Wednesday, April 2, 2025
4/2/2025
Targeted Gene Therapies for the Prevention of Prosthetic Bypass Graft Failure - ABSTRACT This scientific proposal addresses the dismal outcomes of prosthetic bypass grafts that are currently used to treat patients with critical blockages of arterial blood flow in the lower extremities. While the use of greater saphenous vein conduits for lower extremity bypass surgery is the gold standard, as many as 40% of patients do not to have adequate quality saphenous vein. Therefore, prosthetic grafts have become widely utilized as an alternative conduit of choice for lower extremity revascularization. Unfortunately, prosthetic grafts have a significantly higher risk of failure when compared with vein grafts, which leads to an increased need for multiple repeat interventions, a predisposition for sudden graft thrombosis, and the ultimate consequence of limb loss. Prosthetic bypass graft failure is strongly linked to the development of intimal hyperplasia and subsequent narrowing of the vessel lumen at the anastomotic connection between the artery and prosthetic graft. This pathologic process disproportionally affects the distal anastomosis and is triggered by an unregulated overexpression of specific genes, such as TSP-2 and MARCKS, which drive the maladaptive phenotypic changes of vascular endothelial and smooth muscle cells. We have previously shown the ability to downregulate TSP-2 and MARCKS expression using small interfering RNA (siRNA) therapy, successfully mitigating the intimal hyperplastic response after arterial injury. To capitalize on this therapeutic benefit and to ensure clinical translation and applicability, we have since designed, using CLICK-chemistry, a safe and novel biodegradable gelatin hydrogel siRNA delivery system that is applied externally around the arterial-prosthetic graft interface immediately following completion of the surgical anastomosis. Our outside-in method of gene delivery facilitates full penetration of siRNA through the vessel walls while decreasing the risk of systemic loss to circulation. This grant proposal centers on further optimizing the efficiency and efficacy of our hydrogel gene delivery platform, by increasing hydrogel degradation length to 30-days to improve the time of sustained siRNA delivery, increasing arterial tissue adherence of the hydrogel to prevent mechanical disruption, and promoting unidirectional vascular delivery to minimize off-target effects to surrounding tissues. We plan to validate the ability of our gene therapy platform to decrease the intimal hyperplastic response in established models of prosthetic graft failure, namely rabbit end-to-end and canine end-to-side prosthetic grafting. Secondarily, in the canine model of prosthetic graft failure, we plan to use state-of-the-art, high-throughput single-nuclei RNA sequencing and spatial transcriptomic technologies to achieve a more granular understanding of the maladaptive gene signaling pathways occurring at the arterial-prosthetic graft interface, and establish novel gene targets that can be added to improve and ensure safe, effective combinatorial siRNA knockdown of the key pathologic genes that are driving prosthetic graft failure. This work will serve to further the development and use of biomaterials and gene therapies to treat a longstanding clinical challenge that has plagued the field of vascular surgery for several decades.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).