Date of Award

12-2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Bioengineering

Advisor

Dr. Dan Simionescu

Committee Member

Dr. Agneta Simionescu

Committee Member

Dr. Eugene Langan

Committee Member

Dr. Martine LaBerge

Abstract

The gold standards for small diameter peripheral vascular graft replacement are autologous arteries or veins; however, one-third of patients lack such vessels due to previous vessel harvesting or advanced vascular disease. A promising approach for patients in this category is tissue engineering with off-the-shelf biological vascular grafts. Three small diameter acellular scaffolds were developed and evaluated as vascular grafts. Porcine renal arteries (2-3 mm diameter, 20 mm length) were decellularized by immersion and stabilized with penta-galloyl glucose (PGG) with and without subsequent heparinization via carbodiimide chemistry. Bovine mammary (4-6 mm ID, 250 mm length) and femoral arteries (6-8 mm ID, 250 mm length) were decellularized in a purpose-designed, pressurized detergent perfusion system and stabilized with PGG. Decellularization completeness was confirmed by histology, DNA analysis and absence of xenoreactive galactose-(alpha 1,3)-galactose antigen. Histology suggested good preservation of native collagen, elastin and basement membrane components collagen type IV, laminin, and fibronectin. Renal artery scaffolds stabilized with PGG showed increased resistance to elastase and heparinization increased resistance to collagenase. All scaffolds exhibited adequate values of burst pressure and diametrical compliance. Acellular scaffolds were tested for biocompatibility, patency, thrombogenicity and host cell infiltration by intra-circulatory implantation in rats as abdominal aorta interposition grafts (renal artery scaffolds) and as femoral interposition grafts in minipigs (mammary artery scaffolds). Renal artery scaffolds exhibited 100% patency upon explantation at 4 and 8 weeks and demonstrated revitalization with host cells staining positive for factor VIII and alpha-smooth muscle actin. Heparinized / PGG treated renal scaffolds exhibited the most promising short-term results in rats due to reduced thrombogenicity and intimal hyperplasia. Mammary artery scaffolds thrombosed within 1 week of implantation in the femoral position, but supported cellular infiltration. Preliminary studies also showed that cells could be seeded into specific tunics of the acellular scaffolds, thus generating revitalized grafts ready for implantation. These results suggest that acellular scaffolds derived from arterial segments are good candidates for development of vascular grafts and that the combination of targeted matrix stabilization, heparinization and tunic-specific cell seeding might exhibit significant clinical potential for treatment of peripheral vascular diseases.

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