The mechanisms of coronary restenosis: insights from experimental models

Biodegradable Sirolimus-loaded Poly(lactide) Nanoparticles as Drug Delivery System for the Prevention of In-Stent Restenosis in Coronary Stent Application

The administration of drugs using biodegradable polymer nanoparticles as carriers has generated immense interest due to their excellent biocompatibility and the prolonged drug release. The scope of this work was to determine the applicability of sirolimus-loaded biodegradable poly(D,L-lactide) (PDLLA) nanoparticles as drug carriers to prevent restenotic processes after stent implantation. The average 250 nm sized 20%(w/w) sirolimus-loaded nanoparticles were extensively characterized with regard to in vitro degradation, biocompatibility and in vitro drug release. The particles show biphasic release kinetics consisting of a short burst release of 50%(w/w) sirolimus payload, followed by a longer, slower release phase, which are desirable for the application as a drug delivery carrier. All presented results exhibit the potential of sirolimus-loaded PDLLA nanoparticles as promising local and sustained drug delivery systems administered intraluminally to reduce in-stent restenosis after stent implantation.

CCN3 inhibits neointimal hyperplasia through modulation of smooth muscle cell growth and migration

OBJECTIVE

CCN3 belongs to the CCN family, which constitutes multifunctional secreted proteins that act as matrix cellular regulators. We investigated the pathophysiological roles of CCN3 in the vessels.

METHODS AND RESULTS

We examined the effects of CCN3 on the proliferation and migration of rat vascular smooth muscle cells (VSMC). CCN3 knockout mice were created, and vascular phenotypes and neointimal hyperplasia induced by photochemically induced thrombosis were investigated. CCN3 suppressed the VSMC proliferation induced by fetal bovine serum. The neutralizing antibody for transforming growth factor-beta did not affect the growth inhibitory effect of CCN3. Moreover, CCN3 enhanced the mRNA expression of cyclin-dependent kinase inhibitors, p21 and p15. Gamma secretase inhibitor, an inhibitor of Notch signaling, partially inhibited the enhanced expression of p21 induced by CCN3. CCN3 also inhibited the VSMC migration. Finally, the histopathologic evaluation of the arteries 21 days after the endothelial injury revealed a 6-fold enhancement of neointimal thickening in the null mice compared with the wild-type mice.

CONCLUSIONS

CCN3 suppresses neointimal thickening through the inhibition of VSMC migration and proliferation. Our findings indicate the involvement of CCN3 in vascular homeostasis, especially on injury, and the potential usefulness of this molecule in the modulation of atherosclerotic vascular disease.

Catheter thrombosis and percutaneous coronary intervention: fundamental perspectives on blood, artificial surfaces and antithrombotic drugs

Recent reports of catheter thrombosis among patients undergoing percutaneous coronary intervention (PCI) have had a significant impact on the development of new antithrombotic therapies. The overall incidence of this complication is unknown, mainly because of underreporting in contemporary clinical trials of coronary intervention. The etiology and pathophysiology of catheter thrombosis is also poorly understood. Introduction of a catheter or guidewire may not provoke the intense thrombotic response that follows angioplasty or stenting, but factors such as catheter materials and device size, equipment surface properties, flow conditions, procedural time and complexity, as well as the antiplatelet and anticoagulant drugs administered during the procedure influence the likelihood, rate and clinical impact of thrombosis. The crucial role of cellular interactions involving tissue-factor bearing cells and platelets in the process of thrombosis also needs to be critically explored when considering blood contact with an exogenous material. Focusing on the inherently prothrombotic environment of percutaneous coronary intervention, we review the physiologic underpinnings of catheter and guidewire thrombosis, and explore the effect of antithrombotic drugs at the interface between blood and material surfaces. We also propose a clinical classification for the diagnosis and investigation of catheter thrombosis in clinical trials of anticoagulant therapy and PCI.

PDGF-CC induces tissue factor expression: role of PDGF receptor alpha/beta

Tissue factor (TF) is the principal trigger of the coagulation cascade and involved in arterial thrombus formation. Platelet-derived growth factor CC (PDGF-CC) is a recently discovered member of the PDGF family released upon platelet activation. This study assesses the impact of PDGF-CC on TF expression in human cells. PDGF-CC concentration-dependently induced TF expression by 2.5-fold in THP-1 cells, by 2.0-fold in human peripheral blood monocytes, by 1.4-fold in vascular smooth muscle cells, and by 2.6-fold in microvascular endothelial cells, but did not affect TF expression in aortic endothelial cells. A similar pattern was observed with PDGF-BB. In contrast, PDGF-AA did not alter TF expression in THP-1 cells. TF whole cell activity was induced following stimulation with PDGF-BB and PDGF-CC in THP-1 cells. Real-time polymerase chain reaction revealed that PDGF-CC induced TF mRNA. PDGF-CC transiently activated p42/44 MAP kinase [extracellular signal-regulated kinase (ERK)], while phosphorylation of the MAP kinases c-Jun NH(2)-terminal kinase (JNK) and p38 remained unaffected. PD98059, a specific inhibitor of ERK phosphorylation, but not the p38 inhibitor SB203580 or the JNK inhibitor SP600125 prevented PDGF-CC induced TF expression in a concentration-dependent manner. The effect of PDGF-CC was antagonized by both PDGF receptor alpha and PDGF receptor beta neutralizing antibodies; in contrast, PDGF-BB was only inhibited by PDGF receptor beta blocking antibody. PDGF receptor alpha and PDGF receptor beta inhibition prevented PDGF-CC-induced ERK phosphorylation. PDGF-CC induces TF expression via activation of alpha/beta receptor heterodimers and an ERK-dependent signal transduction pathway.

Very late changes in the dilated lesion following coronary balloon angioplasty: a 17 year serial quantitative angiographic study

AIMS

Limited data are available on the changes that occur at the dilated site many years after coronary balloon angioplasty. The development of bioabsorbable stents may increase the importance of understanding the long term changes that occur in an unscaffolded coronary artery following balloon-mediated injury.

METHODS AND RESULTS

This study evaluated, by serial quantitative angiography, the natural history of changes that occurred in the dilated segment between early (mean seven months), late (mean 4.5 years) and very late (mean 17 years) follow-up after balloon angioplasty. Of 127 consecutive patients (174 lesions) with successful coronary angioplasty, 125 underwent early, 84 late and 47 very late angiographic follow-up (75% of eligible survivors). The mean lesion diameter stenosis decreased from 36+/-11% at early to 26+/-15% at late follow-up (p<0.0001), and then increased again to 35+/-25% by very late follow-up (p=0.003). Although stenosis severity at early follow-up angiography predicted lesion regression at late follow-up, there was no significant correlation between late and very late follow-up lesion severity.

CONCLUSIONS

After coronary angioplasty, lesion regression at the dilated site from 7 months to 4.5 years is followed by slow lesion progression over the next 12 years.

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.

CCN1 knockdown suppresses neointimal hyperplasia in a rat artery balloon injury model

OBJECTIVE

CCN1 (Cyr61) is an extracellular matrix-associated protein involved in cell proliferation and survival. CCN1 is bound to vascular smooth muscle cells (VSMCs) via integrins and is expressed in VSMCs in atherosclerotic lesions, suggesting involvement in the regulation of vascular smooth muscle cell (VSMC) proliferation and atherosclerosis. We hypothesized that knockdown of CCN1 may inhibit VSMC proliferation and suppress neointimal hyperplasia.

METHODS AND RESULTS

We examined the effect of the knockdown of CCN1 using rat cultured VSMCs and a rat balloon injury model. CCN1 stimulated adhesion and migration of VSMCs in a dose-dependent manner, and this was blocked by an antibody for integrin alpha(6)beta(1). Moreover, knockdown of endogenous CCN1 by lentiviral delivery of siRNA significantly inhibited proliferation of VSMCs and the uptake of 5-bromo-2'-deoxyuridine (BrdU). Replenishment with recombinant CCN1 reversed the effect of siRNA knockdown. Interestingly, knockdown of CCN1 significantly suppressed neointimal hyperplasia in a rat carotid artery balloon injury model at days 14 and 28 after injury. Gene transfer of CCN1 to smooth muscle reversed the effect of CCN1 knockdown on neointimal formation. These results suggest that endogenous CCN1 regulates proliferation of VSMCs and neointimal hyperplasia.

CONCLUSIONS

Inhibition of CCN1 may provide a promising strategy for the prevention of restenosis after vascular interventions.

Intimal hyperplasia in murine models

The most commonly used procedures to induce arterial injury in mice are carotid artery ligation with cessation of blood flow and mechanically-induced denudation of endothelium in the carotid or the femoral arteries. Both procedures result in neointimal hyperplasia after two to three weeks. A survey of various inbred strains of mice shows that strain-specific differences in susceptibility to injury-induced neointimal hyperplasia are different than those for susceptibility to diet-induced atherosclerosis, with strains identified as susceptible to both neointimal hyperplasia and atherosclerosis, resistant to both, susceptible to atherosclerosis but resistant to neointimal hyperplasia, or resistant to atherosclerosis but susceptible to neointimal hyperplasia. Inflammatory cells such as T and B lymphocytes, which are contributory to atherosclerosis, are protective against injury-induced neointimal hyperplasia. In contrast, the infiltration of monocytes into the site of injury and their differentiation to macrophages favor neointimal hyperplasia similar to their pathogenic role in atherosclerosis. The regulatory role of lymphocytes and macrophages in neointimal hyperplasia is related to the production of cytokines such as interferon-gamma and tumor necrosis factor-alpha, respectively. Interestingly, inducible nitric oxide synthase (iNOS) activity appears to inhibit neointimal hyperplasia in the endothelial denudation model but contributes to neointimal hyperplasia when arterial injury is induced by periadventitial cuff placement. The difference appears to be due to the time required for endothelial recovery and the participation of inflammatory cells. Thus, although arterial injury-induced neointimal hyperplasia results in similar vascular occlusion as progressive atherosclerosis, the pathology and mechanism of the two disease processes are quite different.

The potential role of macrophage migration inhibitory factor on the migration of vascular smooth muscle cells

AIM

Macrophage migration inhibitory factor (MIF) is known as a pro-inflammatory cytokine that regulates a broad spectrum of inflammatory reactions. MIF is expressed in vascular smooth muscle cells (VSMCs), and inhibition of the progression of atherosclerosis was observed in MIF-deficient atherosclerotic mice. However, the functional role of MIF in VSMCs has not been elucidated. The aim of this study was to investigate the role of MIF on the migration of VSMCs.

METHODS

Cultured rat A10 cells, derived from rat embryonic aortic smooth muscle cells, were stimulated with oxLDL, and the effect of MIF knockdown on oxLDL-mediated migration of A10 cells was analyzed.

RESULTS

Intracellular MIF content was significantly increased and a marked increase of MIF concent-ration was observed in the supernatant of A10 cells treated with oxLDL. The migration of A10 cells was significantly accelerated by the stimulation of recombinant MIF in a dose-dependent manner. Notably, knockdown of intracellular MIF by siRNA abolished oxLDL-induced migration of A10 cells.

CONCLUSION

These findings suggest that MIF acts on the migration of VSMCs in an autocrine and paracrine fashion. MIF appears to be a novel target for the prevention of cardiovascular events.

In vivo thrombus formation in murine models

Platelets play a central role in hemostasis, but also in atherothrombosis, as they rapidly adhere to tissue and to one another as a response to any vascular injury. This process involves a large number of surface receptors, signaling pathways, and enzymatic cascades as well as their complex interplay. Although in vitro experiments proved successful in both identifying new receptors and pathways and developing potent and selective antithrombotic drugs, in vitro research cannot mimic the myriad hemodynamic and spatiotemporal cellular and molecular interactions that occur during the generation and propagation of thrombi in vivo. Animal models, and, with the availability of genetically modified mouse strains and of modern intravital imaging techniques, mouse models in particular, have opened new ways to identify both individual roles and the interplay of platelet proteins in complex in vivo settings. In vivo models revealed the important role of, eg, Gas6 or blood coagulation factor XII in thrombus formation, and results obtained in in vivo models raised the interesting possibility that (physiologic) hemostasis and (pathologic) thrombosis might represent 2 mechanistically different processes. This review summarizes in vivo findings that contributed significantly to our understanding of hemostatic and thrombotic processes and which may help to guide future research.

Distinct roles of estrogen receptors alpha and beta mediating acute vasodilation of epicardial coronary arteries

This study investigated the contribution of estrogen receptors (ERs) alpha and beta for epicardial coronary artery function, vascular NO bioactivity, and superoxide (O(2)(-)) formation. Porcine coronary rings were suspended in organ chambers and precontracted with prostaglandin F(2alpha) to determine direct effects of the selective ER agonists 4,4',4''-(4-propyl-[(1)H]pyrazole-1,3,5-triyl)tris-phenol (PPT) or 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) or the nonselective ER agonist 17beta-estradiol. Indirect effects on contractility to U46619 and relaxation to bradykinin were assessed and effects on NO, nitrite, and O(2)(-) formation were measured in cultured cells. Within 5 minutes, selective ERalpha activation by PPT, but not 17beta-estradiol or the ERbeta agonist DPN, caused rapid, NO-dependent, and endothelium-dependent relaxation (49+/-5%; P<0.001 versus ethanol). PPT also caused sustained endothelium- and NO-independent vasodilation similar to 17beta-estradiol after 60 minutes (72+/-3%; P<0.001 versus ethanol). DPN induced endothelium-dependent NO-independent relaxation via endothelium-dependent hyperpolarization (40+/-4%; P<0.01 versus ethanol). 17beta-Estradiol and PPT, but not DPN, attenuated the responses to U46619 and bradykinin. All of the ER agonists increased NO and nitrite formation in vascular endothelial but not smooth muscle cells and attenuated vascular smooth muscle cell O(2)(-) formation (P<0.001). ERalpha activation had the most potent effects on both nitrite formation and inhibiting O(2)(-) (P<0.05). These data demonstrate novel and differential mechanisms by which ERalpha and ERbeta activation control coronary artery vasoreactivity in males and females and regulate vascular NO and O(2)(-) formation. The findings indicate that coronary vascular effects of sex hormones differ with regard to affinity to ERalpha and ERbeta, which will contribute to beneficial and adverse effects of hormone replacement therapy.

Forkhead transcription factor FOXO3a is a negative regulator of angiogenic immediate early gene CYR61, leading to inhibition of vascular smooth muscle cell proliferation and neointimal hyperplasia

Cysteine-rich angiogenic protein 61 (CYR61, CCN1) is an immediate early gene expressed in vascular smooth muscle cells (VSMCs) on growth factor stimulation, and its expression has been suggested to be associated with postangioplasty restenosis. The forkhead transcription factors are reported to play various roles in cellular proliferation, apoptosis, and even adaptation to cellular stress. We hypothesized that the forkhead transcription factor FOXO3a may regulate CYR61 expression in VSMCs and investigated the CYR61-modulating effect of FOXO3a in the process of vascular response to vasoactive signals and vascular injury. To evaluate the effect of FOXO3a on CYR61 expression, rat VSMCs were infected with adenoviral vectors expressing constitutively active FOXO3a (Ad-TM-FOXO3a). Constitutively active FOXO3a gene transduction suppressed CYR61 expression. Luciferase assay with the deletion constructs of the forkhead factor binding motif in CYR61 promoter region, which resulted in a significant decrease in luciferase expression compared with the intact construct, and chromatin immunoprecipitation analysis confirmed transcriptional regulation of CYR61 by FOXO3a. Serum and angiotensin II rapidly induced CYR61 expression, which was significantly reduced by Ad-TM-FOXO3a. Reduction of VSMC proliferation and migration associated with FOXO3a activation was significantly reversed by cotransfection of adenoviral vector expressing CYR61, whereas apoptosis induction by FOXO3a was not influenced. In a rat balloon carotid arterial injury model, CYR61 was rapidly induced in VSMCs in the early stage of injury and remained elevated until 14 days, which was suppressed by Ad-TM-FOXO3a transfection. After 14 days, there was a significant reduction in neointima by FOXO3a transduction compared with the control group (0.06+/-0.02 versus 0.20+/-0.07 mm(2), P<0.01). Such reduction of neointimal hyperplasia by Ad-TM-FOXO3a was reversed by CYR61 replenishment. These data suggest that FOXO3a is a negative transcription factor of CYR61 and that suppression of CYR61 is among several mechanisms by which FOXO3a inhibits VSMC proliferation and neointimal hyperplasia.

Cellular mechanism through which parathyroid hormone-related protein induces proliferation in arterial smooth muscle cells: definition of an arterial smooth muscle PTHrP/p27kip1 pathway

Parathyroid hormone-related protein (PTHrP) is present in vascular smooth muscle (VSM), is markedly upregulated in response to arterial injury, is essential for normal VSM proliferation, and also markedly accentuates neointima formation following rat carotid angioplasty. PTHrP contains a nuclear localization signal (NLS) through which it enters the nucleus and leads to marked increases in retinoblastoma protein (pRb) phosphorylation and cell cycle progression. Our goal was to define key cell cycle molecules upstream of pRb that mediate cell cycle acceleration induced by PTHrP. The cyclin D/cdk-4,-6 system and its upstream regulators, the inhibitory kinases (INKs), are not appreciably influenced by PTHrP. In striking contrast, cyclin E/cdk-2 kinase activity is markedly increased by PTHrP, and this is a result of a specific, marked, PTHrP-induced proteasomal degradation of p27(kip1). Adenoviral restoration of p27(kip1) fully reverses PTHrP-induced cell cycle progression, indicating that PTHrP mediates its cell cycle acceleration in VSM via p27(kip1). In confirmation, adenoviral delivery of PTHrP to murine primary vascular smooth muscle cells (VSMCs) significantly decreases p27(kip1) expression and accelerates cell cycle progression. p27(kip1) is well known to be a central cell cycle regulatory molecule involved in both normal and pathological VSM proliferation and is a target of widely used drug-eluting stents. The current observations define a novel "PTHrP/p27(kip1) pathway" in the arterial wall and suggest that this pathway is important in normal arterial biology and a potential target for therapeutic manipulation of the arterial response to injury.

The Taxus drug-eluting stent: a new paradigm in controlled drug delivery

The advent of drug-eluting stents (DES) has provided the medical community with a technology that is transforming the treatment of coronary artery disease. As the newest treatment modality available to the interventional cardiologist, drug-eluting stents have not only significantly reduced the risk of restenosis, but they are also allowing the interventionalists to treat more complex lesions in patients that would otherwise require more invasive bypass surgery. Development of these drug-device combination products has presented considerable challenges to the device industry because it involves a multi-disciplinary approach that combines conventional device design and manufacturing with the principles of controlled local drug delivery. This review article provides an in-depth discussion of the key elements of drug-eluting stents, focusing on the TAXUS paclitaxel-eluting stent as an example of this new class of product. Specific sections will review the drug and polymer matrix components, formulation development and evaluation, pre-clinical studies and clinical trial results.

Rat carotid arteriotomy: c-myc is involved in negative remodelling and apoptosis

OBJECTIVE

c-myc is the main proto-oncogene responsible for restenosis in cardiovascular surgery. The aim of our study was to evaluate the effects of c-myc antisense (AS) phosphorothioate oligodeoxynucleotides (ODNs) in the remodelling process induced by surgical carotid arteriotomy on an experimental rat model.

METHODS

Fifty-five rats with carotid stenosis and apoptosis induced by arteriotomy were submitted to gene expression analysis 4 h after surgery, to TUNEL assay 48 h after surgery and to histological analysis 30 days later.

RESULTS

AS ODNs induced a 60% decrease in target c-myc mRNA in injured carotid arteries compared to control sense and scrambled ODN-treated carotid arteries (P < 0.05). Histological evaluation revealed that stenosis stimulated by arteriotomy was mainly due to adventitial constrictive remodelling rather than to neointimal hyperplasia, observed only in a limited number of samples. Morphometric analysis showed that lumen area in c-myc AS ODN-treated carotid arteries was 35% greater than in control arteries (P < 0.05), whereas the media/lumen area ratio showed a 63% reduction in AS ODN-treated carotid arteries in comparison to control arteries (P < 0.05). Surgical injury affected the expression of apoptosis-related genes Bcl-2, Bax, Bcl-xL and Bcl-xS, inducing a mean 3.5-fold decrease in the Bcl-2/ Bax ratio and a 9-fold decrease in the Bcl-xL/S ratio 4 h after injury as compared with uninjured carotid arteries. TUNEL assay experiments revealed increased apoptosis in AS ODN-treated carotid arteries in comparison to control carotid arteries.

CONCLUSIONS

c-myc AS ODNs reduce the negative remodelling induced by arteriotomy. The imbalance between proliferative stimulus represented by surgery and the c-myc mRNA decrease induced greater apoptosis in AS ODN-treated carotid arteries without further affecting mRNA levels of Bcl-2, Bax, Bcl-xL and Bcl-xS genes.

Locally administered antiproliferative drugs inhibit hypercontractility to serotonin in balloon-injured pig coronary artery

Although drugs such as sirolimus and paclitaxel are effective in reducing restenosis, their effects on vascular function are often overlooked. In this study, we have examined the effects of local delivery of several anti-restenotic drugs given in vivo after balloon injury on in vitro vascular contraction and relaxation 28 days after injury. Paclitaxel (50 microM), the farnesyl protein transferase inhibitor L744 (25 microM), sirolimus (25 microM) and Van 10/4 (decahydro-1,1,4,7-tetramethyl-1H-cycloprop[e]azulen-4-o-[2-(3-methylpent-2-enoyl)-fucopyranoside]; 25 microM) were delivered to porcine coronary arteries in vivo and the arteries removed 28 days later. Contractions to KCl and 5-hydroxytryptamine (5-HT) and relaxations to calcimycin and 3-morpholinosydnonimine (SIN-1) were measured in control (LCx) and balloon-injured (LAD) rings. In vehicle-infused coronary arteries, contraction to KCl and 5-HT was significantly enhanced 28 days after balloon injury, while the response to calcimycin had recovered fully, indicating endothelial regrowth. The response to SIN-1 was unchanged. None of the four drugs tested had any effect on the enhanced response to KCl 28 days after injury or on recovery of the calcimycin response. The hyper-responsiveness to 5-HT was eliminated by sirolimus, Van 10/4 and L744, but not paclitaxel. This study demonstrates that local drug infusion with structurally different antiproliferative drugs at the time of balloon angioplasty does not affect endothelial recovery and may in some cases prevent hyper-responsiveness to constrictor agents.

Association of the circulating adiponectin concentration with coronary in-stent restenosis in haemodialysis patients

BACKGROUND

Success of coronary stenting is limited by in-stent restenosis. We aimed to determine whether circulating levels of the cytokines, which have anti-inflammatory properties such as adiponectin or interleukin-10, could be associated with the occurrence of coronary in-stent restenosis in patients with end-stage renal disease (ESRD).

METHODS

We enrolled 71 consecutive ESRD patients undergoing haemodialysis (mean age: 64.9+/-8.9 years; 19 women, 52 men; mean haemodialysis duration: 78.2+/-87.5 months), who received stenting for a single coronary lesion. Plasma concentrations of adiponectin and IL-10 were measured within one week before coronary stenting.

RESULTS

Of the 71 patients who had received stenting, in-stent restenosis occurred in 37 patients (52.1%) within 6 months after stenting. In univariate logistic analysis, the homeostasis model assessment index of insulin resistance, blood haemoglobin, serum concentrations of high density lipoprotein-cholesterol or triglycerides and plasma concentrations of insulin or adiponectin were significantly associated with coronary in-stent restenosis. In a multiple logistic regression analysis among these variables, however, only the plasma adiponectin concentration was associated with the coronary in-stent restenosis: the odds ratio of the increase in 1 microg/ml of plasma adiponectin concentration for having restenosis was 0.651 (P = 0.001, 95% confidence interval: 0.506-0.839). Patients with restenosis had lower plasma adiponectin concentrations than those without [6.2+/-2.2 microg/ml (2.1-10.4 microg/ml; n = 37) vs 27.2+/-10.8 microg/ml (17.9-79.8 microg/ml; n = 34); P = 0.0001].

CONCLUSIONS

Circulating adiponectin concentrations may be associated with the occurrence of coronary in-stent restenosis in ESRD patients undergoing maintenance haemodialysis.

PPARgamma gene transfer sustains apoptosis, inhibits vascular smooth muscle cell proliferation, and reduces neointima formation after balloon injury in rats

OBJECTIVE

There is still debate as to whether antiatherosclerotic effect of PPARgamma ligands is dependant on PPARgamma gene itself or some other pathway.

METHODS AND RESULTS

To investigate the effect of PPARgamma gene modulation on neointima formation after balloon injury, we delivered adenoviral vectors expressing the wild-type (WT) dominant negative (DN) PPARgamma, or a control gene (beta-galactosidase [BG]) into carotid artery after balloon injury in rosiglitazone (a PPARgamma ligand)-treated (R+) (3 mg/kg/d) and nontreated (R-) rats. Two weeks after gene delivery, in both R+ and R- animals, the PPARgamma-WT gene transfer showed a significantly lower intima-media ratio (IMR) than control group. Moreover, the delivery of a PPARgamma-DN form showed the highest IMR (in R+WT, 0.51+/-0.15; R+BG, 0.89+/-0.14; R+DN, 1.20+/-0.18, P<0.05 and in R-WT, 0.91+/-0.21; R-BG, 1.44+/-0.23; R-DN, 1.74+/-0.29, P<0.05). Proliferation and migration showed same result pattern as IMR. In addition, apoptotic indices were significantly higher in the PPARgamma-WT gene transferred group than in the PPARgamma-DN group.

CONCLUSIONS

In vivo transfer of the PPARgamma-WT gene was found to inhibit smooth muscle proliferation, sustain apoptosis, and reduce neointima formation after balloon injury irrespective of rosiglitazone treatment. These results indicate that PPARgamma overexpression itself has a protective role against restenosis after balloon injury.

Paratope determination of the antithrombotic antibody 82D6A3 based on the crystal structure of its complex with the von Willebrand factor A3-domain

The antithrombotic monoclonal antibody 82D6A3 is directed against amino acids Arg-963, Pro-981, Asp-1009, Arg-1016, Ser-1020, Met-1022, and His-1023 of the von Willebrand factor A3-domain (Vanhoorelbeke, K., Depraetere, H., Romijn, R. A., Huizinga, E., De Maeyer, M., and Deckmyn, H. (2003) J. Biol. Chem. 278, 37815-37821). By this, it potently inhibits the interaction of von Willebrand factor to collagens, which is a prerequisite for blood platelet adhesion to the injured vessel wall at sites of high shear. To fully understand the mode of action of 82D6A3 at the molecular level, we resolved its crystal structure in complex with the A3-domain and fine mapped its paratope by construction and characterization of 13 mutants. The paratope predominantly consists of two short sequences in the heavy chain CDR1 (Asn-31 and Tyr-32) and CDR3 (Asp-99, Pro-101, Tyr-102 and Tyr-103), forming one patch on the surface of the antibody. Trp-50 of the heavy and His-49 of the light chain, both situated adjacent to the patch, play ancillary roles in antigen binding. The crystal structure furthermore confirms the epitope location, which largely overlaps with the collagen binding site deduced from mutagenesis of the A3-domain (Romijn, R. A., Westein, E., Bouma, B., Schiphorst, M. E., Sixma, J. J., Lenting, P. J., and Huizinga, E. G. (2003) J. Biol. Chem. 278, 15035-15039). We herewith further consolidate the location of the collagen binding site and reveal that the potent action of the antibody is due to direct competition for the same interaction site. This information allows the design of a paratope-mimicking peptide with antithrombotic properties.

Comparison between recombinant baculo- and adenoviral-vectors as transfer system in cardiovascular cells

The development of effective gene-therapeutic applications for cardiovascular disorders is in part limited by the lack of appropriate delivery systems. In an attempt to overcome this deficiency, we investigated the ability of baculoviral vectors to transduce human cardiovascular cells, for which data are missing in literature. Additionally, baculovirus ability to transduce target cells was compared to that of an adenoviral vector, a well characterized and widely used viral vector. Transduction experiments, performed using baculo/adenoviral vectors expressing the enhanced green fluorescence protein, revealed that, under the experimental condition considered, baculoviruses but not adenoviruses efficiently transduce human coronary smooth muscle cells (hCSMC); an opposite behavior was noticed for human coronary endothelial cells (hCEC). Thus, baculoviral vectors are potentially indicated as transfer system in the treatment of coronary restenosis, where growth inhibitory genes should reach hCSMC but not hCEC. When used to transduce human cardiomyocytes and fibroblasts, both vectors behaved similarly. Finally, studies on cellular DNA replication revealed a more prolonged and pronounced negative effect on cells transduced by adenoviral compared to baculoviral vectors. Our data indicate that baculoviruses represent an attractive alternative to adenoviruses as transfer vectors in cardiovascular cells and that baculovirus have the potential to be used as gene transfer system in cardiovascular diseases such as restenosis.

Stimulation of vascular smooth muscle cell migration by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a well known proinflammatory factor that influences the migration and proliferation of various cell types, predominantly monocytes and macrophages. Recent evidence suggests an important role for MIF in the progression of atherosclerosis and restenosis. For this reason, we studied the effect of MIF on platelet-derived growth factor-BB (PDGF-BB)-induced migration and PDGF receptor protein expression in vascular smooth muscle cells (VSMCs). Furthermore, the possibility of MIF influencing the migration of VSMCs was investigated. Our results show that short-term incubation of MIF is able to enhance PDGF-BB-induced migration. Long-term incubation decreases PDGF-BB-induced migration, but preserves a short-term stimulatory effect. These effects are not regulated at the level of PDGF receptor protein expression. MIF also acts as a chemoattractant for VSMCs, with a maximum response at 15 ng/ml. In contrast, the proliferation of VSMCs was unaffected by MIF. We conclude that MIF has a biphasic effect on VSMC migration. It remains unclear whether this effect is direct or involves the secretion of unidentified promigratory factors. Exogenous MIF does not stimulate VSMC proliferation; however, a role for MIF in proliferation cannot be fully ruled out. In view of the known key contributions of macrophage-derived MIF and VSMCs, the observed effects may well play a role in the progression of atherosclerosis and restenosis.

Antiproliferative profile of sirolimus and mycophenolate mofetil: impact of the SI/MPL ratio

BACKGROUND

Recently, preliminary data of the ORBIT study have been presented; coronary restenosis after oral treatment with sirolimus (SRL) was merely 7.7%. The present study thought to investigate the antiproliferative profile of SRL and mycophenolate mofetil (MMF), both as individual compounds and as a combined therapy.

METHODS AND RESULTS

Proliferation studies were carried out with smooth muscle cells of human coronary arteries (human coronary smooth muscle cells, HCMSMC). SRL (0.01-1000 ng/ml) and MMF (0.005-500 microg/ml) were added in six descending concentrations, cell proliferation was studied at day 5. To characterize the clinical relevance of the data, the authors calculated a SI/MPL ratio between a significant antiproliferative effect (SI) in vitro and the maximal systemic plasma level (MPL) in vivo. The SI/MPL ratios of SRL and MMF were 0.16 and 0.014, respectively. Second, SRL (1 and 0.1 ng/ml) was combined with four concentrations of MMF (0.5 and 0.05 microg/ml) and MMF was combined with four concentrations of SRL. Additive and overadditive antiproliferative effects were found, no destruction of alpha-tubulin was detected.

CONCLUSIONS

Thus, SRL and MMF exhibit dose-dependent direct antiproliferative effects with SI/MPL ratios smaller than one. Both agents, as individual compounds or as combined therapy, are candidates for an oral therapy of human coronary restenosis.

Impaired flow-mediated dilation and risk of restenosis in patients undergoing coronary stent implantation

BACKGROUND

Impaired endothelial function is a key event in the atherosclerosis process and predicts future cardiovascular events in subjects with and without coronary artery disease (CAD). We performed the first prospective study evaluating whether early measurement of brachial artery endothelium-dependent dilation (flow-mediated dilation [FMD]) after coronary stenting could predict occurrence of in-stent-restenosis.

METHODS AND RESULTS

The study population included 136 patients with single-vessel CAD undergoing percutaneous coronary intervention (PCI) with stenting and at least 6 months of follow-up. All patients underwent ultrasound detection of brachial artery reactivity 30 days after PCI; FMD was investigated before and after 5 minutes of occlusion of the brachial artery, and nitroglycerin-mediated dilation was investigated before and after administration of sublingual nitrates. Clinical in-stent restenosis was demonstrated in 20 patients (15%), whereas 116 patients (85%) remained free of signs or symptoms of recurrent ischemia. FMD was significantly impaired in patients with restenosis versus those without restenosis (percent diameter variation 4.6+/-5.8% versus 9.5+/-6.6%, P=0.002); moreover, 4% of patients with FMD > or =7% (median value) developed in-stent restenosis versus 28% of those with FMD <7% (P=0.0001). On multivariate analysis, FMD was the strongest predictor of restenosis (OR 4.5, 95% CI 2.4 to 12.0); conversely, nitroglycerin-mediated dilation did not independently predict the risk of restenosis (OR 2.4, 95% CI 0.8 to 6.3).

CONCLUSIONS

This is the first prospective study indicating that impaired FMD independently predicts occurrence of in-stent restenosis in patients undergoing PCI. Early evaluation of endothelial function after stenting may represent a useful screening tool to stratify patients according to future risk of restenosis.

Activated forkhead transcription factor inhibits neointimal hyperplasia after angioplasty through induction of p27

OBJECTIVE

We examined the effects of FKHRL1 (forkhead transcription factor in rhabdomyosarcoma like-1) overexpression on vascular smooth muscle cell (VSMC) proliferation, apoptosis, and cell cycle, in vitro, and the role of FKHRL1 and p27 in the pathophysiology of neointimal growth after balloon angioplasty, in vivo. Furthermore, we tested whether FKHRL1 overexpression can inhibit neointimal hyperplasia in a rat carotid artery model.

METHODS AND RESULTS

Adenovirus expressing the constitutively active FKHRL1 (FKHRL1-TM; triple mutant) with 3 Akt phosphorylation sites mutated was transfected to subconfluent VSMCs. FKHRL1 overexpression in cultured VSMCs increased p27 expression, leading to G1 phase cell-cycle arrest and increased apoptosis. In vivo, the phosphorylation of FKHRL1 increased significantly 3 hours after balloon injury and decreased thereafter, with the subsequent downregulation of p27. Although the phosphorylation of FKHRL1 was greatest at 3 hours, the downregulation of p27 showed a temporal delay, only slightly starting to decrease after 3 hours and reaching a nadir at 72 hours after balloon injury. Gene transfer of FKHRL1-TM increased p27, decreased proliferation, and increased apoptosis of VSMCs, which resulted in a marked reduction in neointima formation (intima-to-media ratio: 0.31+/-0.13 versus 1.17+/-0.28, for FKHRL1-TM versus Adv-GFP; P<0.001).

CONCLUSIONS

Balloon angioplasty leads to the phosphorylation of FKHRL1 and decreased expression of p27, thereby promoting a proliferative phenotype in VSMCs in vitro and in vivo. This study reveals the importance of FKHRL1 in proliferation and viability of VSMCs and suggests that it may serve as a molecular target for interventions to reduce neointima formation after angioplasty.

Serial six year quantitative angiographic follow up in asymptomatic patients following successful coronary angioplasty

OBJECTIVE

To evaluate long term (six years) lumen changes after balloon angioplasty by using quantitative coronary angiography.

METHODS

Complete serial quantitative coronary angiography (before and after angioplasty and at six months, three years, and six years) was performed in 100 patients with successful angioplasty and without subsequent repeated revascularisation. In all, 198 dilated segments were compared with 395 non-dilated segments that were obtained from non-target arteries of study patients.

RESULTS

From six months to three years after angioplasty, minimum lumen diameter (MLD) increased significantly by 0.13 (0.28) (mean (SD)) mm in dilated segments and decreased significantly by 0.04 (0.27) mm in non-dilated segments. From three years to six years, MLD remained stable in dilated segments but decreased further (by 0.04 (0.28) mm) in non-dilated segments. Consequently, the DeltaMLD between six months and six years was larger in dilated segments than in non-dilated segments (0.12 (0.32) v -0.08 (0.34); p < 0.001). Further, DeltaMLD from six months to six years correlated positively with the percentage diameter stenosis (DS) at six months in each group (dilated segments r = 0.47, p < 0.0001; non-dilated segments r = 0.49, p < 0.0001). Multivariate analysis showed that the only independent predictor of DeltaMLD over six years for each group was the DS at six months.

CONCLUSIONS

Lesion regression occurs within the first three years after angioplasty and reaches a plateau thereafter. Moreover, the stenosis severity at six months predicts the magnitude of late regression after angioplasty.

Neointimal Smooth Muscle Cells Display a Proinflammatory Phenotype Resulting in Increased Leukocyte Recruitment Mediated by P-Selectin and Chemokines

Leukocyte recruitment is crucial for the response to vascular injury in spontaneous and accelerated atherosclerosis. Whereas the mechanisms of leukocyte adhesion to endothelium or matrix-bound platelets have been characterized, less is known about the proadhesive role of smooth muscle cells (SMCs) exposed after endothelial denudation. In laminar flow assays, neointimal rat SMCs (niSMCs) supported a 2.5-fold higher arrest of monocytes and “memory” T lymphocytes than medial SMCs, which was dependent on both P-selectin and VLA-4, as demonstrated by blocking antibodies. The increase in monocyte arrest on niSMCs was triggered by the CXC chemokine GRO-α and fractalkine, whereas “memory” T cell arrest was mediated by stromal cell–derived factor (SDF)-1α. This functional phenotype was paralleled by a constitutively increased mRNA and surface expression of P-selectin and of relevant chemokines in niSMCs, as assessed by real-time PCR and flow cytometry. The increased expression of P-selectin in niSMCs versus medial SMCs was associated with enhanced NF-κB activity, as revealed by immunofluorescence staining for nuclear p65 in vitro. Inhibition of NF-κB by adenoviral IκBα in niSMCs resulted in a marked reduction of increased leukocyte arrest in flow. Furthermore, P-selectin expression by niSMCs in vivo was confirmed in a hypercholesterolemic mouse model of vascular injury by double immunofluorescence and by RT-PCR after laser microdissection. In conclusion, we have identified a NF-κB–mediated proinflammatory phenotype of niSMCs that is characterized by increased P-selectin and chemokine expression and thereby effectively supports leukocyte recruitment.

Stabilization of atherosclerotic plaques by blockade of macrophage migration inhibitory factor after vascular injury in apolipoprotein E-deficient mice

BACKGROUND

Macrophage migration inhibitory factor (MIF), a cytokine that controls cell-mediated inflammatory responses, is upregulated in atherogenesis; however, its functional contribution to lesion development has not been evaluated.

METHODS AND RESULTS

We studied the role of MIF on neointima lesion formation after wire-induced injury of carotid arteries in apolipoprotein E-deficient (apoE(-/-)) mice. Immunohistochemistry revealed that MIF expression was detectable in endothelial cells before injury and upregulated in smooth muscle cells (SMCs) 24 hours after endothelial denudation. Three weeks after injury, MIF was predominantly found in endothelial cells and macrophage-derived foam cells. Neutralizing MIF with a monoclonal antibody resulted in a marked reduction of neointimal macrophages and inhibited transformation of macrophages into foam cells. Conversely, the content of SMCs and of collagen in the neointima were increased, amounting to a slight but not significant reduction in neointima and media size after 3 weeks of MIF monoclonal antibody treatment. Notably, serum levels of the cytokines IL-2, IL-4, IL-6, IL-10, and tumor necrosis factor were increased in MIF monoclonal antibody-treated mice. In vitro flow assays revealed that MIF pretreatment of aortic endothelium enhanced monocyte recruitment and that the monocyte arrest induced by oxidized LDL is mediated by endothelial MIF, as shown by monoclonal antibody inhibition.

CONCLUSIONS

Inhibition of MIF resulted in a shift in the cellular composition of neointimal plaques toward a stabilized phenotype with reduced macrophage/foam cell content and increased SMC content. This might be attributable to a reduction of monocyte recruitment mediated by endothelial MIF.

Crucial Role of Stromal Cell–Derived Factor-1α in Neointima Formation After Vascular Injury in Apolipoprotein E–Deficient Mice

Background— Recent evidence indicates that stromal cell–derived factor-1α (SDF-1α) is expressed in human atherosclerotic plaques, whereas high plasma levels are clinically associated with stable coronary artery disease. Herein, we investigate the involvement of SDF-1α in neointimal formation after vascular injury.

Methods and Results— SDF-1α was detected by immunohistochemistry in carotid arteries of apolipoprotein E–deficient (apoE −/− ) mice at various stages of neointima formation after wire-induced injury. Double immunofluorescence revealed that SDF-1α staining was mostly confined to smooth muscle cells (SMCs). Furthermore, SDF-1α plasma levels peaked 1 day after vascular injury. Treatment of apoE −/− mice after carotid injury with a neutralizing SDF-1α monoclonal antibody for 3 weeks reduced neointimal lesion area by 44% (n=5, P <0.05) compared with isotype control. In SDF-1α antibody–treated apoE −/− mice, neointimal SMC content was decreased (21.7±2% versus 39.4±4%, n=5, P =0.005), whereas the relative content of neointimal macrophages remained unchanged. As shown by flow cytometry, carotid injury resulted in a marked expansion of circulating Sca-1 + lineage − progenitor cells (PBPCs) in the peripheral blood of apoE −/− mice after 1 day, which was mediated by SDF-1α. Systemic injection of isolated PBPCs after vascular injury demonstrated their recruitment to neointimal lesions, where they can adopt an SMC-like phenotype.

Conclusions— SDF-1α plays an instrumental role in neointimal formation after vascular injury in apoE −/− mice by regulating neointimal SMC content. This contribution appears to be attributable to SDF-1α–dependent recruitment of circulating SMC progenitor cells.

Constitutively active glycogen synthase kinase-3beta gene transfer sustains apoptosis, inhibits proliferation of vascular smooth muscle cells, and reduces neointima formation after balloon injury in rats

OBJECTIVE

Glycogen synthase kinase (GSK)-3beta is a crucial factor in many cellular signaling pathways and may play an important role in smooth muscle proliferation and apoptosis after angioplasty.

METHODS AND RESULTS

To investigate the effect of GSK-3beta modulation on neointima formation, smooth muscle proliferation, and apoptosis after balloon injury in vivo, we delivered adenoviral vectors expressing the constitutively active form of GSK-3beta (GSK-S9A: 9th serine switched to alanine) or a control gene into rat carotid arterial segments after balloon injury with a 2F Fogarty catheter. Viral infusion mixtures (5x108 pfu) were incubated in the arterial lumen for 20 minutes, and the effects of gene delivery were evaluated 3 days and 2 weeks after gene delivery with morphometry and immunohistochemical staining for proliferating and apoptotic cells. There were no significant differences in intimal, medial, and lumen areas at 3 days after the procedure. However, 2 weeks after gene delivery, the active GSK-3beta gene transfer resulted in a significantly lower intima to media ratio (0.29+/-0.06 versus 0.86+/-0.09, P<0.01) and a greater lumen area (0.41+/-0.02 versus 0.31+/-0.01 mm2, P<0.01) compared with the control gene transfected group. This was attributable to a significant reduction in intimal area (0.05+/-0.01 versus 0.15+/-0.02 mm2, P<0.01), whereas the medial area was similar (0.17+/-0.01 versus 0.18+/-0.01 mm2, P=0.21). Proliferation index was significantly reduced both at 3 days and 2 weeks in the active GSK-3beta gene transferred group (2.97+/-0.29% versus 5.71+/-0.50%, P<0.01). In addition, apoptotic index, which was not significantly different between the 2 groups at 3 days, was significantly higher in the active GSK-3beta gene transferred group at 2 weeks (3.14+/-0.68% versus 22.7+/-1.63%, n=10, P<0.01, for control versus active GSK-3beta gene transfer).

CONCLUSIONS

In vivo delivery of the active GSK-3beta gene inhibits smooth muscle proliferation, sustains apoptosis, and reduces neointima formation after balloon injury in rats and may be a future therapeutic target to limit neointima hyperplasia after angioplasty.

Stent-induced restenosis in the swine coronary artery is inhibited by a platelet-derived growth factor receptor tyrosine kinase inhibitor, TKI963

Activities of vascular smooth muscle cells (SMCs) such as proliferation, migration, and matrix production contribute to restenosis following clinical interventions of angioplasty and stent placement. Because activation of platelet-derived growth factor (PDGF)-receptor tyrosine kinase (PDGFr-TK) influences these processes and promotes restenosis, TKI963, an inhibitor of the PDGFr-TK was discovered, and its efficacy was evaluated in blocking stent-induced restenosis as analyzed by intravascular ultrasound (IVUS). TKI963, a low-molecular-weight compound, inhibited the cell-free PDGFbetar-TK with a K(i) value of 56 +/- 14 nM. TKI963 also inhibited PDGF-dependent events in human aortic SMCs (e.g., in situ PDGFr autophosphorylation, mitogenesis, chemotaxis, and collagen production with median inhibitory concentration values of approximately 300 nM) without affecting the activity of a series of membrane receptor tyrosine kinases and intracellular serine/threonine kinases. In vivo, stent-induced restenosis in the swine coronary artery was reduced by oral administration of TKI963 (1.25, 2.5, and 5 mg/kg BID, for 28 days). Late lumen cross-sectional area (CSA) loss, plaque CSA growth, and plaque volume in the stent determined by IVUS were dose-relatedly decreased (33-62% at 1.25 mg/kg BID to 66-92% at 5 mg/kg BID, depending on the parameter) compared with controls. TKI963 treatment of </=1 week following stent placement had no effect on the prevention of restenosis. TKI963, a selective, orally bioavailable inhibitor of the PDGFr-TK, dose-relatedly reduced stent-induced restenosis and did so by inhibiting PDGF-dependent activities that occur as late events following stent placement.

Bone marrow-derived progenitor cells modulate vascular reendothelialization and neointimal formation: effect of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibition

OBJECTIVE

Atherosclerosis and restenosis after vascular injury are both characterized by endothelial dysfunction, apoptosis, inappropriate endothelialization, and neointimal formation. Bone marrow-derived endothelial progenitor cells have been implicated in neovascularization, resulting in adult blood vessel formation. Despite the anticipated stem cell plasticity, the role of bone marrow-derived endothelial progenitor cells has not been clarified in vascular lesion development.

METHODS AND RESULTS

We investigated vascular lesion formation in mice after transplantation of bone marrow transfected by means of retrovirus with enhanced green fluorescent protein. Carotid artery injury was induced, resulting in neointimal formation. Fluorescence microscopy and immunohistological analysis revealed that bone marrow-derived progenitor cells are involved in reendothelialization of the vascular lesions. Treatment with rosuvastatin (20 mg/kg body wt per day), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, enhanced the circulating pool of endothelial progenitor cells, propagated the advent of bone marrow-derived endothelial cells in the injured vessel wall, and, thereby, accelerated reendothelialization and significantly decreased neointimal formation.

CONCLUSIONS

Vascular lesion development initiated by endothelial cell damage is moderated by bone marrow-derived progenitor cells. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibition promotes bone marrow-dependent reendothelialization and diminishes vascular lesion development. These findings may help to establish novel pathophysiological concepts and therapeutic strategies in the treatment of various cardiovascular diseases.

Surgical injury of rat arteries: genetic control of the remodelling process

OBJECTIVES

Remodelling and restenosis are complex biological processes responsible for bypass and percutaneous transluminal coronary angioplasty failures which are likely to affect many hundreds of genes. We evaluated the effectiveness of topically applied antisense oligonucleotides in reducing the translation of the messenger RNA for the transcription factor c-myc and in reducing stenosis.

METHODS

Surgery was performed under sterile conditions; 60 Wistar-Kyoto male rats were anaesthetized by ketamine. The carotid arteries were isolated through a median incision in the anterior neck region. At the same point, 0.5 mm longitudinal incisions were performed. Haemostasis was obtained by an adventitial 8.0 stitch. Thirty animals were given 150 microg of c-myc antisense oligonucleotide (Group A) while the other 30 animals received 150 microg of c-myc control sense oligonucleotide (Group B). Oligo molecules were locally applied through 100 microl of 20% pluronic gel. Rats were sacrificed at 30 days; carotid arteries were explanted and stained. Qualitative histological analysis was performed in all cases; serial sections were made every 25 micro in seven consecutive rats for each group. Morphometric analysis was also performed, luminal and medial area values recorded and the ratio between the two areas calculated. Data from each animal were compared with the corresponding contralateral carotid artery and expressed as mean+/-standard deviation. Statistical comparison between the two groups was carried out by one-way ANOVA text.

RESULTS

Qualitative histological analysis showed marked remodelling with complete disarray of vessel wall, neointima accumulation and evidence of elastic fibres in the adventitia of all animals of Group B versus Group A. Morphometric analysis showed a significant reduction in the lumen area in Group A animals together with increased values of the medial area versus Group B animals. In addition, the ratio between the lumen and medial area was significantly higher in Group A than in Group B (2.61+/-0.18 versus 1.14+/-0.33, P<0.0001).

CONCLUSIONS

c-myc antisense oligonucleotides applied intraoperatively can reduce post-operative stenosis.

Inhibition of the PDGF beta-receptor tyrosine phosphorylation and its downstream intracellular signal transduction pathway in rat and human vascular smooth muscle cells by different catechins

Abnormal proliferation of vascular smooth muscle cells (VSMC) as well as the platelet-derived growth factor (PDGF) plays an important role in the development of proliferative cardiovascular diseases. In this study, we show that treatment of rat and human aortic VSMC with 50 microM 2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3,5,7-triol (catechin) and epicatechin (EC) fails to inhibit the PDGF-Rb-activated intracellular signal transduction pathway and VSMC growth. In contrast, 10-50 microM epigallocatechin-3 gallate (EGCG), epicatechin-3 gallate (ECG), and catechin-3 gallate (CG), which all have a galloyl group in the 3-position of the catechin structure, effectively inhibit tyrosine-phosphorylation of PDGF-Rb, PI 3'-K, and PLC-gamma1 as well as the PDGF-BB-induced increase in [Ca2+]i. The PDGF-BB-induced increase in DNA synthesis and cell number was inhibited by ECG, EGCG, and CG, but not by catechin and EC. Epigallocatechin (EGC) that has a galloyl group in the 2-position effectively inhibited VSMC growth without affecting the PDGF-Rb signal pathway. A reduction of 45% and 70% of the intimal and medial cell number in the S-phase, respectively, has been observed in the catheter-injured left carotid artery 7 days after treatment of Wistar Kyoto rats with 10 mg/day EGCG. These results suggest that the galloyl group in the P3-position of the catechin structure is essential for inhibiting the PDGF-Rbeta-mediated intracellular signal transduction pathway.

Sustained activation of p38 mitogen-activated protein kinase contributes to the vascular response to injury

The vascular response to mechanical injury involves inflammatory and fibroproliferative processes that result in the formation of neointima and vascular remodeling. The complex cellular interactions initiated by vascular injury are coordinated and modulated by the elaboration of cytokines and growth factors. The production and transduction of many of these mediators require phosphorylation of p38 mitogen-activated protein kinase (MAPK). In the present investigation, we examined the pattern and localization of p38 MAPK activation following balloon vascular injury. The effects of long-term and selective inhibition of p38 MAPK with SB 239063 (trans-1-(4-hydroxycyclohexyl)-4-(4-fluorophenyl)-5-[2-methoxy)pyrimidin-4-yl]imidazole) were also investigated in a model of vascular injury. Western blotting and immunohistochemical staining demonstrated that phospho-p38 MAPK was increased following balloon injury of the rabbit iliofemoral artery. The p38 MAPK activation was noted as early as 15 min after balloon injury and remained elevated for at least 28 days. Phospho-p38 MAPK immunoreactivity (IR) was localized primarily in regions of dedifferentiated, smooth muscle alpha-actin-positive cells in all lamina of the vessel wall. Phospho-p38 MAPK IR was not correlated with the localization of macrophage or proliferating cells (proliferating cell nuclear antigen; PCNA +). Long-term treatment (4 weeks) with SB 239063 (50 mg/kg/day, p.o.) reduced the vascular response to injury in the hypercholesterolemic rabbit. SB 239063 had no effect on platelet-derived growth factor (PDGF)-stimulated migration or proliferation of rabbit vascular smooth muscle cells (VSMCs) in culture. However, SB 239063 produced a concentration-dependent inhibition of transforming growth factor (TGF)-beta-stimulated fibronectin production in VSMCs. In conclusion, sustained activation of p38 MAPK plays an important role in the vascular response to injury and inhibition of p38 MAPK may represent a novel therapeutic approach to limit this response.

Simultaneous intra/extravascular administration of antiproliferative agents as a new strategy to inhibit restenosis: the peak of reactive cell proliferation as a hallmark for the duration of the treatment

BACKGROUND

Strictly intravascular approaches for the treatment of postangioplasty restenosis are effective in the intima and the inner parts of the media but may be insufficient to control redundant pathways in the more outer parts of the media and the adventitia. An inverse situation may occur subsequently to a strictly extravascular approach, like the recently suggested pericardial approach in pigs. We hypothesized that simultaneous intra/extravascular administration of anti-restenotic agents inhibits restenosis by blocking all stimulatory pathways in the entire arterial wall.

METHODS

Fresh hearts of 25 domestic pigs were obtained from a local slaughterhouse. Left anterior descending coronary arteries (LAD) were harvested, cut into cylindric 5 mm segments, and cultured as ex vivo porcine organ cultures (POCs). After 9 bar ballooning simultaneous intra/extravascular administration of high dose diltiazem (50 microg/mL) was carried out for a period of 1, 2, 3, 4, 5, 6, and 7 days. At day 7 and 28 proliferative activity (BrdU), neointimal thickening, and staining against smooth muscle alpha-actin and vWF was analysed.

RESULTS

7 days after ballooning administration of diltiazem for 4, 5, 6, and 7 days inhibited reactive cell proliferation by more than 50% (n.s.) as compared to control, 28 days after ballooning administration for 6 and 7 days inhibited neointimal thickening by more than 75% (p < 0.05). Simultaneous intra/extravascular administration of high dose diltiazem did not affect the expression of vWF in endothelial cells or smooth muscle alpha-actin in smooth muscle cells.

CONCLUSIONS

Simultaneous intra/extravascular administration of high dose diltiazem (50 microg/mL) has to be maintained for at least 6 days to achieve a significant inhibition of neointimal thickening. The data demonstrate the importance of the maximal reactive cell proliferation (= day 7 in the POC-model) for the calculation of the duration of the treatment period.

Short-term local delivery of an inhibitor of Ras farnesyltransferase prevents neointima formation in vivo after porcine coronary balloon angioplasty

BACKGROUND

Mitogenic stimuli present at the site of coronary arterial balloon injury contribute to the progression and development of a restenotic lesion, many signaling through a common pathway involving the small G protein p21(ras). Our aim was to demonstrate in biochemical studies that farnesyl protein transferase inhibitor III (FPTIII) is an inhibitor of p21(ras) processing and that when it is given locally in vivo at the site of coronary balloon injury in a porcine model, it can inhibit neointima formation.

METHODS AND RESULTS

FPTIII (1 to 25 micromol/L) concentration-dependently reduced p21(ras) levels in porcine coronary artery smooth muscle cell membranes. FPTIII also prevented p42/p44 MAPK activation and DNA synthesis in response to platelet-derived growth factor in these cells at a concentration of 25 micromol/L. Application of 25 micromol/L FPTIII locally for 15 minutes to balloon-injured porcine coronary arteries in vivo prevented neointima formation assessed at 4 weeks, reduced proteoglycan deposition, and inhibited adventitial hypertrophy. Coronary arteries from FPTIII-treated pigs had no deterioration in contraction or in endothelium-dependent relaxation.

CONCLUSIONS

The study demonstrates in the pig that short-term local delivery of inhibitors of p21(ras)-dependent mitogenic signal transduction prevents restenosis after balloon angioplasty.

Molecular analysis of arterial stenosis in rat carotids

A new model of surgical injury for the induction and development of stenosis in common rat carotids is described. This model differs from balloon angioplasty or vein graft systems currently applied on animals to develop stenosis, since it involves the entire vessel wall layers and mimics the injury occurring during arterial grafts, endarterectomy or organ transplantation. At different times following arterial damage, the pattern of expression of genes already known to be involved in the proliferation, differentiation, and apoptosis of smooth muscle cells (c-myc, Angiotensin II receptor 1, Bcl-2 and Bax alpha), as well as of Rb and Rb2 genes, whose pattern of expression after arterial injury has not yet been reported, was analyzed by semi-quantitative reverse transcription-polymerase chain reaction technique. Histological and histochemical analysis on carotid sections shows the morphological changes which occurred 30 days after surgical injury in the vessel wall. Molecular and histological data demonstrate that this model of surgical injury induces neointimal proliferation in about 30% of rats. In about 70% of the remaining rats, it induces the processes responsible for negative remodelling, namely the significant accumulation of extracellular matrix and fibers and disorganization of arterial tunics. This model is therefore available for further studies on the expression of genes involved in the arterial stenotic process, as well as for testing drugs aimed at limiting this recurrent pathophysiological phenomenon.

Nitric oxide and postangioplasty restenosis: pathological correlates and therapeutic potential

Balloon angioplasty revolutionized interventional cardiology as a nonsurgical procedure to clear a diseased artery of atherosclerotic blockage. Despite its procedural reliability, angioplasty's long-term outcome can be compromised by restenosis, the recurrence of arterial blockage in response to balloon-induced vascular trauma. Restenosis constitutes an important unmet medical need whose pathogenesis has yet to be understood fully and remains to be solved therapeutically. The radical biomediator, nitric oxide (NO), is a natural modulator of several processes contributing to postangioplasty restenosis. An arterial NO deficiency has been implicated in the establishment and progression of restenosis. Efforts to address the restenosis problem have included trials evaluating a wide range of NO-based interventions for their potential to inhibit balloon-induced arterial occlusion. All types of NO-based interventions yet investigated benefit at least one aspect of balloon injury to a naive vessel in a laboratory animal without inducing significant side effects. The extent to which this positive, albeit largely descriptive, body of experimental data can be translated into the clinic remains to be determined. Further insight into the pathogenesis of restenosis and the molecular mechanisms by which NO regulates vascular homeostasis would help bridge this gap. At present, NO supplementation represents a unique and potentially powerful approach to help control restenosis, either alone or as a pharmaceutical adjunct to a vascular device.