Background: Currently available vascular grafts for pediatric cardiovascular operations are limited by their inability to grow. Tissue-engineering techniques can be used to create vascular grafts with the potential for repair, remodeling, and growth. This study demonstrates the feasibility of constructing an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells (BMVCs) in the ovine animal model.
Methods: Ovine mononuclear cells were isolated from the bone marrow, cultured in endothelial growth medium, and characterized with immunocytochemistry. Biodegradable tubular scaffolds were constructed from polyglycolic acid mesh coated with a copolymer of poly[epsilon-caprolactone-L-lactide]. Scaffolds were seeded at various cell concentrations and incubation times to optimize seeding conditions for the construction of an autologous venous conduit. Using optimized conditions, 6 tissue-engineered vascular grafts were implanted as inferior vena cava interposition grafts in juvenile lambs. Grafts were assessed for patency at days 1 to 30 postoperatively and explanted for histological and immunohistochemical analysis.
Results: A mixed cell population of BMVCs consisting of smooth muscle cells and endothelial cells was cultured from ovine sternal bone marrow. A seeding concentration of 2 x 10(6) cells/cm2 and 7 days of postseeding incubation were optimal for creating a confluent cellular layer on the polyglycolic acid/poly[epsilon-caprolactone-L-lactide]) scaffold. Grafts were explanted up to 4 weeks postoperatively. All grafts were patent without evidence of thrombosis. Histological evaluation of the explanted grafts demonstrated neo-endothelialization. Graft wall was composed of neo-tissue made up of residual polymer matrix, mesenchymal cells, and extracellular matrix without evidence of calcification.
Conclusions: Bone marrow-derived vascular cells, containing endothelial and smooth muscle cells, can be isolated and cultured from ovine sternal bone marrow and used as a cell source for vascular tissue engineering. Our optimized techniques for BMVC harvest and seeding onto biodegradable scaffolds can be used for studying autologous tissue-engineered vascular grafts in the ovine animal model.