Myeloid PHD2 Conditional Knockout Improves Intraplaque Angiogenesis and Vascular Remodeling in a Murine Model of Venous Bypass Grafting.

BACKGROUND: Intraplaque angiogenesis occurs in response to atherosclerotic plaque hypoxia, which is driven mainly by highly metabolically active macrophages. Improving plaque oxygenation by increasing macrophage hypoxic signaling, thus stimulating intraplaque angiogenesis, could restore cellular function and neovessel maturation, and decrease plaque formation. Prolyl hydroxylases (PHDs) regulate cellular responses to hypoxia. We therefore aimed to elucidate the role of myeloid PHD2, the dominant PHD isoform, on intraplaque angiogenesis in a murine model for venous bypass grafting. METHODS AND RESULTS: Myeloid PHD2 conditional knockout (PHD2cko) and PHD2 wild type mice on an Ldlr-/- background underwent vein graft surgery (n=11-15/group) by interpositioning donor caval veins into the carotid artery of genotype-matched mice. At postoperative day 28, vein grafts were harvested for morphometric and compositional analysis, and blood was collected for flow cytometry. Myeloid PHD2cko induced and improved intraplaque angiogenesis by improving neovessel maturation, which reduced intraplaque hemorrhage. Intima/media ratio was decreased in myeloid PHD2cko vein grafts. In addition, PHD2 deficiency prevented dissection of vein grafts and resulted in an increase in vessel wall collagen content. Moreover, the macrophage proinflammatory phenotype in the vein graft wall was attenuated in myeloid PHD2cko mice. In vitro cultured PHD2cko bone marrow-derived macrophages exhibited an increased proangiogenic phenotype compared with control. CONCLUSIONS: Myeloid PHD2cko reduces vein graft disease and ameliorates vein graft lesion stability by improving intraplaque angiogenesis.

Impact of Graft Velocity on Saphenous Vein Graft Atherosclerosis after Coronary Artery Bypass Grafting.

PURPOSE: Saphenous vein grafts (SVGs) sometimes occur as vein graft stenosis or failure in coronary artery bypass grafting. The purpose of this study was to detect the factors affecting vein graft atherosclerosis. METHODS: We performed two analysis. In the first analysis, we enrolled 120 grafts using conventionally harvested saphenous vein graft (C-SVG) and followed-up with multiple coronary computed tomography angiography (CCTA). We examined the factors that contribute to the graft atherosclerosis defined by graft failure at subsequent CCTA or substantial progression of graft stenosis (a decrease of ≥0.6 mm in diameter). In the second analysis, 66 grafts using no-touch harvested saphenous vein graft (N-SVG) were compared with those in the first analysis using C-SVG, focusing on the differences in intraoperative factors using propensity score-matched analysis. RESULTS: In the first analysis, graft atherosclerosis+ group comprised 27 grafts, which had a larger SVG diameter, lower graft velocity, and higher graft/native ratio in diameter than the graft atherosclerosis- group. In the multivariable analysis, slow graft velocity and graft/native ≥2 in diameter were independently associated with the graft atherosclerosis. In the second analysis, the N-SVG group had a much greater graft velocity than the C-SVG group. CONCLUSION: Lower graft velocity and higher graft/native ratio in diameter were associated with the graft atherosclerosis. The N-SVG group had increased graft velocity, which may contribute to prevent the graft atherosclerosis.(Trial registration: UMIN Clinical Trial Registry no. UMIN000050482. Registered 3 March 2023, retrospectively registered.).

Vein graft preservation with an endothelial damage inhibitor in isolated coronary artery bypass surgery: an observational propensity score-matched analysis.

Background: Preservation solutions may be used intraoperatively during coronary artery bypass grafting (CABG) to flush and preserve vein grafts. The aim of this study is to evaluate the effect of DuraGraft, an endothelial damage inhibitor (EDI) preservation solution on major adverse cardiac events (MACEs) after CABG. Methods: We conducted an observational, prospective, longitudinal, single-center study that included patients who underwent isolated CABG. The cohort treated with an EDI was matched 1:1 with a control group treated with conventional vein preservation, and matching was adjusted for possible confounding factors through propensity score (PS) matching. Three years follow-up was conducted, and the occurrence of MACE [defined as all cause-death, acute coronary syndrome (ACS), and new unplanned revascularization] was analyzed using Kaplan-Meier method. Results: The study included 180 patients, 90 in each group. There were no significant differences in baseline characteristics across study groups. The EDI group had a significantly better event-free survival at 3 years (89% vs. 78%, log-rank test P=0.035), with an incidence rate ratio of 0.41 [95% confidence interval (CI): 0.16-0.96]. In the pre-specified subgroups analysis, the use of an EDI was associated with a significantly better event-free survival in diabetic patients (log-rank test P=0.041) and those with two or more saphenous vein grafts (log-rank test P=0.015). Conclusions: The utilization of an EDI for vein flushing and storage after vein harvest in CABG procedures has been shown to significantly decrease the incidence of MACE at 3 years post-surgery. This protective effect is particularly notable in diabetic patients and in individuals who have multiple vein grafts.

Endothelial damage inhibitor preserves the integrity of venous endothelial cells from patients undergoing coronary bypass surgery.

OBJECTIVES: Despite the success of coronary artery bypass graft (CABG) surgery using autologous saphenous vein grafts (SVGs), nearly 50% of patients experience vein graft disease within 10 years of surgery. One contributing factor to early vein graft disease is endothelial damage during short-term storage of SVGs in inappropriate solutions. Our aim was to evaluate the effects of a novel endothelial damage inhibitor (EDI) on SVGs from patients undergoing elective CABG surgery and on venous endothelial cells (VECs) derived from these SVGs. METHODS: SVGs from 11 patients participating in an ongoing clinical registry (NCT02922088) were included in this study, and incubated with both full electrolyte solution (FES) or EDI for 1 h and then examined histologically. In 8 of 11 patients, VECs were isolated from untreated grafts, incubated with both FES and EDI for 2 h under hypothermic stress conditions and then analysed for activation of an inflammatory phenotype, cell damage and cytotoxicity, as well as endothelial integrity and barrier function. RESULTS: The EDI was superior to FES in protecting the endothelium in SVGs (74 ± 8% versus 56 ± 8%, P < 0.001). Besides confirming that the EDI prevents apoptosis in SVG-derived VECs, we also showed that the EDI temporarily reduces adherens junctions in VECs while protecting focal adhesions compared to FES. CONCLUSIONS: The EDI protects the connectivity and function of the SVG endothelium. Our data suggest that the EDI can preserve focal adhesions in VECs during short-term storage after graft harvesting. This might explain the superiority of the EDI in maintaining most of the endothelium in venous CABG surgery conduits.

Prognostic Value of Systemic Immune-Inflammation Index in Predicting Premature Saphenous Vein Graft Disease in Patients With Coronary Artery Bypass Grafting.

BACKGROUND: Systemic inflammation is a risk factor for premature coronary artery disease (CAD), and systemic immune-inflammation index (SII), a new marker of systemic inflammation, is linked to the severity and prognosis of CAD. However, the prognosis of the SII in bypass patients' venous saphenous grafts has not been adequately evaluated. This study aimed to evaluate the prognostic value of SII in predicting premature saphenous vein graft disease (SVGD) in patients who underwent bypass surgery with venous saphenous grafts. METHODS: We retrospectively included 422 patients who had saphenous vein grafts (SVG) at least one year after bypass surgery. Of these, 222 patients had SVGD, and 200 had patent SVG. RESULTS: SII was higher in the SVGD group than in the control group (631.55 ± 397.84, 421.71 ± 351.07, P=0.001). A receiver operating characteristic (ROC) analysis was performed to identify the optimal cutoff point with the highest sensitivity and specificity. The optimal cutoff point for SII was defined as 430. Using a cutoff level of >430, SII predicted SVGD with a sensitivity of 73% and specificity of 56%. CONCLUSION: Our study demonstrated that SII was substantially higher in patients with SVGD than in those with patent SVG. SII predicted SVGD in bypass surgery patients. SII may be a helpful parameter for identifying patients at high risk of SVGD and guiding preventive treatments.

The Role of Preservation Solutions upon Saphenous Vein Endothelial Integrity and Function: Systematic Review and UK Practice Survey.

The long saphenous vein is the most used conduit in cardiac surgery, but its long-term patency is limited by vein graft disease (VGD). Endothelial dysfunction is a key driver of VGD; its aetiology is multi-factorial. However emerging evidence identifies vein conduit harvest technique and preservation fluids as causal in their onset and propagation. This study aims to comprehensively review published data on the relationship between preservation solutions, endothelial cell integrity and function, and VGD in human saphenous veins harvested for CABG. The review was registered with PROSPERO (CRD42022358828). Electronic searches of Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE databases were undertaken from inception until August 2022. Papers were evaluated in line with registered inclusion and exclusion criteria. Searches identified 13 prospective, controlled studies for inclusion in the analysis. All studies used saline as a control solution. Intervention solutions included heparinised whole blood and saline, DuraGraft, TiProtec, EuroCollins, University of Wisconsin (UoW), buffered, cardioplegic and Pyruvate solutions. Most studies demonstrated that normal saline appears to have negative effects on venous endothelium and the most effective preservation solutions identified in this review were TiProtec and DuraGraft. The most used preservation solutions in the UK are heparinised saline or autologous whole blood. There is substantial heterogeneity both in practice and reporting of trials evaluating vein graft preservation solutions, and the quality of existing evidence is low. There is an unmet need for high quality trials evaluating the potential for these interventions to improve long-term patency in venous bypass grafts.

Late Saphenous Vein Graft Disease: Cut to the Chase.

We read with interest the article entitled "The Role of Systemic Immune Inflammation Index for Predicting Saphenous Vein Graft Disease in Patients with Coronary Artery Bypass Grafting." We congratulate the authors for their contribution. We would like to discuss some points about the late development of saphenous vein graft disease.

A five-parameter score for predicting saphenous vein graft degenerative and/or occlusive disease in recurring ischemic symptoms after one year post coronary artery bypass grafting.

BACKGROUND: The recurrence rate of ischemic symptoms after coronary artery bypass grafting (CABG) is increasing in recent years. How to prevent and treat saphenous vein graft disease (SVGD [symptomatic ⩾50% stenosis in at least one Saphenous vein graft]) has been a clinical challenge to date. Different pathogenesis may exist in SVGD of different periods. There are currently few available scores for estimating the risk of SVGD after one year post CABG. OBJECTIVE: We sought to develop and validate a simple predictive clinical risk score for SVGD with recurring ischemia after one year post CABG. METHODS AND RESULTS: This was a cross-sectional study and the results were validated using bootstrap resampling on a separate cohort. A nomogram and risk scoring system were developed based on retrospective data from a training cohort of 606 consecutive patients with recurring ischemia >1 year after CABG. Logistic regression model was used to find the predictive factors and to build a nomogram. To assess the generalization, models were validated using bootstrap resampling and an external cross-sectional study of 187 consecutive patients in four other hospitals. In multivariable analysis of the primary cohort, native lesion vessel number, SVG age, recurring ischemia type, very low-density lipoprotein level, and left ventricular end-diastolic diameter were independent predictors. A summary risk score was derived from nomogram, with a cut-off value of 15. In internal and external validation, the C-index was 0.86 and 0.82, indicating good discrimination. The calibration curve for probability of SVGD showed optimal agreement between actual observations and risk score prediction. CONCLUSION: A simple-to-use risk scoring system based on five easily variables was developed and validated to predict the risk of SVGD among patients who recurring ischemia after one year post CABG. This score may be useful for providing patients with individualized estimates of SVGD risk.

The Role of Systemic Immune Inflammation Index for Predicting Saphenous Vein Graft Disease in Patients with Coronary Artery Bypass Grafting.

As inflammation plays a significant role in the development of coronary artery disease, we hypothesized that there may be a relation between the systemic immune inflammation index (SII) and saphenous vein graft disease (SVGD). The study population consisted of 716 consecutive patients who underwent elective coronary angiography (CAG) >1 year after bypass grafting. The patients were divided into 2 groups depending on the extent of SVG patency. SII value was significantly higher in the SVGD(+) group compared with the SVGD(-) group (P < .001). In multivariate logistic regression analysis, SII (P < .001, odds ratio (OR) = 3.27, 95% CI = 1.94-5.65) and neutrophil-to-lymphocyte ratio (NLR) (P < .001, OR = 2.08, 95% CI = 1.59-3.11) were found to be independent predictors of SVGD. An SII value of >935 (x103/ml) has 89.2% sensitivity and 70.6% specificity for the prediction of the SVGD, and an NLR value of >4.15 has 54.6% sensitivity and 68.5% specificity for the prediction of the SVGD. The AUC of SII was found to be greater than the AUC of NLR (P = .002), platelet-to-lymphocyte ratio (PLR) (P = .009), lymphocyte-to-monocyte ratio (LMR) (P = .013), MPV (P = .011), and C-reactive protein (CRP) (P = .034) in predicting SVGD. In conclusion, we demonstrated that SII, which is among the new inflammation indexes, is a more reliable predictor in determining SVGD than the NLR, PLR, and LMR.

Intimal hyperplasia, saphenous vein graft disease, and clinical outcomes: Insights from the CTSN VEST randomized trial.

BACKGROUND: Diffuse intimal hyperplasia and graft irregularity adversely affect the long-term patency of saphenous vein grafts (SVGs) and clinical outcomes of patients undergoing coronary artery bypass grafting (CABG). The VEST trial evaluated the efficacy of external graft support in limiting the development of intimal hyperplasia (IH) at 1 year postsurgery. In the present secondary analysis, we explored the associations between graft disease and IH and clinical events. We also examined risk factors for early graft occlusion. METHODS: VEST is a within-patient randomized, multicenter trial that enrolled 224 patients with multivessel coronary disease undergoing CABG surgery, of whom 203 were evaluated by 1 year postsurgery. Intimal hyperplasia, lumen uniformity, graft stenosis, and graft perfusion were measured by intravascular ultrasound and angiography. Major cardiac and cerebrovascular events (MACCE; including death, myocardial infarction, stroke, and revascularization) were recorded over a median follow-up of 3 years. RESULTS: Worse lumen uniformity, greater stenosis, and worse graft perfusion were associated with higher IH values and an increased incidence of clinical events. Consistent with previous findings, we identified endoscopic vein harvesting, female sex, and transit time flow measurement of pulsatility index and flow as risk factors for SVG occlusion during the first year postsurgery. CONCLUSIONS: In this secondary analysis of the VEST trial, we observed an association between intimal hyperplasia area and clinical measures of SVG disease at 1 year postsurgery. More severe SVG disease and larger areas of IH were associated with a higher incidence of 3-year MACCE. Ongoing follow-up to 5 years will further elucidate the impact of SVG disease on long-term clinical outcomes of CABG.

The Role of Endothelial Cells in the Onset, Development and Modulation of Vein Graft Disease.

Endothelial cells comprise the intimal layer of the vasculature, playing a crucial role in facilitating and regulating aspects such nutrient transport, vascular homeostasis, and inflammatory response. Given the importance of these cells in maintaining a healthy haemodynamic environment, dysfunction of the endothelium is central to a host of vascular diseases and is a key predictor of cardiovascular risk. Of note, endothelial dysfunction is believed to be a key driver for vein graft disease-a pathology in which vein grafts utilised in coronary artery bypass graft surgery develop intimal hyperplasia and accelerated atherosclerosis, resulting in poor long-term patency rates. Activation and denudation of the endothelium following surgical trauma and implantation of the graft encourage a host of immune, inflammatory, and cellular differentiation responses that risk driving the graft to failure. This review aims to provide an overview of the current working knowledge regarding the role of endothelial cells in the onset, development, and modulation of vein graft disease, as well as addressing current surgical and medical management approaches which aim to beneficially modulate endothelial function and improve patient outcomes.

Effects of the harvesting technique and external stenting on progression of vein graft disease 2 years after coronary artery bypass.

OBJECTIVES: In a post hoc analysis of the VEST III trial, we investigated the effect of the harvesting technique on saphenous vein graft (SVG) patency and disease progression after coronary artery bypass grafting. METHODS: Angiographic outcomes were assessed in 183 patients undergoing open (126 patients, 252 SVG) or endoscopic harvesting (57 patients, 114 SVG). Overall SVG patency was assessed by computed tomography angiography at 6 months and by coronary angiography at 2 years. Fitzgibbon patency (FP I, II and III) and intimal hyperplasia (IH) in a patient subset were assessed by coronary angiography and intravascular ultrasound, respectively, at 2 years. RESULTS: Baseline characteristics were similar between patients who underwent open and those who underwent endoscopic harvesting. Open compared with endoscopic harvesting was associated with higher overall SVG patency rates at 6 months (92.9% vs 80.4%, P = 0.04) and 2 years (90.8% vs 73.9%, P = 0.01), improved FP I, II and III rates (65.2% vs 49.2%; 25.3% vs 45.9%, and 9.5% vs 4.9%, respectively; odds ratio 2.81, P = 0.09) and reduced IH area (-31.8%; P = 0.04) and thickness (-28.9%; P = 0.04). External stenting was associated with improved FP I, II and III rates (odds ratio 2.84, P = 0.01), reduced IH area (-19.5%; P < 0.001) and thickness (-25.0%; P < 0.001) in the open-harvest group and reduced IH area (-12.7%; P = 0.01) and thickness (-9.5%; P = 0.21) in the endoscopic-harvest group. CONCLUSIONS: A post-hoc analysis of the VEST III trial showed that open harvesting is associated with improved overall SVG patency and reduced IH. External stenting reduces SVG disease progression, particularly with open harvesting.

Efficacy of Intraoperative Vein Graft Storage Solutions in Preserving Endothelial Cell Integrity during Coronary Artery Bypass Surgery.

(1) Introduction: Intraoperative preservation solutions for saphenous vein grafts may influence the endothelial structure and increase the risk of graft failure after coronary surgery. The aim of the study was to compare the efficacy of three solutions in maintaining the endothelial cell integrity of venous segments. (2) Methods: We tested the efficacy of physiological saline solution (PSS), heparinized autologous blood (HAB) and DuraGraft® in preserving the endothelium of vein segments by evaluating the degree of endothelial cell apoptosis. Two incubation times (2 and 4 h from harvesting) were used for each solution. The quantification of apoptotic cells was computed as the intensity nuclei/intensity area ratio. (3) Results: After 2 h of ischemia, the degree of apoptosis decreased progressively across the use of DuraGraft, HAB and PSS (p = 0.004), although only the difference between DuraGraft and PSS yielded a statistical significance (p = 0.002). After 4 h, a similar decrease in apoptosis was shown across the three media; however, statistical significance was not reached. The analysis of the elapsed time (2 or 4 h of incubation) showed that this was a relevant factor in maintaining the endothelial structural integrity independently from the storage solution (test for interaction of media and time p = 0.010). (4) Conclusion: Within 2 h of incubation, endothelial structural integrity depended on the incubating medium. DuraGraft better protected the SVG against ischemic-induced apoptosis when compared to saline solution. Prolonged ischemia was associated with extended endothelium damage and none of the studied solutions protected the vein graft.

Association of CHA2DS2-VASc score with thrombus burden in patients with acute myocardial infarction undergoing SVG-PCI.

BACKGROUND: The rate of saphenous vein graft (SVG) occlusion within the first year of bypass graft surgery is 15%. The CHA2DS2-VASc score is used to predict the risk of thromboembolic events in patients with nonvalvular atrial fibrillation. We aimed to evaluate the predictive role of the CHA2DS2-VASc score in the estimation of intracoronary thrombus burden in patients with acute myocardial infarction (AMI) who underwent SVG-PCI. METHODS: We retrospectively evaluated 221 patients who were admitted with AMI and underwent PCI of SVGs at the Department of Cardiology in the Turkiye Yuksek Ihtisas Education and Research Hospital between 2012 and 2018. The study population was divided into two groups according to their Thrombolysis in Myocardial Infarction (TIMI) thrombus grade: low thrombus burden (LTB; TIMI 0-3) and high thrombus burden (HTB; TIMI 4 and 5). RESULTS: The study included 221 patients with a mean age of 63.3 ± 6.7 years. The patients with HTB had significantly higher CHA2DS2-VASc scores (p < 0.001) compared with LTB patients. Univariate and multivariate regression analysis demonstrated that both CHA2DS2-VASc score (OR: 1.573, 95% CI: 1.153-2.147, p = 0.004) as a continuous variable and a binary cut-off level of the CHA2DS2-VASc score > 3 (OR: 3.876, 95% CI: 1.705-8.808, p = 0.001) were significantly associated with HTB. The ability of the CHA2DS2-VASc score to predict HTB burden was evaluated by receiver-operating characteristics analysis curve analysis. The optimum cut-off value of the CHA2DS2-VASc score for predicting HTB was 3 (with a sensitivity of 67.9% and a specificity of 69.3%) according to the Youden index. CONCLUSION: The CHA2DS2-VASc score can be used as an easy practical tool to predict HTB in AMI patients undergoing SVG-PCI.

External stenting of vein grafts in coronary artery bypass grating: interim results from a two centers prospective study.

BACKGROUND: previous studies evaluating external stents for saphenous vein grafts (SVG) in CABG were limited to on-pump isolated CABG and single grafting technique with one external stent per patient. The objective of this prospective study was to evaluate the safety and the short-term performance of external stents in a heterogeneous group of patients who underwent on- and off-pump CABG, single and sequential grafting. METHODS: 102 patients undergoing CABG were enrolled in two centers. All patients received internal mammary artery to the left anterior descending artery and additional arterial and/or venous grafts. In each patient, at least one SVG was supported with an external stent. Grafts' patency and SVG lumen uniformity were assessed using CT angiography at a pre-defined time window of 6-12 months post procedure. All patients were prospectively followed-up via phone call and/or visit every 6 months for Major Adverse Cardiac and Cerebrovascular Events. RESULTS: 51 patients (50%) underwent off-pump CABG and 23 patients (23%) were grafted with bilateral internal mammary arteries. Each patient received one or more SVG grafted in a sequential technique (44%) or as a single graft (56%). All SVG were externally stented in 84% of patients and in 16% (n = 16) one SVG was stented and one remained unsupported. At 6-12 months, patency rates of LIMA, RIMA, externally stented SVG and none-stented SVG were 100, 100, 98 and 87.5% respectively. 90% of the externally stented SVG had uniform lumen compared to 37% of the non-stented SVG. Clinical follow-up was completed for all patients with a mean duration of 20 months (range 6-54 months). During follow up period, one patient experienced myocardial infarction due to occlusion of the LIMA-LAD graft and one patient experienced a transient ischemic attack. CONCLUSIONS: External stenting of SVG is feasible and safe in CABG setting which includes off pump CABG and sequential SVG grafting and associated with acceptable early patency rates. TRIAL REGISTRATION: Study was registered at ClinicalTrials.gov. NCT01860274 (initial release 20.05.2013).

C-Reactive Protein to Albumin Ratio in Patients With Saphenous Vein Graft Disease.

Atherosclerosis plays an important role in saphenous vein graft disease (SVGD). Previous studies showed that inflammatory blood cells play an active role in this process. C-reactive protein to albumin ratio (CAR) is considered as a novel predictor for cardiovascular risk and an indicator of inflammation. We aimed to assess the relationship between SVGD and CAR. A total of 711 participants with saphenous vein graft (SVG) were included; 348 patients had SVGD and 363 patients had patent (no stenosis) SVG. C-reactive protein to albumin ratio was higher in patients with SVGD (P < .001). There was a significant positive correlation between CAR and the age of SVG (r = 0.123; P = .001) and SYNTAX score (r = 0.568; P < .001). Multivariate logistic regression analyses showed that lymphocyte count, CAR, and SYNTAX score were independent predictors of SVGD (P < .05). C-reactive protein to albumin ratio may be a useful marker after bypass surgery to predict SVGD.

Atorvastatin pleiotropically decreases intraplaque angiogenesis and intraplaque haemorrhage by inhibiting ANGPT2 release and VE-Cadherin internalization.

OBJECTIVE: Statins pleiotropically provide additional benefits in reducing atherosclerosis, but their effects on intraplaque angiogenesis (IPA) and hemorrhage (IPH) remain unclear. Therefore, we discriminated statin's lipid-lowering dependent and independent effects on IPA and IPH. APPROACH AND RESULTS: ApoE3*Leiden mice are statin-responsive due to ApoE and LDLR presence, but also allow to titrate plasma cholesterol levels by diet. Therefore, ApoE3*Leiden mice were fed a high-cholesterol-inducing-diet (HCD) with or without atorvastatin (A) or a moderate-cholesterol-inducing-diet (MCD). Mice underwent vein graft surgery to induce lesions with IPA and IPH. Cholesterol levels were significantly reduced in MCD (56%) and HCD + A (39%) compared to HCD with no significant differences between MCD and HCD + A. Both MCD and HCD + A have a similar reduction in vessel remodeling and inflammation comparing to HCD. IPA was significantly decreased by 30% in HCD + A compared to HCD or MCD. Atorvastatin treatment reduced the presence of immature vessels by 34% vs. HCD and by 25% vs. MCD, resulting in a significant reduction of IPH. Atorvastatin's anti-angiogenic capacity was further illustrated by a dose-dependent reduction of ECs proliferation and migration. Cultured mouse aortic-segments lost sprouting capacity upon atorvastatin treatment and became 30% richer in VE-Cadherin expression and pericyte coverage. Moreover, Atorvastatin inhibited ANGPT2 release and decreased VE-Cadherin(Y685)-phosphorylation in ECs. CONCLUSIONS: Atorvastatin has beneficial effects on vessel remodeling due to its lipid-lowering capacity. Atorvastatin has strong pleiotropic effects on IPA by decreasing the number of neovessels and on IPH by increasing vessel maturation. Atorvastatin improves vessel maturation by inhibiting ANGPT2 release and phospho(Y658)-mediated VE-Cadherin internalization.

Interfering in the ALK1 Pathway Results in Macrophage-Driven Outward Remodeling of Murine Vein Grafts.

AIMS: Vein grafts are frequently used to bypass coronary artery occlusions. Unfortunately, vein graft disease (VGD) causes impaired patency rates. ALK1 mediates signaling by TGF-ß via TGFßR2 or BMP9/10 via BMPR2, which is an important pathway in fibrotic, inflammatory, and angiogenic processes in vascular diseases. The role of the TGF-ß pathway in VGD is previously reported, however, the contribution of ALK1 signaling is not known. Therefore, we investigated ALK1 signaling in VGD in a mouse model for vein graft disease using either genetic or pharmacological inhibition of the Alk1 signaling. METHODS AND RESULTS: Male ALK1 heterozygous (ALK1+/-), control C57BL/6, as well as hypercholesterolemic ApoE3*Leiden mice, underwent vein graft surgery. Histologic analyses of ALK1+/- vein grafts demonstrated increased outward remodeling and macrophage accumulation after 28 days. In hypercholesterolemic ApoE3*Leiden mice receiving weekly ALK1-Fc injections, ultrasound imaging showed 3-fold increased outward remodeling compared to controls treated with control-Fc, which was confirmed histologically. Moreover, ALK1-Fc treatment reduced collagen and smooth muscle cell accumulation, increased macrophages by 1.5-fold, and resulted in more plaque dissections. No difference was observed in intraplaque neovessel density. Flow cytometric analysis showed increased systemic levels of Ly6CHigh monocytes in ALK1-Fc treated mice, supported by in vitro increased MCP-1 and IL-6 production of LPS-stimulated and ALK1-Fc-treated murine monocytes and macrophages. CONCLUSION: Reduced ALK1 signaling in VGD promotes outward remodeling, increases macrophage influx, and promotes an unstable plaque phenotype. TRANSLATIONAL PERSPECTIVE: Vein graft disease (VGD) severely hampers patency rates of vein grafts, necessitating research of key disease-driving pathways like TGF-ß. The three-dimensional nature of VGD together with the multitude of disease driving factors ask for a comprehensive approach. Here, we combined in vivo ultrasound imaging, histological analyses, and conventional in vitro analyses, identifying the ambiguous role of reduced ALK1 signaling in vein graft disease. Reduced ALK1 signaling promotes outward remodeling, increases macrophage influx, and promotes an unstable plaque phenotype in murine vein grafts. Characterization of in vivo vascular remodeling over time is imperative to monitor VGD development and identify new therapies.