Sustained reduction of neointima with c-myc antisense oligonucleotides in saphenous vein grafts

Gene therapy with antisense oligonucleotides silencing c-myc reduces neointima formation and vessel wall thickness in a mouse model of vein graft disease

Gene therapy for avoiding intimal hyperplasia of vein grafts after coronary artery bypass grafting is still discussed controversially. A promising application of gene therapy in vein grafts is the use of antisense oligonucleotides to block the expression of genes encoding cell cycle regulatory proteins in vascular smooth muscle cells. C-myc, either directly or by regulating the expression of other proteins, controls cell proliferation, apoptosis and cell survival, tissue remodeling, angiogenesis, cell metabolism, production of inflammatory and anti-inflammatory cytokines, and also participates in cell transformation. Forty C57BL/6J mice underwent interposition of the inferior vena cava from isogenic donor mice into the common carotid artery using a previously described cuff technique. Twenty mice received periadventitial administration of antisense oligonucleotides directed against c-myc (treatment group), the other twenty mice received no treatment (control group). All vein grafts were harvested two weeks after surgery, dehydrated, wax embedded, cut into slides of 2 μm thickness, stained and histologically and immunohistochemically examined under light microscope. In our study, we could show the promising effects of antisense oligonucleotide treatment in a mouse model of vein graft disease including the significant reduction of neointimal, media and total vessel wall thickness with a significantly lower percentage of SMA positive cells, elastic fibres and acid mucopolysaccharides in the neointima and media, a decreased vascularization, and a lower expression of PDGFR ß, MMP-9 and VEGF-A positive cells throughout the whole vein graft wall.

CDDO and Its Role in Chronic Diseases

There has been a continued interest in translational research focused on both natural products and manipulation of functional groups on these compounds to create novel derivatives with higher desired activities. Oleanolic acid, a component of traditional Chinese medicine used in hepatitis therapy, was modified by chemical processes to form 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO). This modification increased anti-inflammatory activity significantly and additional functional groups on the CDDO backbone have shown promise in treating conditions ranging from kidney disease to obesity to diabetes. CDDO's therapeutic effect is due to its upregulation of the master antioxidant transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) through conformational change of Nrf2-repressing, Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1 (Keap1) and multiple animal and human studies have verified subsequent activation of Nrf2-controlled antioxidant genes via upstream Antioxidant Response Element (ARE) regions. At the present time, positive results have been obtained in the laboratory and clinical trials with CDDO derivatives treating conditions such as lung injury, inflammation and chronic kidney disease. However, clinical trials for cancer and cardiovascular disease have not shown equally positive results and further exploration of CDDO and its derivatives is needed to put these shortcomings into context for the purpose of future therapeutic modalities.

Inhibition of neointimal hyperplasia in a rabbit vein graft model following non-viral transfection with human iNOS cDNA

Vein graft failure caused by neointimal hyperplasia (IH) after coronary artery bypass grafting with saphenous veins is a major clinical problem. The lack of safe and efficient vectors for vascular gene transfer has significantly hindered progress in this field. We have developed a Receptor-Targeted Nanocomplex (RTN) vector system for this purpose and assessed its therapeutic efficacy in a rabbit vein graft model of bypass grafting. Adventitial delivery of β-Galactosidase showed widespread transfection throughout the vein wall on day 7, estimated at about 10% of cells in the adventitia and media. Vein grafts were then transfected with a plasmid encoding inducible nitric oxide synthase (iNOS) and engrafted into the carotid artery. Fluorescent immunohistochemistry analysis of samples from rabbits killed at 7 days after surgery showed that mostly endothelial cells and macrophages were transfected. Morphometric analysis of vein graft samples from the 28-day groups showed approximately a 50% reduction of neointimal thickness and 64% reduction of neointimal area in the iNOS-treated group compared with the surgery control groups. This study demonstrates efficacy of iNOS gene delivery by the RTN formulation in reducing IH in the rabbit model of vein graft disease.

'No-touch' saphenous vein harvesting improves graft performance in patients undergoing coronary artery bypass surgery: a journey from bedside to bench

The saphenous vein is the most commonly used conduit in patients undergoing coronary artery bypass surgery yet its patency is inferior to the internal thoracic artery. Vascular damage inflicted to the vein when using conventional harvesting techniques affects its structure. Endothelial denudation is associated with early vein graft failure while damage of the outermost vessel layers has adverse long-term effects on graft performance. While many in vitro and in vivo experimental studies aimed at improving vein graft patency have been performed to date no significant 'bench to bedside' advances have been made. Among experimental strategies employed is the use of pharmacological agents, gene targeting and external stents. A 'no-touch' technique, where the saphenous vein is removed with minimal trauma and normal architecture preserved, produces a superior graft with long term patency comparable to the internal thoracic artery. Interestingly, many experimental studies are aimed at repairing or replacing those regions of the saphenous vein damaged when harvesting conventionally. 'No-touch' harvesting is superior in coronary artery bypass patients with long-term data published 5years ago. Here we describe a 'bedside to bench' situation where the mechanisms underlying the improved performance of 'no touch' saphenous vein grafts in patients have been studied in the laboratory.

Control of cell proliferation in atherosclerosis: insights from animal models and human studies

Excessive hyperplastic cell growth within occlusive vascular lesions has been recognized as a key component of the inflammatory response associated with atherosclerosis, restenosis post-angioplasty, and graft atherosclerosis after coronary artery bypass. Understanding the molecular mechanisms that regulate arterial cell proliferation is therefore essential for the development of new tools for the treatment of these diseases. Mammalian cell proliferation is controlled by a large number of proteins that modulate the mitotic cell cycle, including cyclin-dependent kinases, cyclins, and tumour suppressors. The purpose of this review is to summarize current knowledge about the role of these cell cycle regulators in the development of native and graft atherosclerosis that has arisen from animal studies, histological examination of specimens from human patients, and genetic studies.

Controlled release of small interfering RNA targeting midkine attenuates intimal hyperplasia in vein grafts

OBJECTIVE

Intimal hyperplasia is a major obstacle to patency after vein grafting. Despite of a diverse array of trials to prevent it, a satisfactory therapeutic strategy for clinical use has not been established. However, sufficient inhibition of early stages of intimal hyperplasia may prevent this long-term progressive disease. Midkine (MK) is a heparin-binding growth factor that was originally discovered as the product of a retinoic acid-responsive gene. We previously demonstrated that MK-deficient mice exhibit a striking reduction of neointima formation in a restenosis model, which is reversed on systemic MK administration. In this study, we evaluated a strategy of using small interfering RNA (siRNA) targeting MK as a therapy for vein graft failure.

METHODS

We first made a highly effective siRNA to rabbit MK. Jugular vein-to-carotid artery interposition vein grafts, which are applied to a low flow condition, were made in Japanese white rabbits. Small interfering RNA mixed with atelocollagen was administrated to the external wall of grafted veins. Cy3-conjugated stabilized siRNA was used to confirm its stability and successful transfer into the vein graft wall. Neointimal hyperplasia was evaluated 4 weeks after the operation. The proliferation index and leukocyte infiltration were determined.

RESULTS

MK expression was induced and reached the maximum level 7 days after operation. Fluorescence of Cy3-labeled siRNA could be detected in the graft wall even 7 days after operation. Knockdown of the gradually increasing expression was achieved by perivascular application of siRNA using atelocollagen. The intima-media ratio and the intima thickness at 28 days after grafting were both reduced >90% by this treatment compared with controls. This phenomenon was preceded by significant reductions of inflammatory cell recruitment to the vessel walls and subsequent cell proliferation in MK siRNA-treated grafts.

CONCLUSIONS

These results suggest that midkine is a candidate molecular target for preventing vein graft failure. Furthermore, for clinical applications of siRNA, a single intraoperative atelocollagen-based nonviral delivery method could be a reliable approach to achieve maximal function of siRNA in vivo. This strategy may be a useful and practical form of gene therapy against human vein graft failure.

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.

Pharmacologic inhibition of vein graft neointimal hyperplasia

Although arterial conduits are widely used and have improved the long-term results of coronary artery bypass grafting, vein grafts remain important additional conduits in coronary surgery. Newer studies show a saphenous vein graft patency of 60% or more at 10 years postoperatively. The pathology of vein graft disease consists of thrombosis, neointimal hyperplasia, and vein graft atherosclerosis, which limit graft longevity. Therapeutic strategies to prevent vein graft disease include external stenting, pharmacotherapy, and gene therapy. The potential benefits of a pharmacologic approach are as follows: (1) Drugs with a broad clinical experience can be used; (2) side effects of systemic application can be minimized by local therapy; and (3) no vascular injury, such as pressurizing the vein for a viral transfection approach, is necessary. The different sites for pharmacotherapy in vein graft disease are reviewed in this article.

Anti‐proliferative and anti‐inflammatory effects of topical MAPK inhibition in arterialized vein grafts

Vein graft failure following bypass surgery is a frequent and important clinical problem. The vascular injury caused by arterialization is responsible for vein graft intimal hyperplasia, a lesion generated by medial smooth muscle cell proliferation and migration into the intima, increased extracellular matrix deposition, and formation of a thick neointima. Development of the neointima into a typical atherosclerotic lesion and consequent stenosis ultimately result in vein graft failure. Endothelial damage, inflammation, and intracellular signaling through mitogen-activated protein kinases (MAPKs) have been implicated in the early stages of this process. We therefore investigated the effects of topical inhibition of ERK-1/2 MAPK activation on vascular cell proliferation and apoptosis, and on the inflammatory response in a canine model of vein graft arterialization. For this purpose, vein grafts were incubated with the MEK-1/2 inhibitor, UO126, ex vivo for 30 min before grafting. This treatment effectively abolished arterialization-induced ERK-1/2 activation, decreased medial cell proliferation, and increased apoptosis. UO126 treatment also inhibited the vein graft infiltration by myeloperoxidase-positive inflammatory cells that follows vein graft arterialization. Thus, topical ex vivo administration of MAPK inhibitors can provide a pharmacological tool to prevent or reduce the vascular cell responses that lead to vein graft intimal hyperplasia and graft failure.

c-Myc antisense oligonucleotides preserve smooth muscle differentiation and reduce negative remodelling following rat carotid arteriotomy

OBJECTIVES

The vascular biology of restenosis is complex and not fully understood, thus explaining the lack of effective therapy for its prevention in clinical settings. The role of c-Myc in arteriotomy-induced stenosis, smooth muscle cell (SMC) differentiation and apoptosis was investigated in rat carotids applying full phosphorothioate antisense (AS) oligonucleotides (ODNs).

METHODS

Carotid arteries from WKY rats were submitted to arteriotomy and to local application of ODNs through pluronic gel. Apoptosis (deoxynucleotidyl transferase-mediated dUTP nick end-labelling), SMC differentiation (SM22 immunofluorescence) and vessel morphology and morphometry (image analysis) were determined 2, 5 and 30 days after injury, respectively.

RESULTS

AS ODNs induced a 60% decrease of target c-Myc mRNA 4 h after surgery in comparison to control sense (S) and scrambled ODN-treated carotids (p < 0.05). A significant 37 and 50% decrease in SM22 protein in the media of S ODN-treated and untreated carotids was detected when compared to uninjured contralateral arteries (p < 0.05). This reduction in SM22 expression was prevented in AS ODN-treated carotids. Stenosis was mainly due to adventitial constrictive remodelling. Lumen area in AS ODN-treated carotids was 35% greater than in control arteries 30 days after surgery (p < 0.05). TUNEL assay revealed increased apoptosis in AS ODN-treated carotids (p < 0.05).

CONCLUSIONS

c-Myc AS ODNs reduce arteriotomy-induced negative remodelling. This is accompanied by maintained SMC differentiation and greater apoptosis. The combination of reduced c-Myc-induced proliferation and increased apoptosis may thus underlie the less severe remodelling upon treatment with c-Myc mRNA AS ODN.

Preventing saphenous vein graft failure: does gene therapy have a role?

Gene therapy potentially allows local delivery and expression of cytokines, growth factors, and other mediators. In spite of increasing knowledge of the human genome, applications in clinical practice are only just beginning. The main limitations of effective clinical gene therapy are safety and low transfection efficiency. Saphenous vein grafts permit the transfection of the conduit ex vivo. This allows a variety of transfection techniques to be used, enhancing the transfection efficiency while limiting the risk of systemic complications. This review examines the potential mechanisms of gene delivery and genetic targets that may be applied to saphenous vein graft failure.

Gene expression profiling of human stenotic aorto-coronary bypass grafts by cDNA array analysis

OBJECTIVE

Aorto-coronary bypass graft disease with its increasing clinical signification represents an unsolved problem in cardiological and heart surgery practice. Late occlusion of autologous saphenous vein grafts is due to medial and neointimal thickening secondary to migration and proliferation of smooth muscle cells (SMCs) and the subsequent formation of atherosclerotic plaques. This study is aimed at identifying differentially expressed genes in human stenotic bypass grafts to detect unknown pathomechanism and to identify novel targets for prophylactic treatment options.

METHODS

Stenotic saphenous aorto-coronary bypass grafts (n=5) were retrieved during re-do aorto-coronary bypass surgery. Ungrafted saphenous vein segments (n=5) were taken from the same group of patients and served as internal controls. cDNA samples were prepared and hybridized to cDNA arrays.

RESULTS

Some of the differentially expressed genes complied with expected gene expression including upregulation of c-jun and CDK10. In addition, previously unidentified gene expression patterns were detected such as upregulation of HSP70, fibronectin1, erbB3 proto-oncogene and c-myc. To confirm the latter finding, upregulation of c-myc in neointimal and medial SMCs of stenotic graft segments was confirmed by in situ hybridization studies and by immunohistochemistry.

CONCLUSION

Gene expression patterns of human stenotic bypass grafts retrieved by re-do operations can be reliably analyzed by cDNA array technology. With this technique, new therapeutic targets in patients could be identified as shown by the findings regarding c-myc. c-myc is a proto-oncogene acting as a transcription factor and blocking c-myc has shown a reduction of neointima formation in animal models. Our study yields a rational for the use of antisense c-myc oligonucleotides to reduce neointima formation and to avoid stenosis in patients.

Gene therapy for tissue regeneration

Tissue repair and regeneration are the normal biological responses of many different tissues in the body to injury. During the healing process, profound changes occur in cell composition and extracellular matrix (ECM) formation. Fibroblasts and equivalent reparative cells migrate to the wounded area and subsequently proliferate. These cells and reparative cells from the surrounding tissue are responsible for the rapid repair which results in tissue regeneration. Growth factors, one of which is transforming growth factor-beta (TGF-beta), stimulate fibroblasts and smooth muscle cells to proliferate and synthesize ECM proteins. This process of early repair provides a rapid way to restore new tissue and mechanical integrity. This early tissue repair process is normally followed by involution, which requires the production and activation of proteases, tissue maturation and remodeling, reorganization and finally regeneration. Alternately, failure to replace the critical components of the ECM, including elastin and basement membrane, results in abnormal regeneration of the epithelial cell layer. Although remodeling should occur during healing, provisional repair may be followed by excessive synthesis and deposition of collagen, which results in irreversible fibrosis and scarring. This excessive fibrosis which occurs in aberrant healing is at least in part mediated by persistent TGF-beta. Because of the central role of collagen in the wound healing process, the pharmacological control of collagen synthesis has been of paramount importance as a possible way to abrogate aberrant healing and prevent irreversible fibrosis. Fibrosis is an abnormal response to tissue injury.

Adenoviral delivery of a constitutively active retinoblastoma mutant inhibits neointima formation in a human explant model for vein graft disease

Intimal hyperplasia resulting from vascular injury remains a major obstacle in the long-term success of coronary artery bypass grafts. Inhibition of smooth muscle cell (SMC) proliferation using adenoviral gene transfer of cell cycle inhibitors resulted in reduced neointima formation in various animal models. However, little is known about the effect on human SMCs and neointima formation. Here we report the effects of infection with an adenoviral vector encoding a constitutively active form of the retinoblastoma gene (Ad. delta Rb) on proliferation of human saphenous vein SMCs (HSVSMCs) and neointima formation in organ cultures of human saphenous vein. Proliferation of SMCs was inhibited dose-dependently after infection with Ad. delta Rb. A near-total inhibition was found at an Ad. delta Rb concentration of 10(8) pfu/ml. Organ cultures of human saphenous vein segments were used to evaluate the effect of Ad. delta Rb infection on neointima formation and vein graft disease. Segments cultured for 4 weeks develop a neointima that is morphologically highly similar to early initimal lesions found in pathological vein grafts in vivo. Infection of saphenous vein segments with 2 x 10(9) pfu/ml Ad. delta Rb resulted in a 59% reduction of neointimal area when compared to uninfected counterparts, whereas infection with control adenovirus, Ad.LacZ, had no significant effect. The results of this study show that Ad. delta Rb gene transfer might be an efficient approach to prevent neointima formation in human saphenous vein grafts.

An external, oversized, porous polyester stent reduces vein graft neointima formation, cholesterol concentration, and vascular cell adhesion molecule 1 expression in cholesterol-fed pigs

BACKGROUND

Reducing neointima formation and atherosclerosis are key goals in preventing late vein graft failure. Although pharmacologic and mechanical solutions have been proposed, the demonstration that these influence both aspects of vein graft pathology have been lacking. Supporting grafts externally with an oversized, highly porous polyester stent dramatically reduces neointima formation in normocholesterolemic pigs. However, its effects in the presence of hypercholesterolemia are unknown.

METHODS

We compared wall thickening, cholesterol concentration, foam-cell formation, and the expression of the leukocyte adhesion molecule vascular cell adhesion molecule 1 after 3 months in stented and unstented saphenous vein interposition grafts into the carotid arteries of pigs fed cholesterol to cause modest hypercholesterolemia (11.2 +/- 1.2 mmol/L).

RESULTS

Stenting reduced neointima formation from 5.6 +/- 0.4 to 1.2 +/- 0.2 mm(2) (n = 7; P <.00002, paired t test) and graft cholesterol concentration from 4.7 +/- 1.2 to 2.1 +/- 1.3 mg/g wet weight (P <.02). Foam cells were observed in unstented grafts (mean, 1.5% +/- 0.5% of all cells) but never in stented grafts. Vascular cell adhesion molecule 1 was strongly expressed in 53% +/- 8% of intimal and medial cells in unstented grafts but was weakly expressed in only 19% +/- 3% (n = 4, P <.05) of stented grafts.

CONCLUSIONS

We conclude that external stenting with polyester favorably influences both neointima formation and early atherosclerosis, both of which are key aspects of vein graft disease, and that decreased expression of vascular cell adhesion molecule 1 is part of the underlying mechanism.

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.

Expression of the proto-oncogene c-myc in human stenotic aortocoronary bypass grafts

Proliferation and differentiation of vascular smooth muscle cells (VSMC) are central events in vascular pathobiology and play a major role in the development of stenotic and restenotic lesions. The proto-oncogene c-myc and other early cell cycle-regulating genes have been implicated in the induction of cell proliferation and differentiation under diverse pathophysiological conditions. In the present study we analyzed c-myc mRNA expression by indirect nonradioactive in situ hybridization technique (NISH) in human stenotic venous bypass grafts (n = 32) retrieved during re-do operations of coronary artery disease and compared the results with 28 native veins (vena saphena magna) from the same patients. Stenotic bypass grafts showed enhanced c-myc expression located predominantly in VSMC in the media and neointima (severity score: ++-+++, 32/32 stenotic veins). In native veins we observed only low levels of c-myc mRNA (severity score: +, 28/28 native veins), all signals were restricted to endothelial cells of either the innermost intimal layer or of the vasa vasorum. Our in situ hybridization studies demonstrate enhanced mRNA expression of the proto-oncogene c-myc in stenotic venous bypass grafts. These results suggest that--in analogy to other pathophysiological conditions--c-myc exerts essential regulatory functions in cellular events operative during the initiation and progression of venous bypass graft disease.

Local intracoronary administration of antisense oligonucleotide against c-myc for the prevention of in-stent restenosis: results of the randomized investigation by the Thoraxcenter of antisense DNA using local delivery and IVUS after coronary stenting (ITALICS) trial

OBJECTIVE

This study was designed to determine whether antisense oligodeoxynucleotides (ODN) directed against the nuclear proto-oncogene c-myc could inhibit restenosis when given by local delivery immediately after coronary stent implantation.

BACKGROUND

Failure of conventional pharmacologic therapies to reduce the incidence of coronary restenosis after percutaneous revascularization techniques has prompted interest in the use of agents that target intracellular central regulatory mechanisms.

METHODS

Eighty-five patients were randomly assigned to receive either 10 mg of phosphorothioate-modified 15-mer antisense ODN or saline vehicle by intracoronary local delivery after coronary stent implantation. The primary end point was percent neointimal volume obstruction measured by computerized analysis of electrocardiogram-gated intravascular ultrasound (IVUS) at six-month follow-up. Secondary end points included clinical outcome and quantitative coronary angiography analysis.

RESULTS

Analysis of follow-up IVUS data was performed on 77 patients. In-stent volume obstruction was similar between groups (44 +/- 16% and 46 +/- 14%, placebo vs. ODN; p = 0.57; 95% confidence interval: -1.13 to 0.85). Minimum luminal diameter increased from 0.84 +/- 0.36 and 0.90 +/- 0.45 (p = 0.55) to 2.70 +/- 0.37 and 2.80 +/- 0.37 (p = 0.28) after stent implantation, which decreased to 1.50 +/- 0.61 and 1.50 +/- 0.53 (p = 0.98) by six months, yielding similar loss indexes (placebo vs. ODN, respectively). There were no differences in angiographic restenosis rates (38.5 and 34.2%; p = 0.81; placebo vs. ODN) or clinical outcome.

CONCLUSIONS

Treatment with 10 mg of phosphorothioate-modified ODN directed against c-myc does not reduce neointimal volume obstruction or the angiographic restenosis rate in this patient population.

c-myc activation in early coronary lesions in experimental hypercholesterolemia

This study tested the hypothesis that c-Myc activation, an oxidation-sensitive transcription factor, and its binding partner Max occurs in coronary arteries of hypercholesterolemic (HC) pigs, and can be attenuated by chronic antioxidant intervention. Coronary arteries were isolated from normal, HC pigs, or HC supplemented with antioxidant vitamins (HC + vitamins). The expression of the c-Myc/Max complex, and its target genes GADD45 and p53, was studied in nonatherosclerotic, early lesions (LL), positively staining for oil-red-O, in adjacent lesion-prone regions (PL), and in healthy segments (HV). The expression of c-Myc and Max in HC was 2- to 3-fold greater in PL, and 4-fold in LL, compared to normal vessels (P < 0.01). The expression of GADD45 was down-regulated, and of p53 increased, in the same regions. These alterations were attenuated in the HC + vitamins. Thus, c-Myc activation is an early atherosclerosis, in both PL and LL coronary arterial regions, and can be blunted by chronic dietary antioxidant intervention.

Gene therapy for restenosis

This review provides an overview of candidate genes that are currently being evaluated for genetic strategies in vascular gene therapy. We discuss treatment strategies that have proven efficacious in limiting postinterventional restenosis through evaluation with in vivo model systems. The candidate strategies utilize genes that are either cytotoxic, regulate vascular smooth muscle cell differentiation or proliferation. In addition, we review oligonuclotide and ribozyme strategies that function by suppressing the expression of cell cycle regulators.