical stain) and Western blot were performed on urethral tissues. Both leak point pressure and maximal bladder capacity were significantly decreased in the balloon-injured ovariectomized rats, compared with the sham rats. Muscle was significantly decreased in the urethra of SUI rats compare with sham rats. Collagen I/III and reticular fibers from SUI group were also significantly lower than sham group. Meanwhile, elastic fibers and reticular fibers showed fragmentation and disorganization indicating impairment in the fibromuscular system in SUI rats. TGF-β1, MMP-9, and phosphorylated Smad2 (p-Smad2) were expressed significantly higher in SUI than in sham rats. Simulated birth trauma and menopause induced an upregulation of the TGF-β1/Smad pathway and impairment of the fibromuscular system in the urethra.

Increased MMP-2 in healthy postmenopausal women

Background

Matrix metalloproteases 2 (MMP-2) and 9 (MMP-9) are involved in the atherosclerosis process. The objective of the study was to evaluate MMP-2 and MMP-9 activities and other circulating inflammatory factors in healthy postmenopausal women (PMW) as a model of subclinical atherosclerosis.

Methods

Twenty-three PMW and 13 premenopausal women (PreMW) were selected following established criteria. The main measurements in plasma samples were: lipid–lipoprotein profile, high-sensitivity C-reactive protein (hs-CRP) (immunoturbidimetry), soluble vascular cellular adhesion molecules (sVCAM-1) enzyme-linked immunosorbent assay and MMP activity by zymography.

Results

The relative areas of MMP-2 were increased in PMW: 1.1 (0.1) versus 0.6 (0.05), P < 0.02. MMP-9 was only detected in three PMW and one PreMW. MMP-2 correlated with HDL-cholesterol ( r = −0.51), triglycerides ( r = 0.67), apolipoprotein B ( r = 0.47), hs-CRP ( r = 0.42), homeostasis model assessment ( r = 0.53) and waist circumference ( r = 0.40), at least P < 0.02. sVCAM-1 showed no difference between groups: 28.7 (5.5) versus 35.5 (20) ng/mL, but correlated with MMP-2 and hs-CRP ( r = 0.46 and r = 0.48 respectively, P < 0.05).

Conclusions

In postmenopause, the increase in MMP-2 reflects the systemic specific inflammatory process that accompanies atherogenesis.

Activation of arterial matrix metalloproteinases leads to vascular calcification in chronic kidney disease

BACKGROUND

The objective of the current study was to determine if altered regulation of matrix metalloproteinases (MMPs) may predispose to extracellular matrix degradation, facilitating arterial calcification in chronic kidney disease (CKD) using a progressive model of CKD-MBD, the Cy/+ rat.

METHODS

Sera were collected from normal or CKD rats at various times and MMP-2 and MMP-9 levels determined by ELISA or zymography. Aorta tissue was harvested at sacrifice for RT-PCR and immunostaining. Calcification of aorta rings was assessed with MMP inhibitors.

RESULTS

There was an increase in MMP-2, MMP-9, TIMP-1, and RUNX-2 expression in the aorta with progressive CKD, and increased MMP-2 activity in the serum. Immunostaining revealed increased expression of MMP-2 and MMP-9 in areas of aorta calcification. There was also an upregulation of MMP-2 and MMP-9 in vascular smooth muscle cells (VSMC) from CKD rats. MMP inhibitors decreased calcification of aorta rings from normal and CKD rats. High phosphorus increased MMP-2 and MMP-9 expressions in VSMC from normal rats but not from CKD rats.

CONCLUSION

MMP-2 and MMP-9 expression and activity are increased with progressive CKD, and blockade of MMP activity can inhibit arterial calcification. These data suggest degradation of the extracellular matrix is a critical step in the pathogenesis of arterial calcification in CKD.

Biomarkers of extracellular matrix metabolism (MMP-9 and TIMP-1) and risk of stroke, myocardial infarction, and cause-specific mortality: cohort study

Objective

Turnover of the extracellular matrix in all solid organs is governed mainly by a balance between the degrading matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). An altered extracellular matrix metabolism has been implicated in a variety of diseases. We investigated relations of serum levels of MMP-9 and TIMP-1 to mortality risk from an etiological perspective.

Design

The prospective Uppsala Longitudinal Study of Adult Men (ULSAM) cohort, followed from 1991–1995 for up to 18.1 years. A random population-based sample of 1,082 71-year-old men, no loss to follow-up. Endpoints were all-cause (n = 628), cardiovascular (n = 230), non-cardiovascular (n = 398) and cancer mortality (n = 178), and fatal or non-fatal myocardial infarction (n = 138) or stroke (n = 163).

Results

Serum MMP-9 and TIMP-1 levels were associated with risk of all-cause mortality (Cox proportional hazard ratio [HR] per standard deviation 1.10, 95% confidence interval [CI] 1.03–1.19; and 1.11, 1.02–1.20; respectively). TIMP-1 levels were mainly related to risks of cardiovascular mortality and stroke (HR per standard deviation 1.22, 95% CI 1.09–1.37; and 1.18, 1.04–1.35; respectively). All relations except those of TIMP-1 to stroke risk were attenuated by adjustment for cardiovascular disease risk factors. Relations in a subsample without cardiovascular disease or cancer were similar to those in the total sample.

Conclusion

In this community-based cohort of elderly men, serum MMP-9 and TIMP-1 levels were related to mortality risk. An altered extracellular matrix metabolism may be involved in several detrimental pathways, and circulating MMP-9 or TIMP-1 levels may be relevant markers thereof.

Molecular regulation of contractile smooth muscle cell phenotype: implications for vascular tissue engineering

The molecular regulation of smooth muscle cell (SMC) behavior is reviewed, with particular emphasis on stimuli that promote the contractile phenotype. SMCs can shift reversibly along a continuum from a quiescent, contractile phenotype to a synthetic phenotype, which is characterized by proliferation and extracellular matrix (ECM) synthesis. This phenotypic plasticity can be harnessed for tissue engineering. Cultured synthetic SMCs have been used to engineer smooth muscle tissues with organized ECM and cell populations. However, returning SMCs to a contractile phenotype remains a key challenge. This review will integrate recent work on how soluble signaling factors, ECM, mechanical stimulation, and other cells contribute to the regulation of contractile SMC phenotype. The signal transduction pathways and mechanisms of gene expression induced by these stimuli are beginning to be elucidated and provide useful information for the quantitative analysis of SMC phenotype in engineered tissues. Progress in the development of tissue-engineered scaffold systems that implement biochemical, mechanical, or novel polymer fabrication approaches to promote contractile phenotype will also be reviewed. The application of an improved molecular understanding of SMC biology will facilitate the design of more potent cell-instructive scaffold systems to regulate SMC behavior.

Invariant natural killer T cells: linking inflammation and neovascularization in human atherosclerosis

Atherosclerosis, a chronic inflammatory lipid storage disease of large arteries, is complicated by cardiovascular events usually precipitated by plaque rupture or erosion. Inflammation participates in lesion progression and plaque rupture. Identification of leukocyte populations involved in plaque destabilization is important for effective prevention of cardiovascular events. This study investigates CD1d-expressing cells and invariant NKT cells (iNKT) in human arterial tissue, their correlation with disease severity and symptoms, and potential mechanisms for their involvement in plaque formation and/or destabilization. CD1d-expressing cells were present in advanced plaques in patients who suffered from cardiovascular events in the past and were most abundant in plaques with ectopic neovascularization. Confocal microscopy detected iNKT cells in plaques, and plaque-derived iNKT cell lines promptly produced proinflammatory cytokines when stimulated by CD1d-expressing APC-presenting α-galactosylceramide lipid antigen. Furthermore, iNKT cells were diminished in the circulating blood of patients with symptomatic atherosclerosis. Activated iNKT cell-derived culture supernatants showed angiogenic activity in a human microvascular endothelial cell line HMEC-1-spheroid model of in vitro angiogenesis and strongly activated human microvascular endothelial cell line HMEC-1 migration. This functional activity was ascribed to IL-8 released by iNKT cells upon lipid recognition. These findings introduce iNKT cells as novel cellular candidates promoting plaque neovascularization and destabilization in human atherosclerosis.

Proinflammatory and profibrotic mediators: principal effectors of leiomyoma development as a fibrotic disorder

Leiomyomas are believed to derive from the transformation of myometrial smooth muscle cells/connective tissue fibroblasts. Although the identity of the molecule(s) that initiate such cellular transformation and orchestrate subsequent growth is still unknown, conventional evidence indicates that ovarian steroids are essential for leiomyoma growth. Ovarian steroid action in their target cell/tissue is mediated in part through local expression of various growth factors, cytokines, and chemokines. These autocrine/paracrine molecules with proinflammatory and profibrotic activities serve as major contributing factors in regulating cellular transformation, cell growth and apoptosis, angiogenesis, cellular hypertrophy, and excess tissue turnover, events central to leiomyoma growth. This review addresses the key regulatory functions of proinflammatory and profibrotic mediators and their molecular mechanisms, downstream signaling that regulates cellular events that result in transformation, and commitments of specific cells into forming a cellular environment with a possible role in development and subsequent growth of leiomyomas.

Serum levels of matrix metalloproteinases -1,-2,-3 and -9 in thoracic aortic diseases and acute myocardial ischemia

Background

Matrix metalloproteinases (MMPs) constitute a family of zinc-dependent proteases (endopeptidases) whose catalytic action is the degradation of the extracellular matrix components. In addition, they play the major role in the degradation of collagen and in the process of tissue remodeling. The present clinical study investigated blood serum levels of metalloproteinases- 1, -2, -3 and -9 in patients with acute and chronic aortic dissection, thoracic aortic aneurysm and acute myocardial ischemia compared to healthy individuals.

Methods

The blood serum levels of MMP-1, -2, -3 and -9 were calculated in 31 patients with acute aortic dissection, 18 patients with chronic aortic dissection, 18 patients with aortic aneurysm and in 13 patients with acute myocardial ischemia, as well as in 15 healthy individuals who served as the control group. Serum MMP levels were measured by using an ELISA technique.

Results

There were significantly higher levels of MMP-3 in patients with acute myocardial ischemia as compared to acute aortic dissection (17.33 ± 2.03 ng/ml versus 12.92 ± 1.01 ng/ml, p < 0.05). Significantly lower levels of MMP-1 were found in healthy controls compared to all groups of patients (1.1 ± 0.38 ng/ml versus 2.97 ± 0.68 in acute aortic dissection, 3.09 ± 0.98 in chronic dissection, 3.16 ± 0.51 in thoracic aortic aneurysm and 4.58 ± 1.04 in acute myocardial ischemia, p < 0.05). Higher levels of MMP-1 and MMP-3 were detected on males. There was a positive correlation with increasing age (r = 0.38, p < 0.05). In patients operated for acute type A aortic dissection, the levels of MMP-1, MMP-3 and MMP-9 increased immediately after surgery, while the levels of MMP-2 decrease. At 24 hours postoperatively, levels of MMP -1, -2 and -9 are almost equal to the preoperative ones.

Conclusion

Measurement of serum MMP levels in thoracic aortic disease and acute myocardial ischemia is a simple and relatively rapid laboratory test that could be used as a biochemical indicator of aortic disease or acute myocardial ischemia, when evaluated in combination with imaging techniques.

Digging in the "soil" of the aorta to understand the growth of abdominal aortic aneurysms

Extensive studies into the etiology of aortic aneurysm disease have focused on the characteristic and unique inflammatory infiltration and elaboration of products of inflammatory cells which can result in matrix degradation. While these changes clearly have a significant impact on the development of aneurysm disease, little attention has been paid to the changes in the parenchymal cells of the aorta. Under normal conditions, the vascular smooth muscle cells which populate the aortic wall are responsible for the maintenance of the matrix components of the media, particularly the elastic fibers. As our understanding of the mechanisms of aneurysm formation and normal arterial anatomy become more sophisticated, it is clear that specific changes to these smooth muscle cells make them active participants in the medial matrix destruction characteristic of aneurysm disease. As others have described for intimal arterial disease, this is the "soil" from which aortic aneurysms grow.

Stroke with polyvascular atherothrombotic disease

OBJECTIVE

To study the influence of polyvascular atherothrombotic disease on stroke patient prognosis, its relation with inflammatory markers, and to analyze the progression of atherothrombotic disease.

METHODS

MITICO is a multi-centered prospective observational study recruiting non-anticoagulated ischemic stroke patients. Blood samples were obtained at baseline and at one year follow-up for determination of high sensitivity C reactive protein (hs-CRP), interleukin 6 (IL-6), intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), matrix metalloproteinase 9 (MMP-9), and cellular fibronectin (c-Fn). Patients with polyvascular atherothrombotic disease were considered when presented a history of angina-myocardial infarction, intermittent claudication or ischemic limbs-amputation at inclusion.

RESULTS

The sample consisted of 863 patients, 121 of them considered as polyvascular atherothrombotic disease (14.02%). Recurrence and vascular death were higher in patients with polyvascular atherothrombotic disease, as compared to patients with monovascular atherothrombotic disease (19.8% vs. 12.4%, p=0.022). Baseline plasma levels of IL-6 and VCAM-1 were higher in patients with polyvascular atherothrombotic disease. IL-6 and VCAM-1 levels were independently associated with a new vascular episode/vascular death. This association was stronger in the group of patients with polyvascular atherothrombotic disease. Baseline levels of IL-6, VCAM-1 and c-Fn were significantly higher in patients who developed progression of atherothrombotic disease. The increase from baseline in MMP-9 and c-Fn levels after one year follow-up was associated to progression of atherothrombotic disease.

CONCLUSIONS

Stroke patients with polyvascular atherothrombotic disease showed higher rates of vascular recurrence and a stronger association with inflammatory markers. Progression of atherothrombotic disease was associated with inflammatory markers.

Tissue inhibitor of metalloproteinase-1 is an early marker of acute endothelial dysfunction in a rodent model of venous oxidative injury

Although there are extensive research data regarding arterial endothelial dysfunction, the effects of venous endothelial dysfunction are not well characterized. Matrix metalloproteinases (MMPs) have a defined role in vascular remodeling. MMPs are endopeptidases that are capable of degrading extracellular matrix proteins. We hypothesize that tissue inhibitor of metalloproteinase-1 (TIMP-1) can serve as an indicator of acute venous endothelial dysfunction in a rat model of oxidative injury. The experimental groups evaluated were as follows: rats not undergoing oxidative injury (controls), rats that received rose bengal but no laser (shams), and rats that received both rose bengal and laser illumination, resulting in an oxidative injury. Animals were evaluated at baseline (control, shams) and at 1 hr and 1 day post-oxidative injury. mRNA expression was determined by gene array technology and real-time polymerase chain reaction, plasma and vein wall TIMP-1 protein concentrations were determined by enzyme-linked immunosorbent assay, and vein wall morphometrics (cells/five high-power fields) were performed. B-cell lymphoma 2-like gene expression was upregulated at both 1 hr and 1 day post-injury. TIMP-1 protein and mRNA expression were significantly increased post-oxidative injury. One hour postinjury, vein wall polymorphonuclear leukocytes were present in significant numbers. Our results support the hypothesis that increased expression of TIMP-1 in venous endothelium and plasma may serve as an early indicator of endothelial dysfunction.

MT1-MMP promotes vascular smooth muscle dedifferentiation through LRP1 processing

At sites of vessel-wall injury, vascular smooth muscle cells (VSMCs) can dedifferentiate to express an invasive and proliferative phenotype, which contributes to the development of neointimal lesions and vascular disorders. Herein, we demonstrate that the loss of the VSMC differentiated phenotype, as the repression of contractile-protein expression, is correlated with a dramatic upregulation of the membrane-anchored matrix metalloproteinase MT1-MMP (also known as MMP14 and membrane-type 1 matrix metalloproteinase). Matrix metalloproteinase (MMP) inhibitors or MT1-MMP deficiency led to attenuated VSMC dedifferentiation, whereas the phenotypic switch was re-engaged following the restoration of MT1-MMP activity in MT1-MMP(-/-) cells. MT1-MMP-dependent dedifferentiation was mediated by the PDGF-BB-PDGFRbeta pathway in parallel with the proteolytic processing of the multifunctional LDL receptor-related protein LRP1 and the dynamic internalization of a PDGFRbeta-beta3-integrin-MT1-MMP-LRP1 multi-component complex. Importantly, LRP1 silencing allowed the PDGF-BB-induced dedifferentiation program to proceed in the absence of MT1-MMP activity, supporting the role of unprocessed LRP1 as a gatekeeper of VSMC differentiation. Hence, MT1-MMP and LRP1 serve as a new effector-target-molecule axis that controls the PDGF-BB-PDGFRbeta-dependent VSMC phenotype and function.

The association of serum prolidase activity with the presence and severity of coronary artery disease

OBJECTIVES

Prolidase is a cytosolic exopeptidase that cleaves iminodipeptides with carboxy-terminal proline or hydroxyproline and plays major role in collagen turnover. Collagen is the essential content in atherosclerotic plaque playing a key role in the stability/instability of and progression of coronary artery disease (CAD). Consequently, in this study we sought to determine serum prolidase activity and markers of oxidative stress such as lipid hydroperoxide and total free sulfhydryl in CAD.

DESIGN AND METHODS

We have evaluated 199 patients with CAD and 122 control cases with clinical, electrocardiographic, and laboratory investigation. We have measured serum prolidase activity and serum total free sulfhydryl levels spectrophotometrically. Serum lipid hydroperoxide levels were determined with ferrous ion oxidation-xylenol orange method. We assessed the association of serum prolidase activity with the presence and severity of CAD and clinical characteristics, and laboratory parameters.

RESULTS

Serum prolidase activity (52.5+/-5.6 vs. 46.7+/-5.1 U/l, respectively, P<0.001) and serum lipid hydroperoxide levels were significantly increased in patients with CAD compared with control cases whereas, serum total free sulfhydryl levels were significantly decreased in patients with CAD compared with control cases. Serum prolidase activity and total free sulfhydryl levels were independent predictors of the presence of CAD [(chi=75.532, ss=0.212, P=0.003) and (chi=25.969, ss=-30.486, P=0.019), respectively] and Gensini score [(beta=0.276, P<0.001) and (beta=-0.274, P<0.001), respectively]. Independent predictors of serum prolidase activity were serum high-density lipoprotein cholesterol (beta=-0.138, P=0.023) and urea levels (beta=0.146, P=0.036), and Gensini score (beta=0.317, P<0.001).

CONCLUSION

Findings of this study have shown that serum prolidase activity is significantly associated with the presence and severity of CAD, and elevated serum prolidase activity might be an independent predictor of coronary atherosclerosis.

A model of cerebrovascular injury in rats

Although the pathophysiology of post-angioplasty restenosis has been extensively studied in extracranial arteries using transluminal vascular injury model in rodents, it is still not well known in the intracranial arteries, which have quite different structures from extracranial arteries. Here, we examined whether 1-min placement of modified intraluminal suture could induce an injury in the internal carotid artery (ICA) in rats and observed temporal profile of histological change after the injury. HE staining showed that the injured intracranial ICA was dilated, while the media was markedly thinned at 1 day after injury. The internal elastic lamina was not observed, and the media contained few cells. At 1 week after injury, a thin layer of neointimal hyperplasia was observed on the luminal side of the internal elastic lamina. Neointimal hyperplasia developed until at least 4 weeks after injury. Morphometric analysis demonstrated that the healing process of the injury was related to arterial remodeling. Immunohistochemical staining for alpha-smooth muscle actin and electron microscopic analysis showed that the neointima was composed of smooth muscle cells. Re-endothelialization was observed from 1 to 4 weeks after injury by immunohistochemical staining for von Willebrand's factor and electron microscopic analysis. Vascular endothelial growth factor was expressed in neointima on days 7 and 14. Interestingly, superoxide anion was not increased in injured arteries on day 3, when the infiltration of macrophages was intensive, but increased on day 7, when infiltrating macrophages almost disappeared. These findings might shed new light on pathophysiology of post-angioplasty restenosis in intracranial arteries.