Recent advances to accelerate re-endothelialization for vascular stents

Cardiovascular diseases are considered as one of the serious diseases that leads to the death of millions of people all over the world. Stent implantation has been approved as an easy and promising way to treat cardiovascular diseases. However, in-stent restenosis and thrombosis remain serious problems after stent implantation. It was demonstrated in a large body of previously published literature that endothelium impairment represents a major factor for restenosis. This discovery became the driving force for many studies trying to achieve an optimized methodology for accelerated re-endothelialization to prevent restenosis. Thus, in this review, we summarize the different methodologies opted to achieve re-endothelialization, such as, but not limited to, manipulation of surface chemistry and surface topography.

In vitro differentiation of bone marrow derived porcine mesenchymal stem cells to endothelial cells

Mesenchymal stem cells (MSCs) hold potential for the regeneration of damaged tissues in cardiovascular diseases. In this study, we investigated the potential of porcine MSCs to differentiate into endothelial cells (ECs) in vitro. The cultured bone marrow-derived cells were CD11b⁻CD34⁻CD44⁺CD45⁻CD90⁺ and showed mesodermal lineage differentiation, which is characteristic of MSCs. The MSCs were induced to differentiate into ECs using endothelial growth medium (EGM), with and without high concentrations of VEGF (EGM + VEGF; 50 ng/ml). Endothelial basal medium (EBM) without growth factors served as the control. The EC differentiation was assessed by the presence of vWF, ability to take up acetylated LDL, in vitro angiogenesis assay, flow cytometry and qPCR of EC markers vWF, VE-cadherin, PECAM-1, VEGF-R1 and VEGF-R2 after 10 days of stimulation. Cells cultured in EGM + VEGF medium demonstrated higher amounts of DiI-AcLDL-positive cells and enhanced the presence of vWF (90%), VE-Cadherin- (60%) and PECAM-1 (48%)-positive cells, than in EBM. These cells showed profuse sprouting of capillary tubes and closed polygon formation in the angiogenesis assay. There was 1.5-2-fold increase in the mRNA expression of endothelial markers in the cells stimulated with EGM + VEGF medium when compared to control. The results demonstrate the ability of porcine MSCs to differentiate into ECs under in vitro inducing conditions. The differentiated cells would provide new options for re-endothelialization following interventional procedures and tissue engineering.

Distinctive effects of CD34- and CD133-specific antibody-coated stents on re-endothelialization and in-stent restenosis at the early phase of vascular injury

It is not clear what effects of CD34- and CD133-specific antibody-coated stents have on re-endothelialization and in-stent restenosis (ISR) at the early phase of vascular injury. This study aims at determining the capabilities of different coatings on stents (e.g. gelatin, anti-CD133 and anti-CD34 antibodies) to promote adhesion and proliferation of endothelial progenitor cells (EPCs). The in vitro study revealed that the adhesion force enabled the EPCs coated on glass slides to withstand flow-induced shear stress, so that allowing for the growth of the cells on the slides for 48 h. The in vivo experiment using a rabbit model in which the coated stents with different substrates were implanted showed that anti-CD34 and anti-CD133 antibody-coated stents markedly reduced the intima area and restenosis than bare mental stents (BMS) and gelatin-coated stents. Compared with the anti-CD34 antibody-coated stents, the time of cells adhesion was longer and earlier present in the anti-CD133 antibody-coated stents and anti-CD133 antibody-coated stents have superiority in re-endothelialization and inhibition of ISR. In conclusion, this study demonstrated that anti-CD133 antibody as a stent coating for capturing EPCs is better than anti-CD34 antibody in promoting endothelialization and reducing ISR.

Endothelial repair process and its relevance to longitudinal neointimal tissue patterns: comparing histology with in silico modelling

Re-establishing a functional endothelium following endovascular treatment is an important factor in arresting neointimal proliferation. In this study, both histology (in vivo) and computational simulations (in silico) are used to evaluate neointimal growth patterns within coronary arteries along the axial direction of the stent. Comparison of the growth configurations in vivo and in silico was undertaken to identify candidate mechanisms for endothelial repair. Stent, lumen and neointimal areas were measured from histological sections obtained from eight right coronary stented porcine arteries. Two re-endothelialization scenarios (endothelial cell (EC) random seeding and EC growth from proximal and distal ends) were implemented in silico to evaluate their influence on the morphology of the simulated lesions. Subject to the assumptions made in the current simulations, comparison between in vivo and in silico results suggests that endothelial growth does not occur from the proximal and distal ends alone, but is more consistent with the assumption of a random seeding process. This may occur either from the patches of endothelium which survive following stent implantation or from attachment of circulating endothelial progenitor cells.

Interferon-induced protein 35 inhibits endothelial cell proliferation, migration and re-endothelialization of injured arteries by inhibiting the nuclear factor-kappa B pathway

AIM

Endothelial recovery, or re-endothelialization, plays an important role in intimal hyperplasia and atherosclerosis after endothelial injury. Studying the mechanisms of re-endothelialization and strategies to promote efficient endothelial recovery are still needed. Interferon-induced protein 35 (IFI35) is an IFN-γ-induced protein that plays important roles in the antivirus-related immune-inflammatory response. In this study, we tested whether overexpression IFI35 affects the proliferation and migration of endothelial cells (ECs) and re-endothelialization.

METHODS

Wire injury of the carotid artery was induced in C57BL/6 mice, which was followed by IFI35 or null adenovirus transduction. Evans blue staining and HE staining were performed to evaluate the re-endothelialization rate and neointima formation. In vitro studies, primary human umbilical vein endothelial cells (HUVECs) were transfected with Ad-IFI35 or siRNA-IFI35 to evaluate its potential roles in cell proliferation and migration. Furthermore, the potential mechanism relating inhibition of NF-κB/p65 pathway was elaborated by luciferase assay and IFI35 domain deletion assay.

RESULTS

In IFI35 adenovirus-transduced mice, the re-endothelialization rates at days 3, 7 were significantly reduced compared to those in null adenovirus-transduced mice (5% and 35%, vs 20% and 50%, respectively). Meanwhile, subsequent neointimal hyperplasia was obviously increased in IFI35 adenovirus-transduced mice. In vitro studies further indicated that IFI35 inhibits both EC proliferation and migration by inhibiting the NF-κB/p65 pathway. Subsequent studies demonstrated that IFI35 functionally interacted with Nmi through its NID1 domain and that knock-down of Nmi significantly mitigated the inhibitory effect of IFI35 on EC proliferation and migration.

CONCLUSION

Our study revealed a novel mechanism through which IFI35 affects the proliferation and migration of ECs as well as neointima formation, specifically through inhibition of the NF-κB/p65 pathway. Thus, IFI35 is a promising target for the prevention and treatment of post-injury vascular intimal hyperplasia.

Progress and prospects of endothelial progenitor cell therapy in coronary stent implantation

Drug-eluting stents (DES) have been widely used to treat coronary artery disease (CAD) since their clinical use has significantly reduced the occurrence of in-stent restenosis (ISR) as compared with the initially applied bare-metal stents (BMS). However, analyses of long-term clinical outcome have raised concerns about the serious safety problem of DES, such as ISR caused by late or very late thrombosis. Various studies showed that those complications were associated with vascular endothelial injury/dysfunction or endothelialization delaying. Recently, through biological characterization of endothelial progenitor cells (EPCs), mechanistic understanding of rapid re-endothelialization of the vascular injury sites after coronary stenting has become possible and is a new research hotspot in the prevention of ISR and late/very late stent thrombosis. It has been well recognized that the formation of a functional endothelial layer from EPCs requires a coordinated sequence of multistep and signaling events, which includes cell mobilization, adhesion, migration and finally the differentiation to vascular endothelial cells (VECs). In this review, we summarize and discuss the currently relevant information about EPCs, the mechanism of DES interfering with the natural vascular healing process in preventing or delaying the formation of a functional endothelial layer, and EPCs-mediated acceleration of re-endothelialization at vascular injury sites. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1237-1247, 2016.

Constructing heparin-modified pancreatic decellularized scaffold to improve its re-endothelialization

Pancreas transplantation is considered as a promising therapeutic option with the potential to cure diabetes. However, efficacy of current clinical transplantation is limited by the donor organ. With regard to creating a functional pancreas-tissue equivalent for transplantation, vascularization remains a large obstacle. To enhance the angiogenic properties of pancreatic decellularized scaffold, surface modification of the vasculature was used to promote endothelialization efficiency. In this study, an endothelialized pancreatic decellularized scaffold was obtained through heparin modification under mild conditions. The immobilization of heparin was performed through 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-Hydroxysuccinimide. The morphology, ultra-structure and porosity of the heparinized scaffold were characterized by toluidine blue staining, scanning electron microscope and infrared spectrum. The adhesion, proliferation and angiogenesis of human umbilical vein endothelial cells on heparin-pancreatic decellularized scaffold were also researched in vitro. In vivo transplantation was also performed to observe the location of human umbilical vein endothelial cells and the formation of new blood vessel, which exhibited significant differences with pancreatic decellularized scaffold group (p<0.05). These findings indicated that the endothelialized heparin-pancreatic decellularized scaffold may be used to solve the problem of blood supply and to support the function of insulin-secreting cells better after in vivo transplantation, and therefore, would be a potential candidate for pancreatic tissue engineering.

Nanofibrous vildagliptin-eluting stents enhance re-endothelialization and reduce neointimal formation in diabetes: in vitro and in vivo

BACKGROUND

The high lifetime risk of vascular disease is one of the important issues that plague patients with diabetes mellitus. Systemic oral vildagliptin administration favors endothelial recovery and inhibits smooth muscle cell (SMC) proliferation. However, the localized release of vildagliptin in the diabetic vessel damage has seldom been investigated.

RESEARCH DESIGN AND METHODS

In this work, nanofiber-eluting stents that loaded with vildagliptin, a dipeptidyl peptidase-4 enzyme (DPP-4) inhibitor, was fabricated to treat diabetic vascular disease. To prepare nanofibers, the poly (D,L)-lactide-co-glycolide (PLGA) and vildagliptin were mixed using hexafluoroisopropanol and electrospinning process. In vitro and in vivo release rates of the vildagliptin were characterized using high-performance liquid chromatography.

RESULTS

Effective vildagliptin concentrations were delivered for more than 28 days from the nanofibrous membranes coating on the surface of the stents in vitro and in vivo. The vildagliptin-eluting PLGA membranes greatly accelerated the recovery of diabetic endothelia and reduced SMC hyperplasia. The type I collagen content of the diabetic vascular intimal area that was treated by vildagliptin-eluting stents was lower than that of the non-vildagliptin-eluting group.

CONCLUSION

The experimental results revealed that stenting with vildagliptin-eluting PLGA membranes could potentially promote healing for diabetic arterial diseases.

Arsenic Trioxide-Coated Stent Is an Endothelium-Friendly Drug Eluting Stent

An ideal vascular stent would both inhibit in-stent restenosis (ISR) and promote rapid re-endothelialization. In the current study, the performance of arsenic trioxide (ATO)-drug eluting stent (AES) is compared with the bare metal stent, poly-lactic-co-glycolic acid-coating metal stent, and rapamycin-drug eluting stent (RES). In vivo AES is shown to prevent neointimal hyperplasia more efficiently than the others when implanted into the carotid arteries of rabbits. Moreover, AES promotes endothelial cells proliferation and re-endothelialization more quickly than RES. In vitro ATO exposure significantly increases the viability, proliferation, adhesion, and spreading of primary porcine coronary artery endothelial cells (PCAECs), which are critical for endothelialization. However, ATO exposure reduces the viability of porcine coronary artery smooth muscle cells (PCASMCs). The evaluation of mitochondrial morphology, membrane potential, and function demonstrates that ATO at 2 µmol L^-1 causes enlargement of the mitochondrion, enhancement of mitochondrial membrane potential, and adenosine triphosphate (ATP) production in PCAECs but not in PCASMCs. Thus, both in vivo and in vitro studies demonstrate that AES is an effective strategy for rapid re-endothelialization and inhibition of ISR.

The effect of REDV/TiO2 coating coronary stents on in-stent restenosis and re-endothelialization

The coronary artery stent has been widely used in clinic. In-stent restenosis was mainly caused by the excessive proliferation of smooth muscle cell and the inflammation due to the metal ion released from stent scaffold of the drug-eluting stent. Thus, to reduce the in-stent restenosis and promote the vascular endothelialization have become a hot research point in this area. In this paper, a nano-TiO₂ ceramic coating was deposited on 316L stainless steel to reduce the metal ion release and to inhibit the inflammation reaction. An endothelia cell selective adhesion peptide Arg-Glu-Asp-Val (REDV) coating was prepared on the ceramic coating by a polydopamine technology to promote the endothelialization. The corrosion test indicated that nano-TiO₂ ceramic film could effectively decrease the nickel ion released from 316L stainless steel. REDV/TiO₂ coating could promote the endothelial cell adhesion and proliferation, meanwhile REDV/TiO₂ coating could also increase the nitric oxide concentration. Bare metal stent, TiO₂-coated stent and REDV/TiO₂-coated stent were implanted in the iliac arteries of rabbit model. In-stent restenosis and re-endothelialization were evaluated at 28 days post-implantation of the stents. The results showed that REDV/TiO₂-coated stents could effectively reduce in-stent restenosis and promote re-endothelialization in comparison with TiO₂-coated drug-eluting stent and bare metal stent. These results suggest that REDV/TiO₂-coated drug-eluting stent maybe a good choice of the application for coronary artery disease.

Functional behavior and gene expression of magnetic nanoparticle-loaded primary endothelial cells for targeting vascular stents

AIM

To assess functional competence and gene expression of magnetic nanoparticle (MNP)-loaded primary endothelial cells (ECs) as potential cell-based therapy vectors.

MATERIALS & METHODS

A quantitative tube formation, nitric oxide and adhesion assays were conducted to assess functional potency of the MNP-loaded ECs. A quantitative real-time PCR was used to profile genes in both MNP-loaded at static conditions and in vitro targeted ECs.

RESULTS

Functional behavior of MNP-loaded and unloaded cells was comparable. MNPs induce expression of genes involved in EC growth and survival, while repress genes involved in coagulation.

CONCLUSION

MNPs do not adversely affect cellular function. Gene expression indicates that targeting MNP-loaded ECs to vascular stents may potentially stimulate re-endothelialization of an implant and attenuate neointimal hyperplasia.

The Combined Contribution of Vascular Endothelial Cell Migration and Adhesion to Stent Re-endothelialization

Coronary stent placement inevitably causes mechanical damage to the endothelium, leading to endothelial denudation and in-stent restenosis (ISR). Re-endothelialization depends mainly on the migration of vascular endothelial cells (VECs) adjacent to the damaged intima, as well as the mobilization and adhesion of circulating VECs. To evaluate the combined contribution of VEC migration and adhesion to re-endothelialization under flow and the influence of stent, in vitro models were constructed to simulate various endothelial denudation scales (2 mm/5 mm/10 mm) and stent deployment depths (flat/groove/bulge). Our results showed that (1) in 2 mm flat/groove/bulge models, both VEC migration and adhesion combined completed the percentage of endothelial recovery about 27, 16, and 12%, and migration accounted for about 21, 15, and 7%, respectively. It was suggested that the flat and groove models were in favor of VEC migration. (2) With the augmentation of the injury scales (5 and 10 mm), the contribution of circulating VEC adhesion on endothelial repair increased. Taken together, endothelial restoration mainly depended on the migration of adjacent VECs when the injury scale was 2 mm. The adhered cells contributed to re-endothelialization in an injury scale-dependent way. This study is helpful to provide new enlightenment for surface modification of cardiovascular implants.

Biomedical therapy using synthetic WKYMVm hexapeptide

WKYMVm hexapeptide has been identified as a strong FPR2 agonist through a library screening of synthetic peptides. The FPR2 has been reported to play a crucial role in inflammation and angiogenic responses via stimulation of chemotaxis, migration, cell proliferation, wound healing and vessel growth. Recently, the therapeutic effects of WKYMVm have been reported in various disease models. In cutaneous wound model in diabetic mice, WKYMVm facilitated wound healing processes by stimulating the formation of capillary and arteriole and re-epithelialization. In coronary artery stenosis model, WKYMVm coating on stent promoted re-endothelialization and lowered restenosis rate. In hindlimb ischemia mouse model, intramuscular injection of WKYMVm promoted homing of exogenously transplanted endothelial colony-forming cells and neovascularization, resulting in salvaging hindlimb. Furthermore, a single injection of WKYMVm encapsulated in poly (lactide-co-glycolide) microspheres was demonstrated to be as efficient as multiple injections of WKYMVm in restoring blood flow in hindlimb ischemia model. These observations may open up promising biomedical applications of WKYMVm for tissue repairs and regenerations.

Biological Characterization of Human Autologous Pericardium Treated with the Ozaki Procedure for Aortic Valve Reconstruction

Background: The Ozaki procedure is an innovative surgical technique aiming at reconstructing aortic valves with human autologous pericardium. Even if this procedure is widely used, a comprehensive biological characterization of the glutaraldehyde (GA)-fixed pericardial tissue is still missing. Methods: Morphological analysis was performed to assess the general organization of pericardium subjected to the Ozaki procedure (post-Ozaki) in comparison to native tissue (pre-Ozaki). The effect of GA treatment on cell viability and nuclear morphology was then investigated in whole biopsies and a cytotoxicity assay was executed to assess the biocompatibility of pericardium. Finally, human umbilical vein endothelial cells were seeded on post-Ozaki samples to evaluate the influence of GA in modulating the endothelialization ability in vitro and the production of pro-inflammatory mediators. Results: The Ozaki procedure alters the arrangement of collagen and elastic fibers in the extracellular matrix and results in a significant reduction in cell viability compared to native tissue. GA treatment, however, is not cytotoxic to murine fibroblasts as compared to a commercially available bovine pericardium membrane. In addition, in in vitro experiments of endothelial cell adhesion, no difference in the inflammatory mediators with respect to the commercial patch was found. Conclusions: The Ozaki procedure, despite alteration of ECM organization and cell devitalization, allows for the establishment of a noncytotoxic environment in which endothelial cell repopulation occurs.

Smooth muscle-specific drug targets for next-generation drug-eluting stent

The occurrence of stent thrombosis is one of the major obstacles limiting the long-term clinical efficacy of percutaneous coronary intervention. The anti-smooth muscle proliferation drugs coated on drug-eluting stents (DES) often indistinguishably block re-endothelialization, an essential step toward successful vascular repair, due to their nonspecific effect on endothelial cells (ECs). Therefore, identification of therapeutic targets that differentially regulate vascular smooth muscle cell (VSMC) and EC proliferation may lead to the development of ideal drugs for the next-generation DES. Our recent studies have shown that CTP synthase 1 (CTPS1) differentially regulates the proliferation of VSMC and EC after vascular injury. Therefore, CTPS1 inhibitors are promising agents for DES. In addition to CTPS1, other factors have also shown cell-specific effects on VSMC and/or EC proliferation and thus may become potential molecular targets for developing drugs to coat stents.

Exosomal Transfer of miR-185 Is Controlled by hnRNPA2B1 and Impairs Re-endothelialization After Vascular Injury

Dysfunction of endothelial cells (ECs) contributes to restenosis after vascular reconstruction for patients with coronary artery disease (CAD). The intercellular communication between ECs and vascular smooth muscle cells (VSMCs) might be critical in the development of restenosis and can be mediated by exosomes carrying functional microRNAs. miR-185 is reported to be associated with atherosclerosis, whether it plays a similar role in restenosis is unknown. In this study, we observed an elevated level of extracellular miR-185 in platelet-derived growth factor (PDGF)-stimulated VSMCs. The medium from PDGF-stimulated VSMCs promoted miR-185 expression in rat aortic ECs and inhibited EC angiogenesis. PDGF-stimulated VSMCs transferred miR-185 into ECs via exosomes. Furthermore, we found that the CXCL12 gene, a target of miR-185, is essential for the angiogenic potential of ECs. Exosomes derived from miR-185 mimic transfected VSMCs attenuated re-endothelialization after vascular injury. Moreover, we show that exosome-mediated miR-185 transfer is modulated by hnRNPA2B1. We also observed that hnRNPA2B1 is up-regulated during neointima formation and hnRNPA2B1 inhibition accelerates re-endothelialization and attenuates neointima formation following carotid injury. Taken together, our results indicate that exosomal miR-185 transfer from VSMCs to ECs is controlled by hnRNPA2B1 and impairs re-endothelialization after vascular injury.

Polydopamine-Modified Copper-Doped Titanium Dioxide Nanotube Arrays for Copper-Catalyzed Controlled Endogenous Nitric Oxide Release and Improved Re-Endothelialization

The controllable release is necessary for ideal drug delivery technologies. Because of their high specific surface area and high porosity, titanium dioxide nanotubes (TNTs) have been widely used as drug carriers in medical devices. By loading copper as the catalyst, nitric oxide (NO) generation was facilitated by catalyzing the decomposition of renewable endogenous NO donors in vivo. Herein, the long-term controllable release profile of NO is highlighted owing to the multilayer polydopamine (PDA) cap structure. Different layers of PDA are used to adjust the NO release behavior, and the results show that three layers of PDA can not only effectively prevent the burst release of NO but also maintain long-term stable release of copper ion and NO. The bioactivity of the NO generated from three-layer PDA-modified copper-loaded TNTs (PDA-3L-NTCu2) and unmodified copper-loaded TNTs (NTCu2) are verified by our work, indicating effective inhibition of platelet activation, thrombosis, inflammation, and intimal hyperplasia. Importantly, the PDA-3L-NTCu2 show selectively promote the growth of endothelial cells in vitro and outstanding re-endothelialization for 4 weeks in vivo, as compared to NTCu2, TNTs, and 316L stain steel. This study suggests that copper-loaded with PDA modification helps us achieve controlled long-term stable local NO release with well-retained bioactivity and enhanced re-endothelialization.

Hydroxybutyl Chitosan Polymer-Mediated CD133 Antibody Coating of Metallic Stents to Reduce Restenosis in a Porcine Model of Atherosclerosis

Antibody-coated stents to capture circulating endothelial progenitor cells (EPCs) for re-endothelialization appear to be a novel therapeutic option for the treatment of atherosclerotic disease. Hydroxybutyl chitosan (HBC), a linear polysaccharide made from shrimps and other crustacean shells, is biocompatible, nontoxic, and hydrophilic, making it ideal for biomedical applications. In this study, HBC was explored for the immobilization of anti-CD133 antibodies. We demonstrated that CD133 antibodies mediated by HBC were successfully coated on cobalt-chromium alloy discs and metal stents. The coating was homogeneous and smooth as shown by electronic microscopy analysis. Balloon expansion of coated stents did not cause cracking or peeling. The HBC discs promoted CD133+ EPCs and human umbilical vein endothelial cell growth in vitro. The CD133 antibody-coated but not bare discs bound CD133+ EPCs in vitro. Implantation of CD133 antibody-coated stents significantly inhibited intimal hyperplasia and reduced restenosis compared with implantation of bare stents in a porcine model of atherosclerosis. These findings suggest HBC is a valuable anchoring agent that can be applied for bioactive coating of stents and that CD133 antibody-coated stents might be a potential therapeutic alternative for the treatment of atherosclerotic disease.

Importance of β2AR elevation for re-endothelialization capacity mediated by late endothelial progenitor cells in hypertensive patients

Dysfunction of late endothelial progenitor cells (EPCs) has been suggested to be associated with hypertension. β2-Adrenergic receptor (β2AR) is a novel and key target for EPC homing. Here, we proposed that attenuated β2AR signaling contributes to EPCs dysfunction, whereas enhanced β2AR signaling restores EPCs' functions in hypertension. EPCs derived from hypertensive patients exhibited reduced cell number, impaired in vitro migratory and adhesion abilities, and impaired re-endothelialization after transplantation in nude mice with carotid artery injury. β2AR expression of EPCs from hypertensive patients was markedly downregulated, whereas the phosphorylation of the p38 mitogen-activated protein kinase (p38-MAPK) was elevated. The cleaved caspase-3 levels were elevated in EPCs. The overexpression of β2AR in EPCs from hypertensive patients inhibited p38-MAPK signaling, whereas it enhanced in vitro EPC proliferation, migration, and adhesion and in vivo re-endothelialization. The β2AR-mediated effects were attenuated by treating the EPCs with a neutralizing monoclonal antibody against β2AR, which could be partially antagonized by the p38-MAPK inhibitor SB203580. Moreover, shear stress stimulation, a classic nonpharmacological intervention, increased the phosphorylation levels of β2AR and enhanced the in vitro and in vivo functions of EPCs from hypertensive patients. Collectively, the current investigation demonstrated that impaired β2AR/p38-MAPK/caspase-3 signaling at least partially reduced the re-endothelialization capacity of EPCs from hypertensive patients. Restoration of β2AR expression and shear stress treatment could improve their endothelial repair capacity by regulating the p38-MAPK/caspase-3 signaling pathway. The clinical significance of β2AR in endothelium repair still requires further investigation.NEW & NOTEWORTHY Impaired β2-adrenergic receptor (β2AR) expression with an elevation of p38-MAPK/caspase-3 signaling at least partially contributes to the decline of re-endothelialization capacity of late endothelial progenitor cells (EPCs) from hypertensive patients. β2AR gene transfer and shear stress treatment improve the late EPC-mediated enhancement of the re-endothelialization capacity in hypertensive patients through activating β2AR/p38-MAPK/caspase-3 signaling. The present study is the first to reveal the potential molecular mechanism of the impaired endothelium-reparative capacity of late EPCs in hypertension after vascular injury and strongly suggests that β2AR is a novel and crucial therapeutic target for increasing EPC-mediated re-endothelialization capacity in hypertension.

IMP3 promotes re-endothelialization after arterial injury via increasing stability of VEGF mRNAhv

IMP3, an RNA‐binding protein (RBP) that participates in the process of post‐transcriptional modifications of mRNA transcripts, is capable of altering cellular functions, and in some cases, be involved in specific disease progression. We aimed to investigate whether IMP3 has the ability to regulate the functional properties of endothelial cells and re‐endothelialization in response to arterial injury. Wire injury was introduced to the right carotid arteries of wildtype C57/BL6 mice. As a result, IMPs’ expressions were up‐regulated in the induced arterial lesions, and IMP3 was the most up‐regulated RNA among other IMPs. We overexpressed IMP3 before the wire‐injured surgery using adeno‐associated virus AAV2‐IMP3. In vivo studies confirmed that IMP3 overexpression accelerated the progress of re‐endothelialization after arterial injury. In vitro, endothelial cells were transfected with either ad‐IMP3 or Si‐IMP3, cell functional studies showed that IMP3 could promote endothelial cell proliferation and migration, while reducing apoptosis. Mechanistic studies also revealed that IMP3 could enhance VEGF mRNA stability and therefore up‐regulate activities of VEGF/PI3K/Akt signalling pathway. Our data indicated that IMP3 promotes re‐endothelialization after arterial injury and regulates endothelial cell proliferation, migration and apoptosis via increasing stability of VEGF mRNA and activation of VEGF/PI3K/Akt signalling pathway.

Noninvasive in vivo Assessment of the Re-endothelialization Process Using Ultrasound Biomicroscopy in the Rat Carotid Artery Balloon Injury Model

OBJECTIVES

Ultrasound biomicroscopy (UBM), or ultra high-frequency ultrasound, is a technique used to assess the anatomy of small research animals. In this study, UBM was used to assess differences in intimal hyperplasia thickness as a surrogate measurement of the re-endothelialization process after carotid artery balloon injury in rats.

METHODS

Ultrasound biomicroscopic data from 3 different experiments and rat strains (Sprague Dawley, Wistar, and diabetic Goto-Kakizaki) were analyzed. All animals were subjected to carotid artery balloon injury and examined with UBM (30-70 MHz) 2 and 4 weeks after injury. Re-endothelialization on UBM was defined as the length from the carotid bifurcation to the most distal visible edge of the intimal hyperplasia. En face staining with Evans blue dye was performed at euthanasia 4 weeks after injury, followed by tissue harvesting for histochemical and immunohistochemical evaluations.

RESULTS

A significant correlation (Spearman r = 0.63; P < .0001) was identified when comparing all measurements of re-endothelialization obtained from UBM and en face staining. The findings revealed a similar pattern for all rat strains: Sprague Dawley (Spearman r = 0.70; P < .0001), Wistar (Spearman r = 0.36; P < .081), and Goto-Kakizaki (Spearman r = 0.70; P < .05). A Bland-Altman test showed agreement between en face staining and UBM. Immunohistochemical staining confirmed the presence of the endothelium in the areas detected as re-endothelialized by the UBM assessment.

CONCLUSIONS

Ultrasound biomicroscopy can be used for repeated in vivo assessment of re-endothelialization after carotid artery balloon injury in rats.

Faster smooth muscle cell coverage in ultrathin-strut drug-eluting stent leads to earlier re-endothelialization

Background: The ultrathin-strut drug-eluting stent (DES) has shown better clinical results than thin- or thick-strut DES. We investigated if re-endothelialization was different among three types of DES: ultrathin-strut abluminal polymer-coated sirolimus-eluting stent (SES), thin-strut circumferential polymer-coated everolimus-eluting stent (EES), and thick-strut polymer-free biolimus-eluting stent (BES) to gain insight into the effect of stent design on promoting vascular healing. Methods: After implanting three types of DES in the coronary arteries of minipigs, we performed optical coherence tomography (OCT) at weeks 2, 4, and 12 (n = 4, each). Afterward, we harvested the coronary arteries and performed immunofluorescence for endothelial cells (ECs), smooth muscle cells (SMCs), and nuclei. We obtained 3D stack images of the vessel wall and reconstructed the en face view of the inner lumen. We compared re-endothelialization and associated factors among the different types of stents at different time points. Results: SES showed significantly faster and denser re-endothelialization than EES and BES at weeks 2 and 12. Especially in week 2, SES elicited the fastest SMC coverage and greater neointimal cross-sectional area (CSA) compared to EES and BES. A strong correlation between re-endothelialization and SMC coverage was observed in week 2. However, the three stents did not show any difference at weeks 4 and 12 in SMC coverage and neointimal CSA. At weeks 2 and 4, SMC layer morphology showed a significant difference between stents. A sparse SMC layer was associated with denser re-endothelialization and was significantly higher in SES. Unlike the sparse SMC layer, the dense SMC layer did not promote re-endothelialization during the study period. Conclusion: Re-endothelialization after stent implantation was related to SMC coverage and SMC layer differentiation, which were faster in SES. Further investigation is needed to characterize the differences among the SMCs and explore methods for increasing the sparse SMC layer in order to improve stent design and enhance safety and efficacy.

Zyxin Mediates Vascular Repair via Endothelial Migration Promoted by Forskolin in Mice

Background and Purpose: Endothelial repair upon vascular injury is critical for the protection of vessel integrity and prevention of the development of vascular disorders, but the underlying mechanisms remain poorly understood. In this study, we investigated the role of zyxin and its associated cyclic adenosine monophosphate (cAMP) signaling in the regulation of re-endothelialization after vascular injury. Experimental Approach: In zyxin-/- and wild-type mice, wire injury of the carotid artery was carried out, followed by Evans blue staining, to evaluate the re-endothelialization. Mice with endothelium-specific zyxin knockout were used to further determine its role. An in vitro wound-healing assay was performed in primary human endothelial cells (ECs) expressing zyxin-specific short-hairpin RNAs (shRNAs) or scrambled controls by measuring cell migration and proliferation. The effects of the cAMP signaling agonist forskolin were assessed. Key Results: The re-endothelialization of the injured carotid artery was impaired in zyxin-deficient mice, whereas the rate of cell proliferation was comparable with that in wild-type controls. Furthermore, endothelium-specific deletion of zyxin led to similar phenotypes. Knockdown of zyxin by shRNAs in primary human ECs significantly reduced cell migration in the wound-healing assay. Notably, forskolin enhanced endothelial migration in a dose-dependent manner, and this was dependent on zyxin through its interaction with vasodilator-stimulated phosphoprotein. In addition, forskolin promoted the re-endothelialization of the injured carotid artery, and this was compromised by zyxin deficiency. Conclusion and Implications: This study reveals zyxin as a new player in endothelial repair, which is promoted by forskolin, after vascular injury. Thus, zyxin-mediated signaling might be a potential treatment target for diseases involving vascular injury.

Development of a Highly Hydrophobic Micro/Nanostructured Nanocomposite Coating of PLA-PEG-Cloisite 20A Nanoclay with Excellent Hemocompatibility and Rapid Endothelialization Properties for Cardiovascular Applications

Despite the unique properties of clay nanocomposites for cardiovascular applications, there are few data on the hemocompatibility of these nanomaterials. This study represents the first comprehensive investigation of the hemo/biocompatibility of clay nanocomposites in vitro. Nanocomposite coatings of polylactic acid (PLA)-polyethylene glycol (3 wt %)-Cloisite20A nanoclay (3 wt %) were produced using electrospraying technique as potential drug-eluting stent (DES) coatings. Pristine PLA coating served as a control. The coatings ' different structural and biological properties were assessed, including surface morphology, topography, hydrophobicity, mechanics, and the interaction of nanocomposites with blood components, endothelial cells (EC), and bacteria. Findings indicated that all of the coatings were highly hydrophobic with microbead/nanofiber morphology and had antifouling properties. The absorption profiles of plasma proteins were similar for all groups, and nanocomposites did not trigger the coagulation cascade and complement activation. The nanocomposites did not increase hemolysis or platelet and leukocyte adhesion and activation. Interestingly, the nanocomposites exhibited the lowest levels of interleukin-6 production. Cellular experiments showed that the nanocomposites did not reduce ECs survival compared to the control group, and a continuous layer of ECs covered the nanocomposite surfaces after 4 days. These results demonstrate the exceptional hemo/biocompatibility of as-prepared clay nanocomposites as promising biomaterials for implants such as DESs.

The Supreme Biodegradable Polymer DES in Acute and Chronic Coronary Syndromes: A PIONEER III Substudy

Background

The PIONEER III trial demonstrated noninferiority of 12-month target lesion failure (TLF) with the Supreme DES (Sinomed), a thin-strut cobalt-chromium, biodegradable polymer, sirolimus-eluting stent, compared with a durable polymer, everolimus-eluting (XIENCE/PROMUS) stent (DP-EES). The relative safety and effectiveness of the Supreme DES in patients with acute coronary syndromes (ACS) and those with chronic coronary syndromes (CCS) is not known.

Methods

PIONEER III was a prospective, multicenter, international, 2:1 randomized trial stratified by clinical presentation. The primary end point was TLF at 12 months (a composite of cardiac death, target vessel myocardial infarction, or ischemia-driven target lesion revascularization).

Results

A total of 1628 patients were enrolled, including 41% of patients with ACS (unstable angina and non-ST-elevation myocardial infarction) randomized to Supreme DES (n = 441) versus DP-EES (n = 232) and 59% of patients with CCS randomized to Supreme DES (n = 645) versus DP-EES (n = 310). Patients with ACS were younger, fewer presented with less diabetes, hypertension, and previous revascularization, but more were current smokers. The primary end point of TLF (6.4% vs 4.4%; P = .1), major adverse cardiac events (8.5% vs 6.5%; P = .16), and stent thrombosis (0.4% vs 0.9%; P = .25) at 12 months were similar in the ACS and CCS groups. There was no difference in TLF at 12 months between Supreme DES and DP-EES among patients with ACS (6.6% vs 6.0%; P = .89) and those with CCS (4.5% vs 4.3%; P = .83); interaction P = .51 for TLF by clinical presentation.

Conclusions

Compared with the DP-EES, the Supreme DES seemed safe and effective with a similar TLF at 12 months in both patients with ACS and those with CCS.