For the past decade the advent of stent angioplasty and the even more recent use of drug eluting stents have resulted in a paradigm shift in the care of vascular disease. Deleterious sequelae of vascular interventions are the result of unavoidable mechanical damage to the vessel wall. Disruption of the endothelial monolayer exposes the underlying media and induces a cascade of cellular and biological events, resulting in abnormal vascular wall function. Strategies that enhance the number of endothelial cells in the vessel wall following injury may limit complications such as thrombosis, vasospasm, and neointimal formation, through reconstitution of a luminal barrier and cellular secretion of paracrine factors. Previous strategies to rapidly "endothelialize" implanted devices did not show desired efficacy, safety, and ease of use required for clinical applications. Herein we propose a method for magnetic targeting of endothelial cells to stents based on use of a modest uniform magnetic field to both maximally magnetize the magnetic nanoparticle-loaded endothelial precursor cells and produce large local magnetic field gradients within the steel stent wire network. This mechanism will allow achieving maximized magnetic force that will result in efficient localization of endothelial cells at the blood vessel injured site. Our preliminary data using bovine aortic endothelial cells in the rat carotid-stenting model indicate on feasibility of this approach. In this project we plan to study more therapeutically relevant cells that are capable of differentiating into cells with endothelial phenotype (i.e. allogeneic blood outgrowth endothelial cells, BOEC and endothelial progenitor cells, EPC) derived from same species (rats) that will receive magnetic cell therapy.
Specific Aim 1 of the proposed research will focus on the development of protocols for isolation, culture and characterization of endothelial precursor cells to be used for further magnetic targeting studies.
Specific Aim 2 will concentrate on the optimization of protocols for cell loading by biodegradable magnetic nanoparticles, evaluating the effects of cell loading on cell's morphology, growth, and preservation of functional integrity.
This aim will also address some mechanistic aspects of magnetically loaded and manipulated EC cells, evaluating their gene expression profiles, adhesion and thrombogenicity.
Specific Aim 3 will be dedicated to quantitatively evaluate the efficiency of magnetic cell targeting in vivo using appropriate animal model, to investigate the organ biodistribution of the off-targeted endothelial cells as well as to examine the beneficial therapeutic effect on the injured vessel wall by magnetically localized allogeneic endothelial cells. The long term therapeutic effect will also be assessed. We sincerely believe that resulting data, coupled with concurrent pre-clinical work on magnetic implant development will provide a widely implementable strategy of magnetic cell targeting in vascular and other applications.
The proposed approach has the potential to be a vital alternative to the currently used drug eluting stents (DES) which although have been shown to reduce the incidence of restenosis after stenting, but also result in delayed endothelialization leading to a later vascular complications requiring prolonged use of antiplatelet therapy. Our approach can provide the capability for an accelerated regeneration of vascular tissue via the efficient localization of endothelial cells to stented blood vessels, resulting in fewer restenosis-related complications on the long term scale. Additionally, the outcomes of this study will have broad general implications for targeted cell delivery in a number of therapeutic settings using magnetizable steel implants as targeting devices for the ordered deposition of cell-based therapies.
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