Abstract 254: TSP-2 siRNA Coating of Prosthetic Arterial Graft Material to Reduce Intimal Hyperplasia in a Rat Model

Introduction Intimal hyperplasia represents a complex pathologic vascular response to injury. Our group previously revealed that TSP-2 was associated with this response, and demonstrated that intraluminal delivery of TSP-2 siRNA can suppress the intimal hyperplastic response in an animal model. Furthermore, we have shown that siRNA can be incorporated into prosthetic graft material using a dip-coating technique. We sought to determine whether this method could be employed for siRNA delivery in order to attenuate the response to arterial injury, and to reduce neointima formation in an in vivo model. Methods Carotid artery endothelial cell denudation was performed on male Wistar rats using a 2 Fr Fogarty balloon catheter. ePET graft material was dip-coated in several siRNA solutions (i.e. saline, TSP-2 siRNA, PEI-complexed TSP-2 siRNA) for 50 minutes. The graft was cut longitudinally, and then wrapped circumferentially around the denuded carotid artery. Arterial segments were then isolated at 21 days. TSP-2 gene expression was measured by qRT-PCR, and intimal hyperplasia was assessed by quantitative morphometry. Results Balloon denudation increased TSP-2 gene expression by 10-fold, when compared to non-denuded arteries after 21 days (p = .01). Fluorophore-conjugated siRNA confirmed transmural delivery following denudation. When compared to saline treated animals, TSP-2 siRNA reduced TSP-2 mRNA expression by 70% (p = .001). The addition of the transfection reagent PEI to TSP-2 siRNA treated grafts, however, did not significantly augment gene silencing. Morphometric analysis of arterial cross sections demonstrated significantly less neointima formation–as measured by intima-media (I/M) total area ratio–among grafts dip-coated with unmodified and PEI-treated TSP-2 siRNA (I/M: 0.2 and 0.4, respectively) compared to saline grafts (I/M: 1.0, p < .001). Conclusions In the rat carotid artery balloon injury model, dip-coating of prosthetic graft material with subsequent perivascular delivery of TSP-2 siRNA is an effective method to achieve transmural transfection and consistent gene silencing, while significantly suppressing the intimal hyperplastic response following arterial injury.