Saphenous vein graft protection: effects of c-myc antisense

Large animal model of vein grafts intimal hyperplasia: A systematic review

Coronary artery bypass grafting remains the treatment of choice for a large cohort of patients with significant coronary disease. Despite the increased use of arterial grafts, the long saphenous vein remains the most commonly used conduit. Long-term graft patency continues to be the Achilles heel of saphenous vein grafts. This is due to the development of intimal hyperplasia, a chronic inflammatory disease that results in the narrowing and occlusion of a significant number of vein grafts. Research models for intimal hyperplasia are essential for a better understanding of pathophysiological processes of this condition. Large animal models resemble human anatomical structures and have been used as a surrogate to study disease development and prevention over the years. In this paper, we systematically review all published studies that utilized large animal models of vein graft disease with a focus on the type of model and any therapeutic intervention, specifically the use of external stents/mesh.

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.

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.

Endothelial cells are susceptible to rapid siRNA transfection and gene silencing ex vivo

BACKGROUND

Endothelial gene silencing via small interfering RNA (siRNA) transfection represents a promising strategy for the control of vascular disease. Here, we demonstrate endothelial gene silencing in human saphenous vein using three rapid siRNA transfection techniques amenable for use in the operating room.

METHODS

Control siRNA, Cy5 siRNA, or siRNA targeting glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or endothelial specific nitric oxide synthase (eNOS) were applied to surplus human saphenous vein for 10 minutes by (i) soaking, (ii) applying 300 mm Hg hyperbaric pressure, or (iii) 120 mm Hg luminal distending pressure. Transfected vein segments were maintained in organ culture. siRNA delivery and gene silencing were assessed by tissue layer using confocal microscopy and immunohistochemistry.

RESULTS

Distending pressure transfection yielded the highest levels of endothelial siRNA delivery (22% pixels fluorescing) and gene silencing (60% GAPDH knockdown, 55% eNOS knockdown) as compared with hyperbaric (12% pixels fluorescing, 36% GAPDH knockdown, 30% eNOS knockdown) or non-pressurized transfections (10% pixels fluorescing, 30% GAPDH knockdown, 25% eNOS knockdown). Cumulative endothelial siRNA delivery (16% pixels fluorescing) and gene silencing (46% GAPDH knockdown) exceeded levels achieved in the media/adventitia (8% pixels fluorescing, 24% GAPDH knockdown) across all transfection methods.

CONCLUSION

Endothelial gene silencing is possible within the time frame and conditions of surgical application without the use of transfection reagents. The high sensitivity of endothelial cells to siRNA transfection marks the endothelium as a promising target of gene therapy in vascular disease.

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.

Lower extremity vein graft failure: a translational approach

Abstract

Patients with the most severe manifestations of lower extremity arterial occlusive disease often require peripheral bypass surgery for limb salvage and preservation of function. Although good quality saphenous vein offers the most durable conduit for reconstruction, 5-year failure rates are 30–50% and have remained largely unchanged for the past two decades. The majority of these failures occur within the first year of implantation, which is regarded as the most biologically active time during which the vein graft adapts to the arterial environment. Although intimal hyperplasia is generally regarded as the primary culprit of vein graft failure, geometric remodeling of the healing vein graft has recently emerged as a potentially significant contributing factor. While hemodynamic forces, including an increase in shear stress and wall tension, are undoubtedly central to the magnitude and direction of vein graft remodeling, we have determined that these forces alone cannot account for the extent of variability noted in early remodeling patterns. Therefore, we hypothesize that circulating factors, such as mediators of inflammation, may modulate the vein graft response to mechanical forces. This article reviews the definition and diagnosis of vein graft failure and summarizes our current efforts to understand the mechanisms of normal and abnormal vein graft adaptation to the arterial environment.

Delivery of oligodeoxynucleotides into human saphenous veins and the adjunct effect of ultrasound and microbubbles

Therapy with naked oligodeoxynucleotides (ODNs, molecular weight: 3000 to 7500) provides an elegant means of modulating gene expression without the problems associated with conventional gene therapy, but the relatively low transfer efficiency on intravascular administration is a limitation to clinical application. Ultrasound, which can be potentiated by microbubbles, shows promise as a method of delivering macromolecules such as plasmid DNA and other transgenes into cells. Since uptake of molecules into cells depends on their molecular weight, it might be expected that the delivery of ODNs, which are relatively small, will be facilitated by ultrasound and microbubbles. In the present study, we delivered ODNs into veins using ultrasound and microbubbles. First, we quantified the uptake of fluorescent-labeled ODNs into intact ex vivo human saphenous veins and isolated smooth muscle cells from the veins, evaluating the effect of ultrasound and microbubbles on uptake. Ultrasound potentiated the delivery of ODN in cells, except at high concentrations. When intact veins were studied, we achieved nuclear localization of fluorescent-labeled ODNs in cells. This increased with increasing concentration and incubation time and was not potentiated by ultrasound, even when microbubbles were used. We then applied a therapeutic ODN (antisense to intercellular adhesion molecule 1, ICAM-1) to vein samples and documented a functional inhibition of gene expression in a sequence-specific manner at the protein level with immunohistochemistry and western blot analysis. Again, no significant difference was seen with adjunct ultrasound. These observations suggest high diffusion of ODNs into human saphenous veins in this ex vivo model, indicating potential applications to inhibition of vascular bypass graft occlusion and other vasculopathies. Although microbubble-ultrasound was of value with cells in culture, it was not beneficial with intact veins.

Clinical trials of a new class of therapeutic agents: antisense oligonucleotides

Antisense oligodeoxynucleotides (ODNs) are short stretches of DNA complementary to a target mRNA. The ODNs selectively hybridise to their complementary RNA by Watson-Crick base pairing rules. In theory, the use of antisense ODNs provides a method to specifically inhibit the intracellular expression of any disorder whose genetic aetiology is well known. For this reason, researchers thought that if antisense drugs proved to be so specific there would be no side effects. However, toxicity-related problems arose in initial animal studies of antisense drugs in the early 1990s and since then companies have been using these compounds cautiously. In order to be useful therapeutically, an ODN must (a) exhibit reasonable stability in the physiological environment, (b) be taken up and retained in adequate quantities by the target cells, (c) specifically bind target mRNA with high affinity, (d) have an acceptable therapeutic ratio, free of unwanted toxic and non-specific side effects and (e) be easily synthesised in sufficient quantities to allow clinical use. Most of these criteria have already been met by ODNs recently used in this way. This review describes certain therapeutic applications of antisense techniques currently under investigation in oncology, haematopathology and inflammatory diseases.

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.

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.

Local delivery of mithramycin restores vascular reactivity and inhibits neointimal formation in injured arteries and vascular grafts

Arterial restenosis is responsible for the high failure rates of vascular reconstruction procedures. Local sustained drug delivery has shown promise in the prevention of restenosis. The drug release rate from mithramycin-loaded EVA matrices (0.1%) was evaluated, and their antirestenotic effect was studied in the rat carotid model and rabbit model of vascular grafts. The modulation of c-myc expression by mithramycin treatment was examined by immunohistochemistry in the rat carotid model. The proliferative response of injured rat arteries was studied by bromdeoxyuridine (BrdU) immunostaining. The impact of mithramycin treatment on vasomotor responses of the venous segments grafted into arterial circulation was studied ex vivo using vasoreactive compounds. Mithramycin was released exponentially from EVA matrices in PBS. Matrices co-formulated with PEG-4600 revealed enhanced release kinetics. The perivascular implantation of drug-loaded EVA-PEG matrices led to 50% reduction of neointimal formation, and reduced the c-myc expression and BrdU labeling in comparison to control implants. Decreased sensitivity of mithramycin-treated grafts to serotonin-induced vasoconstriction was observed. Local perivascular mithramycin treatment limits the functional alteration caused by the grafting of venous segments in high-pressure arterial environment, and potently inhibits stenosis secondary to grafting and angioplasty injury. The antirestenotic effect is associated with reduced c-myc expression and with subsequent decrease in SMC proliferation.

Safety of intracoronary administration of c-myc antisense oligomers after percutaneous transluminal coronary angioplasty (PTCA)

We wished to assess the clinical safety and pharmacokinetics of ascending doses of a synthetic oligodeoxynucleotide (LR-3280) administered after coronary angioplasty. Antisense oligodeoxynucleotides designed to hybridize with target messenger ribonucleic acid (mRNA) in a complementary fashion to inhibit the expression of corresponding protein also have the ability to bind to extracellular growth factors. LR-3280 has been shown to reduce c-myc expression, inhibit growth and collagen biosynthesis in human vascular cells, and reduce neointimal formation in animal models of vascular injury. After successful percutaneous transluminal coronary angioplasty (PTCA), 78 patients were randomized to receive either standard care (n = 26) or standard care and escalating doses of LR-3280 (n = 52) (doses from 1 to 24 mg), administered into target vessel through a guiding catheter. Overall safety was evaluated by clinical adverse events, laboratory tests, and electrocardiograms. Patency was evaluated by quantitative coronary angiography. There were no clinically significant differences between treated and control patients. No adverse effects of LR-3280 on the patency of dilated coronary arteries were observed. Pharmacokinetic data revealed that peak plasma concentrations of LR-3280 occurred at 1 minute over the studied dose range and rapidly decreased after approximately1 hour, with little LR-3280 detected in the urine between 0-6 hours and 12-24 hours. The intracoronary administration of LR-3280 is well tolerated at doses up to 24 mg and produces no adverse effects in dilated coronary arteries. These results provide the basis for the evaluation of local delivery of this phosphorothioate oligodeoxynucleotide for the prevention of human vasculoproliferative disease.

Synthetic oligonucleotides as therapeutics: the coming of age

Synthetic oligonucleotides (ODNs) are short nucleic acid chains that can act in a sequence specific manner to control gene expression. Significant progress has been made in the development of synthetic ODN therapeutics since the first demonstration of gene inhibition by antisense ODNs in a cell culture system two decades ago. This new class of therapeutic agents can potentially target any abnormally expressed genes in a broad range of diseases from viral infections to psychoneurological disorders. A number of "first" generation synthetic ODNs have entered into human clinical trials in the last few years. The eminent approval of the first ODN for the treatment of cytomaglovirus retinitis by the FDA in USA will provide much excitement that this new class of compounds holds great promise as a therapeutic "magic bullet". However, many obstacles still exist in the development of this technology. In this review, the current status of synthetic ODN chemistry, drug delivery methods, mechanisms of ODN action, potential clinical applications and its limitations in a wide range of human disorders will be described.

Contractile smooth muscle cell apoptosis early after saphenous vein grafting

BACKGROUND

The media of saphenous veins is composed of two cell populations: smooth muscle (SMC) and non-smooth muscle (NSMC) cells. Previous studies demonstrate a loss of SMCs by 3 days after grafting, despite an increase in cell proliferation. The purpose of this study is to determine the rates of apoptotic cell death versus cell proliferation for the two major cell populations of the media.

METHODS

Veins (six/time point) were examined at 0.5, 1, 2, 4, 8, 24, and 48 hours after grafting in crossbred pigs. Terminal transferase-mediated dUTP nick end labeling (TUNEL) and proliferating cell nuclear antigen (PCNA) stains were used to assess apoptosis and proliferation. Apoptosis was also corroborated with confocal and electron microscopy.

RESULTS

Apoptosis was high in both cell populations: at 8 hours, SMC and NSMC apoptosis peaked at 14.5% +/- 3.5% and 49.9% +/- 7.8%, respectively. In contrast, cell proliferation was different between the two populations. SMC proliferation was low at all time points, whereas NSMC proliferation rose to 22% +/- 5.4% by 48 hours.

CONCLUSIONS

Medial SMCs are removed through apoptosis and appear to be replaced by fibrous tissue (NSMCs) early after vein grafting. This reciprocal change between the medial SMC and NSMC populations may contribute to late vein graft degeneration.

Antisense oligonucleotides as therapeutic agents

Antisense oligonucleotides can block the expression of specific target genes involved in the development of human diseases. Therapeutic applications of antisense techniques are currently under investigation in many different fields. The use of antisense molecules to modify gene expression is variable in its efficacy and reliability, raising objections about their use as therapeutic agents. However, preliminary results of several clinical studies demonstrated the safety and to some extent the efficacy of antisense oligodeoxynucleotides (ODNs) in patients with malignant diseases. Clinical response was observed in some patients suffering from ovarian cancer who were treated with antisense targeted against the gene encoding for the protein kinase C-alpha. Some hematological diseases treated with antisense oligos targeted against the bcr/abl and the bcl2 mRNAs have shown promising clinical response. Antisense therapy has been useful in the treatment of cardiovascular disorders such as restenosis after angioplasty, vascular bypass graft occlusion, and transplant coronary vasculopathy. Antisense oligonucleotides also have shown promise as antiviral agents. Several investigators are performing trials with oligonucleotides targeted against the human immunodeficiency virus-1 (HIV-1) and hepatitis viruses. Phosphorothioate ODNs now have reached phase I and II in clinical trials for the treatment of cancer and viral infections, so far demonstrating an acceptable safety and pharmacokinetic profile for continuing their development. The new drug Vitravene, based on a phosphorothioate oligonucleotide designed to inhibit the human cytomegalovirus (CMV), promises that some substantial successes can be reached with the antisense technique.

Antisense oligonucleotides as therapeutic agents

Antisense oligonucleotides can block the expression of specific target genes involved in the development of human diseases. Therapeutic applications of antisense techniques are currently under investigation in many different fields. The use of antisense molecules to modify gene expression is variable in its efficacy and reliability, raising objections about their use as therapeutic agents. However, preliminary results of several clinical studies demonstrated the safety and to some extent the efficacy of antisense oligodeoxynucleotides (ODNs) in patients with malignant diseases. Clinical response was observed in some patients suffering from ovarian cancer who were treated with antisense targeted against the gene encoding for the protein kinase C-alpha. Some hematological diseases treated with antisense oligos targeted against the bcr/abl and the bcl2 mRNAs have shown promising clinical response. Antisense therapy has been useful in the treatment of cardiovascular disorders such as restenosis after angioplasty, vascular bypass graft occlusion, and transplant coronary vasculopathy. Antisense oligonucleotides also have shown promise as antiviral agents. Several investigators are performing trials with oligonucleotides targeted against the human immunodeficiency virus-1 (HIV-1) and hepatitis viruses. Phosphorothioate ODNs now have reached phase I and II in clinical trials for the treatment of cancer and viral infections, so far demonstrating an acceptable safety and pharmacokinetic profile for continuing their development. The new drug Vitravene, based on a phosphorothioate oligonucleotide designed to inhibit the human cytomegalovirus (CMV), promises that some substantial successes can be reached with the antisense technique.

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

BACKGROUND

Treatment of saphenous veins with c-myc antisense oligomers during preparation for grafting reduces medial cellular proliferation and macrophage infiltration, and preserves medial smooth muscle content at 3 days. Accordingly, the purpose of this study was to examine whether c-myc antisense oligomers have an impact on late vein graft remodeling.

METHODS

Sixty-two pigs underwent unilateral saphenous vein-carotid artery interposition grafting. Harvested veins were incubated either in saline (control group) or 20-micromol/L or 200-micromol/L concentrations of c-myc antisense oligomers (treated groups) for 30 minutes intraoperatively. Three months after surgery, vein graft histology was assessed.

RESULTS

Forty-five of 62 randomized animals survived the experiment; no differences in animal survival or graft patency among the groups were observed (p = NS, chi2). C-myc antisense oligomers significantly decreased neointimal and wall thickness, as well as increased lumenal index, in treated groups (p<0.04, p<0.03, and p<0.001, respectively, analysis of variance). In contrast, there was no difference in medial thickness or perivascular wound healing.

CONCLUSION

Intraoperative treatment of saphenous veins with c-myc antisense oligomers decreased neointimal formation at 3 months after grafting. In conjunction with our previous reports, these findings suggest that early inhibition of cellular proliferation and inflammatory infiltration results in a sustained reduction in neointimal formation and favorable graft remodeling.

Early injury to the media after saphenous vein grafting

BACKGROUND

Injury to the smooth muscle cells of the media affects the remodeling process of vein grafts. The purpose of this study was to determine whether different techniques of surgical preparation influence the degree of medial smooth muscle injury.

METHODS

Carotid-saphenous vein interposition grafting was performed in crossbred pigs (n = 32), using distended (n = 16) or nondistended (n = 16) conduits. After 3 to 90 days, the media was evaluated for the presence of smooth muscle cells (desmin stains), myofibroblast formation (transient alpha-SM actin expression), and apoptosis (TdT-mediated dUTP nick end-labeling [TUNEL]).

RESULTS

Smooth muscle loss was uniformly severe; only 5% +/- 5% (p < 0.01) and 14% +/- 9% (p < 0.01) of the medial area of distended and nondistended veins were desmin positive in comparison with 80% +/- 9% of controls. Apoptosis appeared to contribute to medial smooth muscle loss (5.7% +/- 4.3% in vein grafts versus 0.0% +/- 0.0% of TUNEL-positive cells in controls; p = 0.05). There was a time dependent increase in medial myofibroblast formation (p < 0.05).

CONCLUSIONS

Severe medial smooth muscle loss occurs in vein grafts, even when prepared without distension. Apoptosis contributes to the early disappearance of smooth muscle cells. Adjunctive measures, in addition to ideal surgical techniques, should be developed to prevent medial muscle loss.