Neointimal Thickness Research Articles

Influence of Mesenchymal Stem Cells Seeding on Morphology of Tissue-Engineered Vascular Graft Based on Poly (L-lactide) Scaffold

Introduction - The problem of small-diameter vascular grafts still exists in modern vascular surgery. Autologous or synthetic vascular grafts are used routinely for arterial bypass in patients with cardiovascular diseases. However, some patients either lack suitable autologous tissue or cannot receive synthetic grafts. Such patients could benefit from a vascular graft produced by tissue engineering. The aim of the study is to evaluate the effects of adipose-derived mesenchymal stem cells (AD-MSC) on the formation of tissue-engineered vascular graft (TEVG). Methods - Tubular scaffolds 1.1 mm inner diameter were obtained by the electrospinning method on the basis of nano- and microfibers of poly(L-lactide) (PLLA). AD-MSC were seeded on the scaffolds by the developed filtration method. The subsequent culturing for 14 days was carried out in the constructed flow bioreactor. Cell distribution in the scaffold wall was assessed by the fluorescence microscopy. Obtained grafts were implanted into rat aorta: group 1 without AD-MSC (n=36) with follow-up till 16 months, group 2 with seeded AD-MSC (n=36) with follow-up till 16 months. The material was subjected to histological examination, electron microscopy, immunohistochemistry CD 31+, aSMA and morphometric analysis (cell counting, neointima and neoadventia thickness). To track AD-MSC in vivo PKH-26 labeling and subsequent fluorescence microscopy were performed in 2, 7 and 14 days. Results - Filtration seeding and subsequent cultivation in the flow bioreactor led to a uniform distribution of AD-MSC in the scaffold wall. Graft patency in the first group was 86%, in the second 96%. All grafts formed neointima, with no signs of hyperplasia in the area of anastomoses. The total resorption of PLLA fibers in group 1 was observed by histological examination, new vascular wall consisted of endothelial lining and connective tissue without smooth muscle cells (SMC); in all cases aneurysm formation was detected. Total cells number of implant wall was more in group 2, including SMC that formed neomedia. Also the outer connective tissue layer was much thicker. Histology identified the uniform formation of new tissues in group 2 with no signs of aneurysm. Conclusion - AD-MSC seeding leads to the formation of TEVG, morphologically similar to the natural structure of the vessels. The study was supported by Russian Science Foundation (project 14-33-00003)

Apolipoprotein E deficient rats generated via zinc-finger nucleases exhibit pronounced in-stent restenosis

The long-term success of coronary stent implantation is limited by in-stent restenosis (ISR). In spite of a broad variety of animal models available, an ideal high-throughput model of ISR has been lacking. Apolipoprotein E (apoE) deficient rats enable the evaluation of human-sized coronary stents while at the same time providing an atherogenic phenotype. Whereas apoE deficient rats have been proposed as animal model of atherosclerosis, to date it is unknown whether they also develop pronounced ISR. We sought to assess ISR after abdominal aorta stent implantation in apoE deficient rats. A total of 42 rats (16 wildtype, 13 homozygous apoE−/− and 13 heterozygous apoE+/− rats) underwent abdominal aorta stent implantation. After 28 days blood samples were analyzed to characterize lipid profiles. ISR was assessed by histomorphometric means. Homozygous apoE−/− rats exhibited significantly higher total cholesterol and low-density cholesterol levels than wildtype apoE+/+ and heterozygous apoE+/− rats. ISR was significantly pronounced in homozygous apoE−/− rats as compared to wildtype apoE+/+ (p = <0.0001) and heterozygous apoE+/− rats (p = 0.0102) on western diet. Abdominal aorta stenting of apoE−/− rats is a reliable model to investigate ISR after stent implantation and thus can be used for the evaluation of novel stent concepts. Apolipoprotein E (apoE) deficient rats have been proposed as animal model of atherosclerosis. We investigated the development of restenosis 28 days after stent implantation into the abdominal aorta of wildtype apoE+/+, homozygous apoE−/− and heterozygous apoE+/− rats, respectively. Homozygous apoE−/− rats exhibited significantly higher LDL and significantly lower HDL cholesterol levels compared to wildtype apoE+/+ and heterozygous apoE+/− rats. Restenosis after stent implantation was significantly pronounced in western-diet-fed homozygous apoE−/− rats, accompanied by a significantly increased neointimal thickness. Thus, apoE knockout rats exhibit elevated restenosis and might provide a novel tool for testing of innovative stent concepts.

Filament inadequate wall apposition of the different ends of flow diverters in the abdominal aorta of rabbits.

Flow diverters (FDs) with flared ends (FEs) or straight ends (SEs) are used either alone or when overlapped to treat complex intracranial aneurysms. We evaluated filament inadequate wall apposition (IWA) of the FEs and SEs of FDs invivo. A total of 24 FDs with FEs and SEs were placed in an overlapping manner in the abdominal aortae of six rabbits (two sets per rabbit). Digital subtraction angiography was performed immediately after stent insertion and three months later. The anatomical and histopathological aortic features at FEs and SEs were evaluated. Angiography revealed no significant difference in terms of changes in arterial diameter between the FE and SE groups (p = 0.877). Gross anatomical evaluation revealed IWA of the different ends of FDs but no thrombi or bleeding, showing that the metallic filaments were not in touch with the vessel wall and nor had they penetrated the vessel wall. The filaments' IWA rates of FEs and SEs were 8.33% and 8.85%, respectively. The IWA rate at overlapping ends was lower than that at non-overlapping ends. The maximum neo-intimal thickness at FEs was greater than that at SEs (149.4 ± 48.9 and 98.6 ± 26.6 µm, respectively; p < 0.001). Both the FEs and SEs of FDs can exhibit IMA. IWA events are reduced at the overlapped regions. On pathological evaluation, FEs increased neo-intimal thicknesses more than SEs did, but hyperplasia was minimal on angiography.

Reduced histologic neo in-stent restenosis after use of a paclitaxel-coated cutting balloon in porcine coronary arteries.

The incidence of in-stent restenosis (ISR) has declined dramatically, but once it develops, no current treatment option, such as drug-eluting stents, drug-coated balloons, or cutting balloons (CBs), prevents re-narrowing of the stented atherosclerotic artery. In this preclinical study, we aimed to improve the efficacy of ISR treatment by coating CBs with paclitaxel (paclitaxel-eluting cutting balloon; PECB) and to characterize the histological features of neo-ISRs that arise after ISR treatment. ISR was induced by bare metal stent (BMS) implantation in coronary arteries in pigs. After one month of follow-up, the BMS-induced ISR was treated with either CB or PECB. After another month, we performed quantitative coronary angiography, explanted the treated arteries and assessed histopathological and histomorphometric parameters. In addition, we compared the histological features of neo-ISRs with pre-treatment ISRs. Injury, inflammation, fibrin deposition, and endothelialization scores were similar between the CB and PECB groups at one month after ISR treatment. Neointimal area (0.87±0.61 vs. 1.95±1.14 mm², p=0.02), mean neointimal thickness (0.40±0.39 vs. 0.99±0.56 mm, p=0.01), and percent area stenosis (27.3±20.4 vs. 48.3±22.9%, p=0.04) were decreased in PECB-treated coronary arteries compared to CB-treated arteries, respectively. Density of cells (predominantly smooth muscle cells; SMCs) was increased in neo-ISRs (3.51±3.05×10³ vs. 6.35±2.57×10³ cells/mm², p<0.01), but significantly more CD68⁺ and CD20⁺ cells were found in the pre-treatment ISRs. In conclusion, PECB treatment of ISRs led to better results in terms of smaller neointimal area and %area stenosis of the neo-ISR. SMC density was increased in neo-ISRs in contrast with higher percentage of CD68⁺ and CD20⁺ cells in pre-treatment ISRs.

Histopathologic Analysis of Explanted Polytetrafluoroethylene-Valved Pulmonary Conduits

The expanded polytetrafluoroethylene (ePTFE)-valved conduits as alternative material for right ventricular outflow reconstruction provides satisfactory long-term outcomes. The purpose of this study was to investigate degenerative changes in failed conduits through histopathologic analysis of the explanted specimens. All leaflets of explanted conduits were observed macroscopically, and their longitudinal sections were examined microscopically. Three typical findings, that is, calcification of the leaflet, neointimal proliferation, and proteinaceous infiltration into the leaflet, were evaluated quantitatively by measuring their degree and appearance probability. A total of 15 leaflets from 5 failed conduits (group F) and 12 leaflets from 5 nonfailed conduits (group non-F) were included. The median duration of implantation was 7.6 years (5.3-10.9 years) in group F and 1.3 years (0.7-3.9 years) in group non-F (P = 0.003). In group F, calcification tended to occur in the middle and upper third of the leaflet, causing stiffening, distortion, and exophytic concretion of the leaflet, and mean neointimal thickness on inflow and outflow surfaces were 0.33 ± 0.02 mm and 0.22 ± 0.01 mm, respectively. There was a moderately strong correlation between appearance probability of calcification in group F and that of proteinaceous infiltration in group non-F (correlation coefficient 0.67, P < 0.001). Proteinaceous infiltration into the leaflet was presumed be responsible for future calcification of the leaflet and subsequent stenotic conduit failure. Modification of the ePTFE material to prevent proteinaceous infiltration may contribute to improving the durability of ePTFE-valved conduit.

Different vascular healing process between bioabsorbable polymer-coated everolimus-eluting stents versus bioresorbable vascular scaffolds via optical coherence tomography and coronary angioscopy (the ENHANCE study: ENdothelial Healing Assessment with Novel Coronary tEchnology)

Recent clinical trials have raised concerns about the safety and efficacy of ABSORB™ bioresorbable vascular scaffolds (BVS). The difference in the vascular healing process between SYNERGY™ bioabsorbable polymer-coated everolimus-eluting stents (BP-EES) and BVS remains unclear. The aim of the ENHANCE study was to compare vascular healing on BP-EES versus BVS by optical coherence tomography (OCT) and coronary angioscopy (CAS) at 4- and 12-month follow-ups. This is a prospective, non-randomized, single center clinical trial. Thirteen eligible patients with multivessel disease were enrolled. BP-EES and BVS were simultaneously implanted in the same patients, but in different coronary vessels. Imaging follow-up with both OCT and CAS was completed in 11 patients at 12 months. Neointimal coverage rates were similar between the two groups based on OCT measurements. The neointimal thickness of BP-EES was significantly thicker at the 12th month than at the 4th month, whereas the neointimal thickness of BVS did not change between the measurements taken at the 4th and 12th month. Existence of intra-stent thrombus was significantly higher in the BVS group, compared to the BP-EES group. On the other hand, CAS revealed that red-thrombi and yellow-plaque were more frequently observed in BVS at 4 months and up to 12-month follow-ups than in BP-EES. These findings suggested that the evidence of instability remained up to 12 months in the vascular healing with BVS, compared to that with BP-EES. Vascular healing of the stented wall was recognized at the very early phase after BP-EES implantation. However, vascular healing with BVS was still incomplete after 12 months.

P5629The effect of strut protrusion on local shear stress and neointimal hyperplasia

Abstract Objective To evaluate effect of strut protrusion (SP) on wall shear stress (WSS) and neointimal growth (NG) 1 and 5 year after implantation of Absorb scaffold. Method 8 patients were selected from Absorb Cohort B. After 3-dimensional reconstruction of coronaries, WSS was quantified using Newtonian steady flow simulation (Figure). At 1-year neointimal thickness (NT) was measured by optical coherence tomography and correlated to WSS and SP post-procedure. Results Median SP was 112.9 (90.8, 133.1) μm. A logarithmic (log) inverse relationship between SP and post-procedure WSS (r=−0.425 p&lt;0.001 correlation coefficients range: −0.143 to −0.553) was observed whereas a correlation between baseline log transformed WSS and NT (r=−0.451 p&lt;0.001 correlation coefficients range: −0.140 to −0.662) was documented at 1 year. Mixed effects analysis between baseline log transformed WSS and NT at follow up yielded a slope of 30 μm/ln Pascal (Pa) and a y-intercept of 98 μm. As result of NG, flow area decreased from 6.91 (6.53, 7.48) mm2 post-implantation to 5.65 (5.47, 6.02) mm2 at 1 year (p=0.01) and to 5.75±1.37 mm2 at 5 years (p=0.024). Vessel surface with low WSS (&lt;1 Pa) decreased from post-procedure (42%) to 1 year (35.9%) and 5 years (15.2%) (p-overall&lt;0.0001). Conclusion SP disturbs laminar flow, creates region of low WSS that is mechanistically associated with NG and lumen area reduction. This observation would suggest thin strut with effective embedment would reduce NG and improve WSS towards physiological values.

P2805Initial pathological responses of third-generation everolimus-eluting stents implantation: comparison with second-generation everolimus-eluting stents

Abstract Background Third-generation drug-eluting stent (3rd DES) is commonly used now in percutaneous coronary intervention, and it has not only thinner struts, easier delivery than second-generation drug-eluting stent (2nd DES), but also abluminal biodegradable polymer. Clinical superiority of 3rd DES has been demonstrated compared to 1st and 2nd DESs. However, pathological response after 3rd DES implantation remains unclear. Purpose Pathological study of coronary artery after 3rd DES implantation have not been reported as far as we have referred to the previous studies. This study aimed to examine the initial tissue response after 3rd DES and 2nd DES implantation within one year. Methods Using specimens obtained by autopsy, we compared the histology between 3rd DES (n=3, 8 histological sections) and 2nd DES (n=6, 41 histological sections) lesions within 1 year after stent implantation to evaluate early tissue reaction. Stent segments were fixed with 10% buffered formalin and embedded in plastic, followed by hematoxylin–eosin, Masson's trichrome and elastica van Gieson. Ratio of covered stent struts by neointima was calculated. The thickness of neointima and the area of fibrin deposition were morphometrically evaluated. The degree of inflammation around struts was examined semi-quantitatively (score 0–3). Results The ratio of covered struts and thickness of neointima of 3rd DES were 0.84±0.04 and 68.2±10.3μm, while those of 2nd DES were 0.69±0.05 and 30.4±4.8μm respectively. The inflammation score was similar between two groups (1.00±0.14 vs. 1.02±0.16). The area of fibrin deposition around the struts was larger in 3rd DES compared with 2nd DES (1276.6±490.3μm2 vs. 658.0±173.4μm2). These results suggest that the 3rd DES may obtain prompt as well as rich covering of struts in the initial term after DES implantation. Although the biological feature of the polymers in 3rd and 2nd DESs is different, the inflammatory responses after both 3rd and 2nd DESs implantation were similar, at least within one year after deployment. The degree of inflammation was mild, less than approximately 50 inflammatory cells (score 1) around the struts. Conclusions Our pathological analysis showed advanced healing process in 3rd DES compared with 2nd DES lesions in the viewpoint of strut coverage by neointima. Observation of long-term pathological response may be required to evaluate the superiority of bioabsorbable polymer in 3rd DES.

P2800Impact of plaque vulnerability on vascular response after implantation of two types of biodegradable-polymer drug-eluting stent: coronary angioscopic study

Abstract Background Vascular response after drug-eluting stent (DES) implantation depends not only on stent design but also on vulnerability of target coronary lesions. In this study, non-obstructive coronary angioscopy (CAS) revealed vascular response after two types of biodegradable polymer (BP) DES implantation into patients with acute coronary syndrome (ACS) or stable angina pectoris (SAP). Methods Eighteen Nobori BP biolimus-eluting stents (BP-BES) were successfully implanted into 15 patients (9 ACS and 9 SAP lesions). Twenty-three Ultimaster BP sirolimus-eluting stents (BP-SES) were implanted into 16 patients (6 ACS and 17 SAP lesions). At one year after stenting, CAS semi-quantified degree of neointimal stent coverage (NSC) into 4 grades (0, no coverage; 1, thin coverage; 2, thick coverage; 3, embedded in thick neointima and invisible). When NSC through a stent was composed of plural grades, CAS determined dominant, maximum and minimum NSC grades. Heterogeneity index was defined as subtraction of minimum from maximum grade. CAS also semi-quantified degree of yellow plaques (YP) into 3 grades (0, light; 1, dense; 2, glittering yellow). CAS detected presence of in-stent mural thrombi (ISMT). Results At one year after BP-BES implantation: 1) There was no significant difference with regards to dominant NSC between ACS and SAP lesions (1.00±0.50 vs. 0.89±0.60); 2) Heterogeneity index was greater in ACS than in SAP (1.22±0.44 vs. 0.67±0.50, P=0.02); 3) YP grade was greater in ACS than in SAP (1.89±0.33 vs. 1.00±1.00, P=0.02); and 4) We found one ISMT in ACS lesions and two ISMT in SAP lesions. At one year after BP-SES implantation: 1) There was neither significant difference between ACS and SAP lesions with regards to dominant NSC (1.67±1.21 vs. 1.53±1.01), with regards to heterogeneity index (0.50±0.55 vs. 0.35±0.49), nor with regards to YP grade (1.33±1.51 vs. 0.88±0.99); and 2) We found ISMT neither in ACS nor in SAP lesions. Conclusions For BP-SES implantation, vascular response at ACS lesions was similar to SAP lesions. Even one year after BP-BES implantation, however, plaque vulnerability appeared to remain in ACS lesions.

P4143IL-6 production in the vascular adventitia and adventitia-media-crosstalk in neointima formation

Abstract Background The aim of this study was to analyze the impact of the adventitial layer on vascular remodeling processes and to define the underlying cellular mechanisms. Methods and results Morphometric analysis of human coronary arteries and of murine femoral arteries at several times following vascular intervention revealed a significant correlation of neointimal and adventitial thickening (R2=0.6845, P&lt;0.001 for human samples; R2=0.6845, P&lt;0.001 for human samples. Immunohistochemical staining for the proliferation marker Ki-67 was performed 7, 14, and 21 days following injury of the murine femoral artery. Formation of a neointimal lesion at 21 days was preceded by high adventitial proliferation rates at 7 and 14 days (85.00±6.041 Ki67+adventitial cells vs. 5.118±0.633 Ki-67+neointimal cells at 7d, P&lt;0.0014; 28.80±5.240 Ki-67+adv. cells vs. 19.40±2.468 Ki-67+neoint. cells at 14d, P&lt;0.006, n=17). Complete removal of the adventitial layer prevented neointima formation, attributing pivotal importance to the adventitial layer (luminal stenosis: 71.73±3.77% vs. 7.44±1.71%, n=5, P&lt;0.0001). Re-transplantation of the aortic adventitia of ubiquitously GFP expressing C57BL/6-Tg (CAG-EGFP)1Osb/Jmice around the medial vascular layer of the femoral artery where the native adventitia has been removed completely restored neointima formation. Importantly, only very view GFP+cells were present in the neointimal layer, indicating that a direct contribution of adventitial cells to the neointimal lesion represents an extremely rare event. To investigate a potential paracrine effect of the activated adventitial layer, we explanted adventitial transplants 14 days following injury and transplantation and incubated the respective samples in serum-free media for 24 hours. BrdU incorporation assays and scratch wound assays revealed significantly increased proliferation and migration rates of human coronary artery SMCs in response to the supernatant of adventitial transplants compared to the supernatant of control samples. Further secretome analyses of the same adventitial supernatants identified predominantly interleukin (IL)-6 to trigger SMC proliferation and migration. Accordingly, serum-free media incubated with adventitial grafts of IL-6−/− mice prevented SMC proliferation and migration. Transplantation of the adventitia of IL-6−/− mice into C57BL/6J wild type mice was not sufficient to trigger neointima formation. Plain old balloon angioplasty, bare metal stent implantation, or drug-eluting stent implantation in swine coronary arteries and analysis for Ki-67+ cell counts supported the hypothesis in the large animal model and a more clinical setting. Conclusion Acute vascular injury is followed by an expansion of cytokine-producing adventitial cells, whose paracrine function and especially whose release of IL-6 is essential for the subsequent induction of the proliferation and migration of local SMC and thus for neointima formation.

P5613Proportional relationship between early mobilization of bone marrow progenitor cells and the extent of vascular injury during coronary stenting: insights on the role of systemic mechanisms of vascular

Abstract Background The role of circulating progenitor cells (CPCs) on vascular repair after everolimus-eluting stent (EES) implantation is largely unknown. Objectives The aim of the study was to investigate the quantitative and temporal variations of CPCs levels after EES implantation, and its relationship with the degree of peri-procedural vascular damage, stent healing and neointimal hyperplasia, as measured by optical coherence tomography (OCT). Methods In a consecutive series of patients with stable coronary artery disease undergoing stent implantation CPC subpopulations (CD34+/CD45low, CD133+/CD45low, CD34/KDR/CD45low, CD133/KDR/CD45low) were evaluated using a flow cytometry technique at baseline, 1 and 4 weeks. OCT evaluation was performed immediately after stent implantation to quantify stenting-related injury, and at 9-month follow-up to assess mid-term vascular response. Results Twenty patients (mean age 66±9 years; 80%male) with 24 stenoses treated with EES were included in the study. Vascular injury score was associated with the increase of CD133+/KDR/CD45 low at 1-week (β0.28 [95% CI0.15; 0.41], p&lt;0.001) and with the maximum neointimal thickness at 9-month follow-up (β0.008 [95% CI-0.0004; 0.002]:p=0.04). Mean neointimal area at 9-month was associated with the increase in the number of CD34+/CD45low at 1 week (β0.029 [95% CI0.025;-0.033]; p&lt;0.0001). Inverse relationships between the number of uncoated and apposed struts at 9-month and the 1-week delta values of CD34/KDR/CD45low and CD133/KDR/CD45low (β-4.49 [95% CI-8.17;-0.82]; p=0.017 and β −12.53 [95% CI: −22.17; −2.90]; p=0.011, respectively) were also found. Conclusion Long-term vascular healing after EES implantation is modulated by early changes in levels of CPC subpopulations. This systemic response is proportional to the extent of vessel wall injury. Early mobilization of CPCs influences mid-term strut coverage and the development of neointimal hyperplasia. Acknowledgement/Funding Dr Jimenez-Quevedo is a recipient of the ISCIII (Instituto de Salud Carlos III) grant “Fondo de Investigaciόn Sanitaria” (PI11/00299) to perform this

Preclinical Evaluation of the Accero Stent: Flow Remodelling Effect on Aneurysm, Vessel Reaction and Side Branch Patency.

It has been hypothesized that microstents which are used to prevent coil protrusion in the treatment of cerebral aneurysms may have flow diverting and therefore occlusive effects. In a rabbit elastase aneurysm model, we investigated the aneurysm occlusion rate and vessel reaction of a braided Accero stent prototype with porosity in the lower range of other available (non-flow-diverter) microstents. Ten aneurysms were induced the right subclavian artery in New Zealand white rabbits and treated with the Accero stent prototype. In each subject, a second stent was implanted in the abdominal aorta to cover the origins of branch arteries. Angiographic follow-up and explantation of the devices and aneurysms for histological analysis were performed after 3months (n = 5) and 6months (n = 5). Grades I (< 50%) and II (> 50%) occlusion rates were observed in 9 (90%) and 1 (10%) of ten aneurysms treated with the stent device. The mean reduction in contrast filling at 6months was 42.1% (p = .02). Neointima thickness was significantly higher in the subclavian artery than in the abdominal aorta after 3 (p = .03), whereas not after 6months (p = .1). No cases of inadequate wall apposition, branch artery occlusion or stent thrombosis were observed. The present study showed flow remodelling properties of the device prototype with progredient aneurysm occlusion. A larger in vivo study with induced aneurysm should be done to confirm these results.

Location-Specific Comparison Between a 3D In-Stent Restenosis Model and Micro-CT and Histology Data from Porcine In Vivo Experiments

BackgroundCoronary artery restenosis is an important side effect of percutaneous coronary intervention. Computational models can be used to better understand this process. We report on an approach for validation of an in silico 3D model of in-stent restenosis in porcine coronary arteries and illustrate this approach by comparing the modelling results to in vivo data for 14 and 28 days post-stenting.MethodsThis multiscale model includes single-scale models for stent deployment, blood flow and tissue growth in the stented vessel, including smooth muscle cell (SMC) proliferation and extracellular matrix (ECM) production. The validation procedure uses data from porcine in vivo experiments, by simulating stent deployment using stent geometry obtained from micro computed tomography (micro-CT) of the stented vessel and directly comparing the simulation results of neointimal growth to histological sections taken at the same locations.ResultsMetrics for comparison are per-strut neointimal thickness and per-section neointimal area. The neointimal area predicted by the model demonstrates a good agreement with the detailed experimental data. For 14 days post-stenting the relative neointimal area, averaged over all vessel sections considered, was 20 ± 3% in vivo and 22 ± 4% in silico. For 28 days, the area was 42 ± 3% in vivo and 41 ± 3% in silico.ConclusionsThe approach presented here provides a very detailed, location-specific, validation methodology for in silico restenosis models. The model was able to closely match both histology datasets with a single set of parameters. Good agreement was obtained for both the overall amount of neointima produced and the local distribution. It should be noted that including vessel curvature and ECM production in the model was paramount to obtain a good agreement with the experimental data.

Neointimal coverage after second generation drug-eluting stent implantation has a relationship with pre-existing atherosclerotic lesion characteristics.

The relationship between preexisting atherosclerotic lesion characteristics and neointimal thickness after second-generation drug-eluting stent (DES) placement is still unknown. Thus, we evaluated that relationship using optical coherence tomography (OCT).A single-center, retrospective, observational study was conducted. Patients with stable angina or asymptomatic myocardial ischemia who received percutaneous coronary intervention for a de novo lesion using a second-generation DES under frequency domain OCT guidance and underwent follow-up coronary angiography (CAG) and OCT between December 2010 and December 2015 were included. The relationship between the neointimal thickness on the stent strut and the plaque characteristics was retrospectively evaluated using OCT immediately after stent implantation and at the time of follow-up CAG.We analyzed 3459 struts from 20 stents in 15 patients. The mean follow-up period was 264 days. In the follow-up study, no angiographic in-stent restenosis was found. Of the 3459 struts, 3315 (95.8%) were covered with neointima. The median neointimal thicknesses of the stent struts on calcified, fibrous, and lipid-rich lesions were 20 μm (interquartile range [IQR], 10–50 μm), 70 μm (40–140 μm; P < .001), and 90 μm (50–170 μm; P < .001), respectively. These differences were observed regardless of the type of second-generation DES used.Most of the stent struts were covered with neointima. The neointimal thickness after the second-generation DES implantation had a close relationship with the preexisting atherosclerotic lesion characteristics. In this study, we found differences in arterial healing processes due to underlying plaque; therefore, evaluating the lesion characteristics by OCT may predict the risk for future restenosis and thrombosis.

Sirtuin 3 Therapy Attenuates Aging Expression, Oxidative Stress Parameters, and Neointimal Hyperplasia Formation in Vein Grafts

Vein graft (VG) failure due to neointimal hyperplasia remains an important and unresolved problem in cardiovascular surgery. Sirtuin3 (SIRT3) is associated with oxidative stress and lifespan. We aimed to measure SIRT3 expression in the veins of humans and rats during aging, explore the inhibitory effects of SIRT3 on vascular smooth muscle cell (VSMC) proliferation and neointimal hyperplasia in VGs, and investigate the underlying mechanisms. SIRT3 mRNA and protein levels in saphenous veins of young and older humans and in veins of young and old rats were measured by quantitative real-time polymerized chain reaction (PCR) and Western blot analysis. Young and old male rats were randomized to the control (control), graft (graft), adenovirus-encoding green fluorescent protein (Ad-GFP), and adenovirus encoding SIRT3 (Ad-SIRT3) groups. At 7days after operation, the mRNA and protein levels of SIRT3 and endothelial nitric oxide synthase (eNOS) were measured by quantitative real-time PCR and Western blot analysis. The mRNA levels and enzyme activity of manganese superoxide dismutase (MnSOD) and catalase (CAT) were measured by quantitative real-time PCR and enzymatic activity assay kits, and total nitric oxide (NO) levels were measured by biochemical assay kits. Histomorphometric analysis of VGs and immunohistochemical staining for proliferative activity were performed at 4weeks after operation. The hemodynamic parameters of the VGs were also measured by ultrasonic examination. SIRT3 mRNA and protein levels were lower in older human and rat veins than in younger human and rat veins. Ad-SIRT3 treatment significantly increased the expression and concentration of SIRT3, MnSOD, CAT, eNOS, and NO in VGs at 7days after operation. Ad-SIRT3 gene transfer reduced the neointimal thickness and neointimal area/media area ratio in the VGs of the Ad-SIRT3 groups compared with the graft and Ad-GFP groups, especially in old rats. Proliferative activity was lower in the Ad-SIRT3 groups than in the other groups. The hemodynamic parameters of VGs were obviously improved in the Ad-SIRT3 groups. SIRT3 expression decreases in the veins of humans and rats during aging. Furthermore, SIRT3 overexpression can significantly reduce VSMC proliferation and neointimal hyperplasia in VGs. Local intravenous delivery of adenovirus encoding SIRT3 may be a promising gene therapy for preventing VG failure.

Abstract 492: Adipolin/C1q/Tnf-related Protein 12 reduces Neointimal Formation And Atherosclerotic Lesion Development By Modulation Of Macrophage Inflammatory Response And Endothelial Cell Function

Objectives: Obesity is causally linked to the progression of vascular disorders including atherosclerosis and post-angioplasty restenosis. Recently, we identified adipolin/C1q/Tnf-related protein 12 as an insulin sensitizing adipokine,which is downregulated in rodent models of obesity. Here, we investigated whether adipolin modulates the development of vascular diseases using loss-of-function genetic manipulations. Methods and Results: Under basal conditions, no significant differences were observed in body weight, organ weights, blood pressure and fasting plasma glucose levels between wild-type (WT) and adipolin-knockout (APL-KO) mice. APL-KO mice exhibited enhanced neointimal thickening after femoral artery injury compared with WT mice, which was accompanied by increased expression levels of pro-inflammatory mediators including tumor necrosis factor (TNF)-α and interleukin (IL)6 in injured vessels. Conversely, systemic administration of adipolin to WT mice using adenoviral vector expression systems ameliorated injury-induced neointimal thickening and inflammatory response. APL-KO mice also showed impaired re-reendothelialization after vascular injury compared with WT mice. Furthermore, adipolin deficiency increased atherosclerotic lesion area in an apolipoprotein E-knockout mouse model, which was accompanied by enhanced inflammatory response in the arterial vessel walls. Treatment of cultured macrophages with recombinant adipolin protein attenuated lipopolysaccharide-stimulated expression of inflammatory mediators, such as TNF-α and IL6. The anti-inflammatory actions of adipolin in macrophages were reversed by inhibition of transforming growth factor-β receptor II (TGF-βRII)/Smad2 signaling. In addition, treatment of human umbilical vein endothelial cells with adipolin protein promoted migratory activity and reduced serum starvation-induced apoptosis. Conclusion: These data suggest that adipolin suppresses injury-induced neointimal formation and atherosclerosis development through its abilities to modulate macrophage inflammatory responses and endothelial cell functions in vascular walls.

The relationship of lumen diameter and neointimal hyperplasia with inflation pressure.

The mechanical stretch injury imposed by the intravascular intervention contributes to neointimal hyperplasia. Lessening of this damage without the compromise of luminal dilation could be an alternative way to alleviate restenosis. We aimed to assess the relationship of lumen diameter and neointimal hyperplasia with inflation pressure using color Doppler ultrasound-guided balloon dilation. The anteroposterior diameter of the given aortic segment in rabbits was measured by ultrasonography to ensure the similar original diameter. Then they were assigned into three groups with the inflation force at 1, 5, 10atmosphere pressure (atm), respectively. Balloon dilation and injury of the given aortic segment were performed. Two weeks later, all rabbits were euthanized for histologic evaluation. After operation, the lumen diameter of each group enlarged significantly (P< 0.05) with a similar rate of change. However, neointimal area, circumference and hepatocyte growth factor (HGF) positive cells in group with 1atm were significantly less than those of the other two (P< 0.05). Maximal neointima thickness increased significantly with the elevation of the inflation pressure (P< 0.05). Based on sufficient dilation of the balloon, the balloon inflated with the less pressure caused the similar increase in lumen diameter as the higher pressure but the less neointimal hyperplasia and HGF positive cells.

Healing of Aneurysm after Treatment Using Flow Diverter Stent : Histopathological Study in Experimental Canine Carotid Side Wall Aneurysm

ObjectiveDespite widespread use of flow diverters (FDs) to treat aneurysms, the exact healing mechanism associated with FDs remains poorly understood. We aim to describe the healing process of aneurysms treated using FDs by demonstrating the histopathologic progression in a canine aneurysm model. MethodsTwenty-one side wall aneurysms were created in common carotid artery of eight dogs and treated with two different FDs. Angiographic follow-ups were done immediately after placement of the device, 4 weeks and 12 weeks. At last follow-up, the aneurysm and the device-implanted parent artery were harvested. ResultsHistopathologic findings of aneurysms at 4 weeks follow-up showed intra-aneurysm thrombus formation in laminating fashion, and neointimal thickening at the mid-segment of aneurysm. However, there are inhomogenous findings in aneurysms treated with the same type of FD showing same angiographic outcomes. At 12 weeks, aneurysms of complete and near-complete occlusion revealed markedly shrunken aneurysm filled with organized connective tissues with thin neointima. Aneurysms of incomplete occlusion at 12 weeks showed small amount of organized thrombus around fringe neck and large empty space with thick neointmal formation. Neointimal thickness and diameter stenosis was not significantly different between the groups of FD specification and follow-up period. ConclusionIntra-aneurysmal thrombus formation and organization seem to be an important factor for the complete occlusion of aneurysms treated using the FD. Neointimal formation could occur along the struts of the FD independently of intra-aneurysmal thrombus formation. However, neointimal formation could not solely lead to complete aneurysm healing.

Early strut protrusion and late neointima thickness in the Absorb bioresorbable scaffold: a serial wall shear stress analysis up to five years.

The aim of the study was to evaluate the effect of strut protrusion (SP) on wall shear stress (WSS) and neointimal growth (NG) one and five years after implantation of an Absorb bioresorbable vascular scaffold. Eight patients were selected from a first-in-man study. Following three-dimensional (3D) reconstruction of coronaries, WSS was quantified using Newtonian steady-flow simulation in each cross-section at 5° subunits (sectors) of the circumferential luminal surface. At one year, neointimal thickness (NT) was measured by optical coherence tomography (OCT) and correlated to WSS and SP post procedure. Median SP was 112.9 (90.8, 133.1) µm post implantation. Post procedure, a logarithmic inverse relationship between SP and post-implantation WSS (r=-0.425, p<0.001; correlation coefficients in a range from -0.143 to -0.553) was observed, whereas a correlation between baseline logarithm-transformed WSS (log-WSS) and NT (r=-0.451, p<0.001; correlation coefficients ranged from -0.140 to -0.662) was documented at one year. Mixed-effects analysis between baseline log-WSS and NT at follow-up yielded a slope of 30 µm/ln Pascal (Pa) and a y-intercept of 98 µm. As a result of NG, median flow area decreased from 6.91 (6.53, 7.48) mm2 post implantation to 5.65 (5.47, 6.02) mm2 at one-year follow-up (p=0.01) and to 5.75±1.37 mm2 at five-year follow-up (p=0.024). However, the vessel surface exposed to low WSS (<1 Pa) decreased significantly post procedure (42%) to one year (35.9%) and five years (15.2%) (p-overall <0.0001). SP disturbs laminar flow, creates regions of low WSS (<1.0 Pa) that are associated with NG and lumen area reduction. Low WSS post implantation reduced significantly at long-term follow-up. Thin struts with effective embedment would substantially reduce NG and accelerate homogenisation of WSS towards physiological values.

Prevention of in-stent restenosis with endothelial progenitor cell (EPC) capture stent placement combined with regional EPC transplantation: An atherosclerotic rabbit model.

Even with drug-eluting stents, the risk of in-stent restenosis (ISR) remains high. The goal of this study was to investigate the use of an endothelial progenitor cell (EPC) capture stent plus regional EPC transplantation to reduce the ISR rate. Endothelial progenitor cell capture stents were fabricated using fibrin gel and anti-CD34 plus anti-VEGFR-2 dual antibodies. Twenty male New Zealand white rabbits established as an atherosclerotic model were randomly divided into two groups: group 1 (n = 10), in which EPC capture stents were deployed into the right iliac artery; and group 2 (n = 10), in which sirolimus-eluting stents were placed. In both groups, EPCs were transplanted into target vessels beyond the stents, with outflow blocked. Radiologic-pathologic correlation outcomes were reviewed after 2 months. The technical success rate of EPC capture stent placement plus EPC transplantation was 100%. The ISR rate in group 1 was lower than in group 2 (1/10 vs. 4/10; p > 0.05). Minimal luminal diameters were larger in group 1 than in group 2 (computed tomographic angiography, 1.85 ± 0.15 mm vs. 1.50 ± 0.20 mm; duplex ultrasound, 1.90 ± 0.10 mm vs. 1.70 ± 0.30 mm; p > 0.05). Transplanted EPCs were tracked positively only in group 1. Pathologic analysis demonstrated neointimal hyperplasia thickness of 0.21 ± 0.09 mm in group 1 vs. 0.11 ± 0.07 mm in group 2 (p < 0.05). Endothelial progenitor cell capture stent placement plus local EPC transplant decreases the ISR rate through thrombosis reduction rather than through neointimal hyperplasia inhibition.