The effect of factor XIII and fibronectin on the viscoelasticity of fibrinogen surface layers

The binding of fibrin sealant to collagen is influenced by the method of purification and the cross-linked fibrinogen–fibronectin (heteronectin) content of the ‘fibrinogen’ component

Two fibrinogen preparations, each an intermediate in the manufacture of the 'fibrinogen' component of a commercial human tissue sealant, were made from a common cryoprecipitate source. The first preparation, prepared according to the process described by Schwartz et al. had a higher ratio of clottable to total protein than the second preparation, prepared according to that by Martinowitz and Bal but a much lower ratio of fibronectin to fibrinogen. After clotting with thrombin and solubilization and reduction of the clots, sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a much higher content of high molecular weight polymers of fibrin(ogen) in the second preparation than in the first. The second preparation bound to collagen more strongly than did cryoprecipitate and much more strongly than did the first one. Experiments with highly purified proteins showed that fibronectin was essential in promoting progressive binding of fibrinogen to collagen under the action of activated factor XIII (transglutaminase). It was concluded that, because of their method of purification from cryoprecipitate, preparations of fibrinogen differ in their content of fibronectin and heteronectin. The binding of these proteins to collagen may improve the adhesion of tissue sealant clots to the extracellular matrix.

Antithrombotic benefit of subendothelium-bound urokinase: an experimental study

To improve the outcome of extremity replantation, microsurgeons have administered systemic antithrombotic agents (e.g., heparin, aspirin, dextran). To obviate the risks associated with systemic anticoagulation, we have investigated the use of topically applied urokinase for its binding capacity to arterial subendothelium and for its ability to prevent subsequent thrombosis. An arterial model of thrombosis associated with intimal deendothelialization was developed. Donor rat carotid arteries were everted and mechanically deendothelialized with a scalpel blade. The vessels were next subjected to one of several treatments, which included 30-minute incubation with urokinase, heparin, or vehicle (lactated Ringer's solution). The vessels were then washed, reinverted to normal orientation, sectioned into 5 mm lengths, and grafted into the femoral arteries of recipient rats. Two-hour patency rates were 25% for controls (n = 20), 10% for heparin-treated vessels (n = 10), and 55% for urokinase-treated vessels (n = 20); this last was significantly greater than the other two groups. In vitro investigations revealed that urokinase has a high capacity for binding to subendothelium, with a release half-life of approximately 20 minutes. Surface-bound urokinase was found to have proteolytic activity similar to that of urokinase in solution. These results indicate that urokinase may be a more beneficial irrigating solution additive than heparin for repair of traumatized vessels.