Human Vein Grafts Research Articles

Infrainguinal bypass surgery: Factors determining late graft patency

The results of 373 infrainguinal bypass grafts, in a single centre, between 1980 and 1988 are reviewed. One hundred and thirty in situ vein (ISV), 47 reversed saphenous vein (RSV), 118 polytetrafluoroethylene (PTFE) and 78 human umbilical vein (HUV) grafts were used. The indications for surgery were disabling claudication in 25 per cent of patients and limb salvage in 75 per cent. In 36 per cent of operations the distal anastomosis was above the knee and in 64 per cent it was below the knee. Overall 5-year patency rates and limb salvage rates respectively were, for ISV (41 and 69 per cent), RSV (62 and 90 per cent), PTFE (31 and 67 per cent) and HUV (29 and 59 per cent). There was no significant difference in patency among these grafts at the above-knee level, but significant differences between vein and prosthetic grafts were evident below the knee (P less than 0.001). Using a proportional hazards model the three factors that consistently correlated with late graft patency were graft type (P less than 0.001), site of distal anastomosis (P less than 0.001) and distal run-off (P less than 0.001). Overall, the results suggest that prosthetic grafts are a suitable alternative to autogenous vein when the distal anastomosis is above the knee, but vein should always be used, if available, below the knee joint.

Human umbilical vein and PTFE grafts compared in an artificial circulation

Human umbilical vein and PTFE grafts compared in an artificial circulation

Enhanced virus-mediated endoluminal gene transfer to human vein grafts

Enhanced virus-mediated endoluminal gene transfer to human vein grafts

Early adaptation of human lower extremity vein grafts: wall stiffness changes accompany geometric remodeling

Objective To quantitatively describe the temporal changes in elastic properties and wall dimensions in lower-extremity vein grafts after implantation. Design of study This is a prospective study of patients (N = 38) undergoing lower extremity bypass grafts (N = 41) with autologous veins. Pulse wave velocity (PWV), luminal diameter, and wall thickness measurements were obtained by duplex ultrasound scan intraoperatively and at 1, 3, and 6 months postoperatively for assessment of graft dimensions and wall stiffness. Results Lower extremity vein grafts showed an increase in PWV (from 16 ± 1 to 21 ± 3 cm/s; mean ± SEM; P = .08), reflecting an increase in wall stiffness (from 1.2 ± 0.2 to 2.5 ± 0.7 × 10 6 dynes/cm; P = .02) and wall thickness (from 0.47 ± 0.03 to 0.61 ± 0.004 mm; P = .04) over the first 6 months after implantation. Changes in lumen diameter were positively correlated with changes in external graft diameter ( P < .01) and negatively correlated with initial lumen diameter ( P < .01) but not with changes in the wall thickness. Conclusions These results suggest complex remodeling of vein grafts during the first several months after implantation, with increased wall thickness occurring independent of variable changes in lumen diameter. Simultaneously, a marked increase in wall stiffness over this interval suggests a likely role for collagen deposition.

Improved gene delivery to human saphenous vein cells and tissue using a peptide-modified adenoviral vector

The establishment of efficient gene delivery to target human tissue is a major obstacle for transition of gene therapy from the pre-clinical phases to the clinic. The poor long-term patency rates for coronary artery bypass grafting (CABG) is a major clinical problem that lacks an effective and proven pharmacological intervention. Late vein graft failure occurs due to neointima formation and accelerated atherosclerosis. Since CABG allows a clinical window of opportunity to genetically modify vein ex vivo prior to grafting it represents an ideal opportunity to develop gene-based therapies. Adenoviral vectors have been frequently used for gene delivery to vein ex vivo and pre-clinical studies have shown effective blockade in neointima development by overexpression of candidate therapeutic genes. However, high titers of adenovirus are required to achieve sufficient gene delivery to provide therapeutic benefit. Improvement in the uptake of adenovirus into the vessel wall would therefore be of benefit. Here we determined the ability of an adenovirus serotype 5 vector genetically-engineered with the RGD-4C integrin targeting peptide inserted into the HI loop (Ad-RGD) to improve the transduction of human saphenous vein smooth muscle cells (HSVSMC), endothelial cells (HSVEC) and intact saphenous vein compared to a non-modified virus (Ad-CTL). We exposed each cell type to virus for 10, 30 or 60 mins and measured transgene at 24 h post infection. For both HSVSMC and HSVEC Ad-RGD mediated increased transduction, with the largest increases observed in HSVSMC. When the experiments were repeated with intact human saphenous vein (the ultimate clinical target for gene therapy), again Ad-RGD mediated higher levels of transduction, at all clinically relevant exposures times (10, 30 and 60 mins tissue:virus exposure). Our study demonstrates the ability of peptide-modified Ad vectors to improve transduction to human vein graft cells and tissue and has important implications for gene therapy for CABG.

Regarding “cryopreserved saphenous vein allografts in infrainguinal revascularization: analysis of 240 grafts”

Farber et al (J Vasc Surg 2003;38:15-31) have defined a specific role for the use of cryopreserved saphenous vein in infrainguinal revascularization. However, their reference to the umbilical vein is based on an article published in the Journal of Vascular Surgery in 1988. The authors should have referred to a subsequent publication,1Dardik H. Wengerter K. Qin F. Pangilinan A. Silvestri F. Wolodiger F. et al.Comparative decades of experience with glutaraldehyde-tanned human umbilical cord vein graft for lower limb revascularization an analysis of 1275 cases.J Vasc Surg. 2002; 35: 64-71Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar which clearly showed no aneurysmal degeneration in the series followed during the decade 1990 to 2000. Their comments and conclusions with regard to the current status of the use of umbilical vein grafts would have been different and more accurate in describing the current status of this material.

Neovascularization in intimal hyperplasia is associated with vein graft failure after coronary artery bypass surgery

Vein graft atherosclerosis is the major limitation of arterial bypass surgery. This study was carried out to determine if the number of microvessels per area of intimal hyperplasia correlated with vein graft disease. Vein grafts (n=24, graft age range 2-19 years) were taken from 22 patients undergoing redo-coronary artery bypass surgery. Mean age of the patients was 68 +/- 9 years; 92% were males. Samples were divided into three groups (n=8 per group): in group I segments were from grafts without angiographic or histologic disease, in groups II and III segments were from grafts with significant angiographic stenosis, without (group II) and with (group III) atheroma. Intimal hyperplasia was identified by Masson staining, morphometric analysis was performed with NIH image analysis software. Microvessels in the intimal hyperplasia were identified using immunohistochemical techniques. Significance was determined by single-factor ANOVA p < 0.05. The mean area of intimal hyperplasia was similar in groups I and II at 1.06 +/- 0.25 mm2 and 0.97 +/- 0.37 mm2, respectively. The extent of intimal hyperplasia was significantly greater in group III, 1.70 +/- 0.62 mm2 (p < 0.01). In group I, the microvessel count in the intimal hyperplasia was 5.62 +/- 3.89 vessels/mm2, while in group III it was 15.26 +/- 3.66/mm2 (p < 0.01 versus group I). Interestingly the number of microvessels per area of intimal hyperplasia in group II was similar to that in group III). In this study, the extent of neovascularization in intimal hyperplasia correlated with stenoses in human vein grafts. Strategies designed to limit neovascularization in intimal hyperplasia may lead to novel therapies to prevent vein graft failure.

Marimastat inhibits neointimal thickening in a model of human vein graft stenosis.

There is now accumulating evidence that matrix metalloproteinases (MMPs), the physiological mediators of matrix deposition and degradation, play an important role in the development of intimal hyperplasia following arterial bypass. This study investigated the effect of marimastat, an orally active specific MMP inhibitor, on neointima formation in cultured human saphenous vein. Segments of human saphenous vein obtained from ten patients undergoing arterial bypass surgery were cultured for 14 days in serum-supplemented RPMI medium (controls) or in control medium supplemented with marimastat at three different concentrations (treatment groups). Following culture, half of each segment was prepared for histological examination and MMPs were extracted from the other half for gelatin zymography. Marimastat inhibited neointimal thickening in a concentration-dependent manner; inhibition was significant at 10(-5) and 10(-6) mol/l (P=0.006). This observation was paralleled by a significant reduction in the levels of MMP-2 and MMP-9 in the tissues. Marimastat significantly reduced neointimal thickening in this laboratory model. MMP inhibitors may offer a potential therapeutic strategy in the prevention of intimal hyperplasia.

Neointimal hyperplasia rapidly reaches steady state in a novel murine vein graft model

Neointimal hyperplasia remains a principal cause of vein graft failure. Genetic contributions to vein graft neointimal hyperplasia could be well studied in the mouse; however, surgical approaches to vein bypass surgery in the mouse have yet to replicate approaches commonly employed in human patients. Consequently, the goal of this study was to develop a murine interposition vein graft model that reproduces characteristics of human vein graft disease. Using C57BL/6J mice, we excised inferior venae cavae (IVCs) from donor mice and grafted them, with end-to-side anastomosis, into the carotid circulation of recipients. IVC grafts were harvested from 3 to 56 days postoperatively, and analyzed for the development of neointima and media. Thickening of both the vein graft neointima and media progressed rapidly between postoperative weeks 1 and 4, and reached steady state levels by approximately week four, with a graft-wall thickness of 91 +/- 4 microm (14 cell layers), a lumen area of 0.56 mm(2), an average neointima-media ratio of 0.4 to 0.6, and a predominance of alpha-smooth muscle actin-staining cells. Comprising predominately smooth muscle actin-expressing cells, the neointima was 50% thicker in the proximal than in the distal third of the grafts (P <.001), but proximal and distal vein graft anastomoses were widely patent. In syngeneic murine carotid interposition IVC grafts implanted with end-to-side anastomoses, moderate, nonocclusive neointimal hyperplasia reaches steady state after the fourth postoperative week. This neointimal hyperplasia, like that of human grafts, predominates near vein graft anastomoses. This vein graft model should facilitate genetic analyses of the pathogenesis of neointimal hyperplasia.

Accelerated atherosclerosis and calcification in vein grafts: a study in APOE*3 Leiden transgenic mice.

Vein grafts fail due to development of intimal hyperplasia and accelerated atherosclerosis. Many murine genetic models in which genes are overexpressed, deleted, or mutated have been introduced recently. Therefore, mouse models are very well suited to dissect the relative contribution of different genes in the development of accelerated atherosclerosis. In the present study, we evaluated whether accelerated atherosclerosis in human vein grafts could be mimicked in hypercholesterolemic APOE*3 Leiden transgenic mice. Venous bypass grafting was performed in the carotid artery in APOE*3 Leiden mice fed either a standard chow diet or a high cholesterol-rich diet for 4 weeks. At several time points (0 hour to 28 days), mice were euthanized and the morphology of the vein grafts was analyzed. In normocholesterolemic mice, vein graft thickening up to 10-fold original thickness, predominantly consisting of alpha-smooth muscle cell actin-positive cells, was observed after 28 days. In hypercholesterolemic mice, accelerated atherosclerosis with accumulation of lipid-loaded foam cells was observed within 7 days after surgery. This accelerated atherosclerosis progressed in time and resulted in significant increase in vein graft thickening up to 50 times original thickness with foam cell-rich lesions and calcification within 28 days after surgery. The atherosclerotic lesions observed in these murine grafts show high morphological resemblance with the atherosclerotic lesions observed in human vein grafts. This accelerated, diet-dependent induction of atherosclerotic-like lesions in murine vein grafts provides a valuable tool in evaluating the mechanisms of accelerated atherosclerosis and therapeutic interventions of vein graft disease.

Inhibition of accelerated atherosclerosis in vein grafts by placement of external stent in apoE*3-Leiden transgenic mice.

Vein grafts fail because of the development of intimal hyperplasia and accelerated atherosclerosis. Placement of an external stent around vein grafts resulted in an inhibition of intimal hyperplasia in several animal studies. Here, we assess the effects of external stenting on accelerated atherosclerosis in early vein grafts in carotid arteries in hypercholesterolemic apolipoprotein E*3-Leiden transgenic mice. Venous interposition grafting was performed in apolipoprotein E*3-Leiden mice fed standard chow or a highly cholesterol-rich diet for 4 weeks. After engraftment, external stents with different inner diameters (0.4 or 0.8 mm) were placed. In unstented vein grafts in hypercholesterolemic mice, thickening up to 50 times the original thickness, with foam cell-rich lesions, calcification, and necrosis, was observed within 28 days. The atherosclerotic lesions observed show high morphological resemblance to atherosclerotic lesions observed in human vein grafts. In stented vein grafts in hypercholesterolemic mice, no foam cell accumulation or accelerated atherosclerosis was observed. Compared with unstented vein grafts, stenting of vein grafts in a hypercholesterolemic environment resulted in a 94% reduction of vessel wall thickening. These effects were independent of stent size. Extravascular stent placement results in strong inhibition of accelerated vein graft atherosclerosis in hypercholesterolemic transgenic mice and thereby provides a perspective for therapeutic intervention in vein graft diseases.

Perivenous application of fibrin glue reduces early injury to the human saphenous vein graft wall in an ex vivo model.

From animal and clinical studies it is known that prevention of 'over-distention' of vein grafts by using extravascular support ameliorates the arterialization process in vein grafts with subsequent more favorable patency. The most ideal support is a biodegradable, porous, elastic graft (Biomaterials, 15 (1994) 83). However, a specific graft meeting these criteria is not available yet. Fibrin glue on the other hand, although used for other purposes in cardiac surgery, theoretically meets the criteria for ideal extravascular support. In this ex vivo study, we evaluated the possible beneficial effect of perivenous application of fibrin glue. Segments of human vein graft obtained during CABG procedures in 14 consecutive patients were placed in a side loop of the extracorporeal perfusion circuit. In this way the study vein grafts did meet identical circumstances as the vein grafts implanted. Perfusion in the loop was started with a flow just enough to counteract the collapse of the vein, usually about 8 mm Hg, and alternately around the segments fibrin glue was applied or no perivenous support was administered as control. After 1 min of soldification, perfusion was started with a pressure of about 60 mm Hg (non-pulsatile flow). Perfusion was maintained for 60 min, after which the grafts were collected for light microscopic and electron microscopic assessment. Light microscopy and electron microscopy showed remarkable attenuation of endothelial cell loss and less injury of smooth muscle cells of the circular muscle layer of the media in the fibrin glue supported vein grafts compared to the non-supported group. Fibrin glue is able to accomplish adequate external vein graft support, preventing overdistention, in an ex vivo model. This provides a basis for clinical application. Further investigation is necessary to evaluate long-term effects.

Comparative decades of experience with glutaraldehyde-tanned human umbilical cord vein graft for lower limb revascularization: An analysis of 1275 cases

Purpose: Biological material has been used as an alternative to autogenous vein since the first lower extremity revascularization procedures were performed. Our experience with glutaraldehyde-tanned human umbilical cord vein graft (UVg), which spanned a period of 28 years, forms the basis of this report, with an emphasis on comparative results between the two decades from 1975 to 1985 and from 1990 to 2000. Methods: Between 1990 and 2000, 283 lower extremity bypass grafting procedures were performed in 230 patients (264 limbs), with UVg used as the predominant, or sole, graft material. Our experience with 907 reconstructions in the decade from 1975 to 1985 has been previously documented and now serves as a baseline comparison with the past decade of experience with UVg. Each reconstruction was classified on the basis of the distal anastomotic site with or without distal arteriovenous fistulas (dAVFs). The primary and secondary graft patency rates were determined for each category as was cumulative palliation, which combines the end points of graft failure, amputation, and death Results: The results from the second decade (1990 to 2000) showed a continuation of improving patency rates for UVg grafts in lower extremity revascularization. Comparison results of complications showed no changes in the low incidence rates of infection, stenosis, dissection, and pseudoaneurysm. The original series results showed a 2.9% requirement for aneurysm surgery, with an incidence rate of biodegradation of 57% (36% aneurysms, 21% dilation), whereas the current series results have shown no aneurysms to date. The comparative 6-year secondary patency rates for past and current popliteal and crural bypass grafts (with or without dAVF) were: popliteal, 53% versus 67%, P <.05; and crural, 26% without dAVF versus 47% with dAVF, P <.05. The limb salvage rates for the two series at 6 years showed no significant changes between the decades and the types of bypass grafts. Thrombolysis was performed during the decade from 1990 to 2000 in 27 UVg cases, with lysis achieved in 23 cases (85%) and limb salvage achieved in 20 cases (74%). Since 1996, associated endovascular procedures (fluoroscopy, angioplasty) have assumed increasing importance in the reduction of perioperative graft closure and in the enhancement of patency Conclusion: Our continuing experience with UVg confirms that favorable results can be obtained with this biologic alternative to autologous vein for lower limb revascularization. Concern regarding biodegradation and aneurysm formation even after 5 years are unfounded at this time. Improved patency and limb salvage rates can be achieved in concert with lower nonthrombotic failure rates, increasing performance of associated endovascular procedures, use of tourniquets, and the addition of dAVF for crural bypass grafting. Prospective randomized studies are still necessary for the assessment of the comparative role of all graft materials, a project that continues to evade our specialty. (J Vasc Surg 2002;35:64-71.)

Comparative decades of experience with glutaraldehyde-tanned human umbilical cord vein graft for lower limb revascularization: An analysis of 1275 cases*1

Comparative decades of experience with glutaraldehyde-tanned human umbilical cord vein graft for lower limb revascularization: An analysis of 1275 cases*1

New mouse model of vein bypass graft atherosclerosis

Animal models of vein graft disease are used as preliminary tools to study and understand the pathogenesis of the disease in humans and improve its diagnosis, prevention and therapy. Several animal models that manifest lesions resembling neointimal hyperplasia of human vein grafts have been developed, but there are limitations in studying the mechanism of this disease in these models. We previously established a mouse model of vein bypass graft atherosclerosis that allows us to take advantage of transgenic and knockout techniques. Using this model, we studied the pathogenesis of vein graft atherosclerosis. The lesion in the grafts was characterised by mononuclear cell infiltration followed by smooth muscle cell (SMC) proliferation and matrix protein deposition, which is similar to the human lesion. Studies of the molecular mechanism of pathogenesis in this model revealed that physical force initiated signal pathways, particularly mitogen-activated protein kinases (MAPK), leading to vascular cell death and an inflammatory response, followed by SMC proliferation, which contributed to the development of arteriosclerosis. Suramin inhibited SMC migration and proliferation in vivo and in vitro by blocking platelet-derived growth factor (PDGF)-initiated PDGF receptor activation and MAPK-AP-1 signalling, and was also effective in inhibition of neointima hyperplasia in mouse vein bypass grafts. This new mouse model of vein bypass graft atherosclerosis affords us with a valuable new approach to attain further understanding of the mechanism of vein graft disease with the use of transgenic mice, and in evaluating the effects of drugs and gene therapy on vascular diseases.

Late-Breaking Clinical Trials at the American Heart Association’s Scientific Sessions 2001

The PRoject of Ex-vivo Vein graft ENgineering via Transfection (PREVENT) II trial found that a double-stranded piece of DNA called the E2F duplex decoy significantly reduced failure of vein grafts after coronary artery bypass surgery (CABG), according to Eberhard Grube, MD, of the Heart Center in Sieburg, Germany, during the American Heart Association’s 2001 Scientific Sessions in Anaheim, Calif. During the Late-Breaking Clinical Trials Plenary Session on November 12, 2001, Dr Grube said that his decoy blocks vascular smooth muscle proliferation, which is the core problem in vein graft failure. Eberhard Grube, MD (photo by Paul C. SoRelle) The graft is treated during CABG after the vein has been removed from the leg. A solution containing the E2F decoy is placed in a tube with a stopcock on one side and a syringe at the other, which is used to apply pressure. The vein is placed in the tube and pressure is applied via the syringe to ≈6 lbs/in2 for 10 minutes, Dr Grube said. That is enough to insure that 80% of the cells in the graft will take up the decoy. The transfected graft then is used to bypass blocked coronary arteries. In the study, 101 patients who had undergone CABG were randomly assigned to the treatment group, and 99 were assigned to placebo. In angiographic studies performed on 61 placebo patients and 75 treated patients who received a total of 309 grafts, the E2F decoy was associated with a 30% relative reduction in a composite index of vein graft failure and death, said Dr Grube. In addition, there was a 30% reduction in the size of vessel wall volume. According to Dr Grube, the results are similar to those in the PREVENT I trial, which used E2F to treat bypass veins in peripheral artery disease. He …

Monocyte adhesion to human vein grafts: A marker for occult intraoperative injury?

Objective: Monocyte adhesion to the vessel wall is believed to be an important initiating event in atherosclerosis and intimal hyperplasia. We hypothesized that occult intraoperative vein injury induces an immediate increase in monocyte adhesion that may be critical to the development of vein graft disease. Methods: Vein segments were obtained from patients (n = 23) undergoing lower extremity bypass. The initial segment (V1, n = 17) was excised immediately at the time of conduit harvest. A second segment (V2, n = 23) was obtained from the distal conduit just before performing the distal anastomosis. Segments were incubated with radiolabeled THP-1 cells (monocytoid cell line) for 1 hour at 37°C, then rinsed and solubilized for determination of bound radioactivity. In a subset of grafts (n = 4), THP-1 cells were preincubated with monoclonal antibody (mAB) 7E3 (which binds to the monocyte integrin Mac-1 at its fibrinogen [Fg]-binding site) or control (mAB 14E11). Fg deposition and endothelial coverage were evaluated by immunohistochemistry (n = 10). Statistical analysis was performed using the paired t test and analysis of variance. Follow-up graft patency data were obtained and correlated with adhesion values using an exact test (StatXact, Cytel Software, Cambridge, Mass). Results: Monocyte adhesion was significantly increased after surgical manipulation (V1, 2400 ± 770 versus V2, 7343 ± 1555 cells/cm2; P <.02). Fg deposition was abundant in V2 sections and not seen in V1. Monocyte adhesion to V2 segments was significantly reduced (58% of control, P <.01) by 7E3 treatment. Graft follow-up was complete with a mean interval of 11 months. Higher V2 adhesion values were associated with occluded grafts (P =.07). The median value for the six occluded grafts was 6234 cells/cm2 versus 3892 cells/cm2 for the 17 patent grafts. Conclusions: Monocyte adhesion to the vein wall is immediately increased after surgical manipulation and is inhibited by mAB 7E3. Early monocyte adhesion to vein grafts is likely to involve interactions between Mac-1 and Fg. Heightened levels of monocyte adhesion at implantation may be a marker for subsequent vein graft failure. (J Vasc Surg 2001;34:923-9.)

The effects of extremely low shear stress on cellular proliferation and neointimal thickening in the failing bypass graft

Objective: Previous studies demonstrating a correlation between low shear stress (τ = 5-15 dyne/cm2) and experimental vein graft neointimal thickening (NIT) support the role of low τ in vein graft failure. However, a simple linear relationship between low τ and NIT would underestimate the degree of NIT evident in high-grade occlusive lesions of failing human vein grafts. In this study we used a new experimental model that maintains patency at low τ (< 2 dyne/cm2), to delineate possible deviations from linearity in the low τ → NIT hypothesis. Methods: Thirty-two New Zealand White rabbits underwent creation of a common carotid vein patch with a segment of ipsilateral external jugular vein. Very low τ was created in 13 patches by ligation of the distal common carotid artery, leaving the only outflow through a small muscular branch. Normal τ was created in 11 patches by leaving the common carotid artery outflow intact. High τ was created in eight patches by ligation of the contralateral common carotid artery. Six patches were harvested after 2 weeks for measurement of cell cycle entry by proliferating cell nuclear antigen (PCNA) immunohistochemistry. The remaining 26 patches were harvested after 4 weeks, perfusion fixed, and excised for morphometric analysis. Results: Mean blood flow and τ at implantation ranged from 0.5 to 41 mL/min and 0.07 to 15 dyne/cm2, respectively. At the time of harvest, 30 of 32 patches remained patent, and the artificially created aberrations in blood flow were maintained (range, 0.7-41 mL/min). After 2 weeks PCNA immunohistochemistry showed a significantly higher level of cell cycling in patches exposed to low τ (40 ± 5 vs 1.6 ± 0.3 PCNA-positive cells per high-power field; P <.001), which is equivalent to approximately 20% of the total cells present. In patches harvested after 4 weeks, NIT ranged from 42 to 328 μm and significantly correlated with mean τ at implantation. Patches with very low τ exhibited histologic characteristics similar to those of failing human bypass grafts, including laminar thrombus and flow-limiting luminal stenosis. The relationship between τ and NIT was nonlinear in that extremely low τ (< 2 dyne/cm2) resulted in NIT beyond that predicted by a simple linear correlation (P =.003). Conclusion: Extremely low τ (< 2 dyne/cm2) stimulates high rates of smooth muscle cellular proliferation in arterialized vein patches. NIT is accelerated in these regions of low τ far beyond that predicted by a simple linear model. The nonlinear nature of the cellular proliferative response and NIT at τ less than 2 dyne/cm2 may explain the rapid progression of neointimal lesions in failing bypass grafts. (J Vasc Surg 2001;34:90-7.)

Adenoviral-mediated Gene Transfer in Human and Animal Vein Grafts Using Clinically Relevant Exposure Times, Pressures, and Viral Concentrations

This study examined the efficiency of adenoviral-mediated gene transfer in experimental vein grafts and cultured human saphenous vein under physiologic conditions using clinically relevant exposure times, pressures, and viral concentrations. The external jugular veins of 25 male New Zealand White rabbits were exposed to 0.5 mL of replication-deficient adenovirus vectors encoding beta-galactosidase (AdlacZ), control adenovirus (AdBg/II), or vehicle at pressures ranging from 0 to 120 mmHg for 10 min. Veins were excised and grafted into the carotid circulation. After 5 days, the vessels were reexposed, excised, and stained with X-gal chromagen for beta-galactosidase (beta-gal) activity. Gene transfer was also performed in 13 segments of human saphenous vein discarded at the time of bypass grafting. The veins were cultured for 0-21 days and assayed for beta-gal activity as above. Rabbit vein grafts exposed to high-pressure AdlacZ transfection showed significant transgene expression in 100% of grafts (39 +/- 2% positive cells/hpf) while only 60% of those transfected at low pressure expressed beta-gal (9 +/- 3% positive cells/hpf). All human veins exposed to AdlacZ expressed beta-gal to a variable degree (range 10-50% positive cells/hpf). No control grafts or veins expressed the transgene. Efficient adenoviral-mediated gene transfer in experimental vein grafts and human saphenous vein segments can be achieved using clinically feasible parameters of exposure time, pressure, and viral concentration.

Long-term stabilization of vein graft wall architecture and prolonged resistance to experimental atherosclerosis after E2F decoy oligonucleotide gene therapy

Objective: We tested the hypothesis that a single intraoperative transfection of rabbit vein grafts with a decoy oligonucleotide that blocks cell-cycle gene transactivation by the transcription factor E2F induces long-term stable adaptation that involves medial hypertrophy and a resistance to neointimal hyperplasia and atherosclerosis. Methods: Jugular vein to carotid artery interposition vein grafts in hypercholesterolemic rabbits were treated, using pressure-mediated delivery, with either E2F decoy oligonucleotide, scrambled oligonucleotide, or vehicle alone. E2F decoy inhibition of cell-cycle gene expression was determined by measuring proliferating cell nuclear antigen upregulation and bromodeoxyuridine incorporation in vascular smooth muscle cells. Neointimal hyperplasia and atherosclerosis were compared between groups at 6 months after operation. Wall stress was derived from the ratio of luminal radius to wall thickness. Normal rabbits exposed to 6 weeks of diet-induced hypercholesterolemia starting 6 months after operation were analyzed in the same manner. Results: The E2F decoy oligonucleotide, but not scrambled oligonucleotide or vehicle alone, inhibited proliferating cell nuclear antigen expression and smooth muscle cell proliferation. Furthermore, this manipulation of cell-cycle gene expression yielded an inhibition of neointimal hyperplasia and atherosclerotic plaque formation throughout the 6 months of cholesterol feeding. In normocholesterolemic rabbits, vehicle-treated and scrambled oligonucleotide-treated vein grafts remain susceptible to diet-induced atherosclerosis as well, whereas resistance to this disease induction remained stable in genetically engineered grafts. Conclusion: A single intraoperative pressure-mediated delivery of E2F decoy effectively provides vein grafts with long-term resistance to neointimal hyperplasia and atherosclerosis. These findings suggest that long-term reduction in human vein graft failure rates may be feasible with this ex vivo gene therapy approach. (J Thorac Cardiovasc Surg 2001;121:714-22)