Highly oriented, tubular hybrid vascular tissue for a low pressure circulatory system

A hierarchically structured hybrid vascular tissue was prepared from vascular cells and collagen. First a hybrid medial tissue was prepared by pouring a cold mixed solution of bovine aortic smooth muscle cells (SMCs) and Type I collagen into a tubular glass mold composed of a mandrel and a sheath (inner diameter, 1.5 mm; outer diameter, 7 mm; length, 7 cm). An SMC incorporating collagenous gel was formed with incubation at 37 degrees C. After the sheath of the mold was removed, the resulting fragile tissue cultured in the medium shrank in a time dependent manner to form an opaque, dense tissue. Seeding at a higher cell density and a lower concentration of collagen resulted in rapid and prominent shrinkage. Morphologic investigation showed that with time, bipolarly elongated SMCs and collagen fiber bundles became positioned around the mandrel. When the mandrel was removed, a tubular hybrid medial tissue was formed. A hybrid vascular tissue with a hierarchical structure was constructed by seeding endothelial cells onto the inner surface of the hybrid medial tissue. Prepared tissues tolerated luminal pressures as great as 100 mmHg and mechanical stress applied during the anastomotic procedure. This method allowed the authors to prepare hybrid medial tissues of predetermined size (specifically inner diameter, wall thickness, and length) and mechanical property, which all depend on the mold design, SMC seeding density, initial collagen concentration, and incubation period. Hybrid vascular tissues may provide physiologic functions such as antithrombogenicity and regulation of vasomotor tone when implanted into a venous system.