Histopathology of in-stent restenosis in patients with peripheral artery disease

Hammerhead ribozymes targeted against cyclin E and E2F1 cooperate to down-regulate coronary smooth muscle cell proliferation

BACKGROUND

Anti-proliferative drugs released from endo-vascular stents have substantially contributed to reduce in-stent restenosis rates in coronary arteries bearing single primary lesions by down-regulating coronary smooth muscle cell (CSMC) growth. However, the considerably lower drug efficacy shown in treatment of more complex coronary lesions suggests that alternative anti-proliferative approaches can be beneficial. Thus, we explored the use of hammerhead ribozymes as tools to knock down cyclin E and E2F1, two potent activators of cell proliferation which cooperate to promote the G1 to S phase transition.

METHODS

Two ribozymes, one directed against cyclin E and the other against E2F1 mRNAs, were delivered by liposomes to cultured human CSMCs. The influences on cell proliferation were measured evaluating BrdU incorporation into newly synthesised DNA. The effects on cell cycle phase distribution were determined by BrdU and 7-aminoactinomycin D incorporation into DNA.

RESULTS

Both ribozymes exhibited a sequence-specific and dose-dependent reduction in BrdU incorporation, which, at a concentration of 280 nM, persisted up to 4 days after transfection of CSMCs. A combined administration of the two ribozymes (210+210 nM) resulted in a more pronounced decrease in BrdU incorporation compared to the administration of an equimolar amount (420 nM) of each of them. Finally, both ribozymes induced a significant (P<0.05) reduction in S phase cells with a concomitant increase of G1/G0 and G2-M phase cells, compared to controls.

CONCLUSIONS

The ribozymes selected represent potent tools to prevent CSMC proliferation, especially when administered together, and thus are ideal candidates for in vivo application.

GuardWire emboli protection device is associated with improved myocardial perfusion grade in saphenous vein graft intervention

BACKGROUND

Use of emboli protection devices (EPD) during saphenous vein graft percutaneous coronary intervention (SVG-PCI) has been proven to reduce major adverse cardiac events (MACE). However, the impact of EPD on the microcirculation using Thrombolysis in Myocardial Infarction myocardial perfusion grade (TMP) has not been fully characterized. We sought to analyze TMP after SVG-PCI with and without EPD and determine its impact on inhospital MACE.

METHODS

From August 2001 to December 2002, 305 patients had SVG-PCI suitable for EPD; 210 (69%) had an angiogram appropriate for TMP evaluation. Of those, 46 (22%) had an EPD (GuardWire, Medtronic, Minneapolis, Minn) deployed during the coronary intervention. Both groups were similar with regard to most demographic and clinical features.

RESULTS

A TMP score of 2.5 or 3 was obtained in 98% of the EPD group versus 85% of the unprotected SVG-PCI (P = .01). There was a trend towards reduction in MACE when using EPD (15% vs 27%, respectively, P = .07). Peak postprocedural creatine kinase-MB was somewhat lower in the EPD group (6.03 +/- 7.8 ng/mL vs 14.87 +/- 42 ng/mL, P = .17) Patients with a TMP grade of 2.5 or 3 had a statistically significant reduction in MACE (OR 0.36, 95% CI 0.14-0.87, P = .02).

CONCLUSIONS

Compared with SVG-PCI without emboli protection, EPD significantly improved TMP and trended towards a reduction in MACE.

Pathogen burden, inflammation, proliferation and apoptosis in human in-stent restenosis. Tissue characteristics compared to primary atherosclerosis

Pathogenic events leading to in-stent restenosis (ISR) are still incompletely understood. Among others, inflammation, immune reactions, deregulated cell death and growth have been suggested. Therefore, atherectomy probes from 21 patients with symptomatic ISR were analyzed by immunohistochemistry for pathogen burden and compared to primary target lesions from 20 stable angina patients. While cytomegalovirus, herpes simplex virus, Epstein-Barr virus and Helicobacter pylori were not found in ISR, acute and/or persistent chlamydial infection were present in 6/21 of these lesions (29%). Expression of human heat shock protein 60 was found in 8/21 of probes (38%). Indicated by distinct signals of CD68, CD40 and CRP, inflammation was present in 5/21 (24%), 3/21 (14%) and 2/21 (10%) of ISR cases. Cell density of ISR was significantly higher than that of primary lesions (977 +/- 315 vs. 431 +/- 148 cells/mm(2); p < 0.001). There was no replicating cell as shown by Ki67 or PCNA. TUNEL(+) cells indicating apoptosis were seen in 6/21 of ISR specimens (29%). Quantitative analysis revealed lower expression levels for each intimal determinant in ISR compared to primary atheroma (all p < 0.05). In summary, human ISR at the time of clinical presentation is characterized by low frequency of pathogen burden and inflammation, but pronounced hypercellularity, low apoptosis and absence of proliferation.

Increased adrenomedullin immunoreactivity and mRNA expression in coronary plaques obtained from patients with unstable angina

OBJECTIVE

To examine the expression and localisation of adrenomedullin in human coronary atherosclerotic lesions from patients with unstable angina (UAP) and stable angina (SAP), and to study the relation between adrenomedullin expression and plaque instability.

DESIGN

A retrospective observational study.

PATIENTS

Directional coronary atherectomy samples were obtained from 15 patients with UAP and 12 with SAP.

METHODS

The localisation of adrenomedullin was examined by immunohistochemistry, and adreno-medullin mRNA expression was measured by quantitative polymerase chain reaction.

RESULTS

Adrenomedullin immunoreactivity was preferentially localised in macrophages, intimal smooth muscle cells, and proliferated microvessels. The mean number of adrenomedullin positive cells in five high power fields (x 400) per specimen was higher in patients with UAP than in those with SAP (mean (SEM), 110 (13) v 76 (7); p < 0.05); and the ratio of adrenomedullin positive to total cells was higher in patients with UAP (43.0 (2.2)% v 34.2 (2.0)%; p < 0.01). More adrenomedullin mRNA was expressed in the plaque of patients with UAP than in those with SAP (60.4 (16.9)% v 9.7 (3.3)%; p < 0.01).

CONCLUSIONS

The findings suggest that adrenomedullin is involved in the development of atherosclerosis and plaque instability in human coronary arteries, in an autocrine or paracrine manner.

Impact of peri-stent remodeling on in-stent neointimal proliferation in acute myocardial infarction

Fifty stented lesions in 50 patients with acute myocardial infarction were studied by intravascular ultrasound (IVUS) before and just after stent implantation and at follow-up. Volumetric IVUS analyses revealed that greater peristent positive remodeling after stent implantation was associated with less neointimal proliferation and greater luminal gain at follow-up.

The effect of long-term clopidogrel use on neointimal formation after percutaneous coronary intervention

OBJECTIVE

The purpose of this study was to evaluate the long term effect of clopidogrel-based antiplatelet therapy on neointimal formation.

METHODS

This study comprised 78 patients with typical stable angina pectoris or documented myocardial ischaemia, and with only one angiographic lesion in one native coronary artery undergoing successful stent implantation without predilatation with C-reactive protein levels < or =5 mg/l at 72 h after the procedure. All patients received dual antiplatelet therapy with 75 mg/day clopidogrel and 300 mg/day aspirin for four weeks. Clopidogrel was switched to isochronous placebo in half of the patients (n=39) at the end of the fourth week. This allocation was maintained for 20 weeks, and at week 24 of the study, coronary angiography and intravascular ultrasound imaging were performed again in all cases in order to evaluate the changes that had occurred in the in-stent neointimal formation; rates of restenosis were also recorded

RESULTS

At the end of the follow-up period, angiographic stenosis diameter and restenosis rates were smaller in the clopidogrel group than in the placebo group (23.3% versus 35.6%, p=0.05 and 5.12% versus 10.25%; p=0.03 respectively); the intravascular ultrasonographic neointimal cross sectional area was also smaller in the clopidogrel group (3.6 +/- 2.7 mm(2) versus 5.2 +/- 2.5 mm(2), p=0.03).

CONCLUSIONS

Long-term clopidogrel administration significantly reduced neointimal formation at the stent site as well as reducing major clinical events in patients who did not develop high-risk systemic inflammatory response after percutaneous coronary intervention.

Molecular strategies to treat vascular diseases: circulating vascular progenitor cell as a potential target for prophylactic treatment of atherosclerosis

Atherosclerosis is responsible for more than half of all deaths in Western countries. Numerous studies have reported that accumulation of smooth muscle cells (SMCs) plays a principal role in atherogenesis, post-angioplasty restenosis and transplantation-associated vasculopathy. Although much effort has been devoted to targeting the migration and proliferation of medial SMCs, effective therapy to prevent occlusive vascular remodeling has not been established. Recently, it was suggested that bone marrow-derived precursors can give rise to vascular cells that contribute to the repair, remodeling, and lesion formation of the arterial wall under certain circumstances. This review highlights the recent findings on circulating vascular precursors and describes the potential therapeutic strategies for vascular diseases, targeting mobilization, homing, differentiation and proliferation of circulating progenitor cells.

Rapamycin attenuates atherosclerosis induced by dietary cholesterol in apolipoprotein-deficient mice through a p27 Kip1 -independent pathway

Activation of immune cells and dysregulated growth and motility of vascular smooth muscle cells contribute to neointimal lesion development during the pathogenesis of vascular obstructive disease. Inhibition of these processes by the immunosuppressant rapamycin is associated with reduced neointimal thickening in the setting of balloon angioplasty and chronic graft vessel disease (CGVD). In this study, we show that rapamycin elicits a marked reduction of aortic atherosclerosis in apolipoprotein E (apoE)-null mice fed a high-fat diet despite sustained hypercholesterolemia. This inhibitory effect of rapamycin coincided with diminished aortic expression of the positive cell cycle regulatory proteins proliferating cell nuclear antigen and cyclin-dependent kinase 2. Moreover, rapamycin prevented the normal upregulation of the proatherogenic monocyte chemoattractant protein-1 (MCP-1, CCL2) seen in the aorta of fat-fed mice. Previous studies have implicated the growth suppressor p27(Kip1) in the antiproliferative and antimigratory activities of rapamycin in vitro. However, our studies with fat-fed mice doubly deficient for p27(Kip1) and apoE disclosed an antiatherogenic effect of rapamycin comparable with that found in apoE-null mice with an intact p27(Kip1) gene. Taken together, these findings extend the therapeutic application of rapamycin from the restenosis and CGVD models to the setting of diet-induced atherosclerosis. Our results suggest that rapamycin-dependent atheroprotection occurs through a p27(Kip1)-independent pathway that involves reduced expression of positive cell cycle regulators and MCP-1 within the arterial wall.

Histological findings after angioplasty using conventional balloon, radiofrequency thermal balloon, and stent for experimental aortic coarctation

BACKGROUND

Use of balloon angioplasty or stent implantation has been reported to be effective in relieving coarctation of the aorta. However, restenosis frequently occurs after balloon angioplasty for native aortic coarctation in small infants, and sometimes develops after stent implantation because of vessel growth. The causes of restenosis remain uncertain. The purpose of this study was to assess the histologic differences in vascular responses to angioplasty using conventional balloon, radiofrequency thermal balloon (RFTB), or stent for experimental aortic coarctation.

METHODS

The authors surgically created an aortic coarctation model using 14 puppies. Angioplasty using conventional balloon, RFTB, or stent was performed 1 month after the initial operation. At the acute or chronic phase after angioplasty, the animals were killed and histologic studies were performed.

RESULTS

More vascular injuries were noted in the specimens from animals undergoing conventional angioplasty than in those with RFTB or stent. However, neointimal hyperplasia was seen more often after RFTB or stent because of the proliferation of smooth muscle cells from the tunica media, caused by secretion of growth factors. Apoptosis reached a peak 1-2 weeks after angioplasty, regardless of the type of intervention.

CONCLUSIONS

The authors conclude that angioplasty with RFTB or stent can provide relatively small injuries in the vessel wall for aortic coarctation, but care must be taken to prevent restenosis caused by intimal hyperplasia, because neointima hyperplasia is more frequent after RFTB or stent.

Highly increased cell proliferation activity in the restenotic hemodialysis vascular access after percutaneous transluminal angioplasty: implication in prevention of restenosis

BACKGROUND

The effect of percutaneous transluminal angioplasty (PTA) in the treatment of hemodialysis vascular access stenosis is attenuated by a high restenosis rate, which results mainly from neointimal hyperplasia. Cellular proliferation is one of the most important biological mechanisms involved in neointimal hyperplasia and may be a potential target of intervention to prevent restenosis.

METHODS

We investigated the activity of cellular proliferation of restenotic lesions by means of immunohistochemistry, using an antibody to the proliferating cell nuclear antigen. Specimens from 10 primary stenotic and 20 restenotic lesions of 30 Brescia-Cimino fistulae were obtained during revision.

RESULTS

The proliferation index of the restenotic group was strikingly significantly greater than that of the primary stenotic group (intima, P < 0.001; media, P = 0.001). Proliferation indices of patients with diabetes in the restenotic group were significantly higher than those of patients without diabetes (intima, P = 0.028; media, P = 0.002). In the restenotic group, proliferation indices correlated negatively with the interval from PTA to restenosis (intima, r = -0.741; P < 0.001; media, r = -0.589; P = 0.006) and positively with the number of PTAs per lesion (intima, r = 0.754; P < 0.001; media, r = 0.506; P = 0.004).

CONCLUSION

We show markedly high cellular proliferation activity in early restenotic lesions of arteriovenous fistulae. These findings indicate that adjunctive antiproliferative therapy is mandatory in preventing restenosis after PTA, especially in patients with diabetes.

Cell Cycle Regulator Expression After Coronary Stenting in Humans Immunohistochemical Examination

Proliferation of vascular smooth muscle cells (VSMCs) is under the control of cell cycle regulator activity, which is induced by several growth factors. Recent attention has been drawn to treatments that target cell cycle regulators to prevent the proliferation of VSMCs after coronary angioplasty. However, histopathological evaluation of cell cycle regulator expression after human coronary stenting has not been sufficient. Thirty-one coronary arteries of 23 cadavers were examined. Time from stent implantation to patient death ranged from 0 to 235 days. Sections were stained with antibodies against platelet-derived growth factor (PDGF), basic fibroblast growth factor (b-FGF), cyclin D1, p16, p21, and p27. Staining for macrophage colony stimulating factor receptor (MCSF-R) was conducted to detect dedifferentiated VSMCs. MCSF-R-positive cells were observed in neointima but decreased in the late stage. PDGF was detected in neointima and decreased gradually. Expression of cyclin D1 appeared to be associated with the proliferation of VSMCs, whereas p27 was downregulated with the proliferation of neointima and upregulated in the late stage. Our results suggest that one of the most promising methods for preventing excessive proliferation of neointima after stenting is to limit the decrease in p27 or the increase in cyclin D1.

Old and new cardiovascular risk factors: from unresolved issues to new opportunities

With the aim of identifying areas that may deserve some further thinking the present review deliberately points out controversial issues in cardiovascular research and risk assessment. In the first part of the review general aspects are addressed regarding the evaluation of risk factors. A first point of concern is the frequent practice of combining different vascular events and effects in different vascular beds into a single endpoint. Furthermore, verification of vascular events in clinical reality may be surprisingly inaccurate. Problems in risk assessment also arise from overlapping properties (shared pathophysiological pathways) of traditional risk factors like hypertension, obesity and diabetes. In the second part of the review unresolved issues concerning selected established and emerging risk factors are discussed. The difficulty of establishing causality in cardiovascular disease is addressed, using modification of LDL cholesterol and accumulating evidence for pleiotropic effects of the LDL cholesterol-lowering statins as an example. As an alternative or supplement to the notion of LDL-related cardiovascular risk it is proposed to distinguish between statin-sensitive and statin-insensitive cardiovascular risk. Finally the future prospects of selected new and emerging risk factors like CRP, homocysteine, asymmetrical dimethylarginine (ADMA), oxLDL, and isoprostanes are evaluated. In summary, imprecise terminology and varying definitions of "cardiovascular risk" may lead to a considerable blurring of our current risk estimates, which may also explain some presently controversial issues. With several new risk factors and substantial changes in lifestyle and treatment patterns on the horizon major changes in the hierarchy of risk factors may be inevitable.

Profound negative regulatory effects by resveratrol on vascular smooth muscle cells: a role of p53–p21WAF1/CIP1 pathway

We investigated the role of resveratrol, a polyphenol rich in red wine, in cell cycle progression and apoptosis of vascular smooth muscle cells (VSMCs). Resveratrol inhibited the growth of human aortic VSMCs at concentrations as low as 1 microM. This was due to the profound dose-dependent inhibition of DNA synthesis by resveratrol. DNA synthesis was more effectively inhibited when cells were pretreated with resveratrol. Resveratrol caused a dose-dependent increase in intracellular p53 and p21(WAF1/CIP1) levels. At lower concentrations (6.25-12.5 microM), resveratrol effectively blocked cell cycle progression of serum-stimulated VSMCs without inducing apoptosis, while the higher concentration of resveratrol (25 microM) selectively induced apoptosis in the same VSMCs. Intriguingly, however, the same high concentration of resveratrol could not induce apoptosis in quiescent VSMCs. These differential biological effects of resveratrol on quiescent and proliferating VSMCs suggest that resveratrol may be capable of selectively eliminating abnormally proliferating VSMCs of the arterial walls in vivo.

In vitro cellular aging is associated with enhanced proliferative capacity, G1 cell cycle modulation, and matrix metalloproteinase-9 regulation in mouse aortic smooth muscle cells

Cellular and molecular events in young (passage 1-3) and aged (passage 25-30) primary mouse aortic smooth muscle cells (MASMC) were investigated. Immunoblot and immunofluorescence analyses indicated that smooth muscle alpha-actin (SM alpha-actin) levels were significantly reduced with increasing in vitro age. Aged MASMC showed an increased proliferative capacity in response to fetal bovine serum (FBS) in comparison with young MASMC. The cell cycle-associated proteins such as cyclin D1, cyclin E, CDK2, and CDK4, and kinase activities associated with CDK2 and CDK4 were increased in aged MASMC. In addition, CDK inhibitor p21 was elevated in aged cell, whereas p27 was decreased. These changes of G1 cell cycle machinery could be explained by the increased proliferative capacity. Matrix metalloproteinase-9 (MMP-9) expression was also increased in response to tumor necrosis factor-alpha (TNF-alpha) in aged MASMC, as evidenced by zymography and immunoblot analysis. Transient transfection assays showed an age-dependent increase in transcription from MMP-9 promoter activity in response to TNF-alpha. In addition, the transcription factors NF-kappaB and AP-1 that are involved in the MMP-9 regulation of aged MASMC in response to TNF-alpha were identified by means of mutation analysis and gel shift assays. These results suggest that the age-associated increase in SMC proliferative capacity, accumulative cell cycle regulators, and MMP-9 expression may play a role in vascular remodeling during in vitro aging.

Transgene delivery of plasmid DNA to smooth muscle cells and macrophages from a biostable polymer-coated stent

Metallic stents coated with a polyurethane emulsion containing plasmid DNA were implanted in rabbit iliac arteries to evaluate transgene delivery and expression in the vessel wall. The expression of the plasmid-encoded marker genes, beta-galactosidase, luciferase and green fluorescence protein (GFP), were evaluated at 7 days after implantation. In all cases, plasmid transfer was confined to the vessel wall at the site of stent implantation, plasmid DNA was not observed in vessel segments immediately proximal or distal to the stent and dissemination of plasmid DNA to lung, liver or spleen was not observed. Expression of transgenes occurred only in vessel segments in contact with the stent and analysis of the GFP expression pattern revealed a high frequency of marker protein-positive cells occurring at or near the luminal surface. The extent of transgene expression was dependent upon the quantity of DNA loaded onto the stent and no signal was detected in vessel segments that received polymer-coated stents lacking plasmid DNA. Of significance, colocalization studies identified transgene expression not only in vascular smooth muscle cells but also in macrophages. Hence, polymer-coated stents provide a new capability for transgene delivery to immune cells that are believed to contribute to the development of in-stent restenosis.

Circulating vascular progenitor cells contribute to vascular repair, remodeling, and lesion formation

Exuberant accumulation of smooth muscle cells (SMCs) plays a principal role in the pathogenesis of vascular diseases. It has been assumed that SMCs derived from the adjacent medial layer migrate, proliferate, and synthesize extracellular matrix. Although much effort has been devoted to understanding the molecular pathways regulating migration and proliferation of medial SMCs, no effective therapy to prevent occlusive vascular remodeling has been established. It was recently reported that bone marrow cells substantially contribute to the pathogenesis of vascular diseases, in models of postangioplasty restenosis, graft vasculopathy, and hyperlipidemia-induced atherosclerosis. It was suggested that bone marrow cells may have the potential to give rise to vascular progenitor cells that home in on the damaged vessels and differentiate them into smooth muscle cells or endothelial cells, thereby contributing to vascular repair, remodeling, and lesion formation. The present findings may provide the basis for the development of new therapeutic strategies for vascular diseases, targeting mobilization, homing, differentiation, and proliferation of circulating vascular progenitor cells.

Fracture of popliteal artery stents

In peripheral arterial obstructive disease, more than 50% of all lesions are localized in the femoropopliteal segment and surgical revascularization is the treatment of choice. Percutaneous transluminal angioplasty (PTA) is recommended for short lesions, with subsequent stent implantation if the result is sub-optimal or dissections occur after PTA or for restenosis. There are both acute and late complications with stent implantation. In the present patient, stents were placed in the left popliteal artery where the left knee joint flexes, and obstruction because of stent fracture occurred 6 months later. The patient eventually underwent left femoro-popliteal saphenous vein bypass grafting.

Effect of percutaneous coronary interventions for in-stent restenosis in degenerated saphenous vein grafts without distal embolic protection

OBJECTIVES

This study was designed to investigate the impact of percutaneous coronary interventions (PCIs) in degenerated saphenous vein grafts (SVGs) without distal embolic protection.

BACKGROUND

Distal embolic protection devices have been shown to reduce the incidence of no reflow/slow flow during PCI of de novo lesions in degenerated SVGs. It is unclear whether PCI of in-stent restenosis (ISR) lesions in degenerated SVGs is associated with no reflow/slow flow and whether distal embolic protection is beneficial in these cases as well.

METHODS

We studied 54 consecutive patients with treated ISR lesions in degenerated SVGs who underwent PCI without distal embolic protection in a single center. Procedural and in-hospital outcomes were examined. The average age was 71 +/- 8 years; 32% of the patients had diabetes. The mean lesion length was 13 +/- 6 mm and the procedural success rate was 98% (53/54). Cutting balloon angioplasty was used in 46% (25/54) of cases, and a new stent was inserted in 46% (25/54) of patients. Gamma brachytherapy was performed in 19% (10/54) of patients. During the procedure there were no episodes of no reflow/slow flow, and there were no patients with in-hospital Q-wave or non-Q-wave myocardial infarction. There was one in-hospital noncardiac death.

CONCLUSIONS

In this consecutive series of patients with ISR of degenerated SVGs undergoing PCI without distal protection, there were no episodes of slow flow/no reflow and no procedure-related myocardial infarctions. It appears that distal embolic protection may not be necessary during PCI of ISR lesions in degenerated SVGs.

Quantification of the cell-cycle inhibitors p27(Kip1) and p21(Cip1) in human atherectomy specimens: primary stenosis versus restenosis

Proliferation, a key determinator of vascular proliferative diseases, is dependent on cyclin/cyclin-dependent kinase (CDK) complexes, which are controlled by cyclin-dependent kinase inhibitors (CKIs) such as p27(Kip1) and p21(Cip1). Both have prognostic significance in various human malignancies. We have determined the levels of p27(Kip1) and p21(Cip1) in human directional coronary atherectomy specimens of primary lesions (n = 15) and lesions of in-stent restenosis (n = 18) in comparison to those of other vascular regions and have correlated CKI levels with clinical data. Quantitative immunoblotting demonstrated low expression of p27(Kip1) in primary lesions (5.9 +/- 0.5 ng/mg protein) compared with that in aorta (14.9 +/- 0.9 ng/mg), internal mammary artery (16.7 +/- 1.1 ng/mg), and carotid artery thrombendarterectomy specimens (16.5 +/- 1.7 ng/mg). Similarly, p27(Kip1) levels in lesions of in-stent restenosis were found to be significantly reduced (6.3 +/- 1.1 ng/mg; mean time of restenosis development 367 +/- 61 days). p27(Kip1) levels did, however, not have prognostic significance for the development of restenosis, and expression levels of proliferating cell nuclear antigen and CDK2 were similar in all groups examined, indicating low proliferative activity. Clinically, p27(Kip1) was not of value in predicting the development of restenosis. Furthermore, p27(Kip1) tissue levels were not increased in statin-treated patients, implying that the favorable effect of these drugs is not a result of p27(Kip1) stabilization. However, the relative content of p21(Cip1) was found to be significantly up-regulated in restenosis compared with that in primary lesions (225%) and the other vascular regions. Our data imply that negative-feedback mechanisms are still intact in coronary proliferative disease, thereby contrasting the finding of deregulated proliferation in malignancies.

Involvement of C-reactive protein obtained by directional coronary atherectomy in plaque instability and developing restenosis in patients with stable or unstable angina pectoris

We investigated whether positive immunohistochemical staining of C-reactive protein (CRP) in initial culprit lesions is related to coronary plaque instability and whether it could affect the outcome of directional coronary atherectomy (DCA). The plasma level of CRP is a reliable marker of the risk of coronary events and restenosis after percutaneous coronary intervention. However, the influence of tissue CRP in atheromatous plaque on plaque vulnerability and restenosis remains unknown. Samples of DCA obtained from 12 patients with stable angina pectoris and 15 patients with unstable angina pectoris were immunohistochemically stained with a monoclonal antibody against CRP. We performed follow-up coronary angiography on 22 of 27 patients to evaluate the presence of restenosis after DCA. Immunoreactivity to CRP was localized to macrophages, smooth muscle cells, and necrotic areas. The ratio of CRP positive cells to total cells was significantly higher in DCA samples from patients with unstable (17.9 +/- 2.0%) than with stable angina (11.0 +/- 2.5%) (p <0.05). Follow-up coronary angiography showed that 12 of 22 patients developed restenosis after DCA. The ratio was also significantly higher in DCA specimens from patients with restenosis (19.3 +/- 2.8%) compared with those without restenosis (11.0 +/- 2.0%) (p <0.05). In addition, the ratio significantly correlated with late luminal loss (r = 0.428, p <0.05) and loss index (r = 0.636, p = 0.0011) after DCA. Immunoreactivity to CRP in coronary atheromatous plaque increases in culprit lesions of unstable angina, and it affects restenosis after DCA. These findings suggest that CRP in atheromatous plaque plays an important role in the pathogenesis of unstable angina and restenosis after coronary intervention.

Histopathology of coronary in-stent restenosis following gamma brachytherapy

The histopathology of in-stent restenosis (ISR) following gamma brachytherapy is described. Such histology has not been reported previously. An 82 year old man presented with recurrent ISR three months after gamma brachytherapy to an area of ISR within a native circumflex vessel. The recurrent ISR was treated with directional coronary atherectomy; the histopathology of this directional coronary atherectomy specimen is discussed. These histopathological examinations showed abundant extracellular matrix material. Surprisingly, there was a relatively small cellular (myofibroblastic) component, with an absence of endothelial cells and little evidence of active proliferation. ISR after gamma brachytherapy may be a pathologically distinct entity.

Mechanisms of restenosis after coronary intervention: difference between plain old balloon angioplasty and stenting

BACKGROUND

Restenosis after coronary intervention remains an unsolved and important clinical problem. We histologically examined the mechanism of restenosis after both balloon injury and stenting.

METHODS

Coronary arteries of swine were subjected to balloon injury and stenting. Next, just after stenting or at 7, 14, or 28 days, the animals were sacrificed for the evaluation by morphometric analysis, histological observation, and immunostaining.

RESULTS

The neointimal area peaked at 14 days in the balloon injury group (BG) and increased linearly up to 28 days in the stent group (SG). At 28 days, the total vascular area in the BG was reduced to 78% of the control values. In the SG, the total vascular area remained enlarged. According to the phenotypic analysis, the vascular smooth muscle cells (VSMCs) in the neointimal area at 28 days were the contractile type in the BG and the synthetic type in the SG. Proliferating cell nuclear antigen (PCNA) and macrophage-positive cells were not observed in neointima in the BG at 28 days, whereas they were observed around the stent struts in the SG. In addition, numerous inflammatory cells, such as neutrophils and eosinophils, were also present in the SG.

CONCLUSIONS

Restenosis after balloon injury consisted of arterial remodeling and neointimal hyperplasia, whereas that after stenting consisted mostly of neointimal hyperplasia. The neointimal area in the SG lasted longer than that in the BG. Continuous inflammation may be an important factor in the restenosis of stenting.

Hemobahn stent-grafts for treatment of femoropopliteal arterial obstructions: midterm results of a prospective trial

PURPOSE

To report a prospective study to evaluate safety, effectiveness, and midterm patency of self-expanding stent-grafts in patients with femoropopliteal occlusive disease.

MATERIALS AND METHODS

Sixty-three Hemobahn stent-grafts were used in 52 patients for treatment of medium- or long-segment (>3 cm) occlusions (82.7%) and stenoses (17.3%) of the femoropopliteal artery. The mean length of vessel segments covered was 10.9 cm +/- 5.13. Follow-up with documentation of clinical symptoms, assessment of Rutherford clinical stage of peripheral vascular disease, and color-coded duplex sonography was performed at discharge, at 1, 3, 6, 12, 18, and 24 months after implantation, and yearly thereafter. Mean follow-up duration was 23.8 months +/- 6.9 (range, 8-36 mo). Follow-up data at 12 and 24 months after treatment were available for 47 of 52 (90.4%) and 31 of 52 patients (59.6%), respectively.

RESULTS

Device implantation was technically successful in all 52 patients, yielding an overall technical success rate of 100%. Procedure-related complications were observed in 12 of 52 patients (23.1%) and consisted of distal embolization (n = 4, 7.7%), minor groin hematoma (n = 7, 13.5%), and arteriovenous fistula (n = 1, 1.9%), but prolonged hospitalization and further medical, interventional, or surgical measures were not required. Stent-graft placement induced an initial improvement of the mean resting ankle-brachial index from 0.54 +/- 0.12 to 0.89 +/- 0.14 (P <.01). Primary patency rates at 12 and 24 months were 78.4% +/- 5.8 and 74.1% +/- 6.2, respectively. Primary assisted patency rates were 82.4% +/- 5.3 at 12 months and 80.3% +/- 5.6 at 24 months. Secondary patency rates at 12 and 24 months were 88.3% +/- 4.5 and 83.2% +/- 5.5, respectively. There was no significant difference (log-rank test, P >.3) between primary patency rates in patients grouped according to lengths of implanted grafts (ie, length of the treated lesions).

CONCLUSION

Endovascular placement of Hemobahn stent-grafts for percutaneous treatment of medium- to long-segment high-grade stenoses and occlusions of the femoropopliteal artery is a safe procedure with excellent initial success rates and promising midterm results.

Enhanced extracellular matrix accumulation in restenosis of coronary arteries after stent deployment

OBJECTIVES

The goal of this study was to evaluate the cellular and extracellular composition of human coronary arterial in-stent restenosis after various periods of time following stent deployment.

BACKGROUND

Neointimal in-growth rather than stent recoil is thought to be important for coronary arterial in-stent restenosis. There is only limited data on the cellular and extracellular composition changes with time after stent deployment.

METHODS

We analyzed 29 coronary arterial in-stent restenotic tissue samples (14 left anterior descending coronary artery, 10 right coronary artery, and 5 left circumflex artery) retrieved by using directional coronary atherectomy from 25 patients at 0.5 to 23 (mean, 5.7) months after deployment of Palmaz-Schatz stents employing histochemical and immunocytochemical techniques.

RESULTS

Cell proliferation was low (0% to 4%). Myxoid tissue containing extracellular matrix (ECM) enriched with proteoglycans was found in 69% of cases and decreased over time after stenting. Cell-depleted areas were found in 57% of cases and increased with time after stenting. Versican, biglycan, perlecan, and hyaluronan were present with varying individual distributions in all samples. Positive transforming growth factor-beta1 staining was found in 80% of cases. Immunostaining with alpha-smooth muscle actin identified the majority of cells as smooth muscle cells with occasional macrophages present (< or =12 cells per section).

CONCLUSIONS

These data suggest that enhanced ECM accumulation rather than cell proliferation contribute to later stages of in-stent restenosis. Balloon angioplasty of in-stent restenosis may, therefore, fail due to ECM changes during: 1) additional stent expansion, 2) tissue extrusion out of the stent, or 3) tissue compression.

Human in-stent restenosis tissue obtained by means of coronary atherectomy consists of an abundant proteoglycan matrix with a paucity of cell proliferation

BACKGROUND

In-stent restenosis (ISR) is a shortcoming of percutaneous coronary revascularization. Although neointimal cell proliferation is suspected to be the cause of this problem, little histological characterization of this tissue or data on cell replication exist. The purpose of this study was to examine the histologic features and proliferation profile of coronary ISR tissue derived from atherectomy procedures performed on patients with clinical evidence of ISR.

METHODS

ISR tissue retrieved by means of atherectomy from 20 coronary lesions was subjected to histomorphological analyses and immunocytochemistry as a means of examining proteoglycan expression. Cell proliferation was assessed with 2 sensitive markers of replication, in situ hybridization for histone 3 messenger RNA expression and immunocytochemistry for Ki-67 expression.

RESULTS

The ISR atherectomy specimens consisted primarily of smooth muscle cells, with occasional focal collections of inflammatory cells and organizing thrombus. All specimens had low levels of interstitial collagen and an abundant proteoglycan matrix, with biglycan being overexpressed more commonly than decorin. Cell proliferation was found in only 1 of 20 specimens (2 cells).

CONCLUSION

Established ISR lesions contained an abundant proteoglycan matrix and a paucity of proliferating cells. Future therapeutic strategies for ISR should include targeting extracellular matrix production.

New catheter-based technology for the treatment of restenosis

Catheter-based vascular interventions have been in development worldwide for several decades, leading to remarkable progress in device technology. Mechanical interventional devices, such as angioplasty balloons, atherectomy devices, and stents, were invented and have contributed greatly to the treatment of atherosclerotic vascular stenosis. However, mechanical approaches do not effectively prevent subsequent intimal growth. Recently, several biological approaches, including radiation therapy and drug-eluting stents, have shown striking inhibition of intimal growth. These significant results are likely to change the treatment strategy in the field of interventional cardiology. Furthermore, additional catheter-based technologies for vascular interventions are presently being evaluated. These latest technologies designed to prevent intimal proliferation include intravascular sonotherapy, cryotherapy, photoangioplasty, and soft X ray. To date, intravascular sonotherapy has proven its efficacy in animal studies and safety in human studies. Cryotherapy, the application of cold thermal energy during angioplasty, enhances the acute effects of conventional dilation while decreasing the likelihood of restenosis. Photoangioplasty has a unique property based on its selective mechanism of action to treat atheromatous plaque. Soft X ray systems provide convenient device handling and well-controlled radiation dose. Some of these technologies may play an important role in vascular interventions in the near future.

Tumor necrosis factor-alpha antibody eluting stents reduce vascular smooth muscle cell proliferation in saphenous vein organ culture

Expression of TNF-alpha a vascular smooth muscle cell (VSMC) mitogen, is up-regulated in injured/proliferating vessel wall. Coronary stents are tested worldwide for their use as local drug delivery devices to address vascular pathophysiology. In this study we have investigated the effect of TNF-alpha antibody eluting stents on VSMC proliferation in human saphenous vein (HSV) organ culture. The adsorption and elution characteristics of TNF-alpha antibody was assessed using stent wires. The stents adsorbed up to 0.25 microg of TNF-alpha antibody/mg of stent and showed a biexponential elution curve, with 34.4% (SD 4.4%) antibody remaining on the stent after 72 h of washing in a perfusion circuit. TNF-alpha antibody delivery from loaded stents to the vessel wall was assessed ex vivo. TNF-alpha and proliferating cell nuclear antigen (PCNA) expression in the vascular specimens was assessed by immunostaining or ELISAs. TNF-alpha ELISAs showed a significant increase in the cytokine levels from the vascular lysates prepared from proliferating tissue culture compared with fresh vein (P < 0.05). Immunohistochemical localization showed an increase in the PCNA positivity of VSMC from these cultures. PCNA staining was barely detected from the fresh tissue. However, a decrease in PCNA staining was observed from tissue sections of venous segments cultured with TNF-alpha antibody eluting stents. PCNA ELISAs demonstrated a 23.7% decline in the antigen levels from the day 7 tissue cultured with such loaded stents. In conclusion, activated VSMC in tissue culture showed an up-regulation of TNF-alpha cytokine, in association with an increase in the PCNA expression in the vessel wall. The local neutralization of this cytokine with TNF-alpha antibody eluting stents reduced VSMC proliferation in the wall. We suggest that TNF-alpha antibody eluting stents may limit restenosis in vivo, which may have important clinical benefits.

Can we prevent in-stent restenosis?

Nowadays stent placement has replaced balloon angioplasty as the most commonly performed percutaneous coronary interventional procedure, mainly because of its better acute and chronic outcome. As a result, in-stent restenosis (ISR) has become a widespread problem. The incidence of ISR varies from 10% to 50% and depends on the absence or presence of several risk factors, such as small vessel size, longer lesions, and diabetes. Intravascular ultrasound studies have demonstrated that ISR is mainly caused by neointimal proliferation; consequently, this pathologic process has become the target of many preventive and therapeutic approaches. This article provides an overview of such management strategies, highlighting the rather disappointing experiences with mechanical and systemic drug therapies; the relative merits and disadvantages of intracoronary radiation; and the exciting yet realistic promise, embodied by the recent advancements in drug-eluting stent technology, of potentially eradicating ISR in the near future.

Biocompatibility and performance of the Wallstent and the Wallgraft, Jostent, and Hemobahn stent-grafts in a sheep model

PURPOSE

Three recently developed stent-grafts and the Wallstent were compared directly in an ovine animal model with regard to performance and biocompatibility.

MATERIALS AND METHODS

Three stent-grafts, the Hemobahn (polytetrafluoroethylene [ePTFE]/nitinol), Wallgraft (polyester/Ni-Co-Ti-steel alloy), and Jostent peripheral stent-graft (balloon-expandable ePTFE/stainless steel), and the Wallstent (Ni-Co-Ti-steel alloy), were implanted in sheep iliac arteries (one type of each stent or stent-graft per animal, n = 8). Pre- and postimplantation luminal diameters were measured for each prosthesis and implantation site. Angiography, intravascular ultrasonography (IVUS), and histomorphometric, histologic, and scanning electron microscopic analyses were performed at 3 months.

RESULTS

Early lumen gain, late lumen loss, and patent vessel diameter at angiography were not significantly different. Two stent-grafts had significantly more neointima formation (Hemobahn, 9.88 mm(2) +/- 0.94; Wallgraft, 14.98 mm(2) +/- 0.90) than the other stent-graft (Jostent, 6.52 mm(2) +/- 0.46) and the Wallstent (5.24 mm(2) +/- 0.62; P <.01). Patent lumen area was not significantly different (Hemobahn, 42.57 mm(2) +/- 1.41; Jostent, 39.76 mm(2) +/- 2.04; Wallgraft, 40.22 mm(2) +/- 1.04; Wallstent, 41.64 mm(2) +/- 1.59; P =.57). The Hemobahn had significantly more inflammatory reaction (inflammation score of 0.83 +/- 0.03) than the Jostent (0.58 +/- 0.03), Wallgraft (0.55 +/- 0.04), or Wallstent (0.16 +/- 0.01). Angiography and IVUS demonstrated absence of anastomotic neointima formation. Endothelialization was incomplete and immature for all prostheses.

CONCLUSIONS

The stent-grafts caused a greater degree of neointima formation and inflammatory vessel wall reaction than the bare stent. However, these changes did not interfere with patent lumen areas and occurred in the absence of excessive anastomotic neointima formation.

Cell replication induces in-stent lesion growth in rabbit carotid artery with preexisting intimal hyperplasia

This study examined the responses of rabbit carotid artery with a preexisting intimal lesion, to stent implantation and balloon dilation. Rabbit carotid arteries were injured with a Fogarty catheter, and 28 days later the same arteries were subjected to implantation of a Palmaz-Schatz stent or balloon dilation angioplasty. Intimal size was significantly increased after stent implantation and balloon dilation, and no significant difference was detected between the two procedures. After stent implantation, replicating intimal cells were increased mainly in the inner intima, and the increase of cell replication was prolonged until day 28. In contrast, a significant increase of intimal cell replication was detected only at 2 days after balloon dilation. Intimal cell number after stent implantation was significantly higher than that after balloon dilation from day 7. Abundant leukocytes adhered to the luminal surface until 14 days after stent implantation, and significant infiltration of macrophages was observed in the mid-intima. Activation of proteases was prolonged, and obvious accumulation of proteoglycans was detected after stent implantation as compared with balloon dilation. These findings suggest that, an increase in cell replication is critical in the development of in-stent restenosis, and that inflammatory responses represent a unique property after stent implantation.

Inhibition of neointimal formation after stent placement with adenovirus-mediated gene transfer of I kappa B alpha in the hypercholesterolemic rabbit model: initial results

PURPOSE

To evaluate the feasibility and efficacy of the local application of a replication-defective adenovirus construct for the expression of the antiinflammatory protein I kappa B alpha, inhibitor of nuclear factor kappa B (NF-kappa B), to reduce neointimal formation after stent placement.

MATERIALS AND METHODS

Nitinol stents were implanted in the iliac arteries of hypercholesterolemic rabbits, followed by balloon dilation (30 seconds at 6 atm). Local adenovirus-mediated transfer of I kappa B alpha (3 mL of 10(9) plaque-forming units per milliliter at 6 atm) was performed and compared with three control groups: stent alone, stent plus local delivery of phosphate-buffered saline (PBS) (3 mL at 6 atm), and stent plus local delivery of control adenovirus coding for green fluorescent protein (GFP) (3 mL of 10(9) plaque-forming units per milliliter at 6 atm). A multichannel balloon was used for local drug delivery and balloon dilation. Animals were sacrificed 1 or 4 weeks after treatment. Effective transfection was demonstrated with immunofluorescence staining. Angiographic patency and luminal diameter were evaluated at quantitative angiography. Luminal and neointimal areas were measured on surface-stained ground sections with methylmethacrylate embedding and the cutting-grinding technique.

RESULTS

All vessels with stents were patent at angiography. Neointimal area was negligible in all groups 1 week after stent placement (range, 0.42-0.52 mm(2); P =.44; analysis of variance). Neointimal formation was demonstrated in all groups 4 weeks after implantation but was significantly reduced with I kappa B alpha treatment compared with treatment with stent alone (by 22%, from 2.80 mm(2) +/- 0.20 to 2.28 mm(2) +/- 0.14, P =.05), stent plus PBS (by 43%, from 3.26 mm(2) +/- 0.25 to 2.28 mm(2) +/- 0.14, P =.005), and stent plus GFP (by 53%, from 2.32 mm(2) +/- 0.19 to 1.51 mm(2) +/- 0.08, P <.005).

CONCLUSION

Local adenovirus-mediated I kappa B alpha gene transfer has the potential to reduce intimal hyperplasia after stent placement.

Hematopoietic stem cells differentiate into vascular cells that participate in the pathogenesis of atherosclerosis

Excessive accumulation of smooth-muscle cells (SMCs) has a key role in the pathogenesis of vascular diseases. It has been assumed that SMCs derived from the outer medial layer migrate, proliferate and synthesize extracellular matrix components on the luminal side of the vessel. Although much effort has been devoted to targeting migration and proliferation of medial SMCs, there is no effective therapy that prevents occlusive vascular remodeling. We show here that in models of post-angioplasty restenosis, graft vasculopathy and hyperlipidemia-induced atherosclerosis, bone-marrow cells give rise to most of the SMCs that contribute to arterial remodeling. Notably, purified hematopoietic stem cells differentiate into SMCs in vitro and in vivo. Our findings indicate that somatic stem cells contribute to pathological remodeling of remote organs, and may provide the basis for the development of new therapeutic strategies for vascular diseases through targeting mobilization, homing, differentiation and proliferation of bone marrow-derived vascular progenitor cells.

Pathogenetic heterogeneity of in-stent lesion formation in human peripheral arterial disease

PURPOSE

Intimal hyperplasia is known to promote in-stent restenosis after vascular stent implantation. Although previous studies have presented a variety of evidence that suggests the mechanisms of intimal lesion formation, it is still controversial which factor(s) predominantly contribute to the development of in-stent restenosis. In this study, we hypothesized that heterogeneous mechanisms coexist in the same lesion and then assessed the validity with resected whole arteries with in-stent lesions.

METHODS

Whole arterial specimens with in-stent lesions were surgically resected from five patients who had undergone implantation of a Palmaz-Schatz stent 7 to 19 months previously and were histologically analyzed. For assessment of the pathogenetic heterogeneity of in-stent lesions, we divided each cross section into three parts: the inner intima within 250 microm from the luminal surface (zone A), the area surrounding the stent struts within 250 microm from the strut hole (zone B), and the remaining part of the intimal layer (zone C). We then evaluated cell density, cell replication, and cellular composition in each zone. Cell replication and cellular composition were analyzed with immunohistologic staining with antibodies against proliferating cell nuclear antigen and cell-specific antibodies. Each section was also stained with Alcian blue or Elastica van Gieson method for detection of matrix components.

RESULTS

In all samples, the cell density of zone A was significantly higher than that of zone B (P <.05). Proliferating cell nuclear antigen staining results showed significantly higher cell replication in zone A as compared with that in other zones (P <.05). To the contrary, cell-specific immunostaining results revealed marked accumulation of leukocytes, macrophages, and T lymphocytes in zone B (P <.05). Regarding matrix components, proteoglycan was predominantly stained around stent struts and in the inner intima.

CONCLUSION

The data of this study showed that two different pathogenetic processes in different zones possibly contributed to in-stent lesion formation at the same time. One process was an increase of cell number in the inner intima, which was the result of a prolonged increase of cell replication. The other process was accumulation of matrix around stent struts, which was suggested to be linked to infiltration of inflammatory cells in the same zone.

Endovascular placement of self-expanding nitinol coil stents for the treatment of femoropopliteal obstructive disease

PURPOSE

To report on a prospective two-center study to evaluate safety and effectiveness of a self-expanding nitinol coil stent in patients with femoropopliteal obstructive disease.

MATERIALS AND METHODS

The IntraCoil nitinol stent was used in 37 patients (28 men and nine women; mean age, 62.4 y plus minus 10.7; range, 43-81 y) presenting with high-grade stenoses (n = 23) or short (<3 cm) occlusions (n = 17) of the superficial femoral artery (SFA; n = 33) or popliteal artery (n = 4). Indications for stent placement were significant residual stenosis (>30%) or dissection after angioplasty. Follow-up evaluations with measurement of the Doppler ankle-brachial index (ABI), assessment of Rutherford clinical stage, and color-coded duplex sonography were performed at discharge and 1, 3, 6, 12, and 18 months thereafter. Primary endpoints of the study were immediate technical and clinical success and 1-year patency.

RESULTS

Initial technical success was achieved in all patients. In 10 patients (27%), more than one 40-mm-long device had to be implanted for total lesion coverage; in three patients (8.1%), stents were placed in two separate segments of the SFA simultaneously. The total number of stents deployed was 50. Stent placement induced an initial improvement of the ABI from 0.54 plus minus 0.2 to 0.92 plus minus 0.11 (P <.01). Follow-up data for 12 months after treatment are available for 29 of 37 patients (78.4%); mean follow-up is 15.6 months (range, 1-26 mo). Primary patency rates at 6 and 12 months were 97.1% (SE = 2.9) and 86.2% (SE = 6.5). The primary assisted patency rate was 100% at 12 months.

CONCLUSION

Endovascular placement of the IntraCoil self-expanding nitinol coil stent for salvage of failed angioplasty in patients with femoropopliteal obstructive disease is an effective and safe procedure with promising mid-term results.

Decoy oligodeoxynucleotide against activator protein-1 reduces neointimal proliferation after coronary angioplasty in hypercholesterolemic minipigs

OBJECTIVES

We sought to demonstrate, in an appropriate animal model, that co-medication with a transcription factor-blocking agent limits restenosis after percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Enhanced synthesis in the vessel wall of endothelin-1 (ET-1), a powerful co-mitogen for vascular smooth muscle cells, appears to be one mechanism that promotes restenosis after PTCA. Deformation-induced expression of prepro-ET-1 is governed by the transcription factor, activator protein-1 (AP-1).

METHODS

An anti-AP-1 decoy oligodeoxynucleotide (dODN) strategy was devised in which the dODN-containing solution (20 nmol) was administered locally through a Dispatch catheter into the coronary arteries of hypercholesterolemic minipigs at the time of PTCA (AVE-GFX stent).

RESULTS

Treatment with an AP-1 dODN, mimicking the consensus binding site of the transcription factor, significantly reduced neointimal formation in the coronary arteries of hypercholesterolemic minipigs (n = 10 to 12), compared with vehicle-treated coronary arteries, after four weeks of follow-up (neointimal area 2.64 +/- 0.33 vs. 4.81 +/- 1.04 mm(2) [mean +/- SEM]; p < 0.05). This effect was maintained after eight weeks (neointimal area 2.04 +/- 0.22 mm(2); n = 3) and correlated with a reduction in both nuclear translocation of AP-1 and ET-1 synthesis in the vessel wall 48 h after PTCA (n = 4). In contrast, an AP-1 mutant dODN, to which the transcription factor does not bind, showed no effect on neointimal formation at either time point (n = 3 to 7). Moreover, a consensus dODN directed against CCAAT/enhancer binding protein (C/EBP), another deformation-sensitive transcription factor, did not significantly affect neointimal formation after four weeks (n = 3).

CONCLUSIONS

These findings demonstrate the feasibility, efficacy and specificity of the anti-AP-1 dODN approach to the treatment of restenosis, which principally but not exclusively targets deformation-induced ET-1 synthesis in the vessel wall. Provided that these findings can be extrapolated to the situation of patients with coronary artery disease, the observed extent of the inhibitory effect of the AP-1 dODN treatment suggests that this co-medication may greatly reduce the incidence of in-stent restenosis.

Treating atherosclerosis: local drug delivery from laboratory studies to clinical trials

Treating only the specific section of the vascular bed that is diseased appears to make sense. Giving drugs systematically to treat perhaps only a few centimetres of affected artery carries with it the risk of systemic side effects and reduced efficacy consequent on low concentrations of agent at the site of the problem. There has thus been great interest since the early 1990s in local drug delivery. Initial targets were the thrombotic response to plaque disruption but the problems arising from the incidental damage inflicted by devices used in interventional cardiology and the pathological consequences of this, namely smooth muscle cell initiated intimal hyperplasia, soon became the focus of pre-clinical studies. Problems to be overcome were the low efficiency of delivery of drugs and the low retention rates. Solutions to these problems included the development of strategies to target drugs, through the use of antibodies directed at antigens newly released at the site of damage. As it became clear that stents were becoming central to the attainment of a better clinical response to intervention by their inherent physical properties, it also became obvious that stents could be used to deliver agents. Issues such as which stent, how to load the drug onto the stent and what drug to use to inhibit the unwanted pathobiological response are ongoing issues.

Coronary in-stent restenosis: current status and future strategies

In-stent restenosis (ISR) is a novel pathobiologic process, histologically distinct from restenosis after balloon angioplasty and comprised largely of neointima formation. As percutaneous coronary intervention increasingly involves the use of stents, ISR is also becoming correspondingly more frequent. In this review, we examine the available studies of the histology and pathogenesis of ISR, with particular reference to porcine and other animal models. An overview of mechanical treatments is then provided, which includes PTCA, directional coronary atherectomy and high speed rotational atherectomy. Radiation-based therapies are discussed, including a summary of current problems associated with this modality of treatment. Finally, novel strategies for the prevention of ISR are addressed, including novel developments in stents and stent coatings, conventional drugs, nucleic acid-based drugs and gene transfer. Until recently, limited pharmacologic and mechanical treatment options have been available for both treatment and prevention of ISR. However, recent advances in gene modification and gene transfer therapies and, more particularly, in local stent-based drug delivery systems make it conceivable that the incidence of ISR will now be seriously challenged.

Newly Developed Stent Graft with Micropored and Heparin Impregnated SPU Film. Long-Term Follow-up Study in Vivo

SUMMARY

The use of stents has improved results after balloon carotid angioplasty. Some materials have been reported for covering the metal surface of the stent to reduce the rate of subacute thrombosis and restenosis. We have already developed a new stent graft with thin-walled controlled micropored polymer covering, and in a previous study we confirmed tissue ingrowth via the micropores at one month in a beagle model. The progress of cell migration was controlled by micropore density using a constant micropore diameter (30mum diameter, 125mum inter-pore distance). In the present study, we applied our newly developed stent graft impregnated with heparin for implantation in the rabbit carotid artery, and carried out an angiographic and histological investigation. Our stent graft was made from a Palmaz-Schatz stent and a micropored segmental polyurethane (SPU) thin film with a heparin coating. Micropores 30mum in diameter and 125mum apart were created on the thin SPU film using an excimer laser ablation technique. The surface of the micropored film was then impregnated with photosensitive gelatin that incorporated the heparin. The metal stent was rolled up and fixed to this modified SPU film under microscopic observations. These stent grafts were deployed in the common carotid arteries (CCAs) of rabbits (37 carotid arteries, 20 rabbits). The animals were sacrificed one, two and three months later, and a histological study and scanning electron microscopy study were performed for evaluation of endoluminal endothelialization and intimal thickening at the late stage. CCAs treated with stent grafts of micropored film showed poor-patency and intimal hyperplasia compared with those treated with a simple bare stent or a heparin-impregnated stent. In terms of intimal hyperplasia and patency, the heparin-impregnated stent was superior to the bare stent. Intimal hyperplasia was prevented by control of tissue ingrowth through the micropores. The antithrombogenicity of the impregnated heparin improved patency in the early stage. Our new stent graft with a heparin-impregnated SPU film thus appears promising for prevention of restenosis due to neointimal hyperplasia.

Rationale for coronary artery radiation therapy

Within the past decade, focus on radiation to prevent restenosis has moved from a concept developed in the animal laboratory to a clinical treatment. The initial evaluation of coronary artery radiation therapy focused on changes in the function of the artery or lesion formation following overstretch balloon injury in pigs. A number of concepts emerged from this work: (1) radiation inhibits neointima formation in a dose-dependent fashion, (2) radiation prevents negative remodeling, (3) radiation does not reverse established injury, (4) low dose irradiation in an injured area may be injurious, (5) radiation is a useful adjunct to stenting, (6) benefits of radiation in animal models at 6 months are less pronounced than at 1 month, (7) radiation delays healing, (8) permanent stents and radiation delivered from external sources may have very different effects on restenosis, and (9) radiation interferes with vessel wall function. More recent studies of irradiation have looked at the molecular biological effects of radiation in hopes of understanding how this therapy works, and how it may be improved. This article attempts to summarize the known animal and cellular work on radiation in preventing restenosis.

Laser coronary angioplasty: history, present and future

The efficacy of percutaneous transluminal coronary angioplasty (PTCA) is limited by remaining plaque tissue and the development of restenosis. It has been demonstrated that the restenosis rate is low if a large lumen diameter is achieved after coronary intervention. Debulking of coronary stenoses is a concept to increase the luminal diameter after intervention. Laser angioplasty debulks coronary stenoses by ablation of atherosclerotic plaque. Since the first intravascular laser intervention, the technique has been significantly improved by the use of optimized wavelength, the development of flexible optimally spaced multifiber catheters and an additional saline flush technique. These technical advancements allowed a reduction in the incidence of adverse events, such as the number of dissections and perforations, associated with the use of the laser technique. Coronary laser angioplasty is commonly combined with adjunctive balloon angioplasty to optimize the outcome. Laser coronary angioplasty was not followed by a lower restenosis rate compared with plain balloon angioplasty in lesions without stents, however, a randomized comparison of the techniques including the use of the saline flush technique is not available yet. The value of excimer (acronym for excited dimer) laser coronary angioplasty for treatment of in-stent restenosis is still under investigation. So far, nonrandomized single center studies have not suggested a relevant benefit for this technique used for in-stent restenosis. In nonstented lesions there remain niche indications for laser angioplasty such as the treatment of ostial lesions, diffuse lesions or lesions traversable with a guidewire but not with an angioplasty balloon. Laser coronary angioplasty may also be useful after a failed balloon angioplasty and in patients with chronic total occlusions. The potential advantages of combining laser coronary angioplasty with vaporization of thrombus in patients with acute coronary syndromes are currently under evaluation.

Catalytic oligonucleotides targeting EGR-1 as potential inhibitors of in-stent restenosis

This brief review discusses recent strategies targeting the zinc finger transcription factor and immediate-early gene product Egr-1 with catalytic DNA in efforts to inhibit postangioplasty restenosis.

Tissue-specific expression of an anti-proliferative hybrid transgene from the human smooth muscle alpha-actin promoter suppresses smooth muscle cell proliferation and neointima formation

The retinoblastoma protein (Rb), a key regulator of cell cycle progression, can bind the transcription factor E2F converting it from a positive transcriptional factor capable of driving cells into S phase into a negative complex which arrests cells in G1. We have created a potent transcriptional repressor of E2F-dependent transcription by fusing the C-terminal fragment of Rb (p56) to the DNA and DP1-binding domains of E2F. Because the expression of E2F/56 fusion protein from a constitutive promoter was incompatible with virus growth, adenovirus constructs were prepared where transgenes were expressed from a fragment of the smooth muscle alpha-actin (SMA) promoter. Immunoblot and beta-galactosidase staining demonstrated smooth muscle-specific expression of this transcriptional element in vitro. The SMA-p56 and SMA-E2F/p56 adenoviral constructs also induced G0/G1 cell cycle arrest specifically in smooth muscle cells. Following administration to rat tissues, the SMA-beta-galactosidase construct exhibited expression in balloon-injured carotid arteries, but not in liver, bladder or skeletal muscle. Local delivery of the SMA-E2F/p56 adenoviral construct to balloon-injured carotid arteries inhibited intimal hyperplasia. Our results demonstrate that local delivery of the SMA-E2F/p56 adenoviral construct can limit intimal hyperplasia in balloon-injured vessels, while avoiding toxicity that could occur from the dissemination and expression of the viral transgene.

Selection and characterization of active hammerhead ribozymes targeted against cyclin E and E2F1 full-length mRNA

Proliferation of vascular smooth muscle cells is generally accepted as a key event in the development of restenosis following percutaneous transluminal angioplasty. To prevent human restenosis, we have designed a molecular strategy based on hammerhead ribozymes targeted against the mRNA of cyclin E and E2F1, two proteins relevant in cell cycle progression whose regulation is interconnected by a positive feedback loop. Following the identification of accessible ribozyme target sites by RNase H mapping, several hammerhead ribozymes were generated that cleave with comparable efficiency two different splice forms of cyclin E mRNA and the full-length and a truncated form of E2F1 RNA, respectively. The most active ribozymes were tested in vitro under single-turnover conditions yielding k(react)/K(m) ratios between 36 and 73 x 10(4) M(-1) min(-1), which places them in the top range ribozymes targeted against long and structured substrates. In addition, we show that the most active ribozyme selected in vitro reduces specifically and significantly (p < 0.0028) proliferation of cultured human vascular smooth muscle cells (VSMC).

Local gene delivery to the vessel wall

This review will provide an overview of delivery strategies that are being evaluated for vascular gene therapy. We will limit our discussion to those studies that have been demonstrated, utilizing in vivo model systems, to limit post-interventional restenosis. We also discuss the efficacy of the vectors and methods currently being used to transfer genetic material to the vessel wall. The efficiency of these techniques is a critical issue for the successful application of gene therapy.

Inhibition of the cyclin D1/E2F pathway by PCA-4230, a potent repressor of cellular proliferation

1. Tight control of cellular growth is essential to ensure normal tissue patterning and prevent pathological responses. Excessive vascular smooth muscle cell (VSMC) proliferation is associated with the pathophysiology of atherosclerosis and restenosis post-angioplasty. Thus, drug targeting of pathological VSMC growth may be a suitable therapeutic intervention in vascular proliferative diseases. 2. In the present study, we investigated the mechanisms underlying VSMC growth arrest induced by the pharmacological agent PCA-4230. Addition of PCA-4230 to cultured VSMCs blocked the induction of cyclin D1 and cyclin A expression normally seen in serum-restimulated cells. Moreover, PCA-4230 inhibited cyclin-dependent kinase 2 (CDK2) activity and abrogated hyperphosphorylation of the retinoblastoma (Rb) gene product. Similarly, PCA-4230-dependent growth arrest of transformed cell lines correlated with reduced level of cyclin D1 protein and inhibition of CDK2 activity. Consistent with these findings, PCA-4230 repressed serum-inducible cyclin A promoter activity, and overexpression of either cyclin D1 or E2F1 efficiently circumvented this inhibitory effect. Importantly, adenovirus-mediated overexpression of E2F1 restored S-phase entry in PCA-4230-treated VSMCs, demonstrating that PCA-4230 represses cyclin A gene expression and VSMC growth via inhibition of the cyclin D1/E2F pathway. 3. Because of its ability to inhibit the growth of human VSMCs and transformed cell lines, future studies are warranted to assess whether PCA-4230 may be a suitable therapeutic intervention for the treatment of hyperproliferative disorders, including cardiovascular disease and cancer.

The role of apoptotic cell death in cardiovascular disease

BACKGROUND

Programmed cell death, or apoptosis, is a distinct, managed form of cell death. It is fundamentally different from necrosis. It is a genetically controlled, energy-dependent method of cellular deletion without inflammation. In the cardiovascular system, apoptosis occurs as a primary and secondary event in disease pathogenesis. This review addresses our current understanding of the initiation, propagation and significance of apoptosis in the cardiovascular system, as well as assessing therapeutic potentials arising therefrom.

METHODS

A Medline search was performed and relevant publications reviewed. Further articles were obtained from the references of these publications.

RESULTS

and conclusions Apoptotic cell death is a key element in the pathogenesis and progression of ischaemia-reperfusion (IR) injury, cardiac failure, myocardial infarction, atherosclerosis, endothelial dysfunction and the clinical syndromes which these situations produce. Our increased understanding of the role of apoptosis in the pathogenesis of cardiovascular disease offers potential to develop new therapeutic strategies.