Objective: Stent grafts are increasingly recognized as useful devices for endovascular repair of aortic aneurysms and other vascular diseases. Stent graft-mediated gene delivery into the vascular wall is expected to improve their therapeutic effects. This study evaluated the efficacy of genetically engineered cationized gelatin (CG) hydrogel-coated partially-covered polyester stent grafts that facilitate delivery of an expression plasmid DNA in rabbit aortic wall.
Methods: Partially covered polyester stent grafts coated with CG hydrogel impregnated with 10.0 mg/mL of beta-galactosidase (LacZ)-expression plasmid vector (pCAGGS-LacZ) or empty vector (pCAGGS) solutions were implanted via the femoral artery in rabbit balloon-injured aortas. The aortic segments were removed at 1, 3, or 7 days (4 rabbits/each group) after implantation and evaluated for the transgene (LacZ) delivery and expression by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) staining. Partially-covered polyester stent grafts coated with CG hydrogel impregnated with various amounts (0.1 mg/mL, 1.0 mg/mL, and 10.0 mg/mL) of pCAGGS-LacZ or pCAGGS were also implanted in rabbits' balloon-injured aortas (4 rabbits/each group) to evaluate transgene delivery and expression in the aortic wall 3 days after implantation. The difference of transgene efficiency among each group was compared using one-way analysis of variance (ANOVA) and Newman-Keuls' test according to the result of quantitative RT-PCR.
Results: In all animals, LacZ gene transduction into the aortic wall was detected at the implantation site of pCAGGS-LacZ-loaded, but not pCAGGS-loaded, stent grafts. LacZ expression was not detected in aortic segments immediately proximal or distal to the implanted pCAGGS-LacZ-loaded stent graft or remote organs including the brain, heart, liver, and kidney by either RT-PCR or X-gal staining. The X-gal staining-positive cells were observed at or near the luminal surface in the aortic segments only in contact with the stent graft and the ingrowth tissues within stent grafts. Immunohistochemical studies suggested that the LacZ-positive cells were mainly the neointimal alpha-smooth-muscle actin-positive cells and macrophages. The extent of the transgene expression was dependent on the quantity of the plasmid DNA loaded onto the stent graft (10.0 mg/mL plasmid vs 1.0 mg/mL plasmid, P < .01 and 10.0 mg/mL plasmid vs 0.1 mg/mL plasmid, P < .05). LacZ mRNA expression was maximal at day 1 and declined at day 7 (P < .05) but was still detectable.
Conclusion: Plasmid-loaded CG hydrogel-coated stent graft is a promising vehicle for local transgene delivery to the aortic wall and offers the possibility of transduction of therapeutic genes into the vascular wall.