The endothelialization process of a fibrous polyurethane microvascular prosthesis after implantation in the abdominal aorta of the rat. A scanning electron microscopic study.

The endothelialization process of a fibrous microvascular polyurethane prosthesis (inner diameter 1.6 mm) was studied by scanning electron microscopy. Forty-seven prostheses (1 cm) were implanted into the abdominal aorta of rats between the left renal artery and the bifurcation. Specimens were taken on day 1, 3, 5, 7, 10, 14, 18, 21 and 25, as well as 6 and 9 months after implantation, to evaluate immediate and delayed response and complications. The patency rate of the implants was 91.2%. After an initial recovery period of five days, endothelial cells started to migrate onto the inner surface of the prosthesis with a velocity of approximately 0.3 mm per day, resulting in a completely endothelialized prosthesis at day 21. A smooth continuous inner lining was achieved. A difference in growth pattern between the proximal and distal growth zone was observed, and may be attributed to the direction of the blood flow through the prosthesis. The endothelial cells advanced in a close arrangement. No cells were seen to settle and grow in between the two growth zones on the fibrin layer. If no immediate complications occur, the endothelialization process (21 days) proceeds uneventfully and no late complications are observed. Though it may be argued that the new cells lack some authentic endothelial features, this study indicates that they are at least of endothelial orgin, and behave morphologically like endothelial cells. It can be concluded that the adequate texture of the prosthesis and the cell anchoring, in combination with both an optimal surgical performance and blood flow, ensure that the microvascular prostheses are rapidly endothelialized and retain high patency rates over long periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)