Prevention of neointimal thickening by Mst1

DESCRIPTION (provided by applicant): In-stent restenosis remains an unsolved clinical problem in the era of drug-eluting stents (DES). Current first- generation DES, such as sirolimus- or taxol-ES, target proliferative changes after stenting, but have several problems, including increased thrombus formation and delayed healing processes represented by prolonged inflammation and impaired endothelial regeneration. Thus, an improved modality simultaneously suppressing proliferation and inflammation while preserving endothelial regeneration has been awaited. We have shown that balloon catheter-mediated delivery of adenovirus harboring mammalian sterile 20 like kinase 1 (Mst1) strongly prevents neointimal thickening in rat balloon-injured carotid arteries. Mst1 is a serine threonine kinase having versatile functions, including apoptosis and suppression of cell growth and migration, many of which should contribute to suppression of neointimal thickening. Our long-term goal is to translate our initial findings on Mst1 in the animal model to the clinic and to develop new stents circumventing the outstanding issues of the DES currently available. To obtain efficient and blood vessel-friendly delivery of Mst1 from stents, we will utilize completely biodegradable stents made of noncombustible magnesium and a proprietary technique to coat the stents with mammalian expression plasmids, which can be efficiently delivered to vascular smooth muscle cells (VSMCs), the technique successfully utilized to prevent in-stent restenosis. In addition, to inhibit neointimal thickening without interfering with endothelial regeneration, we will utilize cell type-specific targeting using tissue specific promoters, including SM22a and Tie-2 promoters. In the phase I study, we will demonstrate the efficacy of completely biodegradable stents coated with mammalian expression plasmids harboring Mst1 with or without tissue specific promoters in preventing in-stent restenosis in iliac arteries of rabbits fed with a high cholesterol diet. In the phase II study, we will conduct pre-clinical studies, including long- term and safety experiments, using cynomolgus monkeys. Our specific aims are: 1) To examine the effect of the biodegradable stent coated with mammalian expression plasmid harboring wild type Mst1 driven by CMV, a universal promoter, upon progression of in-stent restenosis in hypercholesterolemic rabbits. 2-1) To examine the effect of the biodegradable stent coated with mammalian expression plasmid harboring Mst1 driven by SM22a, a VSMC specific promoter, upon progression of intimal thickening in rabbits fed with a high-cholesterol diet. 3) To examine the effect of the biodegradable stent coated with expression plasmids harboring CMV-wild type Mst1 and dominant negative Mst1 (DN-Mst1) driven by Tie-2, an endothelial cell-specific promoter, upon progression of intimal thickening in rabbits fed with a high-cholesterol diet. The proposed study will be an essential step for us to test whether or not our initial observations obtained in the balloon injury models can be translated into a clinically relevant form, namely to prevent in-stent restenosis, and, in combination with cutting edge technologies of improved stents, to seek commercialization of a next generation of plasmid eluting stents. Despite the recent progress in drug-eluting stents (DES), failure in coronary revascularization remains a serious problem in cardiovascular medicine. In this proposal, we will demonstrate the efficacy of biodegradable stents coated with a gene encoding a molecule called Mst1, an intracellular signaling molecule, in preventing restenosis of the coronary stent. The proposal is an essential step for us to test whether or not our initial observations obtained in the rat balloon injury models can be translated into a clinically relevant form, namely to prevent in-stent restenosis. Using cutting edge technologies applied to make the stent "vascular-friendly" in combination with the application of novel modalities to reduce restenosis, we will seek commercialization of a next generation of DES.