Over 350,000 open surgical procedures to treat cardiovascular disease are performed each year in the USA, with many more being performed worldwide. A great number of these eventually fail due to intimal hyperplasia (IH), which is primarily caused by smooth muscle cell (SMC) transformation from a quiescent to a pathogenic (proliferative, migratory, and inflammatory) phenotype. Current clinical methods for preventing IH (e.g., drug-eluting stents) are not applicable for traditional open surgical procedures such as bypass, endarterectomy, or dialysis access. Thus, there is a notable lack of clinical options for delivery of drugs that block IH following open cardiovascular surgery. We have developed a novel unimolecular nanoparticle (NP) which provides a unique opportunity to meet this medical need through its multiple favorable properties, which include excellent stability, the ability to provide sustained drug release, and the chemical versatility for conjugation with ligands or molecules that target periadventitial collagen (for the creation of a perivascular reservoir) or pathogenic SMCs (for more precise control of IH). Our preliminary studies demonstrate that NPs are capable of prolonging the release of the clinically used drug rapamycin, resulting in a more durable inhibition of IH in an animal model of IH. The goal of this project is to develop a novel NP- mediated multifunctional drug delivery platform that: (1) is readily applicable to the outer surface of blood vessels at the time of open surgery, (2) produces sustained drug release for periods of up to 3 months and beyond, and (3) specifically targets pathogenic SMCs thereby focusing toxicity to these cells while sparing quiescent cells. To achieve sustained drug release, we will generate a ?perivascular NP reservoir? of rapamycin either by sequestering NPs around the blood vessel using a hydrogel or by ?painting? NPs onto the outer surface of the vessel. In the latter case, the NPs are conjugated with a small molecule or peptide that facilitates their attachment to the adventitia. To test the efficacy of targeted drug delivery, we will conjugate NPs with ligands that bind to receptors that are highly expressed on the surface of pathogenic SMCs. Thus, in Specific Aim 1, we will test the hypothesis that the perivascular application of a rapamycin/NP reservoir maintained in a 1-month durable hydrogel produces sustained inhibition of IH.
In Specific Aim 2, we will test the hypothesis that a rapamycin/NP reservoir ?painted? onto the outer surface of the vessel produces sustained inhibition of IH. And in Specific Aim 3, we will test the hypothesis that rapamycin/NPs capable of targeting pathogenic SMCs are more efficacious in mitigating IH than non-targeted NPs. Our long-term goal is to create a perivascular nanoplatform that can be readily applied at the time of open vascular reconstruction and is effective in preventing recurrent vascular disease via durable and targeted drug delivery. We believe that the success of these studies will be facilitated by a collaborative team including a vascular surgeon scientist, a biomedical engineer and a biochemist, and will benefit hundreds of thousands of patients.
The development of recurrent disease following open vascular reconstruction is a major and expensive public health problem that affects hundreds of thousands of individuals in this country. Despite the availability of multiple techniques to prevent recurrent disease following intraluminal treatments of cardiovascular disease, there is no effective strategy for patients that undergo open surgical reconstruction. We believe that this can be solved with the use of nanotechnology that can be directly applied to reconstructed vessels at the time of open surgery. The combined expertise of a vascular surgeon, a nanotechnologist, and a vascular biologist creates a unique opportunity for creating a drug delivery nanoplatform to effectively prevent the recurrent disease that follows cardiovascular surgery. 1
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