Overview of therapies for prevention of restenosis after coronary interventions

Biophysical and Biochemical Roles of Shear Stress on Endothelium: A Revisit and New Insights

Hemodynamic shear stress, the frictional force exerted by blood flow on the endothelium, mediates vascular homeostasis. This review examines the biophysical nature and biochemical effects of shear stress on endothelial cells, with a particular focus on its impact on cardiovascular pathophysiology. Atherosclerosis develops preferentially at arterial branches and curvatures, where disturbed flow patterns are most prevalent. The review also highlights the range of shear stress across diverse human arteries and its temporal variations, including aging-related alterations. This review presents a summary of the critical mechanosensors and flow-sensitive effectors that respond to shear stress, along with the downstream cellular events that they regulate. The review evaluates experimental models for studying shear stress in vitro and in vivo, as well as their potential limitations. The review discusses strategies targeting shear stress, including pharmacological approaches, physiological means, surgical interventions, and gene therapies. Furthermore, the review addresses emerging perspectives in hemodynamic research, including single-cell sequencing, spatial omics, metabolomics, and multiomics technologies. By integrating the biophysical and biochemical aspects of shear stress, this review offers insights into the complex interplay between hemodynamics and endothelial homeostasis at the preclinical and clinical levels.

Phenotypic switching of vascular smooth muscle cells in atherosclerosis, hypertension, and aortic dissection

Vascular smooth muscle cells (VSMCs) play a critical role in regulating vasotone, and their phenotypic plasticity is a key contributor to the pathogenesis of various vascular diseases. Two main VSMC phenotypes have been well described: contractile and synthetic. Contractile VSMCs are typically found in the tunica media of the vessel wall, and are responsible for regulating vascular tone and diameter. Synthetic VSMCs, on the other hand, are typically found in the tunica intima and adventitia, and are involved in vascular repair and remodeling. Switching between contractile and synthetic phenotypes occurs in response to various insults and stimuli, such as injury or inflammation, and this allows VSMCs to adapt to changing environmental cues and regulate vascular tone, growth, and repair. Furthermore, VSMCs can also switch to osteoblast-like and chondrocyte-like cell phenotypes, which may contribute to vascular calcification and other pathological processes like the formation of atherosclerotic plaques. This provides discusses the mechanisms that regulate VSMC phenotypic switching and its role in the development of vascular diseases. A better understanding of these processes is essential for the development of effective diagnostic and therapeutic strategies.

Experimental study of a heparin-coated venous stent fabricated by atomic layer deposition

OBJECTIVE

To evaluate the safety and efficacy of heparin-coated venous stents in animals.

METHODS

We used atomic layer deposition technology to obtain a heparin coating with good stability and then prepared a heparin-coated venous stent based on this technology. The experimental stents were prepared according to the diameter of the rabbit inferior vena cava and were divided into Ni-Ti alloy stent group, Ni-Ti-Al₂O₃ stent group and Ni-Ti-Al₂O₃-Heparin stent group. 3 days, 7 days and 14 days after stent implantation, the materials were collected, and the three groups of stents were observed by hard tissue section pathology, immunohistochemistry and scanning electron microscope to observe the differences in vascular wall inflammation, thrombosis, lumen stenosis and vascular intima regeneration.

RESULT AND CONCLUSION

The experiment confirmed the safety of the heparin-coated stent in vivo. Compared with the control group, the experimental group showed a high degree of vascular endothelialization and an intact neointimal structure 14 days after implantation. The long-term safety and biological effects of heparin-coated venous stents in animals require further study.

Induction of ferroptosis promotes vascular smooth muscle cell phenotypic switching and aggravates neointimal hyperplasia in mice

BACKGROUND

Stent implantation-induced neointima formation is a dominant culprit in coronary artery disease treatment failure after percutaneous coronary intervention. Ferroptosis, an iron-dependent regulated cell death, has been associated with various cardiovascular diseases. However, the effect of ferroptosis on neointima formation remains unclear.

METHODS

The mouse common right carotid arteries were ligated for 16 or 30 days, and ligated tissues were collected for further analyses. Primary rat vascular smooth muscle cells (VSMCs) were isolated from the media of aortas of Sprague-Dawley (SD) rats and used for in vitro cell culture experiments.

RESULTS

Ferroptosis was positively associated with neointima formation. In vivo, RAS-selective lethal 3 (RSL3), a ferroptosis activator, aggravated carotid artery ligation-induced neointima formation and promoted VSMC phenotypic conversion. In contrast, a ferroptosis inhibitor, ferrostatin-1 (Fer-1), showed the opposite effects in mice. In vitro, RSL3 promoted rat VSMC phenotypic switching from a contractile to a synthetic phenotype, evidenced by increased contractile markers (smooth muscle myosin heavy chain and calponin 1), and decreased synthetic marker osteopontin. The induction of ferroptosis by RSL3 was confirmed by the increased expression level of ferroptosis-associated gene prostaglandin-endoperoxide synthase 2 (Ptgs2). The effect of RSL3 on rat VSMC phenotypic switching was abolished by Fer-1. Moreover, N-acetyl-L-cysteine (NAC), the reactive oxygen species inhibitor, counteracted the effect of RSL3 on the phenotypic conversion of rat VSMCs.

CONCLUSIONS

Ferroptosis induces VSMC phenotypic switching and accelerates ligation-induced neointimal hyperplasia in mice. Our findings suggest inhibition of ferroptosis as an attractive strategy for limiting vascular restenosis.

Co-immobilization of ACH11 antithrombotic peptide and CAG cell-adhesive peptide onto vascular grafts for improved hemocompatibility and endothelialization

Surface modification by conjugating biomolecules has been widely proved to enhance biocompatibility of small-caliber artificial vascular grafts. In this study, we aimed at developing a multifunctional vascular graft that provides not only good hemocompatibility but also in situ rapid endothelialization. Herein, a vascular graft (inner diameter ∼2 mm) was fabricated by electrospinning with poly(lactic acid-co-caprolactone) and gelatin, and then biofunctionalized with antithrombotic peptide with sequence LTFPRIVFVLG (ACH₁₁) and cell adhesion peptide with sequence CAG through adhesive poly(dopamine) coating. We developed this graft with the synergistic properties of low thrombogenicity and rapid endothelialization. The successful grafting of both CAG and ACH₁₁ peptides was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface micromorphology of the modified surfaces was observed by field emission scanning electron microscopy. Our results demonstrated that the multifunctional surface suppressed the denaturation of absorbed fibrinogen, hindered coagulation factor Xa activation, and inhibited platelet adhesion and aggregation. Importantly, this modified surface could selectively enhance endothelial cells adhesion, proliferation and release of nitric oxide. Upon in vivo implantation of 6 weeks, the multifunctional vascular graft showed improved patency and superior vascular endothelialization. Overall, the results effectively demonstrated that the co-immobilization of ACH₁₁ and CAG provided a promising method for the improvement of hemocompatibility and endothelialization of vascular grafts. STATEMENT OF SIGNIFICANCE: Electrospun small-caliber vascular grafts are increasingly used to treat cardiovascular diseases. Despite their success related to their good biodegradation and mechanical strength, they have some drawbacks, such as low hemocompatibility and endothelialization. The single-function ligands are insufficient to modify surface with both good hemocompatibility and rapid endothelialization simultaneously. Therefore, we functionalized electrospun vascular graft by novel antithrombotic peptide and cell-adhesive peptide to construct superior anticoagulation and ECs-selective adhesion surface in present study. The multifunctional vascular grafts benefit for high long-term patency and rapid endothelialization.

The microRNAs Regulating Vascular Smooth Muscle Cell Proliferation: A Minireview

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in atherosclerosis. At the beginning of the pathologic process of atherosclerosis, irregular VSMC proliferation promotes plaque formation, but in advanced plaques VSMCs are beneficial, promoting the stability and preventing rupture of the fibrous cap. Recent studies have demonstrated that microRNAs (miRNAs) expressed in the vascular system are involved in the control of VSMC proliferation. This review summarizes recent findings on the miRNAs in the regulation of VSMC proliferation, including miRNAs that exhibit the inhibition or promotion of VSMC proliferation, and their targets mediating the regulation of VSMC proliferation. Up to now, most of the studies were performed only in cultured VSMC. While the modulation of miRNAs is emerging as a promising strategy for the regulation of VSMC proliferation, most of the effects of miRNAs and their targets in vivo require further investigation.

Efficacy and safety of drug-eluting stent for the intracranial atherosclerotic disease: A systematic review and meta-analysis

Drug-eluting stent (DES) is a potential endovascular treatment for patients with symptomatic intracranial atherosclerotic disease (sICAD). However, evidence regarding the treatment of ICAD with DES is lacking. We systematically searched Pubmed, Embase, Cochrane database (before 2017-12-21) for literature reporting the application of DES in the treatment of sICAD. The main outcomes were as follows: the incidence of any stroke or death within 30 days (perioperative complications), ischemic stroke in the territory of the qualifying artery beyond 30 days (long-term complications), in-stent restenosis rate (ISR) and symptomatic ISR during follow-up. Those studies with mean stenosis rate greater than 70% and less than 70% were defined as severe and moderate stenosis group, respectively. The random effect model was used to pool the data. Of 518 articles, 13 studies were eligible and included in our analysis (N = 336 patients with 364 lesions). After the implantation of DES, perioperative complications (mortality = 0) occurred in 6.0% (95%CI 2.0%-11.9%), long-term complications occurred in 2.2% (95%CI 0.7%-4.5%), ISR rate was 4.1% (95%CI 1.6%-7.7%) and the symptomatic ISR rate was only 0.5% (95%CI 0-2.2%). In addition, subgroup analysis showed that the perioperative complication rate in severe stenosis group [10.6% (95%CI 6.5%-15.7%)] was significantly (p < 0.01) higher than that in moderate stenosis group [1.0% (95%CI 0.3%-3.5%)]. In summary, endovascular DES implantation is a relatively safe and effective method compared with stents or medical management group in SAMMPRIS and VISSIT trials. However, a higher preoperative stenosis rate may imply a higher risk of perioperative complications. Further studies are needed.

Monocyte-mediated drug delivery systems for the treatment of cardiovascular diseases

Major advances have been achieved in understanding the mechanisms and risk factors leading to cardiovascular disorders and consequently developing new therapies. A strong inflammatory response occurs with a substantial recruitment of innate immunity cells in atherosclerosis, myocardial infarction, and restenosis. Monocytes and macrophages are key players in the healing process that ensues following injury. In the inflamed arterial wall, monocytes, and monocyte-derived macrophages have specific functions in the initiation and resolution of inflammation, principally through phagocytosis, and the release of inflammatory cytokines and reactive oxygen species. In this review, we will focus on delivery systems, mainly nanoparticles, for modulating circulating monocytes/monocyte-derived macrophages. We review the different strategies of depletion or modulation of circulating monocytes and monocyte subtypes, using polymeric nanoparticles and liposomes for the therapy of myocardial infarction and restenosis. We will further discuss the strategies of exploiting circulating monocytes for biological targeting of nanocarrier-based drug delivery systems for therapeutic and diagnostic applications.

Identification of PI3K regulatory subunit p55γ as a novel inhibitor of vascular smooth muscle cell proliferation and neointimal formation

AIMS

Phosphatidylinositol 3 kinases (PI3Ks) play a pivotal role in vascular physiology and pathophysiology. We aimed to investigate the role of p55γ, a regulatory subunit of PI3Ks, in vascular smooth muscle cell (VSMC) proliferation and neointimal formation.

METHODS AND RESULTS

We identified p55γ as an important factor that suppresses VSMC proliferation and injury-evoked neointimal formation. Western blot and mRNA analyses showed that p55γ expression declined in balloon-injured rat carotid arteries and in response to PDGF-BB and serum treatment in cultured VSMCs. Overexpression of p55γ inhibited, whereas short hairpin RNA knockdown of p55γ promoted PDGF-BB- and serum-induced VSMC proliferation. Importantly, in vivo adenoviral gene transfer of p55γ into carotid arteries attenuated, while knockdown of p55γ enhanced balloon injury-induced neointimal formation. Furthermore, p55γ sequentially up-regulated p53 and p21, resulting in cell-cycle arrest in S phase; small-interfering RNA knockdown of either p53 or p21 blocked p55γ-induced VSMC growth arrest. Mechanistically, p55γ interacted with and stabilized p53 protein by blocking mouse double minute 2 homologue-mediated p53 ubiquitination and degradation, subsequently activating its target gene p21. Concurrently, p55γ up-regulated Bcl-xl expression, resulting in non-apoptotic growth arrest effect.

CONCLUSION

These findings mark p55γ as a novel upstream regulator of the p53-p21 signalling pathway that negatively regulates VSMC proliferation, suggesting that malfunction of p55γ may trigger vascular proliferative disorders.

Mussel-inspired one-step adherent coating rich in amine groups for covalent immobilization of heparin: hemocompatibility, growth behaviors of vascular cells, and tissue response

Heparin, an important polysaccharide, has been widely used for coatings of cardiovascular devices because of its multiple biological functions including anticoagulation and inhibition of intimal hyperplasia. In this study, surface heparinization of a commonly used 316L stainless steel (SS) was explored for preparation of a multifunctional vascular stent. Dip-coating of the stents in an aqueous solution of dopamine and hexamethylendiamine (HD) (PDAM/HD) was presented as a facile method to form an adhesive coating rich in primary amine groups, which was used for covalent heparin immobilization via active ester chemistry. A heparin grafting density of about 900 ng/cm(2) was achieved with this method. The retained bioactivity of the immobilized heparin was confirmed by a remarkable prolongation of the activated partial thromboplastin time (APTT) for about 15 s, suppression of platelet adhesion, and prevention of the denaturation of adsorbed fibrinogen. The Hep-PDAM/HD also presented a favorable microenvironment for selectively enhancing endothelial cell (EC) adhesion, proliferation, migration and release of nitric oxide (NO), and at the same time inhibiting smooth muscle cell (SMC) adhesion and proliferation. Upon subcutaneous implantation, the Hep-PDAM/HD exhibited mitigated tissue response, with thinner fibrous capsule and less granulation formation compared to the control 316L SS. This number of unique functions qualifies the heparinized coating as an attractive alternative for the design of a new generation of stents.

Gallic acid tailoring surface functionalities of plasma-polymerized allylamine-coated 316L SS to selectively direct vascular endothelial and smooth muscle cell fate for enhanced endothelialization

The creation of a platform for enhanced vascular endothelia cell (VEC) growth while suppressing vascular smooth muscle cell (VSMC) proliferation offers possibility for advanced coatings of vascular stents. Gallic acid (GA), a chemically unique phenolic acid with important biological functions, presents benefits to the cardiovascular disease therapy because of its superior antioxidant effect and a selectivity to support the growth of ECs more than SMCs. In this study, GA was explored to tailor such a multifunctional stent surface combined with plasma polymerization technique. On the basis of the chemical coupling reaction, GA was bound to an amine-group-rich plasma-polymerized allylamine (PPAam) coating. The GA-functionalized PPAam (GA-PPAam) surface created a favorable microenvironment to obtain high ECs and SMCs selectivity. The GA-PPAam coating showed remarkable enhancement in the adhesion, viability, proliferation, migration, and release of nitric oxide (NO) of human umbilical vein endothelial cells (HUVECs). The GA-PPAam coating also resulted in remarkable inhibition effect on human umbilical artery smooth muscle cell (HUASMC) adhesion and proliferation. These striking findings may provide a guide for designing the new generation of multifunctional vascular devices.

Urokinase receptor counteracts vascular smooth muscle cell functional changes induced by surface topography

Current treatments for human coronary artery disease necessitate the development of the next generations of vascular bioimplants. Recent reports provide evidence that controlling cell orientation and morphology through topographical patterning might be beneficial for bioimplants and tissue engineering scaffolds. However, a concise understanding of cellular events underlying cell-biomaterial interaction remains missing. In this study, applying methods of laser material processing, we aimed to obtain useful markers to guide in the choice of better vascular biomaterials. Our data show that topographically treated human primary vascular smooth muscle cells (VSMC) have a distinct differentiation profile. In particular, cultivation of VSMC on the microgrooved biocompatible polymer E-shell induces VSMC modulation from synthetic to contractile phenotype and directs formation and maintaining of cell-cell communication and adhesion structures. We show that the urokinase receptor (uPAR) interferes with VSMC behavior on microstructured surfaces and serves as a critical regulator of VSMC functional fate. Our findings suggest that microtopography of the E-shell polymer could be important in determining VSMC phenotype and cytoskeleton organization. They further suggest uPAR as a useful target in the development of predictive models for clinical VSMC phenotyping on functional advanced biomaterials.

Long-term Outcomes of Drug-eluting Stents in Symptomatic Intracranial Stenosis

Purpose

The use of drug-eluting stent (DES) to treat intracranial stenosis has shown short-term success. However, there are no reports regarding the long-term results of DES. We present the long-term clinical outcome after DES stenting for symptomatic severe intracranial stenosis.

Materials and Methods

Our study included a consecutive series of 11 patients who underwent intracranial stenting using DES between March and July, 2006, during the time when bare metal stents were not available at our medical institution. The mean patient age was 59 years. Lesion location was the middle cerebral artery in five patients, the intradural vertebral artery in three, the basilar artery in one, the vertebrobasilar junction in one, and the cavernous internal cerebral artery in one patient. We evaluated the technical success, defined as reduction of residual stenosis ≤30% in the target lesion) as well as the clinical and imaging outcomes as long as 75 months following the procedure. In addition to a cerebral angiogram (n = 2), follow-up study was obtained by CT angiography (n = 6) or intracranial Doppler imaging (n = 2) during a mean time of 55 months after the procedure (range, 24 to 73 months). Three patients refused imaging follow-up and accepted only clinical follow-up. The mean clinical follow-up period was 67 months (range, 47-75 months).

Results

Stenting in all patients was technically successful and without periprocedural complications. There was thrombus formation during the procedure in one patient who experienced no further complications. There were no new neurological events during the mean follow-up period of 5.6 years. No patients were found to have restenosis ≥50% at during the mean follow-up period of 55 months. One patient died of a sudden heart attack 59 months following the procedure which was regarded as unrelated to the cerebral lesion.

Conclusion

Our study demonstrates that DES shows long-term stability and safety, and results in good clinical outcomes with a low rate of restenosis.

Histological examination of vascular lesions caused by stent implantation in humans and in comparative experimental animal model

A comparative analysis of human and experimental animal (canine) tissues was performed to characterize and describe cellular and histological responses during the processes of newly forming intravascular tissues after stent implantation. Routine histological and immunohistochemical evaluation of 20 human samples and 9 samples from animal models were used one day, one week and one month after the stent implantation. After one day of implantation, there was no difference between the human and canine peripheral arteries, suggesting a similar cellular and histological response in the early phase. In contrast, after one week of implantation, during the proliferative phase the repairing human tissue showed less intensive production of inflammatory cells and more intensive increase in number of vascular cells than did the canine model. In addition, cellular changes normally restituted by the end of one month in canine peripheral arteries, but vascular cells persisted in human atherosclerotic arteries. In conclusion, results of this study suggest differences in both phases of vascular repair in the post-stented period, because both proliferative and regressive phases showed histological differences in canine and human samples. In canine, the restitution of vascular wall was completed by the end of first month but persistent vascular cell proliferation was visible in the human peripheral arteries. It can be suggested that delayed cellular response might indicate restenosis but also can be considered considered as a progression of the original arterial disease.

In vivo PEG modification of vascular surfaces for targeted delivery

OBJECTIVE

Thrombosis and restenosis remain problematic for many intravascular procedures. Previously, it has been demonstrated that modifying an injured vascular surface with a protein-reactive polymer could block undesirable platelet deposition. As an added benefit, it would be advantageous if one could target therapeutics to the injured site. This study investigates a site-specific delivery system to target microspheres to vascular surfaces modified with a reactive polyethylene glycol tagged with biotin.

METHODS

Rabbit femoral arteries were injured with a 2F embolectomy catheter. Modification of the vascular surface was achieved using a channeled balloon catheter or small-diameter tube. Microspheres were injected intravenously through catheterization of the ear vein. Polymer modification on the injured surface and delivery of microspheres was quantified using epifluorescence microscopy at 0, 24, 48, and 72 hours.

RESULTS

Polymer modification of the vascular surface could be achieved using a channeled drug delivery catheter or small-diameter tube with similar results. Maximum polymer coverage occurred at 0 hours and decreased to 85% maximal at 24 hours, 72% at 48 hours, and 67% at 72 hours. The initial number of microspheres per mm(2) binding to modified, injured arteries was 304 versus 141 for the unmodified, damaged control (P < .01). At subsequent times, the number of adherent microspheres to modified, injured arteries decreased by 50%, 70%, and 84% at 24, 48, and 72 hours, respectively; while nonspecific binding to unmodified, injured arteries quickly decreased by 93%. Initial microsphere binding to modified, healthy arteries was 153 microspheres/mm(2) as opposed to 26 microspheres/mm(2) for the unmodified, healthy controls (P < .01).

CONCLUSIONS

Chemical modification of injured vessels following intravascular procedures can be readily accomplished in vivo to create a substrate for targeted delivery systems. As a proof of concept, targeted microspheres preferentially adhered to polymer-modified surfaces as opposed to injured, unmodified, or healthy vascular surfaces.

Haemo- and cytocompatibility of bioresorbable homo- and copolymers prepared from 1,3-trimethylene carbonate, lactides, and epsilon-caprolactone

A series of bioresorbable polymers were prepared by ring-opening polymerization of L-lactide (LLA), DL-lactide (DLLA), epsilon-caprolactone (CL) and 1,3-trimethylene carbonate (TMC), using low toxic zinc lactate as catalyst. The various PLLA, PTMC, PCL homopolymers, and PLLA-TMC, PDLLA-TMC, PCL-TMC copolymers with 50/50 molar ratios were characterized by using analytical techniques such as proton nuclear magnetic resonance, gel permeation chromatography, tensiometer, and differential scanning calorimetry. The haemo- and cyto-compatibility were investigated in order to evaluate the potential of the polymers as coating material in drug eluting stents. Haemolysis tests show that all the homo- and copolymers present very low haemolytic ratios, indicating good haemolytic properties. Adhesion and activation of platelets were observed on the surface of PLLA, PCL, PLLA-TMC, and PDLLA-TMC films, while less platelets and lower activation were found on PTMC. The most interesting results were obtained with PCL-TMC which exhibited the lowest degree of activation with few adhered platelets, in agreement with its outstanding anticoagulant properties. Both indirect and direct cytocompatibility studies were performed on the polymers. The relative growth ratio data obtained from the liquid extracts during the 6-day cell culture period indicate that all the polymers present very low cytotoxicity. Microscopic observations demonstrate adhesion, spreading and proliferation of human umbilical vein endothelial cells ECV304. Therefore, it is concluded that these bioresorbable polymers, in particular PCL-TMC, are promising candidate materials as drug loading coating material in drug eluting stents.

Preventing restenosis in early drug-eluting stent era: recent developments and future perspectives

Restenosis is the major limitation of the successful therapy of percutaneous coronary intervention (PCI) for patients with coronary artery disease. The problem was appreciated in the late 1970s to early 1980s. Only in recent years, anti-restenotic therapy has achieved a breakthrough with the development of drug-eluting stents. Here, we provide an overview about pathological mechanisms of restenosis after PCI. Present therapeutic approaches to overcome restenosis and recent clinical results are revisited, and some major concerns in the post-drug-eluting stent era are discussed.

The evolution and role of endovascular therapy for the treatment of intracranial atherosclerotic disease

Intracranial atherosclerotic disease (ICAD) is being seen as an increasingly important cause of transient ischemic attack and stroke. Attention on this disease entity has been focused as a result of two recent events: the publication of the WASID trial and the recent Food and Drug Administration approval of the Wingspan-Gateway stent system. This manuscript will review the evolution of the role of endovascular therapy in the management of ICAD. In addition, the available devices currently available for endovascular therapy will be reviewed with an eye toward peri-procedural and follow-up complication rates.

The short-term effect on restenosis and thrombosis of a cobalt-chromium stent eluting two drugs in a porcine coronary artery model

The aim of this article was to study the effect of dual drug-eluting stent (DES) on both restenosis and thrombosis in a porcine coronary artery model. This study reports on the use of two drugs coated on the stent to simultaneously minimize both restenosis and thrombosis. The DES was prepared by spray coating a bare metal stent with a biodegradable polymer loaded with sirolimus and triflusal, to treat against restenosis and thrombosis, respectively. The two-layered dual drug-coated stent was characterized in vitro for surface properties before and after expansion, as well as for possible delamination by cross-sectioning the stent in vitro. In vivo animal studies (in a pig model) were then performed for acute thrombosis, inflammation, and restenosis. The results show a significant reduction in restenosis with a stent coated with both drugs compared with the controls (a bare metal stent, a sirolimus-coated, and a pure polymer-coated stent). The reduction in restenosis with a sirolimus/triflusal-eluting stent is associated with an inhibition of inflammation and thrombus formation, suggesting that such dual DES have a role to play for the treatment of coronary artery diseases.

Preparation and in vitro release profiles of drug-eluting controlled biodegradable polymer coating stents

In the present study, the different drug-eluting controlled biodegradable polymer coatings were fabricated on stainless steel stents. The coatings were not only uniform and smooth but also had excellent mechanical property. The drug release profiles of drug-eluting stents were studied in detail in this study. Depending on the drug type, different drug-eluting stents exhibited different drug release profile. There were two basic release profiles for different drug-eluting stents, i.e., two-phase release profile with burst release or linear release profile without burst release. Incorporating heparin in the rapamycin or curcumin eluting stents can improve the average drug release rate of both and the burst release of rapamycin. The average drug release rate increased with the increase of drug loading but was not proportional to increase of the ratio of drug/polymer. Fabricating the control release layer on rapamycin-eluting stent surface can prevent the burst release of rapamycin and prolong the release period of rapamycin. All results showed that the drug release profile of drug-eluting stents depends on many parameters including drug type, ratio of drug/polymer, and drug carrier properties.

Avoiding restenosis: is there a role for glucocorticoids in the drug-eluting stent era?

Restenosis is an important limitation of percutaneous coronary interventions (PCI). In-stent restenosis is mainly due to neointimal hyperplasia, a proliferative process modulated by inflammatory mechanisms. Numerous technical and pharmacological means have been tested to reduce restenosis rates, with frequently disappointing clinical results. Drug-eluting stents (DES) have demonstrated a high efficacy in reducing restenosis, but there are some associated problems that limit its generalized utilization. Glucocorticoids (GC), as potent anti-inflammatory agents, may exert beneficial effects on neointimal proliferation. Clinical studies with oral and intracoronary GC therapy have demonstrated reduction in restenosis rates in selected patients. Although further investigations are warranted, GC might have a potential role for restenosis prevention in selected cases.

Predicting in vivo efficacy of potential restenosis therapies by cell culture studies: species-dependent susceptibility of vascular smooth muscle cells

Although drug-eluting stents (DES) are successfully utilized for restenosis therapy, the development of local and systemic therapeutic means including nanoparticles (NP) continues. Lack of correlation between in vitro and in vivo studies is one of the major drawbacks in developing new drug delivery systems. The present study was designed to examine the applicability of the arterial explant outgrowth model, and of smooth muscle cells (SMC) cultures for prescreening of possible drugs. Elucidation of different species sensitivity (rat, rabbit, porcine and human) to diverse drugs (tyrphostins, heparin and bisphsophonates) and a delivery system (nanoparticles) could provide a valuable screening tool for further in vivo studies. The anticipated sensitivity ranking from the explant outgrowth model and SMC mitotic rates (porcine>rat>>rabbit>human) do not correlate with the observed relative sensitivity of those animals to antiproliferative therapy in restenosis models (rat≥rabbit>porcine>human). Similarly, the inhibitory profile of the various antirestenotic drugs in SMC cultures (rabbit>porcine>rat>>human) do not correlate with animal studies, the rabbit- and porcine-derived SMC being highly sensitive. The validity of in vitro culture studies for the screening of controlled release delivery systems such as nanoparticles is limited. It is suggested that prescreening studies of possible drug candidates for restenosis therapy should include both SMC cell cultures of rat and human, appropriately designed with a suitable serum.

Drug-Eluting Stents

The introduction of percutaneous transluminal coronary angioplasty has revolutionized the field of cardiology by providing patients with coronary artery disease immediate and effective therapy. Overshadowing the early success of angioplasty was the high rate of angiographic restenosis and recurrent symptoms at 6 months. The use of stents reduced the incidence of restenosis; however, the rise in the number of patients undergoing percutaneous interventions produced a new problem of restenosis occurring within the stent: in-stent restenosis (ISR). Mechanical approaches, including directional and rotational atherectomy and systemic pharmacotherapy, have failed to demonstrate a reduction in ISR in randomized clinical trials. Intravascular brachytherapy is currently the only approved therapy for ISR, although this treatment has numerous unresolved questions and is not effective in a large percent of patients. Drug-eluting stents have reduced the incidence of restenosis by providing localized therapy to the targeted lesion without systemic toxicity. The purpose of this review is to synthesize data from major clinical trials involving the 2 most successful agents used in the prevention of restenosis: sirolimus and paclitaxel. The cellular and molecular mechanisms of both ISR and restenosis postangioplasty derived from animal models will be introduced. Second, an overview of 3 alternate interventions that attempt to reduce the rates of restenosis is presented. Finally, the major randomized, controlled trials involving sirolimus and paclitaxel are described, and their clinical implications and use as a possible solution in the prevention of restenosis is discussed.

Early and intermediate-term outcomes with drug-eluting stents in high-risk patients with symptomatic intracranial stenosis

OBJECTIVE

To report the 1-month and intermediate-term results of treatment of symptomatic intracranial stenosis using drug-eluting stents.

BACKGROUND

Patients with intracranial stenosis who are at high risk because of either high-grade stenosis or medication failure may have an annual risk of recurrent ischemic events in excess of 40%. Drug-eluting stents may reduce the rate of ischemic events in patients with a low restenosis rate.

METHODS

We determined rates of technical success (defined as reduction of target lesion to stenosis <30%) and 1-month major stroke or death in patients with symptomatic intracranial stenosis (> or =70% and/or medication failure). Patients' clinical and follow-up information during a mean period of 14.3 +/- 7 months were obtained. Kaplan-Meier analysis was performed to determine the rate of major stroke-free survival during 12 months.

RESULTS

There were 18 patients (mean age, 58 +/- 16 yr; 12 were men) treated with either a sirolimus-eluting stent (n = 14) or a paclitaxel-eluting stent (n = 4) for stenosis located in the: intracranial internal carotid artery (n = 6), proximal middle cerebral artery (n = 4), intracranial vertebral artery (n = 4), vertebrobasilar junction (n = 2), or basilar artery (n = 2). There was one major stroke and no death observed in the 1-month follow-up. At the 6-month follow-up examination, no major stroke or death was observed. Major stroke-free survival was 86% (+/-standard error of 9%) at 12 months after the procedure. One symptomatic angiographic restenosis was observed during the follow-up period.

CONCLUSION

A low rate of major stroke or death was observed after treatment of symptomatic intracranial stenosis using drug-eluting stents in high-risk patients.

Preparation, characterization and anticoagulation of curcumin-eluting controlled biodegradable coating stents

Curcumin is pharmaceutically active in many ways, having properties including anticoagulation, anti-proliferation, anti-inflammatory, and may be used to fabricate drug-eluting stents to treat in-stent restenosis after stent implantation. Here we describe our investigations of curcumin-eluting PLGA coatings formed using the biodegradable polymer PLGA (polylactic acid-co-glycolic acid) as drug carrier and uniformly fabricated on the surface of 316L stainless steel stents by an ultrasonic spray method. Three doses were explored--low dose ( approximately 140 microg per stent or 115 microg/cm(2)), moderate dose ( approximately 280 microg per stent or 230 microg/cm(2)), and high dose ( approximately 490 microg per stent or 408 microg/cm(2)). Pre- and post-expansion morphologies of the stent coating were examined by optical microscopy (OM) and scanning electron microscopy (SEM), indicating that the coating not only was very smooth and uniform but also had the ability to withstand the compressive and tensile strains imparted without cracking from the stent during the expansion process. Atomic force microscopy (AFM) images indicated the topography of the PLGA-only and moderate dose curcumin-eluting stent that showed an average roughness below 1 nm; no drug particles could be seen on the stent surface, indicating that curcumin can be mixed with PLGA at the molecular level using an ultrasonic atomization spray method. The structure of the coating films was characterized by Fourier Transform Infrared (FTIR) spectroscopy and X-ray electron spectroscopy (XPS), with results suggesting that there was no chemical reaction between curcumin and the drug. The results of in vitro measurements of drug release from curcumin-eluting stents showed that all the curcumin-eluting stents studied exhibited a nearly linear sustained-release profile with no significant burst releases within the measurement period. The in vitro anticoagulation behavior of curcumin-eluting stents was investigated by static platelet adhesion and APTT (activated partial thromboplastin time) tests, revealing that the anticoagulation properties of curcumin-eluting stents are superior to those for stainless steel stents and PLGA-only-coated stents. The anticoagulation behavior of curcumin stents improved significantly as the drug dose was increased.

Intravascular magnetic resonance/radiofrequency may enhance gene therapy for prevention of in-stent neointimal hyperplasia

RATIONALE AND OBJECTIVES

We evaluated the potential of using intravascular magnetic resonance (MR)/radiofrequency (RF) to enhance vascular endothelial growth factor (VEGF) gene therapy of in-stent neointimal hyperplasia.

MATERIALS AND METHODS

By using a catheter-based approach, VEGF/lentivirus was locally transferred into 10 (five paired) bilateral femoral-iliac arteries of five hypercholesterolemic pigs, whereas the right arteries were heated up to approximately 41 degrees C by using an intravascular MR/RF system. Then, identical stents were placed immediately into the bilateral VEGF-targeted arteries to create in-stent neointimal hyperplasia. At day 60 after gene/stent interventions, the targeted arteries were harvested for histological correlation.

RESULTS

X-Ray angiography-detectable in-stent stenoses were found in three of the arteries treated with VEGF genes only, whereas there were no in-stent stenoses in arteries treated by using MR/RF-heated VEGF genes. Correlative histological examination confirmed a 138% reduction in average thickness of neointimal hyperplasia in VEGF/RF-treated arteries compared with VEGF-only-treated arteries (P < .01).

CONCLUSION

We report a potential method of using an intravascular MR/RF heating technique to enhance gene therapy of in-stent restenosis.

YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole] inhibits neointima formation in balloon-injured rat carotid through suppression of expressions and activities of matrix metalloproteinases 2 and 9

Matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, and postrevascularization production of vascular smooth muscle cells may play key roles in development of arterial restenosis. We investigated the inhibitory effect of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a benzyl indazole compound, on MMP-2 and MMP-9 activity in a balloon-injury rat carotid artery model. Injury was induced by inserting a balloon catheter through the common carotid artery; after 14 days, histopathological analysis using immunostaining and Western blotting revealed significant restenosis with neointimal formation that was associated with enhanced protein expression of MMP-2 and MMP-9. However, these effects were dose-dependently reduced by orally administered YC-1 (1-10 mg/kg). In addition, gelatin zymography demonstrated that increased MMP-2 and MMP-9 activity was diminished by YC-1 treatment. On the other hand, YC-1 inhibited hydrolysis of the fluorogenic quenching substrate Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH(2) by recombinant MMP-2 and MMP-9 with IC(50) values = 2.07 and 8.20 muM, respectively. Reverse transcription-polymerase chain reaction analysis of MMP-2 and MMP-9 mRNA revealed that YC-1 significantly inhibited mRNA levels of MMPs. Finally, for the YC-1 treatment group, we did not observe elevation of cGMP levels using enzyme-linked immunosorbent assay, suggesting that YC-1 inhibition of neointimal formation is not through a cGMP-elevating pathway. These data show YC-1 suppression of neointimal formation is dependent on its influence on MMP-2 and MMP-9 protein, mRNA expression, and activity, but not through a cGMP-elevating effect. YC-1 shows therapeutic potential for treatment of restenosis after angioplasty.

Study on Adhesion and Biocompatibility of Copolymer of MMA-BMA-MAA for Coronary Stents Coatings

Implantation of drug releasing coronary stents has been developed as an useful method for prevention of the restenosis in blood vessels. Copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and methacrylic acid (MAA) were prepared as the coating polymer for drug releasing stent. The adhesion of the polymer with metal substrate and the biocompatibility were studied. Effect of the polymer composition on the adhesion between polymer coatings and metal substrate, as well as the effect of the polymer purification method on biocompatibility of the polymer, was studied. The results showed that the copolymer coating has good dry and wet adhesion properties, which can be improved by control of the polymer compositions. Biocompatibility of the prepared copolymer comes within the permission limit.

Dysregulation of HSG triggers vascular proliferative disorders

Vascular proliferative disorders, such as atherosclerosis and restenosis, are the most common causes of severe cardiovascular diseases, but a common molecular mechanism remains elusive. Here, we identify and characterize a novel hyperplasia suppressor gene, named HSG (later re-named rat mitofusin-2). HSG expression was markedly reduced in hyper-proliferative vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rat arteries, balloon-injured Wistar Kyoto rat arteries, or ApoE-knockout mouse atherosclerotic arteries. Overexpression of HSG overtly suppressed serum-evoked VSMC proliferation in culture, and blocked balloon injury induced neointimal VSMC proliferation and restenosis in rat carotid arteries. The HSG anti-proliferative effect was mediated by inhibition of ERK/MAPK signalling and subsequent cell-cycle arrest. Deletion of the p21(ras) signature motif, but not the mitochondrial targeting domain, abolished HSG-induced growth arrest, indicating that rHSG-induced anti-proliferation was independent of mitochondrial fusion. Thus, rHSG functions as a cell proliferation suppressor, whereas dysregulation of rHSG results in proliferative disorders.

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Advances in cardiac resynchronization therapy, stents, robotics, and monitoring offer patients new treatment options.