Development of an autologous connective tissue tube as a small caliber vascular substitute.

A small-caliber vascular graft with good healing properties was developed using an autologous connective tissue tube (ACTT) and in situ heparinization. ACTT is the best material for implantable grafts, but as a small-caliber vascular graft, both the high thrombogenicity and requirement for time to preparation in situ were serious problems. To overcome these difficulties, an ultrafine polyester fiber (UFPF) mesh was used for the framework of the graft. it has been shown that UFPF provides a good framework for fibroblast migration and proliferation both in vivo and in vitro. The granulomatous connective tissue tube could be constructed very rapidly and had numerous capillary blood vessels, which opened onto the luminal surface of the graft when it was implanted as a vascular substitute and provided colonies of endothelial cells. These colonies spread rapidly all over the luminal surface, and the graft developed permanent antithrombogenicity by endothelialization. The next problem was attainment of temporary antithrombogenicity of the graft before complete endothelialization. Since collagen fibrils are highly thrombogenic, the fact that ACTT collagen fibrils face the luminal surface requires greater antithrombogenicity. A new technique for binding heparin to collagen fibrils in situ was also developed. This was proved to be useful in maintaining the antithrombogenicity of the grafts (3 mm in inner diameter, 6 to 7 cm in length) in the animal studies. The graft showed rapid healing of the neonintima with endothelialization and long-term stability of the graft wall.