Fighting restenosis after coronary angioplasty: contemporary and future treatment options

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.

A traditional Chinese medicine therapy for coronary heart disease after percutaneous coronary intervention: a meta-analysis of randomized, double-blind, placebo-controlled trials

Huoxue Huayu therapy (HXHY) has been widely used to treat cardiovascular diseases in traditional Chinese medicine (TCM) such as hypertension and coronary heart disease (CHD). The present study describes a meta-analysis of a series of prospective randomized, double-blind, placebo-controlled trials conducted to evaluate the effect of HXHY on patients with CHD after percutaneous coronary intervention (PCI). The Cochrane Library, PubMed, EMBASE, the China National Knowledge Infrastructure (CNKI), the Chinese Biomedical Literature database, and the Wanfang database were searched up until June 2018. A series of randomized controlled clinical trials were included and the subjects were patients with CHD who had undergone PCI. The experimental group was treated with HXHY therapy, and the control group was treated with placebo; meanwhile, all the patients accepted conventional Western medicine. Review Manager 5.3 software was used for the statistical analysis. Ten trials were included in the final study. The overall risk of bias assessment was low. HXHY had a greater beneficial effect on reducing the in-stent restenosis (ISR) rate (RR = 0.57, 95% confidence interval [CI] [0.40-0.80], P=0.001) and the degree of restenosis (MD = -8.89, 95% CI [-10.62 to -7.17], P<0.00001) compared with Placebo. Moreover, HXHY was determined to be more effective in improving Seattle Angina Questionnaires (SAQ) and the revascularization rate (RR = 0.54, 95% CI [0.32-0.90], P=0.02) compared with Placebo, whereas the rate of death and MI of patients treated with HXHY were no different from those treated with the placebo (P>0.05). Therefore, HXHY is an effective and safe therapy for CHD patients after PCI.

Cysteine Protease Cathepsins in Atherosclerotic Cardiovascular Diseases

Atherosclerotic cardiovascular disease (ASCVD) is an inflammatory disease characterized by extensive arterial wall matrix protein degradation. Cysteine protease cathepsins play a pivotal role in extracellular matrix (ECM) remodeling and have been implicated in the development and progression of atherosclerosis-based cardiovascular diseases. An imbalance in expression between cathepsins (such as cathepsins S, K, L, C) and their inhibitor cystatin C may favor proteolysis of ECM in the pathogenesis of cardiovascular disease such as atherosclerosis, aneurysm formation, restenosis, and neovascularization. New insights into cathepsin functions have been made possible by the generation of knock-out mice and by the application of specific inhibitors. Inflammatory cytokines regulate the expression and activities of cathepsins in cultured vascular cells and macrophages. In addition, evaluations of the possibility of cathepsins as a diagnostic tool revealed that the circulating levels of cathepsin S, K, and L, and their endogenous inhibitor cystatin C could be promising biomarkers in the diagnosis of coronary artery disease, aneurysm, adiposity, peripheral arterial disease, and coronary artery calcification. In this review, we summarize the available information regarding the mechanistic contributions of cathepsins to ASCVD.

Biofunctionalization of PEGylated microcapsules for exclusive binding to protein substrates

Targeted delivery of drugs to specific diseased sites in the body is an area of research that has attracted many studies, particularly in drug deliveries that utilize microparticles. By achieving targeted delivery of a drug, one can increase the efficacy of the treatment, thus, reducing unwanted side effects. This study aims to synthesize microcapsules that are able to target and adsorb to specific proteins (i.e., collagen type IV and fibronectin) through antibody-antigen interactions, while simultaneously suppressing any unspecific binding, a characteristic that is commonly observed in polyelectrolyte microcapsule-protein interactions. This is accomplished by creating an antibody-functionalized poly(ethylene glycol) (PEG) assembly within the microcapsule structure. Site-specific adsorption of these microcapsules is tested using protein micropatterns. Results show that significant adsorption is achieved on the target protein, with unspecific adsorptions being heavily suppressed on control proteins. In conclusion, we have successfully manufactured microcapsules that specifically and exclusively bind to their complementary target area. This paves the way for future in vivo experiments using microcapsules as targeted drug carriers.

The experimental study of hemodynamic changes and pathological morphology after artery anastomosis

The purpose of this article is to dynamically observe hemodynamic and medium-term pathomorphological changes and to investigate the pathophysiological variation at the vascular anastomotic stoma. Eighteen New Zealand white rabbits underwent right common carotid artery in situ anastomosis, and the hemodynamic changes of anastomotic stoma were recorded by color Doppler ultrasonography before surgery and 5 minutes, 1 week, 2 weeks, 3 weeks, 4 weeks, 8 weeks, 12 weeks, and 16 weeks after surgery. Pathological sections of stoma were made and the pathomorphological changes viewed. Artery anastomoses were preformed successfully in 15 rabbits; 4 rabbits suffered postoperative death. It took 1.22 ± 0.77 hours to complete every operation. All the data involved, mean velocity, peak systolic velocity, and resistant index, had no significant differences between preoperative and postoperative follow-up. The obvious differences were found in the diameters of stoma 5 minutes, 1 week, 2 weeks, and 3 weeks after operation (P values were .002, .001, .003, and .008, respectively). The variance of stoma diameters 2 weeks later was also different from those after 1 week, but no other differences were observed during other weeks. The decrease in stoma diameters after anastomosis was clear, with the maximum decrease occurring 2 weeks after the operation, after which the diameters of stoma became stable 16 weeks after the operation. Some collagens around anastomoses could be found by the pathological sections of stoma, which indicated that the deposition of collagen might be related to the decrease in stoma diameter.

Cysteinyl cathepsins: multifunctional enzymes in cardiovascular disease

Until recently, the role of lysosomal cysteine protease cathepsins in intracellular protein degradation was believed to be mainly restricted to scavenging. However, recent studies have revealed nontraditional roles for cysteine protease cathepsins in the extracellular space during the development and progression of cardiovascular disease. Although the precise mechanisms are unknown, data from animal studies suggest that members of the cathepsin family, like other extracellular proteases, contribute to extracellular matrix protein remodeling and interstitial matrix degradation, as well as to cell signaling and cell apoptosis in heart disease. Inflammatory cytokines and hormones regulate the expression and secretion of cathepsins in cultured cardiovascular cells and macrophages. Serum levels of cathepsins L, S, and K and their endogenous inhibitor cystatin C may be useful predictive biomarkers in patients with coronary artery disease and cardiac disease. Furthermore, in vivo pharmacological intervention with a synthetic cathepsin inhibitor and cardiovascular drugs (including statins and angiotensin II type 1 receptor antagonists) has the potential for pharmacologic targeting of cathepsins in cardiovascular disease. This review focuses on cathepsin biology (structure, synthesis, processing, activation, secretion, activity regulation, and function) and the involvement of cysteinyl cathepsins in the pathogenesis of several heart and vessel diseases, especially with respect to their potential application as diagnostic and prognostic markers and drug targets to prevent inappropriate proteolysis in cardiovascular disease.

Ultrasound-mediated delivery of echogenic immunoliposomes to porcine vascular smooth muscle cells in vivo

Vascular smooth muscle cells (VSMCs) are important targets in the treatment of atherosclerosis. However, the arterial media, where the majority of VSMCs reside, have proven to be a difficult target for drug/gene delivery. We have demonstrated that ultrasound enhances drug/gene delivery to VSMCs in vitro by using echogenic immunoliposomes (ELIPs) as the vector. This study aimed to evaluate whether ultrasound can similarly enhance the delivery of an agent to VSMCs, particularly within the arterial media, in vivo, using ELIP. Anti-smooth-muscle cell actin-conjugated calcein-loaded ELIP were injected into the peripheral arteries of Yucatan miniswine (n = 8 arterial pairs). The right-sided porcine arteries were treated with 1-MHz continuous-wave ultrasound at a peak-to-peak pressure amplitude of 0.23 +/- 0.05 MPa for 2 minutes. The contralateral arteries served as controls. Arteries were harvested after 30 minutes and imaged with fluorescence microscopy. Image data were converted to grayscale and analyzed by using computer-assisted videodensitometry. There was significant improvement in calcein uptake in all three arterial layers in the arteries exposed to ultrasound (> 300%). This enhanced uptake was site specific and appeared limited to the ultrasound-treated arterial segment. We have demonstrated enhanced delivery of a small molecule to VSMCs in all arterial wall layers, particularly the arterial media, using ultrasound and targeted ELIP. The combined effect of ultrasound exposure and ELIP as a contrast agent and a drug/gene-bearing vector has the potential for site-specific therapy directed at VSMC function.

Liposomal simvastatin attenuates neointimal hyperplasia in rats

Monocytes, macrophages, and inflammation play a key role in the process of neointimal proliferation and restenosis. The present study evaluated whether systemic and transient depletion of monocytes could be obtained by a single intravenous (IV) injection of simvastatin liposomes, for the inhibition of neointima formation. Balloon-injured carotid artery rats (n = 30) were randomly assigned to treatment groups of free simvastatin, simvastatin in liposomes (3 mg/kg), and saline (control). Stenosis and neointima to media ratio (N/M) were determined 14 days following single IV injection at the time of injury by morphometric analysis. Depletion of circulating monocytes was determined by flow cytometry analyzes of blood specimens. Inhibition of RAW264.7, J774, and THP-1 proliferation by simvastatin-loaded liposomes and free simvastatin was determined by the 3-(4, 5-dimethylthiazolyl-2)-2, 5- diphenyltetrazolium bromide assay. Simvastatin liposomes were successfully formulated and were found to be 1.5-2 times more potent than the free drug in suppressing the proliferation of monocytes/macrophages in cell cultures of RAW 264.7, J774, and THP-1. IV injection of liposomal simvastatin to carotid-injured rats (3 mg/kg, n = 4) resulted in a transient depletion of circulating monocytes, significantly more prolonged than that observed following treatment with free simvastatin. Administration to balloon-injured rats suppressed neointimal growth. N/M at 14 days was 1.56 +/- 0.16 and 0.90 +/- 0.12, control and simvastatin liposomes, respectively. One single systemic administration of liposomal simvastatin at the time of injury significantly suppresses neointimal formation in the rat model of restenosis, mediated via a partial and transient depletion of circulating monocytes.

Drug-eluting stents - what should be improved?

Despite the success of drug-eluting stents (DES) in reducing restenosis and the need for target vessel revascularization, several deficiencies have been unraveled since their first clinical application including the risk of stent thrombosis, undesired effects due to the stent polymer as well as the stent itself, and incomplete inhibition of restenosis (especially in complex lesions). Several novel stent systems are being investigated in order to address these issues. In second-generation DES, the rapamycin analogues zotarolimus and everolimus (and more recently biolimus) have been most extensively studied. Furthermore, special stent-coatings to actively promote endothelial healing (in order to reduce the risk of stent thrombosis) and to further reduce restenosis have been employed. To avoid undesirable effects of currently applied (durable) polymers, biocompatible and bioabsorbable polymers as well as DES delivery systems without the need for a polymer have been developed. Bioabsorbable stents, both polymeric and metallic, were developed to decrease potential late complications after stent implantation. Although most of these innovative novel principles intuitively seem appealing and demonstrate good results in initial clinical evaluations, long-term large-scale studies are necessary in order to reliably assess whether these novel systems are truly superior to first-generation DES with respect to safety and efficacy.

Lipoprotein lipase gene polymorphisms and the risk of target vessel revascularization after percutaneous coronary intervention

OBJECTIVES

We sought to identify polymorphisms in genes that predispose to restenosis.

BACKGROUND

Variations in the lipoprotein lipase (LPL) gene have been implicated in a number of pathophysiologic conditions associated with coronary heart disease. The present study examines the impact of polymorphisms in the LPL gene on restenosis (defined by target vessel revascularization [TVR]) in a large patient population undergoing percutaneous coronary intervention (PCI). A mouse model for restenosis was used to further investigate LPL's role in restenosis.

METHODS

The GENetic DEterminants of Restenosis (GENDER) project is a multicenter, prospective study design that enrolled 3,104 consecutive patients after successful PCI. These patients were genotyped for four different LPL gene polymorphisms. In apolipoprotein E (ApoE)*3-Leiden transgenic mice, arterial messenger ribonucleic acid (mRNA) was used to assess LPL expression during a cuff-induced restenotic process.

RESULTS

Using multivariable analysis, carriers of the 447Ter allele of the LPL enzyme showed a lower risk of TVR compared with 447Ser homozygotes (p = 0.005). In the mouse model, LPL mRNA levels were increased 40-fold compared with control arteries at 6 h after cuff placement.

CONCLUSIONS

The LPL C/G polymorphism (Ser447Ter), resulting in a truncation of the two C-terminal amino acids of the mature LPL protein, appears to be an important protective factor for TVR in humans. The role of LPL in this process was further established in a mouse model, where LPL expression was very strongly up-regulated in the target arterial wall, suggesting a contribution of this lipolytic enzyme to restenosis. Possibly, LPL Ser447Ter genotyping may lead to better risk stratification and tailored therapy in the prevention of restenosis after PCI.

Influence of serum cholesterol on atherogenesis and intimal hyperplasia after angioplasty: inhibition by amlodipine

The objectives of the present study were to determine whether serum hypercholesterolemia (HC) promotes the development of spontaneous and angioplasty-induced lesions and whether amlodipine inhibits these lesions and cellular processes underlying their genesis. Rabbits were fed normal, 0.5%, or 2% cholesterol diets for 9 wk, which resulted in the development of increasing HC. After week one, balloon dilation of the abdominal aorta was performed while the thoracic aorta was not disturbed and monitored for the development of spontaneous lesions. Lesion size increased with the degree of HC and was accompanied by increased collagen synthesis and smooth muscle cell (SMC) proliferation at each site. Amlodipine (5 mg/kg p.o.) inhibited lesion size by 50% (P < 0.01) at both sites in cholesterol-fed animals but not at angioplasty sites in animals on a normal diet. Local collagen synthesis was inhibited at both sites by amlodipine in the diet animals. The increase in HC was accompanied by a 1.7-fold increase in basal Ca2+ uptake in SMCs in the thoracic aorta, which was not altered by amlodipine, nifedipine, Ni2+, or La3+, revealing an uninhibitable calcium leak during atherogenesis. In culture, cholesterol enrichment increased SMC proliferation, collagen synthesis, and the secretion of a soluble SMC mitogen, which were inhibited by amlodipine (10(-9) M). Finally, in SMC membranes, amlodipine uniquely restored the cholesterol-expanded membrane bilayer width without any effect on membrane fluidity. This study establishes a causal role between serum HC and the development of spontaneous and angioplasty-induced lesions and the ability of amlodipine to disrupt this action by a novel remodelling action on the SMC membrane.

Development of Efficient Viral Vectors Selective for Vascular Smooth Muscle Cells

The vascular smooth muscle cell (SMC) is integral to the pathogenesis of neointimal formation associated with late vein graft failure, in-stent restenosis, and transplant arteriopathy. Viral vectors transduce SMC with low efficiency and hence, there is a need for improvement. We aimed to enhance the efficiency and selectivity of gene delivery to human SMC. Targeting ligands were identified using phage display on primary human saphenous vein SMC with linear and cyclic libraries. Two linear peptides, EYHHYNK (EYH) and GETRAPL (GET), were incorporated into the HI loop of adenovirus (Ad) fibers and the capsid protein of adeno-associated virus-2 (AAV-2). Exposure of human venous SMC to EYH-modified (but not the GET-modified) Ad vector resulted in a significant increase in transgene expression levels at short, clinically relevant exposure times. Similarly, the EYH-modified AAV vector resulted in enhanced gene transfer to human venous SMC but not endothelial cells in a time- and dose-dependent manner. The EYH-modified AAV vector also enhanced (up to 70-fold) gene delivery to primary human arterial SMC. Hence, incorporation of EYH into Ad and AAV capsids resulted in a significant and selective enhancement in transduction of SMC and has implications for improving local gene delivery to the vasculature.

Grb2 is required for the development of neointima in response to vascular injury

OBJECTIVE

Neointima formation occurs in arteries in response to mechanical or chemical injury and is responsible for substantial morbidity. In this work, the role of the intracellular linker protein Grb2 in the pathogenesis of neointima formation was examined. Grb2 is a critical signaling protein that facilitates the activation of the small GTPase ras by receptor tyrosine kinases.

METHODS AND RESULTS

Cultured rat aortic smooth muscle cells were treated with an antisense morpholino to Grb2 and these cells showed a reduced proliferative response to platelet-derived growth factor stimulation. Grb2-/- mice do not survive embryonic development. Grb2+/- mice appear normal at birth and are fertile but have defective signaling in several tissues. Cultured smooth muscle cells derived from Grb2+/- mice grew at a much slower rate than cells derived from Grb2+/+ mice. Grb2+/- and Grb2+/+ mice were subjected to carotid injury. After 21 days, Grb2+/+ mice developed robust neointima formation that, in some cases, resulted in an occlusive lesion. In contrast, Grb2+/- mice were resistant to the development of neointima

CONCLUSIONS

Grb2 is an essential component of the signaling cascade resulting in neointima formation after arterial injury.