Intraluminal Delivery of Simvastatin Attenuates Intimal Hyperplasia After Arterial Injury

INTRODUCTION

Oral statins reduce intimal hyperplasia (IH) after arterial injury by only ∼25%. Alternative drug delivery systems have gained attention as carriers for hydrophobic drugs. We studied the effects of simvastatin (free vs hyaluronic acid-tagged polysialic acid-polycaprolactone micelles) on vascular smooth muscle cell (VSMC) migration, VSMC proliferation and intimal hyperplasia. We hypothesized both free and micelle containing simvastatin would inhibit VSMC chemotaxis and proliferation, and local statin treatment would be more effective than oral in reducing IH in rats following carotid balloon injury.

METHODS

VSMCs pretreated with free simvastatin (20 minutes or 20 hours) or simvastatin-loaded micelles underwent chemotaxis and proliferation to platelet-derived growth factor. Next, rats that underwent balloon injury of the common carotid artery received statin therapy-intraluminal simvastatin-loaded micelles prior to injury, periadventitial pluronic gel following injury, or combinations of gel, micelle, and oral simvastatin. After 14 days, morphometric analysis determined the -intimal to medial ratio. Findings were compared to controls receiving oral simvastatin or no statin therapy. Statistical analysis was by analysis of variance for the in vitro experiments and a factorial general linear model for the in vivo experiments.

RESULTS

The simvastatin-loaded micelles and free simvastatin inhibited VSMC chemotaxis (54%-60%). IH was induced in all injured vessels. Simvastatin in pluronic gel or micelles reduced IH compared to untreated controls (0.208 ± 0.04 or 0.160 ± 0.03 vs 0.350 ± 0.03, respectively); however, neither gel nor simvastatin-loaded micelles were superior to oral statins (0.261 ± 0.03). Addition of oral statins or combining both local therapies did not provide additional benefit. Micelles were the single greatest contributing factor in IH attenuation.

CONCLUSIONS

Intraluminally or topically delivered statins reduced IH. The efficacy of single-dose, locally delivered statin alone may lead to novel treatments to prevent IH. The different routes of administration may allow for treatment during endovascular procedures, without the need for systemic therapy.

Preclinical evaluation of a paclitaxel-incorporated nanoparticle-coated balloon in rabbit and porcine models

BACKGROUND

The main drawback of current available drug coated balloons (DCB) is that a certain percentage of the coated drug is lost in the bloodstream during its delivery to the target lesion. We integrated the nanoparticle-mediated drug delivery technology and polydimethylsiloxane (PDMS) as a new excipient to facilitate an efficient drug delivery and uptake by endothelial cells. The present study aimed to evaluate the efficacy of the new DCB.

METHOD AND RESULTS

The novel DCB were coated with 5.6mg of paclitaxel-incorporated nanoparticles using PDMS. The efficacy of the new DCB was examined in rabbit iliac stent model (n=12) and in the swine in-stent restenosis model (n=8) by quantitative coronary angiography (QCA) and optical coherence tomography (OCT). At 28days follow-up in the swine in-stent restenosis model, the area stenosis was significantly lower in DCB group as compared with that of the control group in OCT analysis (0.31±0.05 vs 0.49±0.06, p=0.04) though there was no significant differences observed in the rabbit iliac stent model in QCA and OCT analysis.

CONCLUSION

The study results indicated that the paclitaxel-incorporated nanoparticle-coated balloon using PDMS has an inhibitory effect for the proliferation of smooth muscle cell in a swine coronary in-stent restenosis model.

Effect of atorvastatin-eluting stents in a rabbit iliac artery restenosis model

Statins have pleiotropic effects, which include the inhibition of neointima hyperplasia, the inhibition of vascular inflammation, and platelet inhibition. The aim of this study was to examine the effect of an atorvastatin-eluting stent (AES) in a rabbit iliac artery overstretch restenosis model. Ten rabbits were used in this study (10 rabbits, 10 iliac arteries for each stent). An AES and paclitaxel-eluting stent (PES) were implanted in the left and right iliac arteries in a rabbit (2 stents in each rabbit). The stents were deployed with oversizing (stent/artery ratio 1.3:1), and histopathologic analysis was assessed at 28 days after stenting. There were no significant differences in the injury score, lumen area, or inflammation score. There were significant differences in the neointimal area (0.7±0.18 mm² in the AES group vs. 0.4±0.25 mm² in the PES group, p<0.01), in the percentage stenosis area (14.8±5.06% in the AES group vs. 10.5±6.80% in the PES group, p<0.05), and in the fibrin score (0.4±0.51 in the AES group vs. 2.7±0.48 in the PES group, p<0.001). Although the AES did not suppress neointimal hyperplasia compared with the PES, it showed a superior arterial healing effect in a rabbit iliac artery overstretch restenosis model.

Vasomotor function and re-endothelialisation after implantation of biodegradable abluminal polymer coated paclitaxel-eluting stents in rabbit iliac arteries: a time-course study

AIMS

To evaluate the time-course of vasomotor function and re-endothelialisation after implantation of a novel platinum-chromium (PtCr) abluminal biodegradable polymer-coated paclitaxel-eluting stent (PES, Labcoat Element) in rabbit iliac arteries.

METHODS AND RESULTS

Either PES (n=18) or an identical platform of bare metal stents (BMS, Element, n=18) were implanted in rabbit iliac arteries (six animals per time-point). At 14, 30, and 90 days, acetylcholine- and nitroglycerine-induced vasomotor reactivity at 5-10 mm distal to the stent was measured. Subsequently, the animals were terminated. The stented artery was bisected longitudinally for either SEM or en face CD31 immunochemistry examination. All arteries were patent with normal angiographic flow. Decreased endothelial-dependent vasomotion was found at both 14 and 30 days for PES compared to BMS (p<0.01, respectively); however, these differences resolved by 90 days. Endothelial-independent vasorelaxation was similar at all three time-points. Both SEM and en face staining demonstrated equivalent endothelial coverage on the surface of the stented segments above and between struts at all time-points.

CONCLUSIONS

This novel bioabsorbable polymer abluminal-coated PES demonstrated vasomotor function comparable to BMS within three months post-deployment in the rabbit iliac model. Despite indistinguishable endothelial cell coverage on the stent surface between groups, earlier differences in vasomotion were detected: this finding suggests that the timing of restoration vasomotor function lags morphologic endothelial recovery.

Pharmacological actions of statins: a critical appraisal in the management of cancer

Statins, among the most commonly prescribed drugs worldwide, are cholesterol-lowering agents used to manage and prevent cardiovascular and coronary heart diseases. Recently, a multifaceted action in different physiological and pathological conditions has been also proposed for statins, beyond anti-inflammation and neuroprotection. Statins have been shown to act through cholesterol-dependent and -independent mechanisms and are able to affect several tissue functions and modulate specific signal transduction pathways that could account for statin pleiotropic effects. Typically, statins are prescribed in middle-aged or elderly patients in a therapeutic regimen covering a long life span during which metabolic processes, aging, and concomitant novel diseases, including cancer, could occur. In this context, safety, toxicity, interaction with other drugs, and the state of health have to be taken into account in subjects treated with statins. Some evidence has shown a dichotomous effect of statins with either cancer-inhibiting or -promoting effects. To date, clinical trials failed to demonstrate a reduced cancer occurrence in statin users and no sufficient data are available to define the long-term effects of statin use over a period of 10 years. Moreover, results from clinical trials performed to evaluate the therapeutic efficacy of statins in cancer did not suggest statin use as chemotherapeutic or adjuvant agents. Here, we reviewed the pharmacology of the statins, providing a comprehensive update of the current knowledge of their effects on tissues, biological processes, and pathological conditions, and we dissected the disappointing evidence on the possible future use of statin-based drugs in cancer therapy.

Current and future drug-eluting coronary stent technology

Despite the impressive benefits obtained following the introduction of the drug-eluting stent, safety concerns have been raised over their long-term safety with particular regard to stent thrombosis. Various mechanisms such as delayed endothelialization, local hypersensitivity and endothelial dysfunction owing to the durable polymer coating and/or the drug itself have been suggested as possible causes of this phenomenon. Therefore, to address these concerns, a newer-generation of drug-eluting stents has been developed and they are currently undergoing preclinical and clinical evaluation in order to increase both the safety and biocompatibility by optimizing the three major components of drug-eluting stents: the stent platform, the polymer and the drug. This article critically reviews the key clinical trials and the current status of these new coronary devices as well as preventing future perspectives for their continued development.