Pressure distension stimulates the expression of endothelial adhesion molecules in the human saphenous vein graft

Impact of distension pressure on saphenous vein endothelial injury in coronary artery bypass grafting

Introduction

Long saphenous vein grafts (LSVGs) are pivotal conduits in coronary artery bypass grafting (CABG), yet concerns persist regarding early failure and long-term patency. Endothelial damage, a potent initiator of graft failure, necessitates exploration of factors contributing to endothelial injury during LSVG preparation.

Methods

A prospective, single-center study was conducted, assessing the impact of unregulated distension pressure on LSVG endothelium during CABG. Histological and CD31 (cluster of differentiation 31) immunohistochemical analyses were performed on 21 paired vein samples, categorized into non-distended (group A) and distended (group B) groups. Pressure recordings were obtained using different syringe sizes during vein distension.

Results

Histological examination revealed a significantly higher percentage of endothelial cell loss in distended veins (31.95% ± 31.31) compared to non-distended veins (11.67% ± 28.65) (p = 0.034). CD31 immunohistochemistry corroborated greater endothelial cell loss in distended veins (p = 0.001). The pressure recordings with a 20-cc syringe, as opposed to using a 10-cc syringe, were considerably lower (44.5 mmHg vs. 92.75 mmHg) emphasizing the inverse relationship between syringe size and pressure generated. In our study, pre-existing endothelial injury was observed in one-third of diabetic patients (36%), with all instances of such injury exclusively identified in individuals with diabetes.

Conclusion

Unregulated distension pressure during LSVG preparation is associated with greater endothelial damage, as evidenced by histological and immunohistochemical analyses. The inverse relationship between syringe size and pressure underscores the importance of controlled distension.

Consensus statement-graft treatment in cardiovascular bypass graft surgery

Coronary artery bypass grafting (CABG) is and continues to be the preferred revascularization strategy in patients with multivessel disease. Graft selection has been shown to influence the outcomes following CABG. During the last almost 60 years saphenous vein grafts (SVG) together with the internal mammary artery have become the standard of care for patients undergoing CABG surgery. While there is little doubt about the benefits, the patency rates are constantly under debate. Despite its acknowledged limitations in terms of long-term patency due to intimal hyperplasia, the saphenous vein is still the most often used graft. Although reendothelialization occurs early postoperatively, the process of intimal hyperplasia remains irreversible. This is due in part to the persistence of high shear forces, the chronic localized inflammatory response, and the partial dysfunctionality of the regenerated endothelium. "No-Touch" harvesting techniques, specific storage solutions, pressure controlled graft flushing and external stenting are important and established methods aiming to overcome the process of intimal hyperplasia at different time levels. Still despite the known evidence these methods are not standard everywhere. The use of arterial grafts is another strategy to address the inferior SVG patency rates and to perform CABG with total arterial revascularization. Composite grafting, pharmacological agents as well as latest minimal invasive techniques aim in the same direction. To give guide and set standards all graft related topics for CABG are presented in this expert opinion document on graft treatment.

[Method of optimal hydraulic dilatation of venous conduits for coronary artery bypass grafting]

Hydraulic dilatation is used in everyday cardiac surgical practice for assessment of leak-proofness and prevention of spasm of autovenous shunts. The classical technique envisages manual high-pressure solution injection, which exerts a negative effect on venous conduits and is one of the causes of incompetence of shunts in the postoperative period. Limiting pressure during hydraulic dilatation is necessary to minimize morphological changes and preserve functional viability of venous conduits. The purpose of the present study was to develop and assess efficacy of a standardized methodology of controlled hydraulic dilatation of venous conduits. We worked out an original technique of controlled hydraulic dilatation of venous conduits under perfusion pressure of artificial circulation. This was followed by assessing morphological changes and functional viability of venous segments after controlled hydraulic dilatation as compared with veins after conventional uncontrolled hydraulic dilatation and the control intact veins. Uncontrolled hydraulic dilatation was accompanied by endothelial damage (p<0.05), multiple conduit wall tears (p<0.05) according to the findings of light microscopy, leading to a significant decrease in the functional vitality of the venous conduit (a decreased reaction to hyperpotassium solution, phenylephrine, acetylcholine and sodium nitroprusside (p<0.05) according to the findings of biophysical examination. Our original technique of controlled hydraulic dilatation of venous conduits under perfusion pressure of artificial circulation made it possible not only to evaluate leak-proofness of the vessel but also to achieve comparable to the control segments parameters of structural integrity of the venous wall and functional viability of the conduit. Thus, using the developed method of controlled hydraulic dilatation makes it possible to minimize morphofunctional alterations in venous conduits, influencing the function of autovenous shunts.

Preventing treatment failures in coronary artery disease: what can we learn from the biology of in-stent restenosis, vein graft failure, and internal thoracic arteries?

Coronary artery disease (CAD) remains one of the most important causes of morbidity and mortality worldwide, and the availability of percutaneous or surgical revascularization procedures significantly improves survival. However, both strategies are daunted by complications which limit long-term effectiveness. In-stent restenosis (ISR) is a major drawback for intracoronary stenting, while graft failure is the limiting factor for coronary artery bypass graft surgery (CABG), especially using veins. Conversely, internal thoracic artery (ITA) is known to maintain long-term patency in CABG. Understanding the biology and pathophysiology of ISR and vein graft failure (VGF) and mechanisms behind ITA resistance to failure is crucial to combat these complications in CAD treatment. This review intends to provide an overview of the biological mechanisms underlying stent and VGF and of the potential therapeutic strategy to prevent these complications. Interestingly, despite being different modalities of revascularization, mechanisms of failure of stent and saphenous vein grafts are very similar from the biological standpoint.

The Anti-Inflammatory Effects of Anacardic Acid on a TNF-α - Induced Human Saphenous Vein Endothelial Cell Culture Model

BACKGROUND AND OBJECTIVE

Coronary bypass operations are commonly performed for the treatment of ischemic heart diseases. Coronary artery bypass surgery with autologous human saphenous vein maintains its importance as a commonly used therapy for advanced atherosclerosis. Vascular inflammation-related intimal hyperplasia and atherosclerotic progress have major roles in the pathogenesis of saphenous vein graft disease.

METHODS

In our study, we investigated the effect of anacardic acid (AA), which is a bioactive phytochemical in the shell of Anacardium occidentale, on atherosclerosis considering its inhibitory effect on NF-κB. We observed relative ICAM-1 and NF-κB mRNA levels by qRT-PCR method in a TNF-α- induced inflammation model of saphenous vein endothelial cell culture after 0.1, 0.5, 1 and 5 μM of AA were applied to the cells. In addition, protein levels of ICAM-1 and NF-κB were evaluated by immunofluorescent staining. The results were compared between different concentrations of AA, and also with the control group.

RESULTS

It was found that 5 μM, 1 μM and 0.5 μM of AA had toxic effects, while cytotoxicity decreased when 0.1 μM of AA was applied both alone and with TNF-α. When AA was applied with TNF-α, there was a decrease and suppression in NF-κB expression compared with the TNF-α group. TNF-α-induced ICAM-1 expression was significantly reduced more in the AA-applied group than in the TNF-α group.

CONCLUSION

In accordance with our results, it can be said that AA has a protective role in the pathogenesis of atherosclerosis and hence in saphenous vein graft disease.

The Role of Immunomodulation in Vein Graft Remodeling and Failure

Obstructive arterial disease is a major cause of morbidity and mortality in the developed world. Venous bypass graft surgery is one of the most frequently used revascularization strategies despite its considerable short and long time failure rate. Due to vessel wall remodeling, inflammation, intimal hyperplasia, and accelerated atherosclerosis, vein grafts may (ultimately) fail to revascularize tissues downstream to occlusive atherosclerotic lesions. In the past decades, little has changed in the prevention of vein graft failure (VGF) although new insights in the role of innate and adaptive immunity in VGF have emerged. In this review, we discuss the pathophysiological mechanisms underlying the development of VGF, emphasizing the role of immune response and associated factors related to VG remodeling and failure. Moreover, we discuss potential therapeutic options that can improve patency based on data from both preclinical studies and the latest clinical trials. This review contributes to the insights in the role of immunomodulation in vein graft failure in humans. We describe the effects of immune cells and related factors in early (thrombosis), intermediate (inward remodeling and intimal hyperplasia), and late (intimal hyperplasia and accelerated atherosclerosis) failure based on both preclinical (mouse) models and clinical data.

Biomechanics and Mechanobiology of Saphenous Vein Grafts

Within several weeks of use as coronary artery bypass grafts (CABG), saphenous veins (SV) exhibit significant intimal hyperplasia (IH). IH predisposes vessels to thrombosis and atherosclerosis, the two major modes of vein graft failure. The fact that SV do not develop significant IH in their native venous environment coupled with the rapidity with which they develop IH following grafting into the arterial circulation suggests that factors associated with the isolation and preparation of SV and/or differences between the venous and arterial environments contribute to disease progression. There is strong evidence suggesting that mechanical trauma associated with traditional techniques of SV preparation can significantly damage the vessel and might potentially reduce graft patency though modern surgical techniques reduces these injuries. In contrast, it seems possible that modern surgical technique, specifically endoscopic vein harvest, might introduce other mechanical trauma that could subtly injure the vein and perhaps contribute to the reduced patency observed in veins harvested using endoscopic techniques. Aspects of the arterial mechanical environment influence remodeling of SV grafted into the arterial circulation. Increased pressure likely leads to thickening of the medial wall but its role in IH is less clear. Changes in fluid flow, including increased average wall shear stress, may reduce IH while disturbed flow likely increase IH. Nonmechanical stimuli, such as exposure to arterial levels of oxygen, may also have a significant but not widely recognized role in IH. Several potentially promising approaches to alter the mechanical environment to improve graft patency are including extravascular supports or altered graft geometries are covered.

VENOUS CONDUITS IN CORONARY SURGERY: OLD PROBLEMS — NEW SOLUTIONS

The introduction of autovenous coronary artery bypass grafting (CABG) marked the era of surgical revascularization in patients with coronary artery disease. It provided effective treatment for angina and significantly improved the long-term prognosis. Venous transplants today remain the most popular conduits in coronary surgery due to their availability, ease of harvesting, and the absence of length restrictions. Despite the advantages of autovenous CABG, the main disadvantage is the high incidence of venous graft failure, which represents an important and unresolved problem in cardiac and cardiovascular surgery. On the other hand, the traditional allocation of a large saphenous vein implies the dissection of soft tissues throughout the length of the isolated conduit. Traumatic dissection causes a long-lasting persistent pain syndrome after surgery, frequent abnormalities in  skin sensitivity, and a high incidence of wound complications in the lower extremities. These complications lengthen the period of rehabilitation of patients and worsen the quality of life. There is an approach of isolating the vein in a block with surrounding tissues to optimize the long-term functioning of the venous shunt, however, this technique is even more traumatic than the traditional method, and therefore its use is limited in practice. On the other hand, the introduction of minimally invasive methods of isolation allowed to reduce the incidence of wound complications and to improve the cosmetic result, but there is no convincing data regarding the effect on the consistency of shunts in the long-term postoperative period. The problems associated with the use of venous conduits in CABG are multifaceted, and their solutions are necessary to improve the effectiveness of surgical revascularization.

Unregulated saphenous vein graft distension decreases tissue viscoelasticity

OBJECTIVES

Unregulated intraoperative distension of human saphenous vein (SV) graft leads to supraphysiologic luminal pressures and causes acute physiologic and cellular injury to the conduit. The effect of distension on tissue viscoelasticity, a biophysical property critical to a successful graft, is not well described. In this investigation, we quantify the loss of viscoelasticity in SV deformed by distension and compare the results to tissue distended in a pressure-controlled fashion.

MATERIALS AND METHODS

Unmanipulated porcine SV was used as a control or distended without regulation and distended with an in-line pressure release valve (PRV). Rings were cut from these tissues and suspended on a muscle bath. Force versus time tracings of tissue constricted with KCl (110 mM) and relaxed with sodium nitroprusside (SNP) were fit to the Hill model of viscoelasticity, using mean absolute error (MAE) and r²-goodness of fit as measures of conformity.

RESULTS

One-way ANOVA analysis demonstrated that, in tissue distended manually, the MAE was significantly greater and the r²-goodness of fit was significantly lower than both undistended tissues and tissues distended with a PRV (p<0.05) in KCl-induced vasoconstriction and SNP-induced vasodilation.

CONCLUSIONS

Unregulated manual distension of SV graft causes loss of viscoelasticity and such loss may be mitigated with the use of an in-line PRV.

Rac1 Pharmacological Inhibition Rescues Human Endothelial Dysfunction

Background

Endothelial dysfunction contributes significantly to the development of vascular diseases. However, a therapy able to reduce this derangement still needs to be identified. We evaluated the effects of pharmacological inhibition of Rac1, a small GTPase protein promoting oxidative stress, in human endothelial dysfunction.

Methods and Results

We performed vascular reactivity studies to test the effects of NSC23766, a Rac1 inhibitor, on endothelium‐dependent vasorelaxation of saphenous vein segments collected from 85 subjects who had undergone surgery for venous insufficiency and from 11 patients who had undergone peripheral vascular surgery. The endothelium‐dependent vasorelaxation of the varicose segments of saphenous veins collected from patients with venous insufficiency was markedly impaired and was also significantly lower than that observed in control nonvaricose vein tracts from the same veins. Rac1 activity, reactive oxygen species levels, and reduced nicotine adenine dinucleotide phosphate (NADPH) oxidase activity were significantly increased in varicose veins, and NSC23766 was able to significantly improve endothelium‐dependent vasorelaxation of dysfunctional saphenous vein portions in a nitric oxide–dependent manner. These effects were paralleled by a significant reduction of NADPH oxidase activity and activation of endothelial nitric oxide synthase. Finally, we further corroborated this data by demonstrating that Rac1 inhibition significantly improves venous endothelial function and reduces NADPH oxidase activity in saphenous vein grafts harvested from patients with vascular diseases undergoing peripheral bypass surgery.

Conclusions

Rac1 pharmacological inhibition rescues endothelial function and reduces oxidative stress in dysfunctional veins. Rac1 inhibition may represent a potential therapeutic intervention to reduce human endothelial dysfunction and subsequently vascular diseases in various clinical settings.

Traditional graft preparation decreases physiologic responses, diminishes viscoelasticity, and reduces cellular viability of the conduit: A porcine saphenous vein model

Traditional methods of intraoperative human saphenous vein preparation for use as bypass grafts can be deleterious to the conduit. The purpose of this study was to characterize acute graft preparation injury, and to mitigate this harm via an improved preparation technique. Porcine saphenous veins were surgically harvested (unprepared controls, UnP) and prepared using traditional (TraP) and improved preparations (ImP). The TraP used unregulated radial distension, marking with a surgical skin marker and preservation in heparinized normal saline. ImP used pressure-regulated distension, brilliant blue FCF-based pen marking and preservation in heparinized Plasma-Lyte A. Rings from each preparation were suspended in a muscle bath for characterization of physiologic responses to vasoactive agents and viscoelasticity. Cellular viability was assessed using the methyl thiazolyl tetrazolium (MTT) assay and the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay for apoptosis. Contractile responses to potassium chloride (110 mM) and phenylephrine (10 µM), and endothelial-dependent and independent vasodilatory responses to carbachol (0.5 µM) and sodium nitroprusside (1 µM), respectively, were decreased in TraP tissues compared to both UnP and ImP tissues (p ⩽ 0.05). TraP tissues demonstrated diminished viscoelasticity relative to UnP and ImP tissues (p ⩽ 0.05), and reduced cellular viability relative to UnP control (p ⩽ 0.01) by the MTT assay. On the TUNEL assay, TraP tissues demonstrated a greater degree of apoptosis relative to UnP and ImP tissues (p ⩽ 0.01). In conclusion, an improved preparation technique prevents vascular graft smooth muscle and endothelial injury observed in tissues prepared using a traditional approach.

Bilateral internal mammary artery grafting in obese: outcomes, concerns and controversies

Obese patients are generally considered unsuitable to receive bilateral internal mammary arteries (BIMA) during coronary artery bypass grafting (CABG) due to the perceived vulnerability to sternal wound infection and lack of evidence supporting long-term survival benefit. However, no consistent evidence currently discourages the use of BIMA in obese patients. The present review questions the common perception that obesity unacceptably increases the risk of sternal wound complications in patients receiving BIMA grafting. Moreover, the use of skeletonization harvesting technique is expected to further minimize such a risk. Our institutional experience confirmed that BIMA grafting is a safe strategy which does not increase operative mortality and does not significantly affect the incidence of sternal wound complications. On the other hand, a long term benefit in terms of overall survival and freedom from repeat revascularization from the use of BIMA was found.

Pressure control during preparation of saphenous veins

IMPORTANCE

Long-term patency of human saphenous veins (HSVs) used as autologous conduits for coronary artery bypass grafting (CABG) procedures remains limited because of vein graft failure (VGF). Vein graft failure has been reported to be as high as 45% at 12 to 18 months after surgery and leads to additional surgery, myocardial infarction, recurrent angina, and death. Preparation of HSVs before implantation leads to conduit injury, which may promote VGF.

OBJECTIVES

To investigate whether pressure distension during vein graft preparation leads to endothelial injury and intimal thickening and whether limiting intraluminal pressure during pressure distension by using a pressure release valve (PRV) preserves endothelial function and prevents neointima thickening.

DESIGN, SETTING, AND PARTICIPANTS

Segments of HSVs were collected in a university hospital from 13 patients undergoing CABG procedures immediately after harvest (unmanipulated [UM]), after pressure distension (after distension [AD]), and after typical intraoperative surgical graft preparation (after manipulation [AM]). Porcine saphenous veins (PSVs) from 7 healthy research animals were subjected to manual pressure distension with or without an in-line PRV that prevents pressures of 140 mm Hg or greater. Endothelial function of the HSVs and PSVs was determined in a muscle bath, endothelial integrity was assessed, and intimal thickening in PSVs was evaluated after 14 days in organ culture.

MAIN OUTCOMES AND MEASURES

Endothelial function was measured in force, converted to stress, and defined as the percentage relaxation of maximal phenylephrine-induced contraction. Endothelial integrity was assessed by immunohistologic examination. Neointimal thickness was measured by histomorphometric analysis.

RESULTS

Pressure distension of HSVs led to decreased mean (SEM) endothelial-dependent relaxation (5.3% [2.3%] for AD patients vs 13.7% [2.5%] for UM patients; P < .05) and denudation. In the AM group, the function of the conduits was further decreased (-3.2% [3.2%]; P < .05). Distension of the PSVs led to reduced endothelial-dependent relaxation (7.6% [4.4%] vs 61.9% [10.2%] in the control group; P < .05), denudation, and enhanced intimal thickening (15.0 [1.4] µm vs 2.2 [0.8] µm in the control group; P < .05). Distension with the PRV preserved endothelial-dependent relaxation (50.3% [9.6%]; P = .32 vs control), prevented denudation, and reduced intimal thickening (3.4 [0.8] µm; P = .56 vs controls) in PSVs.

CONCLUSIONS AND RELEVANCE

Use of a PRV during graft preparation limits intraluminal pressure generated by manual distension, preserves endothelial integrity, and reduces intimal hyperplasia. Integration of this simple device may contribute to improved long-term vein graft patency.

Oral intake of hydrogen-rich water inhibits intimal hyperplasia in arterialized vein grafts in rats

AIMS

Arterialized vein grafts often fail due to intimal hyperplasia. Hydrogen potently protects organs and cells from many insults via its anti-inflammatory and antioxidant properties. We investigated the efficacy of oral administration of hydrogen-rich water (HW) for prevention of intimal hyperplasia.

METHODS AND RESULTS

The inferior vena cava was excised, stored in cold Ringer solution for 2 h, and placed as an interposition graft in the abdominal aorta of syngeneic Lewis rats. HW was generated by immersing a magnesium stick in tap water (Mg + 2H(2)O → Mg (OH)(2) + H(2)). Beginning on the day of graft implantation, recipients were given tap water [regular water (RW)], HW or HW that had been subsequently degassed water (DW). Six weeks after grafting, the grafts in the rats given RW or DW had developed intimal hyperplasia, accompanied by increased oxidative injury. HW significantly suppressed intimal hyperplasia. One week after grafting, the grafts in HW-treated rats exhibited improved endothelial integrity with less platelet and white blood cell aggregation. Up-regulation of the mRNAs for intracellular adhesion molecules was attenuated in the vein grafts of the rats receiving HW. Activation of p38 mitogen-activated protein kinase, matrix metalloproteinase (MMP)-2, and MMP-9 was also significantly inhibited in grafts receiving HW. In rat smooth muscle cell (A7r5) cultures, hydrogen treatment for 24 h reduced smooth muscle cell migration.

CONCLUSION

Drinking HW significantly reduced neointima formation after vein grafting in rats. Drinking HW may have therapeutic value as a novel therapy for intimal hyperplasia and could easily be incorporated into daily life.

Influences of Geometric Configurations of Bypass Grafts on Hemodynamics in End-to-Side Anastomosis

Background

Although considerable efforts have been made to improve the graft patency in coronary artery bypass surgery, the role of biomechanical factors remains underrecognized. The aim of this study is to investigate the influences of geometric configurations of the bypass graft on hemodynamic characteristics in relation to anastomosis.

Materials and Methods

The Numerical analysis focuses on understanding the flow patterns for different values of inlet and distal diameters and graft angles. The Blood flow field is treated as a two-dimensional incompressible laminar flow. A finite volume method is adopted for discretization of the governing equations. The Carreau model is employed as a constitutive equation for blood. In an attempt to obtain the optimal aorto-coronary bypass conditions, the blood flow characteristics are analyzed using in vitro models of the end-to-side anastomotic angles of 45°, 60° and 90°. To find the optimal graft configurations, the mass flow rates at the outlets of the four models are compared quantitatively.

Results

This study finds that Model 3, whose bypass diameter is the same as the inlet diameter of the stenosed coronary artery, delivers the largest amount of blood and the least pressure drop along the arteries.

Conclusion

Biomechanical factors are speculated to contribute to the graft patency in coronary artery bypass grafting.

Effective silencing of adhesion molecules on venous endothelial cells for protection of venous bypass grafts

OBJECTIVE

The patency of venous conduits after aortocoronary bypass grafting is still not satisfactory and needs to be improved. Atherosclerotic alterations mediated by adhesion molecules triggering the transmigration of leukocytes are regarded as one of the major causes for venous graft failure. This study deals with short interfering RNA (siRNA)-mediated silencing of adhesion molecule expression on venous endothelial cells, which could lead to a new therapeutic strategy, resulting in improved patency rates by inhibiting early graft alterations.

METHODS

Primary human venous endothelial cells (HVECs) were cultured in a newly developed perfusion model and subsequently transfected with specific siRNAs targeting three different adhesion molecules (the E-selectin (ESELE), the intercellular adhesion molecule 1 (ICAM-1), and the vascular adhesion molecule (VCAM-1)), followed by stimulation with tumor necrosis factor-alpha (TNF-α). Isolated leukocytes were perfused under physiological shear stress conditions, and their attachment to HVEC after single and triple transfection was quantified.

RESULTS

siRNA transfection effectively knocks down adhesion molecule expression on venous endothelial cells, which subsequently reduces leukocyte attachment. Leukocyte adhesion to activated HVEC was significantly reduced after transfection by specific siRNAs in each case compared to the controls (p<0.05). Transfection with a mixture of all three siRNA sequences improved this effect even more (p<0.05).

CONCLUSION

For the first time, a functional protection of HUEC in a model simulating physiologic vascular conditions by using nonviral transfection of the cells in a setup with high relevance for clinical applicability was demonstrated. Therefore, siRNA transfection of bypass material may develop into a new therapeutic option to improve the quality of venous graft material in the future.

Biomechanics of coronary artery and bypass graft disease: potential new approaches

The contribution of biomechanical factors to the incidence and distribution of coronary artery and bypass graft disease is underrecognized. This review examined the literature to determine which factors were relevant and the evidence for their importance. It identified two primary biomechanical factors that predispose to disease: (1) low-wall shear stress and (2) high-wall mechanical stress or strain. A range of secondary biomechanical factors have also been identified and include: vessel geometry; vessel movement; vessel wall characteristics and the presence of reflection waves. Potential surgical approaches for minimizing these effects are discussed.

Inhibition of adhesion molecule expression on human venous endothelial cells by non-viral siRNA transfection

Objective: Expression of adhesion molecule receptors on venous endothelial cells crucially influences the fate of venous grafts by mediating leukocyte-endothelium interactions. These interactions include adhesion of leukocytes to the endothelium, followed by transendothelial migration, leading to neointimal hyperplasia and finally graft occlusion. Therefore, inhibition of adhesion molecule expression may be a promising strategy to improve the quality of venous grafts. We tested the efficiency of non-viral transfection of human venous endothelial cells with short interfering RNA (siRNA) to specificially down-regulate adhesion molecule expression. Methods: Primary cultures of human venous endothelial cells (HVEC) were examined for expression of the adhesion molecules ICAM1, VCAM1 and E-selectin (SELE) after non viral siRNA transfection. Adhesion molecule expression was measured by flow cytometry, real-time PCR and immunoblotting after stimulation with TNF-alpha, an inflammatory cytokine. Results: Non-transfected cells showed a strong increase of adhesion molecule expression following cytokine stimulation (p<0.01). Upon transfection with specific siRNAs a six fold decrease in ICAM1 (p<0.001) and SELE expression and cell positivity (p<0.05) and a twofold decrease in VCAM1 expression and cell positivity (p<0.01) could be observed. SiRNA-mediated gene suppression of adhesion molecules was also reflected by corresponding decreases in adhesion protein and transcript levels. Conclusions: The expression of adhesion molecules on HVECs can be effectively inhibited by specific siRNAs using a safe, non-viral transfection approach. This is a promising tool to precondition venous bypass grafts in order to interfere with endothelium-leukocyte interactions and to prohibit neointima thickening or atherosclerosis, which are regarded to be the most important causes of venous graft failure.

Inhibition of adhesion molecule expression on human venous endothelial cells by non-viral siRNA transfection

Objective:

Expression of adhesion molecule receptors on venous endothelial cells crucially influences the fate of venous grafts by mediating leukocyte-endothelium interactions. These interactions include adhesion of leuko-cytes to the endothelium, followed by transendothelial migration, leading to neointimal hyperplasia (NIH) and finally graft occlusion. Therefore, inhibition of adhesion molecule expression may be a promising strategy to improve the quality of venous grafts.We tested the efficiency of non-viral transfection of human venous endothe-lial cells (HVEC) with short interfering RNA (siRNA) to specifically down-regulate adhesion molecule expression.

Methods:

Primary cultures of HVEC were examined for expression of the adhesion molecules ICAM1, VCAM1 and E-selectin (SELE) after non viral siRNA transfection. Adhesion molecule expression was measured by flow cytom-etry, real-time polymerase chain reaction and immunoblotting after stimulation with TNF-α, an inflammatory cytokine.

Results:

Non-transfected cells showed a strong increase of adhesion molecule expression following cytokine stimulation (P < 0.01). Upon transfection with specific siRNAs a sixfold decrease in ICAM1 (P < 0.001) and SELE expression and cell positivity (P < 0.05) and a twofold decrease in VCAM1 expression and cell positiv-ity (P < 0.01) Pcould be observed. SiRNA-mediated gene suppression of adhesion molecules was also reflected by corresponding decreases in adhesion protein and transcript levels.

Conclusions:

The expression of adhesion molecules on HVECs can be effectively inhibited by specific siRNAs using a safe, non-viral transfection approach. This is a promising tool to pre-condition venous bypass grafts in order to interfere with endothelium-leukocyte interactions and to prohibit neointima thickening or ath-erosclerosis, which are regarded to be the most important causes of venous graft failure.

Prebypass histological and ultrastructural evaluation of the long saphenous vein as a predictor of early graft failure

BACKGROUND

Twenty percent of the long saphenous vein (LSV) grafts that are employed as coronary bypass conduits occlude during the first year after the operation. The aim of this study was to evaluate the morphological parameters of the LSV grafts before implantation as predictors for the early occlusion of the grafts.

METHODS

Forty-two samples of LSV grafts were examined via light, transmission electron, and scanning electron microscopy and evaluated clinically and by angiography at 6 months and 2 years after the operation. Morphological parameters were statistically analyzed and examined for their significance on the viability of the vein grafts.

RESULTS

Six (14.28%) of the examined grafts occluded within the first 6 months after the operation, and 11 grafts (26.19%) occluded within the first 2 years. The grafts that occluded at 6 months were characterized by thick intima (mean value, 206+/-32.29 vs. 67.44+/-10.17 in the group functioning normally and 98.42+/-34 in the group occluded within 2 years), low endothelial coverage (22.7+/-4.04 vs. 64.61+/-2.89 and 26.06+/-1.78 in the corresponding groups), and narrow lumen (46.73+/-9.69 vs. 527.18+/-45.78 and 204.26+/-16.5 in the corresponding groups). The presence of foam cells, edema, calcification, neovascularization, and thrombus in the lumen of the veins is frequently observed in the wall of the occluded vein grafts, whereas fibrosis does not seem to be related.

CONCLUSIONS

LSV grafts with low endothelial cell coverage, stenosis of the lumen, and thick walls are at an increased risk of developing intrawall lesions that lead to early graft failure.

Effects of airway distension on leukocyte recruitment in the mouse tracheal microvasculature

We have shown previously that excessive distention of the rat trachea during mechanical ventilation results in enhanced leukocyte recruitment to the airway (Lim LH and Wagner EM. Am J Respir Crit Care Med 168:1068-1074, 2003). The objectives of this study were to develop a mouse model of positive end-expiratory pressure (PEEP)-induced leukocyte recruitment to the airway and begin to pursue molecular mechanisms that may contribute to the in vivo observation of increased leukocyte adhesion after PEEP exposure. We studied C57BL/6 wild-type mice and mice deficient in P-selectin or intercellular adhesion molecule-1 (ICAM-1) exposed to intermittent PEEP (8 cmH(2)O) applied five times for a 1-min duration, at 10-min intervals. After the imposed ventilatory stress, during normal ventilation (0.2 ml/breath, no PEEP), leukocyte adhesion in tracheal postcapillary venules was determined using intravital microscopy. PEEP induced a time-dependent increase in leukocyte adhesion that was significantly increased between 0 and 60 min (P < 0.01). Furthermore, PEEP-induced leukocyte adhesion at 60 min was ablated in P-selectin- and ICAM-1-deficient mice. These findings demonstrate the essential nature of both P-selectin and ICAM-1 within airway postcapillary venular endothelium for leukocyte recruitment after airway distension.

Manual pressure distension of the human saphenous vein changes its biomechanical properties—implication for coronary artery bypass grafting

Patency rates of saphenous vein grafts following coronary artery bypass grafting (CABG) depend on multiple factors. Information regarding the impact of biomechanical properties of vein grafts on patency rates is not available. The objective of the present study was to evaluate whether uncontrolled manual pressure distension during routine preparation of the saphenous vein in CABG-induced changes in the biomechanical properties of the vein. The morphometric and stress-strain properties were studied in isolated segments of the saphenous vein from 12 patients undergoing elective CABG. Six segments were manually distended without pressure control and six were not distended. The mechanical test was performed as a ramp inflation using syringe pump. The vein dimensions were obtained from digitised images at different pressures as well as at the no-load and zero-stress states. The circumferences, the wall and lumen area, the wall thickness, and the outer diameter as function of the applied pressure were largest in the segments with uncontrolled manual distension compared to those without distension (P<0.05). The opening angle and the absolute value of the residual strains were lower (P<0.01) and the circumferential stress-strain curve shifted to the left, indicating the wall became stiffer with uncontrolled manual distension compared to those without distension (P<0.05). In conclusion, manual pressure distension changed the morphometric and biomechanical properties of the saphenous vein. The perspective is that studies on biomechanical properties on the saphenous vein may guide surgeons how to handle graft material without causing major changes of the biomechanical properties during harvesting and preparation.

Simvastatin Reduces CD40 Expression in an Experimental Model of Early Arterialization of Saphenous Vein Graft

BACKGROUND

Saphenous vein graft (VG) failure occurs more frequently compared with arterial grafts, and graft thrombosis represents the main cause of early occlusion. Because CD40-CD40L pathway CD40 represents a culprit link between local inflammation and coagulation cascade, we investigate the role of CD40 and its soluble ligand (sCD40L) in the immediate in vitro response of VG to arterial pressures, and the potential effects of Simvastatin (Merck Sharp&Dohme, White-house Station, NJ) supplementation.

METHODS

Samples of saphenous vein and of internal mammary artery (IMA) were obtained from sixteen patients without history of statin therapy. Segments underwent pulsatile pressure distension and culture with or without supplementation of Simvastatin. CD40 and sCD40L were assessed in tissue lysate and in culture supernatant, respectively. sCD40L serum concentrations were also measured.

RESULTS

During the course of the experiment, the CD40 expression was significantly lower in IMA samples compared with both distended and not distended VG. Pressure distension up-regulated the production of CD40 in VG segments after 24 and 48 h. Statin supplementation significantly reduced the expression of CD40 in both venous (P < 0.001) and arterial samples (P < 0.001). This effect of Simvastatin was not affected by the treatment with L-NAME, but it was reversed by the addition of mevalonic acid. Mean sCD40L content in culture supernatants increased over time, suggesting that not only platelets but also the vessel wall is a source of CD40 and sCD40L.

CONCLUSIONS

Simvastatin treatment modulates endothelial CD40-sCD40L in both venous and arterial grafts, and therefore may represent a useful tool in the pharmacological prevention of graft failure.

Neutrophil adherence to activated saphenous vein and mammary endothelium after graft preparation

BACKGROUND

Interaction of circulating leukocytes and vascular endothelium plays an important role in vasoconstriction, endothelial dysfunction, and vascular injury. Dilation procedures of grafts before coronary artery bypass graft surgery might lead to vascular injury and subsequent bypass graft disease.

METHODS

We analyzed in vitro the adherence of fluorescence-labeled polymorphonuclear neutrophils (PMNs) to endothelium of human saphenous vein grafts or internal mammary artery grafts after stimulation with thrombin (0.5 to 2 U/mL) or dilating procedures. Furthermore, we investigated endothelial function of prepared grafts.

RESULTS

Thrombin stimulation resulted in a dose-dependent increase of PMN adherence to the endothelium of saphenous vein and internal mammary artery, which was attenuated by the selectin-blocking carbohydrate fucoidin or anti-P-selectin monoclonal antibody. Mechanical dilation of saphenous vein or internal mammary artery led to a marked increase in PMN adherence (65 +/- 5 versus 5 +/- 3 PMN/mm2; p < 0.01), which was significantly attenuated by fucoidin or anti-P-selectin monoclonal antibodies. Treatment of internal mammary artery with the vasodilator papaverine led to a marked increase of PMN adherence (59 +/- 8 versus 12 +/- 4 PMN/mm2; p < 0.01) when papaverine was administered directly into the vessel. However, external treatment with papaverine did not affect PMN adhesion. Endothelial dysfunction was observed in dilated venous grafts and in arterial grafts internally treated with papaverine; in contrast, external treatment did not affect endothelial function.

CONCLUSIONS

This study showed that mechanical or pharmacologic dilation of venous or arterial coronary grafts, usually performed before anastomosis of aortocoronary bypass grafts, led to increased selectin-mediated PMN adhesion on vascular endothelium and subsequent endothelial dysfunction.

Endoscopic versus conventional radial artery harvest for coronary artery bypass grafting: functional and histologic assessment of the conduit

BACKGROUND

The radial artery's propensity for vasospasm and vulnerability to surgical trauma are well known. A less invasive endoscopic method to harvest the radial artery was recently introduced, but its effect on radial artery integrity is unknown.

METHODS

To compare the effects of harvest method on radial artery function, we prospectively randomized 54 patients undergoing coronary artery bypass grafting with the radial artery into 3 groups on the basis of harvest techniques: endoscopic, conventional with cautery, and conventional with harmonic scalpel. We assessed endothelium-dependent and endothelium-independent relaxation of radial artery segments to sequential doses of acetylcholine and nitroglycerin, respectively, using standard organ-chamber methodology. Vasospasm was assessed as the vasoconstrictor response to the thromboxane analog U46619. We assessed endothelial integrity using light and electron microscopy and by rating intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and P-selectin expression by means of immunohistochemistry on a semiquantitative 0- to 3-point scale. Harvest procedures were performed by a single surgeon, and data analyses were blinded to the harvesting method.

RESULTS

Maximal relaxation-contraction responses to acetylcholine, nitroglycerin, and U46619 and effective drug concentration yielding 50% response were similar in the 3 groups. Adhesion molecule expression and histologic changes, as assessed by means of light and electron microscopy, were similar in the 3 groups.

CONCLUSIONS

Endoscopic harvest does not alter radial artery vasoreactivity or endothelial integrity compared with conventional harvest techniques. Because the endoscopic technique is less invasive, it might prove to be the technique of choice to harvest the radial artery.

Cardiovascular tissue engineering: state of the art

In patients requiring coronary or peripheral vascular bypass procedures, autogenous arterial or vein grafts remain as the conduit of choice even in the case of redo patients. It is in this class of redo patients that often natural tissue of suitable quality becomes unavailable; so that prosthetic material is then used. Prosthetic grafts are liable to fail due to graft occlusion caused by surface thrombogenicity and lack of elasticity. To prevent this, seeding of the graft lumen with endothelial cells has been undertaken and recent clinical studies have evidenced patency rates approaching reasonable vein grafts. Recent advances have also looked at developing a completely artificial biological graft engineered from the patient's cells with surface and viscoelastic properties similar to autogenous vessels. This review encompasses both endothelialisation of grafts and the construction of biological cardiovascular conduits.

Effects of Resveratrol in Storage Solution on Adhesion Molecule Expression and Nitric Oxide Synthesis in Vein Grafts

BACKGROUND

Endothelial injury in human saphenous vein grafts may occur during harvesting and storage, which may have an adverse effect on coronary artery bypass grafting outcome. In this study, we sought to determine whether resveratrol, a natural antioxidant enriched in grape, can limit endothelial activation and reduce endothelial injury in human saphenous vein grafts.

METHODS

Human saphenous vein grafts, obtained from 8 patients and divided into two equal groups of control and study specimens, were stored in either heparinized blood (group A) or heparinized blood containing 50 microg/mL resveratrol (group B) for 1 hour at room temperature. Specimens were analyzed by Western blotting to quantify intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and inducible nitric oxide synthase-2 expression, as well as tissue cyclic guanylate monophosphate levels. Myeloperoxidase activity, a marker of neutrophil sequestration in human saphenous vein grafts, was also measured in each group.

RESULTS

Intercellular adhesion molecule-1 expression (1,674 +/- 332 versus 559 +/- 282; p = 0.003), vascular cell adhesion molecule-1 expression (753 +/- 183 versus 472 +/- 151; p = 0.025), and myeloperoxidase activity (7.00 +/- 1.05 versus 1.33 +/- 0.45 nm/min; p = 0.004) were significantly lower in group B. In contrast, inducible nitric oxide synthase-2 expression (548 +/- 237 versus 2,234 +/- 726; p = 0.004) and tissue cyclic guanylate monophosphate levels (2.02 +/- 0.53 versus 5.61 +/- 0.89 pmol/mL; p = 0.001) were significantly higher in group B.

CONCLUSIONS

Resveratrol reduced upregulation of leukocyte-endothelial cell adhesion molecule expression in human saphenous vein graft endothelium and decreased neutrophil adhesion to saphenous vein graft endothelium. Resveratrol also augmented inducible nitric oxide synthase-2 expression and increased cyclic guanylate monophosphate levels. These results suggest that resveratrol might improve vascular homeostasis and reduce endothelial injury during the hypoxic storage period of human saphenous vein grafts for coronary artery bypass grafting.

Dexamethasone-eluting stents and plasma concentrations of adhesion molecules in patients with unstable coronary syndromes: Results of the historically controlled SESAME study

BACKGROUND

Plasma concentrations of intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1], and E-selectin may increase after percutaneous coronary intervention (PCI).

OBJECTIVE

The aim of this study was to assess whether anti-inflammatory treatment with steroid-eluting stents influenced concentrations of adhesion molecules after PCI in patients with unstable coronary syndromes.

METHODS

Consecutive patients with unstable coronary syndromes who were prospectively assigned to undergo implantation of a dexamethasone-eluting stent were compared with a control group of consecutive historical patients who received a similar non-drugeluting stent in the period immediately preceding availability of the steroid-eluting stents. Circulating concentrations of adhesion molecules were measured before the procedure and at 6 and 24 hours after implantation.

RESULTS

The study included 50 patients who received the dexamethasone-eluting stent (41 men, 9 women; mean [SD] age, 60 [9] years) and 50 historical controls who received the non-drug-eluting stent (40 men, 10 women; mean age, 63 [11] years). Baseline values for the adhesion molecules were similar in the 2 groups: in patients who received the dexamethasone-eluting stent, mean (SD) values were 210 (41) ng/mL for ICAM-1, 637 (119) ng/mL for VCAM-1, and 46 (9) ng/mL for E-selectin; in the control group, the corresponding values were 218 (42), 618 (140), and 43 (10) ng/mL. Circulating concentrations at 24 hours were significantly lower in patients receiving the drug-eluting stent compared with controls for both ICAM-1 (279 [49] vs 338 [60] ng/mL, respectively; P = 0.001) and VCAM-1 (772 [163] vs 896 [207] ng/mL; P = 0.004). There was no significant between-group difference in E-selectin concentrations at 24 hours (60 [10] vs 56 [11] ng/mL).

CONCLUSION

In this study, dexamethasone-eluting stents reduced plasma concentrations of ICAM-1 and VCAM-1 after PCI in patients with unstable coronary syndromes compared with historical controls.

Influence of ischemic injury on vein graft remodeling: role of cyclic adenosine monophosphate second messenger pathway in enhanced vein graft preservation

OBJECTIVE

Endothelial injury during the harvest of saphenous vein grafts might play an important role in the development of vein graft disease after coronary artery bypass grafting. Using a murine autologous arterialized vein patch model, we tested whether the initial ischemic insult of vein grafts was linked to the later development of graft neointimal hyperplasia and whether the restoration of the cyclic adenosine monophosphate second messenger pathway would attenuate the development of neointimal hyperplasia.

METHODS

A segment of the external jugular vein of a mouse was grafted onto its abdominal aorta. Three weeks after the operation, the degree of neointimal hyperplasia of the implanted graft was compared among (1) grafts without preservation, (2) grafts with 2 hours of preservation (25 degrees C) in heparinized saline, and (3) grafts with 2 hours of preservation in heparinized saline in the presence of a cyclic adenosine monophosphate analog. In addition, cyclic adenosine monophosphate contents of vein grafts and leukocyte adherence to the graft endothelium were assessed.

RESULTS

Cyclic adenosine monophosphate contents were significantly decreased after 2 hours of preservation (212 +/- 8 vs 156 +/- 5 pmol/L, P < .01). The grafts preserved for 2 hours showed greater neointimal hyperplasia compared with the grafts without preservation (neointimal expansion, 68.7% +/- 9.6% vs 46.1% +/- 4.8%; P < .01). The addition of a cyclic adenosine monophosphate analog to the preservation solution significantly suppressed neointimal hyperplasia of grafts preserved for 2 hours (44.3% +/- 5.0%). Inhibiting the cyclic adenosine monophosphate-dependent protein kinase by adding Rp-cAMPS abrogated the beneficial effects. Furthermore, grafts preserved for 2 hours had significantly more leukocytes adhering to the graft endothelium 24 hours after the operation compared with nonpreserved grafts, which was significantly reduced by the cyclic adenosine monophosphate treatment.

CONCLUSIONS

Ischemic insult during vein graft harvest and preservation is a key factor in the development of vein graft neointimal hyperplasia at least in part caused by the depletion of cyclic adenosine monophosphate. We conclude that stimulation of the cyclic adenosine monophosphate second messenger pathway might be a potential strategy for the prevention of vein graft disease.