The incidence rate and histological characteristics of intimal hyperplasia in elastase-induced experimental abdominal aortic aneurysms in mice

Intimal hyperplasia(IH)is a negative vascular remodeling after arterial injury.IH occasionally occurs in elastase-induced abdominal aortic aneurysm(AAA)mouse models.This study aims to clarify the incidence and histological characteristics of IH in aneurysmal mice.A retrospective study was conducted by including 42 male elastaseinduced mouse AAA models.The IH incidence,aortic diameters with or without IH,and hyperplasia lesional features of mice were analyzed.Among 42 elastase-induced AAA mouse models,10 mice developed mild IH(24%)and severe IH was found in only 2 mice(5%).The outer diameters of the AAA segments in mice with and without IH did not show significant difference.Both mild and severe IH lesions show strong smooth muscle cell positive staining,but endothelial cells were occasionally observed in severe IH lesions.There was obvious macrophage infiltration in the IH lesions of the AAA mouse models,especially in mice with severe IH.However,only a lower numbers of T cells and B cells were found in the IH lesion.Local cell-secreted matrix metalloproteinases(MMP)2 was highly expressed in all IH lesions,but MMP9 was only overexpressed in severe lesions.In conclusion,this study is the first to demonstrate the occurrence of aneurysmal IH and its histological characteristics in an elastaseinduced mouse AAA model.This will help researchers better understand this model,and optimize it for use in AAA-related research.

Reducing intimal hyperplasia in vein grafts harvested by a no-touch harvesting technique

Objective To investigate the effect of no-touch harvesting technique in reducing vein graft intimal hyperplasia. Methods This longitudinal trial compared graft angiostenosis of two groups undergoing jugular vein to carotid artery interposition grafting in rabbit model. Conventional group:12 rabbits had their veins stripped,distended,and stored in heparinized saline solution. No-touch group:12 rabbits had veins removed with surrounding tissues,but were not distended,and stored in heparinized blood. The grafts were removed 4 weeks following grafting,and morphometry and immunohistochemistry assessment were performed. Results The intimal thickness,degree of angiostenosis and proliferation index of vascular smooth muscle cells of no-touch group were significantly reduced (P<0.01) compared with those of the conventional group. The proliferating cell nuclear antigen positive-staining cells were significantly increased (P<0.01) in the conventional group compared with whose in the no-touch group. Conclusion Harvesting the vein graft with no-touch harvesting technique could significantly reduce intimal hyperplasia of the vein graft.

Effects of extravascular trestle model coated phosphorus radioisotope on intimal hyperplasia in autologous vein grafts

Objective: To design an extravascular trestle model coated phosphorus-32, an isotope radiating beta rays, and investigate its effects on intimal hyperplasia of autologous vein grafts. Methods: ETA cDNA was used as a gene probe specific to vascular SMCs on the basis of in situ hybridization. The femoral veins were transplanted reversely into colateral femoral arteries in rabbits, and the animals were divided into control, chemical agents and phosphorus-32 groups. The morphometry was applied to calculate the ETA cDNA expression and intimal thickness. Spearman correlation method was utilized to investigate their relationship. Results: Intimal thickness in grafts of phosphorus-32 group was markedly reduced. Additionally, intimal ETA gene expression was also decreased in beta rays group. The values increased at a slower rate significantly different from that of control and aspirin groups (P<0.01). The correlation of ETA cDNA expression and intimal thickness exhibited a strongly positive relation. Conclusion: Beta rays in extravascular model could remarkably inhibit intimal thickening and SMC proliferation. The correlation is an indirect evidence indicating that intimal hyperplasia composed of SMCs proliferation. It suggests that ETA cDNA expression could be a quantitative estimation of vascular SMC because of its specifics.

A bio-instructive parylene-based conformal coating suppresses thrombosis and intimal hyperplasia of implantable vascular devices

Implantable vascular devices are widely used in clinical treatments for various vascular diseases. However, current approved clinical implantable vascular devices generally have high failure rates primarily due to their surface lacking inherent functional endothelium. Here, inspired by the pathological mechanisms of vascular device failure and physiological functions of native endothelium, we developed a new generation of bioactive parylene (poly(p-xylylene))-based conformal coating to address these challenges of the vascular devices. This coating used a polyethylene glycol (PEG) linker to introduce an endothelial progenitor cell (EPC) specific binding ligand LXW7 (cGRGDdvc) onto the vascular devices for preventing platelet adhesion and selectively capturing endogenous EPCs. Also, we confirmed the long-term stability and function of this coating in human serum. Using two vascular disease-related large animal models, a porcine carotid artery interposition model and a porcine carotid artery-jugular vein arteriovenous graft model, we demonstrated that this coating enabled rapid generation of self-renewable “living” endothelium on the blood contacting surface of the expanded polytetrafluoroethylene (ePTFE) grafts after implantation. We expect this easy-to-apply conformal coating will present a promising avenue to engineer surface properties of “off-the-shelf” implantable vascular devices for long-lasting performance in the clinical settings.

Rutaecarpine Inhibits Intimal Hyperplasia in A Balloon-Injured Rat Artery Model

Objective： To investigate the effect and potential mechanisms of rutaecarpine （Rut） in a rat artery balloon-injury model. Methods： The intimal hyperplasia model was established by rubbing the endothelia with a balloon catheter in the common carotid artery （CCA） of rats. Fifty rats were randomly divided into five groups, ie. sham, model, Rut （25, 50 and 75 mg/kg） with 10 rats of each group. The rats were treated with or without Rut （25, 50, 75 mg/kg） by intragastric administration for 14 consecutive days following injury. The morphological changes of the intima were evaluated by hematoxylin-eosin staining. The expressions of proliferating cell nuclear antigen （PCNA） and smooth muscle （SM） oL-actin in the ateries were assayed by immunohistochemical staining. The mRNA expressions of c-myc, extracellular signal-regulated kinase 2 （ERK2）, MAPK phosphatase-1 （MKP-1） and endothelial nitric oxide synthase （eNOS） were determined by real-time reverse chain reaction. The protein expressions of MKP-1 and phosphorylated ERK2 （p-ERK2） were examined by Western blotting. The plasma contents of nitric oxide （NO） and cyclic guanosine 3＇,5＇-monophosphate （cGMP） were also determined. Results： Compared with the model group, Rut treatment significantly decreased intimal thickening and ameliorated endothelial injury （P〈0.05 or P〈0.01）. The positive expression rate of PCNA was decreased, while the expression rate of SM α -actin obviously increased in the vascular wall after Rut （50 and 75 mg/kg） administration （P〈0.05 or P〈0.01）. Furthermore, the mRNA expressions of c-myc, ERK2 and PCNA were downregulated while the expressions of eNOS and MKP-1 were upregulated （P〈0.05 or P〈0.01）. The protein expressions of MKP-1 and the phosphorylation of ERK2 were upregulated and downragulated after Rut （50 and 75 mg/kg） administration （P〈0.05 or P〈0.01）, respectively. In addition, Rut dramatically reversed balloon injury-induced decrease of NO and cGMP in the plasma （P〈0.05 or P〈0.01）. Conclusion： Rut could inhibit the balloon injury-induced carotid intimal hyperplasia in rats, possibly mediated by promotion of NO production and inhibiting ERK2 signal transduction pathways.

Heparin-derived oligosaccharide inhibits vascular intimal hyperplasia in balloon-injured carotid artery

The aims of the present study were to determine the effects of heparin-derived oligosaccharides(HDOs) on vascular intimal hyperplasia(IH) in balloon-injured carotid artery and to elucidate the underlying mechanisms of action. An animal model was established by rubbing the endothelia within the common carotid artery(CCA) in male rabbits. The rabbits were fed a high-cholesterol diet. Arterial IH was determined by histopathological changes to the CCA. Serum lipids were detected using an automated biochemical analysis. Expressions of mR NAs for vascular endothelial growth factor(VEGF), basic fibroblast growth factor(bF GF), vascular cell adhesion molecule-1(VCAM-1), monocyte chemoattractant protein-1(MCP-1), scavenger receptor class B type I(SR-BI), and ATP-binding cassette transporter A1(ABCA-1) were analyzed using reverse transcription polymerase chain reaction assays. Expressions of VEGF, VCAM-1, MCP-1, SR-BI and ABCA-1 proteins were analyzed by Western blotting. Enzyme-linked immunosorbent assays were used to quantify expression levels of VEGF and b FGF. Our results showed that administration of HDO significantly inhibited CCA histopathology and restenosis induced by balloon injury. The treatment with HDOs significantly decreased the m RNA and protein expression levels of VEGF, b FGF, VCAM-1, MCP-1, and SR-BI in the arterial wall; however, ABCA-1 expression level was elevated. HDO treatment led to a reduction in serum lipids(total cholesterol, triglycerides, high-density and low-density lipoproteins). Our results from the rabbit model indicated that HDOs could ameliorate IH and underlying mechanism might involve VEGF, b FGF, VCAM-1, MCP-1, SR-BI, and ABCA-1.

Programmable dual responsive system reconstructing nerve interaction with small-diameter tissue-engineered vascular grafts and inhibiting intimal hyperplasia in diabetes

Small-diameter tissue-engineered vascular grafts(sdTEVGs)with hyperglycemia resistance have not been constructed.The intimal hyperplasia caused by hyperglycemia remains problem to hinder the patency of sdTEVGs.Here,inspired by bionic regulation of nerve on vascular,we found the released neural exosomes could inhibit the abnormal phenotype transformation of vascular smooth muscle cells(VSMCs).The transformation was a prime culprit causing the intimal hyperplasia of sdTEVGs.To address this concern,sdTEVGs were modified with an on-demand programmable dual-responsive system of ultrathin hydrogels.An external primary Reactive Oxygen Species(ROS)-responsive Netrin-1 system was initially triggered by local inflammation to induce nerve remolding of the sdTEVGs overcoming the difficulty of nerve regeneration under hyperglycemia.Then,the internal secondary ATP-responsive DENND1A(guanine nucleotide exchange factor)system was turned on by the neurotransmitter ATP from the immigrated nerve fibers to stimulate effective release of neural exosomes.The results showed nerve fibers grow into the sdTEVGs in diabetic rats 30 days after transplantation.At day 90,the abnormal VSMCs phenotype was not detected in the sdTEVGs,which maintained long-time patency without intima hyperplasia.Our study provides new insights to construct vascular grafts resisting hyperglycemia damage.

Mithramycin inhibits intimal hyperplasia of vein grafts after transplantation of the jugular vein to the abdomainal aorta in rats

Objective: The intimal hyperplasia caused by migration and proliferation of the smooth muscle cells play a most important role in the stenosis of the vein grafts. This study is to explore how the C myc oncogene and its protein contribute to the intimal hyperplasia after the jugular vein is transplanted to the abdominal aorta and to assess the effect of Mithramycin on the intimal hyperplasia. Methods: In 60 Wistar rats, a 0.8 cm segment of the right jugular vein graft was interposed at the level of the abdominal aorta. The experiment group received Mithramycin (150 μg/kg IP) 1 h before and after the operation. The control group received normal saline, specimens of vein graft at 2 and 6 h postoperatively were subjected respectively to in situ hybridization. The vein grafts 4 weeks after operation were perfusion fixed. The specimens were stained with hemotoxylin eosin and the computer morphologic analysis system was used to evaluate the degree of intimal thickening. Immunohistochemistry studies of muscle specific α actin, C myc protein and 5 Bromodeoxyuridine were performed. Results: The areas of neointimal and the ratios of neointimal to medial area were significantly smaller and lower in the Mithramycin treated than in the control rats (P< 0.05 ). The 5 Brdu labeling rate between the two groups were also different significantly (P< 0.05 ). Muscle specific α actin showed that the smooth muscle cells formed the most area of myointimal hyperplasia. Steady state C myc mRNA level was increased from 2 h to 6 h postoperatively. The positive rate of the placebo treated group was higher significantly than that of the Mithramycin treated group (P< 0.05 ). Conclusions: Mithramycin may effectively inhibits transcription of C myc in proliferating vascular smooth muscle cells and could be useful in the prevention of restenosis after vascularization. These results support the hypothesis that systemic administration of Mithramycin might immediately prevent intimal proliferation.

Histopathology and Morphometric Analysis of the Internal Mammary Artery to Study the Incidence of Atherosclerosis and Its Associated Risk Factors

Background: The left internal mammary artery (IMA) is widely used as a conduit for coronary revascularization. The incidence of atherosclerosis is known to be lower in the IMA than in the coronary artery. The aim of this study was to evaluate the reliability of the use of the distal section of the IMA as an anastomotic site for bypass grafting and morphometric studies of IMA in patients with proven coronary artery disease and their associated risk factors. Methods: Patients who underwent Coronary Artery Bypass Graft (CABG) from June 2010 to November 2012 were chosen in this retrospective study and the discarded distal segments of the internal mammary artery were analyzed. The potential risk factors for atherosclerosis considered were age, sex, diabetes mellitus, history of cigarette smoking, hypertension and hypercholesterolemia. The samples were analyzed for the degree of intimal thickening and atherosclerosis by calculating the percentage of Luminal Narrowing, Intimal Thickness Index (ITI) and Intima-to-Media Ratio (IMR). Results: There were seven cases of intimal hyperplasia and two cases of focal medial and intimal hyperplasia with fatty streak and no cases of atherosclerosis and medial calcification. ITI was higher in males when compared to females. There was a strong relationship between IMR and smokers when compared to nonsmokers. Conclusion: In our study, when ITI was used as the dependent variable, diabetes was the most important factor. When IMR was used, the strongest predictor was hypercholesterolemia. There was a strong relationship between IMR and smokers when compared to nonsmokers.

IN VIVO EFFECT OF HEPARIN PRETREATMENT OF SMALL-CALIBER DECELLULARIZED XENOGRAFT

Objective To develop a new vascular xenograft and to compare the in vivo behavior of thrombogenicity and intimal hyperplasia in the heparin-treated and the non-heparin-treated decellularized xenografts.Methods Canine common carotid arteries were decellularized by enzymatic and detergent extraction procedures.Then a part of decellularized vascular grafts were covalently linked with heparin.Xenografts with(n=24)and without(n=24)heparin treatment were implanted in rabbits' left and right carotid artery respectively as bypass grafts.Graft patency were checked by Duplex ultrasonography at 3 and 6 months after implantation.Twelve rabbits were euthanized randomly at 3 and 6 months respectively and bilateral grafts were explanted.Histological examination and immunohistochemical staining were performed to observe the vascular remodeling.The efficiency of heparin release was demonstrated with toluidine blue staining.HE staining and micrograph analysis system were used for valuating the intima hyperplasia(IH)of bilateral grafts.Results During implantation,thrombosis rate was 4% in the heparin-treated xenografts and 25% in the non-heparin-treated xenografts after 3 weeks(P<0.05).After 6 months,it was 8% versus 58% respectively(P<0.01).Both xenografts of two groups harvested at the end of 3 or 6 months showed a satisfactory cellular reconstruction of either smooth muscle cells or endothelial cells.Intimal hyperplasia in the heparin-treated vascular was less than in the non-heparin treated xenografts.In addition,intimal hyperplasia was liable to appear close to the proximal and distal anastomotic stoma.Toluidine blue staining demonstrated that heparin was slowly released during 6 months.Conclusion This study provides a new strategy to develop a small-caliber vascular xenograft through enzymatic-detergent extraction and heparin treatment.Heparin treatment of the decellularized xenograft is helpful for improving bypass graft patency and reducing intimal hyperplasia.If there was no thrombus,bilateral bypass grafts will undergo a vessel remodeling procedure.Canine common carotid artery treated by detergent and enzymatic extraction and heparin treatment may be used as a new small-caliber vascular xenograft.

Differentially Expressed MicroRNAs Associated with Vein Graft Restenosis in Rats

Objective:Intimal hyperplasia is the main cause of restenosis of vein grafts after venous transplantation.MicroRNAs are considered to play a role in vein graft restenosis;however,the expression profi le of microRNAs in neointima has not been reported in detail.We wanted to investigate the differentially expressed microRNAs in the restenosis of vein grafts in rats.Methods:We established a rat model for vein transplantation to explore the pathogenic roles of microRNAs during intimal hyperplasia.Hematoxylin and eosin staining was used to confi rm intimal hyperplasia in the vein grafts.Changes in microRNA expression in the vein grafts were detected 3 and 14 days after surgery by sequencing,reverse transcription–quantitative polymerase chain reaction,and bioinformatics analyses for functional annotation.Results:We detected 711 newly predicted microRNAs among all the comparisons.Among these comparisons,437 differentially expressed microRNAs were detected in the postoperative day 3 group versus the control group,265 were detected in the postoperative day 14 group versus the control group,and 158 were detected in the postoperative day 14 group versus the postoperative day 3 group.Pathway analysis revealed signifi cant enrichment of target genes that mediate Wnt,mitogen-activated protein kinase,vascular smooth muscle contraction,and regulation of actin cytoskeleton signaling.Conclusion:Our results provide insight into the pathogenesis of restenosis and will help develop novel targets in the prevention and treatment of vein graft restenosis.

Computational Investigation of Hemodynamics in Fully Stenosed CABG

Coronary Artery Bypass Graft (CABG) is an important surgical treatment for critically stenosed arteries. Unfortunately restenosis always occurs after CABG surgery, which bring about surgery failure. Intimal thickening in the CABG distal anastomosis has been implicated as the major cause of restenosis and long term graft failure. The nonuniform hemodynamics including disturbed flows, recirculation zones, oscillating wall shear stress, and long particle residence time were thought to be the possible etiologies. Numerical simulation was proved to be of great help and guidance meaning for the biofluid mechanics research and the CABG surgical plan. The present study was based on the hypothesis that the geometry configuration of CABG could greatly influence the hemodynamics in the vicinity of anastomosis. The hemodynamic features of two geometry models of end to side CABG were studied and compared. One simulated a conventional CABG with 1 way bypass graft, and the other simulated a modified CABG with symmetric 2 way bypass graft. The numerical investigations of hemodynamics in these two models with fully stenosed coronary arteries were accomplished using finite element method. The temporal and spatial distributions of hemodynamics were analyzed and compared. Results showed that the presence of symmetric 2 way bypass graft was of reasonable and favorable hemodynamics than 1 way bypass graft. The modified CABG model created a more hemodynamically efficient streamlined environment with higher mean and maximum axial velocities and lower radial velocities than the conventional 1 way model. Meanwhile, the symmetric 2 way bypass graft was featured with low pressure near the wall, high and uniform WSS in the host artery. All of these were favorable for inhibiting the development of intimal thickening, restenosis, and ultimate failure of the CABG, and it could considerably improve the flow conditions and decrease the probability of intimal hyperplasia and restenosis of CABG.

Challenges and strategies for in situ endothelialization and long-term lumen patency of vascular grafts

Vascular diseases are the most prevalent cause of ischemic necrosis of tissue and organ,which even result in dysfunction and death.Vascular regeneration or artificial vascular graft,as the conventional treatment modality,has received keen attentions.However,small-diameter(diameter<4 mm)vascular grafts have a high risk of thrombosis and intimal hyperplasia(IH),which makes long-term lumen patency challengeable.Endothelial cells(ECs)form the inner endothelium layer,and are crucial for anti-coagulation and thrombogenesis.Thus,promoting in situ endothelialization in vascular graft remodeling takes top priority,which requires recruitment of endothelia progenitor cells(EPCs),migration,adhesion,proliferation and activation of EPCs and ECs.Chemotaxis aimed at ligands on EPC surface can be utilized for EPC homing,while nanofibrous structure,biocompatible surface and cell-capturing molecules on graft surface can be applied for cell adhesion.Moreover,cell orientation can be regulated by topography of scaffold,and cell bioactivity can be modulated by growth factors and therapeutic genes.Additionally,surface modification can also reduce thrombogenesis,and some drug release can inhibit IH.Considering the influence of macrophages on ECs and smooth muscle cells(SMCs),scaffolds loaded with drugs that can promote M2 polarization are alternative strategies.In conclusion,the advanced strategies for enhanced long-term lumen patency of vascular grafts are summarized in this review.Strategies for recruitment of EPCs,adhesion,proliferation and activation of EPCs and ECs,anti-thrombogenesis,anti-IH,and immunomodulation are discussed.Ideal vascular grafts with appropriate surface modification,loading and fabrication strategies are required in further studies.

Effects and mechanisms of non-restrictive external stent for prevention of vein graft restenosis in a rabbit model

Background Among various treatments preventing vein graft restenosis, external stent is receiving more and more attention. This study aimed to investigate the effect of non-restrictive external stent on the prevention of vein graft restenosis and the potential mechanisms of platelet-derived growth factor （PDGF） in the process of restenosis.Methods Thirty-six ＂New Zealand white rabbits＂ were randomly divided into two groups, stented group （group S） and control group （non-stented group, group NS）. Each rabbit underwent a reversed autologous external jugular vein into common carotid artery bypass grafting. In group S, the vein grafts were surrounded by a non restrictive stent which was 6 mm in diameter （a kind of Dacron vascular prosthesis）; and in group NS, there was no stent to support the vein grafts.The grafts were harvested at the first week （1W）, second week （2W） and fourth week （4W） after surgery respectively. The dimensions （including the thickness and area of the intima and media, luminal area） were measured by computer-aided image analysis system, and the intimal hyperplasia ratio was defined as the percentage of the area enclosed by the internal elastic lamina occupied by the intima.Results At 1W, the difference of the thickness and area of the intima between groups S and NS was not significant （P 〉0.05）; at 2W and 4W, the thickness and area of the intima and the intimal hyperplasia ratio in group S were less significant than those in group NS （P 〈0.05）; from 1W to 4W, the thickness and area of the media in group S were smaller than those in group NS （P〈0.05）. Immunocytochemistry staining of PDGF-B showed that the percentage of positive cells of intima in both two groups was peaked at 2W, and a significantly smaller percentage was detected in group S compared with that in group NS at 2W and 4W （P 〈0.05）; the percentage of PDGF-B positive cells of media in both two groups was also peaked at 2W, and that in group S was smaller than that in group NS from 1W to 4W （P 〈0.05）; and the percentage of PDGF-B positive cells of adventitia in group S was peaked at 4W, whereas the percentage of adventitia in group NS peaked at 2W, and the percentage of adventitia in group S was greater than in group NS at 4W （P 〈0.05）.Conclusions Non-restrictive external stenting inhibits the hyperplasia of the intima and media of the vein grafts and reduces the thickness and area of the intima and media; Non-restrictive external stenting inhibits the synthesis of PDGF and changes its distribution, and then inhibits the hyperplasia of the intima.

Research progress of CTSL in cardiovascular system

Cathepsin L(CTSL) is a member of cysteine cathepsin and has endopeptidase activity. CTSL exists widely in various tissues and cells and participates in protein degradation, extracellular matrix remodeling, autophagy and other processes. With the deepening of research, it is found that CTSL is related to the occurrence of cardiovascular diseases. This article introduces the research progress of CTSL in atherosclerosis, coronary heart disease,intimal hyperplasia, dilated cardiomyopathy, abdominal aortic aneurysm, hypertension, vascular aging, in order to provide research direction for CTSL.