Antirestenotic effects of a novel polymer-coated d-24851 eluting stent. Experimental data in a rabbit iliac artery model

Revolutionizing Cardiovascular Frontiers: A Dive Into Cutting-Edge Innovations in Coronary Stent Technology

Plain balloon angioplasty was the initial method used to enlarge the intracoronary lumen size. However, it was linked to acute coronary closure due to early vessel recoil. This led to the invention of coronary stents, which offer mechanical support to open and maintain the vascular lumen. Nevertheless, the metallic scaffold introduced other issues, such as thrombosis and restenosis caused by neointimal proliferation. To address these concerns, polymers were employed to cover the scaffold, acting as drug reservoirs and regulators for controlled drug release. The use of polymers prevents direct contact between blood and metallic scaffolds. Drugs within the stent were incorporated to inhibit proliferation and expedite endothelialization in the healing process. Despite these advancements, adverse effects still arise due to the inflammatory reaction caused by the polymer material. Consequently, resorbable polymers and scaffolds were later discovered, but they have limitations and are not universally applicable. Various scaffold designs, thicknesses, materials, polymer components, and drugs have their own advantages and complications. Each stent generation has been designed to address the shortcomings of the preceding generation, yet new challenges continue to emerge. Conflicting data regarding the long-term safety and efficacy of coronary stents, especially in the extended follow-up, further complicates the assessment.

Hsp70 (HSP70A1A) downregulation enhances the metastatic ability of cancer cells

Heat shock protein 70 (Hsp70; also known as HSP70A1A) is one of the most induced proteins in cancer cells; however, its role in cancer has not yet been fully elucidated. In the present study, we proposed a hypothetical model in which the silencing of Hsp70 enhanced the metastatic properties of the HeLa, A549 and MCF7 cancer cell lines. We consider that the inability of cells to form cadherin-catenin complexes in the absence of Hsp70 stimulates their detachment from neighboring cells, which is the first step of anoikis and metastasis. Under these conditions, an epithelial-to-mesenchymal transition (EMT) pathway is activated that causes cancer cells to acquire a mesenchymal phenotype, which is known to possess a higher ability for migration. Therefore, we herein provide evidence of the dual role of Hsp70 which, according to international literature, first establishes a cancerous environment and then, as suggested by our team, regulates the steps of the metastatic process, including EMT and migration. Finally, the trigger for the anti-metastatic properties that are acquired by cancer cells in the absence of Hsp70 appears to be the destruction of the Hsp70-dependent heterocomplexes of E-cadherin/catenins, which function like an anchor between neighboring cells.

A NEW WAY TO OPTIMIZE DRUG RELEASE RATE OF DRUG ELUTING STENT (DES)

Local hemodynamic environment is a determinant factor in drug delivery from a drug eluting stent (DES) to the target arterial tissue. By using a simplified model of a DES, we demonstrated that if a DES had a drug release mode of uniform rate the drug released from the stent will distribute non-uniformly along the stent due to the flowing blood, with a significantly higher drug concentration at the distal part of the stent than that at the proximal one. This may explain why a DES could retard neointimal formation and vascular remodeling in downstream coronary segments. To solve this problem, we thereafter optimized the drug release mode of the DES as an exponential function. The simulation results showed that the optimized drug release mode could lead to a fairly uniform drug concentration distribution along the stent. Therefore, the present study suggested that to achieve a more effective result, optimization of drug eluting strategy (drug release mode) for the DES would be essential.

Hsp70 regulates the doxorubicin-mediated heart failure in Hsp70-transgenic mice

The aim of this study was to investigate the potential protective effect of the Hsp70 protein in the cardiac dysfunction induced by doxorubicin (DOX) and the mechanisms of its action. For this purpose, we used both wild-type mice (F1/F1) and Hsp70-transgenic mice (Tg/Tg) overexpressing human HSP70. Both types were subjected to chronic DOX administration (3 mg/kg intraperitoneally every week for 10 weeks, with an interval from weeks 4 to 6). Primary cell cultures isolated from embryos of these mice were also studied. During DOX administration, the mortality rate as well as weight reduction were lower in Tg/Tg compared to F1/F1 mice (P < 0.05). In vivo cardiac function assessment by transthoracic echocardiography showed that the reduction in left ventricular systolic function observed after DOX administration was lower in Tg/Tg mice (P < 0.05). The study in primary embryonic cell lines showed that the apoptosis after incubation with DOX was reduced in cells overexpressing Hsp70 (Tg/Tg), while the apoptotic pathway that was activated by DOX administration involved activated protein factors such as p53, Bax, caspase-9, caspase-3, and PARP-1. In myocardial protein extracts from identical mice with DOX-induced heart failure, the particular activated apoptotic pathway was confirmed, while the presence of Hsp70 appeared to inhibit the apoptotic pathway upstream of the p53 activation. Our results, in this DOX-induced heart failure model, indicate that Hsp70 overexpression in Tg/Tg transgenic mice provides protection from myocardial damage via an Hsp70-block in p53 activation, thus reducing the subsequent apoptotic mechanism.

Drug-eluting stent restenosis: effect of drug type, release kinetics, hemodynamics and coating strategy

Restenosis following stent implantation diminishes the procedure's efficacy influencing long-term clinical outcomes. Stent-based drug delivery emerged a decade ago as an effective means of reducing neointimal hyperplasia by providing localized pharmacotherapy during the acute phase of the stent-induced injury and the ensuing pathobiological mechanisms. However, drug-eluting stent (DES) restenosis may still occur especially when stents are used in complex anatomical and clinical scenarios. A DES consists of an intravascular metallic frame and carriers which allow controlled release of active pharmaceutical agents; all these components are critical in determining drug distribution locally and thus anti-restenotic efficacy. Furthermore, dynamic flow phenomena characterizing the vascular environment, and shear stress distribution, are greatly influenced by stent implantation and play a significant role in drug deposition and bioavailability within local vascular tissue. In this review, we discuss the performance of DES and the interaction of the different DES components with the hemodynamic milieu emphasizing on the inhibition of clinical restenosis.

Development of a total atherosclerotic occlusion with cell-mediated calcium deposits in a rabbit femoral artery using tissue-engineering scaffolds

This study sought to establish a chronic total occlusion (CTO) model with cell-mediated calcium deposits in rabbit femoral arteries. CTO is the most severe case in atherosclerosis and contains calcium deposits. Previous animal models of CTO do not mimic the gradual occlusion of arteries or have calcium in physiological form. In the present study we tested the strategy of placing tissue-engineering scaffolds preloaded with cells in arteries to develop a novel CTO model. Primary human osteoblasts (HOBs) were first cultured in vitro on polycaprolactone (PCL) scaffolds with 5 ng TGFβ1 loading for 28 days for precalcification. The HOB-PCL construct was then implanted into a rabbit femoral artery for an additional 3, 10 or 28 days. At the time of sacrifice, angiograms and gross histology of arteries were captured to examine the occlusion of arteries. Fluorescent staining of calcium and EDS detection of calcium were used to evaluate the presence and distribution of calcium inside arteries. Rabbit femoral arteries were totally occluded over 28 days. Calcium was presented at CTO sites at 3, 10 and 28 days, with the day 10 specimens showing the maximum calcium. Chronic inflammatory response and recanalization were observed in day 28 CTO sites. A novel CTO model with cell-mediated calcium has been successfully established in a rabbit femoral artery. This model can be used to develop new devices and therapies to treat severe atherosclerotic occlusion.

The impact of vascular endothelial growth factor-transfected human endothelial cells on endothelialization and restenosis of stainless steel stents

OBJECTIVES

The purpose of this study was to investigate the effects of gene transfection of endothelial cells with vascular endothelial growth factor (VEGF) on re-endothelialization and inhibiting in-stent restenosis.

METHODS

Stents coated with human umbilical vein endothelial cells (HUVECs) transfected with VEGF(121) were studied both in vitro and in vivo. In vitro studies were performed using a homemade extracorporeal circulation system. In vivo studies were performed using the rabbit abdominal aorta model.

RESULTS

In vitro studies confirmed that VEGF(121)-transfected cells adhered on the surface of stainless steel stents with over 90% of the surface covered within 24 hours of seeding. In vivo results showed that VEGF(121)-transfected HUVECs-coated stents were covered with seeding cells after implanting, and almost completely covered with cells after stent implantation for 1 week. In contrast, the non-endothelialized areas of bare metal stents and glutin/poly-L-lysine-coated stents were covered at 4 weeks, and the monolayers of cells were not observed, but fragile neointima was found on the surface. After 12 weeks, VEGF(121)-transfected HUVECs-coated stents significantly reduced the neointima area (0.78 ± 0.03 mm(2)) and stenosis (15.69 ± 2.61%) as compared with those for bare metal stents (neointima area = 2.26 ± 0.67 mm(2); the percentage of stenosis = 47.55 ± 7.10%;P < .01) and glutin/poly-L-lysine-coated stents (neointima area = 1.40 ± 0.37 mm(2); the percentage of stenosis = 31.37 ± 8.18%;P < .01).

CONCLUSION

In this small animal study, VEGF transfected human endothelial cells, when coated on stainless steel stents, reduce neointimal hyperplasia, promote endothelialization, and reduce in-stent restenosis. Additional studies with this technology are necessary to determine its ultimate utility in improving stents performance.

Microtubule-binding agents: a dynamic field of cancer therapeutics

Microtubules are dynamic filamentous cytoskeletal proteins composed of tubulin and are an important therapeutic target in tumour cells. Agents that bind to microtubules have been part of the pharmacopoeia of anticancer therapy for decades and until the advent of targeted therapy, microtubules were the only alternative to DNA as a therapeutic target in cancer. The screening of a range of botanical species and marine organisms has yielded promising new antitubulin agents with novel properties. In the current search for novel microtubule-binding agents, enhanced tumour specificity, reduced neurotoxicity and insensitivity to chemoresistance mechanisms are the three main objectives.