Interventional strategies to treat patients with obstructive peripheral artery disease (PAD), which affects 8.5 million adults in the US, are failing due to high rates of restenosis. A vital process in restenosis is the activation of vascular smooth muscle cells (VSMCs), resulting in their migration and proliferation into the intimal layer, re- occluding the artery. In the peripheral vasculature, the majority of stents fracture (up to 68%) due to excessive arterial deformation, resulting in restenosis at the fracture sites and disrupting drug release kinetics. In these cases, balloon angioplasty is often the only treatment option, however, outcomes are inferior to stents. To overcome the limitations of stents and balloon angioplasty in the treatment of PAD, drug coated balloons (DCBs) have emerged as an alternative approach. DCBs deliver drugs locally onto the arterial wall without the need of a metallic permanent stent platform. To date, DCBs have shown acute success but have failed to show long- term therapeutic benefit. Mechanistically though, DCBs have similar limitations to DES in that they deposit non- specific anti-proliferative drugs on the intimal surface, thereby adversely targeting endothelial cells and delaying re-endothelialization. Additionally, anti-proliferative drugs delivered by DCBs can produce downstream emboli, increasing amputation risks. Herein, we propose to develop a new strategy that delivers smooth muscle cell targeted therapy directly to the medial layer. Our preliminary results demonstrate successful delivery of VSMC- specific RNA aptamers directly to the arterial medial layer via a novel perfusion catheter. We confirm that this novel approach inhibits neointimal growth and accelerates re-endothelialization in a clinically relevant pre-clinical model. Overall, this proposal will test the hypothesis that RNA aptamer delivered by a perfusion catheter directly into the medial layer will inhibit neointimal growth and accelerate re-endothelialization during the vascular healing process. Varying conditions to maximize RNA delivery and retention using the perfusion catheter, determining VSMC proliferation and re-endothelization and identifying mechanism(s) of aptamer-medial inhibition of VSMC growth will be explored (Specific Aim 1). These studies will be accomplished using a novel ex vivo porcine artery circulatory system that mimics peripheral artery deformation. We will then quantify RNA retention, vessel remodeling and re-endothelialization in a porcine injury model (Specific Aim 2). Finally, we will evaluate the vascular response and healing of the treated RNA arteries in a diseased porcine in vivo model (Specific Aim 3). Through these aims, we will generate a targeted therapy that inhibits neointimal growth and promotes vascular healing. This innovative break-through will redefine the success of interventional therapy in the treatment of PAD.
For patients with peripheral vascular disease (> 8 million in the US), treatment by intervention remains unresolved. The successful completion of this work is expected to provide an essential foundation for the delivery of RNA-based therapeutics in the treatment of peripheral vascular disease and overcome limitations of current techniques to enhance outcomes.
