Therapeutics of vein graft intimal hyperplasia: 100 years on

Mechanical Strain Induces Transcriptomic Reprogramming of Saphenous Vein Progenitors

Intimal hyperplasia is the leading cause of graft failure in aortocoronary bypass grafts performed using human saphenous vein (SV). The long-term consequences of the altered pulsatile stress on the cells that populate the vein wall remains elusive, particularly the effects on saphenous vein progenitors (SVPs), cells resident in the vein adventitia with a relatively wide differentiation capacity. In the present study, we performed global transcriptomic profiling of SVPs undergoing uniaxial cyclic strain in vitro. This type of mechanical stimulation is indeed involved in the pathology of the SV. Results showed a consistent stretch-dependent gene regulation in cyclically strained SVPs vs. controls, especially at 72 h. We also observed a robust mechanically related overexpression of Adhesion Molecule with Ig Like Domain 2 (AMIGO2), a cell surface type I transmembrane protein involved in cell adhesion. The overexpression of AMIGO2 in stretched SVPs was associated with the activation of the transforming growth factor β pathway and modulation of intercellular signaling, cell-cell, and cell-matrix interactions. Moreover, the increased number of cells expressing AMIGO2 detected in porcine SV adventitia using an in vivo arterialization model confirms the upregulation of AMIGO2 protein by the arterial-like environment. These results show that mechanical stress promotes SVPs' molecular phenotypic switching and increases their responsiveness to extracellular environment alterations, thus prompting the targeting of new molecular effectors to improve the outcome of bypass graft procedure.

Using Graphene-Based Materials for Stiff and Strong Poly(ethylene glycol) Hydrogels

Blood-contacting devices are increasingly important for the management of cardiovascular diseases. Poly(ethylene glycol) (PEG) hydrogels represent one of the most explored hydrogels to date. However, they are mechanically weak, which prevents their use in load-bearing biomedical applications (e.g., vascular grafts, cardiac valves). Graphene and its derivatives, which have outstanding mechanical properties, a very high specific surface area, and good compatibility with many polymer matrices, are promising candidates to solve this challenge. In this work, we propose the use of graphene-based materials as nanofillers for mechanical reinforcement of PEG hydrogels, and we obtain composites that are stiffer and stronger than, and as anti-adhesive as, neat PEG hydrogels. Results show that single-layer and few-layer graphene oxide can strengthen PEG hydrogels, increasing their stiffness up to 6-fold and their strength 14-fold upon incorporation of 4% w/v (40 mg/mL) graphene oxide. The composites are cytocompatible and remain anti-adhesive towards endothelial cells, human platelets and Staphylococcus aureus, similar to neat hydrogels. To the best of our knowledge, this is the first work to report such an increase of the tensile properties of PEG hydrogels using graphene-based materials as fillers. This work paves the way for the exploitation of PEG hydrogels as a backbone material for load-bearing applications.

Endoluminal interventions versus surgical interventions for stenosis in vein grafts following infrainguinal bypass

BACKGROUND

Bypass surgery using a large saphenous vein graft, or another autologous venous graft, is a well-recognised treatment option for managing peripheral arterial disease of the lower limb, including chronic limb-threatening ischaemia (CLTI) and intermittent claudication, peripheral limb aneurysms, and major limb arterial trauma. Bypass surgery has good results in terms of limb preservation rates and long-term graft patency but is limited by the possibility of vein graft failure due to stenoses of the graft. Detection of stenoses through clinical and ultrasonographic surveillance, followed by treatment, is used to avoid graft occlusion. The conventional approach to treatment of patients with graft stenosis following infrainguinal bypass consists of open surgical repair, which usually is performed under general anaesthesia. Endoluminal treatment with angioplasty is less invasive and uses local anaesthesia. Both methods aim to improve blood flow to the limb.

OBJECTIVES

To assess the effectiveness of endoluminal interventions versus surgical intervention for people with vein graft stenosis following infrainguinal bypass.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov to 25 August 2020.

SELECTION CRITERIA

We aimed to include all published and unpublished randomised controlled trials (RCTs) that compared endoluminal interventions versus surgical intervention for people with vein graft stenosis following infrainguinal bypass.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed all identified studies for potential inclusion in the review. We aimed to use standard methodological procedures in accordance with the Cochrane Handbook for Systematic Reviews of Interventions. The main outcomes of interest were primary patency, primary assisted patency, and all-cause mortality.

MAIN RESULTS

We identified no RCTs that met the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

We found no RCTs that compared endoluminal interventions versus surgical intervention for stenosis in vein grafts following infrainguinal bypass. Currently, there is no high-certainty evidence to support the use of one type of intervention over another. High-quality studies are needed to provide evidence on managing vein graft stenosis following infrainguinal bypass.

Saphenous Vein Vasa Vasorum as a Potential Target for Perivascular Fat-Derived Factors

Perivascular adipose tissue (PVAT) is a source of factors affecting vasomotor tone with the potential to play a role in the performance of saphenous vein (SV) bypass grafts. As these factors have been described as having constrictor or relaxant effects, they may be considered either beneficial or detrimental. The close proximity of PVAT to the adventitia provides an environment whereby adipose tissue-derived factors may affect the vasa vasorum, a microvascular network providing the vessel wall with oxygen and nutrients. Since medial ischaemia promotes aspects of graft occlusion the involvement of the PVAT/vasa vasorum axis in vein graft patency should be considered.

Effect of Adding Ticagrelor to Standard Aspirin on Saphenous Vein Graft Patency in Patients Undergoing Coronary Artery Bypass Grafting (POPular CABG): A Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Approximately 15% of saphenous vein grafts (SVGs) occlude during the first year after coronary artery bypass graft surgery (CABG) despite aspirin use. The POPular CABG trial (The Effect of Ticagrelor on Saphenous Vein Graft Patency in Patients Undergoing Coronary Artery Bypass Grafting Surgery) investigated whether ticagrelor added to standard aspirin improves SVG patency at 1 year after CABG.

METHODS

In this investigator-initiated, randomized, double-blind, placebo-controlled, multicenter trial, patients with ≥1 SVGs were randomly assigned (1:1) after CABG to ticagrelor or placebo added to standard aspirin (80 mg or 100 mg). The primary outcome was SVG occlusion at 1 year, assessed with coronary computed tomography angiography, in all patients that had primary outcome imaging available. A generalized estimating equation model was used to perform the primary analysis per SVG. The secondary outcome was 1-year SVG failure, which was a composite of SVG occlusion, SVG revascularization, myocardial infarction in myocardial territory supplied by a SVG, or sudden death.

RESULTS

Among 499 randomly assigned patients, the mean age was 67.9±8.3 years, 87.1% were male, the indication for CABG was acute coronary syndrome in 31.3%, and 95.2% of procedures used cardiopulmonary bypass. Primary outcome imaging was available in 220 patients in the ticagrelor group and 223 patients in the placebo group. The SVG occlusion rate in the ticagrelor group was 10.5% (51 of 484 SVGs) versus 9.1% in the placebo group (43 of 470 SVGs), odds ratio, 1.29 [95% CI, 0.73-2.30]; P=0.38. SVG failure occurred in 35 (14.2%) patients in the ticagrelor group versus 29 (11.6%) patients in the placebo group (odds ratio, 1.22 [95% CI, 0.72-2.05]).

CONCLUSIONS

In this randomized, placebo-controlled trial, the addition of ticagrelor to standard aspirin did not reduce SVG occlusion at 1 year after CABG. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02352402.

Saphenous vein graft disease, pathophysiology, prevention, and treatment. A review of the literature

BACKGROUND

The saphenous vein remains the most frequently used conduit for coronary artery bypass grafting, despite reported unsatisfactory long-term patency rates. Understanding the pathophysiology of vein graft failure and attempting to improve its longevity has been a significant area of research for more than three decades. This article aims to review the current understanding of the pathophysiology and potential new intervention strategies.

METHODS

A search of three databases: MEDLINE, Web of Science, and Cochrane Library, was undertaken for the terms "pathophysiology," "prevention," and "treatment" plus the term "vein graft failure."

RESULTS

Saphenous graft failure is commonly the consequence of four different pathophysiological mechanisms, early acute thrombosis, vascular inflammation, intimal hyperplasia, and late accelerated atherosclerosis. Different methods have been proposed to inhibit or attenuate these pathological processes including modified surgical technique, topical pretreatment, external graft support, and postoperative pharmacological interventions. Once graft failure occurs, the available treatments are either surgical reintervention, angioplasty, or conservative medical management reserved for patients not eligible for either procedure.

CONCLUSION

Despite the extensive amount of research performed, the pathophysiology of saphenous vein graft is still not completely understood. Surgical and pharmacological interventions have improved early patency and different strategies for prevention seem to offer some hope in improving long-term patency.

Coronary artery mechanics induces human saphenous vein remodelling via recruitment of adventitial myofibroblast-like cells mediated by Thrombospondin-1

Rationale: Despite the preferred application of arterial conduits, the greater saphenous vein (SV) remains indispensable for coronary bypass grafting (CABG), especially in multi-vessel coronary artery disease (CAD). The objective of the present work was to address the role of mechanical forces in the activation of maladaptive vein bypass remodeling, a process determining progressive occlusion and recurrence of ischemic heart disease.

Methods: We employed a custom bioreactor to mimic the coronary shear and wall mechanics in human SV vascular conduits and reproduce experimentally the biomechanical conditions of coronary grafting and analyzed vein remodeling process by histology, histochemistry and immunofluorescence. We also subjected vein-derived cells to cyclic uniaxial mechanical stimulation in culture, followed by phenotypic and molecular characterization using RNA and proteomic methods. We finally validated our results in vitro and using a model of SV carotid interposition in pigs.

Results: Exposure to pulsatile flow determined a remodeling process of the vascular wall involving reduction in media thickness. Smooth muscle cells (SMCs) underwent conversion from contractile to synthetic phenotype. A time-dependent increase in proliferating cells expressing mesenchymal (CD44) and early SMC (SM22α) markers, apparently recruited from the SV adventitia, was observed especially in CABG-stimulated vessels. Mechanically stimulated SMCs underwent transition from contractile to synthetic phenotype. MALDI-TOF-based secretome analysis revealed a consistent release of Thrombospondin-1 (TSP-1), a matricellular protein involved in TGF-β-dependent signaling. TSP-1 had a direct chemotactic effect on SV adventitia resident progenitors (SVPs); this effects was inhibited by blocking TSP-1 receptor CD47. The involvement of TSP-1 in adventitial progenitor cells differentiation and graft intima hyperplasia was finally contextualized in the TGF-β-dependent pathway, and validated in a saphenous vein into carotid interposition pig model.

Conclusions: Our results provide the evidence of a matricellular mechanism involved in the human vein arterialization process controlled by alterations in tissue mechanics, and open the way to novel potential strategies to block VGD progression based on targeting cell mechanosensing-related effectors.

A randomized, double-blind, placebo-controlled trial investigating the effect of ticagrelor on saphenous vein graft patency in patients undergoing coronary artery bypass grafting surgery-Rationale and design of the POPular CABG trial

RATIONALE

An estimated 15% of saphenous vein grafts (SVGs) occlude in the first year after coronary artery bypass grafting (CABG) despite aspirin therapy. Graft occlusion can result in symptoms, myocardial infarction, and death. SVG occlusion is primarily caused by atherothrombosis, in which platelet activation plays a pivotal role. Evidence regarding the effect of stronger platelet inhibition on SVG patency after CABG is limited. The main objective of the POPular CABG trial is to determine whether dual antiplatelet therapy with aspirin plus ticagrelor improves SVG patency when compared to aspirin alone.

STUDY

The POPular CABG is a randomized, double-blind, placebo-controlled, multicenter trial investigating the effect of adding ticagrelor to standard aspirin therapy on the rate of SVG occlusion. A total of 500 patients undergoing CABG with ≥ 1 SVG are randomized to ticagrelor or placebo. The primary end point is SVG occlusion rate, assessed with coronary computed tomography angiography at 1 year. Secondary end points are stenoses and occlusions in both SVGs and arterial grafts and SVG failure at 1 year, defined as a composite of SVG occlusion on coronary computed tomography angiography or coronary angiography, SVG revascularization, myocardial infarction in the territory supplied by an SVG, or sudden death. Safety end points are bleeding events at 30 days and 1 year.

CONCLUSION

The POPular CABG trial investigates whether adding ticagrelor to standard aspirin after CABG reduces the rate of SVG occlusion at 1 year.

Carotid artery ligation induced intimal thickening and proliferation is unaffected by ageing

Following interventions to treat atherosclerosis, such as coronary artery bypass graft surgery, restenosis occurs in approximately 40% of patients. Identification of proteins regulating intimal thickening could represent targets to prevent restenosis. Our group previously demonstrated that in a murine model of vascular occlusion, Wnt4 protein expression and β-catenin signalling was upregulated which promoted vascular smooth muscle cell (VSMC) proliferation and intimal thickening. In this study, the effect of age on VSMC proliferation, intimal hyperplasia and Wnt4 expression was investigated. In vitro proliferation of VSMCs isolated from young (2 month) or old (18-20 month) C57BL6/J mice was assessed by immunocytochemistry for EdU incorporation. As previously reported, 400 ng/mL recombinant Wnt4 protein increased proliferation of VSMCs from young mice. However, this response was absent in VSMCs from old mice. As our group previously reported reduced intimal hyperplasia in Wnt4+/- mice compared to wildtype controls, we hypothesised that impaired Wnt4 signalling with age may result in reduced neointimal formation. To investigate this, carotid artery ligation was performed in young and old mice and neointimal area was assessed 21 days later. Surprisingly, neointimal area and percentage lumen occlusion were not significantly affected by age. Furthermore, neointimal cell density and proliferation were also unchanged. These data suggest that although Wnt4-mediated proliferation was impaired with age in primary VSMCs, carotid artery ligation induced neointimal formation and proliferation were unchanged in old mice. These results imply that Wnt4-mediated proliferation is unaffected by age in vivo, suggesting that therapeutic Wnt4 inhibition could inhibit restenosis in patients of all ages.

Platelet adhesion on endothelium early after vein grafting mediates leukocyte recruitment and intimal hyperplasia in a murine model

Intimal hyperplasia (IH) is the substrate for accelerated atherosclerosis and limited patency of vein grafts. However, there is still no specific treatment targeting IH following graft surgery. In this study, we used a mouse model of vein grafting to investigate the potential for early intervention with platelet function for later development of graft IH. We transferred the inferior vena cava (IVC) from donor C57BL/6 mice to the carotid artery in recipients using a cuff technique. We found extensive endothelial injury and platelet adhesion one hour following grafting. Adhesion of leukocytes was distinct in areas of platelet adhesion. Platelet and leukocyte adhesion was strongly reduced in mice receiving a function-blocking antibody against the integrin αIIbβ3. This was followed by a reduction of IH one month following grafting. Depletion of platelets using antiserum also reduced IH at later time points. These findings indicate platelets as pivotal to leukocyte recruitment to the wall of vein grafts. In conclusion, the data also highlight early intervention of platelets and inflammation as potential treatment for later formation of IH and accelerated atherosclerosis following bypass surgery.

Pedicled Vein Grafts in Coronary Surgery: Perioperative Data From a Randomized Trial

BACKGROUND

Less-than-optimal long-term patency of the saphenous vein is one of the main obstacles for the success of coronary artery bypass grafting (CABG). Results from the IMPROVE-CABG trial has shown that harvesting the saphenous vein with a pedicle of perivascular tissue less than 5 mm while using manual distention provides comparable occlusion rates but significantly less intimal hyperplasia at early follow-up. The impact of pedicled veins on duration of operations, leg wound infections, and postoperative bleeding is unknown.

METHODS

One hundred patients undergoing first-time elective CABG were randomly assigned to conventional or pedicled vein harvesting. Perioperative and postoperative data were collected prospectively during the hospital stay and at follow-up.

RESULTS

Duration of extracorporeal circulation was significantly longer in the pedicled vein group (mean: 76 min versus 65 min, p = 0.006); however, no significant difference was found in the cross-clamp time. No significant difference was found in intraoperative vein graft flow, postoperative bleeding, or leg wound infections (4% in each group). No reoperations were due to vein graft bleeding.

CONCLUSIONS

Harvesting a pedicled vein provides comparable postoperative bleeding and leg wound infection rates in selected patients. The technique is associated with a slightly longer duration of extracorporeal circulation than harvesting conventional veins. Promising early results using the pedicled vein technique may contribute to a change in standard vein harvesting technique for CABG in selected patients.

Bolus injections of novel thrombogenic site-targeted fusion proteins comprising annexin-V and Kunitz protease inhibitors attenuate intimal hyperplasia after balloon angioplasty

BACKGROUND

Systemic administrations of conventional antithrombotics reduce neointima formation after angioplasty in experimental animals. However, clinical translation of these results has not been successful due to high risk for bleeding.

OBJECTIVES

We sought to determine whether novel annexin-V (ANV)-Kunitz protease inhibitor fusion proteins, TAP-ANV and ANV-6L15, can specifically target to vascular injury site and limit neointima formation without inducing systemic hypo-coagulation in a rat carotid artery balloon angioplasty injury model.

METHODS

Near infrared imaging was carried out after balloon-injury and injection of fluorescent ANV or ANV-6L15 to examine their bio-distributions. For peri-procedure treatment, TAP-ANV or ANV-6L15 was administered as i.v. boluses 3 times: 30-minutes before balloon-injury, immediate after procedure, and 120-minutes post-balloon-injury. For extended treatment, additional i.v. bolus injection was given on day-2, day-3 and every other day thereafter. Carotid arteries were collected on day-7 and day-14 for analysis. Blood was collected for measurement of clotting parameters.

RESULTS

Near infrared imaging and immunochemistry showed that fluorescent ANV and ANV-6L15 specifically localized to injured carotid artery and significant amount of ANV-6L15 remained bound to the injured artery after 24-h. Peri-procedure injections of TAP-ANV or ANV-6L15 resulted in decrease of intima/media ratio by 56%. Extended injections of both yielded similar results. Both decreased the expression of PCNA on day-7 and increased the expression calponin on day-14 in the intima post-balloon-injury.

CONCLUSIONS

TAP-ANV and ANV-6L15 can specifically localize to balloon injured carotid arteries after i.v. bolus injections, resulting in substantial attenuation of intimal hyperplasia without inducing a state of systemic hypo-coagulation.

Evidence for the Involvement of Matrix-Degrading Metalloproteinases (MMPs) in Atherosclerosis

Atherosclerosis leads to blockage of arteries, culminating in myocardial infarction, and stroke. The involvement of matrix-degrading metalloproteinases (MMPs) in atherosclerosis is established and many studies have highlighted the importance of various MMPs in this process. MMPs were first implicated in atherosclerosis due to their ability to degrade extracellular matrix components, which can lead to increased plaque instability. However, more recent work has highlighted a multitude of roles for MMPs in addition to breakdown of extracellular matrix proteins. MMPs are now known to be involved in various stages of plaque progression: from initial macrophage infiltration to plaque rupture. This chapter summarizes the development and progression of atherosclerotic plaques and the contribution of MMPs. We provide data from human studies showing the effect of MMP polymorphisms and the expression of MMPs in both the atherosclerotic plaque and within plasma. We also discuss work in animal models of atherosclerosis that show the effect of gain or loss of function of MMPs. Together, the data provided from these studies illustrate that MMPs are ideal targets as both biomarkers and potential drug therapies for atherosclerosis.

Histological changes of the unligated vein wall adjacent to the central venous catheter after open cutdown in rats

BACKGROUND

The sequelae of a central venous cutdown usually include venous deformity causing venous stenosis or stricture. However, the cellular mechanisms causing these deformities have not been elucidated.

METHODS

Silicone 2.7-Fr catheters were placed via the right external jugular vein of 16 rats with the cutdown method. After fixation with formalin at scheduled intervals (1week, 2weeks, 4weeks, and 8weeks; 4 rats in each group), the vein segment with the catheter in situ was harvested. Histological changes in the vein wall were studied and serially compared with light microscopy; standard hematoxylin-eosin staining, Masson's trichrome staining, van Gieson's elastin stain, and immunohistochemical stain against α-actin.

RESULTS

Pericatheter sleeve formation, circumferential smooth muscle cell proliferation and infiltration into the pericatheter sleeve by direct contact were noted in all 4 rats of 1-week model; this indicated the initiation of neointimal hyperplasia. The neointimal hyperplasia was located inside the elastin layer. At 2weeks, the SMCs stained faintly but the components of the vein wall were largely replaced by collagen. The proliferation and infiltration of SMCs stabilized at 4weeks and no SMCs were stained around the catheter. At 8weeks, luminal narrowing was noted and the venous wall was composed mainly of collagen.

CONCLUSIONS

Circumferential neointimal hyperplasia occurred after surgical cutdown of the external jugular vein in a rat model and was caused by SMC activation, proliferation, and infiltration into the pericatheter sleeve.

Human Saphenous Vein Response to Trans-wall Oxygen Gradients in a Novel Ex Vivo Conditioning Platform

Autologous saphenous veins are commonly used for the coronary artery bypass grafting even if they are liable to progressive patency reduction, known as 'vein graft disease'. Although several cellular and molecular causes for vein graft disease have been identified using in vivo models, the metabolic cues induced by sudden interruption of vasa vasorum blood supply have remained unexplored. In the present manuscript, we describe the design of an ex vivo culture system allowing the generation of an oxygen gradient between the luminal and the adventitial sides of the vein. This system featured a separation between the inner and the outer vessel culture circuits, and integrated a purpose-developed de-oxygenator module enabling the trans-wall oxygen distribution (high oxygen level at luminal side and low oxygen level at the adventitial side) existing in arterialized veins. Compared with standard cultures the bypass-specific conditions determined a significant increase in the proliferation of cells around adventitial vasa vasorum and an elevation in the length density of small and large caliber vasa vasorum. These results suggest, for the first time, a cause-effect relationship between the vein adventitial hypoxia and a neo-vascularization process, a factor known to predispose the arterialized vein conduits to restenosis.

Adventitial vessel growth and progenitor cells activation in an ex vivo culture system mimicking human saphenous vein wall strain after coronary artery bypass grafting

Saphenous vein graft disease is a timely problem in coronary artery bypass grafting. Indeed, after exposure of the vein to arterial blood flow, a progressive modification in the wall begins, due to proliferation of smooth muscle cells in the intima. As a consequence, the graft progressively occludes and this leads to recurrent ischemia. In the present study we employed a novel ex vivo culture system to assess the biological effects of arterial-like pressure on the human saphenous vein structure and physiology, and to compare the results to those achieved in the presence of a constant low pressure and flow mimicking the physiologic vein perfusion. While under both conditions we found an activation of Matrix Metallo-Proteases 2/9 and of microRNAs-21/146a/221, a specific effect of the arterial-like pressure was observed. This consisted in a marked geometrical remodeling, in the suppression of Tissue Inhibitor of Metallo-Protease-1, in the enhanced expression of TGF-β₁ and BMP-2 mRNAs and, finally, in the upregulation of microRNAs-138/200b/200c. In addition, the veins exposed to arterial-like pressure showed an increase in the density of the adventitial vasa vasorum and of cells co-expressing NG2, CD44 and SM22α markers in the adventitia. Cells with nuclear expression of Sox-10, a transcription factor characterizing multipotent vascular stem cells, were finally found in adventitial vessels. Our findings suggest, for the first time, a role of arterial-like wall strain in the activation of pro-pathologic pathways resulting in adventitial vessels growth, activation of vasa vasorum cells, and upregulation of specific gene products associated to vascular remodeling and inflammation.

Upregulation of let-7a inhibits vascular smooth muscle cell proliferation in vitro and in vein graft intimal hyperplasia in rats

BACKGROUND

Proliferation of vascular smooth muscle cells (VSMCs) is a crucial event in the pathogenesis of intimal hyperplasia, which is the main cause of restenosis after vascular reconstruction. In this study, we assessed the impact of let-7a microRNA (miRNA) on the proliferation of VSMCs.

METHODS

Using miRNA microarrays analysis for miRNA expression in the vein graft model. Lentiviral vector-mediated let-7a was transfected into the vein grafts. In situ hybridization was performed to detect let-7a. Cultured rat VSMCs were transfected with let-7a mimics for different periods of time. Cell proliferation, migration and cell cycle activity were monitored following transfection of the let-7a mimics. Immunohistochemical and Western blotting analysis the expression levels of c-myc and K-ras.

RESULTS

We found that let-7a was the most downregulated miRNA in the vein graft model. In vivo proliferation of VSMCs was assessed in a rat model of venous graft intimal hyperplasia. Let-7a was found to localize mainly to the VSMCs. Let-7a miRNA expression was increased in VSMCs in the neointima of the let-7a treated group. Intimal hyperplasia was suppressed by upregulation of let-7a via lentiviral vector-mediated mimics. In cultured VSMCs, the expression of let-7a increased upon starving, and the upregulation of let-7a miRNA significantly decreased cell proliferation and migration. Immunohistochemical and Western blotting analysis demonstrated that treatment with let-7a mimics resulted in decreased expression levels of c-myc and K-ras.

CONCLUSIONS

The results indicate that let-7a miRNA is a novel regulator of VSMC proliferation in intimal hyperplasia. These findings suggest that let-7a miRNA is a promising therapeutic target for the prevention of intimal hyperplasia.

A compact and automated ex vivo vessel culture system for the pulsatile pressure conditioning of human saphenous veins

Saphenous vein (SV) graft disease represents an unresolved problem in coronary artery bypass grafting (CABG). After CABG, a progressive remodelling of the SV wall occurs, possibly leading to occlusion of the lumen, a process termed 'intima hyperplasia' (IH). The investigation of cellular and molecular aspects of IH progression is a primary end-point toward the generation of occlusion-free vessels that may be used as 'life-long' grafts. While animal transplantation models have clarified some of the remodelling factors, the pathology of human SV is far from being understood. This is also due to the lack of devices able to reproduce the altered mechanical load encountered by the SV after CABG. This article describes the design of a novel ex vivo vein culture system (EVCS) capable of replicating the altered pressure pattern experienced by SV after CABG, and reports the results of a preliminary biomechanical conditioning experimental campaign on SV segments. The EVCS applied a CAGB-like pressure (80-120 mmHg) or a venous-like perfusion (3 ml/min, 5 mmHg) conditioning to the SVs, keeping the segments viable in a sterile environment during 7 day culture experiments. After CABG-like pressure conditioning, SVs exhibited a decay of the wall thickness, an enlargement of the luminal perimeter, a rearrangement of the muscle fibres and partial denudation of the endothelium. Considering these preliminary results, the EVCS is a suitable system to study the mechanical attributes of SV graft disease, and its use, combined with a well-designed biological protocol, may be of help in elucidating the cellular and molecular mechanisms involved in SV graft disease.

Surgical vein graft preparation promotes cellular dysfunction, oxidative stress, and intimal hyperplasia in human saphenous vein

INTRODUCTION

Human saphenous vein (HSV) is the most widely used bypass conduit for peripheral and coronary vascular reconstructions. However, outcomes are limited by a high rate of intimal hyperplasia (IH). HSV undergoes a series of ex vivo surgical manipulations prior to implantation, including hydrostatic distension, marking, and warm ischemia in solution. We investigated the impact of surgical preparation on HSV cellular function and development of IH in organ culture. We hypothesized that oxidative stress is a mediator of HSV dysfunction.

METHODS

HSV was collected from patients undergoing vascular bypass before and after surgical preparation. Smooth muscle and endothelial function were measured using a muscle bath. Endothelial preservation was assessed with immunohistochemical staining. An organ culture model was used to investigate the influence of surgical preparation injury on the development of IH. Superoxide levels were measured using a high-performance liquid chromatography-based assay. The influence of oxidative stress on HSV physiologic responses was investigated by exposing HSV to hydrogen peroxide (H2O2).

RESULTS

Surgical vein graft preparation resulted in smooth muscle and endothelial dysfunction, endothelial denudation, diminished endothelial nitric oxide synthase staining, development of increased IH, and increased levels of reactive oxygen species. Experimental induction of oxidative stress in unmanipulated HSV by treatment with H2O2 promoted endothelial dysfunction. Duration of storage time in solution did not contribute to smooth muscle or endothelial dysfunction.

CONCLUSIONS

Surgical vein graft preparation causes dysfunction of the smooth muscle and endothelium, endothelial denudation, reduced endothelial nitric oxide synthase expression, and promotes IH in organ culture. Moreover, increased levels of reactive oxygen species are produced and may promote further vein graft dysfunction. These results argue for less injurious means of preparing HSV prior to autologous transplantation into the arterial circulation.

Diet-induced obesity drives negative mouse vein graft wall remodeling

INTRODUCTION

The heightened inflammatory phenotype associated with obesity has been linked to the development of cardiovascular diseases. Short-term high-fat feeding induces a proinflammatory state that may impact the blood vessel wall. CD11c, a significantly increased dendritic cell biomarker during diet-induced obesity (DIO), may have a mechanistic role in this high-fat feeding effect. We hypothesized that the proinflammatory effect of short-term DIO accelerates vein bypass graft failure via CD11c-dependent mechanisms.

METHODS

Male 9-week-old DIO mice (n = 13, C57BL/6J recipients; n = 6, CD11c(-/-) recipients) and normal chow controls (n = 15, C57BL/6J recipients; n = 6, CD11c(-/-) recipients) underwent unilateral carotid interposition vein isografting (inferior vena cava from the same diet and genetic background donor), with a midgraft or outflow focal stenosis. Vein grafts were harvested at either 1 week (immunohistochemical staining for early CD11c expression) or 4 weeks later (morphometric analyses and CD11c evaluation).

RESULTS

Despite a 40% larger body size, C57BL/6J DIO mice had 44% smaller poststenosis vein graft lumens (P = .03) than their controls via an acceleration of overall negative vein graft wall remodeling in the day-28 midgraft focal stenosis model but not in the outflow stenosis model. Higher CD11c expression occurred in DIO midgraft-stenosis vein graft walls, both at postoperative days 7 and 28. In contrast, with in vivo CD11c deficiency, DIO did not elicit this poststenotic negative remodeling but attenuated intimal hyperplasia.

CONCLUSIONS

These findings highlight negative wall remodeling as a potential factor leading to vein graft failure and provide direct evidence that short-term dietary alterations in the mammalian metabolic milieu can have lasting implications related to acute vascular interventions. DIO induces negative mouse vein graft wall remodeling via CD11c-depedent pathways.

Epigallocatechin-3-gallate is a potent phytochemical inhibitor of intimal hyperplasia in the wire-injured carotid artery

OBJECTIVE

Epigallocatechin-3-gallate (EGCG), a catechin gallate ester, is the major component of green tea and has been demonstrated to inhibit tumor growth as well as inhibit smooth muscle cell migration. We evaluated the effect of the phytochemicals resveratrol, allicin, sulforaphane (SFN), and EGCG on intimal hyperplasia in the carotid artery injury model.

METHODS

Intimal hyperplasia was induced in carotid arteries of adult Sprague-Dawley rats with a wire injury. Experimental animals received intraperitoneal injections of one of the four phytochemicals daily beginning 1 day prior to surgery and continued for up to 4 weeks. Control animals were administered saline. Carotid specimens were harvested at 2 weeks and subjected to quantitative image analysis. In addition, EGCG specimens were analyzed for cell proliferation, immunohistochemistry, and Western blot analysis.

RESULTS

Quantitative image analysis showed significant phytochemical suppression of intimal hyperplasia at 2 and 4 weeks postoperatively with EGCG (62% decrease in intimal area). Significant decreases were also noted at 2 weeks for SFN (56%) and resveratrol (44%), whereas the decrease with allicin (24%) was not significant. Quantification of intimal hyperplasia by intima:media ratio showed similar results. Cell proliferation assay of specimens demonstrated suppression by EGCG. Immunohistochemical staining of EGCG-treated specimens showed extracellular signal-regulated kinase (ERK) suppression but not of the c-jun N-terminal kinase or p38 pathways. Western blot analysis confirmed reduced ERK activation in arteries treated with EGCG.

CONCLUSIONS

Intraperitoneal injection of the phytochemicals EGCG, SFN, resveratrol, and allicin have suppressive effects on the development of intimal hyperplasia in the carotid artery injury model, with maximal effect due to EGCG. The mechanism of EGCG action may be due to inhibition of ERK activation. EGCG may affect a common pathway underlying either neoplastic cellular growth or vascular smooth muscle cellular proliferation.

Lack of interleukin-1 signaling results in perturbed early vein graft wall adaptations

BACKGROUND

Vein grafts fail as the result of wall maladaptations to surgical injury and hemodynamic perturbations. Interleukin-1 signaling has emerged as an important mediator of the vascular response to trauma and hemodynamically induced vascular lesions. We therefore hypothesized that interleukin-1 signaling drives early vein graft wall adaptations.

METHODS

Using interleukin-1 type I receptor knockout (IL-1RI(-/-)) and wild-type (B6129SF2/J) mice, we investigated morphologic changes 28 days after interposition isograft from donor inferior vena cava to recipient carotid artery, without (n = 19) or with (n = 13) outflow restriction. The impact of mouse strain on the response to vein arterialization also was evaluated between B6129SF2/J (n = 18) and C57BL/6J (n = 19) mice.

RESULTS

No differences were observed in the traditional end points of intimal thickness and calculated luminal area, yet media+adventitia thickness of the vein graft wall of IL-1RI(-/-) mice was 44% to 52% less than wild-type mice, at the both proximal (P < .01, P < .01) and distal (P = .054, P < .01) portions of vein grafts, for both normal flow and low flow, respectively. Compared with the C57BL/6J strain, B6129SF2/J mice exhibited no difference in vein graft intimal thickness but 2-fold greater media+adventitia thickness (P < .01).

CONCLUSION

When lacking IL-1 signaling, the vein graft wall adapts differently compared with the injured artery, showing typical intima hyperplasia although attenuated media+adventitia thickening. B6129SF2/J mice exhibit more media+adventitia response than C57BL/6J mice. The inflammatory networks that underlie the vein response to arterialization hold many roles in the adaptation of the total wall; thus, the utility of anti-inflammatory approaches to extend the durability of vein grafts comes into question.

Mechanotransduction in embryonic vascular development

A plethora of biochemical signals provides spatial and temporal cues that carefully orchestrate the complex process of vertebrate embryonic development. The embryonic vasculature develops not only in the context of these biochemical cues, but also in the context of the biomechanical forces imparted by blood flow. In the mature vasculature, different blood flow regimes induce distinct genetic programs, and significant progress has been made toward understanding how these forces are perceived by endothelial cells and transduced into biochemical signals. However, it cannot be assumed that paradigms that govern the mature vasculature are pertinent to the developing embryonic vasculature. The embryonic vasculature can respond to the mechanical forces of blood flow, and these responses are critical in vascular remodeling, certain aspects of sprouting angiogenesis, and maintenance of arterial-venous identity. Here, we review data regarding mechanistic aspects of endothelial cell mechanotransduction, with a focus on the response to shear stress, and elaborate upon the multifarious effects of shear stress on the embryonic vasculature. In addition, we discuss emerging predictive vascular growth models and highlight the prospect of combining signaling pathway information with computational modeling. We assert that correlation of precise measurements of hemodynamic parameters with effects on endothelial cell gene expression and cell behavior is required for fully understanding how blood flow-induced loading governs normal vascular development and shapes congenital cardiovascular abnormalities.

Role of the renin-angiotensin system in the pathogenesis of intimal hyperplasia: therapeutic potential for prevention of vein graft failure?

The saphenous vein remains the most widely used conduit for peripheral and coronary revascularization despite a high rate of vein graft failure. The most common cause of vein graft failure is intimal hyperplasia. No agents have been proven to be successful for the prevention of intimal hyperplasia in human subjects. The renin-angiotensin system is essential in the regulation of vascular tone and blood pressure in physiologic conditions. However, this system mediates cardiovascular remodeling in pathophysiologic states. Angiotensin II is becoming increasingly recognized as a potential mediator of intimal hyperplasia. Drugs modulating the renin-angiotensin system include angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. These drugs are powerful inhibitors of atherosclerosis and cardiovascular remodeling, and they are first-line agents for management of several medical conditions based on class I evidence that they delay progression of cardiovascular disease and improve survival. Several experimental models have demonstrated that these agents are capable of inhibiting intimal hyperplasia. However, there are no data supporting their role in prevention of intimal hyperplasia in patients with vein grafts. This review summarizes the physiology of the renin-angiotensin system, the role of angiotensin II in the pathogenesis of cardiovascular remodeling, the medical indications for these agents, and the experimental data supporting an important role of the renin-angiotensin system in the pathogenesis of intimal hyperplasia.

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.

Preventing intimal thickening of vein grafts in vein artery bypass using STAT-3 siRNA

BACKGROUND

Proliferation and migration of vascular smooth muscle cells (VSMCs) play a key role in neointimal formation which leads to restenosis of vein graft in venous bypass. STAT-3 is a transcription factor associated with cell proliferation. We hypothesized that silencing of STAT-3 by siRNA will inhibit proliferation of VSMCs and attenuate intimal thickening.

METHODS

Rat VSMCs were isolated and cultured in vitro by applying tissue piece inoculation methods. VSMCs were transfected with STAT 3 siRNA using lipofectamine 2000. In vitro proliferation of VSMC was quantified by the MTT assay, while in vivo assessment was performed in a venous transplantation model. In vivo delivery of STAT-3 siRNA plasmid or scramble plasmid was performed by admixing with liposomes 2000 and transfected into the vein graft by bioprotein gel applied onto the adventitia. Rat jugular vein-carotid artery bypass was performed. On day 3 and7 after grafting, the vein grafts were extracted, and analyzed morphologically by haematoxylin eosin (H&E), and assessed by immunohistochemistry for expression of Ki-67 and proliferating cell nuclear antigen (PCNA). Western-blot and reverse transcriptase polymerase chain reaction (RT-PCR) were used to detect the protein and mRNA expression in vivo and in vitro. Cell apoptosis in vein grafts was detected by TUNEL assay.

RESULTS

MTT assay shows that the proliferation of VSMCs in the STAT-3 siRNA treated group was inhibited. On day 7 after operation, a reduced number of Ki-67 and PCNA positive cells were observed in the neointima of the vein graft in the STAT-3 siRNA treated group as compared to the scramble control. The PCNA index in the control group (31.3 ± 4.7) was higher than that in the STAT-3 siRNA treated group (23.3 ± 2.8) (P < 0.05) on 7d. The neointima in the experimental group(0.45 ± 0.04 μm) was thinner than that in the control group(0.86 ± 0.05 μm) (P < 0.05).Compared with the control group, the protein and mRNA levels in the experimental group in vivo and in vitro decreased significantly. Down regulation of STAT-3 with siRNA resulted in a reduced expression of Bcl-2 and cyclin D1. However, apoptotic cells were not obviously found in all grafts on day 3 and 7 post surgery.

CONCLUSIONS

The STAT-3 siRNA can inhibit the proliferation of VSMCs in vivo and in vitro and attenuate neointimal formation.

Angiotensin-(1–7) Inhibits Vascular Remodelling in Rat Jugular Vein Grafts via Reduced ERK1/2 and p38 MAPK Activity

This study evaluated the effect of angiotensin (Ang)-(1–7) on vascular remodelling in a rat autologous jugular vein graft model in which rats underwent autologous jugular vein graft transplantation (Ang-[1–7] and control groups) or sham surgery (sham group). The animals received continuous jugular infusion of Ang-(1–7) at 25 μg/kg per h (Ang-[1–7] group) or normal saline (control and sham groups) starting 3 days after surgery. Ang-(1–7) infusion reduced venous graft hyperplasia, vascular remodelling, extracellular signal-regulated kinase 1/2 (ERK1/2) activation, p38 mitogen-activated protein kinase (MAPK) activation and levels of proliferating cell nuclear antigen and α-smooth muscle actin compared with control animals. The vascular tissue Ang II level was higher in Ang-(1–7) and control rats than in sham animals. These findings suggest that Ang-(1–7) acts by inhibiting the activation of ERK1/2 and p38 MAPK in vascular tissue. The use of exogenous Ang-(1–7) could improve the outcome of vein grafting through the attenuation of vascular remodelling.

Surgical Skin Markers Impair Human Saphenous Vein Graft Smooth Muscle and Endothelial Function

Marking human saphenous vein graft (HSV) with a surgical skin marker to prevent twisting on implantation is a common practice in peripheral and coronary artery bypass procedures. This study is designed to examine the effects of surgical skin markers on the HSV smooth muscle and endothelial functional responses. De-identified HSV remnants were collected during peripheral and coronary artery bypass procedures. Physiologic responses of the HSV were measured using a muscle bath. Veins that were marked with surgical skin markers intraoperatively generated significantly less contractile force to depolarizing KC1 (110 mM) and receptor-mediated contractile agonists than unmarked HSV, suggesting that surgical skin markers impaired HSV smooth muscle contractility. To directly access the effects of chemical components in the surgical skin markers, unmarked HSV was exposed to isopropyl alcohol (a solvent commonly used in surgical skin markers) or methylene blue (a dye). Smooth muscle contractility was significantly reduced by isopropyl alcohol and methylene blue. Endothelial-dependent relaxation to carbachol was significantly reduced after exposure to surgical skin markers. Our data demonstrated that marking HSV with surgical skin markers reduces smooth muscle and endothelial functional viability.

A role for the cell cycle phosphatase Cdc25a in vitamin D-dependent inhibition of adult rat vascular smooth muscle cell proliferation

We have explored the mechanism(s) underlying 1,25 dihydroxyvitamin D's (1,25(OH)(2)D) suppression of agonist-induced vascular smooth muscle cell (VSMC) proliferation. Quiescent cultured adult rat VSMC were treated with 1,25(OH)(2)D for 48h and endothelin (ET) or angiotensin II (AII) for the final 24h. We show that VSMC responded to 1,25(OH)(2)D or its less hypercalcemic analogue RO 25-6760 with ∼70% inhibition of ET-dependent (3)H-thymidine incorporation. The inhibition was linked to a comparable reduction in ET-stimulated cyclin-dependent kinase 2 (Cdk2) activity and suppression of an ET-induced Cdk2 activator, cell division cycle 25 homolog A (Cdc25A). Both 1,25(OH)(2)D and RO 25-6760 completely inhibited the ET-dependent increase in Cdc25A mRNA and protein levels, phosphatase and promoter activities. 1,25(OH)(2)D also suppressed AII-induced DNA synthesis, Cdk2 activity and Cdc25A gene transcription. Inhibition of Cdc25A gene expression using a siRNA approach resulted in significant inhibition of ET or AII-dependent Cdk2 activity and (3)H-thymidine incorporation. The Cdc25A siRNA-mediated inhibition of ET or AII-induced Cdk2 activity and DNA synthesis was not additive with that produced by 1,25(OH)(2)D treatment. These data demonstrate that 1,25(OH)(2)D inhibits VSMC proliferation through a Cdc25A-dependent mechanism and suggest that this hormone may prove useful in the management of disorders characterized by aberrant proliferation of VSMC in the vascular wall.

The role of ex-vivo gene therapy of vein grafts with Egr-1 decoy in the suppression of intimal hyperplasia

OBJECTIVES

To test the hypothesis that vein graft intimal hyperplasia can be significantly suppressed by a single intra-operative transfection of the graft with a decoy oligonucleotide (ODN) binding the transcription factor Egr-1.

DESIGN

Experimental study.

MATERIALS AND METHODS

Jugular vein to carotid artery interposition grafts in rabbits were treated with Egr-1 decoy, mutant decoy ODN, vehicle alone, using a non-distending pressure of 300 mm Hg for 20 min, or were left untreated. All animals were fed a 2% cholesterol diet. The animals were sacrificed after 48h, 6 weeks and 12 weeks. Paraffin-embedded vein sections were subjected to angiometric analysis.

RESULTS

Successful delivery of the ODN was confirmed by DAPI staining. Quantitative real-time PCR revealed a 60% decrease of the Egr-1 gene expression in the animals in which the Egr-1 decoy ODN was delivered. Cellular proliferation was also significantly decreased as indicated by the Ki-67 labelling index. An increase in intimal and medial thickness was found in all vein grafts. However, intimal thickness was significantly reduced in the grafts treated with Egr-1 decoy ODN, whereas luminal area was significantly increased.

CONCLUSION

A single intra-operative pressure-mediated transfection of vein grafts with Egr-1 decoy ODN significantly suppresses intimal hyperplasia in a rabbit hypercholesterolaemic model.

Cellular mechanisms by which proinsulin C-peptide prevents insulin-induced neointima formation in human saphenous vein

AIMS/HYPOTHESIS

Endothelial cells (ECs) and smooth muscle cells (SMCs) play key roles in the development of intimal hyperplasia in saphenous vein (SV) bypass grafts. In diabetic patients, insulin administration controls hyperglycaemia but cardiovascular complications remain. Insulin is synthesised as a pro-peptide, from which C-peptide is cleaved and released into the circulation with insulin; exogenous insulin lacks C-peptide. Here we investigate modulation of human SV neointima formation and SV-EC and SV-SMC function by insulin and C-peptide.

METHODS

Effects of insulin and C-peptide on neointima formation (organ cultures), EC and SMC proliferation (cell counting), EC migration (scratch wound), SMC migration (Boyden chamber) and signalling (immunoblotting) were examined. A real-time RT-PCR array identified insulin-responsive genes, and results were confirmed by real-time RT-PCR. Targeted gene silencing (siRNA) was used to assess functional relevance.

RESULTS

Insulin (100 nmol/l) augmented SV neointimal thickening (70% increase, 14 days), SMC proliferation (55% increase, 7 days) and migration (150% increase, 6 h); effects were abrogated by 10 nmol/l C-peptide. C-peptide did not affect insulin-induced Akt or extracellular signal-regulated kinase signalling (15 min), but array data and gene silencing implicated sterol regulatory element binding transcription factor 1 (SREBF1). Insulin (1-100 nmol/l) did not modify EC proliferation or migration, whereas 10 nmol/l C-peptide stimulated EC proliferation by 40% (5 days).

CONCLUSIONS/INTERPRETATION

Our data support a causative role for insulin in human SV neointima formation with a novel counter-regulatory effect of proinsulin C-peptide. Thus, C-peptide can limit the detrimental effects of insulin on SMC function. Co-supplementing insulin therapy with C-peptide could improve therapy in insulin-treated patients.

Rationale and practical techniques for mouse models of early vein graft adaptations

Mouse models serve as relatively new yet powerful research tools to study intimal hyperplasia and wall remodeling of vein bypass graft failure. Several model variations have been reported in the past decade. However, the approach demands thoughtful preparation, selected sophisticated equipment, microsurgical technical expertise, advanced tissue processing, and data acquisition. This review compares several described models and aims (building on our personal experiences) to practically aid the investigators who want to utilize mouse models of vein graft failure.

Prelining autogenic endothelial cells in allogeneic vessels inhibits thrombosis and intimal hyperplasia: an efficacy study in dogs

BACKGROUND

The long-term patency rates in vascular transplants (diameter<3.0-4.0mm) are very low due to thrombus formation and intimal hyperplasia. A possible mechanism is the loss of the endothelial cells (ECs) lining. Previous attempts to reseed ECs had poor results due to seeded cell loss, severe antigenicity, and low compliance. The objectives of this study were to generate an allogeneic vascular substitution with autogenic ECs and low antigenicity.

METHODS

ECs from mongrels were obtained and multiplied in vitro, then seeded to the allogeneic vein luminal surface, which was preserved by freeze-drying radiation. The cultivated cells' secretory function was confirmed by von Willebrand factor detection. The allogeneic vascular was then transplanted into animals' necks in situ. The physical properties, EC state, and vascular structure of the allogeneic vascular grafts were studied.

RESULTS

The secretory function of ECs did not vary in vitro. The expression level of MHC-II antigen in freeze-dried radiation-treated vasculature was lower than normal fresh vasculature (P<0.05). ECs covered the vascular inner surface and adhered tightly after implantation. As assessed by scanning electron micrograph, most ECs adhered tightly, and the cell polarity changed in accordance with the direction of the force. Allograft blood vessels with autogenic ECs implanted showed significant decreases in both thrombosis and intimal hyperplasia.

CONCLUSION

Allograft blood vessels seeded with autogenic ECs improved the patency of small-diameter grafts in a canine model. Our study showed a significant decrease in both thrombosis and intimal hyperplasia.

Cyclic stretch upregulates SDF-1alpha/CXCR4 axis in human saphenous vein smooth muscle cells

Cyclic stretch (CS) mediates different cellular functions in vascular smooth muscle cells and involves in neointimal hyperplasia and subsequent atherosclerosis of vein grafts. Here, we investigated whether CS can modulate stromal cell-derived factor-1alpha (SDF-1alpha)/CXCR4 axis in human saphenous vein smooth muscle cells. We found CS induced the upregulation of SDF-1alpha and CXCR4 in human saphenous vein smooth muscle cells in vitro, which was dependent on PI3K/Akt/mTOR pathway. Furthermore, CS augmented human saphenous vein smooth muscle migration and focal adhesion kinase (FAK) activation by PI3K/Akt/mTOR pathway. Interestingly, the upregulation of SDF-1alpha/CXCR4 axis was instrumental in CS-induced saphenous vein smooth muscle cell migration and FAK activation, as showed by AMD3100, an inhibitor of SDF-1alpha/CXCR4 axis, partially but significantly blocked the CS-induced cellular effects. Thus, those data suggested SDF-1alpha/CXCR4 axis involves in CS-mediated cellular functions in human saphenous vein smooth muscle cells.

Impact of saphenous vein graft radiographic markers on clinical events and angiographic parameters

BACKGROUND

Use of saphenous vein graft (SVG) radiographic markers has been associated with shorter cardiac catheterization procedure times and reduced contrast agent volume for postoperative coronary artery bypass graft (CABG) catheterizations. Use of such markers is varied and often operator-dependent, as the effect of SVG markers has not been fully evaluated. The goal of the present analysis was to evaluate the association of SVG markers with clinical outcomes and graft patency.

METHODS

Data were drawn from the Project of Ex-vivo Vein Graft Engineering via Transfection (PREVENT) IV trial of patients undergoing CABG at 107 hospitals across the United States. Repeat angiography was performed within 12 to 18 months after CABG. The SVG markers were used at the discretion of the surgeon and were identified on the follow-up angiogram as any device used to mark the ostium, regardless of shape.

RESULTS

The SVG markers were present in 51.2% of evaluable patients (910 of 1,778) and 52.3% of SVGs (2,228 of 4,240). Among patients with totally occluded SVGs (n = 911), visual identification of the SVG was obtained more frequently in those with an SVG marker (90.7% vs 72.1%, p < 0.001). The SVG stenosis 70% or greater at follow-up did not differ by use of markers (25.8% with marker vs 24.4% without marker, p = not significant). These findings were also consistent in ostial lesions (n = 942). Long-term death or myocardial infarction (MI) was similar by use of marker. The perioperative CABG MI was higher in patients with SVG markers (10.1% vs 5.5%, odds ratio adjusted 1.86, p = 0.021).

CONCLUSIONS

Saphenous vein graft radiographic markers were associated with higher rates of direct visualization of totally occluded SVGs without an adverse effect on graft patency or long-term clinical outcomes, but the association of SVG markers with increased perioperative CABG MI warrants further examination.

Analysis of arterial intimal hyperplasia: review and hypothesis

BACKGROUND

Despite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology?

HYPOTHESIS

I argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign" intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates early in life to form a multi-layer intimal hyperplasia and then continues to self-renew in a controlled manner throughout life, relatively rarely compromising the blood supply to the heart, causing complications requiring intervention only in a small fraction of the population, while all humans are carriers of benign hyperplasia. Unfortunately, this fundamental fact has not been widely appreciated in arteriosclerosis research and medical education, which continue to operate on the assumption that the normal arterial intima is always an "ideal" single-layer endothelium. As a result, the disease is perceived and studied as a new pathological event caused by new mechanisms. The discovery that normal coronary arteries are morphologically indistinguishable from deadly coronary arteriosclerosis continues to elicit surprise.

CONCLUSION

Two questions should inform the priorities of our research: (1) what controls switch the single cell-layer intimal phenotype into normal hyperplasia? (2) how is normal (benign) hyperplasia maintained? We would be hard-pressed to gain practical insights without scrutinizing our premises.