Late vascular response following drug-eluting stent implantation

Research Progress on the Pathogenesis and Treatment of Neoatherosclerosis

Neoatherosclerosis (NA) within stents has become an important clinical problem after coronary artery stent implantation. In-stent restenosis and in-stent thrombosis are the two major complications following coronary stent placement and seriously affect patient prognosis. As the common pathological basis of these two complications, NA plaques, unlike native atherosclerotic plaques, often grow around residual oxidized lipids and stent struts. The main components are foam cells formed by vascular smooth muscle cells (VSMCs) engulfing oxidized lipids at lipid residue sites. Current research mainly focuses on optical coherence tomography (OCT) and intravascular ultrasound (IVUS), but the specific pathogenesis of NA is still unclear. A thorough understanding of the pathogenesis and pathological features of NA provides a theoretical basis for clinical treatment. This article reviews the previous research of our research group and the current situation of domestic and foreign research.

Peri-strut low-intensity area assessed by midterm follow-up optical coherence tomography may predict target lesion revascularisation after everolimus-eluting stent implantation

AIMS

Peri-strut low-intensity area (PLIA) assessed by optical coherence tomography (OCT) has been reported as a potential marker of abnormal neointimal healing. We aimed to evaluate the impact of PLIA on clinical events and its risk factors.

METHODS AND RESULTS

We enrolled 264 consecutive patients treated with an everolimus-eluting stent (EES) who underwent follow-up OCT six to 12 months after stenting. Target lesion revascularisation (TLR) was evaluated at a mean 42.6 months after stenting. PLIA was identified in 102 patients; 162 patients did not exhibit PLIA. Multivariate Cox hazard regression analysis indicated that the presence of PLIA (PLIA+) was an independent risk factor for an increased incidence of TLR (hazard ratio [HR]: 4.608, p=0.003). In both the early (<1 year) and late (>1 year) phases, the incidence of TLR was significantly higher in the PLIA+ group (p<0.001 and p<0.001, respectively). In the Cox hazard regression analysis, current smoking and increased C-reactive protein level were independently associated with PLIA+ (HR: 1.737, p=0.009; HR: 2.435, p=0.008, respectively).

CONCLUSIONS

The presence of PLIA on midterm OCT was associated with TLR after EES implantation. Detailed stent assessment by midterm OCT may help to predict stent failure in patients treated with EES.

Development of Dual Drug Eluting Cardiovascular Stent with Ultrathin Flexible Poly(l-lactide-co-caprolactone) Coating

The pleiotropic effects of the atorvastatin-fenofibrate combination can be effectively harnessed for site-specific therapy to minimize stent-related complications. The present study aims to utilize the pleiotropic effects of these two drugs entrapped in a uniform and defect-free coating of poly(l-lactide-co-caprolactone) (PLCL) on a stainless steel stent to overcome stent-associated limitations. The stent coating parameters were optimized using ultrasonic spray coating technique to achieve a thin, smooth, and defect-free dual drug-loaded polymer coating on the stent. The dual drug-loaded polymer coated stent was characterized for surface morphology, thickness and coating integrity. In vitro drug release kinetics of the fabricated stent reveals a sustained release of both drugs for more than 60 days. Significant reduction of thrombus formation and adhesion of lipopolysaccharide-stimulated macrophages on the dual drug containing polymer-coated stent indicates that the drug combination possesses antithrombotic and anti-inflammatory effects. The combination did not adversely influence endothelialization but significantly retarded smooth muscle cell proliferation indicating its potential to overcome restenosis. No bacterial biofilm formation was observed on the stent due to the antibacterial activity of atorvastatin. A rat subcutaneous model was used to evaluate the biocompatibility of the coated stent and compared with the commercial stent. MicroCT, scanning electron microscopy, and morphometric analyses revealed that the coated stents exhibited excellent histocompatibility with no inflammatory response as evidenced from the cytokine levels measured 28 days postimplantation. Our data demonstrates for the first time that the combination of atorvastatin and fenofibrate can be successfully employed in cardiovascular stents to overcome the current limitations of conventional drug-eluting stents.

In vitro and in vivo evaluation of a dextran-graft-polybutylmethacrylate copolymer coated on CoCr metallic stent

Introduction: The major complications of stent implantation are restenosis and late stent thrombosis. PBMA polymers are used for stent coating because of their mechanical properties. We previously synthesized and characterized Dextrangraft-polybutylmethacrylate copolymer (Dex-PBMA) as a potential stent coating. In this study, we evaluated the haemocompatibility and biocompatibility properties of Dex-PBMA in vitro and in vivo. Methods: Here, we investigated: (1) the effectiveness of polymer coating under physiological conditions and its ability to release Tacrolimus®, (2) the capacity of Dex-PBMA to inhibit Staphylococcus aureus adhesion, (3) the thrombin generation and the human platelet adhesion in static and dynamic conditions, (4) the biocompatibility properties in vitro on human endothelial colony forming cells ( ECFC) and on mesenchymal stem cells (MSC) and in vivo in rat models, and (5) we implanted Dex-PBMA and Dex-PBMA_TAC coated stents in neointimal hyperplasia restenosis rabbit model. Results: Dex-PBMA coating efficiently prevented bacterial adhesion and release Tacrolimus®. Dex-PBMA exhibit haemocompatibility properties under flow and ECFC and MSC compatibility. In vivo, no pathological foreign body reaction was observed neither after intramuscular nor intravascular aortic implantation. After Dex-PBMA and Dex-PBMA_TAC coated stents 30 days implantation in a restenosis rabbit model, an endothelial cell coverage was observed and the lumen patency was preserved. Conclusion: Based on our findings, Dex-PBMA exhibited vascular compatibility and can potentially be used as a coating for metallic coronary stents.

Optimizing endothelial cell functionalization for cell therapy of vascular proliferative disease using a direct contact co-culture system

Increased susceptibility to thrombosis, neoatherosclerosis, and restenosis due to incomplete regrowth of the protective endothelial layer remains a critical limitation of the interventional strategies currently used clinically to relieve atherosclerotic obstruction. Rapid recovery of endothelium holds promise for both preventing the thrombotic events and reducing post-angioplasty restenosis, providing the rationale for developing cell delivery strategies for accelerating arterial reendothelialization. The successful translation of experimental cell therapies into clinically viable treatment modalities for restoring vascular endothelium critically depends on identifying strategies for enhancing the functionality of endothelial cells (EC) derived from high cardiovascular risk patients, the target group for the majority of angioplasty procedures. Enhancing EC-associated nitric oxide (NO) synthesis by inducing overexpression of NO synthase (NOS) has shown promise as a way of increasing paracrine activity and restoring function of EC. In the present study, we developed a direct contact co-culture approach compatible with highly labile effectors, such as NO, and applied it for determining the effect of EC functionalization via NOS gene transfer on the growth of co-cultured arterial smooth muscle cells (A10 cell line) exhibiting the defining characteristics of neointimal cells. Bovine aortic endothelial cells magnetically transduced with inducible NOS-encoding adenovirus (Ad) formulated in zinc oleate-based magnetic nanoparticles (MNP[_iNOSAd]) strongly suppressed growth of proliferating A10 and attenuated the stimulatory effect of a potent mitogen, platelet-derived growth factor (PDGF-BB), whereas EC functionalization with free _iNOSAd or MNP formulated with a different isoform of the enzyme, endothelial NOS, was associated with lower levels of NO synthesis and less pronounced antiproliferative activity toward co-cultured A10 cells. These results show feasibility of applying magnetically facilitated gene transfer to potentiate therapeutically relevant effects of EC for targeted cell therapy of restenosis. The direct contact co-culture methodology provides a sensitive and reliable tool with potential utility for a variety of biomedical applications.