Collagen content is significantly lower in restenotic versus nonrestenotic vessels after balloon angioplasty in the atherosclerotic rabbit model

Biocompatible Liquid Embolic for the Treatment of Microvascular Hemorrhage

Persistent or recurrent bleeding from microvessels inaccessible for direct endovascular intervention is a major problem in medicine today. Here, an innovative catheter-directed liquid embolic (P-LE) is bioengineered for rapid microvessel embolization to treat small vessel hemorrhage. Tested in rodent, porcine, and canine animal models under normal and coagulopathic conditions, P-LE outperformed clinically used embolic materials in both survival and non-survival experiments, effectively occluding vessels as small as 40 microns with no signs of recanalization. P-LE occlusion is independent of the coagulation cascade, and its resistance to displacement is ≈ 8 times greater than systolic blood pressure. P-LE is also found to be biocompatible and x-ray visible and does not require polymerization or a chemical reaction to embolize. To simulate the clinical scenario, acute microvascular hemorrhage is created in the pig kidney, liver, or stomach; these are successfully treated with P-LE achieving immediate hemostasis. Furthermore, P-LE is found to be bactericidal to highly resistant patient-derived bacteria, suggesting that P-LE may also protect against infectious complications that may occur following embolization procedures. P-LE is safe, easy to use, and effective in treating -microvessel hemorrhage.

Balloon neck-plasty to create a wide-necked aneurysm in the elastase-induced rabbit model

PURPOSE

The elastase-induced aneurysm (EIA) model in rabbits has been proposed for translational research; however, the adjustment of aneurysm neck size remains challenging. In this study, the technical feasibility and safety of balloon neck-plasty to create a wide-necked aneurysm in rabbit EIA model were investigated.

METHODS

Male New Zealand White rabbits (N = 15) were randomly assigned to three groups: group A, EIA creation without neck-plasty; group B, neck-plasty immediately after EIA creation; group C, neck-plasty 4 weeks after EIA creation. The diameter of balloon used for neck-plasty was determined 1 mm larger than origin carotid artery diameter. All rabbits were euthanized 4 weeks after their final surgery. Aneurysm neck, height, dome-to-neck (D/N) ratio, and histologic parameters were compared among the groups.

RESULTS

Aneurysm creation was technically successful in 14 out of 15 rabbits (93.3%), with one rabbit experiencing mortality due to an adverse anesthetic event during the surgery. Saccular and wide-necked aneurysms were successfully created in all rabbits. Aneurysm neck was significantly greater in groups B and C compared to group A (all P < .05). D/N ratio was significantly lower in groups B and C compared to group A (all P < .05). Additionally, tunica media thickness, vessel area, and luminal area were significantly greater in groups B and C compared to group A (all P < .05). These variables were found to be significantly greater in group B compared to group C (all P < .05).

CONCLUSION

The creation of a wide-necked aneurysm using balloon neck-plasty after elastase induction in rabbits has been determined to be technically feasible and safe.

World Trade Center-Cardiorespiratory and Vascular Dysfunction: Assessing the Phenotype and Metabolome of a Murine Particulate Matter Exposure Model

Vascular changes occur early in the development of obstructive airways disease. However, the vascular remodeling and dysfunction due to World Trade Center-Particulate Matter (WTC-PM) exposure are not well described and are therefore the focus of this investigation. C57Bl/6 female mice oropharyngeally aspirated 200 µg of WTC-PM₅₃ or phosphate-buffered saline (PBS) (controls). 24-hours (24-hrs) and 1-Month (1-M) after exposure, echocardiography, micro-positron emission tomography(µ-PET), collagen quantification, lung metabolomics, assessment of antioxidant potential and soluble-receptor for advanced glycation end products (sRAGE) in bronchoalveolar lavage(BAL) and plasma were performed. 24-hrs post-exposure, there was a significant reduction in (1) Pulmonary artery(PA) flow-velocity and pulmonary ejection time(PET) (2) Pulmonary acceleration time(PAT) and PAT/PET, while (3) Aortic ejection time(AET) and velocity time integral(VTI) were increased, and (4) Aortic acceleration time (AAT)/AET, cardiac output and stroke volume were decreased compared to controls. 1-M post-exposure, there was also significant reduction of right ventricular diameter as right ventricle free wall thickness was increased and an increase in tricuspid E, A peaks and an elevated E/A. The pulmonary and cardiac standard uptake value and volume 1-M post-exposure was significantly elevated after PM-exposure. Similarly, α-smooth muscle actin(α-SMA) expression, aortic collagen deposition was elevated 1-M after PM exposure. In assessment of the metabolome, prominent subpathways included advanced glycation end products (AGEs), phosphatidylcholines, sphingolipids, saturated/unsaturated fatty acids, eicosanoids, and phospholipids. BAL superoxide dismutase(SOD), plasma total-antioxidant capacity activity, and sRAGE (BAL and plasma) were elevated after 24-hrs. PM exposure and associated vascular disease are a global health burden. Our study shows persistent WTC-Cardiorespiratory and Vascular Dysfunction (WTC-CaRVD), inflammatory changes and attenuation of antioxidant potential after PM exposure. Early detection of vascular disease is crucial to preventing cardiovascular deaths and future work will focus on further identification of bioactive therapeutic targets.

Biomarkers of Endothelial Dysfunction in Women With Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of childbearing age. The criteria required for the diagnosis identify various phenotypes, with different reproductive, metabolic, and cardiovascular (CV) risk characteristics. Emerging evidence links adipocyte-secreted hormones as candidates in the pathogenesis of endothelial dysfunction in PCOS, independently of additional risk factors. The aim of this review was to collect, analyze, and qualitatively resynthesize evidence on biomarkers of endothelial dysfunction (visfatin, vascular endothelial growth factor [VEGF], matrix metalloproteinase 9 [MMP-9]) in women with PCOS. Women with PCOS exhibit (a) increased plasma visfatin concentrations compared with controls with a similar body mass index; (b) increased VEGF production along with chronic, mild inflammation; and (c) increased MMP-9 concentrations, which might be related to either excessive CV risk or abnormalities of ovarian extracellular matrix remodeling, multiple cyst formation, follicular atresia, and chronic anovulation. As PCOS has been associated with CV risk, early identification of endothelial dysfunction is clinically relevant.

An Automated Algorithm to Quantify Collagen Distribution in Aortic Wall

Arterial diseases including abdominal aortic aneurysm and atherosclerosis are biomechanical diseases characterized by significant changes in the structure and strength of the vessel wall. It is now established that local variations in fibrillar collagen and elastin matrix turnover is critical to arterial stiffening and progression of the disease. The collagen content in the aortic wall has nominally been quantified by biochemical assays and immunohistochemical analysis as the total amount because of the difficulty in separating the media and adventitia. In this work, we have developed an algorithm for automatic quantification of layer-specific collagen content from bright-field and polarized microscopic images of histological sections of mouse aorta stained with Picrosirius red (PSR) stain. The images were processed sequentially including separation of layers, erosion, segregation of regions, binarization, and quantification of pixel intensities to obtain collagen content in the media and adventitia separately. We observed that the automated algorithm rapidly and accurately quantified collagen content from a wide range of image quality compared with manual measurements particularly when the medial and adventitial layers overlap. Together, our algorithm will be of significant impact in the rapid, reliable, and accurate analyses of collagen distribution in histological sections of connective tissues.

Proteins mediating collagen biosynthesis and accumulation in arterial repair: novel targets for anti-restenosis therapy

Events contributing to restenosis after coronary interventions include platelet aggregation, inflammatory cell infiltration, growth factor release, and accumulation of smooth muscle cells (SMCs) and extracellular matrix (ECM). The ECM is composed of various collagen subtypes and proteoglycans and over time constitutes the major component of the mature restenotic plaque. The pathophysiology of collagen accumulation in the ECM during arterial restenosis is reviewed. Factors regulating collagen synthesis and degradation, including various cytokines and growth factors involved in the process, may be targets for therapies aimed at prevention of in-stent restenosis.

Uteroplacental insufficiency programs regional vascular dysfunction and alters arterial stiffness in female offspring

Intrauterine growth restriction caused by uteroplacental insufficiency increases the risk of cardiovascular disease in adulthood. Vascular mechanisms in female offspring are poorly understood. The aim of this study was to investigate the effects of uteroplacental insufficiency on blood pressure, vascular reactivity and arterial stiffness in four vascular beds in female offspring born growth restricted. Uteroplacental insufficiency was induced on day 18 of gestation in Wistar Kyoto rats by bilateral uterine vessel ligation (Restricted) or sham surgery (Controls). Wire and pressure myography were used to test endothelial and smooth muscle function, and passive mechanical wall properties, respectively, in uterine, mesenteric, renal and femoral arteries of 18-month-old female offspring. Collagen and elastin fibres were quantified using circular crossed-polarized light microscopy and quantitative real time polymerase chain reaction. Restricted female offspring were born 10-15% smaller. Restricted females were normotensive, had plasma triglycerides 2-fold elevated and had uterine endothelial dysfunction, attributed to a 23% reduction in the maximal relaxation produced by endothelium-derived hyperpolarizing factor. Uterine artery stiffness was increased, with an augmented proportion of thick and decreased proportion of thin collagen fibres. Vascular reactivity and mechanical wall properties were preserved in mesenteric, renal and femoral arteries in growth restricted females. Female offspring born growth restricted have selective uterine artery endothelial dysfunction and increased wall stiffness. The preserved vascular function in other arteries may explain the lack of hypertension in these females. The uterine artery specific dysfunction has potential implications for impaired pregnancy adaptations and a compromised intrauterine environment of the next generation.

Preclinical Models of Restenosis and Their Application in the Evaluation of Drug-Eluting Stent Systems

Coronary arterial disease (CAD) is the leading cause of death in the United States, the European Union, and Canada. Percutaneous coronary intervention (PCI) has revolutionized the treatment of CAD, and it is the advent of drug-eluting stent (DES) systems that has effectively allayed much of the challenge of restenosis that has plagued the success of PCI through its 30-year history. However, DES systems have not been a panacea: There yet remain the challenges associated with interventions involving bare metallic stents as well as newly arisen concerns related to the application of DES systems. To effectively address these novel and ongoing issues, animal models are relied on both to project the safety and efficacy of endovascular devices and to provide insight into the pathophysiology underlying the vascular response to injury and mechanisms of restenosis. In this review, preclinical models of restenosis are presented, and their application and limitation in the evaluation of device-based interventional technologies for the treatment of CAD are discussed.

Thrombus resolution and vein wall injury: dependence on chemokines and leukocytes

Chronic venous insufficiency resulting in post-thrombotic syndrome occurs commonly after acute deep vein thrombosis, and is a prevalent cause of vascular disease morbidity in the community. Therefore, a better understanding of the pathophysiologic mechanisms that promote the development of chronic venous insufficiency could lead to novel approaches to interrupt the natural history and prevent post-thrombotic syndrome. In this paper, we will review the evidence that venous thrombus resolution is an inflammatory process that is dependent on chemokines and leukocytes.

Extracellular matrix turnover and signaling during cardiac remodeling following MI: causes and consequences

The concept that extracellular matrix (ECM) turnover occurs during cardiac remodeling is a well-accepted paradigm. To date, a multitude of studies document that remodeling is accompanied by increases in the synthesis and deposition of ECM components as well as increases in extracellular proteases, especially matrix metalloproteinases (MMPs), which break down ECM components. Further, soluble ECM fragments generated from enzymatic action serve to stimulate cell behavior and have been proposed as candidate plasma biomarkers of cardiac remodeling. This review briefly summarizes our current knowledge base on cardiac ECM turnover following myocardial infarction (MI), but more importantly extends discussion by defining avenues that remain to be explored to drive the ECM remodeling field forward. Specifically, this review will discuss cause and effect roles for the ECM changes observed following MI and the potential role of the ECM changes that may serve as trigger points to regulate remodeling. While the pattern of remodeling following MI is qualitatively similar but quantitatively different from various types of injury, the basic theme in remodeling is repeated. Therefore, while we use the MI model as the prototype injury model, the themes discussed here are also relevant to cardiac remodeling due to other types of injury.

Adenovirus-mediated gene transfer of fibromodulin inhibits neointimal hyperplasia in an organ culture model of human saphenous vein graft disease

Poor long-term graft patency remains a major limitation of coronary artery bypass grafting using saphenous vein aortocoronary grafts. Neointimal hyperplasia (NIH) represents the principal mechanism of graft failure; a substantial body of evidence implicates transforming growth factor-beta1 (TGF-beta1) in the pathogenesis of NIH. The small leucine-rich proteoglycans decorin and fibromodulin possess TGF-beta-antagonist activity to differing extents and with differing avidities for the isoforms of TGF-beta. We compared their ability to inhibit NIH in an ex vivo model of human saphenous vein organ culture following adenovirus-mediated gene transfer. Surgically prepared human saphenous vein segments received adenovirus expressing fibromodulin (Ad5-Fmod), decorin (Ad5-Dcn), beta-galactosidase (Ad5-lacZ) or vehicle-only. Computerized morphometry 14 days after infection revealed significantly reduced neointimal area, neointimal thickness and intima/media ratio in Ad5-Fmod- and Ad5-Dcn-infected veins. Each parameter was significantly smaller in Ad5-Fmod- than in Ad5-Dcn-exposed segments. Fibrillar collagen content and levels of biologically active TGF-beta were lower in vessels receiving Ad5-Fmod or Ad5-Dcn than in those receiving Ad5-lacZ or vehicle-only. Fibromodulin is a more potent inhibitor of NIH in cultured human saphenous vein than decorin and offers potential therapeutic benefits in saphenous vein graft failure (and possibly in other forms of accelerated atherosclerosis) by reduction of associated neointima formation.

MMP and TIMP alterations in asymptomatic and symptomatic severe recurrent carotid artery stenosis

OBJECTIVES

This study aimed to determine whether the plasma levels of matrix metalloproteinases (MMPs)-2 and -9 and their specific inhibitors (tissue inhibitors of metalloproteinases (TIMPs-1 and -2)) were altered in patients with symptomatic and asymptomatic, severe, recurrent carotid artery stenosis.

PATIENTS

Fifty-two patients (out of a total of 621) who had undergone successful carotid artery endarterectomy (CEA) between 1999 and 2003 and developed recurrent carotid artery stenosis (>/=70%) were included in the study. Restenosis was symptomatic in 23 patients and asymptomatic in 29 patients.

METHODS

Recurrent carotid artery stenosis was classified based on presentation, and as early-intermediate (6 months to 3 years) or late (>3 years). A detailed clinical history was taken and two blood samples were drawn from each patient to determine plasma levels of MMPs and TIMPs along with other biological parameters. Recurrent stenosis was confirmed with computed tomographic angiography.

RESULTS

Patients with symptomatic restenosis had significantly (p<0.001) higher active MMP-2 and -9 plasma values and significantly (p<0.001) lower TIMP-1 and -2 plasma values when compared to patients with asymptomatic restenosis. Plasma concentrations of active MMPs were higher and TIMPs lower in patients affected with late recurrent stenosis as compared to early-intermediate restenosis (p<0.001). No differences were recorded in latent MMP plasma values. Multivariate analysis showed that active MMP-2 and -9 were independent predictors of late recurrent carotid artery stenosis (p<0.03 and p<0.001, respectively).

CONCLUSIONS

Higher plasma concentrations of active MMP-2 and -9 were associated with an increased risk of carotid restenosis with plaque recurrence.

Plasmin inhibition increases MMP-9 activity and decreases vein wall stiffness during venous thrombosis resolution

INTRODUCTION

Deep venous thrombosis (DVT) resolution involves the plasmin and the matrix metalloproteinase (MMP) system. This study tested the hypothesis that pharmacological inhibition of the plasmin system would impair DVT resolution and worsen vein wall damage.

METHODS

A rat model of stasis DVT by inferior vena cava (IVC) ligation was performed with intravenous control saline or aprotinin (AP; 2.8 mg/kg at operation), and harvest of thrombosed IVC at 7 days. After laser Doppler imaging, DVT were separated and weighed, and vein wall stiffness was assessed by tensiometry. Thrombus and vein wall tissue analysis included total collagen by colorimetric assay, cytokines, chemokines, and d-dimer by ELISA, urokinase-plasminogen activator (uPA), and plasminogen activator inhibitor-1 (PAI-1) by immuno-blotting, MMP-2 and -9 by zymography, and neutrophil (PMN) and monocyte (ED-1) leukocytes by immunohistochemistry.

RESULTS

DVT weights were 2-fold greater in the AP-treated rats (P < 0.05), but no significant differences in thrombus perfusion, collagen, or d-dimer levels were found. Vein wall stiffness was reduced 50% (P < 0.05), suggesting less biomechanical injury. The total vein wall MMP-9 was increased (P < 0.05) 5-fold in the AP group compared with controls, while MMP-2 was elevated but did not reach significance. No difference was found in vein wall tumor necrosis factor-alpha, tissue growth factor-beta, vein wall or thrombus monocytes, PMN, or uPA/PAI-1 ratio between groups.

DISCUSSION

AP inhibition of the plasmin system was associated with larger thrombi but less vein wall injury, but no difference in other measures of resolution, possibly because of increased vein wall MMP-9 activity. These data suggest an important redundant mechanism for DVT resolution.

TIMP-2 Modulates Neointimal Formation in Experimental ePTFE Arterial Grafts

BACKGROUND

In vascular reconstructive surgery, myointimal hyperplasia contributes to the adverse outcome of synthetic grafts. This phenomenon is because of unregulated extracellular matrix degradation and remodeling, and excessive smooth muscle cell proliferation and migration. Matrix metallopreoteinase 2 (MMP-2) is known as an important contributor to these events. The aims of our study was to investigate the effects of selective MMP-2 inhibitor (TIMP-2) in endothelialization rate, SMC proliferation, and myointimal hyperplasia in experimental ePTFE arterial grafts.

METHODS

In 20 male Lewis rats, a 1-cm long ePTFE graft has been inserted at the level of the abdominal aorta. Animals were randomized in two groups (10 animals each): group A received six subcutaneous inoculations of TIMP-2 (2.5 microg) after surgery, group B received only the vehicle of TIMP-2.

RESULTS

Neointimal thickness, as well as SMC density, were augmented in group B, whereas endothelial cells density was augmented in group A, and these findings were statistically significant. In group A SMC were better organized, just like SMC of thoracic aorta. In group B SMC were no organized. Furthermore, anti-TIMP-2 and anti-MMP-2 coloration revealed higher levels of TIMP-2 and lower levels of MMP-2 in group A versus group-B.

CONCLUSIONS

Use of TIMP-2 affects the neointimal formation of experimental e-PTFE arterial grafts, leading to a better-organized neointima, with improved endothelialization.

The role of genetic variants of matrix metalloproteinases in coronary and carotid atherosclerosis

Current evidence suggests that matrix metalloproteinases (MMPs) have a role in early atherosclerosis, plaque rupture and myocardial infarction. Polymorphisms in MMP genes have been examined for associations with atherosclerosis, but interpretation is complicated by methodological issues. This article presents a systematic review of these association studies and a meta-analysis of available data for polymorphisms where a sufficient number of studies was available. The 5A allele of the MMP3 5A/6A polymorphism was associated with acute myocardial infarction (odds ratio (OR) 1.26, 95% confidence interval (CI) 1.1 to 1.4, p<0.001), suggesting its role in plaque rupture. There was no association with the functional MMP9 -1562C/T polymorphism (OR 1.11, 95% CI 1.0 to 1.3, p = 0.18). Current data provide evidence for the role of MMP3 polymorphism in plaque destabilisation, but elucidation of the role of other MMP gene variants in atherosclerosis will depend on better study design, including a larger sample size, extensive screening of individual genes with haplotype analysis and replication of studies to avoid publication bias.

Vascular effects of TZDs: New implications

The incidence of diabetes, now affecting more than 170 million individuals is growing rapidly. Type 2 diabetes, which accounts for 90% of all diabetes cases, is associated with increased cardiovascular morbidity and mortality. Thiazolidinediones (TZDs), used for the treatment of patients with type 2 diabetes improve insulin sensitivity and endothelial dysfunction and exert beneficial effects on the lipid profile by activating the peroxisome proliferator-activated receptor gamma (PPAR-gamma). Moreover, a large body of evidence indicates that TZDs exhibit antiatherogenic effects independent of their antidiabetic and lipid-lowering properties by modulating inflammatory processes. This review will focus on the role of PPAR-gamma agonists in the vessel wall and summarize their effects on C-reactive protein (CRP), plasminogen activator inhibitor type-1 (PAI-1), matrix metalloproteinase-9 (MMP-9), adiponectin and ATP-binding cassette transporter A1 (ABCA1) and their implications for treatment of advanced stages of atherosclerosis, particularly in a setting of type 2 diabetes.

Short-term atorvastatin treatment does not modify neointimal morphology but reduces MMP-2 expression in normocholesterolemic rabbit stented arteries

The aim of our study was to explore some potential pleïotropic effects of atorvastatin, after stenting in the iliac arteries of normocholesterolemic rabbits. On day 0, 27 rabbits underwent stent implantation and were randomized into either the control group (standard chow, CTRL, n = 15) or the atorvastatin group (10 mg/kg/d per os, Ator, n = 12). On day 30, the stented arteries were harvested for histomorphometry and neointimal analysis [macrophages, matrix metalloproteinases (MMP-2), tissue inhibitor of metalloproteinase-2, vascular smooth muscle cells, and collagen]. Atorvastatin did not induce significant histomorphometric and inflammatory modifications but reduced neointimal expression of MMP-2 with no modification of tissue inhibitor of metalloproteinase-2, and also induced higher neointimal collagen content (Ator vs. CTRL: MMP-2: 0.05 +/- 0.03 vs. 0.70 +/- 0.20, P < 0.01; collagen: 17.0+/-0.7%/mm vs. 12.0 +/- 1.2%/mm(2) P < 0.01). Atorvastatin treatment also induced a significant decrease in neointimal vascular smooth muscle cells and cellular density (respectively: 2.0 +/- 0.2 vs. 1.4 +/- 0.2, P < 0.05; 5406 +/- 241 nuclei/mm(2) vs. 4402 +/- 163 nuclei/mm(2), P < 0.001). Our study provides new insights into the field of MMP response to stenting and the effects of statin therapy, which could have important implications in the field of in-stent restenosis.

Elevated matrix metalloproteinase expression after stent implantation is associated with restenosis

OBJECTIVE

Matrix metalloproteinases (MMPs) play a key role in intimal growth and is responsible for ventricular remodeling after stent implantation. However, little is known about the relationship between early MMPs expression post-stent implantation and follow-up restenosis.

METHODS

We investigated the serial changes of serum MMP-9, MMP-2 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in 16 control subjects with normal coronary angiography (control) and 40 patients before and on the 1st, 3rd and 7th day after uncomplicated stent implantation. Follow-up angiography was performed at 6 months after stent implantation.

RESULTS

Serum MMP-2 level was higher in patients with restenosis on the 1st day post-stent implantation and returned to pre-operation level thereafter. Serum MMP-9 levels consistently increased in patients with restenosis up to 7th day post-stent implantation; MMP-9 levels in the 1st, 3rd and 7th day after stent implantation were positively correlated to the late loss index 6 months after stent implantation.

CONCLUSIONS

Increased serum MMP-9 level is associated with increased risk of restenosis post-stent implantation.

MMP-9 microsatellite polymorphism: Association with the progression of intima-media thickening and constrictive remodeling of carotid atherosclerotic plaques

Intima-media thickening (IMT) of carotid arteries and constrictive remodeling (CR) of atherosclerotic plaques are vascular pathologic characteristics that precede the onset of vascular events. SMC migration and proliferation are linked both to IMT and CR and are matrix metalloproteinase 9 (MMP-9) dependent. A genetic polymorphism (PM) of MMP-9, a CA (13-27) microsatellite in the promoter region, which accounts for differential expression of MMP-9, could be linked to progression of IMT and CR. Progression of IMT and CR of plaques in carotid arteries were studied in 55 consecutive patients with a 12-18 months follow-up. All patients were genotyped for MMP-9 PM. A positive linear relationship between the number of repeats and the progression of IMT (P=0.028) as well as of CR (P=0.018) was found. The analogous relationship was obtained when only the allele with longer microsatellite was considered. Carriers of more than 20 repeats in one allele showed faster both IMT growth (P=0.045) and stenosis progressions of plaques (P=0.019). In multivariate analysis, age, dyslipidemia, and MMP-9 PM were determinants of IMT progression, while MMP-9 PM was the only one of CR. In conclusion, the high number of CA repeats in MMP-9 promoter is positively correlated with faster IMT and CR progression.

Vein wall remodeling after deep vein thrombosis involves matrix metalloproteinases and late fibrosis in a mouse model

HYPOTHESIS

Deep venous thrombosis (DVT) confers vein wall injury associated with fibrosis and extracellular matrix (ECM) turnover, likely mediated by matrix proteases. This study investigated the expression of proteases and collagen involved in early vein wall remodeling.

METHODS

In the mouse, DVT was produced by ligation of the infrarenal inferior vena cava (IVC) or sham operation, and tissue was harvested at 4, 8, and 12 days. The vein wall tissue was processed for real-time reverse transcriptase-polymerase chain reaction (6 to 8 per time point), Western immunoblotting (5 per time point), and gelatin zymography (5 per time point). Analysis of variance was used for multiple comparisons, and a P < .05 was significant.

RESULTS

Thrombus resolution was documented by a 38% decrease in the thrombosed IVC weight from day 4 to day 12 (P = .007). Total vein wall collagen increased over time, with a corresponding increase in procollagen I and III, and expression peaked at 12 days (24-fold and 6.1-fold, respectively, P < .02). Matrix metalloproteinase-2 (MMP-2) gene expression was 23-fold greater at 12 days after thrombus formation compared with sham or 4 days after thrombosis (P < .05). Total MMP-2 activity was also significantly elevated at 12 days compared with sham (P < .05). MMP-9 expression was 19-fold and 27-fold higher at days 4 and 8, respectively, relative to sham (P < .05), with no difference in activity. MMP-14 expression was twofold to 3.6-fold greater at day 12 compared with earlier time points and shams (P < .001), but no differences in protein levels were found. Urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) protein levels were not significantly different from sham over time; however, the ratio of uPA to PAI-1 was decreased through 8 days.

CONCLUSIONS

Vein wall remodeling after DVT is similar to wound healing and is associated with increased procollagen gene expression and total collagen. It is also associated with increased early MMP-9 expression, followed by MMP-2 expression and activity after DVT resolution.

CLINICAL RELEVANCE

Deep vein thrombosis is an often neglected problem that long term is associated with the postphlebitic syndrome of limb swelling, pain, and often ulceration. The basic mechanisms of the vein wall damage that results have not been delineated. The following study describes the vein wall matrix metalloproteinase gene and activity response induced over time in the vein wall after DVT. Additionally, the corresponding collagen upregulation and proximate plasmin system mediators are determined. With this knowledge, potential therapies to reduce vein wall injury directly might be possible.

Increase in Collagen Turnover But Not in Collagen Fiber Content Is Associated with Flow-Induced Arterial Remodeling

BACKGROUND

Degradation and synthesis of collagen are common features in arterial geometrical remodeling. Previous studies described an association between arterial remodeling and an increase in collagen fiber content after balloon injury. However, this does not exclude that the association between collagen content and remodeling depends on arterial injury since the association of collagen fiber content and arterial remodeling, without arterial injury, has not been investigated. The aim of the present study was to study the relation between flow-induced arterial geometrical remodeling, without arterial injury, and collagen synthesis and degradation, collagen fiber content and cell-migration-associated moesin levels.

METHODS AND RESULTS

In 23 New Zealand White rabbits an arteriovenous shunt (AV shunt) was created in the carotid and femoral artery to induce a structural diameter increase or a partial ligation (n = 27 rabbits) to induce a diameter decrease. In both models, arterial remodeling was accompanied by increased procollagen synthesis, reflected by increased procollagen mRNA or Hsp47 protein levels. In both models, however, no changes were detected in collagen fiber content. Active MMP-2 and moesin levels were increased after AV shunting.

CONCLUSIONS

Collagen synthesis and MMP-2 activation were associated with arterial remodeling. However, a change in collagen fiber content was not observed. These results suggest that, during flow-induced geometrical arterial remodeling, increases in collagen synthesis are used for matrix collagen turnover and cell migration but not to augment collagen fiber content.

The natural history of collagen and α-actin expression after coronary angioplasty

BACKGROUND

Restenosis after percutaneous transluminal coronary angioplasty (PTCA) is a result of remodeling and deposition of new mass. The new mass is formed by invading and replicating cells and by extracellular matrix (ECM), of which collagens constitute the dominating component. Smooth muscle actin is an important element in cell contraction. We tested the hypothesis that the accumulation of collagen and actin correlates with the development of postinjury luminal narrowing.

METHODS AND RESULTS

Thirty-five pigs underwent balloon angioplasty and were killed 0, 1, 4, 7, 14, 28, and 56 days later. Tissue samples from the left circumflex artery were in paraffin, sectioned, and immunostained for Collagen Types I and III and alpha1-smooth muscle actin. Collagen accumulation was measured separately in intima, media, and adventitia using computerized semiautomatic planimetry. The injury produced a strong healing response, with a marked accumulation of collagen in all three vessel wall layers. However, the accumulation in adventitia began surprisingly early (1 to 4 days after PTCA) and stopped at Day 7, i.e., before luminal narrowing occurred (14 to 28 days after PTCA in our model). Furthermore, a conspicuous accretion of collagen occurred in the injured area of the medial layer. This response attenuated 14 days after PTCA. Neointimal collagen accumulation took place parallel to neointima formation 2 to 4 weeks after injury. Extramedial smooth muscle actin occurred predominantly from Days 4 to 14 in neointima. Only small quantities of actin were observed in the (neo-)adventitia. Furthermore, adventitial actin was a temporary phenomenon that disappeared between Days 14 and 28.

CONCLUSION

Adventitial and medial collagen deposition apparently occurs before luminal narrowing, indicating that the bulk of new mass in adventitia and media is not the cause of vessel remodeling, but possibly stabilizes the vessel wall and impairs compensatory outward remodeling. The accumulation of actin-positive cells and collagen takes place in neointima parallel to luminal narrowing, which suggests that a contraction within the neointimal mass may contribute to the remodeling process.

2-Cyclopenten-1-one and prostaglandin J2reduce restenosis after balloon angioplasty in rats: role of NF-κB

The aim of this study was to evaluate, using a rat model of balloon angioplasty, whether prostaglandin (PG) J(2) and 2-cyclopenten-1-one are able to reduce restenosis. We found that both PGJ(2) and 2-cyclopenten-1-one, administered by local application on carotid arteries, caused a dose-dependent inhibition of neointimal formation. Furthermore, both agents prevented vascular negative remodeling. The effect of these compounds on restenosis was correlated with an inhibition of nuclear factor-kappaB (NF-kappaB) activation as well as of intercellular adhesion molecule-1 (ICAM-1) protein expression in injured carotid arteries of control animals. Our results show that cyclopentenone PGs and their derivatives reduce restenosis and may have therapeutic relevance for the prevention of human restenosis.

Rapamycin inhibits vascular remodeling in an experimental model of allograft vasculopathy and attenuates associated changes in fibrosis-associated gene expression

BACKGROUND

Rapamycin inhibits extracellular matrix (ECM) accumulation (fibrosis) and vascular remodeling in experimental models of chronic allograft dysfunction (CAD) by poorly understood mechanisms. The aim of this study was to assess the effect of rapamycin on the expression of fibrosis-associated genes and correlate this with observed changes in ECM remodeling in an experimental of model allograft vasculopathy.

METHODS

Vascular remodeling and ECM accumulation (picrosirius red) were measured by computerized histomorphometry of F344-to-Lewis rat aortic allograft sections harvested at serial timepoints. Expression of fibrosis associated genes was studied by means of semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Rapamycin (0.5 mg/kg/day) inhibited intimal hyperplasia, medial ECM accumulation and expansive vascular remodeling (increasing vessel circumference) in rat aortic allografts. This was associated with attenuation of the graft inflammatory infiltrate and a reduction in intragraft gelatinase, collagen III and tissue inhibitor of metalloproteinase 1 (TIMP 1) mRNA levels. At a lower dosage (0.25 mg/kg/day), rapamycin inhibited intimal hyperplasia and medial ECM accumulation, but there was a lesser effect on vascular remodeling. Lower dose allografts were also seen to have a more severe inflammatory infiltrate and larger amounts of intragraft matrix metalloproteinase 9 (MMP 9) mRNA than those treated with the higher dose.

CONCLUSIONS

These data suggest that, in addition to the tissue response to injury, the alloimmune injury itself may contribute directly to the vascular remodeling that occurs in allograft vasculopathy. Rapamycin at higher but not lower doses inhibited both of these pathologic processes.

Collagen synthesis and collagenase activity of cryopreserved heart valves

OBJECTIVE

Durability of the valve seems to be dependent on the remodeling ability of the valve itself, which is controlled by both collagen synthesis and collagenolytic activity of valvular fibroblasts and endothelial cells. However, the balance of collagen synthesis and collagenolysis of the cryopreserved valve has not yet been clearly revealed. Thus, we assessed the collagen synthesis and collagenolysis ability of the cryopreserved valve.

METHODS

Twelve valves were divided into 2 groups: freshly harvested valves (n = 6) and cryopreserved valves (n = 6). We measured the collagen content using Sirius red, a dye selective to the collagen. Collagen synthesis was evaluated by means of the tritiated proline incorporation method. Noncollagenase-digestible counts, which represent protein synthesis, and collagenase-digestible counts, which represent collagen synthesis, were estimated. Collagenase activity of the valves was assessed by gelatin zymography.

RESULTS

The collagen content of the cryopreserved group was maintained. The noncollagenase-digestible counts of the cryopreserved group decreased from 3862 +/- 1180 counts/mg to 1174 +/- 1362 counts/mg, and the collagenase-digestible counts of the cryopreserved group were 831 +/- 762 counts/mg compared with the value of 1062 +/- 136 counts/mg for the freshly harvested group. The collagenase activity of the cryopreserved group was observed at the same level as that of the freshly harvested group, despite the serious endothelial damage of the cryopreserved valves.

CONCLUSIONS

Although the collagen synthesis of cryopreserved valves was relatively maintained, the protein synthesis was highly diminished, and the collagenolysis ability was activated immediately after the thawing process. These results imply that the cryopreservation procedure itself may cause the collagen metabolism to be on the degradable side, which will lead to valve failure.

Mechanisms of angioplasty and stent restenosis: implications for design of rational therapy

Restenosis after angioplasty or stenting remains the major limitation of both procedures. A vast array of drug therapies has been used to prevent restenosis, but they have proven to be predominantly unsuccessful. Recent trends in drug therapy have attempted to refine the molecular and biological targets of therapy, based on the assumption that a single biological process or molecule is critical to restenosis. In contrast, both stenting and brachytherapy, which are highly nonspecific, can successfully reduce restenosis after angioplasty or stenting, respectively. This review examines the biology of both angioplasty and stent stenosis, focussing on human studies. We also review the landmark human trials that have definitively proven successful therapies, such as stenting and brachytherapy. We suggest that the successful trials of stenting and brachytherapy and the failure of other treatments have highlighted the shortcomings of conventional animal models of arterial intervention, and gaps in our knowledge of human disease. In contrast to arguments advocating gene therapy, these studies suggest that the most likely successful drug therapy will have a wide therapeutic range, targeting as many of the components or biological processes contributing to restenosis as possible.

Neointimal thickening after stent delivery of paclitaxel: change in composition and arrest of growth over six months

OBJECTIVES

The purpose of this study was to determine long-term effects of stent-based paclitaxel delivery on amount, rate and composition of neointimal thickening after stent implantation.

BACKGROUND

Paclitaxel prevents vascular smooth muscle cell proliferation and migration in vitro and in vivo. These actions, coupled with low solubility, make it a viable candidate for modulating vascular responses to injury and prolonged effects after local delivery. We asked whether local delivery of paclitaxel for a period of weeks from a stent coated with a bioerodible polymer could produce a sustained reduction in neointimal hyperplasia for up to six months after stenting.

METHODS

Stainless steel stents were implanted in the iliac arteries of rabbits after endothelial denudation. Stents were uncoated or coated with a thin layer of poly(lactide-co-sigma-caprolactone) copolymer alone or containing paclitaxel, 200 microg.

RESULTS

Paclitaxel release in vitro followed first-order kinetics for two months. Tissue responses were examined 7, 28, 56 or 180 days after implantation. Paclitaxel reduced intimal and medial cell proliferation three-fold seven days after stenting and virtually eliminated later intimal thickening. Six months after stenting, long after drug release and polymer degradation were likely complete, neointimal area was two-fold lower in paclitaxel-releasing stents. Tissue responses in paclitaxel-treated vessels included incomplete healing, few smooth muscle cells, late persistence of macrophages and dense fibrin with little collagen.

CONCLUSIONS

Poly(lactide-co-sigma-caprolactone) copolymer-coated stents permit sustained paclitaxel delivery in a manner that virtually abolishes neointimal hyperplasia for months after stent implantation, long after likely completion of drug delivery and polymer degradation.

Detection of dissection and remodeling of atherosclerotic lesions in rabbits after balloon angioplasty by magnetic-resonance imaging

OBJECTIVE

To assess the usefulness of magnetic-resonance imaging (MRI) for monitoring acute changes after angioplasty of preexisting lesions in rabbits with basal lesions similar to those observed in humans.

METHODS

A combination of Fogarty balloon injury (1 week after initiation of diet) and a mildly hypercholesterolemic diet (0.2% cholesterol and 5% peanut oil) was used to promote the rapid formation of atherosclerotic lesions in 16 New Zealand white rabbits. After 5 months of the diet, angioplasty was performed on these lesions with a Grüntzig catheter in both iliac arteries and the abdominal aorta. MRI was used to monitor the initial formation of lesions after 3 and 5 months of the diet, and 2 days, 2 weeks, and 1 and 2 months after angioplasty.

RESULTS

The combination of early Fogarty injury and mildly hypercholesterolemic diet induced fibroproliferative lesions similar to type Vb atherosclerotic lesions seen in humans. Angioplasty induced deep dissections at the shoulders of lesions in the majority of animals. These dissections often extended into the media. The cellular, proliferative response after angioplasty was localized and limited to sites of dissection. A significant increase in area of arterial wall was observed after angioplasty at sites of dissection without any loss of lumen. In contrast, proximal and distal to the sites of injury, there was no change in wall area but a transient reduction in lumen area.

CONCLUSIONS

Comparison of MRI results with histology confirmed that changes in the wall and lumen, including small linear dissections in the lesions and arterial remodeling, are detectable by MRI.

The mechanisms of coronary restenosis: insights from experimental models

Since its introduction into clinical practice, more than 20 years ago, percutaneous transluminal coronary angioplasty (PTCA) has proven to be an effective, minimally invasive alternative to coronary artery bypass grafting (CABG). During this time there have been great improvements in the design of balloon catheters, operative procedures and adjuvant drug therapy, and this has resulted in low rates of primary failure and short-term complications. However, the potential benefits of angioplasty are diminished by the high rate of recurrent disease. Up to 40% of patients undergoing angioplasty develop clinically significant restenosis within a year of the procedure. Although the deployment of endovascular stents at the time of angioplasty improves the short-term outcome, 'in-stent' stenosis remains an enduring problem. In order to gain an insight into the mechanisms of restenosis, several experimental models of angioplasty have been developed. These have been used together with the tools provided by recent advances in molecular biology and catheter design to investigate restenosis in detail. It is now possible to deliver highly specific molecular antagonists, such as antisense gene sequences, to the site of injury. The knowledge provided by these studies may ultimately lead to novel forms of intervention. The present review is a synopsis of our current understanding of the pathological mechanisms of restenosis.

Pentoxifylline inhibits neointimal formation and stimulates constrictive vascular remodeling after arterial injury

Pentoxifylline (PTX) is a phosphodiesterase inhibitor used in the treatment of peripheral vascular disease, and this agent can suppress inflammatory vascular damage. Inflammation has been implicated in vascular lesion formation, and we examined the effects of PTX in a model of arterial injury. Sprague-Dawley rats were treated with intraperitoneal PTX (75 mg/kg/day) or saline starting 3 days before carotid balloon injury, and killed 24 h or 14 days later. Carotid arteries were analyzed by cross-sectional morphometry, immunostaining for proliferating cell nuclear antigen (PCNA) and subjected to terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL). Moreover, the effects of PTX on vascular smooth-muscle cell (VSMC) migration and production of collagen types I, IV, and VI were examined in vitro. At 14 days after balloon injury, PTX reduced the neointimal area (0.074+/-0.001 vs. 0.172+/-0.003 mm2; p<0.001), media area (0.143+/-0.001 vs. 0.176+/-0.001 mm2; p<0.01), intima/media ratio (0.50+/-0.02 vs. 0.99+/-0.12; p<0.001), and total vessel area (0.601+/-0.010 vs. 0.744+/-0.011 mm2; p<0.01). The lumen area, PCNA expression, and TUNEL were similar in the two treatment groups, whereas the neointimal cell density was increased by PTX (3,476+/-504 cells/mm2 vs. 2,215+/-232 cells/mm2; p<0.05). In vitro, PTX inhibited VSMC production of collagen type I in a concentration-dependent manner and did not influence VSMC migration. We conclude that PTX inhibits neointimal formation and induces constrictive vascular remodeling in the rat model of balloon injury by mechanisms involving decreased VSMC collagen type I production.

The extracellular matrix in balloon arterial injury: a novel target for restenosis prevention

The role of the extracellular matrix (ECM) in the pathobiology of restenosis has not been fully appreciated. Recent discoveries have shown the ECM to be a complex, heterogeneous structure whose components are dynamically altered in response to vascular injury. This report reviews the structure and function of vascular ECM and the importance of the matrix in modulating the vascular response to arterial injury such as balloon angioplasty and atherosclerosis.