Intimal thickness associated with endothelial dysfunction in human vein grafts

Vein Morphology in Endoscopic Vein Harvesting: 15-Year Outcomes

OBJECTIVE

Long-term outcomes of vein morphologies in the endoscopic vein harvesting setting are lacking. We analyzed 15-year follow-up for endoscopic versus open vein harvesting and associated vein morphology outcomes in coronary artery bypass grafting at a single center.

METHODS

This single-center, prospectively collected, retrospective, observational study evaluated 15-year major adverse cardiovascular events (MACE) of endoscopic versus open vein harvesting and associated vein morphologies.

RESULTS

Among 729 patients, no differences were found between endoscopic and open vein harvesting in MACE hazard ratios despite increased risks with native Hawai'ian, Pacific Islander, and Filipino patients. Asian and Filipino patients had more thin-walled veins and Asian and multirace patients had more vasovasoral branches than White patients. Bifid veins were associated with increased risk of cardiac catheterization. Varicose veins were associated with myocardial infarction, congestive heart failure, and death. Thick-walled veins were associated with revascularization and dense adhesions with cardiac catheterization and revascularization.

CONCLUSIONS

Fifteen-year adjusted MACE was similar between endoscopic and open vein harvesting in small coronary targets despite increased risks with native Hawai'ian, Pacific Islander, and Filipino patients. Bifid, varicose, thick-walled veins, and dense adhesions had worse MACE.

Intimal Hyperplasia and Arteriovenous Fistula Failure: Looking Beyond Size Differences

The development of venous intimal hyperplasia (IH) has been historically associated with failure of arteriovenous fistulas (AVF) used for hemodialysis. This long-standing assumption, based on histological observations, has been recently challenged by clinical studies indicating that the size of the intima by itself is not enough to explain stenosis or AVF maturation failure. Irrespective of this lack of association, IH is present in most native veins and fistulas, is prominent in many cases, and suggests a role in the vein that may not be reflected by its dimensions. Therefore, the contribution of IH to AVF dysfunction remains controversial. Using only clinical data and avoiding extrapolations from animal models, we critically discuss the biological significance of IH in vein remodeling, vascular access function, and the response of the venous wall to repeated trauma in hemodialysis patients. We address questions and pose new ones such as: What are the factors that contribute to IH in pre-access veins and AVFs? Do cellular phenotypes and composition of the intima influence AVF function? Are there protective roles of the venous intima? This review explores these possibilities, with hopes of rekindling a critical discussion about venous IH that goes beyond thickness and AVF outcomes.

Morphological Lesion Types Are Associated with Primary and Secondary Patency Rates after High-Pressure Balloon Angioplasty for Dysfunctional Arteriovenous Fistulas

BACKGROUND

Neointimal hyperplasia (NIH) is believed to be the main reason for arteriovenous fistula (AVF) dysfunction, but other mechanisms are also recognized to be involved in the pathophysiological process. This study investigated whether different morphological types of AVF lesions are associated with the patency rate after percutaneous transluminal angioplasty (PTA).

METHODS

This retrospective study included 120 patients who underwent PTA for autogenous AVF dysfunction. All the cases were evaluated under Doppler ultrasound (DU) before intervention and divided into 3 types: Type I (NIH type), Type II (non-NIH type), and Type III (mixed type). Prognostic and clinical data were analyzed by Kaplan-Meier analysis and the Cox proportional hazards model.

RESULTS

There was no statistical difference in baseline variables among groups, except for lumen diameter. The primary patency rates in Type I, Type II, and Type III groups were 78.4, 93.2, and 83.2% at 6 months and 59.5, 84.7, and 75.5% at 1 year, respectively. The secondary patency rates in Type I, Type II, and Type III groups were 94.4, 97.1, and 100% at 6 months and 90.5, 97.1, and 94.7% at 1 year, respectively. The Kaplan-Meier curve showed that the primary and secondary patency rates of Type I group were lower than those of Type II group. Multivariable Cox regression analysis demonstrated that postoperative primary patency was correlated with end-to-end anastomosis (hazard ratio [HR] = 2.997, p = 0.008, 95% confidence interval [CI]: 1.328-6.764) and Type I lesion (HR = 5.395, p = 0.004, 95% CI: 1.730-16.824).

CONCLUSIONS

NIH-dominant lesions of AVF evaluated by DU preoperatively were a risk factor for poor primary and secondary patency rate after PTA in hemodialysis patients.

The placental growth factor attenuates intimal hyperplasia in vein grafts by improving endothelial dysfunction

Saphenous vein grafts (SVG) patency is limited by intimal hyperplasia (IH) caused by endothelial dysfunction. This study aimed to explore the effect of placental growth factor (PlGF) on the endothelial function of SVG. In rat models of external jugular vein-carotid artery graft treated with PlGF or saline hydrogel, PlGF inhibited vein graft IH (day 28: 12.0 ± 1.9 vs. 61.7 ± 13.1 μm, P < 0.001), promoted microvessel proliferation (day 14: 33.3% 3+ vs. 50.0% 2+, P = 0.03), and increased nitric oxide (NO) production (P < 0.05 on days 1/3/5) and NO synthase (NOS) expression by immunohistochemistry. In human umbilical vein endothelial cells (HUVECs) cultured under hypoxia and treated or not with PlGF, PlGF restored the survival (50 ng/ml PlGF, 48 h: 91.7 ± 0.6% vs. 84.9 ± 0.5%, P < 0.01), migration (by Matrigel assay), and tube formation ability (junctions, tubules, and tubule total length; all P < 0.01) of HUVECs after hypoxia. PlGF increased NO production through increased eNOS expression (P < 0.05), without changes in iNOS expression. The mRNA expression of eNOS decreased after the addition of the PI3K inhibitor LY294002 (P < 0.05). PlGF promoted the protein expression of eNOS by up-regulating AKT, and the AKT and eNOS protein levels were decreased after adding LY294002 (all P < 0.05). In conclusion, PlGF is a candidate for the inhibition of IH in SVG after coronary artery bypass graft. The effects of PlGF are mediated by the upregulation of the eNOS mRNA and protein through the PI3K/AKT signaling pathway. PlGF promotes the secretion of NO by endothelial cells and thereby reduces the occurrence and development of IH.

The Cholesteryl Ester Transfer Protein Inhibitor, des-Fluoro-Anacetrapib, Prevents Vein Bypass-induced Neointimal Hyperplasia in New Zealand White Rabbits

Coronary artery bypass grafting is among the most commonly performed of all cardiovascular surgical procedures. However, graft failure due to stenosis reduces the long-term benefit of the intervention. This study asks if elevating plasma high density lipoprotein cholesterol (HDL-C) levels by inhibition of cholesteryl ester transfer protein (CETP) activity with des-fluoro-anacetrapib, an analog of the CETP inhibitor anacetrapib, prevents vein bypass-induced neointimal hyperplasia. NZW rabbits were placed on a normal chow diet or chow containing 0.14% (wt/wt) des-fluoro-anacetrapib for 6 weeks. Bypass grafting of the jugular vein to the common carotid artery was performed 2 weeks after starting dietary des-fluoro-anacetrapib supplementation. The animals were euthanised 4 weeks post-bypass grafting. Relative to control, dietary supplementation with des-fluoro-anacetrapib reduced plasma CETP activity by 89 ± 6.9%, increased plasma apolipoprotein A-I levels by 24 ± 5.5%, increased plasma HDL-C levels by 93 ± 26% and reduced intimal hyperplasia in the grafted vein by 38 ± 6.2%. Des-fluoro-anacetrapib treatment was also associated with decreased bypass grafting-induced endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), endothelial dysfunction, and smooth muscle cell (SMC) proliferation in the grafted vein. In conclusion, increasing HDL-C levels by inhibiting CETP activity is associated with inhibition of intimal hyperplasia in grafted veins, reduced inflammatory responses, improved endothelial function, and decreased SMC proliferation.

MiR-551b-5p Contributes to Pathogenesis of Vein Graft Failure via Upregulating Early Growth Response-1 Expression

Background:

Vein graft failure (VGF) is a serious complication of coronary artery bypass graft, although the mechanism remains unclear. The study aimed to investigate the effects of microRNAs (miRNAs) on the endothelial dysfunction involved in VGF.

Methods:

Human umbilical vein endothelial cells (HUVECs) were subjected to mechanical stretch stimulation to induce endothelial dysfunction. Genome-wide transcriptome profiling was performed using the Human miRNA OneArray^® V4 (PhalanxBio Inc., San Diego, USA). The miRNA-messenger RNA (mRNA) network was investigated using gene ontology and Kyoto Encyclopedia of Genes and Genomes. The miR-551b-5p mimic and inhibitor were applied to regulate miR-551b-5p expression in the HUVECs. The 5-ethynyl-2’-deoxyuridine assay, polymerase chain reaction (PCR), and Western blotting (WB) were used to assess HUVECs proliferation, mRNA expression, and protein expression, respectively. The vein graft model was established in early growth response (Egr)-1 knockout (KO) mice and wide-type (WT) C57BL/6J mice for pathological and immunohistochemical analysis. Endothelial cells isolated from the veins of WT and Egr-1 KO mice were subjected to mechanical stretch stimulation; PCR and WB were conducted to confirm the regulatory effect of Egr-1 on Intercellular adhesion molecule (Icam-1). One-way analysis of variance and independent t-test were performed for data analysis.

Results:

Thirty-eight miRNAs were differentially expressed in HUVECs after mechanical stretch stimulation. The bioinformatics analysis revealed that Egr-1 might be involved in VGF and was a potential target gene of miR-551b-5p. The mechanical stretch stimulation increased miR-551b-5p expression by 2.93 ± 0.08 fold (t = 3.07, P < 0.05), compared with the normal HUVECs. Transfection with the miR-551b-5p mimic or inhibitor increased expression of miR-551b-5p by 793.1 ± 171.6 fold (t = 13.84, P < 0.001) or decreased by 26.3% ± 2.4% (t = 26.39, P < 0.05) in the HUVECs, respectively. HUVECs proliferation and EGR-1 mRNA expression were significantly suppressed by inhibiting miR-551b-5p expression (P < 0.05). The lumens of the vein grafts in the Egr-1 KO mice were wider than that in the WT mice. Icam-1 expression was suppressed significantly in the Egr-1 KO vein grafts (P < 0.05).

Conclusions:

Increased miR-551b-5p expression leads to endothelial dysfunction by upregulating Egr-1 expression. EGR-1 KO can improve the function of a grafted vein through suppressing Icam-1.

Inflammation in Vein Graft Disease

Bypass surgery is one of the most frequently used strategies to revascularize tissues downstream occlusive atherosclerotic lesions. For venous bypass surgery the great saphenous vein is the most commonly used vessel. Unfortunately, graft efficacy is low due to the development of vascular inflammation, intimal hyperplasia and accelerated atherosclerosis. Moreover, failure of grafts leads to significant adverse outcomes and even mortality. The last couple of decades not much has changed in the treatment of vein graft disease (VGD). However, insight is the cellular and molecular mechanisms of VGD has increased. In this review, we discuss the latest insights on VGD and the role of inflammation in this. We discuss vein graft pathophysiology including hemodynamic changes, the role of vessel wall constitutions and vascular remodeling. We show that profound systemic and local inflammatory responses, including inflammation of the perivascular fat, involve both the innate and adaptive immune system.

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.

Use of Brilliant Blue FCF during vein graft preparation inhibits intimal hyperplasia

BACKGROUND

Intimal hyperplasia remains the primary cause of vein graft failure for the 1 million yearly bypass procedures performed using human saphenous vein (HSV) grafts. This response to injury is caused in part by the harvest and preparation of the conduit. The use of Brilliant Blue FCF (FCF) restores injury-induced loss of function in vascular tissues possibly via inhibition of purinergic receptor signaling. This study investigated whether pretreatment of the vein graft with FCF prevents intimal hyperplasia.

METHODS

Cultured rat aortic smooth muscle cells (A7r5) were used to determine the effect of FCF on platelet-derived growth factor-mediated migration and proliferation, cellular processes that contribute to intimal hyperplasia. The effectiveness of FCF treatment during the time of explantation on preventing intimal hyperplasia was evaluated in a rabbit jugular-carotid interposition model and in an organ culture model using HSV.

RESULTS

FCF inhibited platelet-derived growth factor-induced migration and proliferation of A7r5 cells. Treatment with FCF at the time of vein graft explantation inhibited the subsequent development of intimal thickening in the rabbit model. Pretreatment with FCF also prevented intimal thickening of HSV in organ culture.

CONCLUSIONS

Incorporation of FCF as a component of vein graft preparation at the time of explantation represents a potential therapeutic approach to mitigate intimal hyperplasia, reduce vein graft failure, and improve outcome of the autologous transplantation of HSV.

Adenosine triphosphate as a molecular mediator of the vascular response to injury

BACKGROUND

Human saphenous veins used for arterial bypass undergo stretch injury at the time of harvest and preimplant preparation. Vascular injury promotes intimal hyperplasia, the leading cause of graft failure, but the molecular events leading to this response are largely unknown. This study investigated adenosine triphosphate (ATP) as a potential molecular mediator in the vascular response to stretch injury, and the downstream effects of the purinergic receptor, P2X7R, and p38 MAPK activation.

MATERIALS AND METHODS

A subfailure stretch rat aorta model was used to determine the effect of stretch injury on release of ATP and vasomotor responses. Stretch-injured tissues were treated with apyrase, the P2X7R antagonist, A438079, or the p38 MAPK inhibitor, SB203580, and subsequent contractile forces were measured using a muscle bath. An exogenous ATP (eATP) injury model was developed and the experiment repeated. Change in p38 MAPK phosphorylation after stretch and eATP tissue injury was determined using Western blotting. Noninjured tissue was incubated in the p38 MAPK activator, anisomycin, and subsequent contractile function and p38 MAPK phosphorylation were analyzed.

RESULTS

Stretch injury was associated with release of ATP. Contractile function was decreased in tissue subjected to subfailure stretch, eATP, and anisomycin. Contractile function was restored by apyrase, P2X7R antagonism, and p38-MAPK inhibition. Stretch, eATP, and anisomycin-injured tissue demonstrated increased phosphorylation of p38 MAPK.

CONCLUSIONS

Taken together, these data suggest that the vascular response to stretch injury is associated with release of ATP and activation of the P2X7R/P38 MAPK pathway, resulting in contractile dysfunction. Modulation of this pathway in vein grafts after harvest and before implantation may reduce the vascular response to injury.

Calcification of Human Saphenous Vein Associated with Endothelial Dysfunction: A Pilot Histopathophysiological and Demographical Study

While the pathophysiology and clinical significance of arterial calcifications have been studied extensively, minimal focus has been placed on venous calcification deposition. In this study, we evaluated the association between calcium deposition in human saphenous vein (HSV), endothelial function, and patient demographic risk factors. Fifty-four HSV segments were collected at the time of coronary artery bypass graft (CABG) surgery. The presence or absence of calcium deposits was visualized using the Von Kossa staining method. Endothelial function was determined by measuring muscle tissue contraction with phenylephrine and relaxation with carbachol in a muscle bath. Additional segments of vein underwent histologic evaluation for preexisting intimal thickness and extracellular matrix (ECM) deposition. Patient demographics data were obtained through our institution’s electronic medical record, with patient consent. Calcium was present in 16 of 54 samples (29.6%). Veins with calcium deposits had significantly greater intimal-to-medial thickness ratios (p = 0.0058) and increased extracellular collagen deposition (p = 0.0077). Endothelial relaxation was significantly compromised in calcified veins vs. those without calcium (p = 0.0011). Significant patient risk factors included age (p = 0.001) and preoperative serum creatinine (p = 0.017). Calcified veins can be characterized as having endothelial dysfunction with increased basal intimal thickness and increased ECM deposition. Patient risk factors for calcium deposits in veins were similar to those for arteries, namely, advanced age and kidney disease. Further studies are needed to determine the effect of preexisting vein calcification on short- and long-term graft patency.

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.

Ephrin type-B receptor 4 activation reduces neointimal hyperplasia in human saphenous vein in vitro

BACKGROUND

Vein bypass is an essential therapy for patients with advanced peripheral and coronary artery disease despite development of neointimal hyperplasia. We have shown that stimulation of the receptor tyrosine kinase ephrin type-B receptor 4 (Eph-B4) with its ligand ephrin-B2 prevents neointimal hyperplasia in murine vein grafts. This study determines whether Eph-B4 in adult human veins is capable of phosphorylation and activation of downstream signaling pathways, as well as functional to release nitric oxide (NO) and prevent neointimal hyperplasia in vitro.

METHODS

Discarded human saphenous veins were taken from the operating room and placed in organ culture without or with ephrin-B2/Fc (2 μg/mL) for 14 days, and the neointima/media ratio was measured in matched veins. Primary human umbilical vein endothelial cells were treated with ephrin-B2/Fc (2 μg/mL) and examined with quantitative polymerase chain reaction, Western blot, immunoassays, and for release of NO. Ephrin-B2/Fc (2 μg/mL) was placed on the adventitia of saphenous veins treated with arterial shear stress for 24 hours in a bioreactor and activated Eph-B4 examined with immunofluorescence.

RESULTS

The baseline intima/media ratio in saphenous vein rings was 0.456 ± 0.097, which increased to 0.726 ± 0.142 in untreated veins after 14 days in organ culture but only to 0.630 ± 0.132 in veins treated with ephrin-B2/Fc (n = 19, P = .017). Ephrin-B2/Fc stimulated Akt, endothelial NO synthase and caveolin-1 phosphorylation, and NO release (P = .007) from human umbilical vein endothelial cells (n = 6). Ephrin-B2/Fc delivered to the adventitia stimulated endothelial Eph-B4 phosphorylation after 24 hours of arterial stress in a bioreactor (n = 3).

CONCLUSIONS

Eph-B4 is present and functional in adult human saphenous veins, with intact downstream signaling pathways capable of NO release and prevention of neointimal hyperplasia in vitro. Adventitial delivery of ephrin-B2/Fc activates endothelial Eph-B4 in saphenous veins treated with arterial shear stress in vitro. These results suggest that stimulation of Eph-B4 function may be a candidate strategy for translation to human clinical trials designed to inhibit venous neointimal hyperplasia.

Identification of a microRNA signature in endothelial cells with mechanical stretch stimulation

The current study aimed to verify an miRNA signature in endothelial cells undergoing mechanical stretch stimulation. In the present study, microarray profiling was conducted in order to identify the differential expression of miRNAs in endothelial cells undergoing mechanical stimulation, compared with unstimulated endothelial cells. The microarray data was then validated by reverse transcription‑quantitative polymerase chain reaction. Genes and signaling pathways regulated by the miRNAs were investigated in silico using Gene Ontology and the Kyoto Encyclopedia of Genes or Genomes, which are ontological and network‑mapping algorithms. The microarray data collected demonstrated that 38 miRNAs exhibited significant differential expression in endothelial cells with mechanical stretch stimulation. Of these, 20 were upregulated and 18 were downregulated. The results from the in silico analysis indicated that the miRNAs identified were participants in mechanical stretch‑induced endothelial dysfunction. During the initial stage of vein graft failure, which is induced by endothelial dysfunction, a unique miRNA signature was identified. The identified miRNAs are suggested to be involved in the pathological processes of traumatic injury.

Preservation solution impacts physiologic function and cellular viability of human saphenous vein graft

INTRODUCTION

Recent clinical data suggest intraoperative preservation of human saphenous vein (HSV) in normal saline is associated with vein graft failure. We evaluated the influence of several preservation media on acute physiologic function and cellular viability of HSV conduit.

METHODS

Unprepared (UP) HSV obtained from coronary artery bypass graft patients was characterized on a muscle bath after 2-hour storage in 6 solutions: Plasma-Lyte A, 0.9% NaCl (normal saline), University of Wisconsin solution, Celsior solution, autologous whole blood, or glutathione-ascorbic acid L-arginine (GALA) solution. Vascular smooth muscle contractility was assessed after exposure to depolarizing KCl and phenylephrine. The relaxation of phenylephrine-precontracted HSV to sodium nitroprusside and carbachol (endothelial-independent and -dependent relaxation, respectively) was also assessed. Cellular viability was determined via the methyl thiazolyl tetrazolium (MTT) assay. Rat aortae were used to assess the effect of pH during graft preservation on endothelial-dependent relaxation.

RESULTS

Preservation of HSV in normal saline and autologous whole blood impaired contractile responses to KCl relative to UP tissues, whereas preservation in University of Wisconsin solution and Celsior solution enhanced contractile responses (P < .05). Relative to UP tissues, responses to phenylephrine were decreased with preservation in normal saline, whereas preservation in University of Wisconsin solution, Celsior solution, and GALA all potentiated these responses (P < .05). Only preservation in normal saline impaired endothelial-independent relaxation (P = .005). Preservation in Plasma-Lyte A (P = .02), normal saline (P = .002), and University of Wisconsin solution (P = .02) impaired endothelial-dependent relaxation. Normal saline preservation decreased MTT viability index relative to UP tissues (0.02 ± 0.002 mg(-1)0.5 mL(-1) vs 0.033 ± 0.005 mg(-1)0.5 mL(-1); P = .03). Endothelial function was impaired by acidic pH in rat aorta.

CONCLUSION

Preservation of HSV in normal saline causes graft injury leading to impaired physiologic function and decreased viability of the HSV. This harm is mitigated by the use of buffered salt solutions as preservation media.

Brilliant blue FCF as an alternative dye for saphenous vein graft marking: effect on conduit function

IMPORTANCE

Surgical skin markers are used off-label to mark human saphenous veins (HSVs) to maintain orientation before implantation as aortocoronary or peripheral arterial bypass grafts. These surgical skin markers impair functional responses of the HSV tissue.

OBJECTIVES

To investigate the effect of brilliant blue dye 1 (brilliant blue FCF [for food coloring]; hereinafter, FCF) as a nontoxic alternative marking dye and to determine whether FCF has pharmacological properties.

DESIGN, SETTING, AND PARTICIPANTS

Segments of HSVs were collected in university hospitals from patients undergoing coronary artery bypass grafting procedures immediately after harvest (unmanipulated) or after typical intraoperative surgical graft preparation (after manipulation). Rat inferior venae cavae were used to determine the pharmacological properties and cellular targets of FCF. Endothelial and smooth muscle functional responses were determined in a muscle bath, and intimal thickening in HSVs was determined after 14 days in organ culture.

MAIN OUTCOMES AND MEASURES

Contractile responses were measured in force and converted to stress. Smooth muscle function was expressed as maximal responses to potassium chloride depolarization contractions. Endothelial function was defined as the percentage of relaxation of maximal agonist-induced contraction. Neointimal thickness was measured by histomorphometric analysis.

RESULTS

Human saphenous veins stored in the presence of FCF had no loss of endothelial or smooth muscle function. Unmanipulated HSVs preserved in the presence of FCF demonstrated a significant increase in endothelial-dependent relaxation (mean [SEM], 25.2% [6.4%] vs 30.2% [6.7%]; P = .02). Application of FCF to functionally nonviable tissue significantly enhanced the smooth muscle responses (mean [SEM], 0.018 [0.004] × 10⁵ N/m² vs 0.057 [0.016] × 10⁵ N/m²; P = .05). Treatment with FCF reduced intimal thickness in organ culture (mean [SEM], -17.5% [2.1%] for unmanipulated HSVs vs -27.9% [3.7%] for HSVs after manipulation; P < .001). In rat inferior venae cavae, FCF inhibited the contraction induced by the P2X7 receptor agonist 2'(3')-O-(4-benzoyl)benzoyl-adenosine-5'-triphosphate (mean [SEM], 14.8% [2.2%] vs 6.5% [1.8%]; P = .02) to an extent similar to the P2X7 receptor antagonist oxidized adenosine triphosphate (mean [SEM], 5.0% [0.9%]; P < .02 vs control) or the pannexin hemichannel inhibitor probenecid (mean [SEM], 7.3% [1.6%] and 4.7% [0.9%] for 0.5mM and 2mM, respectively; P < .05).

CONCLUSIONS AND RELEVANCE

Treatment with FCF did not impair endothelial or smooth muscle function in HSVs. Brilliant blue FCF enhanced endothelial-dependent relaxation, restored smooth muscle function, and prevented intimal hyperplasia in HSVs in organ culture. These pharmacological properties of FCF may be due to P2X7 receptor or pannexin channel inhibition. Brilliant blue FCF is an alternative, nontoxic marking dye that may improve HSV conduit function and decrease intimal hyperplasia.

Tissue-engineered vascular grafts created from human induced pluripotent stem cells

The utility of human induced pluripotent stem cells (hiPSCs) to create tissue-engineered vascular grafts was evaluated in this study. hiPSC lines were first induced into a mesenchymal lineage via a neural crest intermediate using a serum-free, chemically defined differentiation scheme. Derived cells exhibited commonly known mesenchymal markers (CD90, CD105, and CD73 and negative marker CD45) and were shown to differentiate into several mesenchymal lineages (osteogenic, chondrogenic, and adipogenic). Functional vascular grafts were then engineered by culturing hiPSC-derived mesenchymal progenitor cells in a pulsatile bioreactor system over 8 weeks to induce smooth muscle cell differentiation and collagenous matrix generation. Histological analyses confirmed layers of calponin-positive smooth muscle cells in a collagen-rich matrix. Mechanical tests revealed that grafts had an average burst pressure of 700 mmHg, which is approximately half that of native veins. Additionally, studies revealed that karyotypically normal mesenchymal stem cell clones led to generation of grafts with predicted features of engineered vascular grafts, whereas derived clones having chromosomal abnormalities generated calcified vessel constructs, possibly because of cell apoptosis during culture. Overall, these results provide significant insight into the utility of hiPS cells for vascular graft generation. They pave the way for creating personalized, patient-specific vascular grafts for surgical applications, as well as for creating experimental models of vascular development and disease.

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.

Early growth response protein 1 promotes restenosis by upregulating intercellular adhesion molecule-1 in vein graft

OBJECTIVES

To verify the relationship between Egr-1 and vein graft restenosis and investigate the related mechanisms.

METHODS

Mouse vein graft models were established in Egr-1 knockout (KO) and wild-type (WT) mice. The vein grafts in the mice were taken for pathological examination and immunohistochemical analysis. The endothelial cells (ECs) were stimulated by using a computer-controlled cyclic stress unit. BrdU staining and PCR were used to detect ECs proliferation activity and Egr-1 and ICAM-1 mRNA expression, respectively. Western-blot analysis was also used to detect expression of Egr-1 and intercellular adhesion molecule-1 (ICAM-1) proteins.

RESULTS

The lumens of vein grafts in Egr-1 KO mice were wider than in WT mice. ECs proliferation after mechanical stretch stimulation was suppressed by Egr-1 knockout (P < 0.05). Both in vein grafts and ECs from WT mice after mechanical stretch stimulation, mRNA expression and protein of Egr-1 and ICAM-1 showed increases (P < 0.05). However, ICAM-1 expression was significantly suppressed in ECs from Egr-1 knockout mice (P < 0.05).

CONCLUSIONS

Egr-1 may promote ECs proliferation and result in vein graft restenosis by upregulating the expression of ICAM-1. As a key factor of vein graft restenosis, it could be a target for the prevention of restenosis after CABG surgery.

Vein graft failure

After the creation of an autogenous lower extremity bypass graft, the vein must undergo a series of dynamic structural changes to stabilize the arterial hemodynamic forces. These changes, which are commonly referred to as remodeling, include an inflammatory response, the development of a neointima, matrix turnover, and cellular proliferation and apoptosis. The sum total of these processes results in dramatic alterations in the physical and biomechanical attributes of the arterialized vein. The most clinically obvious and easily measured of these is lumen remodeling of the graft. However, although somewhat less precise, wall thickness, matrix composition, and endothelial changes can be measured in vivo within the healing vein graft. Recent translational work has demonstrated the clinical relevance of remodeling as it relates to vein graft patency and the systemic factors influencing it. By correlating histologic and molecular changes in the vein, insights into potential therapeutic strategies to prevent bypass failure and areas for future investigation are explored.