Endovascular manipulation to restrict restenosis

The challenges of treating peripheral arterial disease

Today, peripheral arterial disease (PAD) patients need effective medical care for an extended period of their lifetime. Therefore, different treatment modalities have to be tied sequentially into an effective therapeutic chain. First, preventive measures have to be reinforced and risk factors tightly controlled. Furthermore, antiplatelet agents have to be applied in every PAD patient to reduce the risk of cardiac and cerebral ischemic events, restenosis or reocclusion after revascularization, and possibly also progression of the PAD itself. Angiotensin-converting enzyme (ACE) inhibitors should be entertained in high-risk groups such as PAD patients with diabetes. In the claudicant, exercise therapy should be strongly encouraged and vasoactive drugs considered for those who are not good candidates for either exercise training or revascularization. In patients with disabling claudication or critical limb ischemia, revascularization procedures are highly effective. Especially for high-grade stenoses or short arterial occlusions, percutaneous transluminal angioplasty (PTA) should be the method of fi rst choice followed by the best surgical procedure later on. To achieve good long-term effi cacy, a close follow-up including objective tests of both the arterial lesion and hemodynamic status, surveillance of secondary preventive measures and risk factor control is mandatory.

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.

Engineered polymeric nanoparticles for receptor-targeted blockage of oxidized low density lipoprotein uptake and atherogenesis in macrophages

Strategies to prevent the uptake of modified low density lipoproteins (LDLs) by immune cells, a major trigger of inflammation and atherogenesis, are challenged by complex interfacial factors governing LDL receptor-mediated uptake. We examine a new approach based on a family of "nanoblockers", which are designed to examine the role of size, charge presentation, and architecture on inhibition of highly oxidized LDL (hoxLDL) uptake in macrophages. The nanoblockers are macromolecules containing mucic acid, lauryl chloride, and poly(ethylene glycol) that self-assemble into 15-20 nm nanoparticles. We report that the micellar configuration of the macromolecules and the combined display of anionic (carboxylate) groups in the hydrophobic region of the nanoblockers caused the most effective inhibition in the uptake of hoxLDL by IC21 macrophages. The nanoblockers primarily targeted SR-A and CD36, the major scavenger receptors and modulated the "atherogenic" phenotype of cells in terms of the degree of cytokine secretion, accumulation of cholesterol, and "foam cell" formation. These studies highlight the promise of synthetically engineered nanoblockers against oxidized LDL uptake.