Characterization of differential gene expression in quiescent and invasive human arterial smooth muscle cells

Molecular signatures of atherosclerotic plaques: An up-dated panel of protein related markers

Atherosclerosis remains the leading cause of ischemic syndromes such as myocardial infarction or brain stroke, mainly promoted by plaque rupture and subsequent arterial blockade. Identification of vulnerable or high-risk plaques constitutes a major challenge, being necessary to identify patients at risk of occlusive events in order to provide them with appropriate therapies. Clinical imaging tools have allowed the identification of certain structural indicators of prone-rupture plaques, including a necrotic lipidic core, intimal and adventitial inflammation, extracellular matrix dysregulation, and smooth muscle cell depletion and micro-calcification. Additionally, alternative approaches focused on identifying molecular biomarkers of atherosclerosis have also been applied. Among them, proteomics has provided numerous protein markers currently investigated in clinical practice. In this regard, it is quite uncertain that a single molecule can describe plaque rupture, due to the complexity of the process itself. Therefore, it should be more accurate to consider a set of markers to define plaques at risk. Herein, we propose a selection of 76 proteins, from classical inflammatory to recently related markers, all of them identified in at least two proteomic studies analyzing unstable atherosclerotic plaques. Such panel could be used as a prognostic signature of plaque instability.

Molecular regulation of vascular smooth muscle cell phenotype switching by trophoblast cells at the maternal-fetal interface

INTRODUCTION

Establishment of hemochorial placenta is associated with development and remodelling of uterine vasculature at the maternal fetal interface. This results in calibration of high resistance uterine arteries to flaccid low resistance vessels resulting in increased blood flow to the placenta and fetus in humans and rodents. Mechanisms underlying these remodelling events are poorly understood. In this report, we examine regulation of vascular remodelling using vascular smooth muscle cell (VSMC) phenotype switching as a primary parameter.

METHODS

Cellular dynamics was assessed by Immunofluorescence, qRT-PCR, western blotting in timed pregnant rat tissue. In vitro co-culture of trophoblast cells with vascular smooth muscle cells was used to understand regulation mechanism.

RESULTS

Analysis of cellular dynamics on days 13.5, 16.5 and 19.5 of gestation in the rat metrial gland, the entry point of uterine arteries, revealed that invasion of trophoblast cells preceded disappearance of VSMC α-SMA, a contractile state marker. Co-culture of VSMCs with trophoblast cells in vitro recapitulated trophoblast-induced de-differentiation of VSMCs in vivo. Interestingly, co-culturing with trophoblast cells activated PDGFRβ signalling in VSMCs, an effect mediated by secreted PDGF-BB from trophoblast cells. Trophoblast cells failed to elicit its effect on VSMC de-differentiation upon inhibition of PDGFRβ signalling using a selective inhibitor. Moreover, co-culturing with trophoblast cells also led to substantial increase in Akt activation and a modest increase in Erk phosphorylation in VSMCs and this effect was abolished by PDGFRβ inhibition.

DISCUSSION

Our results highlight that trophoblast cells direct VSMC phenotype switching and trophoblast derived PDGF-BB is one of the modulator.

Serotonin-Exacerbated DSS-Induced Colitis Is Associated with Increase in MMP-3 and MMP-9 Expression in the Mouse Colon

Background. 5-HT enhances dextran sulfate sodium- (DSS-) induced colitis and is involved in inflammatory bowel disease (IBD). Matrix metalloproteinases (MMPs) play roles in the process of intestinal inflammation. Aims. To examine whether 5-HT induces MMPs expression in mouse colon to enhance DSS-induced colitis. Materials and Methods. C57BL/6J (B6) mice were treated with either low-dose (1.0 mg/kg) or high-dose (2.0 mg/kg) 5-HT by enema, low-dose (1.0%) or high-dose (2.5%) DSS, or combined low-dose (1.0%) DSS and (1.0 mg/kg) 5-HT. Mouse colitis was analyzed. MMPs and tissue inhibitors of MMPs (TIMPs) mRNA were measured by real-time quantitative RT-PCR in mouse colon and in human Caco-2 cells and neutrophils. MMP-3 and MMP-9 protein levels were quantified from immunohistochemistry (IHC) images of mouse colons. Results. 5-HT exacerbated DSS-induced colitis, low-dose 5-HT induces both MMP-3 and MMP-9, and high-dose 5-HT only increased MMP-3 mRNA expression in mouse colon. Mouse colon MMP-3 and MMP-9 protein levels were also elevated by 5-HT treatment. The MMP-2, TIMP-1, and TIMP-2 mRNA levels were increased in the inflamed colon. 5-HT induced MMP-3 and MMP-9 mRNA expression in Caco-2 and human neutrophils, respectively, in vitro. Conclusion. 5-HT induced MMP-3 and MMP-9 expression in mouse colon; these elevated MMPs may contribute to DSS-induced colitis.

Detection of TFPI2 methylation in the serum of hepatocellular carcinoma patients

BACKGROUND

DNA methylation plays a key role in hepatocellular carcinogenesis and progression. Analysis of aberrant methylation in serum DNA might provide a strategy for noninvasive detection of hepatocellular carcinoma (HCC).

METHODS

To explore the feasibility of this approach, we compared TFPI2 methylation status in serum samples of HCC, chronic hepatitis B (CHB) patients and normal control groups using methylation-specific polymerase chain reaction.

RESULTS

Our results showed that the percentage of serum TFPI2 promoter methylation was significantly higher in the HCC group (46.5 %, 20/43) compared with the CHB group (16.7 %, 4/24; p = 0.015) and the normal control group (19.2 %, 5/26; p = 0.022), respectively, indicating that TFPI2 methylation frequently existed in the serum of HCC patients. In our study, the detection rate of HCC using serum TFPI2 methylation was 46.5 % (20/43), which was quite close to the reported detection rate of α-fetoprotein (54 %). In cases where we combined both markers, the detection rate was 61.0 %, suggesting that serum TFPI2 methylation could be used as a potential marker for noninvasive detection of HCC. Then, we evaluated the correlation between the serum TFPI2 methylation status of HCC patients and their clinicopathological parameters. Patients with advanced TNM stage (III-IV) showed a significantly elevated serum methylation percentage of TFPI2 in comparison with those with early TNM stage (I-II) (p = 0.025). Moreover, TFPI2 methylation was observed more frequently according to the progression of TNM stage.

CONCLUSIONS

Our present study suggested that TFPI2 methylation in serum tended to be detected more easily in patients with advanced HCC and might be used as a predictor of HCC progression.

Molecular imaging of vasa vasorum neovascularization via DEspR-targeted contrast-enhanced ultrasound micro-imaging in transgenic atherosclerosis rat model

PURPOSE

Given that carotid vasa vasorum neovascularization is associated with increased risk for stroke and cardiac events, the present in vivo study was designed to investigate molecular imaging of carotid artery vasa vasorum neovascularization via target-specific contrast-enhanced ultrasound (CEU) micro-imaging.

PROCEDURES

Molecular imaging was performed in male transgenic rats with carotid artery disease and non-transgenic controls using dual endothelin1/VEGFsp receptor (DEspR)-targeted microbubbles (MB(D)) and the Vevo770 micro-imaging system and CEU imaging software.

RESULTS

DEspR-targeted CEU-positive imaging exhibited significantly higher contrast intensity signal (CIS)-levels and pre-/post-destruction CIS-differences in seven of 13 transgenic rats, in contrast to significantly lower CIS-levels and differences in control isotype-targeted microbubble (MB(C))-CEU imaging (n = 8) and in MB(D) CEU-imaging of five non-transgenic control rats (P < 0.0001). Ex vivo immunofluorescence analysis demonstrated binding of MB(D) to DEspR-positive endothelial cells; and association of DEspR-targeted increased contrast intensity signals with DEspR expression in vasa vasorum neovessel and intimal lesions. In vitro analysis demonstrated dose-dependent binding of MB(D) to DEspR-positive human endothelial cells with increasing %cells bound and number of MB(D) per cell, in contrast to MB(C) or non-labeled microbubbles (P < 0.0001).

CONCLUSION

In vivo DEspR-targeted molecular imaging detected increased DEspR-expression in carotid artery lesions and in expanded vasa vasorum neovessels in transgenic rats with carotid artery disease. Future studies are needed to determine predictive value for stroke or heart disease in this transgenic atherosclerosis rat model and translational applications.

Matrix metalloproteinase (MMP)-3 activates MMP-9 mediated vascular smooth muscle cell migration and neointima formation in mice

OBJECTIVE

Several matrix metalloproteinases (MMPs) have been implicated in extracellular matrix destruction and other actions that lead to plaque rupture and myocardial infarction. Conversely, other MMPs have been shown to promote vascular smooth muscle cell (VSMC)-driven neointima formation, which contributes to restenosis, fibrous cap formation, and plaque stability. MMP-3 knockout reduced VSMC accumulation in mouse atherosclerotic plaques, implicating MMP-3 in neointima formation. We therefore investigated the effect of MMP-3 knockout on neointima formation after carotid ligation in vivo and VSMC migration in vitro.

METHODS AND RESULTS

Twenty-eight days after left carotid ligation, MMP-3 knockout significantly reduced neointima formation (75%, P<0.01) compared with wild-type (WT) littermates, and also reduced remodeling of ligated and contralateral carotid arteries. Gelatin zymography illustrated that MMP-3 knockout abolished MMP-9 activation in ligated carotids and scratch-wounded VSMC cultures. MMP-3 knockout also attenuated VSMC migration into a scratch wound by 59% compared with WT cells. Addition of exogenous MMP-3 or activated MMP-9 restored migration of MMP-3 knockouts to that of WT VSMCs, but exogenous MMP-3 had no effect on migration in MMP-9 knockout VSMCs. MMP-9 knockout or knockdown with small interfering RNA significantly retarded VSMC migration to the same extent as MMP-3 knockout.

CONCLUSIONS

These results indicate for the first time that MMP-3 mediated activation of MMP-9 is required for efficient neointima formation after carotid ligation in vivo and for VSMC migration in vitro, whereas MMP-12 plays a redundant role. These findings add to the understanding of MMP action in plaque stability and restenosis.

Differentiation patterning of vascular smooth muscle cells (VSMC) in atherosclerosis

To investigate the involvement of transdifferentiation and dedifferentiation phenomena inside atherosclerotic plaques, we analyzed the differentiation status of vascular smooth muscle cells (VSMC) in vitro and in vivo. Forty normal autoptic and 20 atherosclerotic carotid endarterectomy specimens as well as 20 specimens of infrarenal and suprarenal aortae were analyzed for the expression of cytokeratins 7 and 18 and beta-catenin as markers (epithelial transdifferentiation) as well as CD31 and CD34 (embryonic dedifferentiation) by conventional and double fluorescence immunohistochemistry and reverse transcription polymerase chain reaction. Looking at these markers, additional cell culture experiments with human aortic (HA)-VSMC were done under stimulation with IL-1beta, IL-6, and TNF-alpha. Cytokeratins and beta-catenin were expressed significantly higher in atherosclerotic than in normal carotids primarily localized in VSMC of the shoulder/cap region of atherosclerotic lesions. Additionally, heterogeneous cellular coexpression of CD31 and/or CD34 was observed in subregions of progressive atherosclerotic lesions by VSMC. The expression of those differentiation markers by stimulated HA-VSMC showed a time and cytokine dependency in vitro. Our findings show that (1) VSMC of progressive atheromas have the ability of differentiation, (2) that transdifferentiation and dedifferentiation phenomena are topographically diverse localized in the subregions of advanced atherosclerotic lesions, and (3) are influenced by inflammatory cytokines like IL-1beta, IL-6, and TNF-alpha.

Benzo[a]pyrene induces expression of matrix metalloproteinases and cell migration and invasion of vascular smooth muscle cells

Benzo[a]pyrene (B[a]P) has been shown to accelerate atherosclerosis development in animal models. However, the mechanisms that B[a]P induces atherogenesis are unclear. Abnormal migration and invasion of vascular smooth muscle cells (VSMCs) is a major contributor to the development of atherosclerotic lesions. In this article, we demonstrated that B[a]P promoted the migration and invasion of rat VSMCs. B[a]P increased the mRNA levels of matrix metalloproteinase (MMP) 1, 2, 3, and 9. The MMPs inhibitor GM6001 inhibited B[a]P-induced invasion of VSMCs. Among the MMPs mentioned above, MMP-3 had the maximal induction. Mechanistic studies indicate that B[a]P-induced transcriptional activation of MMP-3 is not mediated by AP-1, NF-kappaB. B[a]P-induced expression of MMPs was attenuated by alpha-naphthoflavone, the aryl hydrocarbon receptor antagonist. In addition, alpha-naphthoflavone inhibited B[a]P-induced migration and invasion of VSMCs. These results suggest that the aryl hydrocarbon receptor plays an important role in B[a]P-induced expression of MMPs and migration and invasion of VSMC. Our findings may reveal a novel role of B[a]P in inducing atherogenesis.

Tissue factor pathway inhibitor-2 gene methylation is associated with low expression in carotid atherosclerotic plaques

BACKGROUND

The tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine-protease inhibitor which is expressed in atherosclerotic plaques. Epigenetic regulation of the TFPI-2 gene, through methylation of CpG islands, has been advocated in cancer. We hypothesized that TFPI-2 gene methylation could regulate TFPI-2 expression in atherosclerosis.

METHODS

We used Methylation Specific PCR (MSP) and pyrosequencing in order to identify 18 CpG of the TFPI-2 promoter, in 59 carotid atherosclerotic plaques and 26 control mammary arteries.

RESULTS

MSP showed methylation of the TFPI-2 gene (MSP+) in 16 plaques (27%), while no methylation (MSP-) was found in control arteries. Pyrosequencing confirmed that MSP+ plaques presented higher methylation levels than MSP- ones and arteries (p=0.03 and 0.01). Moreover, the TFPI-2 mRNA levels were lower in methylated plaques than in unmethylated ones and than in arteries (p=0.04 and <0.0001). The methylated plaques contained less lipids and macrophage infiltration than unmethylated ones. Their TFPI-2 immunoreactivity was mainly detected in the macrophages located in the media on the adventitial side, rather than in the lipid-rich core.

CONCLUSION

Methylation of the TFPI-2 gene takes place in atherosclerotic plaques and is associated with decreased TFPI-2 expression. The place of this process in atherosclerosis progression remains to be investigated.

Tissue factor pathway inhibitor-2 was repressed by CpG hypermethylation through inhibition of KLF6 binding in highly invasive breast cancer cells

Background

Tissue factor pathway inhibitor-2 (TFPI-2) is a matrix-associated Kunitz inhibitor that inhibits plasmin and trypsin-mediated activation of zymogen matrix metalloproteinases involved in tumor progression, invasion and metastasis. Here, we have investigated the mechanism of DNA methylation on the repression of TFPI-2 in breast cancer cell lines.

Results

We found that both protein and mRNA of TFPI-2 could not be detected in highly invasive breast cancer cell line MDA-MB-435. To further investigate the mechanism of TFPI-2 repression in breast cancer cells, 1.5 Kb TFPI-2 promoter was cloned, and several genetic variations were detected, but the promoter luciferase activities were not affected by the point mutation in the promoter region and the phenomena was further supported by deleted mutation. Scan mutation and informatics analysis identified a potential KLF6 binding site in TFPI-2 promoter. It was revealed, by bisulfite modified sequence, that the CpG island in TFPI-2 promoter region was hypermethylated in MDA-MB-435. Finally, using EMSA and ChIP assay, we demonstrated that the CpG methylation in the binding site of KLF-6 diminished the binding of KLF6 to TFPI-2 promoter.

Conclusion

In this study, we found that the CpG islands in TFPI-2 promoter was hypermethylated in highly invasive breast cancer cell line, and DNA methylation in the entire promoter region caused TFPI-2 repression by inducing inactive chromatin structure and decreasing KLF6 binding to its DNA binding sequence.

Differential display fingerprints: new approach to characterize smooth muscle cells and human coronary atherectomy tissues

AIM OF THE STUDY

Smooth muscle cells build up the normal media and stabilize atherosclerotic lesions whereas an inflammatory component is determinant for unstable angina. Smooth muscle cells, currently identified by alpha-actin, present a phenotypic heterogeneity and alpha-actin can be reduced in pathology. We tried to characterize vascular cell types, particularly smooth muscle cells, and coronary atherosclerotic tissues, by random genes expression fingerprints.

MATERIALS AND METHODS

Expression fingerprints (cDNA electrophoresis) were performed by differential display reverse transcriptase-polymerase chain reaction. Variability of fingerprints was studied for a panel of arterial muscle cell phenotypes and comparisons were made with fingerprints from other cell types (endothelial cells and macrophages). The technique was then applied to human coronary atherectomy samples compared to control human arterial (mammary) smooth muscle.

RESULTS

Arterial smooth muscle cells fingerprints were overall similar whatever the cell phenotype (native contractile, dedifferentiated in culture or epithelioid). Moreover, with two primer pairs, the muscular fingerprints markedly differed from the endothelial and the monocytic fingerprints. Application of differential display to coronary atherectomy samples was feasible. Interestingly, the pathological tissues exhibited either smooth muscle-like or smooth muscle-divergent fingerprints.

CONCLUSIONS

Smooth muscle cells and inflammatory cells exhibited distinct differential display fingerprint patterns. Thus, a simple expression profile of arbitrary genes provides a molecular bar code tool (pattern signature) useful to characterize vascular cell cultures or tissues. The present work proposes a method to analyze coronary atherectomy samples which estimates their whole quality, muscular versus non muscular (inflammatory), this is of interest for clinical research.

Eukaryotic expression of human arresten gene and its effect on the proliferation of vascular smooth muscle cells

The eukaryotic expression of human arresten gene and its effect on the proliferation of in vitro cultured vascular smooth cells (VSMCs) in vitro were investigated. COS-7 cells were transfected with recombinant eukaryotic expression plasmid pSecTag2-AT or control plasmid pSecTag2 mediated by liposome. Forty-eight h after transfection, reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the expression of arresten mRNA in the cells, while Western blot assay was applied to detect the expression of arresten protein in concentrated supernatant. Primary VSMCs from thoracic aorta of male Sprague-Dawley rats were cultured using the tissue explant method, and identified by immunohistochemical staining with a smooth muscle-specific anti-alpha-actin monoclonal antibody before serial subcultivation. VSMCs were then co-cultured with the concentrated supernatant and their proliferation was detected using Cell Counting Kit-8 (CCK-8) in vitro. The results showed that RT-PCR revealed that the genome of arresten-transfected cells contained a 449 bp specific fragment of arresten gene, suggesting the successful transfection. Successful protein expression in supernatants was confirmed by Western blot. CCK-8 assay showed that the proliferation of VSMCs were inhibited significantly by arresten protein as compared with control cells (F=40.154, P<0.01). It was concluded that arresten protein expressed in eukaryotic cells can inhibit proliferation of VSMCs effectively in vitro, which would provide possibility to the animal experiments.

Cell transplantation preserves matrix homeostasis: A novel paracrine mechanism

OBJECTIVES

Cell transplantation prevents chamber dilatation, but the underlying molecular mechanisms remain undefined. Structural cardiac remodeling involves matrix degradation from an imbalance of matrix metalloproteinases (MMP) relative to endogenous tissue inhibitors of metalloproteinases (TIMP). We aimed to determine the capacity of cell transplantation to alter extracellular matrix in the failing heart and, in so doing, identify novel paracrine molecular mediators underlying the beneficial effects of cell transplantation on chamber dilatation.

METHODS

Smooth muscle cells were transplanted to the dilating left ventricle of cardiomyopathic hamsters (CTX, n = 15) compared with age-matched media-injected cardiomyopathic (CON, n = 15) and normal hamsters (n = 7). After 5 weeks, left ventricular volume was measured by computerized planimetry. Fibrillar collagen was examined by confocal microscopy. Matrix homeostasis was quantified by measuring MMP/TIMP expression/activity relative to myocardial collagen synthesis (14C-proline uptake).

RESULTS

Left ventricular dilatation was attenuated in CTX hearts (P = .02). CTX restored perimysial collagen fiber content and architecture to normal levels. TIMP-2 and TIMP-3 expression were enhanced in CTX (TIMP-2, 195% +/- 42% of CON, P = .02; TIMP-3, 118% +/- 3% of CON, P = .002), and correspondingly, gelatinase MMP-2 activity was reduced (P < .05). The TIMP:MMP ratio was increased in CTX hearts (TIMP-2 to MMP-2, 410% +/- 134% of CON, P = .04, and TIMP-3 to MMP-9, 205% +/- 47% of CON, P = .03), reflecting a reduced capacity for matrix degradation. Collagen synthesis was equivalent (CTX vs CON), suggesting that restored matrix architecture was a function of attenuated matrix degradation.

CONCLUSIONS

These data provide the first evidence that cell transplantation limits ventricular dilatation in the failing heart through a paracrine-mediated mechanism that preserves extracellular matrix homeostasis.

Analysis of sequence variations in the promoter region of the human tissue factor pathway inhibitor 2 gene in apoplectic patients and blood donors

Tissue factor pathway inhibitor 2 (TFPI-2) is a Kunitz-type serine protease inhibitor with homology to TFPI-1, an important regulator of the extrinsic pathway of blood coagulation. Recent studies have focused on TFPI-2 and its implications for atherosclerosis. The promoter region and the exons of the human TFPI-2 gene were screened for sequence variations in 41 apoplectic patients and 140 blood donors with no history of ischemic stroke. The sequence variations -567T>C, -546T>C, -353A>G, -161G>C, -167G>A, -47C>A, and -18C>A, which are located in the TFPI-2 promoter, were discovered in both cohorts with allelic frequencies ranging from 0.3 to 2.4%. The influence of these sequence variations on the transcriptional activity of the TFPI-2 gene was investigated in HEK-293 cells using a promoter test system. A wild-type TFPI-2 promoter fragment 716 bp upstream of the translation start site was cloned into a secreted alkaline phosphatase expression vector, and the sequence variations were introduced by site-directed mutagenesis. Interestingly, the promoter activity of the tested mutants was reduced by 1.3- to 2.8-fold compared to that of wild-type control. The variation -18C>A, where a putative binding site of the transcription factor Sp-1 is located, had the strongest effect on transcriptional activity. In conclusion, our present study shows that the transcription of TFPI-2 is changed by single nucleotide polymorphisms and that the sequence variations in transcription factor binding sites of the TFPI-2 promoter may influence the regulation of this gene.

Divergent effects of matrix metalloproteinases 3, 7, 9, and 12 on atherosclerotic plaque stability in mouse brachiocephalic arteries

Matrix metalloproteinases (MMPs) are thought to be involved in the growth, destabilization, and eventual rupture of atherosclerotic lesions. Using the mouse brachiocephalic artery model of plaque instability, we compared apolipoprotein E (apoE)/MMP-3, apoE/MMP-7, apoE/MMP-9, and apoE/MMP-12 double knockouts with their age-, strain-, and sex-matched apoE single knockout controls. Brachiocephalic artery plaques were significantly larger in apoE/MMP-3 and apoE/MMP-9 double knockouts than in controls. The number of buried fibrous layers was also significantly higher in the double knockouts, and both knockouts exhibited cellular compositional changes indicative of an unstable plaque phenotype. Conversely, lesion size and buried fibrous layers were reduced in apoE/MMP-12 double knockouts compared with controls, and double knockouts had increased smooth muscle cell and reduced macrophage content in the plaque, indicative of a stable plaque phenotype. ApoE/MMP-7 double knockout plaques contained significantly more smooth muscle cells than controls, but neither lesion size nor features of stability were altered in these animals. Hence, MMP-3 and MMP-9 appear normally to play protective roles, limiting plaque growth and promoting a stable plaque phenotype. MMP-12 supports lesion expansion and destabilization. MMP-7 has no effect on plaque growth or stability, although it is associated with reduced smooth muscle cell content in plaques. These data demonstrate that MMPs are directly involved in atherosclerotic plaque destabilization and clearly show that members of the MMP family have widely differing effects on atherogenesis.

Platelet-derived growth factor-BB (PDGF-BB) induces differentiation of bone marrow endothelial progenitor cell-derived cell line TR-BME2 into mural cells, and changes the phenotype

Blood vessels are composed of endothelial cells (EC) and mural cells, and the interaction between EC and mural cells is essential for the development and maintenance of the vasculature. EC differentiate from bone marrow-derived endothelial progenitor cells (EPC). Recently, we established a conditionally immortalized bone marrow EPC-derived cell line, TR-BME2, and a brain capillary EC (BCEC) line, TR-BBB, from temperature-sensitive-SV40 T-antigen gene transgenic rats. To understand the function of EPC, it is important to analyze the difference between EPC and mature EC such as BCEC. In this study, we identified EPC-specific genes by means of subtractive hybridization between TR-BME2 and TR-BBB. There was no significant difference between TR-BME2 and TR-BBB in the mRNA level of annexin II, which is expressed in EC. In contrast, the mRNA level of smooth muscle cell (SMC) markers such as smooth muscle protein 22 (SM22), calvasculin, and platelet-derived growth factor (PDGF) receptor-beta, was higher in TR-BME2 than in TR-BBB. Moreover, the mRNA level of contractile SMC markers, such as smooth muscle alpha-actin and SM22, was increased in the absence of EC growth factors, such as vascular endothelial growth factor. The mRNA level of synthetic SMC markers, such as matrix Gla protein, was increased by the addition of PDGF-BB. The SMC derived from TR-BME2 showed an altered phenotype, from contractile-type to synthetic-type, when they were cultured in the absence of PDGF-BB. These results show that TR-BME2 cells have higher levels of SMC markers compared with mature EC, and can differentiate into contractile- or synthetic-type SMC.

Thrombospondin 1 as possible key factor in the hemocompatibility of endocoronary prostheses

Intracoronary stenting has markedly improved the patency of native coronary arteries after percutaneous transluminal coronary angioplasty (PTCA). Advances in stent technology and design, including drug releasing stents, have contributed to reduce the long-term restenosis rate. However, stenosis caused by neointimal hyperplasia, vascular remodeling and thrombosis is still a major problem after endocoronary stent procedures. This study focuses on differential gene expression of circulating peripheral blood cells after 90 min exposure to stents to search for initially activated cellular pathways, which may foster restenosis. Fresh human whole blood (1 IU heparin/ml), taken from non-medicated healthy volunteers, was incubated under flow conditions in an in vitro closed-loop stent-testing model (modified Chandler-Loop). Differential gene expression compared to resting conditions and to the experimental controls was investigated by a DNA-microarray technique encoding for over 17,000 genes simultaneously. As expected, a large variety of genes showed differential gene expression. Interestingly, Thrombospondin 1 (TSP-1), which plays a key role in initial immune defense, was found to be the most markedly up-regulated gene. We propose TSP-1 expression as an early indicator for the activation of immune responses following intracoronary stenting. After clarifying the participation of TSP-1 in vivo, future studies will therefore focus on TSP-1 as a potential prognostic factor, which may also help to develop and control new surface materials with an improved biocompatibility.

Altered expression balance of matrix metalloproteinases and their inhibitors in human carotid plaque disruption: results of quantitative tissue analysis using real-time RT-PCR method

BACKGROUND

The balance between degradation and synthesis of extracellular matrix determines its content in atherosclerotic tissue. To examine the role of expression balance of matrix metalloproteinases (MMPs) to their inhibitors, tissue inhibitors of metalloproteinases (TIMPs) and tissue factor pathway inhibitor-2 (TFPI-2) in the development and disruption of atherosclerotic plaque, these gene expressions in human carotid plaque were quantitatively determined by real-time reverse transcription (RT)-polymerase chain reaction (PCR) method.

METHODS

Total RNA for cDNA synthesis was extracted from tissues in 24 patients with carotid endarterectomy. The amounts of cDNAs for MMP-1, -2, -3 and -9, TFPI-2 and TIMP-1, -2 and -3 were determined by real-time RT-PCR method, and normalized with glutaraldehyde 3-dehydrogenase.

RESULTS

In plaques, the expression MMP-1 (1.53+/-0.25, mean+/-S.E.M.), MMP-3 (1.99+/-0.59) and MMP-9 (2.00+/-0.51) was augmented compared to those in the adjacent control regions (0.60+/-0.16, 0.46+/-0.18 and 0.58+/-0.21, respectively, p<0.05). The expression of TFPI-2 was lower in plaques (0.32+/-0.08) than in controls (0.94+/-0.23, p<0.01). Although the expression of TIMP-1 was higher in plaques (1.28+/-0.23) than in controls (0.81+/-0.10, p<0.05), the indices of MMP-1/TIMP-1, MMP-3/TIMP-3 and MMP-9/TIMP-1 were still significantly higher in plaques. Interestingly, MMP-9 and the resulting MMP-9/TIMP-1 balance in plaques with disruption were significantly higher (3.36+/-1.52 and 1.66+/-0.12, n=11) than those in non-disrupted plaques (1.11+/-0.52 and 0.76+/-0.12, n=13, p<0.05).

CONCLUSION

With the decreased expression of TFPI-2, upregulation of MMPs in atherosclerotic plaque was disproportional to that of TIMPs, suggesting that imbalanced degradation and synthesis of extracellular matrix persists in advanced lesions, particularly in plaques with disruption.

Expression profiling of cardiovascular disease

Cardiovascular disease is the most important cause of morbidity and mortality in developed countries, causing twice as many deaths as cancer in the USA. The major cardiovascular diseases, including coronary artery disease (CAD), myocardial infarction (MI), congestive heart failure (CHF) and common congenital heart disease (CHD), are caused by multiple genetic and environmental factors, as well as the interactions between them. The underlying molecular pathogenic mechanisms for these disorders are still largely unknown, but gene expression may play a central role in the development and progression of cardiovascular disease. Microarrays are high-throughput genomic tools that allow the comparison of global expression changes in thousands of genes between normal and diseased cells/tissues. Microarrays have recently been applied to CAD/MI, CHF and CHD to profile changes in gene expression patterns in diseased and non-diseased patients. This same technology has also been used to characterise endothelial cells, vascular smooth muscle cells and inflammatory cells, with or without various treatments that mimic disease processes involved in CAD/MI. These studies have led to the identification of unique subsets of genes associated with specific diseases and disease processes. Ongoing microarray studies in the field will provide insights into the molecular mechanism of cardiovascular disease and may generate new diagnostic and therapeutic markers.

The effects of high glucose and atorvastatin on endothelial cell matrix production

BACKGROUND

Statins are known to enhance atherosclerotic plaque stability through influences on extracellular matrix homeostasis. Net matrix production reflects the relative balance of matrix production and degradation through enzymes such as matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitor of MMP (TIMPs). The effects of statins on endothelial cell production of these parameters following co-exposure with a proatherogenic stimulus such as high glucose are not known.

METHODS

Human endothelial cells were exposed for 72 h to 5 mm (control) or 25 mm (high) glucose +/- atorvastatin (1 micromol/l). Extracellular matrix homeostasis was assessed by measuring matrix metalloproteinase (MMP)-2 secretion, tissue inhibitor of MMP (TIMP)-1 and -2 secretion and net collagen IV production. Results were expressed as percentage +/- SEM of control values.

RESULTS

Exposure to high glucose increased cellular collagen IV expression to 190.1 +/- 11.7% (P < 0.0001) of control levels. No change in MMP-2 secretion (111.6 +/- 5.2%; P > 0.05) was observed but both TIMP-1 and TIMP-2 expression were increased to 136.3 +/- 6.4% and 144.0 +/- 27.5%, respectively (both P < 0.05). The presence of atorvastatin in high glucose conditions reduced collagen IV expression to 136.1 +/- 20.6%. This was paralleled by increased secretion of MMP-2 to 145.8 +/- 7.8% (P < 0.01), increased TIMP-2 expression to 208.0 +/- 21.3% (P < 0.005 compared with high glucose) but no change in TIMP-1 expression (155.1 +/- 14.6%) compared with high glucose alone. The presence of atorvastatin in control conditions did not affect levels of collagen IV expression (114.5 +/- 13.2%).

CONCLUSIONS

Endothelial cell exposure to high glucose was associated with a MMP/TIMP profile that increased extracellular matrix production which was attenuated by concurrent exposure to atorvastatin. Consequently, a mechanism by which the atherosclerotic plaque regression that is observed in patients taking these drugs has been demonstrated.

Physiological genomics of human arteries: quantitative relationship between gene expression and arterial stiffness

BACKGROUND

Previous genomic studies with human tissues have compared differential gene expression between 2 conditions (ie, normal versus diseased) to identify altered gene expression in a binary manner; however, a potentially more informative approach is to correlate the levels of gene expression with quantitative physiological parameters.

METHODS AND RESULTS

In this study, we have used this approach to examine genes whose expression correlates with arterial stiffness in human aortic specimens. Our data identify 2 distinct groups of genes, those associated with cell signaling and those associated with the mechanical regulation of vascular structure (cytoskeletal-cell membrane-extracellular matrix). Although previous studies have concentrated on the contribution of the latter group toward arterial stiffness, our data suggest that changes in expression of signaling molecules play an equally important role. Alterations in the profiles of signaling molecules could be involved in the regulation of cell cytoskeletal organization, cell-matrix interactions, or the contractile state of the cell.

CONCLUSIONS

Although the influence of smooth muscle contraction/relaxation on arterial stiffness could be controversial, our provocative data would suggest that further studies on this subject are indicated.

Arterial smooth muscle cell heterogeneity: implications for atherosclerosis and restenosis development

During atheromatous plaque formation or restenosis after angioplasty, smooth muscle cells (SMCs) migrate from the media toward the intima, where they proliferate and undergo phenotypic changes. The mechanisms that regulate these phenomena and, in particular, the phenotypic modulation of intimal SMCs have been the subject of numerous studies and much debate during recent years. One view is that any SMCs present in the media could undergo phenotypic modulation. Alternatively, the seminal observation of Benditt and Benditt that human atheromatous plaques have the features of a monoclonal or an oligoclonal lesion has led to the hypothesis that a predisposed, medial SMC subpopulation could play a crucial role in the production of intimal thickening. The presence of a distinct SMC population in the arterial wall implies that under normal conditions, SMCs are phenotypically heterogeneous. The concept of SMC heterogeneity is gaining wider acceptance, as shown by the increasing number of publications on this subject. In this review, we discuss the in vitro studies that demonstrate the presence of distinct SMC subpopulations in arteries of various species, including humans. Their specific features and their regulation will be highlighted. Finally, the relevance of an atheroma-prone phenotype to intimal thickening formation will be discussed.

Decrease of vascular smooth muscle cell locomotion by abciximab, but not tirofiban: a possible role of different affinity to alpha v beta 3 integrins

AIM

The EPISTENT and EPIC studies demonstrated a reduction of clinically driven re-interventions after percutaneous transluminal coronary angioplasty (PTCA) and stent implantation in patients treated with abciximab, while for tirofiban no similar effects could be demonstrated. This may be explained by the different effects on the migratory and invasive potential of vascular smooth muscle cells (VSMCs) by integrin alpha v beta 3 blockade. Therefore, the objective of this study was to compare the effectiveness of abciximab and tirofiban to affect VSMC migration and invasion.

METHODS

Vascular smooth muscle cells were treated with abciximab (0.1-1 microg/ml), tirofiban (0.1-1 microg/ml), and the alpha v beta 3 specific antibody LM609 (1-5 microg/ml), that was used as a positive control during the assay (treatment) over 24 h before the assay (pre-treatment), or before and during the assay (combined treatment). Sodium 3'-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis (4-methoxyy-6-nitro) benzene sulfonic acid (XTT)-assay and cell counting measured the influence of the substances on VSMC proliferation. Using a Boyden Chamber model, the capability of VSMCs for migration and invasion was tested with different chemo-attractants and barriers.

RESULTS

Any influence of the platelet glycoprotein (GP) IIb/IIIa receptor (integrin alpha IIb beta 3) antagonists on VSMC proliferation could be excluded. After combined treatment, abciximab demonstrated a dose-dependent inhibition of migration (IC50 = 33 microg/ml) and invasion (IC50 = 0.5 microg/ml) of VSMCs. Administration during the assay without pre-treatment inhibited migration similarly (IC50 = 32 microg/ml) but invasion to a significant lower extent (IC50 = 44 microg/ml). Administration of tirofiban during the assay with or without pre-treatment had no inhibitory effect on VSMC migration and invasion. Pre-treatment alone with one of the substances also did not alter VSMC migration or invasion.

CONCLUSION

Abciximab administration in physiological concentrations was capable of significantly inhibiting the migratory and invasive potential of VSMCs, while for tirofiban no similar effect could be demonstrated.