Topographic distribution of inflammation factors in a healing aneurysm.

BACKGROUND: Healing of intracranial aneurysms following endovascular treatment relies on the organization of early thrombus into mature scar tissue and neointima formation. Activation and deactivation of the inflammation cascade plays an important role in this process. In addition to timely evolution, its topographic distribution is hypothesized to be crucial for successful aneurysm healing. METHODS: Decellularized saccular sidewall aneurysms were created in Lewis rats and coiled. At follow-up (after 3 days (n = 16); 7 days (n = 19); 21 days (n = 8)), aneurysms were harvested and assessed for healing status. In situ hybridization was performed for soluble inflammatory markers (IL6, MMP2, MMP9, TNF-α, FGF23, VEGF), and immunohistochemical analysis to visualize inflammatory cells (CD45, CD3, CD20, CD31, CD163, HLA-DR). These markers were specifically documented for five regions of interest: aneurysm neck, dome, neointima, thrombus, and adjacent vessel wall. RESULTS: Coiled aneurysms showed enhanced patterns of thrombus organization and neointima formation, whereas those without treatment demonstrated heterogeneous patterns of thrombosis, thrombus recanalization, and aneurysm growth (p = 0.02). In coiled aneurysms, inflammation markers tended to accumulate inside the thrombus and in the neointima (p < 0.001). Endothelial cells accumulated directly in the neointima (p < 0.0001), and their presence was associated with complete aneurysm healing. CONCLUSION: The presence of proinflammatory cells plays a crucial role in aneurysm remodeling after coiling. Whereas thrombus organization is hallmarked by a pronounced intra-thrombotic inflammatory reaction, neointima maturation is characterized by direct invasion of endothelial cells. Knowledge concerning topographic distribution of regenerative inflammatory processes may pave the way for future treatment modalities which enhance aneurysm healing after endovascular therapy.

Zoledronate alters natural progression of tissue-engineered vascular grafts.

Macrophages are a critical driver of neovessel formation in tissue-engineered vascular grafts (TEVGs), but also contribute to graft stenosis, a leading clinical trial complication. Macrophage depletion via liposomal delivery of clodronate, a first-generation bisphosphonate, mitigates stenosis, but simultaneously leads to a complete lack of tissue development in TEVGs. This result and the associated difficulty of utilizing liposomal delivery means that clodronate may not be an ideal means of preventing graft stenosis. Newer generation bisphosphonates, such as zoledronate, may have differential effects on graft development with more facile drug delivery. We sought to examine the effect of zoledronate on TEVG neotissue formation and its potential application for mitigating TEVG stenosis. Thus, mice implanted with TEVGs received zoledronate or no treatment and were monitored by serial ultrasound for graft dilation and stenosis. After two weeks, TEVGs were explanted for histological examination. The overall graft area and remaining graft material (polyglycolic-acid) were higher in the zoledronate treatment group. These effects were associated with a corresponding decrease in macrophage infiltration. In addition, zoledronate affected the deposition of collagen in TEVGs, specifically, total and mature collagen. These differences may be, in part, explained by a depletion of leukocytes within the bone marrow that subsequently led to a decrease in the number of tissue-infiltrating macrophages. TEVGs from zoledronate-treated mice demonstrated a significantly greater degree of smooth muscle cell presence. There was no statistical difference in graft patency between treatment and control groups. While zoledronate led to a decrease in the number of macrophages in the TEVGs, the severity of stenosis appears to have increased significantly. Zoledronate treatment demonstrates that the process of smooth muscle cell-mediated neointimal hyperplasia may occur separately from a macrophage-mediated mechanism.

Immunomodulation of IL-33 and IL-37 with Vitamin D in the Neointima of Coronary Artery: A Comparative Study between Balloon Angioplasty and Stent in Hyperlipidemic Microswine.

Inflammation is a major contributor to the development and progression of atherosclerosis. Interleukin (IL)-33 and IL-37, members of the IL-1 family, modulate inflammation, with IL-33 having a pro-inflammatory effect and IL-37 having anti-inflammatory properties. IL-37 is constitutively expressed at low levels but upregulated in inflammatory contexts. The aim of this study was to evaluate the effect of vitamin D on the expression of IL-33, IL-37, macrophages, and caspase-1 in the neointimal tissue of coronary artery in Yucatan microswine with vitamin D deficient, sufficient, and supplemented status. The intimal injury was induced by balloon angioplasty and stenting in the coronary artery, and tissues were harvested after 6 months. The expression of various proteins of interest was evaluated by immunostaining. Increased expression of IL-33 and IL-37 in the neointimal tissue of the vitamin D deficient, as compared to the sufficient and supplemented microswine, as revealed by histological evaluation and semi-quantitative analysis, suggested the immunomodulatory effect of vitamin D on the expression of IL-33 and IL-37. The minimal expression or absence of IL-33 and IL-37 expression in stented arteries is suggestive of an attenuated inflammatory response in stented arteries, compared to balloon angioplasty. The decreased IL-33 expression in the sufficient and supplemented microswine could be a potential mechanism for controlling the inflammatory process and neointima formation leading to attenuated luminal narrowing of the coronary artery. Overall, these results support supplementation of vitamin D to attenuate inflammation, neointima formation, and restenosis.

Patterns of Neointima Formation After Coil or Stent Treatment in a Rat Saccular Sidewall Aneurysm Model.

BACKGROUND AND PURPOSE: Endovascular aneurysm treatment relies on a biological process, including cell migration for thrombus organization and growth of a neointima. To better understand aneurysm healing, our study explores the origin of neointima-forming and thrombus-organizing cells in a rat saccular sidewall aneurysm model. METHODS: Saccular aneurysms were transplanted onto the abdominal aorta of male Lewis rats and endovascularly treated with coils (n=28) or stents (n=26). In 34 cases, GFP+ (green fluorescent protein)-expressing vital aneurysms were sutured on wild-type rats, and in 23 cases, decellularized wild-type aneurysms were sutured on GFP+ rats. Follow-up at 3, 7, 14, 21, and 28 days evaluated aneurysms by fluorescence angiography, macroscopic inspection, and microscopy for healing and inflammation status. Furthermore, the origin of cells was tracked with fluorescence histology. RESULTS: In animals with successful functional healing, histological studies showed a gradually advancing thrombus organization over time characterized by progressively growing neointima from the periphery of the aneurysm toward the center. Cell counts revealed similar distributions of GFP+ cells for coil or stent treatment in the aneurysm wall (54.4% versus 48.7%) and inside the thrombus (20.5% versus 20.2%) but significantly more GFP+ cells in the neointima of coiled (27.2 %) than stented aneurysms (10.4%; P=0.008). CONCLUSIONS: Neointima formation and thrombus organization are concurrent processes during aneurysm healing. Thrombus-organizing cells originate predominantly in the parent artery. Neointima formation relies more on cell migration from the aneurysm wall in coiled aneurysms but receives greater contributions from cells originating in the parent artery in stent-treated aneurysms. Cell migration, which allows for a continuous endothelial lining along the parent artery's lumen, may be a prerequisite for complete aneurysm healing after endovascular therapy. In terms of translation into clinical practice, these findings may explain the variability in achieving complete aneurysm healing after coil treatment and the improved healing rate in stent-assisted coiling.

Neointimal Hyperplasia.

Neointimal hyperplasia is a physiologic healing response to injury to the blood vessel wall, involving all the three arterial layers and it occurs in the presence of internal (endovascular) or external (surgical) injury. It is a highly complex process involving several tissues (perivascular, vessel wall, and blood) and numerous cell lineages with multiple molecular signaling networks. So, there is a number of possible targets for inhibition of this process. There are known risk factors for Intimal Hyperplasia, such as diabetes, female gender, presence of systemic inflammation, type of arteries treated, types of surgical and endovascular materials, presence of turbulent flow and genetic status. The present paper discusses the pathophysiology of neointimal hyperplasia and the strategies to prevention and treatment of it.

The Role of MicroRNA-21 in Venous Neointimal Hyperplasia: Implications for Targeting miR-21 for VNH Treatment.

The molecular mechanism of hemodialysis access arteriovenous fistula (AVF) failure due to venous neointimal hyperplasia (VNH) is not known. The role of microRNA-21 (miR-21) in VNH associated with AVF failure was investigated by performing in vivo and in vitro experiments. In situ hybridization results revealed that miR-21 expression increased and was associated with fibroblasts in failed AVFs from patients. In a murine AVF model, qRT-PCR gene expression results showed a significant increase in miR-21 and a decrease in miR-21 target genes in graft veins (GVs) compared to contralateral veins in mouse AVF. miR-21 knockdown in GVs was performed using a lentivirus-mediated small hairpin RNA (shRNA), and this improved AVF patency with a decrease in neointima compared to control GVs. Moreover, loss of miR-21 in GVs significantly decreased the Tgfß1, Col-Ia, and Col-Iva genes. Immunohistochemistry demonstrated a significant decrease in myofibroblasts and proliferation with an increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining in miR-21-knockdown vessels, along with a decrease in hypoxia-inducible factor-1 alpha (HIF-1α) and phospho-SMAD2 (pSMAD-2) and phospho-SMAD3 (pSMAD-3) and an increase in phosphatase and tensin homolog (PTEN) staining. Hypoxic fibroblast knockdown for miR-21 showed a significant decrease in Tgfß-1 expression and pSMAD-2 and -3 levels and a decrease in myofibroblasts. These results indicate that miR-21 upregulation causes VNH formation by fibroblast-to-myofibroblast differentiation.

Copper-Based SURMOFs for Nitric Oxide Generation: Hemocompatibility, Vascular Cell Growth, and Tissue Response.

A coating that can generate nitric oxide (NO) for surface modification of cardiovascular stents with adaptable NO release is an efficient approach to prevent thrombosis and neointimal hyperplasia. Herein, we prepared a copper-based surface-attached metal-organic framework (Cu-SURMOFs) of copper(II) benzene-1,3,5-tricarboxylate (CuBTC) using a layer-by-layer assembly method (LBL) for NO generation on the surface of alkali-activated titanium. It was easy to control surface chemistry and NO release by changing the number of LBL deposition cycles. The obtained CuBTC coating was characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis and was able to decompose endogenous S-nitrosoglutathoine (GSNO) to catalytically produce NO. The resulting NO flux increased with increased deposition cycles. The coating prepared with 10 cycles of deposition showed ideal NO release and promoted proliferation of endothelial cells, suppressed growth of smooth muscle cells and macrophages, and inhibited platelet adhesion and activation. Further evaluation of thrombogenicity in an arteriovenous shunt model showed that the CuBTC coating had great ability to prevent thrombosis, and in vivo implantation of CuBTC-coated titanium wire demonstrated a significant inhibition of intimal hyperplasia. The results showed that use of copper-based SURMOFs could be a promising strategy for the surface modification of cardiovascular stents.

Vascular endothelial growth factor-modified macrophages accelerate reendothelialization and attenuate neointima formation after arterial injury in atherosclerosis-prone mice.

Vascular endothelial growth factor (VEGF) is a promising molecule for cardiovascular diseases therapy. But lack of a targeted delivery system limits its translation into clinical application. This study aimed to develop stably overexpressing VEGF macrophages for targeted VEGF delivery to injured arteries and determine their potential for repairing of the damaged endothelium. Wire-induced carotid artery injury model was established in atherosclerosis-prone mice. It was observed that the VEGF-modified macrophages were recruited to the site of vascular injury and incorporated into new endothelium formation. VEGF-modified macrophages therapy accelerated reendothelialization and attenuated neointima formation. The VEGF protein level in tissues of injured arteries treated with VEGF-modified macrophages was increased. The upregulated C-C chemokine receptor type 5 (CCR5) and unaltered CCR2 protein levels were verified in VEGF-modified macrophages in vitro. Moreover, enhanced nitric oxide (NO) production in the culture medium of VEGF-modified macrophages was demonstrated. Our results indicated that VEGF-modified macrophages acted as vectors of VEGF targeting injured arteries, promoting the repairing directly by incorporating into new endothelium formation and indirectly by secreting sustainable VEGF and producing NO locally. This study represents a novel therapeutic application of targeted cell therapy with VEGF-modified macrophages for cardiovascular diseases.

Physical exercises decreases thrombus and neointima formation in atherosclerotic mice.

The practice of physical exercise is highly indicated to prevent cardiovascular diseases and is directly related to the improvement of endothelial function and the regulation of arterial blood pressure. The objective of this study was to analyze the effect of physical exercise in vascular remodeling after FeCl3 chemically induced arterial injury on atherosclerotic mice. To analyze the effect of exercises on thrombus formation, LDL receptor-deficient mice were fed for 6 weeks with a high-fat diet and performed or not physical exercises for 2 weeks before the arterial injury. To verify endothelium recovery the animals were exercised or not 2 weeks before the injury, and 3 weeks after it, when the vessels were analyzed. In this work, we observed that physical exercises done only before arterial injury reduced thrombosis time, protected the endothelial layer, promoted the recruitment of CD34 positive progenitor cells, increased the level of eNOS and gelatinases activities and decreased the number of inflammatory cells in the vessel, but do not avoid the growth of neointima. Otherwise exercises done before and continued after injury, increased gelatinase activities, reduced lipid deposition in the aortic arch and prevented neointima formation. Thus, we could conclude that physical exercises are done before and continued after endothelial injury stimulate endothelial recovery by promoting endothelial cell growth, matrix remodeling and decreasing inflammation in the vessel wall.

Exosomes from mesenchymal stem cells expressing miR-125b inhibit neointimal hyperplasia via myosin IE.

Intercellular communication between mesenchymal stem cells (MSCs) and their target cells in the perivascular environment is modulated by exosomes derived from MSCs. However, the potential role of exosome-mediated microRNA transfer in neointimal hyperplasia remains to be investigated. To evaluate the effects of MSC-derived exosomes (MSC-Exo) on neointimal hyperplasia, their effects upon vascular smooth muscle cell (VSMC) growth in vitro and neointimal hyperplasia in vivo were assessed in a model of balloon-induced vascular injury. Our results showed that MSC-Exo were internalised by VSMCs and inhibited proliferation and migration in vitro. Further analysis revealed that miR-125b was enriched in MSC-Exo, and repressed the expression of myosin 1E (Myo1e) by targeting its 3' untranslated region. Additionally, MSC-Exo and exosomally transferred miR-125b repressed Myo1e expression and suppressed VSMC proliferation and migration and neointimal hyperplasia in vivo. In summary, our findings revealed that MSC-Exo can transfer miR-125b to VSMCs and inhibit VSMC proliferation and migration in vitro and neointimal hyperplasia in vivo by repressing Myo1e, indicating that miR-125b may be a therapeutic target in the treatment of vascular diseases.

Inhibition of Neointima Hyperplasia, Inflammation, and Reactive Oxygen Species in Balloon-Injured Arteries by HVJ Envelope Vector-Mediated Delivery of Superoxide Dismutase Gene.

Extracellular superoxide dismutase (EC-SOD) has been implicated in regulation of vascular function but its underlying molecular mechanism is largely unknown. These two-step experiments investigate whether hemagglutinating virus of Japan envelope (HVJ-E) vector-mediated EC-SOD gene delivery might protect against neointima formation, vascular inflammation, and reactive oxygen species (ROS) generation, and also explore cell growth signaling pathways. The first in-vitro experiment was performed to assess the transfection efficacy and safety of HVJ-E compared to lipofectamine®. Results revealed that HVJ-E has higher transfection efficiency and lower cytotoxicity than those of lipofectamine®. Another in-vivo study initially used balloon denudation to rat carotid artery, then delivered EC-SOD cDNA through the vector of HVJ-E. Arterial section with H&E staining from the animals 14 days after balloon injury showed a significant reduction of intima-to-media area ratio in EC-SOD transfected arteries when compared with control (empty vector-transfected arteries) (p < 0.05). Arterial tissue with EC-SOD gene delivery also exhibited lower levels of ROS, as assessed by fluorescent microphotography with dihydroethidium staining. Quantitative RT-PCR revealed that EC-SOD gene delivery significantly diminished mRNA expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1ß (p < 0.05 in all comparisons). An immunoblotting assay from vascular smooth muscle cell (VSMC) cultures showed that the EC-SOD transfected group attenuated the activation of MEK1/2, ERK1/2, and Akt signaling significantly. In conclusion, EC-SOD overexpression by HVJ-E vector inhibits neointima hyperplasia, inflammation, and ROS level triggered by balloon injury. The modulation of cell growth-signaling pathways by EC-SOD in VSMCs might play an important role in these inhibitory effects.

MicroRNA-146a sponge therapy suppresses neointimal formation in rat vein grafts.

The long-term failure of vein grafts due to neointimal hyperplasia remains a difficult problem in cardiovascular surgery. Exploring novel approaches to prevent neointimal hyperplasia is important. MicroRNA-146a (miR-146a) plays an essential role in promoting vascular smooth muscle cell (VSMC) proliferation. Thus, the aim of the present study is to investigate whether adenovirus-mediated miR-146a sponge (Ad-miR-146a-SP) gene therapy could attenuate neointimal formation in rat vein grafts. (Ad-miR-146a-SP) was constructed to transfect cultured VSMCs and grafted veins. To improve the efficiency of transferring the miR-146a sponge gene into the grafted veins, 20% poloxamer F-127 gel incorporated with 0.25% trypsin was used to increase adenovirus contact time and penetration. miR-146a-SP transduction significantly reduced the expression of miR-146a both in cultured VSMCs and vein grafts. miR-146a sponge markedly attenuated VSMC proliferation and migration. Consistent with this, miR-146a sponge gene therapy significantly attenuated neointimal formation and also improved blood flow in the vein grafts. Mechanistically, we identified the Krüppel-like factor 4(KLF4) as a potential downstream target gene of miR-146a in vein grafts. Our data show that miR-146a sponge gene therapy could effectively reduce miR-146a activity and attenuate neointimal formation in vein grafts, suggesting its potential therapeutic application for prevention of vein graft failure. © 2018 IUBMB Life, 71(1):125-133, 2019.

Local adventitial anti-angiogenic gene therapy reduces growth of vasa-vasorum and in-stent restenosis in WHHL rabbits.

BACKGROUND: Antiproliferative drugs in drug eluting stents (DES) are associated with complications due to impaired re-endothelialization. Additionally, adventitial neovascularization has been suggested to contribute to in-stent restenosis (ISR). Since Vascular Endothelial Growth Factors (VEGFs) are the key mediators of angiogenesis, we investigated feasibility and efficacy of local gene therapy for ISR utilizing soluble decoy VEGF receptors to reduce biological activity of adventitial VEGFs. METHOD: Sixty-nine adult WHHL rabbit aortas were subjected to endothelial denudation. Six weeks later catheter-mediated local intramural infusion of 1.5x10e10 pfu adenoviruses encoding soluble VEGF Receptor-1 (sVEGFR1), sVEGFR2, sVEGFR3 or control LacZ and bare metal stent implantation were performed in the same aortic segment. Marker protein expression was assessed at 6d in LacZ cohort. Immunohistochemistry, morphometrical analyses and angiography were performed at d14, d42 and d90. RESULTS: Transgene expression was localized to adventitia. All decoy receptors reduced the size of vasa-vasorum at 14d, AdsVEGFR2 animals also had reduced density of adventitial vasa-vasorum, whereas AdsVEGFR3 increased the density of vasa-vasorum. At d42, AdsVEGFR1 and AdsVEGFR2 reduced ISR (15.7 ±â€¯6.9% stenosis, P < 0.01 and 16.5 ±â€¯2.7%, P < 0.05, respectively) vs. controls (28.3 ±â€¯7.6%). Moreover, AdsVEGFR-3 treatment led to a non-significant trend in the reduction of adventitial lymphatics at all time points and these animals had significantly more advanced neointimal atherosclerosis at 14d and 42d vs. control animals. CONCLUSIONS: Targeting adventitial neovascularization using sVEGFR1 and sVEGFR2 is a novel strategy to reduce ISR. The therapeutic effects dissipate at late follow up following short expression profile of adenoviral vectors. However, inhibition of VEGFR3 signaling accelerates neoatherosclerosis.

Overexpression of Hepatocyte Growth Factor mRNA Induced by Gene Transfer Attenuates Neointimal Hyperplasia After Balloon Injury.

Hepatic growth factor (HGF) has been widely used in studies on arterial remodeling after injury, and results turn out to be inconsistent. The changes of endogenous HGF expression after injury also remain controversial. This study clarified the role of exogenous human HGF (hHGF) gene transfer in neointimal hyperplasia and investigated the associated alterations of endogenous HGF and c-Met expressions under endothelial denudation with or without hHGF gene transfer using a balloon-injured rabbit aorta model. Sixty-one rabbits were randomly divided into normal controls, endothelial injury, endothelial injury with hHGF, or the control vector gene transfer groups. On weeks 1, 2, 4, and 8 after injury, neointimal hyperplasia and endothelialization were evaluated by the ratio of neointimal area to medial area (N/M ratio), CD31-positive staining, α-smooth muscle actin, and endothelial nitric oxide synthase expressions using histological analysis, immunohistochemistry staining, or real-time quantitative reverse transcriptase polymerase chain reaction. Endogenous rabbit HGF (rHGF) and c-Met expressions were detected with immunohistochemistry staining and quantitative reverse transcriptase polymerase chain reaction. It was found that expressions of endogeneous rHGF and c-Met in endothelial injury upregulated with peak levels on week 2 or week 4 after injury (p < 0.01). On week 1 after hHGF transfer, neointimal hyperplasia was significantly inhibited (p < 0.001), with decreased α-smooth muscle actin expression (p < 0.05) and improved endothelial cells regeneration and function (p < 0.01). More remarkable overexpression of endogenous rHGF and c-Met mRNAs were detected, and lowered positive staining of rHGF and c-Met was shown in the neointima (p < 0.05). These results demonstrated hHGF gene transfer induced further overexpression of endogenous rHGF and c-Met mRNAs but lowered immunoreactivities of rHGF and c-Met in the neointima, thus leading to significant attenuation of neointimal hyperplasia.

AMD3100 Accelerates Reendothelialization of Neointima in Rabbit Saccular Aneurysm After Flow Diverter Treatment.

OBJECTIVE: We sought to inspect the role of AMD3100, which acts as an antagonist of stromal cell-derived factor-1/CXC chemokine receptor 4 on the formation of neointima in rabbit saccular aneurysm after flow diverter (FD) treatment. METHODS: Twenty saccular aneurysm models were established by using porcine pancreatic elastase. Three weeks later, a Tubridge FD was implanted into the saccular aneurysm. All treated models were immediately divided into 2 groups: the AMD3100 group was subcutaneously injected with AMD3100 (5 mg/kg per day), while the control group received saline. Morphology and thickness of the neointima were investigated 2 and 4 weeks after FD treatment, using hard tissue section and masson trichrome staining. Scanning electron microscope was used to observe endothelial-like cells, and fluorescence quantitative polymerase chain reaction was used to determine mRNA expression of neointima biomarkers, such as kinase insert domain receptor, VE-cadherin, CD34, and Tie2. RESULTS: Two and 4 weeks after FD treatment, the AMD3100 group had more endothelial-like cells than the control group in the neointima. Masson trichrome staining showed that the neointima in the AMD3100 group was more intact and thicker than that in the control group. Furthermore, increased mRNA levels of kinase insert domain receptor, VE-cadherin, and Tie2 in the neointima were found in the AMD3100 group compared with the control group. CONCLUSIONS: Interval use of AMD3100 promotes the formation of neointima in rabbit saccular aneurysm and facilitates the endothelialization of the neointima after FD treatment.

Stem cell therapy with skeletal myoblasts accelerates neointima formation in a mouse model of vein graft disease.

Although still a matter of controversial discussion, skeletal myoblasts are one of the options for stem cell transplantation improving cardiac function after myocardial infarction, exhibiting several advantages including the availability, the ability of self-renewal and differentiation, and the lack of ethical and immunological problems. The aim of this study was to investigate the impact of stem cell therapy with skeletal myoblasts on experimental venous bypass grafts in a mouse model of vein graft disease. Forty C57BL/6J mice underwent bypass grafting interposing a venous bypass graft of the donor mouse into the carotid artery of the recipient mouse. Twenty mice received periadventitially treatment with 1 million fluorescence labeled skeletal myoblasts suspended in culture medium (treatment group), the other twenty mice received only culture medium without myoblasts (control group). Two weeks after bypass surgery, the vein grafts of all 40 mice were harvested, stained and histologically investigated under light and immunofluorescence microscope. Against our expectations, skeletal myoblasts stayed in place and were still located in the adventitia after bypass grafting. Additionally, vein grafts of the myoblast group revealed a 2fold increased neoneointima formation, a decreased media thickness, a slightly increased neovascularization, a higher percentage of reendothelialization and also a slightly higher percentage of PDGFR ɑ, PDGFR ß, MMP-7 and MMP-9 positive cells, suggesting a paracrine mechanism responsible for accelerated neointima formation. In conclusion, the results of our study do not support the use of skeletal myoblast for the treatment of vein graft disease after coronary artery bypass surgery.

Comparison of angioscopic findings among second-generation drug-eluting stents.

BACKGROUND: First-generation drug-eluting stents (DES) have reduced short-term stent failure as compared to bare-metal stents due to the inhibition of neointima hyperplasia, but instead increased the risk of very-late stent failure. Although better outcomes have been reported for second-generation DES than for first-generation DES, the difference in the angioscopic findings at 1-year follow-up has not been adequately elucidated among second-generation DES. METHODS: Consecutive 161 patients who received angioscopic examination at 1 year after implantation of second-generation DES, i.e. Nobori biolimus-eluting stents (Terumo, Tokyo, Japan) (N-BES, n=25), Xience everolimus-eluting stents (Abbot Vascular, Santa Clara, CA, USA; X-EES, n=95), or Resolute zotarolimus-eluting stents (Resolute Integrity; Medtronic, Minneapolis, MN, USA; R-ZES, n=41), in de novo native coronary lesions were analyzed. RESULTS: Maximum neointima coverage grade (N-BES, 0.9±0.3; X-EES, 1.2±0.4; R-ZES, 1.5±0.5; p<0.001) was the highest in R-ZES and lowest in N-BES. Heterogeneity score was higher in R-ZES than in N-BES (N-BES, 0.8±0.4; X-EES, 0.9±0.4; R-ZES, 1.1±0.5; p=0.007). Maximum yellow color grade and prevalence of thrombus were not different. Multivariate analysis demonstrated that only stent type was associated with maximum neointima coverage grade; stent type and total stent length were associated with heterogeneity score; and stenting for acute coronary syndrome (ACS) and total stent length were associated with maximum yellow color grade. CONCLUSIONS: Neointima coverage and heterogeneity were mainly determined by stent type even among second-generation DES, while yellow color was determined mainly by whether target lesion was of ACS.

Suppression of neointima formation by targeting ß-catenin/TCF pathway.

Coronary artery disease is treated by vein grafting and stent implantation. Late vein graft failure and restenosis of stented arteries reduce the success rates of these approaches and are caused by neointima formation. We have previously shown that Wnt proteins are up-regulated during intimal thickening, and have speculated that these lead to activation of downstream genes with ß-catenin/T-cell factor (TCF)-responsive promoters. In the present study, we aimed to provide evidence that ß-catenin/TCF signalling promotes neointima formation and assess whether targeting this pathway has potential for reducing neointima formation. We utilized a gene therapy approach selectively targeting cells in which the ß-catenin/TCF pathway is activated by using a recombinant adenovirus Ad-TOPTK, which carries a herpes simplex virus thymidine kinase (HSV-TK) gene under the control of a ß-catenin/TCF-response promoter. Cells with activated ß-catenin will therefore be selectively killed. Ad-TOPTK and ganciclovir (GCV) treatment significantly suppressed the growth of the neointima in a murine model of left carotid artery ligation. In summary, we demonstrated that Wnt/ß-catenin/TCF signalling promotes neointima formation, by showing that the selective death of cells with activated ß-catenin suppressed neointima formation. This highlights the therapeutic potential for reducing late vein graft failure and in-stent restenosis by targeting ß-catenin/TCF signalling.

Evaluation of vascular healing of polymer-free sirolimus-eluting stents in native coronary artery stenosis: a serial follow-up at three and six months with optical coherence tomography imaging.

AIMS: Our aim was to assess vascular response after polymer-free sirolimus-eluting stent (SES) implantation by using an optical coherence tomography (OCT)-derived vascular healing score (HS), quantifying the deficiency of healing. METHODS AND RESULTS: In a prospective, multicentre, single-arm, open-label study, OCT examinations were performed at three months in 45 patients (47 lesions). Per protocol, 24 lesions which had not reached adequate vascular healing according to study criteria were scheduled for OCT examination at six months. The HS was calculated at two time points. Serial OCT imaging demonstrated that the proportion of covered stent struts increased from a median of 87.1% at three months to 98.6% at six months (p<0.001). The neointimal thickness increased from a median of 82.8 µm to 112.2 µm (p<0.001), whereas the median percentages of malapposed struts were 0.2% and 0.0% at the two respective time points. Neointimal volume obstruction increased from 6.3% to 12.8%, and the HS decreased from a median of 28.1 at three months to 2.4 at six months. CONCLUSIONS: In patients who had inadequate vascular healing three months after polymer-free SES implantation, serial OCT showed almost complete vascular healing at six months.