Venous reconstruction using hybrid vascular tissue composed of vascular cells and collagen: Tissue regeneration process

In this study, a tubular hybrid vascular tissue composed of vascular cells and collagen was implanted as a venous substitute, and its remodeling process was histologically investigated. First, a hybrid medial tissue was prepared by pouring a cold mixed solution of canine jugular smooth muscle cells (SMCs) and Type I collagen into a tubular glass mold and subsequent incubation at 37 degrees C. Culture in medium for 10 days produced a dense tubular tissue. Seeding of jugular endothelial cells (ECs) onto the luminal surface of the tissue produced a hybrid vascular tissue with a hierarchical structure. These vascular tissues (inner diameter, 7 mm; length, 3 cm; wall thickness, 1 mm; n = 14) were implanted autologously in the canine posterior vena cava wrapped in Dacron mesh for up to 24 wk. Nine of 14 grafts were patent throughout implantation. In patent grafts, monolayered ECs were oriented in the direction of blood flow at 1 wk. Circumferentially oriented SMCs accumulated at the subendothelial layer and ingrown fibroblasts were sparsely distributed throughout the wall at 12 wk. Contractile phenotype of SMCs was evident at 24 wk. Collagen fibrils, which were sparsely distributed at an early period of implantation, gradually assembled to form fibrous meshes at 24 wk. Sheet-like elastic lamellae were also observed at this time. Marked wall thinning was observed at 12 and 24 wk. The resultant tissues became highly dense. The specific gravity of tissues increased with time, and reached those of natural vessels at 24 wk. Tissue remodeling progressed in a time-dependent manner and appeared to be almost complete within 6 mo of implantation.